jco 2011-03-129-187

VOLUME XLV NUMBER 3 129© 2011 JCO, Inc.

EDITORRobert G. Keim, DDS, EdD, PhD

SENIOR EDITOREugene L. Gottlieb, DDS

ASSOCIATE EDITORSBirte Melsen, DDS, DO (Aarhus, Denmark)Ravindra Nanda, BDS, MDS, PhD (Farmington, CT)John J. Sheridan, DDS, MSD (Jacksonville, FL)Peter M. Sinclair, DDS, MSD (Los Angeles, CA)Bjorn U. Zachrisson, DDS, MSD, PhD (Oslo, Norway)

TECHNOLOGY EDITORW. Ronald Redmond, DDS, MS (San Clemente, CA)

CONTRIBUTING EDITORSR.G. Alexander, DDS, MSD (Arlington, TX)Tiziano Baccetti, DDS, PhD (Florence, Italy)Jeff Berger, BDS, DO (Windsor, Canada)S. Jay Bowman, DMD, MSD (Portage, MI)Robert L. Boyd, DDS, MEd (San Francisco, CA)Vittorio Cacciafesta, DDS, MSC, PhD (Milan, Italy)José Carrière, DDS, MD, PhD (Barcelona, Spain)Jorge Fastlicht, DDS, MS (Mexico City, Mexico)John W. Graham, DDS, MD (Litchfield Park, AZ)Robert S. Haeger, DDS, MS (Kent, WA)Warren Hamula, DDS, MSD (Monument, CO)James J. Hilgers, DDS, MS (Mission Viejo, CA)Masatada Koga, DDS, PhD (Tokyo, Japan)Björn Ludwig, DMD, MSD (Traben-Trarbach, Germany)James Mah, DDS, MS, DMS (Los Angeles, CA)Melvin Mayerson, DDS, MSD (Kettering, OH)Richard P. McLaughlin, DDS (San Diego, CA)James A. McNamara, DDS, PhD (Ann Arbor, MI)Elliott M. Moskowitz, DDS, MS (New York, NY)Jonathan Sandler, BDS, MSC, FDS RCPS, MOrth RCS (Chesterfield, United Kingdom)Georges L.S. Skinazi, DDS, DSO, DCD (Paris, France)Michael L. Swartz, DDS (Encino, CA)Flavio Uribe, DDS, MDS (Farmington, CT)

ExECUTIVE EDITORDavid S. Vogels III

MANAGING EDITORWendy L. Osterman

EDITORIAL ASSISTANTHeidi Reese

BUSINESS MANAGERLynn M. Bollinger

CIRCULATION MANAGERCarol S. Varsos

GRAPHIC DESIGNERJennifer Johnson

Address all communications to Journal of Clinical Orthodontics, 1828 Pearl St., Boulder, CO 80302. Phone: (303) 443-1720; fax: (303) 443-9356; e-mail: [email protected]. See our website at www.jco-online.com.

THE EDITOR’S CORNERExtending a Hand

Those of us in Southern California have a close relation-ship with the orthodontists of Japan. Many of them belong to the Southern California component of the Angle Society, and all are valued colleagues. There is a large contingent of our Japanese friends at every major Southern California ortho-dontic meeting, whether it’s the Angle Society or the Pacific Coast Society of Orthodontists. The Japanese orthodontists always present extraordinarily well-managed cases, and their research projects are interesting and clinically applicable. But some of my most treasured memories are of the great times we’ve had after hours, simply enjoying our camaraderie.

On Friday, March 11, at 2:46 p.m. local time, a massive earthquake, measured at 8.9-9.0 on the Richter scale, struck off the northeast coast of Japan. In Tokyo, hundreds of miles away, skyscrapers shook violently, and workers scrambled into the streets for safety. More than 50 aftershocks followed, seven of which were at least 6.3 on the Richter scale—the size of the quake that struck New Zealand on Feb. 22. Subsequently, a huge tsunami crashed through Japan’s eastern coastline, sweeping buildings, boats, cars, and people miles inland.

It is almost impossible to imagine the scale of devastation caused by this catastrophe. Entire villages were carried away, along with thousands of inhabitants. But of all the news accounts that appeared worldwide, CNN’s story of a nurse in Rikuzentakata is the one that touched me the most. This nurse described the haunting cries of the patients when the tsunami hit her hospital, as she had to decide between trying to save her patients and saving herself. She rescued as many as she could before seeking higher ground. Of the 51 hospitalized patients, doctors and nurses were unable to move 12, who drowned in their beds. Dr. Mikihito Ishiki, a medical director at the hospi-tal, said that “10 of my staff also died with the patients.” On top of this human tragedy, he lost the hospital he proudly called his home. As doctors ourselves, with patients and staff members whom we cherish, our hearts go out to those medical workers and others like them in this period of enormous loss.

JCO has many readers in Japan, and all of them remain in our thoughts and prayers. It was with deep concern that I e-mailed my close friend and colleague, Dr. Masatada Koga,

©2011 JCO, Inc. May not be distributed without permission. www.jco-online.com

our Contributing Editor in Japan, to inquire about his well-being and that of his home and family. Masa reports that things are relatively normal in Tokyo, where he lives and practices. Although he felt substantial shaking at the time of the quake, there was little actual damage in the city. Still, he says, some Tokyo residents have been rushing to hoard food, water, and basic supplies. He also reports that, according to the Japanese press, the loss of life from the earthquake and tsunami are substantially greater than what the international media are reporting, with local estimates approach- ing 20,000 dead. Masa also notes that four or five of the 15 nuclear power plants in the area have lost structural integrity and are considered dangerous —again, substantially more damage than has been reported by the world press.

Dr. Junji Sugawara, lead author of the Case Report on “Non-Surgical Correction of Skeletal Open Bite” in this issue, teaches with his co-authors Zaher Aymach, Hiroshi Nagasaka, and Hiroshi Kawamura at Tohoku University in Sendai, the city at the center of the affected area on Japan’s east coast. A few days after the earthquake he wrote to his colleagues, including our Associate Editor, Dr. Ravindra Nanda, that, although many were leaving the area, his family and community commitments would keep him there: “. . . I have to stay at Sendai while praying God for a disaster no longer spreading. Attached photograph is a vase with tulip on my table. It did not fall down in spite of a strong earthquake. . . it is miraculous tulip indeed. We bear this catastrophe like this tulip per-sistently and wish to recover as soon as possible.”

Dr. Sugawara later e-mailed his colleagues: “It has been an overwhelming experience, but I am very touched by all your support and encourage-ment upon this unprecedented disaster. However, many of those who have lost their homes and fami- lies continue to face great sufferings and challenges of recovery. . . . I feel that it is my responsibility as a survivor of this calamity to help those who are more affected regain hope and courage. Because of the many offers of support I received, I am attempting to coordinate donations for the sake of better restor-ing health to this greatly afflicted city.

“I would like to ask for your continued con-tributions to reputable organizations in your coun-

try, such as the Red Cross or UNICEF. Alter-natively, you may consider ‘Save Sendai 311’, an organization I have started to distribute funds with greater flexibility. . . directly to smaller groups as their needs arise.” For details on how to support Dr. Sugawara’s effort, e-mail him at [email protected] or follow the link on the JCO homepage.

The global orthodontic community is a tightly knit group. Having attended meetings around the world and maintained friendships and correspondence with orthodontists on every conti- nent but Antarctica, I have always been impressed with the familiarity we all feel when we gather together, from Los Angeles to Berlin to Johannes-burg to Tokyo. Although it may be a cliché, there’s no doubt in my mind that we, the orthodontists of the world, constitute one big family. And as in any family, we each feel the pain of the others in times of catastrophe and hardship. At the time of this writing, the AAO is putting together a plan to work with the Japan Orthodontic Society and Japan Dental Association to aid those who have been affected by this horrendous earthquake and tsunami. We can also contribute individually to the Red Cross or similar disaster-relief agencies. To all of our Japanese friends and colleagues: We know that you will overcome this crisis with the dignity and honor so characteristic of your great land and culture. We will not hesitate to help in whatever ways we can. RGK

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EDITOR’S CORNER

JCO/MARCH 2011

http://www.jco-online.com

Skeletal open bite is one of the most challenging malocclu-

sions to treat and maintain.1-4

Although a combination of ortho-dontic treatment and ortho gnathic surgery may be the ideal approach in most cases,5-7 the complica-tions, risks, and costs of surgery have stimulated considerable interest in alternative treatment methods beyond the use of tra-ditional mechanics with ortho-

gnathic-like effects.Adult patients can be treat-

ed without the need for special compliance using the Skeletal Anchorage System (SAS), in which titanium anchor plates and monocortical screws are tempo-rarily placed in the maxilla, the mandible, or both.8,9 The SAS has been used in combination with multibracketed appliances to move molars individually or to

move the entire dentition in three dimensions.8,10 Its mechanics for molar intrusion and distalization have been shown to be highly predictable.11,12

This article describes a goal-oriented strategy for non-surgical correction of skeletal Class II open bite in an adult pa tient using the SAS, with the results evaluated by cone-beam com-puted tomography (CBCT).

VOLUME XLV NUMBER 3 145

CASE REPORTNon-Surgical Correction of Skeletal Open Bite: A Goal-Oriented Approach Evaluated by CBCT

JUNJI SUGAWARA, DDS, PHDZAHER AYMACH, DDS, DOrth, PHDHIROSHI NAGASAKA, DDS, PHDHIROSHI KAWAMURA, DDS, PHDRAVINDRA NANDA, BDS, MDS, PHD

© 2011 JCO, Inc.

Dr. Kawamura Dr. NandaDr. NagasakaDr. AymachDr. Sugawara

Dr. Sugawara is a Clinical Professor, Dr. Aymach is a lecturer, Dr. Nagasaka is a Lecturer, and Dr. Kawamura is Professor and Head, Division of Maxillofacial Surgery, Graduate School of Dentistry, Tohoku University, 4-1, Seiryo-machi, Aoba-ku 980-8575, Sendai, Japan. Dr. Sugawara is a Visiting Clinical Professor and Dr. Nanda is Professor and Head, Department of Craniofacial Sciences, School of Dental Medicine, University of Connecticut, Farmington, CT. Dr. Sugawara is also Chief, SAS Orthodontic Centre, Ichiban-cho Dental Office, Sendai, Japan. Dr. Nanda is an Associate Editor of the Journal of Clinical Orthodontics. E-mail Dr. Sugawara at [email protected].


146 JCO/MARCH 2011

Fig. 1 A. 39-year-old female patient with retrusive mandible, skeletal Class II relationship, severe overjet, and open bite before treatment. B. Craniofacial morphology of patient (black) compared with norms for adult Japanese females (red); note short ramus and small condyle (blue circle).

A

Non-Surgical Correction of Skeletal Open Bite Evaluated by CBCT

B

Diagnosis and Treatment Plan

A 39-year-old female pre-sented at SAS Orthodontic Centre, complaining of an anterior open bite and difficulty in biting with her front teeth (Fig. 1). She had a Class II profile, a mild long-face tendency, an ex tremely wide interlabial gap, and a strained chin musculature on lip closure. Intraorally, she showed a severe anterior open bite with double occlusal planes, Class II denture bases, attritional occlusion of the molars, upper and lower incisor

crowding, a narrow upper arch, and a large overjet.

Radiographs indicated that the third molars had been previ-ously extracted. The condylar processes were unusually short, and the condyles were deformed bilaterally. Cephalometric analy-sis revealed a high-angle skeletal Class II pattern due to a retrusive mandible, a short ramus, and excessive maxillary molar height. A CBCT scan was ordered to clarify the condition of the con-dyles and the dentition; it showed that the right condyle was sig-nificantly smaller than the left

(Fig. 2), suggesting a degenera-tive TMJ, although the patient had no symptoms of TMD.

Because of the condylar condition, we considered options for nonsurgical orthodontic treat-ment. We believed the SAS would produce predictable intrusion and distalization of the maxillary and mandibular molars, which in turn would close the bite, enabling us to resolve the patient’s complex dental issues and adequately cam-ouflage her skeletal problems.

Based on cephalometric, photographic, and setup model predictions (Figs. 3,4), we devel-


Fig. 3 A. Superimposition of pretreatment cephalometric tracing (blue) and predicted treatment results (red). B. Treatment goals shown in occlusal view.

A B

Fig. 2 Panoramic radiograph and cone-beam com-puted tomography (CBCT) images reveal signifi-cantly shortened and deformed condyles (yellow circles), with right condyle smaller than left.

Right Left

oped the goals of intruding the upper molars 3mm and distaliz-ing the upper and lower molars 5mm and 2mm, respectively, while maintaining the lower molars at the same level. This movement would be followed by an auto-matic counterclockwise rotation of the mandible, with simultane-ous correction of the patient’s lower facial height, interlabial gap, and anterior open bite. The CBCT images revealed sufficient space for distalization of the maxillary molars and uprighting of the man-dibular molars, eliminating the need for premolar extractions.

Treatment Progress

Orthodontic miniplates (Orthoanchor*) were implanted in both jaws (Fig. 5): Y-type mini-plates at the zygomatic buttresses, with the first hooks set at the cervical level of the molars, and L-type miniplates in the left and right mandibular bodies, between the first and second molars. Orthodontic treatment started 11 days later, immediately after the sutures had been removed.

Because of the anterior crowding, brackets were initially bonded only to the upper and lower premolars and molars. A continuous .014" nickel titanium archwire was placed in the max-illa, and a segmental nickel tita-nium wire in the mandible (Fig. 6A). Simultaneously, molar intru-sion and distalization were initi-ated with a force of 100g per side. Two months later, an .016" × .016" stainless steel wire was placed in the maxilla, and both intrusion and distalization of the upper buccal segments were gen-erated from elastic chains exert-ing a force of 400g per side. In the mandible, a segmental .019" ×

.026" Copper Ni-Ti** (40°C) wire was engaged, and chain elastics applying a force of 200g per side were attached to the SAS to upright the molars (Fig. 6B). After three months, the elastic chains were replaced by elastic threads (Fig. 6C).

Five months after the initia-tion of treatment, lingual crown torque was added to the rectangu-lar archwires (Fig. 6D). A month later, with the upper molars sig-nificantly intruded and only the premolars in occlusion, an auxil-iary CNA*** intrusion arch was ligated to the main archwire at the central incisors to intrude the upper premolars. In the lower arch, brackets were bonded to the anterior teeth (Fig. 6E). Intrusion and distalization were continued for three more months to correct the Class II canine and molar relationships while controlling

148 JCO/MARCH 2011


Fig. 4 Setup models indicate successful treatment without premolar extractions.

Fig. 5 Implantation of Skeletal Anchorage System (SAS) mini-plates in zygomatic buttresses (Y-type) and mandibular body (L-type).

*Dentsply-Sankin K.K., Azabu Kaisei Building, 1-8-10, Azabudai, Minato-ku, Tokyo 106-0041, Japan; www.dentsply.com.

**Trademark of Ormco Corporation, 1717 W. Collins, Orange, CA 92867; www.ormco.com.

***Trademark of Ortho Organizers, 1822 Aston Ave., Carlsbad, CA 92008; www. orthoorganizers.com.

Y-type

L-type

buccal flaring of the posterior teeth (Figs. 6F,G).

After 10 months of treat-ment, brackets were bonded to the upper incisors and canines, and leveling and alignment were initi-ated with a segmental wire. In the lower arch, space closure was begun with elastic chains (Fig. 6H). Two months later, a continu-ous archwire was placed in the upper arch for final leveling and alignment while the lower arch was stabilized (Fig. 6I). Another two months later, distalization of

the entire dentition was started (Fig. 6J). With four skeletal an chor age units in the molar regions, correction of the dental midline was not difficult.

As treatment approached the finishing stages, we stripped the upper and lower anterior teeth to reduce “black triangles”. After 17 months of treatment, the den-tal midlines coincided with the facial midline, and an esthetic and functional occlusion had been established with good posterior occlusion, proper anterior guid-

ance, and no CO-CR discrepancy (Fig. 6K).

After a total treatment time of 18 months, all brackets were debonded, and the SAS mini-plates were removed under local anesthesia. A wraparound retain-er with tongue spurs was placed in the maxillary arch, and a lin-gual retainer was bonded in the lower anterior segment.

Treatment Results

Post-treatment facial photo-


Sugawara, Aymach, Nagasaka, Kawamura, and Nanda

Fig. 6 Treatment progress. A. Place- ment of SAS. B. At two months after placement. C. At three months. D. At five months. E. At six months. F. At eight months. G. At nine months. H. At 10 months. I. At 12 months. J. At 14 months. K. At 17 months.

A

D

G

J

B

E

H

K

C

F

I

150 JCO/MARCH 2011


Fig. 7 After 18 months of treat-ment, showing improved facial pro-file and occlusion.

graphs showed a remarkable change in the patient’s profile (Fig. 7), especially considering that she had undergone neither surgery nor tooth extractions. The Class II profile, retrusive chin, and interlabial gap were signifi-cantly improved, and the strain in the circumoral musculature dur-ing lip closure had disappeared. Class I canine and molar relation-ships had been achieved, with normal overbite and overjet. The patient displayed a firm posterior occlusion and adequate anterior guidance on jaw excursions.

Cephalometric analysis con-firmed that the entire upper denti-tion was slightly distalized and the lower posterior teeth were uprighted during the first six months of SAS treatment; the mandible showed a slight closing rotation after intrusion of the upper molars (Fig. 8A). After 12 months of SAS treatment, the maxillary posterior teeth had been significantly intruded, and

the occlusal plane had shifted upward. As a result, the mandible showed significant counter-clockwise rotation, while the maxillary dentition was distal-ized (Fig. 8B). A dramatic cor-rection of the open bite and mal occlusion resulted from the radical intrusion and distalization of the posterior teeth. The vertical facial proportion and interlabial gap also improved because of the counterclockwise rotation of the mandible (Fig. 8C).

Post-treatment CBCT imag-es clearly showed both superior and distal movement of the upper molars (Fig. 9). The upper first and second molars had penetrated into the sinus after intrusion, and the mucous membranes had thick-ened significantly. We noted slight root resorption of the first and second molars, but did not consider it clinically significant. The buccodistal roots of the max-illary left and right second molars were distalized 5mm and 4.5mm,

respectively (Fig. 10). No TMJ symptoms were observed after treatment; condylar imaging revealed no further pathological degeneration.

Discussion

When an adult presents with a skeletal Class II open bite, a severe overjet, and crowded den-tal arches, innovative orthodontic mechanics are required to avoid orthognathic surgery or premolar extractions.13-15 Traditional molar-intrusion methods do not produce predictable tooth movements. Miniscrew anchorage has been successfully used to intrude molars in patients with skeletal open bites, but this technique often requires multiple buccal and palatal screw insertions and com-plex mechanics to move a single tooth,16-19 especially when molar distalization is attempted. Con-ventional intraoral distalizing appliances tend to extrude the



Fig. 8 Superimpositions of cephalometric tracings at baseline (blue) and during treatment (red). A. At six months. B. At 12 months. C. After debonding. Mandible rotated counterclockwise after intrusion and distal-ization of maxillary molars, improving vertical facial proportions and interlabial gap.

A B C

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Fig. 9 Pre- and post-treatment CBCT images show maxillary molar intrusion and distalization after treatment with SAS.

Pretreatment Post-Treatment

molars and thus exacerbate the original problem.

The SAS provides simulta-neous three-dimensional control of the maxillary and mandibular molars for both distalization and intrusion.8-10,20,21 Although distal-ization mechanics are used pri-marily in Class II cases, other indications for distal movement with the SAS include maxillary crowding, flared incisors, or both.

Our research group has pre-viously evaluated the effects of maxillary molar intrusion using

SAS on the nasal floor and dental roots in dogs.22 After four months, the root apices of the intruded molars penetrated into the nasal cavity, the nasal floor membrane and a thin layer of newly formed bone (which lifted intranasally) covered the intruded molar roots, and root resorption reached part-ly into the dentin without the for-mation of reparative cementum. In the patient presented here, the mucosal membrane of the sinus thickened significantly over the molars during treatment, although

new bone formation was not yet observed at debonding. Another six months might be required for complete bone formation.

Molar intrusion progressed linearly in this patient, with 1mm of intrusion observed every six months (Fig. 11). In addition, the buccodistal roots of the maxillary left and right second molars were distalized 5mm and 4.5mm, re -spectively, over the 18 months of treatment (Fig. 12). Distal movement of 1.5mm in six months is considered significant.12



Fig. 10 Pre- and post-treatment coronal-section CBCT images, showing distalization of maxillary second molar roots.

Pretreatment Post-Treatment

12.49mm

12.06mm

7.45mm

7.51mm

Although goal-oriented strategies are essential in contem-porary orthodontics,23 there are no published treatment goals for the correction of skeletal open bite through intrusion and distal-ization of the maxillary molars. The individualized goals for mo -lar and incisor positioning and soft-tissue profile development in the present case were established with cephalometric and occluso-gram predictions before treat-ment. SAS treatment was initiated only after confirmation of the 3D treatment goals with setup models and CBCT. The predicted distal-ization of the maxillary first molars, about 5mm, was close to the actual results, and maxillary molar intrusion was similarly reli-able. It is not a matter of simply

trying to distalize or intrude the molars as much as possible; the degree to which specific treat-ment goals are achieved should also be evaluated.12

Conclusion

The Skeletal Anchorage System appears to be a viable and predictable alternative to tradi-tional orthodontic mechanics and surgical correction for treatment of skeletal open bites requiring molar intrusion and distalization. These rigid anchorage units allow the clinician to perform not only single-tooth movements, but 3D en-masse movement of the buccal segments, thus reducing the need for premolar extractions.

REFERENCES

1. Kim, Y.H. and Han, U.K.: Stability of anterior openbite correction with multi-loop edgewise therapy: A cephalometric follow-up study, Am. J. Orthod. 118:43-54, 2000.

2. Tanaka, E.; Iwabe, T.; Kawai, N.; Nishi, M.; Dallabona, D.; Hasegawa, T.; and Tanne, K.: An adult case of skeletal open bite with a large lower anterior facial height, Angle Orthod. 75:465-471, 2005.

3. Aras, A.: Vertical changes following orthodontic extraction treatment in skel-etal open bite subjects, Eur. J. Orthod. 24:407-416, 2002.

4. Saito, I.; Yamaki, M.; and Hanada, K.: Nonsurgical treatment of adult open bite using edgewise appliance combined with high-pull headgear and class III elastics, Angle Orthod. 75:277-283, 2005.

5. Erverdi, N.; Keles, A.; and Nanda, R.: The use of skeletal anchorage in open bite treatment: A cephalometric evalua-tion, Angle Orthod. 74:381-390, 2004.

6. Proffit, W.R.; Phillips, C.; and Dann, C.: Who seeks surgical orthodontic treatment? Int. J. Adult Orthod. Orthog. Surg. 5:153-160, 1990.

7. Capelozza Filho, L.; Cardoso, M.A.; Reis, S.A.B.; and Mazzottini, R.: Surgical-orthodontic correction of long-face syndrome, J. Clin. Orthod. 40:323-332, 2006.

8. White, L.W. and Sugawara, J.: JCO Interviews Dr. Junji Sugawara on the Skeletal Anchorage System, J. Clin. Orthod. 33:689-696, 1999

9. Sugawara, J. and Nishimura, M.: Mini-bone plates: The Skeletal Anchorage System, Semin. Orthod. 11:47-56, 2005.

10. Sugawara, J.: A bioefficient skeletal anchorage system, in Biomechanics and Esthetic Strategies in Clinical Ortho dontics, ed. R. Nanda, Elsevier Saunders, St. Louis, 2005, pp. 295-309.

11. Sugawara, J.; Daimaruya, T.; Umemori, M.; Nagasaka, H.; Takahashi, I.; Kawamura, H.; and Mitani, H.: Distal movement of mandibular molars in adult patients with the Skeletal Anchor-age System, Am. J. Orthod. 125:130-138, 2004.

12. Sugawara, J.; Kanzaki, R.; Takahashi, I.; Nagasaka, H.; and Nanda, R.: Distal movement of the maxillary molars in nongrowing patients with the Skeletal Anchorage System, Am. J. Orthod. 129:723-733, 2006.

13. Hoppenreijs, T.J.; Stoelinga, P.J.; Grace,

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Fig. 11 Intrusion of upper premolars and molars during treatment, showing about 1mm of intrusion every six months.

Maxillary Intrusion

0-6 months 0-12 months 0-19 months

■ first premolar ■ second premolar ■ first molar ■ second molar

3.00mm

2.25mm

1.50mm

0.75mm

0mm

−0.75mm

−1.50mm

K.L.; and Robben, C.M.: Long-term evaluation of patients with progressive condylar resorption following ortho-gnathic surgery, Int. J. Oral Maxillofac. Surg. 28:411-418, 1999.

14. Hoppenreijs, T.J.; Freihofer, H.P.; Stoelinga, P.J.; Tuinzing, D.B.; and van’t Hof, M.A.: Condylar remodelling and resorption after Le Fort I and bi -maxillary osteotomies in patients with anterior open bite: A clinical and radio-logical study, Int. J. Oral Maxillofac. Surg. 27:81-91, 1998.

15. Hwang, S.J.; Haers, P.E.; Zimmermann, A.; Oechslin, C.; Seifert, B.; and Sailer, H.F.: Surgical risk factors for condylar resorption after orthognathic surgery, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod. 89:542-552, 2000.

16. Paik, C.H.; Woo, Y.J.; and Boyd, R.L.: Treatment of an adult patient with verti-cal maxillary excess using miniscrew fixation, J. Clin. Orthod. 37:423-428, 2003.

17. Park, H.S.; Kwon, T.G.; and Kwon, O.W.: Treatment of open bite with microscrew implant anchorage, Am. J. Orthod. 126:627-636, 2004.

18. Kuroda, S.; Katayama, A.; and Takano-Yamamoto, T.: Severe anterior open-bite case treated using titanium screw anchorage, Angle Orthod. 74:558-567, 2004.

19. Lin, J.C.; Liou, E.J.; and Yeh, C.L.: Intrusion of overerupted maxillary molars with miniscrew anchorage, J. Clin. Orthod. 40:378-383, 2006.

20. Umemori, M.; Sugawara, J.; Mitani, H.; Nagasaka, H.; and Kawamura, H.: Skeletal anchorage system for open-bite correction, Am. J. Orthod. 115:166-174, 1999.

21. Sugawara, J.; Baik, U.B.; Umemori, M.; Takahashi, I.; Nagasaka, H.; Kawamura, H.; and Mitani, H.: Treatment and post-treatment dentoalveolar changes follow-ing intrusion of mandibular molars with application of a skeletal anchorage sys-tem (SAS) for open bite correction, Int. J. Adult Orthod. Orthog. Surg. 17:243-253, 2002.

22. Daimaruya, T.; Takahashi, I.; Nagasaka, H.; Umemori, H.; Sugawara, J.; and Mitani, H.: Effects of maxillary molar intrusion on the nasal floor and tooth root using the skeletal anchorage system in dogs, Angle Orthod. 73:158-166, 2003.

23. Burstone, C.J. and Marcotte, M.R.: Problem Solving in Orthodontics: Goal- Oriented Treatment Strategies, Quintes-sence Publishing Co., Chicago, 2000.



Fig. 12 Distal movement of crowns (top) and roots (bottom) of upper premolars and molars during treatment, showing crowns distalized 1.5mm and roots distalized 2.5mm on average every six months.

Distal Crown Movement





4.00mm

3.00mm

2.00mm

1.00mm

0mm

6.00mm

4.50mm

3.00mm

1.50mm

0mm

−1.50mm

Distal Root Movement

A maxillary midline diastema is a common esthetic problem, with a reported incidence

of 5-20% in adults.1,2 A significant midline diastema is frequently associated with an alveolar bone defect, an interproximal soft-tissue defect, or both.3,4 To prevent further gingival recession, root exposure, and potential tooth loss, bone substitutes are often grafted,5,6 and orthodontic treatment is

usually required to close the space.In such a case, the orthodontist must be con-

cerned about whether the bone substitute or the new bone formed in the grafted area will be lost after the diastema is closed. The approach pre-sented here can be used to correct a midline diastema with an infrabony defect using short-term force application.

© 2011 JCO, Inc.

Orthodontic Closure of a Midline Diastema with an Infrabony DefectJUN CAO, DDS, PHDLING WAN, DDS, PHDZICHUAN ZHANG, DDS, MDSSHUFANG MA, DDS, MDS

Fig. 1 22-year-old female patient with 5mm maxillary midline diastema before treatment.

156 JCO/MARCH 2011


Case Report

A 22-year-old female visited our orthodontic clinic for closure of her maxillary midline diastema (Fig. 1). The space was nearly 5mm wide, and the interproximal soft tissue was detached from the mesial aspect of the right central incisor.

According to the patient, the midline diastema had first appeared six years earlier and had worsened over time. One year before present-ing at our clinic, she had visited a periodontist; records taken in that office showed that the upper right central incisor was tipped labially, with a probing depth of 5-7mm on the mesial side. Radiographs had revealed interproximal bone loss with a vertical defect in the mesial aspect of the right central incisor (Fig. 2A). The periodontist had implanted Bio-Oss Collagen* in the infrabony pocket (Figs. 2B,C). By the time the patient pre-sented for treatment to close the midline diastema, new bone had formed in the pocket, and the mesial probing depth had been reduced to about

3mm (Fig. 2D).Establishment of interproximal support

through closure of the diastema was indicated to prevent alveolar bone loss, but we could not predict whether the new bone would be absorbed during orthodontic tooth movement. Our treatment plan was designed to minimize the period of force delivery to the upper right central incisor.

Initially, brackets and bands were placed on all teeth in both arches except for the upper right central incisor. After about seven months of level-ing, we bonded the upper right central incisor and began retraction of the upper incisors to close the diastema. Use of the Bioprogressive technique7 limited active treatment time for the right central incisor to only five months; total treatment time was 11 months (Fig. 3). After three months of fixed retention, we delivered a removable retainer.

The patient’s diastema was successfully

Fig. 2 Periapical radiographs taken before and after periodontal bone-substitute implantation. A. Before implantation. B. One month after implantation, showing bone-substitute material (arrow). C. Three months after implantation, showing implanted material being absorbed. D. One year after implantation, showing new bone formation (arrow).


*Registered trademark of Geistlich Pharma, Bahnhofstrasse 40, CH-6110 Wolhusen, Switzerland; www.geistlich.com.

Dr. MaDr. ZhangDr. WanDr. Cao

Dr. Cao is a Professor and Drs. Zhang and Ma are postgraduate students, Department of Ortho-dontics, and Dr. Wan is an Asso-ciate Professor, Department of Periodontics, School of Sto ma -tology, Fourth Military Medical University, Xi’an 710032, China. E-mail Dr. Cao at [email protected].

A B C D

158 JCO/MARCH 2011

Orthodontic Closure of a Midline Diastema with an Infrabony Defect

closed, and the interproximal soft tissue was restored, with a mesial probing depth of about 2mm at the upper right central incisor. Periapical radiographs taken during and after treatment and one year post-treatment showed no significant loss of the new bone (Fig. 4).

Discussion

A multidisciplinary approach is required in a patient with a substantial midline diastema and infrabony defect.4,5,8 Repair of the infrabony defect with a grafting material such as Bio-Oss Collagen is often the first step,5,9 followed by orthodontic

space closure. Bio-Oss Collagen contains the same grafting material as Bio-Oss—deproteinized, sterilized bovine bone—but includes 10% purified porcine collagen to make the material more pliable and easier to mold.

The forces used to close the midline diastema will exert pressure on the new bone. Few clinical studies have assessed whether the bone substitute or the new bone formed in the infrabony pocket is absorbed during tooth movement. In this patient, the new bone was still intact after active treatment, suggesting that grafting materials and regenerated new bone can indeed withstand orthodontic cor-rection of a midline diastema.

Fig. 3 Patient after 11 months of orthodontic treatment.


Cao, Wan, Zhang, and Ma

1. Richardson, E.R.; Malhotra, S.K.; Henry, M.; Little, R.G.; and Coleman, H.T.: Biracial study of the maxillary midline diastema, Angle Orthod. 43:438-443, 1973.

2. McVay, T.J. and Latta, G.J. Jr.: Incidence of the maxillary midline diastema in adults, J. Prosth. Dent. 52:809-811, 1984.

3. Tarnow, D.P.; Magner, A.W.; and Fletcher, P.: The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla, J. Periodontol. 63:995-996, 1992.

4. Cardaropoli, D.; Re, S.; Corrente, G.; and Abundo, R.: Reconstruction of the maxillary midline papilla following a combined orthodontic-periodontic treatment in adult perio-dontal patients, J. Clin. Periodontol. 31:79-84, 2004.

5. Cardaropoli, D.; Re, S.; Manuzzi, W.; Gaveglio, L.; and

Cardaropoli, G.: Bio-Oss Collagen and orthodontic movement for the treatment of infrabony defects in the esthetic zone, Int. J. Period. Restor. Dent. 26:553-559, 2006.

6. Cardaropoli, D. and Re, S.: Interdental papilla augmentation procedure following orthodontic treatment in a periodontal patient, J. Periodontol. 76:655-661, 2005.

7. Ricketts, R.M.: Bioprogressive therapy as an answer to ortho-dontic needs, Part II, Am. J. Orthod. 70:359-397, 1976.

8. Cortellini, P.; Prato, G.P.; and Tonetti, M.S.: The simplified papilla preservation flap: A novel surgical approach for the management of soft tissues in regenerative procedures, Int. J. Period. Restor. Dent. 19:589-599, 1999.

9. Benke, D.; Olah, A.; and Möhler, H.: Protein-chemical analy-sis of Bio-Oss bone substitute and evidence on its carbonate content, Biomater. 22:1005-1012, 2001.

Fig. 4 A. After seven months of leveling in maxillary arch, excluding right central incisor. B. Just before re -moval of fixed appliances. C. One year after debonding, showing no significant loss of new bone material.

REFERENCES

A B C

© 2011 JCO, Inc.

After rapid palatal expansion, a removable plate, a Hawley or Essix retainer, or a transpalatal

arch is usually placed in the maxilla to retain the correction for 100 days or longer. Each of these appliances requires an impression and a follow-up appointment for placement.

Other authors have previously described techniques for converting a banded expander to a transpalatal arch without the need for impres-sions or a delivery appointment.1,2 I suggest mak-ing conversion even faster by using the following technique:1. Before placing the Hyrax-type expander, sol-der lengths of .040" stainless steel wire to the palatal surfaces of each posterior expansion leg.2. Bend the inner ends of the wires to follow the palatal surfaces on each side of the expansion screw (A) as close to the screw surface as possi-ble, thus avoiding contact with the palate (B).3. After expansion (C), deband the appliance; carefully straighten the wire extensions, then sol-der them together to form a transpalatal arch (D).

4. Cut away the expansion screw (E) and re cement the transpalatal arch in the mouth (F).

This modified conversion technique requires only a single solder joint, minimizing both lab time and chairtime. I would like to see expansion ap pliances manufactured with built-in extension legs to make the procedure even more convenient.

REFERENCES

1. Levy-Bercowski, D.; DeLeon, E.; and Stockstill, J.W.: One-step conversion of a banded expander to a transpalatal bar, J. Clin. Orthod. 41:285, 2007.

2. Pellegrini, P.: Conversion of a rapid palatal expander to a transpalatal arch, J. Clin. Orthod. 43:428, 2009.

Quick Conversion of an Expander to a Transpalatal Arch

E

F

A

B

ASHOK KOTHARI, MDS1106 Larkin Ave.Joliet, IL [email protected]

160 JCO/MARCH 2011

C

D



In recent Cutting Edge columns, I’ve dis-cussed the current technology race to replace polyvinyl siloxane impressions with a digital pro-cess—either cone-beam computed tomography (CBCT) or intraoral scanning. As CBCT images have become more refined and digitally produced models have tested successfully for dimensional reliability, CBCT has seemed to be the horse to back in this race.

Intraoral scanning of individual teeth has been possible for some time, but has required the use of scanning powder because of the trans lucency of enamel and dentin—a rather messy and uncom-fortable process for patients. Now, however, scan-ners can produce full digital arches by “stitching” the images together, with no powder required.

In this month’s Cutting Edge column, Drs. Francesco Garino and Battista Garino demonstrate the practical application of the OrthoCAD intraoral scanner in a busy orthodontic practice. In the race between CBCT and scanning technologies, it appears to me that the intraoral scanner has taken the lead and is sprinting toward the finish line.

W. RONALD REDMOND, DDS, MS

The OrthoCAD iOC Intraoral Scanner: A Six-Month User Report

Although our office had been using computer- ized three-dimensional models processed

from conventional impressions since 2002, along with digital radiographs, charts, and images, our ultimate goal had always been to acquire 3D mod-els directly, thereby eliminating the need for impressions. When we installed the OrthoCAD iOC* intraoral scanner in the summer of 2010, our 20-year project of fully digitizing our operations was finally complete.

Until recently, we were required to ship poly-vinyl siloxane impressions and bite registrations to the OrthoCAD center in the United States to ob -tain digital models, virtual setups, and indirect bonding trays. Once received at the OrthoCAD center, the impressions were poured, trimmed, scanned, and processed to generate the 3D digital model—the starting point for all OrthoCAD ser-

© 2011 JCO, Inc.

THE CUTTING EDGE(Editor’s Note: This quarterly column is compiled by JCO Technology Editor Ronald Redmond. To help keep our readers on The Cutting Edge, Dr. Redmond will spotlight a particular area of orthodontic technology every three months. Your suggestions for future subjects or authors are welcome.)

Drs. Francesco Garino and Battista Garino are in the private practice of orthodontics at Corso Matteotti 0, Torino 10121 Italy; e-mail: [email protected]. Dr. Francesco Garino is a frequent speaker on the topic of paperless practice.

Dr. B. GarinoDr. F. GarinoDr. Redmond

*Trademark of Cadent, Inc., 640 Gotham Parkway, Carlstadt, NJ 07072; www.cadent.biz.


vices (Fig. 1). The digital file was then automati-cally downloaded to our office network. This process remains available for customers who pre-fer to use conventional impressions.

In our new system, however, the iOC in tra-oral scanner generates a 3D model of the dentition in real time and then uploads the information to the OrthoCAD network. The flow of information is reversed from that of the impression-based process.

This article describes our experience with the iOC over its first six months of use and the re -sulting changes in our daily routine.

In-Office Procedure

The new iOC scanner is based on powder-free iTero* intraoral scanning technology, which has been utilized for more than 250,000 dental restorations since 2007. The iOC employs a pat-ented, optical-focus-detection-based technique to capture the 3D geometry of the dentition and gin-givae. The scanning wand emits multiple light waves of discrete wavelengths and captures returned light from the hard and soft tissues in a complementary metal oxide semiconductor (CMOS) imager. A mobile cart houses the com-putational platforms, electronic drivers, and power supplies; an air pump to defog the wand lenses; a flat-screen monitor; a wireless communication module; and a foot pedal.

The iOC can be stationed in the records room or moved around the clinic. Once the patient has been seated, case details are entered and the operator is prompted to select the type of scanning process. Current applications include digital study models, virtual setups, computer-optimized indirect bonding, printed physical models, and appliance fabrication. Further uses are being developed.

Because this is a relatively new technology, we have found it helpful to give each patient a brief instructional session. Shortly before the scan begins, the protective shield on the wand is replaced

162 JCO/MARCH 2011

Fig. 1 Plotted OrthoCAD digital model.

Fig. 2 OrthoCAD iOC scanner in use on patient.

THE CUTTING EDGE

*Trademark of Cadent, Inc., 640 Gotham Parkway, Carlstadt, NJ 07072; www.cadent.biz.

with a disposable sleeve, ensuring sterility. The wireless pedal is placed on the floor, ready to be used for scanning control and navigation. The patient is advised to swallow saliva between scans and, in some instances, to bite down gently on the wand for better positioning.

The iOC uses consecutive, individual scans to display a real-time, aggregated model rendering (Fig. 2). The process typically starts in the left mandibular quadrant, with the operator moving the wand from posterior to anterior. After scanning the lower arch, the operator proceeds to the upper arch, the bite, and the palate. The scan can be stopped and restarted at any point, going forward or back-ward to recapture areas of missing data. (A video-taped example is available via a link from the online version of this article at www.jco-online.com.)

The system takes less than a minute to pro-cess and compile the individual segments into a complete 3D digital model. At this point, the raw model data are viewable only on the iOC unit. To obtain a compressed digital file that can be accessed from the practice’s network or through a secure Internet connection (and for backup pur-poses), the office must submit the information electronically to OrthoCAD. The orthodontist can also submit an online treatment plan (Fig. 3) and receive a virtual setup (Fig. 4) a few days later. Using the OrthoCAD software, the orthodontist can then view, diagnose, and present the case at the office or elsewhere.

Our initial training consisted of a compre-hensive clinical course conducted in the office immediately after installation of the scanner. On the first day, clinicians and staff were trained to scan a model; over the next two days, they scanned fellow staff members and then real patients. Seeing our scanning times improve over just two days helped us gain confidence in the system and over-come apprehensions. Four weeks after the initial training, a one-day follow-up session was provided, with the goals of fine-tuning the process and increasing proficiency.

Over the first six months of iOC use in our office, we scanned 120 patients. The average time required for a full scan (upper and lower arches, palate, and bite registration) was 16.7 minutes for


Fig. 3 Section of online treatment plan prepared by orthodontist after submission of scanning data.

Garino and Garino

Fig. 4 Pre- and post-treatment virtual setups sup-plied by OrthoCAD.

http://www.youtube.com/watch?v=sQi5MeKhlXQ

http://www.youtube.com/watch?v=sQi5MeKhlXQ

164 JCO/MARCH 2011

the first 40 cases, but only 9.5 minutes for the last 20 patients. All 120 patients preferred intra oral scanning over conventional impressions; 95% said the scan was a positive experience, and 95% said they would recommend the “iOC experience” to their friends. We expect to improve our scanning times even more as we handle more patients.

Discussion

The iOC intraoral scanner has benefited our practice in several important ways:1. The tasks associated with conventional impres-sions—tray selection, material mixing, storing of impression materials, cleaning, plaster pouring, and model storage—are all becoming history,1 along with impression failures and model retakes. This is one aspect of orthodontics we were espe-cially eager to get away from.2. Patient reaction has been decidedly positive. The system can be used in young, mixed-dentition patients and in those with excessive gag reflexes or special needs. Patients appear to be fascinated by this new technology, in contrast to the negative experience of conventional impressions. No pow-dering or coating of the teeth is required with the iOC scanner, making the procedure even more comfortable.23. We can diagnose abnormalities and present the 3D virtual models to the patient, in addition to photographic and radiographic records, at the first appointment. This has significantly improved our acceptance rate.34. The iOC is, by definition, an open system. This means that the native scan files are not only avail-able in OrthoCAD’s 3DM format, but also as universal stereolithographic (STL) files, which can be used to print STL models (Fig. 5). These mod-els, in turn, can be used to fabricate retainers and other fixed or removable appliances (Fig. 6). The

same files will soon be consolidated with cone-beam computed-tomographic images,4 providing much-needed high-resolution data on the dentition. Our laboratory has already produced retainers from printed polymer models, and the fit has been exceptional.5. The seamless integration between the iOC and OrthoCAD software allows us to easily order virtual setups and computer-optimized indirect-bonding trays based on scan data.5

Considering that all technology can be en -hanced by frequent upgrades in both software and hardware, a tool such as the iOC must be consid-ered a medium-term investment. Spreading the cost over three to five years might be reasonable for a medium-to-large practice, but perhaps too expensive for a small practice or a consultant orthodontist. We would consider it a good investment for any office that handles digital models, virtual setups, and indirect bonding for colleagues, or for any practice with satellite offices.

The iOC system has fulfilled its promise thus far in our office, and our migration from conven-tional impressions to digital intraoral scanning has been easier than anticipated. We look forward to seeing how new applications will further enhance our daily operations.

REFERENCES

1. Redmond, W.R.: Digital models: A new diagnostic tool, J. Clin. Orthod. 35:386-387, 2001.

2. Farah, J.W.; Reed. C.; and Wojtowicz, D.: Clinical case report: 3M ESPE Lava Chairside Oral Scanner C.O.S., Dent. Advisor 10:1-3, 2009.

3. Christensen, G.J.: Will digital impressions eliminate the cur-rent problems with conventional impressions? J. Am. Dent. Assoc. 139:761-763, 2008.

4. Turpin, D.L.: British Orthodontic Society revises guidelines for clinical radiography, Am. J. Orthod. 134:597-598, 2008.

5. Garino, F. and Garino, G.B.: Digital treatment objectives: Procedure and clinical application, Prog. Orthod. 5:248-256, 2004.

Fig. 5 Stereolithographic (STL) models produced from univer-sal STL files.

Fig. 6 Retainer fabricated on STL model.

(Editor’s Note: In this quarterly column, JCO provides an overview of a clinical topic of inter-est to orthodontists. Contributions and suggestions for future subjects are welcome.)

Studies and case reports featuring the use of mini-implants for temporary orthodontic

an chorage indicate a preference for interradicular screw insertion on the vestibular side. This position-ing does have a number of drawbacks, including:• A loss rate as high as 25%.1• Difficulties in determining the availability and quality of local bone.

• Risk of damage to the root or periodontium.• Risk of intraoperative screw fracture.

In the maxilla, such problems may be avoid-ed by placing the mini-implant in the anterior palate, which involves comparatively simple inser-tion with few complications. Considering that a treatment plan or appliance may require vestibular placement in either arch, however, reliable and suitable locations are needed in both jaws.

The selection of an interradicular insertion site is determined by three factors: the biomechan-ics of the chosen appliance, the patient’s anatomy, and the dimensions of the mini-implant. Only a narrow corridor of bone is suitable for interradicu-

© 2011 JCO, Inc.

OVERVIEWAnatomical Guidelines for Miniscrew Insertion: Vestibular Interradicular Sites

BJÖRN LUDWIG, DMD, MSDBETTINA GLASL, DMD, MSDGERO S.M. KINZINGER, DMD, MSD, PHDTHOMAS LIETZ, DDSJÖRG A. LISSON, DDS, PHD


Dr. LietzDr. KinzingerDr. Glasl Dr. LissonDr. Ludwig

Drs. Ludwig and Glasl are Instructors, Dr. Kinzinger is a Professor, and Dr. Lisson is Professor and Head, Department of Orthodontics, University of Homburg, Saar, Germany. Drs. Ludwig and Glasl are also in the private practice of orthodontics at Am Bahnhof 54, 56841 Traben-Trarbach, Germany. Dr. Lietz is in the private practice of orthodontics in Neulingen, Germany. Dr. Ludwig is a Contributing Editor of the Journal of Clinical Orthodontics; e-mail him at [email protected].


166 JCO/MARCH 2011

OVERVIEW

lar insertion of a mini-implant. From cervical to apical, appropriate sites fall between the clinically invisible crestal bone margin and the clinically visible mucogingival border (Fig. 1); we recom-mend placing the screw as apically as possible within the attached gingiva. From mesial to distal, the roots generally diverge apically, thus determin-ing the available space.

Mini-implants are available with diameters between 1.2mm and 2.3mm.2 If a larger screw diameter (>–1.8mm) is selected because of the need for good primary stability and high loading capac-ity, the interradicular space may be insufficient. Conversely, a smaller screw diameter (<–1.5mm) may resolve the space problem, but also reduce primary stability and loading capacity. Smaller-diameter screws are more likely to bend or fracture during insertion and extraction.2-5 A diameter of 1.6mm or 1.7mm can be a reasonable compromise, providing sufficient mechanical properties5 with-out requiring a wide insertion space.

Published opinions on the amount of sur-rounding bone needed to provide sufficient reten-tion for the implant vary between .5mm and 1mm on either side.6-8 To avoid root contact, periodontal width should be included in this calculation, add-ing .25mm per side. For a 1.6mm-diameter mini-implant, therefore, an adequate amount of

mesiodistal bone width would be 2.6-3.1mm; more than 3.1mm would be an optimum width.

Clinical complications are minimized if the head of the mini-implant rests within the attached gingiva,9 as can easily be confirmed visually. The marginal bone ridge and the bone volume below are more difficult to assess. To measure the amount of bony support for mini-implants in various interradicular spaces, we performed a prospective cone-beam computed tomography (CBCT) study. This article summarizes the results, describing ideal screw-insertion sites that can be identified by means of readily distinguishable anatomical structures.

Materials and Methods

We examined the records of 70 adolescent and adult orthodontic/orthognathic patients who were undergoing CBCT scans as part of their treat-ment. The scans were taken in a German radio -logy practice using a Veraviewepocs 3D scanner* with a pixel size of .125mm × .125mm, producing scans with slice thicknesses of .25mm each.

The patient’s head was fixed to ensure opti-

Fig. 1 A. Ideal insertion site for interradicular mini-implant placement (blue circle). Green line = proximal contact point (vis-ible); black line = crestal bone (invisible); red line = mucogingi-val border; yellow arrow = distance between proximal contact point and mucogingival border; blue arrow = distance between proximal contact point and ideal insertion area. B. Ideal inser-tion site shown on x-ray (blue circle). Green bars = minimum bone surrounding mini screw (.5mm on each side); red bar = screw diameter (1.6mm); white bar = resulting minimum inter-radicular space, calculated as (2 × .5mm) + 1.6mm = 2.6mm.

*Registered trademark of J. Morita USA, 9 Mason, Irvine, CA 92618; www.morita.com.

A

B


Ludwig, Glasl, Kinzinger, Lietz, and Lisson

mal three-dimensional orientation and to avoid movement artifacts. The sagittal-transverse plane was adjusted parallel to the occlusal plane of the patient. An additional jig ensured a secure occlus-al position. The maxilla and mandible were imaged completely, with the images extending upward to the lower aspects of the maxillary sinuses, thus including complete root formations in each arch.

All patients were Caucasian; only the sex and age were indicated on our copy of each image. Scans were thoroughly inspected to verify the cor-rect exposure and, especially, correct positioning in relation to the occlusal plane. Patients with obvi-ous head malpositioning were excluded from the investigation. Although minor positional errors were impossible to identify, they were considered to have minimal influence on our findings. Ex -tended prosthetic restorations, large numbers of

missing teeth, and expressed skeletal dysgnathia were also excluding factors, since the anatomical relationships could not be regarded as representa-tive in such cases. These exclusions left 36 maxil-lae and 38 mandibles of 39 patients in the study sample (Table 1).

The open-source DICOM viewer OsiriX** was used to analyze the digitized data sets for every available interradicular space (Fig. 2). The

Fig. 2 Distance between teeth measured in .5mm intervals from proximal contact to apex, following line perpendicular to corticalis and insertion direction of mini-implant.

**Pixmeo SARL, 266 Rue de Bernex, CH-1233 Bernex, Switz-erland; www.osirix-viewer.com.

TABLE 1PATIENT DISTRIBUTION

Age Male Female Total

12-20 8 6 1421-40 7 6 1341-60 4 8 12Total 19 20 39

168 JCO/MARCH 2011

OVERVIEW

proximal contact of the dental crowns was chosen as the starting or reference point for measurement because it could easily be identified without addi-tional clinical tools. From the reference point, 3D vertical slices were examined at .5mm intervals, ending 15mm apically. Following the insertion path of a mini-implant, the shortest distance between the lateral root surfaces of adjacent teeth was marked parallel to the cortical bone and then measured by the software. All measurements were performed by a single examiner and repeated five times, resulting in about 25,000 values.

Results

To allow us to present the results in a clear and structured manner, the corresponding inter-radicular spaces of two quadrants in the same jaw were combined; for example, the interdental spac-es between both right and left upper first and second molars were identified as “upper 6-7”.

PASW Statistics*** software was used to calculate the mean, median, standard deviation, and minimum and maximum distances for each

.5mm interval (Fig. 3A). We then constructed a virtual set of teeth representing the mean inter-radicular distances of all 39 patients (Fig. 3B).

Unfortunately, a simple mean measurement of a particular space is not an indication of its suit-ability for mini-implant insertion. A further step was needed to determine the likelihood of finding at least adequate bone width at each interradicular site among our study patients (Fig. 4). When an interradicular distance of at least 2.6-3.1mm was present in 61-70% of the patients, the space was categorized as “acceptable”. “Good” indicated adequate space in 71-80% of the patients, “very good” in 81-90%, and “excellent” in 91-100%. Values below 60% were considered “poor”, and values below 50% “unacceptable” for insertion purposes.

MaxillaPreferable spaces: In the maxilla, only the inter-dental space between the central incisors offered the best conditions. Adequate bone width of 2.6-3.1mm was found between the central incisors in 100% of the patients, and optimal width of great-er than 3.1mm in 94.9%. On average, the adequate width was reached at 11.5mm apically, and the optimal width above 13.5mm.

Fig. 3 Interdental bone space between lower first and second premolars. A. Individual interdental measure-ments taken at vertical heights from proximal contact point to root apex: mean, median, standard deviation, minimum, and maximum. B. Graphic representation of mean interdental widths according to suitability for mini-implant insertion: red = unsuitable (mesiodistal width <2.6mm), yellow = adequate (2.6-3.1mm); green = optimal (>3.1mm).

***Registered trademark of IBM, 233 S. Wacker Drive, Chicago, IL 60606; www.spss.com.

Contact point

2.6-3.1 mm

>3.1 mm

B

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)

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00.5

11.5

22.5

33.5

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55.5

66.5

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99.510

10.511

11.512

12.513

13.514

14.515

2.5 2 1.5 1 0.5 0 0 0.5 1 1.5 2 2.5

“Very good”, “good” and “acceptable” spaces: The spaces between the lateral incisor and canine and between the second premolar and first molar offer very good insertion conditions. Both showed a high probability for the required minimal width, with adequate bone width found 10.5mm and 8.5mm apical to the contact points, respectively. Nearly 90% of the subjects showed at least an adequate insertion area between the second premo-lar and first molar, and 85% showed optimal space. Good conditions were noted between the canine and first premolar in only 72% of the patients; the mean vertical location was about 14mm apical to the contact point. Between the first and second premolars, acceptable bone width was found in 68% of patients, 9.5mm above the contact point.Unacceptable spaces: The interdental spaces between the central and lateral incisors and the first and second molars were rarely adequate. Between the central and lateral incisors, only patients age 41-60 had optimal bone width, and then in only 60% of the cases. The space between the first and second molars was appropriate for use only in subjects without third molars or in patients age 21-40. Younger patients or patients with third molars had optimal insertion spaces in only 15.3% of the cases.

MandibleThe mandible appears to have more ideal

insertion sites that may be used without consider-ation of age, sex, or dentition status. Suitable inter-radicular spaces included almost all of those distal to the canines.Preferable spaces: The spaces between the pre-molars, between the second premolar and first molar, and between the first and second molars showed excellent probability for the minimal width of 2.6-3.1mm: 99%, 97%, and 94%, respectively, with areas of adequate bone located 7.5mm, 6mm, and 5.5mm apical to the contact points.“Very good” and “good” spaces: The space be -tween the canine and first premolar was a very good insertion site in terms of adequate bone avail-ability and also a good insertion site for optimal insertion probability—optimal bone width was seen in 74% of the patients—but this area was found nearly 15mm apical to the contact point. Between the lateral incisor and canine, 71% of the subjects showed adequate space and 57.5% showed optimal space; adequate bone width was found a mean 13.5mm apical to the contact point.Unacceptable spaces: Spaces between the lower central incisors and the central and lateral incisors were inadequate.



Fig. 4 Breakdown of patients showing minimal desirable bone width of 2.6-3.1mm and resulting classifica-tion of interdental spaces. Percentage indicates likelihood that adequate bone may be available in specific interdental space.

■ 91-100% Excellent■ 81-90% Very Good■ 71-80% Good■ 61-70% Acceptable■ 51-60% Poor■ <50% Unacceptable

OVERVIEW

Age, Sex, and Third MolarsPatient age, sex, and presence or absence of

third molars were evaluated separately for their relationships to adequate and optimal bone width.Age: Statistically significant differences in bone width of two maxillary interdental spaces were found among the different age groups. Between the central and lateral incisors, the 41-60 age group showed greater incidence of adequate bone width than both patients age 12-20 (p < .05) and age 21-40 (p < .05). For the space between the maxil-lary first and second molars, the percentage of patients age 21-40 showing optimal bone width was significantly higher than both the 12-20 (p < .001) and 41-60 (p < .005) groups. Other inter-radicular areas in the maxilla showed no signifi-cant age-related differences.

In the mandible, patients age 12-20 were significantly more likely to have adequate bone width between the second premolar and first molar compared to the 41-60 group (p < .05), which was more likely to show optimal bone width. Further analysis of the optimal insertion sites revealed significant differences in patients age 12-20 vs. those age 21-40 for the space between the first and second molars, with the middle age group showing optimal root distances more frequently than the younger group (p < .05). None of the other inter-radicular spaces in the mandible exhibited any significant age-related differences.Sex: Only a few gender-specific differences were noted in the study. Two maxillary locations showed statistically significant differences between male and female patients: in the space between the upper lateral incisor and canine, males were more likely to have adequate bone width (p < .05); in the space between the second premolar and first molar, males were more likely to have both adequate (p < .05) and optimal (p < .05) bone width.

In the mandible, females showed a signifi-cantly higher likelihood of optimal bone width in the interdental spaces between the first and second premolars (p < .05) and the first and second molars (p < .05).Third molars: The absence of maxillary third molars always corresponded with a highly sig-nificant bone-width surplus between the first and

second molars in our study (p < .001). All patients without third molars showed increased inter-radicular bone width in the maxillary molar region, indicating a potentially higher success rate for implant insertion. In the mandible, on the other hand, the presence or absence of third molars had no apparent influence on interradicular bone width between the first and second molars or in any of the other interdental spaces.

Bone Width and the Mucogingival BorderAlthough the color-coded graphic representa-

tion of the adequacy of various interdental spaces provides a quick overview for treatment planning (Fig. 4), it does not indicate the vertical location of the suitable bone width or its relationship to the mucogingival border. According to our CBCT measurements, the required bone width is often found apical to the attached gingiva.

This finding led us to measure the distance from the proximal contact points to the mucogin-gival border (Fig. 5) in 58 subjects (25 male, 33 female, mean age 35.7). In this separate (unpub-lished) study, we examined radiological findings and clinical reports of the height of the attached gingiva and compared the results, again using the

170 JCO/MARCH 2011

Fig. 5 Measurement of distance between proximal contact point and mucogingival border with den-tal floss and periodontal probe.



proximal contact as a reference point.Figure 6 illustrates the relationship between

the mucogingival border and the vertical heights of adequate and optimal bone width, with dis-tances measured from the proximal contact points. For example, in the space between the maxillary second premolar and first molar, adequate space of 2.6-3.1mm can be found 8.5mm apical to the contact point. The mini-implant must therefore be placed close to the mucogingival border, which is about 8.1mm apical to the proximal contact point. The equivalent interdental area in the mandible provides adequate bone width at a distance of only 6mm from the contact point, with the mucogingi-val border another 1.5mm away.

It is apparent that only a few interradicular spaces can be considered ideal, with at least ade-quate interdental bone width and attached gingiva:• Between the upper and lower second premolars and first molars.• Between the upper and lower premolars (with caution).• Between the lower first and second molars.

Other spaces can reliably supply sufficient bone width only in areas without attached gingiva.

Discussion

Insufficient bone width can result in contact between a mini-implant and the root. Even though root contact is usually considered harmless due to post-traumatic regenerative capability,10-12 root proximity or contact still results in less-stable anchorage and higher rates of implant failure.13 The results of our study clearly delineate the loca-tions of adequate and optimal insertion space.

Other studies have also found that inter-radicular bone width increases apically and dis-tally in the maxilla, with the exception of the space between the first and second molars,14,15 and that the spaces between the upper central incisors and the upper second premolars and first molars are preferable for mini-implant insertion.16 Studies by Hu and colleagues17 and Lee and colleagues18 did not show inadequate space between the upper first and second molars, but this may be due to the dif-

Fig. 6 Graphic representation of probability of adequate (2.6-3.1mm, yellow) or optimal (>3.1mm, green) mesiodistal bone width for each interdental space. Dashed line = mean level of mucogingival border.

172 JCO/MARCH 2011

OVERVIEW

fering ages of the study subjects. While our data were taken mainly from juvenile and adolescent patients, Lee and colleagues investigated groups age 19 and older,18 and Hu and colleagues’ study patients17 were older than 29—well beyond the pubertal growth spurt.

Our results showed that the most suitable mandibular interdental spaces for mini-implant insertion are between the second premolars and first molars and the first and second molars. Other authors have also reached this conclusion,7,17,18 although it is difficult to compare the findings since different reference points were used in each study. Our reference was the proximal contact point, Poggio and colleagues used the crestal bone margin,7 Lee and colleagues used the enamel-dental border,18 and Hu and colleagues used the dental cervix.17

The noted gender-specific differences in our sample may reasonably be ignored, because the groups were relatively small and the range of interdental distances relatively large. Poggio and colleagues7 found no gender-specific effects in their results, while Lee and colleagues18 and Kim and colleagues16 did not consider sex differences.

The influence of race on interradicular space is as yet unknown. Our population was Caucasian, as was probably true of the study by Poggio and colleagues.7 Data evaluated in the studies by Lee and colleagues18 and Kim and colleagues16 were most likely drawn from Asian populations. In addi-tion, tooth size and shape have yet to be investi-gated in relation to interdental space.

When CBCT records are available, the ideal insertion site may be easily determined by measur-ing the distance to the proximal contact. Ordering

a CBCT scan merely to identify a mini-implant placement site is not justifiable, however. The vertical distance from the proximal contact to an area with sufficient bone width can be measured from a panoramic or periapical x-ray if the mag-nification factor is known.17

Although this area will ideally be located in the attached gingiva, other possibilities should be considered if adequate bone is found only in areas of unattached gingiva. If the mucogingival border is close to the ideal position, the mini-implant may be inserted in the attached gingiva and angulated toward an area of suitable bone width (Fig. 7). If the distance to the ideal bone area is too great, another insertion location should be considered. Alternative strategies can include laser preparation of the unattached gingiva to create a “punched” area for mini-implant insertion (Fig. 8A) and the use of miniplate anchorage (Fig. 8B). The central palatal bone is always a suitable alternative in the maxilla; we will discuss the preferred locations and procedures for palatal insertion in a subse-quent article.

Conclusion

This is the first study to investigate inter-dental bone width in relation to the mucogingival border and the proximal contact point, thus pro-ducing reliable data for identifying suitable mini-implant insertion sites in the maxilla and mandible. Of course, since these data were taken from a cross-sectional study, individual clinical and radio-logical findings must always be respected. The amount of bone width necessary for successful implantation can be calculated in any patient by

Fig. 7 Insertion site between lower canine and first premolar has insufficient available bone; mini-implant is therefore placed at oblique angle, keeping head of screw in attached gingiva (above green line), with threads inserted more apically into adequate bone.


adding the screw diameter plus two times a width of .5mm for bone on either side and an additional two times .25mm to respect the periodontium. This information can reduce the risk of loss or failure in mini-implant anchorage treatment.

In our opinion, only the interdental spaces considered “very good” or “excellent” in this study should be chosen for miniscrew placement, because sufficient bone width is to be expected only in those locations, and is even rarer in combination with attached gingiva (Fig. 6). Of course, any insertion site with less than 100% optimal bone width carries some incremental risk of failure.

ACKNOWLEDGMENT: The authors wish to thank Drs. Marc Schieren and Seong-Hun Kim for their assistance and support with this study.

REFERENCES

1. Chen, Y.J.; Chang, H.H.; Lin, H.Y.; Lai, E.H.; Hung, H.C.; and Yao, C.C.: Stability of miniplates and miniscrews used for orthodontic anchorage: Experience with 492 temporary anchorage devices, Clin. Oral Impl. Res. 19:1188-1196, 2008.

2. Lietz, T.: Mini-screws: Aspects of assessment and selection among different systems, in Mini-Implants in Orthodontics: Innovative Anchorage Concepts, ed. B. Ludwig, S. Baumgaer-tel, and S.J. Bowman, Quintessence Publishing Co., London, 2008, pp. 11-72.

3. Büchter, A.; Wiechmann, D.; Gaertner, C.; Hendrik, M.; Vogeler, M.; Wiesmann, H.P.; Piffko, J.; and Meyer, U.: Load-related bone modelling at the interface of orthodontic micro-implants, Clin. Oral Impl. Res. 17:714-722, 2006.

4. Park, H.S.; Jeong, S.H.; and Kwon, O.W.: Factors affecting the clinical success of screw implants used as orthodontic anchor-age, Am. J. Orthod. 130:18-25, 2006.

5. Sung, J.H.; Kyung, H.M.; Bae, S.M.; Park, H.S.; Kwon, O.W.; and McNamara, J.A. Jr.: Microimplants in Orthodontics, Dentos, Daegu, 2006.

6. Liou, E.J.; Pai, B.C.; and Lin, J.C.: Do miniscrews remain stationary under orthodontic forces? Am. J. Orthod. 126:42-47, 2004.

7. Poggio, P.M.; Incorvati, C.; Velo, S.; and Carano, A.: “Safe zones”: A guide for miniscrew positioning in the maxillary and mandibular arch, Angle Orthod. 76:191-197, 2006.

8. Schnelle, M.A.; Beck, F.M.; Jaynes, R.M.; and Huja, S.S.: A radiographic evaluation of the availability of bone for place-ment of miniscrews, Angle Orthod. 74:832-837, 2004.

9. Wu, T.Y.; Kuang, S.H.; and Wu, C.H.: Factors associated with the stability of mini-implants for orthodontic anchorage: A study of 414 samples in Taiwan, J. Oral Maxillofac. Surg. 67:1595-1599, 2009.

10. Brisceno, C.E.; Rossouw, P.E.; Carrillo, R.; Spears, R.; and Buschang, P.H.: Healing of the roots and surrounding struc-tures after intentional damage with miniscrew implants, Am. J. Orthod. 135:292-301, 2009.

11. Hembree, M.; Buschang, P.H.; Carrillo, R.; Spears, R.; and Rossouw, P.E.: Effects of intentional damage of the roots and surrounding structures with miniscrew implants, Am. J. Orthod. 135:280.e1-9, 2009.

12. Kadioglu, O.; Buyukyilmaz, T.; Zachrisson, B.U.; and Maino, B.G.: Contact damage to root surfaces of premolars touching miniscrews during orthodontic treatment, Am. J. Orthod. 134:353-360, 2008.

13. Kuroda, S.; Yamada, K.; Deguchi, T.; Hashimoto, T.; Kyung, H.M.; and Takano-Yamamoto, T.: Root proximity is a major factor for screw failure in orthodontic anchorage, Am. J. Orthod. 131(4 suppl):s68-73, 2007.

14. Monnerat, C.; Restle, L.; and Mucha, J.N.: Tomographic map-ping of mandibular interradicular spaces for placement of orthodontic mini-implants, Am. J. Orthod. 135:428.e1-9, 2009.

15. Deguchi, T.; Nasu, M.; Murakami, K.; Yabuuchi, T.; Kamioka, H.; and Takano-Yamamoto, T.: Quantitative evaluation of cortical bone thickness with computed tomographic scanning for orthodontic implants, Am. J. Orthod. 129:721.e7-12, 2006.

16. Kim, S.H.; Yoon, H.G.; Choi, Y.S.; Hwang, E.H.; Kook, Y.A.; and Nelson, G.: Evaluation of interdental space of the maxil-lary posterior area for orthodontic mini-implants with cone-beam computed tomography, Am. J. Orthod. 135:635-641, 2009.

17. Hu, K.S.; Kang, M.K.; Kim, T.W.; Kim, K.H.; and Kim, H.J.: Relationships between dental roots and surrounding tissues for orthodontic miniscrew installation, Angle Orthod. 79:37-45, 2009.

18. Lee, K.J.; Joo, E.; Kim, K.D.; Lee, J.S.; Park, Y.C.; and Yu, H.S.: Computed tomographic analysis of tooth-bearing alveo-lar bone for orthodontic miniscrew placement, Am. J. Orthod. 135:486-494, 2009.


Fig. 8 A. Laser used to create “punched” area for mini-implant insertion in area of unattached gingiva, pre-venting soft-tissue coverage of mini-implant head. B. Miniplate providing indirect anchorage to lower canine.

A B

Space for nonextraction Class II treatment can be gained in

many ways through molar distal-ization, with varying levels of required patient compliance and potential for anchorage loss.1-4

This article describes the use of the Carriere Distalizer*5 as a method for simultaneous Class II correction and unilateral space opening in a patient whose facial characteristics called for a non-extraction approach.

Diagnosis and Treatment Plan

An 11-year-old male pre-sented with a Class II subdivision malocclusion, an overjet of 3mm, an overbite of 30%, an upper mid-line deviated 3mm to the right, and an impacted upper right canine (Fig. 1). In profile, he had an obtuse-to-straight nasolabial

angle and a moderately short neck-chin length. The panoramic radiograph indicated a normal eruption pattern except for the blocked-out upper right canine, with all permanent teeth present.

Because of the patient’s facial proportions, a two-phase, nonextraction treatment plan was designed. In the first phase, a Carriere Distalizer would be placed on the right side to correct the Class II molar relationship and regain the space needed for eruption of the upper right canine. The second stage would complete the orthodontic correction with fixed appliances.

Treatment Progress

A passive lower lingual arch was placed, and an 18mm Carriere Distalizer was bonded on the right side from upper first

premolar to first molar. Class II elastics were prescribed for 24-hour wear (Fig. 2).

After 11 months of Distal-izer treatment, a Class I molar relationship had been obtained, with adequate space created for eruption of the blocked-out canine. The upper right second deciduous molar exfoliated during this time, and the Distalizer maintained the leeway space. Upper and lower fixed appliances were then placed for further treatment (Fig. 3).

Treatment Results

Total treatment time for both stages was 28 months (Fig. 4). The midline deviation was corrected without any special mechanics.

Records taken 18 months after debonding show a stable occlusion in a solid Class I rela-tionship, with no significant signs of relapse (Fig. 5).

Discussion

The Carriere Distalizer is a simple-to-use device that is incon-spicuous enough to promote


CASE REPORTUnilateral Application of the Carriere DistalizerHECTOR LUIS RODRÍGUEZ, DDS

© 2011 JCO, Inc.

Dr. Rodríguez is Professor and Coordinator, Department of Orthodontics, Escuela de Odontologia, Universidad Nacional Pedro Henríquez Ureña, Santo Domingo, Dominican Republic. Contact him at Max Henríquez Ureña #31, Santo Domingo, Dominican Re -public; e-mail: [email protected].

*Trademark of Ortho Organizers, Inc., 1822 Aston Ave., Carlsbad, CA 92008; www. orthoorganizers.com.


JCO/MARCH 2011

patient acceptance and compli-ance. Loss of anchorage has not been a significant problem in our practice, although several tech-niques, including miniscrews, are available for anchoring the Class II elastics.

An open-coil spring could have been used for molar distal-ization in our patient, but would have required earlier bracket placement. The Distalizer is also

more effective than an open-coil spring in achieving controlled derotation of the first molar. It rotates the maxillary first molar around its palatal root while pro-ducing bodily distal movement, before other appliances have been placed that could potentially slow treatment with competing forces.5 I have found the Carriere Distal-izer a highly useful addition to my nonextraction armamentarium.

Unilateral Application of the Carriere Distalizer

178

Fig. 1 11-year-old male patient with Class II subdivision malocclusion and midline deviation due to early exfoliation of upper right decidu-ous canine.

Fig. 2 Carriere Distalizer bonded to upper right first premolar and first molar.


Fig. 3 After 11 months of unilateral molar distalization, upper and lower brackets bonded for second phase of treatment.

Fig. 4 A. Patient after 11 months of unilateral distalization and 17 months of full fixed-appliance treat-ment. B. Superimposition of pre- and post-treatment cephalometric tracings.

A B

180 JCO/MARCH 2011

Unilateral Application of the Carriere Distalizer

1. Hilgers, J.: The Pendulum appliance for Class II non-compliance therapy, J. Clin. Orthod. 26:706-714, 1992.

2. Gianelly, A.A.; Bonds, P.W.; and Johnson, W.M.: Distalization of molars with repelling magnets, J. Clin. Orthod.

22:40-44, 1998.3. Carano, A. and Testa, M.: The Distal Jet

for upper molar distalization, J. Clin. Orthod. 30:374-380, 1996.

4. Park, H.S.; Lee, S.K.; and Kwon, O.W.: Grouped distal movement of teeth using

microscrew implant anchorage, Angle Orthod. 75:602-609, 2005.

5. Carriere, L.: A new Class II distalizer, J. Clin. Orthod. 38:224-231, 2004.

Fig. 5 Patient 18 months after debonding.

REFERENCES

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Tube is a low-profile, self-ligating attachment for lower first molars that can be repeatedly opened and closed throughout treatment, according to the manufacturer. A flexible yet robust nickel titanium Micro-Latch is designed to open with any standard instrument and to close easily and securely with an audible click, using just a fin-ger or thumb.

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PRODUCT NEWS

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ASSISTANT/ASSOCIATE PROFESSOR

Department of OrthodonticsCOLLEGE OF DENTISTRY

The NYU College of Dentistry Department of Orthodontics seeks candidates for a full time faculty position at Assistant or Associate Professor level in the Department of Orthodontics. The faculty will join a diverse group of faculty, students, and staff, in their mission to achieve programs of excellence in the areas of teaching, scholarly activity, and service. Responsibilities include didactic and clinical instruction in predoctoral and postdoctoral Orthodontics. In addition, there are opportunities to participate in our Faculty Practice in the heart of Manhattan.

Candidates need to possess a D.D.S or D.M.D. or its equivalent and be educationally qualified in Orthodontics. Eligibility for licensure in New York State is desirable. In addition, a documented history of academic accomplishments in the area of teaching and scholarly activity is desirable. Evidence of funded research, publications, and presentations at significant meetings and forums, is also preferred.

NYU offers an excellent benefits package. Salary and academic rank will be commensurate with credentials and experience. Applicant should send curriculum vitae, statement of academic objectives, and the names and addresses of four references to: George J. Cisneros, DMD, MMSc, Professor and Chair, Department of Orthodontics, New York University College of Dentistry, 345 East 24th Street, 680W, New York, NY 10010.

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Documents

beam computed

class ii elastics

stainless

skeletal anchorage

sufficient

skeletal open

mesial probing

class ii profile