congenitally missing mandibular second premolars: clinical options · 2008. 7. 2. · tally missing...

CLINICIAN’S� CORNER

Congenitally� missing� mandibular� secondpremolars:� Clinical� optionsVincent� G.� Kokicha� and� Vincent� O.� Kokichb

Seattle,� Wash

Introduction:� Congenital� absence� of� mandibular� second� premolars� affects� many� orthodontic� patients.� Theorthodontist� must� make� the� proper� decision� at� the� appropriate� time� regarding� management� of� the� edentulousspace.� These� spaces� can� be� closed� or� left� open.� Implications:� If� the� space� will� be� left� open� for� an� eventualrestoration,� the� keys� during� orthodontic� treatment� are� to� create� the� correct� amount� of� space� and� to� leave� thealveolar� ridge� in� an� ideal� condition� for� a� future� restoration.� If� the� space� will� be� closed,� the� clinician� must� avoidany� detrimental� alterations� to� the� occlusion� and� the� facial� profile.� Significance:� Some� early� decisions� that� theorthodontist� makes� for� a� patient� whose� mandibular� second� premolars� are� congenitally� missing� will� affect� hisor� her� dental� health� for� a� lifetime.� Therefore,� the� correct� decision� must� be� made� at� the� appropriate� time.Purpose:� In� this� article,� we� present� and� discuss� various� treatment� alternatives� for� managing� orthodonticpatients� with� at� least� 1� congenitally� missing� mandibular� second� premolar.� (Am� J� Orthod� Dentofacial� Orthop2006;130:437-44)

Congenital� absence� of� mandibular� second� pre-molars� affects� many� orthodontic� patients.� Theorthodontist� must� make� the� proper� decision� at

the� appropriate� time� regarding� management� of� theedentulous� space.� These� spaces� can� be� closed� or� leftopen.� If� the� space� will� be� left� open� for� an� eventualrestoration,� the� keys� during� orthodontic� treatment� are� tocreate� the� correct� amount� of� space� and� to� leave� thealveolar� ridge� in� an� ideal� condition� for� a� future� resto-ration.� If� the� space� will� be� closed,� the� clinician� mustavoid� any� detrimental� alterations� to� the� occlusion� andthe� facial� profile.� Some� early� decisions� that� the� orth-odontist� makes� for� a� patient� whose� mandibular� secondpremolars� are� congenitally� missing� will� affect� his� or� herdental� health� for� a� lifetime.� Therefore,� the� correctdecision� must� be� made� at� the� appropriate� time.� Wepresent� and� discuss� various� treatment� alternatives� formanaging� orthodontic� patients� with� at� least� 1� congeni-tally� missing� mandibular� second� premolar.

PATIENT� 1

A� girl,� age� 12� years� 4� months,� was� congenitallymissing� the� mandibular� right� second� premolar.� Thedeciduous� right� second� molar� was� present� but� sub-

merged� below� the� occlusal� levels� of� the� adjacent� teeth(Fig� 1,� A).� The� radiograph� of� the� deciduous� toothshowed� that� the� bone� levels� between� the� deciduousmolar� and� the� adjacent� permanent� teeth� were� flat� (Fig� 1,B).� This� indicated� that� the� deciduous� tooth� was� notankylosed� and� had� erupted� evenly� with� the� adjacentteeth.� The� mesiodistal� width� of� the� deciduous� molarwas� 13� mm� (Fig� 1,� C);� the� normal� width� of� an� averagemandibular� second� premolar� is� 7.5� mm.� Although� asingle-tooth implant was the planned replacement forthe missing premolar, the patient was too young andstill growing. To preserve the buccolingual bone for aneventual implant, the deciduous molar was reduced inwidth� (Fig� 1,� D� and� E)� and� restored� with� composite(Fig� 1,� F� and� G),� and� the� remaining� space� was� closed� toproduce Angle Class I molar and canine relationshipsafter� orthodontic� therapy� (Fig� 1,� H� and� I).

PATIENT 2

A girl, age 8 years 3 months, had bilateralsubmerged� mandibular� second� molars� (Fig� 2,� A).� Theradiograph� (Fig� 2,� B)� showed� that� the� bone� levelsbetween the right deciduous second molar and theadjacent permanent first molar were angled oroblique, indicating that the permanent tooth hadcontinued to erupt. All remaining deciduous teethwere extracted, no space-maintaining applianceswere placed, and the remaining permanent teeth wereallowed� to� erupt� (Fig� 2,� C).� Even� though� a� significantvertical bony defect remained immediately afterextraction of the submerged deciduous molar, subse-quent tooth eruption brought the bone and tissue up

From the Department of Orthodontics, School of Dentistry, University ofWashington, Seattle.aProfessor.bAffiliate assisant professor.Reprint requests to: Vincent G. Kokich, 1950 South Cedar, Tacoma, WA98405; e-mail, [email protected], March 2006; revised and accepted, May 2006.0889-5406/$32.00Copyright © 2006 by the American Association of Orthodontists.doi:10.1016/j.ajodo.2006.05.025

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to� their� normal� levels� (Fig� 2,� D)� and� eliminated� thealveolar� defect.� Because� the� mandibular� incisorswere� located� so� far� to� the� lingual� aspect� (Fig� 2,� E),they� were� proclined� labially,� and� space� was� openedbetween� the� premolar� and� the� molar� (Fig� 2,� F)� for� asingle-tooth� implant� (Fig� 2,� G).� This� implant� wasrestored� with� a� second� premolar� crown� (Fig� 2,� H),which� helped� to� reestablish� proper� occlusion� (Fig� 2,I).� The� bone� for� the� implant� was� created� throughorthodontic implant-site development.

PATIENT 3

This woman was missing her right mandibularsecond premolar and first molar. The mandibular sec-ond molar was in an Angle Class II relationship withthe� maxillary� first� molar� (Fig� 3,� A),� and� the� edentulousspace between the second molar and the first premolar(Fig� 3,� B)� was� too� large� for� 1� tooth� and� too� small� for� 2

teeth.� After� initial� orthodontic� alignment� (Fig� 3,� C),� adiagnostic wax-up was constructed to determine theprecise� position� for� a� second� premolar� implant� (Fig� 3,D). After integration of the implant, a provisionalcrown� was� attached� (Fig� 3,� E),� and� a� bracket� was� placedon� the� implant-supported� crown� (Fig� 3,� F).� The� implantwas used as an anchor to move the right mandibularsecond molar mesially into an Angle Class I relation-ship, without jeopardizing orthodontic anchorage, theposition� of� the� remaining� anterior� teeth� (Fig� 3,� G),� orthe patient’s facial profile. The final porcelain crown onthe� implant� (Fig� 3,� H)� was� the� appropriate� size,� and� theeventual posttreatment occlusion was finished in anideal� Angle� Class� I� relationship� (Fig� 3,� I).� The� maxil-lary second molar was left without an occlusal antag-onist. If the maxillary second molar eventually su-pererupts, it can be extracted, or an implant can beplaced distally to the mandibular second molar. Using

Fig 1. A, Girl was congenitally missing permanent right mandibular second premolar; deciduoussecond molar was present and submerged below occlusal plane. B, radiograph showed that roothad not resorbed. Because bone levels were flat between deciduous and adjacent permanent teeth,tooth was maintained. C-E, Tooth was too wide, so mesial and distal surfaces were reducedsubstantially. F and G, Tooth was built up with composite to reduce caries risk. H-I, Pulp was notdamaged after space was closed and posterior teeth were brought into occlusion.

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438 Kokich and Kokich

the� implant� as� an� anchor� for� partial� closure� of� a� 2-toothspace� minimized� the� complexity� of� the� orthodontictreatment� and� the� restorative� management� for� thispatient.

PATIENT 4

This girl, age 13 years 8 months, had an AngleClass II malocclusion, with a 5-mm anterior overjet(Fig� 4,� A).� She� had� a� minor� arch-length� deficiency� inboth arches but was congenitally missing the rightmaxillary, and right and left permanent mandibularsecond� premolars� (Fig� 4,� B).� Her� maxilla� and� mandiblewere� well� related� (Fig� 4,� C),� and� the� maxillary� andmandibular incisors were in a relatively normal antero-posterior position. Extraction of the left maxillarysecond premolar and remaining deciduous second mo-lars and closure of all edentulous spaces would havebeen detrimental to her facial profile by overly retract-

ing the lips relative to the chin. The only options foravoiding the incisor retraction were placement of mini-implants for anchorage to protract the maxillary andmandibular first molars, and extraoral anchorage toachieve the same objective. Because this patient wastreated before the era of mini-implants, a chincup andelastics were used to slide the maxillary and mandibularfirst molars mesially along a continuous archwire. Theposttreatment� dental� casts� (Fig� 4,� D)� show� that� anAngle Class I molar relationship was achieved. Thepanoramic� radiograph� (Fig� 4,� E)� shows� the� amount� oftooth movement, and the cephalometric superimposi-tion� before� and� after� orthodontic� treatment� (Fig� 4,� F)verifies that the mandibular incisors did not movelingually, but that the mandibular molars moved en-tirely mesially with the protraction force. Although thistooth movement required 4 years of orthodontic treat-ment, the patient has no restorations, and her facial

Fig 2. A and B, Girl was missing permanent right and left mandibular second premolars; deciduous firstand second molars were ankylosed and submerged. C and D, All deciduous molars were extracted;permanent first premolar and first molar drifted together and closed the space. E-H, Becausemandibular incisors were positioned lingually relative to chin, treatment plan involved opening secondpremolar space, followed by placement of implant and porcelain crown. I, Treatment plan resulted inAngle Class I molar and canine relationships.

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profile� was� maintained� despite� the� 3� congenitally� miss-ing� premolars.

PATIENT 5

This girl, age 14 years 6 months, was congenitallymissing� her� left� mandibular� second� premolar� (Fig� 5,� A),and the deciduous second molar was ankylosed andsubmerged. The left maxillary second premolar waspresent but delayed in its eruption. After the deciduoussecond molar was extracted, substantial bone resorptionwith significant vertical and buccolingual narrowing ofthe� alveolar� ridge� occurred� (Fig� 5,� B).� This� ridge� defectwould probably have narrowed even further and re-quired a bone graft before implant replacement. How-ever, another approach involved moving the first pre-molar� into� the� second� premolar� position� (Fig� 3,� C-E);this created an adequate ridge for the first premolarimplant. When the flap was elevated to place the

implant, sufficient alveolar bone was located distally tothe� premolar� where� the� ridge� had� been� deficient� (Fig� 5,F). By using the adjacent tooth as the stimulus foralveolar-site development, no bone graft was necessarywhen the implant was placed at 17 years of age, aftercephalometric superimpositions showed that her facialgrowth� was� completed� (Fig� 5,� G).� The� final� crown� onthe� mandibular� implant� (Fig� 5,� H)� provided� the� properspace and support for the occlusion, and the firstpremolar functions nicely in the second premolar posi-tion� (Fig� 5,� I).

DISCUSSION

Congenital absence of mandibular second premolarsaffects many orthodontic patients. The clinician mustmake the proper decision at the appropriate time regardingmanagement� of� the� edentulous� space.1� If� the� space� willbe left open for an eventual restoration, the correct

Fig 3. A, Woman was missing right mandibular second premolar and permanent first molar. B and C,There was too much space for 1-tooth replacement and too little space for 2-tooth replacement. Dand E, Implant was placed in first premolar position and restored. F, Bracket was placed on implantprovisional crown. G, Implant was used to close remaining edentulous spaced. H and I, Widthof final premolar crown was normal, and Angle Class I molar and canine relationships wereachieved.



amount of space must be created and the alveolar ridgemust be left in an ideal condition for a future restora-tion. In the past, either conventional bridges or resin-bonded bridges were used to fill edentulous spaces.However, full-coverage conventional bridges in youngpatients can result in devitalization of the pulp andrequire� root� canal� therapy.2� Resin-bonded� posteriorbridges� have� questionable� survival� rates.3-5� Today,� thefirst choice of restoration for a congenitally missingmandibular� premolar� should� be� a� single-tooth� implant.6

But if the implant cannot be placed until the patient’sfacial growth is complete, how should the edentulousridge be preserved?

Ostler� and� Kokich7� evaluated� the� long-termchanges in the width of the alveolar ridge after extract-ing deciduous mandibular second molars. Their datashowed that the ridge narrows by 25% during the first4 years after deciduous tooth extraction. After 7 years,the ridge narrows another 5%, for a total reduction of30% over 7 years. However, the authors showed thatthese ridges were still broad enough to receive a dentalimplant. Unfortunately, the ridge resorbs more on thefacial side than on the lingual side, and, therefore,although the implant can be placed without a bonegraft, the implant position is more to the lingual side.This factor requires the restorative dentist to alter theloading of the buccal and lingual cusps of the crown onthe implant to prevent fracture of the abutment or theimplant� crown.8

Another option is to maintain the deciduous toothuntil the patient is old enough for the implant. Theappropriate age for implant placement is determined bythe cessation of vertical facial growth. That parameteris determined by comparing serial cephalometric radio-graphs to determine when ramus growth and thereforevertical changes in facial growth have stopped. Fudalejet� al9� showed� that,� on� average,� girls’� facial� growthcontinues until about 17 years of age, whereas theaverage boy’s facial vertical growth is complete atabout 21 years of age. Therefore, maintaining thedeciduous tooth until the end of growth is desirable.But deciduous molars are too wide mesiodistally, andthis could affect the fit of the posterior teeth. Thus, it isadvantageous to reduce the width of the deciduoussecond� molar� to� the� size� of� a� second� premolar.1

The reduction of a deciduous molar should beaccomplished with a sharp carbide fissure bur or adiamond bur. The key is to remove sufficient toothstructure to create space but not enough to cause pulpalnecrosis. A guide to estimating the correct amount ofreduction is to measure the mesiodistal width of thedeciduous molar at the level of the cementoenameljunction� on� a� bitewing� radiograph� (Fig� 1).� This� distancecan be transferred to and marked on the occlusalsurface of the deciduous molar with a pencil or markingpen. Then the bur is positioned to follow this line andcut toward the gingiva to remove a wafer of enamel andthe underlying dentin on both the mesial and distal

Fig 4. A and B, Girl had end-to-end malocclusion with 3 congenitally missing second premolars.C, Facial profile was ideal. D, To avoid future restorations and prevent negative facial changes,chincup and elastics were used to protract maxillary and mandibular molars into Angle Class Irelationship. E and F, Significant tooth movement eliminated need for extensive restorative dentistrywithout jeopardizing facial profile.



surfaces� (Fig� 1).� About� 2� mm� can� be� removed� fromboth surfaces; this should leave the crown about 7 to 8mm wide.

A potential problem of reducing the deciduousmolar in this way is that it leaves exposed dentin on themesial and distal surfaces of the tooth. As the spacesare closed, it is difficult for the patient to adequatelyclean these interproximal surfaces, and the tooth coulddecay easily. Therefore, to prevent decay, a layer oflight-cured restorative composite should be applied tothe mesial and distal surfaces to protect the deciduoustooth. In addition to protecting these exposed dentinalsurfaces, the addition of restorative composite willbuild up the occlusal surface of the typically shortdeciduous molar, so that it can function with the teethin the opposing dental arch and prevent supereruption.After composite restoration, the interproximal spacescan be closed, and the deciduous molar functions as apremolar� (Fig� 1).

A common concern about closing these interproxi-mal spaces after reduction of the deciduous tooth is thatits roots will prevent complete space closure, becausethey tend to diverge beyond the width of the crown.However, in most cases, as the socket wall of thepermanent teeth move near and into contact with thedeciduous tooth roots, the latter will resorb. Afterresorption, these deciduous roots are replaced by bone;this is an ideal way to prepare this site for a futureimplant.1

Occasionally, a deciduous second molar becomesankylosed. If the ankylosis occurs while the patient isyoung and still undergoing significant facial growth,the tooth will become submerged relative to the adja-cent� erupting� permanent� teeth.1� If� this� region� will� berestored with a future implant, the alveolar ridge couldbe� compromised� vertically� and� require� a� bone� graft.10

However, vertical bone grafting is often unpredictableand� an� added� expense� for� the� patient.11� Therefore,

Fig 5. A, Late-adolescent girl was congenitally missing left mandibular second premolar, anddeciduous molar was ankylosed and submerged. B, Deciduous molar was extracted, resulting insignificant narrowing of edentulous ridge. C-E, First premolar was pushed distally into secondpremolar position. F and G, Orthodontic movement allowed implant in newly regenerated bone.H and I, After restoration of first premolar implant in second premolar position, it is difficult to seedifference.



extraction of ankylosed deciduous molars is recom-mended, if the patient is missing the deciduous secondmolar and the face is still growing. But how does theclinician diagnose ankylosis in a child or an adolescent?The most reliable indicator of deciduous molar anky-losis is to evaluate the alveolar bone levels between thedeciduous molar and the adjacent permanent first molarand� first� premolar.1� If� the� bone� is� flat,� this� indicates� thatthe deciduous tooth and the adjacent teeth are eruptingevenly. However, if the alveolar bone level becomesoblique, with the bone level located more apicallyaround the deciduous tooth, this confirms ankylosis(Fig� 2).� If� the� patient� has� little� facial� growth� remaining,and the deciduous molar is submerged only slightly, thetooth can be maintained to preserve the width of thealveolus for the future implant. However, if the patienthas significant growth remaining, the deciduous molarmust be extracted to prevent a significant ridge defect.

A common question after deciduous molar extrac-tion is whether to place a space maintainer to preservearch length. We do not place space maintainers in mostof these situations, especially if implants will be usedfor restoring the edentulous space. If the edentulousspace is not maintained, the adjacent permanent firstmolar� and� first� premolar� should� erupt� together� (Fig� 2).Although this could require longer orthodontic treat-ment to push the teeth apart to create the implant space,this type of tooth movement will also result in a morerobust� alveolar� ridge� (Fig� 2).� As� the� roots� of� adjacentteeth move apart, they deposit bone behind that equalsthe width of the premolar and molar, and will producean excellent ridge in which to place the implant. Thisprocess is called orthodontic implant-site development.

Occasionally, the decision to extract an ankylosedand submerged deciduous second molar will be madetoo late, resulting in a narrow alveolar ridge with avertical defect. If an implant will be placed in this site,a bone graft might be necessary to provide adequateridge width and height. However, another possibilityexists, especially if the patient will undergo orthodontictherapy. It might be advantageous to push the firstpremolar into the second premolar position, therebycreating space for the single-tooth implant in the firstpremolar location. When faced with this decision,clinicians are often fearful that there is insufficientalveolar ridge width in which to move the permanentfirst premolar. However, previous studies showed that awider tooth root can be pushed through a narrowalveolar ridge without compromising the eventual bonesupport� around� the� repositioned� tooth� root.12,13� Weperformed this type of tooth movement on severaloccasions, and it resulted in a much better ridge inwhich� to� place� the� implant� (Fig� 5).

Another possible situation is a patient who ismissing not only the second premolar, but also the firstpermanent� molar� (Fig� 3).� If� some� drifting� of� theadjacent teeth has occurred, the resulting edentulousspace can be too large for a 1-tooth replacement and toosmall for a 2-tooth replacement. Then it could beadvantageous to place a single-tooth implant in theappropriate position before orthodontic treatment. Thisimplant can be restored and used as an anchor to closeany excess and remaining space, by using the implantas an anchor to prevent unwanted occlusal changes inthe� remaining� dentition.14� The� advantage� to� the� patientis that fewer restorations are required to fill the eden-tulous space. The advantage to the orthodontist is thatan immobile anchor in the bone is available to protractor retract the adjacent teeth to close the space. Thisinterdisciplinary treatment requires proper planning,the construction of a diagnostic wax-up, and precisepositioning of the implant to satisfy the orthodontic,surgical,� and� restorative� objectives� (Fig� 3).

If an implant is used to move adjacent teeth andclose an edentulous space, the timing of implant load-ing is an important factor. In the past, implant loadingtraditionally was delayed until the implant had fullyintegrated� with� the� surrounding� bone.15� However,� re-cent studies showed that early or immediate loading ispossible,16,17� especially� in� orthodontic� patients.18� Thedifference is that an orthodontic load is continuous andin 1 direction, whereas an occlusal load is intermittentand� in� different� directions.� Researchers18� have� shownthat a continuous load in the same direction actuallystimulates bone formation, which further enhances theosseointegration of the implant. So, in most orthodonticsituations, implants can be loaded early, soon after therestorative dentist has placed the temporary restoration.

Another alternative for treating a patient with con-genitally missing mandibular second premolars is tosimply� close� the� space.19� If� the� patient� has� crowding� inthe opposite dental arch or a protrusive facial profile,closure of the edentulous space would be advantageous.However, in a patient with no dental crowding and anormal facial profile, closure of the edentulous spacefrom a congenitally missing second premolar couldproduce an undesirable facial profile. In these situa-tions, the orthodontist requires additional anchorage,either extraoral or intraoral, to prevent these unwantedfacial changes. A protraction facemask and a chincup(Fig� 4)� are� examples� of� extraoral� appliances� that� willaccomplish� this� type� of� tooth� movement.� Miniscrews20

and mini-implants are intraoral methods of providingadditional anchorage to close these edentulous spaceswithout altering the patient’s facial profile. Anothermethod of closing the edentulous space is to hemisect



the� deciduous� second� molar� at� an� early� age21,22� andallow the permanent molar to erupt in a mesial directionwithout affecting the position of the mandibular inci-sors. If the orthodontist sees the patient at an early ageand monitors him or her regularly, this alternative isespecially attractive.

SUMMARY

We described and illustrated several methods ofmanaging patients with congenitally missing mandibu-lar second premolars. In the past, orthodontists primar-ily made the treatment decisions for these patients.However, with newer solutions for restoring edentulousspaces, surgeons and restorative dentists can play sig-nificant roles in helping to manage these orthodonticpatients. Although the orthodontist sees the patient at ayoung age, some decisions made at that time will affecthim or her for a lifetime. We emphasized the interdis-ciplinary aspects of treating a patient with congenitallymissing mandibular second premolars to provide thebest possible result that teamwork dentistry can offer.

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congenitally missing mandibular second premolars: clinical options · 2008. 7. 2. · tally missing...

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