some wisdom about the removal of wisdom teeth

Indications for the removal of impacted third molars include

pericoronitis, periodontitis, caries, resorption of the second

molar, cyst formation, and interference with orthodontic

treatment. While the prophylactic removal of asymptomatic

third molars may still be controversial, there is a general

agreement that they should be removed when a patho-

logic condition is present. This article reviews specific

indications for removal of impacted third molars, the argu-

ments for their prophylactic removal, and the specific

instances when such teeth should not be removed.

Indications for Removal of ImpactedThird MolarsPericoronitis

Pericoronitis is the most common condition affecting

impacted third molars. Bacteria gain access into the fol-

licular space through an opening in the overlying gingiva

or through the gingival crevice distal to the second molar.

Such infections may remain localized in the pericoronal

region, spread via the lymphatic system into the sub-

mandibular lymph nodes, or extend directly into the

surrounding tissues. The most frequent site of direct exten-

sion is the buccal vestibule above the attachment of the

buccinator muscle, which causes a vestibular abscess.

Occasionally, however, the infection can spread beneath

the buccinator muscle and give rise to a buccal space

abscess or posteriorly into the pterygomandibular space.

Once there has been an episode of pericoronitis, there is

a tendency for the infection to recur intermittently when

complete eruption of the tooth is not possible.

Periodontitis

Constant food impaction and plaque retention between a

partially impacted third molar and the adjacent second

molar can result in inflammation and considerable loss of

interseptal bone (Figure 1). Such periodontal pocket for-

mation not only weakens the support of the second molar,

which may loosen, but also apical extension of the infec-

tion that can lead to its devitalization. Once a deep perio-

dontal pocket develops, removal of the impacted third

Figure 1. Radiograph of an impacted third molarcausing severe periodontal destruction as wellas caries involving the second molar. This couldhave been prevented by earlier removal ofthe third molar.

Daniel M. Laskin, DDS, MS, DSc (Hon), received a DDS degree

from Indiana University and a Master of Science degree from

the University of Illinois. He is Professor and Chairman of the

Department of Oral and Maxillofacial Surgery, School of

Dentistry, and Professor and Chairman of the Division of Oral

and Maxillofacial Surgery, Department of Surgery, School of

Medicine, Virginia Commonwealth University.

Some Wisdom Aboutthe Removal of Wisdom Teeth

Daniel M. Laskin, DDS, MS, DSc (Hon)

September/October 2001 15

CECONTINUING EDUCATION

5


5

molar will not eliminate it. Therefore, the impacted tooth

should be extracted at the first sign of periodontal infec-

tion. This will not only arrest the condition, but may also

decrease the excessive crevicular depth on the distal aspect

of the second molar.1

Dental Caries

Partial eruption of an impacted third molar in the oral envi-

ronment increases its susceptibility to caries due to the

accumulation of food debris and the difficulty of keeping

the area clean. The restoration of such carious lesions is

often impossible due to poor access. Even when the tooth

is restored, recurrent caries is a frequent finding. For these

reasons, removal of the third molar is indicated, even when

the carious lesion does not extend into the pulp.

The same factors that make the third molar suscep-

tible to caries can also affect the adjacent second molar

(Figure 1). Such lesions should not be restored until the

third molar is removed. This not only reduces the possi-

bility of recurrent tooth decay, but also avoids possible

damage to the restoration during the surgical procedure.

Root Resorption

Pressure from the crown of an impacted third molar against

the root of the second molar may result in pathologic

resorption (Figure 2A & 2B).2 When this diagnosis is made,

care must be exercised not to confuse such areas of root

resorption with the shadows produced in the radiograph

by the overlap of the molars due to improper horizontal

angulation of the cone of the x-ray machine or the bucco-

or linguoversion of the impacted tooth (Figure 3).

Removal of only the impacted tooth is indicated if the

resorptive process has not involved the pulp of the sec-

ond molar. If the second molar has been devitalized and

must be extracted, however, it may be advisable to leave

the third molar in young patients.

Cyst Formation

The third molar is the tooth most often involved in the for-

mation of dentigerous cysts. Eighty percent of the follicles

around the crown of the third molar are wider than 2.5 mm

and have been shown to have an epithelial lining.3 Such

teeth should be removed whenever there is indication of

Wisdom About Wisdom Teeth

16 The Journal of Practical Hygiene

Figure 2A. Impacted third molar causing resorption of thedistal root of the second molar. 2B. Post-extraction radio-graph reveals the extent of the damage.

follicular enlargement. Frequent radiographic evaluation

is indicated in those instances when there is possible

enlargement of the follicle and the tooth has been allowed

to remain. A cyst can develop and remain asymptomatic

for long periods during which it may grow to a large size

and cause considerable bone destruction. Moreover,

ameloblastomas and even carcinomas arising in the walls

of dentigerous cysts have been reported.4,5

Idiopathic Pain

Occasionally, a patient may complain of facial pain, yet

there may be no apparent clinical or radiographic evidence

of any abnormality other than the presence of a deeply

embedded, impacted third molar with no obvious oral com-

munication. Though there may be no satisfactory expla-

nation for why such a tooth can cause pain, some patients

experience relief following its removal. Therefore, it is jus-

tified to remove impacted third molars in such instances.

Presence in an Edentulous Ridge

An impacted tooth is occasionally found during a routine

radiographic examination in a ridge that appears to be

A

B


5

edentulous. Unless the tooth is completely covered with

bone and its extraction would cause considerable destruc-

tion of the alveolar process, it should be removed.

Determining the amount of bone over the tooth from a

radiograph, however, is not always a simple task. Since

the radiograph provides merely a two-dimensional view of

the tooth, it may appear to have considerable bone over

the superior surface when actually it is only partially cov-

ered. If allowed to remain, compression of the overlying

mucosa between the crown of the tooth and a denture

may not only cause considerable pain, but the pressure can

cause an ulceration of the mucosal tissue, which can pro-

duce a pathway for the development of an infection.

Other Indications

In addition to the aforementioned conditions, impacted

third molars may also be involved in other situations that

require their removal. These teeth can sometimes interfere

with the normal path of eruption of the adjacent second

molar and should be removed as soon as this situation is

recognized so that the second molar has the best oppor-

tunity to erupt. Likewise, impacted third molars can inter-

fere with distal orthodontic tooth movement. They can also

interfere with the proper performance of orthognathic

surgery when this involves the third molar region. In such

cases, the impacted tooth must be removed at the time of

surgery or, preferably, prior to it.

Benign and malignant neoplasms of the soft tissues and

bone can occur in the third molar region, and the third

Laskin

September/October 2001 17

Figure 3. Impacted third molar in linguoversion appearingto be causing resorption of the second molar.

molar should never be allowed to remain when its reten-

tion would jeopardize the successful removal of the lesion.

Moreover, an impacted third molar should never be left in

an area that will be subjected to radiation therapy.

The presence of an impacted third molar weakens the

mandible and therefore trauma to the jaw is more likely

to cause a fracture. Should a mandibular fracture occur in

the third molar region, removal of the tooth is often indi-

cated as part of the treatment (Figure 4). It may be advis-

able to consider removal of impacted teeth prophylactically

in persons who engage in contact sports.

Prophylactic Removal of ImpactedThird MolarsClinical experience has shown that most impacted teeth

will ultimately give rise to some difficulty. For example,

the incidence of pericoronitis has been reported to range

from 27% to 34%, and the incidence of caries to range

from 3% to 15% in patients presenting for removal of

impacted teeth.6-8

Several studies have also shown a significant rela-

tionship of periodontitis and periodontal pocket formation

with impacted third molars.9,10 Moreover, an increase in the

visible plaque and gingival bleeding indices as far forward

as the canine teeth has been demonstrated in patients with

partially erupted third molars, and the plaque index was

found to improve after their removal.11-13 With the recent

implication of chronic periodontal infection as a possible

contributor to cardiovascular disease,14 this may also be

an important justification for the prophylactic removal of

impacted teeth. Additionally, removal of these teeth at an

early age (before 25 years) has been shown to result in a

significant postoperative reduction in the depth of the infra-

bony defects, whereas this does not occur in older patients.15

The National Institute of Dental Research Consensus

Development Conference on Removal of Third Molars

recommends that such teeth be removed as soon as it is

obvious that there is insufficient space to accommodate

them or that they are not in a position for normal erup-

tion to occur.16 This conference concluded that impaction

or malposition of a third molar may justify its removal, and

that such treatment is not considered prophylactic. Growth

of the mandible, with the accompanying resorption of the


5

anterior border of the ramus to provide space for the third

molar as well as growth of the maxilla are essentially

completed between 16 and 17 years of age, and therefore

the decision regarding prophylactic removal can generally

be made at about that time.

Although their potential for causing crowding of the

mandibular incisors is frequently given as a reason for

the prophylactic removal of impacted third molars, and

this is sometimes seen as these teeth are erupting, the rela-

tionship between these two events remains unproven.17,18

If an anterior force was caused by the erupting third

molars, it would require a corresponding forward shift of

all of the posterior teeth in order for it to be transmitted

to the incisors, and this does not occur. Moreover, under

such circumstances, the disruption of tooth contact would

be expected to occur in the canine and not the incisor

region. An alternative explanation for the development of

anterior tooth crowding may be the increased plasticity of

the alveolar bone and periodontal ligaments that accom-

panies the hormonal changes in adolescence, which causes

an imbalance between the forces ordinarily contributing to

tooth stability.18 Supporting this concept is the fact that

incisor crowding is also evident in persons with missing

third molars and in those who have had them removed

prior to orthodontic treatment.16,17 In the latter instance, the

crowding may represent the relapse of teeth orthodonti-

cally placed in a physiologically untenable position. Other

possible factors contributing to crowding of the lower

incisors are a restriction of forward mandibular growth

Wisdom About Wisdom Teeth


Figure 4. Mandibular fracture in the third molar region. Figure 5. Radiograph of an impacted third molar in apatient in whom the second molar is at risk due to adeep restoration.

by a deep maxillary overbite and the natural tendency of

these teeth to upright with age.

Contraindications Since the surgical procedure in an adult is generally more

complex,19 it is best to allow deeply embedded, asympto-

matic impacted third molars that are covered with bone and

do not communicate with the oral cavity to remain, even

though there is a possibility that pathologic involvement

may subsequently occur. If one is dealing with serious

pathology, it is generally possible to adopt a temporiz-

ing approach in a patient who is a poor surgical risk.

Pericoronal and/or periodontal infections can be treated

with irrigation and antibiotics, caries can be excavated and

a restoration placed, a pulp can be devitalized, a cyst can

be marsupialized and, if necessary, a second molar can be

extracted to create space in the dental arch. It should be

emphasized, however, that such procedures are compro-

mises and not the usual treatments of choice.

An impacted third molar should not be removed when

there is some question about the future status of the

second molar (eg, deep caries, large restoration, endodon-

tic treatment, or extensive periodontal disease) (Figure 5).

In such cases, it is assumed that if the second molar is

extracted at a subsequent time, the third molar will either

erupt into a more functional position or can at least serve

as a bridge abutment. The position of the impacted tooth

and the age of the patient are important considerations

in making this assumption.


5

ConclusionImpacted third molars are subject to a variety of pathologic

processes, some of which may result in serious irreversible

conditions. Therefore, it is important to carefully examine

these teeth at every dental visit. The dental hygienist plays

an important role in this process. When such teeth are pre-

sent, the advantages and disadvantages of prophylactic

removal need to be discussed with the patient so that

an informed decision about their retention or removal can

be made.

References1. Szmyd L, Hester WR. Crevicular depth of the second molar in impacted

third molar surgery. J Oral Surg 1963;21:185-189.

2. Nitzan D, Keren T, Marmary Y. Does an impacted tooth cause rootresorption of the adjacent one? Oral Surg Oral Med Oral Pathol1981;51(3):221-224.

3. Conklin WW, Stafne EC. A study of odontogenic epithelium in thedental follicle. J Amer Dent Assoc 1949;39:143-148.

4. Shteyer A, Lustmann J, Lewin-Epstein J. The mural ameloblastoma:A review of the literature. J Oral Surg 1978;36(11):866-872.

5. Maxymiw WG, Rood RE. Carcinoma arising in a dentigerous cyst: Acase report and review of the literature. J Oral Maxillofac Surg 1991;49(6):639-643.

6. Nordenram A, Hultin M, Kjellman O, Ramstrom G. Indications forsurgical removal of the mandibular third molar: Study of 2,630 cases.Swed Dent J 1987;11(1-2):23-29.

7. Lysell L, Rohlin M. A study of indications used for removal of themandibular third molar. Int J Oral Maxillofac Surg 1988;17(3):161-164.

8. Stanley HR, Alatter M, Collett WK, et al. Pathological sequelae of“neglected” impacted third molars. J Oral Pathol 1988;17(3):113-117.

9. Ash MM Jr, Costich ER, Hayward JR. A study of periodontal hazardsof third molars. J Periodontal 1962;33:209-219.

10. von Wowern N, Nielsen HO. The fate of impacted lower third molarsafter the age of 20. A four-year clinical follow-up. Int J Oral MaxillofacSurg 1989;18(5):277-280.

11. Ylipaavalniemi P, Turtola L, Rytomaa I, et al. Effect of position ofwisdom teeth on the visible plaque index and gingival bleeding index.Proc Finn Dent Soc 1982;78(1):47-49.

12. Giglio JA, Gunsolley JC, Laskin DM, Short KJ. Effect of removing thirdmolars on plaque and gingival indices. J Oral Maxillofac Surg 1994;52(6):584-587.

13. Grondahl HG, Lekholm U. Influence of mandibular third molars onrelated supporting tissues. Int J Oral Surg 1973;2(4):137-142.

14. Beck JD, Pankow J, Tyroler HA, Offenbacher S. Dental infectionsand atherosclerosis. Am Heart J 1999;138:528-533.

15. Kugelberg CF, Ahlstrom U, Ericson S, Hugoson A. Periodontal heal-ing after impacted lower third molar surgery. A retrospective study.Int J Oral Surg 1985;14(1):29-40.

16. NIH consensus development conference on removal for third molars.J Oral Surg 1980;38(3):235-236.

17. Bjork A, Skieller V. Normal and abnormal growth of the mandible. Asynthesis of longitudinal cephalometric implant studies over a periodof 25 years. Eur J Orthodont 1983;5(1):1-46.

18. Ades AG, Joondeph DR, Little RM, Chapko MK. A long-term study ofthe relationship of third molars to changes in the mandibular dentalarch. Am J Orthodont Dentofac Orthop 1990;97(4):323-335.

19. Osborn TP, Frederickson G, Small IA, Torgeson TS. A prospectivestudy of complications related to mandibular third molar surgery.J Oral Maxillofac Surg 1985;43(10):767-769.

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1. A partially impacted mandibular third molarcan cause loss of the interseptal bone betweenit and the second molar due to:A. Pressure on the bone.B. Movement of the second molar. C. A failure to support the bone.D. Constant food impaction.

2. Which of the following occurs followingremoval of an impacted third molar?A. It can result in regeneration of the interseptal bone

distal to the second molar.B. It can result in decreased crevicular depth distal to

the second molar.C. It can prevent further periodontal disease distal to

the second molar.D. All of the above.

3. Restoration of carious lesions in third molars isseldom done because of:A. The difficult access to the lesion.B. The cost of such restorations.C. The close proximity of the dental pulp in such teeth.D. The weakness of the enamel makes restoration

difficult.

4. A follicular space around the crown of anunerupted third molar greater than 2.5 mmwide is generally considered to be:A. Within the range of normality.B. A dentigerous cyst.C. An early ameloblastoma.D. An eruption cyst.

5. With regard to periodontitis and periodontalpocket formation, removal of impactedmandibular third molars causes decreased:A. Gingivitis in the maxillary teeth.B. Plaque and bleeding indices in the anterior teeth.C. Periodontal pocket formation in the molar and

premolar teeth.D. Plaque and bleeding indices in the posterior teeth.

6. Which of the following statements regardingradiographs of impacted third molars is false:A. There may be only partial bony coverage of the

superior surface even when there appears to befull coverage.

B. Radiographs are helpful in determining the amountof bone over the tooth.

C. Radiographs are not helpful in determining whetherthere is buccal or lingual bone over the crown.

D. A radiograph may show bone over the crowneven when no bone is present.

7. Which of the following is usually not a contraindi-cation to the removal of impacted third molars:A. A deeply embedded, asymptomatic third molar in

an adult.B. The poor systemic condition of the patient.C. The potential risk of having to extract the second

molar at a future time.D. The lack of radiographic pathosis in a patient with

chronic facial pain.

8. Which of the following is not a reason for removingimpacted third molars in orthodontic patients?A. They can interfere with orthodontic tooth movement.B. They can interfere with orthognathic surgery.C. They can cause crowding of the lower incisors.D. They can impede eruptions of the second molar.

9. The most common pathologic condition involvingimpacted third molars is:A. Dental caries.B. Periodontitis.C. Pericoronitis.D. Cyst formation.

10. The most frequent site for the spread of a periocoronal infection is the:A. Submandibular space.B. Buccal vestibule.C. Pterygomandibular space.D. Buccal space.

To submit your CE Exercise answers, please use the answer sheet found within the CE Editorial Section of this issue and complete it

as follows: 1) Identify the Article; 2) Place an X in the appropriate box for each question; 3) Clip the answer sheet from the page and

mail it to the CE Department at Montage Media Corporation. For further instructions, please refer to the CE Editorial Section.

Answers to the 10 multiple-choice questions for this CE exercise are based on the article “Some Wisdom About the Removal of

Wisdom Teeth” by Daniel M. Laskin, DDS, MS, DSc (Hon).

WARNING: The Journal of Practical Hygiene encourages its readers to pursue further education when necessary

before implementing any new procedures expressed in this article. Reading an article in The Journal of Practical

Hygiene does not fully qualify you to incorporate these new techniques or procedures into your practice.

Learning Outcomes:• Review specific indications for removal of impacted third molars.

• Understand the arguments for their prophylactic removal.

• Identify specific instances when such teeth should not be removed.

CONTINUING EDUCATION (CE) EXERCISE NO. 5 CECONTINUING EDUCATION

5