The typical scenario is after orthodontic treatment has been completed, and now the patient is 18 to 21 years of age, he/she is sent back to the orthodontist by the family dentist, or oral surgeon for the recommendation for 3rd molar (wisdom teeth) removal. The myth is that 3rd molars will create pressure and cause the teeth to crowd particularly in the lower arch. The following is an annotated bibliography demonstrating that removal of 3rd molars for the exclusive purpose of relieving interdental pressure/crowding is unwarranted. There are numerous excellent reasons why 3rd molars (I had my 3rd molars removed) should be extracted and the oral surgeon, or family dentist can explain these, but the removal for orthodontic reasons is probably not justified.

The reason for relapse, or crowding to return after orthodontic treatment is not wearing retainers for a lifetime. Moorrees1 and others2 have demonstrated that arch perimeter/length instead of getting larger over time, decreases from age 5 into adulthood. This is the reason for crowding occurring over time. This trend of constriction of the dental arches occurs in orthodontically treated and untreated subjects.3,4 Parents of growing children and often dental practitioners might have difficulty accepting these concepts because the child is growing and one would logically conclude that the arch would enlarge as well.2

(1) Moorrees C. The dentition of the growing child. A longitudinal study of dental development between 3 and 18 years of age. Cambridge: Harvard University Press, 1959.

(2) Little RM. Stability and relapse: Early treatment of arch length deficiency. Am J Orthod Dentofacial Orthop 2002;121:578-81.

(3) Sinclair P, Little R. Maturation of untreated normal occlusions. Am J Orthod 1983;83:114-23.

(4)Little R, Riedel R. Postretention evaluation of stability and relapse: mandibular arches with generalized spacing. Am J Orthod Dentofacial Orthop 1989;95:37-41.

BIBLIOGRAPHY:

Southard TE Third molars and incisor crowding: When removal is unwarranted. JADA 123:75- 79, 1992  

Does removing unerupted mandibular third molars prevent incisor crowding? NO. The general tendency for mandibular incisors to crowd with age occurs well into adulthood with or without the presence of third molars.

van der Schoot EAM, Kuitert RB, van Ginkel FC, Prohl- Anderson B. Clinical relevance of third permanent molars in relation to crowding after orthodontic treatment. J. Dent. 25:167-169, 1997.

No relationship was found between crowding after orthodontic treatment and the presence or absence of permanent third molars.

Bishara S.E. Third molars: A dilemma! Or is it? A JO DO 115(6):628-633, 1999

There is no evidence to incriminate third molars as being the only or even the major etiologic factor in the post treatment changes in incisor alignment.

Gianelly, A Bidimensional Technique: Theory and Practice. GAC International, 2000, p. 192.

(The mandibular intercanine width is immutable to change. Arch length decreases over time). The changes in both arch length and width after (orthodontic) treatment appear to be characteristic changes in many studies. And long term expansion of the intercanine width in the mandibular arch is indistinctly rare, since most reports indicate that the intercanine width tends to return to its initial dimension after retention.

Little, RM, Riedel RA, Artun J. An evaluation of changes in mandibular anterior alignment from 10 to 20 years post retention. AJODO 93:423-428, 1988.

The only way to ensure continued satisfaction alignment post treatment is by the use of fixed, or removable retention for life.