Purpose: To evaluate the prevalence of fourth molars and determine if there are differences in occurrence with respect to gender, race, laterality, and site.
Patients and methods: The charts and panoramic radiographs of all patients referred for third molar consultation between November 2008 and October 2010 at Misawa, US Air Base, Japan were reviewed and data collected included age, gender, and race. Inclusion criteria were minimum age of 18 years and no history of prior third molar surgery. If fourth molars were present, their number, location, size, and shape were noted. Patients with fourth molars were compared to patients without fourth molars with respect to gender and race. Percentages were calculated for laterality and site of occurrence as well. If differences were observed in these parameters, the χ(2) test was used to evaluate if the observed differences were statistically significant.
Results: Four hundred nine patients met the inclusion criteria and their charts and panoramic radiographs were reviewed. Fourth molars were observed in 2.2% of the patients. Their prevalence was slightly higher in males (2.2%) than in females (2.1%). They were notably more common in black patients (6.4%) than in whites (0.9%) (P < .005) and they presented more often in the maxilla (78%) than in the mandible (22%) but this difference was not statistically significant (P < .09). Most patients (55%) with fourth molars had them unilaterally. The maxillary fourth molars were typically peg-shaped and small, while the mandibular ones resembled miniature mandibular third molars.
Conclusions: The prevalence of fourth molars in this population is 2%. They appear to be more common in black patients and tend to occur mostly in the maxilla unilaterally. When present, the decision to remove these supernumerary teeth should be based on a risk/benefit analysis similar to that of third molars.
Published by Elsevier Inc.