Abstract
ObjectivesIt is still not clear why impaction of third molars occurs. Craniofacial morphology and facial parameters have been discussed to be strong predictors for third molar impaction. Thus, this study aimed to investigate the effect of craniofacial morphology on erupted or impacted third molars in a German population sample.Materials and methodsErupted and impacted third molars in 2,484 participants from the Study of Health in Pomerania were assessed by whole-body magnetic resonance imaging. Markers of facial morphology were determined in 619 individuals of those participants in whose 421 participants (16.7%) had at least one impacted third molar. Craniofacial morphology was estimated as linear measurements and was associated in a cross-sectional study design with impacted and erupted third molars by multinomial logistic regression models. Erupted third molars were used as reference outcome category and regression models were adjusted for age and sex.ResultsMaximum Cranial Width (Eurion-Eurion distance) was significantly associated with impacted third molars (RR: 1.079; 95% confidence interval 1.028–1.132). This association was even more pronounced in the mandible. Individuals with a lower total anterior facial height (Nasion-Menton distance) and a lower facial index also have an increased risk for impacted third molars in the mandible (RR 0.953; 95% confidence interval 0.913–0.996 and RR: 0.943; 95% confidence interval 0.894–0.995). No significant associations of third molar status with facial width (Zygion-Zygion distance), and sagittal cranial dimension (Nasion-Sella distance; Sella-Basion distance) were observed.ConclusionIndividuals with an increased maximal cranial width have a higher risk for impaction of third molars in the mandible and in the maxilla. Individuals with a lower anterior total anterior facial height and lower facial index also have an increased risk for third molars impaction in the mandible. These findings could help orthodontic dentists, oral surgeons and oral and maxillofacial surgeons in decision-making for third molars removal in their treatment. These findings highlight the necessity of an additional analysis of the maximal cranial width by the Eurion- Eurion distance.
Highlights
Third molars are the most frequent impacted human teeth and their removal is a frequent surgical procedure in dentistry [1, 2]
Individuals with an increased maximal cranial width have a higher risk for impaction of third molars in the mandible and in the maxilla
Individuals with a lower anterior total anterior facial height and lower facial index have an increased risk for third molars impaction in the mandible. These findings could help orthodontic dentists, oral surgeons and oral and maxillofacial surgeons in decision-making for third molars removal in their treatment. These findings highlight the necessity of an additional analysis of the maximal cranial width by the Eurion- Eurion distance
Summary
Third molars are the most frequent impacted human teeth and their removal is a frequent surgical procedure in dentistry [1, 2]. A similar observation was noted in craniodental allometric analysis of monkeys, where smaller craniums and jaw sizes were discussed to lead to third molars being crowded out of the jaws into an evolutionary loss [4]. This crowding out was associated with a shortening of the face and the mandible [7]. Even though dental eruption sequence may be conserved phylogenetically in primates, it has been suggested that the dental eruption sequence could be related to body and brain size. [8, 9] Facial parameters like face height and face width are discussed as predictors for third molar impaction in humans [3, 10]
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