Prevalence and patterns of tooth agenesis among malocclusion classes in a Japanese orthodontic population

Prevalence and patterns of tooth agenesis among patients aged 12-22 years: A retrospective study

Objective

This study aimed to establish the prevalence and patterns of nonsyndromic tooth agenesis in patients referred to a tertiary health care facility.

Methods

The intraoral records and panoramic radiographs of 9,874 patients aged 12–22 years were evaluated. The study group included 716 patients (371 male, 345 female) with non-syndromic agenesis of at least one tooth (except the third molars). The study data were assessed using descriptive statistics, chi-square test, and Mann–Whitney U test, while patterns were evaluated using a tooth agenesis code (TAC) tool.

Results

A total of 1,627 congenitally missing teeth, were found in patients with non-syndromic tooth agenesis, with an average of 2.27 missing teeth per patient. The prevalence of tooth agenesis was 7.25%, and the most commonly missing teeth were the left mandibular second premolars (10.17%). The age group comparison revealed no significant difference in the median number of missing teeth per patient according to the cutoff values for ages between 12 and 22 years. When the missing teeth were examined separately according to quadrants, 114 different tooth agenesis patterns (upper right quadrant = 28, upper left quadrant = 27, lower left quadrant = 31, and lower right quadrant = 28) were identified, and 81 of these patterns appeared only once.

Conclusions

This study highlights the benefits of applying the TAC tool in a large sample population. The application of the TAC tool in such studies will enable the development of template treatment plans by determining homogenous patterns of tooth agenesis in certain populations.

Size and bridging of the sella turcica in Japanese orthodontic patients with tooth agenesis

The purpose of this study was to investigate the association between the size and bridging of the sella turcica and tooth agenesis, and whether the likelihood of second premolar agenesis can be predicted from the sella turcica size and bridging in Japanese orthodontic patients. Patients were divided into four groups of 32: groups 1 and 2 consisted of patients with agenesis of the maxillary and mandibular second premolars, respectively; group 3, patients with severe tooth agenesis; and group 4, patients without tooth agenesis. Each group was divided into two subgroups of 16 each based on the patient's age: patients under 14 years of age (groups 1A through 4A, group A) and patients 14 years of age or older (groups 1B through 4B, group B). Lateral cephalograms were used to evaluate the size and bridging of the sella turcica. The interclinoidal distance (ID) was significantly shorter in groups 1 and 3 than in group 4, and in group 3 than in group 2. Group B exhibited significantly greater depth, diameter, area, and perimeter of the sella turcica than group A. Groups 3 and 1B had a significantly higher prevalence of sella turcica bridging than groups 4 and 4B, respectively. Maxillary second premolar agenesis and severe tooth agenesis were associated with a reduced ID irrespective of age and increased occurrence of sella turcica bridging. The early emergence in life of a short ID might be a predictor of possible second premolar agenesis in later life.