ABSTRACT
Objective: To measure and analyze the shoulder circumferences of adults' permanent teeth crown preparations based on data collected through the intraoral scanning, so as to provide dental anatomy data for clinical diagnosis and analysis. Methods: Intraoral scanning data of 840 complete crown preparations were collected, and were entrusted to the World Dental Laboratory Co., Ltd. in Fuzhou between March 2021 and June 2022. Except the data of the third molar, the rest data were categorized in terms of 14 tooth positions in the upper and lower jaw (each category involved 30 samples from male group and 30 samples from female group). Image measurement software was used to measure the shoulder circumferences of permanent teeth crown preparations. And analysis was conducted to reveal the difference of shoulder circumference diameters between male and female groups. And then they were grouped according to the mean value at each tooth position, on the premise that the difference between the maximum and minimum values and the mean value of the entire group was≤±1.00 mm. Analysis were further conducted to determine the differences of shoulder circumference diameters between each dental position and the differences between male and female in the same groups. Results: Bivariate analysis of variance showed that gender had no effect on the shoulder circumference of full crown preparations (F=0.55, P=1.457), while tooth position had a significant impact on the shoulder circumference of full crown preparations (F=273.15, P<0.001). The samples were classified into 5 groups according to the mean values of shoulder circumference diameters relating to each tooth position. Statistical analysis showed that Group 1, covering maxillary lateral incisor, mandibular central incisor and mandibular lateral incisor, had shoulder circumference with diameters of (16.62±2.21) mm; Group 2, consisting of maxillary central incisor, maxillary cusp, mandibular cusp, mandibular first premolar and mandibular second premolar, had diameters of (20.78±2.48) mm; Group 3, consisting of maxillary first premolar and maxillary second premolar, had diamerters of (22.09±2.72) mm; Group 4, covering maxillary first molar, maxillary second molar and mandibular first molar, had diamerters of (30.21±2.67) mm; while group 5, with mandibular second molar alone its member, had diamerters of (31.34±3.18) mm. The difference among the 5 groups was statistically significant (P<0.05). Conclusions: Significant differences of shoulder circumference diameters could be found between different tooth positions, while at the same tooth position, the differences between male and female are not significant. The 14 tooth positions could be grouped into 5 groups according to their shoulder circumference diameters. Future research could take the grouping as reference.
ABSTRACT
OBJECTIVE@#To analyze the esthetic proportions of maxillary anterior teeth in term of the apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown in 120 Chinese adults.@*METHODS@#Maxillary gypsum casts were obtained from the dental laboratories of stomatological hospitals in North China, Southeast China, and Southwest China, according to the inclusion criteria and exclusion criteria. Standardized digital photographs of each cast were recorded. The apparent widths and actual widths and heights of the central incisors, lateral incisors and canines were determined by ImageJ software for the calculation of apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown. The ideal apparent widths proportion (Golden proportion and Preston proportion) and width/height ratio (0.80) were tested. The gender, arch side, and regional differences were investigated.@*RESULTS@#The apparent widths proportion of the lateral/central incisor was 0.724±0.047, of the canine/lateral incisor was 0.814±0.092. The width/height ratio of the central incisor was 0.848±0.072, of the lateral incisor was 0.834±0.094, of the canine was 0.883±0.098. The esthetic proportions were different from the predicted ideal ratio (P < 0.001). The apparent widths proportion of lateral/central incisor was significantly larger in the right side than that in the left side (0.730± 0.044 vs. 0.718±0.050), and was significantly smaller in North China than that in Southwest China (0.711±0.051 vs. 0.731±0.044). The width/height ratio of the central incisor was significantly larger in the female than that in the male (0.855±0.074 vs. 0.835±0.068), and in the right side than that in the left side (0.855±0.073 vs. 0.842±0.072). The width/height ratio of the lateral incisor was significantly larger in the female than that in the male (0.843±0.097 vs. 0.817±0.084).@*CONCLUSION@#The apparent widths proportion of adjacent teeth and the width/height ratio of the clinical crown in Chinese adults are different from the foreigner's. The esthetic proportion parameters have significant population specificity, and the measurements cannot be generalized as well as it should be applied with caution.