| Objective:The purpose of this clinical study was to explore the relationship between the width ratios of maxillary anterior teeth,the width/height ratios of maxillary central incisor and the esthetic proportions among individual normal occlusion,and to provide reference for the esthetic design of anterior teeth.To determine if a correlation exists between the mathematical proportions of maxillary anterior teeth and 3 dental arch forms.The clinical crown perceived width,length,and width/length ratios and actual width,length,and width/length ratios of anterior teeth were measured in natural dentition,providing reference for the restoration of anterior teeth.Methods:1.A total of 300 Shanxi nationality participants in normal occlusion(110 males,190 females,aged 18-30 years)were recruited for this study,who attended in Shanxi Medical University from October 2020 to March 2021.Standardized digital photographs of the maxillary anterior tooth in natural head position and maxillary casts were obtained.The perceived width and length of the maxillary anterior teeth were measured on the images by using a software program(Image J),and the width ratios of maxillary anterior teeth and width/length ratios of maxillary central incisors were calculated and compared with 6 aesthetic ratios.The width ratios of maxillary anterior teeth were compared with golden proportion,Preston proportion,the recurring esthetic dental(RED)proportion,golden percentage and modified golden percentage.The width/length ratios of maxillary central incisors were compared with 0.75 ～ 0.85.The independent sample T test was used to compare the sex differences of each measurement project,Single sample T test was used to compare the difference of adjacent maxillary anterior teeth width ratios with golden proportion(0.618 and 0.618),Preston proportion(0.66 and 0.84),RED proportion(0.70 and 0.70).The percentage of anterior tooth width/intercanine width was calculated,the number and proportion of teeth conforming to golden percentage(25%,15%,10%)or modified golden percentage(22.5%,15%,12.5%)were calculated.The number and proportion of width/height ratio of maxillary central incisor in the range of 0.75～0.85 was counted.2.Standardized digital photographs of the maxillary anterior tooth in natural head position and maxillary casts were obtained.The perceived width and length of the maxillary anterior teeth were measured on the images by using a software program(Image J),and mathematical proportions,including width ratios and width-to-length ratios,were calculated for each.The casts were used to categorize each specimen into tapered,ovoid,or square groups by using a specific classification method,and the width ratios and width-to-height ratios of the 3 dental arch forms were compared.Statistical analysis was performed by using analysis of variance(ANOVA)or the Kruskal-Wallis H test to compare the mathematical proportions of maxillary anterior teeth among the 3dental arch forms.The intraclass correlation coefficient(ICC)was used to test the reliability of the investigators.3.From October 2020 to March 2021,a total of 228 participants in normal occlusion(72 males,156 females,aged 18-30 years)were recruited from Shanxi Medical University.Standardized digital photographs of the anterior teeth were used to measure of maxillary the perceived width,length,and to calculate the width/length ratios of central incisors,lateral incisors,canine;the maxillary casts were used to measure actual width,length,and to calculate the width/length ratios,then the differences of the two methods of clinical crown size were compared and the gender differences of each index were compared.Independent-samples t test or Kruskal-Wallis H test of two independent samples compared the differences between perceived width,length,and width/length ratios and actual width,length,and width/length ratios of anterior teeth,as well as the gender differences of each indicator.Results:1.The widths of maxillary central incisor,lateral incisor and canine were(8.50±0.52),(6.23 ±0.53)and(5.18 ±0.55)mm,respectively,the corresponding tooth of male[8.74 ±0.49),(6.37 ±0.52),(5.41 ±0.47)mm] was significantly higher than that of female[8.37 ±0.50),(6.15 ±0.52),(5.04 ±0.54)mm](t=6.40、3.55、6.23,P<0.05).The width ratio of maxillary lateral incisor/central incisor was 0.73 ±0.05,and there was no significant difference between genders(t=-1.06,P > 0.05).The width ratio of canine/lateral incisor was 0.84 ±0.10,male(0.85 ±0.10)was significantly higher than female(0.82 ±0.10),(t=2.42,P<0.05).Two width ratios of maxillary anterior teeth were significantly different from golden proportion and the RED proportion(t=38.50,35.74,P<0.05).The lateral incisor/central incisor was significantly different from that of Preston proportion(t=24.66,P < 0.05),while the canine/lateral incisor was not significantly different from that of Preston proportion(t=-0.92,P>0.05).In this study,a total of 0.0%(0/600)of central incisors,63%(378/600)of lateral incisors and 5.8%(35/600)of canines met the golden percentage ±1%.There were 42.8%(257/600)of central incisors,63%(378/600)of lateral incisors and 56.7%(340/600)of canines met the modified golden percentage ±1%.The width/height ratio of maxillary central incisors was0.86±0.08,and there was no significant difference between genders(t=-0.88,P>0.05).Only 36.3%(218/600)of the subjects in this study ranged from 0.75 to 0.85.2.Except for the width/length ratios of the central incisor,mathematical proportions were affected by the dental arch form.The perceived width ratios of the maxillary lateral incisor-to-central incisor gradually increased from the tapered arch to the ovoid arch and from the ovoid arch to the square arch,with mean ±standard deviation values of 0.71±0.04,0.73 ±0.05,and 0.79 ±0.06.For the maxillary perceived width ratios of canine-to-lateral incisor,the ovoid arch had the maximum perceived width ratios(0.86±0.10),followed by the tapered(0.82 ±0.10)and square arches(0.77 ±0.11).The width/length ratios of the central incisor were not affected by the arch form(P=0.075),and the width/length ratios of the lateral incisor increased as the arch form became flat,with respective values of 0.70 ±0.10,0.74 ±0.10,0.76 ±0.10.For the width/length ratios of the canine,the ovoid arch had the maximum perceived width ratios(0.58 ±0.10),followed by the tapered(0.53 ±0.10)and square arches(0.52 ±0.10).3.The perceived widths of central incisor,lateral incisor and canine were 8.40,6.21,5.15 mm,the perceived lengths were 9.89,8.44,9.02 mm,the perceived width/length ratios were 0.86,0.73,0.57,respectively.The actual widths were 8.65,7.26,8.24 mm,the actual lengths were 9.85,8.56,9.51 mm,the actual width/length ratios were 0.89,0.85,0.87,respectively.Except the lengths of central incisor and lateral incisor,there was significant difference between the perceived value and the actual value of other indicators(P<0.001).The perceived widths,lengths and actual widths and lengths of central incisor,lateral incisor and canine were significantly greater in males than in females(P<0.05).There was no gender difference between the perceived and actual width/length ratios of central incisor,lateral incisor and canine(P>0.05).Conclusion:1.Gender differences should be considered in the esthetic design of anterior teeth;for the width ratios of maxillary anterior teeth,the golden proportion,the RED proportion and golden percentage do not accord with the natural tooth morphological characteristics of Shanxi nationality college students in normal occlusion.Preston proportion and modified golden percentage are of more reference value.The width/height ratio of maxillary central incisors is different from 0.75～0.85.2.The mathematical proportions varied among the 3 dental arch forms,and the dental arch form should be considered during the prosthodontic design of maxillary anterior teeth.3.The data of this study can provide reference for the design of anterior tooth restoration for young people and the development of related products. |
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