Relationship Between The Labial Gingival Thickness And The Alveolar Bone Of Maxillary Anterior Teeth

Objective:The aim of this study is to measure the periodontal morphometric parameters of the maxillary anterior teeth,and to analysis the relationship between the gingival thickness and the alveolar bone thickness and morphology using cone-beam computed tomography(CBCT),which will provide scientific basis for better understanding of the periodontal biotype.Thus clinicians can make the most use of the characteristics of periodontal soft and hard tissue to provide more accurate,safe and effective treatment.Methods:Twenty periodontally healthy subjects were recruited.The CBCT was used for measuring the gingival thickness at the level of 2 mm apical to the gingival margin(GT),labial bone thickness at the distance of 3mm,5mm,and 7mm apical to the cemento-enamel junction(CEJ),the vertical distance from the cemento-enamel junction to the bone crest(CEJ-BC),and the width to length ratio of the crown(CW/CL).Ten subjects were randomly selected to measure the GT by transgingival method and compare with the data measured by CBCT.The variance of each index between different teeth was analyzed by ANOVA,and the LSD-t test was used for comparison between the two groups.The characteristics were compared between the different biotypes using the two-sample t-test.Pearson's correlation analysis was used for the reproducibility of the one examiner and correlation of each index.Results:1.The mean labial gingival thickness of maxillary anterior teeth was 1.22±0.27 mm by transgingival method,while it was 1.27±0.29 mm by the CBCT.There was no significant difference between the two groups(P=0.288).2.Mean labial bone thickness of all maxillary anterior teeth is 0.85±0.36 mm,and the mean labial bone thickness of the central incisors,lateral incisors,and canines were1.07±0.34 mm,0.68±0.26 mm,and 0.80±0.36 mm,respectively.The frequency of occurrence of sites with less than 1 mm of labial bone thickness was higher: 48.3%,68.3%,and 77.5% of the sites were less than 1mm at 3 mm,5 mm,and 7 mm apical to the CEJ,respectively.The proportions of sites with bone thickness less 1mm were 52%,78%,and 66% for maxillary central incisor,lateral incisor,and caine,respectively.3.The alveolar bone thickness(0.52±0.23mm)was thinner in the thin biotype group than in the thick biotype group(0.96±0.32mm),and CEJ-BC was longer(2.39±0.91 mm,2.02±0.54 mm,respectively),and the difference was statistically significant(P<0.05).4.The gingival thickness at the level of 2 mm apical to the gingival margin of the upper anterior teeth was positively correlated with the mean labial bone thickness and each level of the alveolar bone(r=0.714,P<0.001;r=0.597,P<0.001;r=0.608,P<0.001;r=0.543,P<0.001).CEJ-BC was negatively correlated with the gingival thickness and the labial bone thickness,respectively(r=-0.374,P<0.001;r=-0.432,P<0.001).Conclusion:1.CBCT has high accuracy in measuring gingival thickness.2.The proportion of thin biotype on the maxillary anterior teeth is less than that of thick biotype.3.The gingival thickness of the maxillary anterior teeth is positively correlated with the labial bone thickness at different level apical to the CEJ.