Three-dimensional Gingival Morphology In The Aesthetic Zone Of Maxillary Anterior Teeth:A Cone Beam CT Analysis

Objective: In this study,we developed a new method of using Cone-Beam Computed Tomography(CBCT)in conjunction with novel radiocontrast materials for indirect imaging of gingival morphology,and then investigated the feasibility,accuracy of the method,and reliability of judging gingival phenotype.Based on this method,we measured and analyzed the three-dimensional morphology of the maxillary anterior teeth.Methods: The gingival thickness(GT)at 2 mm below the gingival margin and the width of keratinized gingiva(KGW)were measured directly in 180 maxillary anterior teeth from healthy volunteers.The composition of light-cure gingival barrier resin and iohexol injection was applied to the measurement area,then the positioning wires were set up to take CBCT.Then used CBCT imaging to measure the GT at 2mm below the gingival margin,KGW and supracrestal gingiva tissue(SGT).Compared the accuracy of two methods for measuring soft tissue and analyzed the differences and relationship of these parameters under different gingival phenotypes.Results: In comparison to the direct puncture method,the approach of CBCT in conjunction with the novel radiocontrast materials method demonstrated good reproducibility(P>0.05)and reliability(ICC>0.9)when measuring the GT and the KGW on the labial side.The GT and KGW measured by direct puncture method were(1.19±0.24)mm and(5.09±0.69)mm,then measured by CBCT were(1.20±0.24)mm and(5.11±0.68)mm.There was no significant difference between the two methods(P>0.05).The concordance of two approaches to classify gingival phenotypes which was examined by Kappa concordance test showed good consistency(Kappa=0.882).There was no significant statistical differences between the two methods(P>0.05).The central incisors had the thickest GT in the maxillary anterior region,while the canines had the thinnest(P<0.01).The GT of male’s central and lateral incisors were thicker than that of females(P<0.05),and the KGW were wider than that of canines(P<0.05).The mean distance of SGT in central incisors was greater than canines(P<0.05).Correlation analysis: GT-SGT,KGW-SGT and GT-KGW are all positively correlated with each other(r=0.315,0.287,0.406,P<0.01).The thick gingival phenotype was greater than the thin gingival phenotype in the KGW of lateral incisors and canines,as well as the SGT height of canines(P<0.05).Conclusions: 1.CBCT in conjunction with novel radiocontrast materials method could clearly develop the gingival morphology,which shows great feasibility and reliability for measuring oral soft tissue.2.CBCT in conjunction with novel radiocontrast materials method could achieve precise measurement of gingival thickness and keratinized gingival width in the anterior maxillary teeth.3.CBCT in conjunction with novel radiocontrast materials method can serve as a reliable method for determining gingival phenotype.4.There are significant differences in KGW and SGT measurement results among different gingival phenotypes in the anterior maxillary teeth.5.GT is positively correlated with KGW and SGT,while KGW is positively correlated with SGT.In summary,CBCT in conjunction with novel radiocontrast materials method is a non-invasive,convenient and accurate method for measuring gingival soft tissue.There are certain differences among the characteristics of different gingival phenotypes,and personalized treatment plans can be formulated based on gingival phenotype in clinical therapy.