Quantitative Study Of Clinical Parameters Of Anterior Teeth Aesthetics Based On The Data Acquired From Three-Dimensional Digital Models

Background:The positional relationship of the gingival zeniths(GZ)and the coordination of the gingival and crown morphology directly affects the aesthetic effect of the restoration and the satisfaction of the patient,which is the focus of the clinician.The periodontal biotype is closely related to the function and appearance of periodontal soft and hard tissues,and has become one of the key factors for the treatment of varic(?)s oral diseases.The clinicians need to correctly judge the periodontal biotype before treatment and make a corresponding treatment plan to achieve the desired therapeutic effect.With the advancement of computer technology and the rapid development of oral medical equipment and technology,the all-digital oral diagnosis and treatment will become the trend of stomatology.Two-dimensional data obtained by conventional methods such as image measurement software cannot meet the requirements.In order to provide a more accurate reference for digital aesthetic analysis and design,it is necessary to explore new measurement methods and quantify the positional relationship of the dentition.Purposes:This study quantitatively studied the clinical parameters of gingival and crown morphology of Chinese youth anterior teeth,aiming to provide reference for computer-aided anterior aesthetic analysis and design.Further analysis of the correlation between periodontal biotypes and crown morphological parameters provides objective criteria for periodontal biotypes.Methods:1.The maxillary and mandibular arch impressions of the experimental object were taken using alginate impression material,and the plaster model was obtained by pouring in dental stones.The three-dimensional digital model of the maxillary and mandibular jaws was obtained by scanning the plaster model with CEREC Omnicam intra-oral scanner.2.The 3D digitized model was imported into SpaceClaim software to establish the occlusal plane as the reference plane.The positional relationship between the GZs,the angle formed between the gingival line(GL)and the maxillary midline(GLA),the distance between the GZ of the lateral incisor and the gingival line(LID),and the distance between the GZ and the vertical bisected middle surface along the long axis of the clinical crown(VBMS)were measured.The Wicoxon signed rank test or paired sample t test was adopted to verify that there was no statistical difference of the data between left and right sides.Descriptive statistics were used to analyze the gingival morphology.3.The Gingival Angle(GA),Papilla Width(PW),Papilla Height(PH),Crown Length(CL),Crown Width(CW),Crown Width/Crown Length Ratio(CW/CL),Bucco-Lingual Width of the crown(BLW),Contact Surface Width(CSW),Contact Surface Height/Crown Length ratio(CS/CL),and the Arch Form(AF)were measured using SpaceClaim software.Periodontal biotypes were determined through the transparency of the periodontal probe through the gingival sulcus.Logistic regression was used to analyze the independent influencing factors of periodontal biotypes,and the receiver operating characteristic curve(ROC curve)was used to analyze the optimal cutoff value of independent influencing factors.Results:1.There were no statistical differences in the parameters of the crown and gingival morphology between the left and right sides.2.The GLA average was 92.7±3.2°.The GZ ofthe canine,lateral incisor and left central incisor were located to the GZ of the right central incisor coronally at 0.68±0.91mm,0.65±0.66mm,and apically at 0.12±0.42mm respectively.80.3%of the lateral incisors GZ are located coronally to the GL,and the LID was 0.65±0.92mm.The GZ of the canine,lateral incisor and central incisor were located distally to the VBMS at 0.00±0.06mm,0.27±0.19mm.,and 0.73±0.21mm,respectively.3.The GA average of the maxillary central incisors,lateral incisors and canines were 98.19±7.69°,96.24±10,030°and 89.45±6.63°,respectively,and the PW average were 10.05±0.79 mm,7.83±0.60 mm and 7.97±0.65 mm,respectively.The thick biotype accounts for 69.6%,and the parameters of gender,GA,PW,PH,CW and CW/CL are significantly correlated with the periodontal biotypes(P?0.043).GA(OR=1.206)and PW(OR=5.048)are the independent predictive factors of the periodontal biotypes,their areas under the ROC curve(AUC)are 0.807 and 0.881,respectively,and their optimal cutoff values are 95.950 and 10.01mm respectively.Conclusion:1.The crown and gingival morphology of the maxillary anterior teeth is symmetrical when taking the occlusal plane as the reference plane.The clinical parameters of crown and gingival morphology obtained can provide reference for the analysis and design of anterior aesthetic restoration2.The GZ of canine is located coronally to the GZ of central incisor,and most GZs of the lateral incisors are located coronally to the GL.The GZs of the maxillary anterior teeth usually locate distally to the VBMS,and the direction and degree of the GZ deviation from the VBMS are also related to tooth position.3.The thin biotype accounts for a small portion,and the GA and PW are the independent influence factors of the periodontal biotypes.When the GA is 95.95° and the PW is 10.01mm,it is the optimal cutoff value to categorize experimental subjects into thick biotype.