Effect Of Interproximal Distance And Different Impression Methods On The Accuracy Of Class Ⅱ Inlay Models

Purpose:The goal of this experiment is to evaluate the effect of interproximal distance and different impression methods on the accuracy of Class II cavity models.By controlling the distance between adjacent and abutment teeth and comparing the accuracy of models made using traditional and digital methods.Methods:Firstly,a Class II cavity preparation was made on the disto-occlusal surface of the artificial mandibular first molar and scanned by a WIELAND scanner to obtain the original data,which was designated as the control group.The mandibular first and second molars were then fixed on a dental pantom head,and the distance between adjacent and abutment teeth was adjusted to 0.6,0.8,and 1.0 mm.Three different impression methods were used in the experimental groups(n=10 for each group).The model group used a traditional silicone rubber imprint approach to create a plaster model,which was then scanned with the WIELAND scanner to create a digital model.The intraoral scanning group obtained a digital model using a Medit i500 intraoral scanner.The printing group used a Medit i500 intraoral scanner to generate a digital model,which was then paired with a 3D printer to generate a 3D printed model,which was then scanned using the WIELAND scanner to generate a digital model.Nine sets of digital models were obtained in total,with 90 samples.Reverse engineering software was used to analyze the STL files,and the three-dimensional best-fit alignment method was used to measure the average deviation value for quantitative analysis of model accuracy,followed by qualitative analysis of accuracy for the experimental and control groups.Results:The two-factor ANOVA variance analysis revealed that there was no significant difference in accuracy between the model and control groups at distances of 0.6,0.8,and 1.0 mm(P>0.05),while there was a significant difference in accuracy for the intraoral scanning group and the printing group at different distances,with the difference in the intraoral scanning group being more significant,reaching P=0.002.It was found that for the same distance,there were differences in model accuracy among different model-making methods,which had statistical significance(P<0.0001).Post-hoc multiple comparisons showed that there was no interaction between distance and impression method on model accuracy(P=0.2104).In terms of precision comparison,the precision of models in the model group,intraoral scanning group,and printing group was significantly better at a distance of 1.0 mm than at 0.6mm(P<0.001).In the plaster model group,there was a statistically significant difference in precision between distances of 0.6 mm,0.8 mm,and 1.0 mm(P<0.05),while in the intraoral scanning and printing groups,there was a significant statistical difference in precision between distances(P<0.001).For the same distance,the model accuracy of the intraoral scanning group was better than that of the traditional plaster group and the 3D printing resin model group(P<0.01).Conclusion:In Class II cavity preparation,the interproximal distance and the model-making method both have an impact on model accuracy,and the accuracy of models increases with enlarged distance.Digital cavity preparation models are more accurate than plaster and 3D printing models.