Occlusal Analysis Of Restorations By Chairside CAD/CAM System With Functionally Generated Path Technique

Objective:It is the ultimate aim of clinicians to quickly obtain a restoration that is in concordance to the stomatognathic system.Aiming to provide evidence-based basis for clinical work,this study evaluates the occlusion accuracy of Chair-side CAD/CAM restorations with functionally generated path(FGP)technology through T-scan Ⅲ digital occlusal analysis system and Geomagic reverse engineering software.Method:A single-blind clinical crossover clinical trial was adopted,which included 10 participants who had a single posterior tooth defect to be restored.Each subject has three restorations designed differently using conventional fabrication(CON),biogeneric mode(BIO)and FGP technique(FGP).On the try-in visit,the three restorations were adjusted to the preparations randomly,then subjects were inquired to grade their feelings towards the occlusal interference of the crown with Likert’s 3-point scale.At the same time,the change of occlusion time and disclusion time(ΔOT & ΔDT)of above restorations was recorded and measured with T-scan Ⅲ.After best-matching the morphologies of restorations separately with the corresponding natural tooth in the contralateral arch by Geomagic reverse engineering software,the shape similarity value(volume/area),defined as the sum of the positive volumetric deviation and the absolute negative volumetric deviation,divided by the surface area of the difference image,was calculated.And changes of cusps and central fossa’s height(Δh)and inclination of the cusps(a)were measured as well.One-way ANOVA(α=0.05)was conducted to compare ΔOT,ΔDT and Δh among the 3 different designs(CON、BIO and FGP).Paired Student’s test(α=0.05)was used to compare volume/area among the three different designs(CON、BIO and FGP).The Kruskal-Wallis test(α = 0.05)was applying to comparing Likert’s 3-point scale among the 3 different crown designs.Outcome:OT was 0.16±0.05 s,0.28±0.14 s,0.31±0.12 s and 0.19±0.05 s for Baseline,CON,BIO and FGP,respectively,and DT was 0.63±0.29 s,0.91±0.26 s,1.11±0.36 s and 0.70±0.26 s for Baseline,CON,BIO and FGP,respectively.Changes in OT were calculated as 0.12±0.10 s,0.14±0.09 s and 0.03±0.02 s,respectively;and changes in DT were 0.28±0.28 s,0.48±0.34 s and 0.09±0.20 s,respectively.Statistical analysis revealed significant smaller changes in OT and DT in FGP than in CON and BIO(P>0.05).There was no significant difference between Group BIO and CON(P>0.05).The mean difference(volume/area)between natural tooth morphology and CON,BIO and FGP were 449.4±66.7μm,420.8±98.8μm and 400.1±84.1μm,respectively.The volume/area value of FGP group was significantly lower than that of BIO group and CON group(BIO: P<0.001,CON: P=0.026).There was no significant difference between BIO group and CON group(P=0.18).Changes in cusps’ height and inclination were significantly affected by the type of the cusps(functional or non-functional)(P<0.05)but by the different designs(CON,BIO or FGP)(P>0.05).The inclination of natural teeth,CON,BIO and FGP were 30.6±1.5°,19.1±1.8°,27.0±1.7°and 23.3±1.5°respectively.Overall,changes of functional and non-functional cusps were-435 μm and-24 μm,respectively.In addition,comparing to natural teeth.And the subjective feedback was better for FGP than CON and BIO.Conclusion:Compared with conventional fabrication and biogeneric reconstruction,occlusal morphology of functionally generated path technology seems more similar to natural tooth and receive a better feedback.Overall,FGP technique can improve occlusal precision and show more physiological harmonious relationship with stomatognathic system.Significant difference associated with cusps’ height and inclination exist between restorations made by different designs and the occlusal morphology of natural teeth.Functional cusps are generally low and rounded,and central pits are generally high.This provides the evidence-based basis for precise design and occlusion adjustments of the prosthesis clinically.