RESUMO
Objective:To explore the differences of wear resistance of three kinds of glass ceramics and Wieland Zenostar zircona (Zenostar) , and to clarify their influencing factors.Methods:Zenostar were made into flat-shaped specimens (zirconia base sample group) and hemisphere-shaped specimens (zirconia pair grinding group) .There kinds of glass ceramics IPS Empress (Empress) , IPS e.max CAD (e.max) , VITA Suprinity (Suprinty) were used as base specimens.Each group was exposed to UMT-2testing machine to simulate the clinical service.The wear depthes of base specimens were detected by laser confocal scanning.Scanning electron microscope (SEM) was used to evaluate the wear surfaces.Results:In zirconia base sample group, there were no significant differences in the maximum wear depthes to Zenostar between the three kinds of glass ceramics (P＞0.05) .In zirconia pair grinding group, the maximum wear depthes ranked as follows:Zenostar group＜e.max group≈Empress group＜Suprinity group;there was no significant difference between e.max group and Empress group (P＞0.05) , but there were significant differences between other groups (P＜0.01) .The SEM results showed that the wearing surface of the Zenostar in zirconia base sample group was relatively smooth;whereas the wearing surface of Empress in zirconia pair grinding group was rougher with alarge area of clebris desquamation surface.Conclusion:The wear resistance of the three kinds of glass ceramics to Zenostar is related to the compositions and the chemical structures of materials.
RESUMO
Objective:To observe the development of dentinal microcracks after root canal preparation with there kinds of reciprocating nickel-titaninm instruments using an in situ cadaver model by means of micro-computed tomography (Micro CT),and to provide the reference for their clinical application.Methods:A total of 15 mandible bone specimens having at least the anterior teeth (n=60) with single root were selected and there was no dentina microcrack,then they were randomly divided into 4 groups (n=15) according to the preparation protocol:Wave One,Reciproc,One File and ProTaper Universal groups,and ProTaper Universal was used as control group.The root canals were prepared up to 25 # instruments in Wave One,Reciproc and One File groups and F2 instruments in ProTaper Universal groups.After the preparation procedures,the specimens were scanned by Micro CT again,and the number of dentinal microcracks were investigated and analyzed statistically.Results:Compared with ProTaper Universal group,the incidence rates in Wave One,Reciproc and One File groups were significantly reduced (P＜0.05).There were no statistical differences in the incidence rates of dentinal microcracks between Wave One,Reciproc and One File groups (P＞0.05).Conclusion:Root canal preparation can cause the dentinal microcracks,so it is important to choose the types of instruments.Root canals prepared with Reciproc,Wave One and One File produce less dentinal microcracks,which can decrease the risk of vertical root fracture.