| ObjectiveThe use of computer aided design and computer aided manufacturing(CAD/CAM)to design and fabricate one-piece fiber post and core together with three other commonly used post and core materials to repair the mandibular premolar funnel-shaped root canal through the metallurgical microscope Scanning electron microscopy(SEM)was used to observe the root canal adaptability of the post and core.Universal test machine was used to study the fracture resistance of the post and core.The evaluation was more conducive to the repair and preservation of the funnel-shaped root canal,providing experimental basis and reference for clinical application.MethodsForty-four mandibular premolars of similar size and shape were collected and prepared as funnel-shaped root canals.They were randomly divided into four groups by random number table method.Group A: CAD/CAM integrated glass fiber post and core repair;Group B: cast metal piles.Nuclear remediation;Group C: Indirect repair of pre-formed fiber piles with resin post cores;Group D:Direct repair of pre-formed fiber piles with resin post-cores and uniform preparation of cast metal crowns.One sample tooth was randomly selected from each group,and a thickness of 1.0mm tooth section was made at adistance from the apical direction of 12.0mm,9.0mm,and 6.0mm in the direction of the long axis of the vertical sample tooth,using a metallographic microscope at 500 magnification and SEM at At 500 magnifications,the adhesive thickness and adhesiveness between the post and core and the root canal wall at four different points of the root,neck,mid-root,and apical transection were observed,and the root canals of the four groups were compared.Sex;The remaining samples in the four groups were embedded separately and passed through a universal testing machine.The tip of the 30°tilted tooth was loaded at a speed of 1.0mm/min.The maximum bending load and fracture of the fractured tooth were recorded.ResultsUnder the metallographic microscope observation results: In addition to the Group A and Group B in the two groups of root neck,roots,root apex between the three sites and Group C roots,root apex between the two parts of the bond thickness test by variance There were no significant differences(P>0.05),but there were significant differences between the other groups(P<0.05).The mean thickness(μm)of adhesive between the post-core tooth post and the root canal wall in group 4 was 2.5±0.2 in Group A,4.2±0.3 in Group B,7.7±0.5 in Group C,and 60.8±27.6 in Group D.Observation under scanning electron microscope: The material of post and core in Group A and Group B is uniform,and the thickness of the adhesive in the root and neck,the middle of the root,and the apical area of the sample tooth is very thin,and there is no obvious change in the thickness of the three parts;Group C,The core material of the Group D of core resin fillers varies in size.The adhesive from the root of the sample to the root tip of the sample is gradually thickened.Bubbles are visible in the adhesive at the root tip and in the resin contact area between the fiber post and the post and core.The results of the bending resistance test: The maximum bending load(N)was respectively GroupA:494.9±31.1,Group B:530.5±43.6,Group C: 351.1±38.9,Group D: 251.0±30.2.Except that the difference between Group A and Group B was not statistically significant(P>0.05),the differences among other groups were statistically significant(P<0.05).The proportion of specimens destroyed by the four groups of specimens after the flexural strength test was repairable destruction was:Group A: 70.0%;Group B: 10.0%;Group C: 40.0%;Group D:30.0%.ConclusionsThe use of CAD/CAM integrated fiber post and core to repair the mandibular premolar funnel root canal has better root canal suitability and better anti-load performance than the other three traditional methods of repairing,and may achieve better results in clinical applications. |
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