Influence Of Design Patterns Of Co-Cr Alloy Inner Crown On The Marginal Microleakage Of Endocrowns

Endocrown is an effective restorative technique for endodontically treated molars which relies on the pulp chamber as the retentive resource.Particularly suitable for molars with a short clinical crown, occlusal space, and the remaining tooth structure enough to obtain stable and long-term bonding effect. This prothetic method is more convenient than traditional prothetic methods,the operating time is shorter and easier,and reduction of the operation steps reduces the cost,also can be avoided the trauma and pain caused by crown lengthening surgery.However,In order to minimize the amount of tooth preparation and increase the abutment tooth resistance,the margin design of endocrown always use flat margin,Its margin line is longer,will lead to increased microleakage.The risk of plaque formation and caries was increased, and the effect of long-term repair was affected.But there is no report about the influence of this margin design on the microleakage.How to make the design and manufacture of endocrown more reasonable,is a problem to be solved urgently.CAD/CAM all ceramic is a kind of material which is often used in the manufacture of endocrown.But for a considerable number of patients, the higher cost is still difficult to bear.Co-Cr alloy is one of the most commonly used materials,because the good biocompatibility, mechanical properties, aesthetic and low price.Therefore,the purpose of this study was to compare the effect of different processing technologies,different margin designs and different inner crown thickness of cobalt chromium alloy porcelain endocrown,to obtain the optimal crown design of endocrown,hope to provide the reference for the clinical application of endodontically molar restored with endocrown.PART ?:Evaluation of the marginal microleakage of endocrown fabricated with three different processing technologiesObjective: This study evaluates endocrown marginal microleakage fabricated by three technologies of selective laser melting,cast and CAD/CAM milling.Methods:32 isolated mandibular molars were selected and randomly divided into three different groups, casting( Group A) and selective laser melting(Group B) and CAD/CAM milling(Group C) were used to make cobalt-chromium alloy porcelain endocrowns(n=8). After experiencing 5000 times of thermocycling, immersed in a 2.0% basic red fuchsine dye solution for 24 hours.Sectioned along the buccolingual,observing restoration marginal dye leakage by stereomicroscope, and the microleakage depth were analyzed with one-way ANOVA and Duncan multiple comparison. Results: The mean value of marginal microleakage ranked from high to low were groupA,groupC,groupB. The influence of processing technologies on the marginal microleakage has significant statistical difference(P<0.05). Conclusion:Cobalt-chromium alloy endocrown marginal microleakage fabricated by selective laser melting technology is superior to endocrown fabricated by cast and milling.PART ?:The effect of margin designs on the microleakage of Co-Cr PFM endocrownsObjective: To study the effect of different finish line design on the marginal microleakage of cobalt-chromium alloy porcelain endocrowns.Methods:32 isolated mandibular molars were selected and randomly divided into four different finishing line design groups,which were group A with shoulder design , group B with bevel design , group C with chamfer design and group D with flat margin.The inner crown of cobalt-chromium alloy porcelain endocrowns were fabricated by SLM technology,conventional porcelain and adhesived with Multilink N resin cement.After experiencing 5000 times of thermocycling, the specimens were immersed in a 2.0%basic red fuchsine dye solution for 24 hours.Each tooth was sectioned along the buccolingual direction into four equal parts and the marginal dye leakage was observed by NIKON SMZ1500 stereomicroscope. The marginal microleakage grade of four groups were analyzed with one-way ANOVA and Duncan multiple comparison.Results: The mean value of marginal microleakage ranked from high to low were group D,group A,group B ,groupC, the influence of finishing line design on the marginal microleakage has significant statistical difference(P<0.05). Conclusion:For cobalt-chromium alloy porcelain endocrowns, the chamfer design is more helpful to reducing microleakage.PART ?:Influence of inner crown thickness on the marginal microleakage of co-cr alloy porcelain endocrownsObjective:To investigate the influence of the thickness of inner crown on the marginal microleakage of cobalt chromium alloy porcelain endocrown.Method:32 isolated mandibular molars were selected,and randomly divided into 0.3mm (group A),0.5mm (group B), 0.8mm (group C), 1.0mm (group D) four groups(n=8).The cobalt-chromium alloy endocrowns were fabricated by SLM technology.After porcelain, Bonded with the glass Ionomer cement. After experiencing 5000 times of thermocycling, immersed in a 2.0% basic red fuchsine dye solution for 24 hours. Sectioned along the tooth buccolingual direction for four equal parts ,observing restoration marginal dye leakage by NIKON SMZ1500 stereomicroscope and assessed. Statistical analysis of the indicators of microleakage in each group.Results:The mean value of marginal microleakage ranked from high to low were groupD,groupA,groupC,groupB,the influence of inner crown thickness on the marginal microleakage has significant statistical difference(P<0.05).Conclusion:From the point of view of the micro leakage, the thickness of the inner crown of 0.5mm is the best choice for the clinical treatment.