Preliminary Studies On Cellular Biocompatibility Of New CAD/CAM Resin Composite Ceramic

Backgroud and PurposeClinical application of all-ceramic restoration in China gradually increased in recent years.As a substitute for PFM,all-ceramic become the focus of dental restorative materials.New machinable resin composite ceramic material is not only lower costs,modulus of elasticity and hardness also close to natural tooth dentin,becoming a better choice for crown repair materials.However with the current CAD/CAM technology for cutting crown repair materials,the margin of restoration is still not fully fit.There is a small amount of adhesive agent residue around the crown on the clinical.In order to make CAD / CAM composite resin ceramic as a domestic resin ceramic materials,this research combined clinical actual,simulating crown edge situation with a few of bonding agent exposed,using a composite resin ceramic with light curing and zirconia for comparison,to preliminary detect and evaluate the biocompatibility of CAD/CAM composite resin ceramic,providing experiment basis for clinical application.Materials and MethodsThis experiment refer to the GB/T 16175-2008 Biological evaluation test methods for medical organic siliconmaterials,GB/T 16886.5-2003 Biological evaluation of medical devices-Part5: Test for in vitro cytotoxicity,YYT 0127.1-1993 Biological test methods of dental materials---Hemolysis test,GB/T 16886.10-2000 and ISO10993-10-2010 Biological evaluation of medical devices--Part 10: Tests for irritation and skin sensitization,as well as YYT/ 0279-1995 Biological test methods of dental materials--the oral mucosa irritation test.CAD/CAM composite resin ceramic,CAD/CAM zirconia ceramics,light-curing composite resin ceramic and with adhesive agent were tested by cell proliferation test,hemolytic test and oral mucosa irritation test to evaluate their safety.1.Standard test piece preparation: Discs of UR,UZ and SC,5mm in diameter and 2mm thick,were produced.Partially specimens were taken from each group and coated with a thin layer of Rely X^TM U200 resin adhesive（6mg per piece）in only one side with UV curing for 40 s,as the UR+,UZ+ and SC+ standard test-piece.Medical guttapercha test piece were maded by Teflon mold with 5mm of internal diameter and 2mm thick.Two holes were maded in the central of the specimens as the buttons with the aperture about 1mm.2.In vitro cell proliferation test: L929 cell was prepared into a series of concentration gradients cell suspension.According to the L929 cell growth situation in laboratory,established standard curve of the cell growth and metabolism,to determine cell number used in the proliferation test and the incubation time after adding CCK-8.L929 Cells and UR,UZ,SC,UR+,UZ+ SC+ leach liquor were added into 96-wells plates.Negative control is the medium.After 1,3,5 days,plates were added CCK-8.The optical density（OD value）was tested by Universal Microplate Spectrophotometer to calculate the cell proliferation rate.The cell morphology was observed by an inverted microscope.3.Acute hemolysis test: UR,UZ,and SC,UR+,UZ+ and SC+ samples were put into the centrifuge tubes with 0.9% saline solution.Positive control is distilled water.Negative control is 0.9% saline solution.Dilute anticoagulant fresh bloodof rabbit 0.2ml was also added into each tube.After incubation and centrifugation,absorbance value in each group was measured by type 722 spectrophotometer,in order to calculate the hemolysis rate of each material.4.Oral mucosa irritation test: Choose 60-70 days male Syrian Golden hamsters,in 6 groups（n=5）.Respectively the control group on the left and the experimental samples on the right side,test pieces were sutured on the cheek pouches.Hamsters were sacrificed after 2 weeks to observe the mucosa around the specimen.Tissue biopsies with HE stained were observed by optical microscopy and scored.Results1.Cell proliferation test result: UZ、UR and SC group cell morphology was normal during the observation period.L929 cells showed better cell proliferation rate respectively cultured with UZ and UZ+,no statistically significant difference compared with the negative control（P>0.05）in OD value.The cell proliferation rate of UR and SC groups was 87.1% and 75.1% after 5 days.Their OD values had no statistically significant difference compared with the negative control group（P>0.05）.The cell proliferation rate of UR+ and SC+ on the 5th day was 70.6% and 58.4%.Their OD values compared with negative control group had a statistically significant difference（P<0.05）.2.Hemolysis test result: Hemolytic rate of saline group was 0,of distilled water was 100%.Hemolytic rate of UZ,UZ+,UR,UR+,SC,SC+ group material was 0.3%,1.6%,2.4%,3.7% and 4.4%,less than 5%.It can be considered that all the experimental materials will not induce acute hemolysis3.Oral mucous irritation test results: It can be observed directly by eyes that the mucosa was normal where contacted with UZ,UZ+,UR,UR+,SC,SC+ samples,without erythema.Cheek pouch tissues were alse normal under microscope,without significant difference with the negative control group.The score is less 4,which can be considered that the experimental materials were irritation-free for oral mucosa.Conclusions1.CAD/CAM zirconia blocks and CAD/CAM resin ceramic blocks have better cellular biocompatibility than light-cured resin ceramics.Adhensive agent slightly inhibited cell proliferation rates,especially for the light-cured resin ceramics.2.CAD/CAM zirconia,CAD/CAM resin ceramic and light-cured resin ceramic have good blood cell compatibility,no matter with or without adhesive agent.3.CAD/CAM zirconia,CAD/CAM resin ceramic and light-cured resin ceramic have good cellular compatibility of oral mucosa epithelial cells,no matter with or without adhesive agent.