Bond Performance Research Of New-type Nano-hydroxyapatite Composite For Tooth Restoration

Objective:Restoratively dental materials must have good physical and chemical and mechanical properties. It also requires good biocompatibility, and non-toxic to human security. A new type of nano-hydroxyapatite composite resin has been successfully developed. Premenstrual experiments have confirmed that the material has good mechanical properties and biocompatibility. The material also was bioactive. This study used homemade nano-hydroxyapatite composite to test the permeability, shear bonding strength and other mechanical properties of the new material. Through the study, we can evaluate the bonding ability between the tooth and materials to provide experimental basis for its clinical application materials.Methods:Part1:Preparation of new nano-hydroxyapatite composite resin by55%proportion of n-HA in composite materials:The surface of the n-HA particles was modified by using a silane coupling agent KH-570. The composite materials were composed of a visible light-curing monomer mixture as a matrix and n-HA as a inorganic filler. Mix the n-HA and matrix as the proportion of55:45to prepare a composite material.Part2:Microleakage experiments:30healthy premolars extracted were randomly assigned to3groups according to the material employed:New nano-hydroxyapatite composite resin, Karisma composite resin, glass ionomer cement. After the thermal cycling, the teeth were immersed in2%methylene blue dye, and the microleakage depth between the new nano-hydroxyapatite composite and tooth structure were observed.Part3:shearing experiments:36healthy molars extracted were randomly assigned to3groups according to the material employed:new nano-hydroxyapatite composite resin, composite resin karisma, glass ionomer cement. After the thermal cycling, the data of shear bond strength was recorded, and the type of specimen fracture section was observed under stereo microscope.Part4:Observe the bonding interface:15healthy molars extracted were randomly assigned to3groups according to the material employed:new nano-hydroxyapatite composite resin, composite resin karisma,glass ionomer cement. After the thermal cycling, to produce the dental grinding. The bonding interface was observed under the SEM.Results:1. The new nano-hydroxyapatite composite resin was successfully produced with better color and plasticity.2. The microleakage depth of group A、B、C seperately were(1.20±0.81),(1.94±0.70),(1.73±0.54) mm, no statistically significant differences were found among3groups. The depth of methylene blue dye between the charisma and tooth reached the bottom of the cavity; the depth of methylene blue dye between the glass ionomer cement and tooth reached the under of enamel dentine community and the above of the bottom of the cavity; the depth of methylene blue dye between the new nano-hydroxyapatite composite resin and tooth reached the above of enamel dentine community, there was no significant difference in the degree of microleakage.3. The average shear bonding strength of new nano-hydroxyapatite composite resin was (11.23±4.6082) N/mm2, and that of composite resin charisma and glass ionomer cement separately was (14.49±7.9855) N/mm2and (10.08±6.3701) N/mm2, no statistically significant differences were found among3groups. The bonding fracture mode of each specimen had no significant difference.4. The gap between composite resin charisma and enamel was small; the gap between new nano-hydroxyapatite composite resin and enamel bonding interface was smaller; but there was existed a large gap between glass ionomer cement and enamel.Conclusion:The studys of microleakage and shearing and the results of bonding interface all showed that: as a new dental restorative material, new nano-hydroxyapatite composite resin has superior bonding ability, its good performance of marginal sealing can meet the need of clinical therapy.