Study On The Improvement Of Primary Teeth Etching And Resin Adhesive System

Etching process is a crucial technique to the caries restorative treatment and the orthodontic bracket adhesion, and the etching time can affect the bonding strength of composite resin to enamel. However, it can be found that there are different results reported on etching time of primary teeth in comparison with the data from the textbook of our country and from the foreign reports. In experiment I, morphologies of enamel surface and interface etched under different time were observed with SEM and the shear bond strength (SBS) of composite resin to primary enamel was also investigated. At last, an appropriate etching time for primary enamel was obtained.It is well known that the enamel demineralization around fixed orthodontic appliances during active treatment is a hard nut to crack. A bracket in the oral cavity and any excess resin flash will bring on the oral bacterial accumulation and the bacterial plaque will be formed subsequently. It has been recognized that the oral bacterial plaque and their metabolic products are deemed to the main etiological factors of formation and development of white spots under the risk of demineralization of the surrounding enamel, which will affect the health and the appearance of a patient' teeth. In experiment II, LZB-GC antibacterial agent was applied in dental enamel bonding resin (DEBR), and the properties of LZB-GC antibacterial agent and antibacterial DEBR were characterized. The antibacterial abilities of DEBR were investigated by agar disc-diffusion and film tight-adhering tests respectively. Moreover, the shear bond strength of metal brackets bonded to ex vivo human enamel was also measured.The main conclusions are listed as follows:(1) The best acid etching time of 20% phosphoric acid gel to primary enamel was 30-60s.(2) In LZB-GC antibacterial agent, the Ag content was 6wt% and zirconium phosphate was used as the carrier. After the addition of l-5wt% LZB-GC antibacterial agent in DEBR dental enamel bonding resin, no obvious effects on the working time, solidify time, color stability, micro-hardness and surface contact angle which were observed.(3) Fairly stronger suppressive abilities to the growth of Staph. Aureus, Escherichia coli, Streptococcus mutans and Candida albicans were attested on the surface of DEBR containing 2-5wt% LZB-GC antibacterial agent.(4) The addition of l-5wt% LZB-GC antibacterial agent in DEBR had no effect on the shear bond strength of metal brackets bonded to ex vivo human enamel.According to the above mentioned results, it was concluded that the suitable content of LZB-GC antibacterial agent in DEBR was 2-3wt%.