Effect Of Environmental Humidity On Bond Strength Of Orthodontic Brackets

[objective] In the process of orthodontic brackets bonding, moisture contamination is an important factor which affect the bonding strength. According to compare the bonding strength of brackets in different environment, The aim of this study was to evaluate the effect of environmental humidity on bond strength of orthodontic brackets, so that orthodontists can improve the achievement ratio of brackets bonding. [ methods ] Experiment in vitro : A total of 180 extracted premolars were collected and divided equally into 9 groups of 10 teeth each, and brackets were bonded under different experimental conditions: ①dry:23°C/37°C/45°C②100%rh:23°C/37°C③37 °C/dry④37°C/100%rh, placing the teeth in bonding environment for 5Min before the primer apply to the enamel / placing the teeth in bonding environment for 5Min after the primer apply to the enamel. each adhesive group was stored for 24 hours in deionized water at 37°C. All bonded specimens were thermocycled at 10°C and 50°C for 24 hours before debonding. Shear and tensile bond strength of each sample was examined with a testing machine, and adhesive remnant index (ARI) were counted.[results] The results showed that the in dry condition, both mean strengths and bond-failure site, no significant difference was found among three groups under different temperature (P>0.05 ) , but in humidity condition , group 37°C and group 45 °C had similar mean strengths, which were significantly lower than group 23 °C(P<0.05 )and the bond-failure site among the 3 groups have significant difference. In 23 °C, both mean strengths and bond-failure site ,there was significant difference between group dry and group 100%rh (P<0.01). So does in the other two temperature condition. After placing the teeth in humidity environment for 5Min, whenever before...