Effect of different types of enamel conditioners on the bond strength of orthodontic brackets.

AIM: A unique characteristic of some new bonding systems in operative dentistry is they combine conditioning and priming agents into a single acidic primer solution for simultaneous use on both enamel and dentin. Combining conditioning and priming into a single treatment step results in improvement in both time and cost-effectiveness to the clinician and, indirectly, to the patient. The purpose of this study was to determine the effects of the use of a self-etching primer on the bond strength of orthodontic brackets and on the bracket/adhesive failure mode. METHODS AND MATERIALS: Thirty-six fresh bovine incisors were collected and stored in a solution of 0.1% (weight/volume) thymol. The criteria for tooth selection included intact buccal enamel, no cracks caused by the presence of the extraction forceps, and no defects. The teeth were cleansed and polished with pumice and rubber prophylactic cups for ten seconds. Brackets were bonded to the teeth according to one of three protocols following the manufacturers' instructions--Group 1: Conventional multistep bonding system (control group) (n=12); Group 2: Self-etching primer system (n=12); and Group 3: Acid+self-etching primer system (n=12). Specimens were loaded to failure in a Zwick test machine (Zwick GmbH & Co, Ulm, Germany). Shear bond strengths were measured at a crosshead speed of 5 mm/min. RESULTS: The mean shear bond strength in megapascals (Mpa) (standard deviation) were 11.7 (4.2), 10.5 (4.4), and 10.9 (4.8) for Groups 1, 2, and 3, respectively. The analysis of variance (ANOVA) was used to compare the three groups. The results indicated no significant difference in the bond strength between the three groups (P=0.800). The results of the Chi square test, evaluating the residual adhesives on the enamel surfaces, revealed no significant difference between the three groups (P=0.554). CONCLUSION: Results of the present in vitro study indicate the use of self-etching primers may be an alternative to conventional phosphoric acid pre-treatment in orthodontic bonding.

Assessment of DMFT and enamel hypoplasia among junior high school children in Iran.

AIM: The main purpose of this study was to assess the prevalence and distribution of decayed, missing, and filled teeth (DMFT) and enamel hypoplasia in 12-year old students in junior high school in Iran. MATERIALS AND METHODS: This descriptive study was carried out in 2001 on 1,223 12-year old students, which were randomly selected in Yazd and Hadi-Shahr, Iran. A questionnaire was designed to record the status of the teeth along with the occupational and educational levels of parents. Data was analyzed using SPSS software, the Chi-square test, and analysis of variance (ANOVA). RESULTS: The mean DMFT score was 1.8 +/- 1.75 and 28.6% of the students were caries-free. There was no significant relationship between DMFT and the rate of dental caries with parents' education and occupation. The percentage of enamel hypoplasia was 32.7%. No statistically significant relationships were found between hypoplasia and DMFT with regard to gender. The relationship between enamel hypoplasia with DMFT score and dental caries was statistically significant. CONCLUSION: In the present study findings for DMFT scores in 12-year old junior high school children are higher than global standards according to the World Health Organization (WHO) references for the year 2000. There was a strong association between enamel hypoplasia and dental caries, and this subject suggests early diagnosis of enamel defects, health education programs, and suitable treatments should be emphasized in junior high school-aged children.

Resistance of bonded composite restorations to fracture of endodontically treated teeth.

The aim of this in vitro study was performed to evaluate the effect of dentin bonding agents and glass ionomer cement beneath composite restorations and its resistance to fracture of endodontically treated teeth. Fifty sound extracted maxillary teeth were selected; ten of them for controls and the remainder were modified with root canal treatment and a mesial occlusal distal (MOD) cavity preparation. The modified teeth were then divided into five groups: 1. Sound teeth 2. Prepared without restorations for control 3. Prepared and restored with Vitrebond (3M, USA), Singlebond (3M, USA), and Z100 (3M, USA) resin composite 4. Prepared and restored with Concise enamel bonding agent (3M, USA) and Z100 resin composite 5. Prepared and restored using Singlebond and Z100 composite resin The modified specimens were subjected to compressive load by an Instron machine until fracture occurred. Group 1 showed the highest resistance to compressive force followed by Groups 5, 3, 4, and 2, respectively. Statistical analysis using analysis of variance (ANOVA) and a t-test indicated significant difference between all groups. Use of a dentin bonding agent and composite resin increased the resistance of endodontically treated teeth to fracture.