The Effect Of Saliva Contamination On Shear Bond Stress When Using Orthodontic Self-etch Primer

Orthodontic fixed appliances required brackets bond exactly and reach clinically acceptable bond stress. If the brackets failed off frequently, the patients' curative effect and period of treatment were influced. The brackets unfixed were partially attributed to the saliva contamination. Patients presented to the Dept.of orthodontics were mainly children and teen-ages with rich saliva in their mouths. This study discussed the effection of saliva contamination on shear bond stress when using orthodontic self-etch primer.Objective: On the condition of the tooth surface being contaminated with saliva, conventional 37% phosphoric acid and new type orthodontic self-etch prime was used to etch enamel surface respectively. According to the comparison of the two methods shear bond stress (SBS), adhesive remnant index score (ARI) and observation of scanning electron microscopy (SEM), the self-etch primer's superiority on the condition of the tooth surface being contaminated with saliva was discussed.Methods: 1. Tested groups and enamel treatments: eighty-four human premolars extracted with orthodontic indication were used in this study. Eighty-four specimens weredivided into 7 groups of 12 specimens, 4 different surface treatments were performed. Compared tests were conducted under 4 enamel surface conditions: (1) Etched and uncontaminated with saliva (2) Before etching, the enamel surface was contaminated with saliva (3) After etching, the enamel surface was contaminated with saliva (4) Etched, contaminated with saliva and reprised. The seven experimental groups were: HC (phosphoric control group); EC (ESPE control group); EB (saliva contamination occurred before ESPE etched); HA (saliva contamination occurred after phosphoric etched); EA (saliva contamination occurred after ESPE etched); HR (phosphoric etched, saliva contamination and reprimer); ER (ESPE etched, saliva contamination and reprimer). The enamel condition acid was 37% phosphoric acid and orthodontic self-etch primer, adhesive used was light cured TransbondMTXT(3M/unitk), the brackets used were Hang zhou xin ya stainless steel brackets, the bracket base area was 10.5mm2. After the specimen was bonded, the cold-cured denture base acrylic resin block was put into a water bath at 37°C until the time of debonding. 2. Debonding Procedure: the block was clamped in the base of the testing machine. An occlusogingival load was applied to the bracket, producing a shear force at the bracket-tooth surface. Shear bond strengths were measured at a crosshead speed of 1 mm/minute. A computer electronically connected with the test machine recorded the results of each test. The load applied at failure wasrecorded in newtons(N), then dividing by the bracket base area to obtain shear bond stress . 3. ARI score: The debonded teeth were then examined with a stereomicroscope at 16 X magnifications, and an adhesive remnant index (ARI) was used to assess the nature of debonding. The ARI was a 5-point scale used to assess the amount of composite remaining on the tooth surface after debonding: zero score: no adhesive on the surface; one score: less than a third of the surface covered; two score: more than one third but less than two thirds of the surface covered; three score: more than two thirds but less than the whole surface covered; four score: whole surface covered and sometimes included a distinct impression of the bracket mesh. 4. Making and observation of SEM specimens: After phosphoric acid and ESPE etching, the etched specimens were prepared for scanning electron microscopy (SEM) by sputter coating with gold. Photomicrographs were recorded from the central region of each etched area, the quality of each specimen was scored by using the following 3-grade scale: (1) Poor etch pattern: smooth or amorphous surface no evidence of "Type 1" etch pattern (preferential dissolution of enamel prism cores) or "Type 2"pattern (dissolution of prism boundaries) in the area examined. (2) Moderate etch pattern: A least 50% of the examined area showing Type 1 or Type 2 etch pattern. (3) Good etch pattern: Type 1 or Type 2 etch pattern in nearly all the area examined. After debonding, the specimens were ground out vertically by low-speed bur. Specimens were dried and gold coated inpreparation for SEM 5. Statistical analysis: the data were subjected to an analysis of variance using SAS6.12 software and compared post hoc using the Student-Newman-Keuls(SNK)test at p=0.05. The ARI data were then subjected to statistical analysis to determine means for each group and frequency distributions of ARI score (%) for the 7 experimental groups were recorded.Results: l.SBS:HC11.993±2.456MPa.EC9.497±2.585MPa. EB7.038±2.253MPa. EA4.623±1.914MPa. ER8.459±1.716MPa. HA4.505±1.314MPa. HR4.569±1.862MPa. The SBS of group HC was higher statistically than those of other six groups (PO.05). HC and EC, EC and EB, EC and EA, ER and EA, EB and EA, HC and HA.HR had difference statistically (P<0.05) . EC and ER, HA and HR. EA had no difference statistically (P>0.05). 2. ARI score: HC group, frequency distribution of three and four score was 83.3%. EC group was 66.6%. HA group, frequency distribution of zero and one score was 83.3%. HR group was 83.3%. EA group was 91.6%. EB and ER groups frequency distributions were average. HC and EC groups ARI means were higher. EA, HA and HR groups were lower. 3. Observation of SEM: Enamel surface conditioned with 37% phosphoric acid: etched enamel surface with the hydrokinetic system was practical and showed good enamel etch pattern. Enamel surface conditioned with ESPE: ESPE primer created a weaker etched pattern on the enamel surface than phosphoric acid and showed moderate etch pattern. The SEM observation...