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-To assess the clinical bond failure rates of orthodontic brackets bonded using SEP compared with conventional acidetch technique with control adhesive (Transbond), PLUS to investigate whether characteristics of operator, patient, or tooth had any influence on bracket failure. Null Hypothesis -no difference in clinical effectiveness of the 2 methods Strength of the study -prospective randomized clinical trial at single centre -Good randomization procedure -Bonding SOP described Bonding has simplified orthodontic Rx. Conventional system – acid etch + adhesive Recently – 1 step selfecthning system. Claimed Transbond SEP – reduce bond up time and work in a moist condition If bond failure rate is similar or even better – advantageous. Materials and Methods • Ethical approval sought & approved • Sample Size • • • • Based on # of brackets required as this was the unit of measurement Sample of 540 brackets (270 per group) considered to be sufficient 80% power with 5% sig level 32 pts needed to produce 270 brackets Study design Inclusion: all pts in the waiting list who require fixed appl Rx. Not matched for age, sex and malocclusion to obtain wide range of pts Exclusion: single arch + surgical case Pts then randomized (random tables, controlled permuted blocks) SEP = 18 pts (LOST follow up 1) – Completed Rx 17 (299 brackets) TB = 17 pts – completed Rx 17 (298 brackets) Overall 597 brackets placed APC brackets used in both groups to maintain consistency of the amount of composite used. Bonding technique Conventional 1. Prophy 2. Wash and dry 3. Isolation 4. Acid etch 37% phosphoric acid 5. Wash 6. Isolation 7. Dry to a frosted enamel 8. Transbond primer to etched enamel 9. APC brackets placed and cured 10” 10. Final cure 20” SEP 1. 2. 3. 4. 5. 6. 7. • • Prophy Wash and dry Isolation Dry enamel w/o complete desiccation SEP is applied with gentle swirling 3-5” APC brackets placed, cured 10” Final cure 20” An .016 Cu Niti engaged into all of the brackets Any bond failure recorded on data collection sheet when pt attend clinic with breakage. The 1st bond failure - recorded by date and tooth # A failure is considered as AN ALL OR NONE OCCURRENCE, hence subsequent failures were noted but not included in failure rate. Failed brackets were replaced using same SOP (REBONDING TECH not DESCRIBED – not important due to all or none princple). Statistical Analysis • Measured on both PATIENT and TOOTH level • Good, to compare with other studies. • Bond failures at pt level – Mann Whitney • At tooth level – clustering, avoiding 1 individual with high failure influence rate too much • Models was set – exponential – assumes the survival time distribution is exponential & depend on values of a set of independent variables, e.g. stronger bonds – last longer Not sure of the fuzzy buzzy of all this stats !!!! BUT I TRUST O’BRIEN!!! RESULTS Pt Level – no STATS difference between the bonding system and the # of brackets that failed per patient (p=0.758) Tooth level – no STATS difference between the 2 system. NO STATS DIFF in RATE of FAILURE compared to operator, age, Left/Right, Ant/Post. Yet, lower bracket INTERESTINGLY showed less likely to fail. Females is ½ than males – but not SIG After stepwise regression, PREDICTORS of failure were TOOTH LOCATION and GENDER. DISCUSSION • This study didn’t find sig diff between 1 step and 2 step bonding system. • Many other clinical studies showed 2 stage and light cure system were equally reliable. • This study then used 2 stage and light cure as the BENCHMARK as comparison to 1stage SEP system Study Design Authors admitted sample size was adequate but not sufficient to account aggregation of brackets (clustering) within participants – hence POWER IS REDUCED – Recommend to INCREASE sample size for future studies. Other studies used “split mouth”. WHAT IS IT ? Pt works as control – esp in poor appliance care. Yet, the blinding is not good, different SOP will be implemented, alternate bonding systems…… Better to randomly allocating 1 material to each patient. APC to make uniform of consistency of adhesive placed on the brackets on both technique – eliminate adhesive placement tables. Previous studies (Sunna and Rock, 1998; Trimpeneers and Dermaut, 1996) found NO SIG DIFF in bond failures between APC and uncoated brackets. Timing • • • Describing bond fail over the whole Rx time in randomly allocated pt – elininate possible variation due to Rx length If not done – it wont show if 1 material deteriorates over time perio. Measured at 6, 12 month interval and at completion. • This study found failure rate for SEP increased 1.7% at 6mos to 7% at completion. Whist Transbond 2.0% to 7.4% So, although failure rates increased over time – but no diff between the 2 materials at each time intervals. Following pt up to completion is guidelined by COCHRANE review. Other studies found 1.1 to 6.8% • TOOTH FACTORS • Other studies found posterior worse than anterior (perhaps due to difficult isolation, access, high occlusal forces,etc) This study found IN CONTRAST 8.4% for anterior and 4.9% for posterior – not stats dif. • • • • • Between max and mand teeth – stats sig diff. Max brackets (12.4%) were 5x more likely to FAIL than mandibular teeth (2.3%) – perhaps due to habits, poor diet control – hard foods. PATIENT FACTOR Age and gender not stats sig., yet failure was higher in BOYS. Other study, Millet (2000) found boys was better. Norevall (1996) found better in GIRLS. There was 1 patient who had 6 failures out of 22 total recorded failures for Transbond for the entire study. Pts on the W/L should have plaque score <10% before put in the W/L and attend OHI sessin with hygienist – that’s why this study found quite low failures. • FAILURES RATES • This study’s failure rates was LOW at 1.8% Lovious (1987) – found 23.8% Using APC, Littlewood (2001) found 6.8% after 6 mos using the same 2 step system. Sunna and Rock (1998) reported 9.4% on APCs. Grubisa (2004) – in vitro study – found 2 step has 9.8 Mpa than SEP (7.5 Mpa). Yet this study didn’t found any difference. One might suggest difference in vitro may not reflect in vivo clinical environment. House (2006) using different SEP (Ideal 1 – GAC) found higher failure – different manufacturers produce different quality. • • • • • So WHY IN THE HECK SHOULD WE USE 1. 2. 3. 4. 5. SEPs? QUICKER CHAIR TIME – yet depends on the clinical need for each surgery Moisture control may not be too critical – maybe more comfortable for patients (supported by ANECDOTAL evidence). SIMPLER AND PRODUCE SIMILAR BOND STRENGTH AND FAILURE RATE WITH 2 STEPS COST? (1 SEP can bond 2 arches)