Transcript Strength of the study

-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
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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
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Inclusion: all pts in the waiting list who require fixed appl
Rx.
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Not matched for age, sex and malocclusion to obtain wide
range of pts
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Exclusion: single arch + surgical case
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Pts then randomized (random tables, controlled permuted
blocks)
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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.
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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.
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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
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After stepwise regression, PREDICTORS
of failure were TOOTH LOCATION and
GENDER.
DISCUSSION
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This study didn’t find sig diff between 1 step and 2
step bonding system.
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Many other clinical studies showed 2 stage and
light cure system were equally reliable.
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This study then used 2 stage and light cure as the
BENCHMARK as comparison to 1stage SEP
system
 Study Design
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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.
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Other studies used “split mouth”. WHAT IS IT ?
Pt works as control – esp in poor appliance care.
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Yet, the blinding is not good, different SOP will be
implemented, alternate bonding systems……
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Better to randomly allocating 1 material to each
patient.
 APC
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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
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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.
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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%
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TOOTH FACTORS
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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.
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 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.
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FAILURES RATES
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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.
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 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)