Me. Olsen et al., COMPARISON OF SHEAR BOND STRENGTH AND SURFACE-STRUCTURE BETWEEN CONVENTIONAL ACID ETCHING AND AIR-ABRASION OF HUMAN ENAMEL, American journal of orthodontics and dentofacial orthopedics, 112(5), 1997, pp. 502-506
Recently, air-abrasion technology has been examined for potential appl
ications within dentistry, including the field of orthodontics. The pu
rpose of this study was to compare the traditional acid-etch technique
with an air-abrasion surface preparation technique, with two differen
t sizes of abrading particles. The following parameters were evaluated
: (a) shear bond strength, (b) bond failure location, and (c) enamel s
urface preparation, as viewed through a scanning electron microscope.
Sixty extracted human third molars were pumiced and divided into three
groups of 20. The first group was etched with a 37% phosphoric acid g
el for 30 seconds, rinsed for 30 seconds, and dried for 20 seconds. Th
e second and third groups were air-abraded with (a) a 50 mu m particle
and (b) a 90 mu m particle of aluminum oxide, with the Micro-etcher m
icroabrasion machine (Danville Engineering Inc.). Ail three groups had
molar stainless steel orthodontic brackets bonded to the buccal surfa
ce of each tooth with Transbond XT bonding system (3M Unitek). A Zwick
Universal Testing Machine (Calitek Corp.) was used to determine shear
bond strengths. The analysis of variance was used to compare the thre
e groups. The Adhesive Remnant Index (ARI) was used to evaluate the re
sidual adhesive on the enamel after bracket removal. The chi square te
st was used to evaluate differences in the ARI scores among the groups
. The significance for all tests was predetermined at p less than or e
qual to 0.05. The results indicated that there was a significant diffe
rence in shear bond strength among the three groups (p = 0.0001). The
Duncan Multiple Range test showed a significant decrease in shear bond
strength in the air-abraded groups. The chi square test revealed sign
ificant differences among the ARI scores of the acid-etched group and
the air-abraded groups (chi(2) = 0.0001), indicating no adhesive remai
ned on the enamel surface after debonding when air-abrasion was used.
In conclusion, the current findings indicate that enamel surface prepa
ration using air-abrasion results in a significant lower bond strength
and should not be advocated for routine clinical use as an enamel con
ditioner at this time.