Effekte des Sandstrahlens vor adhäsiver Bracketfixation

This study compares the morphology and the irreversible enamel abrasion of the conventional acid-etch technique with the combination of sandblasting and the acid-etch technique. In addition the resulting tensile bond strength was investigated. For the first part of this study 50 extracted human molar teeth were randomly divided into the following 5 groups: (1) 30sec acid etched with 37% phosphoric acid, (2) 5sec sandblasted with 110µm aluminium oxide + acid etched, (3) 10sec sandblasted + acid etched, (4) 5sec sandblasted + acid etched + bracket + debonding, (5) 10sec sandblasted + acid etched + bracket + debonding. After the preparation of slices the correspondent enamel loss was measured microscopically using the computer programm “Discus”: (1) 7,10µm ± 1,25µm, (2) 43,22µm ±17,66µm, (3) 96,32µm ± 36,57µm, (4) 121,17µm ± 14,94µm, (5) 184,31µm ± 36,17µm. The sandblasting followed by acid etching groups had significantly higher enamel abrasion values when compared to the acid etching group. Only between group 3 and 4 no significantly higher enamel loss could be determine. In the second part of this study a Zwick testing machine was used to determine tensile bond strengths between the enamel and the fixed brackets after a 24h immersion in water at a crosshead speed of 1mm/sec. The 2 groups were as follows: (A) 30sec acid etched, (B) 5sec sandblasted + acid etched. The results showed that the bond strength of group A was 3,9MPa ± 1,12MPa and the group that was sandblasted followed by acid etched was 4,49MPa ± 1,26MPa. The statistical analysis documented that the pre-treatment with aluminium oxide does not effect significantly higher tensile bond strength. The occurrence of bond failures in the 2 groups primarily at the bracket-adhesive interface was responsible for that result whereby the exact registration of the maximum tensile bond strength between the enamel and the adhesive was not possible with this experimental setup. Considering the enamel abrasion caused by 5sec sandblasting of 43µm rather 121µm after bracketdebonding, the sandblasting technique does not cause an improved clinical result due to the established bond failures at the bracket base. The sandblasting for 10sec is just due to the very high irreversible enamel abrasion about 180µm to estimate as censorious