{'fraction_non_alphanumeric': 0.04014049172102358, 'fraction_numerical': 0.019066733567486203, 'mean_word_length': 5.02416918429003, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effects of air abrasion and acid etching on the microleakage of preventive Class I resin restorations: an in vitro study.

PURPOSE
To evaluate the effects of air abrasion, acid etching, and the combination of both procedures on the microleakage of preventive Class I resin restorations.


MATERIALS AND METHODS
Eighty-four extracted human molar teeth were randomly assigned to seven groups with 12 teeth each. Occlusal fissures were opened with a diamond bur and etched with phosphoric acid (groups I and VI); prepared with a diamond bur without etching (group VII); air abraded with the KCP 1000, using 50-micron aluminum oxide particles without etching (group II), and with phosphoric acid etching (group III); or air abraded with 27-micron aluminum oxide particles without etching (group IV), and with phosphoric acid etching (group V). Preparations were filled with a low-viscosity resin composite (Liquicoat, groups I to V) or with a low-viscosity polyacid-modified resin composite (PrimaFlow, groups VI and VII). Six teeth in each group were thermocycled (5 degrees-55 degrees C, 2500 cycles). Dye penetration (methylene blue) was evaluated in ordinal scale.


RESULTS
The number of non-thermocycled and thermocycled specimens revealing no microleakage was as follows: group I, 6 and 1; group II, 2 and 2; group III, 4 and 3; group IV, 0 and 0; group V, 1 and 0; group VI, 3 and 2; and group VII, 0 and 0, respectively. No significant differences existed between the thermocycled specimens and non-thermocycled specimens, except within group I.


CLINICAL SIGNIFICANCE
Results indicated that (1) air-abrasion treatment with 27-micron particles is less effective in preventing microleakage compared to 50-micron particles, (2) air abrasion should be combined with acid etching to reduce microleakage of preventive Class I resin restorations, and (3) acid etching significantly reduces microleakage of the low-viscosity polyacid-modified resin composite in preventive Class I restorations.