Kinetic cavity preparation effects on secondary caries formation around resin restorations: a polarized light microscopic in vitro evaluation.

The purpose of this in vitro study was to compare the effect of conventional handpiece and kinetic cavity preparation (KCP, air abrasion) techniques of cavity preparation on caries-like enamel lesion formation. After a fluoride-free prophylaxis, twelve human molars were examined macroscopically to ensure that buccal and lingual surfaces were caries-free. Unfilled cavities were prepared in mesiobuccal (conventional [CU]) and mesiolingual (air abrasion [AU]) enamel surfaces. Cavities were prepared in distobuccal (conventional [CF]) and distolingual (air abrasion [AF]) enamel surfaces and restored with composite resin following placement of a bonding agent. Acid-etching of cavity walls was performed only with the conventionally prepared cavities restored with resin. Air abrasion (KCP) prepared cavities were restored without acid-etching of the cavity walls. Teeth were thermocycled (500 cycles, 5 degrees to 50 degrees C, 500 cycles) and exposed to an artificial caries medium for caries initiation and progression. After caries formation, two longitudinal sections were taken from unfilled and filled cavity preparations and examined by polarized light microscopy for wall lesion presence and mean surface lesion depth. Surface lesion depths were similar among groups after the caries initiation period (CU = 225 microns; AU = 237 microns; CF = 241 microns; AF = 251 [p > .05, ANOVA, DMR]), and progression (CU = 437 microns; AU = 415 microns; CF = 405 microns; AF = 429 um [p > 0.05, ANOVA, DMR]). Extensive wall lesions were present in all CU and AU; while small wedge-shaped wall lesions were significantly (p < .05, ANOVA, DMR) fewer in CF (19 percent & 21 percent) and AF (17 percent & 21 percent) following caries initiation and progression compared with unfilled controls. Resin restorations placed in cavities prepared by air abrasion (KCP) and conventional handpiece techniques provided similar degrees of protection against a secondary caries-like challenge.