Microleakage of composite resin restorations in cervical cavities prepared by Er,Cr:YSGG laser radiation

Evaluation of microleakage is important for assessing the success of new methods for surface preparation and new adhesive restorative materials. The aim of this laboratory study was to assess microleakage at the margins of composite restorations in Er,Cr:YSGG laser prepared cavities on the cervical aspects of teeth by means of dye penetration, and compare this with conventionally prepared and conditioned cavities.

Class V cavities were produced on sound extracted human teeth, which had been assigned randomly to one of three groups (N = 10 each), as follows: Group 1 - prepared using a diamond cylindrical bur and then treated with 37% phosphoric acid; Group 2 - irradiated with an Er,Cr:YSGG laser (Biolase Waterlase) and then treated with 37% phosphoric acid; Group 3 - irradiated only with the laser. After application of bonding agent (Excite, Ivoclar Vivadent), all cavities were restored with composite resin (Heliomolar). After polishing the restorations, the teeth were thermocycled from 5-50 degrees C for 500 cycles. Dye leakage was assessed after immersion in methylene blue, by examining longitudinal sections in a stereomicroscope at x 30 magnification.

The extent of dye penetration was lowest in the laser only group (Group 3). Penetration of dye to dentine and axial walls occurred in 80 per cent of conventionally prepared (bur + acid) specimens, but in the laser group, dye penetration to the axial wall occurred in only 30 per cent of cases. There was a strong statistical association between treatment group and the distribution of microleakage scores (Chi-square, P = 0.0023).

For Class V cavities, with the adhesive materials employed, higher microleakage occurs with phosphoric acid etching of bur- or laser-cut surfaces, than with the surface created by use of the laser alone without additional conditioning.