Introduction:
Minimally invasive dentistry means modern preventive and therapeutic management to preserve the maximum amount of dental tissue. Commonly used treatment methods in the field of prosthodontics include adhesively cemented ceramic restorations, including veneers. As the cementing techniques and the quality of ceramic materials improved, preparation techniques also became more advanced.

Aim of the study:
To compare the precision and repeatability in the amount of reduced tissues using two different methods of tooth preparation for ceramic veneers.

Material and methods:
Thirty phantom teeth were prepared for veneers. Scanning phantom teeth before and after the preparation enabled an accurate assessment of the thickness of the future veneer. Scans were collated and analysed at three control points. Data were statistically analysed.

Results:
Maximum and minimum thickness of the preparation was obtained in the middle of the labial surface, so the greatest discrepancy in tissue reduction occurred in this region of the tooth surface.The least divergent results were obtained in the cervical region.Depending on the method used, discrepancy was: cervical 0.44mm-vertical groove technique,0.21mm-horizontal groove technique;0.65mm and 0.69mm in the center of the labial surface, 0.55mm and 0.46mm at the incisal edge.

Conclusions:
Horizontal grooves technique provides greater repeatibility and precision preparation of the labial surface. The use of the horizontal groove technique resulted in a reduction of more tissue than when the vertical groove technique was used. In the vertical groove technique, some models may need to be reprepared due to insufficient tissue reduction. The use of an intraoral scanner enabled intra-operative preparation control and direct correction not necessitating impressions and cast models.