title: Effect of anatomic, semi-anatomic and non-anatomic occlusal surface tooth preparations on the adaptation of zirconia copings.
abstract: OBJECTIVE
  To compare the accuracy of marginal and internal adaptation of zirconia (Zr) copings fabricated on anatomic (A), semi-anatomic (SA) and non-anatomic (NA) occlusal surface preparations.
  
  
  METHODS
  45 extracted bicuspid teeth were prepared for receiving zirconia crowns, with different occlusal preparation designs A=15, SA=15 & NA=15. The Zr copings were fabricated by using CAD4DENT, CAD/CAM. The copings were adjusted, cemented and were cross sectioned centrally from buccal cusp tip to lingual cusp tip into mesial and distal halves. The copings were examined under electron microscope at ×200 magnification and the measurements were recorded at 9 predetermined areas in micrometers.
  
  
  RESULTS
  Overall mean gap values for the three groups was found to be 155.93±33.98 µm with Anatomical Occlusal preparation design having the least gap value of 139.23±30.85 µm showing the best adaptation among the groups. Post Hoc Tukey's test showed a statistically significant difference (P=.007) between the means of gap for A & NA preparation designs. Measurements recorded at 9 predetermined points showed variations for the three groups.
  
  
  CONCLUSIONS
  Anatomical occlusal preparation designs resulted in better marginal and internal adaptation of Zr copings. There is a considerable variation between the measured marginal and internal gap values for the Zr copings fabricated by the (CAD4DENT-CAD/CAM). This variation may be associated with the lack of standardization of the preparation of teeth, computerized designing of the coping for each tooth, cement used, uniform pressure application during the cementation of the copings, sectioning of the copings and the microscopic measurements.
authors.affiliation: Department of Prosthetic Dental Sciences, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia.
authors.forename: Syed Rashid
authors.initials: SR
authors.lastname: Habib
authors.affiliation: College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia.
authors.forename: Waleed
authors.initials: W
authors.lastname: Asiri
authors.affiliation: College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia.
authors.forename: Mohammed Jameel
authors.initials: MJ
authors.lastname: Hefne
keywords: Adaptation of zirconia crowns; Marginal fit of zirconia crowns; Zirconia copings; Zirconia crowns