A comparison of crown preparation grading via PrepCheck versus grading by dental school instructors.

Recent reports in the literature demonstrate the influence that digital dentistry is having on the preclinical training of dental students. However, none of these articles have discussed the use of PrepCheck (Sirona Dental Systems) in the evaluation of preparation taper in a preclinical environment. The present study compared the subjective grading of student tooth preparations by experienced, well-calibrated faculty with objective digital grading of the same preparations by means of the PrepCheck software. Sixty-nine sophomore dental student preparations were first subjectively graded by their dental instructors, and then the preparations were evaluated by the PrepCheck software. Neither the students nor the instructors were aware that the second PrepCheck evaluation was going to occur. The statistically significant results of this study conclude that the subjective instructor grades were inflated compared with the digital PrepCheck grades. The inflated grading by the instructors may give students a sense that their progress is better than it actually is. The objective, exact nature of the PrepCheck evaluation gives students immediate feedback regarding their preclinical preparations. Although taper was the only parameter examined in this study, PrepCheck allows the operator to examine many other features of a student's preparation. Also made evident in this study is the fact that the present standard for preparation taper is unattainable in a preclinical environment and needs to be readjusted to a wider, attainable range.

Marginal Fit Comparison of CAD/CAM Crowns Milled from Two Different Materials.

PURPOSE: To evaluate the marginal fit of CAD/CAM copings milled from hybrid ceramic (Vita Enamic) blocks and lithium disilicate (IPS e.max CAD) blocks, and to evaluate the effect of crystallization firing on the marginal fit of lithium disilicate copings. MATERIALS AND METHODS: A standardized metal die with a 1-mm-wide shoulder finish line was imaged using the CEREC AC Bluecam. The coping was designed using CEREC 3 software. The design was used to fabricate 15 lithium disilicate and 15 hybrid ceramic copings. Design and milling were accomplished by one operator. The copings were seated on the metal die using a pressure clamp with a uniform pressure of 5.5 lbs. A Macroview Microscope (14×) was used for direct viewing of the marginal gap. Four areas were imaged on each coping (buccal, distal, lingual, mesial). Image analysis software was used to measure the marginal gaps in µm at 15 randomly selected points on each of the four surfaces. A total of 60 measurements were made per specimen. For lithium disilicate copings the measurements for marginal gap were made before and after crystallization firing. Data were analyzed using paired t-test and Kruskal-Wallis test. RESULTS: The overall mean difference in marginal gap between the hybrid ceramic and crystallized lithium disilicate copings was statistically significant (p < 0.01). Greater mean marginal gaps were measured for crystallized lithium disilicate copings. The overall mean difference in marginal gap before and after firing (precrystallized and crystallized lithium disilicate copings) showed an average of 62 µm increase in marginal gap after firing. This difference was also significant (p < 0.01). CONCLUSIONS: A significant difference exists in the marginal gap discrepancy when comparing hybrid ceramic and lithium disilicate CAD/CAM crowns. Also crystallization firing can result in a significant increase in the marginal gap of lithium disilicate CAD/CAM crowns.

Canine guidance via Biogeneric Copy: a clinical report.

The advent of computer-aided design/computer-aided manufacturing (CAD/CAM) technology in dentistry has enabled a wide range of applications. The Cerec Acquisition Center (Cerec AC, Sirona Dental Systems Inc., Charlotte, NC) allows for the construction of all-porcelain restorations, either in-office or through a remote dental laboratory. One feature of the Cerec AC is its ability to duplicate the dental morphology of an existing tooth onto a new CAD/CAM ceramic restoration designed for that tooth. This design mode capability of the Cerec AC is termed Biogeneric Copy. This function has been discussed in the literature where it has been utilized to fabricate a CAD/CAM ceramic crown to fit an existing removable partial denture (RPD).1-3 There are occasions in dentistry where the exact anatomy and position of an existing tooth, not associated with an RPD, should ideally be replicated in a definitive restoration. This case report describes such an occasion.