Preparation Techniques Used to Make Single‐Unit Crowns: Findings from The National Dental Practice‐Based Research Network

Abstract

Purpose: To: (1) determine which preparation techniques clinicians use in routine clinical practice for single-unit crown restorations; (2) test whether certain practice, dentist, and patient characteristics are significantly associated with these techniques. Methods: Dentists in the National Dental Practice-Based Research Network participated in a questionnaire regarding preparation techniques, dental equipment used for single-unit crown preparations, scheduled chair time, occlusal clearance determination, location of finish lines, magnification during preparation, supplemental lighting, shade selection, use of intraoral photographs, and trimming dies. Survey responses were compared by dentist and practice characteristics using ANOVA. Results: Of the 2132 eligible dentists, 1,777 (83%) responded to the survey. The top two margin configuration choices for single-unit crown preparation for posterior crowns were chamfer/heavy chamfer (65%) and shoulder (23%). For anterior crowns, the most prevalent choices were the chamfer (54%) and the shoulder (37%) configurations. Regarding shade selection, a combination of dentist, assistant, and patient input was used to select anterior shades 59% of the time. Photographs are used to communicate shade selection with the laboratory in about half of esthetically demanding cases. The ideal finish line was located at the crest of gingival tissue for 49% of respondents; 29% preferred 1 mm below the crest; and 22% preferred the finish line above the crest of tissue. Average chair time scheduled for a crown preparation appointment was 76 ± 21 minutes. Practice and dentist characteristics were significantly associated with margin choice including practice type (p < 0.0001), region (p < 0.0001), and years since graduation (p < 0.0001). Conclusions: Network dentists prefer chamfer/heavy chamfer margin designs, followed by shoulder preparations. These choices were related to practice and dentist characteristics.

Influence of the Operator`s Experience, Working Time, and Working Position on the Quality of the Margin Width: In Vitro Study

“…Practitioners’ preferred method for tooth preparation margin design is the chamfer or heavy chamfer finish line [ 17 , 18 ]. It offers optimal marginal bulk for the restorations.…”

“…Considering the mean values obtained by all the participants in the study, the determined 0.5 mm value was best approximated by the t1 participant (0.45 mm), followed by the values of T1, T2, and t2 ( Table 2 ). The values achieved by the t1 participant are less than 0.5 mm for most preparations ( Table 1 and Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 ) contradicting the minimum necessary width for preventing the fracture of posterior zirconia crowns [ 17 , 18 ]. The two experienced participants, T1 and T2, obtained the most stable values ( Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 ) due to their higher experience levels.…”

Mechanical behavior of different machinable ceramic crowns using vertical and horizontal preparations: an in-vitro study

“…Although vertical preparations provide more conservative preparations and biological response to tissues as proven by the literature. A recent study in the US in 2018, showed that most dentists still prefer chamfer/heavy chamfer margin designs, followed by shoulder preparations [40]. This reflects on the lack of sufficient data awareness and education of possible other techniques that can be used by dentist in different situations.…”

The finish line location of the cemented crown is an influencing factor for tensile bond strength, marginal adaption and nanoleakage?

“…Adhesion to dentin is more difficulty due to its organic and inorganic composition and high-water content of about 20% [6]. Through the advanced development of composite resin materials, together with the principle of less wear on dental structure [7], there are not many studies in the literature that have focused on the influence of the location of the marginal end and design of the preparation.…”