EC Dental Science

Statement of Problem: Chair time expended in adjusting crown restorations can be reduced, but a systematic protocol has not been universally adopted.

Purpose: The purpose of this study is to test the hypothesis that pre-clinical interproximal contact adjustment of indirect restorations on a pristine mounting-stone cast will save chair time.

Material and Methods: Sixteen single-unit full crowns from dental students’ cases at the University of the Pacific Arthur A. Dugoni School of Dentistry (UOPAASD) were used in this study. Each crown had mesial and distal contacts with adjacent teeth and intact impressions. New casts were made from mounting stone for all 16 crowns. For the first 8 experimental crowns, interproximal adjustments were optimized on the new mounting-stone cast using 11.7-micron shimstock and 21-micron articulating paper, while on the second 8, no adjustments were made. One researcher completed all adjustments. Students were given a form detailing the reporting requirements.

Results: A t-test showed that pre-clinical adjustment of interproximal contacts on new casts resulted in a decrease of chair time between 5.8 minutes and 35.6 minutes with statistical significance of p = 0.007.

Conclusion: Pre-clinical adjustment of interproximal contacts on fresh mounting-stone casts can decrease chair time in a dental school setting.

Clinical Implications: Dentists/technicians can reduce chair time by pre-clinical verification/adjustment of interproximal contacts. A new mounting stone cast can be made from the original impression that demonstrates fidelity to the patient’s intraoral topography. When using a production laboratory, technicians can be taught to use pristine casts with this protocol to titrate interproximal contact adjustments to the clinician’s preferences, or this can be performed by the clinician.

 Keywords: Chair Time; Crown Restorations; pristine Mounting-Stone Cast

1. Bessadet M., et al. “Time efficiency and cost analysis between digital and conventional workflows for the fabrication of fixed dental prostheses: A systematic review”. Journal of Prosthetic Dentistry 1 (2025): 71-84.
2. Derksen W., et al. “Randomized Clinical trial comparing clinical adjustment times of CAD/CAM screw-retained posterior crowns on ti-base abutments created with digital or conventional impressions. One-year follow-up”. Clinical Oral Implants Research 8 (2021): 962-970.
3. Joda T and Brägger U. “Time-efficiency analysis comparing digital and conventional workflows for implant crowns: A prospective clinical crossover trial”. International Journal of Oral and Maxillofacial Implants 5 (2015): 1047-1053.
4. Mühlemann S., et al. “Clinical quality and efficiency of monolithic glass ceramic crowns in the posterior area: Digital compared with conventional workflows”. International Journal of Computerized Dentistry 3 (2018): 215-223.
5. Haghi HR., et al. “A randomized clinical trial comparing the clinical fit and chairside adjustment time for implant-supported crowns fabricated by fully digital and partially digital techniques”. Journal of Prosthetic Dentistry 5 (2024): 865-870.
6. Boyarsky HP., et al. “Occlusal refinement of mounted casts before crown fabrication to decrease clinical time required to adjust occlusion”. Journal of Prosthetic Dentistry 5 (1999): 591-594.
7. Davis RD. “Predictable seating of the single-unit cast restoration”. Quintessence International 8 (1991): 631-635.
8. Dilts WE., et al. “Comparative stability of cast mounting materials”. Your Oklahoma Dental Association Journal 4 (1978): 11-13.
9. Thongthammachat S., et al. “Dimensional accuracy of dental casts: Influence of tray material, impression material, and time”. Journal of Prosthodontics 2 (2002): 98-108.
10. Kim DS., et al. “Measurement of proximal contact of single crowns to assess interproximal relief: A pilot study”. Heliyon10 (2023): e20403.
11. Hansen PA., et al. “The accuracy of clinician evaluation of interproximal contacts using different methods”. Journal of Prosthetic Dentistry 2 (2020): 284-289.