# A comparison of stone-based and diamond strip approaches for adjusting proximal contact tightness in zirconia and PFM crowns

## TL;DR

This study compares stone-based and diamond strip methods for adjusting dental crown contacts, finding that diamond strips may be faster for less experienced clinicians.

## Contribution

The study introduces diamond strips as a potentially more efficient tool for proximal contact adjustment in dental crowns.

## Key findings

- Experienced clinicians achieved higher contact force with green stones compared to diamond strips.
- Less experienced clinicians required more time with green stones than with diamond strips.
- Diamond strips may help untrained practitioners reduce adjustment time.

## Abstract

Adjustment of proximal contact tightness in posterior crowns is critical for preventing food impaction and ensuring patient comfort. This study aimed to determine whether a conventional stone-based approach or a newly introduced diamond strip resulted in more efficient and predictable proximal contact adjustment in zirconia (Zr) and porcelain-fused-to-metal (PFM) crowns, as well as to assess whether clinician experience affects the outcome.

To calculate the mean contact strength (baseline data), the tightness of the proximal connections of clinical crowns from 74 anonymous individuals was measured beforehand. Four working casts (containing premolars, first molars, and second molars) were made using commercially available resin die material. First and second molars were prepped, and metal crowns were cemented on the first molar to prevent errors in proximal contact correction between the first and second molars. Zr (n = 32) and PFM (n = 32) crowns on second molars were positioned 0.5 mm higher than the acceptable crown margin due to excessively tight proximal contacts. The tightness of these contacts was subsequently adjusted until the crowns were seated on the correct margin. Contact force (N) was measured using a force gauge placed between the adjusted crown and its adjacent tooth, and the time (chair time) necessary for proximal contact adaptation utilizing green stones with silicone polishers, and diamond strips was compared based on clinicians’ different experiences. The Mann–Whitney U test was used to assess differences in force and time between the groups.

The mean contact strength of clinical crowns was 4.55 ± 0.89 N. For the more experienced clinician, contact force of the green stone–adjusted restorations was higher than that of the diamond strip–adjusted restorations. The less experienced clinician required a longer duration to adjust with a green stone than with diamond strips, while the more experienced clinician showed similar adjustment times with both tools.

The conventional way of achieving reasonable contact tightness using stones and silicone polishers may be influenced by clinicians’ experience. To shorten adjustment time, untrained practitioners can employ diamond strips.