Effect of Tooth Abutment Height on Retention of CAD/CAM Monolithic Zirconia Crowns Cemented With Two Types of Cement: An In Vitro Study

Statement of the Problem: Retention is still a primary concern in conservatively managing short clinical crowns (SCC) and minimal restorative space. In modern dentistry, there is a growing expectation for the durability and retention of indirect restorations, along with a high esthetic demand, even in unfavorable underlying conditions. Purpose: This study aims to establish a reliable approach for the conservative treatment of SCCs using monolithic zirconia crowns (MZC). Materials and Methods: Sixty human molars were collected and mounted in resin blocks. The teeth were prepared with two different abutment heights (2 and 4 mm). MZCs with buccal and lingual projections were designed and milled after digital scanning. Half of the restorations were cemented with TheraCem (TC) calcium silicate-based self-adhesive resin cement, while the remaining half were cemented with glass ionomer (GI) cement. The specimens underwent thermocycling and cyclic loading. A traction test was then performed in the universal testing machine to evaluate the debonding forces. Data was analyzed using Pearson correlation and one-way ANOVA tests. Results: -value ≤ 0.01). In addition, ANOVA found a significant mean difference in the pairwise comparison of groups. Increasing abutment height in groups with either GI or TC cement type resulted in increased measured force. More importantly, TC groups have shown a greater average value than specimens with GI cement. Conclusions: We demonstrated the significant influence of TC cement on the pull-out force measurement, outperforming the GI cement. The abutment height also showed a smaller contribution to the force measurement. Low-thickness monolithic zirconia restorations cemented with self-adhesive resin cement can be recommended as a reliable and effective treatment option for clinicians managing cases with SCCs and compromised retention.