# Evaluation of two cementation protocols for lithium disilicate crowns on zirconia one-piece implants: a micro-CT analysis of cement thickness, porosity, and excess

## TL;DR

This study compares two cementation methods for dental crowns on zirconia implants using micro-CT to assess cement quality and excess.

## Contribution

The study introduces a comparison of abutment-assisted and conventional cementation protocols for lithium disilicate crowns on zirconia implants.

## Key findings

- Adhesive resin cement produced lower porosity and more uniform layers than self-adhesive resin cement.
- The abutment-assisted protocol reduced excess cement, especially with self-adhesive resin.
- Conical abutment geometry caused localized cement accumulations.

## Abstract

To evaluate the influence of two cementation protocols on lithium disilicate crowns cemented to zirconia one-piece implants by analyzing cement thickness, porosity, and excess cement using micro-computed tomography (micro-CT).

Sixteen Computer-Aided Design (CAD)/Computer-Aided Manufacturing (CAM)-fabricated lithium disilicate crowns were cemented onto zirconia one-piece implants (WhiteSKY, Bredent) using two resin-based cements: an adhesive resin cement (ARC) and a self-adhesive resin cement (SARC) based on multifunctional phosphoric methacrylates.

Each cement was applied with either a conventional apical-half (AH) or an abutment-assisted apical-half protocol (A-AH), creating four groups (n = 4). Samples were scanned with micro-CT for volumetric analysis of the cement. Data were analyzed using Analysis of Variance (ANOVA) with Dunnett’s post hoc test (α = 0.05).

The ARC showed lower porosity and more uniform cement layers than the SARC. The A-AH technique significantly reduced excess cement in both cements, particularly with the self-adhesive resin type. All groups exceeded the 50 µm digital cement space, with the self-adhesive A-AH group showing the highest thickness. Conical abutment geometry contributed to localized cement accumulations.

Both the cement type and the application protocol appeared to influence the characteristics of the cement interface. In this study, the ARC tended to produce a more uniform and less porous cement layer, whereas the abutment-assisted protocol was associated with reduced amounts of excess cement. These findings suggest that modifications to the cementation protocol may help to optimize outcomes for zirconia one-piece implant restorations, particularly when using self-adhesive resin systems.