ABSTRACT Objective To assess the peri‐implant soft‐tissue and hard‐tissue response to monolithic zirconia (ZrO 2 ) compared to porcelain‐fused‐to‐metal implant crowns (PFMs). Methods This report constitutes a pre‐specified secondary analysis of this RCT. Eighty‐three patients rehabilitated with single‐tooth implants in the molar region were originally randomly assigned to receive either a ZrO 2 or a PFM restoration. At 6 months, clinical parameters (plaque control record, probing depth, bleeding on probing, width of keratinised mucosa and marginal bone level changes) were recorded at the implant site and the adjacent natural tooth. In addition, a peri‐implant soft‐tissue biopsy specimen was harvested between the implant site and the adjacent tooth. The number of inflammatory cells and fibroblasts/fibrocytes was evaluated within four regions of interest (oral epithelium, sulcular epithelium, junctional epithelium, connective tissue). Descriptive statistics were arrived at for all outcomes, and differences between prosthetic materials, sites and timepoints were analysed using linear mixed‐effects models. Results The present exploratory secondary analysis included 67 patients (37 ZrO 2 ; 30 PFM) with complete 6‐month clinical, radiographic and histological data. Clinical parameters at both implant and adjacent tooth sites remained generally stable from baseline to 6 months, with limited marginal bone level changes and comparable outcomes between groups. Histologically, mixed‐effects model analysis showed that the tissue region significantly affected both the inflammatory infiltrate and the fibroblast density ( p < 0.001). The crown materials did not substantially influence the histological outcomes. The distribution of inflammatory infiltrate differed between tooth and implant sites, with the highest values in the sulcular epithelium around implants and in the junctional epithelium around teeth. Fibroblast density was highest in the junctional epithelium at both sites. Conclusion Monolithic zirconia and PFM implant‐supported single crowns resulted in comparable clinical and radiographic outcomes. The peri‐implant soft‐tissue response to the two restorative materials showed a greater effect of the tissue region, while the material itself had only negligible effect. Trial Registration ClinicalTrials.gov identifier: NCT02272491
Zhang et al. (Wed,) studied this question.
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