Marginal Bone Loss and Peri-Implant Bleeding Around CAD/CAM Zirconia vs. Titanium Abutments with Concave Emergence Profiles: A Systematic Review and Meta-Analysis

Abstract

Background: Implant abutment material may influence peri-implant hard- and soft-tissue responses. Titanium remains widely used because of its mechanical reliability and established long-term clinical performance, whereas zirconia offers favorable esthetic characteristics and may influence plaque accumulation and peri-implant soft-tissue behavior. Variation in abutment customization, CAD/CAM fabrication, transmucosal contour, implant location, and follow-up duration contributes to heterogeneity in reported clinical outcomes. Objective: This systematic review compared marginal bone-level outcomes and peri-implant soft-tissue health around zirconia and titanium implant abutments and examined abutment design and transmucosal geometry as potential sources of clinical heterogeneity.

Methods: This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) statement. We searched MEDLINE via PubMed, Embase, Scopus, Web of Science, and the Cochrane Central Register of Controlled Trials for prospective clinical studies directly comparing zirconia and titanium implant abutments; we also examined ClinicalTrials.gov and the reference lists of eligible publications. No language restriction was applied. Two reviewers independently screened records, assessed full-text eligibility, and extracted study and outcome data, resolving disagreements by discussion and consensus. We assessed randomized controlled trials with the Cochrane Risk of Bias 2 tool and non-randomized comparative studies with ROBINS-I. Publications originating from the same clinical population were identified by comparing study centers, investigators, sample characteristics, and follow-up periods, and were linked rather than treated as independent cohorts.

Results: Nineteen publications met the eligibility criteria, corresponding to twelve independent clinical investigations. Four publications followed a single randomized cohort over 1, 3, 5, and approximately 13 years (Sailer 2009 [5]; Zembic 2009 [6]; Zembic 2013 [7]; Humm 2023 [8]). Three publications followed a second cohort over 1, 3, and 5 years (Hosseini 2011 [9]; Hosseini 2013 [10]; Hosseini 2022 [11]). Two publications followed a third cohort over 1 and 5 years (Carrillo de Albornoz 2014 [14]; Ferrantino 2023 [15]). Two further publications reported a linked or related cohort at 3 years (de Oliveira Silva 2020 [20]; de Freitas 2021 [21]). The remaining eight publications (Lops 2013 [12]; Lops 2015 [13]; Bressan 2011 [16]; Cosgarea 2015 [17]; Payer 2015 [18]; Baldini 2016 [19]; Bittencourt 2023 [22]; Bharate 2020 [23]) were treated as independent investigations. Follow-up across the evidence base ranged from approximately 1 year to more than 13 years. Quantitative descriptive data for probing pocket depth, peri-implant bleeding, and marginal bone level or bone-level change were available for ten of the nineteen publications. Probing pocket depth was broadly similar between zirconia and titanium groups across these studies. Bleeding parameters were reported using non-interchangeable measures (mean bleeding-on-probing scores, percentages of bleeding sites, and modified bleeding indices) and did not show a consistent direction of difference favoring either material. Marginal bone level or bone-level change was comparable between zirconia and titanium in most studies reporting this outcome, with a numerically greater bone-level change reported for zirconia relative to the titanium/metal group in one cohort at 5 years (Hosseini 2022 [11]). Bharate et al. 2020 [23] similarly reported significantly less 1-year crestal bone-height reduction around zirconia than titanium abutments (0.487 ± 0.159 mm vs 0.621 ± 0.207 mm; P=0.02) — the only study in the evidence base to report a statistically significant between-material difference for a hard-tissue outcome. Because of differences in outcome definitions, measurement time points, and the repeated-cohort structure of the evidence, these findings are reported as a narrative synthesis of study-level results; pooled quantitative effect estimates were not generated. Conclusion: Zirconia and titanium abutments show broadly comparable clinical performance for probing depth, peri-implant bleeding, and marginal bone stability across the available prospective evidence, with an isolated exception in one cohort. Zirconia's principal reported advantage relates to esthetics in mucosally thin sites, whereas titanium is supported by the longest available follow-up data. Interpretation is limited by heterogeneity in abutment design, outcome definitions, incomplete reporting of transmucosal geometry, and the repeated-cohort structure of the literature.