Inflammatory Biomarkers, Microbial Findings, and Clinical Characteristics Before and After Treatment of Peri-Implant Mucositis Around One-Piece and Two-Piece Dental Implants

BACKGROUND Peri-implant mucositis is a plaque-associated inflammatory lesion of the soft tissues around dental implants and is considered the precursor of peri-implantitis. In two-piece bone-level implants, the implant-abutment interface and the internal cavity may act as reservoirs for bacterial penetration and retention, whereas one-piece implants have no such junction and a continuous transmucosal component. Whether this structural difference affects the host response to nonsurgical mucositis therapy had not been investigated together with clinical and microbiological changes. The primary aim of this study was to compare the changes in peri-implant sulcus fluid (PISF) levels of interleukin-1 beta (IL-1β), interleukin-10 (IL-10), matrix metalloproteinase-8 (MMP-8), and tissue inhibitor of metalloproteinases-1 (TIMP-1) over 3 months after nonsurgical therapy around one-piece and two-piece bone-level implants.

STUDY DESIGN The study was conducted at the Department of Periodontology, Faculty of Dentistry, İnönü University, Malatya, Türkiye, and consisted of two phases. In the cross-sectional phase, implants with peri-implant health and implants with peri-implant mucositis were compared for each implant design at baseline. In the prospective phase, implants with peri-implant mucositis received nonsurgical therapy and were re-examined and re-sampled 1 and 3 months after treatment. The one-piece implants were monoblock implants in which the endosseous and transmucosal portions are manufactured as a single unit (Monoimplant Rough B, Novodent SA, Switzerland), and the two-piece implants were bone-level implants from the same manufacturer (Implantswiss, Novodent SA, Switzerland). All implants had been placed by the same periodontist. Diagnoses were based on the 2017 World Workshop classification of periodontal and peri-implant diseases and conditions.

CLINICAL EXAMINATION All clinical measurements were performed by a single calibrated examiner. Plaque index, gingival index, probing depth, and bleeding on probing were recorded at six sites around each implant with a plastic periodontal probe. Keratinized mucosal width was measured at the mid-buccal aspect. Peri-implant soft-tissue phenotype was assessed with a color-coded probe, and mucosal thickness was measured by transgingival probing under topical anesthesia at 1, 2, and 3 mm apical to the buccal mucosal margin using an endodontic spreader and a caliper. Intra-examiner reliability was assessed by repeated measurements 10 days apart.

SAMPLING Samples were collected between 09:00 and 11:00 on the day after the clinical examination to avoid interference from probing-induced bleeding. After isolation and removal of supragingival deposits, subgingival plaque was collected with sterile paper points inserted at the mesial and distal aspects of each implant for 30 s. PISF was then collected with two paper strips inserted into the sulcus for 30 s each. Samples contaminated with blood or saliva were discarded, and all samples were stored at -80°C until analysis.

NONSURGICAL THERAPY Implants with peri-implant mucositis received mechanical debridement with an ultrasonic device fitted with polyetheretherketone-capped tips to avoid alteration of the implant surface. After isolation, 1% chlorhexidine gel was delivered into the peri-implant sulcus in a single session with a syringe and a 22-gauge needle. Participants were asked to avoid food and fluid intake for at least 2 hours and received individualized oral hygiene instructions, including the use of interdental brushes of appropriate size.

LABORATORY ANALYSES PISF IL-1β, IL-10, MMP-8, and TIMP-1 were quantified with sandwich enzyme-linked immunosorbent assay (ELISA) kits and expressed as total amounts per implant (two pooled strips, each collected for 30 s). The IL-1β/IL-10 and MMP-8/TIMP-1 ratios were calculated from the total amounts. Total DNA was extracted from the plaque samples, and Porphyromonas gingivalis, Fusobacterium nucleatum, Treponema denticola, and Filifactor alocis were analyzed by quantitative polymerase chain reaction (qPCR) with species-specific primers and universal 16S rRNA gene primers as the reference for total bacterial load. Relative abundance was expressed as ΔCt (Ct of the target species minus Ct of the 16S rRNA gene), and a species was considered not detected when no amplification occurred within 40 cycles.

SAMPLE SIZE The sample size was calculated with G*Power 3.1.9.7 from previously reported PISF IL-1β total amounts in healthy and inflamed implants (effect size d=0.87). With a two-sided alpha of 0.05 and 80% power, 22 implants per group (88 implants in total) were required.

STATISTICAL ANALYSIS Nonparametric methods were used. The four groups were compared at baseline with the Kruskal-Wallis test followed by Dunn's post hoc test with Bonferroni adjustment. Within-group changes over time were analyzed with the Friedman test followed by Bonferroni-adjusted Wilcoxon signed-rank tests. The two mucositis groups were compared at each time point and for reductions from baseline with the Mann-Whitney U test, with Hodges-Lehmann estimates and 95% confidence intervals for biomarker reductions. Categorical variables were compared with the chi-square test, and detection frequencies with Fisher's exact test between groups and Cochran's Q test followed by exact McNemar tests within groups. A two-sided p<0.05 was considered statistically significant.