Influence of Implant Insertion Torque on Post-Surgical Marginal Bone Stability

This proposed study is a prospective, observational multicenter clinical trial. Ten independent clinical centers will treat partially edentulous patients with dental implants following a specific surgical protocol.

Enrollment Procedure: All patients meeting the inclusion and exclusion criteria will be enrolled in the study after receiving the Information Sheet and providing written informed consent.

Pre-surgical planning will be performed using a CBCT scan with or without the aid of dedicated image reconstruction software. A preoperative periapical radiograph will also be taken using a customized Rinn-type film holder for each patient, with the aid of a silicone key.

Surgical phase: After local anesthesia with 4% articaine containing 1:100,000 epinephrine, a minimally invasive full-thickness mucoperiosteal flap will be elevated to visualize the crest anatomy. The height of the supracrestal soft tissue will be measured using a dedicated probe (SSL, Medesy, Maniago, Italy) and categorized as thin (\<2.5 mm), medium (2.5-3.5 mm), or thick (>3.5 mm).

Implant site preparation will be carried out using a dedicated surgical kit (Anyone, Megagen, Gyeongbuk, South Korea). The implant (Anyone, 4.0×8.5 mm) will then be placed at crestal level, with torque values recorded throughout the entire insertion process using a surgical motor set to 30 rpm (Implantmed, W\&H, Burmoos, Austria). The maximum torque will be limited to 80 Ncm.

If the maximum torque is insufficient to complete insertion, the implant will be removed and the site will be further prepared using the next drill in the sequence.

After crestal-level placement, Patients will be prescribed an NSAID (ibuprofimplant stability (ISQ) will be measured in the mesio-distal, disto-mesial, bucco-lingual, and linguo-buccal directions using a resonance frequency analysis device (Osstell Beacon, Osstell, Göteborg, Sweden) with a single-use magnetic peg specific to the implant (SmartPeg Type 07, Osstell, Göteborg, Sweden). Calibration of the device must be verified prior to each patient procedure using an implant secured in a resin block.

The flap will be closed using non-resorbable monofilament sutures, and the implant will be submerged (two-stage protocol). A periapical radiograph will be taken at this point (T0) using the previously described customized Rinn-type holder. en 600 mg, as needed) and instructed to rinse with 0.2% chlorhexidine mouthwash for two minutes, three times per day, starting on the second postoperative day.

Sutures will be removed 7-10 days after surgery.

Post-surgical follow-ups: After three months of healing (T1), a periapical radiograph will be taken using the previously described customized holder, and a second-stage surgery will be performed to uncover the implant. Following ISQ measurement as previously described, a definitive transmucosal abutment of appropriate length and diameter (OCTA, Megagen, Gyeongbuk, South Korea) will be connected. After a four-week healing period, an abutment-level impression will be taken for the fabrication of the final prosthesis, which may be either a single screw-retained metal-ceramic crown or a screw-retained bridge.

Periapical radiographic follow-ups will be performed as described above at prosthesis delivery and at 6 months, 1 year, 3 years, and 5 years post-loading to assess marginal bone stability.

Radiographic Measurements: All radiographs will be taken using identical radiographic device settings (60 kV, 7 mA). Peri-implant bone levels (PBL) will be measured at T0 and T1 as the linear distance between the implant platform and the bone crest at the mesial and distal aspects of each implant. A positive value will be assigned when the bone crest is coronal to the implant platform, while a negative value will be recorded when the first bone-to-implant contact is apical to the implant platform.

The difference in PBL between T0 and T1 will represent marginal bone loss if PBL_T1 \< PBL_T0, and marginal bone gain if PBL_T1 > PBL_T0. Measurements will be calibrated according to the known implant diameter and length.

Any radiograph showing distortion and/or other quality issues must be immediately retaken.

All measurements will be performed by two blinded examiners using image analysis software (ImageJ 1.52a, National Institutes of Health, Bethesda, MD, USA) on a 24-inch medical-grade monitor. Each measurement will be repeated three times at three different time points, as proposed by Gomez-Roman and Launer.

Examiner calibration will be carried out on a sample of ten radiographs not included in the study. The Cohen's kappa coefficient (k) will be calculated by a third investigator to assess intra-examiner and inter-examiner agreement.

Statistical Analysis: Descriptive statistics will be used to summarize the baseline characteristics of the study population. The relationship between insertion torque and marginal bone loss will be assessed using regression models, adjusting for potential confounding variables. Repeated measures ANOVA will be used to analyze ISQ changes over time. A p-value \<0.05 will be considered statistically significant. Data analysis will be performed using SPSS Statistics v25.0 (IBM Corp., Armonk, NY, USA).

Sample Size Calculation: The sample size was calculated based on a previously published study (Marconcini S, Longitudinal analysis on the effect of insertion torque on delayed single implants: A 3-year randomized clinical study. Clin Implant Dent Relat Res. 2018;20(3):322-332.), which reported a one-year failure rate of 1.72% (1/58) in the low insertion torque group (\<50 Ncm) and 3.45% (2/58) in the high insertion torque group (≥ 50 Ncm). A 1:1 allocation ratio was considered, with a significance level of 0.01 and statistical power of 90%. The minimum required sample size was 68 implants (34 per group). To compensate for potential drop-outs and to allow for repeated measures analysis, 150 implants will be placed across 10 clinical centers (15 implants per center). Each patient may contribute up to 3 implants.