Available online 18 November 2022

This research was nominated as the Malaysia-country-representative paper for KAP-AAP award at the 13th Biennial Congress of the Asian Academy of Prosthodontics (AAP) Philippines held from 25th to 27th of August 2022 and selected as one of the 7 finalists.

The 2-implant mandibular overdenture (2IMO) is a popular treatment for patients with an edentulous mandible, but information on the effect of the optimum implant position on the peri-implant crestal bone level with immediate loading protocols is lacking.

The purpose of this prospective clinical study was to evaluate correlations between different implant positions and crestal bone loss and between interimplant distance and the crestal bone loss in patients with 2IMOs with immediate loading protocols at 1-year follow-up.

A total of 24 participants (13 men, 11 women, mean ±standard deviation age 63.25 ±10.76 years) were treated with 2IMOs (48 Ti-Zr implants) by a single operator between August 2015 and October 2020. The implant diameters (3.3 mm or 4.1 mm) and lengths (10 mm or 12 mm) were selected based on the crestal bone width, and the implants were placed, if possible, in the canine regions. Implant positions and interimplant distance (mm) were measured intraorally with dividers. Prefabricated mandibular dentures were immediately loaded with the LOCATOR-attachments by using a direct intraoral pickup procedure. Crestal bone-level changes were measured with a software program on the mesial and distal sides of each implant from periapical radiographs made with a paralleling technique (at baseline and 1-year follow-up). The measurement values were normalized. The Spearman rho correlation test and paired samples t tests were used for data analysis (α=.05).

The mean ±standard deviation position of the implants from the midline was 8.78 ±2.25 mm (9.00 ±2.22 mm right side, 8.56 ±2.31 mm left side), and the mean interimplant distance was 16.94 ±4.03 mm. At 1-year follow-up, the mean ±standard deviation crestal bone loss was 0.50 ±0.47 mm (n=48) (0.57 ±0.65 mm mesial, 0.43 ±0.53 mm distal). The mean ±standard deviation crestal bone loss was 0.46 ±0.4 mm with Ø3.3-mm implants (n=42) and 0.9 ±0.8 mm with Ø4.1-mm implants (n=6) (P=.005). Implant positions were negatively correlated (rs=-0.37) with the crestal bone loss, and the correlation was significant (P=.009). Interimplant distances were also negatively correlated with crestal bone loss (rs=-0.60; P=.002). Bone loss on the mesial side was positively correlated with that on the distal side rs=0.20; however, the correlation was not significant (P=.16).

A weak and negative correlation was found between the implant position from the midline and the crestal bone loss and also between the interimplant distance and crestal bone loss in patients provided with 2IMOs with immediate loading protocols.

This prospective single-center clinical study was planned in the oral health clinic of the authors’ university. The study was an integral part (as a secondary outcome measure) of a clinical trial3,8 evaluating the clinical performance of 2- or 1-implant overdentures with immediate loading protocols. The participants from the 2-implant group were studied further for possible correlation with crestal bone loss. The study conformed to the consolidated standards of reporting trials (CONSORT) 2010

Of 48 implants, 42 were Ø3.3 mm and 6 were Ø4.1 mm. A total of 37 implants were of 10 mm in length, and 11 implants were of 12 mm in length (Table 1). A strong intraoperator agreement was observed for the measurement values at both time points (κ=.89). The mean ±standard deviation position of the implants from the midline was 8.78 ±2.25 mm (9.00 ±2.22 mm right side, 8.56 ±2.31 mm left side) (Fig. 3, Table 2), and the mean ±standard deviation interimplant distance was 16.94 ±4.03 mm (Table 2).

The research hypothesis was not rejected, as the results indicated a weak and negative correlation between implant positions and crestal bone loss and also between the interimplant distance and crestal bone loss. The position of the teeth may vary according to the age, sex, ethnicity, and physique of an individual. Variations in the size and shape of the jawbone and the available bone volume in the canine region may lead the clinician to place the implants in slightly different positions. A

Based on the findings of this 3D finite element analysis study, the following conclusions were drawn:

A weak and negative correlation was found between the implant position from the midline and crestal bone loss in participants provided with 2IMOs with immediate loading protocols.

A weak and negative correlation was found between the interimplant distance and crestal bone loss in patients provided with 2IMOs with immediate loading protocols.

Pravinkumar G. Patil: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Writing – original draft, Writing – review & editing. Liang Lin Seow: Conceptualization, Data curation, Formal analysis, Funding acquisition, Project administration, Supervision, Validation, Visualization, Writing – review & editing.

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© 2022 by the Editorial Council for The Journal of Prosthetic Dentistry.