Purpose: The aim of this study was to clinically and radiographically evaluate mandibular overdentures supported by four short implants combined with two different doses of photobiomodulation (PBM).

Materials and methods: A split-mouth design was applied; six completely edentulous male subjects received four short implants in the canine and second premolar area. Short implants were inserted via a digital fully guided approach with a stereolithographic surgical guide. All patients received five PBM sessions immediately after surgery and every 48 hours. Group A (n = 6) implants on the right side received a dose of 3.75 J/cm², and group B (n = 6) implants on the left side received a dose of 7.5 J/cm². Evaluation of peri-implant probing depth (PIPD), modified Gingival Index (MGI), and vertical bone loss was performed at the time of prosthetic loading and 6 and 12 months later. The implant stability quotient (ISQ) was also assessed 6 and 12 months after loading.

Results: There was no significant difference between both groups regarding PIPD values. However, a minor but significant increase from the baseline (P < .001) was observed in PIPD values in both groups after 12 months. The MGI scores at the different time intervals were very low for both groups. The mean vertical bone loss after 12 months was minimal for both groups but statistically significant from the baseline (P < .001). ISQ values for both groups after 12 months revealed a significant increase from the baseline, and group B values were significantly higher than those of group A.

Conclusion: Within the limitations of this study, a mandibular overdenture supported by four short implants is a valid treatment modality for atrophic mandibles, and a PBM dose of 7.5 J/cm² has a potential positive influence on implant healing and osseointegration.