Single-implant Versus Two-implant Mandibular Overdentures

Oral health-related quality of life (OHRQoL) will be assessed using the Oral Health Impact Profile for edentulous adults (OHIP-EDENT). OHIP-EDENT includes 19 items across 7 domains: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap. Each item is rated on a 5-point Likert scale from 0 ("never") to 4 ("very often"). Total score range is 0-76; lower scores indicate better oral health-related quality of life (OHRQoL).

McGill Denture Satisfaction Questionnaire (MDSQ) includes 8 core questions. Each item is scored on a 100-mm VAS (0 = "no satisfaction at all"; 100 = "complete satisfaction"). Total score = sum of 8 items (range 0-800); higher scores indicate greater satisfaction.

Masticatory performance will be assessed using the two-color chewing gum mixing test. Chewed specimens are imaged and analyzed using ViewGum® software to calculate the Variance of Hue (VoH; range 0-1). Lower VoH indicates better color mixing (better masticatory performance).

Postoperative pain/discomfort will be measured using a Visual Analog Scale (VAS). The VAS has an intensity range from 0 to 100, where 0 indicates "no pain" and 100 indicates "worst pain." Higher VAS scores indicate worse outcome (greater postoperative pain/discomfort).

Patient-reported treatment burden will be assessed using the Expected and Perceived Treatment Burden Questionnaire (20 items rated on a 4-point Likert scale: 1 = not burdensome at all to 4 = extremely burdensome); overall and stage-specific burden scores will be calculated as the mean item score (range 1-4), where higher scores indicate greater burden (worse outcome), and an expectation-perception discrepancy will be calculated for each stage as perceived burden - expected burden (positive values indicate greater burden than expected).

Marginal bone level (MBL) will be measured on standardized periapical radiographs as the vertical distance (mm) from the implant platform to the first bone-to-implant contact at the mesial and distal aspects; for each implant and timepoint, mean MBL will be calculated as the average of mesial and distal measurements, and mean MBL change (mm) will be computed as the follow-up mean MBL minus the baseline mean MBL.

Presence of implant in situ without removal.

PPD will be measured at 4 sites/implant (mesial, distal, buccal, lingual) with a periodontal probe as the distance (mm) from the peri-implant mucosal margin to the base of the peri-implant sulcus; the implant-level outcome will be the mean of the four site measurements at each timepoint.

Peri-implant plaque will be assessed at 4 sites/implant (mesial, distal, buccal, lingual) using a periodontal probe by visual inspection along abutment surfaces and scored using the Mombelli modified plaque index (0-3): 0 = no plaque; 1 = plaque detected on probing; 2 = plaque visible to the naked eye; 3 = abundance of soft matter; the implant-level outcome will be the mean of the four site scores per implant at each timepoint.

BOP will be recorded at 4 sites/implant (mesial, distal, buccal, lingual) as present/absent after gentle probing; the implant-level outcome is the percentage of bleeding sites per implant (0-100%) at each timepoint.

Number and type of prosthetic maintenance events and complications related to the mandibular implant-retained overdenture recorded from clinical charts through 12 months after overdenture insertion. Events will be summarized as (a) total number of events per participant and (b) number of participants with ≥1 event. Higher values indicate worse outcome (greater maintenance/complication burden).

Total clinician chair time (minutes) for surgical and prosthodontic procedures required to deliver the implant-retained mandibular overdenture. Lower values indicate greater treatment efficiency.