Association between salivary soluble RANKL, OPG concentration and mandibular resorption to clinically predict severe residual ridge resorption risk: a cross-sectional study

The insidious progression of residual ridge resorption (RRR) following tooth extraction remains a formidable clinical challenge in contemporary dentistry. Understanding its underlying cellular and molecular mechanisms is key to developing both patient-specific risk assessments for preventive care and novel therapies to arrest bone loss. Salivary bone turnover biomarkers show promise as a non-invasive method for evaluating the rate of bone loss. This research aimed to identify the association of salivary receptor activator of nuclear factor-KB ligand (RANKL), and osteoprotegerin (OPG) levels with resorbed mandibular edentulous ridges, proposing a clinical tool for identifying high resorption risk. The mandibular ridge height was determined radiographically on 140 systematically healthy edentulous participants. Based on the Cawood and Howell system and the American College of Prosthodontists classification, the subjects were categorized as severe or normal resorption. Complete denture clinical quality was assessed using the Chulalongkorn University-modified Kapur criteria. Whole unstimulated salivary was collected, and salivary RANKL and OPG protein levels were quantified by enzyme-linked immunosorbent assay technique. Logistic regression analysis was used to develop a risk assessment model for severe resorption. Nomograms were generated from the final model to estimate the risk of RRR. Excessive RRR were found in a notably higher percentage of women (36.43%) versus men (13.57%). A strong association between severe RRR and RANKL, OPG concentration, denture quality, edentulous duration was found. Elevated RANKL levels were significantly associated with increased alveolar bone loss, with each 10 pg/ml increase corresponding to a 4-fold and 3.5-fold increase in RRR odds for women and men, respectively. Conversely, higher OPG levels showed a protective effect; for every 10 pg/ml increase, the RRR odds decreased by 60% for women and 73% for men. To estimate accelerated bone resorption risk, a nomogram with high predictive accuracy (AUC = 0.94) was developed using edentulous duration and RANKL level. Salivary RANKL and OPG levels are strongly associated with the severity of RRR, with gender differences observed in resorbed mandibular. Elevated RANKL increases RRR risk, while higher OPG offers a protective effect. This study’s novel nomogram offers a practical chairside tool to assess this risk, enabling tailored patient counseling and proactive treatment plans to preserve mandibular bone.