Mechanical Loading Alleviates BRONJ-Like Lesions Around Implants Under Osteoporotic Conditions: An In Vivo Experimental Model.

Abstract

OBJECTIVES: This study investigated the effects of controlled in&#xa0;vivo repetitive mechanical loading on peri-implant tissue quantity and quality in a bisphosphonate (BP)-treated osteoporosis-like rat model. MATERIALS AND METHODS: At 3&#x2009;months post-ovariectomy, Wistar rats were randomly assigned to receive either alendronate (ALN) or saline. Bilateral maxillary first molars were extracted at 9&#x2009;weeks old, and Grade IV titanium implants were placed in healed alveolar ridges 4&#x2009;weeks after starting treatment. Four weeks postimplantation, sites were randomly assigned to test (Load) or control (Non-load) groups. The Load group received controlled mechanical loading (10&#x2009;N, 3&#x2009;Hz, 1800 cycles, 2&#x2009;days/week) via implants for 2&#x2009;weeks. Peri-implant bone quantity and quality parameters were assessed, including micro-computed tomography (microCT)-derived morphometry, bone-related cell distribution, collagen composition and alignment, and sclerostin expression. RESULTS: BRONJ stage 0-like lesions, characterized by necrotic bone with epithelium coverage, were observed in all ALN-treated maxillae. Despite comparable epithelial and microCT morphometry (p&#x2009;>&#x2009;0.05), the Load group demonstrated significantly improved bone quality around implants, with reduced necrotic bone, higher osteocyte density, fewer osteoclasts and TRAP-positive mononuclear cells at the crestal site (p&#x2009;<&#x2009;0.05), and greater deposition of well-aligned type I collagen (p&#x2009;<&#x2009;0.05). Conversely, the Non-load group exhibited substantially larger necrotic areas, increased empty lacunae, reduced osteocyte density, increased sclerostin expression, and more disorganized type III collagen (p&#x2009;<&#x2009;0.05). CONCLUSIONS: This study is the first to demonstrate that implant loading alleviates BRONJ stage 0-like lesions by enhancing peri-implant bone quality. Mechanical loading promotes peri-implant bone health through cellular adaptation and extracellular matrix remodeling, even under BP-treated osteoporotic-like conditions.