Histological and histomorphometric effects of hyaluronic acid with or without xenograft on rat extraction socket healing

Background Alveolar bone loss following tooth extraction remains a major clinical concern that may compromise future implant placement and prosthetic rehabilitation. Hyaluronic acid (HA), a natural component of the extracellular matrix, exhibits anti-inflammatory, angiogenic, and osteogenic properties that may enhance post-extraction healing. This experimental study evaluated the effect of HA, used alone or combined with a xenograft, on bone regeneration in extraction sockets. Methods Twenty adult female Sprague–Dawley rats were included. Two animals served as untreated baseline histological references, while the remaining eighteen rats underwent mandibular first molar extraction and were randomly allocated into three groups ( n = 6/group): extraction only (control), HA application, and HA combined with xenograft. Each group was further evaluated at 2, 4, and 6 weeks post-extraction, with two animals assessed at each healing interval. Histological evaluation was performed using hematoxylin and eosin (H&E) and Masson’s trichrome staining. Histomorphometric analysis quantified the percentage of newly formed bone area within standardized regions of interest using calibrated ImageJ software. Differences among treatment groups were analyzed separately at each healing interval using one-way ANOVA or the Kruskal–Wallis test, as appropriate, followed by appropriate post-hoc multiple comparisons. Statistical significance was set at p < 0.05. Results Both HA-treated groups demonstrated significantly greater bone formation compared with extraction alone at all healing intervals ( p < 0.001). Histological assessment revealed reduced inflammatory infiltrate and more organized trabecular architecture in HA-treated sockets. Masson’s trichrome staining demonstrated increased collagen deposition and matrix organization, particularly in the HA + xenograft group. Although the combination therapy demonstrated numerically higher bone area values throughout the healing period, no statistically significant difference was observed between HA alone and HA combined with xenograft ( p > 0.05). Conclusion Within the limitations of this exploratory pilot animal study, HA significantly enhanced extraction socket healing by promoting new bone formation, improving trabecular organization, and increasing collagen deposition compared with spontaneous healing. The addition of xenograft resulted in slightly higher histological and histomorphometric values; however, it did not result in statistically superior bone formation compared with HA alone within the experimental timeframe. These findings suggest that HA may represent a promising adjunctive biomaterial for alveolar ridge preservation. Nevertheless, larger preclinical studies and well-designed randomized clinical trials are required to validate these findings and determine their clinical applicability. Clinical relevance The adjunctive application of hyaluronic acid (HA), with or without bone substitute materials, may enhance post-extraction bone quality and accelerate healing dynamics. This could support more predictable ridge preservation outcomes and potentially facilitate early implant placement by improving the quantity and quality of newly formed bone. Therefore, HA may represent a clinically relevant biomaterial in contemporary alveolar ridge preservation protocols.