RESUMEN
OBJECTIVES: To evaluate the effects of a 1% hyaluronic acid (HA) gel in combination with an absorbable collagen sponge (ACS) in the healing of critical-size calvaria defects in rats. MATERIAL AND METHODS: Thirty-two adult Wistar rats were used. Two 5-mm-diameter critical-size defects were created and the treatments were randomly distributed as follows: (1) 1% HA; (2) 1% HA gel-soaked ACS; (3) control (blood clot); and (4) ACS. The animals were sacrificed 60 days post-surgery, when biopsies were collected and processed for histology and histometric analysis. Bone fill was measured as the difference between the initial and the final defect sizes. Non-parametric tests were used to analyze differences between treatments (α=1%) and a t-test for body weight gain in each treatment group (α=5%). RESULTS: Histological analysis showed bone formation on the edges of the defects, although very limited, and a thin layer of connective tissue occupying the midportion of the defects in the control and the ACS groups. Defects filled with a 1% HA gel and 1% HA gel+ACS had a thicker layer of connective tissue and more new bone formed in the margins of the defects. Linear histometric measures showed no significant differences in the initial defect sizes between the groups (P>0.05). The association 1% HA gel+ACS (0.96 ± 0.14 mm) had significantly greater bone fill than the control (0.5 ± 0.02 mm) and ACS (0.56 ± 0.05 mm)-treated groups (P=0.0043 and 0.0173, respectively). Treatment with a 1% HA gel (0.7 ± 0.14 mm) showed no significant differences when compared with the other treatments. CONCLUSION: Within the limits of this study, a 1% HA gel associated with a collagen scaffold can improve new bone formation in critical-size defects. However, this treatment never resulted in complete closure of the defects and healing in the major portion of the defects was characterized by fibrous tissue.