To investigate the effects of intra-articular injection of alendronate on the mandibular condyle in ovariectomized rats.

Sixty female rats were randomly divided into five groups: ovariectomy with vehicle treatment alone, early alendronate treatment at ovariectomy, late alendronate treatment at 4 weeks after ovariectomy, shamoperation with vehicle treatment, and the normal control rats. The changes in subchondral bone were evaluated by microcomputed tomography (Micro-CT), tartrate-resistant acid phosphatase (TRAP) staining and real-time quantitative polymerase chain reaction (RT-PCR).

Compared with late alendronate treatment, early alendronate treatment improved microstructural properties of the subchondral bone, with higher bone volume ratio (46.4 + 2.5 vs 37.5 + 2.1; P= 0.038), increased trabecular thickness (47.3 + 1.7 vs 34.6 + 1.4; P= 0.029), elevated trabecular number (8.5 + 0.6 vs 6.2 + 0.3; P= 0.041) and lower trabecular separation (30.2 + 1.6 vs 37.7 + 2.6; P= 0.034). Fewer TRAP-positive cells (4.2 + 0.2 vs 6.8 + 0.4; P= 0.019) and a higher OPG/RANKL ratio (0.38 + 0.01 vs 0.25 + 0.03; P= 0.043) in the subchondral bone were observed in the animals with early treatment group compared to late treatment or ovariectomy/vehicle treatment group.

Our results suggest the therapeutic potential of intra-articular alendronate injection in the treatment of osteoporosis-associated temporomandibular disorders.