Efficacy of Bisphosphonates in Inhibition of Caries Progression

Objectives: Bisphosphonates have high affinity for hydroxyapatite and can inhibit hydroxyapatite breakdown. Although studies reported that bisphosphonates can be used for caries treatment, its efficacy has not been fully investigated. The purpose of the study was to assess the therapeutic efficacy of bisphosphonates in inhibiting enamel caries progression.
Methods: 13 extracted human teeth were immersed in demineralization solution (0.5M Lactic Acid) for 3 days to create a total of 84 lesions (approximately 2mm in diameter and 100~200 μm in depth). Lesions were divided into 4 groups and spot-treated for 30min with OsteoSense750(OS), a NIR fluorescence bisphosphonate agent; Etidronate (Et); 5% Sodium Fluoride Varnish (NaF); or double distilled water (ddH₂O). Teeth were then rinsed and immersed in demineralization solution for 5 days. A 2^nd round of treatment was then repeated using the same protocol. Average lesion depth at initial (LDin), post-treatment1 (LD1), & post-treatment2 (LD2) time points were measured using high-resolution 3D x-ray microscopy (Xradia MicroXCT-200). Lesion progressions (LD1-LDin, LD2-LD1) were calculated and compared amongst types of treatment and between the first and second treatments by One-Way ANOVA and student’s t-test, respectively.
Results: The average lesion progressions (μm) after treatment1 were 77.3(OS), 69.0(Et), 44.5(NaF) and 60.8(ddH₂O); NaF indicated significantly lower progression depth than others (p<0.05). The progressions after the second treatment were 48.3, 49.5, 52.6 and 63.6, respectively, and there was no significant difference between the treatments. The lesion progressions after 2^nd round treatment with OS and Et were significantly smaller than the progressions after 1^st round treatment (p<0.01). There was no difference observed for NaF and ddH₂O groups.
Conclusions: These results indicate that bisphosphonate has long-term efficacy for inhibiting enamel caries progression. This may be explained by bisphosphonate’s ability to bind with high affinity to hydroxyapatite and penetrate deeply into enamel.