Hydroxyapatite

A meta-analysis of 6 RCTs (n=614) found ossein-hydroxyapatite complex (OHC) preserved +1.02% more BMD than calcium carbonate. The largest comparative study (n=851 perimenopausal women, 3 years) showed OHC maintained stable lumbar BMD while calcium carbonate lost 3.1% (p<0.001), despite the OHC group receiving less elemental calcium (712 vs 1000 mg/day). Additional RCTs in postmenopausal, surgically menopausal, and senile osteoporosis populations consistently favor OHC over calcium carbonate for BMD preservation.

Two controlled trials in corticosteroid-treated patients found MCHC attenuated bone loss. Stellon et al. (1985) showed MCHC halted bone mineral content loss in 36 patients with chronic active hepatitis on corticosteroids over 2 years (p<0.025 for cortical thickness). Pines et al. (1984) found MCHC (6-8 g/day) significantly reduced bone pain (p<0.001) and slowed cortical bone loss in 40 patients on long-term prednisolone.

Multiple RCTs demonstrate hydroxyapatite (HAP) toothpaste is non-inferior to fluoride toothpaste for caries prevention. An 18-month double-blind RCT in 189 adults found no DMFS increase in 89.3% of HAP vs 87.4% of fluoride users. A 1-year RCT in 207 children showed equivalent caries rates. A systematic review and meta-analysis of clinical trials found non-significant differences between HAP and fluoride (RR 0.98, OR 0.90), supporting HAP as a safe, effective fluoride alternative for caries prevention.

Two double-blind RCTs by Vano et al. (2014, 2018) demonstrated nano-hydroxyapatite toothpaste significantly reduces dentin hypersensitivity compared to conventional fluoride toothpaste, with measurable pain reduction at 2 and 4 weeks. An additional RCT on white spot lesions confirmed desensitizing properties. The mechanism involves occlusion of dentinal tubules by hydroxyapatite particles, which is well-established in vitro.

Two RCTs in orthodontic patients with white spot lesions found nano-hydroxyapatite toothpaste performed equal to or better than fluoride for remineralization. Badiee et al. (2020) found nHA outperformed fluoride in both remineralization amount and lesion extent reduction over 6 months in 50 patients. In vitro studies consistently demonstrate HAP's ability to remineralize enamel surfaces and deposit mineral into demineralized lesions.

A single RCT in 100 postmenopausal women (Bristow et al., 2014) found microcrystalline hydroxyapatite produced significantly less acute serum calcium spike compared to calcium citrate and calcium carbonate, while equally reducing PTH and favorably affecting bone turnover markers at 3 months. This blunted calcium spike may have cardiovascular safety implications, though this has not been directly tested.