Table 2. Studies included.

Sr: strontium, nHAP: nanohydroxyapatite, CPP-ACP: casein phosphopeptide-amorphous calcium phosphate, ACP-CPP: amorphous calcium phosphate-casein phosphopeptide, ANOVA: analysis of variance, SEM: scanning electron microscopy, EDX: dispersive X-ray

Author	Size and source of sample	Teeth	Remineralization evaluation	Study groups	Results
Krishnan et al. (2016) [13]	50	Intact premolars	Atomic force microscopy, SEM, and microindentation testing	Group I: control/no treatment, group II: ACP-CPP-based solution used, Group III: Acclaim (commercially available nHAP, Group Pharmaceutical Limited), group IV: nHAP (custom prepared), group V: 25 mol% Sr-doped nHAP group VI: 50 mol% Sr-doped nHAP	The mean and standard deviation values of the Vickers micro-hardness from the dental specimens of all six groups and the results of one-way ANOVA show that the specimens treated with 50% strontium-doped nHAP possess greater hardness in comparison with all other specimens (p=0.001). The increase in crystallinity and reduced particle size favored dissolution and re-precipitation through small incipient carious lesions and soft white spot areas with 25% Sr-doped nHAP. Sr-doped specimens showed more cell viability in comparison with pure nHAP.
Rajendran et al. (2020) [16]	60	Intact premolars	Cytotoxicity by direct microscopic observation and MTT assay remineralization by SEM and EDX analysis	Group I: regular toothpaste, group II: SrnHAP paste	Statistical analysis was done using one-way ANOVA and Tukey’s post hoc test. Intergroup comparison of group I and group II after remineralization was done using Student’s t-test (p<0.001). The result of the study concluded that SrnHAP paste showed better remineralization potential and favorable surface changes in enamel compared to the regular dentifrice.
Rajendran et al. (2021) [17]	90	Intact premolars	SEM and EDX analysis	Group I: conventional toothpaste, group II: CPP-AMP-containing toothpaste, group III: SrnHAP paste	The novel laboratory-synthesized Sr‑doped nanohydroxyapatite showed better remineralization than CPP‑ACP (one-way ANOVA and Tukey’s post hoc test: p<0.001).
Rajendran et al. (2022) [18]	120	Intact premolars	SEM and EDX analysis	Group I: conventional toothpaste (control group), group II: calcium sodium phosphosilicate (NovaMin), group III: CPP-ACP (GC tooth mousse), group IV: novel strontium-doped nanohydroxyapatite paste (SrnHAP paste)	Kruskal‑Wallis, ANOVA, and Mann-Whitney tests showed significant p values. The novel laboratory-synthesized SrnHAP showed better remineralization compared to other groups with GC tooth mousse and NovaMin.