Laser-induced prevention of dental caries has been studied extensively. However, the cariostatic mechanisms of a combined fluoride-laser treatment are not well-understood. Using micro- computed tomography (micro-CT), we quantified the effect of fluoride and/or Er:YAG laser treatment on enamel demineralization. The mean mineral loss (%/V) for each group was 4,870 ± 1,434 (fluoride followed by laser treatment), 6,341 ± 2,204 (laser treatment), 7,669 ± 2,255 (fluoride treatment), and 10,779 ± 2,936 (control). The preventive effect of the laser (p < 0.001) and fluoride (p = 0.010) treatment was statistically significant. Characterized by micro-x-ray diffraction (XRD) analysis, the significant contraction in the a-axis after both laser and combined laser/fluoride treatment was revealed (both p < 0.05). In conclusion, subablative low-energy Er:YAG laser irradiation following fluoride treatment may instantaneously transform enamel hydroxyapatite into fluoridated hydroxyapatite to reduce enamel solubility as a preventive treatment for enamel demineralization.

Objectives: To characterize the cariostatic potential of a low-energy Er:YAG laser treatment. Methods: Twelve sound premolars were selected. Two 2 × 1 mm windows were created on each tooth and randomly assigned to L₁ and L₂ groups. Three sites in each window were chosen with the middle site as the control and the left and right ones receiving Er:YAG laser treatment of 5.1 J/cm² (L₁) or 2.0 J/cm² (L₂), respectively. The teeth were further subjected to 4-day pH cycling to create caries-like lesions. After mineral quantification using a micro-computed tomography scanner, the preventive effects (ΔML = mineral loss of the control area minus that of the lased area) of L₁ and L₂ treatments were calculated based on the difference in the gray value of the control and lased sites. Results: Significant inhibitory effects of L₁ and L₂ on enamel demineralization were demonstrated (both p ≤ 0.001), with the L₁ treatment having a greater effect (45.2%) than the L₂ treatment (25.2%, p = 0.004). Conclusions: Subablative low-energy Er:YAG laser irradiation can significantly prevent enamel demineralization potentially through the retardation of enamel diffusion. This study confirmed that high-energy laser treatment, which may damage the peripheral and underlying tissues, may not be needed for caries prevention.

Poly(N-acryloyl-N ‘-phenylpiperazine) (PAPP) forms miscible blends with poly(p-vinylphenol) (PVPh), and it forms complexes with three stronger acidic polymers, namely, poly(styrenesulfonic acid) (PSSA), poly(vinylphosphonic acid) (PVPA), and poly(acrylic acid) (PAA). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to study the nature of interpolymer interactions in these blends and complexes. All three types of interacting sites of PAPP are involved in interactions with the acidic polymers. PAPP interacts with PVPh and PAA through hydrogen-bonding interaction, whereas it interacts with PSSA and PVPA through a combination of hydrogen-bonding and ionic interactions. As compared to poly(N-acryloyl-N ‘-methylpiperazine), the interactions between PAPP and the acidic polymers are less intense because of the steric shielding effect of the phenyl groups and the lower basicity of the tertiary amine nitrogen.

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