Modification of surface pre-treatment for resin infiltration to mask natural white spot lesions

The aims of this study were to investigate an alternative pre-treatment method for resin infiltration using 37% H3PO4 with a brush applicator and to evaluate the penetration effect of the infiltrant for masking the natural white spot lesions (WSLs) in human teeth.

Seventy extracted human molars and pre-molars with non-cavitated WSLs were collected. Thirty teeth met criteria of ICDAS code 2, and were sectioned, providing a total of sixty paired halves. For the control group, 15% HCl gel was applied for 120s, and 37% H3PO4, gel was gently rubbed with a brush applicator for 30s to the experimental group. Also, to evaluate the penetration effect of the infiltrant by pre-treatment, the specimens were treated with the infiltrant (Icon®). Thicknesses of the removed surfaces and percentages of the infiltrated areas (IA%) were evaluated by CLSM, and micro-morphological changes were observed by SEM.

The mean thicknesses of removed surface layers were significantly different between the control group (36±7.62μm) and the experimental group (13±2.76μm) (p<0.001). But, the means of IA% were similar in both groups (p>0.05). In the SEM images, the prism cores were preferentially dissolved in the control group, while the prism peripheries were preferentially dissolved in the experimental group.

Applying 37% H3PO4 gel with an applicator brush for 30s could increase the permeability and minimize removal of the surface layer of natural WSLs. Moreover, the effect of resin infiltration was similar to the control group which was pretreated 15% HCl gel for 120s in vitro study.

For resin infiltration, applying 37% H3PO4 gel with a brush applicator can preserve the protective surface layers of the WSLs with reduced application time.