An ex vivo study on the correlation between lesion size and resin infiltration area in natural proximal subsurface carious lesions deproteinized with sodium hypochlorite.

OBJECTIVE: This ex vivo study investigated the effects of pre-treatment either with or without a deproteinization procedure using a sodium hypochlorite (NaOCl) solution on percentage resin infiltration in natural non-cavitated proximal subsurface carious lesions of (pre)molars. Moreover, we studied whether a correlation exists between lesion size and infiltration area. METHODS: Extracted human premolars and permanent molars (n = 40 each) with macroscopically non-cavitated proximal subsurface carious lesions (ICDAS code 2/radiographic E2 and D1 lesions) were randomly divided into two groups. In Group 1 (control), the carious lesions underwent a standard resin infiltration protocol (deploying 15 % hydrochloric acid, 99 % ethanol, and Icon Caries Infiltrant). With the specimens of Group 2, a deproteinization step using 1 % NaOCl was applied prior to the standard infiltration procedure. Teeth were sectioned mesio-distally (perpendicular to their occlusal tooth surface and through the proximal lesion) and polished to the deepest lesion extension (as defined by DIAGNOdent). Total lesion sizes and infiltration areas were analyzed via confocal laser scanning micrographs. Paired data were submitted to linear regression analysis employing SPSS (v29.0). RESULTS: With the deproteinized specimens (Group 2), a significantly higher percentage of resin infiltration (p = .003) was observed, along with a strong positive correlation between lesion size and infiltrated area (r = .97; p < .001), if compared to Group 1 (r = .89; p < .001). CONCLUSIONS: Deproteinization with NaOCl prior to resin infiltration significantly enhances the infiltrant's penetration ability into non-cavitated carious lesions, resulting in a strong relationship between lesion size and infiltrated area. CLINICAL SIGNIFICANCE: Deproteinization by means of NaOCl solution should be implemented as an integral step and key component to the standard infiltration protocol to significantly improve the resin infiltrant's penetration ability into initial subsurface lesions.