Effects of chronic daily versus intermittent high-dose ethanol exposure on experimental periodontitis in rats

Alcohol intake has been increasingly recognized as a modifiable factor associated with periodontal disease. However, whether different ethanol exposure regimens differentially influence periodontal destruction remains unclear. This study aimed to directly compare chronic daily ethanol exposure and intermittent high-dose ethanol exposure in experimental periodontitis in rats when total weekly alcohol intake was matched. Experimental periodontitis was induced in male Wistar rats using ligature placement combined with local LPS challenge. Rats entering the formal 6-week intervention were assigned to a water-treated periodontitis group (P), a chronic daily ethanol exposure plus periodontitis group (CDP; 2.5 g/kg once daily, 7 days/week), or an intermittent high-dose ethanol exposure plus periodontitis group (IBDP; 5.8 g/kg, 3 days/week) ( n = 5 per group). Both ethanol groups received a total weekly dose of 17.5 g/kg. Periodontal tissues were evaluated using hematoxylin and eosin staining, micro-computed tomography, quantitative real-time PCR, and tartrate-resistant acid phosphatase staining. Compared with the P group, both ethanol-exposed groups displayed more pronounced periodontal tissue destruction, increased cementoenamel junction-to-alveolar bone crest distance, lower bone mineral density and bone volume fraction, increased TNF-α, IL-6, MMP-3, and RANKL mRNA expression, decreased OPG expression and OPG/RANKL ratios, and increased numbers of TRAP-positive multinucleated cells. Direct comparisons between the CDP and IBDP groups detected no statistically significant differences in the evaluated outcomes. Under matched total weekly ethanol intake, both chronic daily and intermittent high-dose ethanol exposure aggravated experimental periodontitis. No statistically significant differences were detected between the two regimens in the evaluated outcomes. These findings highlight the adverse periodontal effects of both exposure patterns and the value of directly considering alcohol-exposure regimen in periodontal research.