CONCLUSIONS Surface alterations of dental restorations can result in increased plaque biofilm. This leads to increased risk of premature restoration failure. Smokeless tobacco, in common use by some US military personnel, represents a potential source for surface alteration. If smokeless tobacco causes an untoward effect, selection of a more resistant restorative material could increase restoration longevity, thus minimizing lost work time and costs associated with replacement of failed restorations. OBJECTIVE Comparatively assess the effect of smokeless tobacco/salivary substitute mixture on altering surface roughness of amalgam, composite resin, and resin modified glass ionomer (RMGI) restorations. METHODS Sixty cubic restorations (3 groups of 20) were fabricated using a 4 mm by 3 mm Teflon mold. One examiner assessed the restorations at time points representing zero days, one day, one week, 2 weeks, one month, and 3 months. The data obtained were collected using a surface profilometer, measured in micrometers. Data were statistically analyzed using 2-way analysis of variance (ANOVA) test. A difference was significant if P< .05. RESULTS Confidence levels with a 95% overall rating received a clinically acceptable classification. The 2-way ANOVA test detected significant differences between baseline, one day, one week, 2 weeks, one month, and 3-month data for surface roughness (P<.05). With respect to time and restoration type, results proved statistically significant with P<.0001. All restorations were statistically significant with respect to change in surface roughness with RMGIs showing the greatest surface roughness alteration. CONCLUSIONS Smokeless tobacco mixed with a salivary substitute altered restoration surface roughness over time. Resin-modified glass isonomer restorations demonstrate the greatest alteration of surface roughness, with amalgam restorations showing the least. Amalgam remains the preferential restorative material in patients who use smokeless tobacco.