The aim of the study was to determine the association between the number of natural teeth and oral impacts in Sri Lankan adults. The sample consisted of 476, 40-59 and 452, =60 year olds. Oral impacts were assessed using a validated Sinhalese translation of the Oral Health Impact Profile-14 scale. A receiver-operating characteristic (ROC) curve was plotted to determine the number of natural teeth that would best discriminate those with oral impacts from those without. Oral impacts were reported by 26% of the 40-59 year olds and 34% of the older individuals. In both groups there was a significant negative correlation between the number of teeth present and oral impacts. The ROC curve for the 40-59 year olds gave an area under the curve (AUC) of 0.758 (95% CI = 0.702-0.814; P < 0.001) with an optimal cut-off of 24/25 teeth while for the =60 year olds, the AUC of the ROC curve was 0.737 (95% CI = 0.684-0.790; P < 0.001) with an optimal cut-off of 18/19 teeth. Based on the ROC curves the optimal cutoffs of the number of natural teeth that best discriminated between those with and without oral impacts for 40-59 and =60 year olds were 24-25 and 18-19, respectively.