This study investigated the effects that disposable infection control barriers and physical damage through use had on the power output from dental light curing units (LCUs) and light curing tips (LCTs). Five disposable infection control barriers were tested on a number of LCUs and LCTs. Testing involved the repeated measurement of power output of LCUs and LCTs on a radiometer. Two of the barriers tested caused statistically significant reductions in the mean light output intensity when compared to the no barrier control groups. One barrier type reduced the power output by 30 to 40%. It was also noted that physical damage to the LCTs affected power output by between 20 and 30%, which was then further reduced by the disposable barrier. This study showed that three of the five disposable infection control barriers had little effect on the overall efficiency of the power output of the LCUs. It also showed that physical damage to LCUs and LCTs can affect power output significantly. Infection control measures should be carefully considered before use to avoid undue effects on power output delivered from the LCUs/LCTs to ensure that the degree of polymerisation within the resin-based composite and curing efficiency are not affected unduly.