Effect of disinfection on integrity of dental local anesthetic cartridges

Methods: Plastic and glass cartridges containing 3% prilocaine with 0,03UI/mL felypressin (Cristalia) and 2% mepivacaine with 1:100.000 epinephrine (Septodont) respectively were stored inside their boxes or soaked in 70% alcohol or 0.2% peracetic acid for 40 minutes or 24 hours (n=10 for each group). After each regimen the cartridges were placed in a dental syringe with no needle attached and placed in an EMIC testing machine. A force was applied to the cartridge plunger until failure occurred (fracture for glass; leakage for plastic). The force (in Newtons) required to produce failure was recorded. The pH of the cartridges was recorded after each storage regimen. Data were analysed by ANOVA and unpaired t test.

Results: Plastic cartridges failed at forces significantly less than those required to fracture glass cartridges (mean forces 289N and 418N respectively t=5.61; p<0.001). The force required for failure was not affected by the method of storage for plastic (F=1.05; p = 0.36) and glass cartridges (F=1.59; p=0.22). The pH of the solution in glass cartridges was unaffected by the method of storage. Storage in peracetic acid decreased the pH of the solution in plastic cartridges from a mean baseline reading of 4.55 to 4.18 at 40 minutes and 4.17 at 24 hours (F=5.48; p = 0.01). Similarly storage in alcohol decreased the pH of the solution in plastic cartridges to 4.10 at 40 minutes and 4.14 at 24 hours (F= 7.17; p = 0.03).

Conclusions: Disinfection in alcohol or peracetic acid for up to 24 hours did not affect the forces required to produce failure in dental anesthetic cartridges. The pH of the solution in plastic cartridges was significantly lowered after storage in peracetic acid or alcohol.