الفهرس 
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Abstract
The aim of this study was to evaluate the antibacterial action of Trypsin on mature enterococcus faecalis biofilm model and its effect on dentin hardness.
A total of fifty seven human anterior single rooted teeth (resulting in seventy two samples) were used in this study. Teeth were decoronated to length 15 mm, cleaned and shaped. Samples were divided according to the test; for antibacterial testing forty two teeth were used, for biofilm dissolution test ten teeth sectioned into halves (n=20) were used with extra four halves for investigating biofilm development and for dentin hardness test five teeth sectioned into halves (n=10) were used.
Forty whole roots and 20 halves were incubated with previously cultured Enterococcus faecalis to form a biofilm for six weeks in a 37 ºc incubator. Four samples for evaluating biofilm development were scanned using SEM at two time intervals two and six weeks. At the end of the incubation time all teeth were taken out of incubated media and subjected to the planned medication either trypsin 0.5 and 5 % for biofilm dissolution evaluation or trypsin 5 % and TAP for antibacterial testing.
Summary & Conclusion
Page 125
For testing the dentin hardness; five roots sectioned into halves were prepared and set in acrylic moulds then subjected to 200 gram load for 15 seconds dwell time using Vicker’s hardness machine each sample tested in three zones coronal , middle and apical.
After samples treatment, biofilm dissolution samples were evaluated using SEM, while the antibacterial activity samples were collected and tested for bacterial presence and viability using two methods CFU and RT-PCR.
CFU, RT-PCR and dentin hardness values were collected and statistically analyzed.
Results:
Overall, there was a significant bacterial growth reduction in all group tested for antibacterial activity, with the highest antibacterial efficacy shown in the trypsin/TAP treated group followed by the trypsin treated with high significant differences and the least was the TAP treated with less significant difference.
Regarding the biofilm dissolution test all trypsin concentrations showed a massive biofilm reduction and elimination, yet the trypsin 0.5% treated for 5 minutes showed some biofilm remnants in some areas.
Summary & Conclusion
Page 126
The dentin microhardness results showed no statistical significant difference between the means of VHN before and after trypsin treatment.
Conclusions:
Under the condition of the present study, it can be concluded that:
1- Trypsin had promising results as an antimicrobial material having a high efficacy in biofilm dissolution.
2- Application of Trypsin followed by TAP resulted in the highest antibacterial effect.
3- Trypsin had no significant effect on dentin micro-hardness.
Recommendations:
Further investigations for Trypsin are needed regarding its cytotoxic effect & histological examination for living cells after its application.