This study will be conducted to assess the efficacy of caries excavation using the papain-based chemo-mechanical method (Brix 3000) in comparison to conventional rotary tools in the reduction of the bacterial population in occlusal carious cavities

Twenty-three patients who will fulfill the inclusion criteria will be enrolled to the study. For every patient two contra-lateral class I carious molars will be selected, so the total number of included molars will be 46 molars. One contra-lateral molar will be randomly assigned to the chemo-mechanical (Brix 3000) caries removal technique and the other will be assigned to the conventional rotary one. From every molar two dentin specimens will be collected (baseline and after excavation) with a total of 92 samples

Inclusion Criteria:

1. Class I carious lesions
2. Lower molars
3. Bilateral lesions
4. 18 -50 years
5. Males or Females (Both genders)
6. Good oral hygiene
7. Co-operative patients approving the trial

Exclusion Criteria:

1. Pregnancy
2. Systemic disease or severe medical complications
3. Periodontal problem
4. Mobile teeth, arrest caries and non-vital teeth
5. Smokers
6. Xerostomia
7. Lack of compliance
8. Not received antibiotic therapy since 1 month before sampling