• Prior approval from SOD ethical committee has been received.

• All patients presenting to the General OPD of School of Dentistry, Islamabad will be screened. Those patients who fulfill the criteria will be referred to the Prosthodontics department.

• The patients will undergo detailed history and oral examination after informed consent (Annexure-A). Patients will undergo radiographic investigation and based on this information they will be selected for the study according to the exclusion and inclusion criteria.

• Eligible participants will be randomly assigned to one of the following groups using a computer-generated sequence with allocation concealment via sealed opaque envelopes:

  • Group A: Control group
  • Group B: Full-coverage PFM crowns
  • Group C: Full-coverage Zirconia crowns

• Baseline gingival samples will be collected with the help of sterile swab from the target tooth region prior to prosthesis placement and at the follow-up visits i.e. 1, and 3 months; both for experimental groups and control group.

• Microbial analysis will be conducted through culture techniques to quantify CFUs and identify species.

• A summary of the micro-organisms, their incubation media, temperature and time is presented in the following table:

Table 1: Summary of the micro-organisms, their incubation media, temperature and time Micro-organism Growth Media Temperature Incubation time Candida albicans Saboraud Agar 370C 24-48 hours Streptococcus mutans BHI broth 370C 24-48 hours Staphylococcus aureus BHI broth 370C 24-48 hours Porphyromonas gingivalis BHI broth 370C 18-24 hours

• Alongside, the same sample from sterile swabs will be smeared by fixating it on a microscopic slide and then Candida albicans will be stained by Periodic Acid Schiff technique, and the bacterial species using Gram staining.
• All participants will receive standardized verbal and written instructions oral hygiene instructions to control for hygiene-related variation

Inclusion Criteria:

• Age between 20 to 50 years.
• Both male and female patients will be selected.
• Good oral hygiene (Defined as a plaque index score ≤ 1 across all assessed surfaces and no visible calculus deposits)
• Dentate patients require fixed prostheses for the first time on mandibular pre-molars and molars.
• Patient with no history of any dental and bony pathosis (cysts, cancerous lesion).

Exclusion Criteria:

• Untreated periodontal diseases
• Xerostomia
• Pregnancy, lactation
• Smokers
• Individuals with systemic conditions like diabetes and immunosuppressive diseases

• Eligible participants will be randomly assigned to one of the following groups using a computer-generated sequence with allocation concealment via sealed opaque envelopes:

• Group A: Control group
• Group B: Full-coverage PFM crowns
• Group C: Full-coverage Zirconia crowns
• Single blinding: Due to the nature of the dental procedure and patient involvement in treatment planning, participants will be informed of the crown material being used (PFM or zirconia). However, they will not be informed of the specific purpose of the study (partial blinding).
• The microbiologist conducting sample analysis will be fully blinded to participant group allocation. Additionally, the data analyst will be blinded during statistical evaluation as well.