This interventional clinical study aims to compare dentin thickness preservation and tooth discoloration in deep carious lesions treated with Biodentine alone versus diode laser pre-treatment followed by Biodentine. Participants with deep carious lesions will be allocated to one of two treatment protocols, and clinical and radiographic assessments will be performed to evaluate outcomes. The findings of this study may provide evidence on whether diode laser pre-treatment offers additional clinical benefits when used prior to Biodentine application in the management of deep caries.

Deep carious lesions present a clinical challenge due to the need to remove infected dentin while preserving pulp vitality and preventing postoperative complications. Contemporary minimally invasive dentistry emphasizes selective caries removal and the use of bioactive materials to promote pulp healing and reparative dentin formation.

Biodentine is a calcium silicate-based bioactive cement widely used in vital pulp therapy and indirect pulp capping. It provides favorable sealing ability, biocompatibility, and the potential to stimulate reparative dentinogenesis. However, concerns remain regarding the preservation of dentin thickness and the risk of postoperative tooth discoloration when used in deep cavities.

Diode lasers have been introduced as an adjunctive modality in deep caries management due to their antimicrobial effects, ability to achieve hemostasis, and potential to modify dentin surface characteristics prior to placement of restorative materials. Laser pre-treatment may therefore influence clinical outcomes when used before Biodentine application.

This randomized controlled clinical trial is designed to compare two treatment approaches for deep carious lesions in vital posterior teeth. In the control group, selective caries removal will be performed followed by placement of Biodentine. In the experimental group, diode laser pre-treatment of the cavity will be applied prior to Biodentine placement. All procedures will be carried out under rubber dam isolation and standardized aseptic conditions.

Changes in dentin thickness and radiographic density of the remaining dentin will be evaluated using cone beam computed tomography at baseline and during follow-up visits at 3 and 6 months. Tooth color changes will be assessed using standardized digital photography and spectrophotometric analysis. Pulp vitality will be evaluated using cold testing and electric pulp testing, and periapical clinical status will be assessed through percussion, palpation, and tooth mobility examination.

The primary objective of this study is to compare changes in dentin thickness between Biodentine alone and diode laser pre-treatment followed by Biodentine. Secondary objectives include evaluation of radiographic dentin density, tooth color changes, pulp vitality status, and periapical clinical status over a 6-month follow-up period.

This study aims to determine whether diode laser pre-treatment provides additional clinical benefit when used prior to Biodentine application in the management of deep carious lesions.

Inclusion Criteria:

1. Patients aged [ 18-45 years] requiring treatment for a single deep carious lesion and willing to provide informed consent and comply with follow-up appointments. Candidates with good general health.
2. tooth-related criteria included reversible pulpitis or asymptomatic restorable vital permanent posterior molar. (based on clinical and radiographic examination, pulp vitality tests).
3. Radiographic evidence of deep caries approaching the pulp (e.g., inner half of dentin).
4. No signs of irreversible pulpitis or periapical pathology.

Exclusion Criteria:

1. Patients undergoing orthodontic treatment or with significant periodontal disease affecting the study tooth or who cannot tolerate CBCT scanning.
2. patients who are medically compromised (systemic diseases affecting bone metabolism or healing (e.g., uncontrolled diabetes)).
3. pregnant ladies, patients with allergy to any component of Biodentine or other materials used, and patients who are not cooperative.
4. Tooth-related criteria involved teeth that have irreversible pulpitis or necrotic pulp (based on symptoms and vitality tests; spontaneous pain, or sustained pain after vitality tests (electrical or cold tests), teeth with pain on percussion ).
5. Teeth with periapical radiolucency and have been already restored before (previous endodontic treatment)
6. Extensive tooth destruction requiring full coronal coverage.

Individual participant data will not be shared publicly because this is an investigator-initiated academic study conducted at the National Research Centre. Data sharing is restricted by institutional policies and the conditions of ethics committee approval, and the informed consent obtained from participants does not include permission for public sharing of individual-level data.