Introduction
Dental caries is a widespread chronic disease caused by the interaction of dietary sugars, bacteria, and host factors leading to tooth demineralization. Its progression is driven by an imbalance between demineralization and remineralization. Prevention and management are vital to oral health and quality of life. Conventional management relied on removing carious dentin and restoring with materials such as composites, glass ionomer cements, and amalgam but this often required significant tooth structure removal. The Hall technique is a minimally invasive approach in which a preformed metal crown is placed over a carious primary molar without tooth preparation. It seals the lesion, inactivates bacteria, and arrests caries progression. Literature supports its effectiveness, but little evidence exists on its impact on adjacent tooth surfaces compared to modern materials like nano filled composites.

Aim
To compare and evaluate caries progression on tooth surfaces adjacent to primary molars treated with the Hall technique versus nano filled composite restoration.

Objectives
The primary objective is to compare progression of caries on adjacent tooth surfaces. Secondary objectives are to evaluate survival rate of treatments and assess patient acceptance and satisfaction.

Hypothesis
There is a significant difference in efficacy of the Hall technique and nano filled composite restorations in preventing progression of caries on adjacent surfaces.

Review of Literature
Studies from 2019 to 2024 have compared the Hall technique with conventional restorations and atraumatic restorative treatment. Findings generally show higher success rates, lower failure rates, and good acceptance for the Hall technique. Research on nanofilled composites shows clinically acceptable results and potential advantages in restoring primary molars.

Methodology
The randomized controlled study will be conducted in the Department of Paediatric and Preventive Dentistry at King Georges Medical University Lucknow. Ethical approval and informed consent will be obtained. Participants will be children aged five to nine years with primary molars having occluso proximal caries. Exclusion applies to those needing pulp therapy, with poor compliance, lacking adjacent teeth, with systemic issues, or unwilling to participate.

The sample size is thirty nine per group after adjustment for attrition. Participants will be randomly allocated into two groups. Group A will receive Hall technique treatment with preformed metal crowns. Group B will receive nano filled composite restorations with cavity preparation and bonding.

Outcomes
The primary outcome is change in carious lesion status on adjacent tooth surfaces assessed at baseline six months and twelve months using ICDAS. Secondary outcomes are restoration survival rate at twelve months, patient behavior during treatment, patient satisfaction, and reported pain or discomfort.

Data Collection and Analysis
Caries status will be analyzed using non parametric tests. Survival rate will be analyzed with Kaplan Meier survival analysis and log rank test. Patient satisfaction and acceptability will be summarized descriptively. A probability value less than 0.05 will be considered statistically significant.