Background <p>Achieving optimal proximal contacts and marginal integrity is crucial for the success and longevity of dental restorations. This cross-sectional observational in-vivo study aimed to (i) propose a standardized classification index for evaluating proximal contact tightness using dental floss, and (ii) assess the quality of proximal contacts and marginal integrity in various types of direct and indirect restorations using the proposed classification.</p> Methods <p>In this cross – sectional observational study, 344 teeth with diverse restorations (crowns, GIC, composite, amalgam) in posterior teeth were evaluated. Proximal contacts were assessed visually and by tactile methods using a novel index that is standardized. Marginal integrity was assessed using the USPHS-modified criteria. Categories Alpha, Bravo, Charlie, and Delta were used to evaluate restoration performance. Proximal contacts were categorized as open, tight, appropriate, or poor. Marginal integrity was categorized as excellent, acceptable, requirement of clinical intervention and unacceptable. Statistical analyses explored associations between contact/integrity and restoration type, restoration surface, and other factors.</p> Results <p>The prevalence of restorations with appropriate proximal contacts was 34.6%, followed by tight (28.5%), open (24.1%), and poor (12.8%). Crowns exhibited the highest frequency of appropriate contacts (47.4%), followed by GIC (Glass Ionomer Cement) (24.7%), composite (13.4%), and amalgam (14.5%). A substantial amount of the restorations was categorized as acceptable (51.5%) for marginal integrity. 38.9% of the restorations were categorized as charlie, suggestive of repair of the restoration to prevent marginal leakage. Only 8.1% of the restorations were categorized as excellent and 1.5% as unacceptable. A statistically significant association was found between proximal contact tightness and restoration type (<i>p</i> = 0.034), with crowns showcasing superior contact compared to direct restorations. Additionally, a significant association existed between contact tightness and restoration surface involved, with mesio-occlusal surfaces demonstrating more appropriate contacts than distal surfaces. It was seen that single crowns had the most acceptable marginal integrity [<i>n</i> = 110], followed by GIC [<i>n</i> = 50], amalgam [<i>n</i> = 50] and then composite [<i>n</i> = 20]. There is a statistically significant association between marginal integrity and type of restoration.</p> Conclusion <p>A standardized index has been evaluated and this was applied to obtain outcome measures in a quantitative manner. The results suggest that single crowns showed maximum appropriate contacts. Single crowns also had the most acceptable marginal integrity, followed by GIC, amalgam and then composite. This shows that indirect restorations show superior proximal contact and marginal integrity as compared to direct restorations. There is a statistically significant association between the proximal contact and the restoration surface involved.</p>