SHADE STABILITY OF MONOLITHIC ZIRCONIA CROWN IN TOBACCO USER : A COMPARATIVE IN VIVO STUDY

Abstract

The aim of this study was to assess and compare the color stability of monolithic zirconia restorations among four groups of patients: non-tobacco users, smokers, smokeless tobacco users, and dual tobacco users (both smoking and smokeless tobacco). Color stability was evaluated at three time points: baseline, 6 months, and 12 months following restoration placement. Material and Methodology: This prospective in vivo study was conducted in the Department of Prosthodontics at Hitkarini Dental College and Hospital and included 80 patients requiring monolithic zirconia crown and fixed partial denture restorations. The participants were randomly allocated into four equal groups based on their tobacco usage status: non-tobacco users, smokers, smokeless tobacco users, and dual tobacco users (individuals using both smoked and smokeless forms of tobacco). All participants underwent a standardized clinical protocol, including tooth preparation, fabrication of provisional restorations, CAD/CAM milling of monolithic zirconia restorations, and definitive cementation. Color assessment was performed using the VITA Easyshade® V spectrophotometer under standardized operating conditions to ensure consistency. Baseline shade measurements were obtained immediately after final cementation, and subsequent evaluations were carried out at 6-months and 12-months follow-up visits. Color changes were analyzed according to the CIELAB color system. Statistical analysis was performed using SPSS software version 23.0, with a significance level set at P < 0.05. Results: At the 6 months follow-up, no significant differences in the color stability of monolithic zirconia restorations were detected among the four groups (P> 0.05). In contrast, evaluation at 12 months revealed a statistically significant increase in discoloration among participants with tobacco habits compared with non-tobacco users (P < 0.05). Restorations in the non-tobacco group maintained complete color stability throughout the study period. Conversely, color changes were observed in 70% of smokers, 75% of smokeless tobacco users, and 90% of dual tobacco users. The greatest degree of discoloration was recorded in the dual-user group, suggesting that chronic exposure to both smoked and smokeless tobacco has a pronounced negative effect on the long-term esthetic performance and color stability of monolithic zirconia restorations. Conclusion: Monolithic zirconia restorations exhibited excellent color stability during the initial 6-month period. However, extended exposure to tobacco was associated with a significant reduction in long-term shade stability. Non tobacco users preserved the original esthetic appearance of their restorations throughout the study, whereas smokers, smokeless tobacco users, and individuals using both forms of tobacco experienced progressively greater discoloration over the 12-months follow-up. The most pronounced shade alteration was observed among dual tobacco users. These findings indicate that the cumulative duration and extent of tobacco exposure play a more influential role in color deterioration than the type of tobacco consumed, emphasizing the detrimental effect of chronic tobacco use on the long term esthetic performance of monolithic zirconia restorations. Clinical Significance: Monolithic zirconia restorations demonstrate excellent esthetic stability immediately after placement; however, long-term tobacco use can adversely influence their color stability and overall esthetic appearance. Consequently, a patient's tobacco-use history should be incorporated into the treatment planning process. Clinicians should also educate patients regarding the increased risk of restoration discoloration associated with continued tobacco consumption and emphasize the importance of regular maintenance visits and tobacco cessation to enhance the longevity and esthetic success of monolithic zirconia restorations.