Effect of Certain Denture Disinfectants on Surface Topography, Microhardness and Dimensional Stability of CAD/CAM Milled Polymethyl Methacrylate and Polyether Ether Ketone Denture Base Materials

Dentures are custom-made medical devices prescribed by dentists and clinical dental technicians to replace oral hard and soft tissue structures. Dentures consist of the denture base and denture teeth. Denture bases can be fabricated using acrylic (polymethylmethacrylate \[PMMA\]), metal alloys (cobalt-chromium) and polymers, such as nylon-based thermoplastic resins, polyether ether ketone \[PEEK\] and aryl ketone polymer. Heat-cured PMMA is the most commonly used denture base; this is inherently porous, non shedding and readily aggregates denture plaque. Denture teeth can be fabricated from acrylic, composite resin, or porcelain as these are significantly smoother surfaces; however, denture plaque can grow around the 'tooth-gingivae' interface, which represents the interface between the denture teeth and pink resin of the denture, representing the gingival tissue.

Denture plaque contains pathogenic microbes including, Candida albicans (linked with denture stomatitis) and Streptococcus mutans (linked with caries development). Methicillin resistant Staphylococcus aureus has been previously isolated from denture patients in general practice and the general hospital setting; however, it is unknown whether cross contamination or infection can occur when handling dentures. Most patients exhibit poor denture hygiene due to inadequate knowledge of optimal/correct cleaning techniques1 and a lack of standardization in denture hygiene assessments; dentists infrequently assess and record patients' denture hygiene status. Poor denture hygiene leads to increased risk of dental caries, periodontal disease, denture stomatitis and halitosis. Improper denture care negatively impacts denture clinical longevity and increases denture plaque aggregation. For example, scratches due to improper brushing technique, such as brushing with too hard a brush, can increase microbial growth, while inappropriate denture cleaner use can permanently damage a denture beyond clinical use. A working knowledge of denture base/tooth materials and denture cleaning methods should ensure optimal denture cleanliness without compromising material integrity and clinical longevity. Therefore, clinician-assisted patient education can improve patients' denture hygiene. The dental team is best suited to help provide patients with the necessary oral and denture hygiene education. The incorporation of CAD/CAM technology into complete denture design and fabrication streamlines the clinical and laboratory processes and provides improved physical properties that enhance denture quality. Studies have shown that CAD-CAM milled resins typically outperform 3D-printed materials in thermal stress resistance. Also, surface properties such as roughness, microhardness, and color stability are crucial determinants of durability and patient satisfaction. For instance, rougher surfaces can promote microbial adhesion, leading to biofilm formation and staining, while smoother, harder surfaces resist wear and microbial colonization. CAD-CAM milled PMMA showed significantly less C adherence. 3 and superior dimensional accuracy and stability compared with 3D printing and conventional methods. It remains the superior choice for long-term denture durability due to its high mechanical strength and wear resistance.

This study aims to evaluate and compare the influence of different denture cleansing methods using 1% sodium hypochlorite solution, 0.2% chlorhexidine solution and effervescent alkaline peroxide tablet solution -according to manufacturer's instructions- on surface roughness , microhardness and dimensional stability (%) of CAD-CAM Milled both Polymethyl methacrylate and Polyether Ether Ketone denture base materials.

• M0 group (Other): Immersed in distilled water at 37 c for 6 months
• M1 group : PMMA+ Sodium hypochlorite (Other): Immersed in 1% sodium hypochlorite solution for 6 months
• M2 group: PMMA+ Chlorhexidine (Other): Immersed in 0.2% chlorhexidine solution for 6 months
• M3 group : PMMA + Effervescent Alkaline Peroxide Tablet (Other): Immersed in Effervescent tablet denture cleanser solution for 6 months
• E0 group : PEEK control group (Other): Immersed in distilled water at 37 c for 6 months
• E1 group : PEEK + Sodium hypochlorite (Other): Immersed in 1% sodium hypochlorite solution for 6 months
• E2 group : PEEK +Chlorhexidine group (Other): Immersed in 0.2% chlorhexidine solution for 6 months
• E3 group: PEEK + Effervescent Alkaline Peroxide Tablet (Other): Immersed in Effervescent tablet denture cleanser solution for 6 months

Primary outcomes

• Surface Roughness Measurement [6 months]: Surface roughness (Ra) was measured using a profilometer. Each specimen was scanned at three random locations, and the mean value was recorded. The device was calibrated using the manufacturer's reference standard prior to each measurement session.

Secondary outcomes

• Microhardness Evaluation [6 months]: Surface hardness was determined by loading each specimen for 15 s with a force of 50 g, after mounting it on the microhardness tester. A rhomboid-shaped indentation was obtained on each specimen and its image was transferred to the computer monitor with the help of a microscope present along with the microhardness tester. The longest diagonal of the diamond indentation was marked and Vickers hardness number was calculated with the help of the software

Sex: All

Inclusion Criteria:

* Used prefabricated CAD-CAM blocks (PMMA and PEEK, dental grade)
* All specimens milled using standardized CAD-CAM protocols
* Materials from same brand, batch and shade per group
* All specimens polished to a clinical high gloss standard
* Used standardized specimen geometry

Exclusion Criteria:

* Specimens fabricated using a method other than CAD-CAM milling
* Use blocks from different manufacturer, batches or shades within the same test group
* Use specimens with fabrication defects (visible porosity, cracks, internal voids) or obvious milling errors (tool chattering marks, incomplete milling)
* Specimens with dimensional inaccuracy
* Specimens subjected to incorrect immersion time, temp or concentration of disinfectant
* Use contaminated, not freshly prepared or expired disinfectant solutions