One-year clinical investigation of the effect of inclusion of three nanoparticles in the heat-cured acrylic resin denture base on the adhesion with the silicone soft-liner

Abstract

Purpose: To evaluate the effect of incorporating three nanoparticles (Titanium oxide, silicon oxide, and alumina) with 1% and 5% concentration on the bond strength to denture base for one year of clinical service. Methods: Fifty-six completely edentulous patients were selected and divided into seven groups according to the nanoparticle material and concentration (n=8). Upper and lower complete dentures were fabricated for each patient. The adhesion of soft liner was done using a five scale questionnaire at insertion (baseline) 4, 8, and 12 months of denture insertion. The data were analyzed by Friedman test with post-hoc Dunn test. Results: At 4 and 8 months, all the nanoparticles groups showed a non-statistically significant difference from the baseline. At 12 months, all groups with 5% nanoparticle concentration showed a statistically significant decrease in the soft liner adhesion. There were no significant differences between all nanoparticles groups during all follow up intervals Conclusion: The addition of nanoparticles to the denture base effectively improved the bond between the soft-liner and the denture base, especially for 1% concentration. KEYWORD: Acrylic resin, Adhesion, Denture, Nanoparticles, Silicone, Soft-liner (1528) Hesham Samy Borg E.D.J. Vol. 67, No. 2 many appliances such as splints, stents, and night guards (2). Despite the popularity of acrylic resin, it is still inadequate to fulfill the ideal mechanical requirements. Clinicians also experience a material fracture due to low impact resistance, flexural stress, or fatigue stress. Acrylic resin has a low impact resistance that usually results in denture fractures (3). In dentistry, soft liner products have been developed as a solution to many problems. These materials will ensure an even distribution of the functional load in the denture-bearing region and avoid load stress concentration. They also improve denture retention as bone resorption occurs(4). It has been stated that soft liner dentures are more comfortable to use compared to rigid acrylic dentures. The use of these dentures is associated with substantial improvements in articulation, chewing performance, denture retention and stability, a decrease in the perception of pain and oral ulcers under dentures, and an improvement in denture satisfaction and duration use (5). Due to their elastic properties, these liners transmit functional and para-functional stresses and act as shock absorbers. They are used as a cushion in patients who cannot withstand denture stress due to sharp, thin, extremely resorbed ridges or bony undercuts, bruxism, and xerostomia. In edentulous arches opposed to natural dentures, and cases with congenital oral defects requiring obturation. In cases where the lower alveolar nerve is visible and in implant overdenture. Soft liners are either based on acrylic resin or silicone. Autopolymerized or heat-polymerized forms are available in both categories (6, 7). The absence of adequate bonding to denture base materials will override the desired soft liner properties (8). Bond failure is a problem that makes the liner surface vulnerable to fungal and bacterial growth. As oral bacteria and fungi penetration of denture soft liner material can lead to plaque, calculus formation, oral tissue infections, material deterioration, and subsequent failure (9). The tensile bond strength of soft acrylic liners is greater than that of silicone-based materials (10). Sandblasting, silica coating, and silane surface treatment of denture base resin did not improve the silicone base soft liner bond strength to the acrylic resin denture (11). Seven of the eight papers concluded in a systematic review that airborne particle abrasion caused degradation of bonding between the liner and the denture base resin (12). The nanomaterial is classified as a natural or produced material containing particles in a nonagglomerated state, and where 50 % or more of the particles have one or more external dimensions in the range of 1–100 nm` (13). Numerous studies have been conducted to determine nanomaterials’ effect on acrylic resin base resin’s mechanical properties. A study found that acrylic resin reinforced with 1% titanium oxide showed a significant improvement in the tensile and impact strength with no harmful effects on other properties (14). Incorporation of 0.4% titanium oxide nanoparticles into the acrylic resin polymer matrix has been shown to have an antibacterial on the Candida species. The nanocomposite was successfully made by the stereolithographic technique (15). Alumina nanoparticles’ addition to acrylic resin enhances its thermal stability and properties (decreased thermal expansion coefficient and contraction) and acrylic resin’s flexural strength. It also decreases water sorption and solubility. Placing silicon carbide filler powders in the palatal area of dentures may increase acrylic resins’ thermal conductivity without decreasing the strength or increasing the denture weight. (16). Improvement of both the impact and transverse resistance of acrylic resin was achieved by incorporating silica nanoparticles with low concentrations. Increased content has resulted in nanoparticle agglomeration and cracks propagation, decreasing both hardness and fracture strength (17). ONE-YEAR CLINICAL INVESTIGATION OF THE EFFECT OF INCLUSION OF THREE NANOPARTICLES (1529)