Biomechanical Aspects of Various Attachments for Implant Overdentures: A Review.

There have been considerable recent technological developments for implant overdenture attachments. This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. Available articles on attachments for implant overdenture were reviewed from January 1980 to August 2021 in the ScienceDirect, MEDLINE/PubMed, and Web of Science resources, and relevant studies were included in this study. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction.

Wear resistance of a modified polymethyl methacrylate artificial tooth compared to five commercially available artificial tooth materials.

STATEMENT OF PROBLEM: Wear resistance is a limitation of artificial denture teeth. Improving the wear resistance of conventional artificial denture teeth is of value to prosthodontic patients. PURPOSE: The purpose of this in vitro study was to evaluate the wear resistance and hardness of modified polymethyl methacrylate artificial denture teeth compared to 5 commercially available artificial tooth materials. MATERIAL AND METHODS: This study evaluated 180 artificial denture teeth (6 groups) that included 3 groups of conventional artificial teeth (MajorDent, Cosmo HXL, and Gnathostar), 2 groups of composite resin artificial teeth (Endura and SR Orthosit PE), and 1 group of modified surface artificial teeth. The flattened buccal surface of each tooth (n=15) was prepared for investigation with the Vickers hardness test and the elucidate wear test (n=15) by using a brushing machine. Each group was loaded for 18,000 cycles, at 2 N, and 150 rpm. The wear value was identified with a profilometer. The data were statistically analyzed by using 1-way ANOVA and post hoc Turkey honestly significant difference tests (α=.001). The tribologies were observed under a scanning electron microscope, and the cytotoxicities were evaluated by MTT assay. RESULTS: The Vickers hardnesses ranged from 28.48 to 39.36. The wear depths and worn surface area values ranged from 1.12 to 10.79 µm and from 6.74 to 161.95 µm(2). The data revealed that the modified artificial denture teeth were significantly harder and exhibited significantly higher wear resistance than did the conventional artificial teeth (P<.001). The scanning electron microscopic images revealed cross sections of the conventional artificial denture teeth with intensively worn surface areas after brushing. The cytotoxicity test revealed 97.85% cell viability, which indicates the nontoxicity of the modified surface of this material. CONCLUSIONS: Within the limitations of this study, the polymethyl methacrylate modified surface artificial denture teeth was not significantly different from that of the composite resin artificial denture teeth, with the exceptions that the surface was harder and more wear resistant.

The effects of silane-SiO2 nanocomposite films on Candida albicans adhesion and the surface and physical properties of acrylic resin denture base material.

STATEMENT OF PROBLEM: Polysiloxane has been used as a coupling material in restorative dental materials for several decades. However, few studies are available on the application of polysiloxane in other dental prosthesis functions. PURPOSE: The purpose of this study was to investigate the effects of silane-SiO2 nanocomposite films on Candida albicans adhesion and the surface and physical properties of acrylic resin denture base materials. MATERIAL AND METHODS: Specimens were separated into 2 groups, uncoated and coated. They were coated with a film by using the dip-coating method. Specimens were incubated with Candida albicans 10(7) cells/mL for 1 hour, and the adherent cells were counted under an optical microscope. The following surface properties were measured: surface chemical composition with Fourier-transform infrared spectrometry, surface roughness with a surface profiler, surface energy with the sessile drop method, and surface hardness with a microhardness tester. The physical properties, including water sorption, water solubility, ultimate flexural strength, and flexural modulus, were evaluated according to International Organization for Standardization 20795-1 requirements. The adhesion of Candida albicans and the surface properties of the specimens were investigated after cleaning with effervescent tablets and brushing. An MTT assay was used to evaluate the coated specimens. The results were statistically analyzed with the Mann-Whitney U test (α=.05). RESULTS: A significant reduction in Candida albicans adhesion (P=.002) was observed before cleaning. In addition, the surface energy was comparable (P=.100), the surface hardness increased significantly (P=.008), and the surface roughness remained unchanged (P=.310). After cleaning with effervescent tablets, a significant decrease in Candida albicans adhesion (P=.002) and in surface roughness (P=.008) was observed; however, similar surface energies were measured (P=.100). After cleaning with a toothbrush, the adhesion of Candida albicans was significantly higher on the coated specimen than on the uncoated specimen (P=.004). The surface roughness values were significantly different (P=.008), and the surface energies could not be determined. The coated specimen had a silicon-oxygen-silicon peak instead of an ester bond in the polymethyl methacrylate structure. The coating film reduced the water sorption (P=.008) and water solubility (P=.032), and increased the ultimate flexural strength (P=.008) and flexural modulus (P=.032) of the specimen. The coated specimen also had satisfactory toxicity results. CONCLUSIONS: Reduced Candida albicans adhesion was observed on the coated specimens. The polymeric film did not change the surface roughness of the acrylic resin specimen; however, it did slightly reduce the surface energy. The physical properties of the acrylic resin did not decrease after it was coated with the film.