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Purpose: The purpose of this study was to examine the level of evidence (LOE) characteristics and associated factors that change over time in three leading prosthodontics journals. Materials and methods: Articles published in The Journal of Prosthetic Dentistry (JPD), International Journal of Prosthodontics (IJP), and Journal of Prosthodontics (JP) in 2013 and 2020 were reviewed by eight independent reviewers. After applying exclusion and inclusion criteria, the number of authors, the corresponding author's educational degree, corresponding author's origin in each clinical research article were recorded. The included articles were rated by reviewers according to the level of evidence criteria and proposed level of evidence-associated factors. Descriptive statistics, univariable, and binary logistic regression analysis were performed to investigate dependent variables and potentially associated factors. All independent variables with a significant effect were analyzed by using a multivariable test. The entry and exit alpha level were set at αE = 0.15. The statistical significance was set at α = 0.05. Results: A total of 439 articles from 3 selected journals for the years studied met the inclusion criteria. The percentages of level 1, 2, 3, 4, and 5 articles were 2.7 %, 11.4 %, 9.6 %, 13.4 % and 62.9 %, respectively. Univariable analysis results demonstrated significant associations related to the number of authors (P = 0.005), the corresponding author's educational degree (P = 0.022), and the corresponding author's geographic origin (P = 0.042). Multivariable analysis results demonstrated significant associations related to the number of authors (P = 0.002), and the corresponding author's geographic origin (P = 0.014). Conclusions: The number of authors, CA degree, and CA origin had a significant association with the LOE of included prosthodontic studies. Although there was an increase in the number of publications from 2013 to 2020, the level of evidence trend shows no improvement over the years.
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PURPOSE: To evaluate the effect of mechanical, chemical, and mechanical-chemical surface treatment methods on shear bond strength between acrylic denture teeth and thermoplastic nylon denture base. MATERIALS AND METHODS: Maxillary central incisor teeth were treated with five different surface treatment methods: mechanical (sandblasting, T-shape diatoric holes), chemical (5% acetic acid solution, bonding agent), and mechanical-chemical (sandblasting + bonding agent) were embedded in thermoplastic nylon denture base (n = 10). A universal testing machine with a crosshead speed of 0.5 mm per minute was used to test the shear bond strength. Data obtained were statistically evaluated using one-way ANOVA and followed with Tukey post hoc test (α = 0.05) RESULTS: T-shaped diatoric holes exhibited significantly higher shear bond strength among the surface treatment groups, followed by sandblasting + bonding agent, sandblasting, bonding agent, and the acetic acid group (p < 0.001) CONCLUSION: T-shaped diatoric holes as a mechanical surface treatment showed higher shear bond strength than other methods.
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STATEMENT OF PROBLEM: Data on the level of evidence and the characteristics of studies published in peer-reviewed prosthodontic journals are lacking. PURPOSE: The purpose of this study was to investigate the characteristics and level of evidence (LOE) scores of studies published in 3 leading peer-reviewed prosthodontic journals. MATERIAL AND METHODS: Clinical studies published in the Journal of Prosthetic Dentistry (JPD), the Journal of Prosthodontics (JP), and the International Journal of Prosthodontics (IJP) in 2013 and 2020 were included in the analysis. Abstracts, letters to the editor, book reviews, and animal and laboratory studies were excluded from the investigation. For each study, design, type and LOE scores (Levels 1 to 5), publication year, impact factor (IF) of the journals, geographic origins of the first and corresponding authors, and funding status were recorded. Level 1 and Level 2 were defined as high evidence (HE), and Level 3, Level 4, and Level 5 were defined as low evidence (LE). Descriptive statistics and logistic regression analysis were performed (α=.05). RESULTS: Among the 439 studies included in the analysis, the proportion of HE and LE studies was 14.1% and 85.9%, respectively. According to univariate and multivariate analysis results, year of publication (P=.010 and P=.029), geographic origin of the corresponding author (P<.001), and funding status (P<.001 and P=.002) were significantly associated with the LOE of a study. However, the journal IF was not associated with LOE (P=.328). CONCLUSIONS: Although the number of HE studies in 3 leading prosthodontic journals has increased over time, the total number was still limited compared with LE studies. A further improvement in the overall LOE of clinical studies in prosthodontics is needed.
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PURPOSES: The purposes of the present study were to examine the pressure transmission area and maximum pressure transmission of thermoplastic resin denture base materials under an impact load, and to evaluate the modulus of elasticity and nanohardness of thermoplastic resin denture base. METHODS: Three injection-molded thermoplastic resin denture base materials [polycarbonate (Basis PC), ethylene propylene (Duraflex), and polyamide (Valplast)] and one conventional heat-polymerized acrylic resin (PMMA, SR Triplex Hot) denture base, all with a mandibular first molar acrylic resin denture tooth set in were evaluated (n=6). Pressure transmission area and maximum pressure transmission of the specimens under an impact load were observed by using pressure-sensitive sheets. The modulus of elasticity and nanohardness of each denture base (n=10) were measured on 15×15×15×3mm3 specimen by using an ultramicroindentation system. The pressure transmission area, modulus of elasticity, and nanohardness data were statistically analyzed with 1-way ANOVA, followed by Tamhane or Tukey HSD post hoc test (α=.05). The maximum pressure transmission data were statistically analyzed with Kruskal-Wallis H test, followed by Mann-Whitney U test (α=.05). RESULTS: Polymethyl methacrylate showed significantly larger pressure transmission area and higher maximum pressure transmission than the other groups (P<.001). Significant differences were found in modulus of elasticity and nanohardness among the four types of denture bases (P<.001). CONCLUSIONS: Pressure transmission area and maximum pressure transmission varied among the thermoplastic resin denture base materials. Differences in the modulus of elasticity and nanohardness of each type of denture base were demonstrated.