Pressure transmission area and maximum pressure transmission of different thermoplastic resin denture base materials under impact load

Effect of various surface treatment methods on shear bond strength between acrylic denture teeth and thermoplastic nylon denture base

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.

Oral health-related quality of life of conventional removable partial dentures, unilateral nonmetal clasp dentures, and shortened dental arch with 2- or 3-tooth unilateral distal extension tooth loss in the mandible: A randomized, crossover, clinical trial

STATEMENT OF PROBLEM

Conventional removable partial dentures with metal clasps are still a common option for patients with distal-extension tooth loss. However, unilateral nonmetal clasp dentures fabricated by using a thermoplastic denture base resin are increasingly being used. Furthermore, the shortened dental arch concept remains controversial, in spite of being advocated for many years. Nevertheless, these treatment options remain controversial, particularly in patients with the loss of a few distal teeth unilaterally.

PURPOSE

The purpose of this randomized, crossover, clinical trial was to investigate the oral health-related quality of life of participants who requested a new dental prosthesis (unilateral nonmetal clasp dentures or conventional removable partial dentures) at a private practice.

MATERIAL AND METHODS

A 3-period, randomized, crossover design was used in a within-subject, controlled, clinical trial. Twenty-four participants (mean age 59.0 years [7 men: 62.6 {45-85} years; 17 women: 57.5 {24-75} years]) were enrolled. All experimental procedures were approved by the Ethics Committee of Nagasaki University Hospital (#15022313) and registered in the International Standard Randomized Controlled Trial Number registry (ISRCTN49105064). All participants were fully dentate in the maxilla and had unilateral distal-extension loss of 2 or 3 teeth in the mandible. Participants were allocated to 1 of 6 groups and treated with prescribed options in accordance with their allocated sequences and used a dental prosthesis or nothing for 2-week periods. At the end of each intervention, the participants were asked to answer the Oral Health Impact Profile questionnaire. Differences in Oral Health Impact Profile scores among groups were estimated with a mixed-effects model (α=.05).

RESULTS

Total Oral Health Impact Profile scores were higher for unilateral nonmetal clasp dentures (P=.002) and shortened dental arch (P=.049) than for conventional removable partial dentures, with medium and small effects. The unilateral nonmetal clasp dentures had a similar effect compared with shortened dental arch (P>.05). unilateral nonmetal clasp dentures (P=.011) and shortened dental arch (P=.005) demonstrated medium effects in the oral function dimension compared with conventional removable partial dentures. Unilateral nonmetal clasp dentures exhibited large and medium effects in the orofacial appearance dimension compared with conventional removable partial dentures (P=.001) and shortened dental arch (P=.006). In the orofacial pain dimension, shortened dental arch showed effects similar to those of conventional removable partial dentures and unilateral nonmetal clasp dentures (P>.05), and no significant differences were observed in the psychosocial impact dimension (P>.05), but the unilateral nonmetal clasp denture score was lower than the conventional removable partial denture score, with a small effect. Men had significantly lower total Oral Health Impact Profile scores for shortened dental arch than women (P=.033).

CONCLUSIONS

Unilateral nonmetal clasp dentures and shortened dental arch were better than conventional removable partial dentures for the oral health-related quality of life of individuals with unilateral distal-extension tooth loss in the mandible, and sex had a significant effect on removable prosthetic planning.

Comparison of Fracture Resistance in Thermal and Self-Curing Acrylic Resins-An In Vitro Study

Thermal and self-curing acrylic resins are frequently and versatilely used in dental medicine since they are biocompatible, have no flavor or odor, have satisfactory thermal qualities and polishing capacity, and are easy and fast. Thus, given their widespread use, their fracture resistance behavior is especially important. In this research work, we comparatively analyzed the fracture resistance capacity of thermo and self-curing acrylic resins in vitro. Materials and Methods: Five prosthesis bases were created for each of the following acrylic resins: Lucitone®, ProBase®, and Megacryl®, which were submitted to different forces through the use of the CS^® Dental Testing Machine, usually mobilized in the context of fatigue tests. To this end, a point was defined in the center of the anterior edge of the aforementioned acrylic resin bases, for which the peak tended until a fracture occurred. Thermosetting resins were, on average, more resistant to fracture than self-curable resins, although the difference was not statistically significant. The thermosetting resins of the Lucitone® and Probase® brands demonstrated behavior that was more resistant to fracture than the self-curing homologues, although the difference was not statistically significant. Thermosetting resins tended to be, on average, more resistant to fracture and exhibited the maximum values for impact strength, compressive strength, tensile strength, hardness, and dimensional accuracy than self-curing resins, regardless of brand.

The Relationship of Modulus of Elasticity and Micro-Hardness of Denture Bases to Pressure Transmission under the Thermoplastic Nylon Denture Base

Introduction: The purpose of this study was to evaluate the relationship of modulus of elasticity and micro-hardness of denture bases to pressure transmission under the thermoplastic nylon denture base.Material and Methods: Mandibular first molar acrylic denture teeth (Bioeco) embedded on 15x15x3 mm3 thermoplastic nylon (TCS and BioTone) and poly methyl methacrylate denture bases were evaluated (n=9). A 100N force applied on the specimen using universal testing machine and the pressure transmitted under the specimen observed using pressure transducer. The modulus of the elasticity (n=16) measured on 64x10x3,3 mm3 specimens and micro-hardness (n=16) measured on 10x10x3 mm3 specimens. Data were statistically analyzed using One-way Anova followed by Tukey HSD post hoc test. Pearson correlation test used to evaluate the relationship of modulus of elasticity and micro-hardness on denture bases to pressure transmission (α ≥ 0,05).Results: The results showed that poly methyl methacrylate has the highest pressure transmission compared to others. There was a significant relationship between modulus of elasticity and micro-hardness to pressure transmission under the denture base.Discussion: This study can help dentists to determine the design of dentures, especially in the selection of denture base materials.

The Influence of Saliva pH on the Fracture Resistance of Three Complete Denture Base Acrylic Resins

METHODS

Ten prosthesis bases prepared with each brand of resin were subjected to neutral and low pH conditions (pH 7 and pH 4) by submerging them in artificial saliva for 30 days. After exposure, the fatigue resistance of the resins was tested using a Dental CS® Testing Machine. Statistical Analysis Test. The data sets were described quantitatively in terms of mean (M) and standard deviation (SD). Shapiro-Wilk tests and unilateral analysis of variance (ANOVA) were performed and complemented by Tukey's multiple comparison tests. The effect size (η2), whose cohort points followed Cohen's recommendations: 0.01 (low), 0.06 (medium), and 0.14 (high), was calculated. The results were considered significant if p < 0.05 and marginally significant if p < 0.10.

RESULTS

One-way ANOVA showed that Megacryl® had the highest fracture resistance at pH 7 (52.23 Kgf), compared with Triplex Hot® (p < 0.001) and RS Vertex® (p=0.034). Two-way ANOVA confirmed the interaction between brand and pH (p=0.022), also revealing that brands comparison is significant or marginally significant, when pH is not considered (Megacryl® versus Triplex Hot®, p < 0.001, and RS Vertex®, p=0.058; Triplex Hot® versus RS Vertex®, p=0.051), and pH 7 results were significantly higher (p=0.003), even when brands are not considered. Hence, Megacryl® at pH 7 was found to have the highest fracture resistance, detached from other brands and pH values.

CONCLUSION

It can be concluded within the limitations of this study that there are differences in the fracture resistance among the three brands of acrylic resin. Megacryl® was found to have the highest fracture resistance, and Triplex Hot® was the lowest. The results also show that exposure to a low pH environment decreases the fracture resistance of the Megacryl® and RS Vertex® resins.

Classification of the journal category "oral surgery" in the Scopus and the Science Citation Index Expanded: flaws and suggestions

Objectives

The aim of this study was to evaluate the journal category “oral surgery” in Scopus and in the Science Citation Index Expanded (SCIE).

Materials and Methods

The Journal of Oral and Maxillofacial Surgery (JOMS), The Journal of the Korean Association of Oral and Maxillofacial Surgeons (JKAOMS), and The Journal of Prosthodontic Research (JPR) were selected from the Scopus list of journals as oral surgery journals. Maxillofacial Plastic and Reconstructive Surgery (MPRS) was selected from PubMed as a Scopus oral surgery title. From these titles, 10 recently published articles were collected and used for reference analysis.

Results

The percentage of citations from oral surgery journals was 26.7%, 24.5%, and 40.1% for JKAOMS, MPRS, and JOMS, respectively. In total, 1.1% of JPR's citations were from oral surgery journals and significantly fewer from other journals (P<0.001). The percentage of citations from dentistry journals excluding oral surgery journals was 11.9%, 34.4%, and 15.8% for JKAOMS, MPRS, and JOMS, respectively. For JPR, 80.6% of citations were from dentistry journals and significantly more were from other journals (P<0.001).

Conclusion

Selected samples revealed that JPR is incorrectly classified as an oral surgery journal in Scopus. In addition, the scientific interaction among JKAOMS, MPRS, and JOMS was different to JPR in the reference analysis.

The Influence of Graphene in Improvement of Physico-Mechanical Properties in PMMA Denture Base Resins

The clinical performances of dental materials depend on their mechanical profiles, determining their long-term deformation and wear resistance. This paper describes a study on the mechanical properties, water absorption and morphological properties of a polymethyl methacrylate (PMMA) resin enriched with graphene-silver nanoparticles (Gr-Ag). Two different concentrations—1 and 2 wt.%—of Gr-Ag were loaded into the PMMA material. For the mechanical characterization, the compression behavior, flexural strength and tensile strength were evaluated. Optical microscopy in polarized light and scanning electron microscopy were used for filler analysis. The filler addition led to an improvement in all mechanical properties, with slight changes being derived from the filler content variation. Gr-Ag use led to an increase in the applied maximum loads. Moreover, 1 wt.% Gr-Ag determined an increase of 174% in the modulus of rupture, which indicates high flexibility.