Influence of artificial aging and ZrO2 nanoparticle-reinforced repair resin on the denture repair strength

Background: The purpose of this study was to evaluate the effect of aging process on the tensile strength (TS) of repaired acrylic denture base using ZrO2 nanoparticles (nano-ZrO2)-reinforced autopolymerized resin. Material and Methods: A total of 240 heat-polymerized acrylic resin specimens (n=10) were prepared and sectioned creating 2 mm-repair-gap. Autopolymerized acrylic resin, pure and modified with 2.5, 5, and 7.5wt% nano-ZrO2were used for specimens repair. TS of repaired specimens were measured using the universal testing machine af-ter water immersion at 37oC for 2, 7 and 30 days. At each time interval, half the immersed specimens underwent thermo-cycling aging process (5000 cycles at 5/55°C) before TS testing. One-way ANOVA and Tukey-Kramer multiple-comparison tests were used for data analysis at ?=0.05. Results: Aging process for all groups showed significant differences in TS between unreinforced and nano-ZrO2reinforced groups (p<0.05). Within immersed nano-ZrO2-reinforced specimens, 5% group immersed for 30-days showed the highest significant TS value (p<0.05). With regards to thermocycling, 5% group showed the highest TS values after 2-days and 30-days groups while after 7-days, significant differences were found between 2.5% group and 5% and 7.5% groups (p?0.05). SEM images analysis displayed the ductile fracture type for nano-ZrO2reinforced groups.Conclusions: In summary, 5.0%-nano-ZrO2 addition to repair resin showed an improvement in tensile strength of repaired acrylic resin with different aging processes

Cutting efficiency of diamond burs in CADCAM dental ceramics and resulting surface characteristics

PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact [email protected] (DScD) --Boston University, Henry M. Goldman School of Dental Medicine, 2015 (Department of Restorative Sciences and Biomaterials).Includes bibliographic references: leaves 128-132.Objectives: the purpose of this study is to evaluate the cutting efficiency of diamond burs under different conditions (diamond grits, Cutting force, and coolant) when machining 3 CAD/CAM dental ceramics. Also, the study aims at examining the resulting surface topography, edge chipping and kerf size. Materials and methods: Coarse, medium, and fine grit diamond burs (n=10) from 3 manufacturers (Meisinger, Komet, and Brasseler) were used to make 3 cuts each, in fully sintered zirconia blocks (TZ-3YSB-E, TOSOH), fully crystalized lithium-disilicate (IPS e.max CAD, Ivoclar), and feldspathic porcelain blocks (VitaBIocs TriLuxe Forte, Vita) using an electric handpiece running at 200,000 rpm. The cutting forces for zirconia and e.max were 1.47N and 1.96N and for TriLuxe Forte 0.98N. Three Cooling liquids (tapwater, 0.9% saline, and 1:5 mouthwash) at a rate of 100ml/min were used. The ceramic blocks were fixed on a sliding base running on 2 rods using frictionless ball bearings. The cutting distance was recorded using LVDT connected to LabView software. Average cutting rate was calculated for each cut. Instruments weighed and evaluated using SEM before, during and after experiments. Kerfs and edge chippings seen around each cut were recorded using optical microscope connected to a high definition video micrometer. The blocks were then sectioned to reveal machined surfaces for surface roughness measurement. Statistical analysis was conducted using student t-teSt, ANOVA and Tukey post hoc test at [alpha]=0.05. Results: one-way ANOVA revealed a significant difference in material removal rate between the three substrates (P0.05). Large diamond grits produced significantly larger kerfs (P<0.0001). Surface roughness was found to be significantly larger in TriLuxe Forte than other substrates (P<0.0001). Conclusions: A significant differences in material removal rate was found between the three substrates with feldspathic porcelain being the highest followed by e.max then zirconia. Also, bur cutting rate was found to decline with consecutive cuts. Similar grits from different manufacturers behave differently under similar testing conditions. However, fine diamond burs had significantly smaller cutting rates than other grits for all manufacturers. Increasing the cutting force can improve material removal rate. In this study, it was found that the effect of cooling liquid is material dependent with mouthwash improving feldspathic porcelain removal rate and saline improving that of zirconia. Edge chipping increased when the diamond grits were bigger and it was found to be more on bur exit side. Feldspathic porcelain had the highest surface roughness values compared to other substrates

Fit, Precision, and Trueness of 3D-Printed Zirconia Crowns Compared to Milled Counterparts

Precise fit of a crown and accurate reproduction of the digital design are paramount for successful treatment outcomes and preservation of clinician and technician time. The study aimed to compare the internal fit, marginal adaptation, precision, and trueness of 3D-printed zirconia crowns compared to their milled counterpart. A total of 20 monolithic 3 mol% yttria stabilized-zirconia crowns (n = 10) were made using computer-assisted design (CAD) followed by additive (3D-printed) and subtractive (milled) manufacturing. Digital scanning of the master die with and without a fit checker followed by image superimposition, and analysis was performed to evaluate internal and marginal adaptation in four areas (occlusal, axial, marginal, and overall). ISO 12836:2015 standard was followed for precision and trueness evaluation. Statistical analysis was achieved using a t-test at α = 0.05. Internal fit and marginal adaptation revealed no significant difference between the two test groups (p > 0.05). The significant difference in trueness (p p < 0.05) in the 3D-printed crowns (9.59 ± 0.75 µm) than the milled (17.31 ± 3.39 µm). 3D-printed and milled zirconia crowns were comparable to each other in terms of internal fit and marginal adaptation. The trueness of the occlusal and axial surfaces of 3D-printed crowns was better, whereas the trueness of fitting surface of milled crowns was better. 3D-printed crowns provided a higher level of precision than milled crowns. Although the internal and marginal fit of both production techniques were comparable, 3D printing of zirconia produced more precise crowns

Behavior of PMMA Denture Base Materials Containing Titanium Dioxide Nanoparticles: A Literature Review

Titanium dioxide nanoparticles (TiO2NP) have gained interest in the dental field because of their multiple uses in addition to their antimicrobial effect. One of the applications in dentistry involves the incorporation into poly methyl methacrylate (PMMA) resin. However, there is a lack of evidence on their effects on the behavior of the resulting nanocomposite. Therefore, the present review aims to screen literatures for data related to PMMA/TiO2 nanocomposite to figure out the properties of TiO2 nanoparticles, methods of addition, interaction with PMMA resin matrix, and finally the addition effects on the properties of introduced nanocomposite and evidence on its clinical performance. Regardless of the latest research progress of PMMA/TiO2 nanocomposite, the questionable properties of final nanocomposite and the lack of long-term clinical evidence addressing their performance restrict their wide clinical use. A conclusive connection between nanoparticle size or addition method and nanocomposite properties could not be established

Reinforcement of PMMA Denture Base Material with a Mixture of ZrO2 Nanoparticles and Glass Fibers

This study is aimed at evaluating the hybrid reinforcement effects of zirconium oxide nanoparticles (nano-ZrO2) and glass fibers (GFs) at different ratios on the flexural and impact strengths of a polymethylmethacrylate (PMMA) denture base. A total of 160 specimens were fabricated from heat-polymerized acrylic resins using the water bath technique. For the control group, the specimens did not receive any additions; for the test group, different concentrations of nano-ZrO2/GFs at 5% of the PMMA polymer were added. The concentrations of nano-ZrO2/GFs were as follows: 5%–0%, 4%–1%, 3%–2%, 2.5%–2.5%, 2%–3%, 1%–4%, and 0%–5%. The flexural strength was measured using the three-point bending test. The impact strength was measured using the Charpy impact test. Results were tabulated and analyzed using one-way analysis of variance (ANOVA) and the Tukey–Kramer multiple comparison test (p≤0.05). The flexural and impact strengths of PMMA-nano-ZrO2 + GF composites were significantly improved when compared with those of pure PMMA (p<0.05). The maximum flexural strength (94.05 ± 6.95 MPa) and impact strength (3.89 ± 0.46 kJ/m2) were obtained with PMMA (2.5%)/nano-ZrO2 + 2.5% GF mixtures and could be used for removable prosthesis fabrication

Physiomechanical and Surface Characteristics of 3D-Printed Zirconia: An In Vitro Study

The objective of this study is to examine the physiomechanical and surface properties of 3D-printed zirconia in comparison to milled zirconia. A total of 80 disc-shaped (14 × 1.5 ± 0.2 mm) specimens (20 milled and 60 3D-printed (at three different orientations; horizontal, vertical, and tilted)) were manufactured from 3-mol% yttria-stabilized tetragonal zirconia. Five specimens per group were evaluated for crystalline phase, grain size, density, porosity, surface roughness, wettability, microhardness, and SEM analysis of the surface. Biaxial flexural strength (BFS) was measured (n = 15) followed by Weibull analysis and SEM of fractured surfaces. Statistical analysis was performed using one-way ANOVA and Tukey’s post hoc test at α = 0.05. All groups showed a predominant tetragonal phase, with a 450 nm average grain size. There was no significant difference between groups with regards to density, porosity, and microhardness (p > 0.05). The tilted group had the highest surface roughness (0.688 ± 0.080 µm), significantly different from the milled (p = 0.012). The horizontal group presented the highest contact angle (89.11 ± 5.22°), significantly different from the milled and tilted (p > 0.05). The BFS of the milled group (1507.27 ± 340.10 MPa) was significantly higher than all other groups (p p < 0.005). The highest and lowest Weibull modulus were seen with tilted and milled, respectively. Physical properties of all groups were comparable. The surface roughness of the tilted group was higher than milled. The horizontal group had the highest hydrophobicity. Printing orientations influenced the flexural strength of 3D-printed zirconia. Clinical implications: This study demonstrates how the printing orientation affects the physiomechanical characteristics of printed zirconia

Chemo-Mechanical Approach to Improve Repair Bond Strength of Denture Teeth

Background. Detachment of acrylic teeth from denture base material is a common complication in dentistry which accounts for 26–30% of repair cases. This study aimed to evaluate the effect of alumina-blasting, silane coupling agent, and thermal cycling on the shear bond strength of repaired teeth to denture base. Materials and Methods. Specimens (140) of repaired teeth to denture bases were fabricated and divided into 14 groups: 7 groups before thermal cycling and 7 groups after thermal cycling (n = 10). The groups were divided according to surface treatment into no treatment (control), treatment of the base (B), the tooth (T), or both (BT). Each group was further subdivided according to the surface treatment method into alumina-blasting or alumina-blasting and silane coupling agent. After treatment, acrylic discs and teeth were fixed in a jig, and the repair procedure was done. Half the specimens were thermally cycled. Shear bond strength was measured using a universal testing machine. ANOVA and Tukey HSD tests were performed at α = 0.05. Results. Surface treatment significantly improved the bond strength compared to the control group P<0.001. Comparing surface treatments, alumina-blasting with silane coupling agent treatment resulted in significantly higher strength compared to alumina-blasting alone P<0.001. The BT group treated with alumina-blasting and silane coupling agent showed the highest significant shear bond strength (23.91 ± 0.96 MPa) P<0.001. Significant drop in strength value was observed in all groups after thermal cycling P<0.004 except the BT group treated with alumina-blasting P=0.096. Conclusion. Surface treatment using alumina-blasting with silane coupling agent for denture base and tooth increased repair strength

Students&rsquo; Awareness of the Role of Phonetics in Construction of Removable Dental Prostheses: A Questionnaire-Based Cross-Sectional Study

Phonetics plays a major role in the fabrication of prostheses. This study aimed to assess the knowledge of students regarding the role of phonetics in denture fabrication and to improve the educational process and the clinical application. The study was conducted at the College of Dentistry, Imam Abdulrahman Bin Faisal University, and involved a survey of 344 dental students and interns. The questionnaire contained 20 questions and was divided into three sections: general knowledge, clinical correlations, and clinical evaluations. The data were collected and analyzed statistically using independent t-tests, one-way ANOVA, and Tukey&rsquo;s post hoc tests. The response rate was 100%. Male and female students only differed significantly in terms of their scores for answers to general knowledge questions, with females achieving better results (p = 0.023). General knowledge varied significantly between fourth-year students and all other levels (p &lt; 0.001), and fifth-year students and interns (p = 0.027). The clinical correlations varied significantly between fourth-year students and interns (p = 0.01), whereas the clinical evaluations varied between all the academic years and interns (fourth-year, p &lt; 0.001; fifth-year, p = 0.003; and sixth-year, p = 0.017). The interns obtained the highest scores in all sections. There was a lack of awareness among dental students of some aspects of the role of phonetics in denture fabrication. The study highlights the deficiencies that need to be addressed and the need for adjustments to the curriculum related to removable prosthodontics in order to improve the knowledge of students regarding the role of speech in denture fabrication