Color and flexural properties of nanoparticles-modified denture base resin: An in vitro comparative study.

Objectives: Reinforcement of polymethylmethacrylate (PMMA) denture base resins (DBRs) with inorganic fillers with superior properties and accepted aesthetics are favored and still a big dilemma. This study was undertaken to evaluate the color change, flexural strength, and modulus of elasticity of heat-polymerized DBR material modified with silver nanoparticles (AgNPs) and zirconium dioxide nanoparticles (ZNPs). Methods: Sixty acrylic specimens (30/color test, 30/flexural properties) were fabricated and divided according to nanoparticles type and addition into 3 groups (n = 10). Group-I; unmodified specimens, Group-II; modified specimens with 0.5wt% AgNPs (PMMA/AgNPs), and Group-III; modified specimens with 7.5wt% ZNPs (PMMA/ZNPs). Disc-shape (20 × 3 mm) and bar-shape (65 × 10 × 2.5 mm) specimens were fabricated for color and flexural properties, respectively. The spectrophotometer was used for evaluation of the color change (∆E). The flexural strength and elastic modulus evaluation was carried out using a 3-point bending test (5 mm/min). Tukey's post hoc and one-way ANOVA were used to analyze the data at a significant level P ≤ 0.05. Results: PMMA/AgNPs group exhibited a significant increase in color change when compared with PMMA/ZNPs. PMMA/ZNPs showed significantly the highest flexural strength value when compared with unmodified and PMMA/AgNPs groups (P < 0.001), however, there was an absence of significant differences in terms of flexural strength values between PMMA/AgNPs and unmodified groups (P > 0.05). PMMA/AgNPs insignificantly increased its modulus of elasticity strength (P = 0.09410) while PMMA/ZNPs significantly increased its modulus of elasticity strength (P = 0.00396). Conclusion: The AgNPs and ZNPs addition to PMMA increased the color change and AgNPs change the color of DBRs. The flexural attributes of DBRs have been increased by ZNPs.

Effect of Duplication Techniques on the Fitting Accuracy of CAD-CAM Milled, 3D-Printed, and Injection-Molded Mandibular Complete Denture Bases.

BACKGROUND: Digital technology has been introduced in prosthodontics, and it has been widely used in denture duplication instead of a conventional denture duplication technique. However, research comparing different denture duplication techniques and how they affect the fitting accuracy of the denture base is scarce. OBJECTIVES: The aim was to assess the impact of duplication techniques on the accuracy of the fitting surface of computer-aided design and manufacturing (CAD-CAM) milled, 3D-printed, and injection-molded complete denture bases (CDBs). METHODOLOGY: This study involved fabricating a mandibular complete denture base with three marked dimples as reference marks (A, B, and C at the incisive papilla, right molar, and left molar areas) using a conventional compression molded technique. This denture was then scanned to generate a standard tessellation language (STL) file; after that, it was duplicated using three different techniques (milling, 3D printing, and injection molding) and five denture base resin materials-two milled CAD-CAM materials (AvaDent and IvoBase), two 3D-printed materials (NextDent and HARZ Labs), and one injection-molded material (iFlextm). Based on the denture base type, the study divided them into five groups (each with n = 10). An evaluation of duplication accuracy was conducted on the fitting surface of each complete denture base (CDB) using two assessment methods. The first method was a two-dimensional evaluation, which entailed linear measurements of the distances (A-B, A-C, and B-C) between reference points on both the scanned reference mandibular denture and the duplicated dentures. Additionally, a three-dimensional superimposition technique was employed, involving the overlay of the STL files of the dentures onto the reference denture's STL file. The collected data underwent statistical analysis using a one-way analysis of variance and Tukey's pairwise post hoc tests. RESULTS: Both evaluation techniques showed significant differences in fitting surface accuracy between the tested CDBs (p ˂ 0.001), as indicated by one-way ANOVA. In addition, the milled CDBs (AvaDent and IvoBase) had significantly higher fitting surface accuracy than the other groups (p ˂ 0.001) and were followed by 3D-printed CDBs (NextDent and HARZ Labs), while the injection-molded (iFlextm) CDBs had the lowest accuracy (p ˂ 0.001). CONCLUSIONS: The duplication technique of complete dentures using a CAD-CAM milling system produced superior fitting surface accuracy compared to the 3D-printing and injection-molded techniques.

Effect of Different Occlusal Tooth Forms of Mandibular Overdenture Retained by an Immediate Loaded Single Implant on the Masticatory Efficiency and Oral Health-Related Quality of Life.

Aim: To study the masticatory efficacy and oral health-related quality of life (OHRQoL) of participants wearing a mandibular overdenture retained by an immediate loading single implant with different occlusal tooth forms. Materials and Methods: For this nonrandomized controlled trial study, 27 edentulous participants were selected and randomly divided into three groups (n = 9) based on occlusal tooth forms of the mandibular implant overdenture (MIOD). Group I: participants received an MIOD with an anatomical tooth form; Group II: participants received an MIOD with a semianatomical tooth form; and Group III: participants received an MIOD with a nonanatomical tooth form. For each participant, a single implant (screw root form) was inserted into the midline of the mandibular ridge to support the MIOD. For each group, the masticatory efficiency was evaluated after 3 months, and the OHRQoL of the participants was evaluated after 3 and 6 months. One-way ANOVA and post hoc Tukey's test were used for data analysis (P < 0.05). Results: The masticatory efficiency of the anatomic and semianatomic tooth forms was higher than that of the nonanatomic (P < 0.05). Moreover, the improvement in the participants' OHRQoL in the anatomic group was more significant than that of other groups (P < 0.05). Conclusion: There was a greater improvement in masticatory efficiency and participants' OHRQoL when fitted with an anatomic tooth form mandibular overdenture retained by an immediate loading single implant than with a semianatomic or nonanatomic tooth form.

Efficacy of Occlusal Splints and Low-Level Laser Therapy on the Mandibular Range of Motion in Subjects with Temporomandibular Joint Disc Displacement with Reduction.

Aims and Objectives: The study was carried out to evaluate the efficacy of four conservative therapeutic modalities on the mandibular range of motion (MRM) in subjects with anterior disc displacement with reduction (ADDwR) of the temporomandibular joint (TMJ). Materials and Methods: One hundred patients (64 women and 36 men) were selected, and randomly distributed into four groups. Group I: Subjects receiving behavioral therapy (BT). Group II: Subjects receiving low-level laser therapy (LLLT). Group III: Subjects receiving maxillary anterior repositioning splint (MARS). Group IV: Subjects receiving stabilization splint (SS). The MRM was evaluated for each patient before treatment and after 6 months. Paired t test and one-way analysis of variance (ANOVA) tests were used for statistical analysis followed by a post hoc Tukey test (P ≤ 0.05). Results: All groups showed significant improvement in MRM after 6 months of treatment (P ≤ 0.05) except for BT. There was a significant improvement for SS and MARS on the different movements of MRM, more than for LLLT and BT (P ≤ 0.05). Conclusion: The MARS and the SS are effective in increasing the MRM for patients with ADDwR.

In-vitro Comparative Evaluation for the Surface Properties and Impact Strength of CAD/CAM Milled, 3D Printed, and Polyamide Denture Base Resins.

Objective: There is a paucity of data regarding the effect of fabrication techniques and compositions of CAD/CAM milled, 3D-printed, and polyamide flexible denture base resin materials (DBRMs) on the surface roughness (SR), surface hardness (SH), and impact strength (IS). Therefore, this study aimed to evaluate the SR, SH, and IS of CAD/CAM milled, 3D-printed, and polyamide flexible DBRMs. Materials and Methods: Ninety specimens were constructed from different DBRMs and divided into three groups (CAD/CAM, 3D-printed, and polyamide DBRMs; n = 30) with specific measurements: 15 × 10 × 2.5 mm for SR and H tests and 80 × 10 × 4 mm notched specimen for IS test. SR meter and Vickers micro SH tester were used to measure SR and SH, respectively, whereas the IS was evaluated using Charpy's impact testing machine. Data were collected and statistically analyzed using one-way analysis of variance and post hoc Tukey's tests (α=0.05). Results: There were significant differences between the tested materials (P< 0.05). The CAD/CAM milled showed lowest SR when compared with 3D-printed resin and polyamide flexible resin (P< 0.05); however, there was a significant increase in SH of CAD/CAM milled and 3D-printed DBRMs when compared with polyamide materials (P< 0.05). There was a significant increase in IS of polyamide and CAD/CAM milled resins when compared with 3D-printed DBRMs (P < 0.05). Conclusion: CAD/CAM milled resins showed high IS and SH with lower SR.

Polymethylmethacrylate Incorporating Nanodiamonds for Denture Repair: In Vitro Study on the Mechanical Properties.

OBJECTIVE: This study aimed to evaluate the effect of nanodiamond (ND) addition to repair resin with repair gap modifications on the flexural and impact strength of repaired polymethylmethacrylate denture base. MATERIALS AND METHODS: Heat-polymerized acrylic resin specimens (N = 100/test) were prepared and sectioned to half creating two repair gaps: 2.5- and 0 mm with 45 degrees beveling. They were further divided into subgroups (n = 20) according to ND concentration (control, 0.25%ND, and 0.50%ND), thermocycling (500 cycles) was done to half the specimens in each subgroup. Flexural strength was tested using 3-point bending test and impact strength was tested by Charpy's impact test. Analysis of variance and post-hoc Tukey's tests were performed for data analysis (α = 0.05). Scanning electron microscope was employed for fracture surface analysis and ND distribution. RESULTS: Before and after thermocycling, the addition of ND significantly increased the flexural strength and elastic modulus in comparison to control group (p ˂ 0.001), while 0 mm repair gap showed insignificant difference between ND-reinforced groups (p ˃ 0.05). Regarding impact strength, ND addition increased the impact strength with 0 mm gap in comparison to control and 2.5 mm with ND (p˂0.001), while later groups showed no significant in between (p ˃ 0.05). Comparing thermocycling effect per respective concentration and repair gap, thermocycling adversely affected all tested properties except elastic modulus with 0 mm-0.25 and 0 mm-0.5% and impact strength with 2.5 mm, 2.5 mm-0.25%, 2.5 mm- 0.5% (p ˃ 0.05). CONCLUSION: ND addition combined with decreased repair gap improved the flexural strength, elastic modulus, and impact strength of repaired denture resin, while thermocycling has a negative effect on denture repair strength.

Influence of Different Beverages on the Color Stability of Nanocomposite Denture Base Materials.

BACKGROUND: The effect of beverages on nanocomposite denture base materials is neglected. Therefore, this study aimed to investigate the influence of different beverages (coffee, tea, cola, and mineral water) on the color stability of nanoparticles-modified denture base materials (DBMs). MATERIALS AND METHODS: A total of 280 specimens (n = 10/group) were prepared from heat-polymerized acrylic resin modified with different concentrations (3% and 7%) of zirconium dioxide (nano-ZrO2), titanium dioxide (nano-TiO2), and silicon dioxide (nano-SiO2) nanoparticles, while 0% was taken as a control. Color change (∆E) of the specimens was evaluated after simulating 6-month immersion time in four commonly used beverages, coffee, tea, cola, and mineral water, as experimental groups. Color stability was measured using a spectrophotometer, and then values were converted to National Bureau of Standards units (NBS units). The one-way ANOVA test was applied to compare color change (ΔE) results followed by Bonferroni's post hoc test (α = 0.05). RESULTS: The results showed that the heat-polymerized acrylic resin modified with different types of nanoparticles showed lower color changes after being immersed in beverage solutions compared to the unmodified group (P < 0.001), so the color stability of heat-polymerized acrylic resin was significantly enhanced by the addition of several nanoparticles; nano-ZrO2 showed the lowest ΔE followed by nano-TiO2 and then nano-SiO2. Regardless of the filler type, 3% concentration showed lower mean ΔE than 7% concentration. Regarding the beverage solutions, the greatest color change was found in the coffee group followed by tea and cola, while water showed the least changes. CONCLUSION: Modification of heat-polymerized acrylic resin with certain amounts of nano-ZrO2, nano-TiO2, and nano-SiO2 may be useful in improving color stability.

Translucency of nanoparticle-reinforced PMMA denture base material: An in-vitro comparative study.

The aim of this study was to assess the translucency of denture base acrylic resin reinforced with zirconium dioxide (ZrO2NPs), silicon dioxide (SiO2NPs), and diamond (DNPs) nanoparticles. A total of 130 heat-polymerized acrylic discs (15×2.5 mm) were fabricated conventionally and divided into control and experimental groups according to nanoparticle type and concentration (0.5, 1, 1.5, and 2.5 wt%). Unmodified acrylic resin specimens served as control. All specimens were thermocycled (5,000 cycles). Translucency was measured using a spectrophotometer. ANOVA and post-hoc Turkeys' test were used for data analysis at α=0.05. The translucency of modified PMMA was significantly lower than control (p<0.05) except 0.5% ZrO2NPs and SiO2NPs (p>0.05) which exhibited the highest translucency values among modified groups. As the NPs concentration increased, the translucency decreased and the lowest value was seen with 2.5% DNPs (1.18±0.10). The addition of ZrO2NPs, SiO2NPs, and DNPs into denture base resin decreased the translucency.