Denture relining using digital replication method: A dental technique.

The aim of this report was to digitize traditional denture relining using a digital duplication method, in addition to assessing the wear resistance of three-dimensional (3D) printed denture teeth. A complete denture was relined using light body impression. The denture with impression was scanned yielding a standard tessellation language file that was designed to print the denture base and teeth. The printed teeth were fitted into the sockets of the printed denture base and then bonded using auto-polymerized acrylic resins, followed by finishing and polishing. Dentures were inserted and fit and occlusion were adjusted as needed, and the patient was scheduled for follow-up appointments at one week, three months, and six months. At each follow-up visit, dentures were scanned using a 3Shape E3 desktop scanner and scans were superimposed. The occlusal wear was assessed in reference to the first scan after the denture insertion visit. The accuracy of the intaglio surface of dentures was within clinically acceptable limits. The clinical evaluation of inserted dentures in terms of retention, occlusion, esthetic, and patient satisfaction was encouraging. Using digital duplication, conventional dentures could be relined. The advantages of digital records include eliminating polymerization dimensional changes, and reducing cost and clinical time by minimizing the number of visits, which is particularly helpful with geriatric patients.

Influence of different printing orientations and post-polymerization time on the translucency of three-dimensional (3D) printed denture base resins.

PURPOSE: To evaluate the effect of different printing orientations and post-polymerization time with thermal cycling on the translucency of 3D-printed denture base resins. METHODS: Heat-polymerized (HP) acrylic resin specimens were fabricated and 3D-printed denture base materials (NextDent, ASIGA, FormLabs) were printed with different printing orientations (0, 45, 90 degrees) and subjected to different post-polymerization times (15-, 30-, 60-, and 90-min). All specimens were polished and immersed in distilled water for 1 day at 37°C. CIEDE2000 was used to measure the translucency parameters (TP00) before and after thermal cycling (5000 cycles) recording the color parameters (L*, a*, b*) against a black and white background using a spectrophotometer. k-factors ANOVA followed by post hoc Tukey's test (α = .05) was performed for statistical analysis. RESULTS: The k-factors ANOVA test showed a significant effect of resin material, post-polymerization time, and printing orientation on translucency (p < 0.001). In comparison to HP, all 3D-printed resins showed lower translucency with all post-polymerization times and printing orientation (p < 0.001) except FormLabs resin (p > 0.05). For all 3D-printed resins, the translucency increased, with increasing the post-polymerization time (p < 0.001) and 60- and 90-min showed the highest translucency. For printing orientation, 90 and 45 degrees significantly showed high translucency in comparison to 0 degrees (p < 0.001). FormLabs showed significantly higher translucency when compared with NextDent and ASIGA per respective printing orientation and post-polymerization time. The translucency significantly decreased after thermal cycling for all tested resins (p < 0.001). CONCLUSION: The findings of this study demonstrated that the translucency of 3D-printed resins is influenced by the printing orientation, post-polymerization time, and resin type. As a result, choosing a resin type, and printing orientation, with a longer post-polymerization time should be considered since it may improve the esthetic appearance of the 3D-printed resins.

A comparative study assessing the precision and trueness of digital and printed casts produced from several intraoral and extraoral scanners in full arch and short span (3-unit FPD) scanning: An in vitro study.

PURPOSE: To compare precision and trueness of digital and printed casts produced from several intraoral and extraoral scanners in full arch and short span scanning. MATERIALS AND METHODS: A fully dentate maxillary phantom cast was used to represent full arch scanning, and a mandibular phantom cast, including posterior 3-unit fixed partial denture preparations to represent short span scanning. Reference casts (RCs) were fabricated and scanned 10 times by a reference extraoral scanner (Medit T510, Seoul, Korea) to provide reference digital casts. RC was then scanned 10 times by 5 scanners: 2 intraoral scanners (Trios 3shape [Trios 3] and Dental Wings [DW]), and 3 extraoral scanners (3shape E3 [E3], S600 ARTI [S600], and Ceramill Map 600 [M600]). Digital standard tessellation language (STL) files obtained from the 5 scanners were sent to a stereolithography 3D printer to fabricate printed casts. Trueness was obtained by comparing STL files of each digital/printed cast to the RC, while precision was obtained by comparing the digital/printed STL file of each scanner to the other files of same digital/printed group. The lower the precision and trueness values, the higher the accuracy of casts. Multivariate analysis of variance was performed to assess the association of precision and trueness with the type of scanner, type of cast, and scanning span. RESULTS: There was a significant difference in precision and trueness of casts produced from different scanners (p <0.001). The lowest precision and trueness were demonstrated by casts produced from DW. Digital casts showed significantly higher precision and trueness compared to 3D printed casts (p <0.001). Regarding the scanning span, full arch scanning showed significantly lower precision and trueness than short span scanning (p <0.001). CONCLUSIONS: Extraoral scanners exhibited higher trueness and precision than intraoral scanners. Trios 3 showed comparable accuracy to that of the studied extraoral scanners in the case of short span scanning. DW was the least accurate scanner in all studied groups, while E3 showed the highest accuracy level among the mentioned scanners. Digital casts showed higher trueness and precision compared to 3D printed casts.

Flexural Properties and Hardness of CAD-CAM Denture Base Materials.

PURPOSE: To compare flexural strength, elastic modulus, and surface hardness of computer aided design and computer aided manufacturing CAD-CAM milled, 3D-printed, and heat-polymerized denture base resins. MATERIALS AND METHODS: A total of 120 specimens were fabricated from heat-polymerized acrylic resin (HP), milled resin (Avadent and IvoCad), and 3D-printed resin (ASIGA, FormLabs, and NextDent). The specimens were divided into 6 groups according to the type of denture base material (n = 20/material) (10/flexural properties and 10/hardness). Flexural strength and elastic modulus of the specimens were evaluated by 3-point bending test and surface hardness by Vickers hardness test. To test flexural properties, the specimens were fabricated according to ISO 20795-1:2013 standards (64 × 10 × 3.3 ± 0.2 mm). The dimensions for hardness test were 15 × 10 × 2.5 ± 0.2 mm. Scanning electron microscope was used to evaluate the surface morphology of the fractured specimens. The means and standard deviations were calculated, followed by one-way ANOVA and Tukey post-hoc test (α = 0.05). RESULTS: Milled resins showed significantly higher values for flexural strength, elastic modulus, and surface hardness, followed by HP and then 3D-printed resins (p < 0.001). Within milled groups, flexural strength of AvaDent was significantly higher than IvoCad (p < 0.001), while elastic modulus and hardness didn't show significant difference. Within 3D-printed resins, ASIGA showed the highest flexural strength and elastic modulus, insignificantly with FormLabs (p = 0.595) and significantly with NextDent (p = 0.008). ASIGA also showed significantly the highest hardness among the 3D-printed groups. No significant difference was found between FormLabs and NextDent in flexural strength (p = 0.357), elastic modulus (p = 1.00), or surface hardness (p = 0.987). CONCLUSION: CAD-CAM milled resins had greater flexural properties and hardness compared to heat-polymerized acrylic resin and 3D-printed resins. Although 3D-printed samples showed the lowest values of tested properties, the flexural strength and modulus were above clinically acceptable values.

Evaluation of the accuracy of digital and 3D-printed casts compared with conventional stone casts.

STATEMENT OF PROBLEM: Digital scans present an efficient substitute for traditional dental impressions, although physical casts are still needed for some procedures, leading to the use of 3D printing in fixed prosthodontics. However, studies comparing the accuracy of 3D-printed dental casts with digital and conventional casts are sparse. PURPOSE: The purpose of this in vitro study was to compare the accuracy of casts produced from 2 different intraoral scans using a stereolithographic (SLA) 3D- printing technique, their digital versions, and conventional stone casts with a reference cast and with each other. MATERIAL AND METHODS: A reference cast was scanned by using 2 intraoral scanners, the TRIOS 3Shape and the Dental Wings, producing 2 digital scans. SLA was used to print dental casts from the digital scans, and polyether impressions were poured in dental stone to produce conventional stone casts. Measurements of the 4 types of casts (TRIOS 3Shape digital, Dental Wings digital, TRIOS 3Shape printed, and Dental Wings-printed casts) were compared with the reference casts. Measurements of maxillary and mandibular canines, second premolars, and second molars included incisocervical or occlusocervical (crown height) and mesiodistal (crown width). Arch measurements included intercanine and intermolar widths. The Geomagic imaging software program was used to measure the digital casts. ANOVA was used to assess differences among groups in errors relative to the reference cast (α=.05). RESULTS: In occlusocervical and mesiodistal, the errors of digital Dental Wings were significantly greater than the errors of the other 4 groups. For intercanine and intermolar widths, digital TRIOS 3Shape and digital Dental Wings had significantly greater errors (mean=0.11 and 0.15 mm in intercanine width and 0.14 and 0.18 mm in intermolar width) than their printed counterparts and the conventional casts (means=0.02, 0.06, and 0.01 mm in intercanine width and 0.02, 0.04, and 0.01 mm in intermolar width). The digital Dental Wings cast had significantly greater errors than those of the other groups in all measurements. All errors were within the clinically acceptable level (<0.5 mm). CONCLUSIONS: 3D-printed casts had the lowest error rate relative to the reference cast and were similar to those of conventional stone casts. Digital casts had the greatest errors.

Accuracy of 3D Printed and Digital Casts Produced from Intraoral and Extraoral Scanners with Different Scanning Technologies: In Vitro Study.

PURPOSE: To compare the accuracy of 3D printed and digital casts produced from various intraoral and extraoral scanners with different scanning technologies. MATERIALS AND METHODS: A conventional stone cast was fabricated from the reference typodont cast and scanned with two intraoral scanners (TRIOS 3 version 1.4.7.5, and Dental Wings version 2.1.0.421), and two extraoral scanners (S600 Arti, Zirkonzahn, and Ceramill map 600, Amann Girrbach GmbH). All digital scans were saved in the form of STL files and measurements were calculated using Geomagic analysis software. Two types of measurements were assessed on the casts: tooth- and arch-level measurements. Absolute errors were calculated by subtracting the measurements on 3D printed, digital, and conventional stone casts from the measurements on the reference typodont cast. One-way ANOVA was used for comparing different measurement errors between groups. Linear regression was performed to determine the association between different explanatory variables, and the average measurement errors (dependent variable) adjusted to reference cast measurements. Regression coefficients (B) and 95% confidence intervals (CI) were calculated. RESULTS: For both 3D printed and digital casts, Dental Wings showed significantly greater error compared to other scanners and to the conventional stone cast at all measurements except arch lengths (in the 3D printed modality only), while conventional casts showed the lowest error. Error was significantly higher in intraoral than extraoral scanners (B = 0.009, 95% CI = 0.005, 0.02), and in arch level measurements than tooth level measurements (B = 0.03, 95% CI = 0.01, 0.04), and significantly lower in 3D printed than digital casts (B = -0.04, 95% CI = -0.05, -0.04). There were no statistically significant differences between measurement errors of both arches (maxillary and mandibular arches). CONCLUSIONS: Extraoral scanners showed higher accuracy than intraoral scanners, and 3D printed casts showed higher accuracy than their digital counterparts. Dental Wings scanner had the greatest measurement error.

3D-Printable Denture Base Resin Containing SiO2 Nanoparticles: An In Vitro Analysis of Mechanical and Surface Properties.

PURPOSE: To evaluate the flexural strength (FS), impact strength (IS), surface roughness (Ra), and hardness of 3D-printed resin incorporating silicon dioxide nanoparticles (SNPs). MATERIALS AND METHODS: A total of 320 acrylic specimens were fabricated with different dimensions according to test specifications and divided into a control group of heat denture base resin, and 3 test groups (80/test (n = 10) of unmodified, 0.25 wt%, and 0.5 wt% SNPs modified 3D-printed resin. 10,000 thermal cycles were performed to half of the fabricated specimens. FS, IS (Charpy impact), Ra, and hardness were evaluated and the collected data was analyzed with ANOVA followed by Tukey's post hoc test (α = 0.05). RESULTS: Incorporating SNPs into 3D-printed resin significantly increased the FS, IS (at 0.5%) and hardness compared to unmodified 3D-printed resin (p < 0.001). However, the FS of pure 3D-printed and 3D/SNP-0.50% resin and IS of all 3D-printed resin groups were significantly lower than the control group (p < 0.0001). Hardness of 3D/SNP-0.25% and 3D/SNP-0.50% was significantly higher than control and unmodified 3D-printed resin (p < 0.0001), with insignificant differences between them. The Ra of all 3D-printed resin groups were significantly higher than control group (p < 0.001), while insignificant difference was found between 3D-printed groups. Thermal cycling significantly reduced FS and hardness for all tested groups, while for IS the reduction was significant only in the control and 3D/SNP-0.50% groups. Thermal cycling significantly increased Ra of the control group and unmodified 3D-printed resin (p < 0.001). CONCLUSION: The addition of SNPs to 3D-printed denture base resin improved its mechanical properties while Ra was not significantly altered. Thermal cycling adversely affected tested properties, except IS of unmodified 3D-printed resin and 3D/SNP-0.25%, and Ra of modified 3D-printed resin.

Evaluation of the Accuracy of Digital Impressions Obtained from Intraoral and Extraoral Dental Scanners with Different CAD/CAM Scanning Technologies: An In Vitro Study.

PURPOSE: To compare the accuracy of intraoral and extraoral scanners (IOSs and EOSs) with different scanning technologies. MATERIAL AND METHODS: A phantom cast was used to simulate the patient's mouth. Polyether impression was made of the phantom cast and poured to fabricate stone casts. The stone casts were scanned by two IOSs (3shape Trios 3, 3S and Dental Wings, DW) and two EOSs (S600 Arti Zirkonzahn, ZK and Ceramill map 600 Amann Girrbach, AG) to obtain digital casts. Reference teeth (canines, premolar, and molars) dimensions were measured on the digital casts by Geomagic software and compared to measurements of the stone cast done by stereomicroscope. The dimensions were occluso-cervical mesio-distal, and bucco-lingual and their average was calculated. Differences between digital and stereoscopic measurements were assessed using paired t-test. Discrepancies between these measurements were calculated as differences and were compared among the four scanners using ANOVA. RESULTS: The differences among the discrepancies of the four scanners were not significant overall (p = 0.969), in premolars (p = 0.932) or molars (p = 0.069) but significant in canines (p = 0.025). The discrepancies of the EOSs were ≤0.01 mm in canines and molars. DW had the greatest discrepancy in canines and molars. CONCLUSIONS: The IOSs and EOSs had similar accuracy except in canines where EOSs performed better. The accuracy of scanning is affected by the smoothness and regularity of the teeth surfaces as in case of the canine.

CAD-CAM Fabricated Denture Base Resins: In Vitro Investigation of the Minimum Acceptable Denture Base Thickness.

PURPOSE: To investigate the influence of reducing material thickness on flexural properties of computer-aided design and computer-aided manufacturing (CAD-CAM) denture base resins. MATERIALS AND METHODS: Four CAD-CAM denture base acrylic resin materials were selected; two were made via the subtractive method (AvaDent and IvoCad) and two were made with the additive method (FormLabs and NextDent). One heat-polymerized denture base material was used as a control. Specimens were fabricated with varying thicknesses (n = 10/group): 3.3 mm, 2.5 mm, 2 mm, or 1.5 mm. Flexural strength was evaluated via a three-point bending test. One- and two-way ANOVA were used for data analysis along with Tukey's post hoc comparison (α = 0.05). RESULTS: Reducing the thickness of materials made via the subtractive method did not influence flexural strength up to 2 mm (p > 0.05). However, the difference was significant at a 1.5 mm thickness (p ˂ 0.001). For materials made via the additive method, NextDent specimens had no significant decrease in flexural strength when the thickness was reduced to 2 mm (p = 0.58). FormLabs specimens showed a significant decrease (p ˂ 0.001), although the values of flexural strength were clinically acceptable. During testing, specimens manufactured via the additive method at a 1.5 mm thickness bent without fracturing and were therefore excluded. All materials showed a reduction in elastic modulus as the thickness decreased (p ˂ 0.001). CONCLUSION: Heat-polymerized, AvaDent, and IvoCad materials may be used for denture base fabrication at a minimum thickness of 1.5 mm. FormLabs and NextDent may be fabricated at a 2 mm minimum thickness, with clinically acceptable flexural properties.

Closed Repair Technique: Innovative Surface Design for Polymethylmethacrylate Denture Base Repair.

PURPOSE: This study aimed to evaluate the repair strength of a newly introduced repair technique involving zero-gap repair width. MATERIALS AND METHODS: A total of 36 rectangular prism specimens with dimensions of 64 × 10 × 3.3 mm were prepared from heat-polymerized acrylic resin. Nine specimens were kept intact. The other specimens were sectioned into halves and modified to create repair gaps of 2.5-mm beveled (2.5B) as control, 0-mm beveled (ZB), and 0-mm inverse bi-beveled (ZIBB). The ZIBB group was prepared with a V-shaped internal groove on both halves (repair tunnel), while the intaglio and cameo surfaces were kept intact except for two small holes at the cameo surface for repair resin injection. The 2.5B and ZB groups were repaired conventionally while the ZIBB group was repaired by injecting repair resin into the tunnel through one of the holes until excess material oozed from the other hole. Repaired specimens were thermally cycled at 5 and 55°C for 10,000 cycles with 1 min dwell time. A 3-point bending test was conducted using a universal testing machine for flexural strength and elastic modulus measurement. Kruskal-Wallis/Mann-Whitney tests and ANOVA/post hoc Tukey tests were applied for data analysis (α = 0.05). RESULTS: The flexural strength of repaired specimens was substantially lower than that of intact specimens, and significant differences were present between repaired groups (p ˂ 0.05). ZB and ZIBB had higher flexural strength (p ˂ 0.001) and elastic modulus (p ˂ 0.05) than 2.5B. Among the ZB and ZIBB groups, ZB showed the highest flexural strength, and ZIBB had the highest elastic modulus. CONCLUSION: The closed repair technique improved the flexural strength and elastic modulus of repaired acrylic denture base.

Strength and Surface Properties of a 3D-Printed Denture Base Polymer.

PURPOSE: This in vitro study evaluated the flexural strength, impact strength, hardness, and surface roughness of 3D-printed denture base resin subjected to thermal cycling treatment. MATERIALS AND METHODS: According to ISO 20795-1:2013 standards, 120 acrylic resin specimens (40/flexural strength test, 40/impact strength, and 40/surface roughness and hardness test, n = 10) were fabricated and distributed into two groups: heat-polymerized; (Major.Base.20) as control and 3D-printed (NextDent) as experimental group. Half of the specimens of each group were subjected to 10,000 thermal cycles of 5 to 55°C simulating 1 year of clinical use. Flexural strength (MPa), impact strength (KJ/m2 ), hardness (VHN), and surface roughness (µm) were measured using universal testing machine, Charpy's impact tester, Vickers hardness tester, and profilometer, respectively. Data were analyzed by ANOVA and Tukey honestly significant difference (HSD) test (α = 0.05). RESULTS: The values of flexural strength (MPa) were 86.63 ± 1.0 and 69.15 ± 0.88; impact strength (KJ/m2 )-6.32 ± 0.50 and 2.44 ± 0.31; hardness (VHN)-41.63 ± 2.03 and 34.62 ± 2.1; and surface roughness (µm)-0.18 ± 0.01 and 0.12 ± 0.02 for heat-polymerized and 3D-printed denture base materials, respectively. Significant differences in all tested properties were recorded between heat-polymerized and 3D-printed denture base materials (P < 0.001). Thermal cycling significantly lowered the flexural strength (63.93 ± 1.54 MPa), impact strength (2.40 ± 0.35 KJ/m2 ), and hardness (30.17 ± 1.38 VHN) of 3D-printed resin in comparison to thermal cycled heat-polymerized resin, but surface roughness showed non-significant difference (p = 0.262). CONCLUSION: 3D-printed resin had inferior flexural strength, impact strength, and hardness values than heat-polymerized resin, but showed superior surface roughness. Temperature changes (thermal cycling) significantly reduced the hardness and flexural strength and increased surface roughness, but did not affect the impact strength.

A novel variant of RBCK1 gene causes mild polyglucosan myopathy.

Homozygous or compound heterozygous pathogenic variants of the RBCK1 gene can result in a systemic disorder characterized by the accumulation of complex carbohydrate molecules, namely polyglucosan bodies in the muscular tissues. The role of this gene in the pathophysiology of the disorder at the molecular level remains unclear. Being a very rare disorder, the medical knowledge is based on just a few reported cases. Here we report a 7-year-old girl who presented with exercise intolerance and hepatosplenomegaly. Her liver profile was constantly raised. The genetic investigation has revealed a variant of the RBCK1 gene of unknown significance, which has later been confirmed as pathogenic via a variety of clinical, genetic, and histopathological approaches. More importantly, it is evident that the availability of sophisticated genetic testing, such as whole-exome sequencing, has significantly improved the knowledge of and diagnosis of many rare metabolic disorders.

Florid Scurvy in an Autistic Child on a Ketogenic Diet.

ABSTRACT: Ketogenic diets used for treating various neurological disorders can have potentially serious adverse effects. Among these is scurvy, a rarely reported, yet potentially fatal adverse effect of the ketogenic diet caused by vitamin C deficiency. We report a case of a 5-year-old patient with autism, who presented with scurvy secondary to the dietary restrictions of a ketogenic diet. Our review of the literature showed a single previously reported case of vitamin C deficiency in a patient on ketogenic diet. We have also reviewed the clinical indications and adverse effects of ketogenic diets with special reference to scurvy. This case emphasizes the importance of vitamin supplements in patients consuming a special diet.

Effects of Denture Cleansers on the Flexural Strength of PMMA Denture Base Resin Modified with ZrO2 Nanoparticles.

PURPOSE: The additions of zirconium oxide nanoparticles (nano-ZrO2 ) to denture base materials have produced nanocomposites with satisfactory properties, although there is a lack of research investigating the effects of denture cleansers on these materials. This study aimed to evaluate the effect of denture cleansers on the flexural strength of denture base materials modified with nano-ZrO2 . MATERIALS AND METHODS: A total of 270 specimens were fabricated from pure and nano-ZrO2 reinforced acrylic resins at 2.5% and 5%, resulting in 3 main groups. The groups were further divided into subgroups (n = 10) according to immersion solution (distilled water, Corega, sodium hypochlorite, and Renew) and immersion duration. Flexural strength was measured at baseline (T0 ) in distilled water and after 180 and 365 days of immersion (T1 and T2 ) in denture cleansers. Data were collected and analyzed using repeated measure ANOVA and Bonferroni post hoc tests (α = 0.05). RESULTS: The flexural strength of the nano-ZrO2 modified denture base material decreased significantly after immersion in different denture cleansers at different immersion durations in comparison to baseline (T0 ) (p < 0.001). Sodium hypochlorite showed the highest reduction in flexural strength followed by Corega, while Renew cleansing solution resulted in the least change. CONCLUSION: Denture cleansers can significantly affect the flexural strength of nano-ZrO2 modified denture base materials and thus should be used cautiously.

Do Morphological Changes in the Anterior Mandibular Region Interfere with Standard Implant Placement? A Cone Beam Computed Tomographic Cross-Sectional Study.

OBJECTIVE: To determine the morphological features in the anterior mandibular region, the presence of lingual foramen and canal dimensions in Saudi subjects that would interfere with standard implant placement. METHODS: CBCT scans of patients seeking implant treatment were examined. Based on the dentition status, patients were categorized into edentulous (group I) and dentulous (group I). On the panoramic view, the distance between the two mental foramina was divided into vertical segments of 10 mm width. In each segment, vertical bone height and buccolingual thickness at three levels (alveolar crest, 5 mm, and 10 mm apical to the crest) were assessed. The lingual foramen prevalence and canal features were assessed as well. Comparisons between the two groups regarding the assessed parameters were performed using the t-test. The percentage of edentulous mandibles with thickness <6 mm corresponding to the standard implant diameter was also calculated. RESULTS: Following the inclusion and exclusion criteria, group I consisted of 45 subjects and group II comprised 26 subjects. Bone height and thickness at the crestal level were significantly less in edentulous (I) than dentate mandibles (II) (P < 0.0001). The lingual foramen was detected in 90% of patients. In both groups, males had significantly greater mandibular height than females (P=0.02 and 0.005). At the crestal level, the thickness was <6 mm in 50% of the anterior mandibular segments. CONCLUSION: Half of the edentulous patients may receive normal size implants in the anterior interforaminal segments, while the other half will be limited to narrow implants (3.5 mm and less). The lingual foramen location, canal size, and position may represent another limitation for implant placement in that segment.

Influence of Addition of Different Nanoparticles on the Surface Properties of Poly(methylmethacrylate) Denture Base Material.

PURPOSE: To evaluate and compare the surface properties (roughness and hardness) of poly(methylmethacrylate) denture base material modified with zirconium dioxide (ZNPs), silicon dioxide (SNPs), and diamond (DNPs) nanoparticles. MATERIALS AND METHODS: Two hundred sixty heat-polymerized acrylic resin disks (15 × 2 mm) were prepared. ZNPs, SNPs, and DNPs were added in concentrations of 0%, 0.5%, 1.0%, 2.5%, and 5.0% by weight of acrylic powder. This yielded a total of 13 groups for each test according to filler type and concentration (n = 10/group). The control group was made of pure acrylic. A mechanical polisher was used to standardize specimens' surfaces before testing. A profilometer and Vickers hardness indenter were used to test the surface roughness and hardness, respectively. ANOVA and Tukey post hoc tests were used for data analysis (α = 0.05). RESULTS: In comparison to control, results showed a nonsignificant increase in surface roughness (Ra ) of acrylic material after the addition of 0.5% nanoparticles (ZNPs p = 0.168, SNPs p = 0.166, and DNPs p = 0.177), while a significant increase was seen with all other concentrations (p ˂ 0.05). Ra values of ZNP and DNP groups were significantly higher than those of the SNPs group (p < 0.001). The addition of any of the fillers to acrylic denture base materials significantly increased the hardness (p ˂ 0.05), with ZNPs and DNPs having values lower than those of the SNPs group (p < 0.001). CONCLUSIONS: Although nanofiller addition increased the hardness of denture base material, Ra was adversely affected when the concentration exceeded 0.5%. Therefore, 0.5% is suggested to be the most appropriate ratio to improve hardness with acceptable Ra .

A Novel Approach to Improve Repair Bond Strength of Repaired Acrylic Resin: An in Vitro Study on the Shear Bond Strength.

PURPOSE: To evaluate the combined effect of mechanical surface treatment with intermediate bonding agents (methyl methacrylate [MMA] and silane coupling agents) and ZrO2 nanoparticle (nano-ZrO2 ) addition to repair material on the shear bond strength (SBS) of repaired denture bases. MATERIALS AND METHODS: Heat-polymerized acrylic resin was used to fabricate 130 cylindrical blocks (15 mm × 10 mm) and divided into a control group without treatment (C, n = 10), and 3 repair groups (n = 40/group) divided into specimens treated with alumina blasting alone (AB), specimens blasted with alumina combined with silane coupling agent (AB + SCA), or combined with MMA-based composite bonding agent (AB + MA). Treated groups were further subdivided according to nano-ZrO2 concentrations into 0 wt%, 2.5 wt%, 5 wt%, and 7.5 wt% added to repair resin powder. Repair resin monomer and polymer were combined and packed on the repair area and then placed in a pressure pot at 37°C for 15 minutes for polymerization. Shear bond test was performed using a universal testing machine. Scanning electron microscopy (SEM) was used to examine the effect of surface modifications on repair surfaces and to evaluate the topography of fracture surfaces. Tukey-Kramer multiple-comparison test was used to detect significant differences between groups (p ≤ 0.05). RESULTS: SBS (MPa) of specimens treated with alumina blasting and application of intermediate agents were significantly higher than the control group (p < 0.05), while no significant differences were found between AB and control group (p > 0.05). Nano-ZrO2 addition significantly increased SBS except for AB, and 5%, 7.5% MA (p > 0.05). SEM evaluation showed that alumina blasting created rougher and more porous surfaces, while SCA and MA reduced the irregularities and fissures. CONCLUSION: Application of bonding agents to repair surfaces after alumina blasting improved the repair bond strength and proved to be a possible new adhesive method for denture repair. Moreover, nano-ZrO2 addition in combination with surface treatment improved the repair bond strength.

Comparative Effect of Glass Fiber and Nano-Filler Addition on Denture Repair Strength.

PURPOSE: To evaluate and compare the effects of glass fiber (GF), Zirconium oxide nanoparticles (nano-ZrO2 ), and silicon dioxide nanoparticles (nano-SiO2 ) addition on the flexural strength and impact strength of repaired denture base material. MATERIALS AND METHODS: Heat-polymerized acrylic resin specimens were fabricated. All specimens were sectioned centrally and beveled creating 2.5 mm repair gap except for 10 controls. Specimen grouping (n = 10/group) was done according to filler concentration of 0%, 0.25%, 0.5%, and 0.75% of auto-polymerized acrylic powder. Modified resin was mixed, packed in the repair gap, polymerized, finished and polished. Three-point bending test and Charpy type impact testing were done. Data were analyzed using one-way-ANOVA and Post-Hoc Tukey test (α = 0.05). RESULTS: All additives significantly increased flexural strength and impact strength (p < 0.05). Within the modified subgroups, no significant differences were found for GF. Significant increase for nano-ZrO2 and significant decrease for nano-SiO2 as the concentration of additive increased were noted for both flexural strength and impact strength. Highest flexural strength was found with 0.75%-nano-ZrO2 (69.59 ± 2.52MPa) and the lowest was found with 0.75%-nano-SiO2 (53.82 ± 3.10MPa). The 0.25%-nano-SiO2 showed the highest impact strength value (2.54 ± 0.21 kJ/m2 ) while the lowest impact strength value was seen with 0.75%-nano-SiO2 (1.54 ± 0.17 kJ/m2 ). CONCLUSION: Nano-filler effect was concentration dependent and its addition to repair resin increased the flexural and impact strengths. The incorporation of 0.75%-ZrO2 or 0.25%-SiO2 into repair resin proved to be a promising technique to enhance repair strength and avoid repeated fractures.

The influence of simulated aging on the color stability of composite resin cements.

STATEMENT OF PROBLEM: Data for the color stability of dual-polymerized and light-polymerized resin cements used in esthetic dentistry are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the color stability of 4 types of composite resin cements after water aging. MATERIAL AND METHODS: Specimens (n=30) of each resin cement (Variolink Esthetic LC, RelyX Ultimate DC, Nexus 3 DC, Nexus 3 LC) were prepared. The shade selected was Light+ for Variolink Esthetic, B 0.5 for RelyX Ultimate, and White for both Nexus 3 DC and LC. All 120 specimens were aged by water for 30 days at 37°C under dark conditions, using a thermocycling machine. The specimens' color characteristics (L*, luminosity; a*, red-green; b*, yellow-blue) and color differences (ΔE) were measured with a spectrophotometer before day 0, after day 1, and after 30 days of immersion. Statistical analysis used ANOVA and Tukey post hoc tests (α=.05). RESULTS: Considering ΔE<3.3 as clinically acceptable, results showed significant color variations for all cements (RelyX Ultimate=3.69; Nexus 3 LC=3.76; Nexus 3 DC=5.34), except for Variolink Esthetic (0.88). However, this variation was significantly less when day 1 was considered the baseline measurement, showing clinically acceptable ΔE values for all types of cement. CONCLUSIONS: Water aging had a significant effect on color stability; most color variations occurred in the first 24 hours of polymerization, with relatively nonsignificant variations afterwards.

A Novel Extended Range Attachment System to Retain Implant Overdentures: A Clinical Report.

Various attachment systems have been used to facilitate the retention, stability, and support of overdentures. The low profile design, pivoting technology, and durability of the Locator attachment made it one of the commonly used tissue-supported implant-retained overdentures. It has been successfully used to retain overdentures as well as partial dentures. This article describes the uses of the new Locator R-Tx abutment and illustrates both the direct and indirect techniques used to process the denture attachment housing into the prosthesis to retain overdentures and partial dentures.