Preventive and restorative alternatives to caries by irradiation: a scoping review.

PURPOSE: This study is to conduct a comprehensive scoping review to map scientific evidence and clarify concepts regarding the commonly recommended preventive and restorative dental treatments for patients diagnosed with head and neck cancer (HNC) and subjected to radiotherapy. MATERIAL AND METHODS: This systematic scoping review was performed under the PRISMA-ScR guidelines. The study's experimental design was registered in the Open Science Framework. In vitro studies that evaluated preventive and restorative dental treatment over 50 Gy radiation doses were included. The search was conducted in November 2023 in five electronic databases (PubMed, Scopus, Web of Science, Cochrane Library, and Embase) without language or date restriction. A search strategy was applied based on keywords, MeSh terms, or synonyms. A descriptive analysis was conducted. RESULTS: A total of 49 studies, out of 3679 original articles identified, were included and reviewed. Of the included studies, three evaluated saliva stimulants and 35 evaluated fluoride-based preventive materials: gel (n = 18) toothpaste (n = 11) mouth rinse (n = 8) and varnish (n = 5) while 14 evaluated restorative materials: resin composite (n = 12) glass ionomer cement (n = 6) and amalgam (n = 1) Of those studies, 36 were clinical trials and 13 were in vitro studies. CONCLUSION: Fluoride gel was the most frequently recommended preventive material for preventing radiation caries with supportive clinical evidence. Resin composite and glass ionomer were the most frequently used restorative materials, respectively. However, there is not yet clinical evidence to support the use of resin composite in irradiated teeth.

Effect of artificial aging on optical properties and crystalline structure of high-translucency zirconia.

PURPOSE: To investigate the effect of different in vitro aging protocols on the optical properties and crystalline structure of high-translucency (HT) zirconia. MATERIALS AND METHODS: Thirty-six specimens of HT and extra-high translucency (XT) zirconia were divided into three groups: control (CO)-no treatment; hydrothermal aging (HA)-autoclave aging for 12.5 h at 134°C, 2 bar; clinically related aging (CRA)-aging in the chewing simulator for 1.2 million cycles, followed by 50,000 thermocycles (5-55°C) and immersion in HCl (pH 1.2) for 15 h. Optical properties, crystalline structure, and surface roughness were analyzed and compared using analysis of variance (5% significance level). RESULTS: There was no statistically significant effect of aging on translucency (p = 0.10), but CRA promoted the development of a high contrast ratio (p = 0.03). Aging did not cause significant color changes for HT (p = 0.65) or XT (p = 0.36). The proportion of monoclinic crystals increased to 40% for HT-zirconia after HA and 5% after CRA. No monoclinic crystals were detected for XT groups. There was no effect of aging on surface roughness (p = 0.77). CONCLUSIONS: Although hydrothermal aging has been widely used to verify zirconia crystalline stability, it did not generate an effect similar to clinically related aging on the optical properties and crystalline structure of zirconia. HA affected the crystalline structure of HT-zirconia, and CRA compromised the optical properties of XT zirconia.

Preheating of dental composite resins: A scoping review.

OBJECTIVE: The aim of this scoping review was to analyze the available evidence on the preheating process and its effects on physicochemical properties of composite resins. MATERIALS AND METHODS: A systematic search was performed in August 2021 using PubMed/Medline, Embase, Scopus, and ISI Web of Science databases and gray literature without language or date restriction. Inclusion criteria were in vitro studies that assessed the physicochemical properties and marginal adaptation of preheated composite. Exclusion criteria were studies with experimental composite, literature reviews, clinical studies. Data from selected studies were qualitatively analyzed. RESULTS: In total, 104 studies were found from which 39 were included. The most used composite resin was Filtek Z350 XT (3 M/ESPE), preheated at 68°C in a Calset device (AdDent Inc., Danbury, CT, USA) for 5 or 15 min. Most studies showed decreased viscosity, increased conversion degree and microhardness of composite resins, and better marginal adaptation of direct and indirect restorations. Also, flexural strength was not affected, and data about bond strength were inconclusive due to heterogeneity among studies. CONCLUSION: The parameters used for preheating composite resins are heterogeneous. Preheating decreased viscosity, increased the conversion degree and microhardness of composite resins, and improved the marginal adaptation of direct and indirect restorations. CLINICAL SIGNIFICANCE: The analysis of evidence showed a high heterogeneity among preheating protocols. Preheating may benefit the handling and physicochemical properties of composite resins.

Effect of universal adhesives and self-etch ceramic primers on bond strength to glass ceramics: A systematic review and meta-analysis of in vitro studies.

STATEMENT OF PROBLEM: To simplify dental procedures, multicomponent products such as universal adhesives and self-etch ceramic primers have been recommended for glass-ceramic bonding; however, studies have shown a wide range of results. PURPOSE: The purpose of this systematic review and meta-analysis was to analyze the in vitro bond strength promoted by hydrofluoric acid+silane-containing universal adhesives and a self-etch ceramic primer to glass-ceramics and compare it with that of conventional treatments. MATERIAL AND METHODS: A systematic search was conducted in the PubMed/Medline, Scopus, LILACS, and ISI Web of Science databases up to April 2021. In vitro studies assessing the resin-mediated bond to glass-ceramics by using a self-etch ceramic primer and hydrofluoric acid+silane-containing universal adhesives and/or compared with traditional hydrofluoric acid+glass-ceramic primers were included. Selection of studies, data extraction, and risk-of-bias analysis were performed. Statistical analysis was performed by using a review management software program using a random effects model (α=.05). RESULTS: A total of 33 studies were included in the qualitative analysis and 26 studies in the quantitative analysis. Bond strength to lithium disilicate ceramic was higher when a hydrofluoric acid+glass-ceramic primer was used than when using a hydrofluoric acid+silane-containing universal adhesive (P<.05), except when 9% to 10% acid concentration was used in combination with static aging (P=.100). A self-etch ceramic primer promoted bond strength values to lithium disilicate that were similar to those of the hydrofluoric acid+glass-ceramic primer (P>.100). CONCLUSIONS: Hydrofluoric acid+silane-containing universal adhesive was not as effective as the hydrofluoric acid+glass-ceramic primer in promoting bond strength to glass-ceramic. Bond strength values generated by a self-etch ceramic primer to glass-ceramic were similar to those generated by the conventional treatment.

Review of nano-technology applications in resin-based restorative materials.

OBJECTIVE: Nanotechnology has progressed significantly and particles as small as 3 nm are being employed in resin-based restorative materials to improve clinical performance. The goal of this review is to report the progress of nanotechnology in Restorative Dentistry by reviewing the advantages, limitations, and applications of resin-based restorative materials with nanoparticles. MATERIALS AND METHODS: A literature review was conducted using PubMed/Medline, Scopus and Embase databases. In vitro, in vivo and in situ research studies published in English between 1999 and 2020, and which focused on the analysis of resin-based restorative materials containing nanoparticles were included. RESULTS: A total of 140 studies were included in this review. Studies reported the effect of incorporating different types of nanoparticles on adhesive systems or resin composites. Mechanical, physical, and anti-bacterial properties were described. The clinical performance of resin-based restorative materials with nanoparticles was also reported. CONCLUSIONS: The high surface area of nanoparticles exponentially increases the bioactivity of materials using bioactive nanofillers. However, the tendency of nanoparticles to agglomerate, the chemical instability of the developed materials and the decline of rheological properties when high ratios of nanoparticles are employed are some of the obstacles to overcome in the near future. CLINICAL SIGNIFICANCE: In spite of the recent advancements of nanotechnology in resin-based restorative materials, some challenges need to be overcome before new nano-based restorative materials are considered permanent solutions to clinical problems.

Effect of handling material on mechanical and optical properties of feldspathic porcelain.

OBJECTIVE: To evaluate the optical, chemical, and mechanical properties of feldspathic porcelain after handling with different instrument materials. MATERIAL AND METHODS: Feldspathic porcelain was manipulated with different spatula compositions: metal spatula (MS), plastic spatula (PS), and glass spatula (GS) for the fabrication of 30 (n = 10) disks. Contrast ratio (CR), translucency parameter (TP), and surface Knoop microhardness (KHN) were measured. The color change (ΔE00 ) was evaluated using the CIEDE2000 system. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used for surface analysis. Data were analyzed using one-way ANOVA and Tukey test (P < 0.05). RESULTS: All groups presented different morphological surfaces with higher presence of Al on the MS. PS group presented lower Al, Si, K than MS, and GS. Higher CR was observed for PS (0.734; P < 0.043), followed by MS (0.696; P < 0.043) and GS (0.65; P < 0.011). The highest TP (13.06) and KHN (386.27) were presented by GS (P < 0.001). MS and PS presented similar KHN results. The higher ΔE00 were found for plastic/metal comparison. Also, the L* values for the MS group (67.49) were lower than the other groups. CONCLUSION: The use of metal spatula promoted higher color alteration during feldspathic porcelain manipulation than did the other materials. Handling with glass instrument promoted higher microhardness than other spatula materials. CLINICAL SIGNIFICANCE: The effect of the material used for ceramic handling on feldspathic porcelain properties is often ignored. This study shows that the handling spatula material must be carefully chosen to avoid inadvertent changes to the feldspathic porcelain restoration.

Effect of surface treatment on the retention of zirconia crowns to tooth structure after aging.

OBJECTIVE: To evaluate the effect of different surface treatments on the retention between zirconia crowns and tooth structure after in vitro aging. MATERIALS AND METHODS: Human third molars (n = 44) received crown preparations and CAD/CAM zirconia crowns were manufactured. Specimens were divided into two groups: no aging, control (NAC, n = 11) or aging (A, n = 33). NAC were bonded with universal adhesive (UA). Aged specimens were divided into three subgroups (n = 11) according to surface treatment: Control: no abrasion + UA; Alumina: alumina abrasion + UA; Silica: tribochemical silica coating + UA. The crowns were cemented with dual-cure resin cement. Specimens in group A were aged by a combination of mechanical, thermal, and pH cycling. Retention strength values were obtained by tensile tests and results were analyzed by one-way analysis of variance (ANOVA) and Tukey test (P < .05). RESULTS: Aging decreased the retention strength in control specimens (P < .001). Surface treatment improved the retention strength of aged specimens (P < .001), with similar results between alumina and tribochemical silica coating. CONCLUSION: The chemical interaction between the universal bonding system and zirconia's surface was not sufficient to withstand artificial aging. Tribochemical silica coating did not promote additional retention in comparison to alumina blasting. CLINICAL SIGNIFICANCE: The long-term retention of translucent zirconia crowns to tooth structure using phosphate-based materials is improved by means of mechanical surface treatments such as alumina blasting and tribochemical silica coating.

Mechanical properties of aged yttria-stabilized tetragonal zirconia polycrystal after abrasion with different aluminum oxide particles.

STATEMENT OF PROBLEM: A consensus on the benefits of airborne-particle abrasion of zirconia with alumina particles of different sizes is still lacking. Larger particle size may improve micromechanical retention but may generate deep microcracks on the zirconia surface. PURPOSE: The purpose of this in vitro study was to evaluate the effect of different size of Al2O3 particles used for surface abrasion on the mechanical properties of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). MATERIAL AND METHODS: Sixty Y-TZP specimens were divided into 6 groups according to the treatment: control (without treatment) or airborne-particle abrasion with Al2O3 particles (45 µm or 150 µm). Half the specimens were stored for 24 hours in water while the other half was exposed to 1.5×106 mechanical cycles before flexural strength analysis at 1 mm/min crosshead speed. Specimens were also characterized by micro-Raman spectroscopy and X-ray diffraction (XRD) to evaluate the crystalline composition. The data were subjected to 2-way ANOVA and Tukey HSD test (α=.05). RESULTS: Airborne-particle abrasion with alumina (P=.030) and mechanical fatigue (P<.001) had a significant effect on flexural strength. Specimens abraded with 45-µm Al2O3 particles (847 ±204 MPa) presented higher flexural strength than those of the control group (670 ±210 MPa). The size of the alumina particles was not significant for flexural strength. Flexural resistance (664 MPa) significantly decreased after mechanical fatigue. All groups showed only the tetragonal phase on the micro-Raman spectra, which was confirmed by XRD. CONCLUSIONS: Airborne-particle abrasion with smaller Al2O3 particles increased the flexural strength on Y-TZP without causing phase transformation. However, flexural strength was decreased after mechanical fatigue.

Microstructural and Mechanical Characterization of CAD/CAM Materials for Monolithic Dental Restorations.

PURPOSE: To determine and compare the microstructure, flexural strength, flexural modulus, fracture strength, and microhardness of four types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials for monolithic dental restorations. MATERIALS AND METHODS: A lithium disilicate (LD; IPS e.max CAD), a zirconia-reinforced lithium silicate (ZLS; VITA Suprinity), a hybrid high-performance polymer (HPP) composite resin (GC Cerasmart), and a hybrid polymer-infiltrated ceramic network (PICN) material (VITA Enamic) were used to manufacture monolithic ceramic posterior crowns (n = 10) that were adhesively cemented on resin-based composite dies and loaded until fracture. In addition, 40 rectangular bars (n = 10) were milled and polished for three-point flexural strength testing. Microhardness (Vickers indentation), as well as quantitative (energy dispersive spectroscopy) and qualitative (scanning electron microscopy) structural analysis were conducted on fracture surfaces. Data were analyzed by one-way ANOVA and Tukey HSD post-hoc test (p = 0.05). RESULTS: Mechanical testing results showed that the material type has a significant effect on the fracture strength (p < 0.0001) of the monolithic crowns with ZLS and LD presenting significantly higher fracture strength than the PICN and HPP hybrid materials. LD showed the highest flexural strength (p < 0.0001) followed by ZLS, HPP, and PICN, respectively. The lowest flexural modulus and hardness were presented by HPP whereas ZLS had the highest flexural modulus and hardness. The LD presented the highest modulus of resilience and the PICN the lowest. CONCLUSIONS: All CAD/CAM crown materials exhibited high values of fracture and flexural resistance, making them suitable materials for posterior full-crown restorations. Glass-ceramics suffered more from catastrophic and nonreparable fracture patterns, whereas minimal chipping and type II fracture patterns were more common in hybrid materials. The combination of more flexibility, less stiffness, and increased softness with satisfactory flexural and fracture strength values observed in PICN and HPP makes these two hybrid materials suitable choices for chairside monolithic crown fabrication.

Surface and Mechanical Characterization of Dental Yttria-Stabilized Tetragonal Zirconia Polycrystals (3Y-TZP) After Different Aging Processes.

Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) is a ceramic material used in indirect dental restorations. However, phase transformation at body temperature may compromise the material's mechanical properties, affecting the clinical performance of the restoration. The effect of mastication on 3Y-TZP aging has not been investigated. 3Y-TZP specimens (IPS E-max ZirCAD and Z5) were aged in three different modes (n=13): no aging (control), hydrothermal aging (HA), or chewing simulation (CS). Mechanical properties and surface topography were analyzed. Analysis of variance showed that neither aging protocol (p=0.692) nor material (p=0.283) or the interaction between them (p=0.216) had a significant effect on flexural strength, values ranged from 928.8 MPa (IPSHA) to 1,080.6 MPa (Z5HA). Nanoindentation analysis showed that material, aging protocol, and the interaction between them had a significant effect (p<0.001) on surface hardness and reduced Young's modulus. The compositional analysis revealed similar yttrium content for all the experimental conditions (aging: p=0.997; material: p=0.248; interaction material×aging: p=0.720). Atomic force microscopy showed an effect of aging protocols on phase transformation, with samples submitted to CS exhibiting features compatible with maximized phase transformation, such as increased volume of the material microstructure at the surface leading to an increase in surface roughness.

Different Strategies to Bond Bis-GMA-based Resin Cement to Zirconia.

PURPOSE: To evaluate the effect of different bonding strategies on short- and long-term bis-GMA-based resin cement bond strengths to zirconia. MATERIALS AND METHODS: One hundred twenty samples of fully-sintered zirconia (Prettau Zirconia) were sandblasted and randomly distributed into 5 groups (n = 24): UA: Scotchbond Universal Adhesive; SZP: Signum Zirconia Bond I + II; ZPP: Z-Prime Plus; EXP: MZ experimental primer; CO: no primer application (control). After performing these surface treatments, translucent tubes (0.8 mm diameter and 1.0 mm height) were placed on the zirconia specimens, and bis-GMA-based cement (Duo-Link) was injected into them and light cured. Specimens were tested for microshear bond strength either 24 h or 6 months (m) after water storage (37°C) and surfaces were characterized by SEM and EDX. Two-way ANOVA and Tukey's post-hoc test (p < 0.05) were used to evaluate bond strength results. RESULTS: The mean bond strengths (MPa ± SD) were: UA=14.6 ± 4.7a (24 h); 16.0 ± 4.8a (6 m); SZP = 14.0 ± 5.4ab (24 h); 11.9 ± 2.6ab (6 m); ZPP=8.0 ± 1.8b (24 h); 8.6 ± 3.3b (6 m); EXP = 1.2 ± 0.5c (24 h); 0.6 ± 0.7c (6 m); CO=1.0 ± 1.2c (24 h); 1.3 ± 1.2c (6 m). Bonding strategy significantly influenced bond strength (p = 0.0001), but storage time did not (p = 0.841). Groups UA and SZP showed a homogeneous layer covering the zirconia surface. In these groups, EDX demonstrated the presence of phosphorus. Group ZPP resulted in a nonhomogeneous layer, exposing the zirconia substrate underneath. EXP application resulted in an undetectable layer. CONCLUSION: Water storage did not affect resin cement bond strengths to zirconia irrespective of the surface treatment. Bis-GMA-based resin cement bond strengths to zirconia are affected by specific bonding strategies.

Effect of Bleaching Treatment on Fatigue Resistance and Flexural Strength of Bovine Dentin.

PURPOSE: To determine the effects of bleach on dentin fatigue resistance and flexural strength. MATERIALS AND METHODS: Eighty bovine dentin specimens (2 × 2 × 17 mm) were treated with: placebo or 10% carbamide peroxide bleach. Treatment was applied for 6 hours/day for 2 or 8 weeks. After treatment, 10 specimens per group were subjected to fatigue testing (10(6) cycles) whereas the other 10 were stored in artificial saliva as fatigue controls. The specimens undergoing fatigue were checked daily for visible signs of fracture and excluded from subsequent flexural strength tests if fractured. Fatigue control and surviving fatigued specimens were subjected to flexural strength testing. Chi-square, Kruskal-Wallis, factorial analysis of variance (p < 0.05) and Mann-Whitney (p < 0.002) tests were performed. RESULTS: There were significant differences in fatigue resistance (p = 0.003) and flexural strength rank scores (p < 0.0001) among the groups. None of the specimens in the "8-week bleach" group survived the fatigue testing. Fatigue (p = 0.005) and interaction of time and treatment (p = 0.039) were significant factors in the flexural strength results. Fatigued specimens had lower flexural strength than nonfatigued and "8-week bleach" had lower flexural strength than placebo and "2-week bleach" groups. CONCLUSIONS: Prolonged direct bleaching of bovine dentin reduces its fatigue resistance and flexural strength in vitro. Further research is needed in this area. CLINICAL SIGNIFICANCE: It remains prudent to advise patients to limit their exposure to tooth bleaching materials by avoiding direct application of bleach to exposed dentin and by minimizing the duration of bleach treatment.

The use of MDP-based materials for bonding to zirconia.

STATEMENT OF PROBLEM: A strong and stable bond between the luting resin and overlying ceramic restoration is critical to longevity, but no technique has been established for how to provide such a bond when the core material is zirconia. PURPOSE: The purpose of this study was to evaluate the effect of different materials containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) on the bond strength to yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic. MATERIAL AND METHODS: Forty Y-TZP slices (Lava) were cemented to substrates (8 groups; n=5 in each) with or without the previous application of an experimental primer (0.5% MDP) or an MDP-based adhesive (Clearfil S3 Bond Plus or Scotchbond Universal) with either an MDP (Clearfil SA) or a non-MDP (RelyX Ultimate) luting resin. Specimens were cut, stored in distilled water, and microtensile tested (5 beams per specimen) at 48 hours and again at 6 months after luting procedures. The data were analyzed by 4-way ANOVA (α=.05) and the Tukey test (α=.05). The mode of failure was classified with a stereomicroscope, and the treated surfaces were analyzed with energy-dispersive x-ray spectroscopy. RESULTS: Both adhesive (P<.001) and time (P<.001) significantly affected bond strength. The interaction of any of the factors was not significant. The use of an MDP-containing adhesive and the shorter storage time were associated with higher bond strengths. At 48 hours, an overall incidence of 50.5% of Type 1 mode of failure (adhesive at ceramic/resin interface) occurred, as opposed to 68% after 6 months of water storage. Energy-dispersive x-ray spectroscopy results showed peaks of carbon and phosphorus when MDP-based materials were used. CONCLUSIONS: The application of an MDP-based adhesive may improve bond strength to zirconia. However, microtensile bond strength results for all groups did not remain stable over 6 months.

Effects of simulation-based flipped classroom in developing head and neck examination skills in dental students.

OBJECTIVES: To evaluate the effectiveness of a simulation-based flipped classroom in developing dental students' head and neck examination skills. METHODS: Second-year dental students (n = 118) participated in a simulation-based flipped classroom experience. A pre-class recorded lecture and video were posted online one week before the simulation date. In class, students completed a pre-quiz assessing pre-class coursework understanding of head and neck examination content. Then, students attended a question-and-answer session before the patient simulation. A formative assessment of head and neck examination simulation on a patient in the clinic was completed. Lastly, students completed an in-class post-quiz assessing understanding of head and neck examination content after the simulation, classroom simulation discussion, and open-response survey. RESULTS: Student post-quiz scores were significantly higher than pre-quiz scores, with an average improvement of 4.8 ± 7.2 percentage points. There was no difference between male and female improvement in scores. Student survey responses indicated that students liked combining simulation and flipped classroom methodology, flexibility with their schedules, learning at their pace, and opportunities for a deeper level of learning. Students reported wanting more practice sessions for their technical skills and more accessibility to faculty. CONCLUSIONS: According to this study's results, students had significantly higher post-quiz scores than pre-quiz scores and reported positive perceptions of this combined teaching technique. A simulation-based flipped classroom might be an effective teaching approach for developing head and neck examination skills that can be applied at other dental facilities with potentially similar results.

Scoping review: Effect of surface treatments on bond strength of resin composite repair.

OBJECTIVE: to evaluate the existing evidence on surface treatment techniques employed in resin composite repair and their effect on the repair short- and long-term bond strength. DATA AND SOURCE: This scoping review was performed under the PRISMA-ScR guidelines for scoping reviews and registered on the Open Science Framework platform. STUDY SELECTION: A systematic search was conducted in PubMed, Embase, and Scopus and grey literature up to September 2022 without language or date restriction. In vitro studies comparing mechanical surface and/or chemical treatments on repair bond strength of resin composite were included. Studies evaluating experimental adhesive systems or resin composites were excluded. Selection of studies and data extraction were performed. Data from selected studies was qualitatively analyzed. RESULTS: A total of 76 studies were included in the qualitative analysis. Among the mechanical treatments, alumina blasting was the most frequently used, followed by silica coating and diamond bur. As for chemical treatments, dentin bonding systems were the most frequently evaluated, followed by universal adhesive systems and silane/ceramic primer. The combination of mechanical and chemical pre-treatments increased the repair bond strength of resin composite in both short- and long-term simulated aging scenarios. The evidence obtained from the included studies was classified as moderate quality, mainly due to the medium risk of bias observed across most of the studies. CONCLUSION: The techniques used to treat the surface of resin composites for repair are diverse. Incorporating a combination of mechanical and chemical pre-treatments resulted in superior repair bond strength of resin composite materials under both short- and long-term simulated aging conditions. CLINICAL SIGNIFICANCE: The analysis of evidence revealed significant variability among protocols for repairing resin composites. Utilizing both mechanical and chemical pre-treatment methods is important for enhancing the bond strength of resin composites during both short- and long-term simulated aging situations.

Effect of Simulated Gastric Acid on the Interface Between Zirconia and Resin Cement

PURPOSE: To evaluate the effect of simulated gastric acid solution (SGAS) and resin cement composition on the shear bond strength (SBS) of zirconia-based materials with different levels of translucency to composite resin. MATERIALS AND METHODS: A total of 40 medium-opacity (MO; 3Y-TZP) and 40 medium-translucency (MT; 4Y-PSZ) zirconia slabs were distributed into four groups according to the composition of the resin luting system (MDP free or with MDP [primer + Panavia V5]) and storage method (distilled water or SGAS [5% hydrochloric acid]). Composite resin cylinders were cemented on the zirconia surface and stored for 91 hours. SBS, failure mode, and surface characterization analyses via scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were performed. SBS data were analyzed using three-way ANOVA and Tukey test, and failure mode was assessed using one-way ANOVA (P < .05). RESULTS: Storage media (P = .180), resin cement (P = .110), zirconia (P = .404), and their interactions did not affect SBS values. Bond strength ranged from 21.41 to 26.11 MPa. SEM images showed that SGAS modified the surface topography of zirconia and resin cement. The presence of chlorine and silicon (wt%) were higher after SGAS storage than after water storage in both cements used, while barium was higher only for the MDP cement. There was a prevalence of mixed failures for most of the groups. CONCLUSION: The SBS between both types of zirconia and resin cement was not affected by SGAS, although changes in zirconia topography were observed after SGAS exposure. The presence of MDP in the cement layer had no effect on the SBS challenged by SGAS.

A survey of amalgam use to guide dental education curriculums.

OBJECTIVES: To identify behavioral, preferential, and professional factors influencing the use of amalgam in private practices; and to compare the incidence of the placement of amalgam versus composite resin restorations in the province of Ontario and its pedagogical implications on dental curricula. METHODS: Participants responded anonymously to a 23-question online survey about their current use of dental amalgam and composite resins as well as their opinions regarding both dental materials. The explanatory variables were associated bivariately with the outcome variables, and the most significant predictors were identified using the multivariate analysis. RESULTS: Higher percentages of amalgam use were reported among clinicians who trained in Canada only (P = .009), who graduated before 1980 (p = <.001) and who work outside private practice (p = <.001). Familiarity with amalgam was higher among clinicians who are female (p = <.001), older (p = <.001), trained only in Canada (p = .017), who graduated prior to 2000 (p = <.001), and who work in locations with populations over 100,000 (p = .042). Familiarity with composite resin was higher among clinicians who graduated more recently (p = .002). A higher percentage of females (p = <.001), younger clinicians (p = <.001), recent graduates (p = <.001), and clinicians who work in private practice (p = .043) suggested that over 50% of dental student training time be allocated to amalgam. CONCLUSIONS: Decreased amalgam use was reported by later dental graduates and private practitioners; this may be impacted by familiarity with dental amalgam. As amalgam remains a safe and effective dental material, its removal may not be prudent. Dental educators play a crucial role in the future of amalgam opinion and use.

Bonding Efficacy of Universal Resin Adhesives to Zirconia Substrates: Systematic Review and Meta-Analysis.

PURPOSE: To provide an overview of the in-vitro bond strength of universal adhesives to zirconia and analyze whether these adhesives are a reliable alternative to conventional zirconia primers. MATERIALS AND METHODS: A systematic search was conducted in PubMed/Medline, Scopus, and ISI Web of Science databases up to August 2021. Investigations published in English, assessing resin-mediated bond to zirconia using universal adhesives compared to phosphate/silane-based primer or phosphate-based primer were included. After study selection and data extraction, risk of bias analysis was performed. Statistical analyses were performed using RevMan 5.4, with a random effects model, at a significance level of 0.05. RESULTS: In total, 23 studies were included for qualitative and quantitative analysis. Universal adhesives showed higher bond strengths than did phosphate-based primers (p < 0.00001) to aged zirconia without airborne alumina-particle abrasion. Similar results were observed when the zirconia surface was airborne-particle abraded at baseline and after dynamic aging (p < 0.0001). When universal adhesives and phosphate-silane based primers were compared, similar bond strengths (p ≥ 0.001) were observed after surface abrasion, regardless of storage condition. CONCLUSION: The results showed that universal adhesives generate higher bond strengths when compared to conventional zirconia primers.

Perception of COVID-19 pandemic restrictions on dental researchers.

BACKGROUND/OBJECTIVES: Historical evidence shows a gender-based disproportionate effect of pandemics across different populations. In 2020, the coronavirus disease 2019 (COVID-19) pandemic began spreading its devastating effects worldwide. The goal of the present study was to investigate the effect of the COVID-19 pandemic on research productivity, work-life arrangements, and mental health of dental professionals worldwide with focus on gender differences. METHODS: A 38-item survey, concerning demographics, career stage, employer support, family structure, mental health, and relationships, was distributed to 7692 active members of the International Association for Dental Research. Bivariate associations between independent variables and the primary outcome variable were tested using Spearman's correlation test. A logistic regression model was used to assess the simultaneous, independent associations between each variable and researcher productivity. RESULTS: A total of 722 responses were obtained, indicating a 9.4% response rate. Higher productivity was reported by male respondents (p = 0.021), and by those in senior career stages (p = 0.001). Institutional support was associated with higher productivity (p < 0.0001). Lower productivity was reported by younger researchers (p = 0.003). Remote work negatively affected productivity (p < 0.0001) and female respondents reported working more hours, regardless of work location (p = 0.004). Poor mental health was associated with low productivity (p < 0.0001). CONCLUSIONS: Our results showed that the COVID-19 pandemic significantly affected dental professionals' perceived productivity and mental health around the globe. Younger individuals and women were disproportionally affected, and institutional support had a significant influence to mitigate effects of the pandemic for dental researchers.

Surface and bulk properties of zirconia as a function of composition and aging.

Yttria-stabilized zirconia (Y-SZ) materials with different levels of translucency have been used for indirect dental restorations. Y-SZ composition and microstructure are modified to improve translucency, and it is not clear how these materials respond to aging. This study evaluated the effect of hydrothermal aging (HA) performed in an autoclave on the properties of four dental Y-SZ materials with different compositions. Sintered bar-shaped specimens (14 x 4 x 2 mm) were prepared from four different zirconia-based materials (n = 40): low translucency 3 mol % Y-SZ (3Y-LT; Ceramill ZI, Amann Girrbach); high translucency 4 mol % Y-SZ (4Y-HT; Ceramill Zolid); and two high translucency 5 mol % Y-SZ (5Y-HT - Lava Esthetic, 3M; 5Y-SHT - Ceramill Zolid FX). Fully sintered specimens were exposed to HA for different times (control - 0 h, 5 h, 10 h, or 15 h at 134 °C, 2 bar pressure) and characterized for surface roughness, flexural strength (three-point bending), hardness and elastic modulus (nanoindentation), surface wettability (sessile drop technique) and crystalline content (x-ray diffraction, XRD). Data was analyzed by two-way ANOVA and Tukey HSD (p < 0.05). Zirconia composition significantly affected roughness (p = 0.016). Zirconia*aging interaction affected flexural strength (p = 0.012), surface wettability (p < 0.001), and hardness (p = 0.002). Zirconia composition (p = 0.011) and aging (p = 0.001) affected elastic modulus, while the interaction effect was not significant (p = 0.94). HA affects zirconia-based materials in different degrees. For 3Y-LT and 4Y-HT, surface and bulk properties were affected by aging to a similar extent. However, surface and bulk properties may change during clinical use as a result of prolonged degradation of Y-SZ.