Fracture resistance and failure pattern of endodontically treated maxillary premolars restored with transfixed glass fiber post: an in vitro and finite element analysis.

The aims of the study were to determine the effect of different types of endodontic sealers and the presence of a horizontal glass fiber post (HGFP) on the fracture resistance and fracture pattern of mesio-occluso-distal (MOD) restored upper premolars and to analyze the stress distribution. Sixty extracted upper premolars received root canal treatment (RCT) and a MOD cavity preparation. All MOD cavities were restored with the same composite resin (CR). The 60 teeth were divided randomly into 6 groups (n = 10); Group1= AH Plus sealer; Group 2= TotalFill BC sealer; Group 3= BioRoot RCS sealer; Group 4= AH plus sealer + HGFP; Group 5= TotalFill BC sealer + HGFP; and, Group 6= Bio Root RCS sealer + HGFP. All specimens were thermocycled and subjected to cyclic loading. Next, the specimens were subjected to a static load using a universal testing machine. Data were analyzed using two-way ANOVA. Two micro-CTs of the same upper premolar, one without the HGFP and later one with HGFP inserted were made and used to create two finite element (FE) models. For the fracture resistance, two-way ANOVA revealed significant differences for the effect of HGFP (p = 0.029), but no differences for the effect of root canal sealer type (p = 0.561). The HGFP groups showed higher restorable fracture compared to groups without HGFP (p = 0.013). Finite element analysis showed that the inclusion of HGFP reduces stress concentration at the occlusal interface and cervical region. Therefore, it can be concluded that HGFP significantly increased the fracture resistance of endodontically treated upper premolars with MOD cavities and reduced the risk for non-restorable fractures. The FE analysis supports the mechanical test results.

Prospects of Using Gum Arabic Silver Nanoparticles in Toothpaste to Prevent Dental Caries.

There is growing interest in the use of green synthesized silver nanoparticles (AgNPs) to control and prevent dental diseases. The incorporation of green synthesized AgNPs into dentifrices to reduce pathogenic oral microbes is motivated by their presumed biocompatibility and broad-spectrum antimicrobial activity. In the present study, gum arabic AgNPs (GA-AgNPs) were formulated into a toothpaste (TP) using a commercial TP at a non-active concentration, to produce GA-AgNPs_TP. The TP was selected after evaluating the antimicrobial activity of four commercial TPs 1-4 on selected oral microbes using agar disc diffusion and microdilution assays. The less active TP-1 was then used in the formulation of GA-AgNPs_TP-1; thereafter, the antimicrobial activity of GA-AgNPs_0.4g was compared to GA-AgNPs_TP-1. The cytotoxicity of GA-AgNPs_0.4g and GA-AgNPs_TP-1 was also assessed on the buccal mucosa fibroblast (BMF) cells using the MTT assay. The study demonstrated that antimicrobial activity of GA-AgNPs_0.4g was retained after being combined with a sub-lethal or inactive concentration of TP-1. The non-selective antimicrobial activity and cytotoxicity of both GA-AgNPs_0.4g and GA-AgNPs_TP-1 was demonstrated to be time and concentration dependent. These activities were instant, reducing microbial and BMF cell growth in less than one hour of exposure. However, the use of dentifrice commonly takes 2 min and rinsed off thereafter, which could prevent damage to the oral mucosa. Although, GA-AgNPs_TP-1 has a good prospect as a TP or oral healthcare product, more studies are required to further improve the biocompatibility of this formulation.

The influence of horizontal glass fiber posts on fracture strength and fracture pattern of endodontically treated teeth: A systematic review and meta-analysis of in vitro studies.

PURPOSE: This systematic review and meta-analysis aimed to summarize available evidence regarding the effect of horizontal glass fiber posts (HGFPs) on fracture strength and fracture pattern of endodontically treated teeth (ETT) compared to controls without HGFP. The review protocol was registered on the OSF registries. METHODS: Literature searches were conducted in MEDLINE/PubMed, Scopus, Web of Science, Embase, Google Scholar, and ProQuest for all relevant studies published up to February 2022. All in vitro studies that assessed the influence of HGFPs on fracture strength and fracture pattern of ETT whether mesio-occluso-distal or mesio-occlusal or DO cavities were considered eligible. Review Manager (RevMan) was used for the meta-analysis. Subgroup and funnel plot analyses were also performed. Quality assessment was conducted by two independent reviewers. RESULTS: A total of 12 articles met the inclusion criteria, and 10 studies underwent quantitative evaluation. The pooled effect showed that fracture resistance of molar teeth restored with HGFP was significantly higher than teeth without HGFP (standardized mean difference [SMD]: 1.61, 95% confidence interval [CI]: 0.14, 3.09, p = 0.03), whereas marginally significant for premolars (SMD: 1.36, 95% CI: -0.00, 2.73, p = 0.05). Regarding fracture patterns, the presence of an HGFP significantly increased the occurrence of restorable fracture patterns for premolars (odds ratios [OR]: 4.15, 95% CI: 1.60, 10.82, p = 0.004) compared to controls, whereas the difference was not significant for molars (OR: 1.09, 95% CI: 0.43, 2.77, p = 0.85). Moderate risk of bias was identified in 9/12 studies; one study showed a high risk of bias and two studies showed a low risk of bias. CONCLUSIONS: Within the limitations of this study, there is evidence from in vitro studies that the use of HGFP increases the fracture resistance of the ETT when compared to teeth without HGFP and also reduces the occurrence of non-restorable fractures for premolars. However, well-conducted in vitro and prospective clinical studies are warranted to validate this finding.

Antimicrobial Effects of Gum Arabic-Silver Nanoparticles against Oral Pathogens.

Dental caries is considered one of the most prevalent oral diseases worldwide, with a high rate of morbidity among populations. It is a chronic infectious disease with a multifactorial etiology that leads to the destruction of the dental tissues. Due to their antimicrobial, anti-inflammatory, antifungal, and antioxidant properties; silver nanoparticles (AgNPs) are incorporated in dental products to help prevent infectious oral diseases. In this study, the antimicrobial effects of AgNPs synthesized using Gum Arabic extracts (GAE) were examined. The GA-AgNPs were synthesized and characterized using ultraviolet-visible (UV-Vis) spectrophotometer, dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The antimicrobial activity of the GA-AgNPs was evaluated on Streptococcus sanguinis (S. sanguinis), Streptococcus mutans (S. mutans), Lactobacillus acidophilus (L. acidophilus), and Candida albicans (C. albicans) using agar disc diffusion and microdilution assays. The antibiofilm of GA-AgNPs was evaluated on the surface of human tooth enamel that had been exposed to S. mutans with and without the GA-AgNPs using scanning electron microscopy (SEM). GA-AgNPs were spherical in shape with a particle size distribution between 4 and 26 nm. The GA-AgNPs exhibited antimicrobial activity against all the tested oral microbes, with GA-AgNPs_0.4g having higher antimicrobial activity. The GA-AgNPs_0.4g inhibited S. mutans adhesion and biofilm formation on the surface of the tooth enamel. Therefore, this study supports the prospective implementation of the plant extract-mediated AgNPs in dental healthcare.

Plant Extract-Synthesized Silver Nanoparticles for Application in Dental Therapy.

Oral diseases are the most common non-communicable diseases in the world, with dental caries and periodontitis causing major health and social problems. These diseases can progress to systematic diseases and cause disfigurement when left untreated. However, treatment of oral diseases is among the most expensive treatments and often focus on restoration of form and function. Caries prevention has traditionally relied on oral hygiene and diet control, among other preventive measures. In this paper, these measures are not disqualified but are brought into a new context through the use of nanotechnology-based materials to improve these conventional therapeutic and preventive measures. Among inorganic nanomaterials, silver nanoparticles (AgNPs) have shown promising outcomes in dental therapy, due to their unique physicochemical properties and enhanced anti-bacterial activities. As such, AgNPs may provide newer strategies for treatment and prevention of dental infections. However, numerous concerns around the chemical synthesis of nanomaterials, which are not limited to cost and use of toxic reducing agents, have been raised. This has inspired the green synthesis route, which uses natural products as reducing agents. The biogenic AgNPs were reported to be biocompatible and environmentally friendly when compared to the chemically-synthesized AgNPs. As such, plant-synthesized AgNPs can be used as antimicrobial, antifouling, and remineralizing agents for management and treatment of dental infections and diseases.

Patient-reported outcome measures of digitally versus conventionally constructed removable dentures: a systematic review protocol.

OBJECTIVE: This review will evaluate patient-reported outcome measures of treatment with digitally fabricated versus conventionally manufactured removable dental prostheses in partially or completely edentate adults. INTRODUCTION: Compared with conventionally manufactured dental prostheses, digitally fabricated prostheses may simplify and reduce the number of clinical steps and minimize errors in the production of prostheses without compromising occlusal accuracy and fit. This may, in turn, improve patient satisfaction, ability to speak, esthetics, stability, and oral health status. Determining evidence of patient-reported outcomes will assist the dental practitioner when communicating patient expectations. INCLUSION CRITERIA: This review will consider experimental and quasi-experimental study designs, including randomized and non-randomized controlled trials, comparative clinical studies, prospective or retrospective trials, longitudinal clinical studies, clinical reports, and technique articles. The review will include patient-reported outcome measures from fully or partially edentulous adult participants who received either conventionally or digitally fabricated dental prostheses. METHODS: The following databases will be searched for scientific, peer-reviewed literature: Academic Search Complete, CINAHL, Dentistry and Oral Sciences (all via EBSCO), MEDLINE (PubMed), ScienceDirect, and Cochrane Central Register of Controlled Trials. The search strategy will include terms relevant to the intervention, which will be adapted for each bibliographic database, in combination with database-specific filters, where available. The language restriction will be English and Dutch. All included studies will be critically appraised and data will be extracted for synthesis. If possible, a meta-analysis will be conducted. The Grading of Recommendations, Assessment, Development and Evaluation approach will be followed to evaluate the certainty of evidence. SYSTEMATIC REVIEW REGISTRATION NUMBER: PROSPERO CRD42018094357.

Broad Spectrum Anti-Bacterial Activity and Non-Selective Toxicity of Gum Arabic Silver Nanoparticles.

Silver nanoparticles (AgNPs) are the most commercialized nanomaterials and presumed to be biocompatible based on the biological effects of the bulk material. However, their physico-chemical properties differ significantly to the bulk materials and are associated with unique biological properties. The study investigated the antimicrobial and cytotoxicity effects of AgNPs synthesized using gum arabic (GA), sodium borohydride (NaBH4), and their combination as reducing agents. The AgNPs were characterized using ultraviolet-visible spectrophotometry (UV-Vis), dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The anti-bacterial activity was assessed using agar well diffusion and microdilution assays, and the cytotoxicity effects on Caco-2, HT-29 and KMST-6 cells using MTT assay. The GA-synthesized AgNPs (GA-AgNPs) demonstrated higher bactericidal activity against all bacteria, and non-selective cytotoxicity towards normal and cancer cells. AgNPs reduced by NaBH4 (C-AgNPs) and the combination of GA and NaBH4 (GAC-AgNPs) had insignificant anti-bacterial activity and cytotoxicity at ≥50 µg/mL. The study showed that despite the notion that AgNPs are safe and biocompatible, their toxicity cannot be overruled and that their toxicity can be channeled by using biocompatible polymers, thereby providing a therapeutic window at concentrations that are least harmful to mammalian cells but toxic to bacteria.

Career Development of Academic Staff in Faculties of Dentistry by Means of Mentorship Programs: Protocol for a Scoping Review.

BACKGROUND: Globally, the demands on dental educators continue to diversify and expand. Due to their importance and value, mentoring programs have been acknowledged as a means of recruiting, developing, and retaining academics in dental education. OBJECTIVE: This protocol is for a scoping review that aims to identify the goals of mentoring programs for academic staff in dental faculties and determine how these programs were structured, delivered, and evaluated. METHODS: The review will be performed in accordance with the Joanna Briggs Institute's methodology for scoping reviews, which covers both qualitative and quantitative scientific literature as well as grey literature written in English and published between 2000 and 2020. The databases will include PubMed, Ovid, the Educational Resources Information Center database, Science Direct, Scopus, Google Scholar, Trove, Web of Science, Openthesis.org, and the website of the American Dental Education Association. A manual search will also be conducted by using the reference lists of included studies to identify additional articles. Working independently, the authors will participate iteratively in literature screening, paper selection, and data extraction. Disagreements between the reviewers will be resolved by discussion until a consensus is reached or after consultation with the research team. Key information that is relevant to the review questions will be extracted from the selected articles and imported into a Microsoft Excel file. The PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews) will be used to guide the reporting of this protocol. RESULTS: The search for appropriate literature has commenced, and we aim to present the results before the end of the 2021 academic year. CONCLUSIONS: The development of formal mentorship programs for academics in dental education will enhance the retention of academic staff. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/27239.

A Randomized Crossover Trial Comparing Patient Preference for Mandibular Complete Dentures Made with Two Different Techniques: A Short-Term Follow-Up.

PURPOSE: The objective of this trial was to compare short-term patient preference for two mandibular complete denture (CD) fabrication techniques: neutral zone (NZ) and conventional (CV). MATERIALS AND METHODS: A prospective, within-subject, randomized crossover trial was performed on a sample of 37 edentulous patients with complete denture experience. Two new sets of CDs were made for each patient, one set with a CV and one with a NZ mandibular denture. After consecutively wearing each set for at least 2 months after the last adjustment visit, patients indicated their preference (CV, NZ, or none). Associations and comparisons were made using the generalized linear model (GLM) and Fisher exact test between preference and sex, age, period of edentulousness, tissue quality, prosthodontic diagnostic index (PDI), and oral health-related quality of life (OHRQoL) differences of the two interventions assessed using the 20-item oral health impact profile (OHIP-20). Significance was determined at P = .05. RESULTS: A total of 15 (40%) patients preferred NZ, 8 (22%) preferred CV dentures, and 14 (38%) had no preference. Although more women preferred NZ over CV dentures (50% versus 27%), difference in preference according to sex was not significant (P = .359). Neither was difference in preference and PDI scores significant (P = .603). Preference could not be strongly associated to period of edentulousness, age, tissue scores, and differences in OHIP-20 scores (P > .05), except for OHIP-20 scores and NZ preference (P < .001). Better fit, comfort, and eating were reasons patients preferred a type of denture. These reasons were identified for both types of denture. Appearance and speech were not identified as reasons for a particular preference. CONCLUSION: Based on preference expressed by patients, there is no difference between NZ and CV mandibular dentures. Denture preference could not be related to patient variables over the study's time frame.

Analyzing Complete Denture Occlusal Contacts: Accuracy and Reliability.

The aim of this study was to investigate the accuracy and reliability of interpreting occlusal markings made by articulating paper on complete dentures intraorally. Clinical teachers at a training hospital interpreted occlusal markings intended for adjustment. Their scores were compared to a control score to determine accuracy. For reliability determination, the observations were repeated. Only between 20% and 30% of observations were found to be both accurate and reliable. Unless the procedure can be standardized, this technique shouldn't be considered appropriate prosthodontics protocol for balancing the occlusion of complete dentures.

Fracture resistance of endodontically treated premolars with fibre-reinforced composite restorations.

This study investigated the fracture resistance and failure mode of endodontically treated premolars restored with a glass fibre-reinforced composite resin. Endodontically treated maxillary premolars were divided in 4 groups: group O: occlusal access opening restored with direct composite; group O+: as group O but with fibre reinforcement; group MOD: occlusal access opening and mesio-distal (MOD) cavity restored with direct composite; group MOD+: as group MOD but with additional fibre reinforcement. Pairwise comparisons of the fracture force among all groups was performed (95% confidence level). Fractures were classified in 4 groups depending on the type of fracture. Group O was the strongest (452.7N) and group MOD the weakest (292.4N). Fracture resistance was significantly different among all groups, except between groups O+ and MOD+. The majority of the unreinforced teeth displayed unfavourable fractures, while the reinforced teeth displayed more favourable fractures. The incorporation of glass fibre weakened endodontically treated but otherwise intact premolars; premolars with MOD restorations were stronger if reinforced with fibres. Fibre reinforcement led to more favourable fractures.

Temperature changes along a dental implant.

PURPOSE: The aims of this in vitro study were to analyze temperature changes along the surface of a dental implant and to establish the abutment temperature that could cause the critical 47°C/1 min threshold at the implant level. MATERIALS AND METHODS: Eight thermocouples were attached at 1-mm intervals to an abutment/implant configuration. The model consisted of two compartments in a thermostatically controlled environment. The upper compartment represented the oral cavity with the abutment, which was exposed to 20 mL of hot water. The temperature at each thermocouple was logged over a period of 10 minutes. The Spearman rank correlation test and logistic regression model were used for the statistical analysis of the time/temperature databases and the estimation of the "effective dose 50" (ED50) for the abutment (95% confidence interval). RESULTS: For 53 test series, the abutment temperature ranged from 52.80°C to 71.72°C. There was a positive correlation between the maximum temperature at the implant level and the temperature of the abutment. The 47°C/1 min threshold was reached 31 times at the most cervical implant level and decreased in frequency farther away from the heat source (14, 6, 3, 1, and 1 times, respectively). The ED50 was estimated at 62.3°C. This means that for an abutment temperature of 62.3°C, there was a 50% chance that 47°C would be reached at the implant level for 1 minute. CONCLUSION: This in vitro study supports the hypothesis that abutment temperature is transmitted to an implant. Although results of in vitro studies should be interpreted with caution, clinicians should be aware of temperature changes along implants and the potential risks associated with them.

Stress patterns around distal angled implants in the all-on-four concept configuration.

PURPOSE: The All-on-Four concept advocates immediate loading and the placement of distal implants at an angle. The purpose of this study was to do a qualitative descriptive analysis of stress patterns around the distal angled implant of the All-on-Four concept. MATERIALS AND METHODS: Four photoelastic acrylic resin models, each with four implants simulating the All-on-Four configuration, were prepared. The two central implants were placed vertically and parallel in each model, and the distal implant on each side was placed at an increasing angle (0, 15, 30, and 45 degrees) in each model. The four implants were splinted by means of a cast metal bar. The photoelastic models were placed between two parallel anvils. Pairs of abutments were systematically subjected to a load by suspending 5-, 10-, and 15-kg weights from one of the anvils. Photoelastic analysis was accomplished using a circular polariscope. The fringe patterns produced in the photoelastic resin for each implant and load were photographed with a digital camera. Fringe concentrations and the highest fringe order were recorded and described for the apical, central, and coronal regions of the distal angled implant for each load scenario. RESULTS: For the implants placed at 15- and 30-degree angles, little difference in stress patterns was observed between the central straight implant and the distal angled implant. For every load scenario and for all angulations, the lowest fringe order was recorded at the central region of the implant. The highest fringe order for the apical region was always higher than the highest fringe order for the coronal region of the implant. Markedly increased isochromatic fringe concentrations were observed in model 4, which had the distal implants placed at a 45-degree angle. CONCLUSION: Peri-implant bone surrounding the 45-degree-angled distal abutment may be more prone to occlusal overload than bone surrounding implants with lesser tilts.

The effect of different reinforcements on the fracture toughness of materials for interim restorations.

STATEMENT OF PROBLEM: Fracture of an interim fixed partial denture (FPD) may jeopardize the success of the interim prosthodontic treatment phase and cause patient discomfort. PURPOSE: The purpose of this study was to compare the fracture toughness of a polymethyl methacrylate (PMMA) resin and a bis-acryl composite (BAC) resin reinforced with stainless steel wire, glass fiber, and polyethylene fiber. MATERIAL AND METHODS: Four groups (n=13) of each of the 2 materials were prepared for the single-edge notch 3-point-bending test. Three groups had the different reinforcements, and the group without reinforcement served as the control. Using a universal testing machine, peak load to fracture was recorded and fracture toughness (K(IC)) was calculated in MNm(-1.5). Median K(IC) values were compared by means of nonparametric ANOVA (Kruskal-Wallis test, alpha=.05). RESULTS: For the controls, the fracture toughness for PMMA resin (K(IC)=27.9) was significantly lower (P<.01) than for BAC resin (K(IC)=31.2). Glass fibers and stainless steel wire reinforcements produced significantly higher fracture toughness for both PMMA (K(IC)=34.4, P<.01, and K(IC)=39.0, P<.001, respectively) and BAC resin (K(IC)=42.3, P<.001, and K(IC)=44.0, P<.001, respectively), but the polyethylene fibers did not (K(IC)=25.8, P>.10, for PMMA resin and K(IC)=33.1, P>.10, for BAC resin). There was no significant difference between the fracture toughness of the wire and glass fiber reinforcements for both interim materials (P>.10 in both instances). CONCLUSIONS: Of the 3 reinforcement methods evaluated, wire and glass fiber reinforced the PMMA and BAC resin materials best.