Mechanical Behaviour of Novel Nanohybrid Resin Composite Using Two Light Cure Systems.

INTRODUCTION: Zein-incorporated magnesium oxide nanoparticles (zMgO NPs) were found to be effective against the bacteria S. mutans, S. aureus, E. faecalis and C. albicans, and can impart this antimicrobial effect on the resin composite it is integrated with. However, the effect of different light curing systems on the mechanical properties of this novel biomaterial has yet to be investigated. The objective of this study was to assess the effect of light-emitting diode (LED) and quarts-tungsten halogen (QTH) light curing systems on the compressive strength, flexural strength, and microhardness of bulk-fill resin composite modified with zMgO NPs. METHODOLOGY: A Teflon mold was used to fabricate 180 bulk-fill composite samples with concentrations of zMgO NPs at 0%, 0.3% and 0.5% (n = 60). Samples of each group were allocated to light curing by LED or QTH, after which 10 samples of each group were allotted to a mechanical test. Characterization of the specimens was performed by X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. Two-way ANOVA and Tukey's post-hoc test was conducted at P = .05 to determine significance. RESULTS: The characterization revealed a uniform distribution of nanoparticles in the matrix and the formation of a new hybrid composite that maintained its properties. The compressive strength of the 0.3% zMgO composite for the QTH group significantly increased, while the remaining groups underwent no significant change. There was no significant difference among the groups for the flexural strength and microhardness tests. CONCLUSION: The modified composites' compressive strength, flexural strength, and microhardness improved or remained consistent. Long-term clinical studies can further substantiate the enhanced resin composite. CLINICAL RELEVANCE: The modified composite will exhibit similar or improved mechanical properties whether an LED or QTH light cure device is used. The addition of an antimicrobial effect to bulk-fill resin composite will aid in the prevention of secondary caries.

Maximizing Dental Composite Performance: Strength and Hardness Enhanced by Innovative Polymer-Coated MgO Nanoparticles.

INTRODUCTION: Zein-incorporated magnesium oxide nanoparticles (zMgO NPs) can influence the mechanical properties of dental materials. However, the effect of this addition on the mechanical properties of resin composite has yet to be investigated. The objective of this study was to add various concentrations of zMgO NPs to conventional, flowable, and bulk-fill composite and assess the effect on the compressive strength, flexural strength, and microhardness. METHODOLOGY: 150 samples each of conventional composite, flowable composite, and bulk-fill composite (n=450) were enhanced with concentrations of zMgO NPs at 0%, 0.3%, 0.5%, 1%, and 2% (n=30). 10 samples of each group were randomly allotted to the compressive strength, flexural strength, or hardness test. Characterization of the specimens was performed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Two-way ANOVA test was used to compare between groups, and one-way ANOVA followed by Tukey's test was done at p=0.05 to determine significance. RESULTS: Characterization yielded a uniform distribution of nanoparticles in the matrix and the formation of a new hybrid composite that maintained its properties. Composite of all types enhanced with 0.3% and 0.5% zMgO NPs demonstrated a statistically significant increase in compressive strength, flexural strength, and hardness when compared to the control (p<0.05). The bulk-fill composite with zMgO NPs concentrations of all groups demonstrated a statistically significant increase (p<0.05) in hardness when compared to the control. CONCLUSION: The modified composites' compressive strength, flexural strength, and hardness improved or remained consistent. CLINICAL SIGNIFICANCE: An improved dental resin composite will enhance the quality of care and patient experience. The augmented strength and hardness of resin composite is desirable in prolonging the durability of the restoration.

Noninvasive assessment of novel nanohybrid resin cement adaptation using cross-polarization optical coherence tomography.

OBJECTIVES: Zein-coated magnesium oxide nanoparticles (zMgO NPs) can potentially improve cement adaptation to the tooth-restoration interface, which would aid in minimizing marginal leakage and secondary caries. The aim of this study was to assess the effect of incorporating zMgO NPs on the adaptation of self-adhesive resin cement using cross-polarization optical coherence tomography (CP-OCT) and scanning electron microscopy (SEM). METHODS: Resin inlays were fabricated to be cemented in Class-I cavities of extracted human molars. All specimens were randomly divided into five groups (n = 10), and the resin inlays were cemented using self-adhesive resin cement with various concentrations of zMgO NPs (0% [control], 0.3%, 0.5%, 1%, 2%). Characterization was done by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and SEM. The specimens were examined for interfacial adaptation under CP-OCT. Floor and wall adaptation measurements were analyzed by software on 20 B-scans, and samples were sectioned for interfacial measurement by SEM. RESULTS: Results for CP-OCT and SEM showed a statistically significant increase of adaptation in the floor and wall of resin cement filled with zMgO NPs compared to the control. The samples enhanced with 0.3% and 0.5% showed a statistically significantly better adaptation in floor and wall in CP-OCT and SEM. However, there was no significant difference between the 1%, 2%, and control groups for CP-OCT and SEM analysis. SIGNIFICANCE: The incorporation of zMgO NPs in self-adhesive resin cement can enhance the cement's properties by significantly improving its wall and floor adaptation.

Molluscicidal activity of sodium hypochlorite against Biomphlaria alexandrina snails: Immunological and hepato-endocrine alterations with in silico docking study.

Schistosomiasis is a tropical disease that widely neglected. Schistosoma mansoni reproduce asexually within the freshwater snail, Biomphlaria alexandrina. Sodium hypochlorite (NaOCl) is a widely used disinfectant, so its effect against gainst B. alexandrina snails was evaluated. The present results showed that NaOCl has a molluscicidal activity against adult B. alexandrina snails at LC50 1.25 ppm. Hemocytes displayed varied morphological forms after being exposed to the LC10 and LC25 concentrations of NaOCl in B. alexandrina snails, and the phagocytic index of B. alexandrina snail's hemocytes significantly increased. The phagocytic potency of exposed hemocytes to charcoal showed ruptured plasma membrane, engulfed particles, vacuolation in the cytoplasm and degeneration of nuclei. When B. alexandrina snails were treated with sublethal concentrations of NaOCl, transaminases (AST & ALT), alkaline and acid phosphatase activities were significantly increased. In contrast, the total protein, albumin concentrations, Testosterone (T) and 17ß Estradiol (E) showed a significant decrease (p ≤ 0.05) as compared to the control groups. The molecular docking interaction showed high efficiency for the ligand, NaOCl against the receptor binding sites of the acid phosphatase, alanine aminotransferase, estrogen and testosterone. The present results showed that NaOCl could be used as an effective molluscicide against B. alexandrina snails but more attention should be paid to investigate the side effects on the non-target organisms living in the freshwater environment.

Influence of inorganic nanoparticles on dental materials' mechanical properties. A narrative review.

Inorganic nanoparticles have been widely incorporated in conventional dental materials to help in improving their properties. The literature has shown that incorporating nanoparticles in dental materials in different specialties could have a positive effect on reinforcing the mechanical properties of those materials; however, there was no consensus on the effectiveness of using nanoparticles in enhancing the mechanical properties of dental materials, due to the variety of the properties of nanoparticles itself and their effect on the mechanical properties. This article attempted to analytically review all the studies that assessed the effect of different types of inorganic nanoparticles on the most commonly used dental materials in dental specialties such as polymethyl methacrylate, glass ionomer cement, resin composite, resin adhesive, orthodontic adhesive, and endodontic sealer. The results had shown that those inorganic nanoparticles demonstrated positive potential in improving those mechanical properties in most of the dental materials studied. That potential was attributed to the ultra-small sizes and unique physical and chemical qualities that those inorganic nanoparticles possess, together with the significant surface area to volume ratio. It was concluded from this comprehensive analysis that while a definitive recommendation cannot be provided due to the variety of nanoparticle types, shapes, and incorporated dental material, the consensus suggests using nanoparticles in low concentrations less than 1% by weight along with a silane coupling agent to minimize agglomeration issues and benefit from their properties.

Cytotoxic effects of dose dependent inorganic magnesium oxide nanoparticles on the reproductive organs of rats.

INTRODUCTION: Magnesium oxide nanoparticles (MgO NPs) have a variety of applications that have contributed to their elevated popularity, however, the safety and toxic effects on humans are also of concern with these increased applications. There is insufficient data regarding the effect of MgO NPs on reproductive organs, which are crucial aspects to the body's vital physiological functions. The present study was undertaken in male and female rats to assess the reproductive toxicological potential of two doses (low versus high) of MgO NPs on testicular and ovarian tissues. The toxicity was evaluated using histological, hormonal, and oxidative parameters. MATERIAL AND METHODS: In this work, magnesium oxide nanoparticles (MgO NPs) were synthesized by the sol-gel route and were characterized by X ray diffraction analysis (XRD) and Fourier transform infra-red spectroscopy (FTIR). Forty-eight adult Wister albino rats were used in this experiment which were divided into groups of male and female, and then further into control, low dose MgO NPs, and high dose MgO NPs. The low dose used was 131.5 mg/kg b.w. (1/10 LD50) while the high dose used was 263 mg/kg b.w. (1/5 LD50). All doses were given orally by gastric tube. After 4 weeks, blood samples were collected to investigate the level of sex hormones and both ovarian and testicular tissues were examined for variable oxidative parameters and histopathological changes by light microscopy. RESULTS: The obtained findings showed that high dose of MgO NPs produced considerable changes in sex hormones and stress parameters in both male and female rats in comparison to the low dose and control groups. Histomorphometric analysis demonstrated the presence of histopathological alterations in the testicular and ovarian tissues. CONCLUSION: The results of this study showed dose-dependent adverse effects of MgO NPs on the testis and ovary both functionally and histopathologically as compared to the control rats.

Evaluation of the time-dependent osteogenic activity of glycerol incorporated magnesium oxide nanoparticles in induced calvarial defects.

Introduction: Magnesium-based biomaterials have been explored for their potential as bone healing materials, as a result of their outstanding biodegradability and biocompatibility. These characteristics make magnesium oxide nanoparticles (MgO NPs) a promising material for treating bone disorders. The purpose of this investigation is to assess the osteogenic activity of newly-developed locally administered glycerol-incorporated MgO NPs (GIMgO NPs) in rabbits' calvarial defects. Materials and methods: Characterization of GIMgO was done by X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Bilateral calvarial defects were created in eighteen New Zealand Rabbits, of which they were divided into 3 groups with time points corresponding to 2, 4, and 6 weeks postoperatively (n = 6). One defect was implanted with absorbable gel foam impregnated with GIMgO NPs while the other was implanted with gel foam soaked with glycerol (the control). The defects were assessed using histological, Micro-Computed Tomography (Micro-CT), and histometric evaluation. Results: The characterization of the GIMgO nanogel revealed the presence of MgO NPs and glycerol as well as the formation of the crystalline phase of the MgO NPs within the nanogel sample. The histological and micro-CT analysis showed time-dependent improvement of healing activity in the calvarial defects implanted with GIMgO NPs when compared to the control. Furthermore, the histometric analysis demonstrated a marked increase in the total area of new bone, connective tissue, new bone area and volume in the GIMgO NPs implanted site. Statistically, the amount of new bone formation was more significant at 6 weeks than at 2 and 4 weeks postoperatively in the calvarial defects implanted with GIMgO NPs as compared to the control. Conclusion: The locally applied GIMgO NPs demonstrated efficacy in promoting bone formation, with more significant effects observed over an extended period. These findings suggest its suitability for clinical use as a therapeutic alternative to enhance bone healing.

Effect of non-rigid connector on the stress distribution of tooth-implant supported fixed prostheses using different implant length and diameter: A comparative 3D finite element study.

PURPOSE: To investigate the significance of the connector type on stress dissemination within the tooth-implant-supported fixed dental prostheses in the mandibular posterior region with different combinations of implant diameter and length by means of finite element analysis (FEA). MATERIALS AND METHODS: Six models of different designs for tooth-implant fixed dental prosthesis (FDPs) were simulated and divided into two main groups. Implant lengths were 10, 11.5, and 13 mm while implant diameters were 3.7, 4.7, and 5.7 mm. The main difference between the groups was the connector type. Models were evaluated using 3D FEA (Solidworks Premium 2018 × 64 Edition). Group A tooth-implant FDPs (5.7 mm × 10 mm) had a mesial and distal rigid connector while group B tooth-implant FDPs (3.7 mm × 10 mm, 3.7 mm × 11.5 mm, 3.7 mm × 13 mm, 4.7 mm × 10 mm and 5.7 mm × 10 mm) had a mesial non-rigid connector in their design between the pontic and the tooth. Models were analyzed to determine the magnitude of von Misses Stresses at six specific zones (fixed dental prosthesis, bone around distal implant, bone around tooth, cementum, periodontal ligament, implant) under vertical occlusal loading of 100 N after meshing and assigning the material properties. RESULTS: Stress values around the supporting bone were significantly higher in Group B (tooth-implant FDP with non-rigid connection) when compared to Group A (tooth-implant FDP with rigid connection). Also, the stresses measured at the FDP level showed that the rigid connection group (5.7 mm × 10 mm) exhibited 26% lower stress values when compared to the non-rigid group (5.7 mm × 10 mm). CONCLUSIONS: Implant-tooth FDPs with rigid connector design using the combination of implant diameter and length (5.7 mm × 10 mm) demonstrated a better design modality thus predicting a higher success rate and more longevity than using the non-rigid connection option.

The Effect of Implant Length and Diameter on Stress Distribution of Tooth-Implant and Implant Supported Fixed Prostheses: An In Vitro Finite Element Analysis Study.

The aim of this study is to evaluate the effectiveness of the implant diameter and length on force dissemination of tooth-implant and implant retained fixed restorations. A finite analysis model was used via a 3D simulation of a unilateral mandibular Kennedy Class I arch. Through thresholding the resultant assembly, a region of interest was selected from the computed tomography (CT) scan. Details of the diameter (D) and length (L) of implant were introduced. Ds used were 3.7, 4.7, and 5.7, while Ls used were 10, 11.5, and 13. The constant was the use of rigid connectors in both designs (implant-implant and implant-tooth fixed partial dentures [FPDs]) and the mesial implant (D 3.7 and L 11.5). Stress in cancellous bone around mesial abutment, which is the second premolar in tooth-implant FPD and mesial implant in the implant-implant FPD, revealed that the stress was significantly lower in tooth-implant FPD when compared with implant-implant FPD (21.1 ± 0.00 vs 46.1 ± 0.00, P < .001). Stress distribution in the bone around any implant depends on several factors such as diameter, length, and tooth-implant vs implant-implant support. The implant diameter was more significant for improved stress distribution than implant length. A moderate increase in the length of the implant consequently reduced stress.

Noninvasive Adaptation Appraisal of Antimicrobial Nano-Filled Composite.

OBJECTIVE: The aim of this research was to assess the effect of incorporating zein-coated magnesium oxide (zMgO) nanofillers to resin-based composite on the internal adaptation of the restorations using cross-polarisation optical coherence tomography (CP-OCT). METHODS: Thirty noncarious human molar teeth were used. Class V cavities (3 × 5 mm) were prepared on the buccal and lingual surfaces of each tooth. Clearfil SE Bond 2 was applied to all the cavities and then the teeth were divided into 3 groups (n = 10) as follows: group 1-restored with N-Flow composite; group 2 and group 3-restored with N-Flow composite mixed with different zMgO nanoparticle concentrations (0.3% and 0.5% by weight, respectively) and then light cured using an LED curing device. Specimens were examined for interfacial adaptation examination under CP-OCT. Characterisation of the dental composite incorporating zMgO was done by Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Results were analysed with Kruskall-Wallis test followed by Mann-Whitney U test, at a significance level of P < .05. RESULTS: XRD spectra exhibited the sharp peaks of zMgO in the composite enhanced with zMgO nanoparticles. FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the composite and FTIR illustrated no change in the spectra. The gap percentage along the cavity floor was significantly lower in groups 2 and 3 in comparison to group 1 (P < .05). Also there was a significant difference in gap percentages between groups 2 and 3 (P < .05), with group 3 showing the lowest gap percentage. CONCLUSIONS: The incorporation of 0.3% and 0.5% zMgO nanoparticles in flowable composite assists in improving the internal adaptation of the composite to the tooth surface.

Appraisal of empathy among dental interns and postgraduate students at King Abdulaziz University: A cross-sectional study.

PURPOSE/OBJECTIVES: Empathetic communication of dentists with their patients is a primary characteristic of their health care. This study aims to evaluate dental students' empathy levels during the transitional period of internship and postgraduate studies of different specialties at one of the oldest dental schools in Saudi Arabia and explore how this empathy was affected by gender, age, and study duration. METHODS: In this study, the self-reported empathy level among the participants was assessed using the Jefferson scale of empathy-student version (JSE-HPS). This survey includes a 20-question Likert scale formulated to measure clinical empathy in health care professionals. The JSE-HPS was distributed to all registered dental interns and postgraduate students during the academic year 2019-20 in King Abdulaziz University Faculty of Dentistry (KAUFD), Jeddah, Saudi Arabia. RESULTS: Mean total score of empathy of the participants was (101.07 ± 14.8) with a response rate of 89%. A statistically significant higher empathy score appeared among dental postgraduate students in general (p = 0.04) and specifically among the females (p = 0.04) and those with postgraduate programs for more than four years, (p = 0.02). Dental postgraduate students scored significantly higher in the parameters of standing in patients' shoes (p = 0.02). CONCLUSION: Gender, academic level, and duration of postgraduates' studies influenced empathy more than the age of the dental graduates in KAUFD. Our recommendation is to integrate empathy into the dental curriculum emphasizing interactive communication skills and early patient contact.

Antimicrobial properties of dental cements modified with zein-coated magnesium oxide nanoparticles.

The aim of this study was to test the antimicrobial properties of dental cements modified with magnesium oxide (MgO) nanoparticles. Zein-modified MgO nanoparticles (zMgO) in concentrations (0.0, 0.3, 0.5, and 1.0%) were mixed with dental cements (Fuji II, Rely X Temp E, Ionoglass Cem, Es Temp NE, and System P link). Eight discs were fabricated from each zMgO-cement pair for a total of 32 specimens for each cement. Characterization of the dental cements incorporating zMgO was done by X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The antimicrobial properties of the mixtures were tested using direct contact and agar diffusion assays against Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, and Candida albicans. Data was analyzed using two-way analysis of variance and LSD post hoc test at 0.05 significance level. XRD spectra showed sharp peaks of zMgO indicating its high crystalline nature, while the amorphous dental cements with zMgO had broad peaks. FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the cement. There were significant inhibition zone values associated with all concentrations of zMgO-cement mixtures tested compared to controls (p < 0.001) with a dose-response recorded only with Fuji II. Optical density values were significantly lower in zMgO groups compared to controls for all microorganisms. The effect was most prominent with Rely X against C. albicans and S. aureus. Dental cements containing zMgO showed significant antimicrobial properties that were dependent on the specific initial cement substrate.

Assessment of the dose-dependent biochemical and cytotoxicity of zein-coated MgO nanowires in male and female albino rats.

Introduction: Recently, zein-coated MgO nanowires were synthesized, which could be promising as an effective antimicrobial compounds that can be combined in the preparation of a diversity of new dental formulations. However, there is a deficiency of information concerning their toxicological profile regarding the human health.Objective: This in vivo study aimed to explore the hepato- and nephrotoxicity of low versus high doses of zein-coated MgO nanowires in rats.Materials and Methods: A 21-day recurrent dose toxicity research was carried out. Wistar rats were divided into 2 main groups, males and females (n = 18). Each group was further subdivided into 3 subgroups: control, MgO-zein nanowires low dose, MgO-zein nanowires high dose. The low dose used was 100 mg/kg while the high dose used was 200 mg/kg.Results: The results showed that MgO-zein nanowires at both doses did not affect the electrolytes levels compared to the control levels. Also, they did not produce any significant alteration in liver function markers in both rats' genders. MgO-zein nanowires at both doses did not produce any effective alteration in serum creatinine in treated rats of both genders. Moreover, very minimal histological alterations were observed in both doses of MgO-zein nanowires in liver and kidney of both genders.Conclusion: Based on the observed safety of zein-coated MgO nanowires, it can be utilized as an effective antimicrobial compound that can be combined in the preparation of a diversity of new dental formulations.KEY MESSAGESMgO NPs are globally used in multiple fields including the therapeutic field.Zein has wide pharmaceutical applications especially coating the tablet over sugar.There are no cytotoxic studies that investigate MgO-zein nanowires safety until now.

In vitro Investigation of the Antimicrobial Activity of Mouth Washes Incorporating Zein-Coated Magnesium Oxide Nanoparticles.

PURPOSE: This in vitro study was undertaken to investigate the antimicrobial effect of distinctive oral mouth washes after the addition of zein-coated (Magnesium oxide) MgO nanoparticles on exemplary of some oral microorganisms. MATERIALS AND METHODS: Three hundred and twelve samples were used in this study. A set of five concentrations of MgO nanoparticles with zein and without zein-coating were incorporated into three oral mouth washes: Listerine zero, Listerine total control and Oral B in the mass percentages of 0.3%, 0.5%, 1%, 2%, 5% and 10%, in addition to controls with no MgO nanoparticles. The antimicrobial effect of three mouth washes with variable concentrations of MgO was tested against the following organisms: Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis and Candida albicans using the disc diffusion test (DDT) and direct contact test (DCT). Data were analyzed using one-way ANOVA statistical test. RESULTS: The tested mouthwashes with zein-coated MgO nanoparticles showed significant differences of antimicrobial activity on S. mutans, S. aureus, E. faecalis, and C. albicans in the disc diffusion test. While in the DCT, all tested mouthwashes with MgO nanoparticles with and without zein coating showed antimicrobial activity on all tested microorganisms. CONCLUSION: Zein-coated MgO nanoparticles may be considered as a potential antimicrobial agent when added to oral mouthwashes. Future analysis, including in vivo studies, is required in order to incorporate zein/MgO nanoparticles into oral mouthwashes that may improve its antibacterial property.

A Cross-Sectional Study of Empathy Among Dental Students at King Abdulaziz University.

Empathy is the fundamental substructure of moral behavior. Skillful clinicians may not necessarily be successful dentists if they do not have sufficient empathy. The aim of this study was to assess the level of empathy among dental students at King Abdulaziz University with an emphasis on the effect of gender and study level. A cross-sectional study was carried out among third- to sixth-year dental students of King Abdulaziz University in Jeddah, Saudi Arabia. A validated, self-administered Jefferson Scale of Empathy-Health Care Provider Student Version was distributed in academic year 2016-17 to all 380 students in the third to sixth years. A total of 300 students responded, for a response rate of 78.9%. The results showed that the students' mean empathy score was 84.84±11.28 on a range from 20 to 140. The fifth- and sixth-year students had higher scores than the third- and fourth-year students although the differences were not statistically significant. The mean empathy score of women students was significantly higher (p<0.001) than that of men students, and the women demonstrated significantly better perspective-taking (p<0.001) than the men. This study found that the students were empathetic and had a sense of moral obligation although their mean empathy score was not as high as expected. Integrating empathic, ethical, and professional elements into the dental curriculum is needed.

Stress Analysis for Different Designs of Implant-borne and Tooth-implant Fixed Partial Dentures in Mandibular Posterior Region.

AIM: The utilization of fixed partial dentures (FPD) ceramic frameworks for replacing the missing posterior teeth is observed to have reported high failure rates. For this reason, 3-units FPD are designed and used extensively in the clinical practices, particularly for posterior mandibular region. The current study however, aims to carry out an evaluation of different stress patterns that are induced in a 3-units FPD within posterior part of mandible using finite element analysis (FEA). MATERIALS AND METHODS: Different modalities of the implant-supported FPDs such as type of connector, length and diameter of implants were taken into account. A three-dimensional (3D) model simulation of a mandibular Kennedy class II removal partial denture (RPD) was designed from a computerized tomography (CT) input with digital imaging communication on medicine (DICOM) format. In addition, occlusal load of 100 N was also used for central fossae of first premolar, first molar and second molar of the 3-units' reconstruction for each model. The magnitude of von Mises stress including minimum stress, maximum stress and average stress were also evaluated for each loading condition. RESULTS: The findings of the current study showed evidence that tooth-implant design with a nonrigid connector has significantly increased the average stress. Furthermore, it was observed that rigid connector has considerably minimized the stress within the tooth-implant-supported FPD. CONCLUSION: The study concluded that stress designs significantly influence the stress distribution around the bone. CLINICAL SIGNIFICANCE: This study gives some guidance and criteria for the selection of the type of fixed implant prosthesis in the posterior mandibular region.

Zein based magnesium oxide nanoparticles: Assessment of antimicrobial activity for dental implications.

MgO nanoparticles have been recently discovered as an antibacterial, however, they limited by property degradation due to agglomeration. The addition of a coating agent, such as a zein polymer, is effective in preventing agglomeration without affecting nanosized properties. The aim of this study was to assess the antimicrobial property of MgO nanoparticles when coated with a zein polymer against several oral bacteria and fungi. This was done by utilizing various assessment techniques. The ultimate aim is to use these nanoparticles in dental preparations. The antimicrobial activity of zein-coated MgO nanoparticles at different concentrations of 0.5, 1 and 2% were tested against four different microorganisms: Staphylococcus aureus, Streptococcus mutans and Enterococcus faecalis (gram positive bacteria), and Candida albicans (as oral fungus). Two different techniques were utilized: the Kirby-Bauer test, and a modified direct contact test. The results indicated that the antibacterial effect of 1% or 2% zein-coated MgO nanowires were statistically significant (p<0.05) against the four organisms studied: S. mutans, S. aureus, E. faecalis and C. albicans. Zein-coated MgO nanoparticles are a new human friendly and potent antimicrobial agent that can be incorporated in the formulation of a variety of new dental materials and products that should provide improvements in dental care and oral health.

Periodontitis severity plus risk as a tooth loss predictor.

BACKGROUND: Tooth loss can be a consequence of the natural history of periodontitis. Stratification of periodontitis severity, risk, and tooth loss exists within the United States adult population, and tooth loss correlates to severity and risk. We evaluated the loss of teeth for a periodontitis-affected population categorized by the combination of severity and risk in which the subjects predominantly did not receive periodontal treatment. METHODS: The clinical records of 523 subjects enrolled in the Veterans Affairs Dental Longitudinal Study, covering a period of 15 years, were used. Disease severity, risk level, and the number of teeth lost for each subject were determined. RESULTS: A stepwise regression analysis showed that disease and risk scores predicted mean tooth loss rate. The P value for the disease score was <0.0005, and the P value for the risk score was 0.001. The ordinal logistic regression model showed that disease (P = 0.002) and risk scores (P = 0.000) were significantly associated with the probability of subjects losing a specific number of teeth. CONCLUSIONS: Tooth loss is more precisely and accurately predicted by the combination of risk score and periodontal disease score than by either score alone. The combined scores may be a surrogate variable for periodontal status. Because the scores are derived from routine clinical measurements, they may be useful for population surveillance and dynamics, practice management, patient care decisions, practice-based research, and the determination of treatment effectiveness and the factors required for successful treatment, resulting in improved oral health and higher clinician productivity and income.