In silico assessment of biocompatibility and toxicity: molecular docking and dynamics simulation of PMMA-based dental materials for interim prosthetic restorations.

AIM: This study aimed to comprehensively assess the biocompatibility and toxicity profiles of poly(methyl methacrylate) (PMMA) and its monomeric unit, methyl methacrylate (MMA), crucial components in dental materials for interim prosthetic restorations. METHODOLOGY: Molecular docking was employed to predict the binding affinities, energetics, and steric features of MMA and PMMA with selected receptors involved in bone metabolism and tissue development, including RANKL, Fibronectin, BMP9, NOTCH2, and other related receptors. The HADDOCK standalone version was utilized for docking calculations, employing a Lamarckian genetic algorithm to explore the conformational space of ligand-receptor interactions. Furthermore, molecular dynamics (MD) simulations over 100 nanoseconds were conducted using the GROMACS package to evaluate dynamic actions and structural stability. The LigandScout was utilized for pharmacophore modeling, which employs a shape-based screening approach to identify potential ligand binding sites on protein targets. RESULTS: The molecular docking studies elucidated promising interactions between PMMA and MMA with key biomolecular targets relevant to dental applications. MD simulation results provided strong evidence supporting the structural stability of PMMA complexes over time. Pharmacophore modeling highlighted the significance of carbonyl and hydroxyl groups as pharmacophoric features, indicating compounds with favorable biocompatibility profiles. CONCLUSION: This study underscores the potential of PMMA in dental applications, emphasizing its structural stability, molecular interactions, and safety considerations. These findings lay a foundation for future advancements in dental biomaterials, guiding the design and optimization of materials for enhanced biocompatibility. Future directions include experimental validation of computational findings and the development of PMMA-based dental materials with improved biocompatibility and clinical performance.

Attenuation of orthodontically induced inflammatory root resorption by using low-intensity pulsed ultrasound as a therapeutic modality- a systematic review.

Ultrasound is an effective tool for both diagnostic and therapeutic applications. As an imaging tool, ultrasound has mostly been used for real-time noninvasive diagnostic imaging. As ultrasound propagates through a material, a reflected radio-frequency (RF) signal is generated when encountering a mismatch in acoustic impedance. While traditionally recognized for its diagnostic imaging capabilities, the application of ultrasound has broadened to encompass therapeutic interventions, most notably in the form of Low-Intensity Pulsed Ultrasound (LIPUS). Low-Intensity Pulsed Ultrasound (LIPUS) is a form of mechanical energy transmitted transcutaneously by high-frequency acoustic pressure waves. The intensity of LIPUS (30 mW/cm2) is within the range of ultrasound intensities used for diagnostic purposes (1-50 mW/cm2) and is regarded as non-thermal, non-destructive, permeating living tissues and triggering a cascade of biochemical responses at the cellular level. The LIPUS device produces a 200 µs burst of 1.5 MHz acoustic sine waves, that repeats at a modulation frequency of 1 kHz and provides a peak pressure of 30 mW/cm2. Low-intensity pulsed ultrasound (LIPUS) forms one of the currently available non-invasive healing-enhancing devices besides electro-stimulation (pulsed electro-magnetic field, PEMF). This modality has been leveraged to enhance drug delivery, expedite injury recovery, improve muscle mobility, alleviate joint stiffness and muscle pain, and enhance bone fracture healing. Although LIPUS has been embraced within various medical disciplines, its integration into standard dental practices is still in its nascent stages, signifying an unexplored frontier with potentially transformative implications. Low-intensity pulsed ultrasound (LIPUS) has emerged as an attractive adjuvant therapy in various dental procedures, such as orthodontic treatment and maxillary sinus augmentation. Its appeal lies in its simplicity and non-invasive nature, positioning LIPUS as a promising avenue for clinical innovation. One particular area of interest is orthodontically induced inflammatory root resorption (OIIRR), an oftenunavoidable outcome of the orthodontic intervention, resulting in the permanent loss of root structure. Notably, OIIRR is the second most common form of root resorption (RR), surpassed only by root resorption related to pulpal infection. Given the high prevalence and potential long-term consequences of OIIRR, this literature review seeks to evaluate the efficacy of LIPUS as a therapeutic approach, with an emphasis on assessing its capacity to reduce the severity of OIIRR to a level of clinical significance. To conduct this systematic review, a comprehensive automated literature search was executed across multiple databases, including MEDLINE, Embase, PsycINFO, Web of Knowledge, Scopus, CINAHL, LILACS, SciELO, Cochrane, PubMed, trials registries, 3ie, and Google Scholar. Both forward and backward citation tracking was employed, encompassing studies published from database inception through January 2009 to April 2023. The review focused on randomized controlled trials (RCTs) that specifically evaluated the effects of low-intensity pulsed ultrasound therapy on orthodontically induced inflammatory root resorption (OIIRR), without restrictions of publication date. A stringent selection criterion was applied, and only studies demonstrating high levels of statistical significance were included. Ultimately, fourteen studies met the inclusion criteria and were subjected to further analysis. The overall quality of the included randomized controlled trials (RCTs) was rigorously assessed utilizing the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. This analysis revealed certain methodological limitations that posed challenges in drawing definitive conclusions from the available evidence. Despite these constraints, the review offers invaluable insights that can inform and guide future research. Specifically, it delineates recommendations for targeted populations, necessary interventions, appropriate outcome measures, suitable study designs, and essential infrastructure to facilitate further investigations. The synthesis of these insights aims to enhance the development and application of low-intensity pulsed ultrasound therapy within the field of dentistry, thereby contributing to improved patient outcomes.

Variations in the Compressive Strength of a Die Stone with Three Different Sulfates at Eight Different Concentrations: An In Vitro Study.

AIM: The present study aimed to evaluate the alteration in the compressive strength (CS) of the die stone with three different sulfate salt additives, each at eight various concentrations. MATERIALS AND METHODS: The specimens were prepared at specific dimensions (length: 2.5 cm and diameter: 2.5 cm) divided into three test groups based on the type of sulfate additives used [potassium sulfate (K2SO4), zinc sulfate (ZnSO4·H2O), and manganese sulfate (MnSO4·H2O)] and one control group, without any additives. Again, each group was divided into eight subgroups based on concentration of sulfates (ranging from 0.2% to 4%). A total of 375 specimens were tested. CS (in MPa) was evaluated after 72 hours of drying time, using an universal testing machine. STATISTICAL ANALYSIS: A one-way analysis of variance (ANOVA) was used for intergroup comparisons. Individual comparisons were done using the post hoc Tukey HSD analysis. RESULTS: All the three additives at all the concentrations have shown an inferior resistance to compressive forces when compared to the standard specimen. However, the least mean CS was observed at 0.8% of MnSO4 (10.95 MPa) and the highest was at 1% K2SO4 (25.28%). A highly significant difference (p < 0.001) was observed among the concentrations in all the three groups (K2SO4, MnSO4, and ZnSO4 groups) and F values were derived as 69.84, 24.29, and 130.52, respectively. At each concentration, comparisons between the groups have shown a significant difference (p < 0.05) at almost all concentrations. CONCLUSION: The CS of die stone is shown to be decreased with an increase in all three types of sulfate additives when compared to the control specimen. CLINICAL SIGNIFICANCE: Die stone is an often used gypsum material in the field of dentistry. Compressive strength of the die stone is crucial in prosthetic dentistry; chemical additives such as sulfate salts may increase the CS such that the die stone can withstand clinical and laboratory handling forces. How to cite this article: Vyas R, Vaddamanu SK, Gurumurthy V, et al. Variations in the Compressive Strength of a Die Stone with Three Different Sulfates at Eight Different Concentrations: An In Vitro Study. J Contemp Dent Pract 2019;20(11):1297-1306.

Assessment of Fracture Resistance Capacity of Different Core Materials with Porcelain Fused to Metal Crown: An in vitro Study.

Aim: The aim of the study was to evaluate the capacity to resist fracture in different core buildup materials with porcelain fused to metal (PFM) crown. Materials and methods: Totally, 45 mandibular single rooted first premolars were collected, which were sound along with similar shape and size. The teeth were sectioned at 15 mm above the root apex sparing the sound tooth structure. The teeth were endodontically treated with the crown-down technique using nickel-titanium (NiTi) instrumentation. The specimens were randomized into three groups as per the core materials used and were labeled accordingly. Group I consisted of dual-cured composite resin, group II consisted of glass ionomer reinforced with resin, and group III consisted of Miracle mix. Universal loading machine is used for measuring the compres-sive load applied to fracture the tooth. Results: The mean value of compressive strength was maximum in the dual cured composite resin (598.42 ± 22.64) followed by glass ionomer reinforced with resin (478.88 ± 26.74) and Miracle mix (442.16 ± 30.10). The results showed a significant difference statistically within the core materials used with p < 0.05. The results from the Tukey's post hoc test of multiple comparisons between dual-cured composite resin vs glass ionomer reinforced with resin, dual-cured composite resin vs Miracle mix, and glass ionomer reinforced with resin vs Miracle mix showed a highly statistical difference with p < 0.05, which is significant. Conclusion: This in vitro study showed that the dual-cured composite resin had maximum resistance to fracture compared with other core buildup materials on teeth which were endodonti-cally treated. Clinical significance: Restoration of a tooth which is structurally compromised is a tricky job for all the dentists. Restoring it with a proper core buildup material with adequate fracture resistance makes the tooth structure stable. The core material should be able to resist all types of occlusal forces and to distribute it equally within the tooth structure. Keywords: Core buildup, Crowns, Endodontically treated teeth, Fracture resistance.

A Comparative Evaluation of the Bonding Strength, Marginal Adaptation, and Microleakage of Dental Cements in Prosthodontics: An In Vitro Comparative Study.

BACKGROUND: The primary function of dental cement is to seal and support prosthodontic restorative materials. Proper selection of the dental cement contributes to the clinical success of the restoration. METHODS: A total of 166 molar tooth samples were prepared to simulate the type of tooth commonly found in prosthodontic practice. Each sample was restored using one of the tested dental cement materials employing a prestabilized methodology. The performance of resin-modified glass ionomer cement (RMGIC) (GC Fuji PLUS Capsule, GC America, Alsip, IL), zinc phosphate cement (ZPC) (Dentsply Sirona, Charlotte, NC), and resin cement (RC) (RelyX ARC, 3M ESPE, Saint Paul, MN) in bonding strength, marginal adaptation, and microleakage was evaluated and compared. The bonding strength, marginal adaptation, and microgroove were tested using specific established methodologies. The outcomes were then analyzed using statistical analyses for means and standard deviations to compare different types of dental cement. RESULTS: The total outcome shows that the highest bonding strength with the highest mean was the resin cement, rating 24.8 MPa, followed by RMGIC and ZPC at 20.5 and 18.9 MPa, respectively. The marginal adaptation scores indicate that RC had the highest score at a mean of 4, followed by ZPC at 3.2 and RMGIC at 2.5. The dye penetration measurements in millimeters revealed that ZPC had a penetration of 0.31 mm, RMGIC had a penetration of 0.25 mm, and RC had the least penetration at 0.20 mm. The results of the statistical data analysis show significant differences between the dental cements in bonding strength and marginal adaptation. CONCLUSION: In conclusion, resin cement demonstrated superior performance in bonding strength, marginal adaptation, and resistance to microleakage compared to RMGIC and zinc phosphate cement. These findings highlight the importance of selecting resin cement for achieving optimal clinical outcomes in prosthodontic restorations.

Comparative efficacy of photobiomodulation on osseointegration in dental implants: A systematic review and meta-analysis.

AIM: This study aimed to assess the effectiveness of photobiomodulation therapy (PBM) in enhancing bone integration with dental implants. METHOD: PubMed, ScienceDirect, the Cochrane Library, Scopus, and Google Scholar were searched. Studies assessing PBM effectiveness with defined intervention/control groups were included, while those lacking specified laser types, involving severe maxillofacial defects or surgery, and not reporting outcomes related to dental implant osseointegration post-PBM therapy were excluded. The studies' risk of bias was assessed using Robvis for randomized controlled trials (RCTs) and ROBINS-I for non-RCTs. The meta-analysis was conducted utilizing a random-effects model at a significance level of 0.01. RESULTS: The study reviewed 26 papers involving 571 patients undergoing dental implant procedures with PBM/Low-Level Laser Therapy (LLLT) or placebo/control. Implant stability quotients (ISQ) analysis showed a non-significant difference (p = 0.06, mean difference: 1.02, 95 % CI: 0.28 to 1.75, I2=28 %), while the Periotest method indicated significant improvement in stability (p < 0.01, mean difference: -0.51, 95 % CI: -0.78 to -0.24, I2=71 %). PBM resulted in a significant bone density increase (p < 0.01, mean difference: 26, 95 % CI: 6.93 to 45.06, I2=91 %), but marginal bone loss showed no significant difference (p = 0.11, mean difference: 0.00, 95 % CI: -0.06 to 0.05, I2=45 %). Implant survival rate did not significantly differ (p = 0.73, mean difference: 1.56, 95 % CI: 0.38 to 6.46, I2=0 %). Most studies raised concerns regarding randomization. CONCLUSION: PBM could improve implant stability, as assessed with Periotest, and increase bone density, enhancing osseointegration. However, implant stability assessed with ISQ, marginal bone loss, and implant survival rate were comparable between the study groups.

The impact of virtual reality simulation on dental education: A systematic review of learning outcomes and student engagement.

PURPOSE: Virtual reality (VR) simulations have been increasingly employed to train dental students prior to clinical practice. According to the literature, blended learning designs in the form of VR simulations can be utilized by both dental students and instructors to provide quality education. They can also save time and improve motor skills before students enter clinical stages. Therefore, this study was designed to review the importance of available VR simulators and their impact on student learning and outcomes. METHOD: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed to review the literature systematically, and different databases such as PubMed, ScienceDirect, Cochrane Library, Scopus, and Google Scholar were searched (up to December 2023) for relevant articles using keywords: "virtual reality," "virtual reality simulators," "virtual reality simulation," and "dental education." The Mixed Methods Appraisal Tool was used to assess the study quality. RESULTS: After a comprehensive literature search, 1477 research articles were identified, of which 16 were included in the present study. In terms of students' learning outcomes, engagement, and optimal approach, a significant improvement was observed compared to conventional training methods, specifically in their knowledge, performance, confidence, and psychomotor skills. CONCLUSION: The findings suggest that VR simulators enhance the overall learning abilities of dental students and should be regarded as an integral component of the current curriculum. However, it is important to recognize that VR simulators cannot fully substitute traditional training methods; rather, they can effectively complement them.

Quantitative evaluation and comparison of stress transmission characteristics of bar-clip and short coping overdenture attachments under dynamic loading: a photoelastic stress analysis.

STATEMENT OF PROBLEM: When two canine abutment teeth are used to support an overdenture prosthesis, optimal stress distribution to minimize forces to abutments is desired. PURPOSE: This study used photoelastic stress analysis to compare the stress patterns generated around canine abutments using two different overdenture retainer designs. MATERIALS AND METHODS: Two canine abutments were anchored in the photoelastic mandible and overdentures were fabricated using two different overdenture attachments. The fitting surface of dentures were lined with resilient layer of light bodied silicon rubberbase impression material to simulate oral mucosa. The attachments used were Bar-Clip and Short coping type. Verticalload of 5 to 50 lb was applied by jaw simulator. Resultant stress fringes were photographed and evaluated quantitatively. RESULTS: Bar-Clip type of attachment transmitted more amount of stress than short coping type transmitted. There was gross difference in magnitude of stresses between two types of retainers. CONCLUSION: As the retentivity of the attachment increased there was more stress concentration around the abutments.

In vitro Evaluation of Laser vs. Handpiece for Tooth Preparation.

Background: The erbium-doped yttrium aluminium garnet (Er:YAG) laser has been revealed to effectively ablate dental hard tissues, and its utilisation to caries eradication and cavity preparation is envisaged. Nevertheless, only a limited research has been performed on the Er:YAG laser's capacity to treat caries. Aim and Objectives: The efficiency of caries elimination with an Er:YAG laser in vitro was equated to that of traditional mechanical therapy in this study. Methodology: The investigation made use of teeth that had suffered from root caries. The Er:YAG laser was used to treat half of each tooth, while the other half was either removed with a conventional bur or left untouched as a control. Each therapy was evaluated in terms of how long it took to remove cavities, histological examinations of decalcified serial sections, scanning electron microscopy (SEM) analyses and the density of the dentin. Result: A longer treatment time was required for the Er:YAG laser to completely eradicate carious dentin because of its precise irradiation strategy. However, the Er:YAG laser was effective in removing diseased and softening carious dentin with little heat injury to neighbouring intact dentin, much as the bur treatment. It was also shown that the Er:YAG laser treatment had a lower amount of vibration than other methods. The SEM study of the lased dentin surface revealed characteristic micro-irregularities. Conclusion: The Er:YAG laser system appears to be a potential novel technical option for caries therapy, based on our findings.

An In Vitro study to Compare Dental Laser with other Treatment Modalities on Biofilm Ablation from Implant and Tooth Surfaces.

Background: Periodontal and peri-implant disorders are etiologically linked to bacterial biofilms. The researchers wanted to see how well the erbium-doped yttrium aluminum garnet (Er:YAG) laser removed bacterial biofilms along with attached epithelial cells (EC), gingival fibroblasts (GF), in addition to osteoblast-like cells (OC) dentin along with titanium surfaces compared to previous therapy methods. Methodology: 3.5 days were spent growing bacterial biofilms on standardized dentin and also titanium samplings using a sand-blasted along with the acid-etched surface. Following that, the specimens were positioned into pockets that had been formed artificially. The following approaches were used to remove biofilm: (1) Er:YAG, (2) photodynamic therapy (PDT), and (3) curette (CUR) along with supplementary PDT (CUR/PDT). The remaining biofilms' colony forming units (CFUs) were determined, as well as the attachment of EC, GF, in addition to OC. Analysis of variance with a posthoc least significant difference was utilized in the statistical analysis. Results: When compared to untreated dentin and titanium surfaces, all therapy strategies reduced total CFUs in statistically significant biofilms (p = 0.001). On the dentin, Er:YAG was as effective as CUR and PDT, but not as effective as CUR/PDT (p = 0.005). The application of Er:YAG on titanium surfaces leads to statistically significantly improved biofilm eradication equated to the supplementary three therapies (all p = 0.001). On untouched infested dentin and titanium surfaces, the counts of attached EC, GF, and OC were the lowermost. Atop the dentin, increased EC counts were detected after CUR/PDT (p = 0.006). On titanium, all cleaning procedures increased the counts of attached EC by a statistically significant amount (p = 0.001), with no variations between groups. After Er:YAG decontamination, there were statistically substantially elevated amounts of GF (p = 0.024) and OC (p = 0.001) than on untreated surfaces. Conclusion: The usage of Er:YAG laser to ablate subgingival biofilms and, specifically, to decontaminate titanium implant surfaces appears to be a promising strategy that needs further research.

Effect of Food Colorants on Color of Denture Base Acrylic Resins.

BACKGROUND: Acrylic resin has been successfully used for complete denture fabrication for many years. Color stability is very crucial clinical properties for dental materials, and color change may be an indicator of aging or damaging of materials. AIM AND OBJECTIVES: This study has been designed to determine the color stability of heat cure denture base acrylic resins in commonly consumed solutions causing stains. METHODOLOGY: Four hundred disc samples of four commercially used heat cure denture base resins (Trevalon®, DPI®, Veracril®, and Pyrax®) were fabricated (100 in each group). These were checked for any change in optical density by immersing them in four different staining solutions (tea, coffee, turmeric, and betel leaf, i.e., paan) and synthetic saliva for 1-month synthetic saliva was taken as control. The denture cleansers were also evaluated for their efficacy determined by their ability to remove the stains caused by the staining solutions. RESULTS: It was observed that Trevalon® showed least change in optical density and coffee illustrated the maximum potential for staining the denture base resins and is the most difficult to be removed using a denture cleanser. CONCLUSION: It can be concluded that Trevalon® demonstrated maximum color stability. Among the staining solutions, coffee caused maximum stains.

In vitro Results of Scanning Technique on Assessing Cement Thickness and Interfacial Nanoleakage of Luted CAD/CAM-Fabricated Fiber Posts.

BACKGROUND: Fiber posts are broadly used due to their good esthetics and elasticity close to that of dentin, which allows for uniform stress distribution within a root and lowers the possibility of nonrestorable root fractures. AIM AND OBJECTIVES: The study assessed the layer of cement thickness and interfacial nanoleakage of luted fiber posts which were fabricated with CAD/CAM technology following direct scanning of the post space (DS) method, scanning of a polyether impression of the post space (IS), and scanning of a plaster model of the post space (MS). METHODOLOGY: Ninety premolars were chosen randomly and were assigned to three groups according to the scanning technique. Posts were computer designed and milled from experimental fiber-reinforced composite blocks. RESULTS: The mean and standard deviation values of cement thickness, respectively, were: DS 172 ± 39 = m; IS 199 ± 55 = m, and MS MPa 272 ± 81 = m. The fiber posts fabricated following DS technique demonstrated superior performance compared to posts fabricated upon IS and MS, in terms of the post retention. The cement thickness did not differ between DS and IS, whereas in MS group, the cement layer was significantly thicker than in the remaining two groups. The scanning technique did not influence the sealing ability, as all groups showed comparable nanoleakage. CONCLUSION: Fiber posts fabricated following DS technique demonstrated superior performance. Furthermore, scanning technique did not influence the sealing ability, as all groups showed comparable nanoleakage.

Does the quality of residual alveolar bone apical to a periodontal lesion beneath the maxillary sinus play a vital role in preventing the extension of periodontal disease to maxillary sinus? A CBCT-assisted retrospective study.

BACKGROUND: The mucous membrane of the maxillary sinus is sensitivis susceptible to infection or inflammation adjacent to it, which may contribute to mucous membrane thickening (MMT). Residual alveolar bone quality (RABQ) is considered a quality of the remaining bone apical to periodontal defect adjoining to the floor of the maxillary sinus. OBJECTIVE: The current study aimed to analyze the minimum RABQ to prevent the extension of periodontal pathology from reaching maxillary sinus using cone-beam computed tomography (CBCT). METHODS: In this retrospective observational study, 240 sinus exposure CBCT records of 146 patients were evaluated. Patients with at least one sinus exposure were included. RABQ and MMT were calculated using CBCT inbuilt tools. RABQ was divided into four groups based on gray scale values (GSV). Statistical analysis was performed using one way ANOVA and independent sample t-tests. Correlation was completed applying Pearson's correlation coefficient. RESULTS: A significant difference (p< 0.05) was observed between the MMT values of the four RABQ groups. Inverse correlation was observed between mean MMT and GSV values. Mean MMT was higher than pathological MMT range (> 2 mm), with significant differences in groups A and B, where mean GSV values are less than 500. Mean GSV greater than 500 in groups C and D show non-pathological MMT. Prevalence of MMT is 91.4% if GSV is < 500 and 7.5% if GSV is > 500. CONCLUSIONS: Our study suggests that MMT is present if RABQ has GSV values < 500. Maxillary sinusitis and its etiology from periodontal pathology can be excluded based on RABQ adjoining periodontal lesion. Early detection and prompt treatment along with appropriate regenerative protocols can be performed to increase the RABQ. Further microbiological investigation is required to support the present results.

Analysis of surface conditioning methods on core-veneer bond strength of CAD/CAM zirconia restorations.

BACKGROUND: The increased strength of zirconia has resulted in its widespread application in clinical dentistry. Nevertheless, the fracture of veneering porcelains remains one of the key reasons of failure. OBJECTIVE: The objective of this study was to compare and analyze the influence of surface conditioning methods on the core-veneer bond strength of zirconia restorations. METHODS: Thirty specimens of zirconia core with sizes 10 × 5 × 5 mm were layered with porcelain of sizes 5 × 3 × 3 mm. On the basis of different surface conditioning methods, four groups were made: Group I: abrasion with airborne alumina particles of 110 µm size, Group II: sandblasting with silica coated alumina particles of 50 µm in size, Group III (modified group): alteration with a coating of zirconia powder prior to sintering, and Group IV (control group): metal core specimens. The shear force of all specimens was tested using a universal testing machine with a 0.5 mm/min crosshead speed. One-way analysis of variance (ANOVA) and Tukey's post hoc pair wise comparison (p= 0.05) were performed to analyze the shear bond strength. A scanning electron microscope was used to assess the fractured specimens. RESULTS: A statistically significant difference was noted between the groups. The mean value of shear bond strength was 40.25 MPa for Group I, 41.93 MPa for Group II, 48.08 MPa for Group III and 47.01 MPa for Group IV. CONCLUSIONS: The modified zirconia group and control group demonstrated a significantly higher mean bond strength than that of Group I, where airborne particle abrasion was used. The scanning electron microscope showed that cohesive fracture in the porcelain veneers was the main problem of failure in altered zirconia. The modified zirconia specimens in Group III demonstrated significantly improved values of shear bond strength.

In-vitro Evaluation of Transverse Strength of Repaired Heat Cured Denture Base Resins without Surface Treatment and with Chemical and Mechanical Surface Treatment.

BACKGROUND: Denture repair involves joining two parts of a fractured denture with a denture repair material. Hence, a substantial repairing system for denture base fracture should be there to elude frequent fracture. MATERIALS AND METHODS: Surface treatment of conventional heat cure denture base resin with different surface treatments (chemical ethyl acetate, and mechanical roughening with bur), with control group formed without surface treatment. Specimens were repaired with auto polymerizing acrylic resin using sprinkle on technique. The testing of the transverse strength of the repaired specimens was evaluated with three-point bending test on universal testing machine. RESULTS: The study revealed that surface chemical treatment with ethyl acetate improved the transverse strength of repaired heat cure denture base when compared with mechanical and control group. A two-way analysis of variance revealed that there was statistically significant difference in mean strengths of the three groups. CONCLUSION: Surface chemical treatment with ethyl acetate improved the transverse strength of the repaired heat cure denture base when compared with mechanical roughening with bur and group without surface treatment.

Morphological and Dimensional Characteristics of Dental Arch among Tribal and Non-tribal Population of Central India: A Comparative Study.

BACKGROUND: Differences in the dental arch among Bhil Aboriginals were investigated and compared with non-tribal individuals residing in a tribal zone of Central India. Plaster models (120) were made with the help of alginate impression of tribal adults as well as non-tribal adults residing in the same area. The supposition as aboriginals being primitive due to dietary practices maxillary arch size and mandibular arch size is distended in comparison to the non-tribal population as adaptation of soft refined diet has disrupted the growth of the jaws. Hence, an attempt was made to evaluate the arch widths of tribal population and to associate it with non-tribe population in the same area of Central India. MATERIALS AND METHODS: Difference in morphology and dimension of the maxillary and mandibular arches was aimed at Bhil tribes as well as non-tribal residents of tribe rich zone of Central India. The study was steered amid 120 individuals both tribal and non-tribe equally around 60 each through a well-organized out-reach program intermittently. Study models were made of dental arches of all participants. All measurements of the arch dimension were patent on the study casts using an electronic digital sliding caliper. Pair t-test was applied by using SPSS software version-19.0. RESULTS: In the maxillary arch, on appraisal the non-tribal and Bhil tribe's subjects, it showed a statistically significant difference in inter-incisor width (2.95 mm), inter-canine width (2.60 mm), arch depth (3.25 mm). While inter premolar width (0.20 mm) and inter molar width (0.80 mm) anterior arch length (0.60 mm), and posterior arch length (0.10 mm) showed statistically not significant difference between non-tribal population and Bhil tribe subjects. In the mandibular arch, it showed a statistically significant difference in inter-canine width (1.00 mm). Although, inter-incisor width (0.72 mm), inter-molar width (0.80 mm), arch depth (0.90 mm), anterior arch length (0.30 mm), posterior arch length (0.35 mm), and curve of Spee (0.13 mm) showed statistically not significant difference between general population and Bhil tribe subjects. CONCLUSION: When associated non-tribal population to Bhil tribes subjects, for the morphological and dimensional characteristics of dental arches Bhil tribe subjects exhibited: A narrower and shorter maxilla; reduced mandible size; smaller incisor widths for the maxillary and mandibular arches.