Investigating the impact of diameters and thread designs on the Biomechanics of short implants placed in D4 bone: a 3D finite element analysis.

BACKGROUND: Dental implants emerge as a dependable and efficacious alternative for patients experiencing partial or complete tooth loss. The stability of these implants is influenced by surface topography and macro-level design. In cases where the height of the maxillary posterior region is diminished, employing short implants can prove advantageous. With the aim of examining the distribution of von Mises stress, strain, and micromovement in D4 bone quality surrounding platform-switched short implants, measuring 6 mm in length and featuring diameters ranging from 4 to 6 mm, as well as different thread designs, an in-depth finite element analysis was conducted under immediate loading conditions. METHODOLOGY: A 3D finite element model was constructed to simulate maxillary molar crowns, incorporating an implant with a length of 6 mm and varying diameters and thread designs. The diameters utilized were 4/3.6 mm, 5/4 mm, and 6/4.8 mm, while the thread designs included buttress, square, and triangle patterns. Each model underwent analysis with a 100 N force applied in two directions: vertical and oblique, relative to the long axis of the implant. Stress, strain, and micromovement in the peri-implant region were recorded, employing the Ansys Workbench R v.18.1 software for modelling and analysis. RESULTS: When comparing all three diameters, the wide diameter (6 mm threads) exhibited the lowest values of peri-implant von Mises stresses (3.3 MPa and 35.1 MPa), strains (194 Ɛ and 484 Ɛ), and micromovements (0.7 µm and 1.3 Ɛ) subjected to axial and non-axial loading of a 100 N force. Notably, square microthreads yielded the most favorable stress parameters among the different thread shapes, manifesting the minimum values of stress, strains, and micromovements in their vicinity. CONCLUSION: For the treatment of atrophic ridges or in scenarios necessitating extensive surgical preparation of the implant site, a combination of short implants, wide diameters, and platform switching can be employed. In situations with reduced bone height and the requirement for an implant-supported prosthesis to replace a missing permanent maxillary molar, the utilization of wide-diameter platform-switched short implants measuring 6 mm in length, featuring a square thread design, should be taken into consideration.

Ceramic versus Composite Resin Polishing Systems on the Surface Roughness of Milled Leucite-Reinforced Ceramics.

Background and Objective: This study aimed to compare the surface finish of milled leucite-reinforced ceramics polished with ceramic and composite polishing systems based on the manufacturers' recommendations. Materials and Methods: Sixty subtractive computer-aided manufactured (s-CAM) leucite-reinforced glass-ceramic specimens (IPS-Empress-CAD) were assigned into six groups: no polishing, a ceramic polishing kit, and four composite kit groups. The roughness average (Ra) was evaluated in microns using a profilometer, and scanning electron micrographs were obtained for qualitative analysis. A Tukey HSD posthoc test (α = 0.05) was used to determine significant intergroup differences. Results: After surface evaluation of the ceramics, the Ra values of the polishing systems ranked OptraFine (0.41 ± 0.26) < Enhance (1.60 ± 0.54) < Shofu (2.14 ± 0.44) < Astropol (4.05 ± 0.72) < DiaComp (5.66 ± 0.62) < No Polishing (5.66 ± 0.74). Discussion: Composite polishing systems did not provide as smooth surfaces as the ceramic polishing kit for CAD-CAM leucite-reinforced ceramics. Thus, using ceramic polishing systems, polishing leucite ceramics is recommended, whereas composite polishing systems should not be considered as an alternative for use in minimally invasive dentistry.

Effectiveness of antimicrobial photodynamic therapy as an adjunct to mechanical instrumentation in reducing counts of Enterococcus faecalis and Candida albicans from C-shaped root canals.

BACKGROUND/PURPOSE: The aim was to assess the effectiveness of antimicrobial photodynamic therapy (aPDT) as an adjunct to mechanical instrumentation (MI) in reducing Enterococcus faecalis (E faecalis) and Candida albicans (C albicans) counts from C-shaped root-canals. METHODS: Teeth with C-shaped canals as identified on cone beam computed tomographic images were included. Following incubation with E faecalis and C albicans, samples were divided into 4 groups a four follows: Group-1: MI with adjunct aPDT; Group-2: aPDT alone; Group-3: MI alone; and Group-4: no treatment. The pulp chambers of these teeth were exposed and coronal pulp was mechanically derided using sterile endodontic excavators. Using flexible files, all canals were debrided up to size #30 K-files with intermittent irrigation with 2.5% sodium hypochlorite irrigation. In Groups 1 and 3, methylene-blue was injected in all canals and aPDT was performed using a 600 nm diode laser. Sample-size estimation was done on data from a pilot investigation and group-comparisons were done using one way analysis of variance and Bonferroni post-hoc adjustment tests. P < .05 was considered statistically significant. RESULTS: Sixty periodontally hopeless mandibular second molars with C-shaped canals were included. There was a statistically significant reduction CFU/mL of E faecalis (P < .001) and C albicans (P < .001). At post-operative microbial assessments in Group-1. There was no difference CFU/mL of E faecalis and C albicans at post-operative microbial assessments in Groups 2-4. CONCLUSION: MI with adjunct aPDT is more effective in reducing count of E faecalis and C albicans from C-shaped root canals.

Enhancement of the dissolution and in-vitro activity of a new antineoplastic agent.

The cell-surface molecule CD44 plays a major role in the regulation of cancer stem cells. The CD44 inhibitor compound N'-(1-dimethylaminomethyl-2-oxoindolin-3-ylidene)-2-(benzyloxy)benzohydrazide (OYB), anticancer agent is practically insoluble in water. Hence, the solid dispersion (SD) technique was used for enhancing the dissolution of OYB. The SD of OYB was achieved using OYB:poloxamer 188 (1:7) via the fusion method. The anticancer activities of the free-OYB solution and the SD formulation (OYB-SD) were investigated in-vitro. The dissolution rate of OYB-SD (1:7) increased by 2-fold compared with the untreated drug (51.52-100% at pH 1.2 and 8.25-19.15% at pH 7 buffer). In addition, OYB-SD afforded 3-folds cytotoxic effect, against LoVo cells, compared to the untreated compound (IC50 4.72 ± 0.57 and 13.97 ± 0.90 µg/ml, respectively) and against HepG2 (∼3-fold) (4.98 ± 0.368 and 13.85 ± 1.82 µg/ml, respectively) and MCF-7 (1.4-fold) cells (15.20 ± 0.20 and 21.12 ± 0.51 µg/ml, respectively), and enhanced the apoptotic potential in LoVo cells compared with free-OYB. The improved cytotoxic activity of the drug might be attributable to the enhanced dissolution of OYB.

Scanning accuracy with splinted and unsplinted implant scan bodies for the edentulous arch at implant level: an in vitro study.

Accuracy of completely edentulous arch scanning with implant scan bodies has not been completely validated for intraoral scanners. For desktop laboratory scanners validations were found in the literature. The aim of this in vitro study was to compare the dimensional accuracy of scanning with splinted and unsplinted scan bodies on a completely edentulous maxillary arch with 6 implants. A maxillary edentulous master cast with 6 implants was used as control for all implant level impressions. 6 implants were digitally planned and placed at different angulation of 0, 0  17° and 30°. A contact coordinate measuring machine (CMM) was used to generate baseline linear measurements of the master cast. Four test groups included: 2 intraoral scanners Trios (3shape, Copenhagen, Denmark) and True Definition (3M ESPE, St Paul, MN), one industrial scanner Atos (Core optical 3D scanner) and one conventional impression group scanned with laboratory scanner Dental Wings 7 Series. Each scan recording was made with splinted and unsplinted scan bodies. Digital datasets of all measurements were compared with the CMM baseline values using PolyWorks® InnovMetric Software in order to assess the linear and angular deviations and determine the accuracy of complete arch digital impression. Factorial ANOVA showed significant effect with splinting, scanner type, inter-implant distance and implant angulation for linear deviations. Splinted scan bodies revealed elevated linear and angular deviation values for all scanners with significantly highest deviations for True Definition scanner. Significant correlation was found between inter-implant distance and linear deviation (r =0.45, P =<0.001) with increased linear deviations among all scanners, regardless of splinting. ( P <0.05). Significant effect on accuracy was seen for angular deviation with splinting, scanner type and implant angulation; significant difference was found between 0° and 30° implant angulation ( P =0.035) with more deviation with 30° implant angulation. The accuracy of the complete arch implant digital impression using splinted scan bodies was significantly reduced for measurements that crossed the arch midline. The digital impression technique using a broad splint design to connect scan bodies was not found to improve the scan accuracy for intraoral scanners.

A novel approach for the quantification of paclitaxel loaded in ethyl cellulose/kollicoat and ethylcellulose/eudragit colloidal particles by UPLC-PDA.

An optimized rapid reversed phase ultra-performance liquid chromatography (UPLC-PDA) method has been developed and validated for precise and accurate quantification of paclitaxel in drug delivery systems. The chromatographic separation was attained on L1 (USP) column (2.1 ×50 mm, 1.7µm) with an isocratic mobile phase comprised of acetonitrile and water (1:1; flow rate 0.6 mL/min) and detection was executed at 227 nm by PDA detector. The proposed UPLC-PDA method is found to be rapid with retention time of 1.37 min, selective with homogenous peaks and sensitive with Limit of Detection (LOD) of 0.08µg/mL and Limit of Quantification (LOQ) of 2.6µg/mL. The method showed excellent linearity (R2>0.998) over the range of 0.1 to 0.4mg/mL and applied for the paclitaxel quantification in different formulations with no inference of excipients. Thus, the proposed approach has potential for rapid estimation of drug purity, assay and release profile from pharmaceutical preparations.

A novel approach for the quantification of paclitaxel loaded in ethyl cellulose/kollicoat and ethylcellulose/eudragit colloidal particles by UPLC-PDA.

An optimized rapid reversed phase ultra-performance liquid chromatography (UPLC-PDA) method has been developed and validated for precise and accurate quantification of paclitaxel in drug delivery systems. The chromatographic separation was attained on L1 (USP) column (2.1 ×50 mm, 1.7µm) with an isocratic mobile phase comprised of acetonitrile and water (1:1; flow rate 0.6 mL/min) and detection was executed at 227 nm by PDA detector. The proposed UPLC-PDA method is found to be rapid with retention time of 1.37 min, selective with homogenous peaks and sensitive with Limit of Detection (LOD) of 0.08µg/mL and Limit of Quantification (LOQ) of 2.6µg/mL. The method showed excellent linearity (R2>0.998) over the range of 0.1 to 0.4mg/mL and applied for the paclitaxel quantification in different formulations with no inference of excipients. Thus, the proposed approach has potential for rapid estimation of drug purity, assay and release profile from pharmaceutical preparations.

Biological Properties, Bioactive Constituents, and Pharmacokinetics of Some Capsicum spp. and Capsaicinoids.

Pepper originated from the Capsicum genus, which is recognized as one of the most predominant and globally distributed genera of the Solanaceae family. It is a diverse genus, consisting of more than 31 different species including five domesticated species, Capsicum baccatum, C. annuum, C. pubescen, C. frutescens, and C. chinense. Pepper is the most widely used spice in the world and is highly valued due to its pungency and unique flavor. Pepper is a good source of provitamin A; vitamins E and C; carotenoids; and phenolic compounds such as capsaicinoids, luteolin, and quercetin. All of these compounds are associated with their antioxidant as well as other biological activities. Interestingly, Capsicum fruits have been used as food additives in the treatment of toothache, parasitic infections, coughs, wound healing, sore throat, and rheumatism. Moreover, it possesses antimicrobial, antiseptic, anticancer, counterirritant, appetite stimulator, antioxidant, and immunomodulator activities. Capsaicin and Capsicum creams are accessible in numerous ways and have been utilized in HIV-linked neuropathy and intractable pain.

Characterization, Optimization, In Vitro and In Vivo Evaluation of Simvastatin Proliposomes, as a Drug Delivery.

Simvastatin a cholesterol-lowering agent used to treat hypercholesterolemia, coronary heart disease, and dyslipidemia. However, simvastatin (SV) has shown low oral bioavailability in GIT. The main purpose of the work was to develop proliposomal formulations to increase the oral bioavailability of SV. Film deposition on the carrier method has been used to prepare the proliposomes. The proliposomes were assessed for morphology, particulate size, entrapment efficacy, drug-polymer compatibility, in vitro and in vivo studies. FTIR and DSC results revealed no drug-polymer interaction. SEM and XRD analysis conform; proliposomes are spherical, amorphous in nature, so that it enhances the solubility of SV between 15.01 ± 0.026 and 57.80 ± 0.015 µg/mL in pH 7.4 phosphate buffer. The optimised formulation (PL6) shows drug release up to 12 h (99.78 ± 0.067%). The pharmacokinetics of pure SV and SV proliposomes (SVP) in rats were Tmax 2 ± 0.5 and 4 ± 0.7 h, Cmax 10.4 ± 2.921 and 21.18 ± 12.321 µg/mL, AUC0-∞ 67.124 ± 0.23 and 179.75 ± 1.541 µg/mL h, respectively. Optimised SVP shows a significant improvement in the rate and absorption of SV. The optimised formulation showed enhanced oral bioavailability of SV in Albino Wister rats and offers a new technique to improve the poor water-soluble drug absorption in the gastrointestinal system.

Effect of Intraoral Mechanical Cleaning Techniques on Bond Strength of Cast Crowns to Metal Cores.

PURPOSE: To evaluate the effect of cleaning of metal cores from provisional cement, using an intraoral airborne-particle abrasion method, on the bond strength of permanent resin cement with cast crowns to cores. MATERIALS AND METHODS: Thirty stainless steel models of a standard complete crown tooth preparation were fabricated. Thirty Type III gold crowns were fabricated. Each cast crown corresponded to one stainless steel crown preparation model. All crowns were cemented with noneugenol zinc oxide cement and stored for 7 days at 37°C. All crowns were debonded, and the cement was cleaned with airborne-particle abrasion using 50 µm aluminum oxide at 4.1 bar (0.41 MPa) followed by ultrasonic cleaning. Based on the mechanical cleaning technique of the remaining provisional cement on surfaces of cast cores, specimens were equally divided into 3 groups: hand cleaning (HC) with a dental excavator, hand cleaning followed by polishing using a brush and pumice (BP), and hand cleaning followed by intraoral airborne-particle abrasion (APA). All crowns were then cemented to their corresponding cores using universal resin cement. All crowns were stored for 7 days at 37°C. An Instron universal testing machine was used to record the bond strength of crowns. RESULTS: Airborne-particle abrasion method for intraoral mechanical cleaning revealed a statistically significantly higher bond strength compared to the other two methods. CONCLUSIONS: When comparing the three methods of provisional cement cleaning from metal cores, airborne-particle abrasion resulted in the highest bond strength for cast crowns.

Efficacy of calcium hydroxide and resin-modified calcium silicate as pulp-capping materials: a retrospective study.

The aim of this study was to compare the clinical success rates of light-cured, resin-modified calcium silicate (TheraCal LC) and calcium hydroxide (Dycal) as pulp-capping materials in permanent teeth. In this retrospective electronic record review of patients treated in the years 2012 through 2015, the postoperative data of 120 patients (n = 60 per material) were collected. In these 2 groups, 69 teeth were treated with calcium hydroxide (29 in men, 40 in women) and 79 with calcium silicate (37 in men, 42 in women). The following data were recorded: treated tooth; patient age and sex; reason for treatment; direct or indirect pulp cap; date of treatment; date of most recent dental appointment; and treatment outcome. The selected patients met the following inclusion criteria: They had received either a direct or an indirect pulp cap in an anterior or posterior tooth after excavation of deep caries as part of a routine restorative procedure using either amalgam or composite resin; and they had returned to the clinic for other dental care at least 3 months after the pulp-capping treatment. Patients were excluded from the study if they reported symptoms of irreversible pulpitis or chronic tooth pain before the restorative treatment was started. The treatment outcome was considered clinically successful if the tooth was still present and asymptomatic at the appointments following the procedure. The outcome was considered unsuccessful if the tooth was extracted due to symptoms or if endodontic treatment had been performed postoperatively. There was no statistically significant difference between the clinical success rates of calcium silicate (85.5%) and calcium hydroxide (84.8%), according to the Fisher exact test (P < 0.05). Neither the patient's sex nor the tooth location affected the outcome. Within the limitations of this retrospective clinical study, it may be concluded that TheraCal LC calcium silicate can be considered equivalent inefficacy to calcium hydroxide for both direct and indirect pulp capping. A prospective clinical study with a larger sample size is needed to confirm these findings.

Partial Explantation of Failed Dental Implants Placed in Mandibular Canal: A Case Report.

One of the most important concerns during posterior mandibular implant placement is avoiding the mandibular canal. Nerve injury can be very disturbing to the patient, possibly causing mild paresthesia to complete anesthesia. Explantation of a dental implant that gas violated the mandibular canal is the most recommended treatment. However, an osseointegrated implant that placed in the mandibular canal can be left if the patient shows no symptoms. In this case report, we describe a technique to maintain the apexes of the implants while partially removing fractured osseointegrated implants previously placed in the mandibular canal.

Guided Tissue and Bone Regeneration Membranes: A Review of Biomaterials and Techniques for Periodontal Treatments.

This comprehensive review provides an in-depth analysis of the use of biomaterials in the processes of guided tissue and bone regeneration, and their indispensable role in dental therapeutic interventions. These interventions serve the critical function of restoring both structural integrity and functionality to the dentition that has been lost or damaged. The basis for this review is laid through the exploration of various relevant scientific databases such as Scopus, PubMed, Web of science and MEDLINE. From a meticulous selection, relevant literature was chosen. This review commences by examining the different types of membranes used in guided bone regeneration procedures and the spectrum of biomaterials employed in these operations. It then explores the manufacturing technologies for the scaffold, delving into their significant impact on tissue and bone regenerations. At the core of this review is the method of guided bone regeneration, which is a crucial technique for counteracting bone loss induced by tooth extraction or periodontal disease. The discussion advances by underscoring the latest innovations and strategies in the field of tissue regeneration. One key observation is the critical role that membranes play in guided reconstruction; they serve as a barrier, preventing the entry of non-ossifying cells, thereby promoting the successful growth and regeneration of bone and tissue. By reviewing the existing literature on biomaterials, membranes, and scaffold manufacturing technologies, this paper illustrates the vast potential for innovation and growth within the field of dental therapeutic interventions, particularly in guided tissue and bone regeneration.

Current Knowledge on the Healing of the Extraction Socket: A Narrative Review.

The concept of extraction socket healing has been severally researched and reported over the years, since tooth extraction remains one of the most common procedures performed in the dental clinic. Understanding this healing process is of utmost importance because the outcome has a direct bearing on future prosthetic rehabilitation and, by extension, on patients' esthetics and masticatory function, among others. This mini review, therefore, summarized the current knowledge on the different stages of socket healing, including the biologic and clinical events that occur following tooth extraction up until the complete closure of the socket. Additionally, the modeling of the alveolar bone/process post extraction, and the resultant dimensional changes that, altogether, shape the bone, were reviewed and documented. The effects of various socket preservation interventions to mitigate these dimensional changes, and therefore preserve the alveolar process in a condition suitable for future prosthetic rehabilitation, were highlighted. Finally, a review of some of the factors that influence the entire process was also carried out.

Three-Dimensional FEA Analysis of the Stress Distribution on Titanium and Graphene Frameworks Supported by 3 or 6-Implant Models.

Titanium is the main component of dental implants. It is also routinely used as a framework material for implant-supported full-arch prostheses due to its low density, biocompatibility, and other mechanical properties. Remarkable mechanical properties such as lesser mass density and higher young's modulus of graphene have gained popularity among scientists, improving the properties of biomedical implants. Thus, our study aimed to compare the outcome through the von Mises stresses generated on All-on-6 and All-on-3 implant models, as well as on the framework, and evaluate the effect of stress patterns on the crestal bone around implants in the mandible. FEA (Finite Element Analysis) study was carried out using edentulous mandible models. Four 3D FEA models with 3 and 6 implants were used (Model 1: Titanium bar-supported 6 straight implants; Model 2: Graphene bar-supported 6 straight implants; Model 3: Titanium bar-supported 3 implants with 30 degrees-tilted; Model 4: Graphene bar-supported 3 implants with 30 degrees-tilted) in order to simulate endosseous implant designs. The implant measuring 4.2 mm in diameter and 11.5 mm in length were used. The most distal implants in the 3-implant models were placed with angulation of 30 degrees; in 6 implants, they were vertically placed. All the models were analyzed for vertical and oblique axis with a single force magnitude of 100 N. In all four implant models and under loading conditions, the peak stress points were always on the neck of the most distal implant. von Mises stresses were within the normal stress range. In a conventional six-straight implant model supported by a titanium framework, the cortical stress in the region of implants was 25.27 MPa, whereas, in the graphene framework, it was 12.18 MPa. Under vertical load, there was a significant difference in the cortical stress around the tilted implants (30 degrees) in the 3-implant system of titanium and graphene frameworks, respectively, 70.31 MPa and 21.27 MPa. The graphene framework demonstrated better results than the titanium framework for the conventional six-implant system under vertical load, achieving stress of 30.09 MPa and 76.60 MPa, respectively. In the case of the 3-implant system, a significant difference in the bar stress was observed between graphene and titanium, respectively, 256.32 MPa and 180.1 MPa of bar stress. Within the limitation of this study, the peri-implant stresses were decreased using graphene framework models. Hence, it was possible to conclude that the best load-bearing capacity results were found in the graphene framework group compared to the titanium framework for All-on-6 and All-on-3 implant models, even though both materials are reliable options used as framework materials in implant-supported full-arch prostheses.

PEGylated SLN as a Promising Approach for Lymphatic Delivery of Gefitinib to Lung Cancer.

Purpose: The present study aimed to develop gefitinib-loaded solid lipid nanoparticles (GEF-SLN), and GEF-loaded PEGylated SLN (GEF-P-SLN) for targeting metastatic lung cancer through the lymphatic system. Methods: The prepared SLNs were characterized in terms of physicochemical properties, entrapment efficiency, and in-vitro release. Furthermore, ex-vivo permeability was investigated using the rabbit intestine. Cytotoxicity and apoptotic effects were studied against A549 cell lines as a model for lung cancer. Results: The present results revealed that the particle size and polydispersity index of the prepared formulations range from 114 to 310 nm and 0.066 to 0.350, respectively, with negative zeta-potential (-14 to -27.6). Additionally, SLN and P-SLN showed remarkable entrapment efficiency above 89% and exhibited sustained-release profiles. The permeability study showed that GEF-SLN and GEF-P-SLN enhanced the permeability of GEF by 1.71 and 2.64-fold, respectively, compared with GEF suspension. Cytotoxicity showed that IC50 of pure GEF was 3.5 µg/mL, which decreased to 1.95 and 1.8 µg/mL for GEF-SLN and GEF-P-SLN, respectively. Finally, the apoptotic study revealed that GEF-P-SLN decreased the number of living cells from 49.47 to 3.43 when compared with pure GEF. Conclusion: These results concluded that GEF-P-SLN is a promising approach to improving the therapeutic outcomes of GEF in the treatment of metastatic lung cancer.

Development of stealth liposomal formulation of celecoxib: In vitro and in vivo evaluation.

Celecoxib (CLB) is a highly hydrophobic selective cyclo-oxygenase inhibitor with high plasma protein binding and undergoes extensive hepatic metabolism. CLB is highly effective in the treatment of osteo and rheumatoid arthritis as first line therapy but produces severe gastro-intestinal toxicities and cardiovascular side effects. In this research, stealth liposomes of CLB were developed with the intention to reduce the side effects and increase the accumulation of drug in the sites of inflammation. Stealth liposomes were prepared by thin film hydration technique using distearoylphosphatidylcholine and PE-PEG 2000 with variable amounts of cholesterol and characterized. The effects of various lipids such as hydrogenated soy phosphatidylcholine, dipalmitoyl phosphatidylcholine, distearoylphosphatidylcholine and cholesterol content on % drug encapsulation was investigated. The optimized stealth liposomes were characterized by FT-IR and DSC for possible drug excipients interaction. Pharmacokinetics, pharmacodynamics and biodistribution studies were carried out for the stealth liposomes. The results revealed that the stealth liposomes reduced the inflammation to the larger magnitude and have also sustained the magnitude when compared to free drug along with maximum analgesic response. Higher elimination half-life, AUC, MRT and lowered clearance rate denotes the extended bioavailability of the drug in blood. Biodistribution studies revealed that stealth liposomes extend the circulation time of liposomes in blood by decreasing opsonisation and be less concentrated in kidney, thereby reducing the toxicities to RES and renal organs and facilitate the drug accumulation in the area of inflammation. Our results indicated that CLB, without the requirement of modifications to enhance solubilisation, can be encapsulated and released from liposomal formulations. This new-fangled drug delivery approach may be used to circumvent the low bioavailability and toxic side effects of oral CLB formulations.

Evaluation of Shear Bond Strength between Resin Composites and Conventional Glass Ionomer Cement in Class II Restorative Technique-An In Vitro Study.

The success of dental restorations depends mainly on the ability to bond to other filling materials and tooth substances, in order to resist the multitude of forces acting on the bond within the oral cavity. Although the shortcomings of composite resins have been significantly reduced over the past three decades, microleakage due to shrinkage under masticatory loads is unavoidable. In order to overcome such problems, two materials laminated with matched properties can be used to achieve optimum results. The sandwich technique is an approach in which dentine is replaced by glass ionomer cement (GIC), and enamel is replaced by composite resin. In the past, numerous materials have been proposed with adequate properties to be used in this manner, but the results are conflicting in terms of bonding to the various forms of GIC, and the appearance of microcracks or gap formation during functional loading. This study aimed to evaluate the shear bond strength (SBS) and mode of failure between the following core materials: composite resins (CR) (Methacrylate Z350™, Ceram X™, and Spectrum™) with a base material of glass ionomer cement (GIC, Ketac Molar™). Eight samples were made with the help of polytetrafluoroethylene sheets (TEFLON, Wilmington, DE, USA). Each sheet consisted of holes which were 4 mm in diameter and 2 mm in thickness. The combination of materials was sandwiched. The samples were stored in distilled water and then placed in an incubator for 24 h in order to ensure complete polymerization. The samples were thermocycled for 500 cycles between 5-55 °C/ 30 s. Following thermocycling, SBS testing was performed using a universal testing machine. Additionally, scanning electron microscopy (SEM) was performed on representative samples for the bond failure analysis between GIC and the composite resins. The Ceram-X™ nanocomposite showed significantly higher bond strength than Methacrylate Z350™ or Spectrum™ (p = 0.002). The Methacrylate Z350™ and the Spectrum™ composite specimens demonstrated a similar SBS (p = 0.281). The SBS of the Ceram X™ to GIC was the highest compared to Methacrylate Z350™ and Spectrum™. Therefore Ceram X™ may produce a better bond with GIC, and may protect teeth against recurrent caries and failure of the restoration. Methacrylate Z350™ is comparable to Spectrum™ CR and can be used as an alternative. A combination of adhesive and mixed failure was observed in Methacrylate Z350™ CR and GIC, while adhesive failure was predominantly found in both Ceram X™ and Spectrum™ with GIC restorations.

Assessment of PCL between dental implant prosthesis and natural teeth using a digital force analyzer.

BACKGROUND: The prime concern of an implant-supported prosthesis (ISP) is to maintain an optimal proximal contact tightness, which further maintains arch integrity, improves masticatory effectiveness, and minimizes peri-implantitis. OBJECTIVE: To investigate the loss of proximal contact tightness between single tooth implant-supported prosthesis and the adjacent natural teeth. METHODS: Forty patients treated by a single mandibular first molar ISP, aged between 18-50 years were selected. All were randomly allocated in Group I and Group II. Group I, 20 subjects who have received ISP without an insertion of Essix retainer, and Group II patients received an insertion with Essix retainer. The groups were subdivided into Subgroup A, B, and Subgroup C, D, in which A and C are control groups. To measure the tightness at proximal contact points, a digital force analyzer was used. Proximal contact tightness (PCT) was measured immediately after the placement of the prosthesis, 3 months, 6 months, and 1-year follow-up respectively, and the PCT values at end of 1 year were statistically evaluated. Statistical analysis was done, mean and standard deviation was calculated by independent sample t-test wit p< 0.05 as a statistically significant value. RESULTS: In Group I, towards the end of 1 year, 2.09 N (65.5%) and 1.50 N (53.1%) loss of PCT were found on mesial and distal contact areas respectively. In Group II, loss of PCT at mesial contact area was 0.87 N (28.9%) and at distal contact area was 1.77 N (53.3%), which is significantly less compared with the non-usage of Essix retainer (p< 0.05). CONCLUSION: The usage of Essix retainer, PCT increases especially on the mesial contact area. The frequency of contact loss was decreased. Thus, to minimize the loss of proximal contact the usage of Essix retainer is recommended.

Knowledge and Anxiety for Dental Treatments Due to COVID-19 among General Public.

Introduction: The fears, anxiety, and worries created among general population by COVID-19 are severe. The procedures which generate aerosols transmit most of COVID-19 transmission and we know one such procedure is dental treatment. After the COVID-19 pandemic, there is a change in health-care services; hence, this droplet transmission in dentistry became an issue which needs to be addressed. Methodology: A descriptive, online questionnaire survey was conducted among adults above 20 years. The questionnaire consisted of demographic details and questions related to anxiety and fear of considering dental treatment during this pandemic situation. Results: 680 people responded for the study, among which 32% had COVID symptoms. 27% of them said that they are afraid of dental treatment during the pandemic whereas 47% said that they will accept if there is an emergency. The main reason for this fear was droplet infection in dental clinics. Conclusion: The fear of dental treatment during pandemic is moderate. This may be due to the self-care, positive behavior toward oral care by the people, and fear of cross-contamination due to airborne infections though the personal protective measures were followed.