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Biomechanical comparison of implant retained fixed partial dentures with fiber reinforced composite versus conventional metal frameworks: A 3D FEA study

Fiber reinforced composite (FRC) materials have been successfully used in a variety of commercial applications. These materials have also been widely used in dentistry. The use of fiber composite technology in implant prostheses has been previously presented, since they may solve many problems associated with metal alloy frameworks such as corrosion, complexity of fabrication and high cost. The hypothesis of this study was that an FRC framework with lower flexural modulus provides more even stress distribution throughout the implant retained fixed partial dentures (FPDs) than a metal framework does. A 3-dimensional finite element analysis was conducted to evaluate the stress distribution in bone, implant-abutment complex and prosthetic structures. Hence, two distinctly different models of implant retained 3-unit fixed partial dentures, composed of Cr-Co and porcelain (M-FPD model) or FRC and particulate composite (FRC-FPD model) were utilized. In separate load cases, 300 N vertical, 150 N oblique and 60 N horizontal forces were simulated. When the FRC-FPD and M-FPD models were compared, it was found that all investigated stress values in the M-FPD model were higher than the values in the FRC-FPD model except for the stress values in the implant-abutment complex. It can be concluded that the implant supported FRC-FPD could eliminate the excessive stresses in the bone-implant interface and maintain normal physiological loading of the surrounding bone, therefore minimizing the risk of peri-implant bone loss due to stress-shielding.

Microshear bond strength according to dentin cleansing methods before recementation.

PURPOSE The aim of this study was to determine the efficiency of Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet laser in different output powers for removing permanent resin cement residues and therefore its influence on microshear bond strength compared to other cleaning methods. MATERIALS AND METHODS 90 extracted human molars were sectioned in 1 mm thickness. Resin cement was applied to surface of sliced teeth. After the removal of initial cement, 6 test groups were prepared by various dentin surface treatment methods as follows: no treatment (Group 1), ethylene diamine tetra acetic acid application (Group 2), Endosolv R application (Group 3), 1.25 W Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet laser irradiation (Group 4), 2 W Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet laser irradiation (Group 5) and 3.5 W Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet laser irradiation (Group 6). The topography and morphology of the treated dentin surfaces were investigated by scanning electron microscopy (n=2 for each group). Following the repetitive cementation, microshear bond strength between dentin and cement (n=26 in per group) were measured with universal testing machine and the data were analyzed by Kruskal Wallis H Test with Bonferroni correction (P<.05). Fracture patterns were investigated by light microscope. RESULTS Mean microshear bond strength ± SD (MPa) for each group was 34.9 ± 17.7, 32.1 ± 15.8, 37.8 ± 19.3, 31.3 ± 12.7, 44.4 ± 13.6, 40.2 ± 13.2 respectively. Group 5 showed significantly difference from Group 1, Group 2 and Group 4. Also, Group 6 was found statistically different from Group 4. CONCLUSION 2 W and 3.5 W Erbium, Chromium: Yttrium-Scandium-Gallium-Garnet laser application were found efficient in removing resin residues.

Tooth-Implant Connection: A Review

Connecting teeth to osseointegrated implants presents a biomechanical challenge. This is due to the implant being rigidly fixed to the bone and the tooth being attached to the bone with a periodontal ligament. In order to overcome this problem, various connection types such as rigid and nonrigid have been proposed. However, the mechanism of attachment and the perceived problem of the differential support provided by the implant and the tooth have been discussed by many authors, and the ideal connection type is still controversial. The aim of this study was to carry out a review of all available literature addressing the tooth-implant connection and evidence-based understanding of the management of tooth-implant-retained restorations.

Biomechanical comparison of two different collar structured implants supporting 3-unit fixed partial denture: A 3-D FEM study

Abstract Objective. The purpose of the study was to compare the effects of two distinct collar geometries of implants on stress distribution in the bone as well as in the fixture-abutment complex, in the framework and in the veneering material of 3-unit fixed partial denture (FPD). Material and methods. The 3-dimensional finite element analysis method was selected to evaluate the stress distribution in the system composed of 3-unit FPD supported by two different dental implant systems with two distinct collar geometries; microthread collar structure (MCS) and non-microthread collar structure (NMCS). In separate load cases, 300 N vertical, 150 N oblique and 60 N horizontal, forces were utilized to simulate the multidirectional chewing forces. Tensile and compressive stress values in the cortical and cancellous bone and von Mises stresses in the fixture-abutment complex, in the framework and veneering material, were simulated as a body and investigated separately. Results. In the cortical bone lower stress values were found in the MCS model, when compared with NMCS. In the cancellous bone, lower stress values were observed in the NMCS model when compared with MCS. In the implant-abutment complex, highest von Mises stress values were noted in the NMCS model; however, in the framework and veneering material, highest stress values were calculated in MCS model. Conclusions. MCS implants when compared with NMCS implants supporting 3-unit FPDs decrease the stress values in the cortical bone and implant-abutment complex. The results of the present study will be evaluated as a base for our ongoing FEA studies focused on stress distribution around the microthread and non-microthread collar geometries with various prosthesis design.

Biomechanical effects of two different collar implant structures on stress distribution under cantilever fixed partial dentures

Abstract Objective. The purpose of the study was to compare the effects of two distinct collar geometries of implants on stress distribution in the bone around the implants supporting cantilever fixed partial dentures (CFPDs) as well as in the implant-abutment complex and superstructures. Materials and methods. The three-dimensional finite element method was selected to evaluate the stress distribution. CFPDs which was supported by microthread collar structured (MCS) and non-microthread collar structured (NMCS) implants was modeled; 300 N vertical, 150 N oblique and 60 N horizontal forces were applied to the models separately. The stress values in the bone, implant-abutment complex and superstructures were calculated. Results. In the MCS model, higher stresses were located in the cortical bone and implant-abutment complex in the case of vertical load while decreased stresses in cortical bone and implant-abutment complex were noted within horizontal and oblique loading. In the case of vertical load, decreased stresses have been noted in cancellous bone and framework. Upon horizontal and oblique loading, a MCS model had higher stress in cancellous bone and framework than the NMCS model. Higher von Mises stresses have been noted in veneering material for NMCS models. Conclusion. It has been concluded that stress distribution in implant-supported CFPDs correlated with the macro design of the implant collar and the direction of applied force.

A Comparative Study on the Mechanical Properties of a Polymer-Infiltrated Ceramic-Network Material Used for the Fabrication of Hybrid Abutment

Polymer-infiltrated ceramic-network (PICN) material is a new type of material used for the hybrid abutments of dental implants. This study aimed to compare flexural strength, bond strengths, and fracture-resistance values of PICN with lithium disilicate ceramic (LDS) and to evaluate the effect of thermocycling on the tested parameters. Twenty specimens were fabricated using computer-aided design and manufacturing (CAD-CAM) technology for each material according to three-point bending (n = 10), microshear bond strength (µSBS), and a fracture-resistance test (hybrid abutment, n = 10). All specimens of each test group were divided into two subgroups, thermocycled or nonthermocycled. Hybrid abutments were cemented on titanium insert bases and then fixed on implants to compare fracture resistance. Failure loads were recorded for each test and data were statistically analyzed. Thermocycling decreased bond strength to the resin luting agent and the fracture-resistance values of both materials (p < 0.001), whereas flexural-strength values were not affected. LDS ceramic showed significantly higher flexural strength, bond strength, and fracture-resistance values than PICN material (p < 0.001). Within the limitations of this study, LDS may be a preferable hybrid-abutment material to PICN in terms of mechanical and bonding properties.

Effectiveness of non-fluoride and fluoride dentifrices for denture hygiene.

Abstract Objective: To compare the effectiveness of commonly used herbal/non-fluoride with fluoride dentifrices in order to eliminate pathogenic oral microorganisms from denture base material. Materials and methods: Heat-polymerized acrylic resin specimens (n = 288) were divided into three groups and each group inoculated with three various microorganisms (n = 96 for each) Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa (P. aeruginosa). Contaminated specimens were randomly assigned to the application of six herbal/non-fluoride and three fluoride dentifrices. These specimens were divided into two groups: negative and positive control (n = 3 for each). All acrylic specimens were incubated at 37 °C for 24 h for samples inoculated with bacterial strains and 37 °C for 48 h for samples inoculated with yeast strains. After the incubation period, all brain–heart infusion broths that contained disinfectant acrylic specimens were cultured on 5% sheep blood agar for bacterial counts and Sabouraud dextrose agar for yeast counts. The number of colony-forming units per millilitre (CFU/mL) were calculated. The results were analysed by Mann–Whitney U and Kruskal–Wallis tests (p = .05). Results: Both herbal/non-fluoride and fluoride dentifrices were effective against Candida albicans. However, fluoride dentifrices were comparatively better than the herbal/non-fluoride dentifrices against Staphylococcus aureus and P. aeruginosa. Conclusions: Herbal dentifrices could be used, especially among the elderly who lack a degree of manual dexterity during the rinsing of dentifrice chemicals from their dentures.

Bonding strategies of resin cement to Er,Cr:YSGG lased dentin: micro-CT evaluation and microshear bond strength testing

Aims Pretreatment of the tooth surface is essential for establishing effective micromechanical retention between it and the restoration. The purpose of this study was to evaluate the bond strength between the resin and the Er, Cr:YSGG laser irradiated dentin and to examine morphologic characterization of the dentin-resin interface. In addition, the study evaluated the quantity of opened and closed dentinal tubules. Subjects and Methods Thirty extracted human molars were sectioned into samples of 1 mm thickness. The samples were randomly assigned to two groups containing 15 specimens each. Surface treatments were not applied to the samples in the control group and the samples in the experimental group were irradiated with an Er,Cr:YSGG laser. Two resin cement samples were polymerized on the surface of each sliced dentin. The micro-shear bond strength (μSBS) between dentin and cement (n = 30 for each group) was measured with a universal testing machine. The topography and morphology of the resin-dentin interface were evaluated by micro-CT (n = 20 for each group). The areas of closed tubular space, closed porosity, area of open tubular space, open porosity, total area of tubular space and fractal dimension were investigated by micro-CT. Statistical analysis used: The data for each parameter were analyzed by Shapiro-Wilk and Students t test (p<0.05). Results μSBS values for control group were higher than experimental group. Dentin surfaces in the control group revealed less closed and more opened dentin tubules compared to the experimental group. Total area of tubular space was found to have decreased due to the laser ablation. There was no significant difference between the fractal dimensions of the control and experimental groups. Conclusions The lased dentin surface was not favorable for the bonding mechanism due to alterations in the dentinal structure.

Dental Ethiology Triggering Pressure Dermographism: A Case Report

Patients undergoing dental treatment may be exposed to complications such as allergic reactions. Patients with symptoms of stomatitis, burning mouth, etc. are usually experiencing hypersensitivity reactions due to the prosthetic materials after the prosthetic rehabilitation,. Patch testing is a diagnostic test for type IV hypersensitivity reactions. Another infrequent complication release after prosthetic treatment can be dermographism. We presented a case and discuss the significance and principles of management. In the presented case, after the prosthodontic treatment, erytheme itch and pain on the oral mucosa were recorded. The patient was allergy tested by means of patch test on the upper back. No irritantion reaction was observed on testing sites. However, red dermographic line of contact has developed with small islands of edema. She was then tested at the clinic for pressure urticaria, and the test was considered positive.