Showing papers by "Jaafar Abduo published in 2019"
TL;DR: For whole arch accuracy, casts produced from IOS were inferior to those produced from PVS and ALG, and the inferior outcome of IOS appears to be related to the span of scanning.
Abstract: Purpose Comparing the accuracy of casts produced from digital workflow to that of casts produced from conventional techniques. Materials and methods Whole arch alginate (ALG) and polyvinyl siloxane (PVS) impressions were taken with stock trays and custom trays, respectively. The ALG impressions were poured with type III dental stone, while the PVS impressions were poured with type IV dental stone. For the digital workflow, IOS impressions were taken and physical casts were produced by 3D printing. In addition, 3D printed casts were produced from images obtained from a laboratory scanner (LS). For each technique, a total of 10 casts were produced. The accuracies of the whole arch and separated teeth were virtually quantified. Results Whole arch cast accuracy was more superior for PVS followed by LS, ALG, and IOS. The PVS and ALG groups were inferior in the areas more susceptible to impression material distortion, such as fossae and undercut regions. The LS casts appeared to have generalized errors of minor magnitude influencing primarily the posterior teeth. The IOS casts were considerably more affected at the posterior region. On the contrary, the IOS and LS casts were more superior for single tooth accuracy followed by PVS and ALG. Conclusion For whole arch accuracy, casts produced from IOS were inferior to those produced from PVS and ALG. The inferior outcome of IOS appears to be related to the span of scanning. For single tooth accuracy, IOS showed superior accuracy compared to conventional impressions.
24 citations
TL;DR: Occlusal loading of the natural tooth results in lower stress-strain magnitudes in the underlying alveolar bone than those associated with a dental implant of matched occlusal anatomy, and the PDL may function to mitigate axial and bending stress intensities resulting from off-centered Occlusal loads.
Abstract: PURPOSE While dental implants have displayed high success rates, poor mechanical fixation is a common complication, and their biomechanical response to occlusal loading remains poorly understood. This study aimed to develop and validate a computational model of a natural first premolar and a dental implant with matching crown morphology, and quantify their mechanical response to loading at the occlusal surface. MATERIALS AND METHODS A finite-element model of the stomatognathic system comprising the mandible, first premolar and periodontal ligament (PDL) was developed based on a natural human tooth, and a model of a dental implant of identical occlusal geometry was also created. Occlusal loading was simulated using point forces applied at seven landmarks on each crown. Model predictions were validated using strain gauge measurements acquired during loading of matched physical models of the tooth and implant assemblies. RESULTS For the natural tooth, the maximum vonMises stress (6.4 MPa) and maximal principal strains at the mandible (1.8 me, -1.7 me) were lower than those observed at the prosthetic tooth (12.5 MPa, 3.2 me, and -4.4 me, respectively). As occlusal load was applied more bucally relative to the tooth central axis, stress and strain magnitudes increased. CONCLUSION Occlusal loading of the natural tooth results in lower stress-strain magnitudes in the underlying alveolar bone than those associated with a dental implant of matched occlusal anatomy. The PDL may function to mitigate axial and bending stress intensities resulting from off-centered occlusal loads. The findings may be useful in dental implant design, restoration material selection, and surgical planning.
17 citations
TL;DR: The new tray design concept appeared to produce more accurate implant impressions than the other techniques, and the clinical significance of this difference is yet to be determined.
Abstract: Purpose To evaluate implant impression accuracy with a new tray design concept in comparison to nonsplinted and splinted impression techniques for a 2-implant situation. Materials and methods A reference bar titanium framework was fabricated to fit on 2 parallel implants. The framework was used to generate a resin master model with 2 implants that fit precisely against the framework. Three impression techniques were evaluated: (1) nonsplinted, (2) splinted, and (3) nonsplinted with modified tray impressions. All the trays were fabricated from light-cured acrylic resin material with openings that corresponded to the implant impression copings. Ten impressions were taken for each technique using poly(vinyl siloxane) impression material. The impressions were poured with type IV dental stone to generate the test casts. A rosette strain gauge was bonded to the middle of the framework. As the framework retaining screws were tightened on each test cast, the developed strains were recorded until the completion of the tightening to 35 Ncm. The generated strains of the rosette strain gauge were used to calculate the maximum principal strain. Results A statistically significant difference was observed among the different impression techniques. The modified tray design impression technique was associated with the least framework strains, which indicates greater accuracy compared with the other techniques. There was no significant difference between the splinted and the nonsplinted impression techniques. Conclusions The new tray design concept appeared to produce more accurate implant impressions than the other techniques. Despite the statistical difference among the impression techniques, the clinical significance of this difference is yet to be determined.
6 citations
TL;DR: Evaluated fits of zirconia custom abutments and frameworks on implants and to identify the factors that influence their fits appeared to exhibit slightly inferior fits compared with metal abUTments or abutment produced by the same implant company.
Abstract: Purpose The aim of this systematic review and meta-analyses was to evaluate fits of zirconia custom abutments and frameworks on implants and to identify the factors that influence their fits. Materials and methods An electronic search was conducted through PubMed (MEDLINE), Google Scholar, and Cochrane Central Registrar of Controlled Trials. The search was completed in August 2017. Series of meta-analyses were conducted to compare fits of zirconia custom abutments and frameworks on implants with metal abutments and frameworks. The interest variables were the interface gap and the rotational misfit of abutments and the vertical fit of frameworks. Results Initially, a total of 672 articles were identified from the electronic search. After applying the inclusion criteria, 17 suitable articles were selected, including 9 studies on the fit of zirconia custom abutments and 8 studies on the fit of zirconia frameworks. There is a tendency for zirconia abutments to exhibit greater interface gaps and rotational misfits than metal abutments. Abutments produced by manual-aided designs/manual-aided manufacturing (MAD/MAM) exhibited inferior fits compared with those produced by computer-aided design/computer-aided manufacturing (CAD/CAM). Proprietary abutments had superior fits compared with non-proprietary abutments. Milled zirconia frameworks had insignificantly inferior fits compared with milled metal frameworks. Conclusion Within the limitations of this study, custom zirconia abutments and non-proprietary abutments appeared to exhibit slightly inferior fits compared with metal abutments or abutments produced by the same implant company. However, the clinical significance of this difference is yet to be determined. The fit of milled zirconia frameworks is generally comparable to milled metal frameworks.
4 citations