Jaafar Abduo

Clinical considerations for increasing occlusal vertical dimension: a review.

The purpose of this article is to discuss the clinical considerations related to increasing the occlusal vertical dimension (OVD) when restoring a patients dentition. Thorough extraoral and intraoral evaluations are mandatory to assess the suitability of increasing OVD. In the literature, multiple techniques have been proposed to quantify OVD loss. However, the techniques lack consistency and reliability, which in turn affects the decision of whether to increase the OVD. Therefore, increasing OVD should be determined on the basis of the dental restorative needs and aesthetic demands. In general, a minimal increase in OVD should be applied, though a 5 mm maximum increase in OVD can be justified to provide adequate occlusal space for the restorative material and to improve anterior teeth aesthetics. The literature reflects the safety of increasing the OVD permanently, and although signs and symptoms may develop, these are usually of an interim nature. Whenever indicated, the increase in OVD should be achieved with fixed restorations rather than a removable appliance, due to the predictable patient adaptation. The exception to this is for patients with TMD, where increasing the OVD should still be achieved using removable appliances to control TMD-associated symptoms before considering any form of irreversible procedure.

Trends in computer-aided manufacturing in prosthodontics: A review of the available streams

In prosthodontics, conventional methods of fabrication of oral and facial prostheses have been considered the gold standard for many years. The development of computer-aided manufacturing and the medical application of this industrial technology have provided an alternative way of fabricating oral and facial prostheses. This narrative review aims to evaluate the different streams of computer-aided manufacturing in prosthodontics. To date, there are two streams: the subtractive and the additive approaches. The differences reside in the processing protocols, materials used, and their respective accuracy. In general, there is a tendency for the subtractive method to provide more homogeneous objects with acceptable accuracy that may be more suitable for the production of intraoral prostheses where high occlusal forces are anticipated. Additive manufacturing methods have the ability to produce large workpieces with significant surface variation and competitive accuracy. Such advantages make them ideal for the fabrication of facial prostheses.

A comparison of fit of CNC-milled titanium and zirconia frameworks to implants.

BACKGROUND Computer numeric controlled (CNC) milling was proven to be predictable method to fabricate accurately fitting implant titanium frameworks. However, no data are available regarding the fit of CNC-milled implant zirconia frameworks. PURPOSE To compare the precision of fit of implant frameworks milled from titanium and zirconia and relate it to peri-implant strain development after framework fixation. MATERIALS AND METHODS A partially edentulous epoxy resin models received two Branemark implants in the areas of the lower left second premolar and second molar. From this model, 10 identical frameworks were fabricated by mean of CNC milling. Half of them were made from titanium and the other half from zirconia. Strain gauges were mounted close to the implants to qualitatively and quantitatively assess strain development as a result of framework fitting. In addition, the fit of the framework implant interface was measured using an optical microscope, when only one screw was tightened (passive fit) and when all screws were tightened (vertical fit). The data was statistically analyzed using the Mann-Whitney test. RESULTS All frameworks produced measurable amounts of peri-implant strain. The zirconia frameworks produced significantly less strain than titanium. Combining the qualitative and quantitative information indicates that the implants were under vertical displacement rather than horizontal. The vertical fit was similar for zirconia (3.7 µm) and titanium (3.6 µm) frameworks; however, the zirconia frameworks exhibited a significantly finer passive fit (5.5 µm) than titanium frameworks (13.6 µm). CONCLUSIONS CNC milling produced zirconia and titanium frameworks with high accuracy. The difference between the two materials in terms of fit is expected to be of minimal clinical significance. The strain developed around the implants was more related to the framework fit rather than framework material.

A novel in vitro approach to assess the fit of implant frameworks

OBJECTIVE To introduce a new strain gauge approach to assess the fit of fixed implant frameworks. MATERIALS AND METHODS A partially edentulous epoxy resin mandible model received two Straumann implants in the area of the lower left second premolar and second molar. The model was used to fabricate four zirconia and four identical cobalt-chromium alloy frameworks using a laboratory computer-aided design/computer-aided manufacturing (CAD/CAM) system. A total of four linear strain gauges were then bonded around each implant on the peri-implant structure (mesial, distal, buccal, and lingual). The experimental part was composed of two phases: qualitative and quantitative. For the qualitative assessment, the model was verified by recording the response of each strain gauge while applying a near-constant force of known directions on each implant. For the quantitative phase, the frameworks were attached on the implants and the screws were torqued to 15 N cm. RESULTS In the qualitative phase, the strain gauge response to every force direction was recorded. After attaching the frameworks, all frameworks produced measurable strains, but with different strain patterns. Upon correlating the two phases, the zirconia frameworks were found to be slightly smaller than the inter-implant distance, whereas the cobalt-chromium alloy frameworks tended to be slightly larger than the inter-implant distance. CONCLUSIONS The proposed technique is not only valid for detecting implant framework misfit but also for determining the form of inaccuracies. Model verification is an essential informative step to aid the interpretation of the pattern of framework distortion.

Effect of vertical misfit on strain within screw-retained implant titanium and zirconia frameworks

PURPOSE To assess the implication of vertical misfit on strain within implant frameworks manufactured in titanium or zirconia. METHODS A master model was fabricated by inserting a Brånemark implant in left side of a mandibular model in the area of the first premolar and the first molar. This model was used to fabricate identical frameworks, five in titanium and five in zirconia. A single strain gauge was mounted on the occlusal surface of each framework to assess strain development as a result of framework fitting. In addition, the peak-to-peak strain amplitude was measured for each framework to determine the strain pattern fluctuation. The vertical gap of the framework-implant interface was measured using a measuring microscope, when only one screw was tightened (1-screw test) and when both screws were tightened (2-screw test). The vertical fit of the frameworks was altered by adding one to three layers of 30 μm steel shims on one of the implants. RESULTS For all fitting conditions, measurable amount of strains were recorded, however, as the vertical misfit was introduced, linear increase in framework strain was detected. The titanium and zirconia frameworks exhibited similar strain activities. A direct relationship was observed between the framework strain and vertical gap. CONCLUSIONS Framework misfit clearly influenced the framework strain magnitude and pattern. The framework material did not affect the framework strain for a similar level of misfit.

Rationale for the use of CAD/CAM technology in implant prosthodontics.

Despite the predictable longevity of implant prosthesis, there is an ongoing interest to continue to improve implant prosthodontic treatment and outcomes. One of the developments is the application of computer-aided design and computer-aided manufacturing (CAD/CAM) to produce implant abutments and frameworks from metal or ceramic materials. The aim of this narrative review is to critically evaluate the rationale of CAD/CAM utilization for implant prosthodontics. To date, CAD/CAM allows simplified production of precise and durable implant components. The precision of fit has been proven in several laboratory experiments and has been attributed to the design of implants. Milling also facilitates component fabrication from durable and aesthetic materials. With further development, it is expected that the CAD/CAM protocol will be further simplified. Although compelling clinical evidence supporting the superiority of CAD/CAM implant restorations is still lacking, it is envisioned that CAD/CAM may become the main stream for implant component fabrication.

Implications of implant framework misfit: a systematic review of biomechanical sequelae.

PURPOSE The objective of this study was to review all biomechanical investigations that have evaluated the implications of implant framework misfit with fixed prostheses. MATERIALS AND METHODS A detailed electronic search was conducted of PubMed (MEDLINE), Google Scholar, and Cochrane Library with the aid of Boolean operators to combine relevant key words. The search was confined to articles published in English through April 2013. The literature search was enlarged by manual searches of the peer-reviewed literature and the reference lists of the selected articles. RESULTS A total of 633 articles were retrieved from the initial search; however, only 28 articles met the determined inclusion criteria of the review. According to the study design, the selected articles were classified into two categories: laboratory studies (finite element analyses, actual model analyses, and screw stability analyses) and animal studies. The studies evaluated the effects of alterations in the magnitude and configuration of misfit, framework rigidity, type of retaining screws, and implant loading time. In addition to a lack of clear criteria of what constitutes an accurate implant framework fit, the biomechanical implications of framework misfit are unclear. CONCLUSIONS Although implant framework misfit alters the biomechanical situation, negative biomechanical sequelae could not be confirmed from the included studies. Biologically, bone resorption cannot develop as a result of framework misfit. From a mechanical perspective, the framework stresses and screw stresses and instability increase with misfit, but the clinical significance of this remains unclear.

Fit of CAD/CAM Implant Frameworks: A Comprehensive Review

Computer-aided design and computer-aided manufacturing (CAD/CAM) is a strongly emerging prosthesis fabrication method for implant dentistry. Currently, CAD/CAM allows the construction of implant frameworks from different materials. This review evaluates the literature pertaining to the precision fit of fixed implant frameworks fabricated by CAD/CAM. Following a comprehensive electronic search through PubMed (MEDLINE), 14 relevant articles were identified. The results indicate that the precision fit of CAD/CAM frameworks exceeded the fit of the 1-piece cast frameworks and laser-welded frameworks. A similar fit was observed for CAD/CAM frameworks and bonding of the framework body to prefabricated cylinders. The influence of CAD/CAM materials on the fit of a framework is minimal.

Three-dimensional image registration as a tool for forensic odontology: a preliminary investigation.

AbstractFrequently, human dentition is utilized for victim identification. This report introduces a new human identification technique based on the principle of 3-dimensional (3D) image registration of the dentition. With the aid of a dry human skull, postmortem (PM) and antemortem (AM) scenarios were assumed. The skull in its initial state composed the PM scenario. Virtual 3D PM images were reconstructed from medical CT images. The AM scenario was achieved by reconstructing the missing hard and soft tissues of the skull by dental waxes. Virtual 3D AM images were obtained by laser surface scanning. The virtual PM and AM images were registered at 2 levels: arch level and tooth level. At arch level, the deviation between the 2 images was 0.147 mm for the maxilla and 0.166 mm for the mandible. At tooth level, the deviation average ranged from 0.077 to 0.237 mm. Qualitatively, even image fit was observed for the arches, intact teeth, and teeth with minimal deficiencies. As the tooth defect increased, the alignment discrepancy increased. It is concluded that 3D image registration ensured an accurate superimposition of the 3D images and can be used as a robust tool for forensic identification.

Lateral occlusion schemes in natural and minimally restored permanent dentition: a systematic review.

Clinicians commonly encounter the dilemma of which lateral occlusion schemes is most suitable for a specific patient. The aim of this review is to evaluate the prevalence of the lateral occlusion schemes that exist naturally. An electronic search was completed through PubMed (MEDLINE), Google Scholar and Cochrane Library. The search was confined to peer-reviewed studies published in English, up to April 2013. The literature search was supplemented by manual searching through the bibliography lists of the selected studies. The initial search retrieved a total of 575 studies. After applying the selection criteria, only 12 studies were suitable for inclusion. The Critical Appraisal Skills Programme (CASP) tools were utilised to appraise the quality of the studies. The prevalence of canine-guided, group function and balanced occlusions was reported. Overall, there was a clear variability between the studies. The prevalence of the lateral occlusion schemes appears to be influenced by the following factors: (i) the magnitude of excursion, (ii) an individuals age and (iii) the static occlusal relationship. During complete excursion, the canine-guided occlusion tends to be more frequently observed. After partial excursion, the most prevalent lateral occlusion schemes was group function occlusion. With ageing, the prevalence of canine-guided occlusion tends to be reduced and the prevalence of group function occlusion is increased. Dentition that is closer to Class II occlusion exhibits mainly canine-guided occlusion, while for Class III occlusion, group function occlusion is more prevalent. The studies revealed no relationship between the lateral occlusion schemes and TMD development.