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We present results of the updated SuperChic 3 Monte Carlo event generator for central exclusive production. This extends the previous treatment of proton-proton collisions to include heavy ion (pA and AA) beams, for both photon and QCD-initiated production, the first time such a unified treatment of exclusive processes has been presented in a single generator. To achieve this we have developed a theory of the gap survival factor in heavy ion collisions, which allows us to derive some straightforward results about the A scaling of the corresponding cross sections. We compare against the recent ATLAS and CMS measurements of light-by-light scattering at the LHC, in lead-lead collisions. We find that the background from QCD-initiated production is expected to be very small, in contrast to some earlier estimates. We also present results from new photon-initiated processes that can now be generated, namely the production of axion-like particles, monopole pairs and monopolium, top quark pair production, and the inclusion of W loops in light-by-light scattering.
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We investigate the impact of the high precision ATLAS and CMS 7 TeV measurements of inclusive jet production on the MMHT global PDF analysis at next-to-next-to-leading order (NNLO). This is made possible by the recent completion of the long-term project to calculate the NNLO corrections to the hard cross section. We find that a good description of the ATLAS data is not possible with the default treatment of experimental systematic errors, and propose a simplified solution that retains the dominant physical information of the data. We then investigate the fit quality and the impact on the gluon PDF central value and uncertainty when the ATLAS and CMS data are included in a MMHT fit. We consider both common choices for the factorization and renormalization scale, namely the inclusive jet transverse momentum, p ⥠, and the leading jet p ⥠, as well as the different jet radii for which the ATLAS and CMS data are made available. We find that the impact of these data on the gluon is relatively insensitive to these inputs, in particular the scale choice, while the inclusion of NNLO corrections tends to improve the data description somewhat and has a qualitatively similar though not identical impact on the gluon in comparison to NLO.
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OBJECTIVE: No controlled clinical study has evaluated Oral Health Related Quality of Life (OHRQOL) of immediately placed and loaded implants retaining mandibular overdentures. This pilot study evaluated the impact of immediate loading of delayed versus immediately placed dental implants on overdenture patients' OHRQOL. MATERIALS AND METHODS: Two patient treatment groups received a maxillary conventional complete denture, opposing a mandibular overdenture immediately loaded on implants with ball attachments; In group one a delayed implant placement surgical protocol was followed, whereas in group two, patients had mandibular teeth extracted and two implants immediately placed. OHRQOL for these patients was evaluated using a visual analog scale for 48 questions related to 6 domains; comfort, function, speech, esthetics, self-image and dental health. RESULTS: There was no significant difference between the two groups when comparing answers to the pre- and post-treatment questionnaires. Pooled data showed significant differences for all domains between the pre-treatment and post-treatment responses, denoting improvement after an implant retained mandibular overdenture was delivered. CONCLUSION: There was an improved quality of life in patients receiving immediately loaded mandibular overdentures supported by either delayed or immediately placed implants.
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Implantes Dentales , Prótesis Dental de Soporte Implantado , Prótesis de Recubrimiento , Calidad de Vida , Anciano , Diseño de Dentadura , Femenino , Humanos , Masculino , Mandíbula , Persona de Mediana Edad , Proyectos Piloto , Encuestas y Cuestionarios , Factores de TiempoRESUMEN
We investigate the variation in the MMHT2014 PDFs when we allow the heavy-quark masses [Formula: see text] and [Formula: see text] to vary away from their default values. We make PDF sets available in steps of [Formula: see text] and [Formula: see text], and present the variation in the PDFs and in the predictions. We examine the comparison to the HERA data on charm and beauty structure functions and note that in each case the heavy-quark data, and the inclusive data, have a slight preference for lower masses than our default values. We provide PDF sets with three and four active quark flavours, as well as the standard value of five flavours. We use the pole mass definition of the quark masses, as in the default MMHT2014 analysis, but briefly comment on the [Formula: see text] definition.
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We investigate the effect of including the HERA run I + II combined cross section data on the MMHT2014 PDFs. We present the fit quality within the context of the global fit and when only the HERA data are included. We examine the changes in both the central values and the uncertainties in the PDFs. We find that the prediction for the data is good, and only relatively small improvements in [Formula: see text] and changes in the PDFs are obtained with a refit at both NLO and NNLO. PDF uncertainties are slightly reduced. There is a small dependence of the fit quality on the value of [Formula: see text]. This can be improved by phenomenologically motived corrections to [Formula: see text] which parametrically are largely in the form of higher-twist type contributions.
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We investigate the uncertainty in the strong coupling [Formula: see text] when allowing it to be a free parameter in the recent MMHT global analyses of deep-inelastic and related hard scattering data that was undertaken to determine the parton distribution functions (PDFs) of the proton. The analysis uses the standard framework of leading twist fixed-order collinear factorisation in the [Formula: see text] scheme. We study the constraints on [Formula: see text] coming from individual data sets by repeating the NNLO and NLO fits spanning the range 0.108 to 0.128 in units of 0.001, making all PDFs sets available. The inclusion of the cross section for inclusive [Formula: see text] production allows us to explore the correlation between the mass [Formula: see text] of the top quark and [Formula: see text]. We find that the best-fit values are [Formula: see text] and [Formula: see text] at NLO and NNLO, respectively, with the central values changing to [Formula: see text] and 0.1178 when the world average of [Formula: see text] is used as a data point. We investigate the interplay between the uncertainties on [Formula: see text] and on the PDFs. In particular we calculate the cross sections for key processes at the LHC and show how the uncertainties from the PDFs and from [Formula: see text] can be provided independently and be combined.
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We present LO, NLO and NNLO sets of parton distribution functions (PDFs) of the proton determined from global analyses of the available hard scattering data. These MMHT2014 PDFs supersede the 'MSTW2008' parton sets, but they are obtained within the same basic framework. We include a variety of new data sets, from the LHC, updated Tevatron data and the HERA combined H1 and ZEUS data on the total and charm structure functions. We also improve the theoretical framework of the previous analysis. These new PDFs are compared to the 'MSTW2008' parton sets. In most cases the PDFs, and the predictions, are within one standard deviation of those of MSTW2008. The major changes are the [Formula: see text] valence quark difference at small [Formula: see text] due to an improved parameterisation and, to a lesser extent, the strange quark PDF due to the effect of certain LHC data and a better treatment of the [Formula: see text] branching ratio. We compare our MMHT PDF sets with those of other collaborations; in particular with the NNPDF3.0 sets, which are contemporary with the present analysis.
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OBJECTIVE: Peer assessment is grounded in philosophies of active learning, and it would seem that this tool is a viable method for critical thinking development. The purpose of this article was to present how junior students at Case Western Reserve University School of Dental Medicine (CWRU) perceive the value of a peer-assessment activity in the context of a treatment planning course. METHODOLOGY: As a part of the final exam for the junior year Treatment Planning course, students were requested to evaluate a de-identified assignment submitted by one of their peers. Following the exam, a survey was sent to the students to determine how they perceived the peer-assessment activity and how this relates to other learning experiences in the course. RESULTS: Our results show that students' perception of the benefit of peer grading was not associated with any individual peer-assignment characteristics, or course characteristics. Similar results were obtained regarding the perceived benefit of identifying evidence. Moderate correlations were observed between peer evaluation characteristics. CONCLUSIONS: It was concluded that: (i) junior dental students are not homogenous in their opinions regarding the value of an activity related to evaluation of a peer's assignment and (ii) student's perceptions regarding the peer-grading component of peer assessment were not correlated with perceptions related to other learning processes in the treatment planning course.
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Educación en Odontología/métodos , Evaluación Educacional/métodos , Planificación de Atención al Paciente , Revisión por Pares , Estudiantes de Odontología/psicología , Adulto , Femenino , Humanos , Masculino , Percepción , Encuestas y CuestionariosRESUMEN
Motivated by evidence for the existence of dark matter, many new physics models predict the pair production of new particles, followed by the decays into two invisible particles, leading to a momentum imbalance in the visible system. For the cases where all four components of the vector sum of the two "missing" momenta are measured from the momentum imbalance, we present analytic solutions of the final state system in terms of measurable momenta, with the mass shell constraints taken into account. We then introduce new variables which allow the masses involved in the new physics process, including that of the dark matter particles, to be extracted efficiently. These are compared with a selection of variables in the literature, and possible applications at lepton and hadron colliders are discussed.
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STATEMENT OF PROBLEM: New processing techniques have facilitated the use of zirconia core materials in all-ceramic dental prostheses. Zirconia has many potential advantages compared to existing core materials; however, its performance when layered with porcelain has not been evaluated. PURPOSE: This study investigated the strength of a wide variety of layered zirconia and porcelain beams to determine whether the inclusion of zirconia cores results in improved strength. MATERIAL AND METHODS: Eight types of layered or simple zirconia and porcelain beams (n = 10), approximately fixed partial denture-size, were made of a tetragonal polycrystalline zirconium dioxide partially stabilized with yttria core (Lava System Frame) and a feldspathic dental porcelain (Lava Ceram veneer ceramic). Elastic moduli of the materials were measured using an acoustic method. Maximum force and modulus of rupture were determined using 3-point flexural testing and a universal testing machine. Descriptive statistical methods were used. RESULTS: Beams with porcelain tensile surfaces recorded mean tensile strengths or moduli of rupture from 77 to 85 MPa, whereas beams with zirconia tensile surfaces recorded moduli of rupture almost an order of magnitude higher, 636 to 786 MPa. The elastic moduli of the porcelain and zirconia materials were 71 and 224 GPa, respectively. Crack propagation following initial tensile cracking often involved the porcelain-zirconia interface, as well as bulk porcelain and zirconia. CONCLUSION: The layered zirconia-porcelain system tested recorded substantially higher moduli of rupture than have been previously reported for other layered all-ceramic systems.
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Porcelana Dental , Itrio , Circonio , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Coronas con Frente Estético , Elasticidad , Ensayo de Materiales , Docilidad , Resistencia a la TracciónRESUMEN
STATEMENT OF PROBLEM: In vitro dental materials strength testing of ceramic restorations primarily has involved mechanical evaluations of simplified models. The finite element method (FEM) provides a mathematic analysis to predict strength values, but neither methodology is without the potential for errors. PURPOSE: The purpose of this study was to demonstrate the advantages of combining mechanical testing results and FEM data to determine the strengths of a layered ceramic beam when the layered materials and positions are varied. MATERIAL AND METHODS: Eight finite element 5 x 20 x 1-mm layered beams were modeled. Four of the modeled beams were of the same layered arrangements as physical specimens from a previously published study. The remaining 4 modeled beams provided intermediate layered arrangements not evaluated in the earlier study. A force in newtons was applied in the center of the top layer of each beam until fracture. finite element analysis was performed, and the data were compared with mechanical strength test results from the earlier study. RESULTS: The FEM data of the 8 models demonstrated a linear decrease in load-bearing capacity as the layer thickness of the core material decreased and the layer thickness of the veneer material increased. The progressively decreasing values for the FEM beams were 170, 144, 140, 134, 72, 43, 34, and 27 N. The mean load-bearing capacities of 3 of the 4 mechanically tested beams compared favorably with the FEM data. The strength of the fourth mechanically tested beam, a veneer/core layered arrangement, was 110 N, which was lower than the corresponding FEM value (140 N). The 110 N value fell outside the decreasing linear progression for load, indicating that the FEM data were more accurate and reliable than the mechanical data. CONCLUSION: No one perfect method exists for testing the strength of dental materials. The best approach is to use the results from both mechanical testing and finite element analysis, which together may provide more reliable and valid data than either method alone.
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Porcelana Dental , Análisis del Estrés Dental/métodos , Análisis de Elementos Finitos , Ensayo de Materiales/métodos , Óxido de Aluminio , Fuerza Compresiva , Coronas con Frente Estético , Reproducibilidad de los Resultados , Estrés Mecánico , Resistencia a la TracciónRESUMEN
STATEMENT OF PROBLEM: Severe thermal stresses caused by food-induced temperature changes may result in dowel-and-core failure. PURPOSE: This study investigated the influence of thermal stresses on various combinations of dowel-and-core materials of a restored endodontically treated incisor. MATERIAL AND METHODS: A 2-dimensional finite element model was constructed in a labiolingual cross-sectional view of a maxillary central incisor, a dowel, a core, and the supporting tissues to investigate thermal stress distribution. Four combinations of dowel-and-core materials were used: (1) gold/gold, (2) stainless steel/resin composite, (3) stainless steel/amalgam, and (4) carbon fiber-reinforced composite/resin composite. For thermal analysis, a cold irritant (0 degrees C) was applied on the outer surface of a metal-ceramic crown for 7 seconds. RESULTS: The metal dowel and core generated lower thermal stresses in the restorations and dentin than the nonmetallic dowel and cores. CONCLUSION: Stress level is closely related to the degree of thermal gradient. The nonmetallic dowel and cores generated greater thermal stresses than metal dowel and cores.
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Materiales Dentales/química , Técnica de Perno Muñón , Temperatura Corporal/fisiología , Carbono/química , Fibra de Carbono , Frío , Resinas Compuestas/química , Coronas , Aleaciones Dentales/química , Amalgama Dental/química , Diseño de Prótesis Dental , Dentina/fisiología , Análisis de Elementos Finitos , Aleaciones de Oro/química , Calor , Humanos , Incisivo , Aleaciones de Cerámica y Metal/química , Modelos Biológicos , Tratamiento del Conducto Radicular , Acero Inoxidable/química , Estadística como Asunto , Temperatura , Termodinámica , Cemento de Fosfato de Zinc/químicaRESUMEN
STATEMENT OF PROBLEM: Complications such as loosening of the dowel and core or fracture of the remaining tooth root can be influenced by many factors, including the amount of remaining dentin, direction of the occlusal load, and design of the dowel. Most stress analyses of dowel and cores were conducted without including all aspects of the restorations and supporting structures. PURPOSE: The purpose of this study was to investigate the influence of occlusal stresses on various dowel designs in a restored, endodontically treated maxillary incisor by using a 2-dimensional finite element analysis model. MATERIAL AND METHODS: A 2-dimensional finite element model was constructed in a labiolingual cross-sectional view of a maxillary central incisor, a dowel, a core, and the supporting tissues to investigate stresses in various dowel designs. As a control, a metal-ceramic crown on an endodontically treated tooth without a dowel and core was modeled. A 10-kg force was applied as follows: (1) in a vertical load on the incisal edge, (2) in a horizontal load on the labial surface, and (3) in a 20-degree diagonal load on the lingual surface. RESULTS: The use of a dowel reduced the peak dentinal stress to 75% of the magnitude of the control. When a vertical force was applied, the magnitudes of stress of the various dowel designs were similar; however, when loaded horizontally, the short dowel produced the greatest dentinal stress concentration, and the tapered dowel showed the greatest stress concentration within the cement layer. Greater deflections and higher stresses were generated with horizontal loading. CONCLUSION: The dowel and core provided little reinforcement to the remaining tooth. The direction of the functional load had a greater effect than dowel design on maximum stress and displacement. Parallel-sided dowel and cores with a length of 12 mm distributed the stress widely in the restoration and dentin, resulting in the smallest stresses.
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Diseño de Prótesis Dental , Análisis de Elementos Finitos , Técnica de Perno Muñón , Fuerza de la Mordida , Simulación por Computador , Coronas , Porcelana Dental/química , Fracaso de la Restauración Dental , Dentina/patología , Dentina/fisiopatología , Aleaciones de Oro/química , Gutapercha/química , Humanos , Incisivo/fisiopatología , Maxilar/fisiopatología , Aleaciones de Cerámica y Metal/química , Modelos Biológicos , Ligamento Periodontal/fisiopatología , Materiales de Obturación del Conducto Radicular/química , Tratamiento del Conducto Radicular , Estrés Mecánico , Propiedades de Superficie , Fracturas de los Dientes/etiología , Raíz del Diente/lesiones , Cemento de Fosfato de Zinc/químicaRESUMEN
OBJECTIVE: This study was designed to compare 5 modalities with respect to accuracy in mandibular cross-sectional imaging. The modalities tested were tuned-aperture computed tomography (TACT), iteratively reconstructed TACT, multidirectional tomography, linear tomography, and transverse panoramic tomography. STUDY DESIGN: Twenty sites were selected from 3 dry human mandibles, and cross-sectional views were imaged through use of each of the 5 modalities. A quantitative analysis included measurements of 2 linear distances; a qualitative study included image evaluation by 6 observers. A nested mixed analysis of variance model was used to control for mandibles and locations within mandibles for the quantitative analysis; the Cochran-Mantel-Haenszel test was used for the qualitative analysis. RESULTS: There was a significant difference in measurement error for maximum height but not for width. There was also a significant difference in qualitative image evaluation results. CONCLUSIONS: Of the 5 modalities tested, the narrow-layer multidirectional tomographic technique produced the greatest diagnostic accuracy and quality in cross-sectional imaging. The transverse panoramic tomographic technique produced the least diagnostic accuracy and quality. Linear tomography, TACT, and iteratively reconstructed TACT were intermediate in accuracy and quality.
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Mandíbula/diagnóstico por imagen , Radiografía Panorámica/métodos , Tomografía Computarizada por Rayos X/métodos , Tomografía por Rayos X/métodos , Análisis de Varianza , Anatomía Transversal , Cefalometría , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Arcada Edéntula/diagnóstico por imagen , Variaciones Dependientes del Observador , Intensificación de Imagen Radiográfica/métodos , Estadísticas no ParamétricasRESUMEN
PURPOSE: Methods of incorporating radiopaque triphenylbismuth into an experimental compression-molded and injection-molded heat-polymerized resins were determined. The transverse flexural properties, radiopacity, and color stability of the resins containing triphenylbismuth were then compared with a commercially available, compression-molded denture resin. MATERIALS AND METHODS: Varying levels of triphenylbismuth were added to both the monomer and polymer in heat-polymerized denture resin systems to determine the level of the additive that was necessary to achieve a radiopacity similar to 0.2 mm of copper with minimum resin porosity. Specimens were then prepared by incorporating 0% or 30% wt/wt triphenylbismuth into resins. The commercially available polymethyl methacrylate resin served as a benchmark for physical property comparison, and no additive was included during its polymerization. At 30% wt/wt triphenylbismuth, resin color stability, transverse deflection, and radiopacity were evaluated using methods described in International Standards Organization Standard 4049 and American Dental Association Specification No. 12. The transverse deflection results among the resin groups were compared with a reference resin using the Kruskal-Wallis method (alpha = 0.05). RESULTS: Incorporation of triphenylbismuth into the monomer of the injection material, resulting in 30% wt/wt in the polymerized resin, produced a level of radiopacity similar to 0.2 mm copper. Although the injection-molded resin with 30% wt/wt triphenylbismuth remained translucent, the compression-molded resin was opaque, indicating excessive air-entrapment porosity. The additive caused a faint yellowing in both types of resins, but color stability was not affected. Transverse deflection of the injection-molded resin (4.5 +/- 0.5 mm) and the injection-molded resin with triphenylbismuth (3.8 +/- 1.7 mm) was greater than that of the experimental resin (3.5 +/- 0.2 mm), which was equal to the commercial resin (3.6 +/- 0.2 mm). Triphenylbismuth at 30% wt/wt significantly reduced transverse deflection for the experimental resin (2.6 +/- 0.5 mm). CONCLUSIONS: Triphenylbismuth at a final concentration of 30% wt/wt can be added to polymethyl methacrylate injection-molded resins to provide a high level of detection on chest or abdominal radiographs without adversely affecting resin color stability and transverse deflection.
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Bismuto/química , Medios de Contraste/química , Bases para Dentadura , Compuestos Organometálicos/química , Polimetil Metacrilato/química , Compuestos de Terfenilo/química , Benchmarking , Color , Cobre/química , Diseño de Dentadura , Humanos , Inyecciones , Ensayo de Materiales , Docilidad , Porosidad , Presión , Estadísticas no Paramétricas , Estrés MecánicoRESUMEN
The goal of this study was to provide evidence to support simplified treatment of mandibular edentulism using denture fabrication and implant placement to circumvent the need for second-stage surgeries or prosthodontic superstructures. A 5-year prospective clinical trial is reported, which involved treatment of mandibular edentulism using the single-stage surgical placement of a TiOblast microthreaded titanium screw implant with immediate replacement of a relieved mandibular overdenture and eventual retention of the overdenture with reduced ball abutments. Fifty-eight patients were treated; 116 implants were placed using a single-stage surgical approach, with a duplicate mandibular denture as the tomographic/surgical template. Mandibular dentures were relieved and relined with a tissue conditioning material and placed immediately after implant surgery. After 3 months, Conical Seal Design ball abutments were placed and attachments were secured in the overdentures by heat-polymerizing laboratory reline methods. Five of the 116 consecutively placed implants failed at 2 to 4 months, providing an immediate implant survival rate of 95.69% at the time of attachment connection. Pain and inflammation were not common to all failures, and infection was not reported in any of the 5 failures. The immediate placement of implants by a single-stage surgical procedure in the parasymphyseal region of the mandible, followed by placement of a relined mandibular denture, results in predictable and asymptomatic healing of implants that display the clinical and radiographic features of osseointegration. Encouraging results at the immediate observation period (attachment connection) must be tempered by the need for prudent and detailed clinical and radiologic evaluation over the 5-year trial period.
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Pilares Dentales , Implantes Dentales , Prótesis Dental de Soporte Implantado , Retención de Dentadura , Prótesis de Recubrimiento , Arcada Edéntula/cirugía , Mandíbula/cirugía , Adulto , Anciano , Materiales Biocompatibles , Implantación Dental Endoósea , Diseño de Prótesis Dental , Fracaso de la Restauración Dental , Rebasado de Dentaduras , Femenino , Estudios de Seguimiento , Predicción , Humanos , Arcada Edéntula/diagnóstico por imagen , Masculino , Mandíbula/diagnóstico por imagen , Persona de Mediana Edad , Oseointegración , Estudios Prospectivos , Radiografía , Análisis de Supervivencia , Acondicionamiento de Tejidos Dentales , Titanio , Cicatrización de HeridasRESUMEN
OBJECTIVES: To investigate tuned aperture computed tomography (TACT) as an alternative to conventional tomography for cross-sectional imaging of potential implant sites. METHODS: Twenty potential implant sites in three dry human mandibles were selected. Sixteen TACT basis projections were recorded on film using a linear array of source positions. Films were scanned and 20 TACT and iterative TACT slices were reconstructed using TACT Workbench software. Maximum height and width were measured on one representative slice of each site. Results were compared with the ground truth using ANOVA and Wilcoxon signed rank tests. RESULTS: The means of relative difference in maximum height were 1.55 and 1.56% for TACT and iterative TACT respectively (P = 0.8643). The means of relative difference in width were 5.96 and 6.36% for TACT and iterative TACT respectively (P = 0.4845). More than 75% measurements were within +/- 1 mm of ground truth for both modalities. CONCLUSIONS: TACT may provide an alternative to conventional tomography for dental implant imaging. Further investigations should be performed to explore factors affecting image quality.
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Implantación Dental Endoósea/métodos , Arcada Edéntula/diagnóstico por imagen , Tomografía Computarizada por Rayos X/métodos , Anatomía Transversal , Humanos , Modelos Lineales , Mandíbula/diagnóstico por imagen , Planificación de Atención al Paciente , Estadísticas no ParamétricasRESUMEN
STATEMENT OF PROBLEM: Long-span fixed partial dentures usually require splinting of multiple abutments to overcome mechanical problems associated with the long edentulous span. Most information and indications for the use of multiple splinted abutments have been empirically derived. PURPOSE: This study analyzed the stress levels in the teeth and supporting structures of a fixed prosthesis and ascertained how the addition of multiple abutments in a fixed prosthesis modifies the stresses and their deflection. MATERIAL AND METHODS: The finite element method was used to analyze mechanical behaviors of a prosthesis and its supporting structures when a fixed prosthesis with several designs replaced a mandibular second premolar and a first molar. Variations of the standard finite element model were made by changing the number of splinted teeth and the level of bone support. RESULTS: A reduction of stress and deflection was observed in the supporting structures when a fixed partial denture was fabricated and teeth were splinted together. Increasing the number of splinted abutments did not reveal a proportional reduction of stress in the periodontium. Stress concentrations were seen in the connectors of prosthesis and in the cervical dentin area near the edentulous ridge. CONCLUSION: Increasing the number of the splinted abutment did not compensate for the mechanical problems of a long-span fixed partial denture sufficiently.
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Pilares Dentales , Diseño de Dentadura , Dentadura Parcial Fija , Análisis de Elementos Finitos , Pérdida de Hueso Alveolar/fisiopatología , Proceso Alveolar/anatomía & histología , Proceso Alveolar/fisiología , Diente Premolar/fisiología , Fuerza de la Mordida , Diente Canino/fisiología , Dentina/fisiología , Elasticidad , Humanos , Arcada Parcialmente Edéntula/rehabilitación , Diente Molar/fisiología , Periodoncio/anatomía & histología , Periodoncio/fisiología , Estrés Mecánico , Cuello del Diente/fisiologíaRESUMEN
STATEMENT OF PROBLEM: Little is known about the condition of the abutment-screw joint before loading, after the development of the preload. PURPOSE: This study examined the tightening force transmitted to the implant with and without the use of a counter-torque device during the tightening of the abutment screw. MATERIALS AND METHODS: Forty Brânemark implants and 10 CeraOne, Estheticone, Procera, and AurAdapt abutments formed the experimental populations. Samples in each group were further divided into 2 groups, 1 group was tightened with a torque controller without the use of a counter-torque device, whereas the other used the counter-torque device. Samples were positioned in a special holder within the grips of a Tohnichi BTG-6 torque gauge for measuring transmitted forces. RESULTS: There were significant differences (P =. 0001) in the tightening forces transmitted to the implant with and without the use of a counter-torque device when tightening the abutment screws. CONCLUSION: An average of 91% of the recommended preload tightening torque was transmitted to the implant-bone interface in the absence of a counter-torque device. In all abutment systems, less than 10% of the recommended preload tightening torque was transmitted to the implant when the counter-torque device was used.
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Pilares Dentales , Diseño de Prótesis Dental/instrumentación , Prótesis Dental de Soporte Implantado/instrumentación , Diseño de Prótesis Dental/métodos , Diseño de Prótesis Dental/estadística & datos numéricos , Prótesis Dental de Soporte Implantado/métodos , Prótesis Dental de Soporte Implantado/estadística & datos numéricos , Análisis del Estrés Dental/estadística & datos numéricos , Humanos , TorqueRESUMEN
Clinicians who are comfortable with traditional porcelain fused to metal restorations may find the thickness of veneering porcelain addition to the CeraOne single tooth ceramic cap disconcerting. When using a premanufactured ceramic cap to fit the space of the final restoration, substantial amounts of "unsupported" veneer porcelain may be required to achieve tooth contact to adjacent or opposing dentition. A potential problem of weak, unsupported veneer porcelain has been addressed by a modification of an existing manufacturing process. By using CAD/CAM technology, a custom-designed Procera AllCeram coping can be created for the implant abutment that eliminates any concerns regarding the resultant design of the underlying ceramic cap substructure.