RESUMEN

Glass ceramics' fractures in zirconia fixed dental prosthesis (FDP) remains a clinical challenge since it has higher fracture rates than the gold standard, metal ceramic FDP. Nanoindentation has been shown a reliable tool to determine residual stress of ceramic systems, which can ultimately correlate to failure-proneness. OBJECTIVES: To assess residual tensile stress using nanoindentation in veneered three-unit zirconia FDPs at different surfaces of pontics and abutments. METHODOLOGY: Three composite resin replicas of the maxillary first premolar and crown-prepared abutment first molar were made to obtain three-unit FDPs. The FDPs were veneered with glass ceramic containing fluorapatite crystals and resin cemented on the replicas, embedded in epoxy resin, sectioned, and polished. Each specimen was subjected to nanoindentation in the following regions of interest: 1) Mesial premolar abutment (MPMa); 2) Distal premolar abutment (DPMa); 3) Buccal premolar abutment (BPMa); 4) Lingual premolar abutment (LPMa); 5) Mesial premolar pontic (MPMp); 6) Distal premolar pontic (DPMp); 7) Buccal premolar pontic (BPMp); 8) Lingual premolar pontic (LPMp); 9) Mesial molar abutment (MMa); 10) Distal molar abutment (DMa); 11) Buccal molar abutment (BMa); and 12) Lingual molar abutment (LMa). Data were assessed using Linear Mixed Model and Least Significant Difference (95%) tests. RESULTS: Pontics had significantly higher hardness values than premolar (p=0.001) and molar (p=0.007) abutments, suggesting lower residual stress levels. Marginal ridges yielded higher hardness values for connectors (DPMa, MMa, MPMp and DPMp) than for outer proximal surfaces of abutments (MPMa and DMa). The mesial marginal ridge of the premolar abutment (MPMa) had the lowest hardness values, suggesting higher residual stress concentration. CONCLUSIONS: Residual stress in three-unit FDPs was lower in pontics than in abutments. The outer proximal surfaces of the abutments had the highest residual stress concentration.

Asunto(s)

Dentadura Parcial Fija , Circonio , Diente Premolar , Coronas , Circonio/química

RESUMEN

PURPOSE: This study evaluated the effect of different tightening protocols on the probability of survival of screw-retained implant-supported anterior crowns. MATERIALS AND METHODS: Seventy-two implants with internal conical connections (4.0 × 10mm, Ti-6Al-4V, Colosso, Emfils) were divided into four groups (n = 18 each): 1) Manufacturer's recommendations torque (25 N.cm for abutment's screw and 30 N.cm for crown's screw) (MaT); 2) Retightening after 10 min (ReT); 3) Torque 16% below recommended to simulate an uncalibrated wrench (AgT), and; 4) Temporary crown simulation (TeT), where crowns were torqued to 13 N.cm to simulate manual tightening, subjected to 11,200 cycles to simulate temporary crown treatment time (190 N), and then retightened to manufacturer torque (TeT). All specimens were subjected to cyclic fatigue in distilled water with a load of 190 N until 250,000 cycles or failure. The probability of survival (reliability) to complete a mission of 50,000 cycles was calculated and plotted using the Weibull 2-Parameter analysis. Weibull modulus and number of cycles at which 62.3% of the specimens would fail were also calculated and plotted. The failure mode was characterized in stereo and scanning electron microscopes (SEM). RESULTS: The probability of survival was 69.3% for MaT, 70% for ReT, 54.8% for AgT, and 40.3% for TeT, all with no statistically significant difference. Weibull modulus was approximately 1.0 for all groups. The characteristic number of cycles for failure was 105,000 cycles for MaT, 123,000 for ReT, 82,000 cycles for AgT, and 54,900 cycles for TeT, with no significant difference between groups. The chief failure mode for MaT, ReT, AgT groups was crown screw fracture, whereas abutment screw fracture was the chief failure mode for the TeT group. CONCLUSION: Tightening protocol did not influence the probability of survival of the screw-retained anterior crowns supported by internal conical implants (Ti-6Al-4V, Colosso, Emfils).

Asunto(s)

Coronas , Implantes Dentales , Tornillos Óseos , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Probabilidad , Reproducibilidad de los Resultados , Torque

RESUMEN

Abstract Glass ceramics' fractures in zirconia fixed dental prosthesis (FDP) remains a clinical challenge since it has higher fracture rates than the gold standard, metal ceramic FDP. Nanoindentation has been shown a reliable tool to determine residual stress of ceramic systems, which can ultimately correlate to failure-proneness. Objectives: To assess residual tensile stress using nanoindentation in veneered three-unit zirconia FDPs at different surfaces of pontics and abutments. Methodology: Three composite resin replicas of the maxillary first premolar and crown-prepared abutment first molar were made to obtain three-unit FDPs. The FDPs were veneered with glass ceramic containing fluorapatite crystals and resin cemented on the replicas, embedded in epoxy resin, sectioned, and polished. Each specimen was subjected to nanoindentation in the following regions of interest: 1) Mesial premolar abutment (MPMa); 2) Distal premolar abutment (DPMa); 3) Buccal premolar abutment (BPMa); 4) Lingual premolar abutment (LPMa); 5) Mesial premolar pontic (MPMp); 6) Distal premolar pontic (DPMp); 7) Buccal premolar pontic (BPMp); 8) Lingual premolar pontic (LPMp); 9) Mesial molar abutment (MMa); 10) Distal molar abutment (DMa); 11) Buccal molar abutment (BMa); and 12) Lingual molar abutment (LMa). Data were assessed using Linear Mixed Model and Least Significant Difference (95%) tests. Results: Pontics had significantly higher hardness values than premolar (p=0.001) and molar (p=0.007) abutments, suggesting lower residual stress levels. Marginal ridges yielded higher hardness values for connectors (DPMa, MMa, MPMp and DPMp) than for outer proximal surfaces of abutments (MPMa and DMa). The mesial marginal ridge of the premolar abutment (MPMa) had the lowest hardness values, suggesting higher residual stress concentration. Conclusions: Residual stress in three-unit FDPs was lower in pontics than in abutments. The outer proximal surfaces of the abutments had the highest residual stress concentration.

RESUMEN

OBJECTIVES: Controversy exists about whether the elastic modulus (E) mismatch between the loading indenter and ceramic materials influences fatigue testing results. The research hypotheses were that for porcelain veneered Y-TZP crowns 1) A low modulus Steatite indenter (SB) leads to higher fatigue reliability compared to a high modulus tungsten carbide indenter (WC); 2) Different surface damage patterns are expected between low and high modulus indenters after sliding contact fatigue testing. All ceramic crowns will exhibit similar step-stress accelerated life testing (SSALT) contact fatigue reliability (hypothesis 1) and failure characteristics (hypothesis 2) when using high stiffness tungsten carbide (WC, E = 600 GPa) vs. enamel like steatite (SB, E = 90 GPa) indenters. METHODS: Manufacturer (3M Oral Care) prepared Y-TZP-veneered all-ceramic molar crowns were bonded to aged resin composite reproductions of a standard tooth preparation and subjected to mouth-motion SSALT fatigue (n = 18 per indenter type). Failure was defined either as initial inner cone crack (IC), or final fracture (FF) when porcelain fractured (chipping). Selected IC specimens that did not progress to FF were embedded in epoxy resin and sectioned for fractographic analysis. RESULTS: The distribution of failures across the load and cycle profiles lead to similar calculated Weibull Use Level Probability Plots with overlap of the 2-sided 90% confidence bounds. The calculated reliability for IC and FF was equivalent at a mission of 300 N or 700 N load and 50,000 cycles, although the WC indenter had a trend for lower reliability for IC at 700 N. Both indenters produced similar patterns of wear and cracking on crown surfaces. Fractographic landmarks showed competing failure modes, but sliding contact partial inner cone cracks were the most dominant for both groups. SIGNIFICANCE: The more compliant Steatite indenter had similar veneered crown fatigue reliability and failure modes to those found with use of a high stiffness tungsten carbide indenter (hypotheses 1 and 2 rejected).

Asunto(s)

Cerámica , Coronas , Resinas Compuestas , Porcelana Dental , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Ensayo de Materiales , Reproducibilidad de los Resultados

RESUMEN

OBJECTIVE: To evaluate the probability of survival of monolithic and porcelain veneered lithium disilicate crowns comprised by a conventional or modified core when loaded on marginal ridges. METHODS: Lithium disilicate molar crowns (n=30) were fabricated to be tested at mesial and distal marginal ridges and were divided as follows: (1) bilayered crowns with even-thickness 0.5mm framework (Bi-EV); (2) bilayered crowns with modified core design (Bi-M-lingual collar connected to proximal struts), and: (3) monolithic crowns (MON). After adhesively cemented onto composite-resin prepared replicas, mesial and distal marginal ridges of each crown (n=20) were individually cyclic loaded in water (30-300N) with a ceramic indenter at 2Hz until fracture. The 2-parameter Weibull was used to calculate the probability of survival (reliability) (90% 2-sided confidence bounds) at 1, 2, and 3 million cycles and mean life. RESULTS: The reliability at 1 and 2 million cycles was significantly higher for MON (47% and 19%) compared to Bi-EV (20% and 4%) and Bi-M (17% and 2%). No statistical difference was found between bilayered groups. Only the MON group presented crown survival (7%) at 3 million cycles. The mean life was highest for MON (1.73E+06), lowest for Bi-M (573,384) and intermediate for Bi-E (619,774). Fractographic analysis showed that the fracture originated at the occlusal surface. The highest reliability was found for MON crowns. The modified framework design did not improve the fatigue life of crowns. SIGNIFICANCE: Monolithic lithium disilicate crowns presented higher probability of survival and mean life than bilayered crowns with modified framework design when loaded at marginal ridges.

Asunto(s)

Porcelana Dental , Circonio , Coronas , Diseño de Prótesis Dental , Ensayo de Materiales , Reproducibilidad de los Resultados

RESUMEN

This study evaluated the reliability of implant-supported crowns repaired with resin composites. Fifty-four titanium abutments were divided in three groups (n = 18 each) to support resin nanoceramic molar crowns, as follows: (LU) (Lava Ultimate, 3M ESPE); LU repaired with either a direct or an indirect resin composite. Samples were subjected to mouth-motion accelerated-life testing in water (n = 18). Cumulative damage with a use stress of 300 N was used to plot Weibull curves for group comparison. Reliability was calculated for a mission of 100,000 cycles at 400 N load. Beta values were 0.83 for LU, 0.31 and 0.27 for LU repaired with Filtek and Ceramage, respectively. Weibull modulus for LU was 9.5 and η = 1047 N, m = 6.85, and η = 1002 N for LU repaired with Ceramage, and m = 4.65 and η = 766 N for LU repaired with Filtek (p < 0.10 between LU and LU repaired with Filtek). Reliability at 400 N was 100% for both LU and LU repaired with Ceramage which were significantly higher than LU Filtek repair (32%). LU restored crowns failed cohesively. Fractures were confined within the restored material, and detailed fractography is presented. The performance of resin nanoceramic material repaired with an indirect composite was maintained after accelerated-life testing compared to unrepaired controls. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1481-1489, 2017.

Asunto(s)

Resinas Compuestas/química , Coronas , Implantes Dentales , Ensayo de Materiales , Estrés Mecánico , Humanos

RESUMEN

Objetivo: avaliar o comportamento biomecânico de uma prótese fixa com quatro implantes unidos em uma maxila edêntula atrófica, pelo método dos elementos finitos (MEF). Material e métodos: em uma mandíbula totalmente desdentada, foram colocados dois implantes posteriores, inclinados, seguindo a parede anterior do seio maxilar, e dois implantes paralelos na região anterior. Estes quatro implantes foram ligados por uma barra rígida simulando uma prótese fixa, com ou sem extensão distal de 10 mm. As análises foram feitas variando a intensidade do carregamento (100 N, 50 N e 25 N), a direção de aplicação (axial e não axial), bem como a presença ou ausência de cortical em volta dos implantes, simulando carga tardia e carga imediata, respectivamente. Resultados: os resultados mostraram não haver diferenças em relação à presença ou ausência da lâmina dura. A presença da extensão distal na prótese fixa (cantiléver) aumentou significativamente a quantidade de tensão (156,6 MPa), comparado ao modelo sem a extensão distal (52 MPa). Conclusão: a presença do cantiléver em prótese na maxila pelo conceito all-on-four sofre uma deformação em toda a prótese três vezes maior do que na sua ausência. Próteses fixas implantossuportadas imediatas e/ou mediatas mostraram comportamentos semelhantes, quando unidas por uma estrutura rígida.

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Objective: to evaluate the biomechanical behavior of a fixed prosthesis over 4 dental implants splinted in the edentulous maxilla using the finite element analysis (FEA). Material and Methods: using a completely edentulous maxillary model, two inclined posterior implants were placed following the maxillary sinus wall, whereas two anterior implants were parallel to each other. A rigid bar was designed to connect these four implants, simulating a fixed prosthesis with a 10 mm distal extension. The analyses were made varying the load intensities (100 N, 50 N, and 25 N), load direction (axial, non-axial), to simulate delayed and immediate loading protocols, respectively. Results: no differences were seen for the presence (delayed) or absence (immediate) of lamina dura. The presence of cantilever (distal extension) significantly increased the amount of maximum tension (156.6 MPa) when compared with models without cantilever (52 MPa). Conclusion: the cantilever extension in the all-on-four concept has a deformation three times higher than in the lack of it. Immediate/mediate implant-supported fixed prostheses demonstrated similar behavior when splinted by a rigid bar type.

Asunto(s)

Humanos , Fenómenos Biomecánicos , Prótesis Dental de Soporte Implantado , Diagnóstico por Computador , Diagnóstico por Imagen/tendencias , Análisis de Elementos Finitos , Imagenología Tridimensional

RESUMEN

OBJECTIVE: To compare the fatigue life and damage modes of zirconia crowns fabricated with and without framework design modification when porcelain veneered using a fast or slow cooling protocol. METHODS: Composite resin replicas of a first molar full crown preparation were fabricated. Zirconia copings were milled as conventional (0.5mm even thickness, Zr-C, n=20,) or modified (lingual margin of 1.0mm thickness, 2.0mm height connected to two proximal struts of 3.5mm height, Zr-M, n=20). These groups were subdivided (n=10 each) according to the veneer cooling protocol employed: fast cooling (Zr-CFast and Zr-MFast) and slow cooling (Zr-CSlow and Zr-MSlow). Crowns were cemented and fatigued for 10(6) cycles in water. The number of cycles to failure was recorded and used to determine the interval databased 2-parameter probability Weibull distribution parameter Beta (ß) and characteristic life value Eta (η). RESULTS: 2-parameter Weibull calculation presented ß=5.53 and ß=4.38 for Zr-MFast and Zr-CFast, respectively. Slow cooled crowns did not fail by completion of 10(6) cycles, thereby Weibayes calculation was applied. Increased fatigue life was observed for slow cooled crowns compared to fast cooled ones. Groups Zr-MFast and Zr-MSlow presented no statistical difference. Porcelain cohesive fractures were mainly observed in fast cooled groups. Slow cooled crowns presented in some instances inner cone cracks not reaching the zirconia/veneer interface. SIGNIFICANCE: Improved fatigue life in tandem with the absence of porcelain fractures were observed in slow cooled crowns, regardless of framework design. Crowns fast cooled chiefly failed by porcelain cohesive fractures.

Asunto(s)

Coronas , Análisis del Estrés Dental/métodos , Circonio/química , Porcelana Dental , Fracaso de la Restauración Dental , Coronas con Frente Estético , Ensayo de Materiales , Propiedades de Superficie , Temperatura

RESUMEN

PURPOSE: This evaluation aimed to (1) validate micro-computed tomography (microCT) findings using scanning electron microscopy (SEM) imaging, and (2) quantify the volume of voids and the bonded surface area resulting from fiber-reinforced composite (FRC) dowel cementation technique using microCT scanning technology/3D reconstructing software. MATERIALS AND METHODS: A fiberglass dowel was cemented in a condemned maxillary lateral incisor prior to its extraction. A microCT scan was performed of the extracted tooth creating a large volume of data in DICOM format. This set of images was imported to image-processing software to inspect the internal architecture of structures. RESULTS: The outer surface and the spatial relationship of dentin, FRC dowel, cement layer, and voids were reconstructed. Three-dimensional spatial architecture of structures and volumetric analysis revealed that 9.89% of the resin cement was composed of voids and that the bonded area between root dentin and cement was 60.63% larger than that between cement and FRC dowel. CONCLUSIONS: SEM imaging demonstrated the presence of voids similarly observed using microCT technology (aim 1). MicroCT technology was able to nondestructively measure the volume of voids within the cement layer and the bonded surface area at the root/cement/FRC interfaces (aim 2). CLINICAL SIGNIFICANCE: The interfaces at the root dentin/cement/dowel represent a timely and relevant topic where several efforts have been conducted in the past few years to understand their inherent features. MicroCT technology combined with 3D reconstruction allows for not only inspecting the internal arrangement rendered by fiberglass adhesively bonded to root dentin, but also estimating the volume of voids and contacted bond area between the dentin and cement layer.

Asunto(s)

Resinas Compuestas/química , Recubrimiento Dental Adhesivo , Materiales Dentales/química , Vidrio/química , Técnica de Perno Muñón/instrumentación , Cementación/métodos , Cavidad Pulpar/diagnóstico por imagen , Cavidad Pulpar/ultraestructura , Dentina/diagnóstico por imagen , Dentina/ultraestructura , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Incisivo/diagnóstico por imagen , Incisivo/ultraestructura , Microscopía Electrónica de Rastreo , Proyectos Piloto , Cementos de Resina/química , Dióxido de Silicio/química , Propiedades de Superficie , Raíz del Diente/diagnóstico por imagen , Raíz del Diente/ultraestructura , Microtomografía por Rayos X/métodos , Circonio/química

RESUMEN

OBJECTIVES: The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA--In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP--IPS e.max ZirCAD), and metal-ceramic (MC--Ni-Cr alloy) crowns. MATERIAL AND METHODS: Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey's multiple comparison test (p<0.05). RESULTS: No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. CONCLUSIONS: The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS.

Asunto(s)

Cerámica/química , Coronas , Adaptación Marginal Dental , Aleaciones de Cerámica y Metal/química , Óxido de Aluminio/química , Análisis de Varianza , Resinas Compuestas/química , Diseño Asistido por Computadora , Técnica de Impresión Dental , Porcelana Dental/química , Diseño de Prótesis Dental , Humanos , Ensayo de Materiales , Modelos Dentales , Reproducibilidad de los Resultados , Propiedades de Superficie

RESUMEN

OBJECTIVES: The aim of this study was to investigate the internal fit (IF) of glass-infiltrated alumina (ICA - In-Ceram Alumina), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP - IPS e.max ZirCAD), and metal-ceramic (MC - Ni-Cr alloy) crowns. MATERIAL AND METHODS: Sixty standardized resin-tooth replicas of a maxillary first molar were produced for crown placement and divided into 3 groups (n=20 each) according to the core material used (metal, ICA or Y-TZP). The IF of the crowns was measured using the replica technique, which employs a light body polyvinyl siloxane impression material to simulate the cement layer thickness. The data were analyzed according to the surfaces obtained for the occlusal space (OS), axial space (AS) and total mean (TM) using two-way ANOVA with Tukey ’s multiple comparison test (p<0.05). RESULTS: No differences among the different areas were detected in the MC group. For the Y-TZP and ICA groups, AS was statistically lower than both OS and TM. No differences in AS were observed among the groups. However, OS and TM showed significantly higher values for ICA and Y-TZP groups than MC group. Comparisons of ICA and Y-TZP revealed that OS was significantly lower for Y-TZP group, whereas no differences were observed for TM. CONCLUSIONS: The total mean achieved by all groups was within the range of clinical acceptability. However, the metal-ceramic group demonstrated significantly lower values than the all-ceramic groups, especially in OS.

Asunto(s)

Humanos , Coronas , Cerámica/química , Adaptación Marginal Dental , Aleaciones de Cerámica y Metal/química , Análisis de Varianza , Óxido de Aluminio/química , Diseño Asistido por Computadora , Resinas Compuestas/química , Técnica de Impresión Dental , Modelos Dentales , Diseño de Prótesis Dental , Porcelana Dental/química , Ensayo de Materiales , Reproducibilidad de los Resultados , Propiedades de Superficie

RESUMEN

Dentes perdidos podem ser melhores substituídosempregando próteses fixas (dento ouimplanto suportadas). Contudo, algumas limitaçõescomo fatores econômicos, culturais, sociais,distribuição dos dentes, extensão do espaçoprotético e espessura do rebordo, podemlimitar o emprego dessas próteses. Dessa forma,a prótese parcial removível (PPR) torna-se umaalternativa segura e confiável quando a prótesefixa não pode ser indicada. Embora apresentedesvantagens, a PPR convencional preenche todosos requisitos para reabilitar qualquer áreaedêntula, pois recupera dentes e estruturas associadasperdidas (osso e tecidos moles). Entretanto,algumas alterações como modificaçõesdo desenho da infraestrutura, mudança do eixode inserção, tipo de dente usado na prótese(artificial ou natural), dentre outras, podem serrealizadas para melhorar o conforto, satisfaçãoe estética do paciente. Nesses casos, há a transformaçãoda PPR convencional em não convencional.Este trabalho tem objetivo de revisaras categorias de PPR não convencionais, assimcomo suas vantagens, desvantagens, indicaçõese contraindicações, na esperança que mais dentistaspossam considerar seu uso quando a situaçãoaparecer.

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Fixed partial prostheses (tooth or implant based)are considerated as the best choice to replacemissing teeth. However, some clinical (teethdistribution, prosthetic space extension and residualbone thickness) or individual (economical,cultural and social factors) conditions may limitits indication. In such situations, the removablepartial denture (RPD) is a reliable alternative.Although the conventional RPD shows somedisadvantages, it presents all requirements torehabilitate any edentulous space. Moreover,RPD replaces both teeth and adjacent structures(soft and hard tissues) missed. Nevertheless,in order to delivery esthetic, comfort andself-confidence to patient, some specific clinicalconditions require a non-conventional RPD. Thisprosthesis is characterized by presenting a changedframework design, or a different insertionpath, or due to its association with implants,among others. Thus, understanding the nonconventionalRPDs concept is a subject matterimportant and pertinent. The present studysought to review the relevant literature aboutnon-conventional RPDs, including vantages, disadvantages,indications and contraindications,expecting that more dentists may consider thenon-conventional RPD as a treatment option.

Asunto(s)

Estética Dental , Higiene Bucal , Diseño de Prótesis Dental/métodos , Dentadura Parcial Removible

RESUMEN

O desgaste dentário é um processo fisiológico e natural. Entretanto, lesões como abrasão, atrição, abfração e erosão podem ser patológicas dependendo da severidade e relacionada com a idade. Enquanto o declínio da incidência de cárie tem sido observado, o desgaste dentário por aqueles mecanismos tem se tornado um achado clínico importante. Em muitas situações é impossível distinguir qual o principal fator envolvido com as lesões por Perda da Estrutura Dentária (PED) devido a sua etiologia multifatorial e diagnóstico complexo. Adicionalmente, fatores específicos podem atuar sinergicamente com a etiologia da PED, incluindo as atividades funcionais e parafuncionais, dieta, doenças, fatores salivares, hábitos de higiene e atividade ocupacional.Entretanto, a erosão é o principal assunto dos estudos de PED, pois pesquisas clínicas indicam o aumento da sua prevalência e apontam o seu efeito dominante sobre os outros mecanismos.A erosão origina-se por meio do contato crônico dos dentes com substâncias ácidas que podem ser de origem extrínseca e intrínseca, sem o envolvimento bacteriano. A avaliação minuciosa dos hábitos do paciente associado ao exame clínico auxiliam na determinação da etiologia e dos fatores de risco, sendo esses o foco do manejo da erosão. A mensagem deste trabalho é apresentar uma abordagem de base sólida para a PED onde o seu restabelecimento deve ser acompanhado por aconselhamentos e mudanças de hábitos alimentares e quando presente doenças sistêmicas ou aos distúrbios alimentares o tratamento médico deve estar associado.

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Tooth wear is a physiological and natural process. However, lesions like abrasion, attrition and erosion may be pathological depending on their age-related severity. While the rate of caries has decreased, pathological tooth wear has become an increasingly common clinical finding. In most cases it is a challenge to determine the main factor involved with the tooth wear lesion, given its multifactorial etiology and complex diagnostic. Additionally, specific factors can act synergistically with tooth wear etiology including functional and parafunctional activities, diet, diseases, salivary factors, hygiene habits and occupational activity. Erosion seems to be a major source and main topic on tooth wear studies since recent clinical research has pointed its increased prevalence and also its dominant effect over other mechanisms. Erosion is caused by chronic contact of teeth with acid substances that can be of extrinsic or intrinsic origin, without bacterial involvement.A thorough assessment of patient habits, and clinical exam aiming at determination of etiological and risk factors are the goals of erosion management. The message of this paper is to provide a sound basis approach to tooth wear, where restoration of lost dental structure should be coupled with counseling and changes of dietary habits and/or medical treatment if associated with eating disorders or systemic diseases.

Asunto(s)

Abrasión de los Dientes/complicaciones , Abrasión de los Dientes/diagnóstico , Caries Dental/diagnóstico , Caries Dental/etiología , Caries Dental/prevención & control , Desgaste de los Dientes/diagnóstico , Desgaste de los Dientes/prevención & control , Erosión de los Dientes/complicaciones , Erosión de los Dientes/diagnóstico , Reflujo Gastroesofágico/diagnóstico , Estudios Transversales

RESUMEN

Dentes perdidos podem ser melhor substituídos empregando próteses fixas dento ou implanto suportadas. Contudo, algumas limitações como fatores econômicos, culturais, sociais, saúde geral, distribuição dos dentes, extensão do espaço protético e espessura do rebordo, podem limitar o emprego dessas próteses. Desta forma, a prótese parcial removível (PPR) torna-se uma alternativa segura e confiável quando a prótese fixa não pode ser indicada. Embora apresente desvantagens, a PPR convencional preenche todos os requisitos para reabilitar qualquer área edêntula, pois recupera dentes e estruturas associadas perdidas (osso e tecidos moles). Entretanto, algumas alterações como modificações do desenho da infraestrutura, mudança do eixo de inserção, combinação com implantes, tipo de dentes utilizados na prótese (artificial ou natural), dentre outras, podem ser realizadas para melhorar o conforto, satisfação e estética do paciente. Nesses casos há a transformação da PPR convencional em não convencional. Este trabalho tem como objetivo revisar os tipos de PPRs não convencionais, assim como suas vantagens, desvantagens, indicações e contra-indicações, na esperança de que mais cirurgiões-dentistas (CD) possam considerar seu uso quando a situação aparecer

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Fixed partial prostheses (tooth or implant based) are considered as the best choice to replace missing teeth. However, some clinical (teeth distribution, prosthetic space extension and residual bone thickness) or individual (economical, cultural and social factors) conditions may limit its indication. In such situations, the removable partial denture (RPD) is a reliable alternative. Although the conventional RPD shows some disadvantages, it presents all requirements to rehabilitate any edentulous space. Moreover, RPD replaces both teeth and adjacent structures (soft and hard tissues) missed. Nevertheless, in order to delivery esthetic, comfort and self-confidence to patient, some specific clinical conditions require a non-conventional RPD. This prosthesis is characterized by presenting a changed framework design, or a different insertion path, or due to its association with implants, among others. Thus, understanding the non-conventional RPDs concept is a subject matter important and pertinent. The present study sought to review the relevant literature about non-conventional RPDs, including vantages, disadvantages, indications and contraindications, expecting that more dentists may consider the non conventional RPD as a treatment option

Asunto(s)

Estética Dental , Oseointegración , Diseño de Prótesis Dental/métodos , Prótesis Dental de Soporte Implantado , Dentadura Parcial Fija , Dentadura Parcial Removible , Rehabilitación Bucal/métodos , Prótesis de Recubrimiento

RESUMEN

To evaluate the sealing capability of external hexagon implant systems and assess the marginal fit, two groups (n = 10 each) were employed: SIN (Sistema de Implantes Nacional, Brazil) and Osseotite, (Biomet 3i, USA). Sealing capability was determined by placing 0.7 µL of 1% acid-red solution in the implant wells before the torque of their respective abutments. Specimens were then placed into 2.5 mL vials filled with 1.3 mL of distilled water with the implant-abutment interface submerged. Three samples of 100 µL water were collected at previously determinate times. The absorbance was measured with a spectrophotometer, and the data were analyzed by Two-way ANOVA (P < .05) and Tukey's test. Marginal fit was determined using SEM. Leakage was observed for both groups at all times and was significantly higher at 144 hrs. SEM analysis depicted gaps in the implant-abutment interface of both groups. Gaps in the implant-abutment interface were observed along with leakage increased at the 144 hrs evaluation period.

RESUMEN

OBJECTIVES: To evaluate the effect of framework design on the fatigue life and failure modes of metal ceramic (MC, Ni-Cr alloy core, VMK 95 porcelain veneer), glass-infiltrated alumina (ICA, In-Ceram Alumina/VM7), and veneered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP, IPSe.max ZirCAD/IPS e.max,) crowns. METHODS: Sixty composite resin tooth replicas of a prepared maxillary first molar were produced to receive crowns systems of a standard (MCs, ICAs, and Y-TZPs, n=10 each) or a modified framework design (MCm, ICAm, and Y-TZPm, n=10 each). Fatigue loading was delivered with a spherical steel indenter (3.18mm radius) on the center of the occlusal surface using r-ratio fatigue (30-300N) until completion of 10(6) cycles or failure. Fatigue was interrupted every 125,000 cycles for damage evaluation. Weibull distribution fits and contour plots were used for examining differences between groups. Failure mode was evaluated by light polarized and SEM microscopy. RESULTS: Weibull analysis showed the highest fatigue life for MC crowns regardless of framework design. No significant difference (confidence bound overlaps) was observed between ICA and Y-TZP with or without framework design modification. Y-TZPm crowns presented fatigue life in the range of MC crowns. No porcelain veneer fracture was observed in the MC groups, whereas ICAs presented bulk fracture and ICAm failed mainly through the veneer. Y-TZP crowns failed through chipping within the veneer, without core fractures. CONCLUSIONS: Framework design modification did not improve the fatigue life of the crown systems investigated. Y-TZPm crowns showed comparable fatigue life to MC groups. Failure mode varied according to crown system.

Asunto(s)

Diseño Asistido por Computadora , Coronas , Diseño de Prótesis Dental , Fracaso de la Restauración Dental , Coronas con Frente Estético , Óxido de Aluminio , Bisfenol A Glicidil Metacrilato , Aleaciones de Cromo , Porcelana Dental , Maniquíes , Aleaciones de Cerámica y Metal , Polietilenglicoles , Ácidos Polimetacrílicos , Distribución Aleatoria , Cementos de Resina , Análisis de Supervivencia , Itrio , Circonio

RESUMEN

PURPOSE: Chipping within veneering porcelain has resulted in high clinical failure rates for implant-supported zirconia (yttria-tetragonal zirconia polycrystals [Y-TZP]) bridges. This study evaluated the reliability and failure modes of mouth-motion step-stress fatigued implant-supported Y-TZP versus palladium-silver alloy (PdAg) three-unit bridges. MATERIALS AND METHODS: Implant-abutment replicas were embedded in polymethylmethacrylate resin. Y-TZP and PdAg frameworks, of similar design (n = 21 each), were fabricated, veneered, cemented (n = 3 each), and Hertzian contact-tested to obtain ultimate failure load. In each framework group, 18 specimens were distributed across three step-stress profiles and mouth-motion cyclically loaded according to the profile on the lingual slope of the buccal cusp of the pontic. RESULTS: PdAg failures included competing flexural cracking at abutment and/or connector area and chipping, whereas Y-TZP presented predominantly cohesive failure within veneering porcelain. Including all failure modes, the reliability (two-sided at 90% confidence intervals) for a "mission" of 50,000 and 100,000 cycles at 300 N load was determined (Alta Pro, Reliasoft, Tucson, AZ, USA). No difference in reliability was observed between groups for a mission of 50,000. Reliability remained unchanged for a mission of 100,000 for PdAg, but significantly decreased for Y-TZP. CONCLUSIONS: Higher reliability was found for PdAg for a mission of 100,000 cycles at 300 N. Failure modes differed between materials.

Asunto(s)

Pilares Dentales , Aleaciones Dentales , Implantes Dentales , Prótesis Dental de Soporte Implantado/instrumentación , Fracaso de la Restauración Dental , Dentadura Parcial Fija , Porcelana Dental , Análisis del Estrés Dental , Humanos , Reproducibilidad de los Resultados , Circonio

RESUMEN

Avaliar a influência da modificação do desenho da infraestrutura na vida útil à fadiga e no modo de falha em coroas metalo-cerâmicas e alumina infiltrada por vidro. Quarenta réplicas de um primeiro molar superior foram produzidas para receber coroas com infraestrutura padrão ou modificada. A infraestrutura modificada consistiu do desenho padrão (0,5 mm de espessura) aumentada por uma cinta lingual, unindo dois postes proximais. A carga (30-300 N) foi aplicada por um endentador metálico (3,18 mm raio) na superfície oclusal, durante 106 ciclos ou até a falha. A cada 125.000 ciclos o teste era interrompido para avaliar os danos. Fraturas catastróficas ou da porcelana de revestimento e a presença da trinca cone interno estendendo-se a infraestrutura foram os critérios utilizados para definir falha. As superfícies fraturadas e as polidas foram analisadas com estereomicroscópio e por microscopia eletrônica de varredura. A distribuição de Weibull foi utilizada para a análise estatística. A vida útil à fadiga da metalo-cerâmica foi significativamente maior que da alumina; contudo, a modificação não alterou este parâmetro nos grupos metálico ou cerâmico. Os grupos metalo-cerâmico apresentaram trincas cone interno sem fraturas da porcelana de revestimento. O grupo alumina com infraestrutura padrão apresentou principalmente fratura da porcelana de revestimento, enquanto que no grupo alumina com infraestrutura modificada se observou cone interno. A vida útil à fadiga não melhorou com a modificação no desenho das infraestruturas. O modo de falha variou de acordo com o material da infraestrutura.

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To evaluate the effect of framework design on the fatigue life and failure modes of metal-ceramic and glass-infiltrated alumina. Forty composite resin tooth-replica of a prepared maxillary first molar were produced to receive crowns of a standard or modified framework design. Core design modification consisted of a standard, connecting to proximal struts. R-ratio fatigue loading was delivered with a spherical steel indenter (3.18 mm radius) on the center of the occlusal surface at a 30-300 N load range, until completion of 106 cycles or failure. Fatigue was interrupted every 125.000 cycles for damage evaluation. Catastrophic fracture, chipping within veneering porcelain, or inner cone crack reaching the core-veneer interface were the criteria for failure. Fractured and polished surfaces were characterized under light polarized microscopy followed by scanning electron microscopy. Weibull distribution fit was used for examining differences between groups. The highest fatigue life was observed for metal-ceramic crowns, but no significant differences were observed for groups with or without framework design modification. Failure modes of metal-ceramic comprised inner cone cracks without porcelain fracture. Glass-infiltrated alumina standard crowns presented bulk fracture whereas glass-infiltrated alumina modified crowns failed mainly through veneer. Fatigue life was not improved with framework design modification. Failure modes varied according to core material.

Asunto(s)

Cerámica , Corona del Diente , Prótesis Dental

RESUMEN

A Odontologia Restauradora atual funde conceitos estéticos e conservadores. Assim, são preconizados tratamentos que apresentam bom prognóstico em longo prazo, preservação de estrutura dentária e alta satisfação estética do paciente. Inseridos nesse contexto, destacam-se os laminados cerâmicos. O objetivo deste trabalho é descrever, por meio de um relato de caso, os desafios do planejamento e da execução de um laminado cerâmico na reconstrução de um incisivo central esteticamente comprometido.

Asunto(s)

Humanos , Femenino , Adulto , Estética Dental , Incisivo , Rehabilitación Bucal , Diseño de Prótesis Dental , Restauración Dental Permanente , Cementos de Resina , Resorción Radicular

RESUMEN

Alterações anatômicas no rebordo alveolar – como a perda das papilas interproximais, do contorno do arco côncavo regular e a diminuição tanto da espessura quanto da altura do rebordo – dificultam o correto relacionamento entre o pôntico e o rebordo alveolar, e podem comprometer o resultado estético final. As depressões no rebordo alveolar podem ser resultado de extrações traumáticas ou de extrações de dentes com perda óssea avançada devido à doença periodontal ou relacionada com patologias apicais. Essas deformações desafiam a reabilitação protética, exigindo procedimentos corretivos tanto cirúrgicos quanto protéticos. Inúmeras técnicas têm sido utilizadas para reconstituir cirurgicamente os rebordos alveolares. Contudo, o enxerto de tecido conjuntivo subepitelial é a técnica que apresenta melhor resultado estético, pois permite semelhança de cor, de textura e de contorno do rebordo reconstituído com as áreas adjacentes. Abrams, em 1980, descreveu a técnica de enxerto de tecido conjuntivo subepitelial em “rolo”, aonde o enxerto é rodado para a área receptora. Scharf e Tarnow, em 1992, modificaram a técnica de Abrams mantendo o pedículo de tecido epitelial, o qual é utilizado para recobrir a área doadora. A região do segundo pré-molar superior apresentava-se com perda do contorno gengival fisiológico, interferindo no tratamento protético. A técnica cirúrgica de enxerto de tecido conjuntivo subepitelial em “rolo” e os passos clínicos do condicionamento tecidual são descritos. No caso apresentado, ambas as técnicas são previsíveis e contribuíram para proporcionar melhores características estéticas, assim como melhorar o relacionamento entre o pôntico e o rebordo.

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Anatomical changes in the alveolar ridge, such as the loss of the interproximal papillae and of the contour of the regular concave arc, and the decrease of both the thickness and the height of the ridge, complicate the correct relationship between the pontic and the alveolar ridge and may affect the final aesthetic outcome. Depression in the alveolar ridge may be the result of traumatic extractions or teeth extractions with advanced bone loss due to periodontal disease or apical pathology. These alterations challenge the prosthetic rehabilitation demanding corrective procedures both surgical as well as prosthetic. Several techniques have been used to surgically reconstruct the alveolar ridges. However, the subepithelial connective tissue graft is the technique that shows better esthetic results, as it allows resemblance in color, texture and in the contour of the reshaped ridge to the adjacent areas. Abrams in 1980 described the subepithelial connective tissue roll graft technique, in which the graft is rolled to the receptive area. In 1992 Scharf and Tarnow changed Abram's technique keeping the pedicle of the epithelial tissue, which is used to cover the donor site. The site of the second superior maxillary premolar presented loss of physiologic gingival contour, interfering on the prosthetic treatment. Both the "roll" surgical technique of subepithelial connective tissue graft and the clinical steps of tissue conditioning are described. In the case presented both techniques are predictable and contributed to provide better esthetic characteristics as well as better pontic-ridge relationship characteristic.

Asunto(s)

Humanos , Persona de Mediana Edad , Dentadura Parcial Fija , Rehabilitación Bucal , Procedimientos Quirúrgicos Orales , Tejido Conectivo/trasplante , Aumento de la Cresta Alveolar , Diseño de Prótesis Dental , Estética Dental , Acondicionamiento de Tejidos Dentales