Enhanced Bone Bonding to Nanotextured Implant Surfaces at a Short Healing Period: A Biomechanical Tensile Testing in the Rat Femur.

PURPOSE: To compare the bone bonding capabilities of 2 different surface treatments at an early healing period. Titanium alloy (Ti6Al4V) custom-made rectangular plates (1.4 × 2.4 × 4 mm) were either dual acid etched (Ti6Al4V-DAE) or DAE/nanotextured blasted (Ti6Al4V-NTB). MATERIALS AND METHODS: Implants were placed in the distal femurs of 10 Wistar rats and were allowed to heal for 9 days. After euthanasia, the bone immediately proximal and distal to the implant was removed to test the bone bonding force with a universal testing machine. Ultrastructure of the bone/implant interface was assessed by scanning electron microscopy. RESULTS: Ti6Al4V-NTB samples exhibited significantly greater bond strength than Ti6Al4V-DAE samples. Morphologically, the Ti6Al4V-NTB surfaces presented intimate interaction with bone, whereas little interaction between the Ti6Al4V-DAE surface and bone was observed. CONCLUSION: The results of this study indicated a significant increase in bone bonding for the DAE/nanotextured blasted surface, which is suggested to be the outcome of the nanotexturing.

Próteses totais fixas tipo protocolo bimaxilares. Relato de caso / Fixed full-arch prosthesis type protocol bimaxillary. Case report

Os implantes osseointegrados promoveram importantes mudanças nas formas de reabilitação de pacientes parcial ou totalmente desdentados. Os pacientes totalmente desdentados apresentam clara predileção pelas próteses fixas implantossuportas, sobretudo porque proporcionam maior eficiência mastigatória e conforto, menos reparo e manutenção, além de favorecer o aspecto psicológico, uma vez que elimina o caráter removível das overdentures. Dentre os possíveis desenhos de próteses fixas as do tipo protocolo são as que apresentam maior aplicação clínica, e se caracterizam na mandíbula pela colocação de 4 a 6 implantes na região anterior, entre os forames mentuais, e cantilever distal bilateral para substituir os dentes posteriores. Na maxila recomenda-se a colocação de 6 a 8 implantes. Neste tipo de prótese utiliza-se uma infraestrutura metálica e uma base de resina para uni-la aos dentes de resina acrílica. O objetivo deste trabalho foi relatar um caso clínico de próteses totais fixas tipo protocolo bimaxilares, em que foram adotados critérios bem definidos de diagnóstico e planejamento, e empregadas técnicas cirúrgicas e protéticas com fundamentação científica.

The dental implants promoted important changes in the forms of rehabilitation of partially or fully edentulous patients. Edentulous patients show clear preference for implant-supported fixed prosthesis, mainly because they provide greater chewing efficiency and comfort, less repair and maintenance, in addition to promoting the psychological aspect, considering that eliminates the character removable of overdentures. Among the possible designs of the fixed prosthesis, the type protocols are the which have greater clinical application, and characterized by placing the jaw 4-6 implant in the anterior region between the foramina mentuals, and bilateral distal cantilevers to replace the posterior teeth. In the maxilla is recommended to put 6-8 implants. In this type of prosthesis is used a metal infrastructure and a resin base to attach it to the teeth of acrylic resin. The objective of this study was to report a case of protocol type full-arch fixed prosthesis bimaxillaries with employment of well-defined criteria for diagnosis and planning, and surgical and prosthetic techniques scientific evidence-based.

Conventional and modified veneered zirconia vs. metalloceramic: fatigue and finite element analysis.

PURPOSE: The purpose of this study was to test the hypothesis that all-ceramic crown core-veneer system reliability is improved by modifying the core design and as a result is comparable in reliability to metal-ceramic retainers (MCR). Finite element analysis (FEA) was performed to verify maximum principal stress distribution in the systems. MATERIALS AND METHODS: A first lower molar full crown preparation was modeled by reducing the height of proximal walls by 1.5 mm and occlusal surface by 2.0 mm. The CAD-based preparation was replicated and positioned in a dental articulator for specimen fabrication. Conventional (0.5 mm uniform thickness) and modified (2.5 mm height, 1 mm thickness at the lingual extending to proximals) zirconia (Y-TZP) core designs were produced with 1.5 mm veneer porcelain. MCR controls were fabricated following conventional design. All crowns were resin cemented to 30-day aged composite dies, aged 14 days in water and either single-loaded to failure or step-stress fatigue tested. The loads were positioned either on the mesiobuccal or mesiolingual cusp (n = 21 for each ceramic system and cusp). Probability Weibull and use level probability curves were calculated. Crack evolution was followed, and postmortem specimens were analyzed and compared to clinical failures. RESULTS: Compared to conventional and MCRs, increased levels of stress were observed in the core region for the modified Y-TZP core design. The reliability was higher in the Y-TZP-lingual-modified group at 100,000 cycles and 200 N, but not significantly different from the MCR-mesiolingual group. The MCR-distobuccal group showed the highest reliability. Fracture modes for Y-TZP groups were veneer chipping not exposing the core for the conventional design groups, and exposing the veneer-core interface for the modified group. MCR fractures were mostly chipping combined with metal coping exposure. CONCLUSIONS: FEA showed higher levels of stress for both Y-TZP core designs and veneer layers compared to MCR. Core design modification resulted in fatigue reliability response of Y-TZP comparable to MCR at 100,000 cycles and 200 N. Fracture modes observed matched with clinical scenarios.

Fatigue reliability of 3 single-unit implant-abutment designs.

OBJECTIVES: Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. METHODS AND MATERIALS: Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. RESULTS: The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. CONCLUSIONS: The 3 evaluated systems did not present significantly different reliability; however, failure modes were different.

Monolithic CAD/CAM lithium disilicate versus veneered Y-TZP crowns: comparison of failure modes and reliability after fatigue.

PURPOSE: The aim of this research was to evaluate the fatigue behavior and reliability of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate and hand-layer-veneered zirconia all-ceramic crowns. MATERIALS AND METHODS: A CAD-based mandibular molar crown preparation, fabricated using rapid prototyping, served as the master die. Fully anatomically shaped monolithic lithium disilicate crowns (IPS e.max CAD, n = 19) and hand-layer-veneered zirconia-based crowns (IPS e.max ZirCAD/Ceram, n = 21) were designed and milled using a CAD/CAM system. Crowns were cemented on aged dentinlike composite dies with resin cement. Crowns were exposed to mouth-motion fatigue by sliding a WC-indenter (r = 3.18 mm) 0.7 mm lingually down the distobuccal cusp using three different step-stress profiles until failure occurred. Failure was designated as a large chip or fracture through the crown. If no failures occurred at high loads (> 900 N), the test method was changed to staircase r ratio fatigue. Stress level probability curves and reliability were calculated. RESULTS: Hand-layer-veneered zirconia crowns revealed veneer chipping and had a reliability of < 0.01 (0.03 to 0.00, two-sided 90% confidence bounds) for a mission of 100,000 cycles and a 200-N load. None of the fully anatomically shaped CAD/CAM-fabricated monolithic lithium disilicate crowns failed during step-stress mouth-motion fatigue (180,000 cycles, 900 N). CAD/CAM lithium disilicate crowns also survived r ratio fatigue (1,000,000 cycles, 100 to 1,000 N). There appears to be a threshold for damage/bulk fracture for the lithium disilicate ceramic in the range of 1,100 to 1,200 N. CONCLUSION: Based on present fatigue findings, the application of CAD/CAM lithium disilicate ceramic in a monolithic/fully anatomical configuration resulted in fatigue-resistant crowns, whereas hand-layer-veneered zirconia crowns revealed a high susceptibility to mouth-motion cyclic loading with early veneer failures.

Thermal/mechanical simulation and laboratory fatigue testing of an alternative yttria tetragonal zirconia polycrystal core-veneer all-ceramic layered crown design.

This study evaluated the stress levels at the core layer and the veneer layer of zirconia crowns (comprising an alternative core design vs. a standard core design) under mechanical/thermal simulation, and subjected simulated models to laboratory mouth-motion fatigue. The dimensions of a mandibular first molar were imported into computer-aided design (CAD) software and a tooth preparation was modeled. A crown was designed using the space between the original tooth and the prepared tooth. The alternative core presented an additional lingual shoulder that lowered the veneer bulk of the cusps. Finite element analyses evaluated the residual maximum principal stresses fields at the core and veneer of both designs under loading and when cooled from 900 degrees C to 25 degrees C. Crowns were fabricated and mouth-motion fatigued, generating master Weibull curves and reliability data. Thermal modeling showed low residual stress fields throughout the bulk of the cusps for both groups. Mechanical simulation depicted a shift in stress levels to the core of the alternative design compared with the standard design. Significantly higher reliability was found for the alternative core. Regardless of the alternative configuration, thermal and mechanical computer simulations showed stress in the alternative core design comparable and higher to that of the standard configuration, respectively. Such a mechanical scenario probably led to the higher reliability of the alternative design under fatigue.

Design features of a three-dimensional molar crown and related maximum principal stress. A finite element model study.

OBJECTIVE: To evaluate the effects of clinically relevant variables on the maximum principal stress (MPS) in the veneer layer of an anatomically correct veneer-core-cement-tooth model. METHODS: The average dimensions of a mandibular first molar crown were imported into CAD software; a tooth preparation was modeled by reducing the proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. 'Crown systems' were composed by varying characteristics of a cement layer, structural core, and veneer solid, all designed to fit the tooth preparation. The main and interacting effects of proximal wall height reduction, core material, core thickness, cement modulus, cement thickness, and load position on the maximum stress distribution were derived from a series of finite element models and analyzed in a factorial analysis of variance. RESULTS: The average MPS in the veneer layer over the 64 models was 488 MPa (range = 248-840 MPa). MPS increased significantly with the addition of horizontal load components and with increasing cement thickness. In addition, MPS levels varied as a function of interactions between: proximal wall height reduction and load position; load position and cement thickness; core thickness and cement thickness; cement thickness and proximal wall height reduction; and core thickness, cement thickness and proximal wall height reduction. CONCLUSION: Rational design of veneered structural ceramics must consider the complex geometry of the crown-tooth system and integrate the influence of both the main effects and interactions among design parameters.

Encaixes intracoronários de semi-precisão: relato de caso clínico / Intracoronal semi-precision attachments: a clinical case report

Os encaixes são elementos constituintes de uma prótese parcial remivível (PPR), alternativos aos grampos convencionais. Estes retentores podem ser classificados, quanto à localização, com intrarradiculares, intra ou extracoronários; quanto ao modo de confecção, como de precisão ou semi-precisão; e quanto às características de rigidez e resiliência. Os retentores de semi-precisão são conhecidos como encaixes fresados e são obtidos laboratorialmente. As próteses a encaixes são mais estéticas, confortáveis e, do ponto de vista biomecânico, mais favoráveis do que as próteses parciais removíveis convencionais, e requerem maior conhecimento, experiência e tempo, tanto por parte do Cirurgião-dentista quanto do Técnico laboratorial. O presente trabalho tem como objetivo a apresentação de um caso clínico de PPR retida por emcaixes intracoronários rígidos de semi-precisão e discutir os princípios de sua formação