Mechanical comparison of experimental conical-head abutment screws with conventional flat-head abutment screws for external-hex and internal tri-channel implant connections: an in vitro evaluation of loosening torque.

PURPOSE: This study compared the loosening torque of experimental conical-head abutment screws to that of conventional flat-head screws of implants with external-hex (EH) and internal tri-channel (IT) connections before and after mechanical loading. MATERIALS AND METHODS: Forty-four implant/screw/abutment assemblies were divided into four groups: EH/flat-head screw (EH), IT/flat-head screw (IT), EH/conical-head screw (EHCS), and IT/conical-head screw (ITCS). Three assemblies from each group were analyzed in a stereoscopic magnifier and then returned to their respective groups. One assembly was removed from each group and transversely sectioned for optical microscopy analysis. Abutments were tightened at 32 Ncm of torque; after 10 minutes, loosening torque was measured. The same abutments were then retightened with 32 Ncm of torque; after 10 minutes, they were mechanically loaded for 300,000 cycles and loosening torque was again measured. Data were collected and an exploratory analysis was performed. Comparisons were made by orthogonal contrasts using a linear mixed effects model (random and fixed effects). RESULTS: Comparisons before mechanical cycling showed significant differences between groups except for EH vs IT and EHCS vs ITCS. After mechanical cycling, only the comparisons EH vs IT and EHCS vs ITCS showed no significant differences. Considering the same group, before and after mechanical cycling, all comparisons showed significant differences. CONCLUSIONS: The shape of the abutment screw head significantly influenced loosening torque: conical-head screws showed higher loosening torque values than conventional flat-head screws before and after loading. The implant/abutment connection design exerted no significant influence on loosening torque.

Immediate loading of implants placed in fresh extraction sockets in the molar area with flapless and graftless procedures: a case series.

The purpose of this study was to present a protocol for the replacement of single teeth lost in the molar area with immediate implantation in fresh extraction sockets, no flap reflections or grafting procedures, and immediate loading. Twenty-three implants were placed in 20 patients between 2000 and 2006. No implants were lost and no signs of significant bone resorption, loss of osseointegration, or soft tissue complications were reported. The results of this study indicate that this protocol may be a feasible alternative for the replacement of condemned molars.

Abrasion wear resistance of different artificial teeth opposed to metal and composite antagonists.

UNLABELLED: One of the most important properties of artificial teeth is the abrasion wear resistance, which is determinant in the maintenance of the rehabilitation's occlusal pattern. OBJECTIVES: This in vitro study aims to evaluate the abrasion wear resistance of 7 brands of artificial teeth opposed to two types of antagonists. MATERIAL AND METHODS: Seven groups were prepared with 12 specimens each (BIOLUX & BL, TRILUX & TR, BLUE DENT & BD, BIOCLER & BC, POSTARIS & PO, ORTHOSIT & OR, GNATHOSTAR & GN), opposed to metallic (M & nickel-chromium alloy), and to composite antagonists (C & Solidex indirect composite). A mechanical loading device was used (240 cycles/min, 4 Hz speed, 10 mm antagonist course). Initial and final contours of each specimen were registered with aid of a profile projector (20x magnification). The linear difference between the two profiles was measured and the registered values were subjected to ANOVA and Tukey's test. RESULTS: Regarding the antagonists, only OR (M = 10.45 +/- 1.42 microm and C = 2.77 +/- 0.69 microm) and BC (M = 6.70 +/- 1.37 microm and C = 4.48 +/- 0.80 microm) presented statistically significant differences (p < 0.05). Best results were obtained with PO (C = 2.33 +/- 0.91 microm and M = 1.78 +/- 0.42 microm), followed by BL (C = 3.70 +/- 1.32 microm and M = 3.70 +/- 0.61 microm), statistically similar for both antagonists (p>0.05). Greater result variance was obtained with OR, which presented the worse results opposed to Ni-Cr (10.45 +/- 1.42 microm), and results similar to the best ones against composite (2.77 +/- 0.69 microm). CONCLUSIONS: Within the limitations of this study, it may be concluded that the antagonist material is a factor of major importance to be considered in the choice of the artificial teeth to be used in the prosthesis.

Abrasion wear resistance of different artificial teeth opposed to metal and composite antagonists

One of the most important properties of artificial teeth is the abrasion wear resistance, which is determinant in the maintenance of the rehabilitation's occlusal pattern. OBJECTIVES: This in vitro study aims to evaluate the abrasion wear resistance of 7 brands of artificial teeth opposed to two types of antagonists. MATERIAL AND METHODS: Seven groups were prepared with 12 specimens each (BIOLUX & BL, TRILUX & TR, BLUE DENT & BD, BIOCLER & BC, POSTARIS & PO, ORTHOSIT & OR, GNATHOSTAR & GN), opposed to metallic (M & nickel-chromium alloy), and to composite antagonists (C & Solidex indirect composite). A mechanical loading device was used (240 cycles/min, 4 Hz speed, 10 mm antagonist course). Initial and final contours of each specimen were registered with aid of a profile projector (20x magnification). The linear difference between the two profiles was measured and the registered values were subjected to ANOVA and Tukey's test. RESULTS: Regarding the antagonists, only OR (M = 10.45 ± 1.42 µm and C = 2.77 ± 0.69 µm) and BC (M = 6.70 ± 1.37 µm and C = 4.48 ± 0.80 µm) presented statistically significant differences (p < 0.05). Best results were obtained with PO (C = 2.33 ± 0.91 µm and M = 1.78 ± 0.42 µm), followed by BL (C = 3.70 ± 1.32 µm and M = 3.70 ± 0.61 µm), statistically similar for both antagonists (p>0.05). Greater result variance was obtained with OR, which presented the worse results opposed to Ni-Cr (10.45 ± 1.42 µm), and results similar to the best ones against composite (2.77 ± 0.69 µm). CONCLUSIONS: Within the limitations of this study, it may be concluded that the antagonist material is a factor of major importance to be considered in the choice of the artificial teeth to be used in the prosthesis.

Fracture resistance of the implant-abutment connection in implants with internal hex and internal conical connections under oblique compressive loading: an in vitro study.

The objective of this study was to verify if differences in the design of internal hex (IH) and internal conical (IC) connection implant systems influence fracture resistance under oblique compressive forces. Twenty implant-abutment assemblies were utilized: 10 with IH connections and 10 with IC connections. Maximum deformation force for IC implants (90.58 +/- 6.72 kgf) was statistically higher than that for IH implants (83.73 +/- 4.94 kgf) (P = .0182). Fracture force for the IH implants was 79.86 +/- 4.77 kgf. None of the IC implants fractured. The friction-locking mechanics and the solid design of the IC abutments provided greater resistance to deformation and fracture under oblique compressive loading when compared to the IH abutments.

Estudo comparativo da dissipação de tensões em fixações zigomáticas instaladas internamente ou externamente ao seio maxilar: uma análise 3D pelo método de elementos finitos / Comparative study on the stress dissipation of zygomatic fixtures installed internal or external to the maxillary sinus: a 3D finite element method analysis

As fixações zigomáticas são utilizadas em reabilitações de maxilas edêntulas severamente atróficas, proporcionando ancoragem no osso zigomático. Modificações na técnica original de instalação destas fixações possibilitam um melhor posicionamento de sua emergência, favorecendo a reabilitação protética. Atualmente, são utilizadas técnicas de instalação internas ou externas ao seio maxilar. O comportamento biomecânico das fixações zigomáticas sob carregamento mecânico ainda é um tema obscuro, devido à inexistência de modelos confiáveis e elucidativos. Este estudo analisou, através do método de elementos finitos, a dissipação de tensões em fixações zigomáticas instaladas internamente ou externamente ao seio maxilar. Os resultados mostraram uma distribuição de tensões mais homogênea nas fixações zigomáticas instaladas externamente ao seio maxilar. Concluiu-se que a técnica exteriorizada proporcionou maior área de contato osso/fixação, que a posição palatinizada da emergência das fixações na técnica original gerou uma maior angulação da fixação e maior braço de alavanca na prótese, e que para ambas as técnicas foram observadas menores tensões no osso zigomático em relação à maxila.

The zygomatic fixtures are a valuable alternative to the maxillary reconstructions with bone grafts in the rehabilitation of severely atrophic edentulous maxillae. Modifications to the original installation technique of these fixations allowed a better positioning their emergence, favoring the prosthetic rehabilitation. Nowadays techniques internal and external to the maxillary sinus are used. The biomechanical behavior of the zygomatic fixtures under mechanichal loading remain obscure, due to the inexistence of reliable and elucidative models. This study analyzed with the finite element method the stress dissipation on zygomatic fixtures installed internally or externally to the maxillary sinus. The results showed a better stress distribution on the zygomatic fixtures installed externally to the maxillary sinus. It was concluded that the exteriorized technique provided a greater area of bone/implant contact, that the palatal emergence of the fixation on the original technique generated a higher angulation of the fixation and a greater lever arm on the prosthesis, and that low tensions are observed in the zygomatic bone in both techniques.

RM Bridge: uma nova abordagem protético reabilitadora para o tratamento dos desdentados totais / RM Bridge: a new rehabilitation prosthetic approach

A RM Bridge associada ao sistema All-on-4® é uma modalidade de tratamento para o desdentado que elimina a necessidade de enxertos e permite a função imediata do paciente. Este artigo apresenta o protocolo e as particularidades da RM Bridge empregada na reabilitação de desdentados totais.

Reabilitação da maxila atrófica sem enxertos ósseos: resultados de um novo protocolo utilizado em casos de edentulismo total / Rehabilitation of the atrophic maxillae without bone grafts: results of a new protocol utilized in cases of complete edentulism

A reabilitação dos desdentados totais com próteses fixas implanto-suportadas é uma alternativa de tratamento com altos índices de sucesso e mais de 40 anos de aplicação clínica. Os procedimentos de enxertia óssea necessários nas técnicas convencionais são de alta morbidade e indesejados pelos pacientes. Esse artigo avalia os resultados clínicos obtidos com um protocolo no qual a reabilitação dos pacientes edêntulos é realizada sem a realização de enxertos ósseos, mesmo em casos de atrofia severa da maxila, através da utilização de fixações zigomáticas e implantes convencionais.