Effect of a Customised Chairside Polishing Protocol for Zirconia- A Comparative Analysis

The purpose of this study was to develop a customized polishing protocol using standard zirconia polishing kit with polishers of different grit and to study their effect on the surface roughness of zirconia and compare it to that of laboratory polished zirconia samples and machine polished titanium implant abutments. Methods: The samples used in this study were 15 zirconia blocks and 10 machine polished titanium implant abutments (5 Biohorizon and 5 MIS). The 15 zirconia blocks were again divided into three groups. The first group consisted of 5 zirconia samples polished by customised polishing protocol (coarse + medium+ fine). The second group consisted of 5 zirconia samples which were sent to lab1 which used Komet company burs and 5 zirconia samples were sent to lab2 which used carborundum burs and sandpaper for polishing. The fourth group consisted of 5 machine polished titanium implants from MIS system and fifth group consisted of 5 machine polished titanium implants from Biohorizon system. After polishing, the mean surface roughness values (Ra) of zirconia samples and titanium implant abutments were calculated quantitatively by optical profilometer and qualitatively by scanning electron microscope (SEM). Results: The mean surface roughness value of customised polishing protocol using coarse+medium+fine polisher was 0.11 µm which was almost equal to the mean surface roughness values of lab1 polished zirconia samples - 0.131 µm and that of machine polished titanium implant abutments –Biohorizon: 0.201 µm MIS: 0.0859 µm and was within the optimal range of 0.2µm. Conclusions: Within the limitations of this study it was concluded that, the mean surface roughness values of zirconia samples polished by customised polishing protocol , lab1 polished samples and machine polished titanium implant abutments were found to be similar & closer to the critical Ra values (0.2µm) suggesting that the chairside polishing of zirconia can be carried out using the customized polishing technique

Three-dimensional finite element analysis of platform switched implant

PURPOSE: The purpose of this study was to analyze the influence of the platform switching concept on an implant system and peri-implant bone using three-dimensional finite element analysis. MATERIALS AND METHODS: Two three-dimensional finite element models for wide platform and platform switching were created. In the wide platform model, a wide platform abutment was connected to a wide platform implant. In the platform switching model, the wide platform abutment of the wide platform model was replaced by a regular platform abutment. A contact condition was set between the implant components. A vertical load of 300 N was applied to the crown. The maximum von Mises stress values and displacements of the two models were compared to analyze the biomechanical behavior of the models. RESULTS: In the two models, the stress was mainly concentrated at the bottom of the abutment and the top surface of the implant in both models. However, the von Mises stress values were much higher in the platform switching model in most of the components, except for the bone. The highest von Mises values and stress distribution pattern of the bone were similar in the two models. The components of the platform switching model showed greater displacement than those of the wide platform model. CONCLUSION: Due to the stress concentration generated in the implant and the prosthodontic components of the platform switched implant, the mechanical complications might occur when platform switching concept is used.

Effect of Using Nano and Micro Airborne Abrasive Particles on Bond Strength of Implant Abutment to Prosthesis

Connecting prostheses to the implant abutments has become a concern and achieving a satisfactory retention has been focused in cement-retention prostheses recently. Sandblasting is a method to make a roughened surface for providing more retention. The aim of this study was to compare effects of nano and micro airborne abrasive particles (ABAP) in roughening surface of implant abutments and further retention of cemented copings. Thirty Xive abutments and analogues (4.5 D GH1) were mounted vertically in self-cured acrylic blocks. Full metal Ni-Cr copings with a loop on the top were fabricated with appropriate marginal adaptation for each abutment. All samples were divided into 3 groups: first group (MPS) was sandblasted with 50 µm Al2O3 micro ABAP, second group (NSP) was sandblasted with 80 nm Al2O3 nano ABAP, and the third group (C) was assumed as control. The samples were cemented with provisional cement (Temp Bond) and tensile bond strength of cemented copings was evaluated by a universal testing machine after thermic cycling. The t test for independent samples was used for statistical analysis by SPSS software (version 15) at the significant level of 0.05. Final result showed significant difference among all groups (p<0.001) and MPS manifested the highest mean retention (207.88±45.61 N) with significant difference among other groups (p<0.001). The control group showed the lowest bond strength as predicted (48.95±10.44 N). Using nano or micro ABAP is an efficient way for increasing bond strengths significantly, but it seems that micro ABAP was more effective.

A conexão das próteses nos pilares dos implantes dentários é um fator de preocupação e a obtenção de uma retenção satisfatória tem sido objeto de estudos recentes em próteses com retenção cementária. O jateamento é um método de obter uma superfície áspera para aumentar a retenção. O objetivo do presente estudo foi comparar os efeitos de jateamento com nano- e micropartículas abrasivas para tornar áspera a superfície dos pilares de implantes e a consequente aumentar a retenção dos copings cimentados. Trinta pilares Xive com seus análogos (4.5 D GH1) foram montados na posição vertical em blocos de acrílico auto-polimerizados. Copings metálicos de Ni-Cr com uma alça no topo foram feitos com adaptação marginal apropriada para cada pilar. Todas as amostras foram divididas em três grupos: o 1° grupo (MPS) foi jateado com micropartículas de Al2O3 com 50 µm de tamanho médio; o 2° grupo (NPS) foi jateado com nanopartículas de Al2O3 com 80 nm de tamanho médio; e o 3° grupo (C) foi considerado controle. As amostras foram cimentadas com cimento provisório (Temp Bond) e a resistência à tração dos copings cimentados foi avaliada em máquina universal de ensaios após processo de termociclagem. O teste t para amostras independentes foi usado para fins de análise estatística empregando-se o software SPSS v. 15, com nível de significância de 0,05. Os resultados demonstraram diferença significante entre todos os grupos (p<0,001) e o grupo MPS mostrou o maior valor médio de resistência de união (207,88±45,61 N) com diferenças significantes em relação aos outros grupos (p<0,001). Conforme previsto, o grupo controle obteve o menor valor de resistência (48,95±10,44 N). O jateamento com micro ou nano partículas mostrou-se um modo eficaz de aumentar significativamente a resistência de união, mas aparentemente as micropartículas são mais eficazes.

Evaluation of removal forces of implant-supported zirconia copings depending on abutment geometry, luting agent and cleaning method during re-cementation

PURPOSE: To evaluate the effects of different abutment geometries in combination with varying luting agents and the effectiveness of different cleaning methods (prior to re-cementation) regarding the retentiveness of zirconia copings on implants. MATERIALS AND METHODS: Implants were embedded in resin blocks. Three groups of titanium abutments (pre-fabricated, height: 7.5 mm, taper: 5.7degrees; customized-long, height: 6.79 mm, taper: 4.8degrees; customized-short, height: 4.31 mm, taper: 4.8degrees) were used for luting of CAD/CAM-fabricated zirconia copings with a semi-permanent (Telio CS) and a provisional cement (TempBond NE). Retention forces were evaluated using a universal testing machine. Furthermore, the influence of cleaning methods (manually, manually in combination with ultrasonic bath or sandblasting) prior to re-cementation with a provisional cement (TempBond NE) was investigated with the pre-fabricated titanium abutments (height: 7.5 mm, taper: 5.7degrees) and SEM-analysis of inner surfaces of the copings was performed. Significant differences were determined via two-way ANOVA. RESULTS: Significant interactions between abutment geometry and luting agent were observed. TempBond NE showed the highest level of retentiveness on customized-long abutments, but was negatively affected by other abutment geometries. In contrast, luting with Telio CS demonstrated consistent results irrespective of the varying abutment geometries. Manual cleaning in combination with an ultrasonic bath was the only cleaning method tested prior to re-cementation that revealed retentiveness levels not inferior to primary cementation. CONCLUSION: No superiority for one of the two cements could be demonstrated because their influences on retentive strength are also depending on abutment geometry. Only manual cleaning in combination with an ultrasonic bath offers retentiveness levels after re-cementation comparable to those of primary luting.

Zirconia: A Creditable Restorative Material - A Review.

Advanced ceramic materials such as Zirconia have great potential as substitutes for traditional materials in many biomedical applications. Since the end of 1990’s, the form of partially stabilized zirconia has been promoted as suitable for dental use due to its excellent strength and superior fracture resistance as a result of its inherent transformation toughening. The purpose of this review is to know the evolution of zirconia as a biomaterial, to explore the materials physical, chemical, biological and optical properties of the material.