Fit and fatigue behavior of CAD-CAM lithium disilicate crowns.

STATEMENT OF PROBLEM: New computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate glass-ceramics have been marketed. However, information concerning their biomechanical behavior is lacking. PURPOSE: The purpose of this in vitro study was to compare the fit and fatigue behavior of two recently introduced CAD-CAM lithium disilicate materials with the standard IPS e.max CAD ceramic and to investigate the effect of the thermal treatment for crystallization on crown fit. MATERIAL AND METHODS: Monolithic crowns (n=15) were milled from 3 CAD-CAM lithium disilicates: IPS e.max CAD (Ivoclar AG), Rosetta SM (Hass), and T-lithium (Shenzhen Upcera Dental Technology). Marginal and internal fit were evaluated using the replica technique before and after crystallization, and the fatigue behavior of the luted crowns was evaluated by the step-stress method. One-way ANOVA and the Tukey test were used to compare fit among the materials. Fatigue failure load was evaluated by the Kaplan-Meier and Mantel-Cox tests. The effect of crystallization on fit was evaluated with the paired t test (α=.05). RESULTS: Marginal fit was different between IPS e.max CAD (74 µm) and Rosetta SM (63 µm) (P=.02). T-lithium was similar to the other ceramics (68 µm) (P>.05). Occlusal internal space was similar among all materials (P=.69). Fatigue failure loads of Rosetta SM (1160 N) and T-lithium (1063 N) were similar to IPS e.max CAD (1082 N) (P>.05). The fatigue failure load of Rosetta SM was higher than that of T-lithium (P=.04). Crystallization reduced the axial internal space of all materials (P<.05) without significantly affecting marginal fit (P>.05). CONCLUSIONS: The fit and fatigue behavior of Rosetta SM and T-lithium were similar to that of IPS e.max CAD. Crystallization reduced the internal space of the crowns.

Effects of disinfection with a vinegar-hydrogen peroxide mixture on the surface composition and topography of a cobalt-chromium alloy.

STATEMENT OF PROBLEM: Choosing the best disinfection agent for removable partial dentures may be challenging since most commercially available disinfection solutions alter the properties of the metal framework. PURPOSE: The purpose of this in vitro study was to analyze the changes in the surface topography and elemental composition of a cobalt-chromium (Co-Cr) alloy when immersed in a vinegar-hydrogen peroxide mixture. MATERIAL AND METHODS: Disk-shaped specimens (N=50) were fabricated with Co-Cr alloy and randomly distributed into 5 groups (N=10) according to the immersion solutions: distilled water (control) (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water in a 1:1 ratio (HP); vinegar and water in a 1:1 ratio (V); and vinegar and 3% hydrogen peroxide mixture in a 1:1 ratio (VHP). The immersions simulated 90 uses of 10 minutes each. The surface topography and the elemental composition were analyzed with scanning electron microscopy and energy-dispersive spectroscopy, before (T0) and after (T1) the immersions. The 2-way ANOVA for repeated measures was used for statistical comparisons (α=.05). RESULTS: The tested mixture (VHP) did not change the metal surface topography or increase the oxygen proportion, indicating that no corrosion occurred. Similarly, groups W, HP, and V had no topographic changes and nonsignificant statistical differences at T1 for elemental composition (P>.05). However, the specimens immersed in sodium hypochlorite (H) showed staining, surface irregularity, composition change, with an appearance of 22.56% more oxygen, 41% less chromium, and 28.77% less cobalt at T1 (P<.05). CONCLUSIONS: The immersion of Co-Cr alloy in a vinegar-hydrogen peroxide mixture did not change the surface structure of the metal.

Effect of a vinegar-hydrogen peroxide mixture on the surface properties of a cobalt-chromium alloy: A possible disinfectant for removable partial dentures.

STATEMENT OF PROBLEM: A vinegar-hydrogen peroxide mixture has been reported to be effective in eliminating Candida albicans and Staphylococcus aureus from acrylic resin, and its action has been reported to be comparable with that of sodium hypochlorite or peracetic acid. However, the effects of this mixture on cobalt-chromium alloys remain unknown. PURPOSE: The purpose of this in vitro study was to evaluate the surface roughness, Knoop microhardness, surface free energy, and wettability of a cobalt-chromium alloy when exposed to a vinegar-hydrogen peroxide mixture. MATERIAL AND METHODS: Fifty specimens of cobalt-chromium alloy were fabricated and immersed for 900 minutes, simulating 3 months of a daily 10-minute immersion in the following chemical agents (n=10): distilled water (W); 0.5% sodium hypochlorite (H); 3% hydrogen peroxide and water dilution in 1:1 ratio (HP); white-wine vinegar and water dilution in 1:1 ratio (V); and vinegar and hydrogen peroxide mixture in 1:1 ratio (VHP). Surface roughness, Knoop microhardness, surface free energy, and wettability were measured with single blinding before and after immersions. Data were statistically analyzed by using 2-way repeated measures ANOVA (α=.05). RESULTS: The vinegar-hydrogen peroxide mixture did not affect the surface roughness or Knoop microhardness. However, 0.5% sodium hypochlorite significantly increased the roughness and decreased microhardness. Surface free energy and wettability increased after immersions, regardless of the types of solution. CONCLUSIONS: Immersion in a vinegar-hydrogen peroxide mixture did not affect the surface characteristics of a cobalt-chromium alloy.

Keratinocyte Cytotoxicity of Peracetic Acid Used as Sterilizing Agent for Implant Scaffolds.

Peracetic acid (PAA) has been used to sterilize biomaterial scaffolds and allografts before their implantation. Although the antimicrobial effectiveness of PAA is widely known, there are no studies investigating its cytotoxicity on keratinocytes. This study aimed to investigate the cytotoxicity of PAA concentrations on keratinocytes by growing HaCaT cells in culture medium. Different concentrations of PAA (control-untreated, 0.01, 0.1, 1, 10, 100, 200, 400, 800, 1200, 1600, and 2000 ppm) were added to the culture wells and allowed to be in direct contact with cells for up to 24 hours. Cytotoxicity was quantitatively and qualitatively determined by cell viability assay and analysis of morphological changes. Statistical analysis was performed with 1-way analysis of variance and Tukey test at 5% significance. Cells treated with 0.01 and 0.1 ppm followed the same morphological pattern of untreated cells, whereas cells treated with 1.0 ppm presented about 20% of floating cells and dark cytoplasmic granules. More than 50% of the cells treated with 10 and 100 ppm were destroyed, whereas the attached ones showed unclear and interrupted cell membranes. Concentrations of 1 ppm or greater had less than 64.4% of viable cells compared with the control group. This study concluded that exposure of keratinocytes to concentrations of 1 ppm or greater of PAA resulted in strong cytotoxic effects.

Wear Potential of Dental Ceramics and its Relationship with Microhardness and Coefficient of Friction.

PURPOSE: To evaluate, by means of pin-on-disk testing, the wear potential of different dental ceramic systems as it relates to friction parameters, surface finish, and microhardness. MATERIALS AND METHODS: Three groups of different ceramic systems (Noritake EX3, Eris, Empress II) with 20 disks each (10 glazed, 10 polished) were used. Vickers microhardness (Hv) was determined with a 200-g load for 30 seconds. Friction coefficients (µ) were determined by pin-on-disk testing (5 N load, 600 seconds, and 120 rpm). Wear patterns were assessed by scanning electron microscopy (SEM). The results were analyzed using one-way ANOVA and Tukey's test, with the significance level set at α = 0.05. RESULTS: The coefficients of friction were as follows: Noritake EX3 0.28 ± 0.12 (polished), 0.33 ± 0.08 (glazed); Empress II 0.38 ± 0.08 (polished), 0.45 ± 0.05 (glazed); Eris 0.49 ± 0.05 (polished), 0.49 ± 0.06 (glazed). Microhardness measurements were as follows: Noritake EX3 530.7 ± 8.7 (polished), 525.9 ± 6.2 (glazed); Empress II 534.1 ± 8 (polished), 534.7 ± 4.5 (glazed); Eris, 511.7 ± 6.5 (polished), 519.5 ± 4.1 (glazed). The polished and glazed Noritake EX3 and polished and glazed Eris specimens showed statistically different friction coefficients. SEM image analysis revealed more surface changes, such as small cracks and grains peeling off, in glazed ceramics. CONCLUSIONS: Wear potential may be related to the coefficient of friction in Noritake ceramics, which had a lower coefficient than Eris ceramics. Within-group analysis showed no differences in polished or glazed specimens. The differences observed were not associated with microhardness.

Evaluation of tensile strength resistance of different biomaterials in calvarial rats

AIM: The aim of this study was to determine the effect of different grafting materials on bone tensile strength after 6-month wound healing. MATERIAL AND METHODS: Non-critical size defects (3-mm diameter) were created in calvarium of 30 three-month-old Wistar rats. Animals were divided into 3 groups (n=10) treated with different grafting materials: GenOx® (Group 1A); GenMix® (Group 1B); no treatment (blood clot, Group 3). Six months after the surgery, rats were sacrificed; bone specimens were harvested and submitted to tensile strength test using a universal testing machine. The bone fracture surface morphology was evaluated using scanning electron microscopy (SEM) at 200X magnification. Data were compared by One-Way ANOVA at 5% significance. RESULTS: No significant difference was found among the groups although tensile strength decreased in the following order: Group 3 (9.56±3.74MPa), Group 1B (8.58±3.60MPa), Group 1A (7.70±2.41MPa). All tested materials showed similar effects on bone tensile strength, no matter the source (xenogenic or blood clot). CONCLUSION: After six months of bone healing, the type of grafting material is irrelevant to the final outcome and bone tensile strength.

Effect of glazed and polished surface finishes on the friction coefficient of two low-fusing ceramics.

STATEMENT OF PROBLEM: All-ceramic and metal-ceramic dental restorations are potentially harmful because they may wear opposing enamel. Wear is a multifactorial process; however, laboratory procedures can minimize the wear process, thus benefiting clinicians and manufacturers. PURPOSE: This in vitro investigation of wear evaluated the physical and tribological characteristics of 2 low-fusing ceramics and dental enamel. MATERIAL AND METHODS: Quantitative and qualitative analyses of 2 low-fusing ceramics (IPS d.Sign and Vita Omega 900) and enamel were performed using scanning electron microscopy, x-ray diffraction, and energy-dispersive analyses. Each ceramic was tested using 20 disks (10 mm x 3 mm), of which 10 were glazed and 10 were polished. Ten polished enamel specimens (6 mm x 7 mm) served as the control. The specimens were submitted to a Vickers hardness test for 30 seconds using a 200 g load. The coefficient of friction was determined by using a pin-on-disk test without lubrication (5 N load, 600 seconds, 120 RPM). The data were analyzed using a 1-way analysis of variance and Sheffe analysis (alpha=.05). RESULTS: The same chemical elements were found in both ceramics, and tetragonal leucite was the main component of the crystalline phases. The microhardness of the enamel was significantly different ( P <.05) between the glazed and polished ceramics. There was no significant difference found in the friction coefficient (mean +/- SD) of the enamel (0.286 +/- 0.174), glazed Vita Omega 900 (0.309 +/- 0.085), and glazed IPS d.Sign (0.253 +/- 0.068) specimens. The mean friction coefficient of the polished Vita Omega 900 (0.486 +/- 0.036) and IPS d.Sign (0.446 +/- 0.037) specimens was found to be significantly higher than the enamel and glazed specimens ( P <.05). CONCLUSIONS: Both ceramics tested presented similar chemical-structural and tribological characteristics. When glazed, they showed tribological similarity to dental enamel.

Adaptação marginal em copings de dois sistemas cerâmicos livres de metal / Marginal fit in copings of two metal free ceramic systems

Este trabalhou avaliou a adaptação marginal de infraestruturas cerâmicas (copings em alumina) de dois sistemas cerâmicos livres de metal. Foram pesquisados os sistemas In-Ceram e Procera. Os valores de discrepância vertical presentes entre as margens de nove copings de cada sistema cerâmico e a margem de um modelo mestre metálico foram medidos com microscópio eletrônico de varredura em 5 pontos de cada infraestrutura. Esses valores foram medidos em micrômetros (pm). Os resultados foram analisados estatisticamente com o software SPSS (Statistical Package for the Social Sciences 11.0), através do teste t de Student, considerando-se significativos os valores de p<0(05. Os valores médios de discrepância marginal dos dois sistemas, medidos em microscópio eletrônico de varredura, mostraram diferença estatística entre si (p=0,001), sendo observadas desadaptações de 39±11pm (sistemas Procera) e 11 5±56pm (sistema In-Ceram). Conclui-se que os dois sistemas cerâmicos livres de metal avaliados apresentaram adaptação marginal dentro de limites aceitáveis clinicamente.

This work has evaluated the marginal fit of alumina copings of two metal free ceramic systems, namely Procera and In-Ceram systems. The marginal fit values of the margins in nine copings of each ceramic system and in a metal master model were assessed using electron- scanning microcopy in five points of the margin of each coping. Such values were measured in micrometers (pm). The results were analyzed statistically by the SPSS software (p<0.05). The marginal fit mean values for both systems have presented statistical difference (p=0.001), being of 39±11 pm and 115±56pm for the Procera and Inc-Ceram systems, respectively. Both systems have presented marginal fit according to the clinical acceptance.

Fibroma ossificante: relato de um caso / Ossifying fibroma: report of a case

Os autores apresentam um caso clínico de fibroma ossificante em paciente de 46 anos de idade. Säo discutidos a etiopatogenia, aspectos clínicos, radiográficos e microscópicos e diagnóstico diferencial

Estudo comparativo da resistência superficial do titânio comercialmente puro e do titânio nitretado em plasma / Comparison of superficial resistance between commercially pure titanium and plasma nitriding titanium

Com o objetivo de melhorar as propriedades tribológicas da superfície do titânio usado em implantes dentais, particularmente sua resistência ao desgaste, foi desenvolvida na presente Tese uma investigaçäo sistemática do efeito da nitretaçäo em plasma (NP) sobre as referidas propriedades de amostras de titânio comercialmente puras. A NP é um método de modificaçäo superficial capaz de gerar compostos (nitretos e óxidos) que aumentam consideravelmente o rendimento tribológico das superfícies tratadas. Foram utilizados inicialmente 13 diferentes conjuntos de parâmetros operacionais para nitretaçäo (variaçöes de tempo, temperatura da amostra e composiçäo do gás nitretante). As amostras foram testadas com aparelho sônico (Sonicborden, Kavo) e caracterizadas com difratometria de raios-X e icroscopia eletrônica de varredura. As amostras que se destacaram por sua resistência foram novamente produzidas (em três momentos diferentes) e testadas com curetas Gracey, aparelho sônico e teste de pino-sobre-disco. A caracterizaçäo superficial foi novamente realizada com o uso de difratometria de raios-X, reaçäo nuclear e microscopia eletrônica de varredura. A análise dos dados obtidos indica que a nitretaçäo em plasma aumenta a resistência superficial do titânio. Os seguintes parâmetros: 3 horas de tratamento; composiçäo gasosa N²/H² = 80/20 e N²/H² = 20/80; e temperaturas de 600ºC e 800ºC produzem amostras de titânio mais resistentes que o titânio comercialmente puro