Comparative study of intermaxillary relationships of manual and swallowing methods

This study compared the mandibular displacement from three methods of centric relation record using an anterior jig associated with (A) chin point guidance, (B) swallowing (control group) and (C) bimanual manipulation. Ten patients aged 25-39 years were selected if they met the following inclusion criteria: complete dentition (up to the second molars), Angle class I and absence of signs and symptoms of temporomandibular disorders and diagnostic casts showing stability in the maximum intercuspation (MI) position. Impressions of maxillary and mandibular arches were made with an irreversible hydrocolloid impression material. Master casts of each patient were obtained, mounted on a microscope table in MI as a reference position and 5 records of each method were made per patient. The mandibular casts were then repositioned with records interposed and new measurements were obtained. The difference between the two readings allowed measuring the displacement of the mandible in the anteroposterior and lateral axes. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. There was no statistically significant differences (p>0.05) among the three methods for measuring lateral displacement (A=0.38 ± 0.26, B=0.32 ± 0.25 and C=0.32 ± 0.23). For the anteroposterior displacement (A=2.76 ± 1.43, B=2.46 ± 1.48 and C=2.97 ± 1.51), the swallowing method (B) differed significantly from the others (p<0.05), but no significant difference (p>0.05) was found between chin point guidance (A) and bimanual manipulation (C). In conclusion, the swallowing method produced smaller mandibular posterior displacement than the other methods.Este estudo comparou o deslocamento mandibular a partir de 3 métodos de registro da relação cêntrica usando um jig anterior associado com: (A) guia da ponta do mento; (B) deglutição grupo controle (C) manipulação bimanual. As moldagens dos arcos maxilares e mandibulares foram feitas com hidrocolóide irreversível. Os modelos de estudo de cada paciente foram obtidos e montados em máxima intercuspidação como uma posição de referência no microscópio. Foram obtidos 5 registros de cada método em 10 pacientes. Os modelos mandibulares foram reposicionados com os registros interpostos e novas medidas foram obtidas. A diferença entre as duas leituras permitiu a medida do deslocamento mandibular nos eixos ântero-posterior e laterais. ANOVA não demonstrou diferença estatisticamente significativa entre os 3 métodos em relação ao registro do deslocamento lateral (A = 0,38 ± 0,26, B = 0,32 ± 0,25 e C = 0,32 ± 0,23). Quanto ao deslocamento anteroposterior, ANOVA e o teste de Tukey (a=0,05) indicaram diferença estatisticamente significante entre os três métodos (A=2,76 ± 1,43, B=2,46 ± 1,48 e C=2,97 ± 1,51). Não houve diferença estatisticamente significante entre A e C. A deglutição propiciou menor deslocamento mandibular posterior que os outros métodos

Effect of casting atmosphere on the shear bond strength of a ceramic to Ni-Cr and Ni-Cr-Be alloys

The success of metal-ceramic restorations depends on an optimal bond between metal and ceramic. This study evaluated the effect of 3 casting atmospheres on the metal-ceramic bond strength (MCBS) of 2 Ni-Cr alloys, with beryllium (Fit Cast V) and without beryllium (Fit Cast SB). Sixty acrylic resin patterns (8 mm long and 5 mm diameter) were obtained using a fluorocarbon resin matrix. Wax was used to refine the surface of acrylic resin patterns that were invested and cast in an induction casting machine under normal, vacuum, and argon atmospheres at a temperature of 1340ºC. The castings were divested manually and airborne-particle abraded with 100-µm aluminum-oxide. Ten castings were obtained for each group. The IPS Classic V ceramic was applied (2 mm high and 5 mm diameter). The shear bond strength was tested in a mechanical testing machine with a crosshead speed of 2.0 mm/min. The MCBS data (MPa) were subjected to 2-way analysis of variance (&#945;=0.05). There was no statistically significant difference (p>0.05) between the alloys or among the casting atmospheres. Within the limitations of this study, it may be concluded that the presence of beryllium and the casting atmosphere did not interfere in the MCBS of the evaluated metal-ceramic combinationsO sucesso das restaurações metalocerâmicas depende da ótima união entre metal e cerâmica. Este estudo avaliou o efeito de 3 atmosferas de fundição na resistência de união metalocerâmica (RUMC) de 2 ligas de Ni-Cr, com berílio (Fit Cast V) e sem berílio (Fit Cast SB). Sessenta padrões de resina acrílica (comprimento de 8 mm e diâmetro de 5 mm) foram obtidos usando uma matriz de teflon. Foi utilizada cera para refinar a superfície dos padrões de resina acrílica que foram incluídos e fundidos em máquina de fundição por indução nas seguintes atmosferas de fundição: normal, vácuo e argônio, à temperatura de 1340ºC. As fundições foram removidas e usinadas com partículas de óxido de alumínio de 100 mm, sendo 10 fundições por grupo. Foi aplicada a cerâmica IPS Clássico V (2 mm de altura e diâmetro de 5 mm). O ensaio de cisalhamento foi realizado em máquina de ensaios mecânicos com velocidade de 2,0 mm/min. Os dados de RUMC (MPa) foram analisados por meio da análise de variância (&#945;=0,05). Não houve diferença significante (p>0,05) entre as ligas e entre as atmosferas de fundição. Dentro das limitações deste estudo, pode-se concluir que a presença do berílio e a atmosfera de fundição não interferiram na RUMC das combinações metalocerâmicas avaliadas

Effect of laser welding on the titanium composite tensile bond strength

The aim of this study was to analyze the shear bond strength between commercially pure titanium, with and without laser welding, after airbone-particle abrasion (Al2O3) and 2 indirect composites. Sixty-four specimens were cast and divided into 2 groups with and without laser welding. Each group was divided in 4 subgroups, related to Al2O3 grain size: A - 250 µm; B - 180 µm; C- 110 µm; and D - 50 µm. Composite rings were formed around the rods and light polymerized using UniXS unit. Specimens were invested and their shear bond strength at failure was measured with a universal testing machine at a crosshead speed of 2.0 mm/min. Statistical analysis was carried out with ANOVA and Tukey's test (&#945;=0.05). The highest bond strength means were recorded in 250 µm group without laser welding. The lowest shear bond strength means were recorded in 50 µm group with laser welding. Statistically significant differences (p<0.05) were found between all groups. In conclusion, airborne particle abrasion yielded significantly lower bond strength as the Al2O3 particle size decreased. Shear bond strength decreased in the laser welded specimens.O objetivo deste estudo foi analisar a força de união entre o titânio comercialmente puro com solda e sem solda modificado por partículas de óxido de alumínio (Al2O3) e duas resinas indiretas. Um total de 64 espécimes foram fundidas e divididas em dois grupos sem solda e com solda a laser. Cada grupo foi novamente divididos em 4 subgrupos, de acordo com o tamanho de partículas de óxido de alumínio utilizado: A - Al2O3 (250 µm); B - Al2O3 (180 µm); C- Al2O3 (110 µm); D - Al2O3 (50 µm). Anéis de resina foram polimerizados ao redor das hastes de titânio no equipamento UniXS. Os espécimes foram embutidos em gesso e a força de união foi mensurada com auxílio da máquina de ensaios universais. ANOVA e teste de Tukey (p<0,05) foram utilizados para análise estatística. Os maiores valores de força de união foram registrados no grupo de 250 µm sem solda a laser. Os menores valores foram registrados para o grupo de 50 µm com solda a laser. Alterações estatisticamente significantes foram observadas entre todos os grupos (p<0,05). As forças de união diminuíram significantemente com a diminuição dos tamanhos das partículas de óxido de alumínio. A força de união diminuiu nas amostras que receberam a solda a laser.CNP

Effect of laser welding on the titanium ceramic tensile bond strength

Titanium reacts strongly with elements, mainly oxygen at high temperature. The high temperature of titanium laser welding modifies the surface, and may interfere on the metal-ceramic tensile bond strength. OBJECTIVE: The influence of laser welding on the titanium-ceramic bonding has not yet been established. The purpose of this in vitro study was to analyze the influence of laser welding applied to commercially pure titanium (CpTi) substructure on the bond strength of commercial ceramic. The influence of airborne particle abrasion (Al2O3) conditions was also studied. MATERIAL AND METHODS: Forty CpTi cylindrical rods (3 mm x 60 mm) were cast and divided into 2 groups: with laser welding (L) and without laser welding (WL). Each group was divided in 4 subgroups, according to the size of the particles used in airborne particle abrasion: A - Al2O3 (250 µm); B - Al2O3 (180 µm); C - Al2O3 (110 µm); D - Al2O3 (50 µm). Ceramic rings were fused around the CpTi rods. Specimens were invested and their tensile strength was measured at fracture with a universal testing machine at a crosshead speed of 2.0 mm/min and 200 kgf load cell. Statistical analysis was carried out with analysis of variance and compared using the independent t test (

Correlation between metal-ceramic bond strength and coefficient of linear thermal expansion difference

The purpose of this study was to evaluate the metal-ceramic bond strength (MCBS) of 6 metal-ceramic pairs (2 Ni-Cr alloys and 1 Pd-Ag alloy with 2 dental ceramics) and correlate the MCBS values with the differences between the coefficients of linear thermal expansion (CTEs) of the metals and ceramics. Verabond (VB) Ni-Cr-Be alloy, Verabond II (VB2), Ni-Cr alloy, Pors-on 4 (P), Pd-Ag alloy, and IPS (I) and Duceram (D) ceramics were used for the MCBS test and dilatometric test. Forty-eight ceramic rings were built around metallic rods (3.0 mm in diameter and 70.0 mm in length) made from the evaluated alloys. The rods were subsequently embedded in gypsum cast in order to perform a tensile load test, which enabled calculating the CMBS. Five specimens (2.0 mm in diameter and 12.0 mm in length) of each material were made for the dilatometric test. The chromel-alumel thermocouple required for the test was welded into the metal test specimens and inserted into the ceramics. ANOVA and Tukey's test revealed significant differences (p=0.01) for the MCBS test results (MPa), with PI showing higher MCBS (67.72) than the other pairs, which did not present any significant differences. The CTE (10-6 oC-1) differences were: VBI (0.54), VBD (1.33), VB2I (-0.14), VB2D (0.63), PI (1.84) and PD (2.62). Pearson's correlation test (r=0.17) was performed to evaluate of correlation between MCBS and CTE differences. Within the limitations of this study and based on the obtained results, there was no correlation between MCBS and CTE differences for the evaluated metal-ceramic pairs.FAPES

Complete denture hygiene solutions: antibiofilm activity and effects on physical and mechanical properties of acrylic resin

Appropriated denture hygiene is a predictive factor for longevity of rehabilitation treatment and maintenance of the oral mucosal health. Although, disinfectant solutions are commonly used as denture cleansers, the impact of these solutions on acrylic resin-based dentures remain unclear. Objective: To evaluate, in vitro, the antibiofilm activity of complete denture hygiene solutions and their effects on physical and mechanical properties of acrylic resin.&nbsp;Methodology: For antibiofilm activity measurement acrylic resin specimens were contaminated with Candida albicans, Candida glabrata and Streptococcus mutans. After biofilm growth, the specimens were assigned to the hygiene solutions: Distilled water (Control); 0.2% Sodium hypochlorite (SH); Efferdent Power Clean Crystals (EPC) and 6.25% Ricinus communis (RC). The viability of microorganisms was evaluated by agar plate counts. In parallel, physical, and mechanical properties of the acrylic resin were evaluated after simulating a 5-year period of daily immersion in the previously mentioned solutions. The changes in surface roughness, color, microhardness, flexural strength, impact strength, sorption and solubility were evaluated. Data were compared by ANOVA followed by the Tukey test or Kruskal-Wallis followed by the Dunn test depending on the distribution (α=0.05).&nbsp;Results: Regarding antibiofilm action, SH eliminated all microorganisms while EPC and RC exhibited moderate action against S. mutans (p=0.001) and C. glabrata (p&lt;0.001), respectively. Relative to effects on the physical and mechanical properties of the acrylic resin, RC led to higher values of color change (p=0.030), hardness (p&lt;0.001), surface roughness (p=0.006) and flexural strength (p&lt;0.001). Moreover, RC induced the highest values of changes in solubility (p&lt;0.001). EPC promoted greater changes in surface morphology, whereas immersion in SH retained the initial appearance of the acrylic resin surface. All hygiene solutions reduced the impact strength (p&lt;0.05).&nbsp;Conclusion: SH presented the most effective antibiofilm activity. In addition, changes on properties were observed after immersion in RC, which were considered within acceptable limits

Effect of casting temperature and atmosphere on castability of Ni-Cr alloys: a comparative study with direct flame casting method

The purpose of this study was to compare the effect of casting temperature and atmosphere on the castability of three Ni-Cr alloys against direct flame casting method. Vera Bond (VB), Vera Bond 2 (VB2) and Wiron 99 (W99) were cast at three temperatures: VB and VB2 (1310 &deg;C, 1340 &deg;C and 1370 &deg;C); W99 (1400 &deg;C, 1430 &deg;C and 1460 &deg;C) in atmosphere, vacuum and direct flame. Each alloy was cast in seven different conditions. Castability was assessed by the method that verifies the alloy potential to reproduce a nylon mesh. Kruskal-Wallis test demonstrated for VB, while there was no influence in the temperature range, castability was greater by vacuum (99.3%) than by direct flame (96.2%) and atmosphere (93.06%). For VB2, castability was greater at evaluated temperatures (1370 &deg;C = 94.4%, 1340 &deg;C = 91.15% and 1310 &deg;C = 87.9%) than direct flame (77.8%); related vacuum (97.33%) obtained better values than atmosphere (84.6%) and direct flame. For W99, while atmosphere had no influence, castability was higher at 1460 &deg;C (84.3%) than at other temperatures (1430 &deg;C = 70.3%, 1400 &deg;C = 37.05%) and direct flame (62.5%). Comparison among interactions showed that for all alloys it was possible to significantly increase the filling percentage of the mold in a comparative manner with the direct flame cast method