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Three-way ANOVA (three-way + anova)
Selected AbstractsHuman Perception of Dental Porcelain Translucency Correlated to Spectrophotometric MeasurementsJOURNAL OF PROSTHODONTICS, Issue 3 2010Min-Chieh Liu DDS Abstract Purpose: This study evaluated the relationship between instrumental measurements and subjective visual assessment of differences in dental porcelain translucency. Materials and Methods: Unshaded feldspathic porcelain was used with controlled amounts of tin oxide to create two groups of 12-mm diameter disks with incremental changes in opacity. Contrast ratio (CR = Yb/Yw) was determined with a spectrophotometer, and used as a measure of porcelain translucency (Group A = 0.20 to 0.40; Group B = 0.6,0.8). Within each group, there were 14 specimens with 11 CRs. Three observer groups (first year dental students, residents, faculty with >10 years of shade matching experience) were recruited to assess the translucency between porcelain disks under two lighting conditions (reflected light, transmitted light). Each subject's ability to distinguish between specimens of differing translucency was determined. Descriptive statistics and three-way ANOVA followed by a post-hoc Tukey-Kramer test were used to evaluate the translucency perception threshold (TPT) of subjects (,= 0.05). Results: The overall mean TPT (,C) was 0.07, while 50% of the subjects could perceive a 0.06 CR difference between porcelain specimens. Three-way ANOVA revealed a significant difference in translucency perception among the observer groups (p < 0.0001), whereas the main effects for porcelain opacity (p= 0.3038) and lighting condition (p= 0.0645) were not significant, and no significant interactions were found. Post-hoc Tukey-Kramer test indicated that the mean TPT observed in the faculty group (,C = 0.04) was significantly lower than those observed in student (,C = 0.09) and resident groups (,C = 0.08), while there was no significant difference between students and residents. Conclusions: The overall mean TPT of all subjects was 0.07, and 50% of the study population perceived a 0.06 CR difference in translucency. Increased shade matching experience (,10 years) significantly improved the ability to perceive differences in translucency; however, neither the viewing condition nor porcelain opacity affected the perceived translucency threshold. [source] Contemporary landscape burning patterns in the far North Kimberley region of north-west Australia: human influences and environmental determinantsJOURNAL OF BIOGEOGRAPHY, Issue 8 2004T. Vigilante Abstract Aim, This study of contemporary landscape burning patterns in the North Kimberley aims to determine the relative influences of environmental factors and compare the management regimes occurring on Aboriginal lands, pastoral leases, national park and crown land. Location, The study area is defined at the largest scale by Landsat Scene 108,70 that covers a total land area of 23,134 km2 in the North Kimberley Bioregion of north-west Australia, including the settlement of Kalumburu, coastline between Vansittart Bay in the west and the mouth of the Berkeley River in the east, and stretching approximately 200 km inland. Methods, Two approaches are applied. First, a 10-year fire history (1990,1999) derived from previous study of satellite (Landsat-MSS) remote sensing imagery is analysed for broad regional patterns. And secondly, a 2-year ground-based survey of burning along major access roads leading to an Aboriginal community is used to show fine-scale burning patterns. anova and multiple regression analyses are used to determine the influence of year, season, geology, tenure, distance from road and distance from settlement on fire patterns. Results, Satellite data indicated that an average of 30.8% (±4.4% SEM) of the study area was burnt each year with considerable variability between years. Approximately 56% of the study area was burnt on three or more occasions over the 10-year period. A slightly higher proportion of burning occurred on average in the late dry season (17.2 ± 3.6%), compared with the early dry season (13.6 ± 3.3%). The highest fire frequency occurred on basalt substrates, on pastoral tenures, and at distances 5,25 km from roads. Three-way anova demonstrated that geological substrate and land use were the most significant factors influencing fire history, however a range of smaller interactions were also significant. Analysis of road transects, originating from an Aboriginal settlement, showed that the timing of fire and geology type were the most significant factors affecting the pattern of area burnt. Of the total transect area, 28.3 ± 2.9% was burnt annually with peaks in burning occurring into the dry season months of June, August and September. Basalt uplands (81.2%) and lowlands (30.1%) had greater areas burnt than sandstone (12.3%) and sands (17.7%). Main conclusions, Anthropogenic firing is constrained by two major environmental determinants; climate and substrate. Seasonal peaks in burning activity in both the early and late dry season relate to periods of optimal fire-weather conditions. Substrate factors (geology, soils and physiognomy) influence vegetation-fuel characteristics and the movement of fire in the landscape. Basalt hills overwhelmingly supported the most frequent wildfire regime in the study region because of their undulating topography and relatively fertile soils that support perennial grasslands. Within these spatial and temporal constraints people significantly influenced the frequency and extent of fire in the North Kimberley thus tenure type and associated land uses had a significant influence on fire patterning. Burning activity is high on pastoral lands and along roads and tracks on some tenure types. While the state government uses aerial control burning and legislation to try to restrict burning to the early dry season across all geology types, in practice burning is being conducted across the full duration of the dry season with early dry season burning focused on sandstone and sand substrates and late dry season burning focused on basalt substrates. There is greater seasonal and spatial variation in burning patterns on landscapes managed by Aboriginal people. [source] Evaluation of maximal bite force in temporomandibular disorders patientsJOURNAL OF ORAL REHABILITATION, Issue 8 2006E. M. KOGAWA summary, The aim of this study was to evaluate the maximum bite force in temporomandibular disorders (TMD) patients. Two hundred women were equally divided into four groups: myogenic TMD, articular TMD, mixed TMD and control. The maximum bite force was measured in the first molar area, on both sides, in two sessions, using an IDDK (Kratos) Model digital dynamometer, adapted to oral conditions. Three-way anova, Tukey and Pearson correlation tests were used for the statistical analysis. The level of statistical significance was given when P , 0·05. The maximal bite force values were significantly higher in the control group than in the experimental ones (P = 0·00), with no significant differences between sides. Higher values were obtained in the second session (P = 0·001). Indeed, moderate negative correlation was found between age and bite force, when articular, mixed groups and all groups together were evaluated. A moderate negative correlation was also detected between TMD severity and the maximal bite force values for myogenic, mixed and all groups together. Authors concluded that the presence of masticatory muscle pain and/or TMJ inflammation can play a role in maximum bite force. The mechanisms involved in this process, however, are not well understood and deserve further investigation. [source] Effect of Aging on Coronal Microleakage in Access Cavities through Metal Ceramic Crowns Restored with Resin CompositesJOURNAL OF PROSTHODONTICS, Issue 5 2010Ali Abdullah Alwan Al-Maqtari BDS Abstract Purpose: The purpose of this in vitro study was to determine if packable resin composite with/without flowable resin composite has the ability to prevent coronal leakage in restored endodontic access openings following aging. Materials and Methods: Eighty simulated standardized access cavities of metal-ceramic crowns were fabricated and fixed on Vitrebond cavities filled with an epoxy resin. The specimens were randomly divided into two main groups: (1) Group A,Access cavities filled with only packable composite (Filtek P60); (2) Group B,Access cavities filled with Filtek P60 and a flowable composite (Filtek Z350) as liner. Each main group was further subdivided randomly into four subgroups according to water storage and thermocycling periods. All specimens were immersed in blue ink solution for 24 hours and then sectioned into quadrants. The extension of blue ink along the metal-ceramic crown/composite resin interface was measured linearly using image analyzer and then analyzed by three-way ANOVA and independent t -test with a Mann-Whitney test. The level of significance was set at p < 0.05. Results: All tested subgroups demonstrated different levels of microleakage. There was no significant difference related to restorative technique; however, there was a significant difference related to water storage and thermocycling. Conclusions: All tested techniques and materials in this study showed microleakage. Packable composite while a flowable liner showed a marginally better result than packable composite alone. Excessive thermocycling resulted in significant differences among the test groups. [source] Human Perception of Dental Porcelain Translucency Correlated to Spectrophotometric MeasurementsJOURNAL OF PROSTHODONTICS, Issue 3 2010Min-Chieh Liu DDS Abstract Purpose: This study evaluated the relationship between instrumental measurements and subjective visual assessment of differences in dental porcelain translucency. Materials and Methods: Unshaded feldspathic porcelain was used with controlled amounts of tin oxide to create two groups of 12-mm diameter disks with incremental changes in opacity. Contrast ratio (CR = Yb/Yw) was determined with a spectrophotometer, and used as a measure of porcelain translucency (Group A = 0.20 to 0.40; Group B = 0.6,0.8). Within each group, there were 14 specimens with 11 CRs. Three observer groups (first year dental students, residents, faculty with >10 years of shade matching experience) were recruited to assess the translucency between porcelain disks under two lighting conditions (reflected light, transmitted light). Each subject's ability to distinguish between specimens of differing translucency was determined. Descriptive statistics and three-way ANOVA followed by a post-hoc Tukey-Kramer test were used to evaluate the translucency perception threshold (TPT) of subjects (,= 0.05). Results: The overall mean TPT (,C) was 0.07, while 50% of the subjects could perceive a 0.06 CR difference between porcelain specimens. Three-way ANOVA revealed a significant difference in translucency perception among the observer groups (p < 0.0001), whereas the main effects for porcelain opacity (p= 0.3038) and lighting condition (p= 0.0645) were not significant, and no significant interactions were found. Post-hoc Tukey-Kramer test indicated that the mean TPT observed in the faculty group (,C = 0.04) was significantly lower than those observed in student (,C = 0.09) and resident groups (,C = 0.08), while there was no significant difference between students and residents. Conclusions: The overall mean TPT of all subjects was 0.07, and 50% of the study population perceived a 0.06 CR difference in translucency. Increased shade matching experience (,10 years) significantly improved the ability to perceive differences in translucency; however, neither the viewing condition nor porcelain opacity affected the perceived translucency threshold. [source] Evaluation of the Bond Strength of Denture Base Resins to Acrylic Resin Teeth: Effect of ThermocyclingJOURNAL OF PROSTHODONTICS, Issue 5 2009Julię Marra DDS Abstract Purpose: The purpose of this study was to evaluate the thermocycling effects and shear bond strength of acrylic resin teeth to denture base resins. Materials and Methods: Three acrylic teeth (Biotone, Trilux, Ivoclar) were chosen for bonding to four denture base resins: microwave-polymerized (Acron MC), heat-polymerized (Lucitone 550 and QC-20), and light-polymerized (Versyo.bond). Twenty specimens were produced for each denture base/acrylic tooth combination and were divided into two groups (n = 10): without thermocycling (control groups) and thermocycled groups submitted to 5000 cycles between 4 and 60°C. Shear strength tests (MPa) were performed with a universal testing machine at a crosshead speed of 1 mm/min. Statistical analysis of the results was carried out with three-way ANOVA and Bonferroni's multiple comparisons post hoc analysis for test groups (,= 0.05). Results: The shear bond strengths of Lucitone/Biotone, Lucitone/Trilux, and Versyo/Ivoclar specimens were significantly decreased by thermocycling, compared with the corresponding control groups (p < 0.05). The means of Acron/Ivoclar and Lucitone/Ivoclar specimens increased after thermocycling (p < 0.05). The highest mean shear bond strength value was observed with Lucitone/Biotone in the control group (14.54 MPa) and the lowest with QC-20/Trilux in the thermocycled group (3.69 MPa). Conclusion: Some acrylic tooth/denture base resin combinations can be more affected by thermocycling; effects vary based upon the materials used. [source] Effects of 6 Months of Aging in Water on Hardness and Surface Roughness of Two Microhybrid Dental CompositesJOURNAL OF PROSTHODONTICS, Issue 4 2008Rafael Ratto De Moraes DDS Abstract Purpose: This study assessed the effect of 6 months of aging in water on surface roughness and surface/subsurface hardness of two microhybrid resin composites. Materials and Methods: Filtek Z250 and Charisma were tested. Cylindrical specimens were obtained and stored in distilled water for 24 hours or 6 months, at 37°C. For Knoop hardness evaluation, the specimens were transversely wet-flattened, and indentations were made on surface and subsurface layers. Data were submitted to three-way ANOVA and Tukey's test (,, 0.05). Surface roughness baseline measurements were made at 24 hours and repeated after 6 months of storage. Data were submitted to repeated measures ANOVA and Tukey's test (,, 0.05). Results: Surface hardness (KHN, kg/mm2) means (± standard deviation) ranged from 55 ± 1 to 49 ± 4 for Z250 and from 50 ± 2 to 41 ± 3 for Charisma, at 24 hours and 6 months, respectively. Subsurface means ranged from 58 ± 2 to 61 ± 3 for Z250 and from 50 ± 1 to 54 ± 2 for Charisma, at 24 hours and 6 months. For both composites, the aged specimens presented significantly softer surfaces (p < 0.01). For the subsurface hardness, alteration after storage was detected only for Charisma, which presented a significant rise in hardness (p < 0.01). Z250 presented significantly harder surface and subsurface layers in comparison with Charisma. Surface roughness (Ra, ,m) means ranged from 0.07 ± 0.00 to 0.07 ± 0.01 for Z250 and from 0.06 ± 0.01 to 0.07 ± 0.01 for Charisma, at 24 hours and 6 months, respectively. For both composites, no significant roughness alteration was detected during the study (p= 0.386). Conclusions: The 6-month period of storage in water presented a significant softening effect on the surfaces of the composites, although no significant deleterious alteration was detected for the subsurface hardness. In addition, the storage period had no significant effect on the surface roughness of the materials. [source] Degradation of repaired denture base materials in simulated oral fluidJOURNAL OF ORAL REHABILITATION, Issue 3 2000C.-T. Lin This in vitro study evaluates the degradation of repaired denture bases upon immersion in a simulated oral fluid. Denture base materials (Luciton 199®), after being repaired by Repair Material® and Triad®, using three different joint surface designs (butt, round and 45 ° bevel), were immersed onto 99·5 vol.% ethanol/water solution (with similar solubility parameter) for various amounts of time (0,72 h). The flexural loads of the six combination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surface details of the interface were examined with a scanning electronic microscope (SEM). Data were analysed using three-way anova and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fracture mode. The flexural loads (2·72±0·51 Kgf) of the round joint specimens were significantly higher (P<0·05) than those (butt: 1·66±0·38 Kgf, 45 ° bevel: 1·93±0·41 Kgf) of the other two designs. This corresponds to the microscopic examination in which more cohesive failure mode was found for the round joint group after storage. The flexural loads (2·54±0·39 Kgf) of the specimens repaired with Triad® were significantly higher (P<0·05) than those (1·59±0·40 Kgf) of specimens repaired with Repair Material®. Significant progressive reduction of the flexural load and/or AE signals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture base repaired with a round joint design and light-cured material is significantly higher after immersion in simulated oral fluid. [source] | ||||||||||