Effects of cleansing methods on 3-D surface roughness, gloss and color of a polyamide denture base material.

OBJECTIVE: The purpose of this study was to determine the effects of two denture cleansing methods on 3-D surface roughness, gloss and color of denture base materials. MATERIALS AND METHODS: Thirty disks from nylon (Valplast) and 30 from heat-polymerized acrylic denture base material (Paladon 65) were made and 10 of each material were immersed in water (control), Val-Clean (peroxide cleanser) and Corega Extradent (peroxide cleanser) plus microwaving for a period simulating 30 days of daily cleansing. 3-D surface roughness, gloss and color parameters were measured before and after cleansing using an interferometric profilometer, a gloss meter and a colorimeter. The results were statistically analysed by regression, paired-t, Mann-Whitney and Kruskal-Wallis tests at α = 0.05 level of significance. RESULTS: The results showed significant differences at baseline in L* and b* parameters between materials (p < 0.01), with a significantly lower gloss (p < 0.05) and higher roughness (p < 0.05) for Valplast. After cleansing, Δϵ* was significantly greater in Valplast than Paladon 65 (p < 0.05). Gloss of both materials decreased significantly within the Corega Extradent plus microwave solution (p < 0.05), while roughness increased significantly only for Paladon 65 (p < 0.05). CONCLUSIONS: Valplast was found to have a significantly lower gloss and a higher roughness than Paladon 65 before cleansing. After cleansing, ΔE* increased more in Valplast than in Paladon 65, gloss of both materials decreased and roughness only of Paladon 65 increased within the Corega extradent plus microwaving method.

Tooth, skin, hair and eye colour interrelationships in Greek young adults.

The purpose of this study was to investigate the possible interrelationships of teeth, skin, eye and hair colour. A portable colorimeter (Shade Eye NCC/Shofu) was used to record the colour in the CIELAB system of the upper right incisors in 150 dental school students, along with their skin colour at three different areas. Natural hair and eye colour was classified into several categories by a trained examiner (ICC 0.93-0.99). One-way ANOVA and correlation tests were used to statistically analyse the data. Skin was found to have significantly higher L*, b* but lower a* values than teeth (p < 0.05). A significant correlation (p < 0.05) of teeth to skin L* and a*colour coordinate was found, but not to b* coordinate (p > 0.05). Hair tones were not correlated to teeth L* or b*, but only to a*coordinate. Teeth and eye colour coordinates were not correlated (p > 0.05). Eye and hair tones were found to have the highest significant correlation (ρ = 0.369). In conclusion, teeth of this cohort were found to be lighter, less red and yellow than the skin. Teeth colour was not related to eye colour, but lighter teeth were found to be associated with lighter skins, and redder lateral incisors to lighter hair. Darker facial skins or yellower forehead areas were also associated with darker hair and vice versa. The clinical relevance of the study is that the investigated facial characteristics are inter-correlated weakly to moderately, and for this reason predicting the colour parameters of one facial characteristic by another would not be accurate, but helpful for a rough colour selection as associations show.

Flexural and bond strengths of relined denture polymers assessed by four-point bending tests and Weibull analysis.

OBJECTIVES: The aim of this study was to (1) investigate the flexural strengths of three denture resins i.e. heat, photopolymerised and microwaved and how it was affected by relining with auto- and visible light-polymerised hard reliners, (2) investigate the bond strengths between denture resins and hard reliners and (3) interpret the results of both tests by utilising Weibull analysis. MATERIALS AND METHODS: Specimens (65 × 10 × 2.5 mm) from denture resins, relined and bonded combinations were tested using a four-point bending test in a universal testing machine and a crosshead speed of 5 mm/min. Ten specimens for each bulk resin and denture resin-reliner combination for a total of 150 were tested. RESULTS: Statistical analysis indicated significant differences between bulk materials (p < 0.001) and between reliners (p < 0.001) for flexural and bond strength tests. CONCLUSION: was concluded that (1) the four-point flexural strength was different between the denture base materials, (2) flexure strength between bulk and relined or between relined with autopolymerised and photopolymerised bases was different, (3) flexural strength among relined denture bases was different and (4) bond strengths among relined denture bases were different.

Repeatability and interdevice reliability of two portable color selection devices in matching and measuring tooth color.

STATEMENT OF PROBLEM: There is a need to know how shade selection devices perform in matching and measuring tooth color, since these functions are usually evaluated independently and may present significant discrepancies. PURPOSE: The purpose of this study was to evaluate 2 devices which offer both functions to test the null hypothesis that they present no differences in their repeatability and interdevice reliability relating to the 2 functions. MATERIAL AND METHODS: Thirty-one extracted anterior human teeth were measured twice, with each of the devices (ShadeEye NCC and VITA EasyShade), by one investigator experienced and calibrated with both devices. L*a*b* values and shade matches to VITA Classical and Vitapan 3D-Master shade guide systems were determined for all teeth. Paired t tests and intraclass correlation coefficients (ICCs) were used to statistically analyze the data (alpha=.05). RESULTS: The results showed that L*a*b* values with VITA EasyShade were significantly higher than those with ShadeEye NCC (P<.01), with a mean difference of 10.01 Delta E units. Device repeatability ICCs for measuring tooth color ranged from 0.693 to 0.929, with significant differences between devices only with respect to parameter L* (P=.042). Intradevice ICCs for matching tooth color ranged from 0.714 to 0.894, with significant differences between devices only with respect to the VITA Classical shade system (P=.042). Interdevice ICCs for measuring tooth color ranged from 0.402 to 0.486, with no significant differences between L*a*b* parameters, while interdevice matching reliability ranged from 0.189 to 0.430, with no significant differences between shade systems (P>.05). CONCLUSIONS: All tooth color parameters were higher with the VITA EasyShade device. Measuring repeatability of the VITA EasyShade was higher than the ShadeEye NCC only for the L* parameter. Matching repeatability of the ShadeEye NCC was higher than the VITA EasyShade for the VITA Classical system. Interdevice measuring reliabilities were not different for the color parameters, but matching reliability of the VITA Classical system was higher than that of the Vitapan 3D-Master.

Shear bond strength between composite resin and denture teeth: effect of tooth type and surface treatments.

PURPOSE: The purpose of this study was to investigate the strength of the composite resin-denture tooth bond as affected by different tooth surface treatments. MATERIALS AND METHODS: Spectrum TPH was condensed on 112 mandibular first molar acrylic resin and composite resin denture teeth, which received seven different treatments: Four groups were treated with Prime & Bond NT adhesive, and three groups were treated with One Step adhesive. Four groups (two of each adhesive category) were treated with Composite Activator and air abrasion. In one group, AeliteFlo was used just before the condensation of Spectrum TPH. Bond strength was evaluated with a shear test device on a Monsanto testing machine. The results were evaluated statistically with two-way ANOVA and the Scheffé method. RESULTS: There was a significant interaction between denture tooth type and surface treatments. Bond strength of composite resin was greater to composite than to acrylic resin teeth when the bond was mediated only with adhesives. One Step adhesive and AeliteFlo resulted in a higher bond of composite resin to both types of teeth. Wetting tooth surfaces with Composite Activator did not increase the bond. CONCLUSION: When repairing denture teeth with composite resin and adhesives, the bond strength was higher with composite than with acrylic resin teeth, and there were differences between the adhesives used.