Gregory L. Polyzois

Color stability of provisional resin restorative materials

STATEMENT OF PROBLEM Use of temporary crowns and fixed partial dentures is especially relevant when the treatment plan requires restorations for long interim periods, and the in-service discoloration of provisional restorative materials is a major drawback. PURPOSE This study evaluated the discoloration effect of coffee and tea on some materials that are commonly used in the fabrication of provisional restorations. MATERIAL AND METHODS Six commercially available provisional resins (Jet, Caulk TBR, Protemp Garant, Luxatemp Solar, Provipont DC and SR-Ivocron-PE) were evaluated after 1 day, 7 days, and 30 days of immersion in various staining solutions. Color measurements were obtained by using a Dr Lange Micro Color tristimulus colorimeter and color differences (delta E*) were estimated. RESULTS The 2 chemically activated resins (Jet and Caulk TBR) and the heat-cured resin (SR-Ivocron PE) exhibited the least color changes, whereas the Provipont-DC resin was the least color stable. After immersion for 30 days, the combination with the coffee solution resulted in unacceptable discoloration for all the tested materials. CONCLUSIONS Provisional restorative materials, staining solutions, and immersion time were significant factors that affected color stability. After immersion for 7 days, all materials showed observable color changes. The composite-based materials, especially light-curing composites, were the least color stable. The coffee solution exhibited more staining capacity than the tea solution.

Physical properties of a silicone prosthetic elastomer stored in simulated skin secretions

STATEMENT OF PROBLEM Facial prostheses worn over an extended time are exposed to various environmental factors, including sebaceous oils (sebum) and perspiration. PURPOSE This study investigated the physical properties of tensile strength and modulus, elongation, tear strength, hardness, weight, and color change, of a silicone facial elastomer after immersion for 6 months in simulated sebum and perspiration at 37 degrees C. MATERIAL AND METHODS Specimens made of Episil silicone elastomer were immersed in simulated alkaline or acidic perspiration as well as in sebum. Tensile and tear tests were conducted according to ISO specifications no. 37 and 39, respectively, in a Monsanto testing machine. Shore A hardness measurements were run according to ASTM D 2240. Weight changes were followed at 5, 15, 30, and 180 days, and color changes were determined in the CIE LAB system using a tristimulus colorimeter. RESULTS An improvement of mechanical properties for specimens immersed in acidic perspiration was attributed to facilitation of the propagation of cross-linking reaction during aging of the silicone samples. Some weight increase was observed for the specimens immersed into the aqueous solution, whereas for those immersed in sebum, weight loss was recorded, probably because of extraction of some compounds. In this latter case, the color change was lower than that corresponding to simulated perspiration. CONCLUSION The silicone specimens aged for a period, which simulates 1.5 years of clinical service, showed minimal changes with respect to the properties studied.

Acrylic resin denture repair with adhesive resin and metal wires: Effects on strength parameters

The fracture of acrylic resin dentures is an unresolved problem in prosthodontics. In this study one brand of denture base acrylic resin was used to make specimens in the form of strips and maxillary denture bases. The specimens were cut and repaired with one type of an autopolymerizing adhesive resin and metal wires. The mechanical properties of the repaired specimens were measured, and the efficiency of each method was evaluated. The statistical results of this study revealed that geometric characteristics of a maxillary denture combined with the shape and pretreatment of reinforcement were the controlling factors for the overall mechanical behavior. Furthermore this study revealed that data with clinical significance can only be obtained by testing specimens similar to the original items used in dental practice.

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.

Color stability of facial silicone prosthetic polymers after outdoor weathering

STATEMENT OF PROBLEM Color deterioration of silicone prosthetic elastomers affects the life expectancy of facial prostheses in a service environment. PURPOSE This study investigated the color stability of 3 nonpigmented silicone elastomers (Silskin 2000, Elastosil M3500, Ideal) exposed to outdoor weathering for 1 year. MATERIAL AND METHODS A tristimulus colorimeter was used to evaluate the color differences (DeltaE*) of the silicone elastomers every 2 months. Ten disk-shaped specimens for each material were tested. Data were analyzed with a repeated measures ANOVA and Student-Newman-Keuls test at a significance level of alpha = .05. RESULTS All silicone elastomers showed visually detectable, mean color differences (DeltaE* > 2.0), that ranged from 2.13 to 3.98. Silskin 2000 showed greater color differences (P <.05) compared with Elastosil M3500 and Ideal, which showed similar behavior (P >.05). CONCLUSION Outdoor exposure of silicone facial elastomers for 1 year resulted in visually detectable color differences. Duration of exposure and silicone elastomer were significant factors that affected color stability. Silskin 2000 was significantly less color stable than Elastosil M3500 and Ideal, which were not statistically significantly different from each other.

Adhesion properties of resilient lining materials bonded to light-cured denture resins

This study compared the adhesive strength of three resilient denture lining materials with different chemical compositions when bonded to visible light-cured (VLC) denture base resin. Shear adhesive strength was evaluated using a simple overlap-joint model. Three different bonding agents were used and the effect of water on the bonding strength was evaluated by a series of samples tested after storage for 4 months. The findings showed that all of the lining materials were acceptable for clinical use but that water storage reduced their bond strength to VLC resin.

An assessment of the physical properties and biocompatibility of three silicone elastomers

The physical properties of two room-temperature vulcanizing (RTV) silicones, A-2186 and Silbione 71556, and one high-temperature vulcanizing (HTV) material, Mollomed, were compared. The potential cytotoxicity of the silicone materials was assessed with the agarose overlay test. The properties that were investigated were tensile strength, percentage elongation, modulus, permanent set, tear strength, and hardness. The properties tested were selected because of their clinical significance for fabricating facial prostheses. The results of this study indicate that the A-2186 material has a better combination of high tear strength and elongation at break with a softer surface compared with Mollomed silicone, and Silbione 71556 silicone proved to be the weakest material. All materials demonstrated absence of cytotoxicity in the cell culture tests.

Clinical evaluation of three denture cushion adhesives by complete denture wearers

OBJECTIVE The aim of this study was the clinical evaluation of three denture cushion adhesives and whether the results were correlated to Kapur Index for denture-supporting tissues. BACKGROUND Various types of denture adhesives are used among denture patients. However, information on the clinical behaviour of denture cushions is limited. MATERIALS AND METHODS Thirty edentulous patients had their denture-supporting tissues scored by Kapur Index and their old dentures replaced. They received three brands of denture cushion adhesives (Fittydent(®) , Protefix(®) and Seabond(®)) and were instructed to use them in a sequence according to the group they were randomly assigned to. Each brand of adhesive was used for 48 h on the lower denture according to the manufacturers suggestions. After each brand was used, participants spent 24 h without applying any sort of adhesive. Finally, a questionnaire evaluating and comparing the performance of each brand was filled out. RESULTS Denture adhesives generally improved patient satisfaction and masticatory ability, especially in participants with poor Kapur Index and those who reported a poor retention of their old dentures. CONCLUSION Fittydent(®) was the most preferred adhesive, showing the best retention and the longest duration of its effect, but also reported as difficult to remove from the denture-bearing area.

Dimensional stability of dentures processed in boilable acrylic resins: A comparative study

An investigation was conducted to evaluate and compare the dimensional stability of three fast boilable denture resins with a conventional and a high-impact denture resin processed with a long-curing cycle. Although the boilable denture resins have been introduced to the dental profession and offer merits such as faster processing, saving time for the dentist, patient, and technician, reduction of energy costs, and dramatic increase in denture laboratory production without adding personnel or purchasing new equipment, the relevant dental literature is sparse. The results of this investigation indicate that all five denture resins produced dentures that shrink. Also measurements between certain teeth showed shrinkages. Linear shrinkages of denture bases and teeth distances were less than 1%. Flange-to-flange and molar-to-molar changes were less than 0.5 mm and 0.2 mm respectively. Maxillary complete dentures processed in boilable resins presented less distortion in the midpalatal area across the posterior section than dentures processed in the conventional heat-cured resin. Although linear changes reported in this investigation were thought to be clinically insignificant, clinical studies should be conducted to establish correlation with laboratory findings.

In vitro evaluation of dental materials

Biocompatibility has been described as the ability of a material to perform with an appropriate host response in a specific application. Appropriate host response means no (or a tolerable) adverse reaction of a living system to the presence of such a material. An adverse reaction may be due to the toxicity of a dental material. Therefore toxicity may be regarded as one reason for nonbiocompatibility of a dental material. The toxicity of a dental material can be evaluated by in vitro tests, animal experiments and clinical trials. There exists a variety of different in vitro test methods. The most widely used biological systems for toxicity screening of dental materials are cell cultures. Cell cultures for toxicity screening of dental materials are valuable tools for understanding their biological behavior, if the limitations of the methods are taken into consideration, especially concerning the interpretation of the results. Further research should concentrate on better simulations of the in vivo situation in cell cultures. In this review the applications of various cell culture methods to evaluate the cytotoxicity of a wide range of dental materials, e.g. metals, alloys, polymers and cements, are described.