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PubMed2005

In vitro evaluation of the bonding of auto-polymerizing soft denture liner to cobalt-chromium alloy.

This study evaluated the effects of surface pre-treatments on the bonding of auto-polymerizing silicone soft denture liner to a Co-Cr alloy denture base after cyclic thermal stressing. The bonding surfaces of Co-Cr alloy cylinders (8 mm diameter and 4 mm high) were polished with a 600-grit silicon carbide paper. The bonding surfaces received one of three pre-treatments, which included either the application of a metal primer, a metal primer after air abrasion, or a resin primer after adhesive resin coating. Tensile specimens were fabricated by polymerizing a 2-mm thickness of soft denture liner between a pair of pre-treated denture base cylinders. Failure loads were measured by tensile testing after subjecting the specimen to 0, 5, 10, 20, and 30 thousand thermal cycles. Seven specimens were fabricated for 15 groups, including three pre-treatments and five thermal cycle groups. Failure loads of resin-bonded specimens, which were formerly reported, were used as references. All data were statistically analysed by two-way anova and Bonferroni test at the 95% confidence level. Adhesive resin coating of the metal surface was effective in enhancing the failure loads up to 5000 thermal cycles. However, failure loads of all metal-bonded groups were significantly lower than those of resin-bonded groups at all thermal cycling intervals. The results of this in vitro study implied that polymerizing adhesive resin on the Co-Cr alloy might be a promising method, when the clinicians need to acquire improved bonding of an auto-polymerizing soft denture liner to Co-Cr alloy denture bases.

Air Abrasion, Dental↗
PubMed1994

Bonding soft reline materials to base metals.

PURPOSE: In the past it has been difficult to treat soft tissue changes occurring beneath metal frameworks of removable partial dentures or complete dentures using soft reline materials. The main difficulty has been in getting the resilient materials to adhere to the metal. This research investigates the use of microabrading with and without a universal resin bonding system in achieving a clinically useful bond between two soft reline materials and a commonly used base-metal alloy. MATERIALS AND METHODS: 120 disks, 1 inch in diameter, were cast in Ticonium (CPM Industries, Albany, NY). The surface of the disks was finished to a high polish and then evenly microabraded. Four test groups of 15 pairs of disks were established, with two groups receiving Coe-Soft (Coe Laboratories, Chicago, IL) and two groups receiving Soft Oryl (Teledyne Getz, Elk Grove Village, IL). One group of each reline material had the microabraded surfaces on each disk treated with All Bond 2. Then, 1.2 mm of reline material was placed between each set of disks and allowed to cure. The disks were placed on an Instron machine and a tensile force was applied until bond failure occurred. RESULTS: All four groups showed significant bond strengths, with the Soft Oryl groups showing statistically significant higher bond strengths. In both reline material groupings, the groups with only microabrading showed slightly higher bond strengths. CONCLUSIONS: Soft reline materials can be made to adhere to base-metal alloys used in removable prosthodontics with clinically acceptable strengths using microabrading with or without the use of a resin bonding system.

Acrylic Resins↗
PubMedDate not supplied

Effect of disinfectants on the hardness and roughness of reline acrylic resins.

PURPOSE: Potential effects on hardness and roughness of a necessary and effective disinfecting regimen (1% sodium hypocholorite and 4% chlorhexidine) were investigated for two hard chairside reline resins versus a heat-polymerizing denture base acrylic resin. MATERIALS AND METHODS: Two standard hard chairside reliners (Kooliner and Duraliner II), one heat-treated chairside reliner (Duraliner II +10 minutes in water at 55 degrees C), and one standard denture base material (Lucitone 550) were exposed to two disinfecting solutions (1% sodium hypochlorite; 4% chlorhexidine gluconate), and tested for two surface properties [Vickers hardness number (VHN, kg/mm(2)); Roughness (Ra, microm)] for different times and conditions (1 hour after production, after 48 hours at 37 +/- 2 degrees C in water, after two disinfection cycles, after 7 days in disinfection solutions, after 7 days in water only). For each experimental condition, eight specimens were made from each material. Data were analyzed by analysis of variance followed by Tukey's test, and Student's t-test (p= 0.05). RESULTS: For Kooliner (from 6.2 +/- 0.3 to 6.5 +/- 0.5 VHN) and Lucitone 550 (from 16.5 +/- 0.4 to 18.4 +/- 1.7 VHN), no significant changes in hardness were observed either after the disinfection or after 7 days of immersion, regardless of the disinfectant solution used. For Duraliner II (from 4.0 +/- 0.1 to 4.2 +/- 0.1 VHN), with and without heat treatment, a small but significant increase in hardness was observed for the specimens immersed in the disinfectant solutions for 7 days (from 4.3 +/- 0.2 to 4.8 +/- 0.5 VHN). All materials showed no significant change in roughness (Kooliner: from 0.13 +/- 0.05 to 0.48 +/- 0.24 microm; Duraliner II, with and without heat treatment: from 0.15 +/- 0.04 to 0.29 +/- 0.07 microm; Lucitone 550: from 0.44 +/- 0.19 to 0.49 +/- 0.15 microm) after disinfection and after storage in water for 7 days. CONCLUSIONS: The disinfectant solutions, 1% sodium hypochlorite and 4% chlorhexidine gluconate, caused no apparent damage on hardness and roughness of the materials evaluated.

Acrylic Resins↗
PubMedDate not supplied

Effect of microwave disinfection procedures on torsional bond strengths of two hard chairside denture reline materials.

PURPOSE: This study evaluated the potential effects of denture base resin water storage time and an effective denture disinfection method (microwave irradiation at 650 W for 6 minutes) on the torsional bond strength between two hard chairside reline resins (GC Reline and New Truliner) and one heat-polymerizing denture base acrylic resin (Lucitone 199). MATERIALS AND METHODS: Cylindrical (30 x 3.9 mm) denture base specimens (n= 160) were stored in water at 37 degrees C (2 or 30 days) before bonding. A section (3.0 mm) was removed from the center of the specimens, surfaces prepared, and the reline materials packed into the space. After polymerization, specimens were divided into four groups (n= 10): Group 1 (G1)--tests performed after bonding; Group 2 (G2)--specimens immersed in water (200 ml) and irradiated twice (650 W for 6 minutes); Group 3 (G3)--specimens irradiated daily until seven cycles of disinfection; Group 4 (G4)-specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a torsional test (0.1 Nm/min), and the torsional strengths (MPa) and the mode of failure were recorded. Data from each reline material were analyzed by a two-way analysis of variance, followed by Neuman-Keuls test (p= 0.05). RESULTS: For both Lucitone 199 water storage periods, before bonding to GC Reline resin, the mean torsional strengths of G2 (2 days--138 MPa; 30 days--132 MPa), G3 (2 days--126 MPa; 30 days--130 MPa), and G4 (2 days--130 MPa; 30 days--137 MPa) were significantly higher (p < 0.05) than G1 (2 days--108 MPa; 30 days--115 MPa). Similar results were found for Lucitone 199 specimens bonded to New Truliner resin, with G1 specimens (2 days-73 MPa; 30 days--71 MPa) exhibiting significantly lower mean torsional bond strength (p < 0.05) than G2 (2 day--86 MPa; 30 days--90 MPa), G3 (2 days--82 MPa; 30 days--82 MPa), and G4 specimens (2 days--78 MPa; 30 days--79 MPa). The adhesion of both materials was not affected by water storage time of Lucitone 199 (p > 0.05). GC reline showed a mixed mode of failure (adhesive/cohesive) and New Truliner failed adhesively. CONCLUSIONS: Up to seven microwave disinfection cycles did not decrease the torsional bond strengths between the hard reline resins, GC Reline and New Truliner to the denture base resin Lucitone 199. The effect of additional disinfection cycles on reline material may be clinically significant and requires further study.

Acrylic Resins↗
PubMed2006

In vitro biocompatibility of denture relining materials.

OBJECTIVE: The aim of the present study was to evaluate the in vitro biocompatibility of denture relining materials using cell culture tests and a test for irritation mechanisms. BACKGROUND: Denture relining materials contain non-reacted constituents that may leach out during use inducing local toxic or irritative effects. MATERIALS AND METHODS: One chemically cured, four visible light cured and five dual-cured products were included. Cured test specimens were used for the filter diffusion test, and extracts of cured specimens were applied in the MTT and the irritation test using the hen's egg test-chorioallantoic membrane (HET-CAM) method. RESULTS: Five of the tested materials were slightly or moderately cytotoxic in the filter diffusion test, and one product coated with a liner induced severe toxicity. Cell cultures incubated for 24 hour with the test samples were more damaged than those incubated for 2 hour. In the MTT test, extracts of nine of the 11 products induced cytotoxicity. No extracts showed irritation, whereas the coating and two bonding agents tested were strong irritants. CONCLUSION: Most of the tested materials contained water soluble, toxic substances that leach out of the products and that some time was needed to obtain cytotoxic amounts of the leachables. Many dental materials elicit cytotoxic response, but this does not necessarily reflect the long-term risk for adverse effects as the oral mucosa is generally more resistant to toxic substances than a cell culture.

Animals↗
PubMed2006

Oral health care for frail elderly people: actual state and opinions of dentists towards a well-organised community approach.

OBJECTIVE: This study was undertaken to provide an analysis of the actual oral heath care for frail elderly people living in different settings and to explore opinions of dentists towards new concepts in developing a community approach. METHOD: Data were collected from a sample of 101 dentists (15%) in the county of Antwerp using a self-administered 30-item questionnaire including questions about age, gender, education, organisational aspects of dental surgery, questions concerning dentists' own contribution to oral healthcare services for frail elderly people and statements concerning opinions and attitude toward the organisation of oral health care for frail elderly people. At the same time, qualitative data were collected from focus group sessions with all participating dentists. Non-parametric analysis was used to explore possible relationships between opinion and possible explanatory variables. RESULTS: Half of the dentists offered dental services to residential or nursing homes (mean number of treatments a year: 5.4) and at home (mean number of treatments a year: 2.4). Prosthetic treatments such as relieving denture pressure points, repairing, rebasing and making new dentures were carried out in 77.4% and 76.7% of the cases in residential or nursing homes and at home respectively. Extractions were carried out in 16% and 18.6% of the cases in both living situations respectively. The main reasons for dentists refusing domiciliary oral health care were the absence of dental equipment (63%), lack of time (19%), with 11% convincing the patients to be treated in their dental surgery. Analysis showed different opinions of dentists depending on age, gender and university of education; however, statistically significant differences were only found by age. CONCLUSION: The older the dentist, the greater the tendency to refuse domiciliary oral healthcare services. The younger dentists were reluctant to cooperate in the provision of oral health care in a structured community approach.

Adult↗
PubMed1995

Dimensional changes of relined denture bases with heat-cured, microwave-activated, autopolymerizing, and visible light-cured resins. A laboratory study.

The dimensional changes of relined denture bases were evaluated in a laboratory study. Heat-cured resin, two autopolymerizing resins, microwave-activated resin and a new visible light-cured resin were used as relining materials in this study. The gaps between the metal die and the relined denture bases were measured immediately after the relining procedure and subsequently on the first day, first week, fourth week, and eight week. The relined denture bases were stored in distilled water at 37 degrees C between measurements. It was shown that dimensional changes in relined denture bases were influenced by the relining materials and procedures, and that heat-cured resin proved to have the smallest dimensional change as well as the greatest dimensional stability in comparison with the other relining materials and procedures.

Acrylic Resins↗
PubMed2001

Reline materials--handle with care? An investigation into the effect of varying the powder/liquid ratio on some properties of auto-polymerising acrylic resin materials.

INTRODUCTION: The fit of the denture base to the alveolar ridge progressively declines with alveolar ridge resorption. Once a denture becomes ill-fitting there are two main treatment options: to construct a new denture or to restore the fit of the existing denture. A denture may be relined as a laboratory procedure or at the chairside in the dental clinic. The chairside reline technique involves the direct application of auto-polymerising acrylic resin materials to the prepared denture base and the material is allowed to polymerise in the patient's mouth. The reline materials are generally supplied as a powder and a liquid. Clinicians and laboratory dental staff do not always follow manufacturers' recommended guidelines and the tendency can be simply to add varying quantities of powder and liquid until the desired consistency is achieved. This method however may have deleterious effects on the properties of the resultant material. MATERIALS AND METHOD: The aim of the study was to investigate the effect of varying the powder/liquid ratio on some properties of three auto-polymerising acrylic resin reline materials. The properties investigated were the flow characteristics in terms of the manipulation and setting time and the hardness. Four powder and liquid ratios were chosen. RESULTS AND CONCLUSIONS: For all the materials studied, a clinically useful lengthening of the manipulation time can be achieved by increasing the amount of liquid added to the powder. However, this is perhaps offset by the fact that it is associated with a corresponding increase in the setting time and resultant increase in clinical chairside time. There were significant differences in surface hardness when the powder/liquid ratio was altered.

Acrylic Resins↗
PubMed1991

Basic studies on visible light-curing resin for denture base. Part 8. The hardening depth of denture relining material after penetration of light through the denture base resin.

A study was performed to examine how the duration of irradiation at the time of relining with visible light-curing material influences the depth of hardening of the relining material, in relation to the thickness of the denture base placed between the denture and the relining material. It was found that for a range of denture base thickness of 1-2.5 mm, a desirable degree of hardening could be obtained using an irradiation time of 20 s for relining material with a thickness of up to 4 mm used for the basal surface.

Dental Materials↗
PubMed2001

Application of electrolyzed acid water to sterilization of denture base part 1. Examination of sterilization effects on resin plate.

Bactericidal activities of electrolyzed strong and weak acid waters for acrylic denture base resin were evaluated in order to discuss the applicability of these waters for sterilization of denture base. Only 1-minute immersion in the electrolyzed strong or weak acid water could completely eliminate the attached bacteria, Staphylococcus aureus 209P, on the resin plate. When the resin was relined with tissue conditioner, 5-minute immersion or 1- to 2-minute ultrasonic cleaning reduced the number of the bacteria from 10(5)/cm2 level to 10(1)/cm2 and no surviving bacteria could be detected after 10-minute treatment. These findings suggest that both the electrolyzed strong and weak acid waters are well applicable to the disinfectant for acrylic denture base showing excellent bactericidal activities in a significantly shorter treatment as compared with the conventional denture cleaning.

Acrylic Resins↗