Evaluation of Interface Adhesion Between Silicone Soft Liners and Denture Base After Immersion With Denture Cleansers by Scanning Electron Microscope

@#Introduction: The compatibility of denture cleanser is crucial in the prevention of failure of adhesion between silicone soft liner and acrylic denture base, thus ensuring the durability of the prosthesis. This scanning electron microscope (SEM) study was to determine the mode of failure and measured the gap formation between silicone soft liners and Polymethylmethacrylate (PMMA) denture base after immersion in denture cleansers. Methods: A total of 135 specimens of PMMA denture base lined with three different silicone soft liners (GC Reline Soft, Mollosil and Tokuyama Sofreliner Tough) were immersed into denture cleansers (Polident® and Stearadent) daily and stored in distilled water at 37±1°C. Specimens were examined and sectioned at 2.5mm and 5.0mm from the margin after 1 day, 30 days and 90 days before analyzed. Results: No significant difference detected in the mode of failure and gap formation after one-day immersion. Adhesive failure was the commonest failure at the margin after 30 days (71.11%) and after 90 days (95.56%). However, 33.33% of specimens showed mixed failure at 5.0mm sectioned after 90 days. A significant difference of gap formation was demonstrated from Mollosil in Steradent at the margin and at 2.5 mm sectioned after 30 days and after 90 days (p<0.05). It was also observed at the margin and 5.0mm sectioned of specimens from Tokuyama in Steradent after 90 days of immersion (p<0.05). Conclusion: Specimen immersed in Steradent denture cleanser presented with wider gap formation as compared to Polident®, and adhesive failure is the commonest mode of failure.

Biofilm formation on complete denture liners

AIM: To clinically evaluate biofilm growth on 4 liners in complete denture base surfaces of 20 geriatric patients. MATERIAL AND METHODS: Patients received new complete maxillary dentures prepared with 4 chambers (10x10x2 mm) in the tissue surface of acrylic denture base. Each of the 4 chambers was randomly filled with the following denture liners: Eversoft (M1); Kooliner (M2); GC Reline Extra Soft (M3); Elite Soft Relining (M4). Patients were randomly separated into 2 treatment groups: T1- sanitization with soft brush and dentifrice; T2- similar to T1 with daily immersion in cleansing chemical solution (Ortoform). Patients had 8 follow-up sessions over a 3-month period. The internal denture surface was stained with a dental plaque dye at each of the follow-up visits. Standardized photographs were taken, and biofilm growth was scored. Data were tabulated and submitted to Analysis of Variance. Means were compared by Tukey (p<0.05) and T tests. RESULTS: Kooliner (M2) means were significantly different from the others for both groups T1 and T2. Treatment 1 promoted higher biofilm growth scores than treatment 2. The highest score after treatment 1 was Kooliner (M2) and the lowest was Elite Soft Relining (M4). As for treatment 2, Eversoft (M1) was statistically different from Elite Soft Relining (M4). Again, Kooliner (M2) presented the highest score and Elite Soft Relining (M4) the lowest. Kooliner (M2) was statistically different from both GC Reline Extra Soft (M3) and Elite Soft Relining (M4). CONCLUSION: Of the materials and treatments studied, the best clinical selection for lower biofilm growth scores would be Elite Soft Relining (M4) with treatment 2.

Effect of aging on tear strength and cytotoxicity of soft denture lining materials; in vitro

PURPOSE: The aim of this in vitro study was to evaluate the effect of aging on the tear strength and cytotoxicity of four soft denture lining materials. MATERIALS AND METHODS: Four commonly used soft denture lining materials, (Coe-Comfort(TM) GC America Inc., Alsip, IL, USA; Coe-Soft(TM) GC America Inc., Alsip, IL, USA; Visco-gel Dentsply Caulk Milford, DE, USA; and Sofreliner Tough M Tokuyama Dental Corporation Tokyo, Japan) were selected. Sixty trouser-leg designed specimens per lining material were fabricated using a stainless steel mold for tear strength testing. The specimens were divided into non-thermocycling and 1000-, and 3000- thermocycling groups. For the cytotoxicity test, twenty-four disk shaped specimens per material were fabricated using a stainless steel mold. The specimens were soaked in normal saline solution for 24 h, 48 h and 72 h. Cytotoxicity was measured by XTT assay in L929 mouse fibroblasts. Data were analyzed by two way analysis of variance and Dunnett's test (P<.05). RESULTS: Before thermocycling, Sofreliner Tough M (10.36 +/- 1.00 N) had the highest tear strength value while Coe-Comfort(TM) (0.46 +/- 0.10 N) had the lowest. After 3000 cycles, Sofreliner Tough M (9.65 +/- 1.66 N) presented the highest value and Coe-Comfort(TM) (0.42 +/- 0.08 N) the lowest. Sofreliner Tough M, in all incubation periods was the least toxic with significant differences compared to all other materials (P<.05). Coe-Comfort(TM), Coe-Soft(TM), and Sofreliner Tough M did not show any significant differences within their material group for all incubation periods. CONCLUSION: This in vitro study revealed that aging can affect both the tear strength and cytotoxicity of soft denture materials depending on the composition.

Peel strength of denture liner to PMMA and polyamide: laser versus air-abrasion

PURPOSE: This study investigated the effect of laser parameters and air-abrasion on the peel strength of silicon-based soft denture liner to different denture resins. MATERIALS AND METHODS: Specimens (N=180) were prepared out of three different denture base resins (Rodex, cross-linked denture base acrylic resin; Paladent, heat-cured acrylic resin; Deflex, Polyamide resin) (75 mm x 25 mm x 3 mm). A silicon-based soft denture liner (Molloplast B) was applied to the denture resins after the following conditioning methods: a) Air-abrasion (50 microm), b) Er,Cr:YSGG laser (Waterlase MD Turbo, Biolase Technology) at 2 W-20 Hz, c) Er,Cr:YSGG laser at 2 W-30 Hz, d) Er,Cr:YSGG laser at 3 W-20 Hz, e) Er,Cr:YSGG laser at 3 W-30 Hz. Non-conditioned group acted as the control group. Peel test was performed in a universal testing machine. Failure modes were evaluated visually. Data were analyzed using two-way ANOVA and Tukey's test (alpha=.05). RESULTS: Denture liner tested showed increased peel strength after laser treatment with different parameters (3.9+/-0.4 - 5.58+/-0.6 MPa) compared to the control (3.64+/-0.5 - 4.58+/-0.5 MPa) and air-abraded groups (3.1+/-0.6 - 4.46+/-0.3 MPa), but the results were not statistically significant except for Paladent, with the pretreatment of Er,Cr:YSGG laser at 3 W-20 Hz. Polyamide resin after air-abrasion showed significantly lower peel strength than those of other groups (3.1+/-0.6 MPa). CONCLUSION: Heat-cured acrylic resin, PMMA, may benefit from Er,Cr:YSGG laser treatment at 3 W-20 Hz irradiation. Air-abrasion of polyamide resins should be avoided not to impair their peel bond strengths to silicon-based soft denture liners.

Prosthetic rehabilitation for a patient with hypohidrotic ectodermal dysplasia: a clinical case

Hypohidrotic ectodermal dysplasia (HED) is a hereditary syndrome, characterized by a classictriad of hypotrichosis, hypodontia and hypohidrosis. The case of an 8-year-old girl with HEDpresenting oligodontia and marked resorption of maxillary and mandibular alveolar ridges is reported. A specially designed aluminum wire tray was used for taking impressions of both dental arches. Prosthetic rehabilitation included a removable maxillary over denture and a mandibular conventional acrylic resin denture made tissue-compatible by means of a soft denture liner attached to denture base. The proposed treatment plan provided improved esthetics, function,and quality of life.

A study on the adhesion of a soft liner containing 4-META to the base metal alloy and its viscoelastic property / 대한치과보철학회지

STATEMENT OF PROBLEM: Soft lining materials, also referred to as tissue conditioning materials, tissue treating materials, relining materials, soft liners or tissue conditioners, were first introduced to dentistry by a plastic manufacturer in 1959. Since the introduction of the materials to the dental field, their material properties have been continually improved through the effort of many researchers. Soft lining materials have become widely accepted, particularly by prosthodontists, because of their numerous clinical advantages and ease of manipulation. Unfortunately, few reports have been issued upon the topic of increasing the bond strength between the base metal alloy used in cast denture bases and PMMA soft liner modified with 4-META, nor upon the pattern of debonding and material change in wet environment like a intra oral situation. PURPOSE: The purposes of this study were comparing the bond strength between base metal alloy used for the cast denture bases and PMMA soft liner modified with 4-META, and describing the pattern of debonding and material property change in wet environment like the intraoral situation. MATERIAL AND METHODS: This study consisted of four experiments: 1. The in vitro measurement of shear bond strength of the adhesive soft liner. 2. The in vitro measurement of shear bond strength of the adhesive soft liner after 2 weeks of aging. 3. A comparison of debonding patterns. 4. An evaluation the gelation time of modified soft liner. The soft liner used in this study was commercially available as Coe-soft (GC America.IL., USA), which is provided in forms of powder and liquid. This is a PMMA soft liner commonly used in dental clinics. The metal primer used in this study was 4-META containing primer packed in Meta fast denture base resin (Sun Medical Co., Osaka, Japan). The specimens were formed in a single lap joint design, which is useful for evaluating the apparent shear bond strength of adhesively bonded metal plate by tensile loading. Using the 20x20mm transparent grid, percent area of adhesive soft liner remaining on the shear area was calculated to classify the debonding patterns. To evaluate the change of the initial flow of the modified adhesive soft liner, the gelation time was measured with an oscillating rheometer (Haake RS150W/TC50, Haake Co., Germany). It was a stress control and parallel plate type with the diameter of 35mm. CONCLUSION. Within the conditions and limitations of this study, the following conclusions were drawn as follows. 1. There was significant increase of bond strength in the 5% 4-META, 10% 4-META containing groups and in the primer coated groups versus the control group(P<0.05). 2. After 2 weeks of aging, no significant increase in bond strength was found except for the group containing 10% 4-META (P<0.05). 3. The gelation times of the modified soft liner were 9.3 minutes for the 5% 4-META containing liner and 11.5 minutes for the 10% 4-META liner. 4. The debonding patterns of the 4-META containing group after 2 weeks of aging were similar to those of immediaely after preparation, but the debonding pattern of the primer group showed more adhesive failure after 2 weeks of aging.