Clinical evaluation of resilient denture liners. Part 2: Candida count and speciation

Knowledge and attitude about relining of complete dentures in clinical practice: A cross-sectional study

Background

Residual ridge resorption is crucial sequelae of tooth loss. Complete dentures are the most common way of rehabilitating edentulous patients. However, with continuing residual ridge resorption, dentures tend to become loose and unstable causing discomfort, chewing disability, and speech problems. Denture relining is an economical means of improving a denture's stability and retention. An understanding of the clinical indications and limitations of these materials and procedures is crucial for clinical success.

Aim and Objective

The purpose of this survey was to assess knowledge, attitude, and practice in relining dentures among dental practitioners.

Materials and Methods

The cross-sectional survey was conducted using a validated questionnaire on 200 (n = 200) dental practitioners in Nagpur city, Maharashtra. Data analysis was done using proportion test with SPSS EPI INFO software.

Results

Although all 200 practitioners were aware of the relining procedure and were routinely carrying out the procedure in their dental clinics, 50% of the practitioners were unaware of the correct relining step by step procedure and were also not sure about the antimicrobial properties of the relining material available in the market.

Conclusion

Awareness and scientific knowledge about the relining materials and procedure should be enhanced within general dental practitioners through CDE program and workshops. Steps should be taken to include relining procedure as a part of undergraduate clinical curriculum as well as internship program.

Surface Coating of Gypsum-Based Molds for Maxillofacial Prosthetic Silicone Elastomeric Material: Evaluating Different Microbial Adhesion

PURPOSE

To compare the adhesion of three microorganisms on modified and unmodified silicone elastomer surfaces with different surface roughnesses and porosities.

MATERIALS AND METHODS

Candida albicans, Streptococcus mutans, and Staphylococcus aureus were incubated with modified and unmodified silicone groups (N = 35) for 30 days at 37°C. The counts of viable microorganisms in the accumulating biofilm layer were determined and converted to cfu/cm² unit surface area. A scanning electron microscope (SEM) was used to evaluate the microbial adhesion. Statistical analysis was performed using t-test, one-way ANOVA, and post hoc tests as indicated.

RESULTS

Significant differences in microbial adhesion were observed between modified and unmodified silicone elastomers after the cells were incubated for 30 days (p < 0.001). SEM showed evident differences in microbial adhesion on modified silicone elastomer compared with unmodified silicone elastomer.

CONCLUSIONS

Surface modification of silicone elastomer yielding a smoother and less porous surface showed lower adhesion of different microorganisms than observed on unmodified surfaces.

Surface roughness of acrylic and silicone-based soft liners: in vivo study in a rat model

PURPOSE

The aim of this in vivo animal study was to investigate changes in the surface roughness of soft liners over time.

MATERIALS AND METHODS

Forty adult Wistar rats (Rattus norvergicus albinus) were fitted with acrylic custom-made palatal plates relined by dynamic impressions and tested with the following soft liners: Dentuflex (DF), Trusoft (TS), Dentusoft (DS), and Ufi Gel P (UG). Half of the animals for each tested material had the plates fitted during the material reline procedure. Their surface roughness was read immediately (IRa group, n = 5). The other half used the palatal plates for 14 days before roughness readings were performed (FRa group, n = 5). The surface roughness (Ra) of the inner surface from the relined dentures was recorded using a Surftest SJ-401 with eight readings per specimen, and mean values were obtained. Data (μm) were analyzed by two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

IRa means (2.92 ± 0.87 μm) and FRa means (3.35 ± 0.65 μm) were significantly different (p = 0.016). UG showed a lower (p = 0.01) Ra mean (2.1 ± 0.52 μm) than DF (3.94 ± 0.81 μm), TS (4.12 ± 0.64 μm), and DS (3.27 ± 0.64 μm).

CONCLUSIONS

Ufi Gel P showed the smoothest surface among the materials evaluated. The period of use resulted in changes in the surface roughness of the materials tested.

Resilient liners: a review

Resilient liners when used intelligently are an excellent adjunct in removable prosthodontics. However, currently they have to be best considered as temporary expedients because none of the advocated permanent liners have life expectancy comparable to resin denture base. This article reviews the literature regarding their composition, functions, gelation characteristics, bond strength and influence on denture bases. It also presents their drawbacks and attempts made to extend their longevity. A Medline search was completed for the period from 1986 to 2007, along with a manual search, to identify pertinent English peer-reviewed articles and textbooks.

Changes in roughness of denture base and reline materials by chemical disinfection or microwave irradiation: surface roughness of denture base and reline materials

OBJECTIVE

The effect of disinfection by immersion in sodium perborate solution and microwave irradiation on surface roughness of one denture base resin (Lucitone 550 -L), 3 hard chairside reline resins (Tokuyama Rebase II-TR, New Truliner-NT, Ufi Gel hard-UH) and 3 resilient reline materials (Trusoft-T; Sofreliner-S, Dentusil-D) was evaluated.

MATERIAL AND METHODS

Thirty specimens of each material were made and divided into 3 groups: Control - not disinfected; P - daily disinfection by immersing in sodium perborate solution (3.8%); MW - microwave disinfection (6 min/650 W). Roughness measurements were made after polymerization (baseline) and after 1, 3 and 28 days. Roughness differences relative to the baseline readings were analyzed by Student's t-test (P=0.05).

RESULTS

At baseline, Trusoft showed the highest (P<0.001) mean surface roughness (3.54 µm), and its surface roughness was significantly reduced after 28 days of disinfection by immersion in sodium perborate (P=0.013). Roughness measurements of material Trusoft were not performed after microwave disinfection due to the severe alterations on the surface. In the 3 groups evaluated, changes in roughness were significant for materials Ufi Gel hard (from 0.11 to 0.26 µm; P<0.041) and New Truliner (0.19 to 0.76 µm; P<0.019). The roughness of materials Lucitone 550 (0.37 µm), Tokuyama Rebase II (0.37 µm), Sofreliner (0.49 µm) and Dentusil (0.38 µm) remained unaffected (P>0.05).

CONCLUSIONS

The roughness of the hard reline materials Ufi Gel hard and New Truliner was adversely affected by microwave disinfection, immersion in water or in sodium perborate. Microwave disinfection caused severe alterations on the surface of the resilient liner Trusoft.

Enhanced enzymatic activity of Candida species responsible for oral candidiasis in renal transplant recipients

Renal transplant recipients (RTRs) are regarded to be predisposed to oral candidiasis. This study was undertaken to evaluate the activity of hydrolytic enzymes in strains causing oral candidiasis in RTR. A total of 123 Candida albicans and 10 Candida krusei strains were isolated from 200 RTRs (39 RTRs suffered from symptomatic candidiasis, the remaining patients had no clinical symptoms of infection). All fungi were identified based on routine mycological procedures. Because of a small number of non-albicans strains, only C. albicans isolates were compared for enzymatic activity. The activity of 19 hydrolytic enzymes was assessed by API ZYM(®) test. The usage of mycophenolate mofetil was connected with higher ratio of clinically apparent oral candidiasis compared to immunosuppressive regimens without this drug (74.4% vs. 46.8%, respectively, P < 0.01). Candida albicans from RTRs showed higher enzymatic activity compared with strains from immunocompetent patients. Only two enzymes were found to be more active in C. albicans causing symptomatic candidiasis in RTRs (cystine arylamidase: P = 0.001, and α-fucosidase: P = 0.01) compared with saprophytic strains. Atrophic candidiasis showed higher activity of esterase lipase (C8) and α-mannosidase compared with the pseudomembraneous type. We suggest that the enhanced enzymatic activity is responsible for higher invasiveness of Candida residing in the oral cavity of RTRs.

In vitro colonization of an experimental silicone by Candida albicans

Denture soft-lining materials are exposed to the oral cavity for long periods and are in continuous contact with saliva, subject to inhibition of liquid molecules, and susceptible to colonization by microorganisms. The opportunist yeast Candida albicans is of particular concern in this context, being associated with denture plaque and denture-related stomatitis. In this study, penetration of C. albicans into an experimental silicone elastomer soft-lining material was investigated under batch and continuous culture conditions. A model "denture plaque" microcosm was also used. Increasing the filler concentration within the elastomer decreased penetration under both batch and continuous culture conditions. In continuous culture, C. albicans penetration was significantly greater in pure culture than in the presence of bacteria after 72-h incubation (p < 0.05).

Modification of surface properties of biomaterials influences the ability of Candida albicans to form biofilms

Candida albicans biofilms form on indwelling medical devices (e.g., denture acrylic or intravenous catheters) and are associated with both oral and invasive candidiasis. Here, we determined whether surface modifications of polyetherurethane (Elasthane 80A [E80A]), polycarbonateurethane, and poly(ethyleneterephthalate) (PET) can influence fungal biofilm formation. Polyurethanes were modified by adding 6% polyethylene oxide (6PEO), 6% fluorocarbon, or silicone, while the PET surface was modified to generate hydrophilic, hydrophobic, cationic, or anionic surfaces. Formation of biofilm was quantified by determining metabolic activity and total biomass (dry weight), while its architecture was analyzed by confocal scanning laser microscopy (CSLM). The metabolic activity of biofilm formed by C. albicans on 6PEO-E80A was significantly reduced (by 78%) compared to that of biofilm formed on the nonmodified E80A (optical densities of 0.054 +/- 0.020 and 0.24 +/- 0.10, respectively; P = 0.037). The total biomass of Candida biofilm formed on 6PEO-E80A was 74% lower than that on the nonmodified E80A surface (0.46 +/- 0.15 versus 1.76 +/- 0.32 mg, respectively; P = 0.003). Fungal cells were easily detached from the 6PEO-E80A surface, and we were unable to detect C. albicans biofilm on this surface by CSLM. All other surface modifications allowed formation of C. albicans biofilm, with some differences in thearchitecture. Correlation between contact angle and biofilm formation was observed for polyetherurethane substrates (r = 0.88) but not for PET biomaterials (r = -0.40). This study illustrates that surface modification is a viable approach for identifying surfaces that have antibiofilm characteristics. Investigations into the clinical utility of the identified surfaces are warranted.

Effect of microwave disinfection on the hardness and adhesion of two resilient liners

STATEMENT OF PROBLEM

Microwave irradiation has been suggested for denture disinfection. However, the effect of this procedure on the hardness and bond strength between resilient liners and denture base acrylic resin is not known.

PURPOSE

This study evaluated the effect of water storage time and microwave disinfection on the hardness and peel bond strength of 2 silicone resilient lining materials to a heat-polymerized acrylic resin.

MATERIAL AND METHODS

Acrylic resin (Lucitone 199) specimens (75 x 10 x 3 mm) were stored in water at 37 degrees C (2 or 30 days) before bonding (n = 160). The resilient lining materials (GC Reline Extra Soft and Dentusil) were bonded to the denture base and divided into the following 4 groups (n = 10): Tests performed immediately after bonding (control); specimens immersed in water (200 mL) and irradiated twice, with 650 W for 6 minutes; specimens irradiated daily for 7 total cycles of disinfection; specimens immersed in water (37 degrees C) for 7 days. Specimens were submitted to a 180-degree peel test (at a crosshead speed of 10 mm/min) and the failure values (MPa) and mode of failure were recorded. Pretreatment and posttreatment hardness measurements (Shore A) of the resilient materials were also performed. Three-way analysis of variance, followed by the Tukey HSD test, was performed (alpha = .05).

RESULTS

The analysis revealed that, for all conditions, the mean failure strengths of GC Reline Extra Soft (0.95-1.19 MPa) were significantly higher ( P < .001) than those of Dentusil (0.45-0.50 MPa). The adhesion of the liners was not adversely affected by water storage time of Lucitone 199 or microwave disinfection. All peel test failures were cohesive. There was a small but significant difference ( P < .001) between the pretreatment (34.33 Shore A) and posttreatment (38.69 Shore A) hardness measurements.

CONCLUSION

Microwave disinfection did not compromise the hardness of either resilient liners or their adhesion to the denture base resin Lucitone 199.