The Effect of Food-Simulating Agents on the Bond Strength of Hard Chairside Reline Materials to Denture Base Resin.

PURPOSE: To investigate the influence of food-simulating agents on the shear bond strength between direct hard liners and denture base acrylic resin. In addition, mode of failure was evaluated. MATERIALS AND METHODS: One hundred fifty cylindrical columns of denture base resin were fabricated and bonded to three types of hard reline materials (Hard GC Reline, Tokuyama Rebase II Fast, TDV Cold Liner Rebase). Specimens of each reline material were divided into five groups (n = 10) to undergo 12-day immersion in distilled water, 0.02 N citric acid aqueous solution, heptane, and 40% ethanol/water solution at 37°C. The control group was not immersed in any solution. The shear bond strength test was performed, and the failure mode was determined. Statistics were analyzed with two-way ANOVA and chi-square test (α = 0.05). RESULTS: Significant interaction was found between the hard liners and food simulating agents (p < 0.001). The shear bond strength of Tokuyama in 40% ethanol and TDV in heptane decreased significantly (p = 0.001, p < 0.001 respectively); however, none of the solutions could significantly affect the shear bond strength of Hard GC Reline (p = 0.208). The mixed failure mode occurred more frequently in Hard GC Reline compared with the other liners (p < 0.001) and was predominant in specimens with higher bond strength values (p = 0.012). CONCLUSIONS: Food simulating agents did not adversely affect the shear bond strength of Hard GC Reline; however, ethanol and heptane decreased the bond strength of Tokuyama and TDV, respectively. These findings may provide support to dentists to recommend restricted consumption of some foods and beverages for patients who have to use dentures relined with certain hard liners.

Evaluation of Intraoral Burning Sensation in Response to Heat-Cured and Self-Cured Acrylic Resin Denture Base Material.

The objective of this prospective experimental clinical trial was to evaluate intraoral burning sensation in response to heat-cured and self-cured acrylic resin denture base material and carried out in the department of Prosthodontics of Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh from February 2014 to September 2015. Forty eight patients were evaluated in this study; of them 35(72.92%) patients were male and 13(27.08%) patients were female with age range from 24 to 70 years. In this study 48 patients were evaluated in term of burning sensation, of them 24 patients were provided with heat-cured acrylic resin denture and were considered as Group A and 24 patients were provided with self-cured acrylic resin denture and were considered as Group B. In Group A 14(58.4%) at 1st week, 2(8.4%) at 1st month, 10(41.8%) at 3rd month and 5(21.0%) at 6th month developed burning sensation. On the other hand the values were 18(75.0%), 22(91.6%), 14(58.2%) and 2(8.4%) at 1stweek, 1st month, 3rd month, and 6th month respectively. Chi-square test was done for statistical analysis and p value was <0.05. So, results were statistically significant.

Fabrication of denture base materials with antimicrobial properties.

STATEMENT OF PROBLEM: Acrylic resin denture base resins are colonized by oral and nonoral bacteria and Candida species. This reservoir of microorganism causes denture stomatitis, which can be implicated in some life-threating infections in older denture wearers. PURPOSE: The purpose of this in vitro study was to incorporate quaternized N,N-dimethylaminoethyl methacrylate (DMAEMA) monomer into a denture base resin and investigate its antimicrobial and mechanical properties. MATERIAL AND METHODS: Quaternized ammonium monomer (QAM) was synthesized through the reaction of octyl bromide and DMAEMA. The synthesized QAM was incorporated into a denture base resin system (8 to 12 wt%). The resulting material was characterized by Fourier transform infrared spectroscopy. The in vitro antimicrobial property was determined by direct contact test against Escherichia coli, Staphylococcus aureus, and Candida albicans. Release of the QAM was also tested by means of an agar diffusion test. Mechanical properties were measured with a 3-point bend test, and results were analyzed and compared using ANOVA and the Tukey post hoc test (α=.05). RESULTS: Spectroscopy confirmed the formation of quaternized ammonium modified denture base (QAMDB). The decrease in number of viable cells of E coli, S aureus, and C albicans was more than 99% for 12%-QAMDB in comparison with that of the control groups. An overall decline was observed in the flexural strength and flexural modulus of the fabricated resins (P<.05), but no differences were observed for strain at break or fracture work of the specimens (P>.05). CONCLUSIONS: Denture base resins containing immobilized QAM provided high antibacterial activity, but the flexural strength and flexural modulus of the denture base resins decreased.

[PHYSICAL AND MATHEMATICAL GROUNDS LANDFORMS BASIS PLATE DENTURES WHEN APPLYING THE COMPLEX METHOD OF PREVENTION OF PROSTHETIC STOMATITIS].

Objective - to develop the form of the drug reservoir to hold the vegetable oils under the basis of the prosthesis. The research was conducted on the Bench PMMA samples. The comparison group consisted of smooth plate PMMA. Two study groups were PMMA plates with grooves on one side of a square with sides of 2 mm and depth of channel - 1 mm. The third group consisted of the experimental plate with diamond-shaped notches with the same parameters. The lowest value of the stress in the plate having a rhombic grid, they are 54% less than in the smooth plate and 37% less than in the plate with a square lattice (the best strength characteristics in a rhombic plate with grille). Equivalent move from the plate with a rhombic lattice is less than an order of magnitude than that of a smooth plate and by 5.8% more than at the plate with a square lattice, which indicates good performance design plasticity with rhombic grid. Basis with the rhombic lattice on the surface has the best record on the stress-strain state in comparison with other models considered (smooth plate with a square lattice plate).

Biofilm formation and Candida albicans morphology on the surface of denture base materials.

Fungal biofilms may contribute to the occurrence of denture stomatitis. The objective of the study was to investigate the biofilm formation and morphology of Candida albicans in biofilms on the surface of denture base materials. Specimens were prepared from different denture base materials. After determination of surface properties and salivary pellicle formation, mono- and multispecies biofilm formation including Candida albicans ATCC 10231 was initiated. Relative amounts of adherent cells were determined after 20, 44, 68 and 188 h; C. albicans morphology was analysed employing selective fluorescence microscopic analysis. Significant differences were identified in the relative amount of cells adherent to the denture base materials. Highest blastospore/hyphae index suggesting an increased percentage of hyphae was observed in mono- and multispecies biofilms on the soft denture liner, which did not necessarily respond to the highest relative amount of adherent cells. For both biofilm models, lowest relative amount of adherent cells was identified on the methacrylate-based denture base material, which did not necessarily relate to a significantly lower blastospore/hyphae index. The results indicate that there are significant differences in both biofilm formation as well as the morphology of C. albicans cells in biofilms on the surface of different denture base materials.

Acrylic Resin Cytotoxicity for Denture Base--Literature Review.

Acrylic resin is a widely used material in clinical practice, and a satisfactory biocompatibility is essential. When the resin polymerization reaction is incomplete, residual monomers are released into the oral cavity. The aim of this study was to evaluate, through a literature review, the cytotoxicity caused by the denture base acrylic resin used, and its components. The selection of published studies was performed on the Pubmed database from January 2008 to July 2013. The keywords used were: "cytotoxicity and acrylic resins", "cytotoxicity and denture base resins" and "cytotoxicity and oral prosthesis". Inclusion criteria were: in vitro studies and literature reviews published in English that evaluated the acrylic resin cytotoxicity for denture base and its components. Studies with no reference to the search strategy were excluded. A total of 182 articles were found. Among these, only 13 were included for writing this review. The MTT test is the most common test used to evaluate acrylic resin cytotoxicity. Auto-polymerized resin is more cytotoxic than heat-polymerized resin because of its higher quantity of residual monomers which cause cell and tissue changes in the oral mucosa. However, more studies are necessary for the development of biocompatible materials.

Traumatic ulcerative granuloma with stromal eosinophilia around mini dental implants without the protection of a denture base.

This is a report of a case of an unusual oral lesion after the placement of mini implants for the retention of a mandibular overdenture. A patient received four 2-mm-wide dental implants in the anterior mandible and had her mandibular denture relined with a soft material. After 3 months, she was not wearing her mandibular denture, and two nodular ulcerated lesions were observed near the mini implants. The lesions ceased following excision and regular denture wearing. Clinical and microscopic examination led to the diagnosis of traumatic ulcerative granuloma with stromal eosinophilia (TUGSE). TUGSE is rare lesion with a benign course that may occur following injury of the oral mucosa by mini implants under certain circumstances.

The influence of the design of removable dentures on patient's voice quality.

The main condition for speech intelligibility is the specific anatomical characteristics of the human speech apparatus and harmonious work of all organs in the human vocal apparatus. The voice quality is characterized by speech intelligibility (relationship between the voice pitch, volume, timbre and speech speed). Improper functional quality (related to retention,support, stability), inappropriate design of the prosthetic base and disposition of artificial teeth are the basic reasons for dyslalia - impairment of utterance with abnormality of external speech organs. In the case of dyslalia a patient may suffer from a defective utterance of separate phonemes. When designing removable dental prostheses, it is important to evaluate the disposition of the artifical teeth (taking into account phonetic pronunciation), make a phonetically beneficial construction of the base of the dentures and restore the lost alveolar bone with the basis of removable prostheses. The aim of this study was to review literature on voice quality and the way it can be affected after the insertion of removable dental prostheses and to research the literature describing the ways how voice quality can be improved. The literature reviewed in the paper was retrieved from Science Direct, PubMed, MD Consult, Cochrane Libary databases and dates back to the period from 1990 to 2012.

Time course of bone metabolism at the residual ridge beneath dentures observed using ¹8F-fluoride positron emission computerized-tomography/computed tomography (PET/CT).

OBJECTIVE: Excessive pressure due to wearing mal-adapting dentures is well known to cause residual bone resorption beneath the denture. X-rays have been commonly utilized to evaluate the changes in the bone beneath the denture. However, X-ray images merely detect bone density and relatively large changes in the bone shape and structure, whereas nuclear medicine imaging can detect functional changes, which occur prior to structural changes. This article aimed to describe the time course of the bone metabolism at the residual ridge beneath the denture following denture use by (18)F-fluoride positron emission computerized-tomography (PET)/computed tomography (CT) scanning. METHODS: Three subjects, who had a free-end edentulous mandible, were treated with a denture replacing the edentulous region of the dental arch. The metabolic changes in the residual bone beneath the denture were assessed by (18)F-fluoride PET/CT imaging. (18)F-fluoride PET/CT scanning was performed at baseline, and 4-6 and 13 weeks after denture use. A volume of interest (VOI) was placed on their mandibles at the edentulous region beneath the denture on the PET/CT image. CT value and mean standardized uptake value (SUV) of the VOI were calculated. The difference in the time variation between the CT value and SUV was analyzed. RESULTS: The adaptation of the denture base to the residual ridge was successful, and there was no trouble such as pain at the residual ridge beneath the denture. The SUVs of each VOI significantly increased at 4-6 weeks after denture use and then decreased at 13 weeks in all three subjects (P < 0.05; two-way ANOVA, Dunnett test). On the other hand, the CT images showed no obvious changes in the bone shape or structure beneath the dentures, and the CT values of each VOI remained static after denture use in all three subjects. CONCLUSIONS: This study indicates that in the present first-time removable partial denture (RPD) users, wearing of a well-adapted RPD initially increased bone metabolism beneath the denture and then decreased it at around 13 weeks after RPD use without any bone structural changes detectable by clinical X-rays. These metabolic changes are a mechanobiological reaction to the pressure induced by RPD use.

Effect of leaching residual methyl methacrylate concentrations on in vitro cytotoxicity of heat polymerized denture base acrylic resin processed with different polymerization cycles.

OBJECTIVES: Residual methyl methacrylate (MMA) may leach from the acrylic resin denture bases and have adverse effects on the oral mucosa. This in vitro study evaluated and correlated the effect of the leaching residual MMA concentrations ([MMA]r) on in vitro cytotoxicity of L-929 fibroblasts. MATERIAL AND METHODS: A total of 144 heat-polymerized acrylic resin specimens were fabricated using 4 different polymerization cycles: (1) at 74ºC for 9 h, (2) at 74ºC for 9 h and terminal boiling (at 100ºC) for 30 min, (3) at 74ºC for 9 h and terminal boiling for 3 h, (4) at 74ºC for 30 min and terminal boiling for 30 min. Specimens were eluted in a complete cell culture medium at 37ºC for 1, 2, 5 and 7 days. [MMA]r in eluates was measured using high-performance liquid chromatography. In vitro cytotoxicity of eluates on L-929 fibroblasts was evaluated by means of cell proliferation using a tetrazolium salt XTT (sodium 3´-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) assay. Differences in [MMA]r of eluates and cell proliferation values between polymerization cycles were statistically analyzed by Kruskal-Wallis, Friedman and Dunn's multiple comparison tests. The correlation between [MMA]r of eluates and cell proliferation was analyzed by Pearson's correlation test (p<0.05). RESULTS: [MMA]r was significantly (p<0.001) higher in eluates of specimens polymerized with cycle without terminal boiling after elution of 1 and 2 days. Cell proliferation values for all cycles were significantly (p<0.01) lower in eluates of 1 day than those of 2 days. The correlation between [MMA]r and cell proliferation values was negative after all elution periods, showing significance (p<0.05) for elution of 1 and 2 days. MMA continued to leach from acrylic resin throughout 7 days and leaching concentrations markedly reduced after elution of 1 and 2 days. CONCLUSION: Due to reduction of leaching residual MMA concentrations, use of terminal boiling in the polymerization process for at least 30 min and water storage of the heat-polymerized denture bases for at least 1 to 2 days before denture delivery is clinically recommended for minimizing the residual MMA and possible cytotoxic effects.

Effect of leaching residual methyl methacrylate concentrations on in vitro cytotoxicity of heat polymerized denture base acrylic resin processed with different polymerization cycles

OBJECTIVES: Residual methyl methacrylate (MMA) may leach from the acrylic resin denture bases and have adverse effects on the oral mucosa. This in vitro study evaluated and correlated the effect of the leaching residual MMA concentrations ([MMA]r) on in vitro cytotoxicity of L-929 fibroblasts. MATERIAL AND METHODS: A total of 144 heat-polymerized acrylic resin specimens were fabricated using 4 different polymerization cycles: (1) at 74ºC for 9 h, (2) at 74ºC for 9 h and terminal boiling (at 100ºC) for 30 min, (3) at 74ºC for 9 h and terminal boiling for 3 h, (4) at 74ºC for 30 min and terminal boiling for 30 min. Specimens were eluted in a complete cell culture medium at 37ºC for 1, 2, 5 and 7 days. [MMA]r in eluates was measured using high-performance liquid chromatography. In vitro cytotoxicity of eluates on L-929 fibroblasts was evaluated by means of cell proliferation using a tetrazolium salt XTT (sodium 3´-[1-phenyl-aminocarbonyl)-3,4-tetrazolium]bis(4-methoxy-6-nitro)benzenesulphonic acid) assay. Differences in [MMA]r of eluates and cell proliferation values between polymerization cycles were statistically analyzed by Kruskal-Wallis, Friedman and Dunn's multiple comparison tests. The correlation between [MMA]r of eluates and cell proliferation was analyzed by Pearson's correlation test (p<0.05). RESULTS: [MMA]r was significantly (p<0.001) higher in eluates of specimens polymerized with cycle without terminal boiling after elution of 1 and 2 days. Cell proliferation values for all cycles were significantly (p<0.01) lower in eluates of 1 day than those of 2 days. The correlation between [MMA]r and cell proliferation values was negative after all elution periods, showing significance (p<0.05) for elution of 1 and 2 days. MMA continued to leach from acrylic resin throughout 7 days and leaching concentrations markedly reduced after elution of 1 and 2 days. CONCLUSION: Due to reduction of leaching residual MMA concentrations, use of terminal boiling in the polymerization process for at least 30 min and water storage of the heat-polymerized denture bases for at least 1 to 2 days before denture delivery is clinically recommended for minimizing the residual MMA and possible cytotoxic effects.

Fracture incidence in mandibular overdentures retained by one or two implants.

STATEMENT OF PROBLEM: While 2 to 4 implants are preferred to retain and stabilize an implant overdenture, some reports suggest a single implant is adequate to retain an overdenture. Denture fracture is one of the common complications with overdentures; however, there is no information on the incidence of fractures when dentures are retained by 1 implant. PURPOSE: The purpose of this study was to compare the fracture incidence of mandibular overdentures retained by 1 and 2 implants. MATERIAL AND METHODS: The records of 85 subjects enrolled in the Vancouver Implant Prosthesis (VIP) clinical trial between 2003 and 2008 and followed up for at least 17 months were reviewed retrospectively. From the clinical records, subjects who had experienced a fractured overdenture were identified. A fracture was considered as either a visible crack in the acrylic resin or complete separation of the denture parts. The same clinical records listed 3 denture fracture sites: over the implant, elsewhere, or unknown. A chi-square test was used to compare the incidence of fracture (alpha=.05). Kaplan-Meier and log rank tests were used to compare the survival rate of overdenture or "time to fracture" (alpha=.05). RESULTS: Forty-two subjects received a single implant, and 43 received 2 implants. In total, there were 17 fractures recorded for 13 subjects. Nine single-implant subjects experienced 11 denture fractures, while 4 double-implant subjects experienced 6 fractures. There was no significant difference in the incidence of denture fractures in prostheses retained by 1 or 2 implants. When denture fractures did occur, they were found most frequently in areas adjacent to the implant(s). CONCLUSIONS: The incidence of denture base fractures was not significantly different between overdentures retained by 1 implant and those retained by 2 implants. When fractures did occur, they tended to be in areas adjacent to implants.

[Burning mouth caused by denture material]. / Behandeling van mondbrandklachten.

A 60-year-old man with an edentulous maxilla was referred by his dentist to an allergy clinic with complaints of burning mouth and bad taste. In the majority of cases, it is hard or impossible to detect the cause of burning mouth. In this case, ultimately the complaint could be solved by eliminating exposure to possible allergenic components of denture base resins.

Diagnosing denture problems using pressure-indicating media.

Pressure-indicating media have more diverse applications than merely the identification of areas on the denture base that cause mucosal pressure and pain. The purpose of this article is to provide guidelines for optimal use of the media and to identify alternative uses that could be considered in daily practice.

The effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced acrylic resin denture base material on oral epithelial cells and fibroblasts.

Acrylic resin dentures may have cytotoxic effects on oral soft tissues. However, there is sparse data about the cytotoxic effect of fibre-reinforced acrylic resin denture base materials. The purpose of this in vitro study was to determine the effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced heat-polymerized acrylic resin denture base material on oral epithelial cells and fibroblasts. One hundred acrylic resin discs were assigned to five experimental groups (n = 20). One of the groups did not include any fibre. Two groups consisted of silane and monomer treated glass fibres (Vetrolex) impregnated into acrylic resin (QC-20) discs. The other two groups consisted of silane and monomer treated carbon fibres (Type Tenox J, HTA). Untreated cell culture was used as positive control. The human oral epithelial cell line and buccal fibroblast cultures were exposed to test specimens. The cytotoxicity of the test materials was determined by succinic dehydrogenase activity (MTT method) after 24 and 72 h exposures. Data were analysed with a statistical software program (SPSSFW, 9.0). A one-way analysis of variance (anova) test and Bonferroni test were used for the comparisons between the groups. All statistical tests were performed at the 0.95 confidence level (P < 0.05). After 24 and 72 h incubation, cell viability percentages of all experimental groups showed significant decrease according to the positive control cell culture. Fibroblastic cell viability percentages of silane and monomer treated fibre-reinforced groups were lower than the unreinforced group. Cell viability of monomer-treated groups displayed the lowest percentages. Elapsed incubation time decreased epithelial cell viability in silane-treated groups. Fibroblastic cell viability was not influenced by elapsed time except the unreinforced group.

Response of Merkel cells in the palatal rugae to the continuous mechanical stimulation by palatal plate.

The aim of the present study was to investigate the responses of Merkel cells that are numerous in the palatine rugae, due to the continuous mechanical stimulation exerted by the palatal plate. Forty golden hamsters were used in this experiment. The palatal plate was made of adhesive resin and it was set on the palate of the animal. To exert a continuous pressure, a 0.8 mm elevation on the internal surface of the palatal plate was created at the middle portion of the fourth palatine ruga. Thereafter, the number of Merkel cells in the mucosa was calculated by immunohistochemical observation. Morphological changes of Merkel cells were examined by electron microscopy. There was significant difference among the control and any of the treated groups on the number of CK20 positive Merkel cells (p < 0.05) and that numbers were decreased at the sites where continuous mechanical stimulation was exerted. Degeneration of the cytoplasm mitochondria and nerve endings, and a decrease in both the number of neurosecretory granules and cytoplasmic processes were observed. Furthermore, the presence of nuclear chromatin aggregation and fragmentation was recognized. The continuous mechanical stimulation by the palatal plate affected the responses of Merkel cells and nerve endings, thus inducing a decrease in the number of Merkel cells. A portion of these changes was also associated with the expression of apoptosis.

Effect of palate covering on bolus-propulsion time and its contributory factors.

The aim of this study was first to investigate whether the covering of the palatal mucosa with a denture base affects or not the bolus-propulsion time, and second if there was such an effect then investigate the possible contributory factors which have influence on the propulsion time. The propulsion time was measured in 21 young normal edentulous subjects under five different conditions: a complete palatal covering, non-covered palate, anterior palatal covering, posterior palatal covering and surface anaesthetized palate. As possible contributory factors palatal morphometric parameters, as well as tongue pressure were also measured. The data were analysed on the following way: changes when the palate was complete covered and non-covered, effects of sensation reduction after topic anaesthesia, effects of differences in the covering site, effects of palatal morphometric parameters and effects of tongue pressure. Ten subjects exhibited significant differences in the propulsion time when comparing the data between the complete palatal covering and the non-covered palate condition (change group). Eleven subjects did not show changes (unchanged group). Effects in the propulsion time were also recognized with posterior palatal covering-palate and superficially anaesthetized palate. With regard to the tongue pressure, significant differences during swallowing were observed. These results indicated that the bolus propulsion time into the oropharynx was affected by the palatal covering in some subjects. Moreover, the sensation in the posterior region of the hard palate, as well as the tongue pressure were also factors which affected the propulsion time during swallowing.

Use of a light-polymerized composite removable partial denture base for a patient hypersensitive to poly(methyl methacrylate), polysulfone, and polycarbonate: a clinical report.

This article describes a light-polymerized composite denture base used for a patient with hypersensitivity to poly(methyl methacrylate) (PMMA), polysulfone (PSF), and polycarbonate (PC). A urethane-dimethacrylate (UDMA) composite was used as an alternative to fabricate both the denture base and the custom artificial teeth. Immediately after placing the new prosthesis, allergic symptoms disappeared from the patient's mucous membrane. The denture has functioned satisfactorily for more than 2.5 years without recurrence of the hypersensitivity.