Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin

doi:10.1111/j.1741‐2358.2009.00333.x
Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth.     

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.     

Influence of connection type on the biomechanical behavior of distal extension mandibular removable partial dentures supported by implants and natural teeth

Few studies are performed to evaluate the influence of connection type on the stress distribution of distal extension mandibular removable partial dentures (RPDs) supported by both implants and natural teeth. In this study, five three-dimensional finite element models were prepared to simulate mandibular bilateral partially edentulous arches. Four were RPDs supported by both implants and natural teeth, and the other one was RPDs supported only by natural teeth. The maximum equivalent (EQV) stress values of bone around implants, the abutments, and the mucosa displacements of the related supporting structures were measured. It was found that a non-rigid telescopic coping was more favorable to protect the implant than a rigid telescopic coping. Compared with other connection types, the easy resilient attachment (ERA) system seemed to be effective to associate implant without complications. However, the results obtained in the present study should be cautiously interpreted in the clinic.     

Efficacy of antifungal agents in tissue conditioners in treating candidiasis

Chronic atrophic candidiasis is prevalent in up to 72% of institutionalized geriatric populations and is causally associated with Candida albicans. Topical antifungal treatments are difficult to implement in some geriatric patients due to cognitive impairment, reduced motor dexterity and memory loss. Objective: This in vitro study incorporated antifungal agents into tissue conditioners to investigate the effectiveness of this method of drug delivery. Design: Combinations of nystatin, fluconazole, itraconazole and Coe Soft, Viscogel, Fitt were tested at 1, 3, 5, 7, 9 and 11wt/wt%, with and without sterilized saliva. 6 mm diameter cores were punched in Sabouraud plates pre-grown with standardized C. albicans. Antifungal agents plus tissue conditioner mixtures were injected into each core. Inhibition diameters were measured for 14 days. Results: Cores with only tissue conditioners acted as negative control and showed no significant inhibition activity (ANOVA, p>0.05). Peak activity was between 65 to 89 hours; followed by a plateau. Itraconazole had greater fungicidal activity than fluconazole; while nystatin was found to have the least fungicidal activity (ANOVA. p<0.05). The most effective concentration for nearly all combinations was 5%wt/wt (ANOVA, p<0.05). Specimens with saliva showed greater antifungal activity than those without (t-test. p<0.001). Itraconazole altered the physical properties of Viscogel hence this combination is not recommended for clinical use. Conclusion: The treatment of chronic atrophic candidiasis by incorporation of antifungal drugs into tissue conditioners is efficacious. 5% wt/wt itraconazole mixed with Coe Soft or Fitt is recommended for clinical study where compliance of patient or care giver cannot be relied upon. Peak antifungal activity at 3 days suggests that mixtures prepared for clinical study may be replaced soon after this time for maximum effectiveness.     

Colonization of denture plaque by respiratory pathogens in dependent elderly

Objectives: Recently, there has been a resurgence of interest in the interactions between oral conditions and a number of prevalent systemic diseases. The morbidity and mortality of the dependent elderly that result from aspiration pneumonia have been recognized as a major geriatric health problem. The purpose of this study was to gain more information on the microflora of plaque on dentures and to assess the existence of oral infectious pathogens potentially causing the respiratory disease in the dependent elderly. Subjects and Methods: The denture bacterial flora of 50 dependent elderly were examined to identify microorganisms by the culture method. Results: 18 species of microorganisms were detected in denture plaque in this study. A variety of pathogens with the potential to cause respiratory infection pathogens colonized on the dentures of dependent elderly. Conclusion: The results of the present study revealed that bacteria that commonly cause respiratory infection colonized on the dentures of dependent elderly, suggesting that denture plaque may function as a reservoir of potential respiratory pathogens to facilitate colonization on the oropharynx.     

The development of a method for functional assessment of dentures

Aims: To design and validate a method of assessing complete dentures from a functional standpoint. Subjects: A random sample of 40 complete denture wearers took part in the study. Setting: A university clinical department of prosthetic dentistry. Intervention: We undertook a pilot study to refine the protocol and criteria. All participants and their dentures were examined by two authors independently, with no prior knowledge of the patients'complaints. Design: We defined nine clinical factors of functional quality and applied criteria with binary scoring. We analysed the scores for these factors for inter‐rater reliability. Results: The method proved simple to apply and took less than 5 minutes to complete. The inter‐examiner agreement for all factors was 86% to 100% giving Kappa scores of 0.64 to 1.00 (all Good or Very Good). Conclusions: This study successfully demonstrates that the technique, which we call the Functional Assessment of Dentures (FAD), can give good inter‐examiner reliability. It can therefore be used separately as a routine diagnostic tool and to investigate the relationship between denture qualities and functional ‘outcome’ such as difficulty eating or dietary selection.     

Oral mucosal lesions in denture wearers

doi:10.1111/j.1741‐2358.2009.00289.x
Oral mucosal lesions in denture wearers Objective: To determine the prevalence of oral mucosal lesions (OMLs) and denture‐related mucosal lesions (DMLs) in denture wearers and to co‐relate the prevalence with age, gender, type of denture and any systemic conditions. Materials and methods: Dental records of 380 denture wearers were retrospectively reviewed for OMLs and DMLs. Results: We found 45% of the denture wearers had DMLs and 60.8% had OMLs not related to denture wearing. Although the prevalence of DMLs was higher in complete denture wearers than in partial denture wearers (49% vs. 42.2%), this difference was not significant. The most common DMLs were traumatic ulcer (19.5%) and denture‐induced stomatitis (18.1%). When analysed by type, traumatic ulcer, denture hyperplasia, frictional keratosis and candidiasis were more common in complete denture wearers, whereas denture‐induced stomatitis was more common in partial denture wearers. Frictional keratosis was more common in men than in women. The prevalence of OMLs not related to denture wearing was higher in complete denture wearers than in partial denture wearers, and the most common OML was fissured tongue (27.6%). No association between DMLs and systemic conditions or xerostomic drugs was noted. Conclusion: No differences in the prevalence of DMLs in association with denture type were found. The prevalence of OMLs not related to denture wearing was higher in complete denture wearers than in partial denture wearers. This difference was affected by age, and the data were similar to the findings observed in the elderly.     

Evaluation of three indices for biofilm accumulation on complete dentures

doi:10.1111/j.1741‐2358.2009.00285.x
Evaluation of three indices for biofilm accumulation on complete dentures Objectives: The objective of this study was to evaluate the accuracy and reproducibility of three complete denture biofilm indices (Prosthesis Hygiene Index; Jeganathan et al. Index; Budtz‐Jørgensen Index) by means of a computerised comparison method. Background: Clinical studies into denture hygiene have employed a large number of biofilm indices among their outcome variables. However, the knowledge about the validity of these indices is still scarce. Materials and methods: Sixty‐two complete denture wearers were selected. The internal surfaces of the upper complete dentures were stained (5% erythrosine) and photographed. The slides were projected on paper, and the biofilm indices were applied over the photos by means of a scoring method. For the computerised method, the areas (total and biofilm‐covered) were measured by dedicated software (Image Tool). In addition, to compare the results of the computerised method and Prosthetic Hygiene Index, a new scoring scale (including four and five graded) was introduced. For the Jeganathan et al. and Budtz‐Jørgensen indices, the original scales were used. Values for each index were compared with the computerised method by the Friedman test. Their reproducibility was measured by means of weighed κ. Significance for both tests was set at 0.05. Results: The indices tested provided similar mean measures but they tended to overestimate biofilm coverage when compared with the computerised method (p < 0.001). Agreement between the Prosthesis Hygiene Index and the computerised method was not significant, regardless of the scale used. Jeghanathan et al. Index showed weak agreement, and consistent results were found for Budtz‐Jorgensen Index (κ = 0.19 and 0.39 respectively). Conclusion: Assessment of accuracy for the biofilm indices showed instrument bias that was similar among the tested methods. Weak inter‐instrument reproducibility was found for the indices, except for the Budtz‐Jørgensen Index. This should be the method of choice for clinical studies when more sophisticated approaches are not possible.     

Patient ratings of chewing ability from a randomised crossover trial: lingualised vs. first premolar/canine-guided occlusion for complete dentures

Background: Complex procedures involving a facebow transfer and the use of lingualised teeth are deemed to have a positive influence on the chewing ability with complete dentures. Objectives: To determine if patients’ ratings of their ability to chew depend on the method of complete denture fabrication. Methods: Edentulous patients (n = 20) participated in a within‐subject crossover trial. Each patient received two sets of new complete dentures. One pair was manufactured based on intraoral tracing of centric relation and facebow transfer; semi‐anatomical teeth with lingualised occlusion denture (LOD) were chosen. The second pair was made using a simplified procedure without facebow transfer; jaw relations were recorded with wax occlusion rims, and anatomical teeth with a first premolar/canine‐guidance (CGD) were selected. The dentures were delivered in randomised order, and each was worn for 3 months. Three months after delivery, patients’ ratings of each new prosthesis were recorded on visual analogue scales for their ability to chew seven index foods. Repeated measurements analysis of variance was performed to investigate possible carry‐over effects accounting for confounding by treatment period. Results: When comparing the two treatments, participants rated their ability to chew in general, to masticate carrots, hard sausage, steak and raw apple in particular, was significantly better with the CGD (anatomical teeth) than with the LOD (p < 0.05). Conclusion: Comprehensive methods for the fabrication of complete dentures including semi‐anatomical lingualised teeth and a full registration do not seem to influence the perceived chewing ability, when compared with more simple procedures. Chewing ability for tough foods appears to benefit from the use of anatomical teeth.