The effect of carbamide peroxide bleaching agents on the microhardness of dental ceramics

This study examined the effect of 10% and 16% carbamide peroxide bleaching agents on the surface microhardness of micro-particulate feldspathic ceramics (VM7 and VM13, Vita Zahnfabrik). Forty specimens (8-mm diameter, 2-mm thickness) were divided into four groups (n=10): GI-VM7 + 10% Whiteness, G2-VM7 + 16% Whiteness, G3-VM13 + 10% and G4-VM13 + 16% Whiteness. The home-use bleaching agents were applied for 8 hours on 15 days, and the specimens were stored in distilled water at 37 degrees C. The Vickers hardness number (HV) was determined for each specimen. Data were analyzed by the Wilcoxon and Mann-Whitney tests (p < 0.05). The microhardness values before exposure were: g1-433 (57); g2-486 (22); g3-509 (28); g4-518 (24), and after exposure: G1-349 (32); G2-496 (95); G3-519 (38); G4-502 (81). G2 exhibited a higher and significant difference than GI in VM7 groups, and the effect of bleaching concentration was shown to be significant by the Mann-Whitney test. And for VM13, both the Wilcoxon and Mann-Whitney tests showed no significant differences. When using 10% carbamide peroxide, the microhardness of VM7 ceramic was affected, and there were no effect on the microhardness between VM7 and VM13 ceramics when 16% carbamide peroxide was used.     

Dental treatment improves self-rated oral health in homeless veterans--a brief communication

OBJECTIVE: The aim of this study was to assess homeless veterans' perception of their oral health and the impact that oral disease and treatment have on self-assessed quality of life. METHODS: Outcomes included measures of general and oral-specific quality of life and functional status. Single-item self-report of oral health and the General Oral Health Assessment Index were assessed at baseline and after treatment. RESULTS: One hundred and twelve veterans completed the baseline questionnaire, and 48 completed the follow-up. Veterans who were eligible for ongoing dental care had improved General Oral Health Assessment scores, while patients who received only emergency dental care saw a decreased score (2.46 versus -2.12). General Oral Health Assessment improvement was significantly related to fewer teeth at baseline (18 versus 23), a lower baseline General Oral Health Assessment (23.6 versus 28.1), having a denture visit (22 versus 35 percent), and improvement in self-reported oral health (25 versus 42 percent). CONCLUSION: There was significant improvement in homeless veterans'perceived oral health after receiving dental care.     

Saliva promotes Candida albicans adherence to human epithelial cells

Adhesion of Candida cells to oral surfaces is an initial event in pathogenesis. Since specific immobilized salivary components mediate the binding of Candida albicans to hydroxyapatite, we hypothesized that saliva may also promote adherence to oral epithelia via a similar mechanism. In an in vitro model, C. albicans ATCC 10261 yeast cells adhered in a saturable manner to monolayers of three cultured human epithelial cell lines (A549, HEp-2, and HET-1A). The addition of whole saliva to the assay promoted the binding of C. albicans to all cell lines in a dose-dependent manner, but pre-incubation of the epithelial cells with pooled whole saliva had no effect on subsequent adherence. Pre-incubation of the yeast cells with pooled whole saliva, however, significantly enhanced (by up to 120%, P < 0.05) binding to epithelial cell monolayers, and pooled saliva that had been pre-incubated with C. albicans yeast cells was defective in promoting yeast adherence. There was a negative correlation (r = 0.68, P < 0.005) between specific IgA titers against whole cells of C. albicans and adherence-promoting activities for individual saliva samples. The adhesion-inhibitory effect of specific anti-C. albicans IgA was reversed by depletion of IgA from saliva by affinity chromatography. Factors in whole saliva, therefore, bound to the yeast cells, counter the C. albicans-specific salivary IgA inhibitory effect on adhesion and promote the adherence of C. albicans yeast cells to cultured epithelial cells.     

Platelets stimulate proliferation of bone cells: involvement of platelet-derived growth factor,microparticles and membranes

Platelets have been implicated in accelerated bone regeneration in grafting applications. The beneficial effects of platelets may involve their ability to stimulate the proliferation of osteoblasts. We therefore determined the mitogenic response of human trabecular bone-derived cells to human platelets and supernatants of thrombin-activated platelets. We can show a approximately 50-fold increase in DNA-synthesis of bone cells (BC) cultured in the presence of platelets as determined by [3H]-thymidine incorporation. Preventing cell-to-cell contact by a membrane filter did not abrogate the stimulatory effect, indicating the release of soluble factor(s) that are mitogenic for BC. The lipid fraction of the platelets had no effect on [3H]-thymidine uptake into the DNA of BC. Platelet-released supernatant (PRS) increased the rate of [3H]-thymidine incorporation to approximately 20-fold and retained 56% of their activity after incubation at 56 degrees C, and 27% at 100 degrees C, respectively. Neutralizing antibodies raised against platelet-derived growth factor (PDGF) partially suppressed the mitogenic potential of PRS. Gel exclusion chromatography analysis showed that molecules ranging from 25 kDa to more than 70 kDa within the PRS can stimulate BC proliferation. The highest amount of PDGF was detected in fractions corresponding to a molecular weight of 28-37 kDa as determined by immunoassay. The mitogenic activity was not restricted to soluble growth factors because microparticles in the PRS and platelet membranes also increased BC proliferation. Our data indicate that native platelets, the respective PRS, microparticles, and platelet membranes can stimulate the mitogenic activity of BC, thereby contributing to the regeneration of mineralized tissue.     

On-line computerized diagnosis of pain-related disability and psychological status of TMD patients: a pilot study

Temporomandibular disorders (TMD) is a collective term embracing a number of clinical problems, which involve the masticatory musculature, the temporomandibular joint or both. Virtually all theories dealing with the aetiology and treatment of TMD have recognized the importance of psychological factors. This paper reports the development of a computerized on-line program (NUS TMD v1.1) for the diagnosis of pain-related disability and psychological status of TMD patients based on Axis II of the research diagnostic criteria (RDC)/TMD (Dworkin, S.F. & LeResche, L. 1992. Journal of Craniomandibular Disorders: Facial Oral Pain, 6, 301), which was developed to redress the lack of diagnostic criteria in TMD research. Methods adopted by RDC/TMD for use in assessing Axis II status include a seven-item questionnaire for grading chronic pain severity, the Symptom Checklist 90 Revised (SCL-90-R) and a jaw disability checklist. A pilot study, based on 37 new TMD patient records, was conducted to study the pain-related disability and psychological status of TMD patients using this newly developed program. The mean age of the predominantly Chinese population (86.5%) was 32.19 years (range 20-72 years) with a sex distribution of 24 females and 13 males. Most patients (78%) had low disability, with 12 patients having low intensity and 17 patients having high intensity pain. Approximately 73% of the sample population were moderately or severely depressed. Patients that were moderately and severely depressed had significantly higher scores for limitation related to mandibular functioning than normal patients. The three most frequent jaw disabilities were: eating hard foods (84%), yawning (78%) and chewing (65%).     

Recombinant human bone morphogenetic protein-7 in maxillary sinus floor elevation surgery in 3 patients compared to autogenous bone grafts. A clinical pilot study

BACKGROUND/AIMS: This pilot study was designed to determine the clinical bone formation ability of a human recombinant DNA bone morphogenetic protein-7, also referred to as Osteogenic Protein-1 [OP-1] combined with a collagen carrier, implanted in the maxillary sinus of 3 patients. The results were compared with a group of 3 patients treated with sinus floor elevation and autogenous bone grafts. METHODS: 6 consecutive patients, 4 female and 2 male, between 48 and 57 years of age were treated by means of sinus floor elevation for insufficient bone height in the posterior maxilla for implant surgery. 3 patients, 2 female and 1 male, were treated with OP-1 attached to a collagen device. In these patients, 4 maxillary sinus grafting procedures according to Tatum's method were carried out. 1 g of collagen carrier containing 2.5 mg rhOP-1 mixed with 3 ml of saline was placed between the bony floor and the elevated mucosal lining of the most caudal part of the maxillary sinus, in order to increase the vertical bone dimension to place dental implants of a sufficient length. The 3 other patients, also 2 female and 1 male, with a total of 5 sinus sites, were treated with sinus floor elevation and autogenous iliac crest bone grafts. After 6 months, during dental implant preparation, bone cores were taken for histology. Thus, clinical, radiological and histological results of the 2 groups of 3 patients were compared. RESULTS: 6 months after sinus grafting with OP-1, in 1 male, well-vascularized bone-like tissue of good quality was observed clinically. This could be confirmed by histology. In the second, female, patient no bone formation was observed at all. A cyst-like granular tissue mass, without purulent content, was removed. In the 3rd, female, patient, who received bilateral sinus grafts, some bone-like formation was seen, however it showed flexible tissue which led to the decision that at 6 months after the sinus grafting, the implant placement had to be postponed. In all 5 autogenous grafted sinuses a bone appearance similar to normal maxillary bone was observed clinically as well as histologically and dental implants could be placed six months after sinus floor elevation surgery. CONCLUSIONS: These findings indicate that the OP-1 device has the potential for initiating bone formation in the human maxillary sinus within 6 months after a sinus floor elevation operation. However, the various findings in these 3 patients indicate that the behaviour of the material is at this moment insufficiently predictable, in this indication area. Further investigation is indicated before OP-1 can be successfully used instead of the "gold standard" autogenous bone graft.     

A randomised controlled trial of the caries-preventive efficacy of a chlorhexidine-containing varnish in high-caries-risk adolescents

A professionally applied two-stage chlorhexidine varnish, Chlorzoin((R)), was developed to achieve sustained release and minimise the problems of staining and bad taste associated with chlorhexidine mouthrinses. The primary aim of this randomised controlled clinical trial was to assess the efficacy of Chlorzoin in reducing the caries increment in high-caries-risk adolescents. Secondary aims included investigating the effect of compliance upon caries increment, the effect of Chlorzoin upon salivary mutans streptococci levels and assessing the benefit of individual dental health advice by dental auxiliaries in a community setting. 1,240 children, initially aged 11-13 years, assessed to be at high caries risk were recruited into the trial. The trial design involved four arms: an observational group, a control group, an active (Chlorzoin) varnish group and a placebo varnish group. All subjects were examined annually by a calibrated examiner who was blind to the group allocation. Three-year caries increments were calculated using clinical, clinical and fibre-optic transillumination, and clinical and bitewing data sets. The results indicated that the use of Chlorzoin had an initial effect on mutans streptococci levels but that no long-term reduction in caries increment or mutans streptococci infection could be detected. One reason for this lack of efficacy may have been the regimen of reduced frequency of varnish applications after the initial period. Children who followed the protocol and, therefore, were seen regularly by dental auxiliaries had a lower caries increment than those who did not. This finding was independent of varnish allocation. In summary, under this regimen, Chlorzoin has been found to be effective in decreasing salivary mutans streptococci but ineffective as a caries-preventive agent in high-risk Scottish children when applied pragmatically in a community setting.     

Microleakage study of various soft denture liners by autoradiography: effect of accelerated aging

STATEMENT OF PROBLEM: The longevity of soft denture liners is a major clinical problem. Debonding of the soft liner from the denture base material is one of the factors that influence their longevity. Debonding of the soft liner can be attributed to microleakage at the interface. PURPOSE: This study investigated microleakage at the interface of various soft liners and base materials. MATERIALS AND METHOD: Six soft liners were investigated. Forty specimens of each material in disk form (10 mm in diameter, thickness of approximately 4 mm) were prepared. Twenty specimens of each material were stored in an accelerated weathering tester for 900 hours. For 2 days, all disks were immersed in (45)Ca radioisotope solution, then they were embedded in acrylic resin blocks and sectioned longitudinally. Autoradiographic imaging was used to determine microleakage at the interface of the soft liners and their bases. RESULTS: Significant differences between nonaged materials were found (P<.05).The difference between Molloplast B and Mucopren (silanized) was not significant (P<.05). Differences among aged materials were significant (P>.05). Differences between Mucopren (nonsilanized), Mucopren (silanized), and Ufigel P-Tokuyama were not significant (P<.05). Significantly decreased microleakage characteristics were determined for Molloplast B, Mucopren (nonsilanized) and Ufigel P liners after aging. CONCLUSION: Microleakage of Mucopren and Molloplast B lining materials was the lowest. However, the microleakage of Flexor and Simpa was the highest. The aging process did not significantly affect the microleakage characteristics of the Simpa, Flexor, Mucopren (silanized), or Tokuyama materials. Molloplast B, Mucopren (nonsilanized), and Ufigel P materials should significantly decrease microleakage properties after aging.     

An in vitro study of microleakage of occlusal composite restorations polymerized by a conventional curing light and a PAC curing light

With the increase in usage of bonded dentistry procedures, so comes the development of advanced technology to polymerize it. The purpose of this in vitro study was to evaluate the microleakage of sealants and resin restorations utilizing two different curing lights. The conventional Ortholux curing light (OCL) and the Plasma Arc Curing (PAC) light attached to the KCP air abrasion unit of American Dental Technologies were utilized to polymerize sealants and resin restorations on extracted third molars and premolars. Forty-eight caries-free teeth were divided into 4 groups of 12 specimens. Occlusal sealants were polymerized on groups 1 and 3. Class I composite resin restorations were polymerized on groups 2 and 4. The PAC light polymerized group 2 and the OCL was used for groups 3 and 4. Therefore a comparison between the two light sources' polymerization could be measured by evaluating the microleakage of the two sets of specimens. The PAC light polymerized the Z100 adhesive for 5 seconds and the OCL polymerized it for 10 seconds. The Z100 A-1 composite placed in two 1 mm increments was polymerized with the PAC light for 10 seconds and the OCL for 40 seconds. The teeth were thermocycled 200 times between 5 degrees C and 55 degrees C. The teeth, coated with fingernail polish excluding the occlusal surface, were soaked in 5% methylene blue for 4 hours, removed, and rinsed with water. The teeth were invested in clear resin (Castin Craft) and sectioned longitudinally using an Isomet diamond saw. Microleakage was scored "0" if no leakage was present. Scored "1" if the leakage was present to 1/2 the preparation depth. Scored "2" if the leakage was present past the 1/2 way point but not to the pulpal floor of the preparation. A score of "3" was used if the leakage reached the pulpal floor. Unpaired t-Tests were used to statistically analyze the data. A significant difference (p < 0.05) was found between groups 1 and 3. The PAC light used to polymerize the sealants in group 1 produced no microleakage. A significant difference (p < .005) was found between groups 2 and 4. The OCL produced less microleakage (16 and 20 out of 24 sections) than the resin restorations polymerized with the PAC (only 8 of 24 sections with no microleakage. The 10-second cure by the PAC light appears to be insufficient in polymerizing a class I composite resin restoration. Possibly longer exposures with the PAC would produce less microleakage. Further research needs to be performed to evaluate if the PAC light, with an intensity of 1196 mW/cm2, may be producing high levels of strain within the setting composite. This strain may be responsible for the statistically significant increase in microleakage of the restorations polymerized with the PAC light.). It appears the PAC light would be best utilized to cure sealants and/or possibly polymerize orthodontic brackets. The conventional curing light appears to remain the best choice for polymerizing class I composite restorations.