Effect of whitening agents on dentin bonding

Background: Several studies have shown a reduction in enamel bond strengths when the bonding procedure is carried out immediately after vital bleaching with peroxides. This reduction in bond strengths has become a concern in cosmetic dentistry with the introduction of new in-office and waiting-room bleaching techniques. The aim of this in vitro study was to evaluate the effect of three bleaching regimens: 35% hydrogen peroxide (HP), 35% carbamide peroxide (CP), and 10% CP, on dentin bond strengths. Materials and Methods: One hundred and twenty fresh bovine incisors were used in this study. The labial surface of each tooth was ground flat to expose dentin and was subsequently polished with 600-grit wet silicon carbide paper. The remaining dentin thickness was monitored and kept at an average of 2 mm. The teeth were randomly assigned to four bleaching regimens (n = 30): (A) control, no bleaching treatment; (B) 35% HP for 30 minutes; (C) 35% CP for 30 minutes; and (D) 10% CP for 6 hours. For each group, half of the specimens (n = 15) were bonded with Single Bond/Z100 immediately after the bleaching treatment, whereas the other half was bonded after the specimens were stored for 1 week in artificial saliva at 37°C. The specimens were fractured in shear using an Instron machine. Results: For the groups bonded immediately after bleaching, one-way analysis of variance (ANOVA) followed by the Duncan's post hoc test revealed a statistically significant reduction in bond strengths in a range from 71% to 76%. For the groups bonded at 1 week, one-way ANOVA showed that group B (35% HP for 30 min) resulted in the highest bond strengths, whereas 10% CP resulted in the lowest bond strengths. Student's t-test showed that delayed bonding resulted in a significant increase in bond strengths for groups B (35% HP) and C (35% CP); whereas the group bleached with 10% CP (group D) remained in the same range obtained for immediate bonding. Storage in artificial saliva also affected the control group, reducing its bond strengths to 53% of the original. ©2000 BC Decker Inc.

A thirty months clinical evaluation of a posterior composite resin in primary molars

The purpose of this in vivo study was to evaluate the clinical performance of a posterior composite resin TRH (Caulk Dentisply) in class I restorations in primary molars. A total of 30 children aged 5 to 8 years old with 49 class I dental lesions in primary molars participated in the study. The cavity preparations involved removal of carious lesion only and the enamel margins were beveled. The results showed after 30 months that, 82% (32/39) of Alfa ratings and 18% (7/39) of Bravo ratings. We concluded that the composite resin TP-H could be used in conservative restorations in primary molars, particularly in the late mixed dentition.

Efeito dose-resposta de uma formulação de dentifrício com concentração reduzida de fluoreto - estudo in vitro.

The utilization of dentifrices with low fluorine concentration, for children under 6 years of age, has been suggested to reduce the risks of dental fluorosis. However, in order to have anticariogenic potential, the dentifrice should form loosely-bound fluorine (CaF2) on dental enamel. Considering that the formation of CaF2 is a function inversely related to pH, dentifrices with pH 5.5, with 275, 550 and 1,100 ppm F (NaF/silica) were developed in order to assess dose-response effects. A comparison between those dentifrices, a placebo product and the Crest toothpaste (positive control - standard) was carried out. Furthermore, the bioavailability of dentifrices, in terms of formation of total fluorine (TF), CaF2, and fluorapatite (FA) on human dental enamel, was evaluated. An ion-specific electrode was utilized for the determination of the dosage of fluorine. The results revealed that the dentifrice with 550 ppm F was more effective than both the placebo and the dentifrice with 275 ppm, presenting no difference in relation to the positive control (p > 0.05). A dose-effect correlation was observed as to the CaF2 formed. In conclusion, the modified formulation with 550 ppm F can be considered as effective as the standard dentifrice with 1,100 ppm, and its utilization would be safer with regard to dental fluorosis.

Cariostatic effect of fluoride-containing restorative systems associated with dentifrices on root dentin

Objective. The aim of this in vitro study was to evaluate the interaction between two sources of fluoride (restorative systems and dentifrices) in inhibiting artificial root caries development. Methods. One hundred and eighty tooth segments were embedded in polyester resin, and sanded flat. Cylindrical cavities 1.0 mm-deep and 1.5 mm-diameter were prepared in root dentin and randomly restored by fluoride-containing restorative systems: Ketac-fil/Espe (Ke), Fuji II LC/GC Corp (Fj), F2000/3M (F2), Surefil/Dentsply (Su) or a control: Filtek Z250/3M (Z2). Ten experimental groups were made to test the association among the five restorative systems and two dentifrices: with F - (Sensodyne Baking Soda) or without F- (Sensodyne Original) (n = 18). After surface polishing, a 1 mm-wide margin around the restorations was demarcated and initial dentin surface Knoop microhardness values (KHNi) were obtained. The specimens were submitted to a pH-cycling model, and to applications of slurries of dentifrice. Afterwards the final dentin surface Knoop microhardness values (KHNf) were measured. Results. The differences between KHNi and KHNf, and the covariate KHNi were considered by the ANCOVA and Tukey's test (α = 0.05). The interaction between restorative system and dentifrice was statistically significant (p = 0.0026). All restorative systems provided some protection against artificial caries challenge when associated with the fluoride-containing dentifrice treatment. The means (standard deviation) of reductions in Knoop hardness values for systems associated with the fluoride-containing dentifrice were: Ke: 40.0(1.02)a, Fj: 41.9(1.02)b, F2: 43.3(1.04)c, Su: 43.5(1.00)c, Z2: 44.0(1.02)c; and with the non-fluoride-containing dentifrice were: Ke: 42.9(1.02)a, Fj: 44.7(1.01)b, F2: 45.2(1.09)bc, Su: 46.0(0.99)c, Z2: 46.6(0.99)c (statistical differences were expressed by different letters). Conclusion. The cariostatic effect shown by the fluoride-containing dentifrice could enhance that shown by Ketac-fil and Fuji II LC, and could mask that shown by F2000. © 2002 Elsevier Science Ltd. All rights reserved.

Cytokeratins in epithelia of odontogenic neoplasms

Neoplasms and tumours related to the odontogenic apparatus may be composed only of epithelial tissue or epithelial tissue associated with odontogenic ectomesenchyme. The immunohistochemical detection of different cytokeratins (CKs) polypeptides and vimentin has made it easier to explain the histogenesis of many epithelial diseases. The present study aimed to describe the immunohistochemical expression of cytokeratins 7, 8, 10, 13, 14, 18, 19 and vimentin in the epithelial components of the dental germ and of five types of odontogenic tumours. The results were compared and histogenesis discussed. All cells of the dental germ were positive for CK14, except for the preameloblasts and secreting ameloblasts, in which CK14 was gradually replaced by CK19. CK7 was especially expressed in the cells of the Hertwig root sheath and the stellate reticulum. The dental lamina was the only structure to express CK13. The reduced epithelium of the enamel organ contained CK14 and occasionally CK13. Cells similar to the stellate reticulum, present in the ameloblastoma and in the ameloblastic fibroma, were positive for CK13, which indicates a nature other than that of the stellate reticulum of the normal dental germ. The expression of CK14 and the ultrastructural aspects of the adenomatoid odontogenic tumour probably indicated its origin in the reduced dental epithelium. Calcifying odontogenic epithelial tumour is thought to be composed of primordial cells due to the expression of vimentin. Odontomas exhibited an immunohistochemical profile similar to that of the dental germ. In conclusion, the typical IF of odontogenic epithelium was CK14, while CK8, 10 and 18 were absent. Cytokeratins 13 and 19 labelled squamous differentiation or epithelial cells near the surface epithelium, and CK7 had variable expression.

Evaluation of marginal microleakage in Class II cavities: Effect of microhybrid, flowable, and compactable resins

Objective: The goal of the present study was to evaluate the microleakage on the cementum/dentin and enamel surfaces in Class II restorations, using different kinds of resin composite (microhybrid, flowable, and compactable). Method and materials: Forty human caries-free molars were extracted and selected. Eighty Class II standardized cavities were made in the cervical wall at the cementoenamel junction (CEJ) and at the mesial and distal surfaces. The teeth were divided into four groups: G1 - adhesive system + microhybrid resin composite Z100; G2 - adhesive system + compactable resin composite Prodigy Condensable; G3 - adhesive system + flowable resin composite Revolution + Z100 resin composite; G4 - adhesive system + Revolution fluid resin + compactable resin composite Prodigy Condensable. The adhesive system used in this study was Scotchbond Multi-Purpose Plus. The specimens were thermocycled in baths of 5°C and 55°C for 1,000 cycles and immersed in 50% silver nitrate solution. The specimens then were sectioned and evaluated on degree of dye penetration. Results: The results were evaluated using the nonparametric Kruskall-Wallis test, which showed a statistically significant difference between groups G1 and G4, G2 and G4, and G3 and G4. Conclusions: None of the materials was able to eliminate the marginal microleakage at the cervical wall; the application of a low-viscosity resin composite combined with a compactable resin composite significantly decreased the microleakage.

Influence of dental care for infants on caries prevalence: A comparative study

Purpose: The influence of early dental care on the prevalence of dental caries was determined in children ages 35 to 40 months divided into 2 groups of 160 children each, with 1 group participating in a dental care program from the first year of life to the time of the study, while the other group did not receive any dental care. Methods: The clinical conditions considered for the evaluation were: sound teeth, enamel caries without cavitation, enamel caries with cavitation, and dentinal caries. The proportion and chi-square tests were used for statistical analysis with the level of significance set at 5%. Results: A significant difference regarding the presence of dental caries, especially in the number of children presenting enamel caries with cavitation (P<.0001), was observed between the 2 groups. The number of children with enamel caries without cavitation and dentinal caries was similar for the 2 groups. Conclusions: Considering the aspect of dental caries prevention, the authors concluded that children in the age range of 3 to 4 years who received early dental care showed better oral conditions.

Effect of the Clinical Application of the GaA1As Laser in the Treatment of Dentine Hypersensitivity

Objective: The aim of this study was to evaluate the effectiveness of the clinical use of the gallium-aluminum-arsenium (GaAlAs) laser at the maximum and minimum energies recommended by the manufacturer for the treatment of dentine hypersensitivity. Background Data: Dentine hypersensitivity (DH) is a response to a stimulus that would not usually cause pain in a healthy tooth. It is characterized by sharp pain of short duration from the denuded dentin. Its etiology is unknown. The dentin only begins to show sensitivity when exposed to the buccal environment. This exposure can result after removal of the enamel and/or dental cement, or after root denudation. Different treatments are proposed for this disorder. Materials and Methods: In this study, 25 patients, with a total number of 106 cases of DH, were treated with GaAlAs low-level laser therapy (LLLT). 65% of the teeth were premolars; 14% were incisors and molars; 6.6% were canines. The teeth were irradiated with 3 and 5 J/cm 2 for up to six sessions, with an interval of 72 h between each application, and they were evaluated initially, after each application, and at 15 and 60 days follow-up post-treatment. Results: The treatment was effective in 86.53% and 88.88% of the irradiated teeth, respectively, with the minimum and maximum energy recommended by the manufacturer. There was a statistically significant difference between DH and after a follow-up of 60 days for both groups. The difference among the energy maximum and minimum was not significant. Conclusion: The GaAlAs low-level laser was effective in reducing initial DH. A significant difference was found between initial values of hypersensitivity and after 60 days follow-up post-treatment. No significant difference was found between minimum (3 J/cm 2) and maximum (5 J/cm 2) applied energy.

In vitro penetration of bleaching agents into the pulp chamber

Aim: To investigate pulp chamber penetration of bleaching agents in teeth following restorative procedures. Methodology: Bovine lateral incisors were sectioned 3 mm apical to the cemento-enamel junction and the coronal pulpal tissue was removed. Teeth were divided into six groups (n = 10): G1, G2 and G3 were not submitted to any restorative procedure, while G4, G5 and G6 were submitted to Class V preparations and restored with composite resin. Acetate buffer was placed in the pulp chamber and treatment agents were applied for 60 min at 37°C as follows: G1 and G4, immersion into distilled water; G2 and G5, 10% carbamide peroxide (CP) exposure; G3 and G6, 35% CP bleaching. The buffer solution was removed and transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined spectrophotometrically at 596 nm. A standard curve made with known amounts of hydrogen peroxide was used to convert the optical density values of the coloured samples into microgram equivalents of hydrogen peroxide. Data were submitted to ANOVA and Tukey's test (5%). Results: Amounts of hydrogen peroxide found in the pulp chamber of G2 and G5 specimens (0.1833 ± 0.2003 μg) were significantly lower (P = 0.001) when compared to G3 and G6 specimens (0.4604 ± 0.3981 μg). Restored teeth held significantly higher (P = 0.001) hydrogen peroxide concentrations in the pulp chamber than intact teeth. Conclusion: Higher concentrations of the bleaching agent produced higher levels of hydrogen peroxide in the pulp chamber, especially in restored teeth.

Treatment options for the occlusal surface of first permanent molars

Restorative dentistry has been increasingly concerned with preservation of the dental structure. For that reason, ultraconservative cavity preparations have been performed with air abrasion systems. The aim of this study was to present treatment options for the occlusal surface of first permanent molars with employment of the conventional method and the air abrasion system for accomplishment of the cavity preparation and a composite occlusal matrix for an accurate reproduction of the tooth surface.

The effect of adhesive and flowable composite on postoperative sensitivity: 2-Week results

Objective: To measure 2-week postoperative sensitivity in Class II composite restorations placed with a self-etching adhesive (Clearfil SE Bond) or a total-etch adhesive (Prime&Bond NT) with or without a flowable composite as cervical increment. Method and materials: Upon approval by the University of Guarulhos Committee on Human Subjects, 100 restorations were inserted in 46 patients who required Class II restorations in their molars and premolars. Enamel and dentin walls were conditioned with a self-etching primer (for Clearfil SE Bond) or etched with 34% phosphoric acid (for Prime&Bond NT). A 1- to 2-mm-thick increment of a flowable composite (Filtek Flow) was used in the proximal box in 50% of the restorations of each adhesive. Preparations were restored with a packable composite (Surefil). The restorations were evaluated preoperatively and 2 weeks postoperatively for sensitivity to cold, air, and masticatory forces using a visual analog scale. Marginal integrity of the accessible margins was also evaluated. Statistical analysis used a mixed linear model with subject as a random effect. Results: Ninety-eight teeth from 44 subjects were observed at 2 weeks. The type of adhesive and use of flowable composite had no significant effects or interaction for any of the four outcomes of interest, ie, change from baseline to 2 weeks in sensitivity and response time for the cold or air stimulus. For the air stimulus, the overall average change from baseline was not significant for either sensitivity or response time. For the cold stimulus, the overall average change from baseline was significant for both sensitivity and response time. No case of sensitivity to masticatory forces was observed. Conclusion: No differences in postoperative sensitivity were observed between a self-etch adhesive and a total-etch adhesive at 2 weeks. The use of flowable composite did not decrease postoperative sensitivity.

Production of Ti-35Nb alloy by powder metallurgy for aerospace application

Titanium and its alloys provide high strength-to-weight ratios, good fatigue strength and increased corrosion resistance compared with others materials. Its acceptance in aerospace has been limited by costs considerations such as high cost of raw material, high buy-to-fly ratios and expensive machining operations. Significant cost reductions can be obtained by vacuum sintering and powder metallurgy (P/M) techniques by producing near net shapes and consequently minimizing material waste and machining time. The Ti 35Nb alloy exhibit a low modulus of elasticity. Stemming from the unique combination of high strength, low modulus of elasticity and low density, this alloy is intrinsically more resistant to shock and explosion damages than most other engineering materials. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900 and 1600 °C, in vacuum. Sintering behavior was studied by means of dilatometry. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. Density was measured by Archimedes method. Copyright © 2004 Society of Automotive Engineers, Inc.

Temperature analysis during bonding of brackets using LED or halogen light base units

The purpose of our investigation is to compare the intrapulpal temperature changes following blue LED system and halogen lamp irradiation at the enamel surface of permanent teeth. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Several light sources can be used: halogens, arc plasma, lasers, and recently blue LED systems. An important aspect to be observed during such a procedures is the temperature change. In this study, we have used nine human extracted permanent teeth: three central incisors, three lateral incisors, and three canines. Teeth were exposed to two light sources: blue LED system (preliminary commercial model LEC 470-II) and halogen lamp (conventional photo-cure equipment). The surface of teeth was exposed for 20, 40, and 60 sec at the buccal and lingual enamel surface with an angle of 45 degrees. Temperature values measured by a thermistor placed at pulpar chamber were read in time intervals of 1 sec. We obtained plots showing the temperature evolution as a function of time for each experiment. There is a correlation between heating quantity and exposition time of light source: with increasing exposition time, heating increases into the pulpal chamber. The halogen lamp showed higher heating than the LED system, which showed a shorter time of cooling than halogen lamp. The blue LED system seems like the indicated light source for photo-cure of composite resin during the bonding of brackets. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Blue LED equipment did not heat during its use. This could permit a shorter clinical time of operation and better performance. © Mary Ann Liebert, Inc.

Oral manifestations during chemotherapy for acute lymphoblastic leukemia: A case report

A 14-year-old, male patient was referred for the treatment of mucositis, idiopathic facial asymmetry, and candidiasis. The patient had been undergoing chemotherapy for 5 years for acute lymphoblastic leukemia. He presented with a swollen face, fever, and generalized symptomatology in the mouth with burning. On physical examination, general signs of poor health, paleness, malnutrition, and jaundice were observed. The extraoral clinical examination showed edema on the right side of the face and cutaneous erythema. On intraoral clinical examination, generalized ulcers with extensive necrosis on the hard palate mucosa were observed, extending to the posterior region. Both free and attached gingivae were ulcerated and edematous with exudation and spontaneous bleeding, mainly in the superior and inferior anterior teeth region. The tongue had no papillae and was coated, due to poor oral hygiene. The patient also presented with carious white lesions and enamel hypoplasia, mouth opening limitation, and foul odor. After exfoliative cytology of the affected areas, the diagnosis was mixed infection by Candida albicans and bacteria. Recommended treatment was antibiotics and antifungal administration, periodontal prophylaxis, topical application of fluor 1.23%, and orientation on and control of proper oral hygiene and diet during the remission phase of the disease.

Effects of copper vapor laser radiation on the root canal wall of human teeth: A scanning electron microscope study

Objective: The aim of this study is to analyze the effects of copper vapor laser radiation on the radicular wall of human teeth. Materials and Methods: Immediately after the crowns of 10 human uniradicular teeth were cut along the cement-enamel junction, a chemical-surgical preparation of the radicular canals was completed. Then the roots were longitudinally sectioned to allow for irradiation of the surfaces of the dentin walls of the root canals. The hemi-roots were separated into two groups: one (control) with five hemi-roots that were not irradiated, and another (experimental) with 15 hemi-roots divided into three subgroups that were submitted to the following exposure times: 0.02,0.05, and 0.1 s. A copper vapor laser (510.6 nm) with a total average power of 6.5 W in green emission, frequency of 16.000 Hz, and pulse duration of 30 ns was used. Results: The results obtained by scanning electron microscope analysis showed the appearance of a cavity in the region of laser beam impact, with melting, recrystallization, and cracking on the edges of the dentin of the cavity due to heat diffusion. Conclusions: We determined that the copper vapor laser produces significant morphologic changes in the radicular wall of human teeth when using the parameters in this study. However, further research should be done to establish parameters that are compatible with dental structure in order to eliminate thermal damages. © Mary Ann Liebert, Inc.