Adhesives with different pHs: Effect on the MTBS of chemically activated and light-activated composites to human dentin

Purpose: To evaluate the bond strength between human dentin and composites, using two light-activated single-bottle total-etch adhesive systems with different pHs combined with chemically activated and light-activated-composites. The tested hypothesis was that the dentin bond strength is not influenced by an adhesive system of low pH, combined with chemically activated or light-activated composites. Material and Method: Flat dentin surfaces of twenty-eight human third molars were allocated in 4 groups (n=7), depending on the adhesive system: (One Step Plus-OS and Prime & Bond NT-PB) and composite (light-activated Filtek Z-100 [Z100] and chemically activated Bisfil 2B [B2B]). Each adhesive system was applied on acid-etched dentin and then one of the composites was added to form a 5 mm-high resin block. The specimens were stored in tap water (37 degrees C/24 h) and sectioned into two axes, x and y. This was done with a diamond disk under coolant irrigation to obtain beams with a cross-section area of approximately 0.8 mm(2). Each specimen was then attached to a custom-made device and submitted to the microtensile test (1 mm.min(-1)). Data were analyzed using two-way ANOVA and Tukey's tests (p<0.05). Results: the anticipated hypothesis was not confirmed (p<0.0001). The bond strengths (MPa) were not statistically different between the two adhesive systems when light-activated composite was used (OS+Z100 = 24.7 +/- 7.1(a); PB+Z100 = 23.8 +/- 5.7(a)). However, with use of the chemically activated composite (B2B), PB (7.8 +/- 3.6(b) MPa) showed significantly lower dentin bond strengths than OS (32.2 +/- 7.6(a)). Conclusion: the low pH of the adhesive system can affect the bond of chemically activated composite to dentin. on the other hand, under the present conditions, the low pH did not seem to affect the bond of light-activated composites to dentin significantly.

Bond strength of resin modified glass ionomer cement to primary dentin after cutting with different bur types and dentin conditioning

The aim of this in vitro study was to evaluate the effect of different bur types and acid etching protocols on the shear bond strength (SBS) of a resin modified glass ionomer cement (RM-GIC) to primary dentin. Forty-eight clinically sound human primary molars were selected and randomly assigned to four groups (n=12). In G1, the lingual surface of the teeth was cut with a carbide bur until a 2.0-mm-diameter dentin area was exposed, followed by the application of RM-GIC (Vitremer - 3M/ESPE) prepared according to the manufacturer's instructions. The specimens of G2, received the same treatment of G1, however the dentin was conditioned with phosphoric acid. In groups G3 and G4 the same procedures of G1 and G2 were conducted respectively, nevertheless dentin cutting was made with a diamond bur. The specimens were stored in distilled water at 37 degrees C for 24h, and then tested in a universal testing machine. SBS. data were submitted to 2-way ANOVA (= 5%) and indicated that SBS values of RM-GIC bonded to primary dentin cut with different burs were not statistically different, but the specimens that were conditioned with phosphoric acid presented SBS values significantly higher that those without conditioning. To observe micromorphologic characteristics of the effects of dentin surface cut by diamond or carbide rotary instruments and conditioners treatment, some specimens were examined by scanning electron microscopy. Smear layer was present in all specimens regardless of the type of rotary instrument used for dentin cutting, and specimens etched with phosphoric acid presented more effective removal of smear layer. It was concluded that SBS of a RM-GIC to primary dentin was affected by the acid conditioning but the bur type had no influence.

The influence of chlorhexidine on the severity of cyclosporin A-induced gingival overgrowth

THE INFLUENCE OF CHEMICAL PLAQUE CONTROL, using topically applied 0.12% chlorhexidine, on the severity of cyclosporin A (CsA)-induced gingival overgrowth (GO) was evaluated. Forty Holtzman rats were divided into four groups: 1) control; 2) cyclosporin A: a 10mg/kg/day subcutaneous dose of CsA; 3) chlorhexidine: 0.12% chlorhexidine (CHX) was applied to the buccal surface of the right mandibular molars; and 4) cyclosporin A/chlorhexidine: a combination of the treatment described for cyclosporin A and chlorhexidine groups. The animals were fed a high sucrose diet during the experiment and were sacrificed after 14 and 21 days. The histometric analysis revealed a significant increase in buccal gingival area in the cyclosporin A group compared to other groups (P < 0.01) after 21 days. The epithelium thickness of the buccal gingiva was significantly increased in the cyclosporin A group, compared to the control group (P < 0.05). The cyclosporin A/chlorhexidine group exhibited statistically significantly lower gingival overgrowth than the cyclosporin A group. These findings, if replicated in human studies, suggest that topically applied 0.12% chlorhexidine may be a valuable measure in the management of cyclosporin-induced gingival overgrowth.

Influence of different dentin etching times and concentrations and air-abrasion technique on dentin microtensile bond strength

Purpose: To determine the influence of different dentin treatments on the microtensile bond strengths of adhesive resins to dentin. Methods: Fifteen human molars were ground to 600-grit to obtain flat root-dentin surfaces. Five different dentin treatments were evaluated: Group 1 - 10% phosphoric acid for 30 seconds; Group 2 - 37% phosphoric acid for 15 seconds; Group 3 - air-abrasion for 10 seconds followed by 10% phosphoric acid for 30 seconds; Group 4 - air-abasion for 10 seconds followed by 37% phosphoric acid for 15 seconds. The dental adhesive (OptiBond Solo Plus) was applied according to manufacturer's instructions and followed by composite (Z100) application to provide sufficient bulk for microtensile bond testing. All samples were placed in distilled water for 24 hours at 37degreesC, thermocycled for 500 cycles in distilled water at 10degreesC and 50degreesC, and serially sliced perpendicular to the adhesive surface and subjected to tensile forces (0.5 mm/minute). Additional samples were prepared for SEM to observe the adhesive interface. Results: Group 2 exhibited significantly (P< 0.05) lower bond strength values than all other treatments. The bond strengths of the different conditions were (in MPa): Group 1: 43.0 +/- 16.1; Group 2: 29.2 +/- 8.3; Group 3: 48.1 +/- 14.2; Group 4: 41.0 +/- 9.3. The dentin treated with phosphoric acid 37% for 15 seconds showed the lowest values of microtensile bond strength. The results obtained with Groups 1, 3 and 4 were statistically similar.

Alendronate therapy in cyclosporine-induced alveolar bone loss in rats

Background and Objective: Cyclosporine A is an immunosuppressive drug that is widely used in organ transplant patients as well as to treat a number of autoimmune conditions. Bone loss is reported as a significant side-effect of cyclosporine A use because this can result in serious morbidity of the patients. As we have shown that cyclosporine A-associated bone loss can also affect the alveolar bone, the purpose of this study was to evaluate the effect of the concomitant administration of alendronate on alveolar bone loss in a rat model.Material and Methods: Forty Wistar rats (10 per group) were given cyclosporine A (10 mg/kg, daily), alendronate (0.3 mg/kg, weekly), or both cyclosporine A and alendronate, for 60 d. The control group received daily injections of sterile saline. The expression of proteins associated with bone turnover, including osteocalcin, alkaline phosphatase and tartrate-resistant acid phosphatase (TRAP), and also the calcium levels, were evaluated in the serum. Analysis of the bone volume, alveolar bone surface, the number of osteoblasts per bone surface and the number of osteoclasts per bone surface around the lower first molars was also performed.Results: the results indicate that cyclosporine A treatment was associated with bone resorption, represented by a decrease in the bone volume, alveolar bone surface and the number of osteoblasts per bone surface and by an increase in the number of osteoclasts per bone surface and TRAP-5b. These effects were effectively counteracted by concomitant alendronate administration.Conclusion: It is concluded that concomitant administration of alendronate can prevent cyclosporine A-associated alveolar bone loss.

Anatomoradiographic description of the teeth of pacas bred in captivity (Agouti paca, Linnaeus, 1766)

Two newborn males, two adult males 9 and 72 months old, one newborn female and two adult females of 30 and 54 months old pacas were used. Animals were radiographed on lateral recumbency, teeth were extracted and the vestibulolingual and mesiodistal lengths were achieved at the occlusal surface, besides the longitudinal length. The lower incisors presented greater length in relation to the other ones and sinuous shape; the upper incisors, relatively smaller, are practically straight. There is no canine tooth, and after a great diastema there is one premolar and three molars in each hemiarcade. In adult pacas, the enamel of incisors presents yellowish colour, mainly in the labial surface; in the premolars and molars, the enamel is present as internal sheets disposed nearly in a parallel way and in vestibulolingual direction, through practically all the dental length, which provides several joined teeth aspect.

Vertical marginal discrepancy of ceramic copings with different ceramic materials finish lines and luting agents: An in vitro evaluation

Statement of problem. Prosthetic restorations that fit poorly may affect periodontal health and occlusion. Studies that have evaluated the accuracy of fit of ceramic restorations before and after cementation assessed primarily intracoronal restorations.Purpose. This in vitro study evaluated the effect of different finish lines, ceramic manufacturing techniques, and luting agents on the vertical discrepancy of ceramic copings.Material and methods. Two stainless steel molars were prepared for complete crowns with 2 different finish lines (heavy chamfer and rounded shoulder); each molar was duplicated to fabricate 90 copings. A total of 180 copings generated 18 groups (n=10 for each finish line-coping material-luting agent combination). Luting agents tested included zinc phosphate, resin-modified glass ionomer (Fuji Plus), and resin composite cements (Panavia F). A metal frame was developed on which to screw the stainless steel model and a ceramic coping; the distance (mum) between 2 predetermined points was measured before and after cementation by a profile projector under a torquing force. A 4-way ANOVA with repeated measurements was performed to assess the influence of each factor in the vertical marginal discrepancy: 3 between-coping factors (finish line-coping material-luting agent) and 1 within-coping factor (before and after cementation) (alpha=.05).Results. Procera copings presented the lowest mean values (P<.05) of vertical marginal discrepancy before and after cementation (25/44 mum) when compared to Empress 2 (68/110 mum) and InCeram Alumina copings (57/117 mum), regardless of any combinations among all finish lines and luting agents tested.Conclusion. Considering each factor separately, the ceramic manufacturing technique appeared to be the most important factor tested for the definitive vertical discrepancy of all-ceramic copings, with lower mean values for Procera copings.

Effect of the clinical application of the GaAlAs 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 It 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.

Effect of bur type and conditioning on the surface and interface of dentine

The purpose of this in vitro study was to evaluate the surface and resin-dentine interface characteristics of permanent tooth dentine cut with diamond or carbide burs and treated with phosphoric acid (PA) or an acidic conditioner. Labial surfaces of permanent incisors were prepared into dentine with high-speed carbide or diamond burs and divided into two halves. Phosphoric acid 36% was applied on one half and non-rinse conditioner (NRC) was applied on the other half. Ten randomly selected scanning electron microscopy (SEM) fields from each specimen (n = 15) were evaluated. Occlusal surfaces of third molars were divided in two halves for evaluation of the resin-dentine interface. The halves were randomly assigned to one of each conditioner and restored with Prime & Bond NT/Spectrum. Ten specimens were analysed by SEM to evaluate hybrid layer formation and interfacial seal. We observed that surfaces prepared with carbide bur presented less residual smear plugs (P < 0.05) than surfaces prepared with diamond burs. Surfaces conditioned with NRC, which is a smear layer modifier, presented more residual smear plugs than surfaces conditioned with PA (P < 0.05). Treatment with PA resulted in more sealed interfaces than specimens treated with NRC. Within the limitations of this study the results showed that carbide burs leave a surface that is more conducive to bonding than diamond burs.

Caries resistance of lased human enamel with Er : YAG laser - morphological and ratio Ca/P analysis

Objective: In vitro analysis of caries resistance of dental enamel under caries simulation after irradiation with Er:YAG laser. Background Data: More susceptible to caries development spots at adjacent hard tissues from cavity preparations of dental tissues using burrs or lasers are quite common. Methods: Thirteen caries-free third permanent human molars were distributed as follows: G1: sound control and caries control; G2: Er:YAG 100, 200, 300, or 400 mJ/ 10 Hz/ 3 sec.; G3: the same parameters of G2 followed by artificial caries simulation, through dynamic model of demineralization and remineralization (DE/RE). Caries resistance analysis was evaluated through scanning electron microscopy (SEM) and Ca/P rate (X-Rays spectroscopy - EDX). Results: Photomicrographs showed that the Er:YAG laser created craters with rough aspect which became more evident as the energy per pulse was increased, but without change of regular morphology of enamel prisms. Significant statistical changes among the irradiated and control groups was observed considering the Ca/P ratio. Conclusion: Irradiated groups showed higher caries resistance than control groups. However, it is not possible to affirm that the enamel surface accidental irradiation could be a benefit to caries resistance for other situations can be considered, as biofilm deposit, which could increase the caries susceptibility.

Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique

This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 mu g) and human (2.27 +/- 0.41 mu g) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.

Effect of handpiece tip design on the cutting efficiency of an air abrasion system

Purpose : the aim of this study was to evaluate the effect of nozzle angle and tip diameter on the cutting efficiency of an air abrasion system. Materials and Methods: Thirty-six extracted human third molars were air-abraded with the PrepStar microabrasion machine using a handpiece with either 80degrees or 45degrees nozzle angles with 0.38 or 0.48 nun tip orifice diameters. The following parameters were held constant: abrasive particle size (27 mum), air pressure (80 psi), distance (2 mm.) and duration (15 seconds). The cutting efficiency was compared using enamel, dentin and cementum substrates. Width and depth of the cutting patterns were analyzed and measured using scanning electron micrographs. Results: Statistical analysis using three-way ANOVA and Duncan's Multiple Range test revealed that the width of the cuts was significantly greater when the cavities were prepared using the 45degrees nozzle angle. Significantly deeper cavities were produced with the 80degrees nozzle angle. The tip orifice of the nozzle influenced the cutting efficiency in softer substrates, dentin and cementum. Precise removal of hard tissue is best accomplished using the 80degrees angle nozzle tips for all types of tooth surfaces, enamel, dentin and cementum.

The effectiveness of alumina powder on carious dentin removal

This study determined the size of aluminum oxide particles used in an air abrasion system that is able to remove carious dentin tissue with maximum preservation of sound structure. Thirty extracted and carious-free third molars were used in this study. The dentin sample was obtained by sectioning the middle of the crown longitudinal to the long axis of the tooth in a mesio-distal direction. One half of the crown corresponded to the sound dentin group (SD), while the other half was used to develop artificial caries, constituting the, carious dentin group (CD). The specimens were air abraded for 15 seconds. The SD and CD groups were each randomly divided into three subgroups (N=10) according to the particle diameter employed (27, 50 and 125 pm). The prepared cavity was perpendicularly cut in half, and the profiles of all hemi-fragments were observed using SEM microscopy. The cavity measurements were made using a modified cephalometric analysis. The 27, 50 and 125 pun aluminum oxide particles did not present selectivity in the removal of carious dentin. However, when using the air abrasive technique for carious dentin treatment, the use of 27 and 50 pun aluminum oxide particles is recommended, due to their capacity to remove less sound tissue than the 125 pun particles.

Influence of the period after ovariectomy on femoral and mandibular bone density and on induced periodontal disease

Background: This study investigated the influence of the period after ovariectomy on femoral and mandibular bone mineral density (BMD) and on induced periodontal disease.Methods: One hundred and twenty-six female Holtzman rats were divided into nine groups: control, sham surgery (SHAM) with and without induction of periodontal disease for 51 and 150 days, and ovariectomy (OVX) with and without induction of periodontal disease for 51 and 150 days. Periodontal disease was induced by placing ligatures on the first lower molars during the last 30 days of each period. BMD was measured by dual-energy x-ray absorptiometry. Vertical bone loss was determined by measuring the distance from the alveolar bone crest to the cemento-enamel junction on the mesial side of the first lower molar.Results: Statistical analyses (Kruskal-Wallis test) revealed a significant difference between the OVX and SHAM groups' global and femoral proximal epiphysis BMD (P < 0.001) for 150 days and in the global evaluation for 51 days. For mandibular BMD, no difference was found between the groups of each period. Influence of the period on femoral BMD was found only for the SHAM groups, with lower BMD for the 51-day period compared to the 150-day period (P < 0.05). In the global evaluation of the mandible, a lower BMD was found after 51 days. The period was a contributing factor for the vertical bone loss, and it resulted in higher values for the 51-day period (P < 0.05).Conclusion: the period influenced the femoral BMD and the vertical bone loss in induced periodontal disease.

Influence of nutrition on the glucose absorption and tolerance test in horses submitted to different fasting periods

Four groups of horses of Brasileiro de Hipismo bred were submitted to fasting for 24 and 48 hours in order to study the absorption capacity of the small intestine. Two groups were fed with coast cross grass (Cynodon dactylon) and the other two groups with coast cross pasture and grains. At the end of the fasting periods, the groups received 1g of glucose/kg of body weight in a 20% solution through a nasogastric tube. Blood samples were collected immediately before and 70, 60, 120, 180, 240, 300, and 360 minutes after glucose administration. Glycemia was determined by the orthotoluidine method and insulin by radioimmunoassay. The animals which received grains showed larger increase in glycemia and insulinemia than those maintained on pasture regimen alone. The 48-hour fasting period induced higher glycemia and insulinemia levels than those observed after 24-hour fasting.