Daniela Thomazatti Chimello

Tensile bond strength of different adhesive systems to enamel and dentin

The aim of this study was to assess the tensile bond strength of four adhesive systems to enamel and dentin: Clearfil Liner Bond 2V - C, Prime&Bond NT/NRC - PB, Single Bond - SB and All Bond 2 -AB. For such purpose, 40 sound human molars were selected. Crowns were bisected in a mesiodistal direction and each half was ground until flat enamel (E) or dentin (D) surfaces were obtained. A total of 80 specimens were randomly assigned to 4 groups (n=20, 10 in enamel and 10 in dentin). After surface treatment, a composite resin (Z250; 3M) cone was prepared using a split Teflon(R) matrix. Bond strength was tested in an universal testing machine (0.5 mm/min). Bond strength means in MPa were: C - E: 18.66 (+/-2.67) and D: 21.62 (+/-5.29); PB - E: 18.13 (+/-2.96) and D: 3.19 (+/-1.40); SB - E: 20.06 (+/-6.11) and D: 16.95 (+/-2.57); AB - E: 18.20 (+/-3.94) and D: 15.94 (+/-4.72). Statistical analysis of data by two-way ANOVA showed that C presented the best results followed by SB. In conclusion, among the tested materials, Clearfil Liner Bond 2V self-etching primer adhesive syetem had the best performance. The substrate type influenced bond strength, being higher to enamel.

Influence of cavity preparation with Er:YAG Laser on enamel adjacent to restorations submitted to cariogenic challenge in situ: A polarized light microscopic analysis

Er:YAG laser has been used for caries removal and cavity preparation, using ablative parameters. Its effect on the margins of restorations submitted to cariogenic challenge has not yet been sufficiently investigated. The aim of this study was to assess the enamel adjacent to restored Er:YAG laser‐prepared cavities submitted to cariogenic challenge in situ, under polarized light microscopy.

Assessing wear and surface roughness of different composite resins after toothbrushing

The aim of this work was to compare the in vitro wear and roughness of different composite resins after toothbrushing. Six resins were tested: Revolution (Kerr), Natural Flow (DFL), Flow It! (Jeneric-Pentron), Fill Magic Flow (Vigodent) - flowable composites, Silux Plus (3M) - microfilled composite, and Z100 (3M) - hybrid composite. Eight disks were prepared for each group (n = 48), with 12 mm in diameter and 1mm thick. The specimens were stored in distilled water at 37 °C for 7 days, polished (Super Snap), weighed and submitted to the initial roughness test. Each sample was fixed on plexiglass plates and subjected to simulated toothbrushing. After abrasion, the samples were removed from the plates, weighed and submitted to the post-abrasion roughness test. Statistical analysis was performed by using ANOVA and Tukeys test. Pearsons test was used to verify correlation between wear and roughness. Data showed a similar resistance to wear of Natural Flow and Z100, both presenting minimum mass loss and surface roughness. Silux Plus presented the roughest surface after toothbrushing.

Implant-supported prosthesis following Brånemark protocol on electromyography of masticatory muscles.

This research evaluated the effects of Brånemark protocol on electromyography of the masseter and temporal muscles. The patients were divided into two groups: Group I: patients who wore an implant-supported prosthesis in the mandibular arch following Brånemark protocol, and maxillary removable complete dentures; Group II: dentate individuals (control). Electromyography was carried out at rest, right (RL) and left (LL) laterality, protrusion and maximum voluntary contraction (MVC). Data were compared by t-test. At rest, a higher electromyographic (EMG) activity was observed in Group I, and the values were significant in the right masseter and left temporal muscles. In RL, there were statistically significant differences for right masseter (P < 0·01), left masseter and temporal muscles and for the left temporal muscle in LL (P < 0·05). In protrusion, Group I presented a higher EMG activity, and there was a statistically significant difference for the right masseter muscle (RM) (P < 0·05). In MVC, the EMG values were higher in Group II (control), but significant just for the right temporal muscle (P < 0·05). In conclusion, individuals with mandibular fixed dentures supported according to the Brånemark protocol and maxillary removable complete dentures showed a higher activity of masticatory muscles during the mandibular postural clinical conditions examined; however, in the MVC, Group I presented lower values when compared to dentate group. Despite presenting different EMG values in all of the clinical conditions, both groups showed similar EMG patterns of muscle activation which demonstrates that the proposed treatment can be considered as a good option for oral rehabilitation.

Influence of Er:YAG Laser on Microhardness of Enamel Adjacent to Restorations Submitted to Cariogenic Challenge in Situ

OBJECTIVE This study assessed the effect of the Er:YAG laser on enamel adjacent to restorations submitted to cariogenic challenge in situ, by microhardness analysis. BACKGROUND DATA The influence of Er:YAG laser energy on secondary caries formation has been investigated in vitro. However, no research involving demineralization around cavities prepared with the Er:YAG laser under intra-oral conditions has yet been described. MATERIALS AND METHODS Slabs of enamel were randomly assigned to seven groups (n = 12), according to the cavity preparation technique: groups I, II, and III--Er:YAG laser, 250 mJ, at 2, 3, and 4 Hz, respectively; groups IV, V, and VI--350 mJ, at 2, 3, and 4 Hz, respectively; group VII--high-speed handpiece (control). Cavities were restored and the specimens were fixed in intra-oral appliances and worn by 12 volunteers for 14 d. Sucrose solution was applied to each slab 6 times/d. Samples were removed, sectioned, and examined for microhardness at 100, 200, and 300 microm (factor distance), and 30, 60, and 90 microm (factor depth), from the restoration and enamel surface, respectively. RESULTS Analysis of variance according to a split-plot model showed no difference among the cavity preparation techniques, among distances, or among depths, as well as no difference in the interaction between the factors of cavity preparation and distance. A significant difference was found in the interaction of cavity preparation and depth (p < 0.0001), as identified by contrast technique. CONCLUSION The results revealed that the Er:YAG laser did not differ from conventional cavity preparation with regard to enamel microhardness.

Evaluation of the surface hardness of composite resins before and after polishing at different times

Purpose: The aim of this study was to evaluate the surface hardness of six composite resins: Revolution, Natural Flow, Fill Magic Flow, Flow-it! (flowables), Silux Plus (microfilled) and Z100 (minifilled) before and after polishing at different times. Materials and Methods: For this purpose, 240 specimens (5mm diameter, 1.4mm high) were prepared. Vickers hardness was determined before and after polishing at different times: immediately, 24h, 7 and 21 days after preparation of the samples. Statistical analysis was performed by ANOVA and Tukey test. Results: There was no difference in the hardness of flowable resins, which had lower hardness than the minifilled resin. The minifilled resin showed the highest surface hardness as compared to the other materials (p<0.01). All materials exhibited higher hardness after polishing, being more evident after 7 days. Conclusion: It may be concluded that, regardless of the composite resin, surface hardness was considerably increased when polishing was delayed and performed 1 week after preparation of the samples.

Low-Level Laser Therapy Influences Mouse Odontoblast-Like Cell Response in Vitro

OBJECTIVE The purpose of this study was to analyze the influence of two different irradiation times with 85 mW/cm(2) 830 nm laser on the behavior of mouse odontoblast-like cells. BACKGROUND DATA The use of low-level laser therapy (LLLT) to stimulate pulp tissue is a reality, but few reports relate odontoblastic responses to irradiation in in vitro models. METHODS Odontoblast-like cells (MDPC-23) were cultivated and divided into three groups: control/nonirradiated (group 1); or irradiated with 85 mW/cm(2), 830 nm laser for 10 sec (0.8 J/cm(2)) (group 2); or for 50 sec (4.2 J/cm(2)) (group 3) with a wavelength of 830 nm. After 3, 7, and 10 days, it was analyzed: growth curve and cell viability, total protein content, alkaline phosphatase (ALP) activity, calcified nodules detection and quantification, collagen immunolocalization, vascular endothelial growth factor (VEGF) expression, and real-time polymerase chain reaction (PCR) for DMP1 gene. Data were analyzed by Kruskall-Wallis test (α=0.05). RESULTS Cell growth was smaller in group 2 (p<0.01), whereas viability was similar in all groups and at all periods. Total protein content and ALP activity increased on the 10th day with 0.8 J/cm(2) (p<0.01), as well as the detection and quantification of mineralization nodules (p<0.05), collagen, and VEGF expression (p<0.01). The expression of DMP1 increased in all groups (p<0.05) compared with control at 3 days, except for 0.8 J/cm(2) at 3 days and control at 10 days. CONCLUSIONS LLLT influenced the behavior of odontoblast-like cells; the shorter time/smallest energy density promoted the expression of odontoblastic phenotype in a more significant way.

In vitro evaluation of the odontogenic potential of mouse undifferentiated pulp cells

The aim of this study was to evaluate the odontogenic potential of undifferentiated pulp cells (OD-21 cell line) through chemical stimuli in vitro. Cells were divided into uninduced cells (OD-21), induced cells (OD-21 cultured in supplemented medium/OD-21+OM) and odontoblast-like cells (MDPC-23 cell line). After 3, 7, 10 and 14 days of culture, it was evaluated: proliferation and cell viability, alkaline phosphatase activity, total protein content, mineralization, immunolocalization of dentin matrix acidic phosphoprotein 1 (DMP1), alkaline phosphatase (ALP) and osteopontin (OPN) and quantification of genes ALP, OSTERIX (Osx), DMP1 and runt-related transcription factor 2 (RUNX2) through real-time polymerase chain reaction (PCR). Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests (p<0.05). There was a decrease in cell proliferation in OD-21 + OM, whereas cell viability was similar in all groups, except at 7 days. The amount of total protein was higher in group OD-21 + OM in all periods; the same occurred with ALP activity after 10 days when compared with OD-21, with no significant differences from the MDPC-23 group. Mineralization was higher in OD-21+OM when compared with the negative control. Immunolocalization demonstrated that DMP1 and ALP were highly expressed in MDPC-23 cells and OD-21 + OM cells, whereas OPN was high in all groups. Real-time PCR revealed that DMP1 and ALP expression was higher in MDPC-23 cell cultures, whereas RUNX2 was lower for these cells and higher for OD-21 negative control. Osx expression was lower for OD-21 + OM. These results suggest that OD-21 undifferentiated pulp cells have odontogenic potential and could be used in dental tissue engineering.

Resonance frequency analysis of overdenture retainer implants with immediate loading

OBJECTIVE To evaluate 16 patients of both sexes with lower overdenture and upper complete dentures, by analysing the resonance frequency of the initial and late stability of implants used to retain the overdenture under immediate loading. BACKGROUND Oral rehabilitation treatment with complete dentures using implants has been increasingly more common among the specialists in the oral rehabilitation area. This is an alternative for obtaining retention and stability in treatments involving conventional complete dentures, where two implants are enough to retain the overdenture satisfactorily. MATERIALS AND METHODS The Osstell™ Mentor device was used for the analysis in the initial period (primary stability), 3 and 15 months after the installation of the lower overdenture (secondary stability). The statistical analysis was performed with the repeated measures model (p < 0.01). RESULTS The implant stability quotients were observed to increase after 15 months of the rehabilitating treatment. CONCLUSION The use of overdentures over two lower implants should become the treatment of choice for individuals who have a fully edentulous mandible.