Repositório RCAAP

This study aimed to evaluate the mechanical properties of Ti-6Al-4V bars with 3.18mm diameter welded under different conditions to determine the optimal parameters to use of plasma welding machine comparing with specimens of nickel chrome (NiCr) welded by convectional process. Fifty specimens were divided in 5 groups (n = 10), control group (Control) with intact bars of titanium alloy, NiCrB group consisting of cast bars of NiCr and welded for brazing process; and groups welded with plasma process. Group PL3-10 using the regulation of the equipment 3A pulse and 10ms depth, Group PL3- 12: 3A pulse and 12 ms depth. Group PL3-14 3A pulse and 14ms depth. The bars were subjected to 3-bending flexural strength test. The values obtained were analyzed in the formula to achieve the bending stress (MPa). The statistical test ANOVA one way with index of significance (p <0.05) and test Tukey (p=0.05) was used. After carried out the analysis of samples under magnification to check the depth of weld penetration and fracture pattern. We conclude that the highest value was obtained from Control group followed to PL3-10. NiCrB group showed the lowest bending of flexural strength, being statistically different from the PL3-10 and PL3-12 and similar to the PL3-14.In analyzing the area of weld penetration was no statistical difference between groups (p> 0.05).

The aim of this study was to investigate the biomechanical behavior of maxillary premolar teeth regarding root morphology and depth of non-carious cervical lesion - abfraction, submitted to axial and oblique occlusal load. Threedimensional finite element analysis (3D FEA) and strain gauge test was used in extracted maxillary premolars. Single and birradicular roots premolar teeth 3D FEA models were developed using commercial FEA software. For 3D model generation was selected sound maxillary premolar. The tooth was chosen mapped with contact 3D scanner (Model, Roland). The enamel was degraded with hydrochloric acid-10% to perform the coronal dentin scan. Files with extension *. STL (steriolitográficos) were exported to Bio-CAD software (Rhinoceros-3D). Each tooth structure volumes were generated through the association of complex non-regular surfaces (NURBS). The models were exported to the finite element software (Femap, NoranEngineering, USA). Meshing, mechanical properties insertion and boundary conditions were performed in this software. The models generated were: sound, 1,25 mm and 2,5 mm abfraction teeth. A compressive static load of 100 N was applied: axially and 45° angle to the long axis on the palatine surface of the buccal cusp. Two strain gauge were bonded in teeth and these specimens were mounted in a mechanical testing machine. Birradicular sound, 1,25 mm and 2,5 mm abfraction teeth associated with oblique loading showed respectively the highest strain values among samples, 692,6 μS, 1043,31 μS and 1236,14 μS. Single root sound, 1,25 mm and 2,5 mm abfraction teeth associated with oblique loading showed the respective strain values 467,10 μS, 401,51 μS and 420,98 μS. Axial loading showed lower strain rates, ranging from 136.12 to 366.91 μS. The birradicular teeth with cervical furcation, greater lesion depths and oblique loading and the association of these factors promoted a higher stress concentrate in the tooth structure.

Oral Lichen Planus (OLP) is an chronic autoimune mucocutaneous disease, of a relatively high prevalence in the population. This retrospective study is about OLP patients, treated between 1997 and 2010. The aim was to present the clinical aspects of these lesions and improve the knowledge about the biological behavior of this disease, in addition to the potential of malignant transformation. The clinical data such as age, gender, location of the lesions, and symptomatology were recorded. There were 76 (1,65%) patients with OLP trough 4593 medical records. 21 attended the telephone calling for clinical review. In the 21 subjects sample, 17(81%) were females and 4(19%) males, within mean age of 46 years-old, at the diagnosis. Most lesions were localized in the buccal mucosa. Two patients showed leukoplakia concomitant with OLP. There are no malignant transformation, even no relationship between tobacco and alcohol with symptoms or clinical manifestation. In this study, it was possible to follow up the alterations between OLP clinical forms and the symptomatology, which probably does not have relationship with drinking or smoking. Our study did not show any malignant transformation.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Physical and chemical characteristics of specific membranes may influence the regeneration of periodontal tissues using the principles of guided tissue regeneration (GTR). The aim of this study was to analyze cell viability and the presence of growth factor with immortalized osteoblasts and fibroblasts in contact with three commercial bioabsorbable membranes with different compositions and structures. An imported membrane made of polylactic acid (PLA), considered the gold standard , and two of bovine collagen type I (COL1 and COL2), membranes of national manufacture. The results were compared between the groups at different times of culture (04 and 24 hours), to verify that the collagen membranes have a favorable cell development. The control group was the bottom of the culture plate, without any biomaterial. Was performed permanent cell culture with human osteoblasts (SAOS-2) and fibroblast HGF, using both cultured medium. The viability of cells cultured on the membranes were evaluated using the MTT assay. The amount of growth factor TGF-β1 was determined by ELISA assay using the supernatants of cultured cells. The samples were examined using a scanning electron microscope (SEM) to verify behavior and cell adhesion. All analyzed biomaterials are biocompatible, since none of the membranes in the study had lower results than the control group. However, the PLA membranes allowed higher cell viability and showed higher values of growth rates and the membrane COL1 showed similar results with PLA cell viability and release of fibroblast growth factor osteoblasts.

Introduction: The shaping ability of root canal instruments is often assessed in terms of preservation of the original root canal curvature without creating iatrogenic events. The aim of this study was to evaluate the influence of flexion angles produced by files during root canal instrumentation on the final form of apical stop. Methods: Sixty human lower incisors were divided into three groups (n=20). After coronal opening and tooth length measuring, radiographs were taken in two aspects (mesio-distal and buccal-lingual) with the files in working length. The flexion of files was evaluated from radiographs as the angle formed between the divergence of the file and its virtual image on its long axis. Teeth from group 1 were instrumented with stainless steel Flexofiles up to #40 file. For groups 2 and 3, Hand ProTaper Universal and ProTaper Universal rotary files were used respectively, up to file F4. New radiographs were taken for both aspects with a #15 K-file at working length. After gutta-percha insertion the specimen s apexes were ground allowing gutta-percha visualization and a picture was taken from the apex to identify root canal deformation with computer software. Results: Data showed that group 2 presented the highest variation in flexion angles compared to group 1 (0.112) and to group 3 (0.024) p<0.05. ProTaper Universal rotary system promoted lower apical stop deformation than the both manual techniques using NiTi (0.011) and stainless steel files (0.025) p<0.05. Conclusions: Force vectors caused by the flexion angles of files during the instrumentation of curved canals promoted apical stop deformation. Protaper Universal rotary files showed less apical deformation than hand ProTaper Universal and stainless steel files.

Several factors must be considered in the selection of angled abutments. In these situations, the clinician should find a practical way to overcome the lack of retention. The purpose of this study was to evaluate the bond strength of metallic crowns cemented to straight and angled customizable abutments with different definitive luting agents. Ninety one regular external hex analogs and abutments were divided in Control group (C): customizable straight abutment cemented with zinc phosphate (n = 10); three groups (n = 10) with 17° angled abutment cemented with zinc phosphate (A17ZP), Panavia F (A17RM) and RelyX U100 (A17R) cements and more three groups (n = 10) with 30° angled abutment also cemented with zinc phosphate (A30ZP), Panavia F (A30RM) and RelyX U100 (A30R) cements. The metal copings were cemented onto their corresponding metal dies and crowns cemented with Panavia F were pre-treated with an alloy primer containing an acid-phosphated monomer (MDP). Data from the all groups were compared to control group with a 1-way ANOVA (&#945;=.05) and Dunnet s test, and comparison between tested groups were done with 2-way ANOVA (&#945;=.05) and Tukey s test. SEM and CLSM evaluation were performed (n = 3) aiming to investigate microscopic features of the abutment-cement-crown interfaces. The mean force (SD) required to dislodge the crowns in the C, A17ZP, A17RM, A17R, A30ZP, A30RM and A30R groups was 357,26 (62,21) N; 251,50 (20,13) N; 397,05 (88,48) N; 328,71 (79,87) N; 276,70 (17,96) N; 377,81 (90,61) N and 335,42 (88,34) N respectively. Panavia F presented the higher tensile bond strength results and zinc phosphate the lower between the tested groups. Only A17ZP group was different from control group (p=.007) and the abutment taper has no influence in retentive values. Zinc phosphate showed an inhomogeneous cement line in SEM and CLSM analysis. The presence of MDP primer could be perceived in CLSM images of Panavia F group. Within the limitations of this in vitro study, the Panavia F presented the higher bonding strength between tested groups, however, all 3 cements tested were similar to control group except A17ZP group, showing that in the conditions of the study they all can be successfully used.

The aim of this study was to analysis the influence of calcium hydroxide paste, endodontic irrigants and the time of maintenance of the intracanal dressing on bond strength of fiberglass posts in root canals of bovine teeth. 70 bovine incisors were randomly divided into 7 groups (n = 10), a control group without intracanal dressing and 6 groups, with intracanal dressing (CHW calcium hydroxide + distilled water), resulting of the interaction between the factors: endodontic irrigants (SH 1% sodium hypochlorite; SHE - 1% sodium hypochlorite + 17% EDTA) and the time of maintenance of intracanal dressing (I - immediate; 21d - 21 days and 6m - 6 months).After fiberglass post cementation (RelyX U100), roots were serial sectioned to obtain two slices from each third (cervical, middle and apical) and were submitted to micropush-out test. Bond strength data were analyzed by two-way ANOVA in a split-plot arrangement followed by Tukey s test and Dunnet test (α = 0.05) for multiple comparisons. The CHA paste use did not presented statistical difference with control group in 13 of 18 associated factors (p>0.05). There was significant reduction in bond strength in groups irrigated with SH in six months in cervical (p = 0.0216) and middle (p = 0.0017) thirds. Irrigation with HSE reduced the adhesion compared to HS in the middle (p = 0.0488) and apical (p = 0.0252) thirds tested immediately and the middle third (p = 0.0287) in 21 days. The cervical third presented higher bond strength than the apical in all groups I and T (p <0.05), and similarity in S (p> 0.05). The use of calcium hydroxide paste resulted in bond strengths similar to the control group in thirteen of eighteen associated factors. EDTA reduced the bond strength in immediate (middle and apical thirds) and after 21 days groups (middle third). There was a significant reduction in the bond strength of the groups irrigated with HS tested at 6 months (cervical and middle thirds). The behavior of the bonding agent was different in the root thirds.

The aim of this study was to evaluate the effect of internal bleaching agents on fibreglass post bond strength to root dentine, seventy bovine teeth were divided into 7 experimental groups (n=10) varying the bleaching agent used: SpH- sodium perborate + 20%hydrogen peroxide; SpW- sodium perborate + distilled water; Cp37- 37%carbamide peroxide; Cp16- 16%carbamide peroxide; Cp10- 10%carbamide peroxide; H- 35%hydrogen peroxide; C- no bleaching agent (control). After bleaching protocols, posts were cemented with self-adhesive resin cement (RelyX U100) and roots were cross-sectioned to obtain two discs for each third. Posts were submitted to micropush-out test and bond strength values (MPa) were submitted to ANOVA in a split-plot arrangement and Tukey s test (p<0.05). Failure mode was evaluated under a confocal microscope. There was no significant difference between the control and groups with a bleaching agent. 16%carbamide peroxide (Cp16) resulted in higher bond strength value than sodium perborate + 20%hydrogen peroxide (SpH) on cervical third. The cervical third presented higher bond strength value compared to the apical third in the 10%carbamide peroxide (Cp10), 16%carbamide peroxide (Cp16) and sodium perborate + distilled water (SpW) and no significant difference in the other groups. The prevalence of adhesive cement-dentine failure was verified in all groups. The use of internal bleaching agents did not decrease fibreglass post bond strength to root dentin.

Objective: To evaluate dental abnormalities found in patients who underwent chemotherapy and radiotherapy. Methods: We reviewed medical records from 1991 to 2008, and as a criterion for inclusion age limit of 12 years, and clinical examinations and radiographic observation for the changes. Results: The sample of thirty patients, sixteen male and fourteen female, mean age of start for cancer treatment five years. The incidence of childhood cancer in the study was 60% for acute lymphoid leukemia (ALL), 16% lymphomas and 23% other tumors. The median duration of chemotherapy was twenty months, and 6106 cGy irradiation. In this study 56% of cancer patients had at least one change dental enamel hypoplasia in 33% of patients, followed by microdontia with 23%. Hypoplasia enamel committed the crown of all teeth and changes in size, microdontia the second molars and second premolars. Conclusion: The results showed that at the beginning of therapy, patients with a mean initial age of two years and two months showed microdontia and four years and six months hypoplasia.

Mestre em Odontologia

The material used in retrofilling is among others a decisive factor for the success in parendodontic surgeries; therefore they should have investigated their biocompatible characteristics since they remain in direct contact with the periapical bone tissue. This study investigated the inflammatory response of bone tissue when in contact with four types of MTAs available on the market, through intraosseous implants in guinea pigs, using for that purpose, the methodology recommended by the International Dental Federation (1980) which is internationally accepted (ADA, 1982). Forty guinea pigs were used in experimental periods of four and twelve weeks. Each animal received an implant in each side of the mandibular symphysis region. From each implant it was made 24 blades with 144 histological cuts, stained with hematoxylin-eosin and reviewed by two independent observers. There was similarity between the materials tested, since after 4 weeks all the implants with MTAs ProRoot ® gray and white as well as the ones with MTAs Angelus ® gray and white presented an absent/mild inflammatory reaction evolving into a process of scar repair with affixing of mineralized matrix. Thus, through the methodology employed it was possible to conclude that all types of MTAs, regardless the trademark, were biocompatible promoting similar tissue responses when in contact with the bone tissue.

The aim of this study was to investigate the influence of anodization with CaP incorporation on titanium surfaces in the process of osteogenesis in vitro. For this, human fetal osteoblasts (hFOB 1.19) were seeded over commercially pure titanium disks (8x4 mm) with three surface treatments (n= 21 disks/group): machined (Screw®), acid etching (Porous®) and anodized with calcium phosphate (CaP) incorporation (Vulcano®). After 3, 7 and 14 days of culture, the following parameters were evaluated: cell viability (MTT); gene expression of Runx2, alkaline phosphatase (ALP) and bone sialoprotein (BSP) (Real time RT-PCR); and quantification of BMP-2 e TGF-β1 (ELISA). The association between growth factors secretion and Runx2 expression, as well as between this transcription factor with ALP/BSP expressions was also evaluated. Results concerning cell viability showed a greater number of viable cells for rough surfaces, especially for Porous and Vulcano at 7 days (p=0.005) and for Porous at 14 days (p<0.001). There were significant differences regarding gene expression of Runx2, ALP and BSP for all surfaces at 7 days (p<0.05), but with greater fold induction for Porous and Vulcano. Regardless of the surface treatment, a strong positive correlation was observed between Runx2 and ALP/BSP expressions (p<0.0001). Growth factors secretion was not significantly affected by surface treatment in any experimental period (p> 0.05). Vulcano modulated significantly the correlation between the TGF-β1 secretion and Runx2 expression (p<0.05), which did not happen for BMP-2 or for other surfaces studied. The CaP incorporation favored the biological parameters evaluated at 7 days, but in a manner similar to the acid etched surfaces. The results presented here support the observations that surface roughness may play a more important role in determining cellular response than surface composition does.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The aim of this study was to evaluate the bond strength to dentin of three resin cements used for cementation of glass fiber posts in three different root depths (cervical thirds, middle and apical). We selected 30 bovine teeth were endodontically treated and prepared to conduct cementing glass fiber posts. Resin cements were used: Allcem-FGM Dental Products LTD, resin cement RelyX ARC dual-3M ESPE, Self-Adhesive Resin Cement RelyX U100 Universal, 3M ESPE. The samples were cross-sectioned into six slices resulting in two discs 1 mm thick by region: cervical thirds (c1 and c2), medium (M1 and M2) and apical (A1 and A2). The slices were tested with micropush out on a machine EMIC DL 2000, containing a load cell of 50kgf under 0.5 mm / minute. The data were subjected to One-way ANOVA (cement) with split-plot (third root) are using the Tukey test (&#945; <0.05) for comparison between groups. The results showed that the bond strength was influenced by cement, and in the cervical region, the cement RelyX Arc showed the highest bond strength, showing no statistical difference when compared with the the All hundred and statistically different when compared with the RelyX U100.A bond strength was also influenced by root third (p = 0.001) and the third cervical (p = 0.001) and medium (p = 0.015) showed higher bond strength when compared with the apical third. The interaction of cement and root third did not influence the results of bond strength (p = 0.076).

In Pediatric Dentistry there are several materials used for pulp therapy. Therefore, due to the above mentioned diversity, this research aimed to evaluate and compare the biocompatibily of some materials through intra osseous implants indicated for this purpose: pastes Guedes Pinto, Vitapex®, CTZ and CTZ without eugenol, according to the FDI recommendations (1980) and ANSI/ADA (1982). It was used forty guinea-pigs, ten for each material, divided into experimental periods of four and twelve weeks. Two intra-osseous implants were carried out on each animal on the lateral region of the madibular symphysis, lateral to the incisors teeth. The external lateral cup wall served as control for the technique. At the end of the observation periods, the specimens were prepared for evaluation histological. The results showed that the CTZ paste presented severe inflammatory reaction, necrotic tissue, limphocytes, foreign body cells, and bone resorption. The CTZ without eugenol paste decresead the intensity inflammatory reactions, but absent/slight in the period of 4 weeks, started to moderate in 12 weeks. The reactions to Vitapex® and Guedes Pinto pastes were absent/slight presenting a general pattern of replacement by bone tissue newly formed. The results allowed to the conclusion that only the Guedes Pinto and Vitapex® pastes presented compatibility levels in the two periods analysed according to the criteria adopted and CTZ and CTZ without eugenol showed the lack of biocompatibility.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais