Ricardo Armini Caldas

Influence of surface treatments to repair recent fillings of silorane-and methacrylate-based composites

Purpose: The aim of this study was to evaluate the tensile bond strength (TBS) of repairs in recent fillings of methacrylate- (MBC) or silorane-based composites (SBC) subsequent to different surface treatments. Materials and Methods: Fifty slabs of Filtek P60 (3M ESPE, St Paul, USA) and Filtek P90 (3M ESPE) were stored for 10 days in distilled water at 37°C. The surface of adhesion was abraded with a 600-grit silicone paper and repaired using each respective composite: G1, no treatment (control); G2, application of adhesive; G3, application of silane and adhesive; G4, sandblasting (Al2O3) and adhesive; and G5, sandblasting (Al2O3), silane, and adhesive. Further 10 slabs of each composite were also evaluated for cohesive strength (G6). After 30 days immersion in distilled water at 37°C, the TBS was determined. Results: TBS results were higher for MBC than for SBC (P = 0.00012). The experimental groups were similar for SBC and the TBS was 27% of its cohesive strength. For P60, sandblasting significantly improved the TBS compared to other groups. With MBC, G4 and G5, the TBS was approximately 47% of its cohesive strength. Conclusion: Sandblasting (Al2O3) improves the repair-strength of MBC, whilst for the SBC all treatments succeed. MBC presents higher repair strength than SBC.

Biomechanical behavior of teeth without remaining coronal structure restored with different post designs and materials

The aim of this study was to access the biomechanical behavior of teeth without remaining coronal structure when restored with posts of different materials and configurations. Fifty bovine teeth (n=10 per group) with standard dimensions were restored as follows: cast post and core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP) or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure pattern (FP) were evaluated. Finite element models were realized to evaluate the stress distribution with a 100N load. All post-containing teeth survived TC, while CC had 30% of failures. CPC and C-FP had the higher fracture strength, but a high number of irreparable fractures (60%), such as PFM (70%). Von Mises analysis has shown the maximum stresses into the canal in groups restored with metallic posts, while glass-fiber posts and CC presented the maximum stresses at load contact point in the crown. CPC led to higher modified von Mises (mvM) stress in the cervical third of dentin. However, mvM values did not reach the dentin fracture limit for any group. Analysis of maximal contact pressure has shown better stress distribution along with the dentin interface in post-containing groups, especially for CPC.

Adaptation of overdenture-bars casted in different metals and their influence on the stress distribution: a laboratory and 3D FEA.

Adaptation at the implant/abutment interface is important to the long-term success of prosthetic rehabilitations. The aim of this study was to evaluate the adaptation of overdenture bar frameworks casted with different materials and the stress distribution of ill-fitted frameworks placement through 3-D finite element analysis (FEA). Thirty overdenture bar frameworks (n=10) were casted in different materials (Co-Cr, Ni-Cr, Ti). Vertical misfit of both abutments was examined using a single screw test and, after both screws were tightened, using a scanning electron microscope (SEM). The misfit values of each group were used to construct 3-D models, and a displacement with the same extent observed in SEM was applied to the non-tightened abutment to simulate the effect of prosthetic tightening. von Mises stress for prosthetic components, and the maximum principal stress and microstrain for bone tissue were evaluated. The misfit in the non-tightened abutment during the single screw test ranged from 145 to 211 µm. Different bar framework materials did not present significant differences in regard to adaptation. An increase in the misfit values in the other abutment was observed after the final settlement of the bars in Ni-Cr and Ti frameworks. The stress values on prosthetic screw and implant were not influenced by the bar framework material. However, Ti caused lower stress in the bar framework itself and strain in the bone tissue. The bar framework material does not affect the implant/abutment adaptation. Titanium frameworks presented the best behavior for the bar framework itself and bone tissue compared to the other materials.

Piriform Aperture Morphometry and Nasal Bones Morphology in Brazilian Population by Postero-Anterior Caldwell Radiographys

La apertura piriforme y el hueso nasal contribuyen a la formacion de la nariz. Su morfologia varia de acuerdo a los grupos etnicos y al sexo. Este estudio evaluo la morfologia de la apertura piriforme y el hueso nasal y su relacion con el sexo. Las aperturas piriformes y los huesos nasales de 97 personas fueron examinados radiograficamente mediante la tecnica radiografica de Caldwell, y los tipos de huesos nasales se clasificaron de acuerdo con Hwang et al. (2005). Se midio el ancho, la altura y el area de la apertura piriforme para demostrar las diferencias por sexo. El analisis estadistico se realizo a partir de la prueba t de Student y analisis de varianza (ANOVA). El tipo mas frecuente de hueso nasal fue la A, y la D fue la menos comun, en ambos sexos. En la prueba t de Student se obtuvo diferencias significativas entre los sexos, altura, ancho y area de la apertura piriforme, las que fueron mayores en hombres en comparacion a las mujeres. Las dimensiones de la apertura piriforme fueron mayores en los hombres que en las mujeres, por lo que se puede utilizar como parametro para la distincion de sexo en la poblacion brasilena. En la poblacion brasilena el tipo A de hueso nasal fue el mas frecuente, lo que contribuye para la diferenciacion etnica en la identificacion humana.

The Influence of Post System Design and Material on the Biomechanical Behavior of Teeth with Little Remaining Coronal Structure: Posts Restoring Weakened Teeth

PURPOSE To evaluate the influence of different post systems on the biomechanical behavior of teeth with a severe loss of remaining coronal structure. MATERIALS AND METHODS Fifty standardized bovine teeth (n = 10 per group) were restored with: cast post-and-core (CPC), prefabricated metallic post (PFM), parallel glass-fiber post (P-FP), conical glass-fiber post (C-FP), or composite core (no post, CC). The survival rate during thermomechanical challenging (TC), the fracture strength (FS), and failure patterns (FP) were evaluated. Finite element models evaluated the stress distribution after the application of 100 N. RESULTS All specimens survived TC. Similar FS was observed among post-containing groups. Groups P-FP and CC presented 100% repairable fractures. The von Mises analysis showed the maximum stresses into the root canal in groups restored with metallic posts. Glass-fiber posts and CC presented the maximum stresses at the load contact point. Glass-fiber groups showed lower stresses in the analysis of maximal contact pressure; CPC led to the highest values of contact pressure. The modified von Mises (mvM) stress in dentin did not show differences among groups. Moreover, mvM values did not reach the dentin fracture limit for any group. CONCLUSIONS The type of intracanal post had a relevant influence on the biomechanical behavior of teeth with little remaining coronal structure.

Extruded upper first molar intrusion: Comparison between unilateral and bilateral miniscrew anchorage

ABSTRACT Objective: The aim of his study was to evaluate the stress on tooth and alveolar bone caused by orthodontic intrusion forces in a supraerupted upper molar, by using a three-dimensional Finite Element Method (FEM). Methods: A superior maxillary segment was modeled in the software SolidWorks 2010 (SolidWorks Corporation, Waltham, MA, USA) containing: cortical and cancellous bone, supraerupted first molar, periodontal tissue and orthodontic components. A finite element model has simulated intrusion forces of 4N onto a tooth, directed to different mini-screw locations. Three different intrusion mechanics vectors were simulated: anchoring on a buccal mini-implant; anchoring on a palatal mini-implant and the association of both anchorage systems. All analyses were performed considering the minimum principal stress and total deformation. Qualitative analyses exhibited stress distribution by color maps. Quantitative analysis was performed with a specific software for reading and solving numerical equations (ANSYS Workbench 14, Ansys, Canonsburg, Pennsylvania, USA). Results: Intrusion forces applied from both sides (buccal and palatal) resulted in a more homogeneous stress distribution; no high peak of stress was detected and it has allowed a vertical resultant movement. Buccal or palatal single-sided forces resulted in concentrated stress zones with higher values and tooth tipping to respective force side. Conclusion: Unilateral forces promoted higher stress in root apex and higher dental tipping. The bilateral forces promoted better distribution without evidence of dental tipping. Bilateral intrusion technique suggested lower probability of root apex resorption.

Should adhesive debonding be simulated for intra-radicular post stress analyses?

OBJECTIVE Elucidate the influence of debonding on stress distribution and maximum stresses for intra-radicular restorations. METHODS Five intra-radicular restorations were analyzed by finite element analysis (FEA): MP=metallic cast post core; GP=glass fiber post core; PP=pre-fabricated metallic post core; RE=resin endocrowns; CE=single piece ceramic endocrown. Two cervical preparations were considered: no ferule (f0) and 2mm ferule (f1). The simulation was conducted in three steps: (1) intact bonds at all contacts; (2) bond failure between crown and tooth; (3) bond failure among tooth, post and crown interfaces. Contact friction and separation between interfaces was modeled where bond failure occurred. Mohr-Coulomb stress ratios (σMC ratio) and fatigue safety factors (SF) for dentin structure were compared with published strength values, fatigue life, and fracture patterns of teeth with intra-radicular restorations. RESULTS The σMC ratio showed no differences among models at first step. The second step increased σMC ratio at the ferule compared to step 1. At the third step, the σMC ratio and SF for f0 models were highly influenced by post material. CE and RE models had the highest values for σMC ratio and lower SF. MP had the lowest σMC ratio and higher SF. The f1 models showed no relevant differences among them at the third step. SIGNIFICANCE FEA most closely predicted failure performance of intra-radicular posts when frictional contact was modeled. Results of analyses where all interfaces are assumed to be perfectly bonded should be considered with caution.

Implant inclination and horizontal misfit in metallic bar framework of overdentures: Analysis by 3D-FEA method

The aim of this study was to evaluate by three-dimensional finite element analysis (3D-FEA) the biomechanics involved in bar-framework system for overdentures. The studied factors were latero-lateral angulation in the right implant (-10, -5, 0, 5 and 10 degrees), and different bar cross-sections (circular, Hader and oval) presenting horizontal misfits (50 or 150 µm) on the opposite implant. Positive angulation (5 and 10 degrees) for implant inclination to mesial position, negative angulation (-5 and -10 degrees) for distal position, and zero degree for parallel implants. The von Mises stresses evaluated the bar, screw and the implant; maximum principal, minimum principal and shear stress analyses evaluated the peri-implant bone tissue. Parallel implants provide lower stress in alveolar bone tissue; mesial inclined bars showed the most negative effect on prosthetic structures and implants. In conclusion, bar cross-section showed no influence on stress distribution for peri-implant bone tissue, and circular bar provided better behavior to the prosthetic system. Higher stress concentration is provided to all system as the misfit increases.

Relationship between prosthetic factors and oral health-related quality of life in complete denture wearers

OBJECTIVE: The aim of this study was to evaluate the influence of prosthetic-related factors on OHRQoL. METHODS: Twenty-eight edentulous patients, conventional complete dentures wearers, composed the sample. The evaluation of prosthetic factors involved the clinical assessment of quality of dentures, patients’ satisfaction, and masticatory ability, as well as recording of wearing time. The OHRQoL was determined thought the oral health impact profile (OHIP-EDENT) questionnaire. Pearsons correlation coefficient and stepwise multiple linear regression analysis were used to statistical inferences (α=0.05). RESULTUS: The OHRQoL showed a strong correlation with the masticatory ability (r=0.8 / p<0.001) and patients’ satisfaction (r=0.7 / p<0.001), which also displayed a strong correlation between them (r=0.7 / p<0.001). Moreover, the regression model stated that these variables explained 68.2% (r2=0.682) of the variation in the OHIP-EDENT data (p< 0.001). CONCLUSION: The OHRQoL was influenced by prosthetic factors, when these were characterized by the masticatory ability and patients’ satisfaction, and not by the quality of dentures nor wearing time.

Infiltração marginal após envelhecimento em interfaces adesivas de cimento autocondicionante com diferentes técnicas de cimentação

Resumo O objetivo do estudo in vitro foi avaliar quantitativamente a infiltração marginal em interfaces de cimentação, utilizando diferentes técnicas de cimentação adesiva. Para isso, foram utilizados 45 dentes bovinos (n=5). Foram confeccionados blocos de 5x4x1 mm, contendo pelo menos umas das faces de 20 mm2 totalmente em dentina. Os blocos foram aleatoriamente divididos em 3 grupos, onde cada grupo diferiu-se pela técnica de cimentação utilizada sendo: Grupo 1) adesivo autocondicionante de dois frascos (ClearfilTM SE Bond 2, Kuraray Noritake Dental Inc.) e cimento resinoso de dupla cura (Panavia F2.0, Kuraray Noritake Dental Inc.); Grupo 2) primer autoadesivo (ED Primer II, Kuraray Noritake Dental Inc.) e cimento resinoso de dupla cura (Panavia F2.0, Kuraray Noritake Dental Inc.) com fotoativação; Grupo 3) Cimentação utilizando primer dental autoadesivo (ED Primer II, Kuraray Noritake Dental Inc.) e cimento resinoso de dupla cura (Panavia F2.0, Kuraray Noritake Dental Inc.) com aplicação OXYGUARD II (Panavia F2.0 OXYGUARD II, Kuraray Noritake Dental Inc.). Sobre o bloco dental foi cimentado um bloco de mesmo tamanho de resina nano cerâmica (LavaTM Ultimate, 3M ESPE, St Paul, MN, USA). Todos os grupos de cimentação foram divididos em subgrupos (n=5) pra serem submetidos a ciclagem térmica, envelhecimento químico ou armazenamento em água. Após os testes de envelhecimento, todos os blocos foram imersos em tubos de ensaio, separadamente, contendo corante azul de metileno neutro, por 2 horas. Os blocos foram lavados, secos e preparados para as análises de microinfiltração. Os resutaltados foram lidos e interpretados através de análise estatística.