Effect of thickness and shade of CAD/CAM composite on the light transmission from different light-curing units

Abstract The thickness and shade of a restoration will affect the transmission of light from the light-curing unit (LCU). This study determined the power (mW), spectral radiant power (mW/nm), and beam profile of different LCUs through various thicknesses and shades of a CAD-CAM resin composite (BRAVA Block, FGM). Five thicknesses: 0.5; 0.75; 1.0; 1.5, and 2.0 mm, in three shades: Bleach; A2 and A3.5 of a CAD-CAM resin (n = 5). Two single-peak LCUs: EL, Elipar DeepCure-S (3M Oral Care); and OP, Optilight Max (Gnatus), and one multiple-peak LCU: VL, VALO Grand (Ultradent), were used. The LCUs were positioned touching the surface of the BRAVA Block. The power and emission spectrum were measured using a fiberoptic spectrometer attached to an integrating sphere, and the beam profiles using a laser beam profiler. The effect of the material thickness on the light attenuation coefficients was determined. VL and EL delivered more homogeneous beam profiles than OP. The type of the BRAVA Block had a significant effect on the transmitted power, and wavelengths of transmitted light (p < 0.001). There was an exponential reduction in the power and emission spectrum as the thickness of the BRAVA Block increased (p < 0.001). The light transmission through the A2 shade was least affected by the thickness (p < 0.001). The attenuation coefficient was higher for the violet light and higher for A3.5 than the A2 or Bleach shades. No violet light from the VL could be detected at the bottom of 2.0 mm of the BRAVA Block.

Influence of diameter on mechanical behavior of morse taper narrow implants

Dental implants could give back function, esthetics and quality of life to patients. The correct choice of the implant, especially in borderline cases, is essential for a satisfactory result. Aim: Thus, the objective of this study was to evaluate the mechanical behavior of Morse taper implants with two different prosthetic interfaces. Methods: Twenty self-locking Morse taper implants, 2.9 mm in diameter (FAC), and 20 Morse taper implants, 3.5 mm in diameter (CM) were divided into two groups (n=10), and submitted to strength to failure test, optical microscopic evaluation of fracture, metallographic analysis of the alloy, finite element analysis (FEA) and strain gauge test. A Student's t test (α = 0.05) was made for a statistical analysis. Results: For the strength to failure test, a statistically difference was observed (p <0.001) between FAC (225.0 ± 19.8 N) and CM (397.3 ± 12.5 N). The optical microscopic evaluation demonstrated a fracture pattern that corroborated with FEA ́s results. The metallographic analysis determined that the implants of the FAC group have titanium-aluminum-vanadium alloy in their composition. In the strain gauge test, there was no statistical difference (p = 0.833) between CM (1064.8 ± 575.04 µS) and FAC (1002.2 ± 657.6 µS) groups. Conclusion: Based on the results obtained in this study, ultra-narrow implants (FAC) should ideally be restricted to areas with low masticatory effort

Microstructural and mechanical analysis of two CAD-CAM lithium disilicate glass-reinforced ceramics

Abstract The aim of this study was to analyze the structural, morphological and mechanical properties of two different lithium disilicate glass-reinforced ceramics for CAD-CAM systems (IPS e.max CAD and Rosetta SM). Five methodologies were used for both ceramics: microstructure (n = 2) was analyzed using x-ray diffraction (XRD); morphological properties (n = 2) were analyzed by scanning electron microscopy (SEM), with and without hydrofluoric etching; porosity (n = 3) was assessed using 3D micro-computed tomography (micro-CT); flexural strength was measured (n =1 0) using the three-point bending test; and bond strength was determined with self-adhesive resin cement (n = 10), using a microshear bond test. After performing all the tests, the data were analyzed using t-Student test and two-way ANOVA. All the tests used a significance level of α = 0.05. High peak positions corresponding to standard lithium metasilicate and lithium disilicate with similar intensities were observed for both ceramics in the XRD analysis. Morphological analysis showed that the crystalline structure of the two ceramics studied showed no statistical difference after acid etching. Additionally, no significant differences were recorded in the number or size of the pores for the ceramics evaluated. Moreover, no differences in flexural strength were found for the ceramic materials tested, or in the bond strength to ceramic substrates for the resin cements. Based on the study results, no significant differences were found between the two CAD-CAM lithium disilicate glass-reinforced ceramics tested, since they presented similar crystalline structures with comparable intensities, and similar total porosity, flexural strength and bond strength.

Can intra-radicular cleaning protocols increase the retention of fiberglass posts? A systematic review

Abstract The presence of residues within the root canal after post-space preparation can influence the bond strength between resin cement and root dentin when using fiberglass posts (FGPs). Currently, there is no consensus in the literature regarding what is the best solution for the removal of debris after post-space preparation. This systematic review involved "in vitro" studies to investigate if cleaning methods of the root canal after post-space preparation can increase the retention of FGPs evaluated by the push-out test. Searches were carried out in PubMed (MEDLINE) and Scopus databases up to July2017. English language studies published from 2007 to July 2017 were selected. 475 studies were found, and 9 were included in this review. Information from the 9 studies were collected regarding the number of samples, storage method after extraction, root canal preparation, method of post-space preparation, endodontic sealer, resin cement, cleaning methods after post-space and presence of irrigant activation. Five studies presented the best results for the association of sodium hypochlorite (NaOCl) and ethylenediamine tetra-acetic acid (EDTA), while in the other 4 studies, the solutions that showed improved retention of FGPs were photon-induced photoacoustic streaming (PIPS), Qmix, Sikko and EDTA. The results showed heterogeneity in all comparisons due to a high variety of information about cleaning methods, different concentrations, application time, type of adhesive system and resin cements used. In conclusion, this review suggests that the use of NaOCl/EDTA results in the retention of FGPs and may thus be recommended as a post-space cleaning method influencing the luting procedure.

Comparative analysis of optical microscopy, scanning electron microscopy, and micro-computed tomography on measurements

Abstract: Microscopic measurements are widely used in scientific research and the correct equipment to perform these evaluations could be critical to determine study results. Regarding microscopic measurements, three of the most used methods are: Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Micro-computed Tomography (MCT). It is important to select the best method for assessing diverse parameters, considering operational characteristics of the method, the equipment efficiency, and the machinery cost. Aim: Therefore, the main objective of this study was to define which is the most useful measurement method for assessing magnitudes below 0.4 mm. Methods: Ten dental implants, with known dimensions as defined by the manufacturer were randomly distributed. Two blinded observers assessed the distance between the second and the third screw vortex of the implants using three suggested methods. The true distance was defined to be 0.5 mm. Results: The assessed distances were: 0.597±0.007mm for OM, 0.578±0.017mm for SEM, and 0.613±0.006mm for MCT. The assessed distances were significantly different when the methods were compared (P>0.01). All measurements were into the CAD tolerances. Conclusion: It was possible to conclude that linear easurements between 595 and 605 µm could be performed by any of the described technologies (AU)

Influence of dentistry procedures on masticatory function of dentate patients

Aim: Evaluate the masticatory performance in patients with different clinical situations: patients with natural dentition without restorative and/or orthodontic intervention (Group CG) and patients with restorations and/or orthodontic intervention (Group TG). Subjects received instruction before the experiment, related to masticatory movements. Methods: Three capsules containing the granules were delivered separately to chew for 20 seconds each, controlled by the examiner. One capsule was chewed for 20 seconds only on the left side; the second capsule was chewed for 20 seconds only on the right side; and the third capsule was chewed for 20 seconds to simulate each patient's mastication. The mean data and standard deviation of masticatory function of each patient was calculated. Results: The results obtained in this study showed that there were no statistically significant differences (P < 0.05) between both tested groups (0.0320 ± 0.00716, 0.0436 ± 0.00974). Conclusions: Patients who were submitted to orthodontic and/or restorative procedures, with balanced occlusion could be used as a control group, making easier the patient recruitment. Clinicians and researchers on masticatory performance evaluation could apply the colorimetric method. The colorimetric method was a standardize method, effective and easy to execute. (AU)

Masticatory performance with different types of rehabilitation of the edentulous mandible

Abstract Aim: To compare the masticatory performance associated with different rehabilitation strategies for patients with edentulous mandibles. Methods: one portion of the test food "Optocal" was provided to groups: Natural Dentition (n = 15), Mandibular Fixed Implant-Supported Prosthesis with Maxillary Fixed Prosthesis (n = 8), Mandibular Fixed Implant-Supported Prosthesis with Maxillary Removable Prosthesis (n = 14), Mandibular Implant-Retained Overdenture with Maxillary Removable Prosthesis (n = 16), and Complete Dentures (n = 16). The portion was collected after 40 chewing strokes, and then passed through a stack of eight sieves with decreasing apertures. Masticatory performance was determined by weighing the portion of food on each sieve. Results: the masticatory performance was: 71.00% for Natural Dentition, 41.57% for Mandibular Fixed Implant-Supported Prosthesis with Maxillary Fixed Prosthesis, 31.44% for Mandibular Fixed Implant-Supported Prosthesis with Maxillary Removable Prosthesis, 27.70% for Mandibular Implant-retained Overdenture, and 14.33% for Complete Dentures. The data were statistically compared using Student's t-test (p < 0.05). Natural Dentition and Complete Denture groups were statistically different from all other groups, with the Natural Dentition and Complete Denture groups exhibiting the highest and lowest masticatory performance values, respectively. Conclusions: Osseointegrated implants improved the masticatory performance of all implant-supported groups compared to the Complete Dentures group.

Strain analysis of different diameter Morse taper implants under overloading compressive conditions

The aim of this study was to evaluate the amount of deformation from compression caused by different diameters of Morse taper implants and the residual deformation after load removal. Thirty Morse taper implants lacking external threads were divided into 3 groups (n = 10) according to their diameter as follows: 3.5 mm, 4.0 mm and 5.0 mm. Two-piece abutments were fixed into the implants, and the samples were subjected to compressive axial loading up to 1500 N of force. During the test, one strain gauge remained fixed to the cervical portion of each implant to measure the strain variation. The strain values were recorded at two different time points: at the maximum load (1500 N) and 60 seconds after load removal. To calculate the strain at the implant/abutment interface, a mathematical formula was applied. Data were analyzed using a one-way Anova and Tukey’s test (α = 0.05). The 5.0 mm diameter implant showed a significantly lower strain (650.5 μS ± 170.0) than the 4.0 mm group (1170.2 μS ± 374.7) and the 3.5 mm group (1388.1 μS ± 326.6) (p < 0.001), regardless of the load presence. The strain values decreased by approximately 50% after removal of the load, regardless of the implant diameter. The 5.0 mm implant showed a significantly lower strain at the implant/abutment interface (943.4 μS ± 504.5) than the 4.0 mm group (1057.4 μS ± 681.3) and the 3.5 mm group (1159.6 μS ± 425.9) (p < 0.001). According to the results of this study, the diameter influenced the strain around the internal and external walls of the cervical region of Morse taper implants; all diameters demonstrated clinically acceptable values of strain.

Avaliação da eficiência mastigatória por dois métodos: colorimetria e tamises / Mastigatory function avaluation by two methods: colorimetry and sifters

Objetivo: Correlacionar dois métodos para verificação da performance mastigatória. Método: Foram selecionados 13 pacientes que portavam Prótese total superior e prótese parcial fixa classe I de Kennedy inferior para realizar dois testes que medem a performance mastigatória. O primeiro teste, chamado de método das tamises, utiliza-se do Optocal como alimento-teste, dividido em 3 porções com 17 g que o paciente deve mastigar realizando 20 ou 40 ciclos mastigatórios. Após isso, é feita a análise do DGM. Em seguida, o paciente realizava a mastigação de uma cápsula, contendo grânulos de fuccina, seguindo os mesmos ciclos mastigatórios descritos no outro método. Após isso, as cápsulas foram enviadas a laboratório específico para análise da coloração. Resultado: Não houve correlação entre os métodos testados, após análise estatística utilizando o método de correlação de Pearson, com ?=0.05. Conclusão: O método da colorimetria, embora mais simples e de fácil execução do que o método das tamises, não se mostrou correlato a este. Deve-se, portanto, realizar ajustes na cápsula, a fim de torná-la mais macia, ou no método de análise do corante.

Purpose: Correlating two methods of verification of masticatory performance. Method: Thirteen patients were selected with was reabilitated with maxillar total denture and mandibular removible partial Kennedy Class I denture to perform two tests witch measure masticatory performance. The first test, called the method of sieves, uses the Optocal as test-food, divided into three portions with 17 g that the patient should chew doing 20 or 40 masticatory cycles. After that, we perform the DGM? analysis. Then the patient should chew a capsule containing fuchsin beads, following the same chewing cycles described in the other method. Thereafter, the capsules were sent to a specific laboratory for analysis. Results: There was no correlation between the tested methods, after statistical analysis using the Pearson correlation method, with ? = 0.05. Conclusions: Even colorimetric method, was a simple and easy to perform method, it was not correlated to the sifters method. Adjustments are necessary, in the capsule in order to make it softer or in the analisys? method.