Browsing by Author "Torres, Orlanda"
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- Accuracy of the electronic method versus the radiographic method in determining working length: integrative systematic reviewPublication . Marques, Celia Eduarda; Delphim, Marcella; Fidalgo-Pereira, Rita; Melo-Ferraz, António; Miller, Paulo; Torres, OrlandaIntroduction: The radiographic method is widely used to calculate the working length (CT). However, it presents limitations that, to overcome them, apical electronic locators (LEAs) were developed to allow greater accuracy and reliability in determining the CT. Objective: The present study aims to perform an integrative systematic review and gather the available scientific evidence on the method that allows greater accuracy in determining the CT between the radiographic method and the electronic localisation method (LEA). Materials and Methods: The literature search was performed on the PubMed platform using keywords combined through the Boolean operator AND as follows: ("endodontics" AND "electronic apex locator" AND "radiographic measurement") and ("endodontics" AND "electronic apex locator" AND "radiographic measurement" AND "odontometry"). Results: 68 articles reporting comparative studies performed between the methods, radiographic and LEA, were identified. Eleven studies were included, of which, in some cases, LEAs showed better results than non-digital periapical radiographs. The studies indicate that although there are differences between the two methods, with greater accuracy in determining LEA, the differences did not prove to be statistically significant. In the presence of irrigating solutions, sodium hypochlorite revealed more significant discrepancies in CT determination with the LEA method. Conclusion: The two methods, radiographic and LEA, should be used in association since each has particularities that present more significant benefits enhancing the success of endodontic treatment and a better and more complete treatment for patients.
- Contamination of resin-matrix composites on chairside handling using latex or nitrile gloves: an in vitro studyPublication . Cunha, Ivana; Torres, Orlanda; Fidalgo-Pereira, Rita; Henriques, Bruno; Özcan, Mutlu; Souza, Júlio C. M.The aim of this study was to evaluate the efect of diferent gloves and clinical environment on the contamination of resinmatrix composites for restorative dentistry. Specimens of nano-hybrid resin-matrix composite (n=6) were divided in groups regarding the handling with (A) clinical spatula; (B) latex gloves; (C) latex or (D) nitrile gloves with human saliva; (E) latex or (F) nitrile gloves with human blood. After light curing, groups of specimens were analyzed by optical microscopy at magnifcation ranging from x30 up to x500 and by scanning electron microscopy at diferent magnifcation ranging from x50 up to x8000. Handling of resin-matrix composites with unpowdered nitrile gloves or clinical spatulas avoided the presence of contaminants. However, agglomerates of the resin-matrix composite itself became entrapped leading to a heterogenous morphological aspect. SEM images revealed the presence of corn-derived starch released from the powdered gloves. Also, the formation of micro-spaces (voids) occurred after handling with powdered latex gloves. Specimens handled with both type of gloves contaminated with saliva showed a conditioning layer composed of glycoproteins rolls and compounds including calcium-based chlorides, phosphates, and carbonates. Also, blood products were transferred from the contaminated gloves to the resin-matrix composites after handling. Thus, resin-matrix composite restorations are susceptible to contamination with debris from powdered gloves. Also, saliva or blood debris become adsorbed and entrapped in the resin-matrix composites during clinical handling leading to the presence of defects such macro- and micro-scale voids or contaminant agglomerates.
- Effect of inorganic fillers on the light transmission through traditional or flowable resin-matrix composites for restorative dentistryPublication . Fidalgo-Pereira, Rita; Carvalho, Óscar; Catarino, Susana O.; Henriques, Bruno; Torres, Orlanda; Braem, Annabel; Souza, Júlio C. M.Objectives: The aim of this in vitro study was to evaluate the light transmission through five different resin-matrix composites regarding the inorganic filler content. Methods: Resin-matrix composite disc-shaped specimens were prepared on glass molds. Three traditional resin-matrix composites contained inorganic fillers at 74, 80, and 89 wt. % while two flowable composites revealed 60 and 62.5 wt. % inorganic fillers. Light transmission through the resin-matrix composites was assessed using a spectrophotometer with an integrated monochromator before and after light curing for 10, 20, or 40s. Elastic modulus and nanohardness were evaluated through nanoindentation’s tests, while Vicker’s hardness was measured by micro-hardness assessment. Chemical analyses were performed by FTIR and EDS, while microstructural analysis was conducted by optical microscopy and scanning electron microscopy. Data were evaluated using two-way ANOVA and Tukey’s test (p < 0.05). Results: After polymerization, optical transmittance increased for all specimens above 650-nm wavelength irradiation since higher light exposure time leads to increased light transmittance. At 20- or 40-s irradiation, similar light transmittance was recorded for resin composites with 60, 62, 74, or 78–80 wt. % inorganic fillers. The lowest light transmittance was recorded for a resin-matrix composite reinforced with 89 wt. % inorganic fillers. Thus, the size of inorganic fillers ranged from nano- up to micro-scale dimensions and the high content of micro-scale inorganic particles can change the light pathway and decrease the light transmittance through the materials. At 850-nm wavelength, the average ratio between polymerized and non-polymerized specimens increased by 1.6 times for the resin composite with 89 wt. % fillers, while the composites with 60 wt. % fillers revealed an increased ratio by 3.5 times higher than that recorded at 600-nm wavelength. High mean values of elastic modulus, nano-hardness, and micro-hardness were recorded for the resin-matrix composites with the highest inorganic content. Conclusions: A high content of inorganic fillers at 89 wt.% decreased the light transmission through resin-matrix composites. However, certain types of fillers do not interfere on the light transmission, maintaining an optimal polymerization and the physical properties of the resin-matrix composites. Clinical significance: The type and content of inorganic fillers in the chemical composition of resin-matrix composites do affect their polymerization mode. As a consequence, the clinical performance of resin-matrix composites can be compromised, leading to variable physical properties and degradation. Graphical Abstract: [Figure not available: see fulltext.].
- Light transmittance through resin-matrix composite onlays adhered to resin-matrix cements or flowable compositesPublication . Fidalgo-Pereira, Rita; Catarino, Susana O.; Carvalho, Óscar; Veiga, Nélio; Torres, Orlanda; Braem, Annabel; Souza, Júlio C. M.OBJECTIVE: The aim of this study was to evaluate the influence of the thickness of resin-matrix composite blocks manufactured by CAD-CAM on the light transmittance towards different resin-matrix cements or flowable composites. METHODS: Sixty specimens of resin-matrix composite CAD-CAM blocks reinforced with 89 wt% inorganic fillers were cross-sectioned with 2 or 3 mm thicknesses. The specimens were conditioned with adhesive system and divided in groups according to the luting material, namely: two dual-cured resin-matrix cements, two traditional flowable resin-matrix composites, and one thermal-induced flowable resin-matrix composite. Specimens were light-cured at 900 mW/cm 2 for 40s. Light transmittance assays were preformed using a spectrophotometer with an integrated monochromator before and after light-curing. Microstructural analysis was performed by optical and scanning electron microscopy (SEM). Nanoindentation tests were performed to evaluate mechanical properties for indirect evaluation of degree of monomers conversion. RESULTS: Optical and SEM images revealed low thickness values for the cementation interfaces for the traditional flowable resin-matrix composite. The cement thickness increased with the size and content of inorganic fillers. The highest light transmittance was recorded for the onlay blocks cemented with the traditional flowable resin-matrix composites while a group cemented with the dual-cured resin-matrix cement revealed the lowest light transmittance. The elastic modulus and hardness increased for specimens with high content of inorganic fillers as well as it increased in function of the light transmittance. CONCLUSIONS: The light transmittance of flowable resin-matrix composites was higher than that for resin-matrix cement after cementation to resin-matrix composites blocks. The type, size, and content of inorganic fillers of the luting material affected the thickness of the cement layer and light transmittance through the materials. CLINICAL RELEVANCE: On chair-side light curing, the transmission of visible light can be interfered by the chemical composition and viscosity of the luting materials. The increase in size and content of inorganic fillers of resin-matrix composites and luting materials can decrease the light transmittance leading to inefficient polymerization.
- Microscopic inspection of the adhesive interface of composite onlays after cementation on low loading: an in vitro studyPublication . Magalhães, Tiago; Fidalgo-Pereira, Rita; Torres, Orlanda; Carvalho, Óscar; Silva, Filipe S.; Henriques, Bruno; Özcan, Mutlu; Souza, Júlio C. M.Purpose: This study aimed to assess the layer thickness and microstructure of traditional resin-matrix cements and flowable resin-matrix composites at dentin and enamel to composite onlay interfaces after cementation on low loading magnitude. Materials and Methods: Twenty teeth were prepared and conditioned with an adhesive system for restoration with resin-matrix composite onlays manufactured by CAD-CAM. On cementation, tooth-to-onlay assemblies were distributed into four groups, including two traditional resin-matrix cements (groups M and B), one flowable resin-matrix composite (group G), and one thermally induced flowable composite (group V). After the cementation procedure, assemblies were cross-sectioned for inspection by optical microscopy at different magnification up to ×1000. Results: The layer thickness of resin-matrix cementation showed the highest mean values at around 405 µm for a traditional resin-matrix cement (group B). The thermally induced flowable resin-matrix composites showed the lowest layer thickness values. The resin-matrix layer thickness revealed statistical differences between traditional resin cement (groups M and B) and flowable resin-matrix composites (groups V and G) (p < 0.05). However, the groups of flowable resin-matrix composites did not reveal statistical differences (p < 0.05). The thickness of the adhesive system layer at around 7 µm and 12 µm was lower at the interfaces with flowable resin-matrix composites when compared to the adhesive layer at resin-matrix cements, which ranged from 12 µm up to 40 µm. Conclusions: The flowable resin-matrix composites showed adequate flowing even though the loading on cementation was performed at low magnitude. Nevertheless, significant variation in thickness of the cementation layer was noticed for flowable resin-matrix composites and traditional resin-matrix cements that can occur in chair-side procedures due to the clinical sensitivity and differences in rheological properties of the materials.
- Onlays de resina composta CAD/CAM, avaliação da interface adesiva - Um estudo in vitroPublication . Fidalgo-Pereira, Rita; Magalhães, Tiago; Torres, Orlanda; Carvalho, Óscar; Fernandes, Valter; Souza, Júlio C. M.
- Onlays de resina composta CAD/CAM, avaliação da interface adesiva - Um estudo in vitroPublication . Fidalgo-Pereira, Rita; Magalhães, Tiago; Torres, Orlanda; Carvalho, Óscar; Fernandes, Valter; Souza, Júlio C. M.
- A scoping review on the polymerization of resin-matrix cements used in restorative dentistryPublication . Fidalgo-Pereira, Rita; Torres, Orlanda; Carvalho, Óscar; Silva, Filipe S.; Catarino, Susana O.; Özcan, Mutlu; Souza, Júlio C. M.In dentistry, clinicians mainly use dual-cured or light-cured resin-matrix cements to achieve a proper polymerization of the organic matrix leading to enhanced physical properties of the cement. However, several parameters can affect the polymerization of resin-matrix cements. The main aim of the present study was to perform a scoping review on the degree of conversion (DC) of the organic matrix, the polymerization, and the light transmittance of different resin-matrix cements used in dentistry. A search was performed on PubMed using a combination of the following key terms: degree of conversion, resin cements, light transmittance, polymerization, light curing, and thickness. Articles in the English language published up to November 2022 were selected. The selected studies’ results demonstrated that restorative structures with a thickness higher than 1.5 mm decrease the light irradiance towards the resin-matrix cement. A decrease in light transmission provides a low energy absorption through the resin cement leading to a low DC percentage. On the other hand, the highest DC percentages, ranging between 55 and 75%, have been reported for dual-cured resin-matrix cements, although the polymerization mode and exposure time also influence the DC of monomers. Thus, the polymerization of resin-matrix cements can be optimized taking into account different parameters of light-curing, such as adequate light distance, irradiance, exposure time, equipment, and wavelength. Then, optimum physical properties are achieved that provide a long-term clinical performance of the cemented restorative materials.
- The impact of inorganic fillers, organic content, and polymerization mode on the degree of conversion of monomers in resin-matrix cements for restorative dentistry: a scoping reviewPublication . Santos, Marcionilia; Fidalgo-Pereira, Rita; Torres, Orlanda; Carvalho, Oscar; Henriques, Bruno; Özcan, Mutlu; Souza, Júlio C. M.PURPOSE: The main aim of the present study was to carry out a scoping review on the differences in degree of conversion of monomers regarding several types resin cements, indirect restorative materials, and light-curing procedures used in dentistry. METHOD: A bibliographic review was performed on PubMed using the following search items: "degree of conversion" OR "filler" AND "resin cement" OR "inorganic cement" AND "organic" OR "radiopacity" OR "refractive" OR "transmittance" OR "type" AND "resin composite." The search involved articles published in English language within the last thirteen years. A research question has been formulated following the PICO approach as follow: "How different is the degree of conversion of monomers comparing several types of resin-matrix cements?". RESULTS: Within the 15 selected studies, 8 studies reported a high degree of conversion (DC) of the organic matrix ranging from 70 up to 90% while 7 studies showed lower DC values. Dual-cured resin-matrix cements revealed the highest mean values of DC, flexural strength, and hardness when compared with light- and self-polymerized ones. DC mean values of resin-matrix cements light-cured through a ceramic veneer with 0.4 mm thickness were higher (~ 83%) than those recorded for resin-matrix cements light-cured through a thicker ceramic layer of 1.5 mm (~ 77%).CONCLUSIONS: The highest percentage of degree of conversion of monomers was reported for dual-cured resin-matrix cements and therefore both chemical and light-induced pathways promoted an enhanced polymerization of the material. Similar degree of conversion of the same resin-matrix cement were recorded when the prosthetic structure showed a low thickness. On thick prosthetic structures, translucent materials are required to allow the light transmission achieving the resin-matrix cement. CLINICAL RELEVANCE: The chemical composition of resin-matrix cements and the light-curing mode can affect the polymerization of the organic matrix. Thus, physical properties of the materials can vary leading to early clinical failures at restorative interfaces. Thus, the analysis of the polymerization pathways of resin-matrix cements is significantly beneficial for the clinical performance of the restorative interfaces.
- Transmitância ótica de resinas compostas na cimentação de restaurações indiretas - um estudo in vitroPublication . Fidalgo-Pereira, Rita; Fernandes, Valter; Carvalho, Óscar; Torres, Orlanda; Catarino, Susana O.; Souza, Julio C. M.