Microstructural and flexural strength of various CAD-CAM lithium disilicate ceramics.

PURPOSE: To analyze the microstructural and mechanical properties of various commercial trademarks of lithium disilicate ceramics for CAD-CAM systems. MATERIALS AND METHODS: Specimens of different lithium disilicate ceramics were obtained and randomized into 5 groups (n = 14): EM: e.max CAD; RT: Rosetta SM; EV: Evolith; PM: Smile-Lithium CAD; and, HS: HaHaSmile. The microstructural analysis was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM); for flexural strength, the three-point bending flexure test was used. XRD and SEM data were qualitatively evaluated. Data from flexural strength were assessed with one-way ANOVA test (α = 0.05) and Weibull analysis. RESULTS: High peaks corresponding to the lithium metasilicate and lithium disilicate pattern with similar intensities were observed in all ceramics in the XRD analysis. SEM images showed similar patterns of crystalline structure in the EM and RT ceramics, while the other three groups presented different crystal morphologies than the previous ones and were similar to each other. No differences were found in flexural strength among the groups (p = 0.28). CONCLUSIONS: The CAD-CAM lithium disilicate ceramics showed comparable crystalline intensities. The microstructure of the EM and RT ceramics were different from the other groups. Flexural strength was similar among all ceramics.

Influence of different glaze firing protocols on the mechanical properties of CAD-CAM ceramic materials.

STATEMENT OF PROBLEM: The influence of different glaze firing protocols and cooling on the behavior of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics is unclear. PURPOSE: The purpose of this in vitro study was to investigate the influence of different glaze firing protocols on the abrasion resistance, surface roughness, microhardness, and brittleness index of CAD-CAM ceramics. MATERIAL AND METHODS: Rectangular specimens of IPS e.max CAD (MAX), IPS Empress CAD (PRE), and CEREC Blocs (CER) were obtained and divided into 5 groups according to the glaze firing protocol (n=8): control (CO), 1 conventional glaze firing (GF), 2 conventional glaze firings (GF2), 1 extended glaze firing (EG), and 2 extended glaze firings (EG2). The coefficient of friction (µ) was determined with the pin-on-disk test, and specimens were analyzed with an optical interferometer to calculate volume loss and roughness. Vickers microhardness and the brittleness index were obtained with a microdurometer. Microhardness data were evaluated by 2-way ANOVA and the Sidak tests (α=.05). Data from other tests were assessed with nonparametric ANOVA and Bonferroni tests (α=.05). RESULTS: Groups GF2, EG, and EG2 of MAX and PRE and all groups of CER presented higher levels of coefficient of friction. Groups EG and EG2 of MAX and CER showed high volume loss and surface roughness. Groups EG and EG2 of MAX and PRE showed lower hardness, as did all groups of CER. MAX-CO and groups GF and EG of PRE showed a lower brittleness index (P<.05), while CER groups showed no significant differences (P>.05). CONCLUSIONS: Ceramic specimens with conventional glaze firing presented less surface wear than those with extended glaze firing. The number of firings did not have a statistically significant influence.

Impact of Finishing Protocols on Color Stability of CAD/CAM Ceramics: A Systematic Review.

PURPOSE: To analyze the current evidence on the impact of surface finishing protocols (such as manual polishing or glazing) on the color stability of in vitro simulated pigmentation of CAD/CAM ceramics. MATERIALS AND METHODS: Five electronic databases were searched on February 12, 2020. In vitro experimental studies were included based on the following strategy: intervention = surface treatment of CAD/CAM ceramics with glazing agents; comparison = surface treatment of CAD/CAM ceramics with manual polishing; and outcomes = color stability. Two reviewers independently assessed the risk of bias. RESULTS: Among 1,390 articles that were screened, 6 in vitro studies were considered for qualitative analysis. Five articles confirmed changes in the color of ceramics when they were immersed in pigmented solutions. One article investigated the color stability of the samples via ultraviolet (UV) aging. Among the 6 studies analyzed, 4 showed clinically acceptable color alteration values represented by ΔE irrespective of the finishing protocol applied (glazing or mechanical polishing). Two articles presented clinically unsatisfactory color variation (ΔE > 3.3 and ΔE > 2.7) following mechanical polishing of a zirconia-reinforced lithium silicate ceramic. Coffee and red wine proved to be the beverages with the greatest potential for ceramic pigmentation. Only 1 article had a high risk of bias. CONCLUSION: For clinicians, most of the studies demonstrated that both manual polishing and glaze application can prevent significant color alterations on CAD/CAM ceramic surfaces. However, due to the relatively limited amount of evidence to support this conclusion, further studies must be conducted.

Effect of post-space irrigation with acid solutions on bond strength and dentin penetrability using a self-adhesive cementation system.

BACKGROUND: The aim of this study was to evaluate the effects of surface treatments with 1% peracetic acid (PA), solution containing 17% EDTA (SmearClear, Kerr Endodontics), solution containing a combination of 17% EDTA with 2% chlorhexidine (QMix, Dentsply Sirona) on the post-space root dentin compared to 2.5% sodium hypochlorite (NaOCl) on bond strength and resin tags length in dentin. MATERIAL AND METHODS: Forty human-canine roots were endodontically treated and the post space was prepared. The specimens were randomised into four groups (n = 10): control - irrigation with 2.5% NaOCl solution, PA - irrigation with 1% PA, SmearClear - irrigation with SmearClear solution, and QMix - irrigation with QMix solution. The fibre posts were cemented using a self-adhesive resin system (Relyx U200, 3M ESPE). After six months, the specimens were cross-sectioned and subjected to push-out and confocal laser microscopy tests. One-way ANOVA and Tukey's tests were used to analyse the data (α= 0.05). RESULTS: PA and QMix presented the highest bond strength values compared to the other groups (p< 0.05). There was no significant difference between the resin tags length in dentin by the groups (p = 0.75). CONCLUSIONS: Irrigation of the post space with 1% PA and QMix showed a positive clinical impact on the adhesion between the fiber post and root dentin. However, these materials had no influence on resin tags length in dentin by self-adhesive resin cement. Key words:Fiber post, adhesive cementation, self-adhesive resin cement, root dentin, irrigating solutions.

Temporary cement residues affect the bond strength and dentin penetration of self-adhesive resin cement in fiberglass post cementation.

This study evaluated the persistence of eugenol-containing (PR, Provy) or eugenol-free (RT, Relyx Temp, and TB, Temp Bond) temporary cement residues and its effects on push-out bond strength and dentinal penetration of the self-adhesive resin cement (Relyx U200). Eighty human roots were endodontically treated and post space prepared. Fourty specimens were distributed in four groups (n = 10): Control (CO), without any clinical procedure, PR, RT, and TB, where a metallic post was cemented with one of the temporary cements. After metallic post removal, hemi sections post space were submitted to SEM analysis. Another specimens were distributed in similar groups, but fiberglass post was cemented using Relyx U200 cement and submitted to push-out bond strength and dentinal penetration cement analysis, in post space thirds. SEM analysis were evaluated by Kruskal-Wallis and Dunn tests, while bond strength and dentinal penetration were evaluated by ANOVA One-Way and Tukey test (p < .05). Only in apical thirds, PR, RT, and TB showed higher persistence of residues than CO. In bond strength, PR, RT, and TB showed lower values than CO, in all post space thirds (p < .05). But to dentinal penetration, PR, RT, and TB presented lower values than CO only in apical thirds (p < .05). There is the greatest persistence of temporary cement residues only in apical post space third, providing less dentinal penetration of the self-adhesive resinous cement. However, the previous use of temporary cements has negative effects on the bond strength cementation system, regardless of the third evaluated.

Applicability of knowledge of graduates in dentistry: use of irreversible hydrocolloid / Aplicabilidad del conocimiento de licenciados en odontología: el uso de hidrocoloide irreversible

The objective of this study was to evaluate the knowledge applied by dental students on the procedures of disinfection, tempering and pouring of irreversible hydrocolloid impressions. This study was conducted through a questionnaire to 86 undergraduate students, of both genders, of the eighth and ninth period of the School of Dentistry, Pontifical Catholic University, Belo Horizonte, MG. The questionnaire contained 12 multiple choice questions about clinical and laboratory procedures for dental impression. Analyzed data were descriptively and qualitatively. Most subjects (70%) stated they did disinfection of dental impression with 1% sodium hypochlorite spray. However, they did it in open containers (75.4%) and with time control (68.6%). The ratio water / powder is randomly conducted by most students (60.5%), and tap water is the one most commonly used (95.3%). The mixing of the calcium sulfate is done manually by nearly all students (97.7%), and use vibrator during the pouring of the calcium sulfate is common among undergraduates (60.5%). The setting of the calcium sulfate takes place predominantly exposed to air (93%) and the removal of the model is made ??between 30 and 60 min after pouring by 84.9% of students. These results point to the need for awareness of students of adopting practices transmitted during the undergraduate degree. It is also necessary to investigate the possible causes of knowledge transmission problems and how to effectively adopt good clinical practices.

El objetivo fue evaluar el conocimiento aplicado por estudiantes de odontología en los procedimientos de desinfección, templado y vaciado de las impresiones de hidrocoloides irreversibles. Este estudio se llevó a cabo a través de un cuestionario a 86 estudiantes de pregrado, de ambos sexos, del octavo y noveno período de la Escuela de Odontología de la Pontificia Universidad Católica, Belo Horizonte, MG. El cuestionario contenía 12 preguntas de opción múltiple acerca de los procedimientos clínicos y de laboratorio para impresión dental. Los datos fueron analizados de manera descriptiva y cualitativa. La mayoría de los sujetos (70%) declararon que hicieron desinfección de la impresión dental con pulverización de hipoclorito de sodio al 1%. Sin embargo, lo hicieron en recipientes abiertos (75,4%) y con un control de tiempo (68,6%). La relación agua/polvo se realizó de manera aleatoria por la mayoría de los estudiantes (60,5%), utilizando principalmente agua del grifo (95,3%). La mezcla del sulfato de calcio se realiza manualmente por casi todos los estudiantes (97,7%) y el uso del vibrador durante el vertido del sulfato de calcio es común (60,5%). El ajuste del sulfato de calcio tiene lugar predominantemente en exposición al aire (93%), la remoción del modelo se hace entre 30 y 60 min después del vaciado por un 84,9% de los estudiantes. Estos resultados apuntan a la necesidad de que los estudiantes tomen conciencia de las prácticas transmitidas durante la licenciatura. También es necesario investigar las posibles causas de los problemas de transmisión de conocimiento y cómo aplicar efectivamente las buenas prácticas clínicas.

Nd:YAG Laser to obtain Irregularities on the Inner Surface of Porcelain.

AIM: The aim of this study was to evaluate the inner surface of two ceramic systems: IPS Empress II (Ivoclar Vivadent, Germany) and In-Ceram Alumina (Vita Zahnfabrick, Germany) submitted to surface treatments, especially by Nd:YAG laser. MATERIALS AND METHODS: Fifty samples were prepared in pellet form for each ceramic system according to manufacturers' specifications. The samples were stored at room temperature and then be subjected to surface treatment: without treatment (T0) (control), hydrofluoric acid-etched (T1), hydrofluoric acid-etched associated with the airborne particle-abraded (T2); CoJet system (T3), Nd:YAG laser (T4). The data were performed the statistical analysis by ANOVA and Tukey's test (p < 0.001). RESULTS: The group control (T0) of the ceramics, the analysis showed the lowest roughness values; for the System Alumina In-Ceram, treatment with hydrofluoric acid (T1), associated with hydrofluoric acid and airborne particle-abraded (T2) and Nd:YAG laser (T4), had no statistically significant difference, whereas for the IPS Empress System II treatment with hydrofluoric acid (T1) and hydrofluoric acid associated with airborne particle-abraded (T2), had no statistically significant difference between the system and also CoJet (T3) and hydrofluoric acid associated with the airborne particle-abraded (T2). Photomicrographs of scanning electron microscopy showed different characteristics to the treatments for each ceramic system. CONCLUSION: The IPS Empress II had the appearance of favoring the retention when treated with hydrofluoric acid, as well as its association with the airborne particle-abraded. Uncertainty in Alumina, treatment with hydrofluoric acid associated with the airborne particle-abraded and CoJet system and provided a surface with irregularities. With respect to the laser further studies should be performed for parameters that are ideal for your application. CLINICAL RELEVANCE: The ceramic restorations are attractive due of their excellent esthetics and the ability to stay for long periods. However, the retention of ceramic requires further study.

Marginal adaptation of class V restorations with current-generation dentin-bonding agents: effect of different dentin surface treatments.

This study sought to assess the use of chlorhexidine with several excipients as a dentin surface treatment and its effect on marginal adaptation of class V restorations with current-generation dentin bonding agents. A total of 120 human third molars were selected and allocated into 12 groups, with standardized buccal class V restorations randomly divided into preconditioned dentin rinsed with: water; water + chlorhexidine; ethanol; or ethanol + chlorhexidine. After rinsing of dentin (previously conditioned with 35% phosphoric acid) with the test solutions, the Adper single bond 2, prime and bond 2.1, and Excite bonding systems were applied randomly. Restorations were performed with Filtek™ Z350 XT composite resin. The resulting specimens were subjected to thermal and mechanical load cycling. Quantitative analysis of marginal adaptation was performed on epoxy replicas by means of scanning electron microscopy. Results were assessed by means of the Kruskal-Wallis test (percentages of continuous margins) and Wilcoxon test (differences between percentages of continuous margins before and after thermal cycling and mechanical loading), at a significance level of p < 0.05. Outcomes in the chlorhexidine-treated groups were not superior to those obtained with other treatments.

Influence of artificial aging in marginal adaptation of mixed class V cavities.

The aim of this study was to investigate whether the artificial aging by thermal cycling had influenced the marginal adaptation of class V restorations with/without chlorhexidine application in the bond process. Twelve intact human third molars were used. Class V cavity preparations were performed on the buccal surface and the teeth received 35% phosphoric acid-etching procedure (Ultradent Products Inc., South Jordan, Utah, USA). Subsequently, the samples were divided in two groups: Untreated acid-etched dentin and chlorhexidine application as an adjunct in the bond process. The adhesive Single Bond 2 (3M ESPE, St. Paul, MN, USA) was used after 2% chlorhexidine application, and the restorations were performed with Filtek™ Z350 XT (3M ESPE) composite resin. The specimens were submitted to artificial aging by thermal cycling with 3,000 cycles. Analyzes were performed on scanning electron microscopy using replicas of marginal adaptation in percentage of continuous margin before and after the artificial aging. The data were analyzed by paired test and the results showed statistically significant differences in the percentage of continuous margin with/without chlorhexidine treatment before and after thermal cycling. This study concluded that the artificial aging by thermal cycling influenced the marginal adaptation of mixed class V composite restorations.

Influence of filler charge on gloss of composite materials before and after in vitro toothbrushing.

OBJECTIVES: This study evaluated the gloss behaviour of experimental resin composites loaded with different filler percentages, immediately after polishing and after toothbrushing simulation. METHODS: Sixteen disc-shaped specimens were fabricated for each different-charged composite (40%, 50%, 60%, 70% and 75%) and polished with SiC abrasive papers. Gloss measurements were made prior to simulated toothbrushing. The specimens were subjected to the simulation for 5, 15, 30 and 60 min using an electrical toothbrush with a standardized pressure while being immersed in a toothpaste/artificial saliva slurry. RESULTS: Baseline composite gloss values ranged from 69.7 (40%) to 81.3 (75%) GU (gloss units) and from 18.1 (40%) to 32.3 (75%) GU after 1h of brushing. Highest gloss values were obtained by 75%-charged resin, while the lowest values were obtained by the 40%-charged one. CONCLUSIONS: All tested materials showed a gloss decrease. However, the higher filler load a composite resin has, the higher gloss it can achieve. CLINICAL SIGNIFICANCE: Gloss of resin composite materials is an important factor in determining aesthetic success of anterior restorations, and this property may vary according to the filler charge of the restorative material. Higher filler load of a composite resin results in higher gloss values.

Long-term surface hardness and monomer conversion of a nanoflled and a microhybrid composite resin.

OBJECTIVE: This study aims to evaluate the degree of conversion (DC) and hydrolytic degradation through the Vickers hardness test (HV) of a nanoflled (Filtek(TM) Z-250, 3M) and a microhybrid (Filtek(TM)Supreme-XT, 3M) composite resin. MATERIALS AND METHODS: Eight disk-shaped specimens (4 mm diameter × 2 mm thick, ISO 4049) of each material were prepared for each test. Composites were inserted into single increment in a metallic matrix and light-cured for 40 seconds. VH readings were performed for each specimen at predetermined intervals: immediately after polymerization (control), 1, 2, 3, 7, 14, 21, 30 and 180 days. After curing, initial hardness measurements were performed and the specimens were immersed in artifcial saliva at 37°C. For DC (%), specimens were ground, pressed with KBr and analyzed by FT-IR spectrophotometer. RESULTS: Student t-test showed that there was no difference between the resins for DC (p = 0.252). ANOVA analysis revealed that Z-250 VH means were all greater than S-XT, for both top and bottom surfaces, whatever the storage-period in artifcial saliva (p < 0.001). After 180 days of storage, the hardness obtained for S-XT was similar with that at the baseline, for both top and bottom surfaces. While for Z-250 hardness was not signifcantly different from baseline only for top surface, but there was a signifcant decrease observed in hardness for bottom surface. CONCLUSION: The materials tested showed no evidence of hydrolytic degradation in a signifcant way, in a 6-month storage-time in artifcial saliva. Nanoflled resin presents a monomer conversion comparable to the conventional microhybrid.

Using the self-etch adhesives in anterior restoration.

With the arrival of self-etch adhesives systems, there has been a rise in interest among clinicians, making it imperative for health professionals to have knowledge of the properties, characteristics, the association as well as the dental structures of these materials, in order to select them and use them correctly. The self-etch adhesive systems show good values of bond strength, microleakage and performance, and have therefore become an option in direct adhesive restorations. In the regard, this case study aims to describe the technique involving the use of selfetch adhesives system for direct restoration of anterior teeth.

Persistence of endodontic methacrylate-based cement residues on dentin adhesive surface treated with different chemical removal protocols.

The aim of this study was to evaluate the persistence of methacrylate-based cement residues on the dentin, after dentin surface cleaning with ethanol or acetone, with or without previous application of a dentin adhesive. Forty bovine crown fragments were obtained and the dentin surface was washed with 1.0 mL of 2.5% sodium hypochlorite (NaOCl), followed by 0.1 mL of 17% ethylenediaminetetraacetic acid application for 3 min, and final irrigation with 2.5% NaOCl. The specimens were air dried and resin-based cement was rubbed onto the dentine surface with a microbrush applicator. In 20 specimens, previously to cement, a dentin adhesive was applied in all surfaces. After 15 min, the surface was scrubbed with a cotton pellet and moistened with ethanol or acetone, compounding the following groups: G1-99.5% ethanol and G2-acetone, without previous use of dentin adhesive; G3-99.5% ethanol and G4-acetone, with previous use of dentin adhesive. The dentin surface was scrubbed until the cement residues could not be visually detected. Sections were then processed for scanning electron microscopy and evaluated at 500× magnification and scores were attributed to each image according to the area covered by residual sealer, and data were subjected to Kruskal-Wallis at 5% significance. The lower residue presence was observed in G3 (P = 0.005). All surface presented cement residues when acetone was used as cleaning solution (P = 0.0005). The cleaning solutions were unable to completely remove the cement residues from both surfaces. The ethanol used after previous application of the dentin adhesive promoted the lower presence of residues.

Fracture strength of incisor crowns after intracoronal bleaching with sodium percarbonate.

OBJECTIVES: To compare the fracture resistance of bovine teeth after intracoronal bleaching with sodium percarbonate (SPC) or sodium perborate (SP) mixed with water or 20% hydrogen peroxide (HP). MATERIALS AND METHODS: Fifty extracted bovine teeth were divided into four experimental groups (G1-G4) and one control (n = 10) after endodontic treatment. Following root canal obturation, a glass ionomer barrier was placed at the cemento-enamel junction. After that, the pulp chambers were filled with: G1 - SP with water; G2 - SP with 20% HP; G3 - SPC with water; and G4 - SPC with 20% HP. No bleaching agent was used in the control group. Coronal access cavities were sealed with glass ionomer and specimens were immersed in artificial saliva. The bleaching agents were replaced after 7 days, and teeth were kept in artificial saliva for an additional 7 days, after which the pastes were removed and the coronal access cavities were restored with glass ionomer. Crowns were subjected to compressive load at a cross head speed of 0.5 mm min(-1) applied at 135° to the long axis of the root by an EMIC DL2000 testing machine, until coronal fracture. Data were statistically analysed by anova and Tukey test. RESULTS: No differences in fracture resistance were observed between the experimental groups (P > 0.05). However, all experimental groups presented lower fracture resistance than the control group (P < 0.05). CONCLUSION: SPC and SP led to equal reduction on fracture resistance of dental crowns, regardless of being mixed with water or 20% HP.

Multidisciplinary approach of a crown-root fracture using intentional replantation: a case report.

Crown-root fractures are complex traumatic injuries that require multidisciplinary management and afford uncertain prognosis. The purpose of this clinical article was to report the case of crown-root fracture where a multidisciplinary approach was successfully executed. A 10-year-old male patient who suffered a complicated crown-root fracture on a permanent maxillary central incisor was treated using an intentional 180°-rotation replantation technique, followed by endodontic therapy and restoration with resin composite. Two years after the initial treatment, the case was stable and the tooth was restored with a resin core and a ceramic crown. This article describes how adequate multidisciplinary treatment planning, coordination, and execution are necessary for similar cases to be properly managed. It can be concluded that the intentional replantation with 180°-rotation allowed a more conservative approach, showing, in this case, a clinical success without resorption.

Analysis of the internal anatomy of maxillary first molars by using different methods.

The success of endodontic treatment depends on the identification of all root canals so that they can be cleaned, shaped, and obturated. This study investigated internal morphology of maxillary first molars by 3 different methods: ex vivo, clinical, and cone beam computed tomography (CBCT) analysis. In all these different methods, the number of additional root canals and their locations, the number of foramina, and the frequency of canals that could or could not be negotiated were recorded. In the ex vivo study, 140 extracted maxillary first molars were evaluated. After canals were accessed and detected by using an operating microscope, the teeth with significant anatomic variances were cleared. In the clinical analysis, the records of 291 patients who had undergone endodontic treatment in a dental school during a 2-year period were used. In the CBCT analysis, 54 maxillary first molars were evaluated. The ex vivo assessment results showed a fourth canal frequency in 67.14% of the teeth, besides a tooth with 7 root canals (0.72%). Additional root canals were located in the mesiobuccal root in 92.85% of the teeth (17.35% could not be negotiated), and when they were present, 65.30% exhibited 1 foramen. Clinical assessment showed that 53.26%, 0.35%, and 0.35% of the teeth exhibited 4, 5, and 6 root canals, respectively. Additional root canals were located in this assessment in mesiobuccal root in 95.63% (27.50% could not be negotiated), and when they were present, 59.38% exhibited 1 foramen. CBCT results showed 2, 4, and 5 root canals in 1.85%, 37.05%, and 1.85% of the teeth, respectively. When present, additional canals showed 1 foramen in 90.90% of the teeth studied. This study demonstrated that operating microscope and CBCT have been important for locating and identifying root canals, and CBCT can be used as a good method for initial identification of maxillary first molar internal morphology.