Effect of surface treatment and resin cement type on the bond strength of polyetheretherketone to lithium disilicate ceramic.

BACKGROUND: This study aims to evaluate the effect of surface treatment and resin cement on the shear bond strength (SBS) and mode of failure of polyetheretherketone (PEEK) to lithium disilicate ceramic (LDC). This is suggested to study alternative veneering of PEEK frameworks with a ceramic material. METHODS: eighty discs were prepared from PEEK blank and from lithium disilicate ceramic. Samples were divided into four groups according to surface treatment: Group (A) air abraded with 110 µm Al2O3, Group (AP) air abrasion and primer application, Group (S) 98% sulfuric acid etching for 60 s, Group (SP) Sulfuric acid and primer. Each group was subdivided into two subgroups based on resin cement type used for bonding LDC:1) subgroup (L) self- adhesive resin cement and 2) subgroup (B) conventional resin cement (n = 10). Thermocycling was done for all samples. The bond strength was assessed using the shear bond strength test (SBS). Failure mode analysis was done at 50X magnification with a stereomicroscope. Samples were chosen from each group for scanning electron microscope (SEM). The three-way nested ANOVA followed by Tukey's post hoc test were used for statistical analysis of results. Comparisons of effects were done utilizing one way ANOVA and (p < 0.05). RESULTS: The highest mean of shear bond strength values was demonstrated in Group of air abrasion with primer application using conventional resin cement (APB) (12.21 ± 2.14 MPa). Sulfuric acid groups showed lower shear bond strength values and the majority failed in thermocycling especially when no primer was applied. The failure mode analysis showed that the predominant failure type was adhesive failure between cement and PEEK, while the remaining was mixed failure between cement and PEEK. CONCLUSION: The air abrasion followed by primer application and conventional resin cement used for bonding Lithium Disilicate to PEEK achieved the best bond strength. Primer application did not have an effect when self-adhesive resin cement was used in air-abraded groups. Priming step is mandatory whenever sulfuric acid etching surface treatment is utilized for PEEK.

Laser debonding of ultrathin occlusal veneers fabricated from different CAD/CAM ceramic materials.

BACKGROUND: Erbium lasers safely offer the possibility of reuse for debonded restorations. Since these lasers have a high affinity for water molecules, they are absorbed by resin cement causing explosive ablation of the cement and thus, the restoration debonds. The efficiency of this process depends on many factors, including the ceramic type, its chemical composition and thickness. Therefore, this study was designed to test the time taken to debond ultrathin occlusal veneers made of three types of milled ceramic materials and evaluate the integrity of these restorations after debonding. METHODS: Three ceramic types were evaluated in this study: lithium disilicate (IPS Emax CAD), highly condensed lithium disilicate (GC initial®LiSi), and translucent zirconia (Katana zirconia STML). Each group consisted of 8 occlusal veneers of 0.5 mm thickness. The samples were cemented to the occlusal surfaces of the upper molar teeth. An Er; Cr: YSGG laser was applied to the occlusal veneers using the scanning method, and time until debonding was calculated. The debonded samples were then inspected under a stereomicroscope for possible damage. Numerical data are presented as the mean with 95% confidence interval (CI), standard deviation (SD), minimum (min.) and maximum (max.) values. Normality and variance homogeneity assumptions were confirmed using Shapiro-Wilk's and Levene's tests, respectively. Data were normally distributed and were analyzed using one-way ANOVA followed by Tukey's post hoc test. The significance level was set at p < 0.05 for all tests. Statistical analysis was performed with R statistical analysis software version 4.3.2 for Windows (R Core Team (2023). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL https://www.R-project.org/). RESULTS: There was no significant difference in debonding time between the different materials (p = 0.995). The longest debonding time was found for Katana STML (87.52 ± 20.45) (seconds), followed by Emax (86.94 ± 20.63) (seconds), while the lowest value was found for LiSi initial (86.14 ± 25.16) (seconds). In terms of damage to the debonded veneers, The Emax and zirconia samples showed no damage. However, 40% of the LiSi samples fractured during debonding, and 20% exhibited cracks. Only 40% of the LiSi samples were sound after debonding. CONCLUSION: Er; Cr: YSGG laser can be used efficiently to remove ceramic occlusal veneers. However, its effect on LiSi restorations needs further research.

Strain gauge analysis and fracture resistance of implant-supported PEKK hybrid abutments restored with two crown materials: An in vitro study.

BACKGROUND: Polyetherketoneketone (PEKK) was recently introduced as an alternative to titanium and ceramic implant abutments due to its apparent ability to dissipate excessive strain around dental implants. However, the biomechanical behaviors of implant abutment crown systems may change depending on the crown and abutment material combinations used. OBJECTIVES: This study aimed to assess how the crown material affects strain generation and fracture resistance of PEKK hybrid abutment crowns. MATERIAL AND METHODS: Sixteen dummy implants (Ø 3.7 x 11 mm), simulating maxillary first premolars, were restored with 16 milled PEKK hybrid abutments and randomly categorized into two groups according to the crown material (n = 8): Group C, milled composite crowns cemented on PEKK hybrid abutments; and Group Z, ultra-translucent zirconia crowns cemented on PEKK hybrid abutments. Before thermocycling, a cyanoacrylate-base adhesive was used to position two strain gauges on buccal and lingual crestal bone surfaces, and a vertical load (100 N) was applied to the central fossa to record the strain generated. Then, all samples were thermocycled between 5°C and 55°C before being loaded to fracture on a universal testing machine. Modes of failure were observed under an optical microscope, and representative samples were examined using a scanning electron microscope. Independent t-tests were used for intergroup comparisons. The significance level was set at (p < 0.05) for all tests.. RESULTS: The results showed a significant difference between both groups. The zirconia group recorded significantly higher strain and fracture resistance values than the composite group (p < 0.001). There was a positive correlation between the strain developed in peri-implant crestal bone and fracture resistance of the abutment crown complex. CONCLUSIONS: Strains developed in both groups were within the acceptable clinical range. The crown material substantially impacted the strain and fracture of the PEKK hybrid abutment crown system.

The effect of Er, Cr:YSGG laser debonding on the bond strength of two ceramic materials to dentin.

OBJECTIVES: Evaluating the bond strength of two ceramic materials to dentin after Er,Cr:YSGG laser debonding. Would laser debonding affect the bond strength of ceramic to dentin? MATERIALS AND METHODS: Recently extracted human molars were ground to expose dentin. Forty square shaped samples were prepared from CAD/CAM ceramic blocks. Samples were divided into two groups according to the type of ceramic material; group E: Lithium disilicate and group T: Ultra-translucent Zirconia (n = 20) Each group was divided into two subgroups (n = 10) according to the laser debonding effect (subgroup B: bonded samples, subgroup R: re-bonded samples after laser debonding). Ceramic samples were bonded to dentin using dual cure self-adhesive resin cement. Laser debonding of ceramic samples of subgroups R using Er, Cr:YSGG laser, were then re-bonded again to dentin surface with same resin cement. The Shear bond strength test using Universal testing machine was done. The failure mode was analyzed. Two-way analysis of variance was used to compare the mean bond strength and re-bond strength of two materials. The significance level was set at P ≤ 0.05. RESULTS: Two-Way ANOVA showed that ceramic type had a significant effect on the re-bond strength to dentin. The predominant failure mode was adhesive. CONCLUSIONS: Laser debonding of Lithium disilicate and Ultra translucent Zirconia decreased the re-bond strength to dentin. Deterioration in re-bond strength for Lithium disilicate ceramics was more pronounced than for Ultra translucent Zirconia. Clinical Relevance Deterioration in the bond strength between ceramics & dentin after laser debonding still needs improvement to allow its clinical use.

Effect of combining different surface treatments on the surface characteristics of polyetheretherketone-based core materials and shear bond strength to a veneering composite resin.

STATEMENT OF PROBLEM: High-performance polyetheretherketone (PEEK) has been used in dentistry because of its excellent physical and chemical properties. However, its lack of translucency requires the use of a veneering composite resin for esthetic applications. Data on bonding a veneering composite resin to PEEK are still scarce. PURPOSE: The purpose of this in vitro study was to assess the effect of using and combining different surface treatments on the surface roughness and wettability of PEEK core materials and the shear bond strength (SBS) to a veneering composite resin. MATERIAL AND METHODS: Sixty square PEEK specimens were divided according to surface treatments into 6 groups: group N, no surface treatment; group A, airborne-particle abrasion; group L, ER:YAG laser treatment; group LA, laser treatment and airborne-particle abrasion; group P, plasma treatment; and group PA, plasma treatment and airborne-particle abrasion. Surface roughness (Ra) and wettability (contact angle θ) were measured followed by evaluation of the surface topography. After veneering, the SBS was measured. A 1-way analysis of variance (ANOVA) was used to assess all interactions with multiple pairwise comparisons (α=.05). RESULTS: The highest mean Ra values were obtained for the combination treatment groups (LA 2.94 ±0.1 and PA 2.7 ±0.1 µm) (P<.001). While the laser (1.3 ±0.1 µm) and plasma treatment (1.4 ±0.1 µm) groups had the lowest Ra values, LA and PA had the highest wetting of PEEK surfaces (LA 6.9 ±0.7 and PA 4.9 ±0.2 degrees) (P<.001). The highest mean SBS values were demonstrated on PEEK surfaces with combination treatments (LA 22 ±1.3 and PA 21.2 ±0.8 MPa) (P<.001). CONCLUSIONS: Combining airborne-particle abrasion with laser or plasma treatments increased the surface roughness and wettability of PEEK surfaces favorably compared with applying each of the 3 treatments individually. The combinations enhanced the bond strength of PEEK to the veneering composite resin.

Fracture Resistance of Different Designs of a Resin-Bonded Fixed Dental Prosthesis: An In Vitro Study.

PURPOSE: To evaluate the effect of three two-retainer designs of a resin-bonded fixed dental prosthesis (RBFDP) on fracture resistance. MATERIALS AND METHODS: A total of 21 three-unit, all-ceramic RBFPDs were fabricated to replace a missing maxillary lateral incisor. The prostheses were divided into three groups of 7 each: Group L (labial RBFPD); Group ML (modified labial RBFPD, fabricated the same as in Group L with additional preparation that included a shallow proximal groove at the pontic side); and Group P, an all-ceramic palatal RBFPD that acted as control. Preparations were done on the maxillary left central incisor and canine of a typodont model, and 21 epoxy resin models were duplicated for the three groups. The RBFPDs were designed using CAD software and constructed using the heat-pressed technique, after which the prostheses were bonded to their corresponding epoxy resin model according to the manufacturer's instructions. A fracture resistance test was performed on all specimens following aging. Data were analyzed using one-way ANOVA. RESULTS: The highest fracture load values were recorded in Group P (547.5 N), followed by Group ML (462.6 N) and then Group L (418.3 N). The difference among the three designs was not statistically significant (F = 2.5, P = 0.1). CONCLUSION: Both labial and modified labial RBFDPs could be a viable alternative treatment option for replacement of missing maxillary lateral incisors.

An in vitro evaluation of surface roughness, color stability and bacterial accumulation of lithium disilicate ceramic after prophylactic periodontal treatment / Avaliação in vitro da rugosidade superficial, estabilidade de cor e acúmulo bacteriano em cerâmica de dissilicato de lítio após tratamento de profilaxia periodontal

Objective: To evaluate the effect of scaling procedures using different ultrasonic tips on the surface roughness, color stability and bacterial accumulation of lithium disilicate ceramic. Material and Methods: Scaling procedure was carried out using ultrasonic scaler (Satalec, Acteon, North America) with stainless-steel tip (US), titanium tip (UT) and plastic tip (UP), on disc shaped lithium disilicate samples cemented into a cavity prepared onto the labial surface of freshly extracted bovine teeth (10 samples per group). The samples were stored in coffee solution in an incubator at 37°C for 12 days, which is equivalent to 1 year of coffee consumption. The surface roughness was measured before and after the scaling procedure using a profilometer and atomic force microscopy. The color parameters were measured before and after scaling and staining procedures using VITA Easyshade Advance 4.0 according to the CIE L*a*b* color order system. The samples were then incubated with Streptococcus mutans (S. mutans) suspension. After incubation, the plates with 30 to 300 typical colonies of S. mutans were counted in a colony counter and mean values of colony forming units were obtained (CFU/mL). Results:The titanium scaling tip showed a statistically significant higher mean values of change in surface roughness ΔRa and bacterial count than the plastic scaling tip. Color changes (ΔE) were not a statistically significant among the groups. The results showed a statistically significant positive (direct) correlation between surface roughness and color change (p = 0.012) and also between surface roughness and bacterial count (p = 0.00). Conclusion: Within the limitations of this study, titanium scaling instruments cause irreversible surface alterations of lithium disilcate ceramics which was in direct correlation to the color changes and bacterial accumulation; therefore, dentists should proceed with caution when scaling lithium disilicate surfaces. The findings of the current study may indicate the need for instruments or equipment that can remove plaque and calculus without causing surface damage (AU)

Introdução: Avaliar o efeito de procedimentos de raspagem com diferentes pontas de ultrassom na rugosidade superficial, estabilidade de cor e acúmulo bacteriano em cerâmica de dissilicato de lítio. Material e Métodos: O procedimento de raspagem foi realizado usando um aparelho de ultrassom (Satalec, Acteon, América do Norte) com ponta de aço inoxidável (US), ponta de titânio (UT) e ponta de plástico (UP), em amostras de dissilicato de lítio em forma de disco cimentadas em uma cavidade preparada na superfície vestibular de dentes bovinos recém-extraídos (10 amostras por grupo). As amostras foram armazenadas em solução de café em incubadora a 37 ° C por 12 dias, o que equivale a 1 ano de consumo de café. A rugosidade da superfície foi medida antes e após o procedimento de raspagem usando um perfilômetro e um microscópio de força atômica. Os parâmetros de cor foram medidos antes e depois dos procedimentos de raspagem e armazenagem no café usando VITA Easyshade Advance 4.0 de acordo com o sistema de ordem de cores CIE L*a*b*. As amostras foram incubadas com suspensão de Streptococcus mutans (S. mutans). Após a incubação, as placas com 30 a 300 colônias típicas de S. mutans foram contadas em contador de colônias e obtidos os valores médios das unidades formadoras de colônias (UFC / mL). Resultados: A ponta de titânio mostrou valores estatisticamente maiores de mudança na rugosidade da superfície ΔRa e contagem de bactérias do que a ponta de raspagem de plástico. A mudança de cor (ΔE) não foi estatisticamente significativa entre os grupos. Os resultados mostraram uma correlação positiva (direta) estatisticamente significativa entre rugosidade superficial e alteração de cor (p = 0,012) e também entre rugosidade superficial e contagem bacteriana (p = 0,00). Conclusão: Dentro das limitações deste estudo, os instrumentos de raspagem de titânio causam alterações irreversíveis na superfície das cerâmicas de dissilicato de lítio que estão em correlação direta com as mudanças de cor e o acúmulo de bactérias. Portanto, os dentistas devem proceder com cautela ao realizar raspagem em superfícies de dissilicato de lítio. Os resultados deste estudo podem indicar a necessidade de instrumentos ou equipamentos que possam remover a placa e cálculo sem causar danos à superfície. (AU)

Fracture Resistance of Anterior CAD/CAM Nanoceramic Resin Endocrowns with Different Preparation Designs / Resistência à Fratura de Endocrowns de Resina Nanocerâmica CAD / CAM Anterior Com Diferentes Projetos de Preparação

Objective: The aim of the study was to evaluate the effect of extension of endocrown in pulp space and the effect of ferrule on the fracture resistance of anterior endocrowns made of nano-ceramic resin blocks. Material and Methods: Twenty-eight freshly extracted human upper central incisor teeth were prepared to receive CAD/CAM nanoceramic resin endocrowns with four different designs. The specimens were divided into two groups (n = 14) according to the extension of the endocrown inside root canal (A:short and B:long), then each group was further subdivided into another two subgroups (n = 7) according to the presence or absence of ferrule effect (1:ferrule and 2: no ferrule). Endocrowns were then fabricated using CEREC in lab and nanoceramic resin blocks (DENTSPLY Sirona, Germany) and LAVA ultimate (3M ESPE, Germany) blocks size 14L. Results: Two-way ANOVA showed that the ferrule (p > 0.0001) had statistically significant effect on the fracture resistance. However, the extension of the endocrown into the canal had no statistical significant effect on the fracture resistance (p = 0.837). The interactions between the independent variables (extension into the canal and ferrule) had statistically significant effect on the fracture resistance (p = 0.029). Load to fracture for group 1A was 439.53 N, 1B was 306.46 N, 2A was 516.29 N and 2B was 242.04 N. Conclusions: Fracture resistance was not improved by the long or short extensions of the endocrowns in the pulp space, however, the ferrule effect shows significant improvement of the fracture resistance of the nanoceramic resin endocrowns. (AU)

Objetivo: O objetivo deste estudo foi avaliar o efeito da extensão da coroa endocrown na câmara pulpar e o efeito férula na resistência à fratura de coroas endocrowns anteriores confeccionadas através de blocos de resina nanocerâmica. Material e Métodos: Vinte e oito dentes incisivos centrais superiores humanos recém-extraídos foram preparados para receber endocrowns de resina nanocerâmica CAD / CAM com quatro diferentes tipos de preparos. Os espécimes foram divididos em dois grupos (n = 14) de acordo com a extensão da endocrown dentro do canal radicular (A: curto e B: longo), então cada grupo foi subdividido em outros dois subgrupos (n = 7) de acordo com presença ou ausência do efeito férula (1: com férula e 2: sem férula). As endocrowns foram usinadas através do CEREC In Lab e blocos de resina nanocerâmica (DENTSPLY Sirona, Alemanha) e blocos de LAVA ultimate (3M ESPE, Alemanha) tamanho 14L. Resultados: ANOVA dois fatores demostrou que a férula (P> 0,0001) teve efeito estatisticamente significativo na resistência à fratura. No entanto, a extensão do endocrown no canal não teve efeito estatisticamente significativo na resistência à fratura (P = 0,837). As interações entre as variáveis independentes (extensão no canal e férula) tiveram efeito estatisticamente significativo na resistência à fratura (P = 0,029). A carga para fratura do grupo 1A foi de 439,53 N, 1B foi de 306,46 N, 2A foi de 516,29 N e 2B foi de 242,04 N. Conclusões: A resistência à fratura não foi melhorada pelas extensões longas ou curtas das endocrowns na câmara pulpar, no entanto, o efeito férula mostrou uma melhora significativa na resistência à fratura das coroas endocrowns de resina nanocerâmica (AU)

Resin Nano-Ceramic Material Surface Roughness, Color Stability, and Bacterial Adhesion Evaluation After Different Scaling Methods / Rugosidade superficial, estabilidade de cor e adesão bacteriana de resina nano-cerâmica após diferentes métodos de raspagem

Objective: TThe study evaluated in vitro the changes in roughness, color stability, and bacterial count of a CAD/CAM Resin Nano-Ceramic material surface treated by various scaling procedures. Material and Methods: 70 disks (5mm diameter, 0.5 mm thickness) of Resin Nano-Ceramic (Lava ™Ultimate, 3M, ESPE) material were cemented in standardized cavities prepared in bovine teeth. A custom-made scaling apparatus of a double pan balance was used for different scaling methods, simulating standard clinical conditions. The specimens were assigned to three main groups: no scaling(C), ultrasonic scaling (U), and manual scaling (M). Each group was then divided into three subgroups according to scaling tip material; stainless steel tip (St), plastic tip (P), and titanium tip (Ti). The surface texture was analyzed quantitatively and qualitatively with a tactile profilometer and atomic force microscopy. A spectrophotometer was used for color measurement. Streptococcus mutans were counted in a colony counter. All the data were tabulated and statistically analyzed. Results: Two-way ANOVA was used to study the effect while One-way ANOVA was performed to compare between study groups. The significance level was set at p ≤ 0.05. The ultrasonic titanium tip(UTi) revealed the significant highest mean value of alterations (p < 0.001). The integrity of the material surface was altered in the form of deep scratches on the ultrasonically scaled surfaces and numerous smaller scratches on the hand-scaled surfaces. Conclusion: The plastic instrument would appear to be the instrument of choice during a routine maintenance procedure for Resin Nano-Ceramic materials (AU).

Objetivo: Este estudo avaliou in vitro as alterações na rugosidade, estabilidade de cor e quantidade de bactérias da superfície de uma resina nano-cerâmica produzida em CAD/CAM tratada por diferentes procedimentos de raspagem. Material e Métodos: 70 discos (5 mm diâmetro, 0,5 espessura) de resina nano-cerâmica (Lava ™Ultimate, 3M, ESPE) foram cimentadas em cavidades padronizadas preparadas em dentes bovinos. Um aparato customizado de raspagem com pratos duplos de balança foram usados para os diferentes métodos de raspagem, simulando uma condição clínica padronizada. Os espécimes foram distribuídos em três principais grupos: Sem raspagem (C), raspagem ultrassônica (U) e raspagem manual (M). Cada grupo foi dividido em três subgrupos de acordo com a ponta do material de raspagem; ponta de aço inoxidável (St), ponta plástica (P), ponta de titânio (Ti). A textura da superfície foi analisada qualitativamente e quantitativamente por um perfilômetro tátil e microscopia de força atômica. Um espectrofotometro foi usado para a mensuração da cor. Estreptococos mutans foram contados em um contador de colônias. Todos os dados foram tabulados e analisados estatisticamente. Resultados: Anova dois fatores foi utilizado para estudar os efeitos, enquanto ANOVA um fator foi utilizado para comparar os grupos experimentais. O nível de significância foi estabelecido em p≤ 0,05. A ponta de ultrassom de titânio (UTi) revelou o valor significante mais alto de alterações (p < 0,001). A integridade da superfície d matérias foi alterada na forma ranhuras profundas, nas superfícies raspada por ultrassom e numerosas ranhuras menores nas superfícies raspadas à mão. Conclusão: O instrumento plástico poderia apresentar-se como um instrumento de escolha durante o pocedimento de manutenção routineira para materiais de resina nano-ceramica. (AU)

Fracture load of nano-ceramic composite material for anterior endocrown restorations / Carga de fratura de material compósito nano-cerâmico para restaurações endocrown anteriores

Objective: to evaluate ability of Nano Ceramic Composite endocrown to withstand occlusal forces when used in the anterior region. Material and Methods: eighty endodontically treated maxillary central incisors teeth were randomly divided into two main groups according to the restoration type. Forty of these teeth were post, core and crown restorations and 40 were endocrown restorations. Then they were divided by halves into two subgroups according to the material used 20 were made with Lava Ultimate and the other 20 with IPS e.max. Each subgroup was then further subdivided into two divisions according to the remaining tooth structure above the CEJ (n = 10): 2 mm and 0.5 mm above the CEJ. After teeth preparation, the restorations were all made by CAD/CAM system (Cerec MCXL). All samples had undergone cyclic fatigue testing, and then loaded to fracture using a universal testing machine. The specimens were measured and statistically analyzed using Mann-Whitney test for comparing the mean changes between the groups. Results: Lava Ultimate showed higher mean fracture load values than IPS e.max specimens. Conclusions: endocrowns were found to be more favorable when used on endodontically treated teeth than the conventional post, core and crown restorations.(AU)

Objetivo: Avaliar a capacidade do compósito nanocerâmico endocrown para suportar forças oclusais quando usado na região anterior. Material e Métodos: Oitenta incisivos centrais superiores tratados endodonticamente foram divididos aleatoriamente em dois grupos principais, de acordo com o tipo de restauração. Quarenta desses dentes receberam restaurações com retentor intrarradicular, núcleo e coroa e 40 receberam restaurações endocrown. Em seguida, foram divididos pela metade em dois subgrupos, de acordo com o material utilizado, sendo 20 confeccionados com Lava Ultimate e os demais 20 com IPS e.max. Cada subgrupo foi posteriormente subdividido em dois, de acordo com a estrutura dentária remanescente acima da JEC (n = 10): 2 mm e 0,5 mm acima do JEC. Após o preparo dos dentes, todas as restaurações foram realizadas pelo sistema CAD/ CAM (Cerec MCXL). Todas as amostras foram submetidas a testes de fadiga cíclica e submetidas ao esforço até a fratura em uma máquina universal de testes. As amostras foram medidas e analisadas estatisticamente pelo teste de MannWhitney para comparação das alterações médias entre os grupos. Resultados: lava Ultimate apresentaram valores médios mais altos de carga até a fratura do que as amostras IPS e.max. Conclusões: as endocrowns mostraram-se mais favoráveis quando utilizadas em dentes tratados endodonticamente do que as restaurações convencionais com retentor intrarradicular, núcleo e coroa.(AU)

In vitro evaluation of marginal fit of zirconia-reinforced lithium silicate laminate veneers at two thicknesses using different CAD/CAM systems / Avaliação in vitro do ajuste marginal de folheados laminados de silicato de lítio reforçados com zircônia em duas espessuras usando diferentes sistemas CAD / CAM

Objective: The purpose of this in vitro study was to evaluate the marginal fit of laminate veneers made of zirconia-reinforced lithium silicate with two thicknesses using different CAD/CAM systems. Material and methods: 42 Laminate veneers milled from zirconia-reinforced lithium silicate were divided into three main groups according to milling machine used into: group X5, laminate veneers fabricated by inLab MCX5 milling machine; group CM, laminate veneers fabricated by Ceramill motion 2 milling machine; and group XL, laminate veneers fabricated by inLab MCXL milling machine. Each group was divided into two subgroups according to veneer thickness into: subgroup I, 0.5 mm thickness laminate veneers and subgroup II, 0.3 mm thickness laminate veneers. The marginal fit was measured using stereomicroscope. The results were tabulated and statistically analyzed using two-way ANOVA test followed by Tukey's post hoc test. Comparisons of main and simple effects were done utilizing Bonferroni correction. The significance level was set at (p ≤0.05) for all tests. Results: The mean( ± SD) highest marginal discrepancy was recorded in subgroup CMII at 85.45 ± 1.82 µm while the least mean marginal discrepancy was recorded in subgroup X5I (71.24 ± 2.64 µm). Conclusion: Both thicknesses(0.5 mm thickness and 0.3 mm thickness) and all tested CAD/CAM systems produced zirconia-reinforced lithium silicate laminate veneers with clinically acceptable marginal gaps; however, the closed CAD/CAM systems produced veneers with superior marginal fit than open systems at 0.3 mm thickness. The CAD/CAM system with the 5-axis milling machine produced the best marginal fit with 0.5 mm thickness. (AU)

Objetivo: O objetivo deste estudo in vitro foi avaliar a adaptação marginal de facetas laminadas de silicato de lítio reforçado com zircônia com duas espessuras, utilizando diferentes sistemas CAD / CAM. Material e métodos: 42 facetas laminadas fresadas a partir desilicato de lítio reforçado com zircônia foram divididos em três grupos principais de acordo com a fresadora usada em: grupo X5, facetas laminadas fabricados pela fresadora inLab MCX5; grupo CM, facetas laminadas fabricados por Ceramill motion 2; e grupo XL, facetas laminadas fabricados pelo inLab MCXL. Cada grupo foi dividido em dois subgrupos, de acordo com a espessura do laminado, em: subgrupo I, facetas laminadas com 0,5 mm de espessura e subgrupo II, facetas laminadas com espessura de 0,3 mm. A adaptação marginal foi medida usando estereomicroscópio. Os resultados foram tabulados e analisados estatisticamente usando o teste ANOVA de dois fatores seguido pelo teste post hoc de Tukey. Comparações dos efeitos principais e simples foram realizadas utilizando a correção de Bonferroni (P ≤ 0,05). Resultados: A maior discrepância marginal média ( ± DP) foi registrada no subgrupo CMII em 85,45 ± 1,82 µm, enquanto a menor discrepância marginal média foi registrada no subgrupo X5I 71,24 ± 2,64 µm. Conclusão: Ambas as espessuras (0,5 mm e 0,3 mm)e todos os sistemas CAD / CAM testados produziram facetas de laminado de silicato de lítio reforçadas com zircônia com lacunas clinicamente aceitáveis. No entanto, os sistemas CAD / CAM fechados produziam facetas com adaptação marginal superior aos sistemas abertos com 0,3 mm de espessura. O sistema CAD / CAM com a fresadora de 5 eixos produziu a melhor adaptação marginal com 0,5 mm de espessura (AU)

Effect of Different Immediate Implant Loading Protocols on Peri-implant Soft Tissue Health / Efeito de diferentes protocolos de implante com carga imediata no tecido mole peri-implantar

Objectives: This clinical study was conducted to evaluate the effect of immediate loading on peri-implant soft tissue health using three protocols: I) Immediate functional loading using polymer infiltrated ceramic (PIC) material (IFLV). II) Immediate functional loading using polymethyl methacrylate (PMMA) followed by delayed functional loading using PIC material (IFLP). III) Immediate non-functional loading using PMMA followed by delayed functional loading using PIC material (INFLP). Material & Methods: 30 Implants were placed in the upper premolar area and divided randomly according to the immediate loading protocol. In the control group (INFLP), CAD/CAM PMMA crowns were placed out of occlusion for 3 months, and then replaced by CAD/CAM VITA ENAMIC crowns in functional occlusion. For (IFLV) group, CAD/CAM VITA ENAMIC crowns were immediately loaded in functional occlusion; while in (IFLP) group, CAD/CAM PMMA crowns were placed in functional occlusion for 3 months, and then replaced by CAD/CAM VITA ENAMIC crowns. Modified pink esthetic score (MPES) and probing depth were used for evaluation of peri-implant soft tissue at base line and follow up periods. Results: INFLP showed higher MPES results compared to IFLV and IFLP. Moreover, the INFLP probing depth at 3 months showed higher results compared to the other groups. Conclusions: Immediate non-functional loading showed the best outcomes. However, peri-implant soft tissue health of the immediate functional loading using the PIC crown material was clinically acceptable (AU)

Objetivo: Este estudo clínico foi realizado para avaliar o efeito da carga imediata na saúde do tecido mole peri-implantar usando três protocolos: I) Carga imediata funcional usando material de cerâmica infiltrada com polímero (PIC) (IFLV). II) Carga imediata funcional usando polimetilmetacrilato(PMMA) seguida por carga funcional retardada usando material PIC (IFLP). III) Carga imediata não funcional usando PMMA seguida por carga funcional retardada usando material PIC (INFLP). Material e Métodos: 30 implantes foram colocados na área dos pré-molares superiores e divididos aleatoriamente de acordo com o protocolo de carga imediata. No grupo controle (INFLP), as coroas CAD / CAM PMMA foram colocadas sem oclusão por 3 meses, e então substituídas pelas coroas CAD / CAM VITA ENAMIC na oclusão funcional. Para o grupo (IFLV), as coroas CAD / CAM VITA ENAMIC foram carregadas imediatamente em oclusão funcional; enquanto no grupo (IFLP), as coroas CAD / CAM PMMA foram colocadas em oclusão funcional por 3 meses, e então substituídas por coroas CAD / CAM VITA ENAMIC. O escore da estética rosa modificado (PESM) e a profundidade de sondagem foram realizados para avaliação do tecido mole peri-implantar no início e nos períodos de acompanhamento. Resultados: INFLP apresentou resultados de PESM superiores em comparação com IFLV e IFLP. Além disso, a profundidade de sondagem INFLP em 3 meses apresentou resultados superiores em comparação com os outros grupos. Conclusões: A carga imediata não funcional apresentou os melhores resultados. No entanto, a integridade do tecido mole peri-implantar da carga imediata funcional usando o material da coroa PIC foi clinicamente aceitável. (AU)

Assessment of marginal adaptation and fracture resistance of endocrown restorations utilizing different machinable blocks subjected to thermomechanical aging.

OBJECTIVE: This in vitro study was conducted to assess the marginal adaptation and fracture resistance of computer aided design/computer aided manufacturer (CAD-CAM) fabricated endocrowns restoring endodontically treated molars using different machinable blocks with thermomechanical loading protocols. MATERIALS AND METHODS: Devitalized mandibular molars were prepared in a standardized way and divided into 4 groups (n = 10) to receive CAD/CAM fabricated endocrowns using four materials (Lithium disilicate ceramics, polymer infiltrated ceramics, zirconia-reinforced lithium silicate ceramics and resin nanoceramics. Marginal gaps (µm) were measured using stereomicroscope before cementation and after cementation. After thermomechanical aging, marginal gap measurements were repeated, and then fracture resistance test was performed. Two-way analysis of variance (ANOVA) and Tukey HSD multiple comparisons were used to assess the effect of material on the marginal gap before, after cementation, and after thermomechanical aging. One Way ANOVA was used to assess the effect of material on the fracture resistance. RESULTS: The difference between marginal gaps values of the tested materials was statistically insignificant but with significant increase after cementation and after thermomechanical aging. Cerasmart endocrowns showed the highest mean fracture load value (1508.5 ± 421.7N) with statistically significant difference than Vita Enamic endocrowns and Celtra Duo. CONCLUSION: The tested materials showed marginal vertical gap readings within the limits of clinically acceptable standards. Resin nanoceramics and lithium disilicate showed the highest values of fracture resistance followed by polymer infiltrated ceramics favoring their use for endocrown restorations. CLINICAL SIGNIFICANCE: The mechanical behavior of ceramic materials varies with the variation of their structure and mechanical properties. Accordingly, further investigation is always needed to explore the biomechanical behavior of recent materials when used as endocrowns before clinical trials.

Bond strength of resin cement to zirconia treated in pre-sintered stage.

PURPOSE: Aim of this study was to evaluate the tensile bond strength (TBS) between resin cement and zirconia surface treated in different sintering stages. MATERIALS AND METHODS: Eighty zirconia discs having final dimensions of 12 mm diameter and 3.2 mm thickness were milled then divided into three main groups according to the type of surface treatment performed (group 1: air abrasion using 50 µm Al2O3 particles, group 2: silica coating using Rocatec soft, and group 3: a control group receiving no surface treatment). Groups 1 and 2 were divided into two subgroups each according to the stage in which the surface treatment was performed (subgroup A; surface treatment performed in the pre-sintered stage and subgroup B; surface treatment performed in the post-sintered stage). Discs were later bonded to composite core materials using resin cement then tested for TBS either being subjected to 3 days of water storage or 150 days of water storage and 37,500 thermal cycles. RESULTS: Long-term aging caused a significant decrease in TBS of all subgroups except the subgroup air-abraded in the post-sintered stage. After long-term aging, the group silica coated in the pre-sintered stage showed the significantly lowest TBS compared to all other groups. There was also no significant difference between the subgroups air-abraded and silica coated in the pre-sintered stage. All specimens in the control group debonded during long-term aging. SIGNIFICANCE: Air-abrading zirconia with Al2O3 at a reduced pressure in the pre-sintered stage may result in durable bond strength to resin cement.

Fracture resistance and failure modes of polymer infiltrated ceramic endocrown restorations with variations in margin design and occlusal thickness.

PURPOSE: The purpose of this in vitro study was to assess the effect of varying the margin designs and the occlusal thicknesses on the fracture resistance and mode of failures of endodontically treated teeth restored with polymer infiltrated ceramic endocrown restorations. METHODS: Root canal treated mandibular molars were divided into four groups (n=8) and were prepared to receive Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) fabricated polymer infiltrated ceramic endocrowns (ENAMIC blocks). Group B2 represents teeth prepared with a butt joint design receiving endocrowns with 2mm occlusal thickness and the same for group B3.5 but with 3.5mm occlusal thickness. Group S2 represents teeth prepared with 1mm shoulder finish line receiving endocrowns with 2mm occlusal thickness and the same for group S3.5 but with 3.5mm occlusal thickness. After cementation and thermal aging, fracture resistance test was performed and failure modes were observed. RESULTS: Group S3.5 showed the highest mean fracture load value (1.27±0.31kN). Endocrowns with shoulder finish line had significantly higher mean fracture resistance values than endocrowns with butt margin (p<0.05). However, the results were not statistically significant regarding the restoration thickness. Evaluation of the fracture modes revealed no statistically significant difference between the modes of failure of tested groups. CONCLUSIONS: For the restoration of endodontically treated teeth, adding a short axial wall and shoulder finish line can increase the fracture resistance. However, further investigations, especially the fatigue behavior, are needed to ensure this effect applies with small increases of restoration thickness.

Evaluation of surface treatments of monolithic zirconia in different sintering stages.

PURPOSE: This study evaluated the effect of surface treatment of zirconia in pre-sintered and post-sintered stages on its surface roughness, phase transformation, and biaxial flexural strength (BFS). METHODS: Zirconia ceramic discs (n=40) having a final dimensions of 12mm diameter and 1.2mm thickness were milled then divided into three main groups according to the type of surface treatment performed (Group 1 (n=16); air-abrasion using Al2O3 particles, Group 2 (n=16); silica coating using Rocatec soft, and Group 3 (n=8); a control group receiving no surface treatment). Groups 1 and 2 were divided into two subgroups each according to the stage in which the surface treatment was performed (Subgroup A; surface treatment performed in the pre-sintered stage and subgroup B; surface treatment performed in the post-sintered stage). Surface roughness, phase transformation, and biaxial flexural strength (BFS) were later assessed. Data was then analyzed using two-way ANOVA and Tukey post-hoc tests at a significance level of p≤0.05. RESULTS: Subgroups treated in the pre-sintered stage showed higher mean Ra in µm (1.81±0.36) when compared to the subgroups treated in the post-sintered (0.68±0.07) stage and the control group (0.51±0.10) (p≤0.05). The pre-sintered treated group and the control showed no monoclinic phase while the post-sintered group showed significantly higher portions of monoclinic phase. Regarding BFS the post-sintered treated group had statistically significant higher values in MPa (1228±81) when compared to the pre-sintered treated group (940±101) and the control (1019±82) (p≤0.05). CONCLUSIONS: Air abrasion in the pre-sintered stage might be a promising surface treatment method to produce promising surface roughness values of zirconia without subjecting it to early degradation.