Hybrid abutment during prosthetic planning and oral rehabilitation.

INTRODUCTION: The present study aims to describe through a literature review, the characteristics and properties of hybrid abutments, as well as their proper use as a new rehabilitation strategy. EVIDENCE ACQUISITION: A bibliographic search was conducted in the main health databases Pubmed (www.pubmed.gov) and Google Scholar (www.scholar.google.com.br), in which studies published from 2001 to 2020 were collected. Laboratory studies, case reports, systematic and literature reviews were included. Therefore, articles that do not address the characteristics and properties of hybrid abutments were excluded. In addition, studies that did not report the use of hybrid abutments as a new rehabilitation strategy. EVIDENCE SYNTHESIS: According to the inclusion and exclusion criteria, 80 research articles were selected and 20 were excluded, while 25 in vitro, 17 in vivo and 9 in silico studies were reviewed. CONCLUSIONS: The literature demonstrates that hybrid abutments are an excellent alternative in cases of implant-supported rehabilitation, presenting high esthetic results, associated with good soft tissue response, peri implant marginal bone stability and adequate stress distribution during the masticatory loads dissipation.

Influence of different post-endodontic restorations on the fatigue survival and biomechanical behavior of central incisors.

PURPOSE: To evaluate the influence of different post-endodontic techniques on the fatigue survival and biomechanical behavior of crowned restored central incisors. METHODS: The crowns of 69 bovine incisors were cut, and the roots were treated endodontically and assigned randomly into three groups (n=23): resin composite buildup (BUP), glass fiber post-retained resin composite buildup (GFP), and cast post-and-core (CPC). They received full crown preparation with 2 mm ferrule, and a leucite-reinforced ceramic crown was cemented adhesively. Three specimens from each group were tested monotonically. The remaining specimens were subjected to the stepwise stress fatigue test until fracture or suspension after 1.5 x 106 cycles in a chewing simulator. The load and step at which each specimen failed were analyzed by Kaplan-Meier and Mantel-Cox (log-rank test) statistics, followed by multiple pairwise comparisons, at 5% significance level. The three groups tested (BUP, GFP, and CPC) were 3D modeled (Rhinoceros 4.0) and the maximum principal stress (MPa) criteria were used to calculate the results using FEA. RESULTS: There was no statistical difference between the treatments regarding the load or the number of cycles (Mantel-Cox log-rank test for trend, X²= 0.015, df=1, P= 0.901, X²=3.171, df=1, P= 0.995). Crown cracks were the predominant failure mode, and oblique root fractures were only observed in groups GFP and CPC. In endodontically treated incisors with a 2-mm ferrule, the post-endodontic treatment had no significant effect on fatigue survival. Non-restorable fractures only occurred in teeth restored with posts. CLINICAL SIGNIFICANCE: Although the clinical significance of laboratory studies has some limitations, this study suggests that composite buildups without posts may be an option for restoring endodontically treated incisors with 2 mm ferrule height.

Durability of staining and glazing on a hybrid ceramics after the three-body wear.

Hybrid ceramic is a promising material for monolithic restorations that could require an individualization through the extrinsic staining to improve aesthetics. Due to the possibilities to treat this ceramic prior to staining, this study evaluated the wear resistance of surface treatments prior to staining and glazing a hybrid ceramic. Thirty-two specimens (Vita Enamic) were divided into 8 groups according to the surface treatment prior to the staining (Polishing: Pol, Acid etching: Ac, Sandblasting with Al2O3: Sd or Self-etching silane: Ses) and glaze application (with: gl or without: gl). The specimens were submitted to the ACTA wear machine simulating the presence of food bolus and antagonist. The wear rate of the stain was determined after 7 intervals of 20,000 cycles, using a profilometer. The surface before and after staining, and after wear were inspected using Scanning Electron Microscopy (SEM). The rates were analyzed using three-way ANOVA and Tukey test. The wear was affected by surface treatment, glaze application and number of cycles (p < 0.001). 100% of the staining was removed after 20,000 cycles for Pol, 40,000 for Pol + gl, 60,000 for Ses + gl, 80,000 for Ac, 100,000 for Sd and Ses, 120,000 for Ac + gl and 140,000 for Sd + gl. SEM showed similar worn surfaces. Sandblasting followed by glaze application was the most durable treatment to maintain the external staining on the hybrid ceramic surface when subjected to three-body wear.

Survival Probability, Weibull Characteristics, Stress Distribution, and Fractographic Analysis of Polymer-Infiltrated Ceramic Network Restorations Cemented on a Chairside Titanium Base: An In Vitro and In Silico Study.

Different techniques are available to manufacture polymer-infiltrated ceramic restorations cemented on a chairside titanium base. To compare the influence of these techniques in the mechanical response, 75 implant-supported crowns were divided in three groups: CME (crown cemented on a mesostructure), a two-piece prosthetic solution consisting of a crown and hybrid abutment; MC (monolithic crown), a one-piece prosthetic solution consisting of a crown; and MP (monolithic crown with perforation), a one-piece prosthetic solution consisting of a crown with a screw access hole. All specimens were stepwise fatigued (50 N in each 20,000 cycles until 1200 N and 350,000 cycles). The failed crowns were inspected under scanning electron microscopy. The finite element method was applied to analyze mechanical behavior under 300 N axial load. Log-Rank (p = 0.17) and Wilcoxon (p = 0.11) tests revealed similar survival probability at 300 and 900 N. Higher stress concentration was observed in the crowns' emergence profiles. The MP and CME techniques showed similar survival and can be applied to manufacture an implant-supported crown. In all groups, the stress concentration associated with fractographic analysis suggests that the region of the emergence profile should always be evaluated due to the high prevalence of failures in this area.

Three-body wear effect on different CAD/CAM ceramics staining durability.

Regardless the materials properties, the vast majority of ceramic restorations could require an individualization through the extrinsic staining to improve aesthetics. This study aimed to compare the staining wear durability of different monolithic ceramics. Specimens of high translucent zirconia (YZHT), zirconia reinforced lithium silicate (ZLS), hybrid ceramic (HC) and feldspathic ceramic (FLD) were divided in five groups according to each material staining technique. The ZLS ceramic was tested with stained prior (ZLS1) and after crystallization (ZLS2). All specimens were extrinsically characterized, i.e. stained, and crystallized or sintered in specific ovens, according to the manufacturer's recommendation. The specimens were submitted to three-body wear tests in ACTA wear machine, simulating the presence of food bolus and antagonist (pH 7, 15 N, 1 Hz). The wear rate of the stain surface was determined after 5 intervals of 200,000 cycles, using a profilometer. The ceramic surface before and after staining, and after wear were inspected by Scanning Electron Microscopy (SEM). The wear rates were analyzed using two-way ANOVA and post-hoc Tukey test. The wear rates of the staining were affected by ceramic and the number of cycles (P < 0.001). 100% of staining was removed after 200,000 cycles for HC, and after 600,000 cycles for YZHT and ZLS1. Staining of ZLS2 and FLD remained on ceramic surface even after 1,000,000 cycles. Furthermore, FLD showed a significant higher staining durability than ZLS2. SEM revealed different surface morphologies for each group with and without staining and after the wear test. Ceramics with fired staining showed higher durability compared to the polymerized one. The feldspar ceramic presented superior staining durability, followed by zirconia reinforced lithium silicate and high translucent zirconia. The conventional two steps staining technique showed improved durability for zirconia reinforced lithium silicate.

Effects of thickness, processing technique, and cooling rate protocol on the flexural strength of a bilayer ceramic system.

OBJECTIVE: To determine whether the thickness, processing technique, and cooling protocol of veneer ceramic influence the flexural strength of a bilayer ceramic system. MATERIALS AND METHODS: Sixty-four bar-shaped specimens (20mm×4mm×1mm) of yttria-stabilized tetragonal zirconia (Vita In-Ceram YZ, Vita) were fabricated (ISO 6872) and randomly divided into 8 groups (n=8) according to the factors "processing technique" (P - PM9 and V - VM9), "thickness" (1mm and 3mm), and "cooling protocol" (S - slow and F - fast). The veneer ceramics were applied only over one side of the bar-shaped specimens. All specimens were mechanically cycled (2×10(6) cycles, 84N, 3.4Hz, in water), with the veneer ceramic under tension. Then, the specimens were tested in 4-point bending (1mm/min, load 100kgf, in water), also with the veneer ceramic under tension, and the maximum load was recorded at first sign of fracture. The flexural strength (σ) was calculated, and the mode of failure was determined by stereomicroscopy (30×). The data (MPa) were analyzed statistically by 3-way ANOVA and Tukey's test (α=0.05). RESULTS: ANOVA revealed that the factor "thickness" (p=0.0001) was statistically significant, unlike the factors "processing technique" (p=0.6025) and "cooling protocol" (p=0.4199). The predominant mode of failure was cracking. SIGNIFICANCE: The thickness of the veneer ceramic has an influence on the mechanical strength of the bilayer ceramic system, regardless of processing technique and cooling protocol of the veneer ceramic.