Color Stability of Resin Hybrid Ceramic Materials in Comparison to Zirconia-Reinforced Lithium Silicate Ceramic.

Objectives: This in vitro study aimed to compare the effect of external staining agents (black tea and grape juice) on the color change of three hybrid ceramics including a new material in comparison to zirconia-reinforced lithium silicate. Materials and Methods: Ten samples of two hybrid dental ceramics including Vita Enamic (Vita Zahnfabrik) and Crystal Ultra (Digital Dental) in addition to a resin nanoceramic, Lava Ultimate (3M ESPE); and a zirconia-reinforced lithium silicate glass ceramic, Vita Suprinity (Vita Zahnfabrik) were prepared and immersed in black tea or grape juice for 30 days. A spectrophotometer was used to evaluate color change. All samples were carefully chosen in A3 shades or their equivalent. Two-way ANOVA and Bonferroni tests were used to analyze the color differences (ΔE00) among the materials and the staining solutions at a significant level of 0.05. Results: Significant color changes were observed in Vita Enamic and Lava Ultimate groups after immersion in both solutions (P<0.001). The least color changes (ΔE00) belonged to the Vita Suprinity (1.34) and Crystal Ultra (1.92) groups, respectively. Conclusion: The color changes of Vita Enamic and Lava Ultimate materials were beyond clinical acceptability. However, the mean color changes of Vita Suprinity and Crystal Ultra groups were clinically acceptable.

Evaluation of Microshear Bond Strength of Four Different CAD-CAM Polymer-Infiltrated Ceramic Materials after Thermocycling.

PURPOSE: To evaluate the bond strength of three monolithic hybrid ceramics/resin nanoceramics and a zirconia-reinforced lithium silicate to resin cement after thermocycling. MATERIALS AND METHODS: Using four materials, including Vita Enamic (VITA Zahnfabrik), Lava Ultimate (3M ESPE), Crystal Ultra (Digital Dental), and Vita Suprinity (VITA Zahnfabrik), 64 specimens were prepared with dimensions of 4 mm × 3 mm × 1.5 mm. Vita Suprinity samples were sintered at 840°C for 8 min. After polishing and cleaning all the samples in each group (n = 16), they were subjected to their recommended surface treatment: 10% hydrofluoric acid for Vita Enamic (60s) and Vita Suprinity (20s); air abrasion of Lava Ultimate and Crystal Ultra with 50 u Al2 O3 particles. Then, tygon tubes were filled with dual cure resin cement (Panavia F2.0), cured and then subjected to thermal cycling (2000 cycles; 5-55°C). The microshear bond strength was measured using microtensile testing machine. The data were analyzed using Welch and Games-Howell tests (α = 0.05). The mode of failure was also evaluated using a stereomicroscope. RESULTS: The highest and the lowest mean microshear bond strength belonged to the Crystal Ultra (7.71 ± 1.54 MPa) and Vita Suprinity (4.73 ± 1.87 MPa) groups, respectively. The differences between groups were significant and Crystal Ultra had higher bond strength in comparison to all three materials (p < 0.05). CONCLUSION: Hybrid ceramics showed higher bond strength to resin cements in comparison to resin nanoceramics and zirconia-reinforced lithium silicate materials.

The Role of Biomaterials and Biocompatible Materials in Implant-Supported Dental Prosthesis.

The dental implant is one of the appropriate instances of the different dental materials and their application, which is the combined procedure of technology and science in physics, biomechanics, and surface chemistry from macroscale to nanoscale surface engineering and manufactured technologies. In recent decades, biomaterials in implant therapy promote bone response and biomechanical ability, which is long-term from surgical equipment to final prosthetic restoration. Biomaterials have a crucial role in rehabilitating the damaged structure of the tooth and supplying acceptable outcomes correlated with clinical performance. There are some challenges in implantation such as bleeding, mobility, peri-implant infections, and the solution associated with modern strategies which are regarded to biomaterials. Various materials have been known as promising candidates for coatings of dental implants which contain polyhydroxyalkanoates, calcium phosphate, carbon, bisphosphonates, hydroxyapatite, bone stimulating factors, bioactive glass, bioactive ceramics, collagen, chitosan, metal and their alloys, fluoride, and titanium/titanium nitride. It is pivotal that biomaterials should be biodegradable; for example, polyhydroxyalkanoates are biodegradable; also, they do not have bad effects on tissues and cells. Despite this, biomaterials have important roles in prosthetic conditions such as dental pulp regeneration, the healing process, and antibacterial and anti-inflammatory effects. In this review study, the role of biocompatible materials in dental implants is investigated in in vitro and in vivo studies.

Comparison of dimensional accuracy of conventionally and digitally manufactured intracoronal restorations.

STATEMENT OF PROBLEM: Advances have been made in digital dentistry for the fabrication of dental prostheses, but evidence regarding the efficacy of digital techniques for the fabrication of intracoronal restorations is lacking. PURPOSE: The purpose of this in vitro study was to compare the dimensional accuracy of intracoronal restorations fabricated with digital and conventional techniques. MATERIAL AND METHODS: A sound mandibular molar tooth received a standard onlay preparation, and onlays were fabricated with 1 of 3 fabrication techniques. In group CC, the onlays were made after conventional impression and conventional fabrication of a resin pattern. In group CP, the onlays were made after conventional impression and 3-dimensional (3D) printing of the pattern. In group IP, the onlays were made after intraoral scanning, and 3D printing produced the resin pattern. Ten specimens in each group (N=30) were evaluated. Glass-ceramic restorations were fabricated using the press technique. The replica technique was used to assess the marginal fit. Each replica was assessed at 8 points. One-way ANOVA was used to compare the marginal discrepancy among the 3 groups. The Tukey honest significant differences test was applied for pairwise comparisons of the groups (α=.05). RESULTS: No significant differences were noted in the marginal discrepancy at the gingival margin among the 3 groups (P=.342), but significant differences were noted among the 3 groups in the pulpal (P=.025) and lingual (P=.031) areas. Comparison of the absolute discrepancy among the 3 groups revealed that only groups CC and CP were significantly different (P=.020) from each other. CONCLUSIONS: Within the limitations of this in vitro study, the conventional method yielded more accuracy than the 3D printing method, and no differences were found between the methods which used the 3D printer (groups CP and IP).

Effect of screw access hole preparation on fracture load of implant-supported zirconia-based crowns: an in vitro study.

Background. Fracture load of implant-supported restorations is an important factor in clinical success. This study evaluated the effect of two techniques for screw access hole preparation on the fracture load of cement-screw-retained implant-supported zirconia-based crowns. Methods. Thirty similar cement-screw-retained implant-supported zirconia-based maxillary central incisor crowns were evaluated in three groups of 10. Group NH: with no screw access holes for the control; Group HBS: with screw access holes prepared with a machine before zirconia sintering; Group HAS: with screw access holes prepared manually after zirconia sintering. In group HBS, the access holes were virtually designed and prepared by a computer-assisted design/computer-assisted manufacturing system. In group HAS, the access holes were manually prepared after zirconia sintering using a diamond bur. The dimensions of the screw access holes were equal in both groups. The crowns were cemented onto same-size abutments and were then subjected to thermocycling. The fracture load values of the crowns were measured using a universal testing machine. Data were analyzed with ANOVA and Tukey test (P < 0.05). Results. The mean fracture load value for the group NH was 888.37 ± 228.92 N, which was the highest among the groups, with a significant difference (P < 0.0001). The fracture load values were 610.48 ± 125.02 N and 496.74 ± 104.10 Nin the HBS and HAS groups, respectively, with no significant differences (P = 0.44). Conclusion. Both techniques used for preparation of screw access holes in implant-supported zirconia-based crowns decreased the fracture load.

Microleakage of Four Dental Cements in Metal Ceramic Restorations With Open Margins.

BACKGROUND: Fixed prosthodontics is a routine dental treatment and microleakage is a major cause of its failure. OBJECTIVES: The aim of this study was to assess the marginal microleakage of four cements in metal ceramic restorations with adapted and open margins. MATERIALS AND METHODS: Sixty sound human premolars were selected for this experimental study performed in Tehran, Iran and prepared for full-crown restorations. Wax patterns were formed leaving a 300 µm gap on one of the proximal margins. The crowns were cast and the samples were randomly divided into four groups based on the cement used. Copings were cemented using zinc phosphate cement (Fleck), Fuji Plus resin-modified glass ionomer, Panavia F2.0 resin cement, or G-Cem resin cement, according to the manufacturers' instructions. Samples were immersed in 2% methylene blue solution. After 24 hours, dye penetration was assessed under a stereomicroscope and analyzed using the respective software. Data were analyzed using ANOVA, paired t-tests, and Kruskal-Wallis, Wilcoxon, and Mann-Whitney tests. RESULTS: The least microleakage occurred in the Panavia F2.0 group (closed margin, 0.18 mm; open margin, 0.64 mm) and the maximum was observed in the Fleck group (closed margin, 1.92 mm; open margin, 3.32 mm). The Fleck group displayed significantly more microleakage compared to the Fuji Plus and Panavia F2.0 groups (P < 0.001) in both closed and open margins. In open margins, differences in microleakage between the Fuji Plus and G-Cem as well as between the G-Cem and Panavia F2.0 groups were significant (P < 0.001). In closed margins, only the G-Cem group displayed significantly more microleakage as compared to the Panavia F2.0 group (P < 0.05). Paired t-test results showed significantly more microleakage in open margins compared to closed margins, except in the Fuji Plus group (P = 0.539). CONCLUSIONS: Fuji Plus cement exhibited better sealing ability in closed and open margins compared to G-Cem and Fleck cements. When using G-Cem and Fleck cements for full metal ceramic restorations, clinicians should try to minimize marginal gaps in order to reduce restoration failure. In situations where there are doubts about perfect marginal adaptation, the use of Fuji Plus cement may be helpful.