Influence of Teeth Preparation Finishing on the Adaptation of Lithium Disilicate Crowns.

The polishing step of teeth preparations for crowns is a step often performed, so that there is an increased time during the clinical procedure. The aim of this study is to evaluate the marginal and internal adaptation of all-ceramic CAD/CAM lithium disilicate crowns in polished preparations for crown and nonpolished preparations for crowns. For this purpose, 20 first molars were selected, which were divided into two groups (n = 10) G1, teeth that received surface roughening similar to preparation without polishing, and G2 (control), polished preparations. After the preparations were completed the teeth were scanned (Cerec Bluecam, Sirona, Bensheim, Germany), and the crowns were designed and machined using CAD/CAM technology (Sirona, Bensheim, Germany). The adaptation of the pieces was evaluated using polyvinyl siloxane replicas and stereomicroscope photographs with 70x magnifications. The normality test indicated a nonnormal result, so a Man-Whitney nonparametric test was performed. One out of the 24 measured regions showed a statistically significant difference (p = 0.0494). With this study it can be concluded that crowns fabricated by CAD/CAM technology performed on unpolished preparations are not influenced by the internal marginal adaptation and the ceramic part and are different from polished preparations.

Fatigue resistance and crack propensity of large MOD composite resin restorations: direct versus CAD/CAM inlays.

OBJECTIVES: To assess the influence of material/technique selection (direct vs. CAD/CAM inlays) for large MOD composite adhesive restorations and its effect on the crack propensity and in vitro accelerated fatigue resistance. METHODS: A standardized MOD slot-type tooth preparation was applied to 32 extracted maxillary molars (5mm depth and 5mm bucco-palatal width) including immediately sealed dentin for the inlay group. Fifteen teeth were restored with direct composite resin restoration (Miris2) and 17 teeth received milled inlays using Paradigm MZ100 block in the CEREC machine. All inlays were adhesively luted with a light curing composite resin (Filtek Z100). Enamel shrinkage-induced cracks were tracked with photography and transillumination. Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 200 N (5000 cycles), followed by stages of 400, 600, 800, 1000, 1200 and 1400 N at a maximum of 30,000 cycles each. Samples were loaded until fracture or to a maximum of 185,000 cycles. RESULTS: Teeth restored with the direct technique fractured at an average load of 1213 N and two of them withstood all loading cycles (survival=13%); with inlays, the survival rate was 100%. Most failures with Miris2 occurred above the CEJ and were re-restorable (67%), but generated more shrinkage-induced cracks (47% of the specimen vs. 7% for inlays). SIGNIFICANCE: CAD/CAM MZ100 inlays increased the accelerated fatigue resistance and decreased the crack propensity of large MOD restorations when compared to direct restorations. While both restorative techniques yielded excellent fatigue results at physiological masticatory loads, CAD/CAM inlays seem more indicated for high-load patients.

Translucency of value resin composites used to replace enamel in stratified composite restoration techniques.

BACKGROUND: The translucency of enamel shade is a crucial property that affects the color of a layered restoration. OBJECTIVE: This study evaluated the translucency of high-, medium-, and low-value resin composites (4 Seasons, Ivoclar Vivadent, Schaan, Liechtenstein) used to replace enamel in stratified composite restoration techniques. MATERIALS AND METHODS: The color specimens with 12 mm in diameter and various thicknesses (0.5, 1.0, 1.5, 2.0, 3.0, 4.0 mm) were measured after polymerization on a reflection spectrophotometer over white and black backgrounds to calculate the translucency parameter (TP). The statistical analysis of TP was accomplished using two-way analysis of variance (p < 0.05). Significant differences were revealed by the Tukey's Honestly Significant Difference post hoc test. RESULTS: Translucency of the value composite resins was influenced by the value and thickness. Color of value resin composites was dependent on the background contrast at the evaluated thicknesses. CONCLUSIONS: High-value composite resins were more translucent than medium-value composites, which were more translucent than low-value composites. The translucency decreased as the thickness of the specimens increased. CLINICAL SIGNIFICANCE: The results suggest that special attention should be paid to the thickness of the increment of value composite resins when reproducing translucency of natural tooth enamel.

Fragment bonding of fractured anterior teeth: case report.

The unharmonious esthetic appearance of anterior teeth can be caused by changes in tooth color, shape, and size or by traumatic dental injury. Because the fragment bonding technique can restore functionality, morphology, and especially esthetics, it should be one of the choices in the restoration of fractured anterior teeth if the fragment is available. This article describes a clinical case of bonding of fractured anterior teeth and demonstrates how an esthetic appearance can be satisfactorily restored without wear to sound structure.

Chromatic influence of value resin composites.

The current study evaluated the chromatic influence of high, medium and low value composites on a dentin composite substrate (A2 shade) using spectrophotometric analysis. The specimens were divided into the following four groups: a) control (CG), entirely composed of dentin composite (n = 5); b) high value (GHV), dentin composite and high value composite (n = 20); c) medium value (GMV), dentin composite and medium value composite (n = 20) and d) low value (GLV), dentin composite and low value composite (n = 20). The dentin composite was 2.0 mm thick and the value composite was added in four different thicknesses, dividing the groups into four subgroups: S1 = 1.0 mm, S2 = 0.8 mm, S3 = 0.6 mm and S4 = 0.4 mm. The results were determined using the CIELAB system and differences in brightness of the specimens were analyzed using two-way ANOVA. Significant differences were found between different value resin composites, thicknesses and interactions, as revealed by the Tukey's test (HSD). Adding value composite produced lower brightness, and a gray shade was observed, compared to the control, regardless of the value or thickness of the primary composite. Eleven of the 12 subgroups presented clinically unacceptable chromatic changes, except when the 0.4 mm thickness of high value composite was used.

Composite resin reinforced with pre-tensioned glass fibers. Influence of prestressing on flexural properties.

OBJECTIVES: This investigation evaluated the flexural properties of two composite resins, and the influence of unidirectional glass fiber reinforcements, with and without pre-tensioning. METHODS: Two composite resins (Q: Quixfil and A: Adoro) were used to fabricate 2 mm x 2 mm x 25 mm beams (N = 10), reinforced with two fiber bundles along the long axis of the beam and pre-tensioned under a load equivalent to 73.5% of its tensile strength (groups QPF and APF). In two other experimental groups, the bundles were similarly positioned but without pre-tension (groups QF and AF). Two more groups were included without fiber reinforcement (control groups Q and A). After 24h storage, specimens were subjected to a three-point flexural bending test to establish the flexural module, the deflection at initial failure and the flexural strength. Data were analyzed using a two-way analysis of variance (composite resin system and fiber reinforcement type) and the Tukey HSD post hoc tests (alpha = .05). RESULTS: The results showed that prestressing increased the flexural module of Adoro specimens (p<.001) but not Quixfil (p = .17). Prestressed beams reached greater deflection at initial failure than those conventionally reinforced (p<.001), namely .85-1.35 mm for Adoro and .66-.90 mm for Quixfil. Prestressing also significantly increased the flexural strength of beams (p<.001) in both Adoro and Quixfil groups, from 443.46 to 569.15 MPa and from 425.47 to 568.00 MPa, respectively. SIGNIFICANCE: Pre-tensioning of unidirectional glass fibers increased both deflection until initial failure and flexural strength of Quixfil and Adoro composite resins, however, with limited effects on the flexural modulus.

Direct adhesive restoration of anterior teeth: Part 3. Procedural considerations.

Direct composite restorations represent a minimally invasive, aesthetic treatment option. The development of contemporary bonding procedures has allowed for improved aesthetics and restorative success. Incorporation of predictable adhesive protocols will increase the restoration's longevity and durability. This article presents the restorative procedures, adhesive protocol, and insertion considerations that must be addressed when using resin bonded options.

Direct adhesive restoration of anterior teeth. Part 1. Fundamentals of excellence.

Contemporary composite resin materials have significantly evolved, facilitating the delivery of aesthetic and functional restorations. The predictability of this treatment modality has been significantly improved by the introduction of adhesive protocols. This three-part series proposes a simplified protocol and the fundamentals for minimally invasive, aesthetic, direct adhesive restorations of anterior teeth. The first part of this series offers an overview of the state-of-the-art relating to composite restorations, both in situations deemed to be relatively uncomplicated and those that are more challenging.

Direct adhesive restoration of anterior teeth: Part 2. Clinical protocol.

Contemporary adhesive restorations allow clinicians to deliver minimally invasive, functional, and aesthetic treatment for compromised dentition in the anterior and posterior regions. Part 1 of this article discussed the state-of-the-art relating to composite restorations, both in situations deemed to be relatively uncomplicated and those that are more complicated. This second part discusses the clinical protocol for the placement of direct composite materials as well as the tooth preparation considerations that must be addressed when providing minimally invasive treatment options.

Tooth fragment reattachment: fundamentals of the technique and two case reports.

Coronal fractures must be approached in a methodical and clinically indicated way to achieve successful restoration. One option for treatment is reattachment of the dental fragment. Reattachment creates a very positive emotional response in the patient and simplifies the maintenance of the patient's original occlusion. This article discusses dental fragment reattachment techniques and presents clinical cases of coronal fracture involving enamel, dentin, and pulpal exposure.