Influence of Adhesive Core Buildup Designs on the Resistance of Endodontically Treated Molars Restored With Lithium Disilicate CAD/CAM Crowns.

OBJECTIVE: To assess the influence of adhesive core buildup designs (4-mm buildup, 2-mm buildup, and no buildup/endocrown) on the fatigue resistance and failure mode of endodontically treated molar teeth restored with lithium disilicate computer-aided design/computer-aided manufacturing (CAD/CAM) complete crowns placed with self-adhesive cement. METHODS AND MATERIALS: Forty-five extracted molars were decoronated at the level of the cementoenamel junction and endodontically treated. Specimens received different Filtek Z100 adhesive core buildups (4-mm buildup; 2-mm buildup; and no buildup endocrown preparation) and were restored with Cerec 3 CAD/CAM lithium disilicate crowns (IPS e.max CAD). The intaglio surfaces of restorations (n=15) were conditioned by hydrofluoric acid etching and silane, and prepared teeth were treated with airborne-particle abrasion, followed by cementation with RelyX Unicem 2 Automix. Specimens were then subjected to cyclic isometric loading at 10 Hz, beginning 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. Specimens were loaded until failure or to a maximum of 185,000 cycles. The chewing cycle was simulated by an isometric contraction (load control) applied through a 10-mm in diameter composite resin sphere (Filtek Z100). Surviving specimens were axially loaded until failure or to a maximum load of 4500 N (crosshead speed 0.5 mm/min). The failure mode was assessed, and fractures were designated as catastrophic (tooth/root fracture that would require tooth extraction) or reparable (cohesive or cohesive/adhesive fracture of restoration only). Groups were compared using the life table survival analysis (log-rank test at p=0.05). Surviving specimens were loaded to failure and compared with one-way analysis of variance. RESULTS: The survival rates after the fatigue test were 100%, 93%, and 100% for 4-mm, 2-mm, and no buildup (endocrown), respectively and were not statistically different (only one specimen failed with a 2-mm buildup under a crown that cohesively fractured at 1,400 N). Postfatigue load to failure averaged 3181 N for 4-mm buildups (15 specimens), 3759 N for 2-mm buildups (12 specimens), and 3265 N for endocrowns (14 specimens). The 2-mm buildups were associated with higher loads to failure than endocrowns and 4-mm buildups, but no differences were found between 4-mm buildups and endocrowns (p<0.05.) One endocrown and 2 restorations with a 2-mm buildup survived the load-to-failure test (at 4500 N). Only catastrophic fractures occurred after the load-to-failure test. CONCLUSIONS: The buildup design influenced the performance of endodontically treated molars restored with lithium disilicate CAD/CAM complete crowns placed with self-adhesive resin cement. The 2-mm buildups were associated with higher loads to failure than the endocrown and the 4-mm buildup, but all restoration designs survived far beyond the normal range of masticatory forces.

Influence of no-ferrule and no-post buildup design on the fatigue resistance of endodontically treated molars restored with resin nanoceramic CAD/CAM crowns.

OBJECTIVES: To evaluate the influence of adhesive core buildup designs-4-mm buildup, 2-mm buildup, and no buildup (endocrown)-on the fatigue resistance and failure mode of endodontically treated molar teeth restored with resin nanoceramic (RNC) CAD/CAM complete crowns placed with self-adhesive resin cement. METHODS AND MATERIALS: Forty-five extracted molars were decoronated at the level of the cementoenamel junction, and the roots were endodontically treated. Specimens received different Filtek Z100 adhesive core buildups (4-mm buildup, 2-mm buildup, and no buildup, endocrown preparation) and were restored with Cerec 3 CAD/CAM RNC crowns (Lava Ultimate). Restorations (n=15) and prepared teeth were treated with airborne-particle abrasion, followed by cementation with RelyX Unicem 2 Automix. Specimens were then subjected to cyclic isometric loading at 10 Hz, beginning with a load of 200 N (for 5000 cycles), followed by stages of 400, 600, 800, 1000, 1200, and 1400 N at a maximum of 30,000 cycles each. Specimens were loaded until failure or to a maximum of 185,000 cycles (10-mm-diameter composite resin sphere antagonist). The failure mode was assessed: "catastrophic" (tooth/root fracture that would require tooth extraction), "possibly reparable" (cohesive/adhesive failure with fragment and minor damage, chip or crack, of underlying tooth structure), or "reparable" fracture (cohesive or cohesive/adhesive fracture of restoration only). Groups were compared using the life table survival analysis. Intact specimens were loaded to failure and compared with one-way analysis of variance. RESULTS: All specimens survived the fatigue test until the 800 N-step. The survival rates for 4-mm, 2-mm, and no buildup (endocrown) were 53%, 87%, and 87%, respectively, and were not statistically different even though crowns with 2-mm buildups only started to fail at 1200 N. Minor cohesive chips were detected in many samples despite having survived all 185,000 cycles. Postfatigue load-to-failure ranged from 2969 N with 4-mm buildup (eight specimens), 2794 N for 2-mm buildup (13 specimens), and 2606 N for endocrowns (13 specimens) and were also not statistically different. There were only two catastrophic failures during the fatigue test and small subgingival delamination fractures and cracks (only with 4-mm buildup). All specimens in the load-to-failure test exhibited nonrestorable catastrophic fractures. CONCLUSIONS: There was no influence of the buildup design on the performance of endodontically treated molars restored with RNC CAD/CAM complete crowns placed with self-adhesive cement. All restoration designs survived the normal range of masticatory forces. Failure mode tended to be more favorable with the 2-mm buildup or no buildup (endocrown).

Evaluation of an anatomic dual-laminate composite resin shade guide.

BACKGROUND: Color assessment in aesthetic dentistry is one of the most challenging steps for direct restorative treatment. Shade selection tools should be able to mimic closely the materials and layering technique used in the final restoration, hence the development of prefabricated anatomic dual-laminate shade guides. OBJECTIVE: This study aims to compare different shade selection techniques and determine the suitability of a prefabricated anatomic dual-laminate shade guide and its best mode of use compared to a conventional guide and a layered custom guide. MATERIALS AND METHODS: CIELab coordinates of different shade guides were assessed: Vitapan Classical (tab A2; Vita); Miris2 prefabricated anatomic dual-laminate shade guide, enamel WR tab on top of dentine S3 tab and nothing in-between (M2air) or glycerin gel (M2gly) or water (M2w); custom shade guide using prefabricated silicon moulds, Miris2 enamel WR composite resin moulded directly on dentine S3 pre-polymerised base (M2cus). The average values were obtained to calculate DE and compare the different shade selection techniques. Additional samples and measurements were made to compare Vitapan Classical shade tabs A1, A2 and A3 and all possible combinations of Miris2 and establish the closest matching shade (DE 3.3). RESULTS: High DE values were found (6.51­9.11) when comparing M2air to Vita, M2gly M2w M2cus. Differences appeared acceptable (DE 2.09­2.99) between Vita, M2gly and M2w and M2cus. Seven combinations of M2 were found to match Vita tab A1 and A2 and three Miris2 combinations for Vita A3 (DE 3.3). CONCLUSIONS: The use of Miris2 prefabricated anatomic dual-laminate shade guide with interposition of water or glycerin between the enamel­dentine tabs demonstrated acceptable DE values when compared to Vitapan Classical and custom guides. A chart for matching Vita shades with various combinations of Miris2 enamel/dentine shades was produced to assist the clinician in obtaining acceptable restorations. CLINICAL SIGNIFICANCE: The prefabricated anatomic dual-laminate shade guide is as efficient as a custom shade guide, facilitating clinical steps and saving material when doing compositeresin restorations.

Hypoplastic enamel treatment in permanent anterior teeth of a child.

In some patients with labial white stains involving the enamel and dentin, bleaching associated with a restorative procedure using composites may be an appropriate treatment alternative. Although bleaching makes the teeth and the stain whiter, the staining is less evident and easier to restore. Restorative procedures using adequate composites may then recover the natural optical properties while also providing appropriate mechanical properties, thereby ensuring the longevity of the treatment. In this article, the clinical case of a 9-year-old patient who reported dissatisfaction with her smile because of the presence of hypoplastic enamel staining at the central superior and inferior incisors is reported. The treatment consisted of a bleaching protocol followed by composite resin restorations using the stratification technique. The final esthetic result demonstrated the possibility of obtaining a natural smile with an adequate color and natural-looking restorations, thereby ensuring the esthetics and the patient's functional satisfaction.