Fracture Resistance and Failure Mode of Custom-made Post-and-cores of Polyetheretherketone and Nano-ceramic Composite.

CLINICAL RELEVANCE: Custom-made post-and-cores of polyetheretherketone (PEEK) and nano-ceramic composite showed good fracture resistance and failure mode. Clinicians should be aware that these materials might be an efficient alternative for post-and-cores, because they promote esthetics while reducing the risk of root fractures. SUMMARY: Purpose: The purpose of this study was to evaluate the fracture resistance and failure mode of custom-made post-and-cores manufactured with different esthetic materials.Methods and Materials: A total of 48 mandibular premolar extracted teeth were selected, endodontically treated, and prepared to receive the posts. Specimens were randomly divided into four groups (n=12/group): group 1, polyetheretherketone (PEEK, Degos; G1); group 2, nano-ceramic composite (Lava Ultimate, 3M ESPE; G2); group 3, cast metal post (NiCr alloy, control; G3); group 4, fiberglass post (Whitepost, FGM, control; G4) customized with a nano-hybrid resin composite (Z250, 3M ESPE). Experimental post-and-cores (G1 and G2) were manufactured with a computer-aided design/computer-aided manufacturing system. All posts were cemented with self-adhesive resin cement (Rely X U200, 3M ESPE), and specimens were stored in distilled water at 37°C for 60 days. A universal testing machine was used to measure the fracture resistance (0.5 mm/min at an angle of 45° to the long axis of the tooth). Fractures were classified as repairable or catastrophic. One-way analysis of variance with Tukey post hoc and χ2 tests for independence and Bonferroni adjustments were applied (α=0.05).Results: The fracture resistance values (mean ± SD, in newtons) were 379.4 ± 119.8 (G1), 506.4 ± 138 (G2), 939.6 ± 146.5 (G3), and 449.6 ± 66.5 (G4). Only G3 exhibited a significant difference (p<0.05). The χ2 test showed an association between failure mode and post-and-core material [χ2(3) = 23.65; p<0.001]. After Bonferroni adjustment, only G3 presented a higher than expected incidence of catastrophic failures (p<0.001). In the remaining groups, most failures were repairable and related to debonding.Conclusions: Customized post-and-cores of PEEK and nano-ceramic composites exhibited good mechanical performance. Their fracture resistance was comparable to that observed for fiberglass customized posts, yet lower than that for cast metal posts. For PEEK post-and-cores, in particular, additional studies are needed to improve adhesiveness and reduce the risk of debonding.

Effect of Surface Sealants and Polishing Time on Composite Surface Roughness and Microhardness.

The objective of this study was to evaluate the effect of surface sealants and polishing delay time on a nanohybrid resin composite roughness and microhardness. Eighty disc specimens were made with a nanohybrid resin (Esthet-X HD, Dentsply). The specimens were divided into two groups (n=40) according to polishing time: immediate, after 10 minutes; delayed, after 48 hours. Each group was subdivided into four groups (n=10), according to the surface treatment: CG, control-rubber points (Jiffy Polishers, Ultradent); PP, rubber points + surface sealant (PermaSeal, Ultradent); PF, rubber points + surface sealant (Fortify, Bisco); PB, rubber points + surface sealant (BisCover, Bisco). Surface roughness (Ra) and microhardness (50 g/15 seconds) were measured. Surface morphology was analyzed by scanning electron microscopy and atomic force microscopy. The data were analyzed statistically using one-way analysis of variance and the Games-Howell post hoc test (α=0.05). PermaSeal roughness (G2) in the delayed polishing group was significantly higher ( p=0.00) than that of the other groups. No difference was observed among the groups between immediate and delayed polishing ( p=1.00), except for PermaSeal ( p=0.00). Moreover, PermaSeal showed the lowest microhardness values ( p=0.00) for immediate polishing. Microhardness was higher at delayed polishing for all the surface treatments ( p=0.00) except Fortify ( p=0.73). Surface smoothness similar to polishing with rubber points was achieved when surface sealants were used, except for PermaSeal surface sealant, which resulted in a less smooth resin composite surface. However, surface sealant application did not significantly improve composite resin microhardness.

Color Match Between Composite Resin and Tooth Remnant in Class IV Restorations: A Case Series.

Rehydration of the tooth remnant and complete polymerization of the composite resin are aspects that should be considered in shade selection of composite resin. This article presents a case series of Class IV restorations performed to evaluate the color match between the composite resin and the tooth remnant. Thirteen Class IV restorations were performed in maxillary central incisors and evaluated according to the period following the restorative procedure: 10 minutes (baseline), 48 hours before and after finishing and polishing, and seven, 14, and 28 days. The color match of the restorations was evaluated by the ΔE values of the tooth remnant (TR) and the composite resin (CR) in each evaluation period using a spectrophotometer. The translucency, luminosity, and saturation were analyzed qualitatively in digital photographs of the restorations. The CR ΔE was statistically similar to the TR ΔE at 14 and 28 days ( p>0.05). The saturation and luminosity of most of the restorations remained unchanged, but there was a greater change in the translucency. The color match of the composite resin in Class IV restorations was observed after 14 days of clinical assessment in this case series.

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.

All-ceramic post core, and crown: technique and case report.

UNLABELLED: The functional and esthetic restoration of severely compromised anterior teeth is a challenge to clinicians in their daily practice. The duplication of the optical characteristics of an intact tooth, including shade, translucency, and fluorescence, is often made difficult by the use of metal infrastructures, such as post-and-cores and copings. The development of reinforced ceramics and non-metallic post systems made possible the generation of metal-free ceramic restorations in severely compromised anterior and posterior teeth. This article discusses one available technique for the generation of a single all-ceramic restoration involving the use of a zirconia- or leucite-reinforced post-and-core system and of an all-ceramic crown system. A representative clinical case is presented illustrating the potential of the technique. CLINICAL SIGNIFICANCE: Modern ceramic restorative systems offer the possibility to closely match the natural optical characteristics of lost tooth structure. Posts, cores, and copings fabricated in ceramic materials represent a promising alternative to metals in the restoration of severely compromised anterior teeth.