Marginal adaptation, fracture load and macroscopic failure mode of adhesively luted PMMA-based CAD/CAM inlays

Color Appearance of Various Provisional Restorative Materials for Rehabilitation Upon Aging

OBJECTIVES

 Color stability of provisional restoration is crucial for full mouth reconstruction, which is probably influenced by aging. Therefore, this study evaluated the effect of aging on the color appearance of different provisional materials.

MATERIALS AND METHODS

 Rectangular specimens (10 × 10 × 2 mm) were fabricated from computer-aided design-computer-aided manufacturing (CAD-CAM) (Vita CAD-Temp [VC], TelioCAD [TC], artBloc [RC]), autopolymerized (ProtempIV [PA], Luxatemp [LA], UnifastTrad [UA]), and heat-polymerized polymer (Major C&B [MH]). Each was divided into aging (AG, 5,000 thermocycles of 5°/55°C) and non-aging group (n = 21/group). Color parameters were determined using a spectrophotometer through the CIELAB system. The L*, a*, and b* data were calculated for color appearance (∆E), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) for each.

STATISTICAL ANALYSIS

 An analysis of variance and multiple comparisons were determined for a significant difference in color appearance alteration of materials upon aging (α = 0.05).

RESULTS

 Statistically significant differences of L*, a*, b*, ∆E, TP, CR, and OP due to the effect of types of material (p < 0.05), aging effect (p < 0.05), and their interactions (p < 0.05) were indicated. Aging affects the color appearance, lightness, chromaticity, translucency, contrast, and opalescence of various types of provisional materials. Color appearance alteration of provisional materials was significantly indicated upon aging (p < 0.05) but within the perceivable limit of clinical acceptance (∆E diff < 3.0), except for PA and MH. Color stability of CAD-CAM-based poly-methyl methacrylate (PMMA) and autopolymerized PMMA upon aging were better than bis-acryl resin and heat-polymerized PMMA. The TP, CR, and OP alterations of tested materials upon aging were within the perceivable limit.

CONCLUSION

 Color appearance of provisional restorative materials was influenced by aging. The CAD-CAM-based PMMA and autopolymerized PMMA materials showed better color stability than bis-acryl provisional resin and heat-polymerized PMMA upon aging. Therefore, they were suggested as provisional materials for oral rehabilitation.

Effectiveness of Self-Adhesive Resin Luting Cement in CAD-CAM Blocks-A Systematic Review and Meta-Analysis

Self-adhesive resin cements (SARCs) are used because of their mechanical properties, ease of cementation protocols, and lack of requirements for acid conditioning or adhesive systems. SARCs are generally dual-cured, photoactivated, and self-cured, with a slight increase in acidic pH, allowing self-adhesiveness and increasing resistance to hydrolysis. This systematic review assessed the adhesive strength of SARC systems luted to different substrates and computer-aided design and manufacturing (CAD/CAM) ceramic blocks. The PubMed/MedLine and Science Direct databases were searched using the Boolean formula [((dental or tooth) AND (self-adhesive) AND (luting or cement) AND CAD-CAM) NOT (endodontics or implants)]. Of the 199 articles obtained, 31 were selected for the quality assessment. Lava Ultimate (resin matrix filled with nanoceramic) and Vita Enamic (polymer-infiltrated ceramic) blocks were the most tested. Rely X Unicem 2 was the most tested resin cement, followed by Rely X Unicem > Ultimate > U200, and μTBS was the test most used. The meta-analysis confirmed the substrate-dependent adhesive strength of SARCs, with significant differences between them and between SARCs and conventional resin-based adhesive cement (α < 0.05). SARCs are promising. However, one must be aware of the differences in the adhesive strengths. An appropriate combination of materials must be considered to improve the durability and stability of restorations.

Pressable lithium disilicate ceramic versus CAD/CAM resin composite restorations in patients with moderate to severe tooth wear: Clinical observations up to 13 years

OBJECTIVE

To report the long-term clinical survival and failure rates of single-tooth restorations made of pressable lithium disilicate ceramics (LS₂ ) and CAD/CAM resin composite (RC) by two separate clinical observations.

MATERIALS AND METHODS

Twenty-one patients (12 female, nine male) were treated with 436 minimally invasive single-tooth restorations made of 274 pressed LS₂ (n = 12; posterior: monolithic IPS e.max Press; anterior: IPS e.max Ceram veneered, Ivoclar) or 162 milled from RC (n = 9; monolithic exp. CAD/CAM resin composite, Ivoclar). The mean age of patients was 44.1 ± 9.3 years and the mean observation time was 86.2 ± 13.5 months (7.7 ± 1.1 years), with 8.5 ± 2.7 years for LS2 and 6.7 ± 0.5 years for RC. All restorations were observed for technical/biological failures using the modified criteria of the United States Public Health Service (USPHS). Collected data were analyzed using Kaplan-Meier survival analysis and log-rank test (α < 0.025).

RESULTS

The 274 LS₂ restorations showed a survival of 100% and a total failure rate of 5.5%. The 162 RC restorations showed a survival of 100% and a total failure rate of 25.3%. RC restorations exhibited more material fractures (p = 0.020) and higher discoloration rates (p < 0.001).

CONCLUSIONS

Pressed LS₂ single-tooth restorations showed lower long-term failure rates than restorations made of RC.

CLINICAL SIGNIFICANCE

Despite the limitations of the clinical observations, single-tooth restorations of both materials can be recommended for permanent use in patients with severe tooth wear.

Flexural Strength of Various Provisional Restorative Materials for Rehabilitation After Aging

PURPOSE

Durability of provisional restoration is crucial for full-mouth reconstruction, which may be influenced by aging. This study evaluated the effect of aging on the flexural strength of provisional materials for oral rehabilitation.

MATERIALS AND METHODS

Bar specimens (2×2×25 mm) were fabricated from CAD-CAM [Vita CAD-Temp^® (VC), Telio^® CAD (TC), artBloc^® (RC)], autopolymerized [Protemp™IV (PA), Luxatemp^® (LA), Unifast™Trad (UA)], and heat-polymerized polymer [Major^® C & B; (MH)]. Each was divided into aging (AG, 5000 thermocycles of 5°/55°C) and nonaging groups (NG, n = 15/group). Flexural strength (σ, MPa) was determined in a universal testing machine at 1 mm/min crosshead speed. An analysis of variance and multiple comparisons were determined for significant difference (α = 0.05).

RESULTS

TCNG indicated the highest mean of σ (133.49 ±4.32), whereas VCNG indicated the lowest mean of σ (84.62 ±3.73) for nonaging. Upon aging process, TCAG revealed the highest mean of σ (123.11 ±4.55), while VCAG possessed the lowest mean of σ (84.05 ±6.39). Significant differences among various provisional materials were indicated (p = 0.001). Aging significantly affected flexural strength (p = 0.001).

CONCLUSIONS

The CAD-CAM provisional material possessed higher flexural strength than heat-polymerized PMMA and autopolymerized PMMA, which was suggested as a provisional material for rehabilitation. Aging reduced strength for all materials tested.

Comparison of Fracture Strengths of Three Provisional Prosthodontic CAD/CAM Materials: Laboratory Fatigue Tests

Temporary restorations play a fundamental role in oral rehabilitation. They can be used on teeth or implants for a variable period of time during the period prior to rehabilitation with definitive restorations. Temporary or provisional restorations manufactured via CAD/CAM methods are becoming increasingly used in the intermediate phase of the treatment of complex cases. The main objective of this study was to compare the fracture resistance of three materials used in the creation of provisional crowns on implants: polymethyl methacrylate (PMMA), composite resin, and polyether ether ketone (PEEK). Fracture resistance in PMMA (Zirkonzahn Temp Basic® , Gais, South Tyrol, Italy) ranged from 1216.0 N to 1461.2 N, with a mean of 1300.4 N (SD = 97.09). In the composite material (3M Lava Ultimate®, Minnesota, USA), fracture resistance varied between 1343.5 N and 1490.6 N, with a mean of 1425.9 N (SD = 49.03). Lastly, in PEEK (Tecno Med Mineral®, Zirkonzahn®, Gais, South Tyrol, Italy), fracture resistance ranged from 2294.8 N to 2451.7 N, with a mean of 2359.5 (SD = 50.01). The crowns made with the PEEK Tecno Med Mineral® (Zirkonzahn®, Tyrol, Italy) material presented the best fracture resistance, followed by the crowns made with the Lava Ultimate® (3M® ESPE, Minnesota, USA) composite resin material and, finally, those made with the PMMA Temp Basic® (Zirkonzahn®, Tyrol, Italy) material.

The Current State of Chairside Digital Dentistry and Materials

This article describes and illustrates the current state of chairside computer-aided design computer-aided manufacturing technologies and materials. It provides a historical background and discusses the different components of the chairside digital workflow: intraoral scanners, design software, milling machines, and sinter furnaces. The material range available for chairside digital dentistry is broad and includes polymethyl methacrylates, composite resins, and a large variety of ceramics. Clinical applications and success rates of the different material groups are summarized and discussed based on the current scientific evidence.

Structural Integrity Evaluation of Large MOD Restorations Fabricated With a Bulk-Fill and a CAD/CAM Resin Composite Material

AIMS

To evaluate the effect of two composite restorative techniques (direct bulk fill vs indirect CAD/CAM) on the fracture resistance and mode of fracture of extended mesio-occlusal-distal (MOD) cavity preparations.

METHODS

Fifty-one sound human mandibular third molars were divided into three groups (n=17). Extended bucco-lingual MOD cavities were prepared. Teeth in group 1 were restored with a bulk-fill resin composite (Filtek Bulk-Fill Posterior Restorative), teeth in group 2 were restored with composite computer-aided design/computer-aided manufacturing (CAD/CAM) inlays (Lava Ultimate), and teeth in group 3 served as control and remained intact. All specimens were submitted to thermocycling, and a fracture resistance test was performed using a Universal testing machine (0.5 mm/min). Mode of fracture was classified into five types. One-way analysis of variance and the Duncan test were used to analyze the fracture load data at a significance level of α = 0.05. A chi-square test was used for the analysis of fracture mode between the restorative groups.

RESULTS

Statistical analysis showed significant differences in fracture resistance among the experimental groups. The teeth restored with the bulk-fill composite exhibited lower fracture resistance (1285.3±655.0 N) when compared to the teeth restored with the composite CAD/CAM inlays (1869.8±529.4 N) (p<0.05). Mode of fracture showed the same distribution between the restorative groups.

CONCLUSIONS

Although both types of restorations failed at loads larger than those found in the oral cavity, the CAD/CAM composite inlays increased the fracture resistance of teeth with large MOD cavities when compared to direct bulk-fill composite restorations. The majority of fracture types were intraorally repairable for both restorative techniques.

Evaluation of adaptation of ceramic inlays using optical coherence tomography and replica technique

Optical coherence tomography (OCT) has generally been used as a nondestructive technique to evaluate integrities of composite restorations. We investigated marginal and internal adaptations of ceramic inlay restorations with OCT and compared them to results with the silicone replica technique. Round-shaped class I cavities were prepared on 16 human maxillary first premolar teeth. Ceramic inlays were fabricated. Silicone replicas from inlays were obtained and sectioned to measure marginal and internal adaptations with a stereomicroscope (Leica Dfc 295, Bensheim, Germany). Inlays were cemented on respective teeth. Marginal and internal adaptations were then measured with the OCT system (Thorlabs, New Jersey, USA) in 200- μm intervals. Replica and OCT measurements were compared with independent samples t-tests. A paired t-test was used to evaluate the marginal and internal adaptations of each group (p < 0.05). Marginal and internal adaptations were 100.97 ± 31.36 and 113.94 ± 39.75 μm, respectively, using the replica technique and 28.97 ± 17.86 and 97.87 ± 21.83 μm, respectively, using OCT. The differences between the techniques were significant (p = 0.00 and p = 0.01, respectively). On evaluation within the groups, internal adaptation values were found to be significantly higher than the marginal adaptation values for the replica technique (p = 0.00) and OCT (p = 0.00). Therefore, the replica and OCT techniques showed different results, with higher values of marginal and internal adaptation found with the replica technique. Marginal and internal adaptation values of ceramic inlays, whether measured by replica or OCT techniques, were within clinically acceptable limits.

Load-bearing capacity of novel resin-based fixed dental prosthesis materials

To evaluate the influence of different materials on the load-bearing-capacity of inlay-retained fixed-dental-prosthesis (FDP). Ten types of FDPs were evaluated (n=7/group): Group PEEK: CAD-CAM polyetheretherketone (PEEK-TechnoMed), Group RC, made of discontinuous-fiber-composite (EverX Posterior); Group FRC1, made of discontinuous-fiber-composite (EverX Posterior) with two-bundles of continuous-unidirectional fiber-reinforced-composite (FRC) (Everstick C&B); Group FRC2, made of discontinuous-fiber-composite (EverX Posterior) with two-bundles of continuous-unidirectional-FRC (Everstick C&B) covered by two-pieces of short-unidirectional-FRC (Everstick C&B) placed perpendicular to the main-framework; Group FB, CAD-CAM fiber-block (Fibra-Composite Bio-C); Group PMMA, CAD-CAM polymethyl methacrylate block (Temp basic); Group RP, resin-paste; Group FRP1, made of resin-paste (G-Fix) with two-bundles of continuous-unidirectional-FRC (Everstick C&B); Group FRP2, made of resin-paste (G-Fix) two-bundles of continuous-unidirectional-FRC covered by two-pieces of short unidirectional-FRC placed perpendicular to the main-framework and Group exp-FRC, experimental CAD-CAM FRC. The bridges were statically-loaded until fracture. Fracture modes were visually examined. ANOVA revealed that significant differences were observed between FDP-materials (p<0.05). In addition, fiber addition to the framework significantly affected load-bearing-capacity (p<0.05).