Giovanni Tommaso Rocca

A technique to improve the esthetic aspects of CAD/CAM composite resin restorations

Bonded indirect computer-aided design/computer-aided manufacturing (CAD/CAM) restorations are increasingly gaining popularity for the restoration of large defects in posterior teeth. In addition to ceramic blocks, composite resin blocks have been developed. Composite resins blocks may have improved mechanical properties, but have poor esthetics. Thus, an esthetic modification of the restoration after machine milling may be necessary. A step-by-step procedure for the external esthetic layering of a composite CAD/CAM restoration is described. This technique can be used to repair or modify any composite resin restoration.

Fiber-reinforced resin coating for endocrown preparations: a technical report.

Coronal rehabilitation of endodontically treated posterior teeth is still a controversial issue. Although the use of classical crowns supported by radicular metal posts remains widespread in dentistry, their invasiveness has been largely criticized. New materials and therapeutic options based entirely on adhesion are available nowadays, from direct composite resins to indirect endocrowns. They allow for a more conservative, faster, and less expensive dental treatment. However, the absence of a metal or high-strength ceramic substructure as in full-crown restorations can expose this kind of restoration to a higher risk of irreversible fracture in case of crack propagation. The aim of this case report is to present a technique to reinforce the cavity of an endodontically treated tooth by incorporating a fiber-reinforced composite (FRC) layer into the resin coating of the tooth preparation, before the final impressions of the cavity. This technique allows the use of FRCs in combination with any kind of restorative material for an adhesive overlay/endocrown.

In vitro evaluation of marginal and internal adaptation after occlusal stressing of indirect class II composite restorations with different resinous bases and interface treatments. "Post-fatigue adaptation of indirect composite restorations"

The present study evaluated the influence of different composite bases and surface treatments on marginal and internal adaptation of class II indirect composite restorations, after simulated occlusal loading. Thirty-two class II inlay cavities were prepared on human third molars, with margins located in cementum. A 1-mm composite base extending up to the cervical margins was applied on all dentin surfaces in the experimental groups; impressions were made and composite inlays fabricated. The following experimental conditions were tested: no liner (control group), flowable composite treated with soft air abrasion (experiment 1), flowable composite sandblasted (experiment 2) and restorative composite sandblasted (experiment 3). All specimens were submitted to 1,000,000 cycles with a 100-N eccentric load. Tooth–restoration margins were analysed semi-quantitatively by scanning electron microscopy before and after loading; internal adaptation was also evaluated after test completion. The percentage of perfect adaptation in enamel was 79.5% to 92.7% before loading and 73.3% to 81.9% after loading. Perfect adaptation to dentin was reduced before loading (54.8% to 77.6%) and after loading (41.9% to 63%), but no difference was found among groups for pre- and post-loading conditions. No debonding occurred between the base and composite luting. A significant, negative influence of cyclic loading was observed. The results of the present study support the use of flowable or restorative composites as base/liner underneath large class II restorations. Soft air abrasion represents a potential alternative to airborne particle abrasion for treating cavities before cementation. The application of a composite base underneath indirect composite restorations represents a feasible non-invasive alternative to surgical crown lengthening to relocate cavity margins from an intra-crevicular to supra-gingival position.

Microhardness of light- and dual-polymerizable luting resins polymerized through 7.5-mm-thick endocrowns

STATEMENT OF THE PROBLEM The complete polymerization of luting resins through thick indirect restorations is still questioned. PURPOSE The purpose of this study was to evaluate the degree of polymerization of light- and dual-polymerizable luting resins under thick indirect composite resin and ceramic endocrowns by means of Vickers microhardness measurements. MATERIAL AND METHODS The Vickers microhardness measurements of a light-polymerizable microhybrid composite resin and a dual-polymerizable luting cement directly polymerized in a natural tooth mold for 40 seconds with a high-power light-emitting diode lamp (control) were compared with measurements after indirect irradiation through 7.5-mm-thick composite resin and ceramic endocrowns for 3 × 90 seconds. A test-to-control microhardness values ratio of 0.80 at a depth of 0.5 mm below the surface was assumed as the criterion for adequate conversion. RESULTS For the Vickers microhardness measurements of a dual-polymerizable luting cement, no differences (P>.05) were found between Vickers microhardness control values and values reported after polymerization through composite resin and ceramic endocrowns. For The Vickers microhardness measurements (±SD) of a light-polymerizable microhybrid composite resin, control values were significantly (P<.05) higher (111 ±3.3) than those reported after polymerization through composite resin (100.5 ±3.8) and ceramic (99.7 ±2.3) endocrowns. However, the hardness values of The Vickers microhardness measurements of a light-polymerizable microhybrid composite resin polymerized through the endocrowns were approximately 10% to 12% lower than those of the control values. Two-way ANOVA showed the influence of the luting material on the Vickers microhardness values (P<.05). The effect of endocrown material was not significant (P>.05). CONCLUSIONS Under the conditions of this in vitro study, Vickers microhardness values of the dual-polymerizable resin cement and the light-polymerizable restorative composite resin irradiated for 3 × 90 seconds with a high irradiance light-emitting diode lamp through 7.5-mm-thick endocrowns reached at least 80% of the control Vickers microhardness values, which means that both materials can be adequately polymerized when they are used for luting thick indirect restorations.

Fatigue behavior of resin-modified monolithic CAD–CAM RNC crowns and endocrowns

OBJECTIVE To evaluate the influence of different types of modifications with resin on fatigue resistance and failure behavior of CAD-CAM resin nano ceramic (RNC) restorations for maxillary first premolars. METHODS Sixty standardized resin composite root dies received CAD-CAM RNC endocrowns (n=30) and crowns (n=30) (Lava Ultimate, 3M Espe). Restorations were divided into six groups: full anatomic endocrowns (group A) and crowns (group D), buccal resin veneered endocrowns (group B) and crowns (group E) and buccal resin veneered endocrowns (group C) and crowns (group F) with a central groove resin filling. A nano-hybrid resin composite was used to veneer the restorations (Filtek Supreme, 3M Espe). All specimens were first submitted to thermo-mechanical cyclic loading (1.7Hz, 49N, 600000 cycles, 1500 thermo-cycles) and then submitted to cyclic isometric stepwise loading (5Hz) until completion of 105000 cycles or failure after 5000 cycles at 200N, followed by 20000 cycles at 400N, 600N, 800N, 1000N and 1200N. In case of fracture, fragments were analyzed using SEM and modes of failure were determined. Results were statistically analyzed by Kaplan-Meier life survival analysis and log rank test (p=0.05). RESULTS The differences in survival between groups were not statistically significant, except between groups D and F (p=0.039). Endocrowns fractured predominantly with a mesio-distal wedge-opening fracture (82%). Partial cusp fractures were observed above all in crowns (70%). Analysis of the fractured specimens revealed that the origin of the fracture was mainly at the occlusal contact points of the stepwise loading. SIGNIFICANCE Veneering of CAD-CAM RNC restorations has no influence on their fatigue resistance except when monolithic crowns are modified on their occlusal central groove.

Semidirect composite onlay with cavity sealing: a review of clinical procedures

UNLABELLED The evolution in adhesive dentistry has broadened the indication of esthetic restorative procedures especially with the use of resin composite material. Depending on the clinical situation, some restorative techniques are best indicated. As an example, indirect adhesive restorations offer many advantages over direct techniques in extended cavities. In general, the indirect technique requires two appointments and a laboratory involvement, or it can be prepared chairside in a single visit either conventionally or by the use of computer-aided design/computer-aided manufacturing systems. In both cases, there will be an extra cost as well as the need of specific materials. This paper describes the clinical procedures for the chairside semidirect technique for composite onlay fabrication without the use of special equipments. The use of this technique combines the advantages of the direct and the indirect restoration. CLINICAL SIGNIFICANCE The semidirect technique for composite onlays offers the advantages of an indirect restoration and low cost, and can be the ideal treatment option for extended cavities in case of financial limitations.

Multiple diastema closure in periodontally compromised teeth: How to achieve an enamel-like emergence profile.

This article describes a direct composite resin technique for the closure of multiple diastemas. The described procedure allows an anatomic and esthetic emergence profile of the apical third of the tooth to be obtained in periodontally compromised teeth without the use of interproximal wedges.