Didier Dietschi

Comparison of the color stability of ten new-generation composites: an in vitro study.

OBJECTIVES The aim of this in vitro study was to evaluate the color stability of modern light-cured composites when subjected to various physico-chemical and staining conditions. METHODS Ten brands were evaluated including hybrids, microfine hybrids and microfilled composites. Some universal shade samples underwent only staining tests, while others were subjected to one of the following experimental conditions: thermocycling, postcuring, polishing or a 1 wk immersion in saline, prior to staining. The coloring solutions used for the staining tests were: coffee, E 110 food dye, vinegar and erythrosin. A colorimetric evaluation according to the CIE L*a*b* system was performed after experimental periods of 1 and 3 wk. RESULTS Erythrosin caused the greatest color change for the composites tested. A reduced susceptibility to staining was observed where surfaces had been polished. Low water sorption, a high filler-resin ratio, reduced particle size and hardness, and an optimal filler-matrix coupling system were related to improved composite resistance to discoloration. SIGNIFICANCE Resistance of modern composites to discolorations still depends on their structure and manipulation.

Influence of water sorption on resin composite color and color variation amongst various composite brands with identical shade code: an in vitro evaluation

OBJECTIVE The aim of this study was to evaluate the influence of 1 week water storage on color stability of A2 enamel and dentine shade of 13 resin composites intended for anterior restorations and to evaluate the interchangeability of different composite brands of equal color shade. METHODS 6 samples per shade were prepared as 1mm thick discs of 10mm diameter. L*a*b* and contrast ratio (CR) were measured immediately after light curing and after 1 week storage in water at 37°C, in the dark. Then all samples were compared against each other. RESULTS The greatest color change was found for Enamel A2 Artemis (ΔE 3.13) with white background whilst the smallest was Dentine A2 Filtek and Voco (ΔE 0.20) with black background. SIGNIFICANCE Most of resin composite brands showed statistically significant differences between initial and post immersion color values. Some of post ageing dentine and enamel CR values was statistically different amongst them. The color differences in-between all the A2 enamel and dentine composite shades were highly statistically different.

Comparative efficiency of plasma and halogen light sources on composite micro-hardness in different curing conditions

OBJECTIVES Recent developments have led to the introduction of high power curing lights, which are claimed to greatly reduce the total curing time. This study evaluated the effectiveness of a plasma-curing device (Apollo 95 E) and a halogen device (Heliolux DLX), in different curing conditions. METHOD Vickers micro-hardness values were performed on 1 and 2 mm thick composite discs cured in a natural tooth mold by direct irradiation or indirect irradiation through composite material (2 or 4 mm) and dental tissues (1 mm enamel or 2 mm enamel-dentin). Measures were, respectively, performed after a 1, 3, 6 s (SC, step curing mode) or 18 s (3xSC) exposure to the plasma light, and a 5, 10, 20 or 40 s exposure to the halogen light. RESULTS With the PAC light used, a 3 s irradiation in the direct curing condition was necessary to reach hardness values similar to those obtained after a 40 s exposure to the halogen light. Using the indirect curing condition, hardness values reached after an 18 s exposure (3xSC mode) with the plasma light were either equivalent or inferior to those obtained with 40 s halogen irradiation. SIGNIFICANCE Direct polymerization with the plasma light used requires longer exposure times than those initially proposed by the manufacturer. The effectiveness of plasma generated light was lowered by composite or natural tissues, and therefore requires an important increase in the irradiation time when applied to indirect polymerization. The practical advantage of this polymerization method is less than expected, when compared to traditional halogen curing.

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.

In vitro performance of class I and II composite restorations : a literature review on nondestructive laboratory trials - Part I

Posterior adhesive restorations are a basic procedure in general dental practices, but their application remains poorly standardized as a result of the number of available options. An abundant number of study hypotheses corresponding to almost unlimited combinations of preparation techniques, adhesive procedures, restorative options, and materials have been described in the literature and submitted to various evaluation protocols. A literature review was thus conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review discusses the selected literature related to photoelasticity, finite element analysis (FEM), and microleakage protocols. Based on the aforementioned evaluation methods, the following parameters proved influential: cavity dimensions and design, activation mode (light or chemical), type of curing light, layering technique, and composite structure or physical characteristics. Photoelasticity has various limitations and has been largely (and advantageously) replaced by the FEM technique. The results of microleakage studies proved to be highly inconsistent, and the further use of this technique should be strictly limited. Other study protocols for adhesive Class II restorations were also reviewed and will be addressed in part II of this article, together with a tentative relevance hierarchy of selected in vitro methods.

A combined chemo-mechanical approach for aesthetic management of superficial enamel defects

Objective The aim of this article is to describe an easy technique for managing small superficial defects in light to medium fluorosis.Method and materials The proposed technique is based on a selective abrasion of the superficial enamel and a recreation of the superficial macro and micro morphology. The aesthetic appearance can be enhanced by power or home bleaching.Results The presented technique can manage enamel defects which are confined in the most external enamel surface with satisfying aesthetic results.Conclusions This conservative approach may be considered an interesting alternative to more invasive prosthetic techniques based on composite reconstructions or ceramic veneers, minimising invasivity, chairside time and costs for patients.

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.

Marginal adaptation of large adhesive class IV composite restorations before and after artificial aging

PURPOSE To test the marginal adaptation of Class IV restorations made of different composite materials designed for anterior use. MATERIALS AND METHODS Forty-two extracted caries-free human maxillary central incisors were randomly divided into 7 experimental groups - one per composite tested - for which Class IV cavities were prepared. The microfilled composite materials tested (SolidBond/Durafill [D/SB], Syntac classic/Heliomolar [H/SC], Scotchbond1/ Experiment127 [EXI/SB1], Optibond FL/Point 4 [P4/OBFL], Prime&Bond NT/Esthet-X [EX/PBNT], ART Bond/ Miris [MIR/ART], SE Bond/Clearfil ST [CLE/SE-B]) were inserted in two increments after polymerization of their respective adhesive systems. While under simulated dentinal fluid pressure, specimens were submitted to cyclic incisal stress (1,200,000 cycles, maximum load 49 N) and thermal loading (3000 cycles). Both after polishing and after thermomechanical loading, impressions were made of the surface of each restoration, and epoxy replicas were prepared for the marginal adaptation evaluation using SEM. RESULTS Perfect margins before loading in enamel ranged from 49.9% (EXI/SB1) to 98.2% (MIR/ART) and after loading from 25.3% (EXI/SB1) to 91.9% (MIR/ART). For margins located in dentin, perfect margins ranged from 16.8% (EXI/SB1) to 100% (CLE/SE-B) before loading and from 4.6% (EXI/SB1) to 67.1% (CLE/SE-B) after loading. CONCLUSION The poor results obtained in this in-vitro test with the microfilled composites suggest avoiding their use in large Class IV restorations with margins in dentin.

In Vitro Evaluation of Marginal Adaptation of Direct Class II Composite Restorations Made of Different “Low-Shrinkage” Systems

The present study evaluated the influence of various low-shrinkage restorative systems in class II direct composite restorations following simulated occlusal loading. Forty MOD class II cavities were prepared on freshly extracted human lower third molars with proximal margins located mesially 1.0 mm coronal to and distally 1 mm apical to the cementoenamel junction. The samples were randomly distributed into five experimental groups corresponding to the following restorative systems: a conventional resin composite (Tetric) as active control group, a low-shrinkage composite (Extra Low Shrinkage [ELS]) alone or combined with its corresponding flowable version (ELSflow) used as a 1- to 1.5-mm liner, a bulk-filling flowable composite (Surefil SDR) covered by a 1-mm layer of restorative composite (Ceram-X), and a restorative bulk-filling composite (SonicFill). All specimens were submitted to 1,000,000 cycles with a 100N eccentric load into saline. Tooth restoration margins were analyzed semiquantitatively by scanning electron microscopy before and after loading. The percentage of perfect adaptation to enamel varied from 94.15% (SonicFill) to 100% (ELS) before loading and from 69.22% (SonicFill) to 93.61% (ELS and ELSflow) after loading. Continuous adaptation to cervical dentin varied from 22.9% (Tetric) to 79.48% (SDR/Ceram-X) before loading and from 18.66% (Tetric) to 56.84% (SDR/Ceram-X) after loading. SDR/CeramX and SonicFill showed the best cervical dentin adaptation.