34-38 IR Sept Manhart.indd

Composite restoration materials have been in use for more than two decades as an aesthetic alternative to metal restorations in the posterior region, which bears a great deal of the masticatory load, with increasing frequency in recent years (Kelsey et al, 2000). The early clinical data on the posterior region, gathered in the early 1980s, was not encouraging, primarily due to insufficient mechanical properties. The low abrasion resistance of those composite materials led to loss of restoration contours. Fractures, marginal deterioration and leakage following polymerisation shrinkage were further reasons for the limited lifespan of those restorations (Lambrechts, Braem, Vanherle, 1988; Leinfelder et al, 1980; Lutz et al, 1984; Roulet, 1988). Predominantly in recent years, these inadequacies have been greatly reduced through further developments in the materials of the composite and adhesive systems (Manhart, 2006). Nevertheless, the negative effects of polymerisation shrinkage – such as poor marginal integrity, insufficient adherence to the cavity walls or cusp deflections – still represent the greatest problem in compositebased materials (Manhart et al, 2000). Today, hybrid composites or hybrid composites modified with nanoparticles are the material of choice when using a direct restoration technique for the permanent treatment of larger primary carious lesions or the replacement of older, insufficient restorations in the posterior region. Prerequisites are the correct use of the matrix technique and adequate moisture control of the cavity (Manhart, 2008). Composites are processed in the incremental layer technique, usually in single increments with a maximum layer thickness of 2mm. The individual increments are in turn each polymerised separately, with exposure times of 10-40 seconds, depending on the light intensity of the curing device and shade/translucency of the respective composite paste. Above all, in large posterior tooth cavities, this can be a very time-consuming procedure that, for economic reasons, requires a corresponding fee to cover the costs. However, many users wish for an alternative to the complex, time-consuming multiple-layer technique, in order to be able to process composites in a shorter time and therefore more economically (Manhart, 2011). Several interesting innovations have recently become ready to market in respect of this. Economical procEssing In recent years, the dental industry has introduced numerous highly aesthetic composite systems to the market. With correct application, this enables direct restorations to be achieved that are practically impossible to tell apart from the dental hard tissue and can compete with