Depth of cure of radiation ‐ activated composite restoratives‐ Influence of shade and opacity

Abstract

Inadequate depth of cure may reduce the longevity of visible light-activated composite restorations. Radiation-activated composites, originally marketed for the restoration of anterior teeth, have been developed and refined for restoring occlusal and proximal cavities in posterior teeth. Clinical factors such as the accessibility of the light source, the direction of the light, intervening tooth tissue and cavity depth may limit depth of cure. Unfortunately, a hard top surface is no indication of adequate polymerization at the base of the cavity. The current investigation used a penetrometer to evaluate the depth of cure of a range of recently introduced 'universal' composite materials and assess the influence of shade and opacity on depth of cure. Depth of cure of the enamel opacity is always greater than that of the same shade of dentine for each manufacturer's product range.

Influence of shade and irradiation time on the hardness of composite resins

“…This was observed for both surfaces, although it was more evident in the L surfaces than in the U surfaces. Despite the statistically different mean values, a short irradiation time of 10 s was able to produce a high hardness value on the U surface, which is in agreement with other studies (12,17).…”

“…It may become a problem once the manufacturers produce finer particle size in commercial composite resins (3). Other factors that may determine the depth of polymerization remain on the irradiance, irradiation time, emission spectra of the light source, thickness of composite increment, distance from the light source tip to the composite resin and others (10,17).…”

“…It has been reported that loading well-polymerized composite layers that are placed on poorly polymerized layers can lead the composite restoration to bend inward and displace, causing marginal fracture, open margins and cusp deflection (17).…”

“…Insufficiently polymerized composite resin may present quite a lot of problems such as follows: poor color stability, greater stain uptake, risk of pulp aggression by non-polymerized monomers and portions of the material with different values of Young's modulus (1,17). It has been reported that loading well-polymerized composite layers that are placed on poorly polymerized layers can lead the composite restoration to bend inward and displace, causing marginal fracture, open margins and cusp deflection (17).…”

Bracket bond strength dependence on light power density

“…Results may differ for other adhesive systems, since the degree of conversion depends on material characteristics as type and concentration of photoinitiator, monomers and filler as well as composite shade and thickness. 14,19,24,25 Nevertheless, the model applied to our data may be useful for the development of light-curing systems.…”