Hardness comparison of bulk-filled/transtooth and incremental-filled/occlusally irradiated composite resins

Effects of light exposure time on composite resin hardness after root reinforcement using translucent fibre post

“…26 As the adequate polymerisation of resin materials in deeper intracanal regions is sometimes dubious, in clinical practice the lower energy density delivered to these areas might be compensated for by increasing the light exposure time, 13 choosing more intense light sources or using materials that enhance energy transmission. 19,35 The light exposure time influenced significantly the VHN means recorded in the present study, although the times of 40 and 80 s (G1 and G2) provided similar results in all regions of the composite-reinforced roots. It should be emphasised that post-cementation with Duo Link resin cement yielded an additional photoactivation time of 40 s, which might have contributed to the lack of significant differences between these groups.…”

“…15 In a recent study, Lazarchik et al 19 observed that, unlike other shades, translucent composite resins had Knoop hardness values at the top surface similar to those observed at a depth of 3 mm, regardless of the photoactivation technique (incremental or bulk). Due to its translucency, attributed to the absence of opacifying components and presence of quartz load particles, it may be assumed that this type of resin optimises light transmission.…”

“…12 The depth of cure is affected by several factors, including the power and type of light-curing unit (LCU), light exposure time, distance from the LCU tip, composite shade and translucence, as well as the composition, size, amount and type of filler particles. [13][14][15][16][17][18][19] The influence of these factors is directly or indirectly proportional to the density of the LCU energy that reaches and polymerises the resin material. For example, as the depth and percentage of cure are influenced by the LCU energy density (E = power  light exposure time), 13,[20][21][22] longer exposure times may compensate for the loss of energy density caused by the increase in the sectional distance and provide a greater percentage of cure.…”

Impact of Material Shade and Distance from Light Curing Unit Tip on the Depth of Polymerization of Composites

“…Modifications in filler content, the use of additional or more efficient photo-initiators, and/or the use of novel resin monomers and additives providing reduced stress are some of approaches used by manufacturers of bulk-fill composite to allow for the composite to be inserted using this technique (31,32). However, the insertion of socalled conventional composites using increments thicker than 2-mm has been used and evaluated for quite some time (32,33). As the results of the present study seem to suggest, the use of increments thicker than 2 mm might be possible for certain shades of composite.…”

Bond Strength of Fiber Posts to Weakened Roots After Resin Restoration With Different Light-Curing Times

“…However, when light-activated composite resins are placed in deeper regions or regions with a thickness greater than 2-3 mm, polymerization might be affected and, consequently, the material hardness (21,22). It has been reported that the access to the resin material, light-curing tip distance, and power density of the curing light might influence composite resin hardness (9,(21)(22)(23) and negatively affect the mechanical properties (24). Conversely, some authors have observed that a longer light-exposure time might compensate the lower light density and promote adequate polymerization (10,25,26).…”