How the translucency of direct anatomic fiber posts affects the bond strength and microhardness of a self-adhesive luting agent in flared roots.

OBJECTIVES: To evaluate the influence of the composite resin translucency used in direct anatomic fiber posts on the bond strength (BS) and microhardness (VHN) of a luting agent into flared roots. MATERIALS AND METHODS: The root canals of 70 single-rooted premolars were endodontically treated and prepared to simulate an oversized root canal. Prior to post cementation, composite resins with varying translucency (high translucent, HT; medium translucent, MT; high opacity, HO) were placed around the fiber posts to create anatomic fiber posts. The attenuation profile (%) of light passing either through the post or through the anatomic posts (n = 8) was obtained prior to the cementing procedures. A positive control group (PC) in which a prefabricated fiber post (PFP) with the diameter compatible with the root canal was cemented and a poorly adapted fiber post (negative control group, NC) were also evaluated. For both tests, the data were subjected to 2-way ANOVA and Bonferroni tests (α = 0.05). RESULTS: A more severe light attenuation through the post at the cervical (P < .001) and medium (P < 0.001) thirds was noted when less translucent composite resin surrounded the anatomic post. HO groups showed lower BS (P = .009) and VHN (P < .001) values than the other groups, regardless of root third. No significant difference in BS values was noted between PC and HT groups. CONCLUSION: The use of a more translucent composite resin in anatomic fiber posts increased the microhardness and bond strength of a dual polymerization self-adhesive RLA compared to the use of MT and HO composite. A well-adapted PFP showed the highest adhesive and mechanical behavior. CLINICAL RELEVANCE: Clinicians should choose more translucent composite resins to create direct anatomic fiber posts to be cemented in flared root canals. That choice may allow improved mechanical properties of self-adhesive RLA and higher bond strength to the root canal as a consequence.

Influence of delivered radiant exposure values on bonding of fiber posts to root canals.

PURPOSE: To evaluate the effect of different radiant exposure values delivered to two simplified etch-and-rinse adhesive systems on push-out bond strength (PBS) of fiber posts to root canal, as well as nanoleakage (NL) and in situ degree of conversion (DC) within the hybrid layer. MATERIALS AND METHODS: The roots of human premolars were endodontically prepared and divided into 6 groups according to the combination of the main factors adhesive/resin cement (2 commercial brands) and radiant exposure (4, 16, 48, and 288 J/cm2). The posts were cemented and the PBS tested at 0.5 mm/min (n = 7). The NL (n = 3) was evaluated using SEM after immersion of specimens in 50% silver nitrate. Micro-Raman spectroscopy was performed to determine the in situ DC (n = 2). Data were analyzed by three-way repeated measures ANOVA and Tukey's post-hoc test (5%). RESULTS: PBS (MPa) showed a significant difference only for the middle third when an increase in radiant exposure from 4 to 16 J/cm2 or higher was used (p < 0.05). The NL (%) decreased significantly with increasing radiant exposure from 48 to 288 J/cm2 in the middle and apical thirds when compared to lower radiant exposure (p < 0.05). The radiant exposure of 288 J/cm2 significantly increased the DC (%) in the middle and apical thirds, compared the other radiant exposure values (p < 0.05). CONCLUSION: The increase in radiant exposure delivered to the cervical third of root canals during post cementation improved the adhesive performance of simplified etch-and-rinse adhesive systems in the apical and middle thirds.