Influence of pretreatment of radicular dentin with erbium lasers on bond strength of fiber reinforced posts and evaluation of their retention

Abstract

Svrha rada bila je istražiti učinak ispiranja aktiviranog erbijskim laserima na čvrstoću svezivanja konfekcijskih i individualnih vlaknima ojačanih kolčića cementiranih samoadhezivnim cementima na dentin korijenskog kanala, te ispitati njihovu retenciju. Ekstrahirani zubi (n=162) instrumentirani su i napunjeni Reciproc tehnikom, te pripremljeni za postavljanje kolčića. U prvoj skupini (n=132) push-out testom ispitan je utjecaj vrste kolčića (GC FIBER POST ili everStick POST), načina obrade dentina (konvencionalno ispiranje fiziološkom otopinom, ispiranje fiziološkom otopinom i aktivacija PIPS nastavkom Er:YAG lasera ili ispiranje i aktivacija RTF2 nastavkom Er,Cr:YSGG lasera) i tipa samoadhezivnog cementa (G-CEM LinkAce, RelyX U200 ili SpeedCEM) na vrijednost čvrstoće svezivanja. Rezultati su izraženi u MPa, logaritmirani i analizirani faktorskim ANOVA testom (p≤0.05), te post-hoc Tukeyjevim testom. U drugoj skupini (n=30) pull-out testom ispitana je retencija vlaknima ojačanih kolčića (GC FIBER POST i everStick POST) cementiranih samoadhezivnim cementom s najboljim rezultatom push-out testa. Rezultati su izraženi u N i analizirani Studentovim t-testom (p≤0.05). Relacija između duljine cementiranog dijela kolčića i sile popuštanja analizirana je modelom linearne regresije (p≤0.05 ). Za čvrstoću svezivanja statistički značajni bili su način predtretmana dentina korijenskog kanala (p=0.025) te interakcija vrste kolčića i samoadhezivnog cementa. Za retenciju statistički značajna je bila relacija između duljine cementiranog dijela kolčića i vrijednosti retencije u skupini konfekcijskog vlaknima ojačanog kolčića (p=0.01). Ispiranje fiziološkom otopinom aktiviranom Er:YAG laserom smanjilo je čvrstoću svezivanja vlaknima ojačanih kolčića cementiranih samoadhezivnim cementima na dentin korijenskog kanala u odnosu na konvencionalno ispiranje fiziološkom otopinom. Retencija konfekcijskih vlaknima ojačanih kolčića ovisila je o duljini cementiranog dijela kolčića.Objectives: The aim of this in vitro study was to investigate the effect of laser activated irrigation (LAI) with two erbium lasers on bond strength of prefabricated and individually formed fiber-reinforced composite (FRC) posts cemented with self-adhesive composite cements to root canal dentin and to examine their retention. Methods: One hundred sixty two (n=162) single-rooted human teeth were decoronated, endodontically treated and after post space preparation divided in two groups: group for evaluating bond strength using push-out test (n=132) and group for evaluating retention using pull-out test (n=30). In the first group, the teeth were further divided into two groups (n=66 per group) depending on the type of FRC posts: prefabricated GC FIBER POST (GC, Tokyo, Japan) and individually formed everStick POST (GC, Tokyo, Japan). Before cementation of posts, each group was subdivided into three subgroups (n=22 per group), according to the pretreatment of post space preparation: 1) conventional syringe irrigation with saline; 2) irrigation with saline and activation by Er:YAG laser with PIPS tip; 3) irrigation and activation by Er,Cr:YSGG laser with RFT2 tip. One specimen from each group was used for SEM evaluation to confirm the dentin pretreatment. The other specimens were divided into three groups (n=7 per group) according to the brand of self-adhesive cement: G-Cem LinkAce, SpeedCem and RelyX U200. After cementation, specimens were embedded into acrylic resin and perpendiculary sectioned into 1 mm thin sectiones. Push-out test was performed using universal testing machine (0.5 mm/min). The sliced samples were evaluated by the stereomicroscope to determine the type of failure (adhesive, cohesive or mixed). Data were calculated as megapascals, log-tranformed and statistically analyzed using factorial ANOVA (p≤0.05) and post-hoc Tukey's test. Types of failure were analyzed using Pearson's test (p≤0.05). In the second group, for pull-out testing the teeth were divided into two groups (n=15 per group) depending on the type of FRC posts: prefabricated GC FIBER POST (GC, Tokyo, Japan) and individually formed everStick POST (GC, Tokyo, Japan). Post spaces were rinsed with saline and posts were cemented with self-adhesive cement that achieved the best overall results in push-out test, in this case G-Cem LinkAce. The pull-out test was performed using modified universal device (0.5 mm/min). The tearing force (Newtons) was recorded for each sample and data were statistically analyzed using Student's t-test. The relationship between length of the cemented part of post and failure load was examined using linear regression model (p≤0.05 ) Results: In the first group,similar bond strength values were obtained for everStick POSTS and GC FIBER POSTS (p=0.15).Type of self-adhesive cement was not found significantly effective on the push-out bond strength (p=0.86). The type of dentin pretreatment (p=0.025) and interaction between type of the FRC post and self-adhesive cement influenced the bond strength. In the second group, retention was not affected by the type of FRC post. Failure load values of prefabricated FRC post were dependent on length of the cemented part of post (p=0.01). Conclusions: Irrigation with saline activated by Er:YAG lowered bond strength of both types of FRC post cemented with different self-adhesive cements in comparison with conventional syringe irrigation with saline. Retention of prefabricated FRC post was influenced by length of cemented part of the post