Effect of ultrasonic activation of the adhesive system on dentin tubule penetration and the pushout bond strength of fiber posts.

STATEMENT OF PROBLEM: Whether ultrasonic activation of the adhesive system improves dentin tubule penetration and the bond strength of fiber posts to root dentin is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of ultrasonic activation of 2 adhesive systems (etch-and-rinse and self-etch) and 1 glass ionomer cement on the dentin tubule penetration and pushout bond strength of fiber posts to root dentin. MATERIAL AND METHODS: Sixty maxillary central incisors were endodontically treated and divided into 6 groups (n=10) as per the post cementation strategy: etch-and-rinse, etch-and-rinse and ultrasonic, self-etch, self-etch and ultrasonic, glass ionomer cement, and glass ionomer cement and ultrasonic. The primers, the adhesives, and the glass ionomer cement were activated for 20 seconds each, and the fiber posts were cemented with a resin cement. Dentin tubule penetration was evaluated by confocal laser scanning microscopy and the pushout bond strength measured at 3 post locations: cervical, middle, and apical. The failure patterns were also described after pushout testing. RESULTS: Self-etch and ultrasonic showed higher dentin tubule penetration than the other cementation strategies (P<.05) and improved the bond strength values (P<.05), which were higher than etch-and-rinse and ultrasonic and glass ionomer cement and ultrasonic (P<.05). Adhesive failures at the cement and dentin interface were predominant in the etch-and-rinse, self-etch, and self-etch and ultrasonic groups. CONCLUSIONS: Ultrasonic activation improved the dentin tubule penetration of a self-etch adhesive system. The bond strength of fiber posts cemented with a self-etch adhesive system and a resin cement was improved after ultrasonic activation.

Incidence of Dentinal Defects and Vertical Root Fractures after Endodontic Retreatment and Mechanical Cycling.

INTRODUCTION: The aim of this study was to evaluate the incidence of dentinal defects and vertical root fractures (VRFs) after endodontic retreatment and mechanical cycling (MC). METHODS AND MATERIALS: Two hundred mandibular premolars were selected. Forty teeth were left unprepared (control group). The remaining 160 root canals were prepared with ProTaper instruments and filled by using two different techniques [eighty with lateral compaction (LC) and eighty with single-cone (SC)]. Forty canals from each group (LC and SC) received no further treatment. The remaining eighty teeth were divided into two groups (LCR and SCR) (n=40) in order to undergo the removal of the root filling, re-preparation and refilling with lateral compaction and single-cone, respectively. All of the teeth were subjected to MC (1000000 cycles, 130 N, 2.2 Hz and 37°C). The roots were sectioned at 3, 6 and 9 mm from the apex and observed under 20× magnification. The defects were classified as: no defect, VRF and other defects. Statistical analysis was performed using the Fisher's Exact test and the Chi-Squared tests (α=0.05). RESULTS: MC alone did not promote any other defects or VRFs. Experimental groups presented higher dentinal defects than the control group (P=0.021). Retreatment groups did not present a higher amount of dentinal defects than the groups that were subjected to the first treatment (P>0.05). CONCLUSION: Endodontic treatment and retreatment, regardless of the filling technique and MC, did not influence the occurrence of dentinal defects or VRFs in the human premolars.

Effectiveness of final irrigant protocols for debris removal from simulated canal irregularities.

INTRODUCTION: The aim of this in vitro study was to compare the effectiveness of saline, 2.5% sodium hypochlorite, and 2% chlorhexidine, with or without passive ultrasonic irrigation (PUI), in debris removal from simulated canal irregularities within prepared root canals. METHODS: Ninety bovine lateral incisors were randomly divided into 3 main groups (n = 30) based on the irrigant and prepared with hand files attached to an oscillating handpiece (NSK, Tokyo, Japan) up to a size #80 K-file. Next, the teeth were split longitudinally, and a standardized groove was prepared into the apical third and filled with dentin debris. After the halves were reassembled, they were placed in a muffle. Each main group was randomly subdivided into 2 groups (n = 14) and was treated with different final irrigation protocols. In the sodium hypochlorite/PUI, chlorhexidine/PUI, and saline/PUI groups, the solution was ultrasonically activated 3 times for 20 seconds. In the remaining groups, PUI was not performed. Specimens were scored for debris removal and analyzed under a scanning electron microscope. RESULTS: An association was observed between the score of debris removal and protocols using PUI (P < .05). No association was observed between the scores of debris removal and the irrigants (P = .87). CONCLUSIONS: Final irrigation protocols that used PUI were more effective in removing debris from simulated canal irregularities into the apical third than those that did not use it.

Resistência ao deslocamento de quatro materiais retrobturadores à dentina bovina e humana / Bond strength of four root-end filling materials to bovine and human root dentin

Objetivo: O objetivo desse trabalho foi comparar a resis-tência ao deslocamento de quatro cimentos endodônti-cos utilizados para o selamento de retrocavidades (Por-tland, MTA, Super EBA® e Sealapex®) em dentina bovinae humana. Materiais e método: Quarenta raízes bovinase quarenta raízes distais de molares inferiores humanosforam apicetomizadas e cavidades retrógradas forampreparadas. As raízes foram divididas aleatoriamente emquatro grupos e preenchidas com os materiais retrobtu-radores testados. Após uma semana, as raízes foram sec-cionadas transversalmente e os slices foram submetidosao teste de push-out. Os padrões de falha foram analisa-dos em microscopia óptica (10×) e classificados como:adesiva, coesiva do cimento, coesiva da dentina e mista.Os dados foram analisados utilizando o teste de Kruskal--Wallis, Mann-Whitney e Dunn. Resultados: Os maioresvalores de resistência ao deslocamento foram obtidosem dentina bovina (P < 0,05). O cimento Portland eMTA apresentaram os maiores valores de resistência aodeslocamento quando comparados com Super EBA® eSealapex®. Falha coesiva de cimento foi predominanteindependentemente do cimento e do substrato. Conclu-são: Pode-se concluir que a resistência ao deslocamentodos materiais retrobturadores é dependente do tipo decimento utilizado e substrato analisado.

Evaluation of epoxy resin sealer after three root canal filling techniques by confocal laser scanning microscopy.

The aim of this study was to evaluate the penetration of endodontic sealer into the dentin tubules, the integrity of the sealer layer perimeter, and the sealer area at the apical third after different filling techniques by confocal laser scanning microscopy (CLSM). Forty-five mandibular premolars were mechanically prepared with ProTaper files, until F5 file. Thereafter, they were filled with an epoxy-resin sealer (AH Plus) mixed with Rhodamine B dye (0.1% proportion) and allocated in three groups: Group 1, single master cone; Group 2, cold lateral compaction; and Group 3, Thermafil. For confocal laser scanning microscopy analysis, the specimens were transversely sectioned at 4 mm from the apex. The images at ×10 and ×40 were analyzed by Imagetool 3.0 software. Significant differences were not found among the three experimental groups according the dentin-impregnate area by the sealer (P = 0.68) and between the sealer and root canal perimeter (P = 0.18). However, root canal filling techniques were significantly different when apical sealer areas were compared (P = 0.001). Thermafil group showed smaller sealer areas (8.09%) while cold lateral compaction and gutta-percha master cone showed similar areas (17.37 and 21.18%, respectively). The dentin-impregnated area was not dependent on the root canal filling technique. Single master cone, cold lateral condensation and Thermafil techniques presented integrity of the sealer perimeter close to 100% and Thermafil resulted in a significantly thinner sealer layer.