Abstract
The aim of the study was to evaluate the adhesive forces for removing iatrogenically fractured endodontic nickel-titanium instruments using a modified tube technique with various pre-treatment agents in combination with a light-curing composite. 120 Nickel-Titanium-Mtwo instruments were cut at its parallel shaft and fixed in a vise with an overlap of 2 mm. The surfaces were treated with different agents: A) GC Metalprimer; B) Prime and Bond active; C) NaOCl (3%); D) citric acid (15%); E) phosphoric acid (37%) and group (F) was not pretreated (control). One end of a matching microtube, filled with light-curing composite, was placed over the instrument and a transmitting glass fiber inserted from the opposite side guaranteed polymerization. Pull-out tests (1 mm/min) were performed and failure load was measured digitally. Data were statistically analyzed using the ANOVA and Student–Newman–Keuls tests. Interfaces were subjected to SEM analysis. Prime and Bond active created significant higher pull-out values (mean 30.5 N) compared to all other groups (p < 0.001) and Metalprimer (18.5 N) was significantly superior to the untreated (12.6 N) and NaOCl (11.7 N) group (p < 0.05). No significant differences were obtained between the other groups (p > 0.05). Thus, adhesives improved bonding to fractured NiTi instruments.
Highlights
Chemo-mechanical disinfection of the entire root canal system is crucial for successful root canal treatment [1]
Endodontic instruments may fracture due to torsional load or cyclic fatigue with an incidence ranging between 1.8% and 3.3% [2,3]
All efforts in managing this undesired complication should be based on a thorough knowledge of each treatment option considering the success rates and should be well balanced against potential risks of leaving or removal of the fragment [8]. It has to be taken into consideration that fractured endodontic instruments might not directly affect the prognosis of the tooth [3,5,9,11], because fragments made of stainless steel or nickel–titanium (NiTi) itself may not directly lead to infection
Summary
Chemo-mechanical disinfection of the entire root canal system is crucial for successful root canal treatment [1]. Endodontic instruments may fracture due to torsional load or cyclic fatigue with an incidence ranging between 1.8% and 3.3% [2,3] This accidental mishap is undesired and may negatively influence treatment outcome as the fragment may block root canal areas making them inaccessible for both mechanical and chemical disinfection [4,5,6], depending on the stage of root canal-procedure when fracture occurred [3,7,8,9]. It has to be taken into consideration that fractured endodontic instruments might not directly affect the prognosis of the tooth [3,5,9,11], because fragments made of stainless steel or nickel–titanium (NiTi) itself may not directly lead to infection
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