Longitudinal Study on the Influence of Nd:YAG Laser Irradiation on Microleakage Associated with Two Filling Techniques

Abstract

Objective: This study investigates the effects of Nd:YAG laser irradiation on apical and coronal seals, when used prior to two root canal filling techniques. Background Data: Limited information exists regarding the effects of morphologic changes to dentin walls following Nd:YAG laser irradiation on the sealing ability of root fillings. Methods: Two hundred forty teeth were analyzed by observing coronal and apical leakage of Indian ink (DL), and 60 were analyzed for through-and-through leakage using the fluid transport model (FTM). The Nd:YAG laser parameters were 1.5 W, 100 mJ, and 15 Hz (four times for 5 s at 20 s intervals). Each group consisted of a lased and a nonlased subgroup: each subgroup had root fills done by either cold lateral condensation (CLC) or hybrid condensation (HC). Leakage was assessed after 48 h, and then at 1, 6, and 12 months. The DL group was divided into four groups of 15 teeth for each evaluation point. Through-and-through leakage (L in microliters= day) was measured for 48 h under a pressure of 1.2 atm using FTM, and recorded as L ¼ 0 (L1), 0 < L 10 (L2), or L > 10 (L3). Results: Apical and coronal dye leakage was observed in all groups. Significant differences ( p < 0.05) in apical leakage were found between HC and HC þ Nd after 1, 6, and 12 months, and between CLC and CLC þ Nd at 6 and 12 months. No significant differences were found between laser-irradiated and non-laserirradiated groups with FTM. Conclusion: Pulsed Nd:YAG laser irradiation following root canal preparation may reduce apical leakage in association with hybrid gutta-percha condensation.

Investigation of Coronal Leakage of Root Fillings After Smear-Layer Removal with EDTA or Nd:YAG Lasing Through Capillary-Flow Porometry

“…He et al, 45 investigating the temperature at the outer surface of a root after Nd:YAG lasing at different power settings, clearly demonstrated and confirmed what others 13,16,44 had already pointed out: thermal and morphologic changes seen at the apical third of the roots were greater than those in the coronal third, suggesting that caution should be used when irradiating the apical part of the root, to prevent periodontal injury. They demonstrated that root dentin thickness, especially in the apical third, was an important parameter in the conductance of energy and hence temperature toward the periodontal ligament.…”

“…13,16 So the impact of morphologic changes of the rootcanal wall due to the Nd:YAG on the lateral seal of a root filling could be investigated.…”

“…45 Based on their findings, the insertion of the laser fiber 1 mm short of the working length, as done in the present setup, does not interfere with the requested laser-tissue interaction and is a safe way to avoid periodontal damage. 13,16 All samples demonstrated leakage (Table 1). Differences between groups with different cleaning protocols became more obvious when the root tips were resected.…”

“…Data evaluating coronal leakage of root fillings after laser irradiation of the root-canal walls remain scarce. 11,16 To prevent the ingress of new pathogens from the oral cavity and to maintain the success of the endodontic procedure, an adequate three-dimensional obturation and coronal seal, after meticulous cleaning and shaping of the root-canal space, are required. 17,18 The removal of the smear layer plays an important role in this success, with the use of EDTA as a determining parameter.…”

“…To eliminate the effect of morphologic changes at the most apical preparation point just above the apical constriction on the seal of the root filling, 16 all roots were also tested on through-and-through leakage after resection of the root tip, thus exposing the gutta-percha root filling.…”