A comparison of the apical seals achieved using retrograde amalgam fillings and the Nd:YAG laser

Lasers in Apicoectomy: A Brief Review

Since the invention of laser, various applications for lasers in endodontics have been proposed, such as disinfection of the root canal system, canal shaping, pulp diagnosis, and apico-ectomy. One of the major applications of laser in endodontics is apicoectomy. The aim of this article is to review the benefits and drawbacks of laser applications in apicoectomy, including effect on apical seal, effect on dentin permeability, effect on postsurgery pain, effect on crack formation, effect on root-end morphology, effect on treatment outcome, and connective tissue response to laser-treated dentin.

Effect of Nd: YAG laser on the apical seal after root-end resection and MTA retrofill: a bacterial leakage study

Laser irradiation has been investigated in terms of preventing leakage in retrofilled root canals. The aim of the present study was to evaluate the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser on the bacterial leakage of mineral trioxide aggregate (MTA)-retrofilled roots. In this ex vivo experimental study, 90 single-rooted incisor teeth were filled with gutta-percha and AH26 sealer. The apical 3 mm of all the roots were resected and 3-mm retrocavities were prepared by an ultrasonic device. The specimens were randomly divided into two experimental (n = 25), one positive control (n = 10), and two negative control (n = 10) groups. In the laser + MTA group, the cavity walls were irradiated by Nd: YAG laser prior to MTA placement. In the MTA group, MTA was placed without laser irradiation. The root surfaces were covered with two layers of nail varnish except for the apical 2 mm. The specimens were then embedded in a bacterial leakage test system and examined daily for 90 days. Contamination periods were recorded. Data were analyzed by Kaplan-Meier and Mann-Whitney U tests (α = 0.05). Five teeth with and five teeth without laser irradiation underwent scanning electron microscopic evaluation. The specimens in the laser + MTA group were contaminated earlier than those in the MTA group (p < 0.05). Comparison of survival times between the two groups showed significant differences (p < 0.05). Nd: YAG laser irradiation can decrease the sealing capacity of MTA in comparison to the apical seal achieved by MTA without laser irradiation. Further studies are recommended to provide a better seal for the MTA-retrofilled teeth after laser irradiation.

Modern Endodontic Surgery Concepts and Practice: A Review

Endodontic surgery has now evolved into endodontic microsurgery. By using state-of-the-art equipment, instruments and materials that match biological concepts with clinical practice, we believe that microsurgical approaches produce predictable outcomes in the healing of lesions of endodontic origin. In this review we attempted to provide the most current concepts, techniques, instruments and materials with the aim of demonstrating how far we have come. Our ultimate goal is to assertively teach the future generation of graduate students and also train our colleagues to incorporate these techniques and concepts into everyday practice.

Lasers in endodontics

With the rapid development of laser technology, new lasers with a wide range of characteristics are now available and being used in various fields of dentistry. In the past two decades, much experience and knowledge has been gained. This article provides an overview of the current and possible future clinical applications of lasers in endodontics, including their use in alleviating dentinal hypersensitivity, modification of the dentin structure, pulp diagnosis, pulp capping and pulpotomy, cleaning and shaping of the root canal system, and endodontic surgery. Endodontic procedures for which conventional treatments cannot provide comparable results or are less effective are emphasized.

Ultrastructural changes of human dentin after irradiation by Nd:YAG laser

BACKGROUND AND OBJECTIVE

The use of Nd:YAG laser has been proposed for endodontic treatment. However, its ability to reduce dentin permeability, which is important for the success of root canal treatment, remains controversial.

STUDY DESIGN/MATERIALS AND METHODS

Nd:YAG laser irradiation was performed in pulsed mode on human dentin. The parameters were: pulse energy (100 mJ), rate (10 pps), and total irradiation time (4 seconds). The crystalline phases, electron diffraction patterns, morphology, and microstructure of specimens after laser irradiation were observed by dark-field emission transmission electron microscope (TEM).

RESULTS

Three ultrastructural zones could be delineated in the dentin: (1) an outer zone with an ordered columnar structure composed of hydroxyapatite and beta-tricalcium phosphate, (2) an intermediate zone composed of an amorphous substance (about 40-70 nm in diameter), and (3) an inner zone of well-crystallized hydroxyapatite grains. These three zones were free of pores or voids.

CONCLUSIONS

Our study demonstrated that laser-irradiation might be used to reduce dentin permeability.

Occlusal loading of EBA and MTA root-end fillings in a computer-controlled masticator: a scanning electron microscopic study

AIM

The aim of this investigation was to assess the marginal adaptation of Super-EBA (EBA) and Pro Root MTA (MTA) root-end fillings and the occurrence of microcracks in resected root-ends of extracted teeth before and after occlusal loading for a five-year equivalent period in a computer-controlled masticator.

METHODOLOGY

Twenty-four molar teeth were root-filled using lateral condensation and their root-ends resected. Root-end cavities were prepared and either EBA or MTA root-end fillings were placed. All surgical procedures were completed in vitro under an operating microscope. Replicas taken of the root-end fillings and resected root-ends were examined using an SEM before and after they were subjected to in vitro chewing cycles in a computer-controlled chewing simulator for the equivalent of 5 years. Marginal adaptation and integrity of the two root-end filling materials were evaluated and the presence of microcracks recorded.

RESULTS

Before loading, a continuous margin was observed with 99.4 +/- 2.4% of EBA and 99.2 +/- 1.6% of MTA root-end fillings. After loading, the percentage of continuous margin decreased to 93.1 +/- 6.6% and 98.9 +/- 3.2% for EBA and MTA, respectively. After occlusal loading, 39.5% of the EBA root-end fillings were overfilled, whilst 52.6% of the MTA root-end fillings were underfilled. In total, 12.5% of the resected root-end surfaces showed microcracking before loading and 25% after occlusal loading.

CONCLUSIONS

Both EBA and MTA displayed excellent marginal adaptation before masticatory loading. After loading, the amount of continuous margin for both root-end filling materials decreased slightly but was still high.

Lasers in endodontics: a review

Since the development of the ruby laser by Maiman in 1960 and the application of the laser for endodontics by Weichman in 1971, a variety of papers on potential applications for lasers in endodontics have been published. The purpose of this paper is to summarize laser applications in endodontics, including their use in pulp diagnosis, dentinal hypersensitivity, pulp capping and pulpotomy, sterilization of root canals, root canal shaping and obturation and apicectomy. The effects of laser on root canal walls and periodontal tissues are also reviewed. The essential question is whether a laser can provide equal or improved treatment over conventional care. Secondary issues include treatment duration and cost/benefit ratio. This article reviews the role of lasers in endodontics since the early 1970s, summarizes many research reports from the last decade, and surmises what the future may hold for lasers in endodontics. With the potential availability of many new laser wavelengths and modes, much interest is developing in this promising field.

Development of an anaerobic bacterial leakage model

The majority of bacteria associated with infections of endodontic origin are strict anaerobes. The purpose of this study was to develop an endodontic microleakage model using strict anaerobic bacteria in a two-chamber system. Nine species of anaerobic bacteria were tested for viability and detection by either turbidity or color change of the broth. A survey of pH chromogenic substrates revealed that bromcresol purple (pH 5.2 = yellow, pH 6.8 = purple) could be used as a chromogenic indicator to detect the growth of anaerobic bacteria. Peptone-yeast extract-glucose broth (PYG) and brain heart infusion broth (BHI) were each used alone and with bromcresol purple (bpPYG, bpBHI) in this study. Fusobacterium nucleatum and F. necrophorum were viable in all four media for > 2 wk and produced both turbidity and a color change after only 1 day of incubation. Veillonella parvula in either bpBHI or BHI and Peptostreptococcus anaerobius in either bpPYG or BHI were viable for > 2 wk and showed a color change or turbidity after 1 or 2 days. The results indicate that leakage of strict anaerobes may be evaluated in a two-chamber system.

Scanning electron microscopic study of dentin lased with argon, CO2, and Nd:YAG laser

The purpose of this study was to compare morphological changes on the dentin surface induced by laser light delivered perpendicular or parallel to the dentin surface. The surface of the dentin slices and the root canal walls were lased with argon, CO2, and Nd:YAG lasers. When the laser beam was parallel to the dentin, the effects of the laser energy ranged from no effect to eroding and melting of the smear layer and dentin in the samples. When the laser beam was perpendicular to the surface, all three lasers produced well-shaped craters. From this, it was concluded that the angle of the laser beam in relation to the target surface can be a deciding factor of how much energy will be absorbed by the dentin and consequently of the morphological changes induced by the laser.

Connective tissue response to root surfaces resected with Nd:YAG laser or burs

PROBLEM

The Nd:YAG laser beam may be used for root resection, but the tissue compatibility of the resulting root surface has not been confirmed.

OBJECTIVE

This study assessed the connective tissue response over time to implanted root segments with Nd:YAG laser-cut or bur-cut surfaces.

STUDY DESIGN

Endodontically treated roots of 25 extracted human teeth were cross sectioned to form 3.5 mm thick disks by alternating a water-cooled Nd:YAG laser with a high-speed water-cooled tungsten fissure bur. A total of 63 disks were implanted into the dorsal subcutaneous tissue of 16 rats, then recovered with the surrounding tissue after periods of 3, 7, 14, 28, 60, and 90 days, and processed for light microscopic examination. Tissue against the cut surfaces was assessed for intensity and extent of inflammation and fibrous capsule thickness.

RESULTS

A two-factor analysis of variation showed statistically significant (p < 0.05) differences between the laser-cut and bur-cut surfaces.

CONCLUSION

Tissue repair about the root surfaces resected with Nd:YAG laser was delayed when compared with those resected with a bur.

Root end filling materials: a review

When non-surgical attempts prove unsuccessful or are contraindicated, surgical endodontic therapy is needed to save the tooth. The procedure usually consists of exposure of the involved area, root end resection, root end preparation and insertion of a root end filling material. Numerous materials have been suggested as root end filling materials. This article is a review of the literature on the suitability of various root end filling materials based on their leakage assessment, marginal adaptation, cytotoxicity, and usage test in experimental animals and humans.

Permeability, morphologic and temperature changes of canal dentine walls induced by Nd: YAG, CO2 and argon lasers

The permeability, temperature and morphologic changes of the wall of the root canal induced by Nd:YAG, CO2 and argon lasers were studied. The changes were evaluated according to the presence or absence of a smear layer. Root canals of 140 human single-rooted teeth were enlarged using a step-back technique. Permeability was evaluated by the extent of methylene blue dye penetration into the tubules. Temperature changes were measured using a thermovision system, and morphological changes were evaluated by scanning electron microscopy. Laser energy was delivered into the canal by means of a flexible optical fibre or metal tip. There were statistically significant differences in permeability between lased groups with and without a smear layer in the cervical third of the root canal following lasing. In the middle third of the root canal, all three laser types induced permeability increases in groups with a smear layer. In the apical third, statistically significantly decreases in permeability were observed among CO2 laser and Nd:YAG compared with control group (P < 0.01). Rises in temperature ranged from a minimum of +10.1 degrees C (CO2 laser) to a maximum of +54.8 degrees C (argon laser). All three laser devices appeared capable of producing a glazed-like surface and craters.