Oral Health Group
Feature

Laser Assisted Endodontic Therapy

May 1, 2012
by Tzvi Rubinger, DDS


More than 14,000 endodontic procedures are performed in the USA every year (American Association of Endo­dontists). Four percent of that number will require retreatment.1

The accepted objectives of root canal therapy are: Cleaning and shaping of the root canal space, disinfection of the canal space and three dimensional obturation of the root canal system. A number of challenges to these objectives have been described and many technologies have been developed to overcome them. Instrumentation systems, intra-canal medicaments, irrigants and their delivery systems, obturation systems, have all undergone dramatic evolutions with variable results.

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This article will attempt to offer the integration of an Er,Cr:YSGG laser (Waterlase MD Biolase Inc.) as a viable addition to endodontic armamentarium and the ways it could overcome some of the challenges to successful root canal therapy.

This laser is considered to be an “all tissue laser” namely if can ablate soft tissue, tooth structure (and composites), and bone. It operates at a 2780 nm Wavelength. Its ablation is achieved through laser absorbption by target tissues and accelerating water molecules to create a “hydrophotonic” effect of micro explosions. The laser emission is through a tip placed in a hand piece. For intra-canal delivery, radially firing tips are used (RFT). These flexible tips come in 275and 415 micron diameters and 17, 21 and 25 mm lengths.

PROBLEMS IN CONVENTIONAL ENDODONTICS AND THE BENEFITS OF LASER TECHNIQUE

Access Preparation
Since tooth preparation is achieved in non contact mode, it avoids vibration pain even in “hot” teeth that are difficult to anesthetize. There is no heat produced and no micro-fractures are possible. The non contact mode and the dissipation of energy away from the tip make perforations very rare. By virtue of the antimicrobial effect of laser, the access disinfection initiates the “crown down” concept.

Debridement
Cleaning and shaping systems do not always clean the complex root canal space of most teeth in three dimensions. Often attempts at cleaning oval or ribbon shaped canals with cylindrical instruments result in aggressive reshaping of the natural canal space and the inherent dangers of clinical misadventures. As an example Dr. Ove Peters reported on NiTi preparation: “in maxillary molars instrumentation techniques left 35% more of the canal’s surface area unchanged. A strong impact of variations of canal anatomy was demonstrated.”2

The goal is to utilize conventional, conservative techniques to allow the insertion of an RFT to within 1-3 mm of the apex. The laser energy and hydrophotonic activity can remove pulpal tissue, bacteria, smear layers and dentin from canal walls three-dimensionally since the laser tip does not require contact for it to be effective. The cleansing effect is created by the hydrophotonic effect (microagitation) which also results in negative pressure within the canal, resulting in more fluid being drawn in. Since the tips cannot fire through the tip end, “over instrumentation” beyond the apex cannot occur unless the tip is inserted beyond the apex.

Disinfection
Bacterial infiltration into dentinal tubules has been reported to be 400 microns. (Haapasalo & Orstavik).3 Chemical rinses have a penetration depth of 100 microns (Berutti et al)4 which results in the possibility of bacterial entombment and microleakage.

Since laser light is a penetrating modality, it has the ability to penetrate 1000 microns into dentin (Moritz et al).5 The resulting disinfection is 99.7% reduction in dentinal tubules infected with E. Fecalis.6 Similar results were obtained in studies carried out at Temple University leading Chairman of Endodontology Roy H Stevens to conclude that: “A high level of disinfection can be achieved in minutes, saving both the patient and dentist significant time during endodontic procedures.” Schoop et al stated: “the Er,Cr:YSGG laser, in conjunction with radial firing tips, is a suitable tool for the elimination of bacteria in root canals and for removal of smear layer.”7

THREE DIMENSIONAL OBTURATION
The extent of endodontic sealer penetration depends on the extent of canal debridement as well as the properties of the sealer employed. Hydrophilic resin sealers such as EndoRez, display deeper and more consistent penetration (mamooti et al)8 (Fig. 4).

A study at the University of Florida showed that the Er,Cr:YSGG laser treatment resulted in greater number of isthmuses (28%) obturated compared to conventional cleaning and shaping with NaOCl, 17% EDTA and rotary instrumentation9 (Figs. 5A-E).

It is worth noting the short duration of resrbption of EndoRez extruded through the apex (Fig. 6).

CASE PRESENTATION
A 55-year-old male presented with extreme cold sensitivity and chewing pain at #26. Fracture line was observed from mid occlusal over onto the palatal aspect. Tooth #26 tested positive with cold stimulus and bite stick. The patient was informed about the questionable prognosis due to the obvious fracture line however, he chose to attempt saving the tooth with root canal treatment. A fracture line can be seen on the enhanced digital radiograph as well as advanced pulpal calcification (Figs. 7A & B).

Access was initiated with the Waterlase MD to reduce vibration and possible disturbance of the fracture. Once the chamber was accessed, significant calcification was found. The calcification was removed with the same laser tip at modified settings to uncover canal orifices without perforation (Figs. 8 & 9).

Three canals were penetrated with a #10 Hed­strom file and working lengths were established.

The coronal and middle thirds of the canal were instrumented with Tilos stainless steel and NiTi shaping files in an oscillating AET handpiece (Ultradent Corp.). Alternating with hedstrom instruments hand held as well as mounted in oscillating M4 hand piece (Sybron Corp.) File EZ was injected into the canals with Navitips (Ultradent Corp.) was used as canal lubricant. These instruments allow for preservation of the natural anatomy of the canals and open them to extent required to insert the RFT to within 1mm of the apex (Fig. 10).

Laser tips were used to debride the apical one third, irrigate and disinfect the canals (Fig. 11).

Obturation was done with Endorez (Ultradent) and warm gutta percha delivered by Obtura (Fig. 12).

David Brawdy, endodontist, Lynbrook, NY, describes the hybrid technique of conventional and laser endodontic therapy as: “minimally invasive, maximally invasive endodontics.” The use of the Waterlase laser with radial firing endodontic tips offers a viable approach to successful endodontic therapy when used with sound, accepted treatment principles.OH

Dr. Tzvi Rubinger graduated from University of Toronto Faculty of Dentistry in 1985. He has been in private practice in Toronto since. Dr. Rubinger introduced lasers into daily practice in 2006. He has trained extensively in laser procedures in all aspects of dental practice and holds a mastership certification from the World Clinical Laser Institute (WCLI). At present he is the only Biolase certified trainer in Ontario. He can be contacted at rubinger@rogers.com. The author would like to acknowledge the research of literature done by Dr. David Brawdy.

Oral Health welcomes this original article.

REFERENCES

1. American Association of Endodontists, website information.

2. Peters, Schonenberger, Laib IEJ 2001.

3. Berutti et al. JOE 1997 23(12):725-727.

4. Happasalo and Orstavic. J. Dent. Res. 1987 66(8):1375-1379.

5. Moritz et al. Las. Surg. med. (200) 26(3) 250-261.

6. Gordon et al. JADA 2007; 138(7):992-1002.

7. Schoop et al. Lasers Med Sci 2007.

8. Mamooti e
t al. IEJ, 2007 vol. 40 871-873

9. Varella, C.H. and Pileggi, R. “Obturation of Root Canal Systems Treated By

10. Er,Cr:YSGG Laser Irradiation”, JOE, September 2007 33 No 9; 1091-1093.


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