After reading Dr. Divya Jha and colleagues’ January JADA article, "Inability of Laser and Rotary Instrumentation to Eliminate Root Canal Infection" (
JADA 2006;137:67–70
), I was surprised and disappointed to learn that our traditionally excellent editorial staff overlooked thoroughly vetting the methodology utilized by the research group in their study.
Regrettably, the study is characterized by serious, inferior research design flaws, and the conclusion is not a valid one. Moreover, its inaccurate conclusion can serve to deter conscientious clinicians from delivering more comfortable and safe conventional and surgical endodontic therapy by discouraging its integrated use in patient care.
In their study, the researchers totally immersed the initially sterilized test specimens, namely, the entire decoronized single-rooted teeth Groups A through D, in a thioglycollate medium broth of Enterococcus faecalis. By virtually soaking the teeth in this clinically unrealistic manner, the entire lengths of the dentinal tubules were infiltrated or contaminated (infection is reserved for living organisms).
By subsequently performing either intracoronal instrumentation with nickel-titanium instruments or laser treatment solely (without somehow treating the external cemental root surfaces by either planing or scraping in some manner) or even lasering and then culturing the manipulated specimens, the dentist is programming the findings for a positive result. A more clinically realistic situation would have been simply to introduce the E. faecalis broth only within the root canal system, then perform the various procedures and subsequently reculture intracoronally.
It is apparent that every region of the teeth was contaminated: the pulpal dentinal tubules, the cementum and, certainly, any nongloves used by the researchers. Moreover, the researchers did not indicate if their hands-on approach to the in vitro treatment utilized sterile gloves in each and every aspect of their manipulation of the extracted teeth.
This is a very important consideration, since glove and lab desk contamination is a major concern and a critical factor in this study. It is a well-known fact that false-positive results are far more prevalent than false-negative results in micro-biological studies. Perhaps the most essential element in the methodology would have been to culture for the microorganisms that gave rise to the positive turbidity results and specious conclusion before the authors condemned the use of laser technology.
By not culturing and identifying the microorganism, and perhaps not utilizing a sterile gloving and continuous aseptic lab-top technique, the assumption that the turbidity was caused by E. faecalis is an opinion only and, at best, a reasonable assumption. Good research does not result from such opinions.
The late Dr. Herbert Schilder, one of the most dedicated, knowledgeable and skilled educators and clinical endodontists in our profession, frequently stressed that endodontic access is key to any intracanal treatment. One cannot treat what one cannot reach. Very simply, one cannot paint a room through a keyhole. The researchers, by simply making a hole in the decoronized roots and not providing adequate space for the sapphire laser tips to reach the pulpal dentinal tubules in Groups A and B, set up a system of positive turbidity and negative results.
Also one should bear in mind that even culturing one microorganism over a period of three weeks can give rise to turbidity in this study. Of what microorganism? Maybe E. faecalis. Proper use of the laser tip dictates an upward, circumferential stepping of the sapphire tip out of the properly accessed root canal system. The divergent beam of the laser tip covers an approximate 17 degrees. The probe requires working room to exert its effect.
I am very surprised, after reading this fine journal for 32 years, that my esteemed colleagues in our fine profession could have overlooked the serious methodological flaws in this study.
