Formation of dystrophic calcification deposits within the root canal of a tooth, have historically been difficult clinical endodontic complications. Presently, removal of such tissue, mineralized through the deposition of calcareous materials in a root canal (a 'calcified canal'), remains resistant to conventional endodontic techniques. The subsequent treatment primarily involves undesirable surgical procedures and/or loss of the tooth. Described in this clinical trial is a technique using free running (RF) pulsed, Nd:YAG laser energy to ablate hard calcified tissue which obstructed mechanical access of the root canal and root apex--a technique employed after conventional endodontic methods failed. This paper discusses the 'plasma' effect, 'spallation', canal illumination and transillumination using the helium-neon (HeNe) aiming beam. A free running pulsed, FR Nd:YAG dental laser was successfully used at 20 pulses per second and 1.75 watts to photovaporize and photodisrupt enough calcified tissue obstruction, to allow a conventional endodontic file to pass the canal blockage, and access the root apex. This clinical trial achieved the immediate, short term objective of endodontic hard tissue removal via photovaporization and photodisruption. The pulsed FR Nd:YAG dental laser used as described in this clinical report appears to be a very safe and very effective technique; offers a treatment alternative to traditional therapy that suggests high patient acceptance; and is significantly less stressful for the doctor and staff than traditional treatment options. Long-term, controlled scientific and clinical studies are necessary to establish the safety and efficacy of both the helium-neon energy for visualization and the low- watt pulsed FR Nd:YAG energy for photovaporization and photodisruption of hard calcified tissue within the root canal. Research is especially needed to understand the effects of low- watt, pulsed FR, Nd:YAG laser on the activity of osteoclasts and odontoclasts and identify risks for developing external and/or internal resorption after intracanal application of pulsed FR Nd:YAG laser energy.