Conventional local anesthesia techniques are frequently unsuccessful, particularly for endodontic procedures. Supplementary injections are often necessary; the periodontal ligament injection is useful for this purpose. This study examined the effectiveness of injecting into the periodontal ligament with a pistol-type pressure syringe as a supplemental technique in patients who did not have adequate anesthesia for endodontic therapy. Sixty patients received the supplemental injections and 20 patients were reinjected when the first PDL injection failed. Data were obtained by questionnaire. Percentages were computed and comparisons made by X2 analysis. The conclusions about attaining anesthesia included: --Needle size was not important; overall, 25- and 30-gauge needles were equivalent. --Injecting under strong back-pressure was important; the greatest frequency of success was attained when injecting under pressure. Lack of back-pressure on both mesial and distal surfaces resulted in a significantly lower incidence of anesthesia. Proper positioning of the needle and maintaining this position, to force the anesthetic deep into the periodontium, is apparently an effective way to generate the needed back-pressure. --Strong back-pressure could usually be attained on either or both surfaces. --Reinjection was frequently successful if the first periodontal ligament injection failed. --Overall frequency of success in attaining anesthesia with the pistol-type pressure syringe was 83%. This was determined by including the instances in which reinjection was necessary. --Comparing the results of this study with a previous similar study, the pressure syringe were equally effective for supplementary anesthesia.

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				R.W. Edwards and T.W. Head A Clinical Trial of Intraligamentary Anesthesia Journal of Dental Research, July 1, 1989; 68(7): 1210 - 1213. [Abstract] [PDF]