Authors: Michanowicz AE, Czonstkowsky M, Piesco NP.
Title: Low-temperature (70 degrees C) injection Gutta-percha: a scanning electron microscopic investigation.
Journal: J Endod
Date: Feb 1986
Citation: 12(2):64-7
Category: Obturation
Evidence-based Ranking: 5
Purpose/Objective: To determine if there was a structural basis for the difference in leakage noted in our previous studies using low temperature injection technique with or without sealer and to compare this with more conventional technique using lateral condensation and sealer.

Materials and Methods: 130 teeth were instrumented using a flared back technique which involves the working length being instrumented at least three file sizes higher than the first file that bound. The middle and coronal thirds were prepared with Gates Glidden burs and copious amounts of 2.5 % NaOCl were used for irrigation. The teeth were divided into three groups for obturation: 1. low-temp GP technique, 2. low-temp GP technique and Grossman sealer, and 3. lateral condensation with Grossman’s sealer. The teeth were stored for 7 days, and longitudinal grooves were prepared and the teeth were placed in liquid nitrogen to induce fractures along the grooves. The specimens were examined with an ISI mini scanning electron microscope for adaptation, voids, homogeneity of the material, and the location of the sealer in the root canal. Results: 1. Low temp GP w/o sealer- There were no voids and the material was a homogenous mass. This technique reproduced the shape and irregularities of the root canal wall. In the coronal and middle thirds, there were some projections into the dentinal tubules. 2. Low temp GP w/ sealer- The results were similar except there was homogenous layer of sealer between the GP and dentin. In addition there were no projections of GP or sealer extended into the dentinal tubules. 3. Lateral condensation- there was close approximation of the GP and wall, however there were no microscopic ridges or surface features evident in the obturation. No sealer or GP projections were extended into the dentinal tubules.

Author’s Conclusions: The root canal system can be obturated as good or better with the low temperature GP injection system with sealer as with laterally condensed GP with sealer.

Reviewer’s Comments: The study does support some positive claims to injectable GP in terms of adaptation and lack of voids as compared lateral condensation. The work does not mention other criteria for optimal obturation, such as apical control, which becomes more important if using patency techniques with a crown down continuous taper for canal preparation.