Dott. C. Sobrero
Private Practitioner, Trofarello (Turin), Italy

Retrospective considerations about 6 years clinical endodontics with thermoplasticized dental gutta-percha.

Summary
The use of a heat softened dental gutta-percha with a gun shaped electrical appliance (Obtura II from Texceed Corp.), vertically condensed into the root canal, achieves a good quality endodontics, time saving and constant results.

The author clinically uses this techniques for more than six years now. It would be advisable to dispose of softer gutta-percha cartridges, and longer silver needles to handle with particular cases.

Introduction
After my first approach to vertical condensation of gutta-percha in 1992, i found the idea of using the thermoplasticized gutta-percha technique for the obturation of the apical third of the root canal system, very attractive.

In those years I was advised this technique only for the backpacking, that is for the back sealing of the middle and the coronal third of the endodontic space.

The advantage of such a technique was the total indipendence from any kind of pre-formed gutta-percha tip to seal a non pre-formed space.

Marlin and Coll. achieved the first studies on this topic in 1979 in vitro (1) and 1981 in vivo (2).

Materials and methods
The gutta-percha is injected deep in the endodontic space, and condensed up to the foramen with a plugger, after having been heat-softened with a gun-shaped electrical appliance.

This is clinically obtained with the use of Obtura II siringe from Texceed Corp. This appliance warms-up the gutta-percha through a thermostatic electrical resistance, which temperature can be accurately set by the operator.

The same appliance allows to inject the needed amount of softened guttapercha in the canal through a silver needle.

The size of the needle is such that with a conventional conical shaping of the canal, it is possible to introduce it up to ~4mm. from the apex.

To avoid an overfilling it is necessary that the foramen be as small as possible. So thi technique is unadvisable in all the clinical situations in which the size of the foramen is too big.

Besides it is unadvisable in all the cases where the canal is longer than 32 mm. because of the lack of needles of the right lenght.

The letterature (3) gives some definite indications, in which the size of the foramen is small or inexistant:

• Back-packing.
• Blocked canals (wich cannot be probed).
• Immature apex canals after apecification.
• Internal resorptions after sealing the apex with a conventional technique.
• Canals in which it is impossible to introduce or try a gutta-percha tip.
• Canals with a perforation of the apical third.
• In orthograde re-threating of surgical failures.
• In surgical endodontics.

In spite of this, I believe this method can be used in most clinical situations when it is coupled with a cleaning and shaping technique that allows to keep the apical foramen as small as possible. The importance of using a sealer to improve the sealing and the flowing of gutta-percha must be pointed out (2).

The volume shrinking of the cooling gutta-percha is sometimes criticized. It has been proven that the shrinking is directly related with the thermal excursion (4).

But from a clinical point of view Torabinejad (5)showed with SEM studies that with an accurate packing a similar result to more conventional techniques can be achieved.

Last two years
The new NiTi mechanical shaping helped improve this sealing technique.

The shaping with 0.06 instruments allows a funneling that matches the size of the thinner Obtura II siringe needle; very smooth canal walls that make easy the progression of the gutta-percha; last but not least, a very small apical foramen.

The coupling of a NiTi mechanical shaping and a filling in thermoplasticized gutta-percha results in a high quality endodontic therapy, time saving and constant results.

Future developements
The use of a lower viscosity gutta-percha cartridges would be advisable to handle specific cases, while keeping a lower heating temperature.

This probably would involve a change in the siringe gasket and shaft to prevent the low viscosity gutta-percha from leaking backwards.

Besides having longer silver needles would be useful to treat canals longer than 32 mm.

Bibliografy

1. YEE, F.S., MARLIN J., KARAKOW, A.A., GRON, P.: Three dimensional obturation of the root canal using injection-molded, thermoplasticized dental gutta-percha.J.Endod. 3:168, 1977.
2. MARLIN J., KARAKOW, A.A., DESILETS, R.P., GRON, P. : Clinical use of injection-molded, thermoplasticized gutta-percha for obturaton of the root canal system: a preliminary report.J.Endod. 7:277, 1981.
3. CASTELLUCCI, A. Endodonzia – Ed Odontoiatriche Il tridente- 1993
4. SCHILDER, H., GOODMAN, A., ALDRICH, W.I.: The thermo-mechanical properties of gutta-percha. Part III. The determination of phase transition temperatures for gutta-percha. Oral Surg. 38:109, 1974.
5. TORABINEJAD, M., SKOBE, Z., TROMBLY, P.L., KRAKOW, A.A., GRON, P., MARLIN, J. : Scanning electron microscopic study of root canal obturation using thermoplasticized gutta-percha.J.Endod. 4:245 ,1978.

Dr. Carlo Sobrero
Torino 67/a TROFARELLO 10028 (TO)
e-mail: csobrero@galactica.it