Overfilling: Endodontic Failure Vs Clinical Success

Fig. 1

First right mandibular molar with an infiltrated amalgam, and underfilled canal obturation.
After retreatment the Rx shows three-dimensional endodontics and slight surplus after filling on mesial canals obturated with Thermafil #25 and distal canal with warm vertical condensation.
After 5 years the excess has disappeared and periapical tissues are in healthy conditions.
These conflicting results can be attributed to differences in study methodology and to the diversity in composition of the extruded materials.
Generally, the most common causes are related to differences in apical anatomy hampering the performance of endodontic procedures in a variety of clinical situations.

Fig. 2

Main factors for overfilling

• External apical inflammatory root resorption associated with apical lesion in teeth that have undergone previous intervention.
• Incompletely formed root.
• Overinstrumentation with deviation from the canal’s natural path and apical perforation.
• Inadequate manipulation of plasticized or non plasticized gutta-percha and sealers during obturation procedures.

It is critical to define and make a distinction between overfilling, which is the three-dimensionally cleaned, shaped, and packed root canal that exhibits surplus after filling Vs an obturation overextension with internal underfilling.

Fig. 3

Typical aspect of overfilling: note the scratch on the cone.

Fig. 4

Apical foramen is completely filled.

Fig. 5

Correct extension of the obturation but underfilling of canal. Notice the apical transportation during shaping procedure. Courtesy of Dr. M. Vitullo

Fig. 6

Post-operative radiograph of a mandibular first molar reveals a large apical lesion of endodontic origin. Mesial canals were obturated with Thermafil. A 4-year recall demonstrates osseous repair. Filling excess has not prevented bone healing.

Fig. 7

Thermafil carrier overfilling on the distal root. Thermafil is a good technique for obturation as long as the protocol is respected. Notice the  extrusion of the carrier and the obturation underselling the canal. After 6 months the lesion looks smaller than in the pre-op Rx and the patient reports disappearance of pain during function.

Fig. 8

Even MTA can be extruded into the periodontal tissues. In this case the rule is just the same as that of the previous cases: if the canal is clean, excess of MTA canno’t prevent tissues from healing. 6 years follow-up, courtesy of Dr. R. Tonini.

Fig. 9

Obturation is the last step of an endodontic treatment: overfilling of the canals either with sealer or gutta-percha isn'’t necessarily a procedural error during obturation. It can however be due to an error during the shaping procedure, leading to a root canal with parallel walls instead of a tapered one,  or maybe due to apical resorption or a widened apex.

Hence, we have to define the reasons for overfilling of a root canal: what is the direct cause? “Is it an excess of material remained after the three-dimensional obturation or an overextension with canal underfilling?” Surplus material does not constitute an endodontic goal, but it can be seen rather as a result of the hydraulics required to achieve a three-dimensionally packed root canal systems.