Prepared Teeth Isolation: how, when and why
Operative field isolation is a very important step in endodontic and restorative treatments. Therefore, even in prepared teeth the practitioner is called to perform isolation to ensure a safe and predictable endodontic treatment. In these cases, isolation ought to be carefully planned and only material knowledge paired with operative rationale, accurate clinical assessment and a proper operative timing will allow achieving a totally stable and isolated field for the whole treatment duration.
Nevertheless the most important thing to highlight is that, once the field has been isolated, a complex clinical case will become simple, with significant benefit for all subsequent procedures.
HOW Operative rationales for clamp selection in prepared teeth do not differ from standard ones: clamp selection based on the rule of 4 and clamp stability test are the starting point in prepared teeth as well.
In prepared teeth cases, the winning strategy is often to pick clamps with aggressive jaw design since they can reach deep, apically to the finishing line where a very clamp-retentive area due to the radicular cone shape usually begins.nIn prepared anterior teeth, modified clamp 212 (or 212SA) usually works very well, providing good stability.
Even though the dam is placed correctly and the clamp is stable, there still could be a poor fitting of the clamp-dam system to the tooth shape in the cervical area with presence of gaps. In clinical practice gaps can be managed with LIQUID DAM, an EASY-TO-USE photopolymerizable liquid resins capable of sealing quickly and effectively any gaps causing fluid leakage from and to oral cavity.
If no stable clamp is found due to the presence of a very cone-shaped prepared tooth, the winning strategy is to place on the vestibular or palatal face of the tooth a composite layer prior etching and dentin-enamel adhesive application to create a jaw gripping point.
Sometimes, especially in upper canine, the vestibular-palatal diameter could be so wide that the clamp cannot be positioned apically to the prosthetic finishing line, even though it is open to the maximum from the clamp forcep. In cases like this, the winning strategy is to place on both vestibular and palatal faces of the tooth a composite layer in order to create gripping points for the clamp jaws; the same thing can be done with intact but scarcely erupted teeth.
If no stable clamp is found and other teeth are present distally to the tooth to be treated, another possibility is to place a stable clamp in a distal tooth and execute a multiple isolation.
Even in prepared posterior teeth clamp selection based on the rule of 4 and clamp stability test are the starting point for isolation. As for the anterior prepared teeth, the winning strategy is often to pick clamps with a design permitting that prongs contact the tooth apically the finishing line, and if gaps causing fluid leakage from and to oral cavity are present, they can be sealed quickly and effectively with a liquid dam.
In many premolars and in some molars an effective stability could be achieved only by using anterior teeth clamps (6-9-212); their small size and the presence of a double bracket determine a bigger pressure on the remaining dental structure.
In prepared molar teeth, the more aggressive the jaws of the clamp, the easier to find a stable clamp. However, before using these clamps, I always look for stability through less aggressive and flatter jaws such as the ones in clamp 4. The difference can be noticed in operative comfort: when a clamp has almost flat jaw like the 4, the tooth gets actually more exposed (and so more accessible). On the contrary, if isolation is performed using clamps with strongly aggressive jaws (W8A for example), the tooth is going to look more sunk into operative field and the less confortable to access by the clinician.
WHEN Usually in multidisciplinary cases ,the root canal treatment or retreatment is done before the temporary restoration of the teeth. Our philosophy is completely different: what we suggest to do is: before preparing the tooth, then placing the temporary crown and finally performing the endodontic treatment.
WHY Performing endodontic therapy AFTER the temporary restoration gives us many advantages.