the finger posture and pressure in step 2 are maintained, the fingertips should be pushed closer together to form a spine of compound at approximately the midline. (The entire process described should take no more than a few seconds, and the compound should still be soft enough to mold further as the patient’s mandible is closed into it.)
While the compound is still soft, the mandibular positioning previously rehearsed should be repeated, guiding the patient into a centric relation position while arcing the mandible closed until the mandibular incisors have made an indentation in the compound and the posterior teeth are 1.0 mm out of contact (Fig 4-5). The compound is cooled, and the accuracy of the programming device is confirmed. There are two important points to be checked at this time:
1 The condyles are in the optimum position in their fossae, confirmed by lightly tapping the mandibular incisors into the compound. The patient should close precisely into the programming device with no deflection.
2 The patient must not be closed to the point of contact between the maxillary and mandibular teeth. The mandibular teeth should make contact only with the compound programming device and be no closer than 1.0 mm to the maxillary teeth at any location in the arch.
If the patient’s posture is maintained with the chair back and the chin up, the face will be parallel with the floor, and a well-adapted compound programming device should stay firmly in place. If necessary, it can be held in place by the patient, using his or her index finger (Fig 4-6). It need not be removed until the centric relation registration has been completed.
With the programming device in the mouth, the twin-barrel cartridge of bite registration material (eg, Stat BR, Kerr; Regisil PB, Dentsply Caulk) should be placed in the impression material dispenser and a new tip locked on (Fig 4-7). The registration material is then mixed by expressing it from the dispenser with steady pressure on the trigger.
Fig 4-6 The patient holds the programming device in position while the operator manipulates the mandible.
Fig 4-7 The cartridge of bite registration material is placed in the impression material dispenser with a new tip.
Fig 4-8 Registration material is injected between the teeth on the right (a) and left (b) sides.
Fig 4-9 The patient is assisted in opening the mouth.
The registration material should be injected between the teeth on both sides of the arch and allowed to harden (Fig 4-8). When the registration material has set, the patient is assisted in opening the mouth (Fig 4-9). The bite registrations are removed from each side of the mouth (Fig 4-10) and rinsed with running water. The programming device is also removed at this time. A sharp laboratory knife is used to remove excess registration material that extends gingivally beyond the occlusal one-third of the tooth (Fig 4-11). Both the maxillary and mandibular sides of the registrations are trimmed, leaving only the cusp tips of the teeth. The registrations are then trimmed on the facial and lingual sides. The lingual aspect is trimmed, leaving the entire cusp tip indentation in place (Fig 4-12). The facial aspect is trimmed through the facial cusp tips (Fig 4-13). Trimming through the facial cusp tips allows complete seating of the registration to be visualized on the maxillary and mandibular casts (Fig 4-14). The registration is then rinsed with a hospital-grade disinfectant and placed in an unsealed sterilization bag until ready to be used.
Fig 4-10 The registrations are removed from the right (a) and left (b) sides of the mouth.
Fig 4-11 (a and b) Registration material extending gingival to the occlusal one-third of the teeth is removed.
Fig 4-12 Registration material is removed from the lingual aspect of the registration.
Fig 4-13 Registration material is removed from the facial aspect of the registration by cutting along a line through the facial cusp tips.
Fig 4-14 The registration is checked to determine if the teeth seat fully in the registration.
Fig 4-15 (a and b) Registration material is injected between the prepared teeth and the opposing arch.
Fig 4-16 The excess material is removed from the facial and lingual aspects of the registration.
Maximal Intercuspation Record
Although diagnostic mountings are done with the condyles in a centric relation position, casts that are to be used for the fabrication of restorations for a small portion of the occlusion are attached to the articulator in a position of maximal intercuspation. Mounting them in a centric relation position could result in a restoration with a built-in interference.
Armamentarium
Polyvinyl siloxane registration material
Impression material dispenser
Laboratory knife with no. 25 blade
Technique
The technique employed to index the intercuspal position for restoration fabrication produces an interocclusal record with the maxillary and mandibular teeth in full contact.
An impression gun is assembled in the same manner as when obtaining a centric relation record with registration material (see Fig 4-7). With the patient’s mouth slightly open, material is injected between the prepared teeth and the opposing arch (Fig 4-15). The patient is instructed to close firmly until all posterior teeth are contacting normally. The dentist parts the lips and verifies that the patient has not closed in a protrusive