Dental Impressions/Scanning and Bite Registration
Dental impressions with alginate or other desired medium are taken of both the maxillary and mandibular full arches. The impression should adequately capture the dentition and a good deal of the periodontium both facially and lingually. Alginate impressions should be poured immediately for optimal accuracy.
Digital workflow: Among dental laboratories which accept digital workflow, the maxillary and mandibular dental arches may be scanned in.
Next, a bite registration needs to be taken so the dental laboratory technician can relate the maxillary arch to the mandibular one. This registration should be taken with the patient at the 50-60% protrusive level. Some of the previously mentioned protrusion gauges have attachments that serve as bite forks to facilitate the bite registration process. Whether one uses blue mousse or thermacryl as their bite registration of choice, either one can flow into these attachments providing a degree of rigidity. This makes the registration more durable during packaging and handling at the lab. It is best to add the Blue Mousse® onto the bite fork extraorally with a thin layer on either side. Return the bite fork still attached to the gauge to the mouth (gauge set at 50-60% maximum protrusive). Have the patient’s incisors seat back into the gauge. The mousse will intermingle with the teeth. Additional mousse can be added with a syringe tip to fill in voids, gaps or bulk up the registration in select areas (Figure 10).
George gauge with bite fork and bite registration capturing the patient at 50% protrusive.
As an alternative if no gauge is available, a light curable Triad™ ball can be formed and can serve as a bite jig. The patient can be guided to bite into the jig at 50-60% maximum protrusive. Instruct the patient to bite only partially through it, thus leaving 1-2 mm between the upper and lower molars. This space will be filled in by the registration paste later. Light cure with a hand held curing device. Remove the acrylic jig and continue to light cure the lingual aspect until fully cured. Replace the jig back into the mouth and inject blue mousse bite registration paste covering the exposed occlusal surfaces of both arches. Once set, remove and disinfect. Both the jig and the bite registration will be sent to the dental laboratory (Figure 11).
Bite registration taken with the patient’s jaw in the 50% protruded position by way of an acrylic jig.
Regardless of method used, return the jig or bite fork registration to the mouth. Have the patient sit in the chair for 5-10 minutes. If the patient can tolerate this protruded position, continue with the MAD fabrication process. If the patient cannot tolerate this position at all, MAD may not be the right treatment for their OSA. But note that some forms of MAD allow the dentist to decrease the degree of protrusion so this from the original 50% protrusive captured at the first appointment.
Digital workflow: Bite registration with the mandibular teeth at 50-60% protrusive and slightly apart may also be scanned in. Protrusion can be maintained by various means such as a tongue blade or an acrylic jig to hold the position while the dental team scans the protrusive bite. With most digital scanner systems a buccal scan on just one side at the premolar level is sufficient for the lab to piece together the bite (Figures 12-14).Retraction of the cheeks and tongue during image capture is recommended so those structures do not interfere with capture of the dentition and gingiva. Any excess saliva on the teeth or in the mouth should be suctioned out and the teeth gently dried with the air-water syringe.
Preparing for digital scanning of the dental arches and bite registration in lieu of traditional impression taking with alginate and trays.
The maxillary arch has been digitally scanned. Repeat with the mandibular arch.
After capturing the protrusive bite at 50-60% of maximum protrusive ability, the software builds a model relating the mandibular arch to the maxillary one. Based on the scans, the dental laboratory can fabricate a mandibular advancement device.