Indexing the FacebowBy Darin Dichter on October 5, 2016 | comments
The purpose of the facebow is to transfer both esthetic and functional information from the patient to the articulator. While a variety of other methods for transferring this information have been proposed, the facebow transfer remains a highly efficient and predictable approach.
In part, efficiency with the facebow transfer stems from the clinician's ability to delegate this procedure to other team members. The facebow transfer technique we are teaching clinical assistants during the team workshop mirrors closely the work we do in our occlusion workshop.
During a recent team workshop, we had a great discussion about how to index the teeth when making the facebow transfer. Most participants indicated they are currently using bite-registration silicone for this index. Many participants indicated they wanted to use “a lot of material” on the bite fork in order to make sure the model was stable during the mounting procedure. The idea was that, somehow, more was better.
Silicone bite records
While stability is good, there is a potential problem when the entire arch is indexed. The problem here is the same as the problem we encounter with silicone bite records; the silicone bite record is often more detailed than the casts we work with, resulting in the model not seating fully into the silicone.
With silicone bite records, this problem is overcome by careful trimming of the silicone record itself. One could attempt this with the silicone facebow index, but there is a significant risk that the record will detach from the bite fork or break during trimming. Even if the index survives, successful manipulation of the index came at the cost of time.
Rather than index the entire arch, a more efficient approach is to use three discrete dots of silicone. When configured appropriately, the model will be supported by the tripod effect of the three silicon dots. The bite fork component of the SAM facebow system has five large perforations that act to mechanically retain the silicone. Bite forks from other facebow/articulator systems may require adhesive to retain the silicone.
Another alternative involves using thermoplastic modeling compound. Panadent Corp. has created compound stickers that simply remove from a sheet and attach to the bite fork, making assembly very easy.
- Attach stickers in tripod configuration
- Warm the bite fork and compound (in order to avoid burning the patient, be sure to test the temperature of the assembly)
- Index the teeth in the usual fashion; blow air across the bite fork to chill the compound
The thermoplastic compound will not interfere with seating the cast, yet provides a stable tripod for the cast to rest in while attaching the maxillary cast to the articulator.
With either facebow transfer material/technique, accuracy and attention to detail remain important. Even with a focus on detail, the arbitrary facebow transfer can be made in an efficient manner, and we encourage clinician's to delegate this step to their clinical teams.
Darin Dichter, D.M.D., is a member of Spear Resident Faculty.
- Carlsson GE. Critical review of some dogmas in prosthodontics. J Prosthodont Res. 2009;53:3–10.
- Farias-Neto A, Dias AHM, De Miranda BFS, De Oliveira AR. Face-bow transfer in prosthodontics: a systematic review of the literature. J Oral Rehabil. 2013;40:643-722.