Indirect restorations are the mainstay of most general practices. Deciding whether to take triple tray or full arch impressions is a process that represents the classic dilemma we all face. It feels like we are deciding between “quality” and “economics”. In truth I think there are “quality” and “economic” pros and cons to both types of impressions.
From an economic perspective triple tray impressions are a straightforward decision. A triple tray and the VPS to take it represent about $10 in materials compared to two full arch trays, VPS material, facebow and bite registration at a cost of about $25 in materials. Additionally a very important economic factor is productive chair time. A triple tray impression should take about 5 minutes of chair time, whereas full arch impressions and all the accompanying records take approximately 15 to 20 minutes.
The balance to the chair time on the front end is the chair time required to seat and adjust the case. In order to do an accurate comparison of the seat appointment we need to discuss the technical risks and benefits of the two approaches. We are going to assume on the front end that both techniques are done with proper retraction and accurately represent the prep and margins. A triple tray impression captures the occlusal information at maximum intercuspal position extremely accurately, but it is the only functional position they can replicate.
Full arch impressions taken without a facebow transfer, either hand articulated, or with a bite registration only over the prepared teeth only give the same information about maximum intercuspal position to the laboratory as a triple tray. The advantage to taking full arch impressions is that they can be mounted with a facebow transfer and allow the laboratory to see the interaction of the teeth in excursive and end to end positions. A facebow records the relationship of the maxillary arch to hinge axis in all planes of space, and then transfers this information to an articulator. It can also be used to communicate esthetic information about the relationship of the incisal and occlusal plane to the horizon if the bow is leveled when the record is taken.
So the ultimate difference between a triple tray and full arch impressions is the addition of functional information about excursive movements and end-to-end positions. This requires taking a facebow record, and can be increased in accuracy by setting the condylar elements on a semi-adjustable articulator either with a protrusive bite record or an end to end retracted photograph. Using either technique the most accurate bite record is always captured with the unprepared teeth in full occlusal contact. So the decision between the two approaches really depends on the functional and esthetic risk factors of the case. The more esthetic and functional information we send to the laboratory the higher our chances of managing the esthetic and functional issues of the case precisely.
I don’t even know where to start. Your comments may be well intended but seem only to support selling a technique
that markets the concept of the “triple tray”.
It is OK, but like any method only as good as the operator
I think I full arch impression shows shape of teeth in entire arch so u get balance. Triple trays are great. What is important to understand is a practice in Beverly hills is very different then south bronx. I find many lecturers unaware of constraints of doing dentistry in different areas. As far as a face bow it is arbitrary device as no exact way to know where condyles are. Agree with above poster. Some things I’m pretty good at and some things weak. I’ve practiced for 33 years and have been thru no gloves, no triple trays, prophylaxis changes. What I would guess is 50% of dentists don’t remove decay cause of difficulty and inexperience. Look at FMS. Endo by specialist vs generalist. Does my back hurt after all these years? Yup. It is a very difficult field. Hope this helps.
I totally see the tremendous difference in the amount of information you can portray to the lab in regards to full arch vs triple tray impressions. The next question is how does this compare to digital full arch impressions, since excursions,CR bite etc seem impossible at this point in time to take digitally. There have been labs that claim they can articulate a model on a digital articulator but I really don’t see how that could be accurate.
Digital articulation is coming along, and there are great ways to transfer some of this information. However, these systems are not widely used or available. For now for most of us in general practice when we need the information provided to work in CR and create functional results outside the mouth that will transfer predictably to the mouth, an analog approach for me is still the way to go.