Bite blocks and records.
A bite block is the instrument for recording the information every subsequent stage depends on. An error here is not correctable later.
What the block is recording
Five things: the vertical dimension of occlusion, the horizontal jaw relation, the occlusal plane, the amount of lip support, and the midline.
Each is transferred to the articulator and becomes the reference for tooth position. The technician is not guessing at any of them — they are reading what you recorded.
Which means a block returned without marks is a block that has recorded very little beyond a vertical dimension.
Adjusting the rim
Adjust the upper rim first for lip support and incisal display at rest, and trim it so the anterior plane is parallel to the interpupillary line and the posterior parallel to the ala-tragus line.
Then adjust the lower to meet it at the vertical dimension you have determined, checking freeway space with the patient at rest.
The rims should contact evenly across the arch when closed. A rim contacting on one side rotates the record and produces a cant that appears in the finished denture.
Mark the block
The midline, the canine lines, and the high lip line at minimum. Those three marks determine anterior tooth position, tooth width selection and how much of the denture will show when the patient smiles.
Adding a note on the block itself about anything unusual — a facial asymmetry, a patient request for a particular arrangement — is more reliable than a separate written instruction that may become separated from the case.
Photograph the marked block in the patient's mouth if the case is at all demanding.
Recording the jaw relation
The horizontal relation should be a reproducible retruded position rather than a posture the patient adopts on the day. Guide the patient into it and verify it reproduces before recording.
Use a registration material that sets rigid and does not displace the rims. Too much material props the patient open and records a vertical dimension greater than the one you established.
Where the patient cannot produce a reproducible position, say so on the prescription. It changes how the case is mounted and may warrant a different approach.
Common errors
Rims not contacting evenly. Vertical dimension recorded without checking freeway space. Registration material used so generously that the rims separate. Blocks that have warped in transit because they were not supported.
Each produces a mounting that is wrong in a way that only becomes apparent at try-in, by which point a stage has been wasted.
Assessing vertical dimension
The usual approach combines several checks rather than relying on one: freeway space measured between rest and occlusion, the patient's appearance and lip competence, speech, and any pre-extraction records that exist.
Where the patient has an existing denture they tolerate well, its vertical dimension is genuinely useful information even if it is not ideal — a large change from a long-worn dimension is poorly tolerated regardless of whether the new figure is theoretically better.
Record how you determined it on the prescription. It matters if the case needs revisiting.
What to put on the prescription
Tick Bite Block under Procedure when prescribing the stage, and tick the following stage when returning the recorded block.
State the vertical dimension you established and how, note the tooth shade and mould you want, and describe anything about the patient's expectations that will affect tooth arrangement.
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Digital scans and conventional impressions are both accepted. Cases move by UPS and Purolator, and Fairmont works with practices throughout British Columbia and across Canada.