Why this is harder than recall
Reactivating a lapsed patient is a reminder. Acquiring a new one is persuasion, and the difference shows up in every number.
A lapsed patient already trusts the practice, knows where it is, and has a record with you. A household three streets away has none of that, and probably already has a dentist.
Expect a lower response rate — often several times lower — and a longer lag between the drop and the appointment. That does not make it a bad channel. It makes it a channel to judge on a different scale.
Geography does most of the work
For a dental practice, distance is the strongest single predictor of whether someone will become a patient. People do not drive across a city for routine care.
Mail tight. A radius that covers the neighborhoods people actually commute from beats a larger one that pads the count with households who will never come.
If you can see where your existing patients live, use that. The map of your current patient base is the best available description of your realistic catchment, and it is usually smaller and more lopsided than owners assume.
The offer has to overcome inertia
Most recipients have a dentist. The card is asking them to change a working arrangement, which requires more than a modest discount.
The offers that work address the actual friction: a new-patient exam and X-ray at a fixed price, evening or Saturday availability, accepting a specific insurance, or short waits for an appointment. Convenience and certainty move more people than price alone.
Be specific about what is included. A vague "new patient special" makes the reader do work to find out what they would be agreeing to, and most will not.
New movers are the exception
There is one group where acquisition is nearly as easy as recall: people who just moved.
A household that relocated in the last few months has no dentist in the area and is actively replacing every local service at once. They are looking, and the card arrives as help rather than interruption.
If you can source a new-mover list for your area, it is usually the highest-converting acquisition mail a practice can run, and it is worth mailing continuously rather than in campaigns.
Judge it on the relationship
A new-patient drop will look expensive if you measure it against a first appointment.
Mail 1,000 households at $1.19 and you have spent $1,190. If that yields five new patients, your acquisition cost is $238 each — well above a first visit's revenue, and easy to mistake for a failure.
But a dental patient who stays is worth several thousand dollars across the relationship, and often brings family. Measured properly, $238 is inexpensive. Measured against the first cleaning, you would wrongly conclude the channel does not work.