Twenty-first century materials and techniques have made the creation of excellent cast partials more predictable than ever before. Yet, the basic requirements remain the same: good esthetic and functional design achieved through solid communication between patient, practitioner and dental laboratory. In this article, we will concentrate on three critical components of good communication: outlining what makes an excellent cast partial, case planning and accurate impressions and models.

Master model.   Duplicate model with survey and design outlined (rest preparation suggestions highlighted in green).

What makes the best cast partial?

There is no perfect cast partial but we can achieve excellent results by meeting the following criteria as closely as possible. An optimal cast partial:

1. Restores the lost occlusal function caused by the patient’s missing teeth.
2. Minimizes the stress placed on abutment teeth to ensure their longevity.
3. Minimizes the trauma to the supporting and surrounding tissue and bone.
4. Is self-cleaning and does not produce food entrapment areas.
5. Is comfortable for the patient to use and to wear.
6. Meets the particular esthetic needs of the patient.

Case Planning

Good communication begins with collaborative, insightful case planning and consultation. It starts with study models being sent to Aurum Ceramic/Classic for pre-planning and computerized prosthesis design to determine rest areas and adjustments needed to dentition. This takes all the guesswork out of the process.

Aurum Ceramic/Classic provides you with a duplicate model on which a survey and design has been outlined with rest preparation suggestions highlighted in a green colour. You can also request that a custom tray be provided along with the survey and design recommendation.

Impression and Model Tips

All of the careful work put into case planning and design can go out the window with poor impressions or inaccurate models. Many of our dental office clients have found the following simple suggestions very helpful in achieving consistently high quality final results.

Master Impression Tips

1. Ensure that a full mouth impression is taken (using a high quality alginate) with all teeth and anatomical landmarks reproduced.
2. Impression must be fully extended.
3. If for an upper cast partial, make sure that the palate is included in the impression.
4. If for a lower cast partial, ensure full extension of the impression including retromolar pads.

Bite Registration Tips

1. Ensure bite registration is taken in centric.

Model Tips

1. Die stone mixed with water (NO Hardener) is recommended in a very thick, smooth mix. A thick mix will flow under vibration but does not run like a thin mix. Thickly mixed, the model is harder with less chance of air bubbles.
2. Indication of correct thickness of stone: the mix does not drip or fall off when the spatula is inverted.
3. IMPORTANT: After the impression is poured, DO NOT invert the tray onto a stone paddy. Inverting can cause error. The unset stone will try to sag away from the impression. The degree of sag (if it occurs) will not be visible to the eye, but it is sufficient to cause poor fit of the framework. Instead, mound thick stone on top of the tray and allow it to set. Before pouring the model, place Playdoh (or children’s modelling clay) in the tongue area of the lower tray to keep the stone from locking over the lingual flange.

By employing good design and communication techniques, we can achieve our ultimate common goal: esthetic partials that seat quickly and easily with fingertip pressure, yet strongly resist dislodgement.