1. Start With Quality Impressions
Many diagnostic impressions are not viewed with the same attention to detail that a final crown and bridge impression is scrutinized. If these impressions are going to be utilized to for diagnosis, treatment planning, diagnostic waxing, and eventual provisional fabrication, then it makes sense to obtain extremely accurate impressions.
2. Use An Alginate Replacement, Polyvinyl Siloxane Impression Material
Flextime Putty with a light body wash, by Heraeus, is an excellent material way to create and optimum diagnostic impression. It will allow for multiple pours if necessary, and will eliminate the need to pour the model immediately. Be sure to dry the teeth prior to placement of the impression, and be sure to capture all the surfaces of the teeth, extending well beyond the free gingival margins of the teeth, the entire buccal and lingual vestibules, and the entire hard palate
3. Creating Quality Casts
When the casts are poured it is important to follow the water-powder ratio of the specific stone the office will be using. It is also a great idea to consider using a vacuum-mixing machine to eliminate air in the mix. This will give you bubble free, dense casts, with maximum accuracy.
4. Choose An Appropriate Instrument
Many excellent articulators are currently on the market. The most important feature is that accept a facebow transfer, and that the condyle guidance can be altered when needed. One of the simplest instruments on the market is the Denar Combi II Articulator from Whipmix, designed by Dr. Peter Dawson.
Contemporary Product Solutions‘ recommendation is find an instrument that feels good in your hands, one that your laboratory uses, and one that you can teach your staff to use day in and day out. A quality articulation system is worth its weight in gold to the cosmetic/restorative practice.
5. The Corrected Facebow Transfer
The goal of the facebow transfer is to have the maxillary cast mounted on the instrument; in the exact same relationship the maxilla is oriented to the skull when the patient is standing up straight. The distance from the maxillary incisal edge to the axis of rotation of the mandible should also be duplicated.
The Slidematic facebow from Whipmix is an example of a simple ear-bow, which can be utilized to mount the maxillary cast along with a rigid bite registration material, like Venus Bite. We also recommend using a bubble level from Great Lakes Prosthodontics to be sure the facebow is level with the floor when the patient is standing upright. This is important because some patients ears are not level, which can lead to the incorporation of a cant to the maxillary incisal plane.
6. Centric Jaw Relation Records Using Bi-Manual Manipulation
While several methods exist to record centric relation. Bimanual manipulation, described by Dr. Peter Dawson, is an excellent way to find, verify, and record CR. Learning to position the patient, position the hands properly, as well as to employ the proper pressure is the key to success. Taking the time to learn this technique will add tremendous predictability in the diagnosis and treatment of occlusally driven restorative care
7. Techniques For Mounting The Models
Contemporary facebow systems allow for separation of the mounting jig from the earbow. This will allow the maxillary cast to be easily mounted on the articulator. Employing the corrected facebow technique previously described will position the maxillary cast on the instrument, as the maxilla relates to the skull. The maxillary cast is stabilized using a rubber band, and then mounted utilizing mounting stone. The mandibular cast is then related to the maxillary cast via the centric relation record. An excellent way to stabilize the cast is to use a hot glue gun with four nails. This will keep the models in the precise maxillo-mandibular relationship recorded clinically. Stone can be mixed and placed between the cast and the mounting plate without the fear of inadvertently rocking the lower model.
Taking some extra care to carefully mix and smooth the mounting stone will provide presentation quality models. Clyde Schyler once said that “sloppy models were not an indication of sloppy dentistry, it was absolute proof!” Taking extra time with diagnostic impressions, jaw relation records, and mounting procedures, is a critical part of the treatment planning process and great restorative technique.
Contemporary Product Solutions mission is to provide the dental profession with clinically relevant information to all areas of the dental practice. Product review will provide unbiased, up-to-date, evidence-based information on equipment, materials, protocols of treatment, and long term performance. Each evaluation includes a step by step tech spec of each product, clinical overview and summary, technique video and an overall rating.