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When dentists are treating a patient that has a situation that may be more involved than simply filling a few teeth such as replacing one or more missing teeth or restoring a collapsed bite, we need a clear understanding of the patient’s condition in order to plan the case for the best possible outcome. The first step in being able to understand and visualize the patient’s condition and possible outcomes are through the use of the diagnostic casts. The diagnostic cast is a life-size reproduction of a part of parts of the patient’s oral cavity for the purpose of study and to plan for the patient’s treatment.
A diagnostic wax-up is a dental diagnostic procedure is which the final outcomes of what the dentist is planning is developed in wax on the diagnostic cast, which is made using stone to ensure it is durable. This helps the dentist to determine what the optimal clinical and laboratory procedures would look like and the patient can also visualize the potential final outcome. In the first step, the dentist takes a digital impression of the teeth using a scanner, or alternatively using the traditional impression materials in the patient’s mouth and these impressions are poured up in the previously described stone to create the diagnostic casts.
The diagnostic casts are important because it permits the dentists to examine the teeth without interference from the tongue, cheek and other soft tissue and allows the dentists to evaluate the teeth in detail. For instance, when we are restoring teeth whether using implants or as part of a bridge or denture, it is important to examine the curvature of the arch and the length, inclination and rotation of the teeth to be sure that it is possible to attain the outcomes the dentist and the patient have in mind. The diagnostic casts are then mounted on a device know as an articulator so the dentist can reproduce the movements of the teeth and the jaws. The selection of the correct articulator is also important as there are various types. In most cases, the dentist will use a simple non-adjustable articulator or a semi adjustable articulator. The nonadjustable articulator is good for single crowns while the semi adjustable articulator is capable of closely reproducing the movements of the jaw and is used for more involved cases than include the restoration of a collapsed bite or a patient with multiple missing teeth.
Usually, two models of the teeth are created using the diagnostic casts, one that will be used for the diagnostic wax up and one that will be kept as a reference during the procedure. Once we have the two diagnostic casts, we can proceed with the diagnostic wax-up. This is important because it can help the dentist to decide which teeth will be prepared, we can evaluate how the final contour will look, and we can select the best treatment option. It is especially useful to the patient to see the potential final outcomes as well. The diagnostic wax-up is also particularly helpful in helping the dentist make a provisional or temporary restoration while we are waiting for the final appliance. When we are doing any tooth replacement procedure or a cosmetic procedure like porcelain veneers, the wax-up is crucial for visualizing the final outcome.
When we are doing porcelain veneers on a patient, having a plan for making an interim restoration is an important part of treatment. This is referred to as a provisional restoration. These are important because the provisional restoration protects the prepared teeth from the hazards of the oral environment and minimize the sensitivity the patient has as a result of the teeth being prepared for veneers. The provisional restoration is also useful to help the dentist determine if enough tooth structure has been removed to permit the placement of veneers while ensuring that they do not look too bulky or unnatural.
A common approach to creating provisional restorations for veneers include the use of what is known known as a silicone matrix that is created from the diagnostic wax-up. The silicone matrix is filled with a material used to make the provisional veneers and placed over the prepared teeth. Once the material is set, the silicone matrix is removed, and the provisional restoration is examined to ensure that a uniform thickness of the material has been achieved. There may be issues that prevent the removal of the provisional from the teeth because it may be mechanically locked in. Often the provisional can be gently teased off. Some clinicians prefer to leave the provisional restoration on the prepared teeth and only remove them when the permanent veneers are ready for cementation.
When we are making provisional restorations for veneers, crowns or a more complicated case, it is important than we pay attention to the margins to ensure that there is no leakage that could cause the patient sensitivity while they are waiting for the final restoration. After we have trimmed and polished our provisional restoration, we then have to cement them using the appropriate cement. When we are cementing provisional veneer restorations, the use of translucent resin cements is a good choice. Dentists often do what is know as spot etching on the front of the prepared teeth to get better adhesion of the provisional and the need for spot etching decreases as the number of teeth that are involved in the veneer case increases due to mechanical retention. Without the use of spot etching, the resin cement is not as strong a link between the tooth and the provisional restoration. The thickness of the veneers is also a factor then must be considered when deciding on the cement as more opaque cements are less esthetic and give a more unattractive appearance. It is also important that we keep the teeth dry as we are working to get the best adhesion possible between the provisional and the prepared tooth. The provisional restoration closely replicates the shape and contour of the final restoration and is an important part of any treatment plan.
I would also like to spend some time discussing full-mouth rehabilitation. The term full-mouth rehabilitation refers to a combination of different dental procedures that are conducted over time to correct a range of dental conditions and rebuild towards a healthy mouth. The goal of full-mouth rehabilitation is not only to bring back a healthy smile, but to also restore the patient to proper function and confidence by replacing missing teeth and promoting good oral health. Individuals who are excellent candidates for full mouth rehabilitation include but are not limited to patients with excessive tooth wear or abrasion, patients who grind their teeth at night and are clinically in need to rebuilding the lost tooth structure and patients with poor dental hygiene that have affected multiple teeth that need repair.
Before we start with the full-mouth rehabilitation, it is important to spend time diagnosing the problem through the use of diagnostic planning. This includes getting a detailed medical and dental history, performing a detailed clinical examination, getting a full-mouth series of radiographic films or X-rays, mounting the diagnostic casts and completing the diagnostic wax-up. The treatment plan is then developed based on the information just described. Patients with severely worn teeth can have adverse effects on both the esthetics and function and rehabilitation of these cases can be challenging but necessary. The rehabilitation of these cases requires comprehensive planning and may involve the use of both fixed and removable dental appliances. Fixed options include the use of materials such as full coverage porcelain veneers or crowns for the anterior or front of the mouth and full coverage zirconia crowns or porcelain fused to metal crowns for the posterior. For the spaces where the patients are missing teeth, we can consider options such as removable partial dentures, cast partial dentures, implant supported removable prosthesis and implant supported fixed prosthesis. This also includes the use of provisional restorations which the patient may have to wear for an extended period of time to ensure that the patient is comfortable with the way the teeth come together if we have to open the bite a little bit. The proper consideration of all these aspects is important if we want to have a successful outcome when performing full-mouth rehabilitation including the combination of treatment planning and proper diagnosis.
