Lee Ann Brady, DMD
Exquisite provisionals are a key to predictable, beautiful, long lasting clinical results. Is there anything in dentistry more psychological disconcerting and unproductive than redoing your own clinical failures? For me the answer is a definitive “No”, and as I began searching for the answer to reduce failure and frustration in my practice, I kept coming back to provisionals. Now, let’s be clear about one distinction, this is not an article about “temporaries”.
A temporary is a protective covering for a prepared tooth that bridges time (usually as short as we can make it) between preparation and insertion. Provisionals accomplish the same goal of covering the prepared tooth to prevent sensitivity and keep the relative position of the tooth in the arch stable. Provisionals also do much, much more. Beyond the semantics lies a fundamental shift in our thinking that allows us to see an interim acrylic restoration as an essential diagnostic tool and therapeutic modality.
Protecting the prepared tooth is a core responsibility of the provisional restoration. Research tells us that the primary causative factor in pulpal death is introduction of bacteria. As we look at the relative size of the bacteria as compared to the size of dentinal tubules, and the increasing number of tubules by surface area as we travel from the surface of the tooth inward, preventing leakage of oral fluids under an interim restoration becomes critical. This can only be accomplished with creation of marginal seal and adaptation equal to that of the final restoration as evidenced by unmarred cement upon removal of the provisional. If we are successful we will have also created an environment that allows the patient to function without sensitivity. Stability within the arch ensures that you are maintaining the inter-tooth and inter-arch relationships as they are represented to your ceramist on the working model. To accomplish this we need to have adequate inter-proximal contact and at least one cusp tip and one receiving area contact to prevent super-eruption, rotation or tipping.
Strive to create ideal tooth form and inter-proximal contacts to create an optimal environment for tissue health and oral hygiene. For patients who present with combined restorative and periodontal concerns provisionals are a therapeutic tool to encourage optimal tissue health, evaluate tissue response and direct tissue development. Creation of anatomic gingival embrasures, emergence profile and heights of contour in addition to marginal adaptation in the presence of good oral hygiene allow optimal tissue response and healing. Place the initial margins in reference to the crestal tissue based on locating the base of the sulcus and evaluating the risk for recession based on tissue type and sulcus depth. If recession occurs it is preferential for it to happen during provisionalization, so that the opportunity is present to re-evaluate tissue health, biologic width, prep design and restorative contour to create a stable relationship prior to placement of the final restoration. Following adequate time to assess the tissue and completion of adjunctive periodontal procedures if necessary, reevaluate the margin placement prior to finalizing the restorations, with confidence that the relationship between marginal position and crestal tissue will remain stable.
The provisional also plays a role in tissue development. The interdisciplinary team can work together using interim restorations to direct tissue development for creation of ovate pontic sites, following implant placement, and to facilitate crown lengthening procedures. Development of ovate pontic sites begins with having adequate tissue over the ridge and can require tissue grafting. The site can be initially prepared using a laser, electrosurge or even a diamond bur on a high speed handpiece. The provisional is than shaped to extend into the prepared site and replicate the top portion of the root structure with rounded contours that sit down in the pontic site surrounded by tissue. Additionally provisionals are used in restorative cases requiring esthetic crown lengthening as both the surgical guide and to ensure optimal esthetics during healing.
A diagnostic wax-up is completed that changes the tooth and tissue shape and contours. From this work-up create matrices that serve as a guide for crestal tissue placement and to allow fabrication of the interim restorations. Following placement of the crestal tissue using an electrosurge (lasers, scalpels and diamond burs also work) and tooth preparation the teeth are provisionalized. The periodontist is now able to flap the tissue and place the crestal bone to create adequate biologic width using the restorative margin as the guide, and the patient doesn’t have the sensitivity and esthetic concerns of exposed root surfaces and high and dry margins.
Provisonals are the blueprint for making esthetic changes, they allow the patient and dentist to have absolute control over the esthetic parameters of the case and no surprises at delivery. Create a diagnostic wax-up based on discussions with the patient around their esthetic concerns and goals. It is extremely helpful for the patient to bring in 2-4 photos or magazine clippings of smiles that they find attractive, this creates a visual representation for the dentist of the tooth shape and alignment and smile characteristics they are seeking without the struggle to use words. Using this template, create the provisional restorations and allow the patient to experience the esthetic and phonetic changes. The patient and dentist re-evaluate the restorations and any esthetic, phonetic or functional changes are made and the patient is allowed to test these. As we move through the process of evaluation use digital photography, and work through an esthetic work-up of the provisionals to make sure the original goals have been met. Photographs are a valuable tool for patient communication about the restorations, and if the patient is requesting changes snap a photo, print a copy and ask the patient to draw the changes on the photo. Once the patient and dentist are both thrilled with the esthetic, and functional design of the provisionals it is time to take impressions of the provisionals, the preps, the opposing arch, and a facebow transfer and bite registration. The models are mounted on an articulator and sent to the ceramist along with incisal edge guides. Now the ceramist uses the provisional restorations as a blueprint and recreates the esthetic parameters exactly.
As a blueprint provisionals also serve to verify the functional design parameters of a case prior to finalization. The provisional is used to create the occlusal relationships and anterior guidance based on the original diagnostic work-up. Over time the provisional is monitored for cracks, breakage, de-cementation and wear. The patient and dentist work together to smooth the guidance, adjust the transition from canine to central in crossover, even the intensity of the posterior stops until the patient is happy and comfortable and the occlusal relationship works for success. Given the opportunity of time the interim restorations will direct re-evaluation of the occlusal design of the restorations so that the final restorations won’t fail because of inappropriately handled force. Create this opportunity for learning by scheduling a final impression at a separate appointment from the preps, this appointment is arranged once both the patient and dentist are ready to move to the final restorations.
Provisional restorations can become a valuable routine diagnostic tool in your practice. They are an integral part of the protocol for assessing cracked teeth that require full coverage restorations, and being able to evaluate symptom response to our proposed treatment and the potential need for endodontic therapy. Provisionals are used to help clarify restorability in borderline situations before the teeth are condemned to loss.
When interim restorations are used as a tool, and allowed the time to direct the dentist to parameters of the case that need to be evaluated and altered we can move to the final restorations confident of long-term predictable results. Exquisite provisionals also build practice referrals. The time and care you take to develop esthetics and function equal to the final restorations differentiates you and your practice to both patients and the specialists you refer to.
Creation of exquisite interim restorations begins with a comprehensive evaluation and diagnostic work-up of the case. During the comprehensive evaluation the patient and dentist have clarified the present dental condition as well as the patient’s goals for reaching optimal function, structure, health and esthetics. Finalization of the restorative treatment plan and new records if appropriate will follow preliminary
treatment. Working from an accurate set of diagnostic casts that are mounted in centric relation evaluate the parameters of the case. Begin by looking at the anterior coupling and incisal planes. The goal is to create even contact, level incisal planes, and smooth function both on the outgoing and incoming stroke. This process may involve reshaping the anteriors, or an additive process using wax or composite to meet both the proposed esthetic and functional goals for the case. Once the anterior guidance is established adjust the models to eliminate any arc of closure interferences and achieve centric occlusion being equivalent to maximum intercuspal position, and eliminate any posterior working or balancing interferences. As you work through this process refine the proposed treatment plan and blend the findings of the diagnostic workup with health and esthetic concerns. Based on the findings of the work-up proceed forward with the equilibration to create a stable posterior occlusion and obtain a new set of mounted casts. These models are used to finalize the diagnostic work-up. The completed diagnostic work-up, which establishes the esthetic and functional parameters of the case, is than sent to a master wax technician who adds the anatomic detail and produces a creative masterpiece. The final diagnostic wax-up is returned to the dentist along with a duplicate in stone, and a prep model. The duplicate stone model of the wax-up is used to create a matrix for fabrication of the provisionals as well as reduction guides. Silicone lab putty is mixed and shaped over the model covering the teeth to be prepared as well as one to two teeth on either side. Once set this matrix is removed from the model and relined using a light body vinyl polysiloxane impression material which captures all of the primary and secondary anatomy from the waxup. The matrix is than trimmed close to the cervical margin of the teeth on the labial, without scalloping into the interproximal, this allows excess material to come out and the matrix to be fully seated. The lingual is left with adequate soft tissue contact to ensure proper seating and unprepared teeth are covered by the matrix on either side.
Following preparation obtain a retracted impression of the teeth using hydrocolloid to facilitate making the provisionals indirectly, this allows time and concentration to create an excellent result, and allows the patient some time to relax. The impression can either be poured with a quick setting stone, or die silicone (this material will not work with VPS impressions) which is injected into the preps, and than the
remainder of the impression is filled with bite registration silicone, making sure to turn it over (not when using stone) on a counter and create a flat base. Once the prep model is completed fill the putty matrix with a methacrylate or bisacryl interim restorative material. With methacrylate use a salt and pepper technique and layer different color acrylics into the matrix to create incisal translucency, body and cervical shading. This can also be accomplished with some of the slower setting bisacryl materials, or use a single light shade bisacryl and than utilize tints to create the same color affects. Once the matrix is loaded with acrylic place over the prep model, seat to place with the model base against a counter top for resistance, and hold until the acrylic sets. Once the acrylic has set remove the matrix, the provisional normally remains on the model and is removed separately. For multiple unit restoration the flexibility of the die silicone model is an advantage as you can separate the provisional and the model without causing fractures.
Following removal the provisional is checked for voids, marginal integrity and surface anatomy. If needed flowable composite can be used at this point to fill voids or correct marginal integrity. When using a bisacryl submerge the provisional in rubbing alcohol for thirty seconds to remove the air inhibited layer prior to trimming and shaping. The next step is removal of the gross flash and excess utilizing a carbide bur(H79E). Once this is accomplished begin to define the interproximal embrasures with a carbide bur (H261EF), and than polish and finalize with a lab diamond (8860). Embrasures, both incisal and gingival and anatomic contour are created using diamond disks (911HP followed by 934-180). These disks are used with a pulling motion allowing the flexibility of the disk and applied pressure to create a natural curve to the restoration.
The anatomy that was transferred to the restoration from the wax-up is enhanced using a carbide bur (H78E), paying attention to surface texture and light angles. Once this is complete a burlew wheel begins the polishing phase, the sharp edge of a new wheel allows access to the embrasures. Next fine sandpaper discs are used to smooth the interproximal areas of the provisional. Finally polish using fine flour of pumice and than polishing compound on hand held rag wheels. If the provisional is made from bisacryl prior to polishing I will use light cured blue and ochre stains to create the incisal translucency and body and cervical shading. Following staining the provisional is coated with a laboratory unfilled resin and cure for ninety seconds.