Accurate prosthodontic impressions with minimal soft tissue manipulation are essential for the successful and predictable creation of a prosthesis. A new impression technique has been developed with accurate and detailed results and no soft tissue manipulation.
Prosthodontic impressions can prove frustrating for both the clinician and patient. The patient may develop anxiety and fear from the impression material flowing posteriorly, compromising the airway. The clinician may have frustrations from: poor patient cooperation, the working and intraoral setting times of impression materials, poor quality of impressions requiring retakes, high cost of materials from retakes, confusion from the excessive number of materials available to aid in impression taking (hemostatic agents, gingival retraction devices) and the response of the soft tissue following impressions resulting in unpredictable esthetics.
The author has developed a simplified impression technique that is compatible with triple tray or full arch trays. The technique reduces chair time, eliminates the need for hemostatic and gingival retraction devices and results in detailed and accurate impressions without retakes.
BACKGROUND
The goal of prosthodontic impressions is an accurate and detailed record of the prepared tooth to allow the commercial laboratory the ability to produce an ideal prosthesis.1 A poor impression will result in a poor model and ultimately an unsatisfactory prosthesis. In prosthodontics, each step is dependent on the other and failure in one step will affect the final outcome.2
Contemporary prosthodontic impression techniques are based on the triple tray or full arch tray method. The triple tray method is based on the placement of a light body material around the preparation(s), a heavy body material onto the triple tray and then the patient is instructed to bite into the material. The result is a record of the maxillary and mandibular dentition and the bite. However, the technique requires retakes as the light body material flows away from the preparation. The patient also has the freedom to slightly offset the bite, which results in an inaccurate bite and ultimately a poor fitting restoration. The full arch technique is generally used for multiple preparations. Light body is utilized around the preparations and heavy body is loaded into the tray. The tray is seated while the material sets. Shortcomings of this technique include poor patient acceptance due to the gagging nature of the tray and impression material. The light body also has a tendency to be displaced from the preparations, resulting in voids and pulls. Multiple full arch impressions are not uncommon and can prove costly.
Tissue management has become an area of debate. The ultimate goal is to displace the gingival tissue such that the impression registers the delineation of the soft tissue and the tooth preparation.1 However, the act of using chemical, mechanical or other means to displace the tissue tends to result in inflammation and/or postponed recession.3-5 Consequently, aesthetics may be compromised.
METHODS AND MATERIALS
TempTray [Clinician’s Choice Dental Products Inc., London, Ontario] (CCD) is a disposable aluminum quadrant tray recommended for the fabrication of temporaries. Quad tray (CCD) is a prosthodontic tray recommended for the duplication of the maxillary and mandibular dentition and the bite. Template (CCD) is a rapid setting polyvinyl siloxane matrix material recommended for fabrication of temporaries. Affinty Light Body HF (CCD) is a polyvinyl siloxane material recommended for the detailed aspect of prosthodontic impressions.
The use of Template has never before been recommended for prosthodontic impressions. The author has developed the technique through clinical trials.
CLINICAL CASE
A patient presented with a debonded porcelain fused-to-metal (PFM) crown on tooth number 36, (Fig. 1) with fracture of the porcelain (Fig. 2). Clinical examination and diagnosis suggested porcelain fracture due to lack of bulk of material and possibly heavy occlusion. The dislodged crown occurred primarily due to cement failure and secondarily to lack of retention and under preparation of the tooth. The tooth was treatment planned for a new PFM preparation and crown.
Prior to preparation, TempTray (Fig. 3) and Template (Fig. 4) were utilized to take an over impression. TempTray had been loaded with Template (Fig. 5), the material was allowed to set for 30 seconds outside of the mouth and placed intraorally over the failed crown and tooth #36 for 30 seconds (Fig. 6). This allowed for an impression to fabricate a temporary following tooth preparation. The patient was anesthetized with 2% lidocaine and 1:100000 epinephrine (Dentsply) given as a standard inferior alveolar block and the tooth was prepared for a conventional PFM (Fig. 7). The preparation was improved by creating parallelism and proper reduction, allowing for bulk of material.
Step 1
Template had been utilized and loaded into a Quad tray (Fig. 8). The material was allowed to set for 30 seconds, then placed intraorally. The patient was instructed to bite into the material (Fig. 9). Whether the patient closed into centric occlusion or maximal intercuspation is at the discretion of the clinician. Centric occlusion relates to condylar position while maximum intercuspation relates to the interdigitation of the dentition. After 30 seconds the tray and material had been removed (Fig. 10). The resulting impression is a crude reproduction of the maxillary and mandibular dentition, with the bite registered.
Step 2
Affinity Light Body HF impression material (Fig. 11) was then loaded into the initial impression (Fig. 12). The Quad tray was then reinserted intraorally and the patient was instructed to bite back into the material (Fig. 13). The material requires 3 minutes to set and was removed (Fig. 14). Figure 15 illustrates the extreme accuracy and detail of the impression. The author has not used any hemostatic or gingival retraction agents.
Step 3
Integrity (Dentsply) was dispensed into the initial TempTray/ Template impression (Fig. 16). The TempTray was placed onto tooth #36 for 60 seconds. Upon withdrawal, a temporary had polymerized. The temporary was polished and cemented. Occlusion was checked and adjusted (Fig. 17).
Step 4
The impression was disinfected and sent to a commercial lab for the fabrication of a PFM. Figure 18 illustrates the detail of the preparation margins on the die. Figure 19 displays the buccal margin of the PFM, while Figure 20 indicates the lingual margin. Clinically, the patient was anesthetized and the new PFM was fitted and cemented. Occlusion was checked and minor adjustments were made. Figures 21 and 22 illustrate the final restoration intraorally.
CLINICAL CASE #2
The author has utilized the same materials with the same procedure but with a full arch tray. In this situation the tray was loaded with Template and placed intraorally. Affinity Light Body was then placed into the first impression and placed back again intraorally and allowed to set for three minutes. Figure 23 illustrates the final impression. Figures 24 and 25 illustrate the detail and accuracy of the PFM impressions. The author did not utilized any hemostatic or gingival retraction agents prior to the impression.
Analysis
The author performed the ‘rebite’ impression and a contemporary impression technique using Inflex (CCD) on the same tooth. Two separate dies were poured using diestone (performed by a commercial lab) and then measurements were taken to compare dimensional variability. Measurements were taken at the cervical and occlusal extents of the prep in a buccal-lingual and mesial-distal aspect. Measurements were repeated 5 times per die. From the 40 measurements, only two values were not the same. A difference of 1/100th of a millimeter was evident. This fact
is irrelevant as the digital micrometer by Fowler had a accuracy of +/- 1/100th of a millimeter.
DISCUSSION
The rebite impression technique offers some new and exciting advantages over conventional techniques. The initial Template impression provides a matrix around the preparation. The second impression utilizes the patient’s bite to force the light body impression material hydrostatically around the gingival margins of the preparation. The result is an extremely accurate record of the tooth and soft tissue. Measurements indicate that no dimensional variability exists between the two techniques. The fact that hemostatic agents and gingival retraction devices are not utilized ensures that the soft tissues remain healthy and predictable, thereby eliminating inflammation and or recession.6 The rebite technique allows the patient to bite back into the original impression, which allows the clinician to confirm the occlusal relationship.
The new impression technique, termed ‘rebite’ offers the practitioner a simple and efficient method to perform prosthodontic impressions. The technique offers the patient a quick and easy procedure that is easy to tolerate. In addition, the fear and anxiety of impression material traveling posteriorly is eliminated. The technique allows the clinician to perform an accurate, efficient, simple and inexpensive impression for the fabrication of a prosthesis. The advantages of this technique include: extremely simple method, fast and efficient technique, extreme accuracy and detail, no need for specialized equipment (automix), no need for hemostatic agents, no need for gingival retraction devices, dimensional stability of Template, excellent patient acceptance and inexpensive costs.
CONCLUSION
The rebite impression technique allows for the simple and efficient impression of prosthodontic preparations either by triple tray or custom arch tray techniques eliminating the need for hemostatic or gingival retraction devices. The accuracy and detail of the impression allows for the fabrication of predictable and ideal prosthetics. Resulting restorations are cemented without the need for timely adjustments intraorally and the soft tissue remains in an ideal and aesthetically predictable state. Consequently, apprehension and anxiety from both practitioner and patient can be reduced or eliminated.
Acknowledgements
The author has no commercial or other financial interest in any of the products mentioned.
The author would like to recognize SHAW Dental Laboratories for the fabrication of the PFM and dies.
Dr. Les Kalman maintains a private practice in aesthetic and general dentistry in London, Ontario and is an adjunct professor in the department of Oral Diagnosis and Medicine at the Schulich School of Dentistry, University of Western Ontario.
Oral Health welcomes this original article.
REFERENCES
1.Rosenstiel S, Land M and Fujimoto J. Contemporary Fixed Prosthodontics (2nd ed.). Mosby. 1995; 85-107, 301-324.
2.Craig RG. Restorative Dental Materials (9th Ed.) Mosby. 1993; 283-383.
3.Stein RS. and Glickman I. Prosthetic considerations for gingival health. Dent Clin North Am 4: 177-188, 1960.
4.Itoiz M. and Carranza F. The gingiva. in Carranza FA. Jr. and Newman MG.: Glickman’s Clinical Periodontology (8th Ed.) W.B. Saunders Co. 1996; Chapter 4.
5.Eissmann HF., Radke RA. and Noble WH. Physiologic design criteria for fixed dental restorations. Dent Clin North Am 15: 543-567, 1971.
6.Bral M. Periodontal considerations for provisional restorations. Dent Clin North Am 33: 457-475, 1989.
