Fabrication and Use of an Incisal Edge GuideBy Jeffrey Bonk on February 28, 2022 | comments
The esthetic outcome, i.e., to mimic nature, create beauty, and emulate contours of natural tooth structure, is a primary objective of all anterior restorative dentistry. Performing esthetic dentistry is creative, challenging, and fun especially when it is predictable.
A tool that brings a level of predictability to the outcomes and helps make a positive experience for all involved is an incisal edge guide. It is an extremely valuable tool that helps ensure results are predictable and time is not wasted at the try-in and insert appointment.
Without close communication the final restoration can be compromised
With indirect restoration, the dental laboratory plays a significant role in producing the outcome. The dental technician's knowledge, skill, and ability are crucial for achieving success. There must be close communication between the restorative dentist and the dental laboratory technician because without it the final product can be compromised relative to both form and function.
There are many steps in the process of changing esthetics and function through indirect dental restorative means. Comprehensive esthetic planning (e.g., Spear's FGTP process), diagnostic wax-ups, intra-oral mock-ups, and ultimately provisionalization are all integral aspects of determining the desired tooth shape, form, and position that provide the desired appearance.
Provisionals are the so-called test drive component of the process, whereby the patient assesses and analyzes whether the esthetic changes are acceptable and desirable. Once these provisionals are patient approved, they become the critical “go-by” information the dental laboratory uses as the guide for final ceramic restorations.
It is necessary to transfer this critical piece of information to the dental laboratory and provide the incisal edge guide to ensure the dental laboratory technician produces the desired outcome in ceramic. Here is a clinical case study of the fabrication and use of the incisal edge guide.
Samantha presented for treatment to correct the esthetic appearance of her front teeth. Her maxillary anterior teeth were proclined, canted, and a diastema was a result of her anterior bite relationship. After consulting with an orthodontist, it was decided that correction would be performed through restorative means rather than orthodontic therapy.
Following Facially Generated Treatment Planning (FGTP) protocols, esthetic and functional corrections for Samantha involved an occlusal equilibration and the restoration of six maxillary anterior teeth. Also, to manage her parafunctional habits, a bruxism appliance was fabricated.
The restorative process called for complete anterior coverage to correct the proclination and manage the incisor functional contacts. The midline cant and diastema were also corrected to Samantha's liking, and she was pleased with the tooth form, inclination, and comfort the provisionals created.
An impression of the provisionals was obtained and a stone cast was fabricated and mounted on a semi-adjustable articulator (Kavo) to begin the process of fabricating the incisal edge guide.
Silicone putty is used in dentistry in a variety of ways. In direct resin dentistry, palatal shells fabricated from a diagnostic wax-up are utilized as a template tool for rebuilding fractured or broken incisal edges. Many dentists use putty matrices as the form for fabricating intraoral direct provisionals for crown and bridge procedures.
Depth reduction guides are also fabricated from silicone putty to ensure adequate tooth structure removal during crown and veneer preparation. Putty is an important tool in dentistry for these and many other uses.
Silicone putty in dental situations is designed in a catalyst-based format. It presents either in a putty-putty form or a putty-paste form. Many companies make putty for dental use including, Sil-tech (Ivoclar), Platinum 85 (Zhermack), and LT Laboratory Putty (GC America).
Some putty is designed for laboratory use only (therefore cannot be used intraorally), and others are acceptable for intraoral use and application. Intraoral putty is mainly utilized as putty-putty impression material. Both types may be used in fabricating incisal edge guides. Silicone putty comes in many different colors and shore hardness categories. Depending upon the desired use, an appropriate putty is selected. Measuring scoops/devices are provided by the various putty manufacturers to ensure proper proportions.
Models of provisional restorations are mounted on the articulator and closed in maximum occlusal contact. The centric locks on the articulator must be engaged.
An appropriate amount of putty is mixed to the proper consistency (no catalyst/base streaks visible). In the matter of the incisal edge guide, any hardness or color of putty material is acceptable. The putty material is rolled in a “hot-dog” form and applied to the facial aspect of the lower model.
The hot-dog ends are wrapped around the lingual vestibular area of the lower cast to lock the incisal edge guide to the model. The soft and malleable putty is applied by finger pressure to the facial aspect of the lower stone cast. The goal or objective is to push the soft putty into the incisal edge contours of the upper anterior teeth from molar to molar. Approximately 2-3 mm of maxillary incisal edge needs to be included in the edge guide. The overall thickness of the putty on the facial aspect of the lower cast should be 3-4 mm in depth.
Working time varies between putty manufacturers and products. Generally, there is approximately one minute of mixing time and two minutes of working/application time. If the putty begins to harden before appropriate application, voids, pulls, and bubbles may result if the attempts to contouring continue. Again, the goal is to capture, precisely, the incisal edges of the maxillary provisionalized teeth in the index. Once the application of putty is complete, the incisal edge guide is allowed to complete its chemical hardening cycle, which is typically 3-5 minutes for most manufacturers.
Once the putty has hardened, the centric locks on the articulator are opened and the upper member of the articulator is separated from the lower. It is best to vertically remove the upper member from the lower member rather than open the articulator at the hinge. This “hinging” technique may result in fracture of the maxillary incisal edges, especially if greater than 3 mm of incisal edges are covered by the putty material. The lower model (with accompanying incisal edge guide) can now be removed from the articulator.
Using a number 12 straight scalpel blade, excess putty can be removed from the incisal edge aspect of the putty matrix. The goal of the trimming is to expose the incisal edges and incisal embrasures of the upper teeth. Typically, trimming the putty provides approximately 2 mm of incisal edge contour remaining in the index. Once the index is properly trimmed, the upper articulator member and the upper model can be re-engaged to the articulator. Closing the upper member should verify complete containment of the incisal edges and incisal embrasures. The incisal edge guide can now be forwarded to the dental laboratory for use in fabricating the ceramic indirect restorations.
The incisal edge guide is a valuable tool for the dental laboratory to mimic the incisal edge position and contours of the provisionals. These edges have been verified in the patient through function and esthetics.
As these edge positions work for the functional, esthetic, and phonetic patterns of the patient, the putty matrix is a guide for the technician to build the final ceramic restorations contours. As seen in Fig. 8, the proposed incisal edges are demarcated precisely to provide direction to the ceramic technician. There is no question as to the positioning of the edges.
Chair time in dental practice is extremely valuable. Wasted time is costly in both time and dollars. Being efficient and effective in treatment processes creates happy patients and happy doctors. Anterior indirect restorations can be extremely stressful in practice, as there are so many variables that come into play relative to designing and achieving acceptable esthetic and functional results.
The incisal edge guide is used as a quality control device to verify the newly fabricated restorations hit the mark relative to edge position. For example, when the dental office assistant, responsible for managing laboratory cases, unpacks the returned products, they place them on the models and ensure the new ceramic edges fit the edge guide appropriately. If there is a significant disparity, the assistant can immediately discuss this situation with the dental laboratory and return the restorations for adjustment and correction. Thus, there is no wasted patient try-in time.
Once the correction is made and verified, the patient may be scheduled for the try-in/insert appointment. Using the incisal edge guide for this quality control purpose has a positive effect on both the dentist/dental laboratory communication and the bottom line of the practice!
Jeffrey Bonk, D.D.S., is a member of Spear Resident Faculty.