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Inside Dental Technology

July/August 2011, Volume 2, Issue 7
Published by AEGIS Communications


Replicating Nature in Complete Dentures

By understanding the esthetics of prosthetics, technicians can exceed expectations in full-mouth rehabilitations.

By Robert Kreyer, CDT; and Renzo Chiappe

In this article Renzo Chiappe illustrates his technique for completing the removable denture case highlighted in the June issue of IDT. His passion for complete removable prosthetics and his technical skill in the field are showcased here.

Using the Injection Technique

The first step in the completion process is to invest, sprue, and process the waxed processed base plate (Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 and Figure 6). Ivocap injection acrylic (Ivoclar Vivadent, www.ivoclarvivadent.com) was used to process this case.

The injection technique was chosen over the packing technique for several reasons. First was the high density and high-impact characteristics of the material as well as the post-processing color consistency and longevity of color stability. The high density of the material has the potential to keep bacteria from forming, which, if allowed to form, can result in malodor.

However, in the authors’ opinion it is the low 1.6% coefficient of contraction compared to the 7% shrinkage of regular packing acrylic that is most attractive. According to the manufacturer, Ivocap acrylic exhibits the lowest shrinkage factor of any other material in the market, which results in a precise fit for the final prosthesis. Even though the acrylic injection process is slightly more expensive to execute, the occlusion achieved during the articulated wax-up phase will be almost completely replicated using the injection technique with only minor adjustments needed.

After injection, the processed base is divested, finished, and a new silicone working cast is created (Figure 7, Figure 8, Figure 9 and Figure 10). A wax occlusal rim is then created on the processed base using the initial papillameter measurements for incisal edge position (low lip line) combined with denture gauge measurements for proper vertical and horizontal dimension of the wax occlusal rim (Figure 11, Figure 12, Figure 13, Figure 14, Figure 15 and Figure 16). The wax rim former is used to establish the occlusal plane in relation to the hamular notch and incisive papilla meter measurements, then verified with the denture gauge (Figure 17 and Figure 18). The master casts with wax occlusal rims are mounted on a dental articulator according to the established clinical records (Figure 19).

Creating the Anterior Esthetics

When setting the denture teeth, often it is most difficult to replicate the natural beauty of asymmetry and the imperfections of nature while achieving the esthetic outcome desired. Dental technology educational programs teach technicians the textbook method of setting denture teeth using standard values and measurements. Today, patients are demanding a more individualistic and natural-looking approach to removable prosthetics. Even though measurements taken with the papillameter and denture gauge help to establish the location of the incisal edge of the central incisors with respect to the papilla, tooth arrangement still is not a precise science and requires creativity and imagination. Studying pictures of the patient with respect to face shape and smile line can help guide that tooth arrangement. However, the ability to spend time with the patient is critical to understanding the patient’s expectations for final outcome, the patient’s personality, how much the patient smiles, what percentage of the teeth show when smiling or speaking, and how the mandible moves during speech. Even determining if the patient is a tongue thruster is important to creating a natural-looking prosthetic (Figure 20 and Figure 21). Being able to observe and take pictures of the patient while relaxed and speaking or laughing naturally is also critical to replicating nature in the final prosthesis. All of these factors need to be taken into consideration before starting the denture prosthetic set-up. Another helpful approach is to search magazines for images of people that may have the same facial and oral characteristics as the patient. Even though nature repeats itself in patterns with repetitive characteristics, nothing in nature is identical.

Also helpful in tooth set-up is the clinician’s choice to use lingualized occlusion. Many clinicians find that it is easier to adjust in the mouth, and the patient has fewer problems adapting to the set-up. For technicians, the lingualized occlusal approach is even more important. For years, technicians have been taught about the necessity of tripod stabilization. The challenge for technicians has always been to obtain stability in the removable prosthesis along with the proper contacts while balancing the esthetics of the anterior teeth. The lingualized set-up approach provides technicians with more freedom to adjust and customize the esthetics of the anterior teeth without worrying about protrusive and lateral movements, which are guided by the posterior set-up. This factor provides the technician with the freedom to modify the overbite or overjet if needed. The same is true with the canines. Because the canines are no longer involved in the lateral movement, this gives the technician the ability to esthetically position the denture teeth in order to achieve the desired esthetic outcome. In the case presented here, the author was able to create a prosthesis that was unique to the patient and one that brought back the natural beauty of the patient’s smile (Figure 22 and Figure 23).

Prosthetic Passion

There is no greater compliment for a technician than seeing patients smile during their insertion appointments and knowing they feel good about themselves again. This patient endured six appointments while the dentist and technician constantly tweaked the case to achieve the desire outcome.

It is this dedication to creating a unique prosthesis that does not have the appearance of a traditional denture that will continue to drive the passion of the removable technician. In order for dental laboratory technologists to meet future demands, it is critical to concentrate on the value side of removable prosthetic restorations. Understanding this growing trend and desire for esthetic complete prosthetics will not only enable clinicians and technicians to exceed expectations in this full-mouth rehabilitation, it will also help to restore the self-confidence of the compromised edentulous patient. As dental laboratory technicians, the authors make prosthetic replacement parts for the oral environment of the human body and affect the lives of patients every day. In what other profession or industry is this possible? It is truly a blessing to be dental laboratory technicians.

About the Authors

Robert Kreyer, CDT
Director of Removable Prosthodontics
Microdental/DTI
Dublin, California

Renzo Chiappe
Owner
Chiappe Dental Lab
Covington, Louisiana


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Image Gallery

Figure 1  The waxed base plate is invested and sprued.

Figure 1

Figure 2  Using regular-body silicone impression material is the best choice for replicating all of the details of the custom rugae.

Figure 2

Figure 3  The regular body silicone and putty wash are readied for injection.

Figure 3

Figure 4  Once injected, the flask is opened, the wax pulled off, and followed with a traditional wash off.

Figure 4

Figure 5  The base plate is injected.

Figure 5

Figure 6  The base plate after the injection process.

Figure 6

Figure 7  The base plate is then de-vested. Because the master model is now distorted, a new working model is created using putty, paper clips, and die stone.

Figure 7

Figure 8  The putty is packed inside the processed base plate, and the paper clips are placed for the stone retention. Note that the peripheral border should stay exposed so that the base plate sits on solid stone and not on the silicone.

Figure 8

Figure 9  The new working model.

Figure 9

Figure 10  The processed base plate is placed on the new working model.

Figure 10

Figure 11  To fabricate the wax rim, the technician needs some valuable information and the proper tools, including a denture gauge, papillameter, caliper, and the dentist’s prescription notes.

Figure 11

Figure 12  The high lip line measurement is transferred from the papillameter to the caliper.

Figure 12

Figure 13  With the high lip line measurement transferred to the caliper, the measurement can be transferred to the wax rim.

Figure 13

Figure 14  Next, the low lip line measurement is transferred from the papillameter to the caliper.

Figure 14

Figure 15  The low lip line measurement is then transferred from the caliper to the wax rim.

Figure 15

Figure 16  The denture gauge establishes the location both vertically and horizontally of the future incisal edge. This is the reference point for the central papilla.

Figure 16

Figure 17  Using the hamular notch as a rotational reference point, a rim former is used to melt a length of the wax rim to provide the new vertical dimension established for the clinician.

Figure 17

Figure 18  The wax rim is verified with the new vertical dimension established by the denture gauge.

Figure 18

Figure 19  The wax rim is then mounted.

Figure 19

Figure 20  Once the wax rim is mounted, the tooth set-up begins.

Figure 20

Figure 21  This is a lateral view of the denture tooth set-up.

Figure 21

Figure 22  Tooth set-up at first try-in.

Figure 22

Figure 23  The patient’s new smile at the final try-in appointment.

Figure 23