Lifelike results

March 21, 2012

Treating edentulism pursues differing objectives: from a functional standpoint, restoring reasonable mastication and phonetic ability; and from an esthetic standpoint, restoring a patient’s natural smile in unison with age and personality. The aim is to give the individual a better quality of life and greater self-esteem.

Treating edentulism pursues differing objectives: from a functional standpoint, restoring reasonable mastication and phonetic ability; and from an esthetic standpoint, restoring a patient’s natural smile in unison with age and personality. The aim is to give the individual a better quality of life and greater self-esteem.

This dual challenge is met by the control a balanced occlusion provides (correct vertical dimension, centric position and acceptable occlusal plane) with a bilaterally balanced occlusal concept.

The form of denture teeth, especially the cusps of molars, is of vital importance for balanced teeth within this occlusion concept. However, the success of treatment depends as much on the illusion created by the teeth and denture base. For teeth, shape, surface structure and shade (or rather layering) all play leading roles in achieving the desired chameleon effect.

Denture teeth used with removable partial dentures should resemble the remaining teeth in anatomical form and hardness. In accordance with this philosophy, and following intensive research, Heraeus Kulzer developed Mondial® i acrylic denture teeth, which display many of the essential characteristics required for use with partial dentures.

In the following article, we would like to introduce the concept of Mondial i teeth and explain our arguments with the help of a clinical case.

Top of the line teeth

Mondial i denture teeth are seen as the premier product within Heraeus Kulzer’s acrylic denture tooth range. Mondial i teeth are manufactured with NanoPearls®, which are made of various inorganic fillers and integrated within a highly crosslinked and viscoplastic matrix to improve abrasion resistance.
This material has many other advantages. It’s extremely biocompatible, has improved optical properties such as transparency and opalescence, and, similar to dental hybrid composites, displays an abrasion resistance that is constant throughout the whole tooth. This is ideal if excessive grinding is required.

Mondial i denture teeth are designed using CAD/CAM (Fig. A) and validated in a virtual articulator in accordance with the form of natural teeth. The moulds used to produce the teeth are digitally milled (Fig. B)

This bilateral digitalization process ensures one hundred percent symmetrical contralateral teeth and form consistency in every set.

The fabrication process is just as unique: The teeth are made using the INCOMP process (a combined injection and compression method). This differs in two main ways from other standard production processes:

  • Continuous injection of acrylic compensates for polymerization shrinkage (which can be as high as 5%).

  • Pressure densification homogenizes the material and prevents porosities and bubbles.

The three-dimensional multi-layering process for distributing the individual resins used to compose the tooth was developed exclusively for Heraeus Kulzer in conjunction with a team of world class dental technicians.

This method of fabricating Mondial i denture teeth allows interpenetration of margin, dentin and incisal material in all three spatial directions to create a very lifelike appearance, especially in the incisal layering and fluorescence. Shades are designated with Heraeus’ own shade guide, based on the Vitapan Classical shade system.

The upper anteriors are available in square, triangular, oval and rectangular shapes in three sizes, while upper posteriors are available in six sizes. They are designed with vestibular marginal ridges closer together than the oral as it is typical for natural teeth; a “twist” of the vestibular surface; concave palatal surfaces; oral marginal ridges open in a “V” shape toward the incisal edge; a distal proximal surface larger than the mesial proximal surface; and a larger marginal cross section designed to allow correct anatomical papilla formation.

We’ve found that the shade in the cervical region can be intensified by grinding back the cervical dentin layer. This allows an aged appearance to be created quickly (Fig. C)

The posteriors feature a wide base and are available in four sizes. They are designed with equal vestibular oral diameter of all teeth in the set, sagittal and transversal dimensions identical with natural teeth, and multifunctional occlusal surfaces. Additional incisal material allows adjustments that display a natural, three dimensional multilayer build up, and just like the upper anteriors, the cervical areas can be customized by grinding.

Case presentation

A 70-year-old patient presents her old upper and lower dentures for renewal. An early check shows the dentures fit well, and the set up meets the usual requirements of static and dynamic occlusion. However, the denture teeth are quite worn down (Fig. D), and the vertical dimension is reduced (Fig. E). The clinical examination showed the osseous upper and lower jaw in satisfactory condition, even if the upper jaw showed a flabby ridge. The mucous membrane was in good condition with no visible inflammations.

01 An anatomical impression is taken with acrylic impression trays in the classic manner. After removal, the impressions are checked and marked immediately with a tissue marker.

02 The technician casts the anatomical model, defines the center of the alveolar ridge as well as the periphery of the functional impression trays. These are made from self-polymerising acrylic with wax bite walls (Fig. F). The wax walls are essential not only for handling, but also for supporting the soft tissue during impression taking.

03 The next clinical session starts with a check and correction of the special impression tray with high viscosity silicone and an acrylic cutter. The positional stability during free movement of the surrounding soft tissue is checked in the mouth.

04 The functional margin is defined in the usual manner with thermoplastic material, in some sections according to Herbst (Fig. G). Subsequently an impression of the mucous surfaces is made using a high viscosity polysulfide material (Permlastic® light, Kerr Corp.) in the upper jaw because the tissue in the anterior alveolar ridge is easily compressible. In contrast, Zink Oxide Eugenol impression paste is used on the lower jaw because of its hydrophilic properties (Fig. H).

05 The impressions are checked, disinfected and sent to the laboratory.

06 The functional impressions are dammed up (Fig. I) and cast with high strength dental stone. Then the bite blocks are fabricated to be warp resistant, thin and cover the whole area of support as marked by the functional impression. This is then used to control the future denture’s retentive properties. The registration base has a wax bite block; the lower base carries a thin acrylic wall. 

07 The upper bite block is aligned in the frontal plane parallel to the pupil line, and in the sagittal plane parallel to the campers line (Fig. J). The height is adjusted for esthetic and phonetic control.

08 The lower bite block is formed to a satisfactory functional and esthetic vertical relationship (Fig. K). The registration of the intermaxillary position is taken in centric on the upper wax wall with Aluwax®.

09 The reproducibility of the registered jaw position is checked three times (Fig. L).

10 The essential additional information including position of the incisal line, the upper canines, and the upper smile line is communicated to the laboratory.

11 Tooth shape and shade are chosen: Vita® A3, O2 Mondial i, oval (Fig. M).

12 The models are articulated using the bite registration.

13 The Mondial i denture teeth are set-up in wax on acrylic bases according to the clinical specifications provided. Position and course of the occlusal plane are defined by the distance between alveolar ridges, under consideration of the lower arch, to at least provide a stable denture base. The teeth are set up inside the tolerance area in the anterior and posterior region, with provision for the interalveolar lines.

Multiple contact is applied in the position of maximum intercuspation. The anteriors are slightly out of contact (Fig. N). The dynamic occlusion follows the bilateral balanced occlusion concept.

14 Once tried in, the bases with set up teeth are checked for phonetics and esthetics (Fig. O).

15 The posterior occlusion and the anterior distance are checked (Fig. P).

16 The trial set up is returned to the laboratory, where it is transferred to acrylic and finished.

17 At the fitting session, the finish of the denture periphery and the surface in contact with the mucous membrane are checked (Fig. Q) and the balanced occlusion immediately adjusted.

18 The patient is instructed on denture care and aftercare. The esthetic results (Fig. R) are satisfactory for both patient and treatment team.

Conclusion

The Mondial i denture teeth seem well suited to functional dentures because of the intercuspation and balanced guidance achieved. They also are esthetically attractive thanks to the deceptively real appearance of the anteriors and the lifelike shape of all teeth. There are interesting customizing possibilities, either through grinding or staining. Finally, abrasion resistance is closer to natural teeth than traditional PMMA acrylic teeth and therefore upholds the intermaxillary position achieved during set up longer.