The Contact Area and Embrasure Space
Peter Pizzi, MDT, CDT
In restorative work such as fixed, fixed detachable, or detachable prosthetic devices, the laboratory's end goal is to create a product that closely mirrors nature. As dental technicians, our task is to observe, emulate, and even possibly improve upon what nature has already established. In that way, I would argue that we are not merely technicians but also artists who must be just as creative and sensitive to detail as other skilled artisans such as painters and sculptors. Our interpretation of what we see can be influenced by many factors, but we must recognize that we do not have complete artistic freedom as we must seek to follow nature's guidelines and limitations in order to create a functional esthetic result (Figure 1 and Figure 2).
One of the more common trends I see in laboratories today is a lack of understanding of nature's contact area and embrasure space. The contact is defined as the area in which two proximal surfaces touch. Embrasure space is the space that is formed by two adjacent teeth that extend past the contact area. The contact area and the embrasure space both serve important purposes which are largely affected by esthetic design, demonstrating the invaluable relationship between function and esthetic. The contact area aids in keeping food from impacting between the teeth, protects the soft tissue, and also allows the tooth to have movement for protection of its antagonist opposing arch. The amount of contact area is dictated by the tooth form (ie, oval, square, and tapered). In addition, gingivally, the papilla fills the embrasure space to the contact area, while in the incisal area, the contact area defines the amount of space shown.
One of the greatest misunderstandings in contacts regards their size (Figure 3). Contacts are neither a single point nor a very broad surface. Each contact is different depending on the tooth type, orthodontic position, and gingival tissue type. Some contacts, such as the mandibular posterior teeth contact areas, which are located more in the center proximal area, aid both in tooth stability during the crushing and grinding of food and in protecting the ability of the lower jaw to move through a proprioceptive response system (Figure 4 and Figure 5). Maxillary contact areas tend to be found more toward the facial aspect, creating a larger embrasure space lingually. These contact areas allow the maxillary teeth to move as a protection against the antagonist mandibular while also enabling the crushing and grinding of food (Figure 6 and Figure 7). The anterior tooth contact areas play more of an esthetic role and are determined to a greater extent by the tooth shape, tissue type, and age of the tooth, as younger teeth typically have greater embrasure space, while older teeth tend to have less embrasure space due to wear (Figure 8 and Figure 9). A comprehensive understanding of the mechanics of contact area and embrasure space is vital in preserving the function and esthetic designed by nature. In creating an esthetic that mirrors nature's design, the technician must be cognizant of the importance of the contact area and embrasure space and the functional role they play (Figure 10).
Bench Essentials is a quarterly series in which IDT Editor-in-Chief, Peter Pizzi, MDT, CDT, presents educational lessons about the fundamentals of dental laboratory technology based on his decades of working at the bench and lecturing around the world.