Page 6 - GP Spring 2018

The Missing Factor in Cosmetic Dentistry: Occlusion

By Michael Teitelbaum, DMD, MAGD

Imagine your best day ever in the office. Picture finishing work starting point, but why should all excursive forces be concentrated
on your favorite patient. What did the work look like? Was it on one poor canine? Instead, by designing a progressive anterior
easy, almost predictable? How perfect would it be? Were there guidance, it is possible to spread out excursive forces equally, so
good feelings all around; proud at the completion of a job well they are distributed among all of the anterior teeth. Therefore,
done? How about payment; was everyone satisfied with a fair fee although we begin with canine guidance, the guidance should
for excellent service? Wouldn’t it be great if not only our favorite quickly and gently transfer to the lateral incisors, and then to the
patients could be like this, but every patient, every single day? central incisors upon which to ride the rest of the lateral excursion,
All these positives rarely happen by accident. In general, they all all on a pinpoint sized contact.
require advance planning of a specified goal and the underlying
knowledge to accomplish it. Most dentists graduate dental school: 4)Narrow buccal-lingual occlusal width. This concept mostly
1
a) traumatized, and b) with the ability to churn out fillings. Some relates to lab fabricated dentition. It is important to remember that
dentists aspire to more; to do fixed prosthodontics and cosmetic although they may be quite skilled, lab technicians are not doctors;
dentistry, but are turned back by insufficient time, inability to get they are technicians. As craftsmen, lab techs enjoy fabricating
paid superior fees for superior service, and/or fear of breakage. porcelain, lots of porcelain, so much so, in fact, that many times
they will fabricate a crown and actually make it larger than the
Things break because they are overloaded by stress. In the mouth, tooth it was replacing. This over-building can result in unsupported
form follows function or, in other words, stress is caused by factors porcelain - which is more prone to fracture - and extra wide buccal
of occlusion. Conversely, in our practices mental overload and and lingual cusps with porcelain sticking out, presenting the
stress can be caused by things breaking. If our goal is to minimize possibility of the jaw finding eccentric balancing contacts, which
stress in both our practices and our dentistry, then a thorough can lead to bruxism.
understanding of what causes those stresses and a plan to eliminate
them is in order. Thus, by understanding fundamental factors of Occlusal Anatomy
occlusion, we can increase the life span of our restorations, expand
the range of services we offer, improve our financial conditions, as Indeed, to impress dentists with
well as our personal and professional satisfaction. their skill, lab technicians will
routinely decorate the occlusal
Occlusal Considerations surface of restorations with a
myriad of unnecessary stains
There are four major factors in occlusion: and grooves, also known as
1) Simultaneous, pinpoint contact in centric “cat scratches.” Actually, these
2) Immediate anterior disclusion in all excursions embellishments, although Figure 1. Border movements
3) Progressive anterior guidance admired by some dentists, of the mandible recorded on a
4) Narrow buccal-lingual occlusal width are many times offensive to sagittal plane.
patients. The posterior occlusal
These basic generalizations on the surface may not appear to cover anatomy truly necessary from
every situation, yet when considered closely, are quite powerful. a gnathologic standpoint is
quite simple, and consists of
1)Simultaneous, pinpoint contact in centric. In stating that all the “escape grooves” needed to
teeth must contact, this can immediately rule out many styles allow opposing cusps to travel
of occlusion, including most forms of bilateral balance. Further, through fossae in excursions
simultaneous contact assures that forces of occlusion are evenly without hitting throughout
distributed along all teeth. Pinpoint contact is important because it the envelope of motion. The
has been shown that most eccentric interferences happen in an area envelope of motion is most
of 0.3 mm in and around centric. The term centric itself implies popularly thought of in the
a repeatable occlusal position and there are many locations, sagittal plane (Figure 1) ,
2
definitions, and types. The choice must be made by each restorative however it can also be viewed Figure 2. Border movements
doctor for each individual case, and further discussion of the pros from the occlusal plane of the mandible recorded on a
and cons of the various concepts of centric is well beyond the (Figure 2). 3 horizontal plane.
scope of this article.
Another way to think of it is
2)Immediate anterior disclusion in all excursions. Continuing to reconsider our four major
in our model of occlusion, we proceed from our starting point occlusal considerations.
of centric into excursions. Immediately, all posterior teeth are We know from #1 that all
disoccluded by the anterior teeth. In other words, although all Centric that is needed in centric is
teeth are touching in centric, the immediate lift off - guided by a pinpoint contact with an
the anterior teeth - prevents the posterior teeth from touching Figure 3. opposing cusp in a central
anywhere other than centric. Centric: a good fossa (Figure 3). We then can
starting point. imagine this opposing cusp Protrusive
3)Progressive anterior guidance. The most commonly known traveling into protrusive and
form of anterior guidance is canine guidance. This is an excellent the path it would trace (Figure 4). Returning to Figure 4. The
mandible can
www.nysagd.org l Spring 2018 l GP 6 protrude forward.