In The Operatory

The Missing Factor in

Occl usionby Michael Teitelbaum, DMD, FAGD

Dr. Teitelbaum is a Clinical Research conditions, as well as our personal and professional satis-

Associates evaluato~ who taught for 8 faction.as an associate professor of clini- Occlusal Considerations

prosthodontics at N. y: U College of There are four major factors in occlusion:

Dentistry, where he attended the Post- 1) Simultaneous, pinpoint, contact in centricGraduate program in prosthodontics 2) Immediate anterior disclusion in all excursions

after receiving his D.M.D. from the 3) Progressive anterior guidanceUniversity of Pennsylvania School of 4) Narrow Buccal-Lingual occlusal widthDental Medicine. He lectures across theUS. (including this year's AGD annual These basic generalizations on the surface may not appear

meeting in Nashville) on various topics in Cosmetic to cover every situation, yet when considered closely are

Dentistry and is available to lecture for you as well. He is the quite powerful.author of numerous articles in professional publications, and~has a mostly cosmetic practice inBriarcliffMano~NYwhere 2; ,r. ]- ,---" c '-'. r ' ,-~

he proudly wears FA.G.D. after his name. " ,..0 :0. .Kindly direct any questions, comments or lecture requests ' I "':1 "..0-'-- -

to Dr: Teitelbaum at, 1312 Pleasantville Rd, Briarcliff :

Mano~ NY 10510.

I)

I magine your best day ever in the office. Picture finishingwork on your favorite patient. What did the work looklike? Was it easy, almost predictable how perfect it

would be? Were there good feelings all around; proud at thecompletion of a job well done? How about payment, waseveryone satisfied with a fair fee for excellent service?Wouldn't it be great if not only our favorite patients could belike this, but every patient, every single day? All these pos-itives rarely happen by accident, in general they all requireadvance planning of a specified goal and the underlyingknowledge to accomplish it. Most dentists graduate dentalschool: a) traumatized, and b) with the ability to churn outamalgams. Some dentists aspire to more; to minimize oreliminate amalgams, to do fixed prosthodontics, tooth col-ored restorations, cosmetic dentistry, but are turned back byinsufficient time, inability to get paid superior fees for supe-rior service, and/or fear of breakage.

Things break because they are overloaded by stress. Inthe mouth, form follows function or, in other words, stress iscaused by factors of occlusion. Conversely, in our practicesmental overload and stress can be caused by things break-ing. If our goal is to minimize stress in both our practicesand our dentistry, then a thorough understanding of whatcauses those stresses and a plan to eliminate them is inorder. Thus, by understanding fundamental factors of occlu-sion, we can increase the life span of our restorations,expand the range of services we offer, improve our financial

March 2003/PaJ!e 10

larger than the tooth it was replacing. This over build-ing can result in unsupported porcelain -which is moreprone to fracture -and extra wide buccal and lingualcusps with porcelain sticking out, presenting the possi-

bility of the jawfinding eccentricbalancing con-tacts -which canlead to bruxism.

t

our startingpoint of centricinto excursions.Immediately, all

I posterior teethI are disoccludedI by the anteriorI teeth. In other

words, althoughfigure 3 all teeth are

touching in cen-tric, the immediate lift off -guided by the anterior teeth-prevents the posterior teeth from -touching anywhereother than centric.Progressive anterior guidance. The most commonlyknown form of anterior guidance is canine guidance.This is an excel- Ilent starting Ipoint, but whyshould all excur-sive forces beconcentrated onone poor canine? I

Instead, bydesigning a pro-gressive anteri-or guidance, it ispossible tospread out figure 4

excursive forcesequally, so they are distributed among all of the anteri-or teeth. Therefore, although we begin with canineguidance, the guidance should quickly and gentlytransfer to the lateral incisors, and then to the centralincisors upon whicp to ride the rest of the lateral excur-sion, all on a pinpoint sized contact.Narrow Buccal-Lingual occlusal width. This conceptwas taught widely by the late, great Dr. Elliot Feinberg,

and mostlyrelates to labfabricateddentition. Itis importantto rememberthat althoughthey may bequite skilled,lab techni-cians are not

figure 5 doctors, theyare techni-

cians. As craftsmen, lab techs enjoy fabricating porce-lain, lots of porcelain, so much so, in fact, that manytimes they will fabricate a crown and actually make it

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Occlusal Ana-tomyIndeed, to

impress dentists withtheir skill, lab techni-cians will routinelydecorate the occlusalsurface of restora-tions with a myriad fi . .gure 6unnecessary stallSand grooves, also known as "cat scratches." Actu~lly, theseembellishments, although admired by dentists ignorant oftheir pointlessness, are many times offensive to patients.The posterior occlusal anatomy truly necessary from aGnathologic standpoint is quite simple, and consists of the"Escape grooves" needed to allow opposing cusps to travelthrough fossae in excursions without hitting, throughoutthe envelope of motion. The envelope of motion is most pop-ularly thought of in the sagittal plane, as in figure one, how-ever it can also be viewed from the occlusal plane as seen in

figure two.Another way to think of it is to reconsider our four

major occlusal considerations. We know from #1 that allthat is needed in centric is a pinpoint contact with an oppos-

ing cusp in acentral fossa,as in figurethree. We thencan imaginethis opposingcusp travelinginto protrusiveand the path itwould trace,in figure four. figure 7

Returning to centric, we can further picture our opposingcusp traveling into right and left lateral excursions, as infigure five. Even in classic centric relation one must alwaysallow for a small amount of potential retrusive movement,as seen in figure six. Finally, the mandible can make minorborder movements as seen in figure seven. It's no coinci-dence, then, that if we superimpose these movements ontothe occlusal of a mandibular first molar they perfectlymatch the basic necessary dental anatomy (figure eight).

March 2003/Page 11

Mechanical ConsiderationsThe importance of these escape grooves is to eliminate

the possibility of posterior eccentric interferences, and min-imize the occlusal forces on anterior teeth. Imagine trying

tO cut some-thing hardor thickwith a pairof scissors.

Empirically,vou know togain moreIorce youwould not

the tipfigure 8 of the scis-

sors, but cut closer to the handle, or fulcrum. In point of fact,this changes the mechanical advantage from a class threelever system to a Class two lever system (see figure nine),and generates a tremendously greater amount of force. Butwhat if you could have something contact the outer tip at the

contact in

over

between teethand #25 /

11).

'

-

(

began whenactually wereterior teething against these figure 11two teeth. Theseposterior balancing teeth have most likely been long sinceeither extracted or exfoliated. Since this patient had longsince felt that his maxillary central incisors were too longanyway, it was a relatively simple procedure to shorten themto eliminate the fractured area (see figure 12) then roundand polish the incisal edges of both maxillary and mandibu-lar incisors to eliminate any future potential balancingareas. Figure 13 shows the patient having slid all the wayto a maximum lateral excursion finding no area to balanceon.

figure 9

same time as close to the fulcrum? All the force from the ful-crum would be transmitted to the tip.

It's the same with the mandible: more force is generat-ed closer to the fulcrum, or condyle. If there are balancingcontacts or interferences, force is transmitted from the pos-terior teeth, whichare designed todIe it, to the :ors, which are not.This causes manythe fractures andchips we see inrior teeth, and iscritical factorrestoring them.

figure 10Clinical Considerations

Figure ten shows just such a fracture of an anteriortooth. In this simple example we can see that there cur-rently are no posterior balancing contacts and that the dam-age was probably done from a long-term anterior balancing

Our next case shows a young woman who presentedhaving just fractured teeth #9 and #8 (see Figure 14).Sliding her mandible into extreme excursions finds her jaw

naturallywhen tooth"clicks" intofractured area,in figure 15.further Ition it can alsoseen that she

posterioring contacts at the figure 12same lateralcrossover position on both right and left (see figures 16 and17). This balancing tripod effect most likely contributed toexcessive force long-term on the anterior teeth which,unable to take the load, eventually fractured. There is nocomposite material stronger than enamel -the hardest sub-stance in the human body. Her balancing contacts enabledthe patient

developforce toenamel, so itonly reasonableassume thatwould be ablefracture any

positein a much shorter

fi 13. d f .gureperlo o time.Initial attempts, therefore, were to eliminate the poste-

rior contacts in the locking crossover position.

March 2003/Page 12

Unfortunately,only short-her vertical

in this

, deepen-the anterior

into theThe

way, then, tofigure 14 eliminate exces-

sive forces caused)y the posterior contacts was to build up the fracturedncisal edges, creating an anterior guidance with a class,hree lever system.

After first selecting a shade, first tooth #9 then tooth #8separately) were first bevelled, then sandblasted, etched,hen bonded with a hydrophilic bonding system. They were,hen incrementally built up and cured with matching shad-~d composites until the posterior cusps were no longer con-acting in the crossover position. The patient's ability to:moothly j'

hroughout!xcursionsocking wasied and thenlie checkedlO micron

Lrticulating paper.~oth anterior and,osterior teeth

fi 15gure!/ere then highlytolished (see figure 18). Upon examination the patientemarked that her newly restored teeth looked just as theylad when she had been younger, before she'd begun to wearhem down.

ment requires substantially more time throughout all phas-es of treatment. Spending more time per patient obviouslytranslates into not being able to physically treat as manypatients. While it certainly should be our mission to help all~n need, unless weare fairlysated forincreased time

subsequent droppatient flow, itlead to financialficulties, andinability Ione. It isthat a dentist doingthis kind of thorough figure 17

occlusal/ restorative treatment could long survive acceptingmerely a few dollars per restoration as offered by manymanaged care plans, especially when just overhead wouldlikely come to a high multiple of this number. Is it fair toask our patients to pay a higher fee for a higher quality ofservice? As providers of dental care services should wemodel ourselves after ei~her Nordstrom's or Wal-Mart, theFourorInn? This

questioneachmustforself. Justthere mustroom inmarketplace figure 18

for the comprehensive, Pankey-style, occlusally oriented,amalgam free, all bonded, insurance-independent practice,so must there also be room for the opposite. In a free mar-ketplace one cannot exist without the other. Our choice is todecide which we can be, which we want to be, and if we canlive with that decision.

i'inancial ConsiderationsTherefore, it is important to understand how mechani-

al forces effect occlusion throughout the envelope of func-, and in all

of restora-Dentistry. Incases shown

References1. Dawson, Po E.: Evaluation, diagnosis, and treatment of

Occlusal Problems, Bt. Louis, 1974, The C. \1: Mosby

Company.first under-the cause of

problems-attempting

f1X them. Hadfigure 16 the teeth in ques-

,ion been repaired without regard to the occlusal forces onhem that had caused the fractures, there is no questionhat the repairs would have been short lasting, indeed.Jnfortunately, this kind of diagnosis and meticulous treat-

2. The World Book Encyclopedia: 12:194, USA, 1973, Field

Enterprises Educational Corporation

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