periov&>ntics restohative dentistry...the posterior determinants of occlusion, the...

Special reprint from

THEINTERNATIONALJOURNALOF

PERIOV&>NTICSRESTOHATIVE

DENTISTRYVol:23

oCopyright @ 2003 by Quintessence Publ Co, Inc

4

03

325

Occlusion-Based Treatment Planning forComplex Dental Restorations: Part 2

§"

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Bernard Keough, DMD, CAGS*

Part 1 of this article discussed the rationale for a thorough occlusal evaluation of

all patients requiring dental care, Those patients in need of complex reconstruc-

tion frequently require modification of one or more of six inter-related elements

that comprise an occlusal scheme. Two of these elements, the centric relation

position of the mandible and the vertical dimension of occlusion, were discussed.

This article will continue the discussion of the remaining elements, beginning with

the posterior plane of occlusion. The position and function of the maxi!lary incisaledges, as wellas those ofthe mandibularincisaledges, willthen be reviewed, .

followed by a consideration of posterior dental occlusal anatomy. These six ele-

ments dictate the function and esthetic nature of the final prosthesis, and their

successful integration enhances the long-term prognosis of the reconstruction.(lnt J Periodontics Restorative Dent 2003;23:325-335.)

*Private Practice Limited to Prosthodontics, West Palm Beach, Florida.

Reprint requests: Dr Bernard Keough, 2521 North Flagler Drive, WestPalm Beach, Florida 33407.

Careful evaluation of the occlusion of

patients requiring restorative care is

a prerequisite to undertaking any

restorative procedures. Patients with

significant dental problems requiring

complex restorative and surgical

procedures may be more predict-

ably managed if a preestablished

sequence of occlusal evaluation andconstruction is used. Part 1 of this

article reviewed the significance and

relevance of the centric relation posi-tion of the mandible and the vertical

dimension of occlusion (VDO).

Plane of occlusion

Following assessment of the man-

dibular centric relation position and

the VDO through mounted study

models, the next component of the

occlusion to be evaluated is the pos-

terior plane of occlusion. The oc-

dusal plane is "the average plane

established by the incisal and oc-clusal surfaces of the teeth."1 This

plane, the dental arches, and teeth

have a specific relationship to the

temporomandibular joints (TMJ)

and to the horizontal plane. Correct

Volume 23, Number 4, 2003

326

positioning of the models on anarticulator, which replicates theserelationships in the patient, is a pre-requisite for the functional andesthetic success of the prosthesis.When seen from the sagittal view in

the average patient with no missing,supraerupted, or excessively wornteeth, the occlusal plane is at an

angle approximately 10 to 15degrees divergent from and inferior

to the axis-orbital plane. It nearly

parallels the ala-tragus line and hasa slight inclination to the horizontal

when the patient is standingupright.

The axis-orbital plane is "thehorizontal plane established by thetransverse horizontal axis of the

mandible, with a point on the infe-rior border of the right or left orbit(orbitale)."1 This is the horizontal ref-

erence plane to which many articu-lator systems relate the maxillarymodels when a facebow is used in

the mounting procedure. Thisplane, however, does not corre-

spond with the true horizontal planeof the skull when the head is posi-

tioned upright. Its anterior portion isinclined apically, in a cranial direc-tion. Therefore, use of this plane asa reference and transferring it backto the articulator results in dropping

down of the anterior portion of the

plane as it is made parallel with thehorizontal upper member of thearticulator. This results in an abnor-

mally steep angle to the occlusal

plane when the models have beenmounted on the articulator, and itmakes the transfer of critical esthetic

information to the laboratory tech-nician much more difficult.

To facilitate the transfer of this

information, some manufacturershave created a facebow that uses

an anterior reference point, whichcreates a plane that is inferior to theaxis-orbital plane and closer to the

midfacial horizontal plane of thepatient. This places the plane of ref-erence, which is now based on the

actual horizontal plane, parallel tothe upper member ofthe articulator,making an accurate transfer of the

relationship of the patient's occlusalplane to the horizon possible. A sim-ilarmodification may be required fororientation of the occlusal plane in

the frontal plane. This involves mak-ing the frontal member of the face-bow also level with the horizon. The

interpupillary line isfrequently usedas a reference; however, this is use-

ful only ifthe eyes are truly level withthe horizon. In those cases where

they are not, other techniques havebeen suggested to accurately trans-fer this information to the articula-tor.2,3

As the maxilla is the foundation

of the occlusal plane, the maxillaryposterior plane of occlusion willhavedefinite implications in the designand function of the occlusion for the

reconstructed patient. Consequent-ly,tooth shape or position may needto be modified within this arch

before the two arches may be

related together (Fig 1).The positionof the posterior teeth must be estab-lished prior to creating a physiologicanterior guidance. There are two

functional requirements of a properplane of occlusion, as described byDawson.4 The plane must allow theanterior teeth to function to disclude

the posterior teeth in protrusivemovement, and it must allow dis-

clusion of all teeth on the balancingside when the mandible moves lat-

erally.To facilitate the establishment

of these functional objectives of the

restored occlusion, an occlusal planethat is as level as possible should becreated. The posterior determinants

of occlusion, the temporomandibu-lar articulations and their associated

structures, partially determine how

quickly the posterior teeth separatewhen the mandible moves from the

centric relation position. The moreangled those surfaces, the more

rapidly the posterior teeth separate.Conversely, the more shallow those

angles, the less separation is de-

monstrated by the posterior teeth.However, the plane of occlusion willalso affect the separation of the pos-

terior teeth. Teeth uniformly posi-tioned on a level occlusal plane willbe separated much more rapidlyduring mandibular movement than

teeth positioned on a curve or aplane that is excessively angled tothe horizon and that more closelyapproximates the inclination of thecondylar eminences. This is also true

of teeth positioned in an arch that isvery uneven because of missing,

tipped, or supraerupted teeth.Rapid separation of the posteriorteeth helps to preclude posteriorinterferences during mandibular

movement. Consequently, no at-tempt is made to reestablish a curve

of Spee or a curve of Wilson in theocclusion plane. The benefit of elim-

ination of posterior excursive inter-ferences far outweighs any benefit ofincreased chewing efficiency that

The International Journal of Periodontics & Restorative Dentistry

327

, f

such an occlusal design ostensibly

provides.

A third requirement ofthe planeof occlusion is that it must be esthet-

ically positioned in the face.s Thisdetermination must be made clini-

cally, and the plane must be related

to the facial esthetics of the patient.Provisional restorations that have

been fabricated from a preoperative

diagnostic wax-up are used for this

procedure. The plane must be posi-

tioned at an appropriate vertical

level so that there is adequate tooth

display by the patient on smiling,

and the patient must demonstrate

adequate facial vertical dimension

in maximum intercuspation. The final

location of the occlusal plane, aspart

ofthe VDO, is a primary determinant

for establishing an acceptable facial

Fig 1a (left) Patient with complaints offlaring maxillary anterior teeth, "short"posterior teeth, and mobility of the leftfixed partial denture.

Fig 1b (right) Fixed partial denture ex-tends from maxillary left lateral incisor andcanine to the second molar. Cement wash-

out and mobility of the anterior abutmentshas been an ongoing problem. Extrudedmandibular second premolar and molarencroach on the oce/usal plane and mini-mize space for the maxillary pontics.

Fig 1c (left) Following opening of theVDO to gain space, the maxillary oce/usalplane is leveled, and the posterior quad-rant is restored by means of implant-sup-ported crowns.

Fig 1 d (right) Facial view of final restora-

tion. Uneven posterior oce/usal plane hasbeen restored and is more' contiguous with

maxillary incisal plane.

proportion and dimension.6 Finally,

the occlusal plane should be paral-lel with the horizon when viewed

from the frontal plane.

Treatment of esthetic problemsof the anterior teeth is also directly

dependent upon the relationship of

these teeth to the plane of occlusion

established by the posterior teeth. In

the absence of developmentalgrowth anomalies or extensive den-

tal pathology, the posterior teeth will

have erupted to the correct level inthe face and established a reference

plane to which the anterior teeth may

be related. Esthetic treatment plan-

ning for anterior incisal plane dis-

crepancies and eruption abnormali-ties begins by relating these teeth

directly to the posterior occlusal

planeJ Therefore, the amount of

deviation, if any, of the posterior

plane of occlusion from the horizon

will greatly influence treatment plan-

ning for those anterior tooth prob-

lems. Consequently, for both func-

tional and esthetic purposes, the

posterior occlusal plane must be

evaluated and established initially as

part of the reconstructive process.

Maxillary incisaledge

position

'In the intact and healthy ClassI occlu-

sion, the maxillary incisal edge posi-

tion represents the anterior exten-

sion of the posterior occlusal plane.

Consequently, a line extending ante-

riorly from the posterior occlusal

plane, approximately parallel with


~

328

.i'/t~.'~I\j /"\ '\ ~. II

the ala-tragus line,willgive a starting

point from which the position ofthe maxillary incisor teeth may bejudged. Conversely, should the pos-

terior teeth be missing or the planeof occlusion be so deviated that it

must be reestablished, posterior ex-

tension of a line from properly posi-tioned incisal edges of the maxillary

incisors, closely parallel with the ala-tragus line, will establish a plane to

which the posterior teeth may be setin the reconstruction. There is ob-

viously some variability in maxillary

incisor edge position based uponesthetic and phonetic concerns.

However, the posterior occlusalplane represents a good referencefrom which to begin the evaluation.

Eventhough it is possible to reestab-

lish the maxillary incisal edge posi-tion based primarily upon estheticconcerns,8 it must be remembered

that in many instances this isa purely

Fig 2a (left) Preoperative full smile ofpatient complaining of short and darkteeth, giving him the appearance of beingmuch older than he actually is.

Fig 2b (right) Clinical view of patientdemonstrating significant oce/usal andincisal wear resulting from extreme para-functional habits.

Fig 2c (left) Postoperative smile. Incisallength is increased approximately 3 mm,reestablishing an overbite relationship thatis functional and protective, yet not exces-sive. Tooth display on smiling is significantlyimproved, yet minimal by some standards.

Fig 2d (right) Clinical view demonstratesrestored anterior relationship.

subjective endeavor. As there is arange at which the incisal length maybe established, the functional

requirements of the incisors as theanterior determinant of occlusalfunction must not be overlooked.9

In a mutually protected occlu-sion, mandibular elevator muscle

activity is reduced in excursivemovements through the contact of

the anterior teeth.1o From a per-

spective of muscular activity, theideal angle of anterior guidance is

the shallowest one capable of clearly

discluding the posterior teeth. Theshallower the angle of disclusion andthe less muscle activity involved inthe movement, the lower the hori-

zontal forces that are placed onthese teeth. The goal then is toestablish a length of the incisors that

satisfies the patient's esthetic

requirements, yet will provide anoverbite relationship that minimizes

forces on the anterior teeth in excur-

sions. Consideration of this conceptbegins during evaluation ofthe VDO

ofthe patient. Increasing the VDO inthe anterior segment of the mouth

provides the opportunity to de-crease the anterior overbite, which is

of considerable value when maxillaryanterior teeth must be lengthenedfor esthetics. However, as there is a

range in what isconsidered to be an

esthetic display of maxillary incisors,

preference should be given to cre-ating a final length that allows forthe anterior guidance to be as shal-

low as possible, yet still leaves the

patient with an esthetically pleasingresult. This is particularly true ofpatients with weakened periodontalsupport,11 horizontal bruxism12,13

(Fig 2), or dental implants.14

Esthetic treatment planning

begins with locating the maxillary

incisor position,9 and from there a


~

329

smile may be constructed. However,

an average smile in young pa-

tients-exposure of the full central

incisors 15-is not applicable to all

patients, particularly middle-aged

and older patients. All patients neednot receive 11- to 12-mm central

incisors, nor display the full central

incisor on smiling. Different esthetic

standards should be applied to

patients of different age groupsbecause of the effects of aging or

variability of lip mobility. Therefore,

the initial patient evaluation can sug-

gest starting points for establishing

anterior tooth length, overbite and

overjet relationships, and the VDO.However, in reconstruction, these

components are established, tested,

and modified in the provisionalrestorations, which will ultimately be

the blueprint for the final prosthesis.

It is possible to achieve both a func-tional and esthetic result in recon-

struction, assuming that one does

not accept a "one look fits all" con-

cept of anterior esthetics.

Mandibular incisal edgeposition

Initial consideration of mandibular

incisal edge position also begins

early in the diagnostic phase of treat-ment, when the VDO is assessed.Function of the mandibular incisors

with the lingual inclines of the max-

illary incisors will determine the type

and amount of incisal guidance thatwill be established for the final

restoration. This isa crucial decision,

as the pathway of the anterior teeth

is as important, if not more so, as the

influence the TMJs have upon thefunctional occlusion of the denti-

tion.16 An exceptionally steep incisal

guidance may be relieved by anincrease in the VDO and restoration

of the lingual surfaces of the maxil-

lary teeth. On the other hand, the

VDO may be maintained, the incisal

edges of the mandibular incisors

reduced, and the lingual contours

of the maxi Ilary anterior teethrestored to reestablish contact and

shallower guidance. In situations of

inadequate incisal guidance, man-dibular incisors and canines that are

too worn to adequately function with

the maxillary teeth must be restored.

Teeth that are out of position

may require orthodontic therapy to

place them into the proper relation-

ship. In extreme instances, ortho-gnathic surgery may be considered

to position the mandibula,rteeth into

a functional relationship with th~

maxillary teeth. These functional

considerations, as well as phonet-ics17and esthetics, dictate the incisal

edge position of the mandibularanterior teeth.

After determining an appropri-

ate position and length for the max-

illary incisors, the position of themandibular anterior incisal edges

may then be developed. It is reallynot until all of these other elements

of an occlusion have been evaluated

and established that a nonarbitrary,

functionally correct position for themandibular incisors can be estab-

lished. Contact of the mandibular

incisors is best established on a small

horizontal area, a few tenths of a mil-

limeter in dimension, on the lingual

surfaces of the maxillary anterior

teeth. This directs the forces of

occlusion more vertically than if the

contacts were placed on an inclined

plane.18 Movement from these small

areas is onto angled surfaces con-toured to minimize forces on the

anterior teeth, yet they must clearly

separate the posterior teeth in allexcursions. McHorris19 hastheorized

that the angle of incisal guidance

should be at least 5 degrees greater

than the corresponding angle ofcondylar guidance to minimize

potential protrusive interferences on

posterior teeth. This represents a

good starting point, and for many

patients, this incisal guidance will be

acceptable. Forthe average patient,

this represents an angle of approxi-

mately 45 degrees.2o,21However, in

reconstruction, posterior cusp heightmay be modified to accommodate

the incisal guidance created.

Incisal guidance is customized

for each individual patient, with dif-

ferent requirements for patients withdifferent functional habits, and also

for different patient types. For

example, differences in chewing

patterns must be accommodated in

the final occlusal design. Patients

with horizontal chewing strokes

require a different type of guidancethan those with vertical strokes.

Patients with periodontally weak-ened anterior teeth have different

requirements than those with

.healthy, stable periodontal support.Patients with uncontrolled bruxism

habits or implant-supported restora-tions in the anterior segment also

have their own occlusal require-

ments. These patients all typically

require a shallower incisal guidance.


II::::.

330

Additionally, patients not undergo-

ing complete reconstruction, butmerely receiving all-ceramic restora-

tions for esthetic purposes, mustalso have a carefully establishedincisal guidance. Fractured restora-

tions and postoperative sensitivityofteeth can frequently be relateddirectly to the occlusion that hasbeen established on them.

Because of their position in aclass "' lever situation, the anteriorteeth are better suited to absorbocclusal forces than are weakened

posterior teeth22 and must be al-

lowed to do so. Many patients, par-ticularly those with Class II maloc-clusion, willnot demonstrate contact

of anterior teeth; however, every ef-fort should be made to establish

contact. Ifthis is not possible, theremust be contact on at least the

canines in centric relation. This pro-vides the patient with a sense of sta-bility to the occlusion and a starting

point from which to begin and endexcursive movements. In protrusivemovement, the central and lateral

incisors should mediate the separa-

tion of posterior teeth. There shouldbe free and unstrained movement ofthe mandible and no fremitus noted

on the maxillary incisors. A shallow

angle of incisal guidance decreaseshorizontal forces on the anterior

teeth23 as well as decreases muscle

activity24during the movement. As

a means of distributing forces uni-formly, all four incisors should be in

contact throughout the excursion.With weakened anterior teeth, the

canines may also be involved in theguidance. In those instances wherethe incisors are not in contact in

centric relation, the initialsegment of

the protrusive movement must bemediated by the lingual inclines ofthe maxillarycanines. A smooth andharmonious transition of the guid-ance must be maintained until the

mandible has protruded far enoughto establish contact of the incisal

edges of the opposing incisors. Inlateral excursion, the canines should

be the primary mediator of themovement.

In the absence of maxillary ca-nines, or when the- canines and re-

maining anterior. abutments areweak, it is necessary to establish a

posterior group-function occlusalscheme using the posterior teeth fordisarticulation. However, the ante-rior teeth should also be involved in

the disarticulation, and excursive

contact on the buccal cusps of themaxillary premolars and the first

molars should diminish anteropos-teriorly to minimize lateral forces on

those teeth. Group-function occlu-sion isalso desirable for patients withuncontrolled bruxism habits. These

patients apparently do not have thebenefit of a protective functioning

anterior proprioceptive inhibitionand can easily damage a crown or

tooth upon which canine disarticu-lation has been established. Finally,this occlusal scheme is also desir-

able for patients whose canines havebeen replaced by dental implants.14

These patients will derive very littleproprioceptive inhibition from

implants placed in the canine loca-tion.

Anterior guidance must be

established prior to finalizing theposterior occlusal contours, and the

mandibular incisor edge positionmust be established before the lin-

gual contours of the maxillary an-terior teeth may be finalized. Themaxillary and mandibular incisor

contours are frequently establishedsimultaneously, and this is done clin-icallywhile working out the excursive

patterns in the provisional restora-tions. Anterior guidance is devel-

oped in harmony with each patient'sfunctional envelope of motion, inconjunction with neuromuscular re-

quirements.Ifa lack of anterior contact or an

anterior open bite is the result ofhabit patterns, elimination of thishabit would be part of the treatmentgoal. However, some habits, such as

tongue thrusting, may not be read-ilyresolved; therefore, restoration ofmandibular anterior teeth must take

this into account. Finally,the positionand shape of the incisors are alsotested phonetically when evaluatingthe patient's ability to clearly makethe sibilant sounds1? and evaluated

esthetically. The plane should behorizontal for the best appearanceand level with or slightly coronal to

the mandibular posterior occlusalplane. The amount of mandibularincisor exposure during speech isdependent upon the age of the

patient and may be modified ac-cordingly within the dictates of oc-clusal function.

Occlusal surface morphol-ogy of posterior teeth

The final step in establishing an oc-clusion is the creation of occlusal


331

surface morphology for the poste-

rior teeth. This exercise takes place

in the laboratory; however, the clin-

ician has the opportunity to affect

the design through working with the

provisional restorations. Accurately

mounted study models of the final

provisional restorations are trans-

ferred to the laboratory to aid thetechnicians in this task.

To adequately design posterior

teeth, it is helpful to understand their

functions. First, posterior teeth must

support the VDO, which in turn pro-tects the anterior teeth and the TMJs

from overload. Second, the posteriorteeth must function in mastication,

and finally, to a certain extent, playa role in the esthetics of the final

reconstruction. The posterior teeth

must perform these functions andbe designed so they do not interferewith the free and unstrained move-

ment of the mandible as it functions

through the incisal guidance that has

been established (Fig 3). That is, theymust not become occlusal interfer-

ences. If properly established, theforces of occlusion will be directed as

nearly as possible down the longaxes of the teeth. Lateral forces will

be eliminated, or distributed to min-imize the effect of forces within the

system, and the restored posteriorocclusion will demonstrate stability.

Of all aspects in establishing a

physiologic occlusion, the design of

the occlusal surface of the posteriorteeth has been one of the most con-

troversial areas over the years. As

Taylor et aF5 pointed out, there isstill

much debate concerning posterior

cusp height, occlusal groove designand direction, and the nature of

tooth-to-tooth contact itself. How-

ever, in the absence of evidence-based studies on the ideal occlusal

morphology, empiric data from eval-

uation of long-term successfully

treated cases by many different clin-

icians must be given serious consid-eration. These occlusions have been

designed to perform their functions

while promoting freedom of man-dibular movement. They minimize

muscular activity, thereby protecting

the joints, teeth, and periodontium,and they distribute forces on the

prosthesis as Vl{idely as possible.

These requirements of a restored

posterior tooth anatomy have all

been described previGusly,26,27yetthe nature of the ideal static inter-

cuspal position has not been

described satisfactorily for all clini-cians. However, if reduced to its

most basic functional cor:nponents!tooth-to-tooth contact must consist

of only one point of contact per

tooth, preferably a cusp against

a flat area of the opposingtooth.16,28,29This may be in either a

fossa or on a marginal ridge; how-

ever, it may be more stable with con-

tact of a cusp tip to the base of ashallow fossa. The area of contact

need only be small, within 0.5 to 1mm in diameter. This contact satis-

fies the first function of the posteriorteeth-to maintain the established

VDO.

Because of the position and

angulation of the mandibular poste-rior teeth, it is desirable to have the

buccal cusps of those teeth act as

the centric holding contacts with the

opposing maxillary teeth.3o Ideally,this directs the forces of occlusion

through the long axes of both the

maxillary and mandibular teeth. Be-

cause of the slight but measurable

horizontal variability of the centric

relation position of the condyles31(within a few tenths of a millimeter

range), an occlusal scheme with a

single point and area of contact is

easier to establish and adjust than

one with multiple contacts per tooth,

and it is comfortable to the patient.4

As there is also a wide range in theamount of immediate side shift of

the mandible among patients,21

those patients with excessive side

shift will require even greater oc-clusal adjustment and freedom tomove from centric relation than

those patients with no side shift.26. This occlusal scheme makes it easier

to accommodate those patients aswell.

The maxillary lingual cusps mayor may not be used as centric hold-

ing cusps against the mandibularteeth. This determination is based

upon the extent to which these

palatal cusps act as balancing inter-

ferences when testing the occlusionin excursive movements. Because

of the normal buccal inclination of

the maxillary teeth, placing palatal

cusp tips down completely into thecentral fossae of the mandibular

molars frequently results in a cusp

that hangs below the plane of occlu-sion, creating an unesthetic result

and placing it in the path of a man-

dibular cusp tip during excursivemovement. In the formation and

adjustment of the occlusal scheme,

these interfering cusp tips are short-

ened rather than deepening theopposing fossae or shortening the


r--II

332

Fig 3a {left} Patient with failing maxillary reconstruction, recurrentdecay, and extensive mandibular tooth wear.

Fig 3b {below} Preoperative. radiographs reveal multiple weak-ened endodontically treated teeth and a lack of natural abutmentsto predictably support a new fixed prosthesis.

mandibular buccal centric holding

cusps. This occlusal anatomy has

been advocated in the past, al-though it was usually on restorations

with splinted teeth,4 particularly inthe periodontal-prosthetic pa-tient.11,27

Although never demonstratedby research, the omission of the

maxillary lingual cusps as centricholding contacts has been construedby many to contribute to a bucco-

lingual instability of nonsplinted

teeth. However, others32 have repu-diated this notion of buccolingual

instability and demonstrated that

with proper anterior guidance andadequate mesiodistal stability, thisocclusion design is as stable forrestorations on single teeth as it isfor

splinted teeth. This is an importantconsideration for many patients, yet

is of utmost importance for horizon-tal bruxers with intact periodontal

support. These patients must berestored because of excessive tooth

wear and do not require-in factshould not have-splinting of therestored teeth. The relatively flatrestored occlusal scheme that these

patients require nearly always resultsin the recontouring and shortening

ohhe maxillarypalatal cusps to clearthe mandibular cusps in all excur-sive movements.

In reality,the major assets of thisocclusion are its ease of design and

adjustment and its overcompensa-tion in preventing harmful posterior


Fig 3c (right) Final reconstruction.Dental implantsare used toaid compromised teeth in supporting final maxillary prosthesis.

Fig 3d (below) Radiographic survey of final case.

333

Fig 3e Occlusalview of maxillaryanteriorand posterior tooth form demonstratesdiminished but definite cusp height andshallowed anterior guidance to help pro-tect teeth and implants.

Fig 3f Mandibular posterior toothocclusal anatomy.

Fig 3g Strict attention to detail ofocclusal design, shallow anterior guidance,and diminished posterior cusp form do notpreclude an esthetic end result.


"',. in

,r-'i

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-

334

contacts, particularly balancing inter-ferences. The construction of elabo-

rate occlusal surfaces, with multiple

contacts and tall cusps, to provide

for "near miss" of opposing surfaces

for an increase in chewing efficiency

is unwarranted. The diets of patients

requiring reconstruction do not re-

quire tall pointed cusps for mastica-tion. In fact, the masticatory func-

tion of the posterior teeth has been

compared to the action of a pestle

and mortar in crushing and grindingof the food bolus.33 This occlusal

scheme is uniquely designed toallow this function and thus satisfies

the second function of the posterior

teeth. The maxillary teeth attachedto the base of the skull are stable and

may be designed asa perfectly func-

tioning mortar. The mandibular pos-

terior teeth and buccal cusps are

dynamic and function as very effec-

tive pestles.

Finally, in establishing posteriortooth form to enhance the esthetics

of the final reconstruction, the max-

illary buccal and lingual cusps may

be established primarily on esthetic

dictates, ie, their location on the

occlusal plane, with the mandibular

posterior tooth anatomy shaped toaccommodate the maxillary teeth.The characteristics of the occlusal

surface design for complex recon-struction, regardless of whether the

teeth are splinted, may be summa-rized as follows:

1. The buccal cusps of the maxil-

lary posterior teeth are posi-tioned for esthetics on a level

plane of occlusion, confluent

with but slightly apical to the

maxillary anterior teeth. Their

contours may be modified, how-

ever, to accommodate the cre-

ation of a group-function oc-clusal scheme.

2. The maxillary palatal cusps may

be placed into contact with the

mandibular posterior teeth butare always adjusted to prevent

the occurrence of balancing in-terferences in the final occlusal

scheme. They should not be

longer than the buccal cusps and

may be shorter.-

3. The maxillary ,and mandibular

posterior teeth are formed withshallow central fossae.

4. The mandibular buccal cusps are

positioned to direct occlusal

forces as nearly as possible along

the long axes of the teeth, pre-

ferably in contact within the cen-

tral fossae of the maxillary teeth.

They may, however, be in contact

on marginal ridges of the maxil-

lary posterior teeth.

5. The mandibular lingual cusps are

positioned to prevent the tongue

from being trapped on the oc-clusal surface, and because of

the axial inclination of the teeth,

they are shorter than the buccal

cusps when viewed from the

frontal plane.

As the elements of the stom-

atognathic system change with time

following reconstruction, this design

of occlusal anatomy provides the

greatest ease in adjustment and vari-

ability to adapt to the changing en-

vironment. Changes in the joints,

muscles, and teeth of a patient areinevitable, as is wear of enamel and

restoring materials. Control of the

occlusion helps to minimize these

changes, and part of the recall pro-

gram of every patient should consistof a regular and thorough evalua-

tion ofthe occlusion.34 For many pa-

tients, periodic adjustment may be

required, and this modified occlusalanatomy facilitates making and

maintaining those adjustments.

Conclusion

A systematic evaluation ofthe occlu-

sion of patients requiring complex

dental procedures greatly facilitates

the treatment planning process.

During treatment, the systematic cre-

ation of a physiologic occlusiongreatly enhances control of the

reconstructive process through the

completion of the prosthesis. Im-

proved treatment planning and en-

hanced control of case completion

ultimately increase the predictability

of both, thereby increasing the long-

term prognosis of the reconstruction.

Establishing an occlusion is

much more than designing the oc-

clusal surfaces of posterior teeth.This historically controversial issue is

but a small segment in a much larger

and comprehensive undertaking.

Through control of the entire occlu-

sion, the practitioner is able to dis-tribute forces and mediate the level

ofrnuscular activity, thereby control-

ling the load on the prosthesis, TMJs,

and teeth themselves. Additionally,an evaluation of the various elements

of an occlusion and their functional

inter-relationships is also mandatory

if an esthetic prosthesis is to be


335

achieved. Concerns for the functional

aspects of the occlusion and the cre-

ation of an esthetically successful

prosthesis are not mutually exclusive,

but in fact go hand in hand.

It is apparent that the occlusion

must be mastered as part of the

reconstructive process. Consequent-

ly, the team member who is respon-

sible for constructing and maintain-

ing the occlusion must take the lead

responsibility in treatment planning

and supervision of case completion.The success or failure of the restored

occlusion will ultimately determine

the long-term success of the recon-

struction. Although there is not one

occlusion applicable for all people,

one occlusal scheme has proven tobe successful in the reconstruction of

all patients most susceptible to den-tal disease and destruction.

References

1. The glossary of prosthodontic terms. JProsthet Dent 1999;81 :39-110.

2. Lee RL. Standardized head position and

reference planes for demo-facial aesthet-ics. Dent Today 2000; 18(2):82-87.

3. Dickerson WG, Carlson J. Predictable, aes-thetic full-mouth reconstruction. Dent

Today 1999;18(9):50-55.

4. Dawson PK. Evaluation, Diagnosis andTreatment of Occlusal Problems. St Louis:

Mosby, 1974.

5. Mack MR. Facially generated occlusal ver-

tical dimension. Compend Contin Educ

Dent 1997;18:1183-1194.

6. Schlott WJ. Midface collapse: An over-

looked disease. Dent Today 1997;16(9):54-57.

7. Kokich V. Esthetics and anterior tooth posi-

tion: An orthodontic perspective. Part II:

Vertical position. J Esthet Dent 1993;5:174-178.

8. Vig RG, Brundo Ge. The kinetics of ante-

rior tooth display. J Prosthet Dent1978;39:502-504.

9. Spear FM. The maxillary central incisal

edge: A key to esthetic and functional

treatment planning. Compend ContinEduc Dent 1999;20:512-516.

10. Manns A, Chan C, Miralles R.Influence of

group function and canine guidance on

electromyographic activity of elevatormuscles. J Prosthet Dent 1987;57:494-500.

11. Keough BE. Occlusal considerations in

periodontal prosthetics.lntJ PeriodonticsRestorative Dent 1992; 12:359-376.

12. Christensen GJ. Treating bruxism and

clenching. J Am Dent Assoc 2000;131:233-235. .

13. Spear FM. Occlusal considerations for

complex restorative therapy. In: McNeillC (ed). Science and Practice of Occlusion.

Chicago: Quintessence, 1997:449.

14. Weinberg LA. The biomechanics of force

distribution in implant-supported pros-

thesis.lntJ Oral Maxillofac Implants 1993;8:19-31.

15. Tjan AH, Miller GD, The JG. Some esthet-.ic factors in a smile. J Prosthet Dent 1984;51 :24-28.

16. Schuyler CH. The function and impor-

tance of incisal guidance in oral rehab-ilitation. J Prosthet Dent 1963; 13:1011-1029.

17. Whitmyer CC, Esposito SJ. Principles of

speech and their application to dental

reconstruction. Compend Contin EducDent 1998;19:378-385.

18. Katona TR. The effects of cusp and jaw

morphology on the forces on teeth and

the temporomandibular joint. J OralRehabil1989; 16:211-219.

19. McHorris WHo Occlusion with a particular

emphasis on the functional and para-functional role of anterior teeth. Part 2. J

Clin Orthod 1979; 13:684-701.

20. Pelletier LB, Campbell SD. Evaluation of

the relationship between anterior and

posterior functionally disclusive angles.

Part II:Study of a population. J ProsthetDent 1990;63:536-540.

21. Lundeen HC, Wirth CG. Condylar move-

ment patterns engraved in plastic blocks.J Prosthet Dent 1973;30:866-875.

22. Mansour RM, Reynor RJ. In vivo occlusalforces and moments: 1. Forces measured

in terminal hinge position and associatedmoments. J Dent Res 1975;54:114-119.

23. Weinberg LA, Kruger B. A comparison

of implant/prosthesis loading with fourclinical variables. Int J Prosthodont 1995;8:421-433.

24. Williamson EH, Lundquist DO. Anterior

guidance: Its effect on electromyograph-

ic activity of the temporal and massetermuscles. J Prosthet Dent 1983;49:816-823.

25. Taylor TD, Agar JR, Vogiatzi T. Implant

prosthodontics: Current perspective andfuture directions. Int J Oral Maxillofac

Implants 2000;15:68-69.

26. Lundeen He. Occlusal morphologic con-siderations for fixed restorations. Dent

Clin North Am 1971;15:649-661.

27. Levenson E. Requirements for ideal

restorative posterior tooth occlusal anato-

my-A working clinical hypothesis. Alpha

Omegan 1985;78(4):82-86.

28. Weinberg LA. Reduction of implant load-

ing using a modified centric occlusal

anatomy. Int J Prosthodont 1998; 11 :55-69.

29. Beyron H. Optimal occlusion. Dent ClinNorth Am 1969; 13:537 -554.

30. Dempster WT, Adams WJ, Duddles RA.

Arrangement in the jaws of the roots of theteeth. J Am Dent Assoc 1963;67:779-797.

31. Winstanley RB. The hinge axis: A reviewof the literature. J Oral RehabiI1985;12:135-159.

32. Wiskott HWA, Belser Ue. A rationale for

a simplified occlusal design in restorative

dentistry: Historical review and clinical

guidelines. J Prosthet Dent 1995;73:169-183.

33. Stuart CEo Good occlusion for natural

teeth. J Prosthet Dent 1964;14:716-724.

34. Rosenberg MM, Kay HB, Keough BE,Holt RL. Periodontal and Prosthetic

Management for Advanced Cases.

Chicago: Quintessence, 1988:407.


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