Indian Dental Academy Guide to Determining Vertical Dimension and Anterior Guidance

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Part II

Contents
 Vertical dimension
 Neutral zone
 Anterior guidance
 Restoring upper and lower anterior
 Long centric
 Occlusal plane
 Posterior occlusion

Vertical dimension
 Misconceptions about vertical dimension:
I. We cannot determine vertical dimension based on
whether the patient is comfortable.
II. Measuring the freeway space is not an accurate way to
determine the correct vertical dimension of occlusion.
III. Determining the rest position of the mandible is not a
key to determining vertical dimension.
IV. Lost vertical dimension is not a cause of
temporomandibular disorders.www.indiandentalacademy.com

Fallacy of bite raising for TMDs
 Misconception that the TMJs
could be vertically distracted.
 Because all elevator muscles
are posterior to the teeth.
 Upward pull keeps the
condyles loaded and rotates
them placing the first occlusal
contact on the last molar.

 Condyles must move forward
down the eminentiae to pivot
anterior teeth up to gain more
occlusal contact.
 Increased VDO interferes with
repetitive contracted muscle
length and results in increased
bite force causing covered teeth
to intrude and the uncovered
teeth to erupt with the alveolar
process. www.indiandentalacademy.com

 The VDO refers to the vertical position of the
mandible in relation to the maxilla when the upper
and lower teeth are intercuspated at the most closed
position.
 Teeth are not the determinants of vertical dimension.
Rather, their position is determined by the vertical
dimension of the space available between the fixed
maxilla and the muscle-positioned mandible.

 The mandible-to-maxilla relationship, established by
the repetitive contracted length of the elevator
muscles, determines the VDO.
 If muscle contraction length can be changed and
maintained, the teeth will automatically adapt to the
new dimension.
 However, the evidence supporting such change is not
convincing.
 There is an ever-present eruptive force that causes
teeth to erupt until they meet an equal, opposite force.www.indiandentalacademy.com

 Dimension of this jaw-to-jaw relationship is consistent
enough that even severe bruxing, clenching, and
abrading parafunction do not alter the jaw-to-jaw
dimension between bony landmarks in each jaw.
 It is important to ascertain if the obvious loss of facial
height is at the anterior teeth accompanied by
downward displacement of the condyles at maximal
intercuspation.

Evidence for stability of VDO
 Scientific research verifies that:
A. Decreases in tooth height are compensated for by a
commensurate increase in alveolar bone height.
B. Increases in tooth height are compensated for either
by regressive remodeling of the alveolar bone to
commensurately shorten the dento-alveolar process,
or by intrusion into the alveolus of the teeth that had
been lengthened.

Vertical dimension at rest
 When a muscle is neither hypotonic nor hypertonic, it is
said to be "at rest" Even resting muscle is in a mild state
of contraction.
 The rest position is not consistent even in the same
patient.
 Atwood found variations as great as 4 mm at the same
sitting and even greater variations at different sittings.

 The contracted length of the elevator muscles during
the repetitive power cycle used in swallowing is
constant.
 The practical approach therefore is to concentrate on
accurately recording the VDO and allowing the
dimensions of the freeway space to be the natural
result of the difference between the optimum length of
contracted muscles and the length of the muscles at
rest.

Rules for determining the VDO
 VDO that requires the least amount of dentistry to
satisfy esthetic and functional goals is always the VDO
of choice.
 Maximal intercuspation of the posterior teeth
determine the existing VDO.
 Muscle determined VDO must be measured from
origin to insertion of the elevator muscles.

Position of the condyles during maximal intercuspation
must be considered when evaluating VDO.
 If the VDO must be changed, it should be determined at
the point of anterior teeth contact.
Changing the VDO by either increasing or decreasing it
is tolerated well by patients.

And causes no harm to teeth or supporting structures if
tooth contact includes the complete arches and the
condyles are completely seated in centric relation
during maximal intercuspation.
Changes in the true VDO are not permanent. It will
return to its original dimension measurable at
masseter muscle.

Bite raising
I. To relieve a TMD
II. To "unload" the TMJs
III. To restore "lost” vertical dimension in a severely
worn occlusion.
IV. To get rid of facial wrinkles.

When the vertical dimension must
be changed
 Increasing the vertical dimension or perform multiple
pulp extirpations and endodontics to provide enough
room for restorations.
 In some cases, the esthetic needs of the patient cannot
be satisfied without the crown length being increased,
and the choices may be either surgical crown-
lengthening procedures versus increasing the vertical
dimension.

 Changes back to the pretreatment vertical dimension
occurred almost entirely within the alveolar bone by
either progressive or regressive remodeling.
 Where only segments of the occlusion are increased in
height, there seems to be a tendency to intrude those
teeth into the alveolar bone, whereas if the entire arch
contacts simultaneously in centric relation, the
changes take place by regressive remodeling of the
alveolar process.

Neutral zone

 The teeth and their alveolar process are the most
adaptive part of the masticatory system. They can be
moved horizontally or vertically by light forces.
 There is a neutral zone within which muscular
pressure against the dentition is ,equalized from
opposite directions. The entire arch falls within that
zone of neutral pressure.

 If irregularities of tooth position, alignment, or
contour can be corrected within the neutral zone, the
prognosis for long term stability is good.
 A problem occurs when the neutral zone is not where
we want the teeth to be.
 Treatment decision then must allow determination of
if and how we can change the neutral zone to orient it.

Methods for altering the
neutral zone
A. Orthodontics
B. Elimination of noxious habits
C. Myofunctional therapy
D. Surgical lengthening of the buccinator muscle band
E. Vestibuloplasty

Anterior guidance

Sequencing the determination of
anterior guidance

 The first decision determines the
relationship of the lower incisal
edges to the upper anterior teeth.
 Lower incisal edges: The leading
edge should be formed by a
definite labio-incisal line angle.
 The contour of the centric relation
contacts on the upper anterior
teeth must be shaped to form a
definite stop for the cingulum.

Unstable contact
 Failure to provide a definite stop
allows the lowers to continue
erupting.
 The lack of a stable holding
contact combined with contours
that interfere with the envelope
of function invariably leads to
severe wear on the lower labio-
incisal contact area.www.indiandentalacademy.com

 The second step in the process of
defining the functional matrix is to
determine the upper half of the
labial surface.
 The upper half of the labial surface is
a continuation the contour of the
labial surface of the alveolar process.
 There should be no change in
direction or curvature from alveolar
process to the tooth surface.

 Third step is concentrating on
contouring the surface back until the
lower lip can easily slide by the incisal
third to seal contact with the upper lip.
 To achieve this, it is important to
prepare the teeth in two planes.
 Restorations in which the incisal edges
are too far forward are often the result
of inadequate preparation for the lower
half of the labial surface.

 Step four is determining the contour
of the incisal plane. If the labial
contours have been positioned and
shaped correctly, the incisal edges
should fit the internal contour of the
lip when the patient smiles gently.
 If the incisal edges compress into the
outer lip surface during the smile,
the incisal edges are too far forward.

 The contacts of the incisal edges at
the inner vermillion border of the
lower lip during a gentle smile
determine the correct vertical and
horizontal position for incisal
plane.
 F sound is one of the most useful
guides for precisely positioning
the upper incisal plane because to
make an F so air is compressed
into a broad, flat band between
the lip and the upper incisal edges.

 The lip can accommodate
to any incisal edge
position to form F and V
sounds. But the facial
muscles become fatigued
if the incisal plane
requires abnormal lip
activity to squeeze the
sound into a flat band.

 Sit the patient in a relaxed position. Ask the patient to
completely relax, look straight ahead, and very gently
and softly count from 50 to 55.
 Carefully observe the relationship of the upper incisal
edges to the inner vermillion border of the lower when
the provisional restorations are in place.

Step five is harmonizing the anterior guidance
 Preliminary steps:
When indicated, the lower anterior teeth should be
reshaped or restored first.
If restorations are not needed on the posterior teeth, they
must be equilibrated before the anterior guidance can be
worked out.
All interferences to centric relation must be eliminated on
both anterior and posterior teeth to establish stable
contacts at the most closed position.

The five steps to harmony
Step I. Establish coordinated centric relation stops on
all anterior teeth.
 Deviation from first centric contact into a more closed
position. All interferences should be eliminated so that
the mandible may close all the way to maximum closure
without any deviation.
 No contact on some teeth after deviation is
eliminated.
 We can close the vertical dimension by grinding down the
centric stops until all teeth contactwww.indiandentalacademy.com

We can build up teeth to contact
We can "do nothing.“
 Missing Anterior Teeth: Provisional anterior bridge
is made from articulated casts and then all contours
are finalized on the temporary bridge in the mouth.
 Arch-relationship problems that do not allow
centric contact on all teeth: If lower anterior teeth
need to be moved or reshaped, their position and
contours must be correct before we proceed with
finalizing the anterior guidance.

 Habits that keep anterior teeth from contacting
 Contouring the centric stops: The shape of upper
contacts should direct the forces as close as possible up
the long axis, but contacts on slight inclines are not as
stressful as they may seem because the labial vector of
force is counteracted by inward pressure from the lips.

 Step 2. Extend centric stops forward at the same
vertical dimension to include light closure from
the postural rest position.
After centric stops have been established by
manipulation of the mandible into terminal axis
closure, the patient should sit up in a postural position.
Remove the headrest, and instruct the patient to "tap
lightly with the lips relaxed."
Insert the red ribbon between the teeth, and have the
patient repeat the tapping.www.indiandentalacademy.com

 The mouth should be held open while patient is
returned to the supine position, and a manipulated
centric closure into a darker marking ribbon is made.
 If the red marks extend onto inclines forward of the
centric marks, the centric stops should be extended at
the same vertical so that the teeth can be closed either
into centric relation or slightly forward of it without
bumping into inclines. The amount of freedom centric
relation required rarely exceeds 0.5 mm

 Step 3. Determine the incisal edge position.
If the anterior teeth are stable and no contour changes
are needed, the incisal edge position should be
maintained.
If incisal edges are to be altered restoratively, the
changes should always be determined in provisional
restoration first and then copied in final form only
after the patient has approved the comfort and
appearance.

 Step 4. Establish group function in straight
protrusion.
 In most cases, the four incisors fall right into group
function as individual tooth interferences are reduced.
 All reductions should be done on the upper teeth.
 Interferences are marked by sliding forward on
marking ribbon from centric relation to end-to-end. If
one tooth marks by itself, the marked area is hollow
ground until the second tooth shares the load, and on
until all four incisors have continuous contact forward.

 At the completion of the
protrusive movement, the
incisal edges of the lower
central incisors should meet
the incisal edges of the upper
central incisors.

 Step 5. Establish ideal anterior stress distribution in
lateral excursions.
 The procedure for customizing the lateral anterior guidance
starts with closing the mandible into centric contact.
 With firm help from the operator, the patient is asked to slide
the jaw laterally and any movement of any teeth is noted.
 The excursion is repeated with marking ribbon interposed
between the teeth and the marked lateral contacts selectively
ground until there is continuous contact from centric to the
incisal edge of the upper canine.

 Final matrix decision is the
contour from the centric relation
stop to the gingival margin.
 Contour mistakes here can
interfere with T, D, and S sounds.
 Avoid sharp ledges and round off
the cingulum contour to blend
into the centric relation stop.

Esthetic contouring
 Guidelines for Upper
Anterior Tooth Contours
Midline should always be
vertical regardless of incisal
plane.

 Tooth contours: The curvature
of the individual incisal edges
can be related to circles that
guide contour for incisal
embrasures. Starting at the
mesial of central, the size of the
circle progresses from 1/3 width
to '/3 width at the distal. The
lateral is 2/3 at mesial and 3/3 of
the width at distal. This is an
easy guide to follow when
shaping anterior teeth.

Gingival contour formed as
trigonal shape with apex
slightly toward distal. Height
varies, with centrals slightly
higher than laterals.
Canine inclination should
converge inwardly from front
view. From side view, canines
should be straight vertical for
best appearance.

 Canine contours: The ideal
position for canines is facing to the
side. Front view should display the
mesial surface, and there is
typically a line angle at the mesio-
labial juncture. Correct
positioning creates a high contact
with the lateral.
 Contouring labial embrasure form
by shaping sharp-pointed V using
a thin diamond disk.

Lower anterior quality control
 The restoration of lower anterior teeth requires two
key terminations:
I. Incisal edge position
II. Incisal edge contour

Incisal edge position
 The determination of incisal edge position requires
three decisions:
i. The curvature of the incisal plane
ii. The height of the incisal plane
iii. The horizontal position of the incisal edges

Curvature of the incisal plane
 Important to phonetics and
esthetics.
 Mistakes are often responsible
for problems of discomfort as a
result of phonetic disharmony.
 Always use relaxed, gentle, softly
spoken S sounds for harmony
with a comfortable, unstrained
envelope of function.

 Convex upper and lower incisal
planes cannot make a clear S
sound at the end-to-end position
because air leaks out at the sides.
 If a convex lower incisal plane is
flattened, it will no longer relate
correctly to the concave upper
lingual contour and patient fills
the space with the tongue,
resulting in a lisp and produces a
typical eth sound.

The height of the incisal plane
 Relating lower incisal edges to the
occlusal plane
 Lower incisal edges form a
continuous gentle curve that is an
extension of the posterior occlusal
plane.
 There should be no sudden variation
in height between the incisal edges
and the posterior cusp tips

 The critical element in determining the height of the
lower incisal edges is the relationship with the upper
anterior teeth.
 It is often necessary to reshape or reposition the upper
anterior teeth to get an acceptable position and
contour of the lower incisors.
 The goal is to establish stable holding contacts for the
lower incisors at an esthetically acceptable height.

Relating lower incisal edges
to the lips
 A consistency in the amount of
lower anterior tooth surface that
is exposed during certain lip
relationships.
 Lips sealed: The lower incisal
edge is at the height of the
juncture of the upper and lower
lips when the teeth are together.

 Speaking: "The view" when
speaking is of the incisal edges
of the lower anterior teeth.
 Smiling: Only the upper
anterior teeth are typically on
display during smiling. The
lower incisors are usually
hidden during a big smile.

 Lips slightly parted: When
the jaw is at rest and the lips
are slightly parted in a half
smile, both upper and lower
labial surfaces are about
equally on display.

Horizontal position of the lower
incisal edges
 Key to determining the horizontal position of lower
incisal edges lies in establishing stable holding
contacts with upper anterior teeth.
 The diagnostic wax-up is the best possible way to
determine lower incisal edge position.
 Upper and lower provisionals are placed and refined
in the mouth until the patient approves.

Lower incisal edge contour
 The most important contour on the lower incisal edges
is the labio-incisal line angle.
 The "leading edge“ is imp0rtant for natural
appearance but also to achieve a stable holding contact
against the upper lingual stop.
 Loss of this leading edge contour is usually the start of
progressive wear and instability of the anterior
guidance.

 If the diagnostic wax-up indicates a need to move thick
incisal edges lingually the preparation for lower anterior
restorations will require more reduction on the labial to
permit thin normal incisal edge contours on the restorations.
 If the incisal edges need to be moved labially, the bulk of the
reduction will be on the lingual.
 Proper contouring of the labial embrasures completes the
outline of the incisal edge contour.
 The incisal edge is higher on the lingual, and there are no
embrasures on the lingual

Long centric
 Freedom to close; mandible either into centric relation
or slightly anterior to it without varying the vertical
dimension at the anterior teeth.
 Long centric involves primarily the anterior teeth.
 Long centric refers to freedom from centric, not
freedom in centric.
 When the teeth come together in a postural closure,
the lower incisors should not strike an incline before
reaching full closure.www.indiandentalacademy.com

 Contact in centric relation: All
posterior interferences to centric
relation must be completely eliminated
so anterior contact in centric relation
can be verified.
 Postural closure: With the patient in
an upright, relaxed, postural position,
gentle tapping of the teeth together
should not result in striking the upper
lingual incline before complete closure
to the most closed position.

 Clearance for long centric
 The goal is for the patient to be able
to close either into centric relation
or postural closure without striking
the lingual incline. This means a
slight extension of the centric stop
on the upper anterior teeth.
 Postural closure is marked with a
red mark during unguided closure.
The patient is instructed to tap
lightly while the fresh marking
ribbon is held. www.indiandentalacademy.com

 If the incline forward of
centric relation marks, it is
relieved so the incline does
not touch during gentle
unguided closure.
 Amount of relief required is
never more than 0.5 mm

Providing long centric by
equilibration
 When interferences to centric relation are eliminated
by equilibration, long centric is usually provided
automatically.
 By using a red ribbon for postural closure and then
using a black ribbon to manipulate for centric relation
closure:
When each red mark is covered by the black centric
mark.

When red marks extend forward from black centric
marks.
When red marks extend backward from black centric
marks.
When black centric marks are missing from red marks.

Occlusal plane
 The term plane of occlusion refers to an imaginary surface
that theoretically touches the incisal edges of the incisors
and the tips of the occluding surfaces of the posterior
teeth.
 The curvatures of the anterior teeth are determined by
establishment of an esthetically correct smile line on the
upper and the relationship of the lower incisal edges to the
anterior guidance and the requirements for phonetics.

 The curvatures of the posterior plane of occlusion are
divided into
A. An anteroposterior curve called the curve of Spee
B. A mediolateral curve, referred as the curve of
Wilson
 The composite of the curve of Spee, the curve Wilson,
and the curve of the incisal edges is properly referred
to as the Curve of occlusion.

The curve of Spee
 The curve of Spee refers to the anteroposterior
curvature the occlusal surfaces, beginning at the tip of
the lower canine and following the buccal cusp tips of
the bicuspids a molars and continuing to the anterior
border of the ramus. If the curved line continued
further back, it would ideally follow an arc through the
condyle.
 The curvature of the arc would relate, on average, to
part of a circle with a 4-inch radius.

 The curve results from variations in axial alignment of
the lower teeth.
 To align each tooth for maximum resistance to
functional loading, the long axis of each lower tooth is
aligned nearly parallel to its individual arc of closure
around the condylar axis.
 Last molar is tilted forward at the greatest angle and
the forward tooth to be at least angle.
 Directly related to the condylar axis by a progressive
series of tangents.

 Occlusal plane is on an
arc that passes through
the condyle, the posterior
part of the occlusal plane
will always be flat and low
enough to be discluded by
the normal condylar path
on its steeper eminentia.

Determining an acceptable
occlusal plane for restorative cases

The curve of Wilson
 The curve of Wilson is the
mediolateral curve that contacts the
buccal and lingual cusp tips on each
side of the arch. It results from
inward inclination of the lower
posterior teeth, making the lingual
cusps lower than the buccal cusps on
the mandibular arch.
Resistance to loading,
Masticatory function.

 If the buccolingual
inclination of the posterior
teeth is analyzed in relation
to the dominant direction of
muscle force against them,
the axial alignment of all
posterior teeth is nearly
parallel with the strong
inward pull of the internal
pterygoid muscles.

 Because tongue and the
buccinator complex must
repetitively place each bite of
food onto the occlusal
surfaces for mastication,
there must be easy access for
the food to get to the occlusal
table.

Posterior occlusion
 Lower posterior teeth
 Three key determinations must be made:
i. Plane of occlusion
ii. Location of each lower buccal cusp tip
iii. Position and contour of each lower fossa

Placement of lower buccal cusps
 Buccal cusp placement for buccolingual stability
 The buccolingual position of lower buccal cusps is
determined in the following manner on mounted
casts:
Upper central groove position is analyzed. On each
upper occlusal surface, a line is drawn from mesial to
distal in the central groove. The ideal contact point for
each lower buccal cusp tip is usually located
somewhere on this line.

 A mark is made on each lower tooth to indicate the
position of the buccal cusp that would be optimum for
buccolingual stability and direction of force.
 Evaluate the relationship of the selected lower cusp
position against the ideal upper central groove
position.
 If they do not line up precisely, the positions of both
the upper central groove and the lower buccal cusp tip
are equally changed.

 Mesiodistal placement of lower buccal cusps
 Attaining mesiodistal stability
 The best mesiodistal stability is attained by placement
of lower buccal cusps in upper fossae.
 When it is not practical to place lower buccal cusp in
an upper fossa, and it will be necessary for it to contact
on the marginal ridges of two upper teeth.

 Locating the lower buccal cusps for non
interfering excursions
If the lower buccal cusp can move out of the fossa in
protrusive working and balancing excursions without
colliding with another cusp, its position is acceptable.
Place the lower buccal cusps of premolars in a mesial
fossa when possible. This allows egress from centric
relation through all excursions with the least chance of
destroying tooth anatomy in the process .

Molar cusp tips should be placed mesial fossa, or in the
distal fossa with nonfunctional egress through the
transverse groove.
 Contouring cusp tips
For cusp-tip-to-fossa contact, the tip of each lower
buccal cusp should be small enough to fit into a
normally contoured fossa.

When the tip of the cusp serves as the centric contact,
it should be wide enough to provide optimum wear
resistance.
A sharp, pointed cusp tip would have too little surface
contact to resist accelerated wear.
A broad, flat cusp tip could require the upper fossa to
be opened out too much to permit good occlusal
contour.

In general the tip of the cusp should have a fairly flat
area about 1 mm or so wide to withstand wear when
the tip contacts in centric relation and small enough to
permit good fossa contours in the upper.
 In lateral excursions, if group function is desired, the
side of the cusp contacts the wall of the fossa rather
than the tip.

Placement of lower lingual cusps
 Treat the lower lingual cusp as a nonfunctioning cusp
as far as contact is concerned.
 It should still act as a gripper and grinder to aid in
tearing, crushing, and shearing the food that is caught
between the opposing surfaces.
 Responsible for keeping the tongue from getting
pinched between the posterior teeth.

 The cusp tip should rounded and smooth on its lingual
aspect.
 The position the tip should have enough lingual
overjet to hold the tongue out of the way.
 Measurement between buccal cusp tip and lingual
cusp should not be much greater than half of the total
buccolingual width of the tooth at its widest part.

 Generally the lower lingual cusp height should be
about a millimeter shorter than the buccal cusp.
 If upper and lower posterior teeth are to be restored,
simply following the occlusal plane dictated by the
simplified occlusal plane analyzer (SOPA) or the
Broadrick flag will be acceptable for both the curve of
Spee and the curve of Wilson.

 Contouring the lower fossae
 Lateral guidance incline of each upper canine dictates
contours of the buccal inclines of each lower lingual cusp on
the same side and the lingual inclines of each lower buccal
cusp on the opposite side.
 When the canine is not in position to function individually
or in group function as the lateral anterior guidance, the
lingual incline of the most anterior upper tooth that can
assume the role becomes dictator of the lower fossa inclines
facing it.

 Good rule to follow: from the contact point of each
upper lingual cusp, lower fossa inclines should be no
steeper than the anterior guidance inclines they face.
 A concave anterior guidance requires concave fossa
contours.
 The simplest and most practical approach is to open
up the lower fossae by providing more than enough
freedom for lateral paths and making the cusp-fossa
angle flatter than the lateral anterior guidance angle.

Making the fossa contour guide
 Step 1: The regular incisal
guide pin is removed and
replaced with the special
fossa-contour pin. The blade
of the pin is indented into a
mound of wax on a flat plastic
guide table.

 Step 2 and 3: The upper
bow is moved into left and
right excursions allowing
the contours of the lateral
anterior guidance to
determine path that the
guide pin cuts into the wax

 Steps 4 and 5: When the lateral
guidance paths have been cut
sharply into the wax, the special
pin is raised. It is then used to
hold a handle for the fossa guide.
The large end fits snugly onto
the raised special pin.
 Step 6: A creamy mix of self-
curing acrylic resin is flowed
into the indentation in the wax

 Step 7 and 8: Resin is wiped into
the hollow end of the handle,
and the pin is lowered so that
the two portions flow together.
 Step 9: Because of the design of
the special wax-cutter pin, the
lateral anterior guidance angle
will be evident as a sharp line
running along bottom edge of
the acrylic guide.www.indiandentalacademy.com

 Step 10: Hollow-grind the front
surface down to make a scoop-
shaped guide, which is excellent
for shaving out wax from the
fossae.
 Steps 11 and 12: To ensure
posterior disclusion, the fossa
walls must be flatter than the
lateral anterior guidance, so the
fossa guide angle is flattened on
the sides and the tip is rounded
to a more opened-out fossa.

 Steps 13 and 14: The fossa
guide can be used to
contour the wax patterns
or as a guide for shaping
occlusal surfaces in
porcelain.

 Three basic rules for using the fossa contour
guide.
i. Always hold the handle perpendicularly
ii. Never destroy a predetermined cusp tip
iii. Locate fossae in proper relation to cusp tips

 Carving the marginal ridges:
 Failure to evenly line up the marginal ridges of contacting
teeth invites food entrapment and often becomes an
interference.
 The ridges should be contoured to reflect food away from
the contact.
 Contouring ridges and grooves:
 Give beauty and naturalness to the occlusal scheme
 The arrangement of ridges and grooves is to permit the
cusps to pass close enough to each other to mangle the

food between the grooved surfaces without the need
for actual tooth contact.
Extreme preciseness is not required because in cusp-
tip-to-fossa contact only the base of the lower fossa
contacts the upper lingual cusp.
It seems practical to simply work out the fossae
contours first and then functionalize and beautify the
anatomy by placing the appropriate grooves at the
working, protrusive, and balancing excursion.

Upper posterior teeth
Its cusp inclines, grooves, and ridges are placed and
contoured to accommodate the many border
movements of the lower posterior teeth.
When the lower cusp-fossae inclines are then designed
to be discluded by the correct anterior guidance and
the lower cusp tips are precisely located on an
acceptable occlusal upper contours can be refined to
any desired degree.

If the anterior guidance has not been finalized and
the lower posterior teeth are not also in their final
form, it is not possible to determine the amount of
clearance that is actually available for the upper
prepared teeth.
Dentist must decide whether the upper occlusal
inclines are to be in group function, partial group
function, or total disclusion in excursive movements.

 Length of group function
contact in working excursion:
 All teeth do not stay in excursive
contact for the same length of
stroke.
 The disengagement is
progressive, starting with the
back molar forward to the
canine.

 If the occlusion must be grossly adjusted on the
finished restorations:
i. Improper recording of centric relation
ii. Errors in mounting.
iii. Improper fit of finished restorations.
iv. Errors in cementation.

Types of posterior occlusal
contours
 There are three basic decisions to make regarding the
design of posterior occlusal contours:
A. Selection of the type of centric relation contacts
B. Determination of the type and distribution of
contact in lateral excursions
C. Determination of how to provide stability to the
occlusal form

Types of centric holding contacts
 Centric relation contact is usually ,established on
restorations in one of three ways:
i. Surface-to-surface contact
ii. Tripod contact
iii. Cusp-tip-to-fossa contact

 Surface-to-surface contact:
"mashed -potato occlusion.“
Results if the articulator is
simply closed together when
the wax on the dies is soft.
It is stressful, and it produces
lateral interferences in
anything other than near-
vertical "chop chop“ function.

 Tripod contact:
 The tip of the cusp never touches
the opposing tooth. Instead,
contact is made on the sides of
the cusps that are convexly
shaped.
 Three points are selected from
the sides of the cusps, and each
point in turn is made to contact
the side of the opposing fossa.

 If tripod contact is to be used with concave anterior
guidances, the contacts must be confined to the tip of
broad flat cusps.
 If functional movements, anterior periodontal
support, arch relation, and tooth position are best
served by posterior disclusion, tripod contact can be
very comfortable, functional and beautiful.

 Should not be used when lateral stress distribution is
best served by including posterior teeth into group
function.
 Any degree of shifting of any tooth produces an incline
interference.
 Extremely difficult or impossible equilibrate without
losing tripodism and ending up with contacts on
inclines.

 Cusp to-fossa contact:
 Offers excellent function
and stability with the
flexibility to choose any
degree of distribution of
lateral forces that is
warranted.
 Easiest occlusion to
equilibrate.

 Resistance to wear is excellent, since the centric stops
are on the cusp tips
 If group function is needed in working excursions,
contact is on the sides of the cusp tips as they travel
along the inclines of the opposing teeth.
 If disclusion of any tooth is desired in any eccentric
excursion, it is accomplished by adjustment of the
fossa inclines without disturbing the centric holding
contacts.

Variations of posterior contact in
lateral excursions
I. Group function
II. Partial group function
III. Posterior disclusion

Group function
 Refers to the distribution of lateral forces to a group of
teeth rather than protecting those teeth from contact
in function by assigning all forces to one particular
tooth.
 Group function of the working side is indicated
whenever the arch relationship does not allow the
anterior guidance to do its job of discluding the
nonfunctioning side.

a. Class I occlusion with extreme overjet
b. Class 3 occlusion with all lower anterior teeth outside
of the upper anterior teeth
c. Some end-to-end bites
d. Anterior open bite
 Contacting inclines must be perfectly harmonized to
border movements of the condyles and the anterior
guidance.
 Convex-to-convex contacts cannot be used to
accomplish this.

Partial group function
 Refers to allowing some of the posterior teeth to share
the load in excursions, whereas others contact only in
centric relation.
 A very strong first premolar may work with a
moderately weak canine and incisors to disclude a
second premolar and molars.

Posterior disclusion
 Refers to no contact on any posterior teeth in any position
but centric relation.
 It can be accomplished easily with cusp-tip-to-fossa
morphology.
 Must be accomplished with tripod or surface-to-surface
morphology to prevent lateral interferences in any case
with centric contact on inclines that are steeper than the
lateral border movements of the mandible.

 Two methods of accomplishing posterior disclusion:
1. Anterior guidance is harmonized to functional
border movements first, and then the lateral inclines
of posterior teeth are opened up so that they are
discluded.
2. Posterior teeth are built first and then discluded by
restriction of the anterior guidance. This method is
backward.

 Can be achieved by two different types of anterior
guidance:
a) Anterior group function
b) Canine protected occlusion.

 Anterior group function:
Distributes wear over more teeth.
Distributes the stresses to more teeth.
Distributes stress to teeth that are progressively farther
from the condyle fulcrum.
 Concave anterior guidances permit group function,
whereas convex lateral guidances make it difficult to
accomplish.

 Canine-protected occlusion:
 Refers to disclusion by the canines of all other teeth in
lateral excursions.
 Serves as the cornerstone of what is called mutually
protected occlusion.
 Defined as an occlusal arrangement in which the
posterior teeth contact in centric relation only, the
incisors are the only teeth contacting in protrusion,
and the canines are the only teeth contacting in lateral
excursion.

 All lateral stresses must be resisted solely by the
canine.
 Lateral stresses are minimal if the lingual contours are
in harmony with the functional border movements.
 In natural canine-protected occlusions, the pattern of
function is rather vertical.
 Canines have extremely good crown-root ratios and
have densest bone in the alveolar process.

 Their position in the arch, far from the fulcrum makes
it more difficult to stress them.
 Changing from canine protection to anterior group
function is contraindicated if it would require a major
change in the envelope of function or extensive
reduction of sound lingual enamel.

Selecting occlusal form for stability
 Type 1. Lower buccal cusps
contact upper fossae. There no
other centric contacts:
 Continuous contact can be
maintained in working excursions
on the lingual incline of the upper
buccal cusps, or if disclusion of
posterior teeth is desired, it can be
easily accomplished by
modification of the upper inclines.

It is the easiest contour to fabricate when is restoring
posterior teeth because cusp-fossae angle the lower are
not critical.
Disadvantage to this type of occlusal relationship is its
lack of dependable buccolingual stability.

 Type 2. Centric contact on the tips
of lower buccal cusps and upper
lingual cusps:
 Addition of the upper lingual cusps
as centric holding contacts
contributes to the stability of the
posterior teeth.
 The vector of force against the cusp-
tip-to-fossae contacts is directed
toward the long axis when the teeth
are stressed laterally.

 Type 3. Centric contact on
tips of lower buccal cusps
and upper lingual cusps:
 Identical to type 2 except that
the buccal incline of the lower
lingual cusp becomes a
functioning incline.
 No clinical advantage or
recognizable difference in
patient comfort or function.

 Type 4. Tripod contact.
There are two types of
tripod contact:
 Contact on the sides of cusps
and the walls of fossae
 Contacts on the brims of
fossae and on tops of wide
cusp tips

 Contact on the sides of the cusps does not permit any
lateral or protrusive movement on a horizontal plane
 If the anterior guidance has been flattened even for a short
distance from the centric stops to permit a lateral side shift
of the mandible, this type of occlusal form is
contraindicated.
 Also contraindicated for any patient who requires a "long
centric.“
 Used in vertical or near-vertical functional cycles with
either canine-protected occlusion or anterior protected
occlusion.

 Centric contact on the brims of fossae and the top
of wide cusp tips with no contact in eccentric
excursions can be made to function with any type of
anterior guidance because it permits horizontal lateral
movement without interference.
 It is a flat occlusal contour and cusp tips do not fit into
fossae, it is only necessary to make sure the fossa width
is narrower than the width of the cusp.

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Indian Dental Academy Guide to Determining Vertical Dimension and Anterior Guidance

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Indian Dental Academy Guide to Determining Vertical Dimension and Anterior Guidance