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vertical jaw relation horizontal jaw relation shade selection pontic size mounting
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Prosthodontic seminar ll
vertical jaw relation
Horizontal jaw relation
Shade selection
Pontic size
mounting
• Vertical dimension refers to the length of the face.
• It is maintained either by the
occlusion of the teeth or the
balanced tonic contraction of
the opening and closing
muscles of mandibular
movements.
Vertical jaw relation
Significance
• Provides optimal separation between maxilla and mandible.
• If not measured accurately, the joint will be strained.
• If the VD is altered, severe discomfort to both TMJ and muscles of mastication.
FACTORS AFFECTING VERTICAL DIMENTION
• Tooth : Acts as a vertical stop.
• Musculature : Opening and closing muscles tend to be in a state of minimal tonic contraction.
Vertical dimension of rest
(VDR).
• Vertical separation of the jaws when the opening and closing muscles of mandible are in a state of minimal tonic contraction sufficient only to maintain posture.
Vertical dimension of
occlusion (VDO).
• Vertical separation of the jaws when the teeth or occlusion rims are in contact.
It is generally considered that the teeth should not be in
contact when the jaws are at the vertical dimension of rest
position. The 2 to 4mm distance between the upper and lower
teeth when the mandible is at physiologic rest position is
called interocclusal distance (IOD) frequently referred to as the
“free way space”.
Interocclusal Distance (IOD)
VDR = VDO + IOD
VDR – IOD = VDO
INCREASE IN VDO / DECREASE IN IOD
• The chin-nose distance will increase, and then patients will have an appearance of open mouth.
• Constant pressure to the basal seat area which will lead to bone resorption.
• Soreness of the tissues of the basal seat.
• “Clicking”, of dentures during speech.
• Improper phonetics
DECREASE IN VDO / INCREASE IN IO
• Potentially damaging to the TMJ.
• The normal tongue space is
limited. Facial distortion appears
more noticeable with over
closure
• The muscles of facial expression
lose their tonicity and the face
appears flabby instead of firm
and full.
• Over closure of jaws may lead to
angular chelitis
HORIZONTAL JAW RELATION
Maxillo-mandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterior superior position against the shapes of the articular eminences.
DEFINITION
TYPES OF HORIZONTAL JAW RELATION
CENTRIC Reference relation with
which the desired occlusion can be coordinated and is constant for each patient, provided that the soft tissue structures in the temporomandibular joints are healthy
ECCENTRIC
Any relationship of mandible to maxilla other than centric relation which include protrusive and lateral relations.
OCCLUSAL RIM Simulate teeth
and help in establishing vertical dimension and centric relation
ORIENTATION OF THE OCCLUSAL PLANE
INTERPUPILLARY LINE CAMPER’S PLANEALAE-TRAGUS LINE
REGISTERING CENTRIC RELATION
Shade selection
Selection of shade
- Color and shade of tooth
The shade consist of:
a. Hue i.e specific color
b. Saturation i.e. amount of color per
unit area.
c. Translucency i.e ability of color to
permit light to pas through it.
Patients age – With
olderage, darker,
while lighter teeth
are suitable for young
patients.
Patients complexion: light teeth
for fair skin, blue eyes, dark
teeth usually for dark skin and
black eyes.
The color should be matched
with the skin of the cheeks
The following facts are true for nearly all natural
teeth:
a.The neck of the tooth has a more pronounced color
than the incisive edge.
b.The incisive edge if not worn, is more transluscent
that the body of the tooth and is usually of a bluish
shade (composed entirely of enamel)
c. The upper central incisors are lightest teeth in the mouth followed
by the laterals and canines. Posterior teeth are usually uniform in
color.
d.Teeth darken slightly with age.
- Aid for selecting the shade
Shade guides – The shade guide tooth should be moistened and
selection made in the normal light.
a.Outside the mouth along the side of the nose.
b.Under the lip with the incisal edge exposed
c. Under the lip with only the cervical end covered and the mouth
open.
Objectives:1.Esthetics2.Masticatory function3.Correction of speech defects4.Preservation of the remaining tissue and
muscle tone
- Primary selection of the teeth must be carried out at the first appointment.
pontic selection
Selection of size (width and length)
a. Size of the face and head
b. Size of the contour of the maxillary arch
c. Maxillomandibular relations
i. In class I – Normal relationship, the teeth in
one arch are compatible with the teeth in the other
arch.
ii. In class II – The mandible is retruded and
the mandibular teeth are frequently smaller
iii. In class III – The mandibular teeth are
frequently larger than normal
Selection of size
Bizygomatic width – The average width of the maxillary central incisor is estimated to be 1-16 of the bizygomatic width that is, the distance between the cheek bones measured just in front of the ears. Some simple devices are available from tooth manufacturers for making this determination or caliper may be used to measure this distance. A face bow maybe used as caliper to make this determination. The combined width of the six maxillary anteriors is slightly less than one third the bizygomatic width.
Width of the anterior teeth
Selection of the form:• Guides for selecting
the form of anterior teeth.
• Shape of the arch.
Posterior teeth selection – Posterior teeth should have a small bucco-lingual width to keep forces on the supporting structure to a minimum.
The mesiodistal measurements of the upper posterior teeth is taken from the distal surface of the canine to the prominence of the tuberosity. The total mesiodistal width of the four posterior teeth is often used as a mould number. The lower posterior teeth should not extend posterior to the mesial border of the retromolar pad.
Posterior teeth selection
Mounting
The master cast must be
accuretly positioned on
an articulator so that
proper occlusion will be
developed during the
tooth arrangment
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