Selection of teeth

Selection & Arrangement of Teeth

Classification of patients
1. Patients with remaining natural teeth
2. Patients who have old denture
3. Patients without remaining natural teeth and without old denture

Objectives:

1. Esthetics
2. Masticatory function
3. Correction of speech defects
4. Preservation of the remaining tissue and muscle tone

- Primary selection of the teeth must be carried out at the first appointment.

Anterior teeth selection
Guides for the anterior teeth selection
1. Pre-extraction guides
a. Study cast
b. Photographs
c. Radiographs
d. Extracted teeth


2. Post extraction guides

- 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

Anterior teeth

Size of anterior teeth
Size of the face
Width of maxillary central incisor = 1/16 bizygomatic width of the face
Size of maxillary arch
Not dependant in sever resorption
Width of the alae of the nose
If the base of the nose is wide the central incisor should be wide, if the root of the nose is narrow the lateral incisor should be narrow.

Corners of the mouth

The distance measured between the two commisures (angles of the mouth ) will represent the width of the upper six anteriors from the distal surface of the canine to the distal surface of the other canine.

Canine eminence

Cranial circumference

Anterior teeth

Incisal papilla & cuspid eminences
Distance = width of six maxillary anterior teeth
Line drawn from the distal termination of the eminence (or anterior to buccal frenum attachment) following the contour of the ridge , reaching the anterior border of incisal papilla, then terminate distal to canine eminence of opposite side
A mark is placed at occlusion rim at each corner of the lips when the patient is relaxed

Anterior teeth

Maxillomandibular relations
Mandibular anterior teeth size & length
Retruded mandible : the mandibular anterior teeth smaller
Protruded mandible : the mandibular anterior teeth larger
Protruded mandible : the face is longer the mandibular anterior teeth longer
Contour of residual ridges
Direction of resorption
Maxilla : anterior segment resorption in vertical & palatal direction
Maxilla : posterior segment resorption in vertical & medial direction
Mandible : anterior segment resorption in vertical direction
Mandible : posterior segment resorption in vertical & lateral direction


Anterior teeth
Vertical distance between the ridges
Length of the anterior teeth
The lips
Length of the anterior teeth
High lip line (when the patient smiles) : cervical third of anterior teeth
Low lip line (when the patient relaxed) : incisal third of anterior teeth

Anterior teeth

Form of anterior teeth
The form & contour of the face
Square, taper, or ovid
Sex
Curved features = female
Square features = male
Age
Older age = outline more square

Anterior teeth

Color or shade of anterior teeth
Patients age – With age, 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 following facts are true for nearly all natural teeth:

a. The neck of the tooth has a more pronounced color than the incisive edge.
• 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.




The color should be matched with the skin of the cheeks.

General consideration for selection of anterior teeth

1. Sex
a. Females – All teeth are more curved, rounded line and point angles, the teeth more ovoid or tapeing than square.
b. Male – The teeth are larger with sharp line and point angles, the teeth more square than ovoid or tapeing.
2. Age
3. Personality

Posterior teeth

Shade of posterior teeth
Shade of posterior teeth should harmonize with the shade of anterior teeth (bicuspids)

Posterior teeth

Size & number of posterior teeth
Buccolingual width
Buccolingual width of artificial teeth less than natural teeth to reduce the size of food table but don’t lose the support for cheeks, & not great enough to embarrass the tongue or encroach on a normal buccal corridor

Posterior teeth

Vertical height
The height of the maxillary first premolar should be comparable with that of the maxillary canines to have the proper esthetic effect
Vertical height (occlusal plane) should be comparable to the (occlusal table) , this table is an area bounded by cheek tissues buccally, tongue lingually, pterygomandibular raphe distally, and the contraction of the corner of the mouth mesially (modiolus). WHY?

Posterior teeth

Anteroposterior dimensions
Anteroposterior dimensions of posterior teeth are determined by the edentulous area between the distal of canine and the ascending area of the mandible. Why?
To place teeth on the ascending area of the mandible would direct the forces at an inclined plane, which are more dislodging than forces directed at right angles to the support

Posterior teeth

Occlusal form
Cusp angles are measured from a horizontal axis when the tooth is set with its long axis perpendicular to the horizontal axis

Posterior teeth

Cusp form teeth ( anatomical teeth ):
Were designed for the function of mastication. Their cusps were arranged so that during closing movements they would shear & crush food when the patient applied a reasonable biting force.
Advantages:
• Ease in developing bilateral balanced articulation between the maxillary & mandibular teeth during eccentric movements
• Excellent esthetic quality
• Chewing usefulness
• Disadvantages:
• Possible damage to the supporting tissues due to deflective contacts when vertical dimension is lost through resorption
• When bone loss occur lead to denture movement , discomfort, irritation of soft tissue,& more bone loss


Indications
In well formed ridges where good support and retention can be expected.
Where balanced occlusion is planned.
When it is possible to record and transfer accurate jaw relationships to the articulator.

Posterior teeth

Monoplane teeth ( non anatomical teeth )
They were designed without cusps to allow for intercuspation anywhere along the occlusal plane anteroposteriorly.
Advantages:
• Freedom in movement
• Used in class II & class III jaw relation ships
• Closure of jaws over a broad contact area
• Minimal horizontal pressure
• Easier maintenance
• Fabrication of dentures with simple techniques & articulators
• Disadvantages:
• Lack of esthetic quality
• Less chewing efficiency

Indications

They are indicated in flat ridge cases to minimize the lateral destabilizing forces.
When balanced occlusion is not planned.
In abnormal jaw relationships or when it is difficult to record centric relation.


Posterior teeth
Zero- degree posterior teeth:
These teeth have zero- degree cuspal angles in relation to the horizontal occlusal surface.

Posterior teeth

Semianatomic
- The 20o posterior denture teeth enjoy a great deal of popularity. They are considered to cause less lateral, denture-displacing force than 30o teeth, and to have better esthetics than 0o teeth.

Material composition of teeth

Acrylic resin teeth
Less resistant to wear & staining
Less likely to chip or fracture
Chemical means of retention with the denture base
Used in cases of small inter arch distance. Why?
Ease of occlusal reshaping
Used in cases where the opposing teeth (natural or have metalic restorations). Why?


Porcelain teeth
More resistant to wear & staining
More likely to chip or fracture
Mechanical means of retention with the denture base
Not used in cases of small inter arch distance. Why?
No occlusal reshaping
Not used in cases where the opposing teeth (natural or have metalic restorations). Why?

Position of teeth

Horizontal positions
Anterior teeth
• Incisive papilla
• Lip
• Crest of the ridge
Upper anterior teeth anterior to the crest of the upper ridge
Lower anterior teeth over the crest of the lower ridge

Position of teeth

Posterior teeth
Neutral zone
Forces exerted by the cheeks & tongue should be equal
Crest of the ridge
Mandibular posterior teeth positioned along a line extending from the tip of canine to the middle of retromolar pad. This line should pass through the central fossa of mandibular premolars & molars
Lingual cusps of maxillary posterior teeth occlude in the central fossae of the mandibular posterior teeth. This relation ship places the buccal cusp of maxillary posterior teeth lateral to the buccal cusps of mandibular posterior teeth so supporting the cheek & prevent cheek biting
Distance from distal of the canine to ascending area of the mandible

Position of teeth

Vertical positions
Anterior teeth
Low lip line
Incisal edges
Over jet & over bite
Phonetics (f, v,& s sounds)
Posterior teeth
Retromolar pad (2/3)