L8: Tooth morphology and Occlusion (Introduction)

Question 1

Teeth alignment:

When does teeth alignment occur?

Answer 1

It occurs as a result of multidirectional forces.

• The major opposing forces that influence tooth position originate from the surrounding musculature.
• The lips and cheeks provide constant lingual forces.
• The tongue provides labially and buccal forces to the lingual surface of the teeth.

Question 2

What is neutral position?

Answer 2

A stable tooth position in the oral cavity where labiolingual and buccolingual forces are equal.

Question 3

What helps in normal alignment?

Answer 3

Proximal contact between adjacent teeth helps in normal alignment.

Question 4

What does the alveolar bone and gingival fibers result in?

Answer 4

The surrounding alveolar bone and gingival fibers result in a mesial drifting of the teeth toward the midline.

Question 5

What happens to the position of a tooth distal to an extraction?

Answer 5

A tooth distal to an extraction site will lose proximal contact and drift mesial into the space.

Question 6

What is termed as occlusion?

Answer 6

The relationship between the incising or masticating surfaces of the maxillary or mandibular teeth when they approach each other, as occurs during mastication or rest.

• It is unique for every person.
• A lot of dental procedures involve treatment on the occlusal surfaces of teeth.
• Knowledge of occlusion, its normality and how to properly, examine stomatognathic system is a key to prevent uncontrolled changes in inter-arches relationships and development of temporomandibular disorders.

Question 7

What does static occlusion refer to?

Answer 7

Static occlusion refers to contact between teeth when the mandible is closed and stationary.

Question 8

What does dynamic occlusion refer to?

Answer 8

Dynamic occlusion refers to occlusal contacts made when the mandible is moving during function.

Question 9

Functional cusps:

Answer 9

• The upper palatal and lower buccal cusps.
• They occlude in the opposing fossae and marginal ridges.
• Can also include the incisal edges of lower anterior.
• They determine the vertical dimension at maximum intercuspation.

Question 10

Non-functional cusps:

Answer 10

• The buccal upper and lower lingual

Question 11

Centric Stops:

What are centric cusps?

What do centric stops determine?

Answer 11

• the cusp tips of the functional cusps (marked as red dots in photos below).
• They determine the vertical dimension.

Question 12

Guiding inclines:

Which is the function of guiding inclines?

Answer 12

They dictate the course of the functional cusp during the natural, lateral and protrusive movements.

Question 13

Based on the following image answer the questions.

1. What does the blue line show?
2. What does the red line show?
3. What does the green line show?

Answer 13

1. Palatal inclines of the buccal cusps of the maxillary posterior teeth (blue line).
2. Buccal inclines of the lingual cusp of the mandibular posterior teeth (red line).
3. Lingual surfaces of the of the upper anterior teeth (green line).

Question 14

Incisal Guidance:

What is incisal guidance?

Answer 14

Is the ability of the palatal surfaces of the maxillary anterior teeth to guide the lower anterior teeth.

Question 15

Occlusal surface:

What is an occlusal surface?

Answer 15

A surface of a tooth that is intended to make contact an opposing occlusal surface (occlusal table).

Question 16

What is Plane of occlusion?

Answer 16

An imaginary surface that theoretically touches the incisal edges of the incisors and the tips of the occluding surfaces of the posterior teeth.

Question 17

What is Curve of Spee?

Answer 17

An arc of a circle that touches the buccal cusp tips of all the posterior mandibular teeth and the canine, when the skull is viewed laterally.

• When continued, it touches the anterior surface of the condyles.

Question 18

What is Curve of Wilson?

Answer 18

The arc of the occlusal surface of the posterior teeth, that is shaped from the cusp tips of the one side to the cusp tips of the other side when is projected to the coronal plane.

Question 19

Stomatognathic system:

Answer 19

• The stomatognathic system represents an extremely complex system
• It involves the temporomandibular joint, the teeth and the muscles of mastication
• It is influenced and controlled via the neuromuscular regulatory circuit.
• Disorders or problems in one part of the system will frequently have an effect on one or more of the muscles involved in the movements of mastication. - Ex. a change in the bite can be the result of a recently ill fitted crown (incorrect occlusion) can cause eventually muscle pain and discomfort.

Question 20

TMJ:

What is TMJ composed of?

Answer 20

The temporomandibular joint consists of articulations between three surfaces:

• the mandibular fossa
• articular tubercle (from the squamous part of the temporal bone)
• the head of the condyle

Question 21

Muscles of Mastication:

Answer 21

• Masseter
• Temporalis
• Lateral Pterygoid
• Medial Pterygoid

Question 22

Centric Relation:

What is CR?

Answer 22

A maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences.

• It is a clinically useful, repeatable reference position.

Question 23

CR:

Which movement is mandible restricted to in this position?

Answer 23

• In this position, the mandible is restricted to a purely rotary movement.
• From this unstrained, physiologic, maxillomandibular relationship, the patient can make vertical, lateral or protrusive
  movements.

Question 24

Centric Occlusion:
What is CO?

Answer 24

The occlusion of opposing teeth when the mandible is in centric relation; this may or may not coincide with the maximal intercuspal position.

Question 25

Maximal intercuspal position (MIP)/intercuspal position (ICP): What is defined as MIP?

Answer 25

The complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position * If condyles are in CR ➜ MIP=CO.

Question 26

Vertical dimension of occlusion (VDO): What is VDO?

Answer 26

The lower facial height measured between two selected anatomic or marked points when in maximal intercuspal position (MIP). * In fully dentate patients VDO is determined by the functional cusps and the centric stops.

Question 27

Working vs Non-Working side:

Answer 27

* _Working side:_ The side which the mandible moves towards, in a lateral movement. * _Non-working side_: The side opposite to the working side.

Question 28

Canineguidance: What is canine guidance?

Answer 28

The vertical and horizontal overlap of the canine teeth disclude the posterior teeth in the excursive movements of the mandible.

Question 29

Mutually protected occlusion: What is defined as mutually protected occlusion?

Answer 29

An occlusal scheme in which the posterior teeth prevent excessive contact of the anterior teeth in maximal intercuspal position, and the anterior teeth disengage the posterior teeth in all mandibular excursive movements.