2.5 Physiologic rest position

what are the requirements for something to be referred to as physiologic or phsyiological in dentistry?

• characteristic or conforming to the innate function of a tissue or organ

• organic processes or to functions in an organism or in any of its parts

• opposite of pathologic

what is the physiologic rest position?

the natural, comfortable position of the mandible when a person is in an upright position and at rest

what is the position of the lips, muscles and joints of the face at the physiologic rest position?

• Lips are slightly touching each other, small distance of about 2-5mm between the front teeth

• muscles that control the jaw movements are in a state of balance and minimal activity

• condyles (jaw joints) are in a neutral, unstrained position

What is occlusion?

• the way the upper and lower teeth come together when you close your mouth, the static relationship between the biting surfaces of the mouth

what is physiologic occlusion?

when teeth come together in harmony with the functions of your chewing system, bite is aligned properly and allows for efficient chewing.

Physiologically balanced occlusion takes into account aesthetic and the function of the temporomandibular joint and the neuromuscular system.

what is articulation?

contact relationship between the biting surfaces of the teeth furing function. how the upper and lower teeth come together and interact when you chew or perform other oral functions.

Focuses on the static and dynamic contact between the occlusal surfaces of the teeth.

what are the basic positions of the mandible?

• centric relation

• centric occlusal

• myocentric occlusion

• retruded contact position

• centric position

what is centric occlusion?

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; in this position, the mandible is restricted to a purely rotary movement’ maxillomandibular relationship, the patient can make vertical, lateral or protrusive movements; it is a clinically useful, repeatable reference position

where do the condyles articulate in centric relationship?

in articular eminence

what is the more retruded physiologic relationship?

centric relation

what is centric occlusion?

occlusion of the upper and lower teeth when the mandible is in centric relation, may or may not be same as maximal intercuspal psoition

what is maximal intercuspal position?

It is when the teeth fit perfectly together, regardless of the centric relationship

what is myocentric occlusion?

terminal point in space where, with the mandible in its rest position, subsequent uniform muscle contraction (unlike in maximal muscle tonus) will raise the mandible along the myocentric trajectory

Its a position between centric occlusion and centric relation

what is retruded contact point?

The occlusal relationship that occurs when the condyles are in their most retruded position in the joint cavities.

In retruded contact position there is no ability for lateral moveement

What is centric position?

position of the mandible when the jaws are in centric relation

what are the border occlusions?

protrusive occlusion

lateral occlusion

balanced occlusion

what is protrusive occlusion?

Occlusion of the teeth when the mandible is protruded forward

The frontal teeth have an edge-to-edge relationship, meaning they meet each other directly

distal teeth experience disocclusion, they are not in contact with opposing teeth in natural dentition

what is lateral occlusion?

occlusal contact of teeth on the side toward which the mandible is moved

what is lateral occlusion also known as?

working articulation, working bite or working bite relation

what is the working and non-working side of lateral occlusion?

working side is the side toward which the mandible moves during lateral excursion (sideway movement)

non-working side is the mandible that moves towards the medial line during lateral excursion

is there any occlusions during lateral excursion?

there is no occlusal contacts on the non-working side but in complete dentures there can be occlusal contacts

what is balanced occlusion?

occlusal contact on both sides of the mouth, both in the front and back

this occurs in different jaw positions, including the centric position (when teeth come together in correct bit) and eccentric position

what is eccentric positions?

it includes the protrusive positions (lower jaw pushed forward) and lateral positions on both working and balances sides

balanced occlusion is optimal for stability of complete dentures, ensuring that they fit well and function properly

what is canine guidance?

a mutually protected articulation that involves the vertical and horizontal overlpa of the canine teeth

what is purpose of canine guidance?

to disengage the posterior teeth during the sideways movements of the lower jaw

what is group function?

another type of contact relation between the upper and lower teeth, occurs during lateral movements on the working side

it is where multiple teeth make simultaneous contact to distribute occlusal forces

what is dental occlusion?

when teeth line up with eahother

what is malocclusion?

when teeth don’t line up together

what is angles classification of occlusion?

class I (normal occlusion or neutrooclusion)

Class II (distoclusion)

Class III (mesiooclusion)

Class IV (no longer used)

What is Class I neutrooclusion?

mesiobuccal cusp of maxillary first permanent molar aligning with the mesiobuccal groove of the mandibular first molar

it is a dental relationship with normal anterposterior relationship

what is dental dysplasia?

overcrowding and tooth rotation caused but there not being enough space for the teeth to align properly

what is class II distoclusion?

mesiobuccal cusp of the mandibular first molar is aligned with the buccal groove of the maxillary first molar.

this is because the lower jaw is positioned behind the upper jaw in one or both sides of the mouth

Convex facial profile

what can be a cause of class II distoclusion?

Can be caused by overcrowding of teeth which happens when the lower jaw is smaller

What is class III mesioocclusion?

• mesiobuccal cusp of maxillary first molar occludes interdentally between the permanent first and second mandibular molar

• occurs when the lower jaw is positioned in front of the upper jaw in one or both sides of the mouth

• can be subdivided by unilateral mesial occlusion where one side of the lower jaw is further forward compared to the upper jaw

• Concave facial profile

what is class III mesiooclusion often accompanied by?

an anterior crossbite, where the lower front teeth are in front of the upper front teeth when biting down

what is Class IV?

occlusal relations of the dental arches are in distal occlusion in one lateral half and in mesial occlusion in the other. this classification is no longer used

what can Class II be divided into (subdivisions)?

• proclined maxillary anterior

• Retroclined maxillary anterior

what are subdivisions of class III mesiooclusion?

skeletal - down to bone structure

Pseudo class - due to habitual activities

What is a bite?

act of incising or crushing between the teeth

What are the different types of malocclusions?

• overbite

• underbite

• crossbite

• open bite

• deep bite

• crowding

what is overbite?

upper front teeth overlap significantly with the lower front teeth

what is underbite

lower front teeth protrude in front of the upper front teeth

what is crossbite?

upper teeth sit inside the lower teeth instead of outside

what is open bite?

gap between the upper and lower front teeth when the back teeth are closed

what is deep bite?

upper front teeth excessively cover the lower front teeth

what is crowding?

there isn’t enough space for all the teeth, causing them to overlap or twist

what is prognathism?

condition where the upper or lower jaw protrudes forward

what are the two types of prognathism?

maxillary and mandibular

what is masticatory apparatus?

the organs and structures involved in chewing

what does the masticatory apparatus include?

teeth, supporting structures, joints that connect skull and lower jaw, mandible, muscles that help with positioning and movement, tongue, lips cheek and oral mucosa

what is the main function of the masticatory apparatus?

1. mastication and digestion (chewing food to break it down to give more surface are for digestive enzymes to work on)

2. Speech (forming sounds and speech production)

3. Aesthetic (appearance and alignment of the teeth and jaw contribute to the overall aesthetic of the face

what is mastication?

teeth and supporting structures work together to break down food into smaller particles, this increases surface area of the food, making it easier for digestive enzymes to act upon it.

what is masticatory dimensional cycle?

movement of the mandible during chewing process, consists of three phases: opening, closing and grinding

what are protective reflexes?

nausea and vomiting are natural reflexes that help protect the body

what does the masticatory unit consist of?

1. SUPPORTING PART - tooth, peridontal ligamnet, bond

2. MOTOR PART - muscles

3. NEURO-SENSORY PART - nerve

4. TROPHIC PART - blood

what is masticatory reflexes?

• process of communication between the muscles involved in chewing and the central nervous system

what does masticatory reflexes consist of?

Masticatory unit to CNS - when chewing signals sent from masticatory muscles to CNS to let the CNS know about the movement of muscles involved in chewing

CNS to masticatory unit - signal gets sent to masticatory unit from CNS which are instructions to help regulate the force and coordination of the muscle contractions involved in chewing

what is Physiological articulation cycles?

also known as mastication cycles, pathway of mandible during chewing, it ha three phases: opening, closing and intercuspal phase

explain the three phases of physiological articalution phase?

1. OPENING - mandible is depressed as the teeth and condyle move down and out

2. CLOSING - mandible is elevated, during early closing, it moves laterally to the desired chewing side

3. ICP (INTERCUSPAL PHASE) - reached during rest of the closing phase. the chewing condyle moves slightly forward and medially , known as BENNET MOVEMENT. condyle of the nonchewing side lags behind

how many chews are there per food swallow in articulation cycle?

15 chew per food swallow

what is the average vertical clearance during chewing in the articulation cycle?

Vertical clearance is space or distance between the upper and lower teeth during mastication, ensures teeth do not collide prematurely

16-20mm

what is lateral displacement during chewing in the articulation cycle?

Lateral displacement during chewing refers to the side-to-side movement of the jaw as food is processed.

It is around 3-5 mm

What is articulation?

the enunciation of words and sentences in speech

what is speech articulation consist of?

• production of individual sounds in connected discourse

• movement and placement of the organs involved in creating meaningful sounds

• speech function performed through the movements of the lower jaw, lips, tongue and soft palate

what do the components of speech include?

• respiration

• audition

• neurologic integration (speech production is coordinated by CNS)

• Articulation (sound that is transformed into meaningful words which is aided by tongue, lips, palate, teeth and mandible)

• Resonation (modification of sound in the pharynx, oral cavity, nasal cavity and paranasal sinuses)

• Phonation (air from lungs travels through trachea which vibrates vocal cords in the larynx)

what is speech aid?

any therapy or instrument used to improve speech quality

what is speech aid prosthesis?

removable device that helps people who have defects in their soft palate

how do speech aid prosthesis’ help patients?

it extends into the pharynx and separates the oropharynx and nasopharynx, this separation is important in speaking and swallowing

By completing the palatopharyngeal sphincter, the prosthesis helps improve the function of the soft palate.

What should be the main factors when looking into aesthetics of teeth?

1. shape

2. size

3. shade

What are Flush and Fisher’s SPA Factors?

1. Sex: male or female

2. Personality: soft or vigorous

3. Age: old or young, with mamelons (small bumps on teeth) in younger individuals

How is the perfect size for a tooth determined?

divide the cervicoincisal length of tooth by the mesiodistal width

optimal width/length ratio for central incisor is 0.75 to 0.8

ratio below 0.75 indicates a narrower tooth, ratio above 0.8 indicates a wider tooth

What should the shape of female and male teeth look like?

Feminine smiles tend to have rounded incisal angles, open incisal and facial embrasures

Masculine smiles often show close incisal embrasures with prominent incisal angles

what is the golden proportion for teeth?

• ratio of 1.618 : 1 : 0.618

• proportion that is calculated by dividing the width of each central incisor, lateral incisor, and the canine by the total width of all 6 maxillary anterior teeth