Week 5 - Oral Anatomy and Biomechanics Flashcards
(50 cards)
What are the different ways of replacing lost soft and hard tissues (3)
- implants
- fixed partial denture (FPD or bridges)
- Removable dentures, partial (RPD) and complete
What happens to soft tissue when teeth are lost
The lack of teeth leads to a process called alveolar bone resorption
- alveolar bone gradually shrinks because it no longer receives the mechanical stress it needs to stay robust. This resorption primarily affects the upper part of the mandible
- this shrinking happens upward and inward
What are functional consequences of tooth loss
- chewing efficiency decreases
- speech impairments
- occlusal imbalance (opposing tooth may over erupt and adjacent teeth may drift)
What are structure consequences of tooth loss
- bone resorption
- shifting of adjacent teeth
- loss of vertical dimension of occlusion may decrease
What are aesthetic consequences of tooth loss
- facial collapse
- smile alteration
- soft tissue changes - gingival contours may recede
What are psychological and social consequences of tooth loss
- reduced self esteem
- anxiety about treatment
dietary limitation
why does the mandible provide less occlusal support than maxilla
has less denture bearing area
maxilla = 24 cm squared
mandibular = 14m^2
What is the primary tress bearing area in the lower denture
buccal shelf
due to its dense bone, strategic location, large surface area and its ability to withstand masticatory forces.
What is flabby ridge
Flabby ridges refers to a condition in the mandible or maxilla where the alveolar ridge (the bone that holds the teeth) is soft, resorbed and mobile due to the loss of teeth and underlying bone structure.
This occurs where there is a lack of sufficient bone
What happens to the supporting tissue on the mandible due to tooth loss
- mandible becomes wider and seems prognathic
- the stress bearing area becomes flat and concave
attaching structures become very close to the residual ridge and fall over onto the ridge surface
What happens to the mylohyoid ridge after tooth loss
mylohyoid ridge itself doesn’t change much in structure, but it becomes more noticeable and significant as the surrounding bone resorbs after a patient becomes edentulous (alveolar bone)
What happens to the mental foramen after tooth loss
- usually sits in the midway between the upper and lower borders of the mandible however appears to shift upward due to loss of alveolar height.
- also appears more prominent or exposed as overlying bone thins out
- clinical implications as pressure on the area might irritate the mental nerve leading to discomfort or numbness in the chin and lower lip
What is the genial tubercles
small bony projections on the inner/lingual surface of the mandible
- serve as attachment points for the genioglossus and geniohyoid muscles which help control tongue movement and support the floor of the mouth
What happens to the mental genial tubercles after tooth loss
- the genial tubercles don’t typically resorb in alveolar bone resorption however they appear more pronounced as the mandible becomes thinner and shorter in height
Where does the labial vestibule run
runs from labial frenum to buccal frenum
What are the muscles in the labial vestibule
- Orbicularis Oris
- Mentalis
- Buccinator
Where does the buccal vestibule run
buccal frenum to retromolar pad
What are the muscles in the buccal vestibule
- buccinator - due to the orientation of its myofibrils, it doesn’t displace the denture. therefore, some extension on this area is possible
- masseter - located at the end of buccal vestibule. Due to its orientation, it may have a significant effect on the distobuccal flange of the denture
What are the mandibular arch anatomical landmarks: limiting structures
- Labial frenum
- labial sulcus
- buccal frenum
- buccal sulcus
What are the mandibular arch anatomical landmarks - limiting structures (anatomical features that play a critical role in defining the shape, size and stability of dentures)
- lingual frenum
- alveolo- lingual sulcus (lingual vestribule)
- anterior region
- middle region
- posterior region
What is the lingual border
Mylohyoid Muscles
- anterior part has an indirect effect on the impression
- posterior part has a direct effect when elevated during swallowing
What is the retro mylohyoid fossa
- creates an S curve on the impression
- depression on the mandible behind the mylohyoid muscle and the mandible
- helps in retention and stability of the lower denture
What are the limiting structures of distal extensions
- Ramus
- Buccinator muscles, Pterygomandibular raphe, superior constructor
- Lateral bony boundaries of retromolar fossa
What is the retromolar pad
- A prominent, bony area located at the back of the mandibular ridge, just behind the last mandibular molar.
- includes the lower edge of the pterygomandibular raphe
- this is the practical limit for the denture based because extending beyond it would encroach on the ramus and the attached muscles (buccinator and masseter)
