DOH110 Midterm: DOH110 - Detailed session 1 summary
DOH – Session
Dental Anatomy Introduction:
Introduction:
• The face is an important part of anatomy as it allows for breathing,
seeing, swallowing, chewing), and consists of many tissues (bones,
muscles, glands, vessels and nerves) that are important in dental
treatment
Hard and Soft Tissue Anatomy:
Cementum
• Protective cover over the root (yellow coloured layer)
• Mineralized connective tissue resembling bone, that covers the roots of teeth
and serves to anchor gingival and periodontal fibres
Periodontal Ligament (PDL)
• Periodontal fibres - (e.g. trampoline, mat = tooth, PDL = springs). Made up of
type 1 collagen fibres, and in different angles to allow for support during
pressure from all areas
• Classify into groups based on their anatomic location:
o Alveolar crest fibres
o Horizontal fibres
o Oblique fibres
o Periapical fibres
o Interradicular
• The periodontal ligaments are of different diameters at the mineralized surfaces where the fibres are
continuous with their mineralized portion (Sharpey's fibres)
Alveolar Process and Bone:
• The alveolar process is the portion of the jawbone that contains the teeth and the alveoli in which they are
suspended. The alveolar process rests on basal bone
• The alveolar bone proper lines the alveolus (tooth housing) which is contained within the alveolar process. It is
composed of a thin plate of cortical bone with numerous perforations (or cribriform plate) that allow the
passage of blood vessels between the bone marrow spaces and the periodontal ligament
Alveolar Crest
• The coronal rim of the alveolar bone forms the crest, which generally parallels the cemento-enamel junction at
the distance of 1-2 mm in apical to it
Enamel
• Enamel is the hardest and most mineralised part of the teeth and the body
• 96% = hydroxyapatite, 4% = 4% water and organic material
• Structure of enamel is tightly packed rods, which is strong enough to withstand the stress of biting, chewing
and grinding. Although, this same trait also makes it susceptible to cracking and chipping
Dentine
• Dentine is tissue that is calcified and consists of tiny tubes
• The second layer of the tooth, making up the majority of the structure
• Denser and harder than bone, and generally yellow (although can be grey to black)
Pulp
• The most vital part of the tooth, found in the pulp chamber
• Contains blood vessels, connective tissue and large nerves
• The functions of the pulp include:
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DOH – Session
o Sensory function - pain from trauma to the dentin and/or
pulp, differences in temperature, and pressure are caused
by simulation of the pulp
o Formation of dentin - the pulp is responsible for the
formation of dentin. In the response to trauma, the pulp
forms secondary dentin, also known as reparative dentin
o Nourishment - the pulp contains blood vessels that help to
prevent the tooth from becoming brittle by keeping it
moisturized and nourished
• Inflammation of the pulp from tooth decay, infection, trauma can result in pulpitis (where root canal therapy
needs to be done to remove the pulp when it is dead)
Oral Cavity and Pharynx:
Divisions of the oral cavity - jaw alveolar processes and teeth:
• The maxilla
o Paired, symmetrical bones
o The two maxillae form the upper jaw and occupy the middle
third of the facial skeleton
o Joined in the midline by the intermaxillary suture
o Contains maxillary sinuses
o Contain alveolar process in which upper teeth are allocated
• The maxilla - compostition
o Hollow body that encloses sinus/antrum, shhaped like a pyramid lying on its side
o 4 processes include:
• Frontal
• Zygomatic
• Alveolar
• Palatine
• The mandible
o The strongest and largest facial bone, forms the lower jaw and thus
occupies the lower third of the facial skeleton
o Bone into which lower teeth are attached
o Articulations:
• Mandible does not have bony articulation with cranium, but
is help in place via muscles, ligaments and a moveable (ball
in socket) joint called the Terperomandiular Joint
o Functions:
• Mastication, swallowing, speech
o Composition:
• Body - curved horseshoe shaped horizontal portion. Alveolar process created by a thick buccal and
thin lingual plate of bone
• Ramus - two vertical rami projected upwards from each posterior end
Divisions of the oral cavity - gingival tissue
• Whiter gingival (gum) - attached gingival
• Gingival that connects to teeth - marginal gingival
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DOH – Session
• Area where whiter gingival meets darker gingival - mucogingival junction
• Darker gingival (lips, cheeks gums) - free gingiva
• Wiggly tips of gingiva in between teeth - papilla
Impression Materials
What is an impression:
• Operators are required to taken an impression of teeth and soft tissues for:
o Study models
o To create appliances i.e. mouthguards, bleaching trays
o For orthodontic comparison
o Creation of crowns, bridges and dentures
• Soft material mixed and placed into the oral cavity in trays will produce a mould
• Use of plaster or stone is then used to pour up a cast
o Generally algenate (gelatine and seaweed) which is an irreversible hydrocollate
Impression material properties:
• Flowable before set
• Able to pick up fine detail
• Sufficient working time
• Pleasant tasting
• Easy to use
• Hydrophilic
o Generally takes 2 minutes to set
• Strong - does not set too hard in the mouth, therefore easy to remove
• No adverse effect after removal
• Elasticity not advisable for endentious cavities
Classes of Impression Materials
Classification:
• Impression materials can be classified as either elastic or non-elastic
• Can also be classified by the type of setting reaction (chemical vs temperature)
Elastomers:
• Indicated when accuracy is paramount
• Not generally used by OHT's
• Elastomers are silicone based materials of differing strengths and properties
• The more viscous the material, the higher it's dimensional stability but the poorer the ability to record surface
detail
Hydrocolloids:
• The material used for the taking of impressions by an OHT is an irreversible hydrocolloid material (alginate)
• Colloids are suspensions of molecules, or groups of molecules, in some type of dispersing medium
• The term hydrocolloid means that the dispersing medium is water. In this fluid condition the colloid is referred
to as a SOL
o E.g. gelatine powder after it has been added to hot water
• Porous
• Chemical reaction required (alginic acid and water)
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