Oral Biology Flashcards
In a specimen of mature human enamel with organic components visible, the enamel prism patterns can be visualised. What does the appearance of prisms indicate regarding the prismatic structure of enamel?
That the prisms run in different directions which gives enamel strength
What is the significance of hunter-Schreger bands?
- They strengthen enamel and prevent cracks from occurring
- they also optimise resistance to processes such as attrition or abrasion
What are the three potential origins of enamel lamellae?
- Damage ( e.g. mastication forces)
- Cracked from ground section processing
- Developmental defect
Do enamel tufts follow the direction of enamel prisms?
Yes
Are enamel spindles or tufts shorter?
Enamel spindles
In which part of the crown are enamel spindles best developed?
At the cusps
What is the relationship between enamel spindles and dentinal tubules?
Enamel spindles are short extensions of the dentinal tubules
What inorganic substance is enamel mostly made up of?
Hydroxyapatite
What percentage of hydroxyapatite makes up enamel by weight?
96%
What is the basic unit of enamel?
Enamel prisms
What are enamel prisms?
Repeated arrangements of hydroxyapatite crystals running from ADJ to outer junction
What is the shape of an enamel prism?
Complex ‘key hole’ shape
What two components comprise an enamel prism?
- Prism core
- Prism sheath
What component of enamel prisms has more tightly packed hydroxyapatite crystals?
Prism core
What component of enamel prisms has a micro-retentive surface where resin can lock into and mechanically bond?
Prism sheath
Hydroxyapatite crystals are less tightly packed in prism sheath compared to prism core. True or false?
True
Why do enamel prisms run an undulating course?
For strength. If enamel prims ran straight, there would be points of weakness and they would split easier.
What is the term used to describe enamel prisms appearing twisted around each other at the cusps?
Gnarled enamel
What structural component of enamel makes up the large majority of its thickness?
Enamel prisms
Better bonding to sub-surface enamel will result in less retention. True or false?
False. Better bonding to sub-surface enamel = better retention.
What substance may make acid etching more difficult and why?
Fluoride, as it strengthens the surface of the tooth.
What are the ‘Striae of Retzius’ also known as?
Incremental growth lines
What do incremental growth lines represent?
The different layers of enamel during crown formation
How would Striae of Retzius be visualised on virtual microscope?
As periodic dark lines through enamel
Why do striae of Retzius appear as dark lines?
The dark lines may represent occasional metabolic disturbances of mineralisation
What are the shallow furrows, where striae of Retzius reach the surface of enamel known as?
Perikymata
What feature on the tooth surface might wear away if abrasive toothpaste is used?
Perikymata
What are the ridges between Perikymata called?
Imbrication lines of pickerill
What feature of enamel is referred to as hypomineralised?
Enamel tufts
Enamel tufts form due to…?
Incorrect enamel formation
Define hypomineralised
Condition that affects enamel. Occurs due to a disturbance during tooth development.
How do early enamel caries present?
As white spot lesions
How do you initially treat white spot lesions?
Apply high dose/concentration of fluoride in the aim to arrest caries process
Where does demineralisation of enamel start and why?
It starts in the prism sheaths of enamel prisms. This is because easier diffusion of acid into prism sheaths as the hydroxyapatite crystals are not as tightly packed as in the prism core.
What are the four histological zones of enamel caries?
- Translucent zone
- Dark zone
- Body of lesion
- Surface zone
Which zone of enamel caries is the advancing front?
Translucent zone
Which zone of enamel caries is the most porous and therefore looses the most enamel in caries process?
Body of lesion
Why should you not probe a carious lesion?
It could break the thin surface zone layer into the body of the lesion. This may create a cavity.
How does arrested caries appear histologically?
As a wide, well-developed dark zone
What factors may favour caries arrest?
- plaque control
- use of flouride
- altered diet
What are ground sections?
Cut hard tissues ( mineral present)
In a ground section, how would an area that is less mineralised ( hypomineralised) appear?
Dark
In a ground section, how will an area where light passes through easily appear in comparison to a hypomineralised area?
Lighter
In a ground section, areas that are more mineralised ( hypermineralised) will appear?
Light
What type of tissue is dentine?
Specialised connective tissue
What structural feature gives dentine strength?
Direction of collagen fibres that are parallel to ADJ
What cells produce dentine tubules?
Odontoblasts
What can be found within primary curvatures of dentinal tubules?
Secondary curvatures
What has more tubules per mm^2, surface or deep dentine?
Deep dentine (pre-dentine)
Is dentine vital?
Yes
Where are most of the nerves in dentine found?
At the pulp horns
What are the three classifications of dentine?
- Developmental
- Primary, Secondary and tertiary
- Tubule
What are the two types of developmental dentine?
- Mantle dentine
- Circumpulpal dentine
What is the first formed dentine called and where is it found?
Mantle dentine, adjacent to enamel.
What type of dentine lies between the enamel and pulp chamber?
Primary dentine
What type of dentine is deposited in the pulp chamber after the formation of primary dentin is complete
Secondary dentine
What type of dentine forms as a reaction to stimulus such as caries, wear and fractures?
Tertiary dentine
What are the two types of tertiary dentine?
- reactionary
- reparative
What type of tertiary dentine uses existing odontoblasts?
Reactionary
Where would you find peri-tubular/ intra-tubular dentine? And is it mineralised or not?
Around the tubule, yes its mineralised.
Where would you find inter-tubular dentine?
Between tubules
What are line features of dentine?
- incremental lines of von ebner
- contour lines of Owen
what are zone features of dentine?
- interglobular dentine
- granular layer of tomes
What feature of dentin shows the position of odontoblast a at different times during development?
Incremental lines of von ebner
What feature of dentine is a coincidence of secondary curvatures?
Contour lines of Owen
What feature of dentine forms as a result of failure of calcospherites to fuse?
Interglobular dentine
What is the layer on the subsurface toot of dentine that has a granular appearance?
Granular layer of tomes
The process which blocks of dentinal tubules, in turn, slowing down the advance of caries, is known as?
Sclerosis
What feature of dentine forms as a result of odontoblast overcrowding, causing odontoblast death?
Dead tracts
what type of dentine has a fracture risk for extraction and why?
Translucent sclerotic dentine, because it is less flexible at the roots
What are the three zones of a carious lesion?
- Advancing front
- Zone of bacterial penetration
- Zone of destruction
What occurs at the advancing front of carious lesion?
Acid damage
What occurs at zone of bacterial penetration of a carious lesion?
Bacterial invasion
What occurs at the zone of destruction of carious lesions?
Breakdown of organic matrix
What are the principle periodontal ligament fibres?
- transeptal fibres
- bundles of circumferential fibres
In between teeth, what three cells are found in the crestal bone?
Osteoclasts in their lacunae
Osteoblasts
Osteoclasts
Which cell is trapped in the organic matrix of bone?
Osteocytes in their lacunae
What cell associated with bone is considered alive?
Osteocytes in their lacunae
what bone associated cell deal with new bone resorption?
Osteoblasts
What bone associated cell deals with aged bone resorption?
Osteoclasts
What is the purpose of osteoclasts?
They eliminate weakened or damaged bone tissue
What area of the tooth cementum is the thickest?
Apical cementum
What areas of the tooth cementum are the thinnest?
Cervical and inter-radicular cementum
Which is laid down the quickest? Cellular or acellular cementum.
Cellular
The porous nature of what bone is utilised in infiltration and intraligamentary LA?
The porous nature of the buccal bone
What direction to the cannaliculi in cementum point and why?
They point towards the PDL for nutrition
what is hyper-cementosis?
Excessive deposition of cementum
What are the three types of mucosa found in the oral cavity?
- masticatory mucosa
- lining mucosa
- specialised mucosa
What do all epithelial cells contain?
Filaments and desmosomes
What are the four layers (from superficial to deep) of non-keratinised lining mucosa?
- epithelium
- lamina propria
- submucosa
- bone/muscle
What glands are found in lining submucosa?
Salivary glands
What are the four epithelial layers of non-keratinised lining mucosa? ( from superficial to deep)
- superficial layer
- intermediate layer
- prickle cell layer
- basal cell layer
What is another term for non-keratinocyte?
Clear cells
In what layer are clear cells normally found?
Basal layer:
- basal clear cells
- supra-basal clear cells
What are the four layers (from superficial to deep) of keratinised masticatory mucosa?
Epithelium
Lamina propria
periosteum
Bone
What are the four epithelial layers of keratinised masticatory mucosa? ( from superficial to deep)
Keratinised
Granular
Prickle cell
Basal cell
What do ‘clear cells’ lack?
Filaments and desmosomes
What two types of clear cells only exist in the basal cell layer?
Merkle cells and melanocytes
What two types of clear cells exist in the supra-basal layer?
Inflammatory cells and langerhan’s cells
what are the three layers of specialised mucosa? ( superficial to deep)
Epithelium
Lamina propria
Muscle
What are the four epithelial papillae found in specialised mucosa?
- circumvallate
- foliate
- filiform
- fungiform
What are serous glands of von ebner?
Accessory minor salivary glands
What type of mucosa is flexible and slightly permeable?
Lining mucosa
What type of mucosa is inflexible and impermeable?
Masticatory mucosa
What lining material has a potential therapeutic effect on the pulp and why?
Dycal, as it may stimulate tertiary dentine formation
What four cells are contained in the pulp?
- odontoblasts
- fibroblasts
- stem cells
- defence cells
How far do the odontoblast processes extend into dentine?
1/3 of the way
Where does the blood supply of the pulp terminate?
In the rich sub-odontoblastic capillary plexus
How does pulpal death occur?
Due to stasis of blood in vessels as a result of competing pressures in the capillary beds within the tissues
What types of nerve supply does the pulp have?
Mainly sensory (afferent), also efferent ( post-ganglionic sympathetic)
What is the predominant type of nerve fibre in te pulp?
Unmyelinated C fibres
What pulpal zone is the plexus of Raschkow classically in?
The cell free zone
What is the negative impact of pulp stones?
Can causes issues when trying to access pulp with instruments
What is the pulpal response to formation of reactionary tertiary dentine?
-TGF beta is released from carious/demineralised tissue
- increase in odontoblast dentine formation
What is the pulpal response to exposure?
- Ca(OH)2 and MTA cement induces a dentine bridge
What is a dentine bridge?
A new reaction tissue that preserves pulp vitality and protects it from abnormal and continuous physical stimuli
What type of epithelium is found in oral mucosa?
Stratified squamous epithelium
What cell is predominant in connective tissue?
Fibroblasts
What is the rare condition characterised by slowly progressive overgrowth of the gingiva?
Hereditary gingival firbomatosis
What are the primary lymphoid organs?
Bone marrow and thymus
What are the secondary lymphoid organs?
Spleen and lymph nodes/nodules
What does MALT stand for?
Mucosa-associated lymphatic tissue
