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Flashcards in Oral Cavity Deck (310)
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271

What is the importance of rectangular collimation?

Changes tube head from circular to rectangular
Red. dose by 50%

272

Describe the 2 mechanisms by which radiation can cause damage

Direct: more catastrophic
DNA/RNA; disturbs nucleic acid bonds, causes mutations

Indirect: more likely
Water molecules; radiolysis of water creates free radicals H2, H2O2 cause cellular damage

273

What are the 3 types of harmful radiation effects?

1. Somatic deterministic: threshold (only caused if above)
cataract formation: lens becomes opaque
obliterative endarteritis: radiolysis of small vessels
2. Somatic non-deterministic: no threshold (potential every time)
malignancy
3. Genetic non-deterministic

274

Describe dental pulp

Unmineralised tissue composed of soft CT, vasculature, lymphatics and nerve endings
Mostly water: 75-80%
Developmentally, structurally and functionally closely related to dentine: both from neural crest-derived CT that forms dental papilla
Occupied pulp chamber and root canals
Pulp chamber molars ~4x larger than incisors
No inorganic components in normal pulp: pulp stones found pathologically in ageing pulp

275

What is the primary function of pulp?

Provide vitality to tooth: loss of pulp (RCT) doesn't mean lose tooth; tooth functions w/o pain but loses protective mechanisms

Maintains health of dentine through odontoblast layer

276

What are the inductive, formative and protective functions of pulp?

Inductive: early development; future pulp interacts w/ surrounding tissues initiating tooth development

Formative: odontoblasts of outer layer pulp organ form dentine that surrounds and protects

Protective: pulp reacts to stimuli; cold, hot, pressure, operative cutting, caries,

277

What are the 2 types of pulp?

1. Coronal
2. Radicular

278

Compare the 2 types of pulp

Coronal: occupies crown, 6 surfaces; mesial, distal, occlusal, floor, buccal, lingual

Radicular: extends down from cervix to apex, pre/molars have multiple radicular pulps, tapered and conical

279

Describe the fibrous matrix of pulp

Composed of T1 and 2 collagen
Unbundled and randomly dispersed, greater dentistry around blood and nerve vessels

T1: thought to be formed by odontoblasts
T2: probably produced by pulp fibroblasts

Older pulp contains more collagen

280

What is present in the GS of pulp?

Glycoproteins
Proteoglycans
Water

281

Where are odontoblasts found in pulp?

Outermost region, immediately adjacent to dentine
Responsible for secretion of dentine, formation of dentinal tubules

282

What is special about pulp fibroblasts?

Shown ability to degrade and form collagen

283

Describe perivascular cells

Undifferentiated mesenchymal cells present in pulp
Give rise to odontoblasts, fibroblasts, macrophages

284

What other cells are common in the pulp?

Lymphocytes, plasma cells, eosinophils

285

What are the 4 zones of pulp from outer to inner?

1. Odontoblastic
2. Cell-free
3. Cell-rich
4. Pulpal-core

286

Describe the odontoblastic layer of pulp

Lines outer pulpal wall, consists of odontoblast cell bodies
2ndary dentine may form here from apposition of odontoblasts

287

Describe the cell-free zone of pulp

Fewer cells than odontoblastic
Capillary and nerve plexus

288

Describe the cell rich zone of pulp

Inc. density cells, more extensive vasculature
@ base; nerve plexus of Raschow

289

Describe the pulpal-core of pulp

Located in centre of pulp chamber
Many cells, extensive vasculature
Similar to cell-rich

290

Describe odontoblasts

Polarised columnar cells w/ single process extending into dentinal tubules
Form continuous lining @ junction between pulp and dentine
Form dentine
Contribute to protection of pulp

291

What inflammatory cells are present in the pulp?

1. T lymphocytes
2. Macrophages
3. Dendritic antigen presenting cells

292

Describe the distribution of inflammatory cells found in the pulp

T lymphocytes: usually low no. inc. w/ inflammation

Macrophages: predominately around central blood vessels, adjacent to odontoblast layer

Dendritic presenting cells: similar to macrophages; may be found between odontoblasts and dentine

293

Describe the vascular supply to the pulp

1. Small arterioles enter pulp via apical foramen
2. Ascend through radicular pulp of root canal
3. Branch peripherally to form dense capillary network immediately under and extending into odontoblast layer
4. Small venules drain capillary bed, eventually leave as vein through apical foramen

294

Describe the structure of vascular supply in pulp

Pulpal vessel walls v thin as pulp protected by unyielding sheath of dentine
Capillary walls have many pores reflecting metabolic activity of odontoblast layer
Blood flow more rapid and BP quite high
Arterio-venous anastomoses freq.

295

Describe the innervation of the pulp

Pre/molars: several large nerve fibres enter apical foramen of each
Ant.: one fibre enters

1. Autonomic
2. Afferent

296

Describe the autonomic innervation of the pulp

Sympathetic fibres, unmyelinated
From neurons whose cell bodies lie in sup. cervical ganglion at base of skull
Travel w/ blood vessels
Innervate arteriole SM, function in regulation of blood flow

297

Describe the path of afferent nerves in the pulp

Maxillary and mandibular branch of CN5
Terminate in central pulp
Send out small individual fibres that form subodontoblastic plexus under odontoblast layer
Terminate as free nerve endings: extend up between odontoblasts or further up into dentinal tubules

298

Describe the afferent fibres of the pulp

Transmit pain sensation from heat, cold, pressure
Subodontoblastic plexus: found in lat. walls and root of coronal pulp, less developed in root canals
Few nerve endings found among odontoblasts of root

299

What is the clinical importance of pulp?

1. Living pulp required to maintain dentine integrity and sensitivity
Inflammation causes high fluid conc. and swelling; nerve fibres compressed causing pain
Mechanical injury to dentine may induce pain and tertiary dentine formation
Severe damage/infection result in removal, filling of pulp chamber and root canal

2. Age related: cell death results in dec. no. cells, fibroblasts respond by producing more fibrous matrix but less GS w/ less water
Pulp becomes: less cellular, more fibrous, red. vol. due to continued dentine deposition

300

Define absorbed, equivalent and effective dose

Absorbed: amount of energy absorbed from radiation beam per unit mass tissue; Gray

Equivalent: absorbed dose x radiation weighting factor; Sievert

Effective: equivalent x tissue weighting factor; Sievert