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Organismal senescence is
the aging of whole organisms
Aging is generally characterized by the _________ ability of ____ or __________ systems to respond ___________ to ______.
cells or organisms
Theories of senescence divided into?
Programmed: regulated by biologic clocks
Stochastic: aging based on environmental stress
Major source of ROS and free radicals?
Mitochondria: ROS accumulate overtime and are major determinant to aging
Lee and Wei on aging suggested:
- MAjor contributors to human aging
- 1. oxidative stress
- 2. inc mtDNA mutations
- 3. altered expression of mitochon genes
- 4. mito dysfunction
- 5. apoptosis
Harman's free radical theory
production and accumlation of free radicals in aerobic organisms is an important determinant of cellular life span
Oxidative stress is
excessive accumulation of ROS caused by an imbalance between production and destruction of ROS
Replicative senescence, cells lose ability to divide, cell with shortened telomeres
Senescence is the result of an ________ between free radical __________ and __________ defenses.
Characterisitc changes with aging in fully formed human teeth were first described by Lacasagne in 1889.
IgG levels and MHC II in older patients?
Decreased with age
With decreased collagen turnover what do we see with MMP activity?
Decreased MMP 2,8,9 and increased TIMP activity
Cell-rich zone of pulp was compared to the less cellular middle zone, it was found that the cell number decreases in all 3 zones starting at ___ yr of age, by age ___, the total cell number is reduced by __%
Murray et al, younger patients aged 10-30, crown odontoblasts decreased by __%, density of root odontoblasts decreased by __% in patients 50-59. Density of fibroblasts decreased by __% in the crown and by __% in the root with aging.
Cell density of the pulp decreases by about ____ as a person ages from 20-70, as odontoblasts _______ in number and become ______ and _________.
Bernick and Nedelmann found with aging of 100 teeth, 15-75
- 1. calcification of ECM
- 2. dec number of BVs and nerves
- 3. inc fibrosis
- 4. inc collagen fibers thickness
- 5. fusion of von Korff
What modified amino acid is a major cross linker of collagen, a decrease of is found in aging pulp?
What is the name of the line that delineates the primary and secondary dentin?
Some have considered renaming mature odontoblasts as
SEM and radiographs were used to measure pulp chamber in patients 40-70 and 40-97, chamber size became in restricted in which direction?
Mesiodistal rather than coronoapically
Aging induces several degenerative processes including
- 1. fibrosis
- 2. atrophy
- 3. loss of cellularity
- 4. decalcification
- 5. degeneration of odontoblasts
Connexin 43 gap junction protein, decreased in aged dental pulps
Changes to blood vessels in aging pulp:
- 1. dec number of vessels entering tooth
- 2. vascular plexus reduced
- 3. intimal hyperplasia of arterioles
- 4. narrowed vessel lumen
- 5. calcification of vessels
- 6. loss of fenestrations
The number of myelinated fibers ________ with age, and both myelinated and unmyelinated fibers show an _________ threshold of response to stimulation.
small unmyelinated axons predominate
decreased A fibers, decreased C fibers predominately
One study examined pulpal neurons from 150 teeth in individuals 40-70 years. Calcification occured in __% of all pulps
The assessment of ________ symptoms and ____ intensity was found to be the best predictor of whether elderly individuals utilize dental care.
In most studies, no differences in pain threshold to electrical stimulation are found between young and elderly patients
Changes in the structure of secondary dentin that limit fluid movement in dentinal tubules may also explain why older patients are less responsive to cold stimulation.
In older tooth pulps the decrease in number of fast-conducting afferents and mineral apposition of tubules impaired nerve activation especially by heat.
Two types of calcified bodies in the dental pulp:
1. mass filling pulp chamber with epithelial remnants surrounded peripherally by odontoblasts
2. several pulp stones, compact degenerative masses of calcified tissue
Gulsahi et al confirmed what about pulp stones?
Increases with age, higher in molar over premolars and incisors
No relationship has been found between pulp calcification and renal disease or carotid artery calcifications
Secondary dentin formation begins...
... in the coronal portion and extends apically
In subjects covering an age range of 10-97 years, it was found that the pulp chambers and root canal spaces became constricted in the mesiodistal but not the faciolingual direction.
Age is the most important risk factor to reduction of pulp chamber over time.
Two types of secondary dentin formed in old teeth:
1. transparent dentin
2 secondary dentin circumferentially
Indices to identify age of tooth, best correlators?
1. transparency of radicular dentin
2. magnitude of secondary dentin formation
The reliability of pulp chamber or root canal dimensions has been questioned because the teeth of certain aging individuals show no detectable change in canal size in a 10 year period.
The capacity to mineralize predentin may decrease with age, rendering the teeth of elderly individuals less protected from external stimuli
Findings of Pouezat in 1975?
Root tubules size decreased from 3.75um in 18yr to 1.50um in 65
Increase in vol of intertubular dentin from younger to older by 18%
Another age-related process is the absence of the odontoblast process in the tubules .7mm beyond the pulp, which Osborn and Ten Cate said is required for aging histology.
Dentin maturation is governed by:
- 1. inc intertubular thickness
- 2. formation of peritubular dentin
- 3. intratubular sclerosis by apatite or whitlockite precipitation
Pulp capping in older patients is no different in success vs younger, two studies, both 88% success