2-Cementum Flashcards
Define cementum?
Layer of calcified tissue
covering the dentin of the
root
difference between cementum and bone?
1-cementum is avascular and has not innervation, and is less readily resorbed than bone
2-there is a continuous deposition of cementum (unlike bone, it doesn’t resorb under normal conditions)
Why is cementum less readily resorbed than bone?
some theories are:
1-due to the difference in physiochemical or biological properties between bone and cementum
2-the presence of cementoid on the surface of cementum (the unmineralized layer of cementum)
3-increased density of sharpey’s fibers.
4-the proximity of epitelial rests to the root surface
Physical characteristics of cementum?
Light yellow color with a hardness less than that of dentin
what is the Composition of cementum?
-45&-50% inorganic substance
1-calcium and phosphate (hydroxyapatite)
2-Numerous trace elements
3- Highest fluoride content in the body
-50%-55% organic substance
1-Type I collagen
2-Proteoglycans
Regarding the structure of cementum? what are its types?
1-Acellular
2-Cellular
What are features of Acellular cementum?
1-Do not incorporate the spiderlike cementocytes
2-covers the root dentin from the CEJ to the apex, but not the apical third.
What are features of cellular cementum?
1-Incorporate cementocytes in space called lacunae
2-the cementocytes has numerous cell processes or canaliculi radiating from the cell body
3-these processes branch with others directed towards periodontal surface of the cementum.
where does the collagen fiber exist in cementum?
both cellular and acellular types
what are Sharpeys fibers?
collagen fibers of the periodontal ligament embedded in cementum and alveolar bone to attach the tooth to the alveolus
What are the functions of cementum
1-provide a medium for attachment of collagen fibers that bind the tooth to the alveolar bone
2-serves as a major reparative tissue for root surfaces
What are the types of bone root resorption according to severity?
1-surface resorption
2-inflammatory
3-replacement
Characteristics of surface resorption?
1-it occurs as microdefect to all roots
2-it repair itself without notice
3-occur mostly periapically
4-stops when the causative agent is removed
Characteristics of inflammatory resorption?
occurs when root resorption progress into the dentinal tubules to reach the pulpal tissue
what is replacement resorption?
Produces ankylosis of a tooth because bone replaces the
resorbed substance.
According to Brezniak and Wasserstein what is the classification of Orthodontically induced root resorption ?
- Cemental or surface resorption with remodeling
- Dentinal resorption with repair (deep resorption)
- Circumferential apical root resorption.
Describe cemental or surface resorption?
only the outer cemental layers are resorbed, and they are later fully regenerated or remodeled.
which resorption type resembles the trabecular bone remodeling?
surface or cemental resorption
Describe dentinal resorption with repair?
-the cementum and the outer layer of dentin are resorbed
-usually repaired with cementum material
-the root shape will change later.
Describe Circumferential apical root resorption?
-In this process, full resorption of the hard tissue
components of the root apex occurs, and root
shortening is evident.
-this type is irreversible
Etiology of root resorption
- Dental trauma / surgical procedures / Infections
- Orthodontic treatment
- Pressure from tumors / cysts
- Irritation from chemicals ( Eg. H2O2 during bleaching)
what is the most common stimulation
factor for root resorption?
pulpal infection.
what initiates external or internal root resorption?
injury to the precementum or pre-dentin
cause of orthodontic root resorption is ?
the pressure applied to the roots
during tooth movement
Orthodontic Force applied on teeth leads to ?
adaptive changes in the entire surrounding periodontium.
Orthodontically induced root resorption begins
adjacent to hyalinized zones and occurs during
and after elimination of hyaline tissues
The studies in mice and rats conducted by Brudvik and
Rygh confirmed that orthodontically induced root
resorption is a part of the hyaline zone elimination
process.
- so basically as long as there still hyaline tissue the resorption will keep going until its done.
Key cells and factors involved in root resorption
1-Monocytes and macrophages
2- Osteoclasts
3- Odontoclasts
Definition of EARR?
EARR can be defined as the degree a root has shortened
from its original ( or expected ) length by clastic activity
what are the methods used to quantify
resorption ?
1-Ordinal scale data (visually assessed)
2-ratio scale data (measurements with calipers or come computer aided device)
Why is class II div 2 associated with the most bone resorption?
due to the excessive intrusion mechanic necessary to correct deep overbite
the extracting pattern with the greatest resorption
extraction of all the
first premolars
does the archwire sequence affect bone root resorption?
there’s no statistical significance
Why do fixed appliances have been shown to cause more
root resorption than removable appliances?
due to the increased range of tooth movement
afforded by fixed appliances
Nonextraction treatment of Class II malocclusions with Class II elastics
associated with fixed appliances produces similar root resorption as
does treatment with extraoral headgear and fixed appliances
It is generally agreed that the use of rapid
maxillary expanders is associated with increased
levels of root resorption
most associated movements with the resorption process?
intrusion and torque
The highest root resorption is reported to occur when? how many mm were performed?
3 to
4.5 mm of torquing movement was performed.
in 2005, what did Fox find, in regard to root resorption and treatment ?
treatment related root resorption is correlated with the distance the apex moves and the length of time the treatment took.
ontinuous force produced significantly
more root resorption than discontinuous force
application
amount of force which lead to root resorption?
more than 20-26 g/cm2
Optimal force for orthodontic tooth movement but not
causing root resorption should be?
7-26 g/cm2 on root
surface area
why is intermittent force associated with less resorption?
because the intermittent force protects from formation
of hyalinized areas or it allows reorganization of
hyalinized periodontal ligaments and restoration of
blood circulation at the time, when forces are not active.
and continous force leave no time to repair of damaged B.v and other oeriodntal tissue
relation ship between root resorption and length of treatment
Most studies agree that the risk and severity of external apical
root resorption increases as the duration of orthodontic
treatment increases.
which force is associated with more resorption (direction wise)?
intrusive force
which teeth are more susceptible to resorption?
maxillary incisors, then molars, then canine (all macillary )
which teeth are more susceptible to resorption in the mandible?
canine, then laterals, then centrals
which posterior teeth are more susceptible to resorption?
mandibular molar, then maxillary molars, mandibular premolars, and finally maxillary 1st then 2nd premolars
The most frequently affected teeth with resorption, according to
severity:
- Maxillary laterals
- Maxillary centrals
- Mandibular incisors
- Distal root of mandibular first molars
- Mandibular second premolars
- Maxillary second premolars.
which is more prone to resorption? long or short roots?
Longer roots are more prone than shorter ones to resorption.
why is there a positive
correlation between an increase in overjet and
root resorption?
due to the greater amount of torque and greater root
displacements required to correct excessive overjet
in healing which type of cementum is laid first?
acellular type
non-invasive method to reduce
root resorption in humans.?
low intensity pulsed ultrasound
