Principles & Techniques 2 Flashcards
What forces oppose eruption of teeth?
chewing and soft tissue forces
______ pressures of ______ duration are more significant in producing tooth movement than heavy intermittent pressures like chewing.
light pressures of long duration
Teeth that are in function erupt at a rate that parallels the rate of what?
the rate of vertical growth of the mandibular ramus
As the _____ grows longer it creates space between the maxillary arch and mandibular arch.
ramus
Before the tooth is in occlusion, it’s primarily effected by forces _________ eruption.
promoting
After the tooth is in occlusion, it’s primarily effected by forces _________ eruption.
opposing
The total eruption path of a first permanent molar is about _____ cm.
2.5 cm
Why do ankylosed teeth appear “sunken” down compared to adjacent teeth?
Because half of the eruption path (i.e. 1.25 of 2.5cm) is achieved after tooth is on occlusal level. Ankylosed tooth will stop at the halfway point.
How can a lateral tongue thrust affect eruption of teeth?
It can prevent teeth from fully erupting to fill the space created by ramus growth. Causes a posterior open bite.
What treatment options do we have for ankylosed permanent teeth?
Extraction, crowns, or surgery (i.e. distraction osteogenesis)
When is extraction of an ankylosed primary tooth recommended?
When it drops below the height of contour and there is not an adult tooth to replace it.
For ankylosed primary teeth without an adult tooth replacement, what options are there for treatment?
extraction, build-up of primary tooth, or leave as is
During adult life, teeth continue to _______ at an extremely slow rate.
erupt
opposing forces required to keep teeth from hyper eruption
How does wear of teeth affect vertical dimension?
Vertical dimension is maintained by further eruption of teeth
The bone remodeling involved in orthodontic treatment is mediated by the _____.
PDL
PDL phenomenon
What happens if the PDL is destroyed during orthodontic treatment?
ankylosis
Under normal circumstances, how wide is the PDL?
0.5mm
What constantly remodels the collagens of the PDL?
fibroblasts and fibroclasts
What remodels and recontours the alveolar bone and cementum?
osteoclasts and cementoclasts, respectively
What kind of nerve endings are in the PDL?
unmyelinated free nerve endings for proprioception and pain
What does the fluid function as in the PDL?
A shock absorber for the tooth
If pressure is maintained on the tooth, what happens to the PDL fluid?
It is rapidly expressed to create more fluid pressure in the PDL (pain is felt)
On mandibular anterior teeth, does the lip or tongue put more pressure on the teeth?
tongue
Is lip or tongue pressure greater on maxillary incisors?
lip
______ ___________ of the PDL implies that there is a threshold for orthodontic force, and any force less than this wouldn’t move the tooth.
active stabilization of the PDL
What is the threshold for orthodontic force (in g/square cm)
5-10 grams/square cm
Active stabilization produced by _________ _______ in the PDL explains why teeth are stable in the presence of imbalanced (natural) pressures.
metabolic effects
What is a lip bumper?
Appliance that holds the lip away from the anterior teeth to allow for maximum forward movement of teeth
What is the envelope of stability?
Teeth occupy a space where soft tissue pressures are in equilibrium (but remember it isn’t balanced pressure)
After a tooth emerges into the mouth further eruption depends on metabolic events within the PDL including…
formation of cross-linkages and maturational shortening of collagen fibers.
If a tooth is moved, does the bone and gingiva follow the tooth?
Yes
When the alveolar bone socket bends (acting as shock absorber) it generates a ___________ _______.
Piezoelectric current
What do piezoelectric currents do?
They stimulate skeletal regeneration and repair, which is how bone adapts to functional demands
What two unusual characteristics do piezoelectric signals have?
An initial “quick decay rate” that quickly reduces to zero within a second. An equal signal of opposite direction when the force is released.
Piezoelectric signals are the migration of ________ when the crystal structure of bone is deformed.
electrons
When a maintained force bends the alveolar bone, what happens to electrons in the crystal structure?
structure is stable and electrons don’t move
When a maintained force on the alveolar bone is released, what happens to the electrons in the bone’s crystals?
crystal returns to original shape and electrons reverse direction back toward the original position
Small voltages seen in fluid ions of the bone fluid are called a ________ _________, and have a rapid onset and alteration (like piezoelectric signals)
streaming potential
Without streaming potentials or piezoelectric currents, what happens to bone?
skeletal atrophy
What does the AcceleDent appliance claim?
That vibration of teeth will shorten length of orthodontic treatment. (but it’s a lie!)
The classic theory of orthodontic tooth movement relies on ________ rather than electrical signals to stimulate cellular differentiation.
chemical signals
What two things are necessary for chemical signal release to cause differentiation seen in orthodontics?
mechanical compression of tissues, and change in blood flow
Mechanical effect on the PDL causes the release of what?
cytokines, prostaglandins, and other chemical messengers
Will there be more blood flow to the compressed or stretched PDL?
stretched
What chemical messengers are important in cellular differentiation?
PG-E, IL-1beta, cAMP
Is release of prostaglandins a primary or secondary response to pressure?
primary
How long of sustained pressure does it take for cAMP levels to increase?
4-6 hours (therefore, orthodontic appliance must be worn for 6+ hours to facilitate tooth movement)
What happens to the PDL if too much pressure is placed on the tooth in orthodontics?
sterile necrosis of PDL (aka hyalinized) due to ischemia
Differentiation of _________ isn’t possible without adequate blood flow to the PDL.
osteoclasts
When blood flow to the PDL is cut off, what kind of resorption happens?
undermining resorption
Where do osteoclasts come from during undermining resorption?
adjacent marrow spaces outside the alveolar socket
Undermining resorption causes tooth movement to take ____ time.
more time
_______ resorption happens when light, continuous force is applied and blood flow to PDL is maintained.
frontal resorption
Frontal resorption causes tooth movement to take ____ time.
less
During frontal resorption, bone is ______ on the tension side of PDL and ________ on the pressure side.
formed, remodeled
What kind of resorption results in smooth continuous tooth movement?
frontal resorption
What kind of resorption causes more pain?
undermining resorption
Which kind of resorption is the rate limiting step in tooth movement?
undermining resorption
clinically, what kind of resorption happens during tooth movement?
both frontal and undermining
Is there evidence to suggest self-ligating brackets accelerate tooth movement?
Nope.
Does lateral expansion of the dental arch by self-ligating brackets “grow” buccal alveolar bone?
No
Is lateral expansion of the dental arch by self-ligating bracket systems comparable with lateral expansion gained by rapid maxillary expansion (RME) followed by conventional edgewise treatment?
No
Is lateral expansion of the dental arch gained by self-ligating bracket systems stable in the long term?
No
Do self-ligating bracket systems provide lower clinical forces compared with conventional brackets?
No, they may even cause more forces
Do patients treated with self-ligating bracket systems experience less pain during treatment?
No
In what age range and which teeth are likely experience dental trauma?
7-10 years old, and the anterior incisor region
What do we worry about happening to replanted avulsed teeth?
- periodical abscess
- internal root resorption
- ankylosis
Should you replant primary teeth?
No, you fool
What are some good things to transport an avulsed tooth?
Saline, milk, saliva, water
If the tooth has been out for less than an hour, what should you do?
Replant immediately, clean with water or saline the root off but do NOT touch the root surface
If the tooth has been avulsed for more than an hour, what should you do?
Soak tooth in fluoride solution for 20 min, rinse with saline, and replant
How do you treat the socket of an avulsed tooth?
Do NOT curette, do NOT vent, do NOT make flap, gently aspirate without entering socket
What should you do to manage soft tissues?
tightly suture, especially if in cervical region
How long should you leave a splint in place to treat an avulsed tooth?
7-10 days
What are possible drug considerations in conjunction with treating avulsed teeth?
systemic antibiotics, refer to physician for tetanus, chlorhexidine rinse, analgesics
