Biomechanics III Flashcards
What is the effect on the bone to the compressed area?
Pressure –> resorption (osteoblastic activity)
What is the effect on the bone to the stretched area?
Tension –> apposition (osteoblastic activity)
What are the resorption areas? (2)
- Frontal resorption
- undermining resorption
What occurs with frontal resorption? (2)
- LIGHT forces < capillary blood pressure
- Force doesn’t disrupt blood supply
What occurs with undermining resorption? (2)
- HEAVY forces > capillary blood pressure
- Forces block blood supply
Frontal resorption light forces: blood supply?
Reduced
Frontal resorption light forces: cells?
2
- cellular activation and differentiation
- local osteoclasts resorb bone
Frontal resorption light forces: resorption?
frontal (periodontum - bone)
Frontal resorption light forces: tooth movement?
takes place lapsed 4-6 hours
Frontal resorption light forces: tooth movement progression?
smooth
Result of continuous light forces? (4)
- osteoclasts initiate resorption of lamina dura from side of PDL
- 1st wave of osteoclasts derived from PDL itself
- 2nd wave (larger) from distance areas via blood flow
- leads to FRONTAL RESORPTION
Undermining resorption heavy forces: Blood supply
- cut off/totally occlude blood vessels
Undermining resorption heavy forces: cells?
4
- cell lysis
- sterile necrosis
- hyalinized (36 hours)
- PDL fibers and cells reorganize
Undermining resorption heavy forces: resorption? (3)
- marrow resorption (bone - periodontum)
- tunnel resorption
- osteoclasts com from far away
Undermining resorption heavy forces: necrosis?
eliminated
Undermining resorption heavy forces: tooth movement?
- begins at 7-14 days
- jump movement
What does Gianelly 50 gr do?
Doesn’t affect vessel bundle
What does Gianelly 100 gr do?
Blood supply is reduced
What does Gianelly 150 gr do?
Total block of blood supply
Undermining resorption heavy forces: PDL fibers and cells?
reorganize
Heavy forces: 3-5 seconds? (2)
◼ Minutes: Blood Flow cut off compressed PDL areas
◼ Hours: cell death in compressed area
Heavy forces: 3-5 days? (3)
◼ Cell differentiation in adjacent marrow spaces
◼ Osteoclasts get to necrotic spot: tunnel resorption
◼ Undermining resorption begins
Heavy forces: 7-14 days? (3)
◼ Resorption of all necrotic material
◼ Resorption removes lamina dura adjacent to compressed PDL
◼ Tooth movement occurs in a “jump”
What are the cellular changes that occur with forces? (4)
Loss of blood flow causes sterile necrosis of the PDL
A “Hyalinized” area devoid of cells and vasculature
develops
Osteoclasts appear within the adjacent bone marrow
spaces and begins an attack on the underside of the
bone immediately adjacent to the necrotic PDL area
An initial delay in tooth movement occurs
There a delay in tooth movement with forces because…? (2)
• stimulating cell differentiation in the marrow
• A considerable thickness of bone has to be removed
from the underside
look at slide 12
do it
Apposition area? (2)
- later than resorption: transient increase of periodontal space
- to maintain bone thickness
What does the apposition area need? (3)
- Blood supply
- Cell proliferation
- cell activation
What steps occur with apposition? (6)
- Tension caused by PDL fiber stretching
- Negative potentials
- Osteoblastic activity deriving from PDL stem cells
- Nonabsorbable osteoid tissue formation - 9 or 10 days
- Tissue calcification through salt deposit
- Reconstruction and organization of fibers
What are the effects on the pulp from force? (4)
Transient inflammatory response
- vessel trauma
- hyper sensibility or pain
- spontaneous remission
There is risk of pulp necrosis with force if…(4)
◼ Intense and continuous forces with many hyalinizations
◼ Previous trauma to the tooth
◼ Rude intrusion or extrusion movements
◼ More frequent in adults
Pulp from force: devitalized teeth? (2)
- Treatment possible
- more risk of radicular resorption
Root remodeling occurs by…? (3)
- Resorption and apposition of cementum
- Action of intense and lasting forces
- Intense load may cause kinking of the root apex
What are the two types of root resorption? (2)
- lateral
- longitudinal
What are the types of lateral root resorption?
- Surface resorption (only cementum
- Deep resorption (cementum and dentin)
What is surface root resorption? (6)
- Lateral resorption ◼ Most frequent ◼ Caused by excessive load and cementoclasts ◼ Microscopic ◼ Can be repaired if forces are removed - only cementum
What is deep resorption? (6)
- Lateral resorption
- Cementum and dentin
◼ Macroscopic crater defects
◼ Caused by uprooting (tear down)
◼ Excessive load
◼ Can’t be repaired
What happens with longitudual resprtion?
- Minimal loss can’t be observed on OPG
- Intense continuous lasting forces
Where are longitudinal resorptions more frequent? (4)
◼ Lateral upper incisor
◼ Central upper incisor
◼ Lower incisors
◼ 1st lower premolar
(all incisors and 1st lower premolar)
What are the risk factors for longitudinal resorption? (8)
◼ Intense and lasting forces ◼ Conic Sharp roots ◼ Tooth shape anomalies (dilaceration) ◼ Previous trauma ◼ Endodontic treatment ◼ Adults ◼ Tooth with previous resorption ◼ Contact of apex with cortical plate
How do we clinically manage root resorptions? (6)
Explain risk to parents
Periapical X-ray of lateral upper incisor every 6 months
◼ Periapical X-rays of all teeth
◼ Release force for 4 weeks
◼ Resorption will continue 9-10 days after force release
◼ Formation of nonabsorbable restorative cementum
What does white spot lesions and decalcification signify? (2)
- Absence of hygiene
- Gingival fluid filtration through adhesión material (bad technique)
What happens to the PDL during orthodontic tooth movement ? (2)
- PDL reorganizes from month to month.
- PDL fibers detach from bone and cementum and insert again
What is the contraction to force on the PDL?
- active periodontal disease
What is needed to apply force on the PDL? (2)
- Healthy periodontal status is necessary
- Controlled periodontal disease may be treated
What is the effect of force on the PDL? (5)
Increased periodontal space between resoption-apposition periods
Increased tooth mobility
Excessive mobility:
◼ Heavy forces
◼ Discontinue treatment until mobility decreases
Position of the teeth determines…
The position of the alveolar bone
- Intrustion: height loss
- Extrusion: height increase
The height of bone attachment along the root will be…
about the same at the conclusion of movement as at the beginning (not active
periodontal disease)
When does the dehiscence risk occur?
when apex close to alveolar cortical plate
What is the effect of force on gingival tissue? (2)
- Inflammation (frequent)
- Gingival recessions
Force on gingival tissue: inflammation types? (2)
- Marginal gingivitis
- Hyperplasic gingivitis
Force on gingival tissue: gingival recessions? (3)
- Excessive labial protrusion
- Frequent: incisors and canines
- Hard to repair
FACTORS THAT MODIFY BIOLOGIC RESPONSE? (4)
- FORCE DECAY
- INTENSITY
- DURATION
- TYPE OF MOVEMENT
What are the classifications of force decay rate? (3)
- Continuous
- Interrupted
- Intermittent
What is continuous force decay rate? (2)
- Force maintained at some apreciable fraction of the original from one patient visit to the next. (visit to visit)
- Fixed appliances
What are the types of continuous force decay rate? (2)
- Light forces
- Heavy forces
What is a light continuous force decay rate? (2)
◼ Smooth and progressive movement since the beginning
◼ IDEAL FORCES
What is a heavy continuous force decay rate? (5)
◼ Undermining resorption ◼ No OTM until 7-14 days ◼ Jump to a new position ◼ Destructive forces ◼ Heavy continuous forces are to be avoided
What is a interrupted force decay rate? (2)
- Force levels decline to zero between activations.
- Fixed appliances
What are the types of interrupted force decay rate?
- light forces
- heavy forces
What is a light interrupted force decay rate? (2)
◼ Smooth and progressive movement from the beginning
◼ Frontal resorption
What is a heavy interrupted force decay rate? (2)
◼ Undermining resorption and hyalinization
◼ Allows repair and regeneration between appointments
What is intermittent force decay rate? (2)
-Force levels decline abruptly to zero
intermittently, when orthodontic appliance is removed.
- Removable appliances
How does intermittent force decay rate work? (4)
Removable appliances
Also during normal function
To produce tooth movement: at least 6h acting
Even being high level forces, they’re aceptable because
they allow recovery periods (rest).
What are the different intensities that modify biologic response?
- Light
- Moderate
- Heavy
- Extra heavy
What is the light intensity that modifies biologic response? (2)
- <25gr
- Intrusion
What is the moderate intensity that modifies biologic response? (2)
- 25-50 gr
- extrusion
What is the heavy intensity that modifies biologic response? (3)
- 50-75gr
- inclination
- rotation
What is the extra heavy intensity that modifies biologic response? (3)
- > 75gr
- Bodily: 100 - 150 gr
- Torque: 100 - 150 gr
What is the duration that modifies biologic response? (2)
Force acting 4h initiates biological response Human Threshold for clinical tooth movement: force acting 6h
What is the type of movement that modifies biologic response?
PDL response depends on force magnitude and it’s
determined by the surface of an object per unit
area over which that force is distributed
What are the optimum forces for OTMs? (6)
- Tipping
- Bodily movement (translation)
- Root uprighting
- Rotation
- Extrusion
- Intrusion
What is the force required for tipping?
35-60 gr
What is the force required for bodily movement (translation)?
70-120 gr
What is the force required for root uprighting?
50-100 gr
What is the force required for rotation?
35-60 gr
What is the force required for extrusion?
35 - 60 gr
What is the force required for intrusion?
10 - 20 gr
Types of movement that modify biological response: inclination/version?
Tooth tilts over center of resistance
Where is the PDL compressed with inclination/version ? (2)
◼ Near apex on the side following the movement
◼ Alveolar crest on the side opposing movement
Where does inclination / version act on the PDL? (3)
- only half the surface of the PDL
- pressure in this area is high: hyalinization
- Hazardous movement in adults
Where can a tooth be inclined or versed? (4)
- mesial
- distal
- lingual
- buccal
How can a tooth be inclined/versed? (2)
removable or fixed appliance
What is mass or bodily movements? (3)
- Pure translation
- all PDL surface with the same pressure
- low risk movement
How can pure translations occur?
- Only with fixed appliances and rectangular arch wires
- all PDL surface withstands the same pressure
- Low risk movement
- 100-150 gr
How does torque occur?
ask
What is rotation?
Tooth rotates along its axis
What are the root types? (2)
- conic
- oval
How to conic roots rotate? (3)
- Rotation without pressure
- Only PDL stretching
- Allows heavy forces
How do oval roots rotate? (2)
- Great areas of pressure on PDL
- Allows heavy forces
Does pure rotation exist? (3)
- No
- always with slight inclination movements
- don
t exceed 50-75 gr
What is intrusion? (3)
- Force focused on a small surface area of the apex
- very dangerous movement
- done very slowly
What is extrusion? (4)
- Theoretically no pressure, just tension on PDL
- easy movement
- give time for PDL fibers to relax
- Risk of harming vessels bundle
What questions do we ask before applying a force? (6)
- Force magnitud?
- At what distance is the force going to act?
- How much time is the force going to act?
- What rate of decay is the force going to have?
- What direction do I want to apply the force?
- How is that force going to distribute along the PDL?
What is optimum orthodontic force?
That which produces a maximum of desirable biologic
response with minimum tissue damage, resulting in
rapid tooth movement with little or no clinical
discomfort
What force causes pain related to orthodontic treatment?
Heavy force: immediate pain (PDL crushing)
What pain is felt when there is an appropriate force with orthodontic treatment? (5)
- No pain / negligible
◼ Related with areas of ischemia within PDL that stimulate pain receptors
◼ Slight Hyperemic pulpitis
◼ Appears few hours after applying the force
◼ Proffit recommends chewing 8h after appliance activation
When does pain develop with an appropriate force?
- After several hours
- Patient feels mild aching sensation and the teeth are quite sensitive to pressure
- Lasts for 2-4 days and disappears until appliance is reactivated
For most patients pain with an orthodontic appliance is most sever with…
initial activation
Why does pain occur with an appropriate force?
- Due to the development of ischemic areas in the PDL
- Pain is proportional to the area of PDL that has undergone sterile necrosis (hyalinization)
What do heavier forces than the appropriate force do in an orthodontic appliance?
Produce larger areas of hyalinization and greater pain
How can you manage orthodontic pain?
Analgesics
ex. acetaminophen
What do you do if there is great tooth mobility after force application?
Release force and let tooth rest
What do you do if there is no tooth movement after applying a force?
Have to wait three weeks, don’t apply more force magnitude
What should you do every 6 months with an orthodontic appliance?
X-ray lateral incisor every 6 months
How much rest should there be during the orthodontic movement?
periods of rest of 1-2 months
