Lecture 6 Flashcards
Most dental trauma occurs in what age range? What is the most common location?
7-10
Anterior incisor region
True or false… avulsed primary teeth should not be replanted.
True
Avulsed permanent teeth that are replanted require follow-up evaluations for a minimum of ___ to determine outcome of therapy
2-3 years
Look for periapical abscess, internal root resorption, ankylosis and tooth submergence
What should you do with an avulsed permanent tooth?
Replant immediately if possible
If contaminated, rinse with water before replanting
When immediate replantation is not possible, place tooth in the best transport medium available
What are some transport media to keep a permanent avulsed tooth in?
Hank’s balanced salt solution
Milk
Saline
Saliva (buccal vestibule)
Saliva (spit in cup)
If none are available, use water
You should replant the tooth immediately if…
Extraoral dry time is less than one hour with or without storage in transport media
How should you manage the root surface of an avulsed tooth?
Keep the tooth moist at all times
Do not handle the root surface. (Hold tooth by crown)
Do not scrape or brush the root surface or remove the tip of the root
If the root appears clean, replant as is after rinsing with saline
If the root surface is contaminated, rinse with HBSS or saline (or water if necessary)
What should you do if extraoral dry time is over 60 minutes?
Soak tooth in an accepted dental fluoride solution for 20 minutes. Rinse with saline and replant
(Research shows that ankylosis is prevented by applying the root surface to a medium that favors regeneration of injured parts of the PDL)
How should you manage the socket in an avulsed tooth?
Gently aspirate without entering them socket
Do not curette the socket
Do not vent socket
Do not make a surgical flap unless bony fragments prevent reimplantation
If the alveolar bone is collapsed and prevents reimplantation, carefully insert a blunt instrument into the socket to reposition the bone to its original position
After reimplantion, manually impress facial and lingual bony plates
What should you do to manage the soft tissues in a dental traumatic event?
Tightly suture any soft tissue lacerations, particularly in the cervical region
Splints should extend how far?
Distally to at least two non-involved teeth
How long should splints remain in place?
7-10 days
However, if tooth demonstrates excessive mobility, splint should be replaced until mobility is within acceptable limits (<1mm)
Bony fractures resulting in mobility require longer splinting periods of 2-8 weeks
Why should rigid composite splints be avoided when possible?
Difficult to maintain patients oral hygiene
Difficult to remove
Extremely rigid and doesn’t allow for minor tooth movement to stimulate normal PDL development
What are the steps for an avulsed tooth that has been lingually displaced with a fracture of the alveolar bone?
Bend wire to touch passively on non-involved teeth, while approximating the anterior arc of the wire to position the avulsed teeth in their prior positions
Prepare all teeth for bonding
Bond the wire to the non involved teeth using composite
Place composite on the labial surface of the involved teeth and press/pull the teeth forward until they are in their proper position and the composite has surrounded the arch wire (cure composite)
Squeeze alveolar bone together Bucal and lingually
Place any necessary sutures
What are some adjunctive drug therapy considerations?
Systemic antibiotics
Referral to physician for tetanus consultation within 48 hours
Chlorhexidine rinses
Analgesics
Define force
A load applied to an object that will tend to move it to a different position in space
Define center of resistance
A point at which resistance to movement can be concentrated for mathematical analysis. For an object free in space, the center of resistance is the same as the center of mass
(If an object is partially restrained as is the case for a tooth root embedded in bone, the center of resistance is located approximately halfway (6/10ths between the root apex and crest of alveolar bone)
Where is the center of resistance found in a tooth?
6/10ths between root apex and crest of alveolar bone
Define moment
A measure of the tendency of a force to rotate an object around some point
A moment is generated by a force acting at a distance to the center of resistance
Quantitatively it is the product of the force times the perpendicular distance from the point of force application to the center of resistance
Define couple
Two forces equal in magnitude and opposite in direction
A couple will produce pure rotation, spinning the object around its center of resistance
while the combination of a force and a couple can change the way an object rotates while it is being moved
Define center of rotation
The point around which rotation actually occurs when an object is being moved
When two forces are applied simultaneously to an object, th econeter of rotation can be controlled and made to have any desired location
The application of a force and a couple to the crown of a tooth, in fact, is the mechanism by which bodily movement of a tooth, or even greater movement of the root than the crown can be produced
If a single force is applied to the crown of a tooth the tooth with rotate around the center of ___
Resistance
(In this case, the center of rotation and center of resistance are identical because a moment is created by applying a force at a distance from center of resistance without a couple)
The perpendicular distance from the point of force application to the center of resistance is the ___
Moment arm
Pressure in the PDL will greatest in which locations?
Alveolar crest
Opposite the root apex
Describe how rectangular archwires work
The wire fits into a rectangular slot and can generate the moment of a couple necessary to control root position. The wire is placed into torsion as it is put into the bracket slot.
The moment arm is therefor quite small but the force is large to generate the necessary moment
The ratio between _____ and ___ determines the type of tooth movement
The moment produced by the force applied to move a tooth (Mf)
Counterbalancing moment produced by the couple used to control root position (Mc)
The ____ determines where the center of rotation will be on the tooth and thus what type of tooth movement will occur
Moment couple ratios
What happens when there is no Mc?
The tooth rotates around the center of resistance which equals the center of rotation, creating a pure tipping movement
What happens as the moment-to-force ratio increases? (More Mc and less Mf)
The center of rotation is displaced further and further apically, away from the center of resistance to produces controlled tipping
What happens when Mc/Mf = 1?
The center of rotation is displaced to infinity apically and bodily movement occurs with no tipping
What happens when Mc/Mf >1?
The center of rotation is displaced incisally and the root apex will move more than the crown, producing lingual root torque. It causes tipping in the opposite direction
The center of resistance of a single-rooted tooth lies approximately ___ of the distance between the apex of the tooth and the crest of the alveolar bone
6/10ths
Loss of alveolar bone height moves the center of resistance in which direction?
Closer to the root apex. (6/10ths rule still applies)
Magnitude of the tipping moment produced by a force is equal to ___ times ___ from the point of force application to the center of resistance
Force
Distance
What happens to Mf when bone loss occurs?
The center of resistance moves apically, thus the tipping moment increases because the moment arm is longer
True or false… in moving teeth that have had bone loss a larger countervailing moment produced by a couple is necessary to produce bodily movement
True
For all practical purposes, a ___ is required if root movement is the goal in patients who have experienced loss of alveolar bone height
Fixed appliance
Removable appliances dont work
True or false.. although heavy pressure is felt at the root apex and crest of the alveolar bone, the pressure decreases to zero at the center of resistance in a tipping motion
True
What is the optimal force to create a rotational movement of a tooth?
35-60 grams (lower number for incisors and higher number for molars)
Tipping movements create an ___ movement if the tooth is moved lingually and an ___ moment if the tooth is moved bucally
Extrusive
Intrusive
It is important to anticipate intrusive and extrusive movements when tipping forces are used
True or false… Translation or bodily movement of a tooth requires that the PDL space be loaded uniformly from alveolar crest to apex
True
____ as much force must be applied to the crown of the tooth to produce the same pressure within the PDL for bodily movement when compared to tipping movements
Twice
What is the optimal force to create a translational movement?
70-120grams
When a tooth is intruded, the force is concentrated over a small area at the apex. What is the significance of this?
Extremely light forces are needed to produce appropriate pressure within the PDL during intrusion
What are the optimal forces for intrusion and extrusion?
Intrusion = 10-20 grams
Extrusion = 35-60 grams
What is the difference between ideal springs and real springs?
An ideal spring would maintain the same amount of force regardless of distance a tooth had moved
But with real springs the force decays at least somewhat as tooth movement occurs
Forces that are maintained between activations of an orthodontic appliance, even though the force declines are defined as ____ (such as ___)
Continuous forces
Nickel titanium arch wire
In contrast to continuous forces, ____ forces drop to zero between activations (such as ___)
Interrupted
Stainless steel arch wire bends
Intermittent forces fall to zero when …
A removable appliance is taken out, only to resume when the appliance is reinserted into the mouth.
These forces also decay as tooth movement occurs
In a typically force-deflection curve for an elastic material like an orthodontic arch-wire, define stiffness
The stiffness of the material is given by the slope of the linear portion of the curve
(The greater the slope or steeper the line the stiffer the material)
In regards to a typical force-deflection curve, define the range
The range is the distance along the X-axis to the point at which permanent deformation occurs, usually taken as the yield point, at which -.1% permanent deformation has occurred)
In regards to a typical force-deflection curve, define strength and proportional limit
The strength of a wire is a mathematical calculation of the stiffness times the range
The proportional limit is the point below which the force placed on the wire creates a proportional deflection in the wire (the graph remains linear)
In regards to a force-deflection curve, define spring back and the point of arbitrary clinical loading, and the failure point
Spring back is the position the wire will return to after it has been deflected. If deflection has exceeded the proportional limit to the yield point, the spring back will not return the wire to its original position
The point of arbitrary clinical loading is a point at which increasing deflection causes minimal changes in force to occur (the wires force has been maxed out)
The failure point is when the wire breaks
Each of the major elastic properties of an orthodontic wire (strength, stiffness, springiness, range, etc) is affected by…
A change in length, shape, and cross section area of a wire
True or false… smaller brackets means increased length of the wire between teeth which means less force is required
True
