Lecture 6 Flashcards
most dental trauma occurs between what age range? where do most injuries occur?
- 7-10 years old
- anterior incisor region
should avulsed primary teeth every be replanted?
no
avulsed permanent teeth require follow-up evaluations for a minimum of ___ years to determine the outcome of therapy. what are some possible complications of replanted avulsed teeth?
- 2-3 years
- periapical abscess, internal root resorption, ankylosis and tooth submergence
if possible, should an avulsed tooth be replanted immediately? what if it is contaminated?
- yes
- if it is contaminated, it should be rinsed with water before replanting
- sometimes immediate replantation is not possible, so the tooth should be placed in the best transport medium possible
what are the best options for transport media for an avulsed tooth?
- hank’s balanced salt solution
- milk
- saline
- saliva (buccal vestibule or have pt spit into a cup)
- if none of these are available, use water
if extraoral dry time is less than ___ with or without storage in a physiological media, it should be replanted immediately
1 hour
how should the root surface of an avulsed tooth (<1 hour) be managed?
- keep tooth moist at all times
- do not handle the root surface - hold the tooth by the 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 hanks or saline; if debris remains, use cotton or a wet sponge to gently remove whatever debris is left
if extraoral dry time is greater than 1 hour, how should you manage an avulsed tooth?
- soak in accepted dental fluoride solution for 20 minutes
- rinse with saline
- replant
the american academy of pediatric dentists recommends that an avulsed tooth (>1 hour) be placed in what type of solution and for how long before replantation?
1/23% sodium fluoride solution for 5-20 minutes
according to recent research, how can ankylosis of a replanted avulsed tooth (>1 hour) be prevented?
- apply to the root surface a medium that favors the regeneration of injured parts of the PDL
- examples are fluorides, steroids, sodium alendronate, enamel matrix derivatives, and basic fibroblast growth factor
how should the socket of an avulsed tooth be managed?
- gently aspirate without entering the socket (if a clot is present, use light irrigation with saline)
- 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 reimplantation, manually compress (if alveolar bone is spread apart) facial and lingual bony plates
what are some things that should be avoided in managing the socket of an avulsed tooth?
- do not curette the socket
- do not vent the socket
- do not make a surgical flap unless bony fragments prevent reimplantation
how should soft tissues be managed in the area of an avulsed tooth?
tightly suture any soft tissue lacerations, particularly in the cervical region
what are some splinting options in the treatment of avulsed teeth?
- use acid etch/resin alone
- use acid etch/resin with a soft arch wire
- use orthodontic brackets with a passive arch wire
- examples: .0195 braided stainless steel bond with composite, .017x.025 stainless steel wire bond with composite, 018 round stainless steel wire bond with composite, or monofilament nylon (20-30lb test) with composite
when constructing a split for the treatment of an avulsed tooth, the splint should not interfere with the patient’s capability to perform ___ and should allow ___; it should be rigid enough to ___, while allowing for ___
- correct hygiene
- physiological movement of the tooth
- hold the teeth in their proper positions
- minor tooth movement to occur during normal function to stimulate normal PDL healing
___ wire splints are contraindicated in the treatment of avulsed teeth
circumferential
a splint should remain in place for how long? what are the exceptions?
- 7-10 days
- the splint should be replaced if the tooth demonstrates excessive mobility (should be within acceptable limits of <1mm)
- bony fractures resulting in mobility usually require longer splinting periods (2-8 weeks)
home care during the splinting period should encompass what 3 things?
- no biting on splinted teeth
- soft diet
- maintenance of good oral hygiene
why should rigid composite splints be avoided when possible?
- difficult to maintain patients oral hygiene
- difficult to remove
- is extremely rigid, and doesn’t allow for minor tooth movement to stimulate normal PDL development
what are the steps for making a splint 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 bucally and lingually
- place any necessary sutures
splints should extend distally to at least how many non-involved teeth?
2
what are some adjunct drug therapy considerations for the treatment of dental trauma?
- systemic antibiotics
- referral to physician for tetanus consultation within 48 hours
- chlorhexidine rinses
- analgesics
___ is a load applied to an object that will tend to move it to a different position in space
force
___ is a point at which resistance to movement can be concentrated for mathematical analysis
center of resistance
for an object in free 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 embedded in bone, the center of resistance is located where?
approximately halfway (3/5) between the root apex and the crest of the alveolar bone
___ is a measure of the tendency of a force to rotate an object around some point
moment
how is a moment generated?
by a force acting at a distance to the center of resistance
quantitatively, a moment is the product of the ___ times the ___
force times the perpendicular distance from the point of force application to the center of resistance
___ describes two forces equal in magnitude and opposite in direction
couple
a ___ will produce pure rotation, spinning the object around its center of resistance
couple
the combination of a ___ and a ___ can change the way an object rotates while it is being moved
force and a couple
___ is the point around which rotation actually occurs when an object is being moved
center of rotation
what happens when two forces are applied simultaneously to an object (a moment and a couple)?
the center of rotation can be controlled and made to have any desired location
the application of a ___ and a ___ to the crown of a tooth is the mechanism by which bodily movement of the tooth, or even greater movement of the root than the crown, can be produced
a force and a couple
if a single force is applied to the ___ of a tooth, the tooth will rotate around the center of resistance; what does this do to the center of resistance and center of rotation?
- crown
- 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 the 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 be greatest at the ___ and opposite the ___
at the alveolar crest and opposite the root apex
T or F:
you can achieve effective root movement with a removable appliance in the same way as a fixed appliance
- false
- removable appliances can only achieve tipping movements
the ratio between the ___ and ___ determines the type of tooth movement
the moment produced by the force applied to move a tooth and the counterbalancing moment produced by the couple used to control root position
as the moment-to-force ratio increases, the center of rotation is displaced further and further apically, away from the center of rotation, it will produce ___
controlled tipping
without a moment of the couple, the tooth rotates around the center of resistance which equals the center of rotation, creating what type of movement?
a pure tipping movement
when the moment of the couple divided by the moment of the force equals 1, the center of rotation is displaced to infinity and ___ movement occurs
bodily movement (translation)
if the moment of the couple divided by the moment of the force is greater than 1, the center of rotation is displaced incisally and the root apex will move more than the crown, producing what type of movement?
lingual root torque
what happens to the center of resistance in a tooth with loss of alveolar bone height?
it is moved closer to the apex
the magnitude of the tipping moment produced by a force is equal to ___
the force times the distance from the point of force application to the center of resistance
what happens to the tipping moment produced by the force if the center of resistance moves apically due to bone loss?
- it increases because the moment arm is longer
- thus, a larger countervailing moment produced by a couple applied to the tooth would be necessary to produce bodily movement
for all practical purposes, ___ is required if root movement is the goal in patients who have experienced loss of alveolar bone height
a fixed appliance
what type of movement is produced by the application of a single force to the crown of a tooth? how is the movement created?
- creates rotation around the center of resistance
- heavy pressure is felt at the root apex and at the crest of alveolar bone, but the pressure decreases to zero at the center of resistance
optimal force to create a rotational movement of a tooth is around ___ grams
35-60 grams (lower for incisors and higher for molars)
a hawley retainer with a finger spring is only capable of moving a tooth by which type of movement?
it places a single force at a distance from the center of resistance, which will cause the tooth to tip around the center of resistance
tipping movements create an extrusive movement if the tooth is moved ___, and an intrusive movement if the tooth is moved ___
lingually, buccally
what is required, with respect to the PDL space, for translation (bodily movement) to occur? what shape loading diagram is created by this movement?
the PDL space must be loaded uniformly from the alveolar crest to apex, creating a rectangular loading diagram
how much more or less force must be applied to the crown of a tooth to produce the same pressure within the PDL for translation (bodily movement) compare to tipping movements?
twice as much force for translation
what is the optimal force to create a translational movement?
70-120 grams
what is the optimal intrusive force?
10-20 grams
why are extremely light forces needed to produce appropriate pressure within the PDL during intrusion?
because the force is concentrated over a small area at the apex during intrusion
what is the optimal extrusive force? what other movement requires the same amount of force?
- 35-60 grams
- same as rotational movement
an ideal spring should maintain the same amount of force regardless of ___
- the distance a tooth moves
- this would be the most ideal force system for orthodontic tooth movement
- however, 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 ___ forces
continuous
what is an example of a wire that exhibits continuous force?
nickel titanium arch wire
forces that drop to zero between activations of an orthodontic appliance, even though the force declines, are defined as ___ forces
interrupted
what is an example of a wire that exhibits interrupted force?
stainless steel arch wire bends
what type of force falls to zero when a removable appliance is taken out, only to resume when the appliance is reinserted into the mouth?
intermittent force
what happens to intermittent forces as tooth movement occurs?
the forces decay
in a typical force-deflection curve, what is represented by the slope of the linear portion of the curve?
- the stiffness of the material
- the greater the slope, the stiffer the material
in a typical force-deflection curve, what part of the curve is the range? what does the range represent?
the distance along the x-axis to the point at which permanent deformation occurs (usually taken as the yield point, at which 0.1% permanent deformation occurred)
the strength of a wire is a mathematical calculation of the ___ x ___
the stiffness x the range
___ is the point below which the force placed on the wire creates a proportional deflection in the wire. which part of the force-deflection curve represents this?
- proportional limit
- the part of the curve that remains linear
___ is the position the wire will return to after it has been deflected
spring-back
if ___ has exceeded ___, the spring-back will not return the wire to its original position
- deflection
- the proportional limit to the yield point
___ is the point at which increasing deflection causes minimal changes in force to occur (wire’s force has been maxed out)
point of arbitrary clinical loading
___ is the point on the force-deflection curve that represents the wire breaking
the failure point
each of the major elastic properties of an orthodontic wire is affected by a change in what 3 components?
length, shape, and cross-sectional area
