Operative Dentistry Flashcards
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Describe retention form.
Ability of restoration to RESIST forces along the long axis of the tooth.
Describe resistance form.
Prevents dislodgement of restoration under occlusal forces in apical or oblique direction.
In the study, “Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs” JVD 2011.2 what was the overall mean CA?
26.7 degrees
In the study “Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs,” JVD 2011.2, what were the main takeaways?
An ideal CA of 12 degrees is almost never attained. But the more clinical crown (high H/D) the less concerned we need to be about achieving a low CA.
In the study “Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs,” JVD 2011.2, the CA_lim can be used as a guide for determining the necessary CA for retention and resistance. What is the formula?
CA_lim = arcsin (H/D)
In the study, “Effect of Preparation Surface Area on the Clinical Outcome of Full Veneer Crowns in Dogs” JVD 2014.1 what was the success rate?
84.4 % or 27/32 crowns
In the study, “Effect of Preparation Surface Area on the Clinical Outcome of Full Veneer Crowns in Dogs” JVD 2014.1, how many crown failures were due to fractures vs cohesive/adhesive failures?
Fractures - 2/5 (40%)
Cohesive/adhesive failures - 3/5 (60%)
In the study, “Effect of Preparation Surface Area on the Clinical Outcome of Full Veneer Crowns in Dogs” JVD 2014.1, what was the mean surface area for successful crowns, crown failure due to adhesive/cohesive failure and crowns that failed due to fracture?
1.9 cm2 - success
1.23 cm2 - failed due to adhesion
1.73 cm2 - failed due to fracture
In the study, “Effect of Preparation Surface Area on the Clinical Outcome of Full Veneer Crowns in Dogs” JVD 2014.1, what was the importance of the axial grooves?
They decrease the CA, and therefor increase resistance and retention. They also increase SA.
In the study, “Effect of Preparation Surface Area on the Clinical Outcome of Full Veneer Crowns in Dogs” JVD 2014.1, what was the main take away of the study?
There is a positive correlation between preparations with greater surface area and successful clinical outcome, but this was not found to be statistically significant.
What is the definition of convergence angle?
Soukup, Synder. Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs. JVD 2011.
angle between two opposing axial walls, equals the sum of the taper of two opposing axial walls
Ideal convergence angle 3-14 degrees, not clinically achievable
What is the defintion of and formula for limiting average taper?
Soukup, Synder. Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs. JVD 2011.
The point at which resistance form is lost
CAlim = arcsin (H/D)
If H/D > 1 then there is no CAlim –> adequate resistance/retention
In Soukup’s 2011 article “Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs,” restorations that failed from adhesive/cohesive failure vs teeth that fractured had higher or lower H/D ratios significantly?
JVD 2011
Restorations that failed from adhesive failure had a lower H/D ratio (not stat sig)
Restorations that failed from tooth fracture had higher H/D ratio (not stat sig)
In the study, “The Influence of Crown Height to Diameter Ratio on the Force to Fracture of Canine Teeth in Dogs” JVD 2015.3, when the H/D is decreased by 10% and 20% what is their probability of fracture decreased by?
10% decrease in H/D - 24.1%
20% decrease in H/D - 60.4%
What has been shown to be the amount of force required to displace a crown with a convergence angle of 22? What force in N do dogs generate when chewing and when military dogs are biting/pulling with their canine teeth?
Soukup. Crown Preparation Design: An Evidence-Based Review. JVD 2013
Crown displacement force: 1386N
Chewing: 20-937N
Biting/pulling: 180-1120N
Dogs generate forces lower than forces required to displace crown
In the study, “The Influence of Crown Height to Diameter Ratio on the Force to Fracture of Canine Teeth in Dogs” JVD 2015.3, across 2 canine teeth, decreasing H/D by 20% decreases the probability of fracture by?
86.5%
In the study, “The Influence of Crown Height to Diameter Ratio on the Force to Fracture of Canine Teeth in Dogs” JVD 2015.3, decreasing H/D by 20% increases the probability of fracture of the contralateral canine by?
54.4%
What effect have internal grooves been shown to have on effective CA?
Soukup. Crown Preparation Design: An Evidence-Based Review. JVD 2013
Internal grooves decrease the “effective” CA to improve resistance/retention form
In the study, “The Influence of Crown Height to Diameter Ratio on the Force to Fracture of Canine Teeth in Dogs” JVD 2015.3, the mean force to fracture an unaltered canine is?
494 Newtons
What was the main take away in the study, “The Influence of Crown Height to Diameter Ratio on the Force to Fracture of Canine Teeth in Dogs” JVD 2015.3?
There was a significant inverse relationship between H/D and force to fracture.
The amount of force required to dislodge a crown cemented onto a die with CA of 24 degrees and height of 4mm increased how many times when a resin-based cement was used instead of zinc phosphate?
Soukup. Crown Preparation Design: An Evidence-Based Review. JVD 2013
3.5 times
According to Soukup’s 2011 article “Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs,” resin-based cements allowed successful use of up to what convergence angle?
JVD 2011
70 degrees
What level of evidence suggest that CAs of 25-30 degrees may be clinically acceptable in dogs?
Soukup. Crown Preparation Design: An Evidence-Based Review. JVD 2013
Grade III
Only Grade IV evidence for use of CA 5-12 degrees
According to Soukup’s 2011 article “Achievable Convergence Angle and the Effect of Preparation Design on the Clinical Outcome of Full Veneer Crowns in Dogs,” H/D ratios of less or greater to what values are associated with adhesive/cohesive failure vs failure due to fracture respectively?
JVD 2011
H/D ratios < 1.6 may be more likely to fail due to adhesive/cohesive failure
H/D ratios > 1.8 may be more likely to fail due to fracture