screw loosening is one of the complications that often implant patients deal in day to day life. so , as it is to be managed with mere an small effort.
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Management of abutment screw loosening: a review and a case report -jc-8-subharti dental college and hospital, Meerut
1.
2. Management of abutment screw loosening :
Review of Literature and a case report
J Indian Prosthodont Soc 2014,
Vol. 14(3):208-214
Review article
3. • Can Prosthetic Screws Be Permanently
Tightened?....
• Why Do they get often Loosen?....
4. Introduction
• Dental implants are considered as one of the marvels created in the
dentistry.
• The use of root form endosseous implants has increased and its
restoration with newer designs and concepts.
• But….long term post placement studies reveals about screw
loosening, screw framework and implant fracture.
5. • Among all of them…..screw loosening
considered most common problem, specially in
single implant supported prosthesis.
6. Review
Preload
• The contact force clamping together the abutment and the implant is
called the preload.
• Preload is primarily dependent on the applied torque and
secondarily on the component material, screw head and thread
design and surface roughness.
• Optimum preload of a screw is generated when the screw is
elongated until it reaches but does not exceed its yield strength.
Ideally the preload should be 75 % of the yield strength or 65 % of
the screws fracture strength.
7. Bending of the Screw Joint
• Connection of two separated parts has inferior resistance to
withstand tensile and shear forces and the bending moment.
• The stress is concentrated on the implant abutment connection.
• The strength and stability of the implant abutment connection play
an important role in protecting the screw preload
• The internal connection demonstrated increased resistance to the
bending moment compared to a conventional external hexagon
connection.
8. Settling Effect
• Settling occurs as the rough spots flatten under load, since they are
the only contacting surface when the initial tightening torque is
applied.
• When the settling effect is greater than the elastic elongation of the
screw, screwloosening occurs due to the reduction in forces holding
the surfaces together.
• 2–10 % of the initial preload is lost as a result of settling within the
first few seconds or minutes after tightening.
9. Screw Material
• Gold alloy retention screw with gold coating and titanium alloy
retention screw with aluminum titanium nitride coating had low
percentage of the torque retained in the screw for maintenance of
preload.
10. Connection Geometry
• Connection geometry influences the amount of screw loosening.
• They influence the amount of micro motion,stress distribution and
micro gap formation.
• The internal conical abutment produced the highest magnitude of
micro motion.
11. Implant Number and Diameter
• Screw loosening will be less when two implants are used instead of
one to replace a missing tooth.
12. Restoration Design and Occlusal Table
• Dykema advocated narrowing the
buccolingual dimensions of the pontics up to
40 % as means of reducing the load on the
abutments .
• Narrowing the occlusal table and/or moving
the occlusal contact area more in line with the
implant location reduce the shearing stress on
the retaining screws.
13. Coefficient of Friction
• Coefficient of friction is a major factor in influencing the preload
achieved at a given torque force.
• This is influenced by the hardness of the threads, surface finish,
speed of torquing, surface treatments, presence and quality of
lubricants, and fit and machining tolerances.
15. Chief complaint
• A 45 yr. old lady reported…
• Mobility in recently cemented implant supported crown
w.r.t 22,
• Mobility observed after next day from cementation.
16. • Oral examination :-
• Mild Inflammation seen around the gingiva of cemented crown.
• Crown showed slight rotation along its long axis.
25. Comparison of screw loosening, rotation, and
deflection among three implant designs.
J Prosthet Dent 1995 Sep;74(3):270-8
26. • Dixon DL, Breeding LC, Sadler JP, McKay ML studied
that micromovement and torque levels required to loosen
abutment screws for straight and angled antirotational
screw-retained abutment/implant combinations from
three different manufacturers were examined in the
in-vitro investigation.
27. • A custom-built machine was used and each sample was
subjected to compressive horizontal reciprocal
movements over a 25-degree incline for a simulated 1-
month period.
• Data were generated that showed movements of the
crown/abutment complex during force application.
28. • The amount of torque necessary to loosen the abutment screws
before and after testing was also recorded and compared for each
system.
• The results indicated no significant differences (p < 0.05) among all
the straight and angled abutments for the variables studied.
29. Conclusion
• Inadequate preload is the most common reason for abutment screw
loosening in two piece endosseous root form implants.
• Centering the occlusal contact, flattening the cuspal inclination,
narrowing the buccolingual width of the restoration and reducing the
cantilevers add to the longevity of the implant supported prosthesis.
30. Refrences
• Lang LA, Kang B, Wang R-F, Lang BR (2003) Finite element analysis
to determine implant preload. J Prosthet Dent 90:539–546
• Stuker RA, Teixeira ER, Beck JCP, da CostaNP(2008) Preload and
torque removal evaluation of three different abutment screw for
single standing implant restorations. J Appl Oral Sci 16(1):55–58
• Rafee Al, Nagy WW, Fournelle RA, Dhuru VB, Tzenakis GK, Pechous
CE (2002) The effect of repeated torque on the ultimate tensile
strength of slotted gold prosthetic screws. J Prosthet Dent
88(2):176–182
• K-T Yao, H-C Kao, C-K Cheng, H-W Fang, S-W Yip, M-L Hsu (2011).
The effect of clockwise and counterclockwise twisting moments on
abutment screw loosening. Clin Oral Implant Res 23:1–6
31. • Ameen K, Akihiko H, Shuichi N, Osamu M (2004) Effect of lateral
cyclic loading on abutment screw loosening of an external hexagon
implant system. J Prosthet Dent 91:326–334
• Dixon Donna L, Breeding Larry C, Sadler Peter J, Mckay Mathew L
(1995) Comparison of screw loosening, rotation and deflection among
three implant designs. J Prosthet Dent 74:270–278
• Tsuge T, Hagiwara Y (2009) Influence of lateral oblique cyclic loading
on abutment screw loosening of internal and external hexagon
implants. Dent Mater J 28:373–381
• Beaty K (1994) The role of screws in implant systems. Int J Oral
Maxillofac Implant 9(suppl):52–54
• English CE (1992) Externally hexed implants, abutments and transfer
devices: a comprehensive overview. Implant Dent 1:273–282
32.
33. • What is causes and prevention and
management of abutment screw loosening?
• Which luting cement is used in the article?
Hinweis der Redaktion
The proximal contact of the crown with the
adjacent tooth restricted its rotation and held it in position and it
is removed at the long axis.(Fig.3).
using tapering fissure and round wheel diamond points in an airotor hand piece.
The crown and the abutment with the connecting screw were then kept in the
This resulted in disintegration of the luting cement.
The abutment with the connecting screw was tightened back into the fixture with a tightening torque of 35 N using a torque wrench.
