This presentation is about important topic in dentistry/removable prosthodontics. It talk about removable partial denture design related to clasp selection in distal extension cases according to the position of retentive undercut.

1. Removable Partial DentureRemovable Partial Denture
DesignDesign
Clasp selection according toClasp selection according to
the position of retentivethe position of retentive
undercut in distal extensionundercut in distal extension
casescases
Dr. Mohammad Ayham Hakkoum
University of Kalamoon
Faculty of Dentistry
Department of Prosthodontics

2. Selecting suitableSelecting suitable direct retainers or claspsdirect retainers or clasps is ais a
primary consideration in removable partialprimary consideration in removable partial
denture designdenture design..

3. TheThe position of retentive undercutposition of retentive undercut is one of theis one of the
most important factors in selecting claspsmost important factors in selecting clasps
especially in distal extension casesespecially in distal extension cases..
These undercuts are determined by dentalThese undercuts are determined by dental
surveyorsurveyor..

4. AA simple methodsimple method may be followed to selectmay be followed to select
suitable clasps according to the position ofsuitable clasps according to the position of
the retentive undercut inthe retentive undercut in distal extensiondistal extension
removable partial dentureremovable partial denture..

5. AnAn accurate surveyingaccurate surveying procedures should beprocedures should be
done to determine the retentive undercutsdone to determine the retentive undercuts..

6. If the abutment tooth has theIf the abutment tooth has the retentive undercutretentive undercut
at the middleat the middle of the buccal surfaceof the buccal surface
(mesiodistally) or slightly mesial to it,(mesiodistally) or slightly mesial to it, RPIRPI
claspclasp assembly may be usedassembly may be used..

7. If the undercut is found to beIf the undercut is found to be locatedlocated
distobuccallydistobuccally, then another type of, then another type of bar claspsbar clasps
may be used such as T-clasp or modified T-may be used such as T-clasp or modified T-
claspclasp..
But we should notice that bar clasps (orBut we should notice that bar clasps (or
infrabulge clasps)infrabulge clasps) may be contraindicatedmay be contraindicated inin
some cases such as in the presence of tissuesome cases such as in the presence of tissue
undercuts or shallow buccal vestibuleundercuts or shallow buccal vestibule..

8. Therefore, IfTherefore, If bar clasps are contraindicatedbar clasps are contraindicated andand
there is onlythere is only distobuccal retentive undercutdistobuccal retentive undercut,,
we can use thewe can use the reverse RPA claspreverse RPA clasp assemblyassembly..

9. When there is onlyWhen there is only mesiobuccal retentivemesiobuccal retentive
undercutundercut,, RPA claspRPA clasp assembly orassembly or
combination claspcombination clasp may be usedmay be used..

10. We found that theWe found that the clasp of choice may varyclasp of choice may vary
according to the position of retentive undercutaccording to the position of retentive undercut
and other factorsand other factors..
However, we should keep in mind that we canHowever, we should keep in mind that we can
achieve the best results byachieve the best results by wise mouthwise mouth
preparationpreparation and accurate alteration ofand accurate alteration of
abutment teeth contour, and so we can avoidabutment teeth contour, and so we can avoid
the use of less acceptable types of claspsthe use of less acceptable types of clasps..

11. ReferencesReferences::
11..Hakkoum, M. A. (2015), New Clasp Assembly forHakkoum, M. A. (2015), New Clasp Assembly for
Distal Extension Removable Partial Dentures:Distal Extension Removable Partial Dentures: TheThe
Reverse RPA ClaspReverse RPA Clasp. Journal of Prosthodontics.. Journal of Prosthodontics.
doi: 10.1111/jopr.12313doi: 10.1111/jopr.12313
http://onlinelibrary.wiley.com/doi/10.1111/jopr.12313/absthttp://onlinelibrary.wiley.com/doi/10.1111/jopr.12313/abst
22..Carr AB, Brown DT. McCracken's removable partialCarr AB, Brown DT. McCracken's removable partial
prosthodontics. 12th ed. St. Louis: Mosby, 2011prosthodontics. 12th ed. St. Louis: Mosby, 2011..
33..Phoenix RD, Cagna DR, DeFreest CF. Stewart'sPhoenix RD, Cagna DR, DeFreest CF. Stewart's
clinical removable partial prosthodontics. 4th ed.clinical removable partial prosthodontics. 4th ed.
Chicago: Quintessence, 2008Chicago: Quintessence, 2008..