attachments and their use in removable partial denture fabrication

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Attachments And Their Use InRemovable Partial Denture Fabrication

Dr. Jeff Shotwell

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What is an attachment?

An attachment is a connector consisting of twoor more components. One component isconnected to a tooth, tooth root, or an implantand the other component is connected to aprosthesis.

This component of the attachment is typicallyincorporated in the crown of a tooth. To do this,the tooth needs to be restored with a full orpartial coverage crown either all gold or aporcelain fused to metal.

This component is typically incorporated in theprosthesis. For our discussion, this would be aremovable partial denture.

Source: Jeff Shotwell, University of Michigan, 2008

Types of Attachments

Intracoronal Attachment Extracoronal Attachment

Source: Peter E. Staubli, MDT, CDT . Attachments & Implants Reference Manual, 6th Ed. Implant Dentistry. 7(4):377, 1998.

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IntracoronalAttachment

Intracoronal attachments are incorporated entirely within the contour of the crown.The advantage of an intracoronal attachment is that the occlusal forces exertedupon the abutment tooth are applied close to the long axis of the tooth. Adisadvantage arises when the abutment is overcontoured by placing the“intracoronal attachment” outside the crown contour. This often results frominsufficient tooth reduction. It it is not possible to create a box preparation thatwill totally incorporated the female element, then an extracoronal attachmentshould be considered. These attachments are non resilient. When limited spaceexists, a miled lingual surface should be provided on the crown. Most wear occurson these attachments during placement and placement.

Source: Attachments and Implants reference manual 6th edition

Source: Removable Partial Denture Designby Krol et al Fourth Edition

Intracoronal AttachmentsAn intracoronal attachment is one which is contained withinthe normal contours of the crown portion of a natural tooth.The placement of the attachment requires that the abutmenttooth be restored with a full or partial coverage (3/4) crown.

As seen in the image onthe right, the intracoronalattachment has beenincorporated on the distalsurface of the PFMcrown on tooth #28

Source: Removable Partial Denture Design by Krol et al Fourth Edition

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Intracoronal attachment as suppliedwith a dime for size comparison. Theimages at the right show thecomponents of the attachment and anend on view to see the retentive crosssection.


The components can be seenhere close up.

Male portion of theattachment on the partialdenture

Female portion of theattachmentincorporated in thecrown

Partial denture in placewith the attachmentserving the function of theocclusal rest, and theclasp components


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Components for intracoronal precision attachment removable partial denture.A. Occlusal view of PARPD (note position of attachments)B. Male portion of attachment which is integral with the partial denture.C. The view of the PFM crown with the intracoronal attachment in place.D. Lingual close up of the attachment retained RPD in place.Source: Removable Partial Denture Design by Krol et al Fourth Edition

The attachments obviously have to “draw”, that is they require a commonpath of insertion. A surveyor is used with a mandrel to place theattachments in the wax patterns of the crowns with a common path ofinsertion.


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With the crown waxed up for labial contour, occlusion and proximalcontact, the working cast is placed on the surveyor table. The surveyortable is adjusted for the path of insertion and the attachment carried toplace in the pattern on a mandrel which is specific to the type ofattachment being used. Wax is flowed around the attachment in the imageon the left securing it in the pattern for casting in the appropriate alloy.


A lug must be fabricated which is castto the male portion of the attachment.The lug allows the male portion of theattachment to be affixed to the partialdenture framework.


Source : Jeff Shotwell, University of Michigan, 2008

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The male portion of the attachment is seen in place with the crown on the leftand on the right you can see the crown attachment complex related to thepartial denture framework. Self cure acrylic will be flowed around the lugsecuring it to the framework. The area that the acrylic will be placed inindicated within the circle.


ExtracoronalAttachment

Extracoronal attachments are positioned entirely outside the crown contour ofthe tooth. The advantages of this type of attachment are that the normal toothcontour can be maintained, minimal tooth reduction is necessary and thepossibility of devitalizing the tooth is reduced. Also, the path of insertion iseasier for patients with limited dexterity. It is more difficult to maintainhygiene with extracoronal attachments and patients need to be instructed onthe use of hygiene accessories such as proxi brushes etc. Keeping theunderside of the attachment area clean, greatly improves the tissue response inthe area indicated by the arrows.

Source : Jeff Shotwell, University of Michigan, 2008

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Extracoronal AttachmentsAn extracoronal attachment extends outside the normal contoursof the crown of an abutment tooth. It is still necessary to place arestoration on the abutment tooth.

Here you can see an extracoronalattachment incorporated in thecrown on tooth #21.


The image on the left is anadvertisement from a journalfor an extracoronalattachment.

The image below shows theuse of the attachment in thefabrication of the abutmentcrown.


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This group of images shows the extracoronal attachment componentsand the esthetics of the removable partial denture when viewed from thebuccal aspect.


Clinical case for combination case uitilizinga maxillary complete denture and amandibular precision attachment removablepartial denture (PARPD)


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Patient’s oral condition with the previous complete denture andperiodontal involvement of several lower teeth. First step, interimlower removable partial denture.


The teeth are extracted, an immediate insertion temporary lower removableappliance placed, and healing allowed. The lack of fit seen on lower right anterior isdue to tissue change during healing.


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Tooth preparation


The maxillary impression and cast is made as well as the lower working cast.The working casts are then articulated as seen in the images below.


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After articulation, the teeth are set on the maxillary record base andtried in the patient to verify esthetics and phonetics. The lower teethare set to define the spacing for the wax patterns for the PFM castings



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Stages of framework construction from duplicated master cast, through waxpattern, and finally casting in cobalt, chrome alloy. Note lingual reciprocalarms on casting to relate the framework to PFM crown castings


Framework related to crowns, attachments can now be related to theframework, teeth set and the teeth set and final wax up for processing.


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Completed case in place and patient. Note smallremoval “studs” placed on removable partial dentureto aid in the removal of the lower appliance.


Another case using just two lower cuspid teeth for abutments.


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Images showing alignment of female portion of attachmentsin the all gold crowns on the lower cuspid teeth


With two teeth remaining, the choicemay be made to use a bar typeattachment rather than theintracoronal attachments seen at theupper right. For the edentulouspatient two implants may be placedand a bar fabricated to retain thelower complete denture.


Source: University of Michigan School of Dentistry, 2008

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Over time, the attachmentswear. How to make a wornattachment PARPD againserviceable for the patient.In this case even makingthe appliance over was aproblem as the abutmentteeth were very short. Thecomponents had worn withtime from insertion andremoval. The solutionused here was the additionof clasps.

Maintenance Issues for PARPDs


The stainless steel wire is adapted tothe buccal surface of the abutmentteeth. As seen in the image at thelower right the wire is firstembedded in the acrylic flange andthen adapted to the teeth. For thispatient, this treatment offered themost acceptable solution to theproblem of looseness of themaxillary PARPD.


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Radicular and intraradicular stud type attachments are connected to aroot preparation. The female or male is soldered or cst to a root capcoping as seen in the image top left. Some stud type attachments aredirectly cemented to the prepared root without requiring a cast coping.Stud type attachments may promote improved or easier oral hygiene andenhance the crown-root ratio due to the low profile. The image at theright shows such an attachment utilized with an implant.

Source: University of Michigan School of Dentistry, 2008

Radicular and Intraradicular Stud Type Attachments

These images demonstrate the use ofan intraradicular attachment to repaira lower removable partial denturewhich still has a usable tooth rootfrom a former abutment. Thedecision was made not to rebuild apost core and crown to fit the pre-existing lower removable partialdenture.


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The use of a postand coping as aretainer for aremovable RPD

Choices for the abovetooth since it was treatedendodontically.Post and core followedby a crown to fit anexisting RPD.Post and coping with aretentive element.


Maxillary bicuspids present challenges with preparation due to the shape of the root of thetooth and the concavities that exist mesially and distally.


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In this case, it was possible to use both canals for posts due tothe minimal divergence of the canals. Often times we mustchoose one canal. Note also that the retentive anchor is keptas low as possible and as lingually placed as possible to allowthe setting of a tooth on the RPD later.


The vertical height of the copingand attachment combination is apotential problem if not taken intoaccount. Leave room to set thedenture tooth both buccally andocclusally!!


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A tooth was added to the pre-existing RPDin the place of the natural tooth which is nowcut off at the FGM. A recess is cut in theunderside of the RPD to fit around theattachment coping. Self cure acrylic willnow be painted around the coping making itpart of the RPD.


Source: Jeff Shotwell, Universityof Michigan, 2008

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We now have a replacement tooth on the RPD. Thereis still a natural tooth under the RPD providing supportand retention. We have eliminated the need for a claspin this area as well.


attachments and their use in removable partial denture fabrication

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