A reliable index for correct positioning of precision attachments into an existing overdenture Harold Kolodney, Jr., DMD,a Ray Holder, Jr., MS, William C. Grayb University of Mississippi, School of Dentistry, Jackson, Miss. Limited space over abutment ment system within an existing tic index can be made to depict abutment teeth. This index is incorporation, as well as the attachment system. A method incorporation into an existing 1992;67:335-8.)

V arious

attachment

DMD,a

and

teeth may make incorporation of a precision attachoverdenture technique sensitive. A special diagnosthe available space within the prosthesis over the critical to determine the feasibility of attachment selection and correct positioning of an appropriate to improve predictability for precision attachment overdenture is described. (J PROSTAET DENT

systems have been developed

and describedto increaseretention of an overdenture.l-ll A key factor for their use is the available spaceover the abutments, which must be determined in advance for optimum placement of the attachments. To correctly visualize this space, a diagnostic index shouldbe madeprior to vertical and horizontal positioning of the attachments. Incorrect horizontal positioning will result in perforation of the polished surfacesof the existing prosthesis,and incorrect vertical positioning will result in disorientation of the occlusal scheme. This article

aAssistant Professor, Department bFourth-year dental student. 10/1129492

of Restorative Dentistry. Fig. 2. Denture hasbeenremovedfrom putty impression, recording both basalsurfaceand selectedpolishedsurface parts.

1. Embedded denture is removed from polyvinyl siloxane putty impression.Excessmaterial on polishedden-

Fig.

ture surface has been trimmed

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Fig. 3. Copingswaxed into a modified dome configuration around plastic resin post patterns.

KOLODNEY,HOLDER,ANDGRAY

Fig. 4. Push-pin positioned in polished-to-basalsurface index to indicate proper laboratory placement of attachment over abutment tooth. A, Too far buccal; B, correct placement; C, too far lingual.

Fig. 5. Castingswith Rothermann attachments soldered to copings are seatedon abutment teeth.

Fig.

describes a technique for correct positioning of attachments into an existing overdenture.

If acceptable, the existing overdenture can be converted into a precision attachment prosthesis.Otherwise, a new prosthesisshould be constructed. The existing overdenture is usedto make a polishedsurface/basal surface index. This index shows the space between the abutment surface and the polished denture surface. Available space for attachment placement can then be evaluated.

PROCEDURE Pretreatment

evaluation

Placement of attachments in an existing overdenture is selective. Strong patient desirefor increasedretention and the availability of spaceover the abutmentsfor attachment placement are important factors. Other critical factors are periodontal health, abutment stability, mucosal health, oral hygiene, and the nature of the opposingocclusion. Adequacy of the existing overdenture is carefully evaluated for contour of polished surfaces, border extensions, centric and vertical relation of occlusion,and occlusalwear.

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6. Attachment copingswith spacersand C-clips in position prior to incorporation into prosthesis.

Index

construction

A rigid shellac baseplateis coated on one surface with polyvinyl siloxane adhesiveand a mound of mixed polyvinyl siloxane putty is placed on it. Some putty material is adapted into the basalsurface of the denture, taking care

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not to trap air inside the abutments. The denture is then partially embedded into the mound of putty material, which is adapted against the parts of the polished surface immediately adjacent to the abutment teeth. After the material has set, the excess is trimmed with a surgical laboratory blade. The resiliency of the polyvinyl siloxane putty allows the partially embedded denture to be removed (Fig. l), and the resulting index leaves an impression of the basal surface of the denture and of portions of the polished surfaces (Fig. 2). The facial and lingual surfaces of the existing prosthesis can be visualized during the waxup of the attachments. Abutment

preparation

Gutta-percha is removed from part of the overdenture abutment canal and its occlusal portion is widened. The occlusal surface of the abutment is rounded to a modified dome shape approximately 1 mm above the gingival margins and its edges are bevelled. Impression

and laboratory

phase

Correctly sized plastic impression posts are placed in the abutment canals and incorporated into a full arch elastomeric impression. The master cast is poured in improved dental stone and the dies are subsequently trimmed. Plastic burnout posts are placed in the lubricated canals of the dies and Duralay resin (Reliance Dental Mfg. Co., Worth, Ill.) is added to shape the posts to conform to the widened portions of the canals. The occlusal portions of the prepared roots are waxed to the shape of an overdenture abutment coping (Fig. 3). The attachment system used as an example in this article is the resilient Rothermann precision attachment (APM-Sterngold, Attleboro, Mass.) that we utilized because of its low interocclusal height. However, a variety of other overdenture systems can be used. The wax patterns are sprued and cast in gold alloy. With the aid of the polished-to-basal surface index (Fig. 4), the attachments are correctly positioned buccolingually on the occlusal portions of the copings with the aid of a surveyor and are then soldered to the copings. The denture path of insertion and the occlusal plane are determining factors in the alignment. Attachment

incorporation

The castings are fitted to the abutment teeth (Fig. 5) and the proper spacer is placed over the male section of each abutment tooth. The Rothermann C-clips are then placed over the spacers (Fig. 6). These spaces are needed to provide vertical clearance for the attachments to remain resilient after a relining. The internal spaces within the abutment regions of the overdenture are reduced until the overdenture fully seats over the castings. Kerr disclosing

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Fig. 7. After chairside reline with light-curing acrylic resin, spacersare removed and C-clips are incorporated into prosthesis.

wax (Kerr-Sybron Inc., Romulus,Mich.) is helpful to effect the clearance. The castings are then permanently cemented to their respective abutment teeth. The C-clips of the Rothermann attachments can be connected to the overdenture in the mouth with either lightcuring or autopolymerizing acrylic resin. A chairside reline in conjunction with incorporation of the attachments can alsobe done usinglight-curing acrylic resin. A lingual window is prepared through the denture to provide an escape path for excessacrylic resin. With the attachment components seated on the castings,the remaining exposedsurfaces of the copings are blocked out. The C-clip attachmentsbecomeembeddedin the acrylic resin oncethe denture is fully seated. A chairside light-curing unit can initiate polymerization. The polymerization is completed in the laboratory with the Triad light-curing unit (Dentsply International, York, Pa.). After polymerization of the acrylic resin, the spacers are removed and the regions around the female attachments (C-clips) are finished and refined (Fig. 7). After basalseat and occlusaladjustments, the transition of the prosthesisto an attachment overdenture is complete. ADVANTAGES Space available to incorporate an attachment system into an existing overdenture is often limited. A polyvinyl siloxane putty material can be usedto obtain a polishedto-basal surface index of the existing overdenture. The index provides a critical guidefor selectionof the attachment system to be usedand for correct visualization of attachment placement both vertically and horizontally. This index also has applications for dental implants. SUMMARY When the decisionis madeto incorporate a precisionattachment systeminto a preexisting overdenture, availability of spacemust be determined. A polished-to-basalsur-

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face index with polyvinyl siloxane putty material is a critical guide for subsequent clinical and laboratory procedures. Available space inside the existing prosthesis for correct positioning of the attachment is uniquely visualized. The risk of having an attachment perforate through a polished or occlusal surface of the prosthesis is best avoided in this manner.

6. 7. 8. 9. 10.

REFERENCES 1. Mensor MC Jr. Classification and selection of attachments. J PROSTHET D~~~1973;29:494-7. 2. Dodge CA. Prevention of complete denture problems by use of overdentures.J PROSTHET DENT 1973;30:403-11. 3. Mensor MC Jr. Attachment fixation for overdentures. Part I. J PROSTHET DENT 1977;37:366-73. 4. Mensor MC Jr. Attachment fixation for overdentures. Part II. J PROSTHET DENT 1978;39:16-20. 5. Preiskel HW. Precision attachments in prosthodontics: Overdentures

Guides

for authors

11.

HOLDER,

AND

GRAY

and telescopic prostheses. vol 2. Chicago: Quintessence Publishing Co Inc, 1985. Moghadam BK, Scandrett FR. Magnetic retention for overdentures. J PROSTHETDENT~~~~;~~:~~-~. Gillings BRD. Magnetic retention for complete and partial overdenhues. Part I. J PROSTHET DENT 1981;45:484-91. Gillings BRD. Magnetic retention for complete and partial overdentures. PartII. J PROSTHET DENT 1983;49:607-18. Brewer AA, Morrow RM. Overdentures. 2nd ed. St. Louis: CV Mosby Co, 1980:208-43. Arbee NS, Galovic G. The use of an attachment system for overlay pr0stheses.J PROSTHETDENT 1986,56:51-5. APM-Sterngold Instruction Booklet. Stern ERA overdenture. Attleboro, Mass: APM Sterngold Co, 1986.

Reprint requests to: DR.HAROLD KOLODNEY,JR. SCHOOLOFDENTISTRY UNIVERSITY 0~ MISSISSIPPI 2500 NORTH STATE ST. JACKSON,MS 39216

available

The Guide to Preparing Articles for THE JOURNAL OF PROSTHETIC DENTISTRY, revisedby ProfessorPaul Barton, Editorial Consultant to the JOURNAL, and the editors, is available to prospective authors. The guide provides the format for developing different types of scientific manuscripts, a checklist for effective writing, and detailed instructions for preparing manuscripts in the style acceptableby the JOURNAL. Also available are the Guidelines for Reporting Statistical Results and an Author’s Guide to Controlling the Photograph. Guides can be obtained from the office of the Editor (Dr. Glen P. McGivney, The Journal of Prosthetic Dentistry, State University of New York at Buffalo, School of Dental Medicine, 345 Squire Hall, Buffalo, NY 14214).

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A reliable index for correct positioning of precision attachments into an existing overdenture.

Limited space over abutment teeth may make incorporation of a precision attachment system within an existing overdenture technique sensitive. A specia...
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