DENTAL DANIEL

TECHNOLOGY

H.

GEHL,

Section

editor

Dolder bar joint mandibular overdenture: for nonparallel abutment teeth George

1. Marquardt,

A technique

D.D.S.*

Veterans Administration Hospital, Hines, Ill.

T

his article discusses a method of overdenture construction utilizing the Dolder bar joint attachment.lm3 In addition, it presents a step-by-step technique to solve the problem of nonparallel abutment teeth. The great interest in dental implants has developed a whole new science of dental implantology.4 The search to find the ideal dental implant has drawn attention to the most biologically compatible implant of all, the roots of the patient’s own teeth. The overdenture concept is gaining ever-increasing acceptance as the treatment of choice when a patient is faced with extraction of the remaining teeth.j-” The prime motivation for overdenture construction is preservation*“-I*---preservation of the remaining teeth, the surrounding alveolar bone, and the attached gingival tissue supporting the denture.l”-16 Preservation of the sensory receptors within the periodontal ligament retains the discrete proprioceptive feedback for proper motor responses of the masticatory system.17-‘” DOLDER

BAR JOlNTt

Cotiponents. The male portion of the Dolder bar joint consists of a rigid bar of metal which lies on the edentulous tissue and is attached to the abutment teeth by means of copings and metal posts extending into the root canals. The bar is eggshaped with the narrower part closest to the tissue. The female portion is a thin, flexible metal sleeve of a length similar to that of the bar, which fits exactly the widest part of the egg-shaped bar. Attached to the top of the sleeve is a perforated metal plate for retention in the denture. An auxiliary brass wire is placed between the bar and sleeve during construction and is removed when the denture has been processed (Fig. 1) . This allows a vertical translation and sagittal rotation of the denture from the rest position in function. The stressbreaker action displaces tissue a maximum of 1 mm. before the stress is taken up by the bar and abutment teeth (Figs. 2 and 3). *Career tAPM/Stern

Senior

Prosthodontic Gold,

San

Mateo,

Resident. Calif.

101

102

J. Prosthet. Dent. July, 1976

Marquardt

Fig. 1. The Dolder C, a sleeve

with

bar joint a perforated

consists of: A, an egg-shaped metal plate.

Fig. 2. An assembled Dolder brass wire; and C, the sleeve.

bar

joint

as viewed

Fig. 3. An assembled

bar

joint

viewed

the bar;

Dolder and B, the sleeve.

from

from the

bar; the end

B, an auxiliary

end:

A, the

without

brass wire;

bar;

B, the

auxiliary

brass

and

auxiliary wire:

A,

The Dolder bar joint is available in two sizes: 3.0 by 2.2 mm. and 2.3 by 1.6 mm. and in lengths of 2, 3, and 5 cm. The smaller size of bar, though it allows more room for placement of artificial teeth, may distort when used in long spans. The larger 3.0 by 2.2 mm. size is the bar of choice. Indications for use. The overdenture should be considered only as an alternative to the extraction of the teeth. If the teeth are sound enough for fixed or removable partial dentures, that should be the treatment of choice rather than an overdenture.20j *I The teeth selected as abutments should have approximately one-third of the supporting alveolar bone remaining and no more than Class II hypermobility. The arrangement of the remaining teeth should follow the Kennedy Class I, modification I, where either a canine or premolar remains on each side of the arch. An exception to this rule is when the edentulous maxillae are opposed by a mandibular arch with only anterior teeth remaining. Utilization of a bar attachment overdenture reduces the otherwise traumatic occlusal forces of natural anterior teeth on the supporting bone and tissues of a maxillary complete denture.22 To resist the forces of mastication, the bar should be parallel to the plane of occlusion and at right angles to the median axis (the line bisecting the angle formed by the posterior edentulous ridges). The alveolar ridge between the teeth must be relatively straight in a vertical and horizontal plane. It may be necessary to bend the bar or surgically remove excess tissue to accommodate the bar to the ridge. The bar should rest on or be as near as possible to the tissues at the crest of the residual ridge for ease of plaque removal and to prevent filling of the space by hyperplastic tissue. Contraindications for use. When insufficient interarch space exists, there will not be enough room to accommodate both the bar assembly and the anterior teeth. If

Volume Numhr

36 1

Fig. 4. The silver” liner;

Dolder

bar joint

mandibular

overdenture

103

pivot: A, the pivot seated in the silver liner; B, the pivot removed from the C, thl e liner seater tool; and D, Ackerman burs.

Stutz

the labial curve of the alveolar ridge between the abutments is too great, the bar will lie lingual to the ridge and interfere with the space for the tongue. Consideration should be given to the patient’s age and physical and psychologic conditions to determine tolerance to the required dental procedures. Finally, the patient with poor oral hygiene is not a good candidate for an overdenture. Advantages of use. Increased retention and stability of the denture plus retained proprioceptive responses mean better control and function of the dentures. This is especially important for the physically handicapped patient. Reduction of the clinical crown of periodontally involved abutment teeth improves the crown/root ratio, bringing the support for the overdenture bar closer to the bone than that of an occlusal rest of a partial denture. Cross-arch splinting reduces the mobility of the abutment teeth. The supporting bone is retained around the abutments and the residual ridge beneath the bar. The bar joint resists traumatic buccolingual movement of the posterior denture base rotating around the vertical axis. Less force is applied to the abutment teeth by the stressbreaker action of the bar joint. When the opposing arch is edentulous, the occlusal forces can be distributed more equally to the supporting tissues. The esthetic result is improved because retainers are not visible. A better choice of the mold, size, and shade of artificial teeth, not usually possible with removable partial dentures, may be achieved. There is a psychologic advantage to the patient in maintaining some of his teeth, and he is better prepared to accept overdenture treatment. Disadvantages of use. A somewhat thicker denture labiolingually is required for retention of the bar joint sleeve. The dental procedures are more time-consuming and expensive than those required for conventional dentures. TECHNIQUE Preprosthetic but sometimes,

treatment. Canines are ideal abutments for the Dolder bar joint, a first premolar can be used if its alignment meets the requirement.

104

J. Prosthet. Dent. July, 1976

.Marquardt

Fig. 5. (Left) The bar is soldered directly canals for Stutz pivots. (Right) Schubiger the root canals are not parallel.

Fig.

6. The

Fig.

7. More

Stutz than

pivots

are seated

adequate

retention

in their

to the copings with parallel preparation of the root screws are used to attach the bar to the copings when

liners.

is provided

for

the cast copings

by the posts.

Necessary preprosthetic surgery and periodontal treatment are accomplished. Endodontic procedures are performed, and the root canals are filled with gutta-percha. teeth by removing the Preparation of abutment teeth. ( 1) P re p are the abutment coronal portion almost to the crest of the surrounding gingival tissues. (2) Bevel the axial-gingival margins. The final preparation must be within 1 mm. of the gingiva to allow enough room to set the lower anterior teeth over the barcoping assembly. Post and coping procedure. Adequate retention of the copings will depend almost entirely upon the root canal post. Stutz pivots* are employed for the post-coping because they afford excellent retention. The Stutz pivot consists of a tapered post which fits precisely into a tapered silver liner. (1) Prepare the root canal for the silver liner using an Ackerman bur* of the same size and taper as the silver liner (Fig. 4). (2) Place the Stutz pivots in the canal, and check for the desired depth for re*APM/Stern

Gold,

San Mateo,

Calif.

Fig.

8. The

bar-coping

Fig.

9. The

Stutz

assembly

pivots

is checked

are in divergent

root

for

adaptation

to the abutments

and arch

position.

canals.

tention of the post. A slight divergence of the canals is compensated for by parallel drilling in the root canals with the Ackerman bur. If the divergence of the canals is great, no attempt is made to parallel them, and Schubiger screwsIcz3 are used to attach the bar to the copings (Fig. 5). (3) Cement the silver liners to place with either the liner seater tool or a latchtype contra-angle bur which is shaped to conform with the silver liner. (4) Remove the seating tool from the silver liners, and the preparation of the teeth and liner is completed to the level of the gingival crest. (5) Seat the Stutz pivots into their liners (Fig. 6). (6) Apply adhesive to the posts. (7) Make a rubber-base impression of the anterior quadrant, extending at least 5 mm. distal to the teeth. (8) Lubricate the posts with petroleum jelly. (9) Pour the impression with die stone, and invest in a Di-Lokf tray. (10) Cut the cast at the midline for ease of wax-up. ( 11) Wax the copings to the post with an average thickness of 1 mm., invest, and cast with Type III hard gold (Fig. 7). (12) Rough polish the castings using rubber wheels. Soldering the bar and copings. ( 1) Anneal the bar and copings. Every effort must be made to eliminate soldering discrepancies which are magnified because of the length of the bar between the copings. (2) Use the cast in the Di-Lok tray for the soldering procedures. (3) Notch the ends of the bar to fit over the copings with the bar resting on the crest of the anterior ridge. (4) Use DuraLay$ to hold the bar in position on the copings. (5) Solder the copings to the bar one at a time. (6) Heat treat the soldered bar and copings at 750’ F. for 15 minutes. *AP:M/Stern

Gold,

San Mateo,

tLac:tona

Corp.,

Morris

Plains,

$Reliance

Dental

Mfg.

Company,

Calif. N. J. Worth,

Ill.

106

J. Prosthet. Dent. July, 1976

Marquardt

Fig. 10. The Schubiger screw system: A, the matched nut; threaded stud base; and D, the assembled Schubiger screw.

B, the

cylindrical

sleeve;

C, the

(7) Polish the soldered assembly. Sufficient solder should have been used to round off the ends and blend the bar into the copings. (8) Try the soldered bar and copings in the mouth to verify the adaptation of the copings to the abutments and the position of the bar in relation to the anterior ridge (Fig. 8).

ALTERNATE TECHNIQUE FOR DIVERGENT CANALS When the divergence of the Stutz pivots in the root canals is great, the Schubiger screw system is employed most effectively (Fig. 9). This system consists of a threaded stud on a base that is soldered to the post-coping. A cylindrical sleeve fits over the screw thread, and the sleeve is held in place by a matched nut screwed over it (Fig. 10). The bar is soldered to the sleeve. The paralleling of the threaded studs to the post-copings is accomplished with a surveyor and a special mandrel supplied with the unit. The Schubiger base is the same size as and is interchangeable with the Gerber stud units.” Should it become necessary to extract one of the roots, the bar-sleeve unit can be unscrewed and a Gerber stud unit attached to the threaded base of the remaining root, A disadvantage to this system is that it tends to raise the bar off the tissue, creating a space between the tissue and the bar. It may be necessary to bend or notch the bar near each end to bring the bar in contact with the tissue. (1) Make an impression of the anterior quadrant with the divergent Stutz pivots seated on the abutment teeth. (2) Construct the post-copings on the cast in the Di-Lok tray. This time the copings are made with a flat superior surface and parallel to each other for the base of the Schubiger screw. The tools needed for parallel soldering of the Schubiger screws are the Gerber screwdriver, a paralleling mandrel, and a soldering core. (3) Screw a Gerber 686C male post onto the Schubiger base, and insert it into the paralleling mandrel. *APM/Stern

Gold,

San Mateo,

Calif.

Volume Number

36 1

Dolder

Fig.

11. The

post-coping

Fig.

12. The

Dolder

_

Schubiger bar is notched

.-...-.-

14. The

sleeve

is fully

on the bottom

assembled for

mandibular

overdenture

is cut to fit over

107

on the cast.

the coping

and on the side for the sleeve.

-

Fig. 13. The Dolder bar/Schubiger ments and arch position. Fig.

screw

bar joint

.screw

coping

the soldered

assembly bar between

is checked

for

adaptation

to abut-

the copings.

(4) Place the Di-Lok cast with copings on the surveyor table, and align the copings with the paralleling mandrel. (5) Grind the copings to receive the Schubiger base; center as close as possible to a line drawn along the crest of the ridge between the copings and at right angles to the plane of occlusion. (6) Slightly loosen the Gerber post from the base. (7) Align the base to the coping, and attach the base to the coping with sticky wax. (8) Carefully remove the post with the paralleling mandrel. Repeat the same procedure with the second coping. (9) Screw the soldering core on, and antiflux the joint with a mixture of chloroform and rouge. (10) Invest the base and coping, and solder. ( 11) Assemble the post-copings with their soldered Schubiger base and sleevenut units on the cast (Fig. 11) . (12) Polish the soldered margins with the Schubiger screw fully assembled. (13) Place the Dolder bar on the cast to decide how it should be modified to

108

J. Prosthet.

Ma,rquardt

Fig.

15. The

Fig.

16. ‘The

spacer spacer

July,

is in position is cut

between

slightly

longer

the bar than

Dent. 1976

and the sleeve. the

sleeve

for

easy

removal

after

processing.

fit the ridge. The bar may need to be notched on the bottom for the coping and on the side for the sleeve (Fig. 12). (14) Attach one sleeve at a time to the annealed bar with sticky wax, antiflux, invest, and solder. (15) Heat treat the entire bar-screw coping assembly at 750’ F. for 15 minutes, and polish. (16) Check the completed unit in the mouth (Fig. 13).

FINISHING THE OVERDENTURE ( 1) Seat the bar assembly on the abutments. (2) Make final impressions using either rubber-base or silicone impression materials. The impression must be accurate and properly extended. When the root canals are not parallel, the soldered bar-sleeve unit is removed from the copings, and just the post-copings with their Schubiger bases attached are seated on the abutments. Examine the inner surface of the copings for undercuts in the path of withdrawal of the post, block out with wax, and lubricate with a light coat of petroleum jelly. (3) Box the impression, and pour it in artificial stone. (4) Reassemble the Dolder bar/Schubiger screw unit on the edentulous cast. (5) Make stabilized occlusion rims using Coe-Soft* in the undercuts and selfcuring orthodontic resin for the bases. (6) Register the vertical and centric relation. The interocclusal registration and wax try-in are accomplished without the bar-coping assembly to achieve the stressbreaker action of the bar joint. The bar and copings are removed from the master cast. (7) Mount the upper cast to the articulator with a face-bow and the lower cast with the vertical and centric registration. (8) Indicate a short to long range for the length of the upper anterior teeth on the upper occlusion block. This acts as a guide for space available when setting the lower anterior teeth over the bar assembly. (9) Return the bar and copings to the master cast. *Coe

Laboratories,

Inc.,

Chicago,

Ill.

Fig. 17. The bar assembly is fixed to the master anterior teeth are reset to the plaster core. Fig. 18. Retention sleeve.

-Fig.

19. The

Dolder

Fig. 20. 1Schubiger parallel.

of the lower

denture

--

can

cast

with

be adjusted

plaster

before

by bending

processing. the retentive

The

lower

clip

of the

. bar is soldered screws

are

used

directly to attach

to the copings the bar

with

to the

parallel copings

Stutz when

pivots. root

canals

are not

(10) Remove the records from the instrument to observe the interridge space. (11) Remove the bar-copings. (12) Arrange the teeth for the try-in. The artificial teeth must be set and reset until they meet both the functional and esthetic requirements of the indvidual patient. (13) Make a labial plaster core over the lower anterior teeth. (14) Remove the occlusion rim, and seat the bar-coping assembly on the cast. (15) Cut off the sleeve to fit over the soldered bar between the copings (Fig. 14). ( 16) Place the spacer in position between the bar and the sleeve, and cut slightly longer than the sleeve for easy removal after processing (Figs. 15 and 16) . (17) Fix the bar assembly to the master cast before processing. Scrape the surface of the master cast to be covered to be sure that the plaster will adhere to the stone. (18) Extend the plaster from the cast up to include the lower half of the spacer, leaving the retentive plate of the sleeve exposed. The copings should be covered with about 1 mm. of plaster to allow vertical activation of the denture and prevent

110

hdarquardt

J. Prosthet. Dent. July, 1976

denture base resin from creeping underneath the sleeveduring processing.Care must be taken not to let the plaster impinge on the border lingual to the anterior ridge. There should be a slight taper of the plaster occlusally with no undercuts for easein trial packing the denture (Fig. 17). (19) Remove the lower anterior teeth, and modify the occlusion rim to fit over the plaster bar-sleeve assemblyon the master cast. The plaster core is used as a guide to reset the lower anterior teeth. (2Ojl Grind the lower anterior plastic teeth to fit the bar assembly as closely as possible, yet with a minimum of space for retention by the denture base resin. The cingulum of the teeth must be slightly above the sleeve (Fig. 17). (21) Wax the dentures with adequate thickness over the sleeve to prevent breakage. (22) Make a plaster index of the upper denture with a remount jig, and set aside for remount at the time the dentures are placed in the mouth. (23) Invest the dentures, boil out, and apply tinfoil substitute. (24) Trial pack the lower denture at least twice, and processthe dentures. (25) Remount the processeddentures, wet the denture base resin opposite the attachment with a small amount of monomer, and correct the processing changes. (26) Remove the dentures from the master casts, take out the spacer, and polish the dentures. PLACEMENT OF THE DOLDER BAR ATTACHMENT AND DENTURES (1) Insert the dentures without the bar, and make necessaryadjustments in the tissue adaptation. (2) Try the bar in the mouth without cement, and insert the lower denture to check retention of the sleeve to the bar. Adjustments can be made by bending the retentive clip (Fig. 18). The proper amount of retention is that which will hold the denture in place when the patient speaks. (3) Make new interocclusal records, and with the aid of the remount jig, return the dentures to the articulator. (4) Cement the copings to the abutments (Figs. 19 and 20). While waiting for the cement to set, correct the occlusion on the remounted denture. (5) instruct the patient in oral hygiene procedures for plaque removal around the bar-coping assemblybefore final placement of the dentures. (6) Make postinsertion adjustments as needed. (7) Recall the patient at six-month intervals to check the occlusion and tissue adaptation of the denture. SUMMARY A ma.ndibular overdenture technique has been presented that utilizes the Dolder bar joint attachment. Endodontically treated lower canines were retained as abutments. Two techniques for attaching the bar to teeth with divergent root canals were discussed: ( 1) the Schubiger screw system for those teeth with extremely divergent canals and (2) the Stutz pivots system for teeth with only slightly divergent root canals.

Volume 36 Number 1

The use crown/root bone, forces offers slight action.

Dolder

bar joint

mandibular

overdenture

111

of the Dolder bar joint offers periodontally involved teeth an improved ratio and splinting of the teeth. Because the bar is close to the alveolar of mastication exert much less leverage to the teeth. Finally, the bar joint vertical and rotational movement of the denture as well as a stressbreaker

References 1. Dolder, E. J.: The Bar Joint Mandibular Denture, J. PROSTHET. DENT. 11: 689-707, 1961. 2. Dolder, E. J.: Bar Dentures, Int. Dent. J, 14: 249-251, 1964. 3. Preiskel, H. W.: Precision Attachments in Dentistry, ed. 2, St. Louis, 1973, The C. V. Mosby Company, pp. 141-150. 4. Linkow, L. I., Cherchtve, R., and Jones, M.: Theories and Techniques of Oral Implantology, St. Louis, 1970, The C. V. Mosby Company. 5. Morrow, R. M., Feldman, E. E., Rudd, K. D., and Trovillion, H. M.: Tooth-Supported Complete Dentures: An Approach to Preventive Prosthodontics, J. PROSTHET. DENT. 21: 513-522, 1969. 6. Morrow, R. M., Powell, J. M., Jameson, W. S., Jewson, L. G., and Rudd, K. D.: ToothSupported Complete Dentures: Description and Clinical Evaluation of a Simplified Technique, J. PROSTKET. DENT. 22: 414-424, 1969. 7. Swoope, C. C.: Prosthodontic Considerations in Tooth Removal, Dent. Clin. North Am. 13: 871-881, 1969. 8. Kabcenell, J. L. : Tooth-Supported Complete Dentures, J. PROSTHET. DENT. 26: 251-257, 1971. 9. Loiselle, R. J., Crum, R. J., Rooney, G. E., and Stuever, C. H.: The Physiological Basis for the Overlay Denture, J. PROSTWET. DENT. 28: 4-12, 1972. 10. Brill, N.: Adaptation and the Hybrid Prosthesis, J. PROSTHET. DENT. 5: 811-824, 1955. 11. Miller, P. A.: Complete Dentures Supported by Natural Teeth, J. PROSTHET. DENT. 8: 924-928, 1958. 12. Bascom, P. W.: Preservation in Prosthodontics, J. PROSTHET. DENT. 25: 489-492, 1971. 13. Brewer, A. A.: The Overdenture, Dent. Clin. North Am. 17: 7?3-746, 1973. 14. Brewer, A. A.: The Tooth-Supported Denture, J. PROSTHET. DENT. 30: 703-706, 1973. 15. Dodge, C. A.: Prevention of Complete Denture Problems by Use of “Overdentures,” J. PROSTHET. DENT. 30:403-411, 1973. 16. Maurer, C. R.: Complete Denture Construction on an Alveolar Process Containing Endodsontically Treated Roots, J. PROSTHET. DENT. 30: 756-758, 1973. 17. Crum, R. J., Loiselle, R. J., and Hayes, C. K.: The Stud Attachment Overlay Denture and Proprioception, J. Am. Dent. Assoc. 82: 583-586, 1971. 18. Crum, R. J., and Loiselle, R. J.: Oral Perception and Proprioception: A Review of the Literature and Its Significance to Prosthodontics, J. PROSTHET. DENT. 28: 215-230, 1972. 19. Crum, R. J.: Rationale for the Retention of Teeth for Overdentures, in Brewer, A. A., and Morrow, R. M.: Overdentures, St. Louis, 1975, The C. V. Mosby Company. 20. Zamikoff, I. I.: Overdentures-Theory and Technic, J. Am. Dent. Assoc. 86: 853-857, 1973. 21. Lord, J. L., and Teel, S.: The Overdenture, Dent. Clin. North Am. 13: 871-881, 1969. 22. Prince, I. B.: Conservation of the Supportive Mechanism, J. PROSTHET. DENT. 15: 327338, 1965. 23. Preiskel, H. W.: Precision Attachments in Dentistry, ed. 2, St. Louis, 1973, The C. V. Mosby Company, pp. 163-165. VETERANS ADMINISTRATION HOSPITAL 4150 CLEMENT ST. SAN FRANCISCO, CALIF. 94121