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The lower distal extension partial denture using the Hart-Dunn attachment
THE LOWER DISTAL EXTENSION PARTIAL USING THE HART-DUNN ATTACHMENT
DENTURE
ARVIN WILLIAM MANN, D.D.S. Fort
Lauderdale,
Fla.
ARIOUS SOLUTIONS TO THE distal extension partial denture problem have been described by Roach,l n’eurohr,’ Shopper, 3, 4 Branzi and associates,5 and others. Dunn6, 7 offered a new approach to the stabilization of partial dentures by using wires inserted into the interproximal embrasures just under the contact points. These were used to stabilize a transitional or temporary partial denture which was to be inserted immediately after extraction to preserve esthetics. It was to be worn only until the form of the tissues had become stabilized enough to allow construction of the permanent prosthesis. It remained for Hart,* however, to prevent the settling of the wires into the interproximal papillae and to stabilize the “embrasure hooks” by adding occlusal rests. He first used’this principle in distal extension partial denture construction by utilizing the Hart-Dunn attachment on the abutment of the opposite (denture base) side. This article will describe the technique for using a Hart-Dunn attachment to stabilize a distal extension partial denture. The attachment can be utilized with equal effectiveness on maxillary and mandibular partial dentures.
V
SELECTION
OF
ABUTMENT
TEETH
Either a second bicuspid or a first molar can be selected to engage the HartDunn attachment. It is preferable to locate the attachment in a fixed bridge pontic or a crowned tooth, but this is not essential. Occlusal rest seats are prepared mesially and distally to the embrasures which are to be used. These occlusal rest seats are more shallow and do not extend as far toward the center of the tooth as conventional occlusal rest seats. They also extend onto the occlusal surfaces of the teeth, adjacent to the one to be engaged by the Hart-Dunn attachment, so that a “bridging effect” is achieved with the occlusal rests. No preparation of the embrasures is required. The abutment tooth on the denture base side can be prepared either for a conventional clasp or for a precision attachment. SURVEYING
Because the Hart-Dunn attachment is inserted in a horizontal direction just prior to seating the clasp on the denture base side, the conventional surveys as Read before the Academy of Denture Prosthetics, Received for publication May 20, 1957. *E. R. Hart, personal communication. 282
Columbus,
Ohio,
April
30, 1957.
Volume 8 .\:umber 2
LOWER
DISTAL
EXTENSION
PARTIAL
DENTURE
283
described by Schmidt8 are of little value. Instead, a divider is used for surveying the cast. One point of the divider is placed on the center of rotation for the attachment (at a point midway between the embrasure hook and the occlusal rests), and the other end of the divider is swept over the buccal and lingual surfaces of the abutment tooth on the opposite side and over the lingual denture base area (Fig. 1) on the study cast. Either a precision attachment or a circumferential clasp can be utilized on the denture base side to lock the partial denture in position. However, these retainers must be on the arc scribed by the divider (Fig. Z),
Note how one Point of the divider is at the rotation center of the Fig. l.-Cast survey. The other point sweeps over the buccal surface of the tooth to be Hart-Dunn attachment. clasped and indicates freedom from objectionable undercuts.
Fig. P.-The arcs described by dividers (Fig. 1) on the abutment tooth and denture base. A, The solid tooth outline indicates the ideal alignment. The buccally inclined tooth (dotted outline) presents objectionable undercuts which must be eliminated. B, The arc of insertion of a precision attachment. C, The arc of insertion of the lingual clasp arm. D, The lingual margin of the denture base must be finished high enough to eliminate any undercut at this region. R, The point of rotation of the Hart-Dunn attachment.
284
in order that the attachment can first be seated horizontally, then the clasp or attachment on the denture base side is seated occlusogingivally. If the abutment on the denture base side is inclined toward the buccal, it presents an undercut problem. This can be solved best by constructing a cast crown to eliminate the undercut. Care should be exercised to keep the lingual border of the denture base high enough to prevent it from engaging an undercut. If a precision attachment is used, it may be necessary to round the linguogingival angle of the male attachment to allow it to seat on the correct arc.
(Note the holes punched in the Fig. 3.-The impression tray made of air chamber metal. These holes lock the alginate impression in the tray and metal with a rubber dam punch. A cast which is used for modeling plastic on the rim insures a sufficient bulk of algin’ate.) final fitting of the Hart-Dunn attachment is obtained from the impression. Note the detail in the interproximal embrasure areas. IMPRESSIOWS
A complete alginate impression which includes all detail of the entire proposed denture area is used for making the master cast. Since it is very difficult to record the correct interproximal detail from an impression which is withdrawn occlusally, an additional impression is made to record the occlusal rest areas and the interproximal embrasures in minute detail. A small tray is fashioned from air chamber metal, and retention for the alginate is effected by punching holes in the metal with a rubber dam punch (Fig. 3). Modeling plastic is adapted to the occlusal and gingival margins of the tray to provide a definite seat and adequate bulk of alginate impression material. The tray should extend over at least one tooth on each side of the abutment tooth selected, and it should stop short of the buccal surfaces. The tray is filled with the alginate impression material, additional alginate is wiped into and through the interproximal embrasures, and the filled tray is seated. After the alginate has set, the excess impression material in the buccal embrasures is removed so that when the impression is withdrawn lingually, a perfect impression of the lingual embrasure as well as the occlusal surfaces of the
LO\VER
DISTAL
ESTEXSIOK
I’ARTIAL
Dl:NTCRE
285
tooth selected is obtained: The cast poured from this impression is then used to refine the embrasures in the master cast (Fig. 3) and for the final fitting of the Hart-Dunn attachment after casting.
Undercuts are blocked out and the master cast is duplicated in a refractor! investment. Hart* suggests drilling holes in the refractory cast to carry 18 or 19 gauge rouiid clasp wires at a 35 degree angle from the occlusal plane. The wires are placed just under the contact areas in the mesial and distal embrasures of the selected abutment tooth (Fig. 4). The wires should be curved to allo\v eas) insertion and protection of the interproximal papillae. Plastic pins* have been inserted and used in a similar manner. The skeleton can be cast either with mesh for acrylic resin denture bases or with complete metal bases with tube teeth. Either stainless steel or gold can be utilized, although gold is preferable. .
Fig. 4.-The
embrasure
hook is placed at a 35 degree angle to the occlusal plane.
FINISHIKG
After casting, the Hart-Dunn attachment is carefully finished on the small cast so it fits accurately without binding. It is then fitted to the master cast (Fig. 5)) and the appliance is completed in a routine manner (Figs. 6 and 7). In seating the appliance in the mouth, the Hart-Dunn attachment must seat first, then the denture base and abutment clasp are seated on the survey arc. The denture is removed in just the opposite manner.
The dentist may choose to use either a precision attachment or conventional clasp on the denture base side. Either will work very effectively. Humphreys,” *E. R. Hart, personal communication.
286
Fig.
L-The
Fig.
G.-The
Fig.
7.--The
casting
finished
finished
is fitted
first
partial
denture.
to the small cast and then of the occlusal rests.
denture
Note
on the
the
cast.
Note
detail of attachment.
the
to the master
the
restoration
embrasure
cast.
Note
of functional
hooks
of
the
the detail
occlusion.
Hart-Dunn
LOWER
DISTAL
EXTENSION
PARTLIL
DEXTURE
287
Hollenback,l” and Pankey’l utilize a hook fitted into the pontic casting of a fixed bridge instead of embrasure hooks. One manufacturer* supplies a conventionally fabricated hook for the same purpose. RIOIJTH
IIYGIENE
Interdental stimulation, twice daily with a round wooden toothpick as described by 1Vestbrook,is McKenzie,13 Chace,l” and others, and diligent brushing of the lingual areas by Charter’s method, with a Twinhead+ toothbrush as described by I>ementl” is essential to prevent recurrent caries and also to keep the gingival tissues healthy. l)iligellt home cave is csselltial fo oval health rrlitlz any partial dc~ltzwe. DISCCSSION
The use of this attachment provides stable unilateral partial dentures which the patient is unable to “play with.” It not only prevents the upper teeth from extruding but supplies an astonishingly efficient masticatory surface. Thus, it appears that utilizing this attachment offers a good solution to the problem where one side has a sound distal abutment tooth and the other requires a distal extension denture base. A bridge (fixed partial denture) can be constructed on the one side, and a removable distal extension partial denture can be made to lock into the pontic of the fixed bridge on the other. This is much more effective than any design which involves the use of a bilateral partial denture.
1. The Hart-Dunn attachment utilizing an embrasure hook on a bicuspid or molar opposite the distal extension denture base has been described. 2. The method of surveying for the construction of this restoration has been described. 3. A small embrasure impression is used in addition to the complete arch impression in order to make the master casts for the construction. 4. The technique for casting, finishing, and completing the unilateral partial denture has been described. 5. Possible variations in the design of the partial denture have been discussed. The author manuscript.
gratefully
acknowledges
the help of Dr. E. R. Hart
in the preparation
of this
REFERENCES
1. Roach, F. E. : Mouth Survey and Design of Partial Dentures, J.A.D.A. 21:1166. 1934. 2. Neurohr. F. G.: Spring Lock and Insertion Pin Lock Attachments in Saddle Designs for Partial Dentures, J.A.D.A. 23:1530, 1936. 3. Schopper, A. F.: Value of Stressbreakers for Unilateral Partial Dentures \Vith Free End Saddles, J.A.D.A., 38:185, 1949 4. Schopper, A. F.: Value of Stress Breaker for Unilateral Partial Dentures 1Vith Free End Saddles, J. South. California D. A. 23:34, 1955. “Williams
:Lactona,
Gold Inc.,
Refining St. Paul,
Co., Buffalo, Minnesota.
N.
Y.
MANN
288 5. Branzi, 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
J, Pros. IJ~ii. March, 195s
A., and Zuccoli, G.: The Problem of Unilateral Removable Appliances, J. Philippine D. A. 6:9, 1953. Dunn, A. L.: A Safe Temporary Partial Denture, J.A.D.A. 23:96, 1936. Dunn A. L.: A Safe Transitional Partial Denture, D. Digest 45:64, 1939. Schmidt, A. H.: Planning and Designing Partial Dentures, D. Digest 54:444, 1948. Humphreys, Karl: Removable Bridge Using a Hook Attachment in a Tinker Pontic, J. California D. A. 2:372, 1935. Hollenback. G. M. : Personal communication. Pankey, L.’ D. : Personal communication. Westbrook, J. C., Jr.: A Pattern of Centric Occlusion, J.A.D.A. 39:407, 1949. McKenzie, J. S.: Some Periodontal Considerations in Partial Denture Planning, J.A.D.A. 45:314, 1952. Chace, R. : Personal communication. Dement. R. L.: Home Care of the Mouth and Its Importance, Fort. Rev. Chicago D. Sot. 24:11-14, 1952.
PR~FESSI~N.AL
RLDG.
SITKHISE CENTER FORT I..\mmn.mx
Fr,.l.
DENTURE
ARVIN WILLIAM MANN, D.D.S. Fort
Lauderdale,
Fla.
ARIOUS SOLUTIONS TO THE distal extension partial denture problem have been described by Roach,l n’eurohr,’ Shopper, 3, 4 Branzi and associates,5 and others. Dunn6, 7 offered a new approach to the stabilization of partial dentures by using wires inserted into the interproximal embrasures just under the contact points. These were used to stabilize a transitional or temporary partial denture which was to be inserted immediately after extraction to preserve esthetics. It was to be worn only until the form of the tissues had become stabilized enough to allow construction of the permanent prosthesis. It remained for Hart,* however, to prevent the settling of the wires into the interproximal papillae and to stabilize the “embrasure hooks” by adding occlusal rests. He first used’this principle in distal extension partial denture construction by utilizing the Hart-Dunn attachment on the abutment of the opposite (denture base) side. This article will describe the technique for using a Hart-Dunn attachment to stabilize a distal extension partial denture. The attachment can be utilized with equal effectiveness on maxillary and mandibular partial dentures.
V
SELECTION
OF
ABUTMENT
TEETH
Either a second bicuspid or a first molar can be selected to engage the HartDunn attachment. It is preferable to locate the attachment in a fixed bridge pontic or a crowned tooth, but this is not essential. Occlusal rest seats are prepared mesially and distally to the embrasures which are to be used. These occlusal rest seats are more shallow and do not extend as far toward the center of the tooth as conventional occlusal rest seats. They also extend onto the occlusal surfaces of the teeth, adjacent to the one to be engaged by the Hart-Dunn attachment, so that a “bridging effect” is achieved with the occlusal rests. No preparation of the embrasures is required. The abutment tooth on the denture base side can be prepared either for a conventional clasp or for a precision attachment. SURVEYING
Because the Hart-Dunn attachment is inserted in a horizontal direction just prior to seating the clasp on the denture base side, the conventional surveys as Read before the Academy of Denture Prosthetics, Received for publication May 20, 1957. *E. R. Hart, personal communication. 282
Columbus,
Ohio,
April
30, 1957.
Volume 8 .\:umber 2
LOWER
DISTAL
EXTENSION
PARTIAL
DENTURE
283
described by Schmidt8 are of little value. Instead, a divider is used for surveying the cast. One point of the divider is placed on the center of rotation for the attachment (at a point midway between the embrasure hook and the occlusal rests), and the other end of the divider is swept over the buccal and lingual surfaces of the abutment tooth on the opposite side and over the lingual denture base area (Fig. 1) on the study cast. Either a precision attachment or a circumferential clasp can be utilized on the denture base side to lock the partial denture in position. However, these retainers must be on the arc scribed by the divider (Fig. Z),
Note how one Point of the divider is at the rotation center of the Fig. l.-Cast survey. The other point sweeps over the buccal surface of the tooth to be Hart-Dunn attachment. clasped and indicates freedom from objectionable undercuts.
Fig. P.-The arcs described by dividers (Fig. 1) on the abutment tooth and denture base. A, The solid tooth outline indicates the ideal alignment. The buccally inclined tooth (dotted outline) presents objectionable undercuts which must be eliminated. B, The arc of insertion of a precision attachment. C, The arc of insertion of the lingual clasp arm. D, The lingual margin of the denture base must be finished high enough to eliminate any undercut at this region. R, The point of rotation of the Hart-Dunn attachment.
284
in order that the attachment can first be seated horizontally, then the clasp or attachment on the denture base side is seated occlusogingivally. If the abutment on the denture base side is inclined toward the buccal, it presents an undercut problem. This can be solved best by constructing a cast crown to eliminate the undercut. Care should be exercised to keep the lingual border of the denture base high enough to prevent it from engaging an undercut. If a precision attachment is used, it may be necessary to round the linguogingival angle of the male attachment to allow it to seat on the correct arc.
(Note the holes punched in the Fig. 3.-The impression tray made of air chamber metal. These holes lock the alginate impression in the tray and metal with a rubber dam punch. A cast which is used for modeling plastic on the rim insures a sufficient bulk of algin’ate.) final fitting of the Hart-Dunn attachment is obtained from the impression. Note the detail in the interproximal embrasure areas. IMPRESSIOWS
A complete alginate impression which includes all detail of the entire proposed denture area is used for making the master cast. Since it is very difficult to record the correct interproximal detail from an impression which is withdrawn occlusally, an additional impression is made to record the occlusal rest areas and the interproximal embrasures in minute detail. A small tray is fashioned from air chamber metal, and retention for the alginate is effected by punching holes in the metal with a rubber dam punch (Fig. 3). Modeling plastic is adapted to the occlusal and gingival margins of the tray to provide a definite seat and adequate bulk of alginate impression material. The tray should extend over at least one tooth on each side of the abutment tooth selected, and it should stop short of the buccal surfaces. The tray is filled with the alginate impression material, additional alginate is wiped into and through the interproximal embrasures, and the filled tray is seated. After the alginate has set, the excess impression material in the buccal embrasures is removed so that when the impression is withdrawn lingually, a perfect impression of the lingual embrasure as well as the occlusal surfaces of the
LO\VER
DISTAL
ESTEXSIOK
I’ARTIAL
Dl:NTCRE
285
tooth selected is obtained: The cast poured from this impression is then used to refine the embrasures in the master cast (Fig. 3) and for the final fitting of the Hart-Dunn attachment after casting.
Undercuts are blocked out and the master cast is duplicated in a refractor! investment. Hart* suggests drilling holes in the refractory cast to carry 18 or 19 gauge rouiid clasp wires at a 35 degree angle from the occlusal plane. The wires are placed just under the contact areas in the mesial and distal embrasures of the selected abutment tooth (Fig. 4). The wires should be curved to allo\v eas) insertion and protection of the interproximal papillae. Plastic pins* have been inserted and used in a similar manner. The skeleton can be cast either with mesh for acrylic resin denture bases or with complete metal bases with tube teeth. Either stainless steel or gold can be utilized, although gold is preferable. .
Fig. 4.-The
embrasure
hook is placed at a 35 degree angle to the occlusal plane.
FINISHIKG
After casting, the Hart-Dunn attachment is carefully finished on the small cast so it fits accurately without binding. It is then fitted to the master cast (Fig. 5)) and the appliance is completed in a routine manner (Figs. 6 and 7). In seating the appliance in the mouth, the Hart-Dunn attachment must seat first, then the denture base and abutment clasp are seated on the survey arc. The denture is removed in just the opposite manner.
The dentist may choose to use either a precision attachment or conventional clasp on the denture base side. Either will work very effectively. Humphreys,” *E. R. Hart, personal communication.
286
Fig.
L-The
Fig.
G.-The
Fig.
7.--The
casting
finished
finished
is fitted
first
partial
denture.
to the small cast and then of the occlusal rests.
denture
Note
on the
the
cast.
Note
detail of attachment.
the
to the master
the
restoration
embrasure
cast.
Note
of functional
hooks
of
the
the detail
occlusion.
Hart-Dunn
LOWER
DISTAL
EXTENSION
PARTLIL
DEXTURE
287
Hollenback,l” and Pankey’l utilize a hook fitted into the pontic casting of a fixed bridge instead of embrasure hooks. One manufacturer* supplies a conventionally fabricated hook for the same purpose. RIOIJTH
IIYGIENE
Interdental stimulation, twice daily with a round wooden toothpick as described by 1Vestbrook,is McKenzie,13 Chace,l” and others, and diligent brushing of the lingual areas by Charter’s method, with a Twinhead+ toothbrush as described by I>ementl” is essential to prevent recurrent caries and also to keep the gingival tissues healthy. l)iligellt home cave is csselltial fo oval health rrlitlz any partial dc~ltzwe. DISCCSSION
The use of this attachment provides stable unilateral partial dentures which the patient is unable to “play with.” It not only prevents the upper teeth from extruding but supplies an astonishingly efficient masticatory surface. Thus, it appears that utilizing this attachment offers a good solution to the problem where one side has a sound distal abutment tooth and the other requires a distal extension denture base. A bridge (fixed partial denture) can be constructed on the one side, and a removable distal extension partial denture can be made to lock into the pontic of the fixed bridge on the other. This is much more effective than any design which involves the use of a bilateral partial denture.
1. The Hart-Dunn attachment utilizing an embrasure hook on a bicuspid or molar opposite the distal extension denture base has been described. 2. The method of surveying for the construction of this restoration has been described. 3. A small embrasure impression is used in addition to the complete arch impression in order to make the master casts for the construction. 4. The technique for casting, finishing, and completing the unilateral partial denture has been described. 5. Possible variations in the design of the partial denture have been discussed. The author manuscript.
gratefully
acknowledges
the help of Dr. E. R. Hart
in the preparation
of this
REFERENCES
1. Roach, F. E. : Mouth Survey and Design of Partial Dentures, J.A.D.A. 21:1166. 1934. 2. Neurohr. F. G.: Spring Lock and Insertion Pin Lock Attachments in Saddle Designs for Partial Dentures, J.A.D.A. 23:1530, 1936. 3. Schopper, A. F.: Value of Stressbreakers for Unilateral Partial Dentures \Vith Free End Saddles, J.A.D.A., 38:185, 1949 4. Schopper, A. F.: Value of Stress Breaker for Unilateral Partial Dentures 1Vith Free End Saddles, J. South. California D. A. 23:34, 1955. “Williams
:Lactona,
Gold Inc.,
Refining St. Paul,
Co., Buffalo, Minnesota.
N.
Y.
MANN
288 5. Branzi, 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.
J, Pros. IJ~ii. March, 195s
A., and Zuccoli, G.: The Problem of Unilateral Removable Appliances, J. Philippine D. A. 6:9, 1953. Dunn, A. L.: A Safe Temporary Partial Denture, J.A.D.A. 23:96, 1936. Dunn A. L.: A Safe Transitional Partial Denture, D. Digest 45:64, 1939. Schmidt, A. H.: Planning and Designing Partial Dentures, D. Digest 54:444, 1948. Humphreys, Karl: Removable Bridge Using a Hook Attachment in a Tinker Pontic, J. California D. A. 2:372, 1935. Hollenback. G. M. : Personal communication. Pankey, L.’ D. : Personal communication. Westbrook, J. C., Jr.: A Pattern of Centric Occlusion, J.A.D.A. 39:407, 1949. McKenzie, J. S.: Some Periodontal Considerations in Partial Denture Planning, J.A.D.A. 45:314, 1952. Chace, R. : Personal communication. Dement. R. L.: Home Care of the Mouth and Its Importance, Fort. Rev. Chicago D. Sot. 24:11-14, 1952.
PR~FESSI~N.AL
RLDG.
SITKHISE CENTER FORT I..\mmn.mx
Fr,.l.