Precision attachment for denture construction

A prosthesis construction assembly for use in placement and alignment of dental bridge components for the fabrication of human tooth replacements, having a female member adapted to be deposited in a cavity provided in the distal side of an anchor tooth, with its longitudinal recess having two parallel side walls and a rounded mesial wall somewhat longer than the side walls so as to provide an end well in which a male member can pivot; and the male member having a rod portion also with a rounded first end and being sized to permit its sliding engagement and retention within the recess of said female portion; an outwardly oriented second flange portion integral with one arc of the rod portion surface and not extending beyond the point of said first rounded end. The second flange is adapted to provide a sliding abutment to the external surface of said first flange. An elongated bar portion is integrally attached to the other end of said male portion and abuts the proximal end of the second flange; and a transverse bar is disposed intermediate the ends of the mandrel portion and pinned thereto.

FIELD OF THE INVENTION 
This invention relates to the construction and mounting of partial 
dentures. In another aspect, it relates to a precision attachment which 
serves as a direct retainer of the partial or full denture made for 
support by abutment teeth. 
BACKGROUND OF THE INVENTION 
The individual component parts of partial dentures are the saddles, 
occlusal rests, direct and indirect retainers, and connectors. The saddle 
is that part of the partial denture which replaces lost alveolar tissue 
and carries the artificial teeth; they may be designated as free-end or 
bounded. In the former, an abutment is present only at the mesial 
(forward) end of the saddle; in the latter, an abutment tooth is present 
at both ends. 
Precision attachments are one type of direct retainer, the principal other 
one being the clasp. Retainers function to provide positive retention to 
the denture; and second, to provide bracing for the denture against 
lateral forces and to transmit these forces to the abutment teeth. They 
may be more efficient than a clasp but the clinical circumstances in which 
they are required calls for a careful assessment. Where their use is 
indicated, the attachments currently used are commercially prefabricated 
and may be classified into several types. The present invention is 
directed to an improvement in the intracoronal precision type. Such 
attachments have two parts - male and female. The female part is in the 
form of slot that is embedded into some type of restoration, such as a 
crown or inlay in the abutment tooth. The male portion of the flange that 
fits into the slot and is attached into the saddle of the denture (see 
FIG. 9.42 of Osborn et al.). This type of attachment provides rigid 
connections between the tooth and the saddle and further serves the 
purposes of a retentive clasp arm, a bracing clasp arm and an occlusal 
rest, all in one unit. Disadvantages of the present attachments include: 
a) extensive preparation of the abutment tooth is necessary, and for 
free-end saddle dentures, a minimum of two teeth on each side of the arch 
must be prepared and splinted together. The chair side and laboratory 
preparation times required are substantial together. Together with the 
cost of the precious metal attachments themselves, this results in an 
expensive partial denture. 
OBJECT OF THE INVENTION 
It is a principal object of this invention to provide a novel 
semi-precision type of attachment, using male and female matching parts, 
which are completely absorbed during the high temperature casting process 
for the crown and partial denture. It is another object to provide 
attachment mating parts which are interchangeable rather than calling for 
the precision tolerances of the prior art metal parts. It is still a 
further object to provide an attachment which, because of its reduced 
dimensions, can be utilized on any abutment tooth, and in particular, on 
the canines, that have markedly small surfaces than the premolars. 
Yet another object is the attachment that can be used as the free-end 
connector (normally a rigid bar or plate) in a broken-stress 
non-removable, partial denture. A still further object is a novel 
attachment which can stabilize the non-ridge connector in a broken-stress 
bridge (fixed partial denture). A yet further object is an attachment 
usable in either all tooth-borne (supported) or in a distal extension 
saddle (no natural teeth distal to the abutment tooth) removable partial 
dentures. 
These and other objects are accomplished by the accompanying specification, 
beginning with a summary of the invention and a brief description of the 
drawing. 
BRIEF SUMMARY OF THE INVENTION 
Accordingly, there is provided a prosthesis construction assembly for use 
in placement and alignment of dental bridge components for the fabrication 
of human tooth replacements, comprising a rod-like female member adapted 
to be deposited in a cavity provided in the distal side of an anchor tooth 
comprising a longitudinal recess within said rod having two parallel side 
walls and a rounded mesial wall somewhat longer than the side walls so as 
to provide an end well in which a male member can pivot during the biting 
stresses to be imposed on the replacement teeth, and wherein the recess 
presents an arched roof with parallel walls when viewed in a transverse 
section; a distally outwardly oriented first flange integral with the ends 
of the open face of the recess and defining an external planar surface 
except for the recess portion; and a male member comprising (i) a rod 
portion also with a rounded first end and being sized to permit its 
sliding engagement and retention within the recess of said female portion; 
(ii) an outwardly oriented second flange portion integral with one arc of 
the rod portion surface and not extending beyond the point of said first 
rounded end, said second flange adapted to provide a sliding abutment to 
the external surface of said first flange; (iii) an elongated bar portion 
integrally attached to the other end of said male portion and abutting the 
proximal end of said second flange, which bar serves as an upwardly 
positioned mandrel during manipulation of the female member for spatial 
orientation thereof during fabrication; and (iv) a transverse bar disposed 
intermediate the ends of the mandrel portion and pinned thereto which 
serves to permit manipulation of the assembly to attain the desired 
placement of the female portion relative to the sagittal plane of the 
prosthesis.

Referring now to the drawing wherein like parts have been designated by a 
like reference numeral, and to FIG. 1 in particular, in which a preferred 
form of the partial denture attachment assembly is shown. 
The denture construction attachment, generally 11, consists of two mating 
parts. The first of these is a smaller female member generally 12, adapted 
to be positioned and secured in a cavity (not shown) provided on the face 
of an abutment tooth. It includes an elongated generally cylindrical rod 
13, optionally having a rounded first end 14 and a distal flat second end 
15. A longitudinal recess 16 is disposed fully within said rod. This 
presents a rounded arch recess 16b (FIG. 4) having parallel opposing side 
walls, 17a and 17b, when viewed in a transverse section, taken along line 
IV--IV of FIG. 2. 
Hollow rod 13 is provided with an outwardly oriented first bilateral flange 
18a and 18b, which is integral with the wall ends (19a and 19b) of the 
open face 21 of the recess 16. This defines an external planar surface 22, 
except for the break caused by the recess portion 16. 
The other component is a larger male member, generally 23, comprising a 
smaller smooth rod portion 24, also preferrably with a rounded first end 
25, it being sized to permit its sliding engagement and retention within 
the long recess 16, both lengthwise and transversely, of female component 
12. There is an outwardly oriented second flanged portion 26 integral with 
one arc 27 of the rod surface (FIG. 7) with the flange end 28 extending 
slightly beyond the point of the rod's rounded end 25. Second flange 26 is 
adapted to provided for a sliding abutment with the external surface 22 of 
the first flange 18. The integration of arc 27 of solid rod 24 and flange 
26 is conveniently provided by a longitudinally aligned cradle 29 disposed 
between them and provided with a concave upper surface 30 (FIG. 7) that 
abuts rod arc 27. 
The preferably cylindrical, elongated handle portion, generally 31, is 
pinned to the proximal end 32 of solid rod portion 24, the proximal end 33 
of the flange 26, and the proximal end 34 of cradle 29 (FIGS. 5 and 6). 
Bar 31 serves as an upwardly positioned mandrel during manual manipulation 
of the male portion for spatial orientation thereof, to attain parallelism 
of abutting teeth during fabrication of the denture. A transverse bar 35 
is disposed intermediate the ends 36 and 37 of the mandrel rod 31. It is 
pinned thereto and serves to permit manipulation of the attachment to 
attain desired placement of the female portion relative to the sagittal 
plane. 
The typical dimensions of the attachment components in actual denture 
fabrication would run as follows: As to the female component 12, the well 
portion of the recess 16 will be 1.5 mm in length, an open face 21 width 
of 1 mm and an overall component recess 16 length of 5.5 mm. The parallel 
opposing side walls, 17a and 17b, are about 2 mm in height with arch 16a. 
The outward planar surface 22 is 7 mm in height and 3 mm in width with a 
flange 18 thickness of 0.5 mm. 
As to the male component 23, the rounded end 25 extends about 1 mm beyond 
the distal end of cradle 29 and has an overall solid rod length of 6 mm. 
Contiguous flange 26 is 7 mm in height, 4 mm in width, and 0.5 mm thick. 
The handle portion 31 of the male component 23, serving as a mandrel, is 22 
mm in length, with a transverse bar 35 being 18 mm wide. This bar is 
necessarily perpendicular to portion 31 and offset but parallel to in the 
plane 38 of the flange 26. 
In FIG. 8 is a perspective view of one of the male members 24a on which is 
already cemented a partial denture, generally 41, that includes artificial 
tooth 42, cross-arch support 43 and clasp 44 for the arch or tooth (not 
shown). This removable appliance would be joined in the mouth with a 
prepared anchor tooth (mating portion in place) as is shown in FIGS. 9 and 
10. 
The male and female portions of the novel attachment allow for frictional 
engagement of the parallel walls, 17a and 17b, of recess 16 with the 
parallel walls 39a and 39b of cradle 29, along with the sliding engagement 
of the flanged faces 22 and 26 in a vertical direction. There is no 
lateral or rotational movement of the male or female portions of the 
attachments when engaged. However, the attachment is so designed that 
there is possible a distal rotational movement of the male rod end 25 from 
the female portion 14 to allow for the functional displacement of the one 
from the other, and also to allow for functional displacement movements of 
the saddles, as in the case of a unilateral or bilateral distal extension, 
removable partial denture. 
Referring to FIG. 9, there is shown a top plan view of a molar tooth 
generally with the female part generally 12 being already mounted as an 
inlay in the distal aspect 42 of the anchor tooth 41. The parallel walls 
17a and 17b and arch 16 are evident and ready to engage the mating rod 24. 
By averting to FIG. 10, which is a vertical section of the attachment 
inlaid tooth of FIG. 9, taken along line X--X, elongated recess 16 with 
its pivoting well 47 to receive rotatably tip 25 of rod 24, is seen. 
Both attachment components are made of a precision moldable, thermoplastic 
resin material, which is also chemically inert, and can regulated to 
produce the typical dimensions described above to fairly close tolerances, 
so as to permit interchangeability of molded components. Each mating part 
should be capable of being volatilized in the high temperature casting 
process. Suitable inert resins are the polyolefins, for example, 
polyethylene or polypropylene. 
METHOD OF USE OF THE ATTACHMENT INVENTION 
The versatility and indications for its use and accuracy, simplicity, 
rapidity of setup and economy, allow for ready acceptability of the novel 
attachment. When the attachment is selected for use in a specific case, 
the study cast prepared from the patient's mouth is analyzed for vertical 
parallelism of the abutments (to permit partial denture insertion and 
removal). Attachment lengths (a minimum of four mm) are outlined in pencil 
on the cast, where, and in which direction the attachments will be placed. 
The anchor teeth are prepared in the mouth, and the areas outlined on the 
study cast are used to guide the placement (by drilling) of the recessed 
cavities for the inlaid attachment. 
The ensuing working guide model is again placed on the surveyor and the 
anchor teeth recess areas are analyzed for parallel placement of the 
attachments. Placement of the attachments are determined by placing the 
mandrel rod of the male portion into the surveyor arm (not shown). With 
the female portion in place on the male portion in the surveyor, placement 
of the position of the female portion of the attachment is determined for 
each tooth abutment. In the design of a bilateral, distal extension, 
removable partial denture abutment, the placement of the female portion is 
critical. The female portions when placed in crossarch abutment retainers 
must be parallel in both the vertical and sagittal directions. 
Mandrel portion 31 of the male member allows for parallel vertical 
placement of the female portion 12 in cross-arch abutments on the 
surveyor. 
The cross-arch rod 35 of the male portion allows for parallel placement of 
the female portion relative to the sagittal plane of the denture for 
cross-arch abutment on the same surveyor. 
This necessary parallelism in both the vertical and sagittal planes allows 
the male cross-arch portion of the attachment, as placed in the framework 
of a removable partial denture, to pivot (rotate) distally about the pin 
well from the female portion of the cross-arch abutment, with gingival 
displacement of distal extension saddles of a removable partial denture. 
The female portion is waxed to place on the wax-up, as part of the wax 
pattern for the abutment retainer. The abutment retainer, wax pattern, 
with the female portion 12 as an integral part of it, is invested and 
cast. After casting and finishing, the casting is seated on the abutment 
die in the model, and it is again checked for accuracy and fit of the male 
portion of the attachment into the female portion. 
When accuracy of the attachments (parallelism, etc.) is established and 
confirmed on the surveyor, the continuation and fabrication of the other 
parts of the denture may continue. Depending upon the use of the 
attachment, the male portion thereof may be cast as part of the pontic 
(replacement for absent tooth) directly in a brokenstress bridge. 
In the case of the use of an attachment for a bilateral distal extension 
type of removable partial denture, the parallelism is established for the 
female portions of the cross-arch abutment retainers. The lingual 
(tongue-side) portions of these bilateral cross-arch abutment retainers 
waxed patterns are surveyor-carved to receive non-retentive lingual 
bracing arms, on the framework of the removable partial denture. A notch 
or dimple is cut into the wax of the non-retentive lingual surface on the 
mesial (front facing) aspect. The cast lingual arms of the framework of 
the removable partial denture, will, in turn, have a small raised bleb 
(boss) on the internal surface of the clasp to engage the notch or dimple 
in the non-retentive surface of the lingual surface of each cross-arch 
abutment retainer. 
In the case of the use of the attachment with a removable partial denture, 
the male portion of the attachment can be cast separately, as part of the 
partial denture framework along with the clasp arm.