US2682706A - Denture clasp - Google Patents

Description

July 1954 L. E. JOHNSON 2,682,706

DENTURE CLASP Filed Jqn. 12, 1953 INVENTOR. Leonard E. Johnson ATTORNEY Patented July 6, 1954 UNITED STATE t ATENT OFFICE.

This invention relates to prosthetic dentures 8 Claims. (Cl. 32-5) and dental restorations and appliances of the,

type characterized by mounting and positioning means detachably engageable with a remaining natural tooth, or teeth, adjacent the denture, restoration, or appliance, and more particularly to the tooth-engageable mounting and positioning a novel and improved denture clasp susceptible of convenient and repetitious separation from an associated abutment tooth without deformation or permanent distortion.

A further object of the invention is to provide a novel and improved denture clasp adapted for secure, operative coaction with a selected abut- .ment tooth of any particular conformation ap-' propriate for such use.

A further object of the invention is to provide a novel and improved denture clasp amenable to production in fitted relation with a selected abutment tooth through moderate and facile variation of conventional techniques and laboratory practices.

A further object of the invention is to provide a novel and improved denture clasp that is simple of economical production, characterized by wide utility and pronounced operative advantage, variable in detail with full retention of primary operative relationships, and reliable throughout a long life of practical usefulness.

With the foregoing and other objects in view, my invention consists in the construction, arrangement, and combination of elements as hereinafter set forth, pointed out in my claims, and illustrated by the accompanying drawing, in which- Figure 1 is a plan view of an exemplary dental restoration as mounted and retained in position of practical use by means of a plurality of clasps typically embodying the principles of the invention.

Figure 2 is a side elevation of the arrangement simple dental restoration as positioned for practical use through the agency of clasps embodying the principles of the invention.

Figure 4 is a side elevation of the arrangement according to Figure 3.

Figure 5 is a fragmentary, detail elevation, on a relatively enlarged scale, of a representative denture clasp exemplifying the principles of the invention.

Figure 6 is a cross section taken substantially on the indicated line 66 of Figure 5.

Figure '7 is an elevation, relatively enlarged, of associated elements requisite to the production of the improved clasps as interrelated at one stage of such production.

Figure 8 is a vertical section medially of the organization shown in Figure '7.

In the art of prosthetic dentistry it is conventional practice to construct partial restorations of diverse particularity as removable and replaceable units characterized by an embedded, rigid, metallic member carrying integral end extensions formed as clasps adapted to embracingly engage with and about sound natural teeth functioning as abutments for the proper support and detachable positioning of the restoration. To accomplish the ends for which they are designed, the clasps associated with partial dentures should engage the abutment teeth to which they are fitted without damage to or occasion for deformation of such teeth and in a manner to positively secure and support the denture for use while facilitating optional and repetitious removal and replacement of the denture, all without the presence of tissue-lacerating and foodentrapping features. The design and production of suitable denture clasps' has long taxed the ingenuity of technicians with results somewhat less than satisfactory, hence the instant invention is directed to the provision of a novel and improved denture clasp susceptible of production with but slight modification of known techniques and procedures and characterized by enhanced operative properties.

Representative of the many particular restorations wherewith the clasps of the instant invention may be utilized With advantage, Figures 1-4,-

inclusive, illustrate approximate forms of the improvement as developed for and applied to practical use. ance accomplishing the restoration of the four incisors and of the two first molars of a single upper jaw as arranged to be positioned and securely mounted by means of four clasps adapted to engage the second premolar, or bicuspid, and

Figures 1 and 2 show a dental applithe second molar at each side of the jaw, while Figures 3 and 4 show an appliance accomplishing the restoration of the first molar and second premolar, or bicuspid, at one side of a lower jaw as arranged to be positioned and securely mounted by means of two clasps adapted to respectively engage the first premolar, or bicuspid, and the second molar adjacent the ends of the restoration; such appliances being, in and of themselves, conventional and' merely typical of restorations with which the novel clasps of the invention may be advantageously employed.

Briefly, in Figures 1 and 2 is shown a rigid; metallic, T-shaped member comprised fronr a transverse bar and a stem ll perpendicularly,

interrelated to project the stem H anteriorly of" the jaw. The free end of the stem ll. carries;

four incisor restorations i2 thereon disposed to fill the gap between the canines l3 and the free ends of the bar it) individually mount a first molar: restoration. MI thereon: disposed: to fill the gap: at. each side of the jaw between the second molar I5 and the proximate: second premolar, or:=bicuspi'd-,.la6; The second-molars I5; and second premolars l6 of the diSClOSllhB'fl'BPfGSBIlt' soun'd natural teeth suitable to. serve: as abutments? for anchorage of the appliance through the agency of end-opening, yoke-type clasps ll integrally and oppositely outstanding from free ends- 0f about" the first premolar, or bi'cuspid, 20 as anabutment and from'thezposterior end. of which extends aside-opening, yoke-type clasp I' l" for engagement with: and about: the second molar 21' aszanj abutment. Endor side-opening yoke type: cl'asps in association with and for toothengagement to. position and operatively mount dental?restorationsare, in general, old in the arrangements illustrated" and in many: other particular dispositions, that which distinguishes-the clasps. of the present invention being a novel construction. applicable to either or both of-"tha arms. of. a. given clasp, as hereinafter described; to condition the clasp for automatic, positive,- interl'ockzing' coaction with: the associated abutment tooth inan enhancement of" claspgrip readily yieldable to" pressures appliedior disengagement' ofthe clasp from the tooth,

The essential novelty of the invention, clearly manifest in Figures 5 and 6; resides in a contour of the clasp'arm inner'wallsor facesconformed to and tooverlie the maximum bulgezone of theabutm'ent tootlr wherewitli the particular claspis adapted"- to' engage, in the": provisionof a slit intersecting the thickness of eitheror both of the clasp arms longitudinally thereof and extending from an open end adjacent the clasp arm root to a closed end'termination spaced inwardly from the clasp arm tip: along the. line of maximum tooth bulge as evidenced on the clasp arm inner face or wall, and in an inclination of said slit through the clasp arm thickness sucl t as resists; by'v-i'rtue of wedging: action: between the're1ative1yslidable=, adjacentislit' faces, flex-ure' of the slit-freedi clasp: arm portion away from the root area of the clasp arm. Whileathe. novelties of the invention are manifestly applicable to side-opening, yoke-type clasps H the general construction represented in plan Figure 3, Figures 5 and 6 show such novelties edeveloped in and to modify both arms of an endopening, yoke-type clasp H integrally outstanding from a rigid, metallic, denture base member or bar 22, such as one end of the bar H). As shown, and is usual practice, the arms 23 and 23' of the clasp ll taper in elevation and in thickness fromimaximumat the I'OOtC-ffthG clasp where it merges with the member or bar 22 to minimum at the spaced, free tips 2t and 25, respectively, of said arms, thus to progressively, and, obviously, vary the inherent flexibility of the so-constituted arms. Giving effect to the principles of the invention, the inner, spacedlyopposedfaces of the arms 23 and 23' are conformably contoured to overlie the zone of maximum bulge characterizing the abutment tooth wherewith the clasp is toicoact, such contouring resulting from; molding or' casting the clasp arms ona-ndabout a replica of the actual tooth, as hereinbelow elaborated, and. a slit, 25 for.

the: arm:.23 and 25 forthe arm 23 divides the:

width. and: opens through thethickness of: each of, the clasp arms' in: a disposition longitudinally of: each arm.- determined. at the arm inner face.

by the line'of maximum; inner face concavity, or maximum: tootht bulge, and such as to open through the; root. of: the; arms. at one end; and to terminate at the. other end in spaced relation inwardly from. ther arm tip 2 or 24", such" slit disposition resulting in the definition of: an arm finger portion, 26 for the arm 23L'and126? for the arm: 23., havin'gJa. free end adja'c'ently'underlying. the. root portion of the: associated clasp arm and. a. zone of; attachmentzto. said: arm; not farremoved from the arm tip where the arm origin-a1 thickness has been: reduced by normal: arm. taper to.-accommodate:aniavailable degree. of fiez-rure at the junctionof. the arm finger portion with the arm body. from which said. finger portion is freed for limited lateral relative swingsby' virtue of the slit just described. The: arm finger'portion 26; or: 26., is' conditioned to engage with its concaved inner face conf'ormably fitted againstthe inwardly=tapered, or undercut, area of the abutment tooth thereby. circumferentiall'y: embraced at' the gingival side. of the tooth line of maximum bulge, thereby. introducing occasi'on forlat'erall'y' outward swing of the finger portion relative to the associated. arm whenever the clasp. H, or I1 is shifted' in either direction axially of the abutment tooth to pass=the gingival margin of the clasp across the tooth line of respondingly more resistive to fiexure from. its

junction with theclasp arm to its-tip and the associated clasp arm 23', or 23, is progressively thinner andcorrespondingly less resistive to fiexure from said junction and to its tip 2 1, or

2 whence it follows that the forces incident to claspshift on the" abutment t'oothwhich tend to swing the finger portion free end laterally and outwardly relative to the clasp act through said" finger' portion,- and" the associated clasparm to bind the arm tip2'4'; or2'4 in a close overlay with the tooth bulge zone thereby engaged and to introduce the necessity for a slight springing.

apart' o'f the. clasp arms 23." and 23", as. well as outward springing of the finger: portions 25- and- 261,..to p'ermitiseatingofrtherolaspmn, or separation of the clasp from, the abutment tooth. Thus, influences t'ending to unseat the clasp H, or H from coacting relationwith the abutment tooth are resistedby the reluctance of the relatively-stiff finger portion 26, or 26', to yield outwardly and by the consequently enhanced grip of the arm tip 24,; or 24', against the abutment tooth in reaction to initial outward swing of the finger portion, which resistances and reactions serve to retain the clasp in firmly-seated engagement with the abutment tooth until theunseating influences attain a magnitude adequate to separate the clasp arms 23 and 23' and to simultaneously flex the associated finger portion, or portions, outwardly beyond the superjacent clasp arm reaches.

While embodiments of the concept characterized'by a slit '25, or 25', formed with its plane transverse ofth'e associated clasp arm-perpendicular to a plane tangent to the tooth maximum bulge throughout the slit length, thus to accommodate relative lateral swing of the finger without resistance other than that deriving from the stillness of the materials employed,'are 'within the contemplation of the invention, it is expedient in many clasp constructions, particularly those developed from more pliant materials and with relatively thin sections, to augment the resistance of the finger 26, or 26', to

outward lateral swing relative to the associated clasp arm through an inclination of the slit transverse plane outwardly and convergently with respect to the arm and finger gingival margin such as operates to develop a wedging action between the adjacently-parallel slit faces when and as the finger issprung outwardly relative to the clasp arm,jsuch inclination of the slit transverse plane being clearly indicated in Figures 5 and 6. With the slit transverse plane inclined as shown and described, it is obvious that resistance to finger portion outward swing increases as the outward relative displacement of the finger portion increases and it is likewise manifest that the degree of resistance to outward finger swing introduced through inclinae tion of the slit transverse plane may be varied and adjusted at the time of clasp production through appropriate variation in the degree of plane inclination.

Either sideor end-opening, yoke-type clasps incorporating the novel features of the invention in either one or both of the clasp arms are susceptible of production through the application of but slightly modified, known techniques; the significant modifications of conventional techniques requisite for such production being exemplified in Figures '7 and 8. In the lastnoted views, the numeral 21 designates a cast facsimile or replica, commonly constituted from plaster, of an abutment tooth to and for which a denture clasp is to be fitted, the development of such replicas and facsimiles as a phase of denture and denture clasp production being a customary incident of conventional laboratory procedure, and the numeral 28 designates the wax mock-up, or pattern, representing the ultimately-desired metallic clasp elements as partially perfected on and in appropriate relation with the facsimile 21 in accordance with established practice. Conventionally, the wax pattern 28 is completed in simulation and in the use position of the ultimately-desired clasp and is then invested, together with its' supporting facsimile 21, within a suitable refractory overlay adapted to receive and shape molten metal thereto introduced in replacement for the pattern 28. Adapting the conventional techniques indicated to the production of the novel and improved clasp hereinabove described, the facsimile 21 is first marked, in any suitable manner and by any appropriate means, to clearly indicate thereon the line interjoining successive points of maximum tooth bulge or lateral protrusion and the area to be covered by the clasp is then outlined on the surface of the facsimile as a guide in shaping the pattern 28. Prior to application of the pattern 28 material, the line of tooth maximum bulge is scored or incised intothe material of the facsimile 21, as at 29, to groove the facsimile surface at the location and along the length of the slit, or slits, to be developed in the ultimate clasp arms, and thin sheets or laminae 30 of smooth, refractory material, such as mica, are edge-engaged in and shaped to follow the length of the scored or incised grooves 29 in position to simulate the slits 25, or 25', of the finished clasp arms. With the sheets or laminae 30 in place on the facsimile 21 in widths greater than the clasp arm thicknesses, the pattern 28 is shaped and completed on the facsimile and at both sides of said elements 30 with outer edges of the latter projecting beyond the pattern outer surface, whereafter the pattern and the outer edges of the elements 30 are invested in a usual manner and the moulding of the metallic replacement of the pattern is conventionally completed, engagement of the element 30 inner edges in the groove of the facsimile 21 and of the element 30 outer'edges in the refractory investment positioning and immobilizing said elements during substitution of molten metal for the wax pattern 28. Casting of the metallic clasp having been completed, the investment is broken away and the clasp unit is separated from the facsimile 21 and elements 30, all in an obvious manner, to leave ready for trimming, polishing, and use the clasp l1 featured by its slits and finger portions in the operative arrangement shown and hereinabove described and in a transverse inclination of the adjacent slit faces determined by the inclination of the elements 30 when and as embedded in and to traverse the material of the pattern 28.

Since changes, variations, and modifications in the form, construction, and arrangement of the elements shown and described may be had without departing from the spirit of my invention, I wish to be understood as being limited solely by the scope of the appended claims, rather than by any details of the illustrative showing and foregoing description.

I claim as my invention:

1. A denture clasp comprising an interrupted, yoke-type band adapted to removably and replaceably embrace and to conformably overlie the maximum bulge zone of an abutment tooth and an integral finger portion at the gingival side of said band defined by a slit intersecting the band thickness in registration at its inner edge with the line of maximum tooth bulge and extending at one end through the gingival margin of the band, whereby to condition said finger for independent fiexure relative to the hand;

2. A denture clasp comprising an interrupted, yoke-type band adapted to removably and replaceably embrace and to conformably overlie the maximum bulge zone of an abutment tooth, the arm portions of said band being tapered in width and in thickness from a substantially rigid, common root area to their relatively more flexible sesame 7. tips=,.and an integral finger portion at the gingival side of at least one; of said arm portions defined; by a slit intersecting theband thickness in registration at, its inner edge with the lineof maximum tooth bulge, saidslit terminating, in inward-1y spaced relation with the tip of the associated arm and opening to the'gingivalside'of the arm through the root area thereof.

3' A' denture clasp. comprising an interrupted; yoke' type band adapted to removably' and: replaceably embrace and to-conformably overlie the maximumbulge: zone' of an abutment tooth; an integral finger'portion at thegingival side of said band defined by a slit intersecting the band thickness registration: at its inner edge-with thel-inezot maximum tooth bulge, and an inclination of: the slit plane laterally and toward the gingivalsideof the-associated arm productive of wedging' action in resistance to flexure of said finger portion outwardly of its clasp arm.

4; A. denture clasp comprising an interrupted, yoke-type band adaptedto removably and replaceably' embrace. andto conformably overlie the maximum. bulge zone of an abutment tooth, the arm portions: of said band being tapered in Width and in thicknessfr-om a substantially rigid, common root area to their relatively more flex-- ible tips,.an integral finger portion-atthe ging-ival side, ofat least one of said arm portions defined by a. slit intersecting the band thickness in registration-at its-inner edge with the line of maximum tooth bulge, said slit terminating in inwardly spaced relation Withthe tipof the associated arm and opening to' the gingival side of. the arm through the root area thereof, and an inclination oi the slit plane laterally and toward the gingivalisideof the associatedarm-productive of wedging actionin resistance to fiexure of said finger. portionoutwardlyof its clasp arm.

5s Ina denture clasp-characterizedlby' an inter-- rupted, yokeetype band adapted. to embrace and to. conformably overlie the maximum bulge zone ofan abutment tooth, means for detachably clamping said bandito and in secure mounted re-- lation. on said tooth, said means comprising an integral finger portion at the'gingival side of andcapable. Of independent. fiexure relative tothe band defined by a slit intersecting the band-thickness inregistration at its/inner edge. with the: line ofv maximum tooth bulge and extending at one endithrough the gingival margin of the band 6-. In a dentureiclasp characterized byan-interrupted, yoke-type bandadapted' to' embrace andto: conformably overlie the maximum bulge zone ot an: abutment. tooth means for detachably clamping said band to-aml in secure-mounted re=-* lation' on said tooth, saidmeans comprising an integralv finger portion at the gingivalsideof the band defined by'a slit intersecting the band thickness in inner edge registration with the line of maximum tooth bulge, and an inclination or the slit plane laterally" and toward the gingivalside of the band productive: of wedging. action in re'- sistance to fi'exure of said finger portion outw ardly of'the band.

'1. In a denture clasp characterized by an interrupted, yoke-type band having. arr-n portions tapered in- Width and thickness from asubstantially rigid, common root area to-relatively more flexible tips and inner faces on-saidarmportions contoured to embrace andconformably overlie the maximum bulge zone of an abutment tooth; meansfor detachably clamping said band to and insecure mounted relation on said tooth, said means comprisingan integral finger portion at the gingivalsideof at. least one of said arm portions defined: andconditioned for fiexure relative to the associated arm portion by a slit intersectingthearmiportion thicknessin inner edge registration withv the line of maximum tooth bulge and opening to the'gingival side of the said arm portion through the root areathereoi 8. In a. denture clasp characterized by aninterrupted,. yoke-type bandv having armportions tapered-inwidth and thickness from asubstantially rigid, common root area to relatively more flexibletips andinnerv faces. on said. arm portions contoured'to embrace and conformably overlie the maximum. bulge zone of an abutment tooth, means. for detachably clamping said band to and in secure mounted relation on. said tooth, said means comprising an integral. finger portion at the gingival side of at least one ofsaid arm portions defined and conditioned for fiexure relative to the associated arm portion by a slit intersecting the arm portion thickness in inner edge registration with the line of. maximum tooth bulge and opening to the gingival side of the said arm portionthr'ough the root area thereof, and an inclination of, the slit plane laterally and toward the gingival side of. the said armportion productive of'wedgin'g action in resistance to flexure of said finger portion outwardly of the band.

Name Date Aderer May 13, 1924 Number

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