he correct distribution of stressbetween the abutment teeth and the denture base has been a point of contention among the three schoolsof thought advocating broken stress,functional bases,and wide distribution of stress.Each of these methods has certain advantages and disadvantages.l This article describesa technique that takes advantage of the beneficial aspectsof each method. INDICATIONS FOR USE This method has been used only for patients demonstrating loss of supporting bone through periodontal disorders. The increase of the length of the clinical crowns of abutment teeth markedly increases the lever effect on these teeth. In addition, becauseof the taper of the root, the bony support decreasesat a faster rate than the vertical lossof bone might indicate. In many patients, this brings about a situation in which both the anterior and posterior segmentsof the mandibular dental arch are edentulous. A double rocking motion of the removable partial denture often ensues. ACCOMMODATION
FOR DISTRIBUTION OF STRESS
The first consideration should be mutual support for the teeth when the remaining teeth show bone lossand mobility.* A cast chrome-cobalt splint is designed to function in conjunction with the metal framework. The splint procures maximum gripping of each tooth without covering the buccal or labial surfaces. An embrasuretype rest preparation is made on the proximal occlusal surfaces of the remaining teeth and is extended onto the buccal or labial surfaces so that the teeth are retained by the splint. The lingual surface may be contoured to lower the survey line asthe splint should not go below the height of contour. The lateral segmentsof the splint are joined by a round, straight bar (Fig. 1). The bar is positioned so that it is horizontal and perpendicular to a line drawn be*AssociateProfessor
J. Pros. Dent. May, 1969
Fig. 1. The remaining natural teeth are stabilized by the splint which is in place. The round rigid bar serves as the major connector for the splint.
Fig. 2. The splint is designed to engage all remaining natural teeth, thus providing wide distribution of stress. The tabs on the framework fit over the bar and provide vertical support for the removable partial denture. The circumferential clasps are constructed of wrought wire.
tween the cuspids. The bar is placed at the lowest possible point without contacting the crest of the lower ridge. In some instances, paralIe1 surfaces are developed on the mesial surface of the cuspids to improve both the position of the bar and esthetics. By incorporating the splint and by distributing the stress over all remaining teeth, the removable partial denture satisfies the philosophy of distribution of stress (Fig.
FOR BROKEN STRESS
The partial denture framework is designed to rotate in the vertical plane only with the bar of the splint as the only vertical stop. Three tabs are cast as a part of the framework so they go over the bar at its lateral and middle aspects (Fig. 2). The tabs must be long enough so that they can be bent slightly around the bar, holding the two pieces together and allowing rotation of the framework. The framework is also cast in chrome cobalt and has the rigidity inherent in this alloy. Wrought-wire retentive clasps are used on the second bicuspids (Fig. 2). Any torquing force on these teeth is minimized, because they are held by the splint. To insure rotation about the bar, the shouIder of the clasp is ground slightly so that it is not in tight apposition with the splint. After the castings have been tried in the mouth and after the fit is verified, the
Fig. 3. The framework
has been joined with the bar.
Fig. 4. The completed appliance in the mouth.
castings are held firmly on the master cast, and the tabs of the framework are bent around the bar of the splint. This negates the possibility of the patient swallowing the smaller spiint. By incorporating the stress-breaking effect of rotation of the denture base around the bar, the removable partial denture satisfies the philosophy of broken stress (Fig. 3). Artificial teeth are selected, and the denture of wax is applied to the bar so that a space will the bar; otherwise, rotation may be impossible. ACCOMMODATION
base is processed. A slight coating exist between the acrylic resin and
After the denture has been processed and finished, the final step is a functional correction of the denture bases. The flanges and the tissue surface of the bases are reduced slightly. A tissue-conditioning material is utilized until a satisfactory impression has been obtained. Then the denture base is relined. The philosophy of a functional impression is now satisfied. ADDITIONAL
This method is much easier, quicker, and cheaper than fixed splinting. no margins which may be a factor in preserving the periodontal health.
There are The splint,
J. Pros. Dent. May, 1969
can be used if any of the remaining
SUMMARY A method for constructing a removable partial denture, which incorporates broad distribution of stress and the principles of broken stress and functional bases, has been described. This technique minimizes lateral stresses by keeping all forces in a vertical direction and by allowing rotation without torquing of the teeth. Stresses are distributed maximally by ( 1) employing a rigid splint on the remaining teeth, (2 ) the use of a rigid major connector on the partial denture framework, (3) lowering the fulcrum of rotation, and (4) extending the denture bases to the physiologic limit. References 1. 2.
Steffel, V. L.: Fundamental Principles 42: 534-544, 1951. Vig, R. G.: Splinting Bars and Maxillary tures, J. PROS. DENT. 13: 125-129, 1963. 129 E. LOUISVILLE,
J. A. D. Partial