Treatment planning for removable partial dentures

REMOVABLE

TREATMENT

PARTIAL

DENTURES

PLANNING FOR REMOVABLE

PARTIAL

DENTURES

BENJAMINW. DUNN, COLONEL, USAF (DC) * USAF Hospital,

T

Lackland

Air Force Base, Texas

IS RESPONSIBLE for the design of removable partial dentures. This is not, and should not be, the responsibility of the dental laboratory technician. The dental laboratory technician has the responsibility to his profession to demand a quality of leadership and competence from the dentist which he can respect and f0110wwith confidence. The prescription for technical fabrication of removable partial dentures by a dental laboratory should consist of completely designed diagnostic casts and written instructions. This article offers an orderly step by step procedure that the dentist may follow to provide an adequate design on diagnostic casts. HE DENTIST

ARMAMENTARIUM

Certain materials are required to correctly design restorations on diagnostic casts. These are (1) a surveyor complete with a cast holder, an analyzing tool or stylus, and a carbon marker, (2) undercut gauges-O.010 inch, 0.020 inch, and 0.030 inch, (3) a red and blue? and a brownt crayon type pencil, and (4) a 4H or 5H lead pencil (Fig. 1) . COLOR CODE

Different colors are used on the diagnostic casts to indicate parts of the denture or procedures to be performed. The colors used are: (1) red-tooth surfaces to be ground, prepared, or recontoured, (2) blue-the acrylic resin denture base, (3) brown-the metal (framework or denture base), and (4) black-survey line and tissue undercuts. Presented as an essay tistry, Chicago, Ill. This article represents as a statement of oihcial Air *Chief, Department of tVenus-Unique 1211. tVenus-Unique 1212.

and table clinic

before

the American

Academy

of Restorative

Den-

the personal viewpoint of the author and is not to be construed Force policy. Prosthodontics, Directorate of Dental Services.

247

I?ig~ l.- The armamentarium

required

to design removable

Fig. 2 Pig. Z.-The marks indicate the teeth that will require Fig. 3.-The location of cuspal grinding to provide indlcared with red crayon pencil.

partial

dentures

Fig.

on diagnostic

casts.

3

rest preparations. additional space for

occlusal

rests is

“NilZE% ‘2’ PRELIMINARY

TREATMENT

PLANNING

EXAMINATION

FOR REMOVABLE

OF DIAGNOSTLC

PARTIAL

249

DENTURES

CASTS

The diagnostic casts are mounted on an articulator and examined carefully. The rest preparations are located and indicated by a mark on the base portion of the diagnostic cast (Fig. 2). Adequate rest preparations are essential. The extent and location of cuspal reductions to provide additional space for occlusal rests are indicated in red crayon pencil (Fig. 3). The lingual aspect of the occluded diagnostic casts is examined for adequate space on the maxillary anterior teeth for proposed lingual rests, indirect retainers, etc. A black lead pencil line is drawn on the lingual surface of the maxillary anterior

Fig. 4.-The

occluded lower anterior line on the lingual

Fig. 5.- Tube teeth, facings,

teeth are used as a guide to draw a black surface of the maxillary anterior teeth.

or metal pontics

are indicated

lead pencil

by a symbol on the diagnostic

cast.

250

Fig. G.-The

location

and extent

Fig. 7.

of occlusal corrections red crayon pencil.

and recontouring

are indicated

with

Fig. 8.

Fig. ‘I.-Three orientation or tripod marks are made on the maxillary diagnostic cast. Fig. 8.-- The tripod marks are crossed to pinpoint the position for orientation of the cast.

YceEr ‘,’

TREATMENT

PLANNING

FOR

REMOVABLE

PARTIAL

251

DENTURES

Fig. 9.

Fig. 10. are drawn on the teeth with a red crayon pencil. Fig. 9.- The rest preparations Fig. lO.-The metal denture base and framework design are outlined with brown pencil. Acrylic resin denture bases are outlined with blue crayon pencil.

Fig. Il.--The

survey

line is drawn

on the abutment teeth in the restoration

and other

teeth that

crayon

are involved

252

DUNN

Fig. 12.-The

selected undercut

gauge is placed so it contacts in the undercut.

the tooth at the survey

line and

teeth using the occluded lower anterior teeth as a guide to indicate the gingival and incisal limits of anterior rests or indirect retainers (Fig. 4). Tube teeth, facings, or metal pontics are indicated with a pencil, using the following symbols: T-tube teeth, G-facings, and M-metal pontics. Each symbol is marked on the art portion of the cast adjacent to the area where it applies (Fig. 5). ANALYZING

THE DIAGNOSTIC

CAST

The diagnostic cast is placed on a surveyor-cast holder at a level or horizontal tilt. The abutment teeth are examined with an analyzing tool to locate usable undercuts and to determine contour. If the teeth require recontouring, the location and extent are indicated with a red crayon pencil (Fig. 6). The most favorable tilt that will permit convenient and proper placement of clasps, minor connectors, anterior teeth, and denture bases is determined at this time.

Fig. 13.-The

undercut

gauge is positioned so that the head and shank touch the tooth simultaneously.

YE%:‘2’

TREATMENT

Fig. 14.- The location

ORIENTATION

PLANNING

FOR REMOVABLE

of the head of the undercut

OF THE DIAGNOSTIC

PARTIAL

DENTURES

253

gauge is marked with a black lead Pencil.

CAST

Using the tip of the surveyor carbon marker, a position of the cast is located that will permit three widely separated points to be scribed. The surveyor is locked and these three positions are marked in the same plane of orientation (Fig. 7). The marks are crossed with a black lead pencil to pinpoint the position of orientation (Fig. 8). This procedure permits accurate reorientation of the cast on the cast holder by either the dentist or the dental laboratory technician. DEVELOPING

THE BASIC FRAMEWORK

DESIGN

The diagnostic cast is removed from the cast holder for convenience. The rest preparations that are to be prepared in the mouth are drawn with a red crayon pencil (Fig. 9). Acrylic resin denture bases are outlined with blue and metal denture bases are outlined with brown crayon pencil. The metal framework design is drawn with a brown crayon pencil to harmonize and join the major connectors, indirect retainers, and minor connectors (Fig. 10).

Fig. 15.-The

mark

shown

in Fig. 14 represents the gingival engage the undercut.

edge of the clasp tip that

will

J. Pros. Den. March-April, 1961

DUNN

254 COMPLETING

THE DESIGN

The diagnostic casts are remounted on the cast holder by use of the orientation or tripod marks. Survey lines are drawn on the abutment teeth and other teeth that will be involved in the restoration (Fig. 11) . The carbon marker in the surveyor is replaced with the indicated size of undercut gauge depending on the undercut condition, length, and size of the proposed clasp arm. As a general rule, with chrome-cobalt alloy castings, the 0,010 inch gauge will suffice for short clasp arms and the 0.020 inch gauge for long clasp arms. The 0.030 inch gauge is used for extremely long, wrought wire, flexible clasp arms. Gold alloy castings of the same dimension will accommodate slightly larger undercuts than chrome-cobalt alloy castings.

Fig. l&--The

clasp arm is drawn with a double line so that the occlusal will be indicated to the dental laboratory technician.

Fig. 17.~Undesirable

soft tissue undercuts that may interfere restoration are indicated.

and gingival

with the insertion

of the

parts

“Nzz-‘2’

TREATMENT

PLANNING

Fig.

l&-The

FOR

designs

REMOVABLE

PARTIAL

DENTURES

255

are completed.

The selected gauge is placed on the undercut (Fig. 12) so that the head and the shank simultaneously touch the tooth (Fig. 13). This spot is marked with a pencil (Fig. 14), and it is verified with the head of the undercut gauge. The mark represents the gingival edge of the clasp tip that will engage the undercut (Fig. 15). The clasp arms are drawn with brown crayon pencil, scribing a double line so that the occlusal and gingival parts will be indicated to the dental laboratory technician (Fig. 16). The clasp arms must conform with the position and location of the survey line and the depth of the undercut to be engaged by the clasp tip. The position and extent of undesirable soft tissue undercuts that may interfere with the insertion of the restoration are indicated (Fig. 17). This completes the design of the restoration (Fig. 18). SUMMARY

A step by step sequence for the design of removable partial denture diagnostic casts by the dentist has been presented. CONCLUSIONS

1. Adequately designed diagnostic casts are an invaluable aid and guide in treatment planning. 2. Diagnostic casts designed by the dentist who initiates removable partial denture restorations constitute the best prescription for the dental laboratory. 3. Diagnostic casts serve as an excellent “blueprint” for the mouth preparation. ~F~QUA;TERS, Sk

&ANCISCO,

PACIFIC CALIF.

AIR

FORCES