Vibrator for casting amalgam dies in copper band and hydrocolloid impressions

Vibrator for casting amalgam dies in copper band and hydrocolloid impressions

VIBRATOR IN COPPER FOR CASTING AMALGAM DIES BAND AND HYDROCOLLOID IMPRESSIONS SAM KARLSTR~M, ODONT. DR., L.D.S., D.M.D. G&de, Sweden has been us...

2MB Sizes 0 Downloads 38 Views

VIBRATOR IN COPPER

FOR CASTING AMALGAM DIES BAND AND HYDROCOLLOID IMPRESSIONS

SAM KARLSTR~M,

ODONT.

DR., L.D.S., D.M.D.

G&de, Sweden

has been used for casting amalgam dies in copper band impressions of single teeth. The instrument and technique can be used for the preparation of amalgam dies in hydrocolloid impressions of entire dental arches and for vibration of plaster and acrylic resin to avoid air bubbles. The vibrator has two types of rotor components for the Inka Universal vibrator, model II. The lighter one, with a head of large diameter, produces a high frequency vibration with small amplitude. The heavier one, with a smaller head, produces a low frequency vibration and a larger amplitude which has a powerful penetrative effect. The lighter rotor is used for amalgam, and the heavier one is used for materials which exert a heavy damping action, such as plaster of Paris and acrylic resin. The former rotor gives forty-seven vibrations per revolution of the driving shaft, the latter six.

A

SPECIALLY

DESIGNED VIBRATORI

CASTINGAMALGAMDIESIN

COPPERBANDIMPRESSIONS

The lighter of the two rotors is used for casting amalgam dies in copper band impressions (Fig. 1). A suitable speed of the driving shaft is 4,000 r.p.m. or slightly higher.i AMALGAMDIESIN

HYDROCOLLOIDIMPRESSIONSOFENTIREDENTALARCHES

The vibrator unit fitted with the light rotor is inserted in the rubber-base block (Fig. 2). The water-jacketed impression tray containing the hydrocolloid impression is mounted on the vibrator. The amalgam is mixed, and by means of heavy finger pressure, the mercury is squeezed out so that the amalgam eventually contains less than that used for the preparation of dies made by the usual methods in compound impressions. The motor is switched on, and a small portion of the amalgam is inserted into the impression, where, under the influence of the vibration, it assumes a semifluid consistency so it is easily formed into all details of the impression. The condensation of the first small portion of amalgam is carried out with the help of a thin peg of wood wrapped in a few fibers of cotton, A larger portion of amalgam is then introduced and carefully condensed. When condensing amalgam in hydrocolloid impressions, it is advisable, but not absolutely necessary, to supplement the vibration from below with vibration from the surface. (This does not refer to the portions of amalgam first condensed.) For the surface vibration, the Inka intraoral vibrator2 is a suitable aid. The extra 962

Volume Numbrr

for

12 5

VIRRATOR

FOR

CASTING

Fig. l.-The Inka Universal vibrator, casting amalgam dies in copper band

AMALGAM

model impressions.

II,

DIES

adapted

IN

IMPRESSIONS

to a Doriot

handpiece

063

and

mounted

vibration ensures still denser and more compact amalgam dies. The Inka amalgam press can be used to squeeze out the excess mercury from the amalgam. The amalgam tablet produced in this way is broken into pieces which are placed in the impression and “melted” by double vibration, from below and on the surface. It is important that practically no pressltre be applied, otherwise deformation of the impression will result, and the die will not be a true representation of the shape of the original tooth. By means of a parallelometer, accurately paralleled model pins are inserted in each of the amalgam dies, and amalgam is packed around their bases. The Inka intraoral vibrator is an effective aid in this operation. VIRRATIOK

OF STRONGLY

DAMPING

MATERIAL

For the vibration of a strongly damping material, the vibrator unit is fitted with the heavier of the two rotors (Fig. 3). A suitable speed of the driving shaft is 4,000 r.p.ni.

Fig. a.--The vibrator with a water-jacketed impression tray mounted for preparation of amalgam dies in hydrocolloid impressions of entire dental arches. The two mutually opposite positions of the bridge plate demonstrate (A) a tray with the cooling tubes in the same plane as the bottom of the tray and (B) a tray with the cooling tubes forming an angle with the bottom of the tray.

Fig. damping

J. Pros. Sept.-Oct.,

KARLSTRijM

964

3.-The material.

vibrator

unit

fitted

with

the

heavier

rotor

mounted

for

vibration

Den. 1962

of a strongly

When the vibrator is to be used for removing air from freshly stirred plaster or stone (previbration) , the plaster bowl is placed on the vibrator table and kept in contact with it by pressing down with the plaster spatula. By moving the spatula to different places in the bowl, it is possible to make the entire mass practically bubble-free in a few seconds. During vibration of plaster or acrylic resin, the impression tray or bowl of acrylic resin is pressed firmly on the vibrator table throughout the procedure. VIBRATION

IN

FLASKING

PROCEDURES

The vibrator can also be used in flasking dentures. While the previbrated plaster is poured, the flask is placed over the vibrator and pressed firmly upon it. The absence of air bubbles during embedding of the denture in the plaster ensures an accurate reproduction of the wax surfaces of the flasked denture, and final polishing is facilitated. During vibration of plaster casts or flasks, the vibrator may be enclosed in a plastic bag so that the plaster does not spill and contaminate the vibrator. ADVANTAGES

OF THE

INKA

UNIVERSAL

VIBRATOR,

MODEL

II

1. The use of the different rotors enables the frequency of vibration to be varied practically at will. Thus, the vibrator has a wide range of use, including the vibration of amalgam, plaster, and acrylic resin. 2. In contrast to vibrators of the electromagnetic type, the instrument is not damped even when heavily loaded. This is important, especially when vibrating heavy flasks. 3. The sound the vibrator emits is not so loud as to be disturbing. Even when the instrument is fitted with the high frequency rotor for condensation of amalgam in hydrocolloid impressions and is workinpat several thousand vibrations per second, the sound is not irritating.

plgr

;2

VIBRATOR

4. Vibration strong dies.

FOR

CASTING

of amalgam

AMALGAM

into impressions

DIES

IN

IMPRESSIONS

produces extremely

96.5 smooth and

REFERENCES

1. Karlstrijm, S.: Vibrator for the Casting of Amalgam Dies in Copper Band Impressions, J.A.D.A. 59:266-269,1959. 2. Karlstrtim, S.: A New Vibrator for Amalgam Condensation and Removal of Calculus, J. PROS. DEN. NYCATAN 37 GAVLE, SWEDEN

10:586-590,

1960.