Revised American Dental Association Specification No. 4 for dental inlay casting wax

Revised American Dental Association Specification No. 4 for dental inlay casting wax

Revised American Dental Association Specification No. 4 for dental inlay casting wax Council on Dental Materials and Devices The following revision ...

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Revised American Dental Association Specification No. 4 for dental inlay casting wax

Council on Dental Materials and Devices

The following revision of American Dental A s­ sociation Specification No. 4 for dental inlay casting wax has been approved by the Council on Dental Materials and Devices of the Amer­ ican Dental Association. The revision of the specification was carried on through the Amer­ ican National Standards Committee MD-156 and its subcommittee on waxes. The Council acknowledges, with thanks, the work of the sub­ committee members: George Dickson (chair­ man), Dental Research Section, National Bu­ reau of Standards, Washington, DC; T. E. Fis­ cher, School of Dentistry, University of Ala­ bama, Birmingham; F. H. Freeman, Kerr Mfg. Co., Romulus, Mich; Paul R. Kulp, Dentsply International, York, Pa; John M. Powers, School of Dentistry, University of Michigan, Ann Arbor, Mich; and J. D. Eick (secretary), Department of Dental Materials, School of Den­ tistry, University of N ew York at Buffalo, Buf­ falo. The major differences between the following revision and the previous specification are the inclusion of synthetic waxes in Section 1.1 Scope, and in a change to three types: A , B, and C, under Section 1.2 Types and Classes. Addi­ tionally, a change in Section 3.7 outlines flow requirements in the Table. Sections 3.7.1 through 3.7.2.3 have been deleted. The revision becomes effective Jan 1, 1976. American Dental Association Specification No. 4 for dental inlay casting wax Third revision, approved May 1974, effective Jan 1, 1976. American National Standard MD-156.4, 1969 (revised 1974).

1. Scope and classification. 1.1 Scope. This specification is for inlay casting wax used in making patterns in the production o f in­ lays and crowns. The wax consists essentially of nat­ ural and synthetic w axes, resins, and hydrocarbons o f the paraffin series. 1.2 T ypes and classes. Inlay casting wax covered by this specification shall be o f the following types and classes: Type A . Hard Class 1. Sticks Class 2. Cones Class 3. Other shapes Type B. Medium Class 1. Sticks Class 2. Cones Class 3. Other shapes Type C. Soft Class 1. Sticks Class 2. Cones Class 3. Other shapes 2. Applicable specifications. 2.1 Specification. There are no other specifica­ tions applicable to this specification. (Copies o f Amer­ ican Dental Association specifications may be ob­ tained on application to the Council on D ental Mater­ ials and D evices, American Dental A ssociation, 211 E Chicago A ve, Chicago, 60611.) 3. Requirements. 3.1 Uniformity. The wax shall be uniform and free o f foreign materials. 3.2 Size. Sizes shall be as specified by the pur­ chaser. 3.3 Color. The color o f the waxes shall be the color specified by the purchaser.

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T a b le ■ F lo w re q u ire m e n ts . F lo w %

W ax te m p e ra tu re , C

M in

M ax

T yp e A

Type B

Type C

1 50 70

1 15 85 90

43 46 49 52

37 40 43 46

34 37 40 43

3 .4 S o fte n in g . T he wax shall soften w ithout be­ com ing flaky. It shall not show laminations w hen form ed into a w orking mass. 3.5 C h ip p in g . T h e wax shall not show appre­ ciable chipping or flaking w hen trim m ed to a fine m ar­ gin at 23.0± 2.0 C. 3.6 R e sid u e . T he melted w ax, when vaporized at 500 C , shall leave no solid residue in excess of 0.1% of the original w eight of the specim en when tested as described in 4.3.3. 3 .7 F lo w . R equirem ents for flow shall be as given in the T able.

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4.

Sampling, inspection, and testing procedures. F iv e packages o r approxim ately 5 oz of w ax shall be procured at retail by a m em ber of the A m erican D ental A ssociation. This sample shall be 'forw arded in the original, unopened package or packages to the A m erican D ental A ssociation C oun­ cil on D ental M aterials and D evices, 211 E Chicago A ve, C hicago, 60611. 4.2 In s p e c tio n . V isual inspection shall be used in determ ining com pliance w ith the requirem ents stated in 3.1, 3.3, 3.4, 3.5, 3.9, and 5. 4.1 S a m p lin g .

4.3 P h ysica l te sts. 4.3.1 F low . 4.3.1.1 P rep a ra tio n o f sp e c im e n s .

A quantity of wax shall be broken into pieces and placed in a m etal pouring pan as illustrated in Figure 1. T he pan shall be placed on a surface which is 130 mm below a 250-w infrared lamp. T he w ax, while being stirred, shall be allow ed to reach a tem perature of 75±5 C and be main­ tained at this tem perature until the sample is melted throughout. A therm om eter shall be used to m easure the tem perature. T he melted wax shall then be poured into a mold that has been lubricated with a silicone grease w hose melting point is higher than 75±5 C. T he mold (Fig 2) shall consist o f a stainless steel plate 6.0 mm thick, having flat, parallel top and bottom sur-

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0

30.0 C shall be not m ore than 0.2% when tested as in 4.3.2.2. 3.8 .2 T he linear therm al expansion from 25.0 C to 37.0 C shall be not more than 0.6% when tested as in 4.3.2.2. 3.9 M a n u fa c tu r e r ’s in stru ctio n s. Instructions, in­ cluding m ethod fo r softening, working tem perature, and data show ing the therm al expansion of the wax from 25.0 C to 30.0 C and to 37.0 C, shall be supplied with each package o f wax. T he therm al expansion data shall be required for the T ype B wax only.

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3 .8 L in e a r th e r m a l ex p a n sio n , T y p e B w ax. 3.8.1 T he linear therm al expansion from 25.0 C to

A

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Fig 2 ■ M o ld fo r fo rm in g flo w s p e c im e n s .

iaces, and containing four holes 10.0 mm (0.394 inch) in diam eter. T he axes of the holes shall be perpen­ dicular to the surfaces of the plate. T h e sides of the holes shall be finished smooth. T he mold shall be pre­ heated to a tem perature of 55±5 C and placed on a sm ooth glass slab 152 mm long, 76 mm wide, and 19 mm thick preheated to the sam e tem perature. A s the w ax freezes and a shrinkage void appears, liquid wax shall be added. W hen the wax has lost its m irrorlike surface, a sm ooth, flat tinfoil or alum inun foil covered glass plate, preheated to 55±5 C , shall be placed on the top o f the mold. A load of 9,000 g shall be applied to the top of the foil covered glass plate for 30 m inutes. T he weight and the glass plate shall then be rem oved and the excess wax trim m ed aw ay. T his may be ac­ com plished by draw ing the specim en flush with the surface. T he mold shall be rem oved from the glass slab by gently tapping the side of the mold. T h e speci­ mens of wax shall be rem oved from the mold by chill­ ing in w ater at 10 C and shall then be stored at 23.0± 2.0 C for 24 hours before testing. 4 .3 .1 .2 M e th o d o f te st. T h e initial length o f the specim en shall be determ ined at 23.0±2.0 C , using a m etric m icrom eter caliper. F o u r m easurem ents shall be m ade around the circum ference and one m easure­ m ent shall be m ade in the cen ter of the specim en. The m easurem ents shall be averaged and recorded to the n earest 0.005 mm. T he specim en and flow testing in-

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F ig 4 ■ B ra ss m o ld fo r th e rm a l e x p a n s io n s p e c im e n . A, to p p la te ; B, w ax s p e c im e n ; C, s p a c e r (2); a n d D, m o ld .

4.3.2 L in e a r th erm a l exp a n sio n . 4.3.2.1 P reparation o f sp e c im e n s.

Fig 3 ■ F lo w te s tin g in s tru m e n t. A, w e ig h t; B, s h a ft; and C, brass p la te n .

strum ent shall be placed in a w ater bath and held at the testing tem perature for 20 minutes prior to testing. Load shall be applied by a suitable flow testing in­ strum ent such as show n in Figure 3, consisting of the following: A , a weight; B, a shaft having low therm al conductivity; and C , a brass platen. T he total weight, in air, o f these three com ponents shall be 2,000 g. The weight, A, shall be separated a minimum distance of 75 mm from the brass platen by the nonconducting shaft. T his shaft shall be of hard rubber or a similarly poor therm al conductor to avoid loss of heat from the specim en. T he diam eter of the brass platen shall be not less than 50 mm. T he thickness shall not exceed 6.35 mm. T he tem perature of the bath shall be con­ trolled to within ±0.1 C of the required tem perature. (A calibrated therm om eter shall be used for deter­ mining the tem perature.) A gitation shall be provided in the w ater bath by m eans of a m echanical stirrer. A thin sheet of polyethylene or cellophane shall be placed betw een the instrum ent and each end of the specim en. T he bottom of the specim en shall be 51 mm below the surface of the w ater in the bath. A constant axial load of 2,000 g shall then be applied to the speci­ men for ten m inutes, after which the specim en shall be rem oved and cooled in the air to 23.0±2.0 C. The polyethylene or cellophane shall be stripped off and the final length determ ined in the sam e m anner as the original length. The flow, as evidenced by the change in length, shall be reported as percentage of the initial length. T he value for flow at any tem perature shall be the average value for tw o specim ens and shall be re­ ported to the nearest 0.1%.

T he wax shall be melted as described in 4.3.1.1 and shall be poured into a brass mold lubricated w ith a silicone grease w hose melting point is higher than 75±5 C (Fig 4) and having an opening of 6.35 x 6 .35 mm running the length of the mold, until the mold is overfilled. S pacers, 19 mm in length, shall be placed in the opening at each end of the mold (Fig 4, C). T he mold shall be preheated to 55±5 C. As the wax freezes and shrinkage occurs, liquid wax shall be added. W hen the wax has lost its mirrorlike surface, a lubricated brass plate preheated to 55±5 C shall be placed on top of the overfilled mold. A load of 9,000 g shall be applied to the top of the brass plate shall then be rem oved and the excess wax trim m ed aw ay until the specim en is flush with the top of the mold. The size of the specim en thus prepared will be approxim ately 2 6 7x6.35x6.35 mm and is suit­ able for use with the m icrom eter m icroscope com par­ ato r (4.3.2.2). T he specim en shall be rem oved from the mold and shall have em bedded in its surface near each end, small metal pins having crossm arks which shall serve as reference m arks for subsequent linear m easurem ents. A fter the te st specim en is prepared, it shall be stored at 37 C for 24 hours before testing. 4 .3 .2 .2 M e th o d o f te st. T he specim en shall be heated to three different tem peratures, and the dis­ tance betw een the reference m arks shall be deter­ mined at each tem perature. A m icrom eter m icroscope com parator or equipm ent of equal accuracy shall be used to make the m easurem ents. T he specim en shall be placed under a suitable holder w ith openings for viewing the reference m arks as show n in Figure 5. T he openings shall be located 6.35 mm from each end of the holder and shall be 9.52x12.7 mm in size. T he holder shall be so constructed that the wax specim en shall ride against only tw o narrow ed sections, having 7.94x7.94 mm openings (Fig 5, A ), located 25.4 mm from each end, to enable alignm ent but a minimum of restraint to the expansion during heating. An initial m easurem ent shall be m ade in w ater after 20 minutes at 2 5 .0 ± 0 .1 C. The tem perature shall then be raised in the w ater bath to 3 0 .0 ± 0 .1 C. T h e specim en shall rem ain 20 minutes at that tem perature before the dis-

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furnace, placed in a desiccator, and allowed to cool to 2 3 .0± 2.0 C before weighing. T he value for residue shall be the average value of tw o determ inations and shall be rep o rted to the nearest 0.02%. 5. Preparation for delivery. T he m aterial shall be packaged in accordance with accepted com m ercial practice. 5.1 P a c k a g in g .

5.2 M a rkin g . 5.2.1 L o t n u m b e rs.

tance betw een m arks is determ ined. T he sam e proce­ dure shall be carried out at 37.0±0.1 C. A repeat test starting at 25.0±0.1 C shall be made on the same spe­ cim en. U sing the 2 5 .0 ± 0 .1 C tem perature m easure­ m ent as zero, the value for linear therm al expansion shall be the average value of the tw o determ inations at each tem perature and shall be reported to the near­ est 0.05%. 4 .3 .3 R e s id u e . A pproxim ately 1 g of w ax shall be placed in a crucible previously conditioned to con­ stant weight by repeated heatings to 500 C and cooling to 23.0± 2.0 C. The conditioned, tared, and loaded crucible shall be transferred to a furnace at 23.0±2.0 C. T h e tem perature of the furnace shall be increased to 500 C and m aintained at this tem perature for one hour. T he crucible shall then be rem oved from the

Each container shall be m arked with a serial num ber or a com bination of let­ ters and num bers that shall refer to the m anufacturer’s records for th e p articu lar lot or batch o f wax. 5 .2 .2 D a te o f m a n u fa c tu re . T he date of m anufac­ tu re (year and m onth) shall be given on the container either as a separate item or as part of the lot num ber (5.2.1). 5 .2 .3 N e t w eig h t. T he minimum net weight of the co n ten ts shall be indicated on all containers. 5 .2 .4 T y p e a n d c la ss. T he type and class (1.2) of wax shall be indicated on all containers. 6. Notes. In te n d e d u se. T he usual uses for w axes of T ypes B and C are: T ype B. direct technique wax suit­ able for making pattern s in or out of the oral cavity for the production of inlays and crow ns; T ype C , indirect technique w ax, suitable for making patterns outside the oral cavity for the production of inlays and crow ns. 6.1

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