A S S O C I A T I O N R E P O R T S

Revised ANSI/ADA specification no. 5 * for dental casting alloys

Council on Dental Materials, Instruments, and Equipment

R evised Am erican Dental Association specification no. 5 for dental casting a llo y s has been ap p ro v ed by the

C ouncil on D ental M aterials, In s tru m en ts , an d E q u ip m e n t of th e A m erican D en ta l A ssocia tion . T h is a n d o th e r sp ec ifica tio n s for dental m aterials, instrum ents, and equ ip ­m ent are being form ulated by subcom mittees of the Accredited Standards Com m ittee MD156 for Dental Materials, Instrum ents, and E q u ip ­m ent. T h e council acts as ad m in istra tiv e sponsor of that comm ittee, w hich has represen­tation from all interests in the U nited States in the stan d ard iza tio n of m ateria ls , in s tru ­m en ts , a n d e q u ip m e n t in d e n tis try . T h e council has adopted the specifications, show ­ing professional recognition of their usefulness in dentistry, and has forwarded them to the Am erican N ational Standards Institu te w ith a recom m endation that the specifications be approved as A m erican N a tio n a l S tandards. A pproval of revised ADA sp ec ifica tio n no. 5 as an A m erican N a tio n a l S ta n d a rd was granted by the American N ational Standards In s t i tu te on Dec 14, 1988. T h is s ta n d a rd becomes effective Dec 14, 1989.

T h e c o u n c il th a n k s th e su b c o m m itte e members and organizations w ith w hich they were a ffiliated a t the tim e the specification was developed: Clyde Ingerso ll (chairm an), W illiam s D en tal, B uffalo ; Ken A nusav ice, U n iv e rs ity o f F lo rid a , G a in esv ille ; A ru n Prasad, Jeneric Industries, W allingford, CT; Marcy Kram er, JF Je len k o 8c Co, A rm onk, NY; R onald Dudek, Austenal Dental, Chicago; L aw rence G etllem an, M etairie, LA; R obert H in m an , N aval D ental C lin ic , San Diego; T . K. V aidyanathan , New Y ork U niversity Dental Center, New York; Edward Kaufm an, Brookdale Dental Center, New York University, New York; Leon Laub, Loyola University, Maywood, IL; Robert Lorey, University of M ichigan, Ann Arbor; and H erbert Mueller, ADA, Chicago.

Revised ANSI/ADA specification no. 5 for dental casting alloys is w ritten to assure both the efficacy and safety of clinical restorations in the m outh. Requirem ents for com position of a llo y , m ec h an ic a l p ro p e rtie s , p h y sica l p ro p erties , casting characteris tics , toxicity , ta rn ish an d corrosion resistance, and pack­ag ing inserts are included to meet these goals. T h e clinical significance of these requirem ents follows.

In addition to m ajor elem ents and noble m etal constituents, quantitative determ ination of any hazardous elem ents m ust be stated. It is im portan t for the clin ician to have this in fo rm a tio n w hen se lec ting an a lloy for a p a tie n t w ith know n m eta l hypersensitiv ity and in the general assessment of health risk to the patient.

D epending on its use as an in lay , onlay, crown or bridge, a dental casting alloy should have a com bination of m echanical properties th a t w ou ld preserve the an a to m y designed into the restoration and perm it the clinician to adjust or finish the appliance. A clinician m ay then designate a b ra n d of a lloy based on its m echanical p roperties. For exam ple, if the m argin on an inlay is short, the clinician may need to burn ish the region. T o achieve this result, the alloy should have a relatively low-yield strength and hardness, and a h igh elongation.

W hen an alloy for a bridge is selected, a m aterial having a h igh m odulus of elasticity and h igh-yield strength w ould be desirable. Y ield s tre n g th is a m easu re of how m uch stress is needed to d efo rm a re s to ra tio n . E longation is a measure of the relative ductility or brittleness of an alloy. M odulus of elasticity is a measure of stiffness of an alloy. Hardness is a m easure of the d iff icu lty in f in ish in g o r p o lis h in g a re s to ra t io n , as w ell as an indicator of po tential wear of opposing natural tooth structure.

M elting co n d itio n s w ill affect p roperties (for ex am p le , g ra in size an d hom o g en e ity of th e a llo y ), a n d u ltim a te ly th e c lin ica l perform ance of a cast restoration. T o achieve the p roperties described by a m anufacturer, th e c o n d it io n s necessary fo r m e ltin g and casting, according to that m anufacturer, must be followed.

C lin ica lly , a cas tin g sh o u ld no t co n ta in m arg in a l d isc rep an cies an d sh o u ld fit the prepared tooth. Because there is no com po­sition requirem ent in the specification (that is, the alloy can be predom inantly noble or base m eta l), c as ta b ility a n d f it need to be clinically acceptable.

B io lo g ica l safety of th e a llo y w ill be indicated th rough three toxicity evaluations: in v itro test of cy to tox icity , A m es’ test for p o te n tia l m u ta g e n ic ac tiv ity , a n d m ucous m em brane irrita tion testing.

N e ith e r c o m p o s itio n re q u ire m e n ts no r

d es ig n a ted lim its o n m ech an ica l p ro p e rty values assure tarn ish or corrosion resistance of a cas tin g a llo y in the m o u th . A ta rn ish test and evaluation of the effect of corrosion on m echanical properties are included.

Packaging requirem ents include the p ro ­cessing in fo rm a tio n needed to ach ieve the c o m b in a tio n of p h y s ic a l a n d m ec h an ic a l properties reported by the m anufacturer. Alloys are ch o sen fo r c lin ic a l use based o n th e ir p roperties and if c lin ical failure occurs, the p a c k in g in fo rm a t io n w ill h e lp d e te rm in e whether the cause was a m aterials problem.

In this revision of ANSI/ADA specification no. 5 ,1981, the Accredited Standards Com m ittee MD156 su bcom m ittee has m ade extensive changes to the specification in response to recent developm ents in the casting alloy field. No longer are gold alloys dom inan t in the crown and bridge app lication of casting alloys.

T h e firs t re v is io n is the su b c o m m itte e ’s reco m m en d a tio n for a change in the nam e of the sp ec ifica tio n . T h e w ord “ g o ld ” has been rem oved to re flec t the fact th a t i t is no lo n g e r re s tr ic te d to g o ld a llo y s. T h ere a re no c o m p o s itio n a l re q u ire m e n ts in the p roposed revision of the specification. T h is reflects the clinical use and general acceptance of a llo y s c o n ta in in g less th a n 75% w eig h t of gold and p la tin u m group elements.

T h e reason for the previous restriction to noble m etals was the widespread belief that alloys w ith less than 75% (or 78%) noble metal content w ould tarn ish or corrode in the m outh. T h is corre lation has been disproved. Lower cost a lte rn a tiv e s have been d em an d ed by d en tistry an d have been fu rn ish ed th ro u g h advances in m etallurgy, and greater knowledge of raw m ateria ls and oral ta rn ish /co rro s io n effects. Since th e o rig in a l spec ifica tion no. 5, a considerable p ro liferation of alloys and a llo y system s have p ro v ed to be v iab le substitutes for the h igh-gold alloys.

* A N S I/A D A sp e c if ic a tio n no . 5, 1988. Approved Dec 14, 1988.

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Copies of this an d o ther ANSI/ADA specifications are available from the Am erican N ational Standards Institu te , 1430 Broadway, New York 10018.

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