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HP KIM C NHA KHOA GS. Hong T Hng

MC TIU:

Sau khi nghin cu bi ny, sinh vin c th: 1. Tho lun c lch s pht trin ca hp kim nha khoa, 2. Trnh by c nhng i hi ca hp kim nha khoa, 3. Lit k v m t s lc c cc cng ngh to mu kim loi, 4. Trnh by c s pht trin ca cc phn loi v phn bit hp kim c nha khoa, 5. Trnh by c cc tnh cht vt l ca hp kim c nha khoa, 6. Trnh by c s co c v cc phng php x l nhit hp kim qu v rt qu, 7. Lit k c cc hp kim c rt qu, qu v thng trong cc ng dng nha khoa.

1. I CNG V LCH S Cc kim loi c th chia lm hai nhm:

St (ferrous), v Khng st (nonferrous).

Kim loi st gm st, bao gm cc loi thp. Cc kim loi khng st gm:

Cc kim loi qu (noble metals), Cc kim loi thng (base metals), v Cc kim loi nh (light metals).

Kim loi qu gm vng, nhm platinum (gm platinum, palladium, ruthenium, rhodium, iridium v osmium). Chng c c trng bi tnh bn vng v ha hc i vi s oxy ha, khng n mn v i mu. Cc hp kim qu thng c gi l qu kim (precious metal) v gi c ca n. Mc du bc (silver) cng l mt qu kim, nhng khng phi l kim loi qu trong nha khoa v km khng vi n mn v i mu. Cc kim loi nh nh titanium, c trng bi khi lng ring thp; cc kim loi thng bao gm nickel, cobalt v cc kim loi nng khc.

Hu ht kim loi dng trong nha khoa l di dng hp kim (alloys). Hp kim c nhiu u im so vi cc kim loi nguyn cht v c tnh c hc v l hc do c ch to t n ti u t nhng kim loi thnh phn.

Th d: vng nguyn cht mm, d un, d dt mng, nhng khng p ng c i hi lm mo (chp) hoc cu rng, nu thm 10% ng vo vng, s to thnh mt hp kim c bn ko v cng tng gp bn ln.

1.1. S lc lch s Lch s hp kim c nha khoa chu nh hng ca ba yu t: nhng thay i cng ngh

lm phc hnh, cc tin b v luyn kim v nhng thay i v gi c ca kim loi qu t 1968. Nm 1907, Taggart trnh by ti tp on nha khoa New York (New York Odontological

Group) v thc hin inlay c, y l bo co u tin v p dng k thut c thay th sp (lost wax technique) trong nha khoa. K thut ny mau chng c p dng cho c onlay, mo, cu, hm khung. Sau , v vng nguyn cht khng p ng v tnh cht vt l, cc hp kim vn dng lm trang sc (c thm ng, bc, platinum) c s dng trong nha khoa. T nm 1948, cc hp kim qu nha khoa tr thnh mt phn nhm ring, vi nhng cng thc mi, khuynh hng vt liu b i mu c khc phc, v bc c thay th bng palladium.

Khong nhng nm 30 ca th k XX, hp kim thng lm hm tho lp c gii thiu. T , c nikel-chromium ln cobalt-chromium ngy cng tr nn ph bin so vi hp kim vng Typ IV vn c dng cho loi hm gi ny. Nhng u im ni bt ca hp kim thng l nh, c tnh c hc tt v gi thnh r, v vy, cc loi hp kim thng ngy cng thay th hp kim qu lm phc hnh kim loi.

Cui nhng nm 50, mt bc t ph din ra trong cng ngh nha khoa, nh hng su sc n vic ch to cc phc hi. l s thnh cng trong vic lm mt dn s trn kim

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loi. Cho n trc thi im , h s dn n nhit ca cc hp kim vng cao hn hn s, lm cho khng th t c s dn gia hai cu trc ny. Ngi ta nhn thy thm c platinum v palladium vo vng, s lm gim h s dn n nhit, kt dnh vt l hai cu trc. Mt cch tnh c, nhit nng chy ca hp kim cng tng ln cho php nung (thiu kt) s trn hp kim qu 1400C (1900F) m khng lm bin dng ln (ln) kim loi.

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Thnh cng ca cc hp kim thng lm hm khung hng n vic ch to nhng hp kim mi cho nhng ng dng khc trong nha khoa phc hi. Nhng n nhng nm 70, v nht l t 1978, khi gi vng tng cao, vn mi thc s thu ht.

Do s phong ph ca cc loi hp kim vi cc thnh phn khc nhau cho nhng ng dng a dng, vic phn loi cc h thng tr nn kh khn, cn c s uyn chuyn bao gm nhng vt liu mi hoc nhng thay i i vi vt liu ang c. V vy, cc phn loi c thng xuyn xem xt li (xem phn phn loi) 1.2. Nhng i hi ca hp kim c nha khoa

Hp kim c nha khoa c dng trong labo lm inlay, onlay, mo (chp), cu, cc phc hnh c nh kim loi-s, kim loi-nha, cht ng ty, hm khungHp kim cn p ng c cc i hi chung nh sau:

1. Phi c tnh tng hp sinh hc, khng to ra c cht gy nguy him hoc gy d ng i vi ngi s dng v vi bnh nhn.

2. Phc hnh phi c tnh khng n mn v khng b thay i trong mi trng ming. 3. Cc c tnh l hc v c hc, nh tnh dn nhit, nhit nng chy, h s dn n v

nhit, bn cn c p ng, tho mn cc gi tr ti thiu v thay i theo nhng i hi khc nhau ca cc ng dng phc hnh.

4. Phi khng c nhng i hi qu ng trong s dng, cn t c tnh kh thi i vi i hi v trnh chuyn mn thng thng ca k thut vin cng nh bc s.

5. Cc kim loi, hp kim v vt liu i km phi y , khng t qu. 6. Ring i vi gia cng trong labo, hp kim cn d nu chy, d c, d hn, d nh

bng, t co, khng phn ng vi vt liu lm khun c, khng mn, khng b ln khi nung s.

1.3. Cng ngh to mu kim loi

Cc phc hnh ton kim loi c th c thc hin trc tip trn ming: trm bng vng l v amalgam. Mt loi vt liu nhi nn lin kim loi khc (intermetallic compound) cng c nghin cu pht trin bi Vin quc gia tiu chun v cng ngh Hoa k (National Institute of Standards and Technology) thay th amalgam nhng cha c trin khai trong thc hnh. Cng ngh c: Cc loi phc hnh kim loi: inlay, onlay, mo (chp), cu, cc phc hnh

c nh kim loi-s, kim loi-nha, cht ng ty c thc hin bng phng php c t mt th k qua. Hp kim vng chng t c u th v cng v bn so vi cc vt liu phc hi khc. Phc hnh s-kim loi c lm vi sn (li) kim loi c (alloy casting coping) cng chng t s bn vng v thm m.

i vi sn kim loi c s dng lm nn cho s, cng ngh l kim loi (metal foil) cng c s dng thay cho sn c. Cc lp l kim loi c p nng (swage) trn dye v x l nhit trn la gas lm tng bn trc khi p s. Qu trnh ny tuy trnh c vic phi to mu sp nhng phi to khun chu la (refractory mold), nu chy v c kim loi vo khun, cng cn nhiu thi gian p nng v chnh sa sn kim loi. Hn na, b mt cc lp kim loi p sp cn c nhng vng tch t ng sut (stress concentration areas) c th lm gim bn ca phc hnh. Tuy vy, k thut ny cho php to nhng li kim loi c dy ch khong 100 m hoc mng hn, do c th gip tit kim m rng v tng dy ca lp s, nh tng tnh thm m.

Cng ngh CAD-CAM c s dng trong nha khoa thit k (computer-aided designing) kch thc v hnh dng ca phc hi, v ch to (computer-aided machining) phc hi bng s t cc khi s (ceramic block) hoc cc chi tit kim loi kh c: titanium v hp kim titanium.

Cng ngh mi: trong phng php ny, ngi ta khng dng cng ngh c thc hin mo ton kim loi hoc sn kim loi. Qu trnh mi bn sao (copy milling process) gm to

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mt ngoi v ly b phn li to b mt bn trong cn c theo b mt ca dye chnh c ghi li trong computer.

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Tuy vy, phng php nu chy v c hp kim vn l phng php c s dng ph bin nht cho cc qu trnh lm vic ngoi ming. Phng php c c in gm vic to mt khong trng do mu sp c ly i, thay th bng hp kim. Mu sp c to trn mu hm c t du trong ming, sau dc bao li bng vt liu to khun (mold material) gi l bt c hay bt bao (investment). Bt c l hn hp ca nc, silica v cht gn (binder) gm thch cao (calcium sulphate hemihydrate), magnesium ammonium phosphate, ethyl silicate. Sau khi va bt c (investment slurry) cng, sp c t chy khi khun c, kim loi nng chy c c vo khong trng trong khun c di p lc hoc lc ly tm.

Nhiu lu v k thut c a ra, ph thuc vo hiu bit v hp kim. Trong khong 20 nm tr li y, c nhiu tin b trong lnh vc ny. Do c nhiu loi hp kim khc nhau, bc s cn bit la chn cho nhng ch nh khc nhau: nha-kim loi, s-kim loi, ton kim loi K thut vin cng cn hiu bit hn v cc loi hp kim, v nhiu bc s khng r li ch cng nh bt li ca cc h thng hp kim trong cc ng dng c th khc nhau. Nh vy, s lin h gia bc s v k thut vin l iu quan trng cho s la chn.

2. PHN LOI V THUT NG 2.1. Cc phn loi hp kim trong nha khoa 2.1.1. Nm 1932, Ban vt liu nha khoa ti Vn phng quc gia v tiu chun Hoa k (dental

materials group at National Bureau of Standards) phn loi i th thnh bn typ: Typ I: mm, Vickers hardness number (VHN) t 50 90 Typ II: trung bnh, VHN t 90 120 Typ III: cng, VHN t 120 150 Typ IV: rt cng, VHN 150

Phn loi ca American Dental Association (ADA), gm bn loi: t typ I n IV nh trn ch p dng cho hp kim vng.

Trong na cui th k XX, nhiu hp kim thng pht trin, thay th cho hp kim qu

nhiu lnh vc. Hu ht hm khung cng nh cc phc hi mo, cu...c lm t hp kim thng,

2.1.2. Nm 1984, ADA a ra mt phn loi n gin da trn c s thnh phn kim loi qu i vi hp kim nha khoa.

H thng ny phn loi thnh cc hp kim rt qu (high noble: HN); qu (noble: N) v thng (predominantly base metal: PB) (c nu trong bng 20-1). Phn loi hp kim nha khoa theo thnh phn kim loi qu cn c lng gi ca phc hi, cn cho bc s, k thut vin, bnh nhn v c quan bo him.

TABLE 20 -1. Phn loi hp kim nha khoa ca ADA 1984 (Alloy Classification of the American Dental Association (1984)) Typ hp kim Tng lng kim loi qu trong thnh phn (theo khi

lng) Rt qu (HN) Qu (N) Thng (PB)

40 wt% Au & 60 wt% nguyn t kim loi qu (Au + Ir + Os + Pd + Rh + Ru) 25 wt% nguyn t kim loi qu < 25 wt% nguyn t kim loi qu

T hp kim bn qu (precious, semipreciuos) khng nn dng v khng chnh xc.

Cc k thut vin thng dng t bn qu ch cc hp kim c nn l palladium hoc bc. Cc hp kim c >50% khi lng paladium, bao gm Pd-Ag, Pd-Cu, Pd-Co, Pd-Ga-Ag, Pd-Au, Pd-Au-Ag c gi l qu. T qu cng c dng cho hp kim Ag-Pd nu cha >25%

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palladium v cc kim loi qu khc. Cc hp kim rt qu v qu thng c ng gi v tnh gi theo cc l 1, 2, hoc 20 dwt (pennyweight)

2.1.3. T 1989, phn loi vn gm bn typ a thm tt c cc hp kim c p ng i hi cc test v c tnh, i mu, gii hn chy do, phn trm dn di. (Bng 20-2 cho thy bn cnh cng, gii hn chy do v % dn di l c s ca phn loi ny). Bng 20 -2. i hi v c tnh c hc ca hp kim (Mechanical Property Requirements of American Dental Association Specification No.5)

Typ hp kim

Gii hn chy do (MPa) ( lch 0,1%)

sau sau lm cng

Dn di ti thiu (%)

sau sau lm cng

I (mm) II (trung bnh) III (cng) IV (rt cng)

Ti a 140 khng 140 200 khng 200 340 khng 340 500

18 khng 19 khng 12 khng 10 2

Typ I: mm, cho nhng phc hi t chu lc: inlay Typ II: trung bnh, phc hi chu lc trung bnh: onlay Typ III: cng, cho nhng phc hi chu lc: onlay, mo, cc cu ngn Typ IV: rt cng, cho nhng phc hi chu lc cao: cht ng ty, mo

veneer mng, cu di, khung. Theo phn loi 4 typ cua ADA v tu chnh nm 1989, 4 typ hp kim lm phc hi ton

kim loi v mt dn nha c sp xp, da theo c tnh (ch khng theo thnh phn) nh sau:

Typ I: mm, VHN t 50 90, cho nhng phc hi t chu lc: inlay Typ II: trung bnh, VHN t 90 120, phc hi chu lc trung bnh: onlay, mo

dy, ci rng, pontic, mo y Typ III: cng, VHN t 120 150 cho nhng phc hi chu lc cao: onlay, mo,

cc cu ngn, mo mng, cc pontic v ci nh, nn hm Typ IV: rt cng, VHN 150 cho nhng phc hi chu lc rt cao: cht ng ty,

mo veneer mng, cu di, khung v cc thanh ngang ca khung. Loi I v II thng cn c gi l hp kim inlay, loi III v IV cn c gi l hp kim mo v cu.

2.1.4. Nm 2003, Hi ng khoa hc ca ADA xem xt li s phn loi, bao gm thm titanium nh mt mc ring trong nha khoa. Titanium l mt trong nhng kim loi c tnh tng hp sinh hc cao nht trong cc ng dng nha khoa v c ng dng rng vi c tnh tng t kim loi qu.

Ngoi cc phn loi chnh thc nu trn, cn cn ch hai cch phn bit sau:

2.2. Phn bit hp kim nha khoa Do c nhiu loi h thng hp kim la chn, cn phi xem xt theo ch nh p dng

v thnh phn ca hp kim. 2.2.1 Phn bit loi cc hp kim theo ch nh: Bng 20-3 lit k cc loi hp kim theo ch nh p dng i vi mo ton kim loi, kim loi-s v hm khung. Cn ch l hp kim dng

1troy ounce = 20 pennyweight www.hoangtuhung.com

cho phc hnh s-kim loi c th dng cho ton kim loi nhng khng phi l ngc li. Nguyn nhn chnh l do hp kim khng th to mt lp oxid mng v n nh lin kt vi s, nng chy c th thp nn gy bin dng ln hoc b chy nhit thiu kt (nung) s, dn n nht cng khng tng thch vi s.

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Bng 20-3. Phn loi hp kim lm phc hnh ton kim loi, s-kim loi, hm khung (Classification of Alloys for All-Metal Restorations, Metal-Ceramic Restorations, and Frameworks for Removable Partial Dentures). Typ hp kim Ton kim loi Kim loi-s Hm khung Rt qu Qu

Thng

Au-Ag-Cu-Pd Hp kim cho s-kim loi

Ag-Pd-Au-Cu Ag-Pd Hp kim cho s-kim loi Ti nguyn cht Ti-Al-V Ni-Cr-Mo-Be Ni-Cr-Mo Co-Cr-Mo Co-Cr-W Al-ng thic

Au-Pt-Pd Au-Pd-Ag (5-12 wt% Ag) Au-Pd-Ag (>12 wt% Ag) Au-Pd Pd-Au Pd-Au-Ag Pd-Ag Pd-Cu Pd-Co Pd-Ga-Ag Ti nguyn cht Ti-Al-V Ni-Cr-Mo-Be Ni-Cr-Mo Co-Cr-Mo Co-Cr-W

Au-Ag-Cu-Pd Ag-Pd-Au-Cu Ag-Pd Ti nguyn cht Ti-Al-V Ni-Cr-Mo-Be Ni-Cr-Mo Co-Cr-Mo Co-Cr-W

2.2.2. Phn bit hp kim bng cc nguyn t chnh

Khi phn bit hp kim theo thnh phn, ngi ta xp theo trnh t gim dn, t thnh phn chim nhiu nht ri n cc thnh phn khc. Cc bng 20-3, 20-7 v 20-8 sp xp theo trnh t ny. Ngoi l cho s sp xp l khi c thnh phn nh hng nhiu n c tnh hoc nh hng n tnh tng hp sinh hc ca vt liu hoc c hai. Th d, hp kim nickel-chromium-molybdenum-beryllium thng c gi l hp kim nickel-chromium-beryllium v beryllium va gp phn quan trng i vi tnh d c v kim sot s to thnh lp oxid nhit cao nhng c c tnh so vi cc kim loi khc. Molybdenum (Mo), tungsten (W) thng c nhiu hn beryllium lm gim h s dn n nhit.

2.3. Cc kim loi dng trong hp kim nha khoa

Trn bng tun hon cc nguyn t ha hc, c tm kim loi qu: vng, cc kim loi nhm platinum (platinum, palladium, rhodium, ruthenium, iridium, osmium) v bc. Tuy vy, trong mi trng ming, bc kh hot ng nn khng c coi l kim loi qu. Cc kim loi qu thng c dng trong hp kim lm inlay, onlay, mo, cu, s-kim loi. Chng l nhng hp kim t b i mu v n mn. T kim loi qu ch c nghi tng i. Trong s by kim loi qu, ch c vng, palladium v platinum ng vai tr quan trng trong cc hp kim nha khoa.

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2.3.1. Karat v Fineness

Karat (carat) dng ch phn ca vng nguyn cht c trong 24 phn ca mt hp kim. Th d: vng 24 karat l vng nguyn cht, vng 22 karat l hp kim cha 22 phn vng nguyn cht v 2 phn kim loi khc.

Fineness dng m t hp kim c vng bng s phn vng trn 1000. Th d: vng nguyn cht c fineness 1000; hp kim 650 cha 65% vng. Nh vy, thang o fineness chnh l bng 10 ln ca thang o %. Trong th d trn, 650 fine alloy c 65% vng nguyn cht.

Trong thc t, fineness c coi l thc t hn karat, nhng ni chung, khng c dng ph bin trong hp kim nha khoa. Bng 20-4 trnh by phn loi hp kim vng theo karat v fineness.

Bng 20-4. Cc hp kim vng phn loi theo karat v fineness (Gold alloys commonly use karat and fineness classifications)

% khi lng vng Karat Fineness 100 24 1000 75 18 750 58 14 583 42 10 420 2.4. Hp kim kim loi thng (hp kim thng)

L nhng hp kim cha 75% khi lng l cc nguyn t kim loi thng hoc < 25% khi lng l kim loi qu. Kim loi thng (base metal) l thnh phn khng c gi tr ca hp kim c nha khoa, v chng r v thng c mc phn ng cao vi mi trng. Tuy vy, chng c nh hng n khi lng ring, bn v cng, cng nh to thnh lp oxid (iu ny li rt cn cho phc hi kim loi-s); cng c mt vi kim loi thng c th dng bo v kim loi khi b n mn bng cch th ng ha (passivation)). Kim loi thng c mt trong thnh phn hp kim nha khoa kh phong ph: bc, nickel, chromium, nhm, ng, km, indium, thic, gallium, molybdenium, beryllium, tungsten

T hp kim ch yu l kim loi thng (predominantly base metal alloys) c dng l do trc trc y, trong hp kim loi ny, c mt lng nh palladium. Ngy nay, cc t hp kim kim loi thng, hp kim thng v hp kim ch yu kim loi thng c dng ng ngha. Theo trnh t thi gian, c ba loi hp kim thng c s dng trong nha khoa:

Hp kim thp khng r (stainless steel alloys) Hp kim nickel-chrome (nickel-chrome alloys) Hp kim cobalt-chromium (cobalt-chromium alloys) Titanium v cc hp kim titanium, nickel-titanium siu n hi (super-elastic) s c

trnh by trong mt bi ring

3. C IM CA HP KIM C NHA KHOA 3.1. S co c (casting shrinkage)

Hu ht kim loi, hp kim, k c vng, co li khi chuyn t trng thi lng sang rn. y l im quan trng i vi nha khoa. Th d, nu khun c va vn vi mu c, vt c s nh hn so vi mu do b co li.

S co din ra theo ba giai on: Co do nhit ca kim loi lng t nhit nng chy n khun c, giai on ny

khng nh hng n vt c v khi kim loi co li trong khun c, kim loi nng chy tip tc chy vo b tr.

Co ca kim loi trong qu trnh thay i t lng sang rn Co do nhit ca kim loi t khi rn n nhit thng

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co c ca mt s hp kim c ghi trong bng 20-6. s co khc nhau ca cc hp

kim l do thnh phn ca chng. Platinum, palladium, ng lm gim co c; vng nguyn cht co nhiu, xp x co dn v nhit.

Ni chung, co c t hn co tuyn tnh v nhit (linear thermal shrinkage), iu ny c v bt hp l v hai suy lun gi nh sau:

- Khi khun c c lp y kim loi lng, kim loi s c li bt u thnh khun do nhit ca khun thp hn nhit kim loi nng chy.

- Trong giai on cng u tin, lp kim loi cng st vi thnh khun cn yu, v n c khuynh hng dnh vo thnh khun cho n khi cng. Khi kim loi cng co mt cch c lp vi khun, n tip tc co do gim nhit cho n nhit phng.

Tuy vy trn thc t, s co do nhit ca lp kim loi yu u tin c hn ch do s dnh c hc vo thnh khun, trong qu trnh ny, n thng b cng do thm nhp vo bt c, nh vy, s co trong qu trnh ha rn c gim thp, mt khc, s co ton b do nhit cng c hn ch. Nh vy, s co c t hn s co nhit. Do s co nhit t khi kim loi rn n nhit phng ng vai tr ln trong co c, hp kim c nng chy cao hn c khuynh hng co nhiu hn, iu ny cn c b tr trong k thut c. Bng 20-6. co tuyn tnh khi ha rn ca hp kim c (Linear Solidification Shrinkage of Casting Alloys) Hp kim co c(%) Typ I, hp kim vng Typ II, hp kim vng Typ III, hp kim vng Ni-Cr-Mo-Be Co-Cr-Mo

1.56 1.37 1.42 2.3 2.3

1.2. Tnh cht vt l Cc tnh cht vt l quan trng ca cc hp kim rt qu v qu c nu bng 20-5, ca cc hp kim thng trong Bng BBB. Nhng bng tng t cng c cc nh sn xut c th cung cp. Khong nng chy l nhit c s ca vic c, gii hn trn l trng thi liquidus (lng). Nh vy, i hi tng 75 C n 150 C (150 - 300 F) t c nhit c ng. Gii hn di ca khong nng chy c th dng c lng nhit hn ti a. Cc hp kim dng cho s-kim loi cn c khong nng chy cao gi c trng thi cng trong qu trnh thiu kt s, trnh hin tng bin dng ln. Mt khc, cc hp kim t typ I n typ IV cn c nhit nng chy (fusion temperature) thp khi c dng vi cc phng php c c in hoc bt c thuc loi thch cao. Chnh lch rng ca khong nng chy cng cn ch v khong ny cng rng, cng c xu hng to thin tch dng nhnh cy (coring) trong qu trnh ha cng1. Th tch ring (specific volume) tnh bng (cm3/g) c lin h tng h vi khi lng ring (mt : specific density), l mt ch t ca trung bnh s n v c th c t mt n v khi lng hp kim. T s ca mt ti a trong cc bng (th d t 10, 7 n 18, 3 i vi hp kim-s) ch ra rng nhiu vt c tng ng c th c t cc hp kim mt thp hn l t cc hp kim c mt cao (trong th d ny l trn 70%). Gii hn chy do (yield strength), gii hn t l (proportional limit), gii hn n hi (elastic limit) v c bn cng phn nh mt c tnh, l kh nng ca mt hp kim trc cc lc c hc m khng b bin dng vnh vin. Ni chung, gii hn chy do tng dn t typ I n typ IV. Lm cng theo thi gian c th lm tng gii hn chy do ln n 100%.

1 Thin tch dng nhnh cy xy ra trong x l nhit, khi hp kim dc lm lnh trong iu kin khng cn bng, lp bn ngoi ca vt liu vn cn nhiu nguyn t c nng chy cao hn. Cc nhnh bn ngoi c thnh phn hp kim khc vi phn bn trong. www.hoangtuhung.com

cng (hardness) ca hp kim qu t l thun vi gii hn chy do. cng dng ch s thch hp ca mt hp kim i vi mt ch nh lm sng cho trc.

dn di (elongation) l s o d un hay mc bin dng do ca mt h p kim c th vt qua trc khi gy. dn di cn thit l i hi c bn trong trng hp cn c s bin dng trong lm sng. Lm cng theo thi gian lm gim dn di. Hp kim c dn di thp d b gy v dn.

Hu ht hp kim Ni-Hau het hp kim Ni-Cr s dung lam mao rang va cac phuc hoi co nh tng phan cha t 61% - 81% Ni, 11% - 27% Cr, 2%- 5% Molypen (theo trong lng). Thanh phan ien hnh mot so hp kim c s dung trc ay (vai loai en nay van con s dung) cho cac phuc hoi s co sn kim loai c cho bang 20-8. Trong hp kim, Crom rat can thiet e cung cap s oxi hoa chong g va khang mon. Nhng cong thc hp kim khac nh Cr-Co va Fe-Cr. Cac hp kim nay co the cha 1 hay nhieu nhng nguyen to sau: Al, Beri, Bo, Co, ong, Xeri, Gali, Sat, Mn, Niobi, thiec, Titan, Ziriconi. Nhng hp kim Co-Cr ien hnh cha 53%- 67% Co, 25%-32% Cr, 2%- 6% Molupen (theo trong lng). Nhng hp kim khong quy nong chay nhiet o cao, bot uc s dung cho hp kim nay phai co chat ket dnh la photphat hay silica. Them vao o, phai s dung nguon nhiet cao khi uc. Quan trong hn la bu tr s co rut cua vat uc oi hoi nhiet o cao e at c s kht sat chap nhan tren lam sang. Gan ay, nhng hp kim Ti-Al-V va Titan nguyen chat c a vao thc hien nhng phuc hoi s sn kim loai.

. So sanh vi hp kim vang loai IV a c ADA chng nhan, nhng hp kim cua Co, Ni va Titan nguyen chat co ac iem la gia thanh va ty trong thap hn, o cng cao hn, moun an hoi cao hn va co the so sanh c kha nang khang m va khang mon tren lam sang. Bng 20-5. c tnh l hc ca mt s hp kim kim loi qu nha khoa hin i (Physical Properties of Some Modern Noble Metal Dental Alloys)

Typ

Nguyn t

chnh

Khong nng

chy

Khi lng ring

(g/cm3)

Gii hn chy do (MPa) (psi)

cng

(VHN)

dn

di% hp kim

943-960oC (1730-1760oF)

924-960oC (1695-1760oF)

924-960oC (1710-1760oF)

843-916oC (1550-1680oF) 1021-1099oC

(1870-2010oF) 921-943oC

(1690-1720oF) 871-932oC

(1600-1710oF) 930-1021oC

(1705-1870oF) 1271-1304oC

(2320-2380oF) 1232-1304oC

Rt qu Rt qu Rt qu

I II III IV S

16.6 103 (15,000) 186 (27,000)

207 (30,000) H275 (H40,000) 241 (35,000) H586 (H85,000) 262 (38,000) H323 (H47,000) 275 (40,000) H493 (H71,000) 372 (54,000) H720 (H104,000) 434 (63,000) H586 (H85,000) 572 (83,000)

462 (67,000)

80

101

121H182

138H213

143H154

149H264

186H254

180H270

220

189

36

15.9

15.5

12.8

10.6

15.2

13.6

11.3

39H19

Qu

30H13

Ag-Pd Qu Rt qu Rt qu

10H8

Qu

-kim loi

* Rt qu

13.5

Qu 10.7

35H738H210H620

20

8

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9

*Mu trng. +Mu vng. H: Lm cng theo thi gian. (cc s liu khc l trong iu kin x l nhit lm mm). VHN: Vickers hardness number.

Bng BBB. Tnh cht vt l v c hc ca hp kim thng Physical and mechanical properties of dental metal materials

Alloy Condition

Tensile strength (MPa)

Yield strength (MPa)

Elastic modulus (GPa)

Elongation (%)

Density(g/cm2)

Stainless steel 18-8 wire As received 2035-2849 965-1680 134-200 2-3.2 8 Stress relieved

2160 1034-1950

134-200

__

8

316 wire

As received

2275-2351

1955-2070

185-191

__

__

316L

Annealed

550-600

220-331

190-200

50-55

7.95

Cold- worked 896-1014

790-827

167-200

20-25

7.9-7.95

108 Annealed 931 586 188 52 7.63 Cold- worked 1344 1179 188 35 7.63 Ni-Cr Ni- Cr Be Casting 778-1355 325-838 165-210 3-23.9 7.9-8.1Ni-Cr Casting 539-919 180-858 141-248

Ti- 6A1-7Nb Ti- 15Mo

10

Annealed 978-1024 913 105 __ 4.52 Annealed/aged 874 544 78 __ 4.96

TMA wire As drawn __ 621-1172 60-69.6 __ __ Heat treatmed/aged __ 1220-1390 92.4-95.1 __ __ Nickel - Titanium __ __ __ __ __ Ni-Ti wire A 527-1380 230-379 120 13-40 6.45 Ni-Ti wire M __ 207-552 32-50 __ __ Other __ __ __ __ __ Pure gold 130 20 90 10-39 11.3-15Type III and IV __ __ __ __ __ Gold casting __ 207-434 90 10 - 39 11.3-15Cortical bone 100-200 130 10-20 1-3 0.7 (dryCancellous bone 10-20 __ 0.2-0.5 5-7 __

Abbreviations: ELI, extra low interstitial; Gpa, gigapascal; Mpa, megapascal

3.2. X l nhit cc hp kim rt qu v qu

Cc hp kim vng c th lm cng ng k nu cha mt lng ng nht nh. Typ I v II khng th lm cng hoc cng thm t hn so vi typ III, IV. C ch ca s cng ln l do nhiu tc ng ca s chuyn dng trng thi rn (solid-state transformation), qu trnh ny cn thi gian v nhit .

Nhng hp kim c th lm cng hn c th cng c th lm mm hn c. Theo thut ng luyn kim, vic x l nhit gm x l nhit lm mm (softening heat treatment), x l nhit lm cng (hardening heat treatment) gi l lm cng theo thi gian (age-hardening treatment).

1.2.1. X l nhit lm mm

Vt c c t trong l in nhit 700 C trong 10 pht, sau lm ngui nhanh (quench) trong nc. Trong qu trnh ny, tt c cc pha trung gian c th thay i thnh cc dung dch rn hn n (disordered solid solution), vic lm ngui nhanh lm qu trnh lp li trt t khng thc hin c. Cc c tnh v bn ko, gii hn t l (proportion limit) v cng gim nhng tnh d ko si (d un: ductility) tng ln.

X l nhit lm mm c ch nh cho nhng cu trc s dng trong ming hoc ngoi ming, nh dng hoc gia cng ngui (cold working). Mc d 700 C l nhit trung bnh lm mm, mi nh sn xut thng c ch dn c th v nhit v thi gian.

1.2.2. X l nhit lm cng X l nhit lm cng c th c thc hin theo nhiu cch. Mt trong nhng cch thng

dng nht l thm (nung kh co: soaking), hay lm cng theo thi gian nhit v thi gian thch hp. Thng l khong 15 30 pht, trc khi n c lm ngui nhanh trong nc. Nhit lm cng theo thi gian ca hp kim ty thuc thnh phn, thng khong 200 - 400 C, thi gian do nh sn xut qui nh.

Trc khi hp kim c lm cng theo thi gian, n cn c x l nhit lm mm lm du cc lc ho cng do bin dng (strain hardening), nu cn cc lc ny, v hp kim c lm cng khi cn l dung dch rn hn n, qu trnh ny s khng th kim sot ng, do s tng ln ca sc bn, gii hn t l, cng v gim tnh d un c quyt nh bi lng chuyn dng trng thi rn cho php. S chuyn dng ny, ngc tr li, c kim sot bi nhit v thi gian ca qu trnh x l nhit lm cng theo thi gian.

Do gii hn t l c tng ln trong qu trnh lm cng theo thi gian, s tng ca modun nng lng n hi (sut bin dng n hi: modulus of resilience) c th t c. Lm cng theo thi gian c ch nh cho hm khung, yn, cu, v cc cu trc tng t. i vi cc chi tit nh, nh inlay, lm cng khng c t ra.

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4. THNH PHN, TNH CHT CA HP KIM C NHA KHOA

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4.1. Hp kim rt qu v qu cho phc hnh kim loi-s

Hp kim dng cho phc hnh s-kim loi l mt trong ba nhm theo ch nh ng dng (ton kim loi, s-kim loi v hm khung). Cc hp kim s dng trong k thut s-kim loi bao gm c cc hp kim rt qu, qu, v hp kim thng (Bng 20-5) (xem bi H thng s-kim loi). Thnh phn cc hp kim rt qu v qu c lit k trong bng 20-7

4.1.1. Hp kim rt qu cho phc hnh kim loi-s Cc hp kim vng cho kim loi-s (Gold-based Metal-Ceramic)

Hp kim PFM cha trn 40% khi lng vng v >60% kim loi qu (vng + platinum v palladium v/hoc kim loi qu khc) ni chung c phn loi l rt qu gm cc hp kim thng gp sau y:

Hp kim Vng-Platinum-Palladium C th cha n 88% vng, palladium v platinum; mt lng nh kim loi thng c th

c mt, mt s hp kim loi ny c mu vng. Nhng hp kim ny c th b bin dng lm (sag deformation), ch nn lm cu n 3 n v, trnh cc cu di v cc phn vi.

Hp kim Vng-Palladium-Bc Hp kim cha t 37 n 77% vng, cha n 35% palladium, khong 22% bc. Bc lm

tng h s co nhit, c th lm i mu s. Hp kim Vng-Palladium Vng: 44-55%, palladium: 35-45%. Hp kim loi ny dng cho cc loi s c h s co

nhit thp trnh cc ngu lc cng (tensile stress) theo trc v theo chu vi s trong pha lm lnh ca chu k nung s.

Bng 20- 7. Thnh phn (theo % khi lng) ca cc hp kim typ I n IV truyn thng v bn loi hp kim cho s-kim loi (Composition Range (weight percent) of Traditional Types I to IV Alloys and Four Metal Ceramic Alloys) Typ hp kim Nguyn t chnh Au Cu Ag Pd Sn,In,Fe, Zn, Ga I II III III III IV IV Metal-ceramic Metal-ceramic Metal-ceramic Metal-ceramic

Hp kim vng, rt qu Hp kim vng, rt qu Hp kim vng, rt quHp kim vng, qu Hp kim bc, qu Hp kim vng, rt qu Hp kim bc, quHp kim vng, rt quHp kim palladium, qu Hp kim vng, rt qu Hp kim palladium, qu

83 77 75 46

56 15 52

88 0-6

6 7 9 8

14 14

0-15

10 14 11 39 70 25 45

30 1

0-6

0.5 1

3.5 6

25 4

25 38 60

7 (+4Pt) 88

lng cn

bng thch hp

4.1.2. Hp kim qu cho phc hnh kim loi-s: Cc hp kim palladium (palladium-based

alloys)

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Theo phn loi ca ADA 1984, hp kim qu cn phi cha 25% kim loi qu nhng

khng bt buc phi c vng. Ni chung hp kim qu ch tt c cc hp kim ca palladium, cha khong 54 n 88% palladium, v cho c hp kim bc-palladium (ch cha 25% palladium) lm ton kim loi hoc kim loi-nha. Hp kim qu t palladium to nn s chuyn tip gia hp kim rt qu v hp kim kim loi thng, c v gi c, ln v t trng. Di y l cc hp kim nha khoa ca palladium

Hp kim palladium-bc Hp kim Pd-Ag c gii thiu nm 1974, l hp kim qu khng vng (gold-free noble

metal) u tin cho phc hnh s-kim loi. Thnh phn ca Pd-Ag l 53-61% palladium v 28-40% bc. Thic v indium thng c thm lm tng cng v to thnh lp oxid cho vic dn s. Mt s cn bng ng v thnh phn l cn thit duy tr nhit c thch hp v h s co tng thch. Palladium thay th vng c lm tng khong nng chy nhng cng lm gim h s co ca hp kim. Tng lng bc ni chung lm gim khong nng chy v tng h s co.

T trng (specific gravity, relative density) ca hp kim Pd-Ag thp (10,7 n 11,1) v gi r, hp kim ny rt hp dn thay th hp kim vng. Mt s hp kim loi ny ch cha lng bc thp (khong 28%). Hp kim c cng 170-180 DPH2, gii hn chy do khong 462 Mpa (67.000 psi) v dn di 25%, d mi, d nh bng v mit bng hn so vi cc hp kim qu.

S tng thch v nhit ni chung l tt.

Hp kim Pd-Ag c s dng rng ri t cui nhng nm 70, nh mt c gng ca cc nh sn xut a n cho ngi dng mt sn phm d c, dn s c gii quyt nhng vn ca nhng hp kim thng trc . Tuy vy, vic s dng c gim sau mt vi nm v lm lan mu (discolor) s trong qu trnh nng. Thuyt gii thch hin tng ny l do hi bc thot ra t b mt ca hp kim lan ta thm nhp cc ion vo s trong qu trnh nung, v ngn cn s to thnh keo (colloidal) bc kim loi trn lp b mt ca s. Khng phi tt c s b i v c mt s s khng cha cc nguyn t cn thit lm gim ion bc.

Mt hp kim palladium khc cha 75 n 90% palladium, khng c bc c pht trin loi tr hin tng xm xanh(greening). Mt s hp kim c lng palladium cao to mt lp oxid sm mu trn b mt trong qu trnh lm lnh, lp ny gy kh khn cho vic che mu. Cc hp kim cha palladium cao khc: Pd-Ga-Ag-Au khng gy hin tng ny. V palladium t hn bc, vic thay th bc bng palladium lm gi thnh cao hn hp kim Pd-Ag. Cc hp kim palladium c gi mt cch ngu hng l hp kim bn qu (semiprecious). Nh ni trn, tn ny khng nn dng v n khng chnh xc v v d c xu hng gy ra s ln ln do gp nhng hp kim khng tng t nhau vo mt nhm.

So snh vi hp kim vng, vn ln nht l cc hp kim cha lng bc cao lm lon mu. Hp kim cha vng, v vy, c qung co l nongreening. K thut vin cn ch khi lm nhng rng trc, nht l khi rng cn mu rng trng.

bm dnh (adherence) ca s l iu c quan tm i vi cc hp kim Pd-Ag. Nh ni trn, cn to mt lp oxid b mt c s dn kim loi vi s. Trn thc t, mt s cng thc, s to thnh oxid din ra bn trong tri hn trn b mt. Tnh trng ny c th chp nhn v mt lm sng nhng khng phi l mt tnh trng l tng. Cc ht hnh thnh trn b mt do oxy ha bn trong to s lu c hc hn l ha hc. Hp kim palladium-ng L loi hp kim mi c pht trin trong nha khoa, v vy, cn c thm nhiu thng tin

hn na v kt qu lm sng. Cc hp kim Pd-Cu thng c 74-80% palladium v 9-15% ng. Do khong nng chy

thp (1170-1190 C), hp kim ny c th b bin dng lm khi thiu kt s, cn c ch , nht l i vi cu di. Vi cu trc ca hp kim Pd-Cu-Ga khi c v sau khi nung s b thay i, tuy thay i v th tch v s bin dng khng ng k nhng y l vn i vi hp kim ny. Mt s hp kim Pd-Cu cha 2% vng.

2 DPH: Diamond Pyramid Hardness, cng l cng Vickers www.hoangtuhung.com

13

Hp kim Pd-Cu c gii hn chy do ln n 1145 MPa (166.000 psi), dn di 5-11%,

cng cao nh mt s hp kim kim loi thng. Nh vy, cc hp kim ny c xu hng kh mit bng, tr nhng b tng i mng. Tuy vy, hu ht k thut vin cho l hp kim loi ny d lm hn hp kim thng. Mc d s khng tng thch nhit (thermal incompability) l khng ng k, nhng cc chi tit mng di 0,1mm c th d b nh hng. Khng tng thch ng sut gia s v hp kim (metal-porcelain incompability stress) c th l nguyn nhn ca s bin dng, c bit l hp kim Pd-Cu c chy (creep) kh cao nhit gn vi nhit chuyn dng glass ca s. Cc yu t khc c th l nguyn nhn ca bin dng l hin tng hi phc ngu lc n hi (relaxation of elastic stress) do ha rn, mi, thi ct...

Gii php cho hin tng bin dng l lm cc chi tit dy hn, thay i s hoc hp kim cho ph hp.

Lon sc s c th c nhng khng phi l vn ln. Gn y c mt s bo co v c

tnh ca hp kim Pd-Cu do ng phng thch vo mi trng ming. Mc d cha c cc nghin cu khoa hc kt lun, iu ny cng cn ch . Lng nh vng trong hp kim khng c ng gp ng k tr vic n c coi l hp kim c vng i vi cc hng bo him (c gi tng ng hp kim palladium-bc).

Cn ch n nh hng v thm m do s to thnh oxid mu sm hoc en trong qu trnh oxy ha v nng s. K thut vin cn ch che cn thn lp oxid v trnh di mu en mt thm m tip ni s-kim loi. Cng cn ch l lp mu en thng gy kh khn nhiu so vi lp oxid nu.

Mt vi hp kim loi ny kh nhy cm v k thut c, chun b hn v x l oxy ha. Th d, mt s loi hp kim nng chy (molten alloy) cn c mt lp mng oxid xut hin trn b mt nhit c (casting temperature). Mt s hng dn nhn mnh nhit cn c duy tr thm 7 giy sau thi im quan st c vn ng quay ca hp kim. Do thiu nhng ch dn c th v biu hin ca s nng chy, thng c khuynh hng lm qu nhit loi tr lp mng mng. Sai lm ny c th a n lm thay i tnh cht ca hp kim v lm gim bn dn s-hp kim. Nhit di mc nng chy cng c th gp do kh nh gi ng s nng chy, iu ny a n sai st ca vt c: khng hoc cc cnh b trn. Hp kim palladium-cobalt Thnh phn ca hp kim qu palladium cha t 78 n 88% palladium, t 4 n 10%

Cobalt, c th c 8% gallium theo th tch. Hp kim Pd-Co in hnh c cng 250 DPH, gii hn chy do 586 Mpa (85.000 psi), dn di 20%, modul n hi 85,2 Gpa (12,35 x 106 psi). Chng tng i d thao tc s dng.

Hp kim Pd-Co ni chung c h s co nhit kh cao, thch hp vi cc loi s c dn n cao.

V gi c, hp kim ny xp x hp kim Pd-Ag hoc Pd-Cu. Thng c qung co l hp kim khng vng, khng nickel, khng beryllium, khng bc. S khng c mt nickel v beryllium ch ra rng hp kim ny , cng nh cc hp kim qu thc s khc, c tnh tng hp sinh hc. Cng nh nhiu hp kim qu, chng c ht nh (fine grain size) gim thiu s co rt trong qu trnh ha rn. Nhm hp kim Pd-Co ny c khng bin dng cao nht trong s cc hp kim qu.

Tuy khng c bc, cc hp kim ny cng gy i mu s do cobalt, nhng khng ng k. K thut che mu lp oxid ca k thut vin mi l nguyn nhn chnh ca nhng khim khuyt v thm m. Cc hp kim palladium-gallium-bc v palladium-gallium-bc-vng L nhng hp kim qu mi xut hin gn y. Chng ra i khc phc nhc im v

lp oxid sm mu ca cc loi hp kim Pd-Cu v Pd-Co, v tng thch nhit vi cc s dn n thp.

Lng bc kh thp (5-8%), thng khng gy ra hin tng xm xanh (greening). Cn t ti liu v bn dn v tng thch nhit.

H s co nhit thp, thch hp vi s c dn n thp nh Vita. Nhn chung, trnh cc sai lm, cn xem vn bn chp nhn (acceptable) ca ADA;

cng cn i chiu vi danh mc tng thch gia cc loi s vi loi hp kim c chn ca nh sn xut (ch khng phi l ch hi ngi bn hay k thut vin). www.hoangtuhung.com

14

4.2. Hp kim cho phc hnh ton kim loi, kim loi-s v mt dn nha

4.2.1. Cc hp kim bc-palladium

Hp kim c mu trng, ch yu l bc, c 25% palladium; l mt hp kim qu v hn ch c s i mu ca bc. C th c mt lng nh ng, vng.

Hp kim Ag-Pd khng c ng gm 70-72% bc v 25% palladium c c tnh c hc tng ng typ III hp kim vng. Hp kim Ag-Pd-Cu gm khong 60% bc, 25% palladium, 15% ng c c tnh tng ng typ IV. Tuy vy, chng c khuynh hng d b i mu v n mn hn hp kim vng. Ch ng nhm cc hp kim ny vi hp kim Pd-Ag dc dng cho phc hi s-kim loi.

Do nhu cu thm m, ngy cng t dng mo ton kim loi. Cc hp kim dng cho mo, cu s-kim loi s c trnh by sau. c im l hc cc hp kim rt qu v qu (bao gm Ag-Pd) lm phc hnh ton kim loi v s-kim loi c trnh by trong bng 20-5.

4.2.2. Cc hp kim nickel-chromium v cobalt-chromium

S pht trin ca cc hp kim thng (khng qu) cobalt-chromium (Co-Cr) cho cc ng dng c trong nha khoa nm bt u t 1928, trong nhng nm sau , cc hp kim Ni-Cr v Ni-Co-Cr c a vo s dng v c chp nhn ngy cng rng ri, chim u th trong vic la chn lm mo, cu, hm khung(bng 20.8)

So snh vi hp kim vng loi IV c ADA chng nhn, nhng hp kim ca Co, Ni v Titan nguyn cht c c im l gi thnh v t trng thp hn, cng cao hn, mun n hi cao hn v c th so snh c kh nng khng m v khng mn trn lm sng. Gn y, cc hp kim Ti-Al-V (vanadium) v Titan nguyn cht c a vo thc hin cc phc hi s sn kim loi.

Nm 1978, mt kho st trn 1000 ch labo Hoa k, cho thy ch 29% cc labo s dng cc hp kim Ni-Cr hoc Co-Cr cho nhng phc hi bng kim loi, s-kim loi. Vo nm 1980 v 1981, t l cc labo s dng nhng hp kim khng qu ni trn tng ln ln lt 66% v 71%, do s khng n nh v gi ca hp kim qu trong giai on ny. Hu ht cc labo nha khoa thch s dng hp kim Ni-Cr hn Co-Cr. Cc hp kim Ni-Cr-Be vn ph bin mc d cha kh nng gy c ca Beryllium (Be) v d ng ca Nickel.

Cc hp kim Ni-Cr: s dng lm mo rng v cc phc hnh c nh tng phn cha t 61% - 81% Ni, 11% -

27% Cr, 2%- 5% Molybdenum (theo khi lng). Cc hp kim Co-Cr in hnh cha 53%- 67% Co, 25%-32% Cr, 2%- 6% Molybdenium (theo khi lng). Trong hp kim trn, Chromium rt cn thit to c tnh th ng v khng n mn;

cc hp kim ny v cc hp kim Cr-Co, Fe-Cr cng c th cha mt hay nhiu nhng nguyn t sau: nhm (aluminum: Al), beryllium ( Be), borium (B), cobalt (Co), ng (Cu), cerium (Ce), gallium (Ga), st (iron: Fe), mangan (manganese: Mn), niobium (Nb) (cn gi l columbium), silic (silicon: Si), thic (tin: Sn), Titanium (Ti), Zirconium (Zr). Thnh phn in hnh mt s hp kim khng qu cho cc phc hi s-kim loi c nu bng 20-8.

Cc hp kim khng qu nng chy nhit cao, bt c s dng cho hp kim ny phi c cht kt dnh l phosphate hay silica. Hn na, phi s dng ngun nhit cao khi c v i hi quan trng hn l b tr s co rt ca vt c nhit cao t c s kht st chp nhn c trn lm sng.

4.2.3. Cc hp kim khng qu khc

Hp kim nhm-ng thic (aluminum bronze alloy) ng thic (cn gi l ng : bronze) gm ng (copper: Cu) v thic (tin: Sn). Trong

nha khoa, hp kim nhm-ng thic (aluminum bronze alloy) c th c s dng gm 81-88% Cu, 7-11% Al, 2-4% Ni, 1-4% Fe (theo khi lng). Tuy vy, n t c dng v ng c khuynh hng phn ng to thnh sulfide, lm i mu.

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Titanium v hp kim titanium C th dng cho ton kim loi, s-kim loi v khung. S c trnh by trong bi

Tianium v hp kim titanium). Bng 20-8. Cc hp kim thng in hnh cho phc hi s kim loi (Typical base

metal alloys for metal-ceramic restorations)

Thnh phn ( phn trm khi lng) Tn hp kim&Nh SX Ni Co Cr Be Mo W Ru Rexillium III (Jeneric/Pentron) 76 0.3 14 1.8 5 Litecast B (Williams Dental Co.) 78 13 1.7 4 Neptune (Jeneric/Pentron) 62 22 9 Forte(Unitek/ 3M) 62 22 9 Genesis II (J. F. Jelenko & Co.) 53 27 3 Ultra 100 (Unitek/ 3M) 52 28 Novarex (Jeneric/Pentron) 55 25 10 5

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