PEDIATRIC DENTISTRY/Copyright@ 1982 byThe American Academy of Pedo~ontics/Vol. 4, No. 2 SCIENTIFIC

A clinical evaluation .of polishing amalgamsimmediately after insertion: 18 month results

Richard E. Corpron, DDS, MS, PhD Lloyd H. Straffon, DDS, MSJoseph B. Dennison, DDS, MS Susan H. Carron, DDS, MSKamal Asgar, BS, MS, PhD

AbstractThirty-three patients, 7-13 years of age,

demonstrated 96 pairs of contralateral occlusal fissurea_~d buccal and lingual pit cavities which were restoredwith a high-copper amMgam. One restoration of eachpair was polished with a slurry of XXX Silex in anunwebbed rubber cup at eight minutes followingtrituration. The contralateral restoration was finishedat least 24 hours after iasertion with pear-shapedfinishing burs and polished with a slurry of XXX Silex,followed by a slurry of tin oxide. Each restoration wasexamined clinically for five criteria by three examinersand black and white photographs were taken atbaseline and at each six-month recall.appointment for18 months.

Clinically, marginal adaptation worsened frombaseline to 18 months with both methods of polishing,but there was no significant differences between thetwo methods. However, a significant difference inmarginal adaptation was evident by photographicevaluation. The surface textureof eight-minutepolished restorations at baseline was granularcompared to the glossy surface of restorations polishedat 24 hours, but by 18 months, the surface texture ofthe restorations poh’shed by the two methods was verysimilar.

marginal adaptation, reduced surface tarnish andmarginal corrosion, and smoother surfaces andmargins which are less susceptible to plaqueaccumulations."5 At least a 24-hour delay following in-sertion has been considered as the minimum periodfor conventional-amalgams to attain adequatephysical properties before such restorations could bepolished effectively. The faster setting time and theearlier rate of development of high compressivestrength of the newer "high copper" dentalamalgams support the possibility that earlierfinishing and polishing may be possible withoutsignificant detriment to the final restoration.6s

While few clinicians appear to dispute the meritsof finishing and polishing of amalgam restorations,the most practical time following placement remainsunresolved. It is the purpose of this investigation tocompare clinically the effects of early polishing of"high copper" dental amalgam restorations at an in-terval of eight minutes following the trituration ofthe amalgam with those observed after finishing andpolishing at the more conventional time of at leasttwenty-four hours.

Perhaps the greatest challenge to the longevity

of amalgam restorations is observed in children in theprimary, mixed, and young permanent dentitions.During such periods, when dynamic changes in thedeveloping occlusion and peaks in caries activity arecharacteristic, the majority of decayed primary andyoung permanent teeth are restored with amalgam.Failures of such amalgam restorations are generallydue to faulty cavity design, improper manipulationof the amalgam, or inadequate physical properties ofthe amalgam which lend to poor marginal adaptationand significant potential for recurrent decay.

Benefits reported for the well-finished and pol-ished amalgam restoration include improved

Methods and Materials

Thirty-three patients, age 7-13 years, whodemonstrated a total of 66 contralateral pairs ofClass I occlusal cavities and 30 contralateral pairsinvolving buccal or lingual pits or grooves wereselected. Mesio-occlusal and disto-occlusal surfaceson the maxillary molars were considered as separatepairs, but were designated for the same polishingvariable in the study due to problems of isolation ofthe polishing agents in a small area. The restorationswere designated for either immediate polishing ateight minutes or polishing at 24 hours after the startof trituration by following a randomized numericalchart for right or left and then adjusting for the last

98 EARLY POLISHING OF AMALGAMS: Corpron et al,

pairs in order to obtain equal numbers of right andleft immediate-polish pairs.

Selected teeth were anesthetized with 2% Carbo-caine (Mepivacaine) containing 1:20,000 Neo-Cobefrinvasoconstrictor, isolated with a rubber dam, andClass I occlusal preparations were performed bythree operators with a #56 fissure bur utilizing a highspeed handpiece. Deep caries were removed with theappropriate size round bur in a contra-angle slowspeed handpiece. The cavity was refined with a #57fissure bur in a slow speed. After debridement of thecavity, varnish was applied with a smallcotton pellet.The amalgam was triturated with an S.S. White Cap-master amalgamator? according to manufacturer’sspecification for regular set Tytin amalgamb

(800 mg}. Condensation of the amalgam was mainlyaccomplished with a 1.4 mm round condenser andoverpacked with a 1.4 mm x 2.0 mm elliptical shapedcondenser using hand pressure.

Carving ProcedureImmediately following condensation, the amalgam

was burnished with a #21B anatomical burnisherc

and carved with the cleoid end of a 7C cleoid/discoidcarverd for good definition of the enamel-amalgammargin and occlusal pattern. A 5C cleoid/discoidcarver° and an S.S. White #3 explorerf were used forrefinement and for removal of flash at the margin.All amalgams were packed and carved during an in-terval of eight minutes from the start of triturationof the amalgam.

Polishing TechniqueMarginal adaptation, anatomic form, surface tex-

ture, occlusai morphology and recurrent caries wereselected as the criteria to clinically compare the twomethods of finishing and polishing utilized in thisinvestigation. The first method of polishing was ac-complished at the operative appointment eightminutes from the start of trituration of the amalgamfor one restoration of each pair. A creamy paste ofSilex XXXg and water on an unwebbed black rubber

cup in a slow speed contra-angle handpiece was ap-plied to the tooth for a period not to exceed oneminute per surface. The second method wasdesignated that the other contralaterally paired toothbe finished and polished after twenty-four hours.Pear-shaped finishing burs of decreasing size wererun along the enamel-amalgam margin utilizing slowspeed. Grooves were refined with a #0 round finishingbur by carrying the bur from the enamel-amalgam

as.s. White Division of Pennwalt Corp., King of Prussia, PA.bS.S. White Dental Products International, Holmdel, NJ.c d eE. F. Wessler Manufacturing Co., Cleveland, OH.fS. S. White Division of Pennwalt Corp., Philadelphia, PA.gMoyco Industries, Inc., Philadelphia, PA.

margin into the center of the amalgam. Any ex-tremely small grooves were finished with a #0 flame-shaped bur. The amalgams were then highly pol-ished with a creamy paste of XXX Silex and wateron an unwebbed black rubber cup with slow speed,followed by a creamy paste of tin oxideh and water.

EvaluationEvaluation of the two techniques of finishing and

polishing amalgam was accomplished by twomethods. The first method of analysis was a clinicalexamination based upon a Modified Ryge Explorerexamination?" A qualitative visual clinical assess-ment was made utilizing a #4 mirror and an S.S.White #3 explorer by the three independentevaluators. The criteria for evaluation included:margin adaptation, anatomic form, surface texture,occlusal morphology, and caries (Tables 1-3). Theteeth were examined at the baseline examination (at

Table 1. Criteria for quality evaluation.

Marginal Adaptation (Dry)

Restorative material iscontinuous with adjacent toothstructure -- not detectablewith a sharp explorer, passesin either direction

Margin detectable by explorerexamination only -- along lessthan 50% of exposed margin

Margin detectable by explorerexamination only -- alongmore than 50% of exposedmargin

Visible evidence of creviceformation into which theexplorer will penetrate alongless than 50% of exposedmargin

Visible evid6nce of creviceformation into which theexplorer will penetrate alongmore than 50% of exposedmargin

Crevice formation with exposureof underlying dentin or base

HealthModified CenterRa ring Criteria

1 Alfa

2 Alfa

3 Alfa

4 Bravo

5 Bravo

6 Charlie

hMatheson, Coleman & Bell, Norwood, OH.

PEDIATRIC DENTISTRY: Volume 4, Number 2 99

Table 2. Criteria for quality evaluation.

Surface Texture Rating

Glossy 1

Satiny 2

Granular 3

Dull 4

Voids, pits, or scratches present — lessthan 50% exposed area 5

Voids, pits, or scratches present —more than 50% exposed area 6

Evidence of dark discoloration 7

used to assess the amount of marginal flash:Category 1 — no flash; Category 2 — one or two areasof flash; Category 3 — three or four flash areas; andCategory 4 — more than 4 flash areas.

Black and white photographs were taken at thebaseline examination and at 6-, 12-, and 18-monthrecall appointments with a Medical Nikkor C camera

least 24 hours after placement of the restoration) andat 6-, 12-, and 18-month recall appointments.

The second method of analysis was a modificationof that developed by Mahler et al.l2 which comparedthe marginal adaptation from photographs of eachrestoration to photos of six representative restora-tions depicting specific stages of amalgam failure"(Figure 1 and Table 2). Additionally, the second stepin the evaluation of the margins from the photos was

Figure 1. Photographic evaluation (See Table 1)(6x).

Table 3. Criteria for quality evaluation.

Anatomic Form Rating

Harmonious and continuous withocclusal morphology — no changefrom original anatomic form

Evidence of loss of material fromoriginal anatomic form in one localarea

Evidence of loss of material fromoriginal anatomic form in multipleareas

Loss of material with exposure ofunderlying dentin or base (designatesurface number)

Total loss of all material or fractureof restoration

Occlusal Morphology Rating

Harmonious and continuous withexisting cuspal inclines — central pitsand fissures well defined 1

Slightly discontinuous with existingcuspal inclines or central pits andfissures not well defined 2

Occlusal morphology not continous andharmonious with existing cuspalinclines — central pits and fissurespoorly defined or not evident 3

Caries Formation Ratings

No caries associated with treatedsurfaces 1

Secondary caries related to treatedsurfaces 2

Replacement of material due tononrelated caries 3

100 EARLY POLISHING OF AMALGAMS: Corpron et al.

with a 200 mm macro lens set at 1.5x and enlarged6x for evaluation. The baseline examination was per-formed at least 24 hours after placement of restora-tion in order to complete the conventional finishingand polishing method and to obtain sufficientstrength to restorations polished at eight minutes.

A concensus was reached for each evaluation whenat least two examiners agreed independently on thesame rating for each clinical and photographicevaluation. When no agreement occurred followingindependent evaluation, a consensus was reached byre-examination and consultation by the three ex-aminers. As a check on the consensus method ofevaluation, the values obtained from the ratings ofthe three examiners using the Modified Ryge Ex-plorer examination were converted to correspondingratings of the Dental Health Center9 rating scale,and interexaminer agreement was calculated for bothmethods.

Recall examinations will continue to be completed

every six months for a period of three years. At eachappointment, the recall procedures, except thefluoride treatment, will be completed prior to secur-ing the necessary photographs and the explorer ex-aminations. The recall procedures to be accom-plished are: posterior bitewing radiographs, pro-phylaxis, oral examination, and a fluoride treatment.Any newly decayed teeth not involved in the studywill be referred to the regular pedodontic clinic forrestoration.

Results

Initally, 96 pairs of amalgam restorations wereevaluated independently at the baseline appointmentby each investigator with a mirror and explorer forfive criteria, and two criteria were evaluated fromphotographs of the restorations {Tables 1-3). Subse-quently, at the 6-, 12-, and 18-month recall appoint-ment, the numbers of pairs of restorations evaluatedwere 90, 85, and 81 respectively.

Table 4. Consensus ratings for criteria of quality evaluation.

Clinical Evaluation

Criteria Baseline 6 Months 12 Months 18 Months

8 Min 24 Hr 8 Min 24 Hr 8 Min 24 Hr 8 Min 24 Hr

~-- S.D. ~-- S.D. X+_ S.D. ~_+ S.D. ~_- S.D. ~-+ S.D. ~+_ S.D. ~__ S.D.

Marginal 1.58 _ 1.66 + 1.96" + 1.96" ___ 2.00 _ 2.03 _+ 2.12" + 2.14" _Adaptation .49 .48 .47 .44 .31 .32 .36 .44

Surface 3.97 _ ° 1.06 + 2.89*_+ o 2.12" _+ 2.76* _+ ° 1.94" _+ 2.50* _+ o 2.04 _+Texture .31 .43 .66 .74 .57 .44 .57 .46

Anatomic 1.09 +_ 1.03 +_ 1.07 +_ 1.08 +_ 1.20 + 1.10 +_ 1.01 _+ 1.01 _+Form .29 .17 .25 .27 .43 .31 .11 .11

Occlusal 1.10 _+ 1.21 _+ 1.06 +_ 1.04 +_ 1.05 -+ 1.05 _+ 1.04 _+ 1.00 _+Morphology .31 .41 .23 .21 .21 .21 .19 .00

Caries 1.00 _+ 1.00 _+ 1.00 _+ 1.00 _+ 1.00 _+ 1.00 _+ 1.00 _+ 1.00 _+.00 .00 .00 .00 .00 .00 .00 .00

Photographic Evaluation

Marginal 1.32" _+ o 1.93 _ 2.02* _+ o 2.47* _+ 2.44* _+ o 2.70* _+ 2.56 _+ o 2.71 _+Adaptation .49 .39 .52 .60 .73 .55 .69 .53

Flash 2.02* + o 1.70 _+ 1.84" _+ 1.77 _+ 1.86 _+ 1.82 + 1.80 -+ 1.79 _+.75 .54 .65 .60 .65 .56 .66 .51

*Signifiant difference {p<0.05) in restorations polished by the same method for two time periods.°Significant difference (p<0.05} in restorations polished by the two methods at one time period.Statistical test: Michigan Interactive Data Analysis System (MIDAS: Paired t-test)

PEDIATRIC DENTISTRY: Volume 4, Number 2 101

Figure 2 A-D. Eightminute polished res-torations (6x): A —Baseline; B — Sixmonths; C — Twelvemonths; D — Eighteenmonths.

Our consensus agreement for all clinical evalua-tions averaged 98% for marginal adaptation com-pared to 96% when the ratings were converted to theDental Health Center scale (Table 1). The consensusagreement for surface texture was 97%. Additionally,the consensus agreement among examiners from thephotographic evaluations of marginal adaptation andflash exhibited a range of 94-99% and 93-98%respectively.

From baseline to the 18-month evaluation, therewas no significant difference (p<0.05>* betweenrestorations polished at 8 minutes and 24 hours, norbetween each method at the various time intervalsfor anatomic form, occlusal morphology, and cariesformation (Table 4). Conversely, a significant dif-ference was initially obvious in surface texture be-tween restorations polished at 8 minutes and 24hours (Tables 4 and 5). At baseline, the eight minuterestorations appeared uniformly granular with a dullfinish (Figure 2A), whereas restorations polished at24 hours exhibited a shiny, reflective surface (Figure3A). Although the significant difference in surfacetexture between restorations polished at 8 minutesand those at 24 hours persisted throughout thestudy, by 18 months the granularity of the restora-tions polished at 8 minutes had decreased markedly(Tables 4 and 5), and the difference in the appearancein the surface texture between the two methods hadnarrowed enough that many pairs of restorationsdemonstrated a similar appearance at 18 months(Figures 2D and 3D).

The clinical evaluation of marginal adaptationrevealed no significant differences between the two*MIDAS (Michigan Interactive Data Analysis Systems): pairedt-test.

methods of polishing at baseline nor during subse-quent recall appointments throughout 18 months(Tables 4 and 6). However, the ratings for marginaladaptation progressively worsened for restorationspolished at both 8 minutes and 24 hours, beginningat baseline and continuing through the 18-monthrecall (Table 6). Significant differences from priorratings were observed at the 6- and 18-month recallappointments (Table 4).

The photographic evaluation of the marginal adap-tation revealed that the margins for restorationspolished at both 8 minutes and 24 hours graduallyworsened from baseline to 18 months with significantdifferences between the two methods at baseline,6-, 12-, and 18-months (Table 4). Additionally, theamount of flash observed for restorations polishedat 24 hours was significantly less than the 8-minuterestoration at baseline, but at subsequent recallintervals no significant differences were observedbetween the two methods (Tables 4 and 7).

DiscussionThe development of the high copper amalgams

which are reported to be superior clinically to the con-ventional amalgams has led to their widespreaduse.14'9 Their adoption has required changes in thehabits of dentists in the manipulation and finishingof such new alloys. The polishing of high copperamalgam restorations shortly after insertion hasbeen postulated from the results of a variety oflaboratory investigations,81420 based upon theassumption that the improved physical properties ofthe high copper amalgams (i.e., low static anddynamic creep, early high and final compressivestrength, faster rate of hardening, and eliminated

Figure 3 A-D. Twenty-four hour polishedrestorations (6x): A —Baseline; B — Sixmonths; C — Twelvemonths; D — Eighteenmonths.

102 EARLY POLISHING OF AMALGAMS: Corpron et al.

Baseline 6 Months 12 Months 18 Months

Rating 8Min 24Hr 8Min 24Hr 8Min 24Hr 8Min 24Hr

Table 5. Clinical consensusratings for surface texture. Number 96 96 89 91 85 86 82 81

1 -- Glossy 1 94 2 8 10 2 6

2 -- Satiny 13 70 26 72 38 67

3 -- Granular 71 I0 53 3 41 7

4 -- Dull 95 2 3 3 6 1 1 1

gamma-2 phase) would provide the resultingamalgam restoration with properties adequate towithstand the effects of early polishing while en-hancing the surface texture and marginal adaptation.Busquets et al. TM demonstrated the effects of earlyfinishing and polishing of amalgam restorations us-ing the scanning electron microscope, and observedthat finishing burs should not be used on 8-minuteamalgams, whereas carefully carved high copperrestorations followed immediately by polishing pro-duced a restoration with acceptable surface textureand favorable marginal adaptation.

Nitkin and Goldberg8.~° examined the effects ofearly polishing of a variety of amalgams andpostulated that restorations of high copper amalgamcould be polished at the time of placement, but sug-gested that the time of polishing varied with the in-dividual alloy. We selected 8 minutes after tritura-tion of regular set Tytin amalgam as a feasible, yetpractical period at which newly inserted amalgamrestorations could be polished without detriment tothe structures of the restoration. Additionally, 8minutes appeared to be a reasonable time to allowfor the insertion and carving of a quadrant of newlyplaced, regular set restorations by an experienceddentist.

The benefits of polished amalgam restorations overthose which remained unfinished following carvinghave been suggested by a variety of investigators,’5

generally without the benefit of qualitative lon-gitudinal clinical comparison of such restorations. Inorder to compare the effects of early polishing tothose resulting from conventional polishing methods,the most precise methods available were modifiedand utilized for the present investigation. The clinicalserviceability of the amalgam restorations is gen-erally defined in terms of marginal integrity whichwas evaluated clinically in this study using amodification of the method reported by Ryge andSnyder9 in 1973. Their criteria for the assessment ofmargin adaptation (Table 1} was further subdivided

to allow for identification of the gradual marginalchanges observed to occur prior to marginal creviceformation or recurrent decay" (Table 1). This methodof evaluation assumes significant relevance to clini-cians since the decision to replace restorations isbased upon evidence derived by clinical examination.

Similar criteria used for clinical evaluation weresubsequently applied to the photographic evaluationof marginal adaptation using a modification of themethod by Mahler et al. ’2 In comparing the clinicaland photographic evaluations of marginal adapta-tion, the results of both methods of evaluationdemonstrated that all marginal ratings graduallyworsened from baseline to 18 months, although thegreatest decrement occurred during the first sixmonths (Figures 2A-D and 3A-D). The statistical dif-ferences between the two polishing methods ob-served from the photographic evaluation appeareddue to the much higher magnification 16x} of thephotographs utilized as compared to the visual andexplorer phases of the clinical examination.

The early polishing of restorations producedmarginal adaptation similar to those polished at 24hours, with the polish at 8 minutes requiring con-siderably less time. At 8 minutes the amalgam is notcompletely set, allowing further refinement of themargins after carving with the careful application ofa polishing agent. We consider the success of therestorations polished at 8 minutes to be contingentupon a careful carving method whereby all possiblemarginal excesses are removed prior to polishing.Even though more flash was evident photograph-ically up to 6 months with the restorations polishedat 8 minutes, the subsequent loss of such flash didnot prove detrimental, leading to the speculation thatany flash observed following the polishing at 8minutes was very thin and its loss did not causesignificant marginal voids (Figures 2A-D).

One of the problems with early polishing is theresultant granular surface texture which wouldpossibly allow for greater plaque accumulation than

PEDIATRIC DENTISTRY: Volu’me 4, Number 2 103

Rating

Clinical Evaluation

Baseline 6 Months 12 Months 18 Months

8 Min 24 Hr 8 Min 24 Hr 8 Min 24 Hr 8 Min 24 Hr

Table 6. Marginal ::atings forclinical and photo,graphicevaluation.

N 96 96 90 91 85 86 82 81

1 -- Alpha 40 33 10 10 3 2 1

2 -- Alpha 56 63 76 76 80 80 73 70

3 -- Alpha 2 4 1 3 8 8

4 -- Beta 2 1 1 1 1 2

5 -- Beta No Ratings

6 -- Charlie No. Ratings

Photograptn’c Evaluation

N 93 95 90 91 85 86 82 82

1 64 11 10 1 2 1 2 1

2 28 80 69 50 49 27 38 24

3 1 4 10 36 29 55 37 55

4 1 4 3 3 4 2

5 2 1

6 No Ratings

the smoother, conventionally polished restorations.In this study, though plaque accumulation was notmeasured, increased plaque around the restorationspolished early as compared to the restorations pol-ished at 24 hours was not readily evident at the recallappointments. Also, in this study there was no recur-rent decay along the margins, so new interproximaldecay involving t:he pairs of teeth studied, and norestorations of either the groups polished at 8minutes or those at 24 hours were judged clinicallyunacceptable at 18 months. Additionally, there wasclearly an improw~ment in the surface texture suchthat by 18 months, many restorations polished at 8minutes approached the surface texture of theirpaired restorations polished at 24 hours {Table 5}.This effect was noticeable on the occlusal surfaceswhere direct self-polishing from mastication wasmost effective, but future investigations should beconducted to evaluate plaque retention on the

granular texture of a proximal surface after earlypolishing.

Final adoption of the early polishing method foramalgam restorations in occlusal fissures and smoothsurface pits should await continued longitudinalassessment of this method.

Conclusions

In a controlled study, the marginal adaptation ofpit and fissure restorations of a high copper amalgam(Tytin} worsened from baseline to 18 months forrestorations polished at either 8 minutes or 24 hoursafter placement. Clinically, there were no significantdifferences between the marginal adaptation ofrestorations polished by the two methods. However,a significant difference in marginal adaptation wasevident by photographic evaluation. At baseline thesurface texture of restorations polished at 8 minuteswas granular compared to the glossy surface of

104 EARLY POLISHING OF AMALGAMS: Corpron et al.

Table 7. Consensus of areas offlash from clinical evaluation.

Baseline 6 Months 12 Months 18 Months

8 Min 24Hr 8 Min 24 Hr 8 Min 24 Hr 8 Min 24 Hr

(N) 93

Areas of Flash

None 20

1-2 56

3-4 12

More than 4 5

96 90 91 85 86 82 82

32 25 29 22 23 24 21

59 56 54 54 56 53 57

4 7 8 7 7 2 4

2 2 3

restorations polished at 24 hours, but by 18 monthsthe surface texture of restorations polished by the

two methods were similar. Additional data will be col-lected through the remaining 18 months of the study.

Dr. Corpron is chairman and professor of pedodontics; Dr.Straffon is professor of pedodontics; Dr. Dennison is professor ofoperative dentistry; Dr. Carron is assistant professor of pedo-dontics; and Dr. Asgar is professor of dental materials, School ofDentistry, The University of Michigan, Ann Arbor Michigan48109. Requests for reprints should be sent to Dr. Corpron.1.Kantorowicz, G. F. Finishing amalgam restorations. Dent Prac-

tit 3:64, 1957.2. Phillips, R. W. Amalgam -- its properties and manipulation.

N Y J Dent 23:105, 1953.3. Nadal, R. Amalgam restorations: cavity preparation, condens-

ing and finishing. JADA 65:66, 1962.4. Charbeneau, G. T. An appraisal of finishing and polishing pro-

cedures for dental amalgam. Mich Dent A J 46:135, 1964.5.Charbeneau, G. T. Polishing amalgam restorations. Mich Dent

A J 47:320, 1965.6.Brown, D. The clinical status of amalgam. Brit Dent J 141:80,

1976.7.Moffa, J. P. and Jenkins, W. A. Two-year clinical evaluations

of a dispersed phase and a single phase amalgam. Abstr, J DentRes 56:114, 1977.

8.Nitkin, D. A. and Goldberg, A. J. The effect of immediatepolishing on amalgam restorations. Abstr J Dent Res 57:81,1978.

9. Ryge, G. and Snyder, M. Evaluating the clinical quality ofrestorations. JADA 87:369, 1973.

10.Cvar, J. F. and Ryge, G. Criteria for the clinical evaluation ofdental restorative materials. U.S. Dept. H.E.W. Dental HealthCenter, San Francisco, 1973, pp vii+39.

l l.Dennison, J. B., Straffon, L. H., Corpron, R. E., andCharbeneau, G. T. A clinical comparison of sealant and amalgamin the treatment of pits and fissures. Part 1: Clinical perform-ance after 18 months. Pediatr Dent 2:167, 1980.

12.Mahler, D. B., Terkla, L. G., Van Eysden, J., and Reisbick, M.H. Marginal fracture versus mechanical properties of amalgam.J Dent Res 49:1452, 1970.

13.Corpron, R. E., Carron, S. H., Asgar, K., Straffon, L. H., andDennison, J. B., Clinical study of different finishing andpolishing methods of Tytin amalgam. Abstr, J Dent Res 59:333,1980.

14.Busquets, D. J., Osorno, C., and Turner, D. R. Effects offinishing and polishing of amalgams at specific time intervals.University of Michigan, Ann Arbor, Michigan, Typed thesis,1978, 96 p.

15.Binon, P., Phillips, R. W., Swartz, M. L., Norman, R. D., andMehra, R. Clinical behavior of amalgam as related to certainmechanical properties. Abstr, J Dent Res 52:509, 1973.

16.Duperon, D. F., Nevile, M.D., and Kasloff, Z. Clinical evalua-tion of corrosion resistance of conventional alloy, spherical-particle alloy, and dispersion-phase alloy. J Pros Dent 25:650,1971.

17.Mahler, D. B and Van Eysden, J. Occlusal extrusion of clinicalamalgam restorations. Abstr, J Dent Res 53:26, 1974.

18.Sockwell, C. L., Leinfelder, K. F., and Taylor, D. F. Two-yearclinical evaluation of experimental copper additive amalgams.Abstr, J Dent Res 56:249, 1977.

19.Osborne, J. W. and Gale, E. N. Clinical performance of certaincommercial high-copper content amalgams. JADA 100:867,1980.

20.Nitkin, D. A. and Goldberg, A. J. The effects of immediatepolishing on amalgam restorations, Part II. Abstr, J Dent Res58:351, 1979.

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