Alternative Treatments to Replacement of Defective Amalgam Restorations

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842 JADA 142(7) http://jada.ada.org July 2011

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The relative low cost and long-

term cost-effectiveness ofamalgam restorationsaccount for their use in gen-

eral dental practices.1-3 Thelongevity rates for amalgam restora-tions are better than those for otherdirectly placed restorations,4-6 butamalgam restorations also may fail.In 2004, 40 percent of restorationsreplaced in general practice wereamalgam.1 Secondary caries is themain reason (approximately 40 to50 percent) for replacement ofamalgam restorations, followedby fracture of the restoration(22 percent).1,4,6

The criteria for replacement ofamalgam restorations in generaldental practice and in dental schoolclinics are subjective and not well

Dr. Gordan is a professor and the program director forDental Practice-Based Research, Department ofRestorative Dentistry, Division of Operative Dentistry,College of Dentistry, University of Florida, HealthScience Center, P.O. Box 100415, 1395 Center Drive,Room D10-33, Gainesville, Fla. 32610-0415, [email protected]. Address reprint requeststo Dr. Gordan.Dr. Riley is an associate professor, Department of Com-

munity Dentistry and Behavioral Sciences, College ofDentistry, University of Florida, Gainesville.Dr. Blaser is an emeritus clinical professor, Departmentof Operative Dentistry, College of Dentistry, Universityof Florida, Gainesville.Mr. Mondragon is a research coordinator, Departmentof Operative Dentistry, College of Dentistry, Universityof Florida, Gainesville.Dr. Garvan is the statistics director, Office of Educa-tional Research, College of Education, University ofFlorida, Gainesville.Dr. Mjr is an emeritus professor, Department ofOperative Dentistry, College of Dentistry, University ofFlorida, Gainesville.

Alternative treatments to replacementof defective amalgam restorations

Results of a seven-year clinical study

Valeria V. Gordan, DDS, MS; Joseph L. Riley III, PhD; Paul K. Blaser, DDS, MSD;Eduardo Mondragon; Cynthia W. Garvan, PhD; Ivar A. Mjr, BDS, MSD, MS, DrOdont

ABSTRACTBackground. The authors conducted aprospective cohort clinical study to investigatethe effectiveness of alternative treatments to thereplacement of defective amalgam restorations.Methods. Fifty patients aged 21 through 77 years(mean age, 56 years) with 113 defective amalgam restorations thatwere diagnosed during treatment planning participated in thestudy. The authors assigned each tooth to one of five treatmentgroups: repair with amalgam (n = 20), sealing of defective margins(n = 23), refinishing (n = 23), replacement (n = 22) or no treatment(n = 25). The replacement and no-treatment groups served as com-parison groups, and the authors assigned 47 teeth randomly to

these groups. Two clinicians examined the restorations before andafter the assigned treatment and at subsequent recall visits byusing modified U.S. Public Health Service criteria including mar-ginal adaptation, anatomic form, occlusal and proximal contact,postoperative sensitivity and secondary caries.Results. The clinicians examined 94 restorations (83 percent) atthe one-year recall visit, 74 (65 percent) at the two-year recall visitand 54 (48 percent) at the seven-year recall visit. They observedmost of the downgraded and failed restorations after the first twoyears of clinical service.Conclusions. The study results show that some degree of degra-dation occurred in all treatment groups, including the replacementgroup, at the seven-year recall examination, with no significant

failure rate. The results support the repair of defective amalgamrestorations as an alternative to replacement. Furthermore, thestudy findings show that in future controlled clinical trials, all teethmay receive random assignment.Clinical Implications. The study findings support repair ratherthan replacement of amalgam restorations with localized defects.Randomized controlled trials are needed to confirm these findings.Key Words.Amalgam; clinical trial; repair; replacement;sealant; polishing; tooth; restoration.JADA 2011;142(7):842-849.

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defined. Too often, dentists replace restorationsthat could have been treated differently.7,8

Replacement of restorations involves removal ofsignificant amounts of healthy tooth structure9,10

and negatively affects the tooths longevity.11,12

Therefore, treatments that preserve tooth struc-ture are highly desirable for the longevity of res-

torations and, consequently, increase the life-time of the tooth.Possible options for treating defective

amalgam restorations include repairing,sealing, refinishing and replacement.13

Repairing involves removal of the part of therestoration that is defective, as well as anyaffected tissue adjacent to the defective restora-tion; sealing consists of applying a resin-basedsealant on the defective site or margin; refin-ishing consists of using finishing burs to removesurface defects or excess amalgam from restora-tions; and replacement entails removal of the

entire restoration and placement of a newrestoration.The specific aim of this prospective cohort

study was to assess the longevity of a group ofamalgam restorations that had been diagnosedclinically with one or more features that devi-ated from ideal and were scheduled for replace-ment. Clinicians treated the defective restora-tions by means of repair, placement of sealant,refinishing or total replacement. We assessedlongevity by determining the percentage offailed and degraded restorations. Additionalaims were to identify and quantify the mainreasons for diagnosing restorations as defective.

PARTICIPANTS, METHODS ANDMATERIALS

Study design. Fifty patients aged 21 through77 years (mean age, 56 years) with 113 defectiveamalgam restorations that were diagnosed inde-pendently during treatment planning at theCollege of Dentistry, University of Florida,Gainesville, participated in this prospective lon-gitudinal cohort study. Clinical staff membersassigned patients routinely for treatment at theoperative dentistry clinic.

The institutional review board (IRB) at the

University of Florida approved the study. Third-and fourth-year dental students provided therestorative treatment under faculty supervision.

We assigned the restorations that had local-ized defects to one of the following treatmentgroups: repair (n = 20), sealing of defective mar-gins (n = 23) or refinishing (n = 23). We assignedrestorations to the three experimental groupsaccording to treatment need, as described later inthis section. We assigned the remaining 47 resto-

rations to one of two comparison groups: totalreplacement (n = 22) or no treatment (n = 25).

Inclusion criteria. Our inclusion criteriawere patients who had defective amalgam resto-rations that could be corrected with repair,sealant or refinishing of the margins; absence ofcontraindications to dental treatment; age older

than 18 years; and ability to read English. Atbaseline, the defective restorations needed toreceive a score of Bravo, according to modifiedU.S. Public Health System (USPHS) criteria14

(Table 1), in either marginal adaptation oranatomic form.

Exclusion criteria. We excluded patientswith contraindications to regular dental treat-ment owing to medical history, those with xero-stomia or receiving treatment with medicationsproven to significantly reduce regular salivaryflow, and those with defective restorations thatreceived a score of Charlie (unacceptable or

failed, according to modified USPHS criteria14

)for any characteristic.All patients who met the study criteria

agreed to participate and signed informed con-sent forms after receiving a full explanation ofthe nature of the procedures.

Evaluation. We used modified USPHS cri-teria14 (Table 1) to evaluate the clinical qualityof the restorations. Two clinicians (P.K.B.,I.A.M.) recorded the scores for each restorationat baseline, immediately after treatment and atone-, two- and seven-year recall examinations.Calibration exercises conducted at the begin-ning of each examination revealed an interex-aminer agreement ratio of between 85 and 92percent. In cases of disagreement between theevaluators, a third evaluator examined the res-toration to reach a final decision. The cliniciansdetermined clinical failure of the restoration orof treatment according to the criteria outlined inTable 1 under Charlie. In addition, the clini-cians recorded restoration failure if the toothhad a crown or if the restoration was missing atany of the recall examinations.

Treatment groups.Repair. The clinicianremoved the amalgam at the defective site witha carbide bur to allow for a proper diagnosis and

an evaluation of the extent of the defect. Pro-vided that the defect was limited and localized,the clinician then removed any defective toothtissue. He or she roughened the amalgam sur-face with a diamond bur and repaired the resto-ration with a dispersed-phased amalgam (Orig-inal D, Wykle Research, Carson City, Nev.).

ABBREVIATION KEY. IRB: Institutional review board.USPHS: U.S. Public Health Service.



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Resin-basedsealant. Restora-tions with a creviceor a ditch at thecavosurface marginreceived a resin-based sealant

(Delton, DenstplyCaulk, Milford, Del.)after the clinicianperformed acidetching with 34 per-cent phosphoric acidfor 15 seconds. Theclinician polymerizedthe sealant with alight-curing unit(Optilux 401,Demetron, Divisionof Kerr, Danbury,

Conn.). The researchcoordinator (E.M.)measured the outputof the light-curingunit routinely with acuring radiometer(Demetron, Divisionof Kerr) to ensure aconstant value of atleast 470 milliwatts/square centimeter. The clinician used rubberdam isolation for this procedure.

Refinishing. The clinicians used carbideburs (12 or 30 blades, Brasseler USA, DentalRotary Instruments, Savannah, Ga.) to removedefective areas of the restorations that con-tained excess amalgam. They used silicone-impregnated rubber points (Brownie, Greenieand Supergreenie, Shofu, San Marcos, Calif.) topolish the occlusal and buccolingual surfaces ofthe restorations.

Replacement or no-treatment groups.We randomly assigned 47 (42 percent) of the113 defective restorations to the replacement(n = 22) or no-treatment (n = 25) groups becausethey could not be improved substantially withany of the three other treatment options (that

is, the score raised to an Alfa, according to themodified USPHS criteria14).

Replacement. The clinicians removed andreplaced the defective restorations (n = 22).

After completing the cavity preparations, theyrestored the teeth with a dispersed-phasedamalgam (Original D). They did not use anybonding agent or liner underneath the amalgamrestorations.

No treatment. The clinicians examined the

restorations visually but did not perform anytreatment in the defective area.

Outcome measurements.Rating of clin-ical characteristics. The clinicians evaluatedeight clinical characteristics, when applicable,according to modified USPHS criteria14:docclusal marginal adaptation;dproximal marginal adaptation;danatomical form (occlusal);danatomical form (proximal);docclusal contact;dproximal contact;dsecondary caries;dpostoperative sensitivity.

The clinicians (P.K.B., I.A.M.) assigned ascore of Alfa, Bravo or Charlie for each charac-teristic, according to modified USPHS criteria14

(Table 1).Timeline.All restorations received a score

for each clinical characteristic at the preopera-tive evaluation. We then assigned the restora-tions to the treatment groups. After treatment,the clinicians re-evaluated all restorationsexcept those in the no-treatment group andassigned posttreatment scores.

We used the postoperative treatment scoresas baseline values for our analysis of the longi-tudinal data. In the no-treatment group, we

TABLE 1

Modified U.S. Public Health Service clinical criteria.*

CLINICALCHARACTERISTIC

ALFA BRAVO CHARLIE

MarginalAdaptation

Explorer does not catchor has one-way catchwhen drawn across therestoration/toothinterface

Explorer falls intocrevice when drawnacross the restoration/tooth interface

Dentin or base isexposed along themargin

AnatomicalForm

General contour of therestoration follows thecontour of the tooth

General contour of therestoration does notfollow the contour ofthe tooth

Restoration has anoverhang

Occlusal andProximalContact

Normal Light None

PostoperativeSensitivity

No sensitivity when anair syringe is activatedfor two seconds at adistance of one-halfinch from therestoration with the

facial surface of theproximal tooth coveredwith gauze

Sensitivity is presentwhen an air syringe isactivated for twoseconds at a distance ofone-half inch from therestoration with the

facial surface of theproximal tooth coveredwith gauze; sensitivityceases when thestimulus is removed

Sensitivity is presentwhen an air syringe isactivated for twoseconds at a distance ofone-half inch from therestoration with the

facial surface of theproximal tooth coveredwith gauze; sensitivitydoes not cease whenthe stimulus is removed

SecondaryCaries

No clinical diagnosis ofcaries

NA Clinical diagnosis ofcaries

* Source: Cvar and Ryge.14

NA: Not applicable.



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used the preoperative scores for our analysis ofthe longitudinal data. The clinicians performedthree additional evaluations of the clinical char-

acteristics of the restorations at one-, two- andseven-year recall visits.Changes in clinical outcome.At each

recall visit, clinicians evaluations of restora-tions resulted in one of four outcomes: a finalrating of 1 (upgraded from Bravo to Alfa), 0 (nochange), 1 (downgraded from Alfa to Bravo orfrom Bravo to Charlie) or 2 (downgraded from

Alfa to Charlie).Statistical analysis. We used statistical

software (SPSS Version 17.0, SPSS, Chicago) toperform data management and analysis. Theordinal dependent variable was change inlevel of the modified USPHS criteria from thebaseline scores. We assigned a score to each res-toration that reflected the worst outcome forany of the applicable modified USPHS criteria.For example, if a restoration had two nochanges (that is, a score of 0) and two down-grades (that is, a score of 1) from baseline, weassigned a change-in-restoration score of 1(downgrade) for that evaluation.

To reduce attrition bias, we analyzed the datain two ways. Rather than including all 94 resto-rations that completed any follow-up, weincluded in the first analysis the restorationsthat were available for the seven-year recall

visit and the restorations that had downgradedor failed at the two-year recall visit, on thepremise that downgrades would remain down-grades. For the second analysis, we includedrestorations that were available for the seven-year recall visit and only those restorations thathad failed at the two-year recall visit. We testeddifferences between groups by using generalizedestimating equations to adjust for clusteringresulting from multiple restorations in patients.

RESULTS

Nineteen (17 percent)of the 113 restora-tions were not avail-able for any of thefollow-up evaluations.Of the 94 restorations

that were followedup, two were unavail-able after the one-year evaluation and38 were unavailableafter the two-yearevaluation, leaving 54restorations thatwere available at theseven-year follow-up

(Table 2). Of restorations examined at follow-up,study attrition was higher for those in the refin-ishing group than it was for those in the no-

treatment, repair, sealant or replacementgroups (P < .05). Analyses involving variouscombinations of treatment groups revealed nosignificant differences in study attrition.

The clinicians examined 94 restorations (83percent) at the one-year recall visit, 74 (65 per-cent) at the two-year recall visit and 54 (48 per-cent) at the seven-year recall visit (18 restora-tions evaluated at the one-year recall visit werenot evaluated at the two-year recall visit butwere evaluated at the seven-year recall visit).We reported the results of the one- and two-yearrecall examinations elsewhere.13All 113 restora-tions were placed on posterior teeth (Class I =27; Class II = 76 and Class V = 10). Twenty-twopatients had one restoration, 15 had two resto-rations and 13 had three or more restorationsdiagnosed as defective. We found no associationbetween patients with only one restoration andthose with multiple restorations with regard tothe final outcome (that is, the results showed nosignificant relationship between the number ofrestorations per patient and the final outcome[2 = 21.555,P = .25]). In addition, we observedno statistically significant differences (P > .05)between the restoration surfaces (that is,occlusal, proximal or occlusoproximal) and any

of the clinical characteristics evaluated.Tables 3 and 4 provide the outcomes for the

restorations. Table 3 shows the final status(that is, upgrade, no change, downgrade orfailure) of all 94 restorations seen at any of thefollow-up examinations. Eleven (69 percent) ofthe 16 downgrades reported at the seven-yearrecall evaluation occurred at the one- or two-year evaluation and remained downgrades atthe seven-year evaluation, whereas five (31 per-

TABLE 2

Attrition rates across the study.*GROUP NUMBER (%) OF RESTORATIONS

Lost toFollow-Up

Last EvaluationYear 1



No Treatment (n = 25) 2 (8) 0 (0) 10 (40) 13 (52)

Repair (n = 20) 6 (30) 1 (5) 5 (25) 8 (40)

Sealant (n = 23) 0 (0) 0 (0) 5 (22) 18 (78)

Refinishing (n = 23) 8 (35) 0 (0) 12 (52) 3 (13)

Replacement (n = 22) 3 (14) 1 (5) 6 (27) 12 (54)

TOTAL (N = 113) 19 (17) 2 (2) 38 (34) 54 (48)

* These data show the final evaluation time for each of the restorations. They do not represent thenumber of restorations assessed at each follow-up visit.

Percentages do not total 100 because of rounding.



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cent) of the 16 downgrades were observed onlyat seven years. Table 4 shows the status of eachrestoration at seven years, with the outcomes

carried forward for restorations last evaluatedat one or two years. Of the 94 restorations thatwere followed up, 53 (56 percent) were upgradesor no change, 35 (37 percent) were downgradesand six (6 percent) were failures.

When we excluded restorations that were lostto follow-up before the seven-year recall visitand that had not already been classified as adowngrade or a failure, 75 restorationsremained, of which 34 (45 percent) were classi-

fied as upgrades or no change, 35 (47 percent)were classified as downgrades and six (8 per-cent) were classified as failures. Using this clas-

sification scheme and no treatment as the com-parison, we found that the repair group had aclinical failure rate of 7 percent (one downgradeand no restoration failures), which was signifi-cantly different from that of the no-treatmentgroup (clinical failure rate of 48 percent [ninedowngrades and two restoration failures])(P = .041). None of the findings for the othergroups were significantly different from thosefor the no-treatment group.

TABLE 3

Final evaluation status, according to treatment groupfor 94 defective amalgam restorations.*GROUP NUMBER (%) OF RESTORATIONS

One- or Two-Year Follow-up Results Seven-Year Follow-up Results

Upgrade No Change Downgrade Failure Upgrade No Change Downgrade FailureNo Treatment(n = 23)

3 (13) 1 (4) 5 (22) 1 (4) 1 (4) 7 (30) 4 (17) 1 (4)

Repair (n = 14) 0 (0) 5 (36) 1 (7) 0 (0) 0 (0) 8 (57) 0 (0) 0 (0)

Sealant (n = 23) 0 (0) 2 (9) 2 (9) 1 (4) 1 (4) 9 (39) 8 (35) 0 (0)

Refinishing(n = 15)

0 (0) 2 (13) 9 (60) 1 (7) 0 (0) 2 (13) 1 (7) 0 (0)

Replacement(n = 19)

0 (0) 4 (21) 2 (11) 1 (5) 0 (0) 8 (42) 3 (16) 1 (5)

TOTAL (n = 94) 3 (3) 14 (15) 19 (20) 4 (4) 2 (2) 34 (36) 16 (17) 2 (2)

* Final evaluation status for the 94 restorations examined at any of the follow-up visits. An upgrade or downgrade was defined as a changein one or more of the clinical characteristics, according to the modified U.S. Public Health Service criteria 14 for marginal adaptation,anatomic form and proximal and occlusal contacts.

Nineteen of the original 113 restorations were not seen at any of the follow-up evaluations and are not included in this table.

Percentages do not total 100 because of rounding.

TABLE 4

Status of 94 defective amalgam restorations at seven-year recallexamination, according to treatment group.*GROUP NUMBER (%) OF RESTORATIONS

Upgrade or No Change Downgrade Failure

No Treatment (n = 23) 12 (52) 9 (39) 2 (9)

Repair (n = 14) 13 (93) 1 (7) 0 (0)

Sealant (n = 23) 12 (52) 10 (44) 1 (4)

Refinishing (n = 15) 4 (27) 10 (67) 1 (7)

Replacement (n = 19) 12 (63) 5 (26) 2 (11)

TOTAL (n = 94)# 53 (56) 35 (37) 6 (6)

* Final status of the 94 restorations evaluated at the seven-year recall evaluation and the restorations assigned a change-in-level score atthe one- or two-year evaluation but lost to follow-up at the seven-year visit.

The status of only five restorations changed between the two- and seven-year evaluations. One restoration in the no-treatment group wasdowngraded, one restoration in the sealant group was upgraded, one restoration in the sealant group was downgraded and two restora-tions in the replacement group were downgraded.

Includes restorations in Table 3 that were classified as an upgrade or no change at the two- or seven-year evaluations. Includes restorations in Table 3 that were classified as a downgrade at the two- or seven-year evaluations. The results for the repair group were superior to those for the no-treatment group (the control group) (P = .041); the other groups were not

different from the no-treatment group.# Percentages do not total 100 because of rounding.



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We then excluded restorationsthat were lost to follow-up beforethe seven-year recall examinationand that had not been considereda failure. With this approach, 54restorations remained, of which36 (67 percent) were upgrades or

no change, 16 (30 percent) weredowngrades and two (4 percent)were failures. Using this subset ofrestorations and no treatment asthe comparison group, we foundthat the results for the repairgroup (no downgrades or restora-tion failures) were statisticallysignificantly different from thosefor the no-treatment group (four downgradesand one restoration failure; 38 percent clinicalfailure rate) (P = .035). None of the othergroups results were significantly different from

those for the no-treatment group.We observed a significant difference in thestatus of restorations at the seven-year recallexamination when we compared the main rea-sons for the restorations having been diagnosedas defective (2 = 6.420,P = .04) (Table 5). Resto-rations that were diagnosed as defective owingto anatomical form or wear exhibited a tendencyto be downgraded more often than did restora-tions diagnosed as defective owing to ditching orstaining at the margin (bothP < .05).

DISCUSSION

Despite study findings having shown that thepresence of a marginal defect on the occlusalsurface of an amalgam restoration does not nec-essarily indicate the presence of secondarycaries or the predisposition of the tooth todevelop caries,15-17 marginal defect has been amain reason for replacement of amalgam resto-rations in general dental practice.1,18,19 Unneces-sary replacement of amalgam restorations notonly represents a significant oral health careexpense but also, most importantly, leads to lossof healthy tooth structure.20-22 When treatingpatients in whom the presence of active cariescannot be determined, some dentists still elect

to replace defective amalgam restorationsrather than repair them.23

The results of this study show that repairwas an effective alternative to replacement ofamalgam restorations that were diagnosed asdefective owing to anatomical form, ditching ofthe margins or marginal staining. Results forrestorations in the repair group were superior tothose for restorations in the no-treatmentgroup. Although our study findings showed no

significant failures in any of the treatmentgroups during the observation period, theresults also showed that the repair optionresulted in no significant deterioration among

restorations in that group at the seven-yearrecall visit.Repair is an inexpensive treatment that can

improve the longevity of the existing restorationwith minimal loss of healthy tooth struc-ture.13,24,25 Jessup and colleagues26 and Baratieriand colleagues27 reported that the strength ofthe repaired restoration was acceptable, with noincidence of fracture at the repaired inter-face13,24,25; our study results after seven years ofclinical service confirm their findings.

Another important observation in our studyis that, with the exception of restorations in therepair group, most restorations that receivedalternative treatments exhibited no significantdifference in status compared with that of resto-rations in the no-treatment group. One of theinclusion criteria for restorations in this studywas that they must have received a Bravorating in marginal adaptation or anatomicalform; this means that the explorer would haveentered a crevice when drawn across the inter-face between the restoration and the tooth, andthe general contour of the restoration would nothave followed the contour of the tooth. The clini-cians did not determine the size of the crevice atthe defective margin at baseline; however, on

the basis of the inclusion criteria, we know thatno dentin or base was exposed.

Despite the fact that some investigators haveassociated microleakage with secondary cariesformation,28,29 the majority of evidence16,17,30 sug-gests that no relationship exists between thedevelopment of secondary caries and the size ofthe leakage, except in cases in which theocclusal crevice exceeds 250 micrometers29 or400 m.31 Therefore, researchers have presented

TABLE 5

Comparison of main reasons forrestorations diagnosis as defective,according to outcome at seven-yearrecall examination.

REASON FOR RESTORATIONSDIAGNOSIS AS DEFECTIVE

OUTCOME AT SEVEN YEARS,NO. (%) OF RESTORATIONS

No Change Downgrade Failure

Anatomical Form or Wear (n = 26) 10 (39) 14 (54) 2 (8)

Ditching at Margin (n = 64) 39 (61) 21 (33) 4 (6)

Staining at Margin (n = 4) 4 (100) 0 (0) 0 (0)

TOTAL (n = 94) 53 (56) 35 (37) 6 (7)



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substantial evidence that in amalgam restora-tions with defective margins and crevicessmaller than 400 m, no secondary caries willdevelop.15-17

Because we observed most of the downgradedand failed restorations during the first twoyears of clinical service, we elected to carry for-

ward the change-in-level scores for restorationsnot seen at the seven-year evaluation for analyt-ical purposes. As shown in Table 3, 11 of the 16downgrades reported at the seven-year recallexamination occurred at the one- or two-yearexamination and remained downgrades at theseven-year recall examination. This finding sup-ports the notion that if a restoration is weak,most likely it will deteriorate within the firstfew years of clinical service.25

Repair versus replacement. Despite thefinding that some restorations in the replace-ment group performed superiorly to restorations

in the other treatment groups during the firstfew years of clinical service, at the end of theseven-year observation period, restorations inthe replacement group performed similarly tothose in the other treatment groups (that is, nosignificant difference was evident at the seven-year recall examination). Repaired restorationscould outlast restorations that are replace-ments, and one possible reason for this is thatmost of the original restoration is kept intact.When considering other factors associated withthe removal of existing restorations, such asstress on the tooth, postoperative sensitivity,loss of tooth tissue and re-exposure of thedentinal tubules with possible pulpal dentinalreaction to thermal or mechanical stimulus,32,33

we can conclude that the repair of defectiveamalgam restorations is a predictable and con-servative approach to preserving toothstructure.

Conversely, investigators in several studies20-22

reported the negative effects of restorationremoval and replacement, in particular the lossof a significant amount of healthy tooth struc-ture. Also of importance are the cost, time andpatients behavioral responses associated withpain, anxiety and distress that may stem from

undesirable outcomes of replacement of anamalgam restoration.

Study limitations.A potential limitation ofthis study is that the evaluators were maskedonly to the extent possible. For example, in thesealant group, the evaluator might have noticedthe presence of sealant. Another limitation isthat this was a prospective cohort study and theIRB could not approve randomization of allstudy groups, as takes place in controlled clin-

ical trials. However, our study findings are ofimportance because they establish the fact thatparticipants in future studies can be assignedrandomly to all study groups (that is, repair,sealant, refinishing).

We should point out that because of the smallsample size, we must consider the probability of

a type 2 error. Using the data from the analysisof 75 restorations, we find that at a power of 0.8,detecting a difference between the no-treatmentgroup of 23 restorations (48 percent downgradeor failure rate) and the smallest grouptherepair group of 14 restorationsat a signifi-cance ofP = .05 would require that the repairgroup have a downgrade or failure rate of only16 percent (a difference of 32 percent). Cer-tainly, smaller differences are clinically rel-evant. However, differences between the no-treatment group and the replacement group(the next lowest downgrade or failure rate of 50

percent) would require a sample size of morethan 100 to reach statistical significance.Another limitation of this study was the dif-

fering follow-up times. In our analysis of 75 res-torations, it is possible that some downgradescould have reversed, treatment differences couldhave emerged after seven years for the restora-tions classified as a success, or both. Ouranalysis of 54 restorations included only thoserestorations for which the seven-year follow-upstatus could be confirmed, and we made noassumptions about the status of restorationsthat were lost to follow-up. Only the refinishinggroup experienced rates of attrition that dif-fered from those for the other treatment groups.

Amalgam restorations most often exhibitsigns of deterioration with respect to marginalintegrity and problems associated with anatom-ical form.34 The results of this study show thatrestorations diagnosed as defective as a result ofanatomical form or wear tended to downgrademore often than did restorations diagnosed asdefective because of ditching or staining at themargins. It is understandable that problemsrelated to anatomical defects and wear would bemore difficult to solve, because achieving anideal anatomy would require removal of most of

the remaining restorative material. Neverthe-less, the results of this study show that withregard to treatment failure, the reason for a res-torations having been diagnosed as defectivewas not associated with the outcome at sevenyears. The long-term cost-benefit ratio clearlyfavors the alternative treatments over replace-ment of defective restorations. This is especiallytrue when we assess other important clinicalaspects, such as secondary caries, fracture,



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occlusal wear and postoperative sensitivity,because none of the groups exhibited significantdifferences during the seven-year observationperiod.

CONCLUSION

The results of this study support the repair of

localized defects in amalgam restorations as analternative to restoration replacement. The find-ings show that restorations in all of the treat-ment groups experienced some degree of degra-dation at the seven-year recall examination, butwe observed no significant failure rate.

Disclosure. None of the authors reported any disclosures.

This research was supported by University of Florida, Gainesville,Division of Sponsored Research research grant no. 01042678.

The authors obtained the informed consent of all human partici-pants in this investigation after the nature of the procedures hadbeen explained fully.

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Alternative Treatments to Replacement of Defective Amalgam Restorations