sistematic review of conservative operative caries management strategies

8/13/2019 Sistematic Review of Conservative Operative Caries Management Strategies

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1154 Journal of Dental Education Volume 65, No. 10

Systematic Review of Conservative OperativeCaries Management StrategiesDorothy McComb B.D.S., M.Sc.D., F.R.C.D.(C)Abstract: The relationship between cavity preparation extension and restoration longevity is examined through a systemic reviewof the available evidence on specific conservative, operative caries-management strategies. Evidence tables are provided for threespecific techniques in the permanent dentition: 1) the proximal tunnel restoration, 2) the proximal box-only restoration, and3) the preventive resin restoration. In the primary dentition, the clinical trials involving the proximal box-only restoration, most ofwhich involved glass-ionomer materials, are reviewed. In the permanent dentition, the evidence reveals low effectiveness fortunnel restorations, limited but supportive results for proximal-only restorations, and generally favorable outcomes for theocclusal composite resin-sealant restoration. The weak link in the latter is the overlying fissure sealant, which requires adequateongoing maintenance. Conservative operative strategies in the primary dentition have not been uniformly successful, anddeleterious material effects dominate restoration performance. This systematic review concludes that operative conservatism perse does not guarantee increased restoration longevity and that all restorations are vulnerable to caries recurrence, materialfailures, and technical deficiencies. The more successful conservative strategies are expected to enhance tooth longevity, providedconcomitant caries control is effective.

Dr. McComb is Professor and Head, Restorative Dentistry at the University of Toronto. Direct correspondence to her at the

Faculty of Dentistry, University of Toronto, Restorative Dentistry, 124, Edward St., Rm. 352C, Toronto, Ontario, Canada M5G1G6; 416-979-4934 (4418) phone; 416-979-4936 fax; [email protected]. The complete version of this paper can be viewedat http://www.nidcr.nih.gov/news/consensus.asp.

Key words: conservative operative dentistry, tunnel restoration, proximal box-only restoration, slot restoration, preventive resinrestoration, glass ionomer

This paper proceeds from the decision to ini-tiate operative intervention and examines theevidence for specific, conservative, operativecaries-management strategies. The operative decisionis a significant one as the action is irreversible and res-

torations have a finite lifespan. Such a decision assumesthat an active caries lesion is present and that no othermore conservative therapy is possible to effect a suc-cessful outcome. Traditional cavity preparation includesvarying degrees of extension for prevention in anattempt to remove adjacent caries-prone tooth struc-ture. The high rates of re-restoration performed in clini-cal practice, largely due to a diagnosis of recurrent car-ies, cast doubt on the effectiveness of this concept. Inmore recent years, traditional extension for preven-tion has been challenged, and more conservative formsof operative intervention have been recommended.Three specific techniques are 1) the proximal tunnel

restoration, 2) the proximal box-only restoration, and3) the occlusal preventive resin restoration. How dothese conservative procedures perform in terms of lon-gevity and causes of failure?

MethodsThe clinical questions for the systematic review

were developed in conjunction with the planning com-

mittee for the NIH Dental Caries Consensus Develop-ment Conference on Diagnosis and Management ofDental Caries Throughout Life. At issue is the evidenceconcerning the relationship between cavity preparationextension and restoration survival in 1) permanent and2) primary teeth. A search strategy for human clinicalstudies since 1975 was developed in concert with aconsultant. A Medline/Embase search resulted in 995/92 (total 1087) references for the permanent dentitionand 169/116 (total 285) for the primary dentition. Allabstracts were reviewed, and a final database of fifty-four (permanent) and forty-four (primary) referenceswas studied further. Appropriate references were in-

cluded in systematic review tables for the specific in-terventions involved. The full report entitled The Sci-entific Basis for the Teaching and Practice ofConservative Operative Dentistry is available on the

NIH web sit e at http://www.nidcr.nih.gov/news/consensus.asp. The quality and nature of the literature


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October 2001 Journal of Dental Education 1155

were highly variable. Many clinical studies were incom-plete with regard to controls, patient data, particularlycaries-activity, and operator/examiner details, makingdefinitive comparisons and analysis difficult. Studyduration was often minimal.

The Permanent Dentition

The Proximal Tunnel Restoration

The tunnel concept1accesses proximal den-tinal caries through a sound occlusal pit and was de-signed to preserve the overlying proximal marginal ridgeand maintain greater tooth integrity. It provides no ex-tension for prevention. A total of nine clinical trials 2-10in permanent teeth resulted from the search strategyand are included in Table 1. Almost all utilized a glass-

ionomer silver-cermet cement as the restorative mate-rial. Both partial tunnel and total tunnel are de-scribed, depending on the extent of external perforationand amount of remaining demineralized enamel.

Clinical reports from early usage1,11and the firstclinical trial2utilized small numbers and indicated thetechnique to be promising. Larger clinical studies en-countered higher failure rates. The most frequent causes

of restoration failure were marginal ridge fracture orcaries. Amalgam controls were included in only threetrials. Conventional amalgam significantly outper-formed tunnels over two years10and five years,3butthe situation was reversed in the third trial.2The long-est clinical study (seven years) reported a 50 percent

survival time of six years6

for the tunnel restoration,and recent multi-operator trials provide evidence of veryhigh rates of associated caries (up to 41-45 percent) asearly as three years.4,8,9 Residual caries, recurrent car-ies, and progression of demineralized enamel are allfactors cited in failures, emphasizing the high cariesrisk of the interproximal area. The presence of a glass-ionomer was unable to overcome this ongoing carieschallenge in the majority of studies.

Many studies utilizing baseline radiographsreported evidence of inadequate initial caries re-moval5,6,9,12due to the blind access. The technique isclearly more difficult to execute than the traditional

approach. Low restoration survival was associated withthe limited preparation extension.4,5,8,9The low effec-tiveness reported reveals the difficulties involved witharresting caries in the caries-prone proximal contactarea. Extremely poor performance has been documentedin primary teeth.12,13

Table 1. The proximal tunnel restoration: clinical studies


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The evidence suggests that this conservativestrategy results in a high incidence of early re-restora-tion and cannot be recommended for routine use. Asthe presence of external cavitation is becoming acceptedas the earliest stage necessitating operative interven-tion, the tunnel technique has increasingly limited ap-

plication. The low effectiveness reported argues in fa-vor of a more direct approach that includes judiciousremoval of adjacent demineralized tooth structure inthe proximal contact area.

The Proximal Box-OnlyRestoration

Proximal box-only or slot preparations foramalgam were introduced in 197314and adhesive slot

preparations for resin composite in 1978.15They includeno occlusal dovetail or extension for prevention. Only

three clinical studies3,16,17

in permanent teeth resultedfrom the literature search (Table 2). Two involved ad-hesive proximal slot restorations with resin composite.

No failures were recorded for sixty-eight compositebox-only restorations over five years.16The ten-yearsuccess rate for composite proximal saucer prepara-tions was 68.6 percent.17Half of the failures were dueto recurrent decay, and half were technique-related.Recurrent caries, when present, occurred only at thegingival margin, not bucco-lingually, justifying theminimal lateral and occlusal extension. Loss of reten-tion did not occur. One clinical trial of tunnel resto-rations included a small number of control silver amal-

gam proximal slot restorations. No failures wererecorded for these over a period of five to seven years.3

Despite the limited evidence, the available clini-cal trials in permanent teeth support the proximal slot-only restoration as a viable treatment option, providingsimilar or better longevity compared to conventionalClass 2 composite or amalgam restorations, combined

with greater tooth preservation. The technique is supe-rior to tunnel restorations, likely due to improvedoperator visibility, but also possibly due to removal ofall demineralized enamel.

Gingival Margin LocationGingival extension of Class 2 restorations,

whether traditional or box-only design, is of particularinterest as the vast majority of recurrent decay occursin the gingival proximal location.18,19 Shorter-length

proximal restorations with gingival margins endingclose to the contact area had a significantly higher rateof recurrent caries over a two-year period.20Althoughthere was a trend for long proximal preparations tohave less recurrent caries than intermediate at eachof the three time intervals, the difference was not sta-tistically significant. Another study21of the effect ofcavity design concluded that recurrent caries over eightto ten years was primarily associated with gingival-

proximal cavity design features of amalgam restora-tions, including narrow gingival extension. As a self-cleansing location for the gingival margin of proximalrestorations is impossible, good patient home care isessential. There is thus some evidence that overly con-servative gingival extension increases the risk of recur-rent caries in the absence of good patient compliance.

The Preventive Resin Restoration

The preventive resin restoration (PRR) is a

conservative occlusal restoration that involves replace-ment of discrete areas of carious tooth structure withresin composite, followed by use of an overlying fis-sure sealant instead of traditional extension for pre-vention.22 A total of eighteen clinical studies23-40have

been published, of which fifteen were prospective andthree retrospective investigations. Success rates are not

Table 2. Proximal-only restorations: clinical studies in permanent teeth


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easily comparable from study to study as the definitionof failure was variously reported as actual presence ofcaries or loss of sealant. The difficulties are com-

pounded by the practice of replacing deficient areas offissure sealant during the trial period. Nonetheless, asystematic review table has been produced (Table 3).

All the clinical studies show generally favorable out-comes; however, all universally report total or partialloss of the sealant as a major problem. Three studies

performed a direct comparison with silver amal-gam.24,25,27The PRR was at least as successful as amal-gam in two of the trials, up to five years, with the addedadvantage of preservation of sound tooth structure.Sealant failure was a significant problem in the other,25

which led to an occurrence of 8.1 percent recurrentcaries, with no amalgam failures recorded over the threeyears. No occlusal caries was reported with intact seal-

ants in any of the clinical studies, though many did notutilize radiographs at recalls. All cases of occlusal car-ies, up to 24 percent at nine years,36were associatedwith sealant failure, though the incidence of sealantfailure was significantly higher than the presence ofcaries. Loss of sealant was increased over glass ionomer

restorative materials35,33

and larger areas of compositerestoration.32

In a different but related type of study, theability of sealed composite restorations to halt the ra-diographically observed progress of frank carious den-tine over a period of ten years has been reported.23This

provides some welcome reassurance concerning inad-vertent sealing of dentinal caries under fissure sealantsand has positive implications for the conservative treat-ment of deep carious dentine in the vicinity of the pulp.The apparent arrest of frank, extensive dentinal cari-

Table 3. The preventive resin restoration: clinical studies


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ous lesions under modest sealed restorations, how-ever, requires further study.

In summary, the preventive resin restoration isan effective conservative treatment for localized areasof occlusal dentinal decay. The weak link is the overly-ing fissure sealant, and loss of sealant was variously

reported from 13 to 70 percent. As the sealant replacesextension for prevention, it is an integral part of therestoration and requires regular monitoring and main-tenance.

The Primary DentitionLongevity of restorations is very low in the

primary dentition.41Generally, the earlier the age at res-toration, the lower the longevity.42,43The predicted lifespan of re-restorations is even shorter.42The vast ma-

jority of clinical research on the primary dentition from

the systematic review involves relatively short-termcomparisons of dental materials, particularly newer

proprietary materials, as they enter the marketplace.Qvist et al.44 found that the major reasons for replace-ment of restorations in the primary dentition were res-toration fracture or total loss. There is a continuingsearch, to the present day, for improved materials as arestorative solution to caries management in the pri-mary dentition.

Only one consistent conservative restorative strat-egy resulted from the search. Twelve clinical studies45-56involved proximal box-only conservative restora-tions, and the results of these have been summarized ina systematic review table (Table 4). Almost all clinicalstudies involving glass ionomer materials in the poste-rior primary dentition involved proximal-only restora-tions. For completeness, the few other clinical studiesof glass ionomer performance in primary molars areincluded. The first four references57-60in Table 4 involveglass ionomer-type materials in traditional Class 2 res-torations in comparison with silver amalgam. The re-maining references in the table all involve box-only

proximal restorations, with the last three54-56involvingpoly-acid-modified-composites or compomers, a rela-tively new class of dental materials. No clinical studies

resulted involving silver amalgam or composite proxi-mal box-only restorations in the primary dentition.A significant omission in many of the trials is the pres-ence of a control amalgam or resin-composite tradi-tional restoration. The varying success rates reportedwith use of these more established materials in the pri-mary dentition reveal the significant operator and/or

patient factors involved in restoration failure, whichmust be controlled in any clinical trial. The results of

the uncontrolled studies are therefore difficult to com-pare, and only generalized conclusions can be made.

Material effects dominate the performance ofprimary molar restorations. Both conventional and sil-ver-cermet glass-ionomers provided consistently poorresults in both traditional and box-only restorations,

generally due to their strength limitations. Failures in-volved mostly restoration fracture, bond breakdown, andtotal loss of restoration. Recurrent caries was recordedin association with a significant proportion of failedrestorations. Due to the high failure rates, it has beenstated that conventional and silver-cermet glass-ionomers are not suitable for the permanent restorationof primary molars.46They may be useful as a short-term solution only for Class 1 restorations.53

Deleterious material effects therefore over-whelmed the assessment of the conservative prepara-tion per se on tooth longevity, pulpal response, and re-current caries. The minimal preparation may even have

increased failure rates due to technical and material limi-tations. Better results45have been reported for resin-modified glass-ionomer materials in proximal box-onlyrestorations. Improved, but varying, results are reportedfor the newer acid-modified composite materials orcompomers in conservative proximal restorations.54-56

In summary, conservative operative proceduresin the primary dentition have not been uniformly suc-cessful to date. Initial trials of innovative non-trau-matic caries-management strategies, which involvedincomplete caries removal, have been reported.61

Cariostasis occurred over a period of eighteen months

in the primary dentition, which parallels somewhat theresults for the permanent dentition.23

Further research

is required in this area.

ConclusionsThis systematic review of conservative interven-

tions has revealed that conservatism per se does notguarantee increased restoration longevity. All restora-tions are vulnerable to caries recurrence, material fail-ures, and technical deficiencies. Indeed, misguided

conservatism in some cases may accelerate restorationdemise due to the technical difficulties involved, thematerials used, and the absence of disease control. Thisis particularly evidenced by the poor effectiveness ofthe tunnel restoration for the treatment of proximal car-ies. On the other hand, more successful conservativestrategies, such as the preventive resin and proximalslot restorations, which can provide equivalent longev-ity to traditional restorations in the permanent denti-


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Table 4. Glass ionomer and modified restorations in primary teeth

tion, should enhance tooth longevity over larger-sizedrestorations, due to the initial reduction in tooth struc-ture removal. Concomitant and future caries control isessential.

AcknowledgmentsThe text of this paper is a summary version of

a full evidence report prepared for the NIH Consensus

Development Conference on Diagnosis and Manage-ment of Dental Caries Throughout Life, 2001. The in-valuable role of the search consultant in the process(P.F. Anderson, Dentistry Library, University of Michi-gan) is acknowledged. The assistance of a second re-viewer (Dr. P.R. Walshaw, Assistant Professor, ClinicalSciences, Faculty of Dentistry, University of Toronto)for the assessment of the clinical research on specific


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conservative operative treatments in permanent teethis also gratefully acknowledged.

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sistematic review of conservative operative caries management strategies

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