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designed at the option of the operating dentist. Dentalamalgam, frequently formulated by lhe dentist, had littlestandardization, which resulted in m aterials dem onstrat-ing poor performance. Black, a dentist of considerableexperience and observational skills, noted the frequentfailure of dental amalgam restorations with recurrentcaries at the corroded margins of the restorations. Therestorations of that time used an alloy that corroded rap-idly and experienced problems with expansion; there-fore, they failed relatively quickly Patients were observedto develop caries on virgin interproximal surfaceshecause of the stagnation of food in these uncleansableareas. Patients also were observed to develop cariesaround occlusal restorations that failed to include sus-ceptible pits and fissures.

Black wrote a series of papers that addressed theproblems of caries at the margins of restorations.^' amal-gam composition," and tooth re storations.' These papersrepresented the earliest workbooks on the quality ofoperative dentistry of that era, and these papers werebased on the best knowledge available. Black describedthe placement of the outer enamel margins in "self-cleansable areas" so that they terminated in regions lesssusceptible to recurrent caries. Black wrote:

"Certainly that portion near the proximate contact...ismosi liable to be attacked; and the U abilily diminishes as werecede from that point.... It is to cut the enamel ma rginsfrom lines that are not selj-cleansing to lines that are self-cleansing.... When a cavity has occurred in the occludingsurface of a molar, the dentist prepares for filling with theidea that the fissures in this part ofthe enamd ha\e favoredthe occunencc ofthe cavity For this reason, the fissures andgrooves adjoining lhe cavity, even though not decayed, arecut away to such a point as seems to give opportunity for asmooth, evenfinish of lhe margins of the filling. This is doneas a prevention of future recunence of decay...."

Th e restorations of that tim e usedan alloy that co rroded rapidly andexperienced problems w ith expansion.This led to the now infamous term "extension forprevention," which could be summarized as "...theremoval of the enamel margin by cutting from a point ofgreater liability to a point of lesser liability to recurrenceof caries ...." Black developed an amalgam alloy less like-ly to corrode and suffer marginal breakdown, whose for-mula remained essentially unchanged until the 1970swhen high copper silver amalgams were introduced.'"Black developed standard and meticulous placementtechniques for dental amalgam diat used proper isolation:"...Restorations of cohesive gold and amalgam... requirethe apphcation of the rubber dam....The student or den-tist who earnestly desires to give the best service will,

when in doubt, apply the rubber dam.'' This remained the

state of dental education and clinical practice until the1950s, 1960s, and 1970s. During this period, severalevents occurred that allowed for ihe improvement of den-tal amalgams and the introduction of bonded restorations:(1) Amalgams were improved by the development of aprocess where the amalgam alloy was triturated with theideal quantity of mercury (Eames Technique"); (2) clini-cal research resulted in the determination that higher cop-per content alloys have less creep and marginal break-down'''"'; and (3) clinical research demonstrated thatsmaller preparations last longer.'^ These breakthroughseach led to changes in preparation design and restorationsthat were smaller and more effective.

Du ring this period, several eventsoccurred that allov^ed for the improvementof dental amalgams and the introductionof bonded restorations.It is in the breakthroughs associated with bondingihat MID has had its greatest advances. In 1955,Buonocore described a technique for etching enamel sur-faces to make them retentive for a restoration.'* In 1962,Bowcn submitted a patent, entitled a "Dental fillingmaterial comprising vinyl silane treaied fused silica anda binder consisting of BIS phenol and glycidyl acrylic,"that enabled the restoration of a tooih with a tooth-col-ored plastic better known today as Bis-GMA. These 2developments have led to the creation of tooth conserva-tion or minimally invasive surgical dentistry.

DiscussionDentists have a variety of treatment options for therestoration of cavitated caries lesions. Restorationoptions range from minimal tooth preparation on theocclusal surface to placement of a crown over the entirecoronal tooth structure. What factors determine thetreatment decisions? The minimal intervention philoso-phy mandates thai the least invasive effective therapy,preparation, and restoration be used to restore lesionswith cavitation. This philosophy m aintains as a tenet thatsurface deniineralization is the first stage in lhe develop-ment of a caries lesion and is a condition thai may bereversed with remineralization therapy (not discussed inthis paper'"'"). The basic philosophy recognizes the factthai all restorations have a finite life and thai largerestorations (composite or amalgam) have a shorterlongevity than smaller ones.'

Black made a similar observation over a century ago(1891) saying: "...And if the filling should serve for five,ten, or fifteen years, valuable teeth will have been savedto the patient that much longer by filling and afterwardcrowning, than by present crowning...." In other words,always choose the least invasive option because the moreinvasive option is usually available for a later date. The


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Figure 1 (A] MInoi decay Isolated to the pll areas on o maxillary molar, (B) Typical amalgam lesroration temoving lheentire groove. |C1 Preventive resin restoration, removing decoy from the pits and sealing the temainirg groove struclure(odopted from Rlpa, LW and Wolff MS, 19921.

Figure 2C anss p.';:;..cTil l^- ihe dentoenamel |unctian (DEJI on lhe diMul ul idemaxillary first and second bicuspid, almosl ro lhe DEJ on the mesial o( themoxillary second piemolar, and minimol penetrolion on lhe mesial of the max-illary first mdof. Note the cxxJusal caries on the mandibular first mdar.following are a few examples of the application of MIDprinciples w ith esthetic restorations:

The changes in the paradigms for restoration ofocclusal caries lesions using a bonded restoration areamong Lhe most dramatic changes in treatment philoso-phy. Black recommended the removal of the entire grooveand the placemen t of an amalgam regardless of the size ofthe caries lesion (Figure lA). This protected the unin-volved groove from future caries (Figure IB). Minimalintervention on the occlusal surface was first described bySimon sen'" and refined by Ripa and W olfP' as a preventiveresin restoration. The preventive resin preparationrequires the removal of only the caries lesion followed bya composite restorative material. The remaining suscepti-

ble groove or groovereceive an acid-etched pand fissure sealant materal (Figure lC). The historic rationale for removaof the groove was prevention of future caries. Thconcern ol future caries ithe groove is easily deawith hy placement of sealant, a technique wedocumented over the pas25 years to prevent ca riesIt has even been demonstrated ihat properly placed sealants, even if placed oveactive caries, have the ability to arrest caries activity fomore than a decade.^' This is the same concept as Blackextension for prevention but uses the advantages of threlatively new restorative materials without the need fosurgical extension.Minimally invasive surgical procedures apply trestoration of the proximal surlace as well.A proper diagnsis of the location of the caries is essential. Caries that cabe identified radiographically on the proximal surface apenetrating at least to the dentoenamel junction (somwould advocate penetration even further before inter\'enlion) requires preparaiion and removal The conventiona"Black" preparation requires the incorporation of thocclusal groove as part of the restoration. M inimal int ene ntion mandates thai the groove remain intact unless there caries on the surface (even if it is stained) (Figure 2). If thgroove is intact, it can l e sealed at the end of ihc p rocedu reThe preparation of the proximal box for the "slotpreparation differs from the design discussed by Blackwhich requires thai the margins be brought into a cleanable area of the interproximal embrasure. Where possiblfor composite restorations, the facial and lingual embrasure.s are designed to remain closed, providing that thdecay can be accessed and removed. .\s proximal cariegenerally occur gingival to the contact area, the gingivaembrasure must always be open to ensure the removal oall decay (Figure 3A). Afu-r ihe decay is excavated and thfinal restoration is placed, the remaining grooves receiva sealant to complete the restoration (Figure 3B).

Figure 3A-Decay 5 - .covo red. Focial and lingual ^^ alls may Figure 3BToaih is restored wifh compos ite and the occlusal surfacenot require removal depe nding on Ihe extension of the cories. sealed.


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Figure 4Alateral Incisor wi th o dios temo

Posterior teeth requiring cusp replacement can berestored using gold restorations as described by Black over100 years ago. These gold restorations may be an onlayreplacing only missing tooth structure. The teeth also maybe restored using full-coverage crowns. The process ofpreparing a full crown involves the destruction of a signif-icant amount of sound tooth structure to develop parallelwalls tocreate a retentive preparation. A minimally inva-sive esthetic alternative restoration could be the placementof a direct placement composite. However, large directcomposite restorations are diflicult to place because of theneed to both maintain strict and complete isolation forlong periods of time and to achieve good physiologicalcontours with well-polished interproximal areas.

These teeth, requiring replacement of a cusp, also maybe restored using indirect composite or porcelain materials.The indirect onlay restorations take advantage of the abili-ty to design and produce a restoration outside the mouth.The restorations may he adjusted, modified, and recon-toured, providing ideal contours in the dentists or techni-cian's hands. These large, indirect esthetic restorations maybe prepared with minimal destruction of additional soundtooth structure as would occur in the fabrication of lull-coverage crown s. The onlays are bonded into the prepara-tion so that there is less need todesign the restorations lobe mechanically retentive (beyond lhe bonding).

The changes in the pa radigms for restorationof occlusal caries lesions using a hondedrestoration are am ong the m ost drama tic

changes in treatm ent philosophy.These restorations can be fabricated using either indi-rect laboratory techniques or using computer-aided designand computer-assisted manufacturing (CAD/CAM). Thelaboratory indirect technique involves making an impres-sion of lhe preparation, tem porizaiion, and the return for asecond visit for the hna! insertion. The CAD/CAM tech-nique involves an optical impression, computer design ofthe restoration, and a final milling of lhe onlay during thepatient visit. These restorations, when etched and treatedwith silane, are honded in place using composite resins

modified from the original Bowen composition.

Figure 4B lateral incisor with diostemo closed wi l f i compo Mie

The philosophy of minimal surgical intervention andminimal tooih destruction extends lo lhe anterior esthet-ic procedures (eg, diastema closure atid peg laterals). Theaddition of a small amount of direct bonded com posite, awell-respected art form in the 198()s, can still he usedrather than aggressively preparing the tooth for a porce-lain laminate or lull-coverage porcelain crown. The finalrestorative results are esthetic, functional, and can berepaired or replaced without any tooth destruction,(Figures 4A and 4B).

The final restorative results are esthetic.functional, and can be repaired or replacedwithou t any tooth destruction.

Minimal surgical intervention possibilities have beenfurther expanded by the introduction of new technolo-gies. Hard-tissue lasers, air abrasion, and mini-burs makesmaller, less invasive preparations possible. Fach devicepermits the clinician to use a more conservative, lessdestructive approach toward lhe removal of infectedtooth structure. These devices, along wilh adhesive den-tistry, allow for a truly defect-specific approach towardcaries removal.Conclusion

MID is the natural evolution of dentistr)-. As newmaterials and techniques are developed, dentistry is obli-gated to review and use the most conservative techniques.Overly aggressive tooth preparation results in increasedincidence of unneeded .sequelae, often at great pain andexpense for the patient. The concept of MID is more thana series of "surgical" techniques. MID is a comprehensivepackage of dental care and caries intervention thatinvolves: (a) identifying patients for risk of developingdental caries using existing oral and health conditions as apredictor'^ (b) itnplem enting aggressive preventive strate-gies including fluoride therapy, antimicrobial therapy, dietmodification, xylitol and calcium supplementation toreduce the risk such as those described in lhe lenet of min-imal intervention^ and (c) conservative use of sitt;gicaldentistry to improve the well-being of the patient at the


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lowest monetary cost, preserving the maximum amount oftooLh structure.

MID recognizes that dental caries is a reversible dis-ease that starts wiih deminerahzation of the tooth andmay eventually progress to cavitation if the risk factorsare not brought unde r control. Black commented hack in1896 on the future of dentistrj' and the philosophy ofprevention in a speech to young dentists":

"The day is surely coming and perhaps within thelifetime of you young men before me, when we will beengaged in practicing preventive, rather than reparativedentistry. When we will so understand the etiology andpatholog)' of dental caries that we will he able to combatits destructive effects witb a systemic medication."

References1. Mclniyrc ]. Minimal inierveniion dentisiry, Ann R Ausl GoU

Dent Surg. 1994; 12:72-79,2. Chalmers JM, Minimal intervention d entis try: pan 1,

Strategies for addressing the new caries challenge in olderpatients, J Can Dent Assoc. 2006;72:427-433,3. Tyas MJ, Anusavice KJ, Frencken JE, et al. Minimal interven-tion dentistry-a review, FDI Commission Project 1-97, IntDentf. 20O0;50 ;M2,

4. Mo unt GJ, Minim al inier\'Cntion dentistr y rationale of cavitydesign, Opci Dent. 2003;28:92-99,

5. Black GV, The m anagem ent of enamel m argins. Denial Cosmos,1891:33:1-14,

6. Black GV, The man agem ent of enamel marg ins. Dental Cosmos,1891;.33:85-100,

7. Black GV The managem ent of enamel margins. Dental Cosmos,1891; 33:440-447,

8. Black GV, The effect of oxidati on on cul alloys for dental amal-gams, DcnWi Cosmos. 1896:38:43-48,

9 Black GV A Work on Operative Dentistry in Two Volumes,Chicago, 111: Medico-Dental Publishing Co; 1908.to , Anusavice KJ. Phillips' Science oj Dental Materials, lUh ed. St

Louis, Mo: Saunders; 2003.

11, Eames WB- Preparation and condetisation of amalgam withlow mercur)- alloy ratio. J Am Dent Assoc. 1959;58;78-83.

12, Osborne JW, Norman RD. 13-year clinical assessment of 10amalgam alloys. Dent Mater. 1990;6:189-194.

1.5. Lctzel H, van'i Hof MA. Ma rshall GW , et al. The inf luence oamalgam alloy on (he survival of amalgam restorations: a sec-ondary analysis of multiple c ontro lled clinical trial, J Den) Res1997:76:1787-1798.

14. Mahler DB, The high-co pper dental am algam alloys, J DenRes. 1997:76:537-541.

15 . Osborne JW, Gale EN. Relationship of restoration width, toolhposition, and alloy lo fracture at the margins of 13- to H-yearold am algams. J Dent Res, 1990;69:t599-I 601,

16. Buonocore MG, A simple m ethod of increasing adherence oacrylic filling m aterials lo enam el surfaces. J Dent Res, 1955:34849-853.

17. Reynolds EC, Walsh LJ, Additional aids to remineralization oftooth structure. In: Mount GJ, Hume WR. Presei-vctt'wn aRestoration of Tooth Striictwre, Los Gatos, Calif: KnowledgBooks and Software; 200 5:111-118,

18 . Reynolds F,C. Atiticariogetiic complexes of amorphous calcium phosphate stabilized by casein phospbopeptides: a reviewSpec Care Dentist, 1998;18:8-16,

19. Tung MS, Eichmiller FC, Amorphous calcium phosphates fotooih tnineralization, Compend Conlfn Educ Dent. 2004;25(9supp] 1):9-13,

20 . Simonsen RJ, The preventive resin restoration: a minimallyinvasive, nonmetallic restoration. Compcnd Contin Educ Dent1987;8:428-432.

21 . Ripa LW, Wolff MS, Preventive resin re storat ions: indic ation stechnique, and success. Quintessence Inf. 1992;23:307-315.

22 . Bader JD, Shugars DA. The evidence supporting alternativemanagement strategies for early occktsal caries and suspectedocclusal dentinalcarie s.JEviiJ Base Dtnl Pruct. 2006:6:91-100

23 . Me rtz-Fair hursl EJ, Cur tis JW Jr, Ergie JW, et al, Ultraco nser\'ative and tariostatic sealed restorations: resttlts at year 10J Am Dent Assoc. 1998;l29:55-66.

24 . Fontana M, Zero DT, /Assessing patients' caries risk, J Am DemAssoc. 2006;137:1231-1239.25 . Black GV Speech to young dental s tudents 1896, In: Ring MEDcniistry and lUustraled Histoiy. New York, NY: Moshy-YeaBook, Inc; 1985:276,


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