Class II (interproximal) decayand/or a failing restoration that involvesa posterior proximal surface is still a com-mon finding in most dental patients.Many of these problems can be handledby using directly placed restorative mate-rials. The challenge for the dentist alwayshas been to create contact with the adja-cent tooth and, at the same time, restoreproper interproximal anatomic form giventhe limitations of conventional matrixsystems. The thickness of the matrix bandand the ability to compress the peri-odontal ligaments of the tooth beingrestored as well as the one adjacent to itcan sometimes make the restoration ofproximal tooth contact arduous at best.

THE MORPHOLOGY OF THEPROXIMAL SURFACE OF POSTERIOR TEETHAnatomically, the posterior proximal sur-face is convex occlusally and concavegingivally. The proximal contact is ellip-tical in the buccolingual direction andlocated approximately 1 mm apical to theheight of the marginal ridge. As thesurface of the tooth progresses gingival-ly from the contact point toward thecementoenamel junction, a concavityexists that houses the interdental papilla.Conventional matrix systems are made ofthin, flat metallic strips that are placedcircumferentially around the tooth tobe restored and affixed with some sort ofretaining device. While contact with theadjacent tooth can be made with a cir-cumferential matrix band, it is practical-ly impossible to re-create the naturalconvex/concave anatomy of the posteri-or proximal surface because of the inherent

limitations of these systems. Attempts to“shape” or “burnish” matrix bands withelliptical instrumentation may help cre-ate non-anatomic contact, but only “dis-torts” or “indents” the band and does notre-create complete natural interproximalcontours. Without the support of toothcontour, the interdental papilla may notfill the gingival embrasure completely,leading to potential food traps and areasfor excess plaque accumulation. DirectClass 2 composite restorations can pres-ent even more of a challenge to place forthe dentist because of the inability of resinmaterials to be compressed against a ma-trix to the same degree as amalgam.

This article describes the use of an inno-vative sectional matrix system (Walser®,Vi-dent, Brea, CA) and instrumentation de-signed to facilitate placement of these ma-trices to assure maximal results, both inphysiologic contact and anatomic form.When using this system with the latest incomposite resin technology, direct Class 2tooth-colored restorations can be placedthat exhibit natural anatomic proximal formand have predictable proximal contact.1-3

TOOTH PREPARATION ANDMATRIX ARMAMENTARIUMClass 2 preparations that need a matrixband for restoration require rebuilding ofthe marginal ridge, proximal contact, andoften a large portion of the interproximalsurface. The goal with composite place-ment is to do so in a way that the amount ofrotary instrumentation for contouring andfinishing is limited. This is especially truefor the interproximal surface. Because ofthe constraints of clinical access to theproximal area, it is extremely difficult to

sculpt and contour this surface of therestoration correctly. Proper reconstruc-tion of this surface is based largely on theshape of the matrix band and the accuracyof its placement.4 After removal of cariesand old restorative material, the outlineform of the cavity preparation is assessed.If any portion of the proximal contactremains, it does not necessarily need tobe removed. As much healthy, unaffect-ed tooth structure as possible should beconserved. If the matrix band cannot bepositioned through the remaining con-tact easily, the contact can be lightenedusing a Gateway® 30-µm diamond strip(Brasseler USA, Savannah, GA).

A sectional matrix system, such asWalser, is an excellent choice for Class 2composite restorations for many reasons.

The matrix band is anatomically correct,and the unique design of the matrix allowsfor the proper restoration of interproximalanatomy as described. Also, the manymatrix designs in the Walser systemallow for accurate matrix fit for anteriorClass 3 and 4 restorations, premolars,molars, and adjacent (back-to-back)proximal surfaces as well.

CASE REPORT: A CLASS 2DIRECT COMPOSITERESTORATIONThe patient presented with an old Class2 composite that had decay on the lin-gual aspect of the proximal portion ofthe restoration (Figure 1). After removalof the restorative material, associateddecay, and preparation of the proximal

Sectional Matrices and the Restoration of Class II Direct Composite RestorationsRobert A. Lowe, DDS

Robert A. Lowe, DDS Diplomate

American Board of Aesthetic Dentistry

Private Practice

Charlotte Center for Cosmetic Dentistry

Charlotte, North Carolina

Figure 4 Using placement forceps, the Walsermatrix (No. 6 for small bicuspid) was placedaround the prepared tooth. If the matrix does noteasily slip through the proximal area, lighten thecontact with a 30-µm diamond strip. A flexiblewedge helped seal the gingival floor of the proxi-mal box tightly against the cavosurface margin.

Figure 3 An ET® 3 (Brasseler USA) was usedto contour the adjacent restoration before theplacement of the matrix on tooth No. 5.

Figure 2 After isolation, the defective restora-tion was removed, and the preparation was mod-ified to remove the recurrent caries. Note theovercontouring of the composite restoration intooth No. 4 and how this helped to create a con-cavity in the distoproximal of the restoration (seeFigure 1) that is now to be replaced on tooth No. 5.

Figure 1 Preoperative occlusal view of toothNo. 5, which had recurrent caries in the lingual-proximal area of a 10-year-old composite resinrestoration.

cavity form, the operative area was iso-lated with a rubber dam (Figure 2). Noticethe overcontoured proximal restorationin the adjacent tooth. This surface wasrecontoured and polished before place-ment of the matrix to create an idealproximal contact for the restoration thatis being placed (Figure 3).

The Walser sectional matrix systemwas chosen for this case to aid in theanatomic restoration of the mesial-prox-imal tooth morphology of this maxillaryfirst premolar (Figure 4). The appropriatematrix band was chosen that best corre-sponded anatomically to the tooth beingrestored and also to the width and heightof the proximal surface. The height ofthe sectional matrix should be no higherthan the adjacent marginal ridge whenproperly placed. Because of the concaveanatomic shape when applied, the proxi-mal contact was located approximately 1mm apical to the height of the marginalridge. Next, the gingival portion of theband was stabilized and sealed againstthe cavosurface margin of the preparationusing the appropriate size FlexiWedge™

(Common Sense Dental Products, Inc,Spring Lake, MI). The size of the flexiblewedge should be wide enough to holdthe gingival portion of the matrix bandsealed against the cavosurface of thepreparation, while the opposite side ofthe wedge sits firmly against the adjacent

tooth surface. If openings exist around theisolated teeth after rubber dam placement,a light-cured “liquid dam”(OraSeal® Ultra-dent Products, Inc, South Jordan, UT)can be used to seal the area(s) and pre-vent salivary contamination.

After the Walser matrix was properlywedged and in place, the restorative processbegan. A 15-second total-etch technique(10 seconds on enamel margins and 5seconds on dentin surfaces) was per-formed using a 37% phosphoric etch(Figure 5). The etchant then was rinsedoff for a minimum of 15 to 20 seconds toensure complete removal (Figure 6). Thepreparation was then air-dried and rewetwith Acqua Seal™ G desensitizer (Acqua-Med Technologies, Inc, West Chicago, IL)to disinfect the cavity surface, create amoist surface for bonding, and begin ini-tial penetration of hydroxyethylmethacry-late (HEMA) into the dentinal tubules(Figure 7). A fifth-generation bondingagent (OptiBond® Solo Plus™, Kerr Cor-poration, Orange, CA) then was placedon all cavity surfaces (Figure 8). The sol-vent was evaporated by spraying a gentlestream of air across the surface of thepreparation. The adhesive was light-curedfor 20 seconds.

The first layer of composite was placedusing a flowable composite (Beautifil®

Flow F10, Shofu Dental Corp, San Marcos,CA) to a thickness of about 0.5 mm (Figure

9). The flowable composite “flowed” intoall the irregular areas of the preparationand created an oxygen-inhibited layer tobond subsequent layers of microhybridmaterial. After light-curing for 20 sec-onds, the next step was to layer themicrohybrid composite material. First,using a unidose delivery, the first incrementof composite resin (Beautifil® II, ShofuDental Corp) was placed into the proximalbox of the preparation. Beautifil II isdescribed by the manufacturer as “anano-hybrid composite with fluoriderelease and recharge.” A smooth-endedcondensing instrument (Goldstein Flexi-Thin Mini 4, Hu-Friedy, Chicago, IL)was used to adapt the restorative materi-al to the inside of the sectional matrixand preparation.A contact-forming instru-ment, such as the Trimax™ compositeinstrument (AdDent Inc, Danbury, CT),can be used to aid in the creation of a“composite bridge” to hold the matrixagainst the adjacent tooth and to create aproximal contact, if necessary (Figure 10).Each increment of composite materialshould be no more than 2 mm thick. Thebuccal increment was placed into thefacial portion of the preparation (Figure11), including the facial portion of themarginal ridge. The cuspal projectionswere sculpted and the depressions betweenwere created using the FlexiThin Mini 4.A No. 2 Flat Keystone brush (Patterson

Dental, St. Paul, MN) was dipped lightlyin resin, dried thoroughly with a 2 in x 2in sponge, and used to feather the mate-rial toward the margins (Figure 12) andsmooth the surface of the composite.The palatal increment of microhybridcomposite (Beautifil II) was placed in thesame manner as previously described(Figure 13 and Figure 14). After completionof the composite placement and beforematrix removal, the restoration was light-cured using an LED curing light (TransluxPower Blue™, Heraeus Kulzer, Inc, Ar-monk, NY) (Figure 15 and Figure 16).

The occlusion was checked with artic-ulation paper after removal of the rub-ber dam and adjusted as needed using aneedle-shaped composite finishing dia-mond (Brasseler USA). When placingcomposite materials using the describedtechnique, very little finishing should berequired, except at the marginal areas.Rubber polishing abrasives were used topolish the adjusted areas. After a 5-sec-ond etch of the restorative margins with37% phosphoric acid (Figure 17), thesurface sealant (ClearCheck SLP, ShofuDental Corp) was placed with the No. 2Flat Keystone brush, air-thinned, and light-cured for 20 seconds. Surface sealants helpto seal microscopic marginal imperfec-tions that may remain after the finishingand polishing process. Figure 18 shows anocclusal view of the completed Class 2

Figure 6 The etchant was rinsed for at least15 seconds (a longer rinse time can be used).Then, the preparation was air-dried thoroughly,removing all moisture.

Figure 5 A total-etch technique was used witha 15-second total-etch time of enamel anddentin. Start with the application of etchant onthe enamel only, then continue to dentin, whichrequires only 5 seconds of etching.

Figure 8 A fifth-generation adhesive(OptiBond Solo Plus) was applied copiously tothe enamel and dentinal surfaces.

Figure 7 A desensitizer was placed to rewetthe enamel and dentin surfaces and gain initialpenetration of HEMA and fluoride into the denti-nal tubules to aid in formation of the hybridzone.

Figure 10 A composite-contact forminginstrument (Trimax composite instrument) wasused to help push the matrix and adapt thecomposite firmly against the adjacent proximalsurface. The composite then was cured in place,forming a “composite bridge” that guarantees astrong contact on removal of the matrix.

Figure 9 A thin layer of flowable composite(Beautifil Flow F10) was placed no thicker than0.5 mm then, using an explorer tip, was spread tocover the dentin and fill all the geometric line andpoint angles of the restoration. The goal was tocreate a uniformly thin layer of resin in intimatecontact with the cured adhesive, eliminating thepossibility for voids between the composite andadhesive layer. Also, on curing, the oxygen-inhibit-ed layer will form a sticky surface onto which thesuccessive layers of composite resin will be adapt-ed more easily with less chance of “pull back.”

Figure 12 A No. 2 Flat Keystone brush wasused to smooth and adapt the composite to themarginal area. This will help to reduce theamount of rotary finishing needed.

Figure 11 A FlexiThin Mini 4 was used toplace the facial increment of composite(Beautifil II) in the preparation.

composite restoration. Notice the beauti-ful chameleon effect that was achievedusing one shade of composite (Beautifil II)and how well the restorative materialblends with the adjacent tooth structure.5,6

CONCLUSIONA technique has been described using asectional matrix system (Walser) and asso-ciated armamentarium and a nanofilledmicrohybrid composite (Beautifil II) tocreate an anatomically precise Class 2posterior composite restoration. The inter-proximal surface was re-created with nat-ural anatomic contour and elliptical contactwith the adjacent tooth. With proper oc-clusal and proximal form, this “invisible”direct composite restoration will servicethe patient for many years to come.7

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Figure 18 Occlusal view of the completed res-toration after light-curing of the surface sealant.

Figure 17 After checking occlusion, adjustingwhere necessary, finishing, and polishing therestoration, a 5-second etch was performed toclean the marginal area, then copiously rinsedwith water and air-dried.

Figure 14 The FlexiThin Mini 4 was used to sculptthe lingual (palatal) surface of the restoration.

Figure 13 With the facial increment placedand sculpted, the lingual increment is about tobe placed.

Figure 16 Occlusal view of the completedrestoration before removal of the matrix and fin-ishing procedures were performed.

Figure 15 The lingual increment was light-cured for 30 seconds.

EsTHetics