Oral Health Group
Feature

Class II Direct Composite Restorations with the Use of Sectional Matrix Systems

March 1, 2006
by Robert A. Lowe, DDS, FAGD, FICD, FADI, FACD


Class II (interproximal) decay and/or a failing restoration that involves a posterior proximal surface is still a common problem in daily practice. Many of these problems can be corrected utilizing directly placed restorative materials. The challenge with Class II restorations has always been to recreate contact to the adjacent tooth and at the same time, restore proper interproximal anatomic form given the limitations of conventional matrix systems. The thickness of the matrix band and the ability to compress the periodontal ligaments of the tooth being restored and the one adjacent to it can sometimes make the restoration of proximal tooth contact laborious at best.

Anatomically, the posterior proximal surface is convex occlusally and concave gingivally. The proximal contact is elliptical in the bucco-lingual direction and located approximately one millimeter apical to the height of the marginal ridge. As the surface of the tooth progresses gingivally from the contact point toward the cementoenamel junction, a concavity exists that houses the interdental papilla. Conventional matrix systems are made of thin, flat metallic strips that are placed circumferentially around the tooth to be restored and affixed with some sort of retaining device.

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While contact with the adjacent tooth can be made with a circumferential matrix band, it is practically impossible to recreate the natural convex/concave anatomy of the posterior proximal surface because of the inherent limitations of these systems. Attempts to “shape” or “burnish” matrix bands with elliptical instrumentation may help create non-anatomic contact, but only “distorts”, or “indents” the band and does not recreate complete natural interproximal contours.

Without the support of tooth contour, the interdental papilla may not completely fill the gingival embrasure leading to potential food traps and areas for excess plaque accumulation. Direct Class II composite restorations can present even more of a challenge to place for the dentist because of the inability of resin materials to be compressed against a matrix to the same degree as amalgam, as well as the shrinkage factor of most composite materials.

This article will describe the use of an innovative sectional matrix system (Composi-Tight Gold: Garrison Dental Solutions) and instrumentation designed to facilitate placement of the matrix to assure maximum results, both in physiological tight contact and in anatomic form. When utilizing this system with the latest in composite resin technology, direct Class II tooth colored restorations can be placed that exhibit natural anatomic proximal form and have predictable proximal contact.

PREPARATION OF THE TOOTH AND MATRIX ARMAMENTARIUM

Class II preparations that need a matrix band for restoration will require extensive rebuilding of the marginal ridge, proximal contact, and often a large portion of the interproximal surface. The goal of composite placement is to do so in such a way that the amount of rotary instrumentation for contouring and finishing is limited. This is especially true for the interproximal surface. Because of the constraints of clinical access to the proximal area, it is extremely difficult to sculpt and correctly contour this surface of the restoration. Proper reconstitution of this surface is largely due to the shape of the matrix band and the accuracy of its placement.

After removal of caries and old restorative material, the outline form of the cavity preparation is assessed. If any portion of the proximal contact remains, it does not necessarily need to be removed. Conserve as much healthy, unaffected tooth structure as possible. If the matrix band cannot be easily positioned trough the remaining contact, the contact can be lightened using a Gateway 50 micron diamond strip (Brasseler USA). Another technique to open the contact area is the placement of the Composi-Tight Gold G-Ring for a few minutes, prior to placing the matrix band. This will open the contact enough to more easily position the matrix band.

A sectional matrix system, such as Composi-Tight Gold (Garrison Dental Solutions) is an excellent choice for Class II composite restorations for many reasons. First, the matrix band is anatomically correct. Rather than being flat, like conventional matrix bands, the sectional matrix band is “kidney bean” shaped with a concave inner surface. This allows for the proper restoration of interproximal anatomy as described above, without additional finishing with rotary instruments. Secondly, the “G-Ring”, which holds the sectional matrix in place, also causes a slight separation of the affected tooth and the adjacent surface by compression of the periodontal ligament.

When the “G-Ring” is in place, and the matrix touches the adjacent tooth surface, proximal contact is assured. Also, some instrumentation has been developed to aid in accurate placement of the sectional matrix to maximize the restorative result. Sectional matrix pliers known as “DryerPliers” were developed specifically for use with sectional matrix systems to aid in the accurate placement and positioning of the matrix band. There is one plier for placement of the mesial sectional matrix, and one for the distal. Since the sectional matrix band is extremely thin, it can be difficult to place with a hemostat or cotton pliers without deforming the band.

The DryerPliers maintain the shape of the band while positively holding the matrix in the proper position for placement. After positioning of the matrix band, initial stabilization is secured through the use of a proximal wedge.

WedgeWands (Garrison Dental Solutions) were developed as an adjunct to the Composi-Tight Gold system to stabilize the matrix band and help create a gingival seal. The wedge is plastic, so that it is bendable and able to conform better to the convex root (tooth) surface when pressure is exerted on it by the “G-ring”. The delivery is unique, since the wedge is on a plastic handle and can be bent to the desired angle for placement prior to being placed in the oral cavity. Once positioned, a twist of the handle releases the wedge and the handle is discarded. This delivery system avoids awkward placement using cotton pliers where many times wedges are hard to angle into place and often dropped or mishandled. The handle can also be left in place, to assist during possible repositioning and final removal of the wedge.

CASE REPORT

A Class II direct composite restoration

The patient shown in Figure 1 presented with an old Class I amalgam that had decay on the mesial proximal surface. A fracture line can also be seen radiating from the restorative material across the mesial marginal ridge and down the proximal surface near the palatal portion of the proximal contact. After removal of the restorative material, associated decay, and preparation of the proximal cavity form, the operative area is isolated with a rubber dam (Fig. 2) in preparation for the restorative process. Due to the depth of the preparation, a glass ionomer base (Fuji IX: G.C. America) was placed (Fig. 3).

The potential for remineralization using glass ionomer cements in preparations close to the dental pulp is well documented by Ngo1-3 and others. A non-serrated plugger is used to shape the pulpal floor and proximal axial wall of the glass ionomer base (Fig. 4). After the base is fully set, a flat, cylinder diamond bur is used to refine the internal form of the preparation, including the walls of the glass ionomer base (Fig. 5).

The Composi-Tight Gold Sectional Matrix System (Garrison Dental Solutions) has been chosen to aid in the anatomic restoration of the mesial proximal tooth morphology of this maxillary first molar (Fig. 6). The appropriate matrix band size is chosen which will best correspond anatomically to the tooth being restored and also, to the width and height of the proximal surface. The height of the sectional matrix should be no higher than the adjacent marginal ridge when properly placed.

Because of t
he concave anatomic shape, the proximal contact will be located approximately one millimeter apical to the height of the marginal ridge. The mesial DryerPlier is used to place the selected sectional matrix band in the correct orientation. It is important to maintain the proper concave shape to the band, that the appropriate DryerPlier be used in band placement. This is the reason that there is a separate plier for mesial and distal applications.

Figure 8 shows the matrix band oriented in the mesial DryerPlier ready for placement. The AU100 small sectional matrix band (Composi-Tight Gold: Garrison Dental Solutions) is positioned and placed using the mesial DryerPlier, to the mesial proximal area of tooth number 14 (Figs. 9 & 10).

The orientation of the band and the positive fit in the DryerPlier makes precise placement possible, even in posterior areas with tight access. Next, the gingival portion of the band is stabilized and sealed against the cavosurface margin of the preparation using the appropriate size WedgeWand flexible wedge (Garrison Dental Solutions) (Fig. 11). The size of the WedgeWand flexible wedge should be wide enough to hold the gingival portion of the matrix band sealed against the cavosurface of the preparation, while the opposite side of the wedge sits firmly against the adjacent tooth surface. To place the wedge, the Wedge Wand is bent to 90 where the wedge meets the handle (Fig. 12).

The flexible wedge can now be placed with pressure conveniently, without the use of cotton forceps, that often times can be very clumsy. Once the wedge is in the correct orientation, a twist of the wand releases the wedge.

As mentioned earlier, the handle may remain attached for repositioning and final removal of the wedge. The “G-Ring” forceps is then used to place the “G-Ring” into position. The tines of the “G-Ring” are placed behind the flexible wedge and the ring is released from the forceps. There are many options for the placement of the “G-Ring” legs. With placement behind the wedge, the force of the “G-Ring” causes a slight separation of the teeth due to periodontal ligament compression, and bends the flexible wedge to better adapt and conform to the external tooth surface creating an excellent seal at the gingival margin of the preparation (Fig. 13).

Once the sectional matrix is properly wedged and the “G-Ring” is in place, the restorative process can be started. A 15-second total etch technique, 10 seconds on enamel margins (Fig. 14) and 5 seconds on dentin surfaces (Fig. 15) is performed using a 37% phosphoric etch. The etchant is then rinsed off for a minimum of 15 to 20 seconds to ensure complete removal (Fig. 16).

The preparation is then air-dried and rewet with AcQuaSeal desensitizer (AcQuaMed Technologies) to disinfect the cavity surface, create a moist surface for bonding, and begin initial penetration of HEMA into the dentinal tubules (Fig. 17). A fifth generation bonding agent (Optibond Solo Plus: Kerr Corporation) is then placed on all cavity surfaces (Fig. 18). The solvent is evaporated by spraying a gentle stream of air across the surface of the preparation (Fig. 19). The adhesive is then light cured for 20 seconds (Fig. 20). The first layer of composite is placed using a flowable composite (Revolution 2: Kerr Corporation) to a thickness of about .5 millimeters (Fig. 21).

The flowable composite will “flow” into all the irregular areas of the preparation and create an oxygen-inhibited layer to bond subsequent layers of microhybrid material. After light curing for 20 seconds (Fig. 22), the next step is to layer in the microhybrid material. First, using a unidose delivery, the first increment of microhybrid composite (Premise: Kerr Corporation) is placed into the proximal box of the preparation. A smooth ended condensing instrument is used to adapt the restorative material to the inside of the sectional matrix and preparation.

This first increment should be no more than two millimeters thick. After light curing the first increment, the next increment should extend to the apical portion of the interproximal contact and extend across the pulpal floor. Once cured the replacement of the dentin is complete. At this point, an endodontic file is used to place stain (Kolar Plus — Ochre: Kerr Corporation) in the areas where the major anatomic grooves will be placed in the subsequent layers and light cured (Fig. 24). The enamel increment is placed into the facial portion of the preparation, including the facial portion of the marginal ridge. The cuspal projections are sculpted and the depressions between are created so that some of the stain in the previous layer will show through (Fig. 25).

A #2 Keystone brush (Patterson Dental) is lightly dipped in resin and used to feather the material toward the margins and smooth the surface of the composite. The palatal increment of microhybrid composite (Premise: Kerr Corporation) is placed in the same manner as previously described (Fig. 26). Figure 27 shows the restoration after completion of the enamel layer prior to matrix band removal. The DryerPlier is used to remove the sectional matrix (Fig. 28) after removal of the flexible wedge and “G-Ring”.

Occlusion is checked with articulation paper and adjusted, as needed using a carbide-finishing bur. When placing composite materials using the described technique, very little finishing should be required except at the marginal areas. Rubber polishing abrasives are used to further polish and adjusted areas. In this case, some Kolar Plus White (Kerr Corporation) was placed after polishing to recreate a “snow capped” appearance to the cuspal areas as seen on the adjacent natural tooth.

Figure 29 shows the completed restoration prior to the placement of surface sealant. The surface sealant (Optiguard: Kerr Corporation) is placed with the #2 Keystone brush (Fig. 30), air thinned, and light cured for 20 seconds. Figure 31 shows an occlusal view of the completed Class II composite restoration.

CONCLUSION

A technique has been described utilizing a sectional matrix system and associated armamentarium (Composi-Tight Gold, WedgeWands: Garrison Dental Solutions), DryerPliers, and a nanofilled microhybrid composite (Premise: Kerr Corporation) to create an anatomically precise Class II posterior composite restoration. Using this armamentarium, the interproximal surface has also been recreated with natural anatomic contour and has a predictable, elliptical contact with the adjacent tooth, with very little rotary finishing necessary. With proper occlusal and proximal form, this “invisible” direct composite restoration will service the patient for many years to come.

Oral Health welcomes this original article.

REFERENCES

1.Remineralisation of artificial carious dentine exposed to two glass-ionomers, H.C.Ngo, M. Fraser, G.Mount, J.Mcintyre, and L.G.Do, The university of Adelaide, Australia; IADR 2002 San Diego, Abstract 3109

2.Remineralisation of carious dentine by glass ionomer, an in-vivo study; HC Ngo, M.Fraser, G.Mount, J.Mcintyre, J.Tuisuva, R.Von Doussa (Dental School, Adelaide University, South Australia 5005, Dental dept., fiji School of Medicine, Suva); 79th General Session & Exhibition of the IADR, Chiba; Abstract 0919

3.Fluoride Release and Recharge of Fluoride-Releasing Restorative Materials, X. Xu, J.O. Burgess and J.S. Turpin-Mair, Louisiana State University, School of Dentistry, New Orleans, Louisiana, USA, IADR 1999, Abstract 431