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Management of posterior proximal restorations. (Photograph courtesy of Dr. Sonali Gandhi)

Management of proximal posterior lesions: A case report

By Dr. Sonali Luthra Gandhi
November 12, 2018

Successful resin composite restorations can be achieved when a careful restorative technique is employed. Use of a sectional matrix band and elastic ring helps achieve a tight proximal contact, and the centripetal restorative technique can help to obtain contour and anatomy, minimizing the use of rotary instruments during the finishing procedures.

Resin composites have been used largely as direct restorative materials because of their tooth-like appearance, low cost, long working time/command cure, and acceptable clinical behavior. One important problem faced by clinicians when performing Class II composite restorations is to reestablish proximal contact.

The lack of condensability of composite materials allied to the thickness of the matrix band poses a challenge when trying to achieve adequate interproximal contact. Several instruments and techniques have been developed in an attempt to solve this problem. The aim of this report is to present a clinical case in which successful Class II restorations were achieved using a centripetal technique with pre-contoured sectional matrices and a separation ring to obtain a tight proximal contact.

CASE REPORT

A 25 year old female entered the clinic with a chief complaint of food lodgement in her upper right region. On oral examination tooth number 14 and 15 showed proximal carious lesions (Fig: 1). Radiographic evaluation depicted that the teeth did not require any endodontic treatment. Isolation was achieved with a rubber dam. Additional isolation was achieved by using polytetrafluoroethylene tape (PTFE) also known as plumber’s tape/ Teflon tape (Fig: 2). Excavation was performed using a small round diamond bur followed by a carbide bur in the deeper areas (Fig: 3).

After excavation the extension of the cavity seemed close to the pulp thus pulpal protection was achieved by placing a thin liner of Resin Modified Glass Ionomer Cement (RMGIC) (Fig: 4). In this case 3M, Vitrebond has been used. This liner was cured for 30 seconds. As the excavation extended deep into the dentin the deep layers needed to be protected from the 1st solution that is the etchant. This was done using the PTFE tape (Fig: 5).The cavity was now conditioned with 37% phosphoric acid for 30 seconds only in the enamel layer. (Fig: 5) The dentin was not subjected to the etchant thereby following the selective etching protocol. The cavity was thoroughly rinsed and air dried. The dentin bonding agent was applied (self etch adhesive, 3M/ESPE), gently air dried to evaporate the solvent, and light cured for 20 seconds (Fig: 6).The proximal lesions were adjacent to each other thus the placement of the band and ring was tricky. For predictable results sectional matrices were placed adjacent to each other followed by placement of a wedge and lastly the ring was placed to stabilize the entire system (Fig: 7).

After the placement of the ring system it was ensured that there was no open space between the tooth and the band on all surfaces. In this case the Palodent system, Dentsply was used. The advantage of placing both the bands together is to determine the contours and contact of the restoration rather than building it free hand. Nanofilled composite was incrementally applied (3M Filtek Z350 XT). A centripetal technique was used to restore the lost tooth structure from the periphery toward the center of the cavity in order to achieve a better contour and anatomy with less excess. First the proximal wall of tooth number 15 was built (Fig: 8). Light cured for 20 seconds. This was followed by building of the buccal cusp which was also cured for 20 seconds and then final layer of the palatal cusp which was also cured for 20 seconds. While layering it is important to flush the composite with the tooth margins and also give nice anatomic contours to the tooth. After one tooth was completely restored the entire matrix system was removed.(Fig: 9)

The proximal surface of tooth number 15 was finished and polished using 3M Soflex discs and spirals(Fig: 10). The sectional matrix was now placed on tooth number 14, followed by placement of a wedge and stabilized by a ring. The adaptation of the ring is important as it will compensate for the band thickness thereby achieving a tight contact. Once the entire assembly is in place, a ball burnisher is used to burnish the middle third of this matrix band, thereby determining the exact location of the contact point. The same centripetal technique is used here and the restoration is completed (Fig: 11). Tints are finally placed in the grooves created during the layering protocol giving a natural appearance. An oxygen barrier solution (KY Jelly Lubricant) was then applied onto the final layer of cured composite and light cured for 20 seconds.

Finishing and polishing procedures were accomplished with the use of a diamond bur (FO- 30F) followed by 3M Soflex Spirals and lastly using cotton wheel buff. Proximal and occlusal embrasures were refined with fine discs (Soflex Finishing/Polishing Kit, 3M/ESPE), followed by spirals and buff. The final was then achieved.(Fig: 12)(Fig: 13)

DISCUSSION

Although resin composite materials are considered easy to handle, reestablishing proximal contact is sometimes a challenging procedure, especially when the clinician is placing large Class II restorations. Unlike amalgam, which can be laterally condensed to obtain an optimal proximal contact, esthetic composite materials depend entirely on the contour and position of the matrix and wedge.

The lack of condensability because of the visco-elastic properties of the composite materials makes reestablishment of proximal contact more difficult and requires much care in adapting the matrix and wedge. Different types of matrix systems have been specially developed for use with composite restorations. Compared with plastic matrices, metal matrices are considered easier to install, maintain their shape better, are thinner, and can be burnished to the adjacent tooth, so the interproximal contacts can be more easily developed. The great advantage of this system is the presence of an elastic ring that holds the contoured matrix in place. These rings provide progressive tooth separation, resulting in an efficient contact.

The separation promoted by the rings can compensate for the thickness of the matrix band and allows for good adaptation of the composite material to the neighboring tooth. To reduce the stress generated during the polymerization contraction, oblique increments contacting the maximum of two walls were used to reduce the C-factor. Increments were applied to replace one cusp at a time. The uncured composite is contoured to the final anatomy of the cusp and then light-cured. This procedure allowed for the achievement of an ideal contour without the need to use the bur extensively during the finishing procedure.

The use of the centripetal technique also contributed to the better access of the occlusal box once the matrix and ring were removed, allowing better visualization and positioning when replacing the missing dental structures at the cusps. This technique was first described in 1994 by Bichacho18 and was intended to restore the lost tooth structure from the periphery toward the center of the cavity in order to achieve a better contour and anatomy with less excess, thereby minimizing the use of rotary instruments during the finishing procedures.

CONCLUSION

Successful resin composite restorations can be achieved once the characteristics and limitations of these materials are understood and taken into consideration. Because of the peculiar features of resin composite materials, such as the stress generated as a result of polymerization shrinkage, viscoelastic properties that preclude proper condensation, thickness/cure ratio, and technique sensitivity of the bonding protocol, a careful restorative technique should be used.

In conclusion, all phases involved in the restorative procedure should be meticulously implemented to ensure the success of the resin composite restorations.

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