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Clinical General Dentistry

Dual-Force pre-molar and molar rings. (Photo: Clinician’s Choice)
Mar 3, 2017 | General Dentistry USA

Demanding more from your sectional matrix system

by Douglas Harvey, BSc, DDS

There are many challenges to restoring a tooth to its natural shape, contour and shade using a direct composite technique. Advances in composite restorative material and adhesion have enabled today’s dentist to control most of the esthetic variables that result in restoring a tooth close to its original state. However, there is still the matter of a properly established proximal contact.

Proper contour, tightness and location of the contact can be elusive and difficult to control at the time of placing the restoration. An open or loose contact can be harmful to the periodontium and can shorten the lifespan of the restoration, in addition to being a daily source of frustration for the patient because of food impaction. The answer to this dilemma simply lies in the selection of your sectional matrix system.

Update your contacts: It’s about WHAT you know

The interproximal margins of your Class II restoration may finish at varying distances from the contact area, while the height of the clinical crown can differ from case to case. These factors have to be considered when choosing an appropriate matrix band.

Having a selection of matrix bands of varying heights will enable you to properly fit the matrix to the preparation. Dual-Force matrix bands from Clinician’s Choice (New Milford, Conn.) are available in three occluso-gingival heights (4.5 mm, 5.5 mm, 6.5 mm) to accommodate almost all sizes of interproximal preparations.

These thin, contoured stainless-steel matrices are placed using a Punch Plier that grips and perforates the occlusal tab of the wedge for secure placement. Once the restoration is cured, the same Punch Pliers can be placed anywhere on the matrix band for easy removal.

Dual-Force Active-Wedges wrap snugly around the proximal line angles, resulting in the reduction of composite flash on the buccal and lingual surfaces. Less flash means less finishing time on these areas. A curved occlusal lip on the properly fitted Dual-Force Matrix Band ensures a rolling marginal ridge, further reducing your finishing time.

The Dual-Force Matrix has an interproximal contour that establishes the ideal shape for your proximal contact. A sectional matrix that wraps the tooth well, is contoured both proximally and occlusally and is available in the most frequently required heights provides the first step on your way to an esthetic and functional Class II composite restoration. The Dual-Force Sectional Matrix fits all these criteria.

One more degree of separation

Once the appropriately sized sectional matrix band is accurately in place, it is essential that it be securely held and the matrix band sealed against the gingival margin by a wedge. Failure to ensure this may result in excess composite flash that is difficult and time-consuming to remove. This excess may also be under-polymerized, leading to a potential void in the margin.

The lowly dental wedge has undergone many transformations during its long history. From sycamore wood wedges to plastic wedges that can be cured through, their primary role has remained the same: fill the interproximal space and do their best to seal off the gingival margin with the matrix.

We need more from this wedge. We need it to be able to physically adapt to the contour of the gingival margin with even pressure and, speaking of pressure, cause the interproximal space to expand temporarily and rebound upon removal of the wedge.

Triangular wedges of any material have a tendency to want to back out of the space and inadequately seal the matrix to the tooth when they do stay in place. Plastic wedges were designed with a more anatomical shape in order to address the challenge of sealing the matrix throughout its contact with the proximal margin. However these lacked the ability to supply any separation pressure. On the other hand, larger wooden wedges could separate the teeth but lacked the complete sealing effect.

Dual-Force Active Wedges have several design features that provide up to 2 lbs of separation force while sealing the matrix band gap-free against the gingival margin. Placing these active wedges is smooth, as the leading tip collapses and re-opens once fully positioned. Small, lateral fins act independently of each other in order to apply the appropriate sealing pressure along the matrix band. A strong internal spine is responsible for exerting the separation pressure and provides stability when stacking Active-Wedges, should it be necessary to do so in cases of excessive interproximal space.

The #5 Active-Wedge, or Deep Seal Wedge, is designed for deep, subgingival margins. A convex extension of the Deep Seal Active-Wedge fits into the anatomical depression often encountered with deep subgingival margins, completing the seal at the band/tooth interface even in this difficult clinical scenario.

The ring: Essential for intimate proximal contacts

While the technological advancement of the Active-Wedge is impressive, the evolution of the separating ring in today’s sectional matrix systems is the game changer when it comes to proximal contact formation.

The ideal separating ring is easy to place; engages the sectional matrix in such a way that all cavosurface margins are sealed; provides separation forces that are adequate and consistent; constructed of both metal and plastic that are resistant to fatigue/breakage and resist the sticking of composite and adhesive; provides adequate vision for the clinician to place and polymerize the restoration; is available in smaller versions capable of fitting pre-molars or to provide more separating force; and can be stacked and oriented in a manner to avoid interference with rubber dam clamps and over-erupted cusps.

A separating ring that could satisfy this exhaustive list would result in a Class II composite restoration that would mimic the natural tooth’s proximal contour and function and would require very little marginal finishing. Most separating rings available today cannot fulfill the expectations of such a list.

Some rings require excessive hand pressure to open the ring in order to place it on the tooth. Vertical tines, intended to press the matrix firmly against the tooth, may only make a point contact with the matrix, possibly springing unexpectedly off the tooth or allowing flash to be formed from composite overflow.

Separating forces of various levels are generated in each of these systems but can diminish over time as the metal ring fatigues. Some rings have plastic tines or ring covers that can fracture, and both metal and plastic components of most systems become sticky with excess adhesive and composite, making clean up tedious. Separating rings that seat parallel to the occlusal plane may not be able to be stacked for MO/DO/MOD applications or be able to clear a neighboring rubber dam clamp or tooth.

Clinician’s Choice has re-engineered the separating ring using dual fatigue-resistant NiTi wires. Dual-Force Forceps easily open the ring, and an ideal engagement angle allows for easy placement. Strong, balanced separation forces generated by the dual NiTi rings remain consistent and resist dislodgement. Four lateral tines separated by a V enable the ring to sit atop the Active-Wedge and engage the Dual-Force Matrix at its gingival and occlusal edges. This stabilizes the wedge and seals the vertical proximal margins to minimize any flash formation.

The Dual-Force Ring sits at a 20-degree angle to the occlusal plane, enabling the stacking of two Dual-Force Rings or clearing of an adjacent rubber dam clamp or prominent cusp. Errant composite and adhesive is easily wiped off. The autoclavable ring, along with its superior fatigue-resistance, will provide reliable and predictable service restoration after restoration.

Any attempt to restore a tooth to its original form and function includes a plethora of variables, any of which, if not properly controlled, can lead to a clinical disappointment or even failure. Utilizing a sectional matrix system, such as Dual-Force by Clinician’s Choice, that addresses the challenges of the proximal contact, is vital to achieving your clinical success.

 

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