Written by Howard S. Glazer, DDS Thursday, 31 May 2007 19:00
Composite resin shrinkage is the cause of frequent class II open contacts. The scope of this problem is exemplified by observing the amazing diversification of matrix system solutions that purport to resolve this dilemma. What is interesting, however, is the attempt to create contact by aggressive over-wedging of the teeth. The over-wedging approach hinges on separating teeth enough to compensate for both resin polymerization shrinkage and the interproximal thickness of the matrix. Though over-wedging methods can produce a degree of success, too often clinicians find themselves with inadequate contact. The reason is simple. Over-wedging does not always produce enough separation to offset resin shrinkage and the matrix wall thickness. The result is open contacts.
This article will describe a new and innovative approach to achieving excellent contacts when placing class II composite restorations.
|Figure 1. Contact Perfect matrix bands: Universal MO/DO (a); Bicuspid MOD (b); Molar MOD (c).||
Figure 2. Contact Perfect in a Tofflemire retainer.
Figure 3. How Contact Perfect works.
Contact Perfect, recently introduced by Miltex, resolves the open contact problem by allowing the clinician to place a MOD restoration with a singular band. Contact Perfect is a series of 3 matrix bands (Figure 1) that utilizes standard Tofflemire retainers (Figure 2). Contact Perfect takes a novel approach to compensate for matrix thickness and resin shrinkage. Very simply, it is a band with a window portion that aligns interproximally. It works by selectively removing the matrix window to establish direct contact. After resin compaction is completed, you can remove the window to build direct resin contact against the opposing tooth (Figure 3).
Creating the contact is simple. Use an explorer to poke the uncured resin surface once only (Figure 3). Because resin behaves according to fluid dynamic principles, it will bulge or displace through the window when an explorer tip is inserted into it. This creates a nicely contoured contact point. All this is accomplished without over-wedging the teeth and subjecting them to potential periodontal ligament insult. Moderate wedging is used, however, to secure the gingival aspect of the band and thus prevent unwanted gingival extrusion. The result is remarkable. The contact predictability is nearly certain, and the quality of contact is anatomically excellent. Contact Perfect uses standard Tofflemire retainers and requires no extraordinary instruments or devices. The technique is novel and differs slightly from present modalities. The learning curve it presents can easily be mastered after a couple of band placements.
As noted, there are 3 Contact Perfect band styles: Universal MO/DO, Bicuspid MOD, and Molar MOD (Figure 1). For clarification, typodont illustrations are interspersed with clinical photos.
The Contact Perfect Procedure
Step 1: Mount the band on the retainer, align the window with the preparations,and place the band
Figure 4a. The band’s window is aligned and placed.
|Figure 4b. Contact Perfect is mounted on a tooth. The band’s window is aligned interproximally.|
After placing Contact Perfect on the retainer, the windows are aligned with the prepared aspect of the tooth. The band is then placed on the tooth and gently wedged interproximally to prevent subgingival extrusion during compaction of the resin (Figures 4a and 4b). Suggestion: Gently wedge the unprepared side of 2 surface restorations to facilitate band insertion.
Step 2: Snip the window connector tab
Figure 5. Contact Perfect’s connecting band is snipped.
Once in place, this connector is snipped. This physically detaches the window from the matrix band so the window can be withdrawn later. Note: do not cut the tabs with the eyelets. These eyelets are used to withdraw the windows later. Cutting the connector tabs can be done in 2 ways: sever with a fine diamond and high-speed handpiece, or snip the tab with a scissors (Figure 5). I recommend holding a gauze pad or using high-speed suction over the tabs to contain the clipping.
Step 3: Pack a first increment, bevel it, and light-cure
Figure 6. A ramped axial increment is packed and cured.
Etch and prime in your preferred manner. Although not necessary, you may precoat the adjacent proximal surface with a thin lubricant to preclude resin adhesion. The initial increment is a departure from conventional technique. The goal is to create a layer that ensures excellent axial wall resin adaptation to provide deep photo-curing. The critical key here is to bevel the resin, leaving the windowed wall free from resin impingement. Remember, the goal ultimately is to create direct contact. If we occlude the windowed portion with resin, then we will not be able to displace the resin to create direct contact. I pack a 2-mm increment of resin into the box. Then, using a plastic instrument, I bevel the resin away from the window portion of the band. This keeps the resin from impinging on the windows’ surface. Once done, the bevel is photo-cured (Figure 6). Note: For Contact Perfect, it is recommended to use a universal, non-sticky, sculptable resin.
Step 4: Pack a Second Increment
|Figure 7. A second increment is placed. Gross occlusal and marginal ridge sculpting is done (no photo-cure has been done at this point).|
The remainder of the prep is bulk packed. Using a plastic instrument, carve some initial occlusal anatomy, paying special attention to forming a well-rounded marginal ridge as seen in Figure 7. The band’s secure and circumferential envelopment of the tooth permits aggressive resin compaction and adaptation to the interior and exterior line angles. Once satisfied with the gross sculpting, the uncured restoration is ready for direct contact.
Step 5: Remove Window
Figure 8. The eyelet is engaged to remove the band’s window cover.
With an explorer, engage the removable shield’s eyelet (Figure 8) and withdraw the shield with a continuous swift motion (resin is still uncured).
Step 6: Tap Uncured Resin Once With An Explorer
Figure 9a. The uncured resin is “tapped” once with an explorer to displace resin and establish contact.
Figure 9b. After the “tap.”
Figure 10. The tap hole is filled.
Remember, the resin should not have been photo-cured yet…this is critical. Using an explorer, I tap the resin surface once only (no more than 2- to 3-mm deep; Figure 9a). The volume of the inserted explorer tip causes the resin to displace uniformly or flow through the open window and directly touch the adjacent tooth’s natural anatomical contact point. After the tap, there will be a visible “tap hole” in the resin surface (Figure 9b). Again, only poke the resin once per mesial and/or distal side (if doing an MOD). Caution: Additional taps could result in hyper-extrusion of the uncured resin and compromise perfect contact.
I then photo-cure the restoration from an occlusal, buccal, and lingual approach (you can cure through the now-open window). The light is applied for 20 seconds from each aspect. After curing, I then use a small amount of resin to fill the tap hole (Figure 10). Note: You can direct the curing light through the exposed proximal walls to enable additional light penetration if desired. The resulting resin-displacing tap hole is then filled with a flowable resin and cured.
Step 7: Remove Matrix Band
Figure 11. The connecting arch is severed to help remove the matrix band.
Figure 12. The retainer is tightened to effect a buccal-lingual separation.
Figure 13. Postoperative film of a Contact Perfect procedure.
Contact Perfect has a unique removal system. It eliminates having to withdraw the band through the newly formed contact area. The removal is a 2-step process that will allow the band to be removed buccally and lingually without disturbing the contact area.
(1) Using a finishing diamond on a high-speed handpiece, sever the occlusal connecting arch. Just look for the visible notch and slice through it (Figure 11).
(2) Upon severing the notch, tighten (not loosen) the retainer to separate the remaining gingival connection of the band (Figure 12). Note: The matrix should be secure in the retainer to prevent band slippage during the tightening phase.
Patient demand has made it imperative for dentists to become proficient with posterior composites, in particular class II restorations. Contact Perfect is a Tofflemire-like matrix system that allows the clinician to achieve contoured, direct contact class II restorations by utilizing the liquid dynamics property of composite resin to displace or flow when compacted. There is a minor learning curve, and the band’s usage must be employed in proper sequence. This band presents an effective approach to resolve one of resin dentistry’s continual problems.
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