TOWNIE CLINICAL: The Tri-Clip Sectional Matrix System By: Marshall White, DMD

In early 2003, a small company from New Zealand introduced a pre-assembled and single-use patented sectional matrix system for placing Cl. II restorations. It is composed of three elements: a rather horseshoe-shaped plastic retaining ring with tines that actually engage the embrasure in a manner more in keeping with dental anatomy, a pre-contoured metal sectional matrix, and a clear elastic polymer wedge that is pulled, rather than pushed, betwixt the adjacent teeth. Invented by Dr. Simon McDonald, a dentist with a penchant for modular application, it is aptly named the Tri-Clip (www.triclip.com).

I hesitated a bit at first, but was immediately struck by the degree of efficiency this system afforded me when doing Cl. II restorations. I’d always chaffed at the use of all the componentry needed when using other sectional systems, but had to muster the courage because admittedly they gave a consistently tighter contact and much superior embrasure anatomy compared to tofflemire-style methods. Assembling these in the mouth, as it were, seemed tedious at best, perhaps even dangerous at worst, but I’d sigh and have at it again and again.

The Natural Evolution of a Great Idea
Any way one looks at it, if we are to have the benefits of a tight contact and optimal embrasure anatomy, ultimately we must create a mold into which we place our composite. Most of us have spent our own valuable time and motion to build this mold using components that are themselves not exactly cheap. Now we can very quickly place the pre-assembled Tri-Clip in less than half the time, and with fewer fumbles, whilst maintaining outstanding efficacy and gaining a few other advantages as well. I’ve found the Tri-Clip to not only speed things along predictably, but after it’s all said and done I’ve experienced less gingival wedge trauma, fewer hassles and less stress. And that can only be a good thing.

Following is a short primer on the Tri-Clip, some cases using this little dental widget, and a bit of explanation when appropriate.

The Tri-Clip comes in two configurations. A white “Innie”, with the contoured sectional matrix curving into the ring; and a blue “Outtie”, with the matrix facing away from the ring (Figs. 1 & 2). They are color coded for easy identification; in general the white innies are for DO restorations and the blue outties are for MOs. The elastomeric double-ended wedges come stretched between cleats on either end of the horseshoe, and a thin connecting isthmus of that material passes across the points of the pincers which engage the embrasure just behind the matrix per se (Fig. 3).

Fig. 1 & 2

Fig. 3

Case 1: Use of the “Innie” Tooth #5 DOB
The pre-op image (Fig. 4), after initial removal of restorative, and the final preparation (Fig. 5). The mesial enamel of #4 was then recontoured with a Two-Striper 799 MF-3 diamond and polished (Fig. 6).

Fig. 4

Fig. 5

Fig. 6

The Innie Tri-Clip viewed from the gingival aspect (Fig. 7) and properly mounted on the forceps (it is worthwhile to mention that a conventional rubber dam forceps is inappropriate for use). The matrix must be centered between the pincers of the retainer, and its convexity touching the stretched isthmus of the double wedge. Once placed and the wedge released from its cleats and pulled through to the buccal (Fig. 8), then the matrix is firmly burnished against #4 to confirm contact. The current state-of-the-art calls for creating readily cleansable margins of high integrity using bevels (i,ii,iii,iv,v,vi,vii,viii). For example, a 1999 study by Hilton & Farracane concluded:

“Vertical walls without bevels exhibited pronounced micro leakage. Beveled vertical proximal walls exhibited significantly less facial and lingual wall micro leakage compared to all other groups, and less gingival marginal leakage compared to the control group.” (3)

Fig. 7

Fig. 8

Coincidentally, such beveling also yields greater ease in placement of the Tri-Clip.

Simplicity bonding agent is applied as directed (www.simplicityadhesive.com) then a thin layer of PermaFlo flowable (www.ultradent.com) is applied and light cured (Fig. 9). Once the preparation is incrementally filled with Gradia Direct (www.gcamerica.com) and its final layer pulse-cured, the retaining ring is expanded with the forceps and NOT moved coronally but rather is moved mesially to completely disengage the pincers by sliding them off the ends of the matrix (Fig. 10). At this point, the matrix ends can be reflected distally, and the axial margins inspected whilst the elastomeric wedge remains in place preventing hemorrhagic or serous contamination. These margins can be carefully revised if needed. Finally, the resultant restoration (Fig. 11) exhibits excellent contours with a tight contact (finished, polished and sealed with PermaSeal [(www.ultradent.com]).

Fig. 9

Fig. 10

Fig. 11

Case 2: MODBL #14 using two “Outties”
This case would be a challenge with traditional sectional matrices due to the breadth of the ‘boxes’ potentially allowing the tines of a conventional retaining ring to collapse the matrices (Figs. 12-14). With practice, the clinician can quickly learn to routinely perform these MOD+ restorations with precision and maximum efficiency using Tri-Clips.

Fig. 12

Fig. 13

Fig. 14

Case 3: Back-to-back Cl. II restorations; #3 MOL, #4 MOD, #5 DO
Using two “Innies” (with their matrices for #3 and #5) and two conventional sectional matrices (both for #4) also retained by the Tri-Clips, these 3 teeth were restored in expeditious fashion in about an hour including anesthesia and several photos (Figs. 15-17).

Fig. 15

Fig. 16

Fig. 17

Purchased in bulk, the Tri-Clips work out to roughly $1.20 apiece ($300/250#). In my experience, the savings in time and ease make it well worth the small cost. An intro kit is available, which includes the proper forceps, instructional CD and a practice model. The clinician does well to use a few of these to construct restorations on the provided practice model or a Typodont, and then to first choose in vivo cases involving a single proximal surface on a lower bicuspid. One can progress rapidly through the learning curve and ultimately develop an appreciation for the Tri-Clip, as well as hone one’s skill to a level commensurate with the cases shown here.

Bibliography:
i. Quintessence Int 2000 Apr;31(4):231-9. The axial bevel technique: a new technique for extensive posterior resin composite restorations. Liebenberg WH.

2. Am J Dent 2000 Aug;13(4):171-ii. Effect of light source position and bevel placement on facial margin adaptation of resin-based composite restorations. Hoelscher DC, Gregory WA, Linger JB, Pink FE.

iii. Am J Dent. 1999 Jun;12(3):123-30. Cavity preparation factors and micro leakage of Class II composite restorations filled at intraoral temperatures; Hilton TJ, Ferracane JL.

iv. Am J Dent 1998 Aug;11(4):189-96. Extension for prevention: is it relevant today? Osborne JW, Summitt JB.

v. J Prosthet Dent 1998 Sep;80(3):274-9. Necessity of bevels for box only Class II composite restorations. Opdam NJ, Roeters JJ, Kuijs R, Burgersdijk RC.

vi. Dent Mater J 1992 Jun;11(1):26-37. The effects of various clinical factors on marginal enamel micro-cracks produced around composite restoration. Han L, Okamoto A, Iwaku M.

vii. Actual Odontostomatol (Paris) 1989 Sep;43(167):609-18. [Bonding and enamel prisms. Importance of cavity margin preparation for posterior composites] [Article in French] Nebot D, Goldberg M, Fortier JP, Aldin P.

viii. J Oral Rehabil 1977 Oct;4(4):305-9. Effect of beveling on the occurrence of fractures in the enamel surrounding composite resin fillings. Oilo G, Jorgensen KD.

Marshall White, DMD is a general dentist in private practice since 1985, and tireless advocate of scientifically-based dental treatment. An author and teacher, he has written and spoken in the United States and abroad on endodontics, operative dentistry and Minimally Invasive Dentistry. Dr. White has worked with several dental manufacturers on product development and market trends.

Following completion of this article, Dr. White was impressed with the Tri-Clip and asked if he could contribute to its further development and represent Triodent in the USA. This request was granted. The Tri-Clip is the only product in which Dr. White has a financial interest.