Author: Dr. David J. Clark, DDS AMED Founder & Past President 2002-2004
Article published in the journal AMED Vision News | vol 3 issue 4
In this article, I will briefly summarize the history and shortcomings of posterior composites. I will then examine new techniques, materials and instruments that allow minimally traumatic tooth preparations and address the most serious flaws of traditional posterior composite restorations.
Twenty-five years after their inception, posterior composites remain unpredictable. In comparison to amalgam restorations, Class I and Class II composites show significantly higher failure rates, are more costly, take longer to place, have more postoperative symptoms, leak, stain, chip, and cause food impaction. My former operative dentistry instructor (a legend in the Pacific Northwest) recently shared this opinion with me – he "hates" posterior composites and hates to teach the technique. This sentiment shared at many dental schools across North America and therefore the posterior composite curriculum is limited.
To understand how clinicians can be infuenced by a cultural and scientifc icon, it is helpful to look at medical history.
Claudius Galen was a Roman physician who boldly devised a medical model that doctors followed for fourteen centuries. Though his medical judgments were remarkably advanced for his day, today, not surprisingly, we know that most of Galen’s theories and treatments were completely wrong, and that the rest were seriously fawed. In a parallel to Galen’s example, G.V.Black was a consummate dentist/scientist and his exquisite designs for cavity preparation were a huge step forward for dentistry. Unfortunately, we are discovering today that those cavity shapes weaken the posterior dentition and lead to fracturing in even the most conservative applications (Fig. 1).
Fig. 1: Extracted bicuspid with a conservative G.V.Black Class II features classic iatrogenic fracturing pattern
I utilized 16X magnification to evaluate each posterior tooth that was treated for retreatment of an amalgam or posterior composite. I classified and documented incomplete fractures. I found:
In the previous articles, I have highlighted the widespread problem of amalgam tooth preparations that predispose the tooth to fracture. One of dentistry’s myths is that amalgam expansion causes tooth fracture. Expansion failures have never been proven. The fracture problem does not originate with amalgam, per se. It originates in iatrogenic GV Black cavity peparations. And just as many of us feared, we are seeing the same pattern of fracturing in teeth with posterior composites now that enough time has elapsed to assess their longevity.
Dr. Richard Simonson is widely recognized as a pioneer in new cavity preparation shapes for minimally invasive, bonded, resin-based posterior composites. In spite of his innovations, the GV Black preparations that I was taught in school twenty years ago have been only slightly modifed for posterior composites in the typical dental practice and in most dental schools.
Fig. 2: The gingival margin in this class II composite demonstrates the pervasive problem of microleakage. There was unfavorable C factor at the margin, creating suck back. Uncured and contaminated flashing results from a metal matrix that blocks light curing and visualization
As we study and document the many problems with posterior composites we find out problems associated with current posterior composite placement techniques:
Fig. 3: Case in Figure 2 is retreated with Clark Class II filling techniques and instruments overcoming multiple problems
The Clark Class II is a radical departure from our notions of preparing and restoring posterior teeth. (Fig 4)
The goal of first-time interproximal caries restoration is to avoid connecting the occlusal to the interproximal, which is a concept that Simonson first advocated. The next evolution of this design is the saucer shape with serpentine/ disappearing margins. The final change is discarding and replacing old filling techniques, matrixing systems and curing techniques.
|Fig. 4: Diagrams of the Clark Class II (a), the slot preparation created by Simonson and others (b), and the original G.V.Black class II (c)|
To be continued