Composite Resins and Vertical Dimension: Treating Severely Worn Lower Incisors

INTRODUCTION
Aging patients present unique challenges that require innovative solutions. Each patient treatment should be based on a multitude of factors. However, in the end, 2 simple questions should be posed to patients who have reached the twilight of their life, defy the odds, and live on, and on, and on. These are the 2 questions that I like to ask patients in their 80s and 90s:
• Mr. Smith, do you think that you will live or could live another 5 or 10 years?
• Do want to outlast your teeth or would you like your teeth to outlast you?
In this, the third of my series of articles dealing with the restoration of mandibular incisors, I present an interesting and fairly typical dilemma. As discussed in my previous article (“Composite Overmolding of the Worn Lower Incisor,” April 2012, Dentistry Today), lower incisors can play into a snowball effect when it comes to wear. As the percentage of incisal enamel decreases and dentin increases, the rate of wear increases proportionately. In this case (Figures 1 to 3), another 2 mm of incisal attrition would have rendered the central incisors to be unrestorable without drastic measures, such as crown lengthening.

CASE REPORT
I consulted with James and his wife. I proposed 3 options: nontreatment, porcelain reconstruction, or composite reconstruction. They chose the third, that of composite. While the treatment will not make the cover of any cosmetic dentistry journals, it is nonetheless a life changing treatment for this wonderful elderly gentleman.
This case presented 4 unique challenges.

Figure 1. Preoperative view of an 89-year-old male in good health. After 3 decades of porcelain occlusion, the lower incisors were showing critical wear.	Figure 2. With the mandible fully closed, the devastating wear of the porcelain crowns opposing the natural teeth was evident.
Figure 3. Close-up view (4x) of the worn incisors. The secondary and tertiary dentin is visible. This type of sclerotic dentin typically has reduced bond strength, but any freshly cut dentin will also typically have an improved bond over orally exposed dentin.	Figure 4. Composite addition to the lower partial denture.

Challenge 1: He Had Just Paid for a New Partial
Because James had lost an abutment tooth 2 years previously, he had finally consented to have me fabricate a new lower partial for him. The partial had an excellent fit, so I opted to modify it by increasing its vertical dimension. Instead of rebasing or replacing the partial, I opted for a more immediate solution (Figure 4). The denture teeth were quickly and carefully abraded with a coarse diamond bur. A universal adhesive (Scotchbond Universal [3M ESPE]) was applied to the surfaces, air-thinned, and light-cured. The second molars were heightened by approximately 2.0 mm by “patty caking” paste composite to lengthen the teeth; the first molar by 2.5 mm; and the second bicuspid by 3.0 mm (Figures 5 and 6). This created enough clearance for the planned 4.0 mm incisal addition without shortening the already decimated lower incisors to provide clearance for adding the composite.

Challenge 2: How Do I Overlay a Porcelain Crown?
Porcelain crowns can be predictably overlain with composite if the porcelain is first carefully abraded with a coarse diamond bur and then treated with hydrofluoric (HF) acid. Any areas where the glaze is undisturbed will not retain the bond. Be mindful that the HF acid will not attack a glazed porcelain surface. Silane application, as a separate step, can now be skipped with the use of Scotchbond Universal. One of the “deal makers” for me to switch to this new universal adhesive was the inclusion of a silane coupler. Separate silane couplers have always annoyed me; in general, these chemicals are expensive, and they have a relatively short shelf life. In addition, under the microscope, I am often disappointed at the uneven and blotchy appearance of the silanated surface of porcelain.

Challenge 3: Where Do I Start?
In James’ case, we first made the addition to the partial denture because it allowed me to build both right and left side together; furthermore, it was the most reversible and easiest thing to do. Once that was finished, I inserted the partial and did a quick occlusal equilibration. Once even bilateral contact on the denture teeth was achieved, I had the patient in a stable and comfortable vertical dimension of occlusion (VDO) into which I could now build the remaining natural teeth and crowns.

Challenge 4: How Do I Avoid Getting “Lost” While Adding so Much Freehanded Tooth Structure?
Many clinicians would prefer to do a diagnostic wax-up, making some sort of stint to guide the placement of the composite. Alternatively, a relatively experienced clinician attains a good feel for the mechanics of increasing the VDO, and that step can be avoided if anatomic matrices are used.

Figure 5. The partial denture teeth on the lower right side, shown preoperatively.	Figure 6. The initial composite addition for the opening of the vertical dimension of occlusion (VDO) was completed.
Figure 7. Low-magnification view of the blasted teeth ready for matrix placement.	Figure 8. Medium-magnification view of the blasted teeth ready for matrix placement.

A Skeptic Might Be Asking, “This Never Worked Before; Why is This Going to Work Now?”
The skeptic would certainly look at the preoperative condition of the lower incisors (Figures 7 and 8) and scoff at the ability to do this treatment in a reasonable time frame. In addition, one might also question the ability of direct composite to withstand the occlusal forces. After seeing traditional attempts fail throughout time, the skeptic’s point is well supported, but out of touch with injection molding techniques using current composite resins (Table). The reason that the overmold can be a predictable option is simple: the treatment is essentially unrelated to what we have done in the past. This approach maximizes composite’s strengths and minimizes its weaknesses.
One of the biggest changes, if not the biggest change, is that of design and the creation of an enamel-driven procedure. I am not a big fan of dentin bonding when it comes to retention of a restoration; the impressive immediate dentin bond strengths slowly diminish throughout time and fall into the range of about 8 MPa at 5 years. In contrast, the enamel bond strength remains strong for decades. Yes, we want to eliminate postoperative sensitivity and we do not want any microleakage and the resulting brown margins. In an enamel-driven procedure, at least half of the bondable surface area is enamel. With the Bioclear technique and injection molding, the entire tooth is ensconced in composite and all available enamel is accessed. In the old method, most of the little “beret” of composite on the incisal edge was bonded to dentin, meaning that very little enamel was ever engaged; and, after adjusting the occlusion, even less enamel was engaged. Furthermore, the small amount of enamel that was bonded to generally had the little white line. Remember that the evidence of a white line indicates a poor bond.
In terms of clinical difficulty, the beautiful embrasures created by the Bioclear Matrix allow for a minimum of finishing in the hard-to-reach areas. The bulk of the finishing is required at the midfacial and midlingual. These areas can be quickly and safely finished, even when a fair amount of excess is present.
Now let’s entertain a few more typical questions.

Aren’t These Teeth Going to Be Too Thick if You Don’t Prep Them First?
I love that question! Take a careful look at Figure 9; the enamel is only about 0.75 mm thick, and when James was young, his enamel was easily twice as thick. Even if I were to add one full millimeter to both the lingual and facial, the tooth would be only slightly wider than when the patient was younger. In this case, I added about 0.75 mm of thickness to both the facial and lingual.

I See That You Closed the Black Triangles. Was That Necessary?
James isn’t going to compete in any beauty pageants this month. There is a hygiene and health advantage to eliminating black triangles in seniors (Figures 10 to 12). It is also a quality of life issue as it eliminates embarrassing social ramifications created by dark food accumulation. More importantly, injecting a significant volume of composite under and around the contact does a superb job of locking the composite onto the tooth. Once again, we are striving to convert the procedure to an enamel-driven procedure instead of dentin-driven technique. By surrounding the entire tooth, we are able to capitalize on bonding to every last remnant of enamel on these extremely worn teeth.

Figure 9. The 8x magnification (G-6 microscope [Global]). An encouraging amount of enamel remains around the sides of the teeth; the incisal dentin has been very lightly brushed with a diamond bur to freshen the sclerotic/contaminated dentin.	Figure 10. The case, as partly restored. Two Bioclear A-103 matrices, one on the distal and one on the mesial, will contain the composite and leave the tooth with crownlike aesthetics and contours.
Figure 11. The last 2 anterior teeth shown ready to be injection molded. The author finds it helpful to do a quick gross shaping of the incisal edges and facial contours as each pair of teeth is finished. If this is done before moving on to the next teeth, it lessens the chance of the clinician losing his or her way during the composite addition.	Figure 12. Incisal view of the lateral incisor and canine with matrices (Bioclear) in place.
Figure 13. Side view and facial view of the newly designed A-103 or small incisor matrix (Bioclear).	Figure 14. Final view of reconstructed lower incisors before removal of rubber dam. All of the surfaces are highly polished except for the incisal edges, which will need to be equilibrated after the dam is removed.

Figure 15. Final view of the full arch composite rehabilitation.

Figure 16. Before and after comparison. Note generous increase in the VDO.

The final “deal maker” is the fit and shape of the new Bioclear A-103 small incisor matrix (Figure 13). Instead of fighting against a flat matrix, the exquisite shape of the A-103 matrix fights for me. The final photographs demonstrate an aesthetically adequate and functionally superb improvement (Figures 14 to 16).

What Is in Injection Molding of Composite?
Before placing the matrices, the teeth must be blasted clean to remove biofilm. Blasting is using high pressure air and water with aluminum tri-hydroxide (DENTSPLY Caulk) and the Bioclear Blaster.
Then, the teeth to be restored are surrounded with fully anatomic clear matrices (Bioclear Matrix). The teeth are etched with 37% phosphoric acid, and then the enamel and dentin are coated with a bonding agent; preferably with a self-etching resin that allows “rinse-etching” of the dentin. Next, the universal adhesive resin is air-thinned and cured. Then, the knife-edge tooth-matrix interface is rewetted with the bonding resin, but not light-cured. A small amount of flowable composite is injected along the gingival margins and also not light-cured. Then, those more flowable resins are “chased” with a creamy paste composite (such as Filtek Supreme Plus Ultra [3M ESPE]). The bulk of the flowable composite is pushed out of the matrix by, and ahead of, the paste composite in this update of the snowplow technique.
And just when we learned to perform the snowplow and injection molding technique, we have a new and practice changing development: the obsolescence of flowable composite!

Figure 17. Tip size of a typical paste composite tip. It is far too large for this case, displacing the anatomic matrix significantly.	Figure 18. The brand new medium Micro-Flo Step-Down Tip (Bioclear and Vista Dental) is threaded over the tip of any paste composite tip. The small version is similar in size to the gauge of most flowable tips.

Figure 19. High-magnification view of Figure 19.

The End of Flowable Composites?
The advent of flowable composite resins ushered in a host of new possibilities as well as clinical advantages. In this case, it afforded me the ability to use anatomic clear matrices to do crownlike composite dentistry, to close diastemas, and to eliminate black triangles, etc. In the last months, the final clinical trials were completed for the prototypes of the Micro-Flo Step-Down Tips (Bioclear and Vista Dental) which are currently available. The use of these tips in a very recent case shows the tip, which is screwed over the end of the 3M paste compule (3M ESPE), “steps down” the gauge of the compule tips with a medium or small tip. Astoundingly, it behaves about the same as flowable composite during extrusion. This should be a very big deal! This can only work if the composite is heated to 155°F (Calset [AdDent]) but that is a small price to pay (Figures 17 to 19). The heated composite moves through tiny canulas the size of flowable canulas. So now, instead of injecting a flowable and then paste composite resin, we can use only a paste composite. This means less mess, fewer steps, and less disturbance of the matrix by the large and clumsy paste compule tips. This system forces paste composite to perform with the same clinical ease of flowable composite, but without flowable’s mildly inferior strength, hardness, shine retention, and wear resistance.

CLOSING COMMENTS
All clinicians seem to have a tipping point wherein they will only put up with a certain amount of fuss and finishing when it comes to direct composite. Once that threshold is crossed, they often scamper back to the comfort of crowns or implants. Hopefully, the contemporary materials, matrices, and methods presented in this case will inspire the reader to rethink the possibilities of rejuvenating the aging dentition with direct composite.

Dr. Clark founded the Academy of Microscope Enhanced Dentistry, an international association formed to advance the science and practice of microendodontics, microperiodontics, microprosthodontics, and microdentistry. He is a course director at the Newport Coast Oral Facial Institute in Newport Beach, Calif. He is codirector of Precision Aesthetics Northwest in Tacoma, Wash, and an associate member of the American Association of Endodontists. He lectures and gives hands-on seminars internationally on a variety of topics related to microscope-enhanced dentistry. He has developed numerous innovations in the fields of micro-dental instrumentation, imaging, and dental operatory design. He is proud to join with the CR Foundation in the “Update Series” lectures and also to participate in the important research at their world-class facility in Provo, Utah. He is also developing new techniques and materials to better restore endodontically treated teeth, including the endo-restorative casting. A 1986 graduate of the University of Washington School of Dentistry, he can be reached at drclark@microscopedentistry.com or at lifetimedentistry.net.

Disclosure: Dr. Clark has a financial interest in the Bioclear Matrix System.