We’ve all experienced it. You see a patient for a periodic examination, and the patient says, “You know that crown you made for me up here (pointing to the crown on tooth Nos. 14 or 15)? I get all kinds of food stuck in there every time I eat. It’s driving me crazy. Can you fix it?”
You know that the space was closed when you inserted the crown. The tooth has drifted distally. So now what do you do?
Or, maybe you’re seeing a patient for the first time, and the patient tells you of a food entrapment between posterior molars. Is there a history of crown and bridge? Maybe—maybe not.
What do you do when a patient has an unwanted interproximal space between first and second molars, creating a food trap? Occasionally this problem will occur after placing a crown on the second molar. Do you replace the crown on the second molar and close the contact? Or perhaps place a DO class II restoration on the first molar to close the contact? There is an easier, less invasive way. This article describes a simple, noninvasive method to close interproximal spaces and eliminate food entrapment using an occlusal adjustment technique.
Teeth Move
We know that teeth move when we consider successful orthodontic procedures. In addition, the topography of the occlusal surfaces of teeth, when maxillary opposes mandibular, creates vectors of force in various directions (Figures 1 and 2). The sum total of these vectors of force will determine if a tooth migrates or not.
Regardless of the method of determination of occlusion during crown fabrication and crown seating, there will be at least some movement of the tooth over the succeeding weeks and months. Normally, this movement is scant and meaningless, in that the tooth appears to maintain its position without problem.
 |
 |
| Figure 1. The distal vectors on this lower second molar will cause distal movement, and an opening between first and second molar. | Figure 2. The mesial and distal vectors are now equal and cancel each other out (tooth is now stable at the unwanted distalized position). |
However, there are rare times where a “domino effect” will occur. The tooth moves a few microns, bringing into effect another occlusal contact that creates a vector of force, perhaps causing the tooth to move a few microns distally, which creates yet another vector of force (Figure 1). Before you know it, there is a space between teeth (Figure 2) collecting food and creating an unhappy patient. We even see this with virgin teeth, simply because of normal wear of the teeth that creates changes in vectors of force, and the domino effect can happen here, too. But this phenomenon most often occurs after a restoration, especially a crown.
So, what do we do about it? If vectors of force can cause unwanted movement to the distal, opposite vectors of force can guide movement to the mesial, thus closing the interproximal contact and correcting the problem.
 |
 |
| Figure 3. Second molar has moved distally, and now has equal vertical forces on mesial and distal, preventing any movement mesially. | Figure 4. As the tooth tilts (rotates) to the mesial (around the axis of rotation) the distal marginal ridge elevates (moves in an occlusal direction). If there is a vertical occlusal contact on the distal half of the tooth (such as distal marginal ridge), or if during forced mesial movement (rotation/tilting) the distal again comes into vertical contact, this will prevent further mesial movement of the second molar. Another occlusal adjustment, removing distal vertical contacts, would then become necessary. |
Let’s assume that the second molar has drifted distally, opening up the interproximal contact between the first and second molar, causing a food trap (Figure 2). Mark the area with articulating paper and inspect the marks on the distalized second molar (Figure 2). You may see marks on cuspal inclines (Figure 2) and on flat areas such as marginal ridges (Figure 3), cusp tips, and fossae. Look for vertical marks on the mesial marginal ridge and on the distal inclines of the cusps. These are the marks that create forces that want to move the tooth forward (mesially). These marks are “our friends.” The marks on the mesial inclines and the vertical marks on the distal marginal ridge, as well as other vertical marks on the distal half of the tooth, are “our enemies.” Marks on mesial inclines cause forces that push the tooth distally, which is the opposite of what we want. And the vertical stops on the distal marginal ridge and other vertical stops on the distal half of the tooth would tend to prevent the distal half of the tooth from moving in an occlusal (eruptive) direction, which is what happens when a tooth tilts (rotates) to the mesial (Figure 4).
The Solution
 |
 |
| Figure 5. Space (food trap) is apparent between first and second molars. All occlusal forces have been relieved other than on the mesial marginal ridge. This will create a mesial movement of the tooth, closing the interproximal space. | Figure 6. Only mesial vectors of force have been left and will cause mesial movement of the second molar. The second molar will move mesially until either the second molar comes in contact with the first molar (desired result) or until vectors of force (occlusal contacts on the mesial inclines) in the distal direction occur and stop the mesial movement (which then would require another occlusal adjustment). |
Adjust occlusion in the following way: Leave vertical stop contacts on the mesial half of the tooth, especially the mesial marginal ridge (Figures 4 and 5). If there is no contact on the mesial marginal ridge, create one by bonding a thin layer of composite on the ridge. Also, leave any contacts on distal inclines (Figure 6). Minimally remove vertical contacts on the distal half of the tooth (Figure 4), and all contacts on mesial inclines (Figure 6).
 |
 |
| Figure 7. Four weeks later, the interproximal space has closed fully. There is a “friendly” vertical occlusal contact on the mesial marginal ridge. However, there is an “unfriendly” vertical contact on the distal half of the tooth, and an “unfriendly” contact on the mesial incline of the mesio-buccal cusp. | Figure 8. To create absolute stability and certainty that there will be no more distal movement of the second molar, both “unfriendly” occlusal contacts were slightly relieved. The remaining vertical contact on the mesial marginal ridge will prevent distalization of the second molar. |
The patient should be seen in approximately 4 weeks to evaluate movement. If the open interproximal contact was originally minimal, often the contact will be fully closed at 4 weeks (Figure 7). Inspect the occlusion again and make any appropriate adjustments (Figure 8). If the space is not fully closed, check occlusion again with articulating paper, and perform adjustments as before to ensure continued movement. Most contacts will be closed after one or two adjustments (Figures 7 and 8), however, occasionally more adjustments may be necessary.
We all know that teeth do not drift mesially in a bodily movement; instead, they tilt forward (Figure 3). We show this to our patients when discussing the need to replace missing posterior teeth with bridges. Leaving (or creating) the vertical contact on the mesial marginal ridge will help cause the distalized tooth to move mesially (Figure 4). And of course, removing any vertical contact on the distal marginal ridge will allow mesial movement of the tooth (Figure 4).
On successive visits, in the rare case where, after some mesial movement, the mesial marginal ridge is no longer in occlusion, it is very simple to acid etch the mesial marginal ridge and add a very thin layer of flowable composite to bring the marginal ridge into occlusion. If the tooth in question has a porcelain crown, consider use of hydrofluoric acid to etch the porcelain, followed by silane, bonding agent, and flowable composite. Even though the flowable composite may not be as wear-resistant as we’d like, it will serve to help the tooth finish its mesial migration (tilting), and the other forces you’ve created should serve to hold it in place.
Of course, as mentioned previously, the same can be done on the first adjustment visit if the mesial marginal ridge happens not to be in occlusion. Remove any vertical stops on the distal half of the tooth, be they fossae, cusp tips, or marginal ridges, because as the tooth moves (tilts) mesially, the distal half will move occlusally (as in eruption of a tooth) (Figure 4).
Those with inquiring minds have already posed the question, “What about the physical law that states that each force has an equal and opposite force?” In other words, “Won’t these vectors we are creating to influence the tooth to move mesially cause the opposing tooth to move distally?” This was also my original question. But in 23 years of performing this procedure at least 100 times, I’ve yet to find even one case where the opposing tooth has moved distally. I think there may be two reasons for this. First, the opposing tooth has most likely been in a stable position for a number of years, and the tooth we are trying to move mesially has only recently (within a year or so) moved distally, opening up the interproximal contact. The bone may not be as dense around this tooth, and this tooth may be the one to “yield” instead of the opposing tooth. Second, we’ve all been told of the phenomenon of “mesial drift,” which indicates that posterior teeth “want” to move mesially because of certain curvatures of the jaw.
Finally, the vertical stops will be your most important adjustments. If possible, make certain to have a nice, heavy stop on the mesial marginal ridge of the tooth that is intended to move, and remove all vertical stops on the distal half of this tooth (Figure 5). These vertical forces will cause mesial movement of the tooth in question with minimal effects on the opposing teeth. And keep in mind, when you make these adjustments you should tell the patient to be prepared to return to your office for additional adjustments after 4 weeks. I find that, depending on the size of the interproximal space, these usually require one to three adjustments. I may have had one or two cases with such large interproximal spaces that four adjustments were required.
Each time you make an adjustment, adjust only enough tooth structure to remove the articulating paper mark on the mesial inclines of the cusps, and vertical marks on the distal marginal ridges.
Dr. Kurthy maintains a full-time practice in Mission Viejo, Calif. He has been involved in clinical research and product testing for 25 years. Dr. Kurthy is the recipient of numerous awards and honors including the Mosby Publishers Scholarship award, Fairleigh Dickinson University Prosthodontic and Pediatric Dentistry Awards, the Omicron Kappa Upsilon Gold Key Award and membership, and a Commendation from the Chief Attorney of the United States Department of Defense for his role in supporting patients’ rights in disputes with insurance carriers. He has appeared numerous times in various media, including television, radio, and magazines. He was also the personal dentist of the 1994 United States World Cup Soccer Team. Dr. Kurthy may be reached at (949) 588-1600 or drrodger@cox.net.
