How to Establish the Proper Plane of Occlusion With No Reliable Landmarks

One of the most rewarding aspects of practicing contemporary dentistry is the improvement of a patient’s smile. The importance of a smile was related more than 70 years ago by Dale Carnegie, who stated in his book How To Win Friends and Influence People that the smile was the big secret of dealing with people.  Seeing the change that takes place in a patient’s self-esteem and quality of life is amazingly rewarding. Many aspects of someone’s smile can be addressed, often with quite simple techniques. We have been able to categorize a good number of rules concerning smile design.1-3 Many of these involve the use of landmarks to transfer information to the laboratory technician so he or she can provide the patient with the most accurate and beautiful restorations possible.4 We rely heavily on these landmarks to construct harmonious, lifelike restorations. But what happens when the landmarks are unreliable?

One of the first steps in establishing an aesthetic reconstruction is to define the proper plane of occlusion.5 Without a proper plane of occlusion the remaining features that establish proper form are adversely affected. Embrasures will not be perpendicular to the proper plane of occlusion. All tooth dimensions will be nonconforming. Therefore, it is essential to find some way of establishing and transferring the proper plane of occlusion to the laboratory technician.

CASE REPORT

Figure 1. Irregular appearance of smile.

A female patient presented with concerns about the discoloration of her teeth, the canting, and irregular appearance of her smile (Figure 1). One of our first objectives was to establish her proper plane of occlusion.

We have learned from the past that a number of techniques are available for capturing and relating to the laboratory technician the proper plane of occlusion.6 These include the following:

(1) Properly taken face-bow.

(2) Establishing a plane parallel to the intrapupillary line.

(3) Having all incisal edges of preparations parallel to the proper plane of occlusion.

(4) Temporary restorations that are properly contoured parallel to the plane.

(5) Making the plane perpendicular to the Nasion-Philtrum (N-P) line.

(6) Using a stick bite.

Figure 2. All landmarks on different planes. Figure 3. Nose canted to the right.

In studying landmarks on this patient we discovered that neither external auditory meatus was in the same plane. The same held true for her intrapupillary line. Her right orbit was lower than her left orbit (Figure 2). In addition, her nose was canted slightly to the right (Figure 3). All of these factors contributed to the complexity of beginning this case.

In this patient both the pupil and external auditory meatus were lower on the patient’s right. This skeletal circumstance caused a canting of the maxilla, and subsequently the midline of her maxillary incisors, from right to left (Figure 2). Our goal was to select a midline more perpendicular to the horizon and more in balance with her face (Figures 2 and 3).

Figure 4. External auditory meatus plane canted. Figure 5. External auditory meatus error transferred to articulator.

If you take a proper face-bow transfer with one external auditory meatus lower than the other, the mounted cast will be lower on the side with the higher external auditory meatus (Figures 4 and 5). By utilizing the Wynne 2003 (articulator occlusal plane augmenter) with a stick bite, we are able to overcome this situation. The Wynne 2003 is a prototype developed for the Sam III articulator. It is not available commercially, but was designed to aid in tipping the Sam III to correct the position of the occlusal plane. In combination with the stick bite we are able to simulate the correct position of the occlusal plane. Any device that can be attached to the base of the articulator and allow you to tilt the entire articulator until the stick bite is parallel to the floor will accomplish this goal.

The stick bite is placed with the patient standing and oriented so as to capture the horizontal plane as it relates to the patient’s face (Figure 6). In her situation it was very close to being perpendicular to her N-P line (Figure 3). This occlusal plane is the most aesthetic and in balance with more of her facial structures.

Figure 6. Stick bite relates patient’s face to horizontal plane. Figure 7. Face-bow error corrected.
Figure 8. Stick bite is parallel to the floor. Figure 9. Technician must focus on occlusal plane, not tilted articulator.

To relate this to the laboratory technician, we placed the stick bite on the model and elevated the right side of the articulator until the stick bite was parallel to the floor or horizon (Figures 7 and 8). It would be possible to correct the face-bow by taking it out of the lower ear and elevating the face-bow until it was in the same plane as the left ear. However, this is not as accurate, since the face-bow assembly covers the visual center of the face we are trying to balance.

The Wynne 2003 is capable of adjusting both sides to tip the articulator until it brings the stick bite into position parallel to the floor (Figures 8 and 9). This device does the following:

(1) Corrects the landmark error or external auditory meatus discrepancy.

(2) Transfers the corrected midline to the orientation of the new occlusal plane.

The only caution is that the laboratory technician should not pay any attention to the tilted articulator but focus on the occlusal plane as it relates to the bench top or horizon (Figure 9).

The material selected for this case was Authentic (Micro-star). A variety of restorations were to be used in this case, including porcelain laminates and metal-supported pressed porcelain. The excellent marginal adaptation with pressed porcelain was another factor in favor of this product. While the marginal integrity associated with gold alloy castings can approximate 25 to 40 µm, those associated with the pressable porcelains could be even less. The Authentic system was ideal for these applications.

CONCLUSION

Figure 10. Completed case showing proper location of occlusal plane.

Aesthetic results can be achieved even if guiding landmarks are not accurate. Use of a stick bite and articulator augmentation system allows us to control the proper location of the desired occlusal plane (Figure 10). As with all procedures, complete communication between the patient, dentist, and laboratory technician is essential in order to achieve the maximum aesthetic result.4


References

1. Johnson PF. Racial norms: esthetic and prosthodontic implications. J Prosthet Dent.1992;67:502-508.

2. Peck S, Peck L. Selected aspects of the art and science of facial esthetics. Semin Orthod. 1995;1(2):105-126.

3. Nanda RS, Ghosh J. Facial soft tissue harmony and growth in orthodontic treatment. Semin Orthod. 1995;1(2):67-81.

4. Paul SJ. Smile analysis and face-bow transfer: enhancing aesthetic restorative treatment. Pract Proced Aesthet Dent. 2001;13(3):217-222.

5. Ahmad I. Geometric considerations in anterior dental aesthetics: restorative principals. Pract Periodontics Aesthet Dent. 1998;10(7):813-822.

6.Chiche GJ, Aoshima H. Functional verses aesthetic articulation of maxillary anterior restorations. Pract Periodontics Aesthet Dent. 1997;9(3):325-342.

Acknowledgement

The author would like to thank John Wilson and Carol Hendrix of Wilson Dental Arts, Raleigh, NC, for the beautiful ceramics.



Dr. Wynne maintains a private practice in Raleigh, NC, focusing on aesthetic and restorative dentistry. He graduated from the University of North Carolina School of Dentistry, Chapel Hill, NC, in 1971. He has recently achieved the status of Pankey Scholar. He is a member of the American Academy of Cosmetic Dentistry and a long-time member of the American Academy of Dental Practice Administration. He has completed Levels I and II of the Ultimate Esthetic Continuum at Americus in New York City. His past lecturing has been with the Ultimate Esthetic Continuum, the Esthetic Epitome in Charlotte, NC, and various educational study groups. He has published numerous articles on aesthetic dentistry, occlusion, and eating disorders. He can be reached at (919) 851-3716.