OneBite Case Study
The primary objective of aesthetic dental treatment is to generate a natural, healthy appearance for an otherwise damaged dentition. The word “aesthetic” implies beauty, naturalness and a youthful appearance relative to one’s age, and aesthetic dentistry has been called the “art of the imperceptible” by McLaren and Rifkin. A pleasing dental appearance is the subjective appreciation of the shade, shape and arrangement of the teeth and their relationship to the gingiva, lips and facial features. Symmetry, the property of being symmetrical, with a correspondence in size, shape and relative position of parts on opposite sides of a dividing line or median plane or about a center or axis, plays a large part in the perception of dental aesthetics (Fig. 1). In a study by Dunn, when evaluating photographs of male and female smiles, 24 out of the 25 demographic groups picked the same attractive female smile, which was characterized by natural teeth having a light shade, a high lip line, a large display of teeth and radiating symmetry. Multiple studies show that society places a great amount of importance on appearance, with attractive people having more success, higher paying and more prestigious jobs, better luck in obtaining dates, more favorable jury verdicts and more positive responses, even from infants. The ability of the dentist to communicate the location and orientation of the patient’s facial landmarks to the dental technician will dictate the success of the esthetic outcome.
Figure 1: The facial midline, interpupillary line and incisal line should be in symmetrical harmony (note minor nasal asymmetry).
This article will look at the aesthetic parameters of dental midline position, incisal cant and incisal horizontal plane, and provide a simple methodology to relate these parameters to the dental technician when multiple anterior restorations are prepared. Of course, details of the smile arc, the curve formed by the incisal edges of the maxillary anterior teeth in relationship to the lower lip, need to be communicated to the laboratory technician. The maxillary incisal curve and the lower lip curve should be roughly parallel to one another and perpendicular to the vertical midline drawn between the maxillary central incisors (Fig. 2). For complicated cases, itis critical to give an accurate relationship of the casts in a sagittalor lateral axis when designing the curvature and angle of the smile line (bicuspids to molars), as the potential form is alignment of the casts increases with the number of restorations involved.
Figure 2: The smile arc shows the anteriors in harmony with the curvature of the lower lip.
Figure 3: The facial and dental midline should coincide for optimum esthetics.
Figure 4: This patient’s midlines do not coincide, thus the mandibular midline cannot be used as a reference point for the final restorations.
Figure 5: The patient in Figure 4 with temporaries in place.
Figure 6: The dental technician cannot use the mandibular midline to decide where to place the maxillary midline when multiple teeth are prepared.
The Dental Midline
Figure 7: A midline cant is consistently rated as unaesthetic.
Midline Cant or Oblique Midline
If the clinician is to transfer these important parameters of the maxillary dental midline, the lack of midline cant, and the incisal horizontal plane to the dental technician, which should all be referenced to the facial midline and interpupillary line, how is this reliably accomplished? In the past, classic stick bites, cotton swabs, pencils, plastic stir sticks and symmetry bites have been used to capture these dimensional relationships. 10 The limitations of these systems are many. All have limitations due to the short working time of many bite registration materials, so the clinician is forced to work quickly to center and place these before the material sets. If the stick bite or symmetry bite is slightly off, the whole process needs to be repeated. With fixed symmetry bites, the vertical and horizontal are fixed at 90 degrees to each other, assuming the horizontal incisal plane matches exactly to the interpupillary line and no correction is indicated or anticipated. A stick bite to the horizontal assumes the patient can keep his or her head perfectly still and upright. A simple solution to the transfer of the required data to the dental technician is the Onebite™ (Precision Dental Products; Draper, Utah) facial plane relator. There are a number of distinct advantages to the Onebite over other available systems. The bite fork portion is separate from the adjustable horizontal and vertical components, so that if the bite fork is placed slightly off center when placed into the bite material, the ability to move the components laterally eliminates the need for repeating the procedure. Figure 11–13 show the placement of the bite registration material Affinity™ Quick Bite (Clinician’s Choice; New Milford, Conn.) onto the anterior teeth, onto the bite fork and the intraoral placement of the bite fork. After the vertical and horizontal components were placed firmly into the bite fork slot, it can be seen (Fig. 14) that the bite fork was placed slightly off laterally to the patients left side. The bite fork placement does not have to be redone; Figure 15 shows the horizontal adjustment is easy to accomplish by loosening the screw, sliding the component laterally until centered to the patient facial midline and then securely tightening the locking screw. Another benefit of Onebite is that the vertical and horizontal component can be left in a locked 90-degree relationship to each other if the patient demonstrates symmetry of the midline, horizontal and interpupillary line, or the components can be unlocked by rotating the horizontal bar so the locking pins are facing the clinician, if there is a discrepancy with the interpupillary line. Figure 16 shows the patient’s right side horizontal portion of the Onebite is slightly lower than the interpupillary line. This can easily be adjusted by unlocking the components, rotating the horizontal bar until it is in harmony with the interpupillary line, securely tightening the locking screw and then fixing the components together by injecting temporary C&B material into the lateral slot and screw. For illustrative purposes, the rotation has been exaggerated in Figure 17 to show the wide range of adjustments that are easily managed by the Onebite. The components are then taken apart by placing lateral force on the locking screw, which facilitates transport to the laboratory. Another advantage of the Onebite is that in the laboratory, the vertical component can be reduced in length at the plastic cross supports to fit easily onto a semi-adjustable articulator.
Figure 11: Quick Bite is injected onto the anterior teeth
Figure 12: Quick Bite is injected onto the bite fork of the Onebite, and the bite fork is centered on the face when the patient closes.
Figure 14: When the components are mated, it can be seen that the bite fork is off center.
Figure 15: By loosening the screw and sliding the components to the patient’s right, the vertical bar now corresponds to the patient’s facial midline.
Figure 16: The horizontal bar does not line up with the interpupillary line and can be adjusted parallel to it by unlocking the bars, aligning the horizontal and tightening the locking screw.
Figure 17: For illustrative purposes, the angulation of the horizontal bar has been exaggerated and fixation is achieved with Temptation acrylic temporary material (Clinician’s Choice).
The rationale for the need of accurate communication by the dental clinician to the laboratory technician of the dental midline, incisal midline cant and incisal horizontal plane have been discussed. A simple technique that facilitates this communication has been presented and should minimize the need for expensive remakes for esthetically driven restorations.
A study by Chan quantifying a layperson’s ideal and maximum deviation of the midline found the smile became unattractive when the maxillary midline deviated 2.9 mm, or once the maxillary-mandibular midlines deviated 2.1 mm.
1. Rifkin R. Facial analysis: a comprehensive approach to treatment planning and aesthetic dentistry. Pract Periodont Aesthet Dent 2000;12(9):865–71.
2. McLaren EA, Rifkin R. Macroesthetics: facial and dentofacial analysis. Journal of California Dental Association 1993;103(5):295–411.
3. Nohl FSA, Steele JG, Wassell RW. Crowns and other extra-coronal restorations: Aesthetic Control BDJ 2002;192(8):443–50.
4. Bryan M, Calhoun K. All about chin augmentation facial proportions and analysis. Dept of Otolaryngology, UTMB, Grand rounds, Chin and Malar Implants Sept 6, 1995. http://www.chinaugmentation.com/facial_formula.htm.
5. Dunn WJ, Murchison DF, Broome JC. Esthetics: Patients’ perceptions of dental attractiveness. J of Pros Mar 2005;5(3):166–71.
6. Patnaik VVG, Singula RK, Bala S. Anatomy of a beautiful face & smile. J Ant. Soc. India 2003;52(1):74–80.
7. Ackerman MB, Ackerman JL. Smile analysis and design in the digital era. JCO April 2002;26(4):221–36.
8. Rufenacht CR. Principles of esthetic setup. In: Rufenacht CR, editor. Principles of esthetic integration. Quintessence Publishing 2000. P 205041.
9. Sarver DM. The importance of incisor positioning in the esthetic smile: the smile arc. American Journal of Orthodontics and Dentofacial Orthopedics 2001;120(2):98–111
10. Chan CA. Architecting the occlusal plane. Las Vegas Institute for Advanced Dental Studies.
11. Chiche GJ, Aoshima H. Functional Versus Aesthetic Articulation of Maxillary Anterior Restorations. PP&A 1997;9(3):335–42.
12. http://medical-dictionary.thefreedictionary.com/ Frankfort+horizontal+plane
13. Morley J, Eubank J. Macroesthetic elements of smile design. J Am Dent Assoc 2001;132(1)39–45.
14. Beyer JW, Lindauer SJ. Evaluation of dental midline position. Seminars in Orthodontics Sept 1998;4(3):146–52.
15. Thomas JL, Hayes C, Zawaideh S. The effect of axial midline angulation on dental esthetics. Angle Orthod. 2003;73:359–64.
16. Miller EL, Bodden WR Jr, Jamison HC. A study of the relationship of the dental midline to the facial median line. J. Prosthet Dent. Jun 1979;41(6):657–60.
17. Soares GP, Valentino TA, Lima DANL, Paulillo LAMS, Lovadino JR. Esthetic Analysis of the smile. Braz J Oral Sci April-June 2007;6(21):1313–18.
18. Sheats RD, McGorray SE, Musmar Q, Wheeler TT, King GJ. Prevalence of orthodontic asymmetries. Seminars in Orthodontics Sept 1998;4(3):138–45.
19. Johnston CD, Burden DJ, Stevenson MR. The influence of dental to facial midline discrepancies on dental attractiveness ratings. European Journal of Orthodontics 1999;21:517–22.
20. Chan RW, Ker AJ, Fields HW, Beck FM, Rosenthiel SF, Johnston W. 0366 Esthetics and smile characteristics from the patient’s perspective, Part II. http://iadr.confex. con/iadr/2008Dallas/techprogram/abstract_100215.htm.
21. Cardash HS, Ormanier Z, Ben-Zion L. Observable deviation of the facial and anterior tooth midlines. JPD March 2003;89(3):282–85.
22. Kokich Vo, Kikak A, Shapiro PA. Comparing the perception of dentists and laypeople to altered dental esthetics. J of Esth and Rest Dent 1999;11(6):311–24.
23. Paul SJ. Smile analysis and face-bow transfer: Enhancing esthetic restorative treatment. Pract Proced Aesthet Dent 2001;13(3):217–22.
24. Tipton PA. Esthetic tooth alignment using etched porcelain restorations. Pract Proced Aesthet Dent. 2001;13:551–55.
25. Reikie DF. Orthodontically assisted restorative dentistry. JCDA Oct 2001;67(9):516–20.
26. Spear FM, Kokich VG, Mathews DP. Interdisciplinary management of anterior dental esthetics. J Am Dent Assoc 2006;137:160-69.
27. Javaheri D. Considerations for planning esthetic treatment with veneers involving no or minimal preparation. JADA March 2007;138:331–37.
28. Sasbri R. The eight components of a balanced smile. J Clin Orthod 2005;39(3):167.
29. Chiche G, Pinault A. Esthetics of Anterior Fixed Restorations. Carol Stream, IL: Quintessence Publishing, 1988. Reprinted with permission of Oral Health Journal, ©2010 Oral Health Journal
Dr. Len Boksman is adjunct clinical professor at the Schulich School of Medicine and Dentistry and maintains a private practice in London, Ontario, Canada. He is also a paid part-time consultant to Clinical Research Dental Inc. and Clinician’s Choice. Contact him at firstname.lastname@example.org or 519-641-3066, ext. 292.
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