Restoring in Harmony
The importance of relating facial and dental planes of symmetry
Joseph R. Greenberg, DMD, FAGD, FCPP
Esthetic dentistry remains a key market driver for dentistry and dental manufacturing.1,2 Today's patients are more aware of the effect that an attractive smile has on overall facial attractiveness and seek improvement in this area from their dentists.3,4
The current scientific literature concludes that the dental midline to facial midline relationship is the most important treatment planning parameter in esthetic restorative dentistry.5-7 This clears up the confusion left by two earlier studies, which downplayed the importance of the dental midline to facial midline relationship.8,9 Both of these studies chose not to use full-face image references in their designs. It is important to note that it is the maxillary dental midline that should coincide with the facial midline, as is found in 70% of the population.10 When in view, the mandibular dental midline is usually in motion or covered by the lips or maxillary teeth and does not correspond with the facial midline in 75% of the population.10
Once the facial midline to dental midline relationship is determined, the relationship of the facial vertical axis to the dental vertical axis should be ascertained. The goal is for the facial vertical axis and the dental vertical axis to be parallel to each other when the facial midline is equal to the dental midline. Next, the facial horizontal axis is found and compared to the dental horizontal axis. Published studies agree that these two horizontal parameters should also be coincident.9,12 The most consistent methodology finds the relationship of the facial horizontal axis and the dental horizontal axis as perpendicular to the determined relationship between the facial vertical axis and the dental vertical axis. The commissural line (lips), interpupillary line (eyes), and ophraic lines (eyebrows) are not consistently reliable guides to determine the facial horizontal axis.10,11
Relating the dental midline, dental vertical axis and dental horizontal axis to the facial midline, facial vertical axis and facial horizontal axis, respectively, can be accomplished using one of several available devices, including the Facial Plane Relator (Ho Dental Company)12 or the Kois Dento-Facial Analyzer (Panadent Corporation).
A patient presented with defective crowns on all four of her maxillary incisors and a noticeable discrepancy between her facial vertical axis and dental vertical axis. The crowns were canted to her right (Figure 1 and Figure 2). There was a horizontal imbalance whereby her dental horizontal axis and facial horizontal axis clashed, and the incisal lengths of her laterals unnaturally dominated the centrals (ie, the facial horizontal axis does not harmonize with the dental horizontal axis). Her facial midline and dental midline were in relative harmony.
The preparations were completed with an effort to straighten their long axes to facial vertical axis, and 000 retraction cord (Ultradent Products, Inc.) was placed (Figure 3). A long piece of dental floss was used to find a facial vertical axis at the facial midline that satisfied both the patient and the dentist. Guide markings were placed on the bridge of the patient's nose that corresponded to the agreed upon facial vertical axis at the facial midline. Next, an impression was made using the Harmony Tray (Ho Dental Company) (Figure 4) and a vinyl polysiloxane impression material (Vaccu-sil, Ho Dental Company). The Harmony Tray is a device that combines the Facial Plane Relator with an anterior dual-arch impression tray to help dentists produce restorations that correct for dental/facial symmetry. While the patient is biting into the impression material of the tray, a bite registration material (Blu-Mousse®, Parkell Dental Products) is expressed into the receptacle in the handle. Then, the vertical member of the device is inserted into this unset material in alignment with the target markings that were previously placed along the bridge of the patients nose.
The assembled Harmony Tray with impression and facial plane guide is then sent to the laboratory. The dental laboratory pours both the maxillary and mandibular casts and articulates them using the bite registration and facial plane guides of the Harmony Tray (Figure 5). A thin marker has been used to mark the maxillary cast in Figure 8 so that the technician has that information to guide his fabrication endeavors once the tray complex is removed.
After the final porcelain-fused-to-zirconia crowns have been placed (Figure 6), it can be seen that the information transferred from the clinical procedure to the dental laboratory utilizing the Harmony Tray has enabled the correction of the orientation of the restored teeth to harmonize with facial symmetries (Figure 7 and Figure 8).
Dentists and dental laboratory technicians are eager to satisfy the increasing esthetic and cosmetic demands of their patients. Enhanced communications and information transfer are critical to success in these endeavors. In addition to making an accurate impression, the Harmony Tray described here provides the opportunity to record and transfer the patient's dental midline to facial midline relationship, dental vertical axis to facial vertical axis relationship, and dental horizontal axis to facial horizontal axis relationship. The added time expenditure is minimal, the predictability of enhancing the overall harmony of dental and facial symmetries is high, and the intentional involvement of the patient in confirming the location of the facial planes results in increased satisfaction with the final result.
Dr. Greenberg is a paid consultant for Ho Dental Company and receives compensation for articles and lectures. He can be reached at: firstname.lastname@example.org.
1. Dental services – Top 3 Market Drivers and Forecasts, Reports Technavio Page. https://www.businesswire.com/news/home/20161025006349/en/Dental-Services-%E2%80%93-Top-3-Market-Drivers. Updated October 25, 2016. Accessed September 27, 2017.
2. Cosmetic Dentistry Market – Global Industry Analysis, Size, Share, Growth, Trends and Forecast 2016 – 2024 Page. https://www.transparencymarketresearch.com/cosmetic-dentistry-market.html. Accessed September 27, 2017.
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