A Need for a Unanimous Tooth Numbering System

Despite many efforts to reduce the incidence of wrong site procedures in the medical/dental field, it not only continues to exist, but is even increasing (Knight). A completely preventable complication, wrong site procedures persist to devastate patients, and are most often irreversible. Furthermore this medical complication can be very costly for a practitioner. The Oral and Maxillofacial Surgeons National Insurance Company (OMSNIC), reports that 12% of all claims reported to the company were for wrong-site tooth extractions. However, while other types of claims reported to OMSNIC may be reasonably defended and attributed to factors other than the practitioner, it is very difficult to defend a wrong-site extraction (Lee, et al). Overall, there are three widely recognized and used numbering systems by practitioners worldwide—the Universal Numbering System, the International (FDI) Numbering System, and the Palmar Numbering System. The authors believe that a major contributor in the miscommunication that leads to wrong-site extractions is the use of multiple different tooth numbers among different specialists.  The authors carried out a study to statistically identify the tooth numbering system that is most effective based on accuracy and recall speed. This may serve the dual purpose of increasing communication quality, while creating a Universal Protocol.

The authors designed a study that tested 111 first year dental students at the University of Pennsylvania. Each test contained two embedded video tutorials (Primary and Permanent Dentition), containing diagrams explaining the Universal and International Numbering Systems.  Students were notified that their answers would be analyzed on the basis of both timing and accuracy.  The two types of questions utilized were aimed to simulate each aspect of health professionals utilizing a tooth number (i.e. sending out a referral, interpreting a referral). In "Hot Spot" questions, the student was given a tooth number to identify with an image of a dentition (either Panorex radiograph, human dentition photograph, or dentoform) and a tooth number (i.e. Universal Tooth #21) to identify.  The student was instructed to click their mouse on Universal Tooth #21 in the diagram. The second type of question was referred to as an "Identification" question, whereby the student was given an image of a dentition with a bold red arrow pointed at a respective tooth number as the question instructed the student to type the correct tooth number. 

Results were analyzed based on timing and accuracy.  For both variables, questions were categorized based on numbering system (International or Universal) and dentition type (Permanent or Primary), shown in Figure 1.  Average time/questions correct per category per person was calculated. 

Using a Matched Pairs T-Test, the Permanent Universal Numbering System was found be both significantly more accurate (p=.02), and faster to recall (p<.001) than the Permanent International Numbering System.  Meanwhile, there was no significant difference between either accuracy or timing between Pediatric Universal and Pediatric International Numbering Systems. 

In conclusion, it was found that the Permanent Universal Numbering system was found to be faster and more accurate than the Permanent International Numbering system.  This may be explained, as the Universal Numbering System is one sequential number, whereas the International Numbering System is essentially two numbers in one (a quadrant number, and a tooth number), therefore, it is more likely that an error will be made in accounting for two aspects, rather than one.  By encouraging the global dental field to adopt one unanimous numbering system, there may be a potentially significant decrease in miscommunication resulting in decreased wrong site procedures.   

Sources:

Lee, Prevention of wrong-site tooth extraction: clinical guidelines. JOMS. 2007

Knight, Use of an anatomic marking form as alternative to universal protocol for preventing wrong site surgery. Am J Surg. 2010