Our thanks to both Drs. Schroeder and Tesini for their letters. In response to Dr. Tesini’s first inquiry about the previous reports, the first and second references to which he refers1,2 are the same study. The abstract was published as a research abstract for the 2005 American Academy of Pediatric Dentistry (AAPD) meeting,1 which included the OMNII research presentations.2 As stated in Pediatric Dentistry, the abstract was not edited or reviewed.
In addition, we did not realize that the research abstract was going to be published in Pediatric Dentistry and did not have a chance to edit the proofs. This resulted in several errors. However, this abstract does state, "Toothprints wafer impressions material appears to be a valid bite registration material." After more critical analyses of the data and critical reviews by the JADA reviewers and a forensic dentist, the conclusion was that the Toothprints (Kerr, Orange, Calif.) bite registration was of value, but it was not good enough for forensic identification.
The actual sequence of data collection is stated in our JADA article, and we agree that rinsing prior to taking the bite impression would certainly reduce the quantity of DNA available for capture. Therefore, this was not the sequence performed.
To address Dr. Tesini’s second question, this study was conducted by using the manufacturer’s original fabrication technique. The patient was instructed "to bite hard onto the softened wafer and hold for 20 seconds to record dentition and capture saliva." It is very interesting that the video describing the technique on the Web site, "dentrek.com/class/FlashClass/DTST/TPrints/Toothprints_Control.swf", now states that the patient should bite hard for 50 seconds. And Dr. Schroeder noted in his letter that the small percentage of his bite registrations that needed to be redone were due to patients "not biting long enough or firmly enough."
It would be very interesting to determine if having the patient bite two and one-half times longer would significantly increase the quality of the bite registration obtained from the Toothprints. We realize that changes or modifications to the fabrication technique will affect the quality of the bite registration obtained from the Toothprints. Future studies with the modified manufacturer’s directions should be conducted to determine the effects of these modifications on the quality of the bite registration, as well as DNA capture.
The presentation at the AAPD meeting2 was reported as preliminary results, before further analyses and statistical tests were performed and before reviews by a forensic dentist and by JADA. It is interesting that Dr. Tesini’s statement that "this thermoplastic material itself is actually more accurate than alginate" is based on unpublished data from Kerr, the manufacturer of Toothprints. Other evidence that he cites in his letter is his own article, his third reference.3 Our report appears to be one of perhaps two independent studies examining Toothprints.
In response to Dr. Tesini’s third point, the American Board of Forensic Odontology (ABFO) defines a bite mark as "a physical alteration in a medium caused by the contact of teeth."4 The markings on the Tooth prints material certainly constitute a bite mark, according to this definition. Consequently, a bite mark analysis was used to compare the markings on the Toothprints material with models of the teeth of the subjects.
The toothprint was scanned at 300 dots per inch (dpi) by using a flatbed scanner along with an ABFO no. 2 ruler. The stone models were placed on the flatbed scanner so that the incisal edges of the teeth were in contact with the scanner bed and scanned at 300 dpi. An ABFO no. 2 ruler was included in the scan at the level of the incisal edges. An overlay was created with the scan of the study model captured at 50 percent transparency. The overlay was placed over the scan of the toothprint that corresponded with the model. The number of teeth incisal edges/occlusal surfaces captured in the scan of the model that corresponded to marks in the Toothprints material were counted. The number of matches was divided by the number of tooth marks present in the bite and multiplied by 100 to produce a percentage of matches.
ABFO guidelines4 list three degrees of certainty: reasonable medical certainty, probable (more likely than not) and exclude. The guidelines also state that "terms assuring unconditional identification of a perpetrator, or without doubt, are not sanctioned as a final conclusion." with regard to bite mark analysis. This level of certainty would not be acceptable in a dental forensic identification. In this study, only one Toothprint/model set had 100 percent matching. The rest had between one and four mismatches. Utilizing the ABFO guidelines, the range of one to four mismatches would place the match somewhere between "probable" and "exclude."
Dr. Tesini’s fourth reference, the Dailey and McGivney study,5 is an abstract in the proceedings of the annual session of the American Academy of Forensic Sciences. It appears that these authors were comparing an electronic image of the Toothprints material with a manipulated "positive" image of the original image. Additionally, these authors only looked at one tooth per age group (for example, permanent first molar for 7-year-old children). Bite mark analysis looks at all marks left by teeth rather than one type of tooth in a dental arch.
Further, Dailey and McGivney5 note, "Toothprints is a reliable method to record dental information that is of forensic value." It is difficult to determine what "forensic value" means. We found that the impression wafer in Toothprints did not appear to make a bite registration with enough accuracy to be used for forensic identifications. The conclusion should not be misconstrued to imply that the Toothprints wafer has no forensic value. It can provide dental information (as well as DNA) to assist in getting close to an identification. Our conclusion is that it should not be used as the sole source of antemortem dental information for the purpose of definitive identification.
We hope this explains, in part, Dr. Tesini’s concerns. We still agree that Toothprints can be used for collection of DNA for identification, and that it has some forensic value in regard to bite registration, but that it cannot under the manufacturer’s directions utilized in this study be used for absolute identification.
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