Lewis Lorton

The incidence of unerupted permanent teeth and related clinical cases

The impacted or mal-erupted tooth and its associated pathosis provide great diagnostic challenges to the dentist. The frequency of occurrence of impaction was found to be over 10,000 in 5,000 Army recruits. The type and position of impaction are summarized in tables. The incidence of impactions was higher than previously reported and may reflect some sampling bias. The incidence of impacted second and fourth molars is higher than expected. Impactions or mal-eruptions were seen to involve every permanent tooth except the mandibular incisors and first molars. Impactions can occur because of malpositioning of the tooth bud or obstruction in the path of eruption. However, the exact mechanism is still unknown. Six unusual cases of impacted permanent teeth are described to illustrate the importance of panoramic radiographs in the discovery of some anomalously located impactions.

Bifid mandibular nerve as a possible cause of inadequate anesthesia in the mandible

Failure to achieve complete mandibular anesthesia is a problem that often occurs. The explanations include faulty anesthetic solutions, faulty technique, and anatomic or physiologic variations. Bifurcation of the mandibular nerve, rarely mentioned in the literature, may be a cause of inadequate anesthesia in a small percentage of cases.

Adult pulpal diagnosis. I. Evaluation of the positive and negative responses to cold and electrical pulp tests

This study investigated the positive and negative responses of 1488 teeth in 60 patients to two electric pulp testers and a cold thermal pulp test. Three subgroups of known pulpless or pulpally diseased teeth (teeth receiving root canal therapy, teeth with root canal fillings, or teeth with confirmed associated apical radiolucencies) were identified and their responses evaluated separately. Testing was performed on two tooth surfaces, the facio-occlusal and faciocervical, and on all restorations. The gingival tissue of each patient also was tested using both electrical tests. The primary findings were: (a) teeth not responding to cold and either not responding or responding at readings greater than the tissue response to electrical had a high probability of being in the known pulpless or pulpally diseased subgroups; (b) the only false positive responses to cold in the three subgroups were in multirooted teeth with probable vital tissue remaining in at least one canal; and (c) in the three subgroups, if the false positive responses to electrical that responded at levels higher than the patients tissue response were considered to be negative responses, the difference in false positives between cold and electrical became not statistically significant (p = 0.07).

A comparison of the area of the canal space occupied by gutta-percha following four gutta-percha obturation techniques using procosol sealer

Sixty anterior teeth were filled using four gutta-percha sealer techniques: lateral, vertical, mechanical, and chloroform dip. The teeth were mounted in groups and sectioned. Four levels were evaluated for area of canal obturated by gutta-percha versus area empty or obturated with sealer. Lateral condensation had significantly less gutta-percha in the apical two levels than the other three techniques. By the third and fourth levels, the vertical technique had significantly more sealer present than the chloroform dip and mechanical techniques. The mechanical and chloroform dip techniques were not significantly different at any level.

Gemination and twinning in the permanent dentition.

Gemination and twinning are uncommon developmental anomalies of the hard dental tissue. These aberrations are manifested either as anomalous teeth or as supernumerary teeth. Six cases of gemination and twinning are presented in this article. A simplified classification of these anomalies has been suggested.

Evaluation of the effects of carbon dioxide used as a pulpal test. 3. In vivo effect on human enamel

A carbon dioxide thermal pulp test was used clinically for 2 min on the buccal surfaces of 10 teeth scheduled for extraction. The scanning electron microscope was used to evaluate whether the extreme cold caused any surface changes. Polyether impressions of the tooth surfaces and acrylic replicas made from the impressions were evaluated. The carbon dioxide did not damage the tooth surface. Direct evaluation of the polyether impressions was shown to be an excellent means of evaluating surface changes up to about original magnification x400.

The Computer-Assisted Postmortem Identification (CAPMI) System: A Computer-Based Identification Program

The Computer-Assisted Postmortem Identification (CAPMI) system was developed at the U.S. Army Institute of Dental Research to facilitate rapid identification of human remains. The increasing requirement for dental based identification of high-energy fatalities and decomposed remains has dovetailed with the development of computer capabilities permitting automation of most of the highly repetitive chart-by-chart screenings characteristic of traditional identification taskings. This report summarizes the concepts upon which CAPMI is based, describes how it works, and reviews suggested applications and limitations. CAPMI software is available to governmental, civic, or humanitarian organizations at no cost.

Design and use of a computer-assisted postmortem identification system.

The organization and rationale for the design of a computer-assisted postmortem identification system are discussed along with results of the use of this system in extensive simulation trials on a database of 578 records. The selectivity of dental characteristics is so great that any individual with 4 or more characteristics (either fillings or missing teeth), can be separated from a group of 578 people for final verification of the identity match. The effects of errors in the database are discussed and the actual effects of different error rates on identification are shown. Error rates of up to 30% have only small effects on the ability of the system to pick out correct identity matches. The system is presently implemented on a portable microcomputer, a representative desktop computer, and a large minicomputer. The present efforts include statistical analysis of an enlarged database and testing of a data acquisition system to allow the building of a large identification database (25 000 records) in a quick and economical manner.

A new algorithm for use in computer identification.

On 9 May 1987, a Soviet-made IL-62M Polish airliner, LOT Flight 5055, crashed, exploded, and burned, killing the crew and 183 passengers. A forensic science team from the Armed Forces Institute of Pathology, comprised of 6 dental officers, 3 forensic pathologists, and 3 medical photographers, worked in concert with the Polish forensic science team. The small number of antemortem records and the extreme fragmentation of the remains presented a new scenario for computer use. Typically, the Computer-Assisted Postmortem Identification (CAPMI) software is used to compare remains against an antemortem database. Results are listed by the number of tooth-to-tooth matches based on restorative or other characteristics or both. The Polish disaster confounded this approach to some degree, however, and suggested a reconsideration of the theory on which the sort is made, that is, that the cases with maximum number of matches to preexisting dental records would be the most likely identification (ID) match. A hypothesis was constructed that, if searches were accomplished for fragments with a minimum number of mismatches, the correct matches would appear higher in the rank order. Six antemortem records (that had all dental information) were sorted against one hundred and twelve postmortem fragmented records. The resulting report was reordered so that records were listed by minimum number of mismatches. There was significant improvement in rank placement for all of the records. Thus it was accepted that in the situation of highly fragmented remains a different sorting based on the number of mismatches is indicated. Programming changes to make this option available have been implemented in the new version of CAPMI.

A clinical and laboratory comparison of irreversible hydrocolloid impression techniques

I rreversible hydrocolloid is used extensively in dentistry, and several articles have established guidelines for its proper handling and also emphasized the importance of selecting an appropriate impression tray.le4 There are many methods of modifying an impression tray to obtain maximum accuracy of an irreversible hydrocolloid impression. The purpose of this investigation was to determine which tray modification is instrumental in producing the most accurate irreversible hydrocolloid impression. Resulting impressions were evaluated clinically and measured in the laboratory.