Forensic dentistry

Forensic dentistry deals with the science of dentistry to aid in the administration of justice, Dental identification depends mainly upon comparison between records of the missing persons and the findings in the bodies in relation to Restorative work, Unusual features and Comparison of ante-mortem with postmortem X-rays.

The following particulars should be noted :

  • The number, spacing and situation of the teeth present, with special note of UN-erupted and deciduous teeth, permanent teeth (surface and configuration), decayed teeth and undersized or over sized teeth.
  • The number and situation of absent teeth.
  • Extraction: evidence of old or recent, healed or unhealed.
  • The general condition of teeth: erosion, cleanliness, conservation – fillings – cavities, color and periodontosis.
  • Peculiarities of arrangement: prominence or reverse, crowded or ectopic teeth, overlapping, malposition, deformities and rotation.
  • Supernumerary teeth.
  • Denture: full, partial, upper or lower, type, shape, restorative materials used.
  • Mesiodistal width of the teeth.
  • Any recognizable peculiarity of jaws, e.g., prognathism (prominence of the lower law).
  • Old injury or disease. Recently dislodged, loosened, chipped or broken teeth.
  • Special features, incisal edges, fractures, ridges, caries, etc.
  • Restoration and prostheses (surfaces, morphology, configuration and material).
  • Root canal therapy on X-ray examination.
  • Bone pattern on X-ray examination.
  • Oral pathology (tori, gingival hyperplasia).

Most workers believe that no two persons have identical dentition. Conservative dental work or fillings is most reliable in identification and includes fillings of various materials, root fillings, inlays and crown and bridge work. These can be compared with dental records and radio graphs if available in forensic dentistry. In some persons the lower teeth protrude beyond the upper incisors which is known as over-bite.

forensic dentistry

PINK TEETH

In a decomposed or skeletonised body, pink teeth may be noted especially near the gum-line, due to deposition of protoporphyrin, the cause of which is not known. Death is usually of an asphyxial nature and a damp environment is involved.

RADIOGRAPHY

X-Rays accurately reveal root shape, shape of pulpal canal, shape of fillings, abnormalities, bone trabeculation patterns, caries, tooth formation and fractures. They are widely used in antemortem and postmortem comparisons. In mass disasters, a list of the possible persons involved is necessary. The more recent the antemortem record, the more reliable the evidence. If antemortem records are not available, dental information must be obtained from relatives and friends.

Medicolegal Importance of forensic dentistry

(1) Dental identification is the most sophisticated method of comparative identification, except dactylogrphy, if there are some features to compare and some record of those features in a missing person. It is not of much help in developing countries as dentists often do not keep records. Teeth and jaws are usually protected from fire and mechanical trauma, and are highly resistant to postmortem destruction and decomposition.

Dental findings establish the identification of single individuals after accidental death or homicide, and differential identification of large numbers of individuals after mass disasters, such as explosions, house fires, aircraft accidents, earthquakes and shipwrecks. Identifications have been made from intact, mutilated, decomposed, skeletonised or even burnt material. Diseases such as caries, syphilis (Hutchinson’s teeth) help in identification in forensic dentistry.

(2) Teeth are useful in estimating the age of an individual.

(3) Sex and blood group can be determined from cells of pulp cavity.

(4) Loss of tooth due to assault is grievous hurt.

(5) Dentures, partial or complete, are useful in identification, especially if they have the patients name or code number included in them.

(6) Criminals can be identified through bite marks left either in human tissues or in food stuffs.

(7) Poisons (arsenic, mercury) can be detected.

(8) Color change occurs in sulphuric and nitric acid poisoning.

In antemortem tooth loss or extraction, the bony rim or the alveolus is sharp and feathered. A blood clot forms within the alveolar cavity and in one to two days there is early organization. In about a week, socket is filled with organized clot, which is replaced by fibrous tissue in 2 weeks.

In two to three weeks, soft tissues are healed and the socket is partially filled with new bone. Reparative bone resorption of the alveolar rim results in a smooth rounded rim of socket. In six months, the socket is filled with new bone, but the location of the root outline is visible. In one year, the whole socket is filled with a new bone and there is depression of the bone outline.

If the entire tooth was knocked out, irregular edges of remaining bone, splintering of buccal or lingual plates, areas of compressed bone, or fracture of roots or crowns of adjacent teeth are seen. It is difficult to dislodge a healthy tooth without fracturing or loosening neighboring teeth. These changes can be demonstrated by X-ray of the jaw adjacent to the dislodged teeth.

CHARTING OF TEETH in forensic dentistry

There are more than 150 different methods of identifying, numbering, charting of teeth. The most widely used systems are:

(1) Universal System: Teeth are numbered 1 to 16 from upper right to upper left, and 17 to 32 from lower left to lower right. This follows the plan advocated by the American and International Society of forensic dentistry.

(2) Palmer’s notation

(3) Haderup System: It is similar to Palmer’s notation except that it uses a plus sign(+) to designate upper teeth, and a minus sign (—) for the lower.

(4) FDI (Federation Dentaire Internationale) two-digit System: It bears a slight resemblance to Palmer’s system in that both utilise the same numbers, but the F.D.I. system substitutes a number for the quadrant side and that number is placed before the tooth number. Thus the lower right canine will be number 43 in this system.

(5) Modified FDI system

(6) Diagrammatic or anatomical chart in forensic dentistry: In this each tooth is represented by a pictorial symbol that gives the same number of teeth surfaces as those on the same teeth in the mouth. The incisors and canines are represented by four surfaces, and the premolars and molars by five (due to the occlusal surface). The positions of crowns, caries, fillings, or other abnormalities are marked on these diagrams. The diagram also includes deciduous teeth.

ANIMAL BITES

Rodents gnaw (bite persistently) away tissue over fairly limited areas. They produce shallow craters of the borders of the areas by nibbling and leave long grooves. The bites by dogs which attack suddenly are usually clear-cut, showing narrow squarish arch anteriorly, as the animal bites to hold on to the attacked person.

Teeth impressions are usually deep and small in area. Cat bites show small rounded arch with puncture marks made by canines, and are usually associated with scratch marks from claws. Rat bites are usually very small and round.

RACE in forensic dentistry

In Caucasians, small nodules on lingual surface of maxillarys (Carbelli’s cups) are common.Lateral incisors in upper jaw are smaller than the central, especially in females. In Mongoloids upper incisors are shovel-shaped, canine roots are long and pointed, enamel pearls are frequent, pulp cavity of molars is wide and deep and the roots are fused and bent; lack of upper molar is common. In Negroids teeth are large with more cusps in their molars with two lingual cusps on mandibular first premolars.

SEX

In the male, the upper central and upper lateral incisors are equal in size, but in the female, the size varies. The canines are usually smaller and more pointed in the female, compared to male, especially in the lower jaw. in the female, the mandibular first molar has four cusps.

V chromosome may be isolated in the tooth pulp cells up to three to five months post-extraction or postmortem. Quinacrine staining is useful for this purpose in forensic dentistry.

The teeth are markedly resistant to heat. If heated suddenly or severely, they may disintegrate and fracture. If a dead body is burnt, the oral cavity and teeth have a better chance of remaining intact, but in a living person the lips may be drawn back exposing the anterior teeth. Depending on the temperature, intensity and duration of the fire, the crowns of anterior teeth may be scorched, ashed or explode at the gum line.

OCCUPATION, HABITS AND SOCIAL POSITION in forensic dentistry

Cobblers, carpenters, seamstresses, electricians, dress-makers, etc. have central notches in the incisal edge of the front teeth, due to the holding of the thread, needle, nails, etc. Musicians have localised attrition of their teeth. Some of them have wide defects on the front of the teeth, while others have defects on the incisal edges.

In pipe smokers and cigarette smokers who use holders, there is a visible loss of material on the incisal edges of the teeth, mostly at the angle of the mouth. In heavy smokers, a black stain is deposited upon teeth. Loosening of certain teeth can be found in almost all those who habitually bite various objects or hold them in their teeth.

The labial enamel and later the exposed dentin are dissolved in workers exposed to corrosive acids. Excessive chewing of acid foods causes erosion of all surfaces of teeth. Copper causes a green, silver a black, and lead, aniline and bismuth a bluish color, particularly at the neck of the teeth or at the marginal part of the gum. Social position and sometimes the country of origin can be ascertained from the quality and type of restorations.

CASES of forensic dentistry

(1) Prinz (1915) reported the murder of a banker. A cigar- holder with a mouth piece of amber which had a tip worn down in a characteristic way was found near the body. The lesion was thought to have been caused by the teeth of the owner of the mouthpiece. The Judge saw this mouthpiece.

During the trial when the Judge was questioning a witness, he noticed a deformity in the teeth of that man which reminded him of the defect in the cigar-holder. The witness, a cousin of the deceased, and his heir was shown how well the mouthpiece fitted the deformity in his own teeth and he finally admitted to being a murderer.

(2) A train loaded with petrol, and a passenger train ran into each other in Norway in 1944. The first carriage of the passenger train was engulfed in burning petrol for 12 hours, due to which only burnt remains of bodies were left. The teeth and dental restorations were little affected in some cases.

(3) Ried (1884) reported the murder of a doctor and his mother. The bodies were found in the kitchen. A few dislocated teeth were found, two of which did not belong to those murdered, which were later proved to belong to the murderer, who had lost them during the fight with his victims.

(4) Paulick (1949) reported the murder of an old man by whose side was found an apple with characteristic bite marks. The marks showed three teeth close to each other, two of which were broad and the third small, irregular, probably due to a carious tooth.

The bite did not correspond to the teeth of the victim. A prostitute was arrested, and dental examination proved that the bite marks were produced by her teeth.

(5) Euler (1925) reported the investigation of multiple murders, in which a large number of extracted teeth were found. An insane person had collected only caries-free teeth from his victims. Out of the 351 teeth, Euler found 20 left lower canines.

Considering all the teeth in relation to the curve for caries development, he arrived at the number of 29 individuals. Later, a note book was found which contained the names and ages of all the murdered numbering from one to 31.

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