Dr S K Padmakumar has been, for long, the Kerala Police’s go-to forensic odontologist for piecing together dental evidence and bite mark analysis, which can play a crucial role in cracking complex cases. In this wideranging interview, Dr Padmakumar, who recently retired as head of the Oral Pathology and Microbiology Department at Government Dental College in Thiruvananthapuram, reflects on the cases that shaped his career. Some harrowing, some quietly heroic. He also throws light on oral cancer, common dental ailments, and the basics of dental hygiene
Forensic odontology has been a niche subject. Shall we start with a flashback?
Dr Jacob Zacharia has been regarded as the father of forensic odontology in Kerala. For decades, our work was limited. We did little more than confirm whether a sample was a bite mark or not. It changed in 2011, when I came across Dr Ashith B Acharya’s published work and realised that bite marks could be analysed in far greater depth… that suspects and victims could be identified from them. We then trained under Dr Ashith, a renowned forensic odontologist.
What was the first case that you took up?
It was a rape attempt on a 55-year-old woman. She had been bitten on her ear. The suspect was 18 or 19 years old. We took dental impressions, prepared models, made the necessary measurements and compared them against the mark using software. The analysis confirmed the suspect.
Is it possible to determine the gender or age of the person by analysing a bite mark?
That would be difficult from the bite mark alone. What a bite mark gives us is confirmation of identity. Teeth are arranged in an arch, and no two people’s arches are identical. Individual teeth carry their own characteristics — their position, degree of wear, rotation, and sharp or irregular edges. We examine whether these features are reproduced in the mark, take precise measurements, and superimpose the suspect’s dental model onto the mark using software.
Could you please elaborate on the process?
We take impressions from all suspects and cast plaster-of-Paris models, which are then cross-checked against the bite mark, either directly or indirectly. In the direct method, we place the model against the wound and check. The indirect method comes into play when there is a delay. By then, the wound would have begun to heal. But if individual characteristics are still discernible, software allows us to scale the images to life size and verify them through superimposition. This way, even from a healing wound, we can often identify the actual perpetrator from among the suspects.
How is the model prepared?
We use a reversible impression compound — the same material used in implant dentistry. This gives an exact replica. From this, we take measurements and cast working models in plaster of Paris or dental stone. The model and photographs of the bite mark are then scanned. Superimposition is carried out in Photoshop.
How is DNA extracted from teeth?
Forensic odontology extends well beyond bite mark analysis. One of its most vital applications is in mass disasters — tsunamis, plane crashes and fires that leave bodies charred beyond visual recognition. Teeth are the hardest substance in the human body, more durable than bone. Inside each tooth is a pulp of soft tissue, and that pulp contains DNA.
In the recent Ahmedabad plane crash, the bodies were charred. Can teeth recovered from such a scene help determine age or gender?
Yes, a team of experts worked on that. Both age and gender can be determined. When a tooth is ground down and examined under a microscope, its internal layers become visible. Enamel, dentin and cementum are laid down incrementally over the years, much like the annual rings of a tree. The individual’s age can be estimated by reading those layers. Gender determination from teeth alone is not straightforward. But when teeth are recovered along with the skull, its morphology is far more informative. Male and female skulls have distinct characteristics.
You said analysis becomes harder as the bite mark heals. How do you manage in such cases?
In our final reports, we use four categories: positive, when there is a complete match; probable, for a match of about 75%; possible, for about 50%; and not matching, when there is no correspondence. If the victim is brought to us promptly and all the features align, we can issue a positive report. When there is a delay and the wound has partially healed, we work with whatever individual characteristics remain and categorise our findings accordingly.
Do your reports get challenged in court?
Yes. Our analysis is submitted as supplementary evidence alongside the findings of the forensic medicine department. In rape cases, there is typically a range of evidence, and ours is one thread among several. In rape-attempt cases, however, it can become the central evidence. We are called to testify as to whether a particular bite mark was made by the accused.
Could you describe such a case?
One that stands out was a Pocso case. The child had managed to escape from the accused and, in the struggle, had bitten him. Our analysis established that he was the culprit. The defence counsel argued that the bite mark had been made by the accused’s wife. The court directed us to conduct a fresh analysis after taking an impression of her teeth. It did not match. The evidence that the mark had been made by the child held firm. The court awarded life imprisonment to the accused.
In another case, the victim had a bite mark on her body. The dental impression of one of the suspects matched the mark. The defence argued that the mark may have been caused by the victim’s fall from the train. But the bite-mark evidence was clear, and the court eventually punished the accused.
Any experience in disproving a false allegation?
Once, a 16-year-old girl came to the department with her mother. She claimed she had been abused by four men who abducted her and showed bite marks as evidence of the assault. I took the dental impressions of the four suspects, but none matched the bite mark. Suspecting something, I took her impression as well. It matched — the girl had made the bite mark herself. The accused were let off.
It’s said that forensic dentistry played a vital role in the Nirbhaya case…
Yes. The distinctive characteristics of bite marks proved significant. It aided the forensic medicine team. Usually, our findings are treated as corroborative evidence in courts.
Are there cases done using photographs of bite marks?
For bite-mark cases, we specifically tell the police to take photographs with a scale. If they provide the photo with a scale, we can calculate the variation and use software to bring it to exact life size. For this, there is a scale called the ABFO Scale from the American Board of Forensic Odontology.
Do teeth vary across geographies?
There are ethnic and racial variations in teeth — among Caucasians, Europeans, Mongolians, South Africans and Asians. This is useful in victim identification during mass disasters such as plane crashes.
Do eating habits bring about changes in teeth?
More than eating habits, structural variations in the body are reflected in the teeth as well. We can draw inferences about body structure from teeth, though it is not a fully reliable assumption.
What is the role of lifestyle in teeth? Does this aspect play a role in investigations?
Staining from smoking and betel leaf chewing is easily identifiable. It shows up on the mucosa as well as the teeth. Tailors who habitually hold thread between their teeth develop a distinct notch. Bagpipers who hold the pipe for long periods show characteristic wear. People who grind their teeth at night or chew excessively can also be identified through wear-and-tear patterns. Occupation and habits can thus play a significant role in identifying a person.
Are the teeth of identical twins similar?
Because of chromosomal similarities, they can be. The arch form of the teeth and the number of teeth will be the same. A pair of twins brought up in different environments may, however, develop different tooth variations. Environmental factors such as food habits, tooth decay and trauma can make a difference.
Can one actually improve their teeth’s strength?
Enamel cannot be repaired. Nutrition is important during the formation of teeth. Calcium, phosphorus and other minerals are vital. Blood Rh variations and some drugs may also affect a child’s teeth.
Can regular consumption of medical drugs or lifestyle diseases affect tooth health?
The last set of teeth a person develops are the wisdom teeth. Their formation is usually completed between the ages of 18 and 21. After that, apart from wear and tear, nutritional insufficiency is unlikely to have much effect.
Some social media ‘experts’ claim drinking water before brushing teeth in the morning is beneficial because there are many healthy bacteria in the mouth…
That is not completely true. During sleep, saliva dries up, causing some proteins and carbohydrates to remain trapped in the teeth. Bacteria naturally grow there. Our body already has a set of innate microbes. The microbial flora in the mouth is different. Some of them can even be pathogenic. Ingesting them could sometimes cause disease, especially if immunity is weak.
How vital is toothpaste? Manufacturers often make tall claims…
Proper brushing is more important than toothpaste. Pastes with fluoride can help dental health to some extent, but they are not mandatory.
Earlier, people used umikkari (charcoal dust) mixed with salt to clean their teeth...
Our teeth undergo wear and tear through food, mostly at the points where teeth come into contact with each other. Firm brushing or the use of abrasive substances can add to this. In paste form, the damage is usually minimal. Irrespective of what you use, the method of brushing is important. Vertical movement of the brush is preferred over horizontal brushing. Fine charcoal, tooth powder or paste can all be used.
There are different opinions about the use of tongue scrapers…
It is recommended not to clean the tongue vigorously. Taste buds are located as tiny projections on the surface of the tongue, and vigorous cleaning may affect them. Even though saliva can replenish them, it is ideal to use a brush gently for cleaning the tongue.
We generally eat more processed food these days. Can that affect jaw development?
Human jaw size has gradually reduced. Unlike our ancestors, we no longer need to use our jaws roughly. There is also a tendency towards a reduced number of teeth, some of which may remain inside the bone. Perhaps they may disappear altogether in the distant future!
What are the factors that trigger the risk of oral cancers?
Smoking and tobacco chewing are injurious to overall health, but it has an amplified impact on the oral mucus. Alcoholism increases toxicity in the oral cavity. This can also lead to cancer. The oral cavity has a comparatively rich blood supply and is also prone to inflammation from gum disease, tooth disease and other infections.
Is oral cancer on the rise?
The pattern has changed over time. Oral cancers, once mostly seen among older people, are now increasingly found in younger age groups. Lifestyle changes are one reason. Sachet products are more commonly used outside Kerala, where many people begin using them at a very young age.
Is it true that chewing gum helps oral health, as shown in ads?
Saliva acts as the natural cleansing mechanism of the oral cavity. Stimulating saliva strengthens this cleansing action and also helps digestion. Chewing gum increases saliva production, and saliva has antibacterial properties. So, in that sense, it can be beneficial. However, excessive chewing over long periods can lead to wear and tear of the teeth.
How would you rate the oral health of Keralites in general?
Compared with Western populations, oral health here is generally better. In many Western countries, snacking habits are more common and oral hygiene practices are poorer. However, such habits are increasingly being seen here too. It is very important to rinse the mouth even after having tea or lemon juice.
Earlier, root canals were mostly associated with middle-aged people, Nowadays, even youngsters are seen undergoing the treatment…
Earlier, people believed that since we have 32 teeth, losing one would not matter much. Today’s generation understands that losing even one tooth can affect neighbouring teeth and overall oral health. They are more willing to restore damaged teeth through fillings and root canal treatment.
Is teeth whitening a healthy procedure?
Teeth whitening is generally fine, especially as more people now give importance to appearance. One has to maintain it well, that’s all.
We have heard that tooth infection can lead to a brain infection. Is that correct?
It is possible. Most veins have valves, but some veins in this area do not. These valveless veins communicate directly with the fluid surrounding the brain. An infection can travel through these veins and lead to meningitis. This is more common in immunocompromised people. Hence, oral health is critical for patients undergoing chemotherapy, radiation, dialysis, or cardiac surgery. We must eliminate potential sources of infection in the mouth before treatment.
As we come to a close, let’s return to your specialisation. Are there any cases that still haunt you?
We mostly deal with deceased individuals. I only examine bodies when bite marks or other dental evidence are present. Not all my students were willing to participate in post-mortems. Rigor mortis — the stiffening of the body after death — makes it difficult to open the mouth. If a suspect has bitten someone and then dies, we need to take impressions of their teeth for comparison. To do this, we sometimes have to make incisions. All this is done alongside the general autopsy.
Are investigators aware of forensic odontology procedures?
Initially, they weren’t. They would bring photographs of bite marks without a scale. Since I started working with them, they have begun to include a scale. If there is no scale, we report the findings as possible or probable and leave the final decision to the judge.
Have suspects ever tried to tamper with evidence?
One suspect claimed about undergoing a dental procedure to hide evidence, but comparing it with previous records helped uncover the truth. We also had a case involving a foreigner, which is still ongoing.
You have just retired from service. What next?
I will still be called to court for cases I have already reported on. I will have to travel to various courts to testify. I have trained my students and junior staff. One junior recently completed a case successfully. It requires a willingness to work with deceased individuals, which can be challenging for some.