Effect of Concentrated and Dilute Hydrochloric Acid on Tooth Morphology: A Forensic Study

Introduction: Teeth are the most durable structure present in our human body because of the presence of enamel which persist and resist destruction more than any other bony structure. Hard nature with high amount of resistance of tissues present in the tooth prevents any destruction which increases the lifespan of the tooth. Aim: The main aim of this study is to observe the changes in tooth morphology when immersed in dilute and concentrated hydrochloric acid. Original Research Article Britina et al.; JPRI, 34(4B): 37-46, 2022; Article no.JPRI.81363 38 Materials and Methods: Non-caries teeth extracted due to periodontal reasons were used from the department of oral and maxillofacial surgery. The tooth added to alternate dilute and concentrated hydrochloric acid was observed till 6th day and the changes were noted along with the photographs as observations. Results: The tooth left in concentrated HCl showed rapid dissolution and was completely dissolved within 24 hours. Tooth left in dilute HCl dissolved gradually and showed less dissolution when compared to concentrated HCl. Conclusion: Most durable teeth also undergo erosion and dissolution when placed in dilute HCl and concentrated HCl. Teeth act as a major clue in the field of forensic odontology.


INTRODUCTION
Teeth are the most sustainable part of a body when compared to other skeletal tissue, teeth persist any kind of destruction that happens externally or internally. Also apart from chewing,biting, tearing teeth also plays an important role in forensic odontology [1]. Age estimation can also be performed from the tooth in an acidic environment [2]. Present studies show that now DNA can be extracted from teeth even after decades of death. It is possible to employ these identification techniques until there has been complete destruction of the teeth.Even though they can persist many kinds of destruction, teeth do undergo corrosion or complete dissolution when exposed to certain agents.
When a tooth is immersed in an acid the tooth undergoes corrosion or complete dissolution within a certain time period [3]. The corrosion or the complete dissolution also depends on the type of acid along with the time period.It acts as a major clue for forensic scientists because of its indestructible nature. Many criminals use hydrochloric acid in order to destroy the body in the crime scene by using acids to dissolve the body [4,5]. So the changes in tooth morphology can help us to identify the nature of acid along with the time elapsed in the crime scene.
Teeth are taken as essential organs in both living and nonliving populations for anthropological, genetic, odontologic and forensic cases [6]. This is due to the hard nature of tooth with high amount of resistance of tissues of teeth which prevents degradation, which enable the teeth to survive for longer periods than other skeletal tissue, making them more irresistible to trauma, decomposition, water immersion, chemicals and fire, serving as an invaluable evidential source. To match these natural needs, the external materials kept in the mouth by the dental practitioner like fillings, dentures, crowns, bridges and implants must be equally resistant to deep mechanical demands which decides survivability [4]. Dental erosion is consequent loss of tooth structures in the tooth which are results of exposure to acids, with absence of bacteria also characterised clinically as corrosive-abrasive wear [7]. Our team has extensive knowledge and research experience that has translate into high quality publications [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The main aim of this study is to observe the changes in tooth morphology when immersed in dilute and concentrated hydrochloric acid.

MATERIALS AND METHODS
Non-caries teeth (n = 6) extracted due to periodontal reasons were used from oral and maxillofacial surgery departments. These were cleaned with distilled water and were photographed prior to the experiment.
These teeth were added to alternate conical flasks containing dilute HCl and concentrated HCl. After every 5hours, 24 hrs, 36 hrs, 48 hrs, 72 hrs, 96 hrs, 120 hrs, 144 hrs tooth immersed in dilute and hydrochloric acid was observed along with which tooth was photographed and was measured using vernier callipers with proper precautions.

Statistical Analysis
The data were statistically analysed using the statistical package for social sciences version 23 (SPSS). From this bar graphs were used to interpret the results.

RESULTS
The tooth left in concentrated HCl showed rapid dissolution and was completely dissolved within 24 hours.Tooth left in dilute HCl dissolved gradually and showed less dissolution as compared to concentrated HCl.

DISCUSSION
Identification of teeth with the help of unique characters in a population has been around for a long time like the Romans used to do. Teeth undergo erosion when the pH of the oral cavity is less than 3.5. Consumption of beverages having acid buffers cannot be produced by the mouth immediately and leads to acid erosion of the tooth [28]. Erosion of enamel is of intrinsic origin [29,30]. Features which are morphological assists any investigator or forensic scientist in understanding the tooth whether it is from any human or originated from animals, single rooted or multi-rooted, deciduous or permanent.
HCl solution showed that the tooth was dissolving within 3 to 5 hours itself and completely dissolved within 8 hours [1,31] showed and reported that few deep cracks developed in the tooth in around 30 minutes, and the tooth dissolution started in 1 hour, the tooth was completely dissolved in 8 hours. Jadhav et al. [3] 2 used diluted acid for their study and showed that the tooth became translucent and then transparent in stages. Further breakdown of apical 3rd and adjacent to complete dissolution took place in 2 and 8 hours respectively [1].
Acids are capable of etching enamel at either high or low concentrations. Because Enamel is composed of 96% inorganic material which undergoes acid destruction. In other studies different patterns of varying depth were produced based on the type of concentration of acid taken as well as the etching time [32]. Use of forensic sciences comprises person or victim identification. Destroying the evidence involving dead bodies by immersing it into concentrated inorganic acids is one of methods used by criminals [4,32]. Some limitations of this study were less sample size, limited time period and usage of the limited concentrations of hydrochloric acid. This study is really helpful to the forensic odontology and other forensic departments as by observing the morphological changes in the teeth, it is possible to conclude which acid has been used by the criminals to destroy the body and the time elapsed after body immersion in acid to some extent.

CONCLUSION
This study shows that most durable teeth also undergo erosion and dissolution when placed in dilute HCl and concentrated HCl. In some cases the acid that may be used by criminals for destruction of a human body and to find out the approximate time taken for total destruction of a body when immersed in an acid. This study on morphological changes helps in forensic sciences. Further studies with different types of acids on tissues and bones may be carried out to analyse its effect on the tissues, which may further be helpful in indepth forensic sciences.

CONSENT
As per international standard or university standard, respondents' written consent has been collected and preserved by the author(s).

ETHICAL APPROVAL
It is not applicable.