Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2017  |  Volume : 35  |  Issue : 3  |  Page : 249--253

A comparative study to associate the presence of neonatal line in deciduous teeth of infants with the occurrence of live birth

Shruti Srinivasan1, Prashanth Sadashiva Murthy1, Seema Deshmukh1, NM Shamsundar2,  
1 Department of Pedodontics and Preventive Dentistry, JSS Dental College and Hospital, JSS University, Mysore, Karnataka, India
2 Department of Anatomy, JSS Medical College, JSS University, Mysore, Karnataka, India

Correspondence Address:
Prashanth Sadashiva Murthy
Department of Pedodontics and Preventive Dentistry, JSS Dental College and Hospital, JSS University, Mysore - 570 015, Karnataka


Context: The prominent striae of retzius corresponding to the occurrence of live birth is known as the neonatal line (NNL). The very presence of this line indicates the exposure of the infant to the stressful event of birth. Aims: The study was aimed at locating the NNL in the developing primary teeth of the neonate and associating the presence of NNL to the occurrence of live birth. Materials and Methods: The donated bodies of the neonates were taken, and a surgical incision was made along the crest of the alveolar ridge in the maxillary anterior region, enabling the careful removal of the tooth germs from within the jaw segment. The maxillary central incisor tooth germs were embedded in acrylic and viewed under the stereomicroscope, polarized microscope, and scanning electron microscope (SEM). Statistical Analysis: This being a pilot observational study, no statistical analysis methods were employed. Results: The NNL was best visualized under polarized microscopy and was clearly appreciated in the control samples and faintly seen in the 10-day-old neonate. No evidence of the line was present in the tooth germ of the stillborn child. Conclusion: The very presence of the NNL indicates that the infant was alive during the stressful process of birth. This can be used as substantial evidence in infanticide cases brought before the law.

How to cite this article:
Srinivasan S, Murthy PS, Deshmukh S, Shamsundar N M. A comparative study to associate the presence of neonatal line in deciduous teeth of infants with the occurrence of live birth.J Indian Soc Pedod Prev Dent 2017;35:249-253

How to cite this URL:
Srinivasan S, Murthy PS, Deshmukh S, Shamsundar N M. A comparative study to associate the presence of neonatal line in deciduous teeth of infants with the occurrence of live birth. J Indian Soc Pedod Prev Dent [serial online] 2017 [cited 2020 Aug 13 ];35:249-253
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Female infanticide is one of the evils that plagues our society to this day. It has led to an imbalance in the male to female ratio in our country. Most of these cases are never brought to court, and even those that are brought to light remain unproven because of the state in which the body is usually discovered, mostly putrified. The soft tissue remains of the lungs and heart can be used to predict the separate existence of the infant, but in cases where the soft tissue is lost, we must determine the time of death of the infant using hard tissues such as bones and teeth. Although skeletal parameters are a valuable asset in determining the age of the infant, no particularly relevant method provides conclusive evidence of the separate existence of the infant and helps in distinguishing live birth from a stillborn child.[1] Thus, we turn our attention to the dental hard tissues to provide us with some answers regarding the birth of the child.

Mature human enamel is the hardest and the most mineralized component of a tooth with a unique microstructure. Enamel deposition by the ameloblasts is not a continuous process; rather, it follows rhythmic periods of formation and rest. As the ameloblasts deposit enamel in an incremental pattern, an artifact is created which is called as the striae of retzius. The ameloblasts being highly sensitive when exposed to noxious stimuli record a change in the enamel matrix formation by creating accentuated lines of retzius. One of these lines is exaggerated and more prominent than others. This line of retzius corresponding with the event of birth is called as the neonatal line (NNL). The NNL is the prominent incremental line in the tooth enamel, demarcating between the enamel formation occurring before birth which is more regular and highly calcified and enamel formation occurring after birth which is less regular and less homogeneous in calcification.[2] This NNL has its application in forensic dentistry. Theoretically, the presence of the NNL in primary teeth indicates the independent existence of the infant recording the event of live birth. Furthermore, as per the review of literature, the thickness of the NNL would provide the additional information on the kind of delivery.[3] Hence, the microstructure of enamel describing the NNL can be considered as a diagnostic possibility for differentiating between live birth and stillbirth and can be an important tool for the forensic experts.

The present study was aimed at:

Locating the NNL in the developing primary teeth of the neonateAssociating the presence of NNL to the occurrence of live birth.

 Materials and Methods

The study comprised of (a) test group which included tooth sample retrieved from jaws of a neonate who survived for a period of 10 days but unfortunately passed away due to cardiovascular issues and the tooth samples collected from the jaws of a full-term stillborn fetus. Both the bodies were donated to the Body Donation Center, Department of Anatomy, JSS Medical College, JSS University.

(b) Control group consisted of primary teeth extracted due to pathological causes from a 5-year-old child in the Department of Pedodontics and Preventive Dentistry, JSS Dental College and Hospital, JSS University, Mysore. The control group was included as this would act as a reference for comparison of the samples obtained from the test group.

A mock surgery was performed before the retrieval of samples from the individuals on a replica of the upper alveolar ridge made of wax and embedded with upper anterior extracted teeth.

The armamentarium was prepared for retrieval of samples from the individuals. The surgery was done on two donated bodies: a stillborn [Figure 1]a and a neonate who had died 10 days after birth [Figure 1]b. A no. 15 blade was used to make the initial horizontal incision along the upper alveolar ridge of the neonate. Moreover, the flap was raised using a periosteal elevator to expose the underlying bone. Since the bone was not completely ossified, an incision with the BP blade was enough to expose the developing tooth underneath.{Figure 1}

Once the tooth was exposed, it was gently scooped out using the blunt end of the periosteal elevator. The tooth sample so obtained was stored in a sterile container containing formalin. Since the samples obtained were very brittle, the following steps of processing were carried out before the examination. The developing upper central incisor teeth from both the neonates were embedded in clear acrylic using L-formers. Once the acrylic was set, thin sections of the sample were prepared (approximately 0.5 mm) in the mesiodistal as well as the buccolingual plane using a double-sided carborundum disc with constant irrigation with normal saline followed by fine sectioning using abrasive sheets and Arkansas stone. The same processing was done for all the four samples. These sectioned samples were once again stored in distilled water. No such embedding technique was followed for the extracted primary teeth as they were sturdy enough to withstand the process of sectioning.


The thin sections were viewed directly under stereomicroscope and polarized microscope.

Scanning electron microscopy (SEM): for the sample to be viewed under SEM, it was first washed for 30 s in 1% nitric acid followed by thorough washing using copious amounts of distilled water. The samples were dried before viewing under SEM.


The NNL was most clearly visualized in the control samples, where the line was seen clearly under stereomicroscopy at ×20 magnification [Figure 2]c. The line was seen running along the dentinoenamel junction (DEJ), closer to the DEJ near the cervical aspect of the crown but closer to the enamel surface near the coronal third of the crown. The NNL was best visualized as a birefringent band under polarized microscopy in the sections prepared along the buccolingual plane and was clearly seen to run parallel to the external tooth surface, gradually fading away at the cervical part of the crown and the root [Figure 3]c. The line was visible distinctly under SEM in ×500 magnification [Figure 4] as a region of alteration in enamel rod pattern with the width of the line estimated as 2.620 μ.{Figure 2}{Figure 3}{Figure 4}

A faint line was seen in the samples obtained from the 10-day-old neonate and was seen close to the enamel surface in both stereomicroscopy as well as polarized microscopy [Figure 2]a and [Figure 3]a. SEM images of the 10-day-old neonate samples did not reveal a distinct NNL.

No NNL was seen in the stillborn child in any of the three microscopic techniques [Figure 2]b and [Figure 3]b.


Age estimation using teeth was first published by Edwin Saunders in 1837, who confirmed that dental tissue is more reliable in age estimation as compared to the other anthropometric measurements.[4] The two main limitations of the skeletal approach for age estimation are: first, the accuracy of age estimations and second, the extent to which purification and burial affect preservation and identification of the incompletely mineralized infant skeletons.[5]

Tooth development occurs in a much more protected environment than that of skeletal tissues, and subsequently provide a much more reliable source of information regarding the age of the individual.[6],[7],[8] Enamel deposition and calcification the primary tooth germs is not complete at the time of birth, and NNL marks the zone of hypomineralization that demarcates the prenatal and postnatal enamel being laid down.

Dental hard tissues have major applications in forensic odontology.[9] Application of the knowledge of calcification of dental tissues in forensic odontology is uniformly applicable from infancy through adolescence. The NNL is present in primary teeth and demarcates the process of birth confirming the independent existence of the neonate. Knowledge of incremental pattern of enamel deposition particularly the demarcation of enamel deposition occurring before and after birth can be of paramount importance in cases of female infanticide.

When the sensitive ameloblasts are subjected to a stress or noxious episode (either internal or external), as corresponding to the birth process, there appears a temporary change in the enamel matrix deposition recorded as a structural disturbance. Another hypothesis states that this zone of hypomineralization can be attributed to the fall in the rerun calcium levels in the first 2–3 days after birth.[10] This optical phenomenon is due alterations in height and degree of mineralization of the enamel prisms. However, these changes may not be evident if the infant has not gone through the process of birth. Since all the primary teeth begin calcifying the 20th week in utero, the NNL can be identified on any of the primary tooth germs and usually on the first permanent molar provided that the infant survives for at least 7–10 days – the time necessary for visualization of the NNL as a band between pre- and post-natal enamel.[11],[12]

In cases where the child is stillborn, there occurs no drastic environmental and functional change coinciding with birth, so it can be safely assumed that there would be no NNL as is also proved by our current study. Thus, the mere presence of NNL indicates live birth.

To the best of our knowledge, there is only one other similar study correlating the presence or absence of NNL to female infanticide. In the study conducted by Janardhanan et al. in 2011, samples were collected from the developing permanent molar of an 18-month-old boy whose tooth was extracted due to the presence of an associated dentigerous cyst. Our test samples were taken from two different infants, one who had died 10 days after birth due to cardiac complications and another, a stillborn. Two fully developed primary central incisors were used as controls.

In our study, we noticed no evidence of NNL in the teeth obtained from the stillborn child. On the other hand, a clear NNL could be visualized in the extracted teeth when viewed under the stereomicroscope (at × 20 magnification), best visualized under the polarized microscope, and the width of the line was determined as 2.620 μ using the SEM.

Under the polarized microscope, the line was visualized as a birefringent band in the sections prepared along the buccolingual plane, running parallel to the external tooth surface, and gradually fading away into the cervical aspect of the tooth.

The major setback during the use of SEM was the need to additionally process the samples before viewing and also the fact that to visualize the line along its entire course, we had to lower the magnification each time and increase it to locate the line.

The morphology of the NNL may be altered by systemic conditions too. For example, infants born to diabetic mothers were found to be prone to hypocalcemia, showing thicker and less mineralized NNL s as compared to those from healthy mothers.[13]


The fact that female infanticide is not only prevalent in our country but has also lead to a gender-based skewing of the population is indeed horrifying. An awareness must be spread among the members of the dental fraternity about the potential role that we may play in bringing justice to the infants who are sacrificed in this brutal manner. Analysis of the NNL can prove as substantial evidence in cases of female infanticide and must be added to the protocol for postmortem analysis of the bodies of dead infants under suspicion.


One of the major limitations of this study was the fact that not many bodies of infants who died in the perinatal period could be recovered for analysis.

Certain shortcomings were also encountered during standardizing the protocol for sample processing, such as the acrylic used for embedding the samples reacted and faintly disrupted the enamel margin in places, the results were not hampered by them.

Further research would focus on a more suitable material to embed the samples, increasing the sample size, and also study the alternations in NNL morphology and its significance.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


1Smith P, Avishai G. The use of dental criteria for estimating postnatal survival in skeletal remains of infants. J Archaeol Sci 2005;32:83-9.
2Eli I, Sarnat H, Talmi E. Effect of the birth process on the neonatal line in primary tooth enamel. Pediatr Dent 1989;11:220-3.
3Janardhanan M, Umadethan B, Biniraj K, Kumar RV, Rakesh S. Neonatal line as a linear evidence of live birth: Estimation of postnatal survival of a new born from primary tooth germs. J Forensic Dent Sci 2011;3:8-13.
4Shamim T, Varghese V, Shameena PM, Sudha S. Age estimation: A dental approach. J Punjab Acad Forensic Med Toxicol 2006;6:14-6.
5Guy H, Masset C, Baud CA. Infant taphonomy. Int J Osteoarchaeology 1997;7:221-9.
6Davidson LE, Rodd HD. Interrelationship between dental age and chronological age in Somali children. Community Dent Health 2001;18:27-30.
7Deutsch D, Tam O, Stack MV. Postnatal changes in size, morphology and weight of developing postnatal deciduous anterior teeth. Growth 1985;49:207-17.
8Liversidge HM, Dean MC, Molleson TI. Increasing human tooth length between birth and 5.4 years. Am J Phys Anthropol 1993;90:307-13.
9Nayak SD, George R, Shenoy A, Shivapathasundaram B. Age estimation in forensic dentistry – A review. Int J Sci Res 2014;3:333-8.
10Seow WK. Oral complications of premature birth. Aust Dent J 1986;31:23-9.
11Zanolli C, Bondioli L, Manni F, Rossi P, Macchiarelli R. Gestation length, mode of delivery, and neonatal line-thickness variation. Hum Biol 2011;83:695-713.
12Sabel N, Johansson C, Kühnisch J, Robertson A, Steiniger F, Norén JG, et al. Neonatal lines in the enamel of primary teeth – A morphological and scanning electron microscopic investigation. Arch Oral Biol 2008;53:954-63.
13Norén JG. Microscopic study of enamel defects in deciduous teeth of infants of diabetic mothers. Acta Odontol Scand 1984;42:153-6.