Analysis of dental injuries with clinical implications: A forensic case report

Introduction

According to Chinese criminal law, the severity of injury is one of the most important factors in conviction and sentences in violent crimes, particularly in domestic-violence cases. In some cases of unconfirmed violent attacks, the police may commission a forensic examination in order to make an assessment of the cause of the injury and the manner in which it was inflicted. It is a frequent challenge in forensic medicine to determine whether an injury was accidental, self-inflicted or a crime. ¹ To ensure fair and equitable administration of justice, it is critical that the details of the case are clear. In the practice of clinical forensic medicine, proper examinations are helpful for analysing the manner of injury, especially in complex cases.

Multi-slice spiral computed tomography (MSCT) is widely used in clinical medicine, as well as in clinical forensic medicine. MSCT is highly sensitive in detecting fractures, and possesses three-dimensional imaging reconstruction technologies, such as maximum intensity projection and volume rendering, which transcend the limitations of axial imaging. It not only improves the sensitivity of damage detection, but also provides a critical view for judging the manner of injury. Here, we report a case of a woman who suffered traumatic dental injuries in which the manner of the injury was determined using MSCT and imaging reconstruction technology.

Case report

A 58-year-old woman was injured when fighting with her son-in-law over domestic matters at home on 15 July 2012. She lost four incisors in the incident, and was sent with the teeth to the local county hospital designated by the police for injury assessment. Clinical medical records documented: ‘42, 41, 31, 32 completely dislocated with a small amount of bleeding in the gingiva, gingival laceration and pain of 33’. A diagnosis of complete dislocation of the lower incisors and concussion of the lower left cuspid was determined. After 10 days’ treatment, she attended a hospital affiliated with a medical college. No fracture was found in X-rays of her maxilla and mandible. As the dislocated teeth were not conserved properly, she eventually underwent alveolar bone repair surgery instead of tooth replantation. However, the clinician found no evidence of hard- or soft-tissue injury on the alleged assailant.

During the police investigation, neither side could reach a consensus. The woman said that her face was beaten by the man, resulting in the loss of her teeth, while the man argued that the dental injury to his mother-in-law was self-inflicted when she bit his fingers. There were no witnesses to the incident. To clarify the cause of the woman’s injury, and to deal with this case fairly, the police assigned us to make a judicial judgment based on our forensic expertise.

Forensic medical investigations

Examination of clinical and documentary data

Dental X-ray imaging (Figure 1) performed on 15 July 2012 showed that the lower incisors were avulsed without obvious fracture of the alveolar bone. Dental X-rays and CT imaging of the head on 25 July 2012 showed that both the maxillary and ethmoidal sinuses were normal with no fracture of the skull.

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Figure 1.

The lower central and lateral incisors are missing, with normal alveolar bone, and clear and complete bone walls. The alveolar depth is normal, with no apical lesions.

Forensic examination

On 27 August 2012, the forensic practitioners investigated the case. The following results were presented.

On physical examination, the woman’s lower central and lateral incisors were found to be completely dislocated with normal gingiva. There was no pain in the temporomandibular joint, and no obvious limitation of mouth-opening. The upper central and lateral incisors remained normal.

Forensic radiologists examined the woman using a 40-slice MSCT system (Definition AS; Siemens Medical Solutions, Munich, Germany) on 6 August 2012. Raw data were acquired using the following settings: voltage, 120 kV; current, 240 mA; and slice thickness, 0.75 mm. Image review and three-dimensional reconstructions were carried out on a MSCT workstation (Figure 2). The MSCT imaging revealed loss of the lower central and lateral incisors, accompanied by fracture of the mandibular alveolar process and a loss of a small piece of medial alveolar bone. The residual alveolar bone was of normal depth, and the root tip showed no lesions.

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Figure 2.

The lower central and lateral incisors are missing, accompanied by fracture of the local alveolar process and loss of alveolar bone.

Discussion

Violent crime, such as domestic violence and inter-relationship violence, is listed as the second most common cause of injury after accidents. ² Research has shown that aggression in domestic violence often occurs in the form of blunt trauma and slapping, ³ and the face is the area most predisposed to injury. Among all facial injuries, dental traumas are common, especially to the incisors, because of their anatomical location. According to the statistics, more than 60 cases of tooth injury were identified in 6000 cases of living injury identification every year in our institution.

From the standpoint of therapy, anatomy and prognosis, five different types of traumatic dental injuries are recognised: concussion, subluxation, extrusive luxation, lateral luxation and intrusive luxation. The classification includes injuries to the hard dental tissues and the pulp, the periodontal tissues, the supporting bone and the gingiva or oral mucosa (Figure 3). ⁴ The type of lesion depends on the force and direction of the impact. ⁵ Intrusive luxation occurs when the force of the impact causes an axial displacement of the tooth towards the alveolar bone. The damaged tooth is usually displaced through the labial bone plate, or can impinge upon the succedaneous tooth bud. Radiographically, the apical tip can be visualised and appears shorter than the contralateral tooth, or cannot be visualised. Extrusive luxation occurs when an impact in a coronal direction causes axial displacement. The injured tooth appears elongated and is excessively loose. This injury could increase the periodontal ligament space apically in the radiographic findings. The above two kinds of damage are the result of forces from different directions. Therefore, forensic practitioners should collect anamnestic data and perform objective clinical examinations, carry out further instrumental diagnostic examinations and analyse the manner of the injury, the severity of the traumatic events and the extent of the injury.

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Figure 3.

Sagittal anatomy cartoon of incisor. The alveolar bone and ridge are identified.

Fracture or loss of the maxillary or mandibular alveolar process is one type of injury to the supporting bone. These are closed fractures or comminutions (crushing or compression injuries) that involve the socket walls in the case of alveolar process fractures. ⁶ The fracture or loss is generally seen in conjunction with tooth luxation, and usually occurs when an external force impacts directly on the face, especially in the case of forceful blunt trauma and slapping. There is often gingival laceration in a corresponding position and lateral alveolar bone fracture when damage occurs. ⁷ Radiographic findings can show total displacement of the teeth and obvious fracture lines.

However, the health of the teeth can affect the outcome of the injury. Internationally recognised risk factors, such as diabetes mellitus and cigarette smoking, could result in periodontal disease^8,9 which would weaken the defence capacities of the teeth, rendering them more susceptible to injury. For people suffering from periodontal disease, traumatic dental injuries can be caused by slight violence. Therefore, forensic practitioners should also consider the victim’s general health when analysing the manner and outcome of traumatic dental injuries. In this case, the woman’s medical history did not refer to her dental condition before her traumatic dental injury, so it was difficult to ascertain whether she had periodontal disease. However, there was no radiological evidence of dental, dental pulp or periodontal disease, or of alveolar bone osteoporosis.

The crux of this case was the detection of alveolar bone and alveolar process fractures. Currently, the most common auxiliary examinations used in the dental department are radiological technologies such as X-rays, cone beam computed tomography (CBCT) and MSCT. X-ray imaging, including dental film and panoramic imaging, is two-dimensional and thus could not resolve this case because the images overlap. Limited CBCT scanners have recently become available in orthodontic practices, and have the advantages of lower cost, smaller scanner size and lower radiation dose compared to MSCT. ¹⁰ However, CBCT is not as widely used as MSCT in most areas of China. MSCT has superior advantages in analysing the cause of the injury by improving the detection of minor fractures and revealing the bone’s morphological characteristics. It is effective to use a combination of axial and reconstructed imaging in the diagnosis of dental trauma.

The woman alleged that she had been beaten, which led to the loss of teeth. The forensic practitioners reviewed the images and found fractures of the medial alveolar process and defects in the alveolar bone which indicated that the woman’s teeth had been subjected to external force. Additionally, there was no loosening of the upper incisors, and she was in a good oral health. The alleged assailant could not provide any evidence such as teeth marks on his fingers that could prove his innocence. Hence, the experts concluded that the dentoalveolar injury in this case was caused by criminal behaviour rather than being self-inflicted. The result was finally confirmed by the police following a confession by the son-in-law.