Imaging in Oral and Maxillofacial Surgery

The scope of oral and maxillofacial surgery treatment and care is very broad, from dentoalveolar surgery, to pathology and reconstruction, to treatment of craniofacial deformities. The effective surgical treatment of patients requires appropriate and accurate diagnostic imaging. The various imaging modalities used in oral and maxillofacial surgery are typically for diagnostic and treatment planning purposes. With the improvements of three-dimensional imaging and software programs, surgical treatment and care have been enhanced with patient-specific guides, hardware, and implants. This article discusses the various imaging modalities used for a variety of typical oral and maxillofacial surgery procedures.

Key points

  • There are many types of imaging modalities commonly used in oral and maxillofacial surgery.

  • The more ubiquitous use of three-dimensional (3D) imaging has allowed for advances in the field of oral and maxillofacial surgery.

  • The advances in 3D imaging and surgical software programs have allowed for improved surgical planning and the creation of patient-specific surgical guides and implants.

Introduction

The scope of oral and maxillofacial surgery treatment and care is very broad, from dentoalveolar surgery, to pathology and reconstruction, to treatment of craniofacial deformities. The effective surgical treatment of patients requires appropriate and accurate diagnostic imaging. The various imaging modalities used in oral and maxillofacial surgery are typically for diagnostic and treatment planning purposes. With the improvements of three-dimensional (3D) imaging and software programs, surgical treatment and care have been enhanced with patient-specific guides, hardware, and implants. This article discusses the various imaging modalities used for a variety of typical oral and maxillofacial surgery procedures.

Imaging for dentoalveolar surgery and implants

The most common procedures for oral and maxillofacial surgeons are dentoalveolar surgery and dental extractions. Imaging with periapical radiography can be used for diagnosis of single-tooth issues such as caries, or for evaluation of single-tooth dental implants with angulation and postoperative documentation. However, panoramic imaging is the typical first-line imaging modality for most dentoalveolar needs and diagnosis in the oral surgery setting.

Panoramic imaging allows evaluation of a broad area of the dentofacial complex. With panoramic imaging, oral surgeons are able to evaluate multiple teeth, impactions, relation of teeth to other relevant structures, the bony architecture, generalized periodontal bone health, and other pathologic conditions such as cysts or masses.

Cone-beam computed tomography (CBCT) imaging is particularly useful for dentoalveolar surgery to allow 3D analysis of anatomy and structures. CBCT can be used for evaluation of proximity of teeth to vital structures, or to measure distances and evaluate bone for dental implant placement.

Clinical Applications

Third molars

The panoramic radiograph is the standard radiographic image taken to evaluate third molars for extraction. The approximation of the teeth to the maxillary sinus and inferior alveolar nerves, as well as angulation and depth of impaction, is easily determined with a panoramic image. When evaluating mandibular third molars in close proximity to the inferior alveolar nerve (IAN), findings such as root darkening, root deflection, root narrowing, bifid apex, overlap of the canal, as well as loss of cortical lines of the IAN canal, deflection of the canal, or narrowing of the canal could indicate potential for increased risk of paresthesia or nerve injury if the teeth were to be extracted. , Fig. 1 shows a pantomogram where tooth 17 overlaps the IAN, with root darkening, and nerve canal deflection.

Fig. 1
A panoramic radiograph with tooth 17 showing classic signs of close proximity to the IAN (overlap with the IAN, root darkening, deflection of the canal).

CBCT imaging may be beneficial to better understand the proximity of teeth to the IAN when the signs mentioned earlier on pantomogram are present. Although CBCT imaging typically does not change the surgical approach or technique of extracting teeth, the added information may be beneficial in deciding between extraction versus coronectomy to prevent nerve injury. An example of this is Fig. 2 , which shows the CBCT of tooth 17 for the patient in Fig. 1 . This CBCT image shows the IAN traveling through the roots of tooth 17, thus making coronectomy the procedure of choice if surgery is indicated. 3D imaging with CBCT may be a useful diagnostic tool to aid in surgical planning for procedures on mandibular third molar teeth.

Fig. 2
CBCT of tooth from Fig. 1 showing IAN traversing through the roots of tooth 17.

Exposure of Impacted Teeth

A common procedure for oral and maxillofacial surgeons is the exposure and bonding of impacted teeth for orthodontic treatment. Panoramic imaging is useful to visualize these impacted teeth and their general locations, such as in Figs. 3 and 4 . If these impacted teeth cannot be palpated on clinical examination, intraoral imaging with the commonly known SLOB (same-lingual, opposite-buccal) rule can be performed for localization of the tooth, but the increased use of CBCT imaging allows 3D localization of these teeth and more anatomic information. This ability is clinically relevant because the location of the teeth in question determines whether the surgical approach should be accomplished from the buccal or the palatal or lingual, leading to decreased morbidity from the procedure. Figs. 5 and 6 also show the CBCT of the same patients in Figs. 3 and 4 , respectively, allowing the surgeon to have a better understanding of the surgical access.

Fig. 3
A panoramic radiograph of impacted canines.

Fig. 4
A panoramic radiograph of impacted premolars.

Fig. 5
Cross-sectional and panoramic views of CBCT of impacted canines from Fig. 3 .

Fig. 6
Coronal and axial views of CBCT of impacted premolars from Fig. 4 .

Implants

As described elsewhere in this article, imaging for dental implant placement has progressed to 3D analysis via CBCT imaging. Plain film radiography such as periapical radiographs can be used for specific situations where no vital anatomy (IAN, maxillary sinus, bony concavities) is nearby, and clinically sufficient bone width and height are present. If these criteria are not met, then panoramic or CBCT imaging are recommended to allow more precise measurements to relevant anatomy. Panoramic imaging is useful for evaluation of bone height in the posterior maxilla and mandible, to see general distance to the maxillary sinus and IAN, respectively. CBCT imaging can evaluate distances more accurately to vital structures and allow 3D visualization of edentulous spaces. Technological advances with CBCT imaging, planning software, and 3D printing and milling have allowed the creation of surgical guides and guided implant surgery. Figs. 7–10 show a patient that had an ameloblastoma surgically resected, and bone continuity restored with a free fibula flap, using 3D imaging and dental software programs to surgically plan dental implant placement and subsequent dental rehabilitation.

Fig. 7
3D surgical plan for surgically guided implant placement in a mandible reconstructed with a fibula free flap.

Fig. 8
A panoramic radiograph of implant placement in fibula reconstruction of mandible.

Fig. 9
Software design and lab processed final implant-supported prosthesis.

Fig. 10
( Left ) Pantomogram of final prosthesis. ( Right ) Clinical photograph of final prosthesis.

Imaging for dentoalveolar and maxillofacial trauma

Dental and maxillofacial injuries range from fractured teeth to complex fractures involving the entire osseous facial skeleton. Diagnostic imaging plays a critical role in the initial diagnosis, treatment planning, and intraoperative and postoperative management of these patients. Until the 1980s, diagnostic imaging consisted of plain films and panoramic radiographs. A major advancement in imaging for facial trauma occurred with the introduction of computed tomography (CT) imaging. , CT allowed the visualization of injuries in multiple planes. With advances in software, 3D reformatted images became widespread. Continued advancement in CT hardware and software have now changed the way patients with facial trauma are managed.

Dentoalveolar Trauma

Evaluating dental and dentoalveolar trauma begins with a detailed physical examination. Mobile teeth moving in a segment suggest an alveolar fracture, whereas nonmobile fractured teeth suggest an isolated dental trauma. Changes in occlusion could arise from a maxillary or mandibular fracture. The imaging technique selected varies based on the physical examination findings. Isolated dental trauma is best evaluated with periapical films because they provide the highest-resolution image. With changes in occlusion or mobile segments of dentition, additional imaging is necessary. Panoramic radiographs may be used to detect mandibular fractures and alveolar fractures. Midface fractures often require 3D imaging to detect.

Dental Luxation Injuries

The diagnosis and management of dental luxation requires careful physical examination and radiographic evaluation. Depending on the type of injury, the treatment and overall prognosis varies. , Primary teeth are generally managed conservatively, so the following discussion relates to management of permanent tooth luxation injuries.

  • Concussion injuries present with pain with percussion without loosening or displacement of the tooth. The injury cannot be detected with radiographs and is generally managed conservatively with a soft diet for 1 to 2 weeks.

  • Subluxation injuries present with a loose tooth in the appropriate position. A periapical radiograph may show widening of the periodontal ligament (PDL) space. A CT scan appears normal. This injury is generally managed conservatively with a soft diet or semirigid fixation if the tooth is severely mobile.

  • Lateral luxation injuries present with eccentric displacement of a tooth. A periapical radiograph may show widening of the PDL space and can identify a tooth root fracture. A CT scan may identify a comminuted alveolar socket. The injury is treated with repositioning and semirigid fixation.

  • Extrusive luxation presents with coronal displacement of the tooth. A periapical radiograph confirms partial displacement of the tooth out of the socket. This injury can be managed with repositioning and semirigid fixation.

  • Intrusive luxation presents with apical displacement of the tooth. A periapical radiograph often confirms the apical displacement and is able to identify any tooth root fractures. A CT scan may identify the comminuted alveolar socket. This injury can be managed with repositioning and splinting or orthodontic extrusion.

  • Avulsion injuries present with a tooth completely displaced from the alveolar socket. A periapical radiograph shows an empty socket and confirms there is no retained root fragment. This injury is managed with timely reimplantation and semirigid fixation.

Alveolar Fractures

An alveolar fracture presents with multiple mobile teeth moving as a single unit. A periapical radiograph may be able to identify a fracture line in the alveolar bone. Panoramic radiograph often appears normal. CT scan is the best modality to radiographically confirm the fracture as well as to ensure there is not a more significant skeletal fracture such as a mandible fracture or a maxillary (Le Fort) fracture. These injuries in both the adult and pediatric population are managed with repositioning and splinting.

Mandibular Fractures

Imaging modalities for mandibular fractures consist of plain films, panoramic radiographs, or CT scans. Given the complex anatomy and various treatment options, CT has become the gold standard for mandibular fractures. Plain films have an overall sensitivity of 62% in identifying mandibular fractures; however, they may be useful in identifying certain fractures, especially in the pediatric population, where there is a concern for the amount of radiation a patient is receiving. In the outpatient dental setting, a pantomogram is able to evaluate the mandible and has a sensitivity of 92% in identifying mandibular fractures. Fig. 11 shows a 3D rendering from a CT scan that shows a mandibular symphysis and left mandibular subcondylar fracture in detail.

Jul 11, 2021 | Posted by in General Dentistry | Comments Off on Imaging in Oral and Maxillofacial Surgery
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