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Cone Beam Imaging In Orofacial Cleft Therapy

Various imaging modalities, including cone beam computed tomography, play an important role in the diagnosis and pre- and postsurgical phases of orofacial cleft therapy.

By Gustavo M. Santaella, DDS, MS, PhD, Bruno C. Azevedo, DDS, MS and William C. Scarfe, BDS, FRACDS, MS On Sep 11, 2020

PURCHASE COURSE
This course was published in the September 2020 issue and expires September 2023. The authors have no commercial conflicts of interest to disclose. This 2 credit hour self-study activity is electronically mediated.

EDUCATIONAL OBJECTIVES

After reading this course, the participant should be able to:

Discuss common congenital craniofacial anomalies, as well as their etiology and prevalence.
Explain appropriate imaging techniques for treating patients with cleft lip and/or palate.
Describe management strategies when caring for this patient population.

The most common congenital craniofacial anomalies are orofacial clefts, which include cleft lip and/or palate (CLP). These defects develop as a result of a complex interaction of genetic and environmental factors, resulting in a failure of the fusion of bony and soft tissue growth elements of the cranial and maxillofacial bones in utero. During this period, ultrasound and magnetic resonance imaging can assist in prenatal diagnosis, helping to prepare parents of children born with this condition.^1–3 In addition, other forms of radiographic imaging, including cone beam computed tomography (CBCT), are key tools for diagnosing and managing these defects. Clinicians also rely on the Tessier⁴classification system, which is a comprehensive method of categorizing orofacial clefts based on craniofacial anatomy. The system describes 14 types of clefts according to their location in relation to eye and orbit. Facial clefts are numbered 0 through 7, and cranial clefts are numbered 8 through 14. Clefts of the lip, alveolus and palate are numbered 1, 2 and 3 (Figures 1A and 1B).

In this system, the most common orofacial clefts are those involving the upper lip, maxillary anterior alveolus (primary palate) and/or hard palate (secondary palate; groups 2 and 3). Other systems have been proposed to further describe CLP conditions, the most popular of which was suggested by Kernahan.⁵ From a treatment perspective, these conditions can be grouped into those that affect the lip with or without cleft palate, or cleft palate only. In this embryologically based system, the clefts are a result of specific anatomic derangements that fall along embryonic lines of fusion within the face. In the United States, there are an estimated 6.45 cases per 10,000 live births for cleft palate alone, and 10.89 for cleft lip with or without cleft palate.⁶

The comprehensive treatment of CLP is complex and involves addressing various surgical, dental, masticatory, esthetic, speech and hearing problems from immediately after birth into early adulthood. Surgical intervention usually occurs in three or four stages: initial cleft lip repair at about 3 months of age; palatal cleft repair between 9 and 12 months; pharyngeal flap procedure or pharyngoplasty (if required) between 3 and 5 years of age; and primary palate repair (alveolar process) between ages 9 and 12.⁷ Patients are optimally managed through a multidisciplinary approach involving orthodontists, oral and maxillofacial surgeons, pediatric dentists, plastic surgeons, dermatologists, otolaryngologists, geneticists and radiologists. In turn, these teams are supported by speech pathologists, social workers and psychologists.⁸

**FIGURES 1A and 1B.** Schematic representation of facial and cranial clefts and their localization on the soft tissues (A) and skeleton (B). Dotted lines are uncertain localizations or clefts. (Adapted from Tessier, 1976)4

ROLE OF IMAGING

As noted, radiographic imaging plays an important role in the diagnosis, monitoring, and pre- and postsurgical phases of treatment. Multiple radiographic procedures are performed on patients with CLP throughout childhood and adolescence. These may include panoramic, periapical, occlusal, and frontal or lateral cephalometric radiographs, as well as multidetector computed tomography and, more recently, cone beam imaging. Compared to the general population, patients with CLP are exposed to a greater radiation detriment and therefore have greater radiation risk.⁹ Radiation exposure to patients with CLP, particularly children and adolescents, should therefore be as low as diagnostically acceptable (ALADA).^10–12 This concept proposes that radiographic acquisition parameters should be selected to produce images of diagnostically acceptable quality suitable for task-specific interpretation, rather than just at the lowest settings.

More recently, Oenning et al¹³ provided guidelines on the appropriate use of cone beam imaging in pediatric dentistry, with specific reference to patients with CLP. Because these patients are subject to serial imaging, Oenning and colleagues¹³ suggest imaging protocols include low-dose optimization techniques. For procedures involving CBCT, this would include the restriction of the field of view to the maxillary area, the use of half-scan modes (decreasing the number of basis projections), and reduction in exposure (such as milliampere-seconds). They propose a modification to ALADA that incorporates considerations of patient presentation and appropriate timing — namely, ALADAIP (as low as diagnostically acceptable being indication-oriented and patient-specific).

De Mulder et al¹⁴ recently proposed an optimized, comprehensive maxillofacial imaging protocol for patients with CLP (Table 1), with time points based on age: 6 years (start of treatment); 7 to 9 years (or 10 years in conventional treatment planning); 15 years (presurgical records); and 20 years (end of the craniofacial growth period).^8,14 Except for the initial radiographic examination, all imaging of patients with CLP is performed using CBCT at various fields of view and image quality exposure settings (e.g., resolution and number of basis images).

CBCT of a patient showing the presence of a large gap defect — **FIGURE 2.** Three-dimensional volumetric rendering from a cone beam computed tomogram of a patient showing the presence of a large gap defect (G3) on the left side, and missing permanent left maxillary lateral incisor (D3).

**FIGURE 3.** Three-dimensional volumetric rendering of a cone beam computed tomogram in an inferior view of the same patient seen in Figure 2 showing the maintenance of the alignment of both arch forms (A1).

**FIGURE 4.** Coronal view of the orofacial cleft on the same patient seen in Figure 2 and Figure 3 showing the small defect involvement (N2) of the left nasal floor.

CLINICAL PERSPECTIVE

The authors of this article have been involved in CBCT imaging of patients with CLP from referring clinicians since 2004. In the past three years, we have become an imaging referral center from an expanding group of external practitioners, including plastic surgeons and orthodontists. Most cases are referred to us for diagnostic assessment of patients with CLP at stages 2, 3 and 4. Because of the variability in patient timing, presentation, and potential complexity of the defect, we have adopted a comprehensive approach incorporating both image reformatting and interpretation to improve diagnosis and communication between referring practitioners.^15,16

We describe the overall cleft defect and affected adjacent tissues on appropriately formatted CBCT images according to the gap, arch, nasal floor and dental (GAND) classification¹⁵ (Table 2, and Figure 2 through Figure 4). This includes a qualitative assessment of the severity of involvement in each region within the maxilla. There are three possible levels of severity for each of the four GAND parameters evaluated, ranging from less to more affected. As a supplement to the “G” component of the GAND classification and measuring the physical dimensions of the cleft, we use the Chelsea scale to describe the patterns of bone bridging of the interdental septum associated with the cleft.¹⁶ The Chelsea system categorizes the volume and position of the interseptal bony bridge into one of six categories: A to F (Figures 5A through 5F). Of these, A, B and C are considered to be acceptable, whereas D, E and F are less than satisfactory.

**FIGURES 5A through 5F.** Sketches of the six categories used in the Chelsea system to assess the radiographic success after secondary alveolar bone grafting through the position of the bone relative to the cleft teeth. The categories are: (A) there must be bone at the cementoenamel-junction (CEJ) and at least 75% of both roots covered with bone; (B) there must be bone at the CEJ and at least 25% of both roots; (C) there must be bone across at least 75% of the cleft roots from an apical direction; (D) there must be bone across at least 50% of both roots from an apical to coronal direction; (E) any cleft site that has a bony bridge, but does not have bone apically or coronally; (F) bone of 25% or less is present across both roots from an apical direction. (Adapted from Witherow et al, 2002)¹⁶

Because the treatment of patients with CLP is multidisciplinary, these individuals often have diagnostic records obtained from multiple clinicians from different disciplines. This can include not only cone beam imaging data, but also extra- and intraoral optical scans obtained using different systems. Distribution of this data between healthcare providers is essential for timely and appropriate treatment. Sharing and immediate access to data can be facilitated using a secure Health Insurance Portability and Accountability Act (HIPAA)-compliant picture archiving and communication system (PACS) server that houses all records for the team’s immediate access.

At our institution, we internally distribute records using a medical PACS that incorporates a dental reformatting module. Because our referral base has expanded to include many more referrals from external clinicians, we are investigating the use of a subscription-based cloud PACS system. This would eliminate redundant imaging, providing a cost-efficient, central, HIPAA-compliant storage and external on-demand distribution and visualization portal.

CONCLUSION

In closing, treating patients with CLP is a complex and multidisciplinary task requiring periodic age-based radiographic imaging. Protocols for imaging should be based on specific diagnostic criteria designed to support optimal treatment planning and case management. These protocols should use the nominal number of radiographic examinations required, and all imaging should use exposure settings that produce diagnostically acceptable images at the lowest possible radiation dose to the patient.

REFERENCES

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