P. A. Monsour

Variability of the styloid process and stylohyoid ligament in panoramic radiographs

This article deals with the incidence of anatomic variations in the styloid process and stylohyoid ligament as found in panoramic radiographs. Also, the accuracy was determined for measuring the length of styloid processes from panoramic radiographs, the variation in length of the styloid process with age, and the relationship of elongated styloid processes and ossified stylohyoid ligaments to symptoms of styloid-stylohyoid syndrome. Variations in styloid process and stylohyoid ligaments are not uncommon, especially segmentation of the process in young subjects. The apparent length of the styloid process was magnified approximately 1.37 times and was never diminished by panoramic radiographs. A steady increase in styloid process length was observed to age 30 years, with another slight increase starting at age 60 years. Subjects with elongated styloid processes (greater than 40 mm) had the highest incidence of discomfort on swallowing, whereas subjects with ossification of the stylohyoid ligament had the highest incidence of discomfort on turning the head from side to side.

Implant radiography and radiology

The practitioner placing dental implants has many options with respect to pre-implant radiographic assessment of the jaws. The advantages and disadvantages of the imaging modalities currently available for pre-implant imaging are discussed in some detail. Intra-oral and extra-oral radiographs are generally low dose but the information provided is limited as the images are not three-dimensional. Tomography is three-dimensional, but the image quality is highly variable. Computed tomography (CT) has been the gold standard for many years as the information provided is three-dimensional and generally very accurate. However, CT examinations are expensive and deliver a relatively high radiation dose to the patient. The latest imaging modality introduced is cone beam volumetric tomography (CBVT) and this technology is very promising with regard to pre-implant imaging. CBVT generally delivers a lower dose to the patient than CT and provides reasonably sharp images with three-dimensional information. A comparison between CT and CBVT is provided. Magnetic resonance imaging is showing some promise, but the examinations are not readily available, generally expensive and bone is not well imaged. Magnetic resonance imaging is excellent for demonstrating soft tissues and therefore may be of great use in identifying the inferior dental nerve and vessels. All of the above technology is of little value if the information required is not obtained and so information is also provided on imaging of some of the vital structures. Of particular interest is the inferior dental canal, incisive canals of the mandible, genial foramina and canals, maxillary sinus and the incisive canal and foramen of the maxilla.

Imaging of craniofacial fibrous dysplasia.

Fibrous dysplasia is a relatively common disorder of bone. It may affect the bones of the face and skull and, in so doing, produce a wide variety of clinical presentations. Plain film assessment of craniofacial fibrous dysplasia may be difficult because of varying appearances and complex, overlapping structures. The MRI appearances of fibrous dysplasia are often non‐specific and may be confusing. Findings on CT are also variable, but more commonly lead to a specific diagnosis. This is because of the characteristic ground‐glass appearance of woven bone, seen on CT in most if not all cases of craniofacial fibrous dysplasia.

Chronic recurrent multifocal osteomyelitis involving the mandible: case reports and review of the literature.

Chronic recurrent multifocal osteomyelitis (CRMO) is an aseptic inflammatory disorder of unknown cause occurring in children and adolescents. It is characterized by multifocal bone lesions with pain and swelling recurring over months to years. Lesions usually involve the metaphyses of the long bones and involvement of the jaw is rare. The clinical presentation, radiographic appearance and histology of a case of CRMO involving the mandible in an 8-year-old girl are documented. The radiographic appearance of another three cases is also described.

Accuracy of angular measurements and assessment of distortion in the mandibular third molar region on panoramic radiographs.

OBJECTIVE The objective of this study was to examine distortion on panoramic radiographs by assessing the accuracy of angular measurements in the mandibular third molar region on panoramic radiographs using computed tomography (CT). METHODS Images from patients referred to a radiology practice for low-dose CT scans of their lower third molars were used in this study. The angle between the long axes of the second and third molars was assessed on panoramic radiographs and the corresponding CT images. Apparent tilting of the tooth across the arch on the panoramic image and the bucco-lingual inclination on CT were also recorded and compared. RESULTS Eighty-eight patients had 163 mandibular third molars. The mean difference between the panoramic measurements and the CT measurements was -1.44 degrees, indicating that on the panoramic radiograph the third molar appeared less mesially inclined on average. This pattern was present in most cases, but in 64 cases the third molar appeared more mesially inclined on the panoramic radiograph. It was not possible to predict the direction of the discrepancy based on the radiographic findings. The discrepancy between the 2 measurements was greater if the third molar appeared tilted across the arch on the panoramic image, and tilted teeth showed a higher bucco-lingual inclination on reformatted CT images. CONCLUSIONS Distortions inherent in panoramic imaging because of projection geometry produce discrepancies in the angular measurements in the mandibular third molar regions on panoramic radiographs. Interpretation of third molar angulation from panoramic radiographs is often unreliable and may not accurately reflect the true orientation of the tooth. Apparent tilting of the tooth across the arch on the panoramic radiograph exacerbates the problem and appears to correlate with the bucco-lingual inclination of the third molar as visualized on reformatted CT images.

Age-related changes in maxillary and mandibular cortical bone thickness in relation to temporary anchorage device placement

BACKGROUND The aim of this study was to investigate the correlation between alveolar bone cortical thickness (ABCT) and age in the maxillae and mandible in humans. This information could then be translated into clinical application with temporary anchorage devices (TADs) in orthdontics. METHODS Samples comprised 82 post-mortem CT datasets (41 males and 41 females) aged between 11 to 50 years, and were divided into five different age groups and gender. Alveolar ABCT was measured in the labial/buccal and palatal/lingual sides of the incisor, canine, premolar, molar and tuberosity/retromolar regions of the maxillae and mandible. Correlations between ABCT and age and gender were analysed with linear regression analysis. RESULTS Strong correlation between ABCT and age was found for the maxilla on the labial side of the maxillary incisor region (p < 0.001). On the palatal aspect, significant correlations between ABCT and age were found in the maxillary incisor and maxillary premolar regions (p = 0.01 and p = 0.047 respectively). Significant correlation between ABCT and gender was found only at the buccal aspect of the maxillary molar region (p = 0.022). In the mandible, a statistically significant correlation between ABCT and age was found in the cortical bone of the labial side of the mandibular incisor region (p = 0.017). However, statistically significant negative correlation between ABCT and age was found in the mandibular canine region (p = 0.033). The only site to demonstrate a significant difference in change in ABCT with age between males and females was the lingual side of the retromolar region, in which female ABCT increased more than in males (slope = 0.015). CONCLUSIONS There is minimal clinically significant correlation between ABCT and age at the alveolar bone level. Although investigations show statistically significant correlations, these may not be clinically significant as those regions are not ideal for anchorage reinforcement with TADs in orthodontic practice.

A histochemical study of the effects of high doses of sodium fluoride on dipeptidyl peptidase II activity in the rat incisor ameloblast

Female Wistar rats, 3 weeks old, were given sodium fluoride in saline solution (isotonic) by intraperitoneal injection at a dose of either 0, 10 or 20 mg per kg body weight. This treatment was given 9 times over 4.5 days. After fixation by perfusion and demineralization in neutral EDTA, hemi-mandibles were sectioned in a cryostat. Sections were stained for dipeptidyl peptidase II activity, using the specific substrate Lys-Ala-MNA and the coupler Fast Blue B for histochemical localization. Staining indicative of dipeptidyl peptidase II was found in the enamel organ of the incisor, particularly in cells of the stratum intermedium and in both secretory and maturation ameloblasts. This staining was markedly reduced in ameloblasts of rats given either 10 or 20 mg sodium fluoride per kg body weight.

Effects of a Single Intravenous Dose of Sodium Fluoride on Plasma Electrolytes and Metabolites in Rats, Rabbits, and Cockerels

This study assessed the effect of a single intravenous dose of sodium fluoride (20 mglkg body wt.) on plasma ionic fluoride and on some other plasma electrolytes and metabolites in rats, rabbits, and cockerels. At any given time following sodium fluoride administration, the plasma ionic fluoride was highest in rabbits and lowest in cockerels. The rate of removal of fluoride from plasma was slower in rabbits as compared with that in the other two species. Plasma sodium, chloride, total protein, albumin, total globulins, and osmolality were not significantly altered by sodium fluoride in any of these three species. However, plasma phosphate (inorganic), urea, creatinine, and glucose were elevated, and plasma calcium was reduced in the rats and the rabbits, but none was significantly altered in the cockerels. The analyses indicated that species variability does exist in fluoride toxicity.

THE GLANDULAR ODONTOGENIC JAW CYST: REPORT OF A CASE

&NA; A case of a rare odontogenic cyst arising in the lateral periodontal membrane in the mandible in a 14 year old girl is reported. This lesion appeared to be a new entity and has been named glandular odontogenic cyst (GOC) or sialo‐odontogenic cyst. Histologically the lesion was lined by mucous producing cuboidal epithelium containing several areas of thickening and numerous duct‐like structures. The cyst recurred with the same histology two years postoperatively.

Panoramic ghost images as an aid in the localization of soft tissue calcifications

Mapping of the ghost envelope for an Orth Oralix panoramic x-ray unit (Philips Medical Systems) was carried out with a lead sphere suspended at various locations around a dry mandible. The ghost envelope is a three-dimensional zone within which an object or anatomic structure must lie to produce a ghost image on panoramic radiographs. If the three-dimensional shape of the ghost envelope for a particular panoramic unit is known, information can be gained about the clinical location of objects appearing on radiographs produced with that machine. Objects outside the envelope will not result in ghost image formation. Objects within the envelope will result in characteristic ghost images depending on their position. This article analyzes ghost image characteristics in relation to object position and discusses the limitations of the method. A series of ready reference diagrams is provided, which may aid in the localization of soft tissue calcifications and foreign objects observed on panoramic radiographs.