Thickness of the articular soft tissue of the temporal component in temporomandibular joints with and without disk displacement.

OBJECTIVE: The purpose of this investigation was to test the hypothesis that temporomandibular joint disk displacement is associated with significant functional adaptive changes of the articular soft tissue of the articular eminence. STUDY DESIGN: Thirteen temporomandibular joint autopsy specimens with normal superior disk position and 12 with complete anterior disk displacement were cryosectioned, and sections were stained and photographed. At a magnification of x20 the soft tissue was measured (1) at the inflection point, (2) on the posterior slope, (3) at the apex, and (4) on the anterior slope of the articular eminence. RESULTS: Displacement of a deformed or nondeformed temporomandibular joint disk without perforation of the posterior disk attachment was associated with significantly increased thickness of the articulating soft tissue at the apex and on the posterior and anterior slopes of the articulating eminence. When disk displacement was associated with a perforation of the posterior disk attachment, the soft tissue was not significantly thicker than in joints with normal superior disk position. CONCLUSIONS: Increase in articulating soft tissue thickness is interpreted as an adaptive mechanism to maintain the condyle path and withstand excessive loading at interposition of the temporomandibular joint components. When the plasticity of the tissues is surpassed, the adaptation will be thwarted and replaced by tissue breakdown.

Sources of radiographic distortion in conventional and computed tomography of the temporal bone.

OBJECTIVES: To identify those bony regions of the glenoid fossa where, due to the inclination, there is an increased risk of radiographic distortion in conventional and computed tomography (CT). METHODS: The inclination of the roof and posterior wall of the glenoid fossa was determined relative to established imaging planes. Measurements were performed on 50 corrected coronal MR and 50 axial CT images and 200 sagittal cryosections of 50 temporomandibular joints (TMJs). The location of regions with unfavourable bone wall inclination was identified using the condyle as a reference. RESULTS: The inclination of parts of the fossa roof exceeded the limit for reliable depiction in corrected sagittal and coronal planes in 40% and 8% of the joints respectively. The inclination of parts of the posterior wall of the fossa exceeded the limit for reliable depiction in corrected sagittal and in true sagittal planes in 100% and 84% of the joints respectively. In 84% of the joints the inclination exceeded the limit for reliable depiction in the axial plane. For both bone walls the regions with unfavourable inclination were in the medial part of the joint. CONCLUSIONS: The angulation of parts of the roof and posterior wall of the glenoid fossa in relation to established imaging planes makes them highly susceptible to distortion. The oblique coronal projection is well suited for depiction of the roof of the fossa and preferable to a sagittal projection. An oblique axial projection is required for the posterior wall.

Effects of contrast equalization on energy imparted to the patient: a comparison of two dental generators and two types of intraoral film.

Technical evolution in maxillofacial radiology has in the last decade provided faster films and the constant potential generator. The consequences of these innovations for radiographic contrast and energy imparted to the patient are analysed. On the basis of physical measurements a test model has been developed for correcting exposure parameters in order to maintain or restore image contrast. These measurements are expressed in and developed from basic radiological concepts and physical formulas presented in an earlier paper (Helmrot E. et al., Dentomaxillofac. Radiol. 1991; 20: 135-46). The test model can also be used to demonstrate the balance between contrast and energy imparted to the patient in the radiographic process. Changing to constant potential generators and faster film may each result in a degradation in contrast, which is possible to restore by a controlled adjustment of the kV-setting. Maintenance of constant image quality results in a slight reduction in the net gain in energy imparted, due to the generator and/or film shift. When, for example, a conventional single-pulse generator operated at 65kVp tube potential was replaced by a modern constant potential unit, the kV-setting had to be decreased by 5 to 8 kV to maintain the same radiographic contrast. This correction could be done without increasing energy imparted to the patient, taking into account the fact that the spectral characters of the photon energy are not identical. If, in addition, faster intraoral film with lower film contrast was introduced, together with the constant potential unit, the kV-setting had to be further decreased to maintain the radiographic contrast.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of scattered radiation and tube potential on radiographic contrast: comparison of two different dental X-ray films.

The fundamental concept in image quality of contrast has been analysed in terms of its elements; film, radiation and object contrast, and the theoretical formula to describe their interrelationship have been evaluated. Experiments were designed to investigate the dependence of radiographic contrast on the kV, the type of generator and dental film used (D and E speed). An ivory wedge was used as the object, both alone and within a polymethyl methacrylate phantom as scattering medium. Precise definition and control of the X-ray generators were achieved by means of measurements of the primary X-ray spectra using a Compton spectrometer. D speed was found to have higher film contrast than E speed when compared at the same optical density, due to its lower base and fog and lower level of saturation in these experiments. On the other hand, E speed was found to have wider latitude. The experimental object was reproduced with the highest radiographic contrast using D-speed film and, with a given type of generator, this increased when the kV was decreased. While no difference in scatter/primary ratios was observed using the two different films, a weak dependence on kV in the range from 36 to 77 kV was found and confirmed by Monte Carlo calculations. The results indicate that the D and E speed films used had equal energy absorption properties; the difference in radiographic performance is due to their different film characteristics. The importance of controlling the physical parameters (photon energy spectrum, base and fog and optical density level) when comparing image qualities is clearly demonstrated.

Osseointegrated implants in the oral habilitation of a boy with ectodermal dysplasia: a case report.

The most characteristic oral feature in ectodermal dysplasia is hypodontia. Children and adolescents suffering from ectodermal dysplasia often need extensive and complicated prosthetic treatment. The development of techniques for osseointegrated implants offers new possibilities for the oral habilitation of these children. This paper describes the oral habilitation of a boy with severe ectodermal dysplasia and where Brånemark osseointegrated implants have been used as part of the treatment. The patient was seen at the dental department at the age of 1.5 years. Two conically-shaped upper incisors were at that time the only teeth that had erupted. The treatment was planned in a multidisciplinary odontological group involving paediatric dentistry, orthodontics, prosthodontics, oral surgery and maxillofacial radiology. At the age of 3 years it was verified that the boy had four primary teeth (53, 51, 61, 63) and four permanent teeth (16, 11, 21, 26). There were no teeth in the lower jaw. The alveolar ridges in the edentulous areas were low or missing. During the period 3-6 years of age the boy used an upper partial denture adapted to allow the mesial drift of the 16 and 26 teeth. At the age of 6 years, two Brånemark implants were inserted in the lower front-cuspid region. A specially designed overdenture for the lower jaw was constructed. The overdenture was retained in contact with the male attachments by two cuffs of heat-polymerized resilient silicone. Over the next 4 years the dentures were modified due to the eruption of permanent teeth and growth. However, only minor corrections were necessary concerning the retention system of the lower denture. The implants are well osseointegrated and stable and allow the boy to use a lower denture without any complications.

Craniomandibular function in juvenile chronic arthritis. A clinical and radiographic study.

Craniomandibular function was studied in 70 subjects with juvenile chronic arthritis (JCA). The subjects represented the total group of children and adolescents with the diagnosis JCA in a Swedish county. At examination, the median age of the subjects was 11.9 years and the median duration of the disease was 2.6 years. The most important finding of the study was the high prevalence (41%) of radiographic signs of temporomandibular joint (TMJ) pathology. Few subjects showed the typical craniofacial abnormalities associated with JCA, like mandibular micrognathia, facial asymmetries and open bite. Subjective symptoms of dysfunction were almost absent in subjects younger than seven years but were reported by 56% of the older subjects. TMJ sounds and pain on jaw movements were the most frequent symptoms reported. At the clinical examination, TMJ crepitations and restricted horizontal jaw movements were noted in 26% and 32% respectively. The high prevalence of TMJ involvement found in this study underlines the importance that dentists become part of the medical team responsible for the treatment of children and adolescents with JCA.

The petrotympanic fissure: a link connecting the tympanic cavity and the temporomandibular joint.

Morphological traits of the petrotympanic fissure, a soft tissue containing connection between the middle ear and the temporomandibular joint, are described. The description is based on sagittal histological sections of 67 petrous bones with the proximal part of the mandible. The morphological pattern of the soft tissues within the petrotympanic fissure does not, other than in association with exceptional anatomic conditions, support the opinion that forces may be transferred from the joint to the middle ear. The petrotympanic fissure is mainly to be looked upon as a reminder of earlier evolutionary stages. It may also call attention to a developmentally caused special neurological pattern where the innervation of chewing muscles and some middle ear and pharyngeal muscles are closely related to each other. Taking the developmental facts into account in the clinical situation, it may not be so confusing that a primary pathological stimulus in the chewing apparatus and its muscles may, secondarily, manifest itself as ear symptoms. This symptomatology is known as the "otomandibular syndrome."

Presurgical planning for osseointegrated implants in the maxilla. A tomographic evaluation of available alveolar bone and morphological relations in the maxilla.

A clinical tomographic method of defining and demonstrating the hard and soft tissue morphology of those parts of the maxilla which are intended for osseointegrated implants is described. This preoperative examination is an useful aid in the choice and planning of the treatment as such, and in the decision concerning the calibre and position of the implants. Hence, it facilitates the surgical procedure.

Skeletal remodelling in the temporomandibular joint after oblique sliding osteotomy of the mandibular rami.

Skeletal remodelling of the temporomandibular joints took place in 80% of cases after oblique sliding osteotomies of the rami. The new bone formation was found in both the condylar and temporal parts of the joint. It was mostly located on the posterior surface of the condyle and in the roof of the temporal part of the joint. No differences in skeletal remodelling were found between wiring and nonwiring cases.

Intraosseous wiring in ramus osteotomy.

The value of intraosseous wiring of the fragments after oblique osteotomy of the mandibular rami was studied. A wired group (14 patients) and a nonwired group (15 patients) were compared cephalometrically. There were only small differences between the groups but there was a tendency toward a smaller postoperative posterior rotation of the mandible in the wired group. It was concluded that in routine cases of mandibular prognathism wiring is not necessary.

Changes in the temporomandibular joint after oblique sliding osteotomy of the mandibular rami. A longitudinal radiological study.

Changes in the temporomandibular joint following oblique sliding osteotomy of the mandibular rami were studied using axial, frontal and lateral radiographs. The condyle/fossa relationship was also studied with regard to the effect of intraosseous wiring of the proximal fragment. Antero-inferior displacements of the condyles were regularly seen after the osteotomies. The use of intraosseous wiring had no adverse effects on the temporomandibular joint.

Reproducible positioning of the skull at tomography.

Description of a method for obtaining sufficient reproducibility in odontologic examinations using a vacuum pillow.

External bony auditory canal and the tympanic bone. Morphologic properties and influences on the tomographic reproduction.

The external bony auditory canal is morphologically defined as concerns the shape and calibre in successive plane parallel histologic sections of the petrous bone. The sagittal dimensions and structural appearances of the tympanic bone are demonstrated. The morphologic properties defined constitute a basis for the evaluation of the tomographic image formation in this region.

[Hypocycloidal tomography of the temporomandibular joint region]. / Hypozykloidale tomographie des Kiefergelenkbereichs.

Tomography has become an important diagnostic method today. Clinically it is necessary to recognize the interpretative problems with tomographs. The reason for and the development of a few frequent tomographic phenomena were described using the results of comparative anatomic and roentgenographic examinations.

Thin bony walls of the temporomandibular joint. Morphologic properties and tomographic reproduction.

The morphology of two thin bony walls in the medial third of the mandibular fossa is described on the basis of successive microtome sections of undecalcified temporomandibular joint specimens. The requirements for reproduction on thin bony walls at tomography with hypocycloidal movement are defined and discussed.