The effect of interocclusal appliances on temporomandibular joints as assessed by 3D reconstruction of MRI scans.

Magnetic resonance imaging (MRI) enables simultaneous visualization of hard and soft tissues. The aims of the present study were to computer generate three-dimensional (3D) images, reconstructed from MRI scans of normal temporomandibular joints (TMJ), to assess the relative positions of the disc, condyle and articular surface of the temporal bone and to study the effect of two mandibular group function interocclusal appliances (IOAs). Bilateral MRI scans of 2 mm slice thickness were generated for the TMJs of 12 asymptomatic subjects with the image acquisition coils orientated in a corrected oblique sagittal plane. MRI scans were generated for all subjects with 3 mm interincisal distance IOAs, while a subgroup (n = 4) was also scanned with a 5 mm interincisal IOA in situ. An average of 10 slices through each TMJ were generated for the closed mouth and IOA positions. Three-dimensional reconstruction was performed on a 486 IBM compatible computer using a suite of nine programs not commercially available. Three-dimensional images allowed visualization of composite images of joint relationships. Subjective assessment indicated that joint relations in 3D were more informative than multiple separate 2D MRI scans. With the 3 mm IOA in situ, the disc was positioned posteriorly and superiorly to the condyle in three of 12 cases. In four of 12 cases the condyle, and in two of 12 cases both the disc and condyle, were positioned anteriorly and inferiorly. With the 5 mm IOA changes in condyle/disc and condyle/fossa relationships were more variable. It was concluded that 3D images of TMJs enabled the assessment of the positional changes of the condyle/disc and condyle/fossa relationships as altered by IOAs. However, the role of IOAs on the internal arrangements within the TMJ remains variable and is deserving of further study.

Oral rehabilitation using dental implants and guided bone regeneration.

The advent of osseointegrated dental implants focused initially on functional rehabilitation. Interest today centres on aesthetics and the philosophical ideal of replicating nature. Implants can be placed beyond resorbed anatomic limitations where the final prosthesis should be, rather than within the pre-existing resorbed bone. In order to achieve this, the following must be considered: implant positioning, adequate bone support and the overlying soft tissue envelope. Common techniques to modify the surgical environment include different methods of bone grafting and regeneration, ridge expansion and sinus augmentation. With the advent of growth factors like bone-morphogenetic proteins, restoration of bony contours will become more predictable. Soft tissue management techniques include tissue expansion and contouring, gingiva grafts and advancement or rotational flaps. Though some of these procedures can be done concurrently with implant placement, a secondary surgical procedure is often required. Ideal implant positioning involve establishing correct orientation in all dimensions. Due consideration should also be given to occlusion and harmony of the final restoration with the adjacent dentition.

Computerized three-dimensional magnetic resonance imaging reconstructions of temporomandibular joints for both a model and patients with temporomandibular pain dysfunction.

The aim of this study was to assess computerized three-dimensional reconstruction of magnetic resonance images generated of a temporomandibular joint model and the temporomandibular joints of five patients with varying degrees of temporomandibular joint pain and dysfunction. The three-dimensional image reconstruction of an artificial temporomandibular joint model, consisting of a human dried skull and synthetic disk, was used to test the accuracy and reproducibility of the three-dimensional technique. It was found that computerized three-dimensional reconstruction improved the display format of magnetic resonance imaging by enabling multiple two-dimensional images in shades of grey to be viewed as one three-dimensional image with anatomic structures colored as desired. Further, by rotating this image, the anatomic relationships of the temporomandibular joint could be seen from any viewpoint. Volume measurements showed accuracy and reproducibility by independent operators. Computerized three-dimensional reconstruction was applied to the magnetic resonance images obtained from patients. They were used to assess magnetic resonance imaging technique and its applications for interpreting the clinical findings. Disk position, as revealed by the three-dimensional images, was found to correspond with the clinical assessment, except in two instances when the original, right-sided, magnetic resonance imaging was unclear. Three-dimensional reconstruction was simple to apply, required no patient involvement, and made multiple magnetic resonance images easier to interpret.

Stability of captopril in powder papers under three storage conditions.

The stability of captopril in powder papers under three different storage conditions was determined. Captopril 12.5-mg tablets were triturated with lactose to a final concentration of 2 mg of captopril in 100 mg of powder. A total of 240 powder papers were prepared and stored in class "A" prescription vials (80 papers), 002G plastic zip-lock bags (80 papers), and Moisture Proof Barrier Bags (80 papers). Immediately after preparation and at 1, 2, 3, 4, 8, 12, and 24 weeks of storage at room temperature, powder papers under each storage condition were reweighed and the contents were assayed for captopril concentration by a stability-indicating high-performance liquid chromatographic method. More than 90% of the initial captopril concentration was retained under all storage conditions during the first 12 weeks of the study. Captopril disulfide, a degradation product, was detected in one sample stored in a plastic zip-lock bag at 24 weeks. Captopril was stable for the entire 24-week period in powder papers stored in either the class A prescription vial or the Moisture Proof Barrier Bag. Captopril in powder papers is stable for at least 12 weeks when stored at room temperature under all three storage conditions.