Comparison of three facebow/semi-adjustable articulator systems for planning orthognathic surgery.

Our aim was to measure the steepness of the occlusal plane produced by three different semi-adjustable articulators: the Dentatus Type ARL, Denar MkII, and the Whipmix Quickmount 8800, and to assess the influence of possible systematic errors in positioning of study casts on articulators that are used to plan orthognathic surgery. Twenty patients (10 skeletal class II, and 10 skeletal class III) who were having pre-surgical orthodontics at Liverpool University Dental Hospital were studied. The measurement of the steepness of the occlusal plane was taken as the angle between the facebow bite-fork and the horizontal arm of the articulator. This was compared with the angle of the maxillary occlusal plane to the Frankfort plane as measured on lateral cephalometry (the gold standard). The Whipmix was closest to the gold standard as it flattened the occlusal plane by only 2 degrees (P<0.05). The results of the Denar and Dentatus differed significantly from those of the cephalogram as they flattened the occlusal plane by 5 degrees and 6. 5 degrees (P<0.01), respectively. Clinicians are encouraged to verify the steepness of the occlusal plane on mounted study casts before the technician makes the model.

Use of articulators in the United Kingdom by consultant orthodontists in planning orthognathic surgery.

This questionnaire survey aimed to investigate articulator use in orthognathic surgical planning by consultant specialists in the United Kingdom (UK). A total of 205 questionnaires was sent to all consultant orthodontists in the UK. One hundred thirty questionnaires were completed, representing a 63.4% response rate. Consultants had been in their post for a median of 10.5 years (range 0 to 30 years) with a mean of 11.3 (SD 8.4) surgical cases per year. When asked which cases had been planned on a semiadjustable articulator, two thirds of consultants (67.7%) planned maxillary single-jaw procedures, 45.4% planned mandibular single-jaw procedures, and 77.7% planned bimaxillary procedures. While 98.5% of consultants reported access to at least one type of articulator, 14.6% of maxillary single-jaw and 5.4% of bimaxillary surgery was not planned on any articulator. Twice as many consultants who had been in their post fewer than 11 years had been trained on a semiadjustable articulator, compared to those who had more than 11 years of experience. Semiadjustable articulators were the most popular for planning orthognathic surgery. Consultants with less than 11 years of experience completed more surgical cases each year and were more likely to have been trained on a semiadjustable articulator than consultants with more than 11 years of experience. However, no link exists between the age of the consultant and the type of articulator selected for planning; this suggests that more mature consultants have received further training on contemporary articulator systems since receiving their accreditation.

Purification and characterization of ryanodine receptor 3 from mammalian tissue.

The ryanodine receptors are intracellular Ca2+ release channels that play a key role in cell signaling via Ca2+. There are three isoforms. Isoform 1 from skeletal muscle and isoform 2 from heart have been characterized. Isoform 3 is widely distributed in many mammalian tissues although in minuscule amounts. Its low abundance has hampered its study. We now describe methodology to isolate mammalian isoform 3 in amounts sufficient for biochemical and biophysical characterization. Bovine diaphragm sarcoplasmic reticulum fractions enriched in terminal cisternae containing both isoforms 1 (>95%) and 3 (<5% of the ryanodine binding) served as starting source. Isoform 3 was selectively immunoprecipitated from the 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonic acid (CHAPS)-solubilized fraction and eluted with peptide epitope. Isoform 3 thus prepared is highly purified as characterized by SDS-polyacryamide gel electrophoresis, Coomassie Blue staining, and by high affinity ryanodine binding. The purified isoform 3 was incorporated into planar lipid bilayers, and its channel properties were studied. Channel characteristics in common with the other two isoforms are slope conductance, higher selectivity to Ca2+ versus K+ (PCa/K approximately 6), and response to drugs and ligands. In its response to Ca2+ and ATP, it more closely resembles isoform 2. The first two-dimensional structure of isoform 3 was obtained by cryoelectron microscopy and image enhancement techniques.

Congenital aplasia of major salivary glands in a 4-year-old child.

The case of a 4-year-old girl with marked xerostomia and rampant caries is described. Investigation revealed complete aplasia of all four major salivary glands, which is extremely rare. Eleven primary teeth were extracted and a strict caries-preventive regime introduced. The patient had previously been advised to suck citrus-flavoured sweets to stimulate saliva flow, but this must be discouraged.