Journal of Orthodontics

The findings of some 26 papers covering the results of Andresen and Fränkel appliances, as analysed from cephalometric radiographs, are reviewed. These findings show a high degree of consistency. They have been combined to produce larger samples and compared with a control group produced from reports of untreated Class II division 1 individuals, with consequent gains in statistical significance. Generally, there is no appreciable holding back of maxillary advancement in either group (although a slight relative reduction in the angle SNA). There is a slight mean increase in mandibular growth, mainly in a vertical direction. This seems similar to that reported by several authors in conventional appliances. There is a wide variation in response.

A commonly used cephalometric analysis was performed repeatedly on five lateral cephalometric radiographs using a variety of methods, and the angular values obtained compared. Two computerized methods, one utilizing direct digitization of the radiograph and the other digitizing an enhanced video image of the radiograph, were compared with each other and also against the traditional manual method of tracing. In addition, a single manual tracing of each of the radiographs was digitized using each computer method. It was found that direct digitization is less precise than both the traditional method and digitization of a tracing. The facility to enhance the radiographic image using video techniques did not produce any significant improvement in precision of the cephalometric variables studied.

The reliability and validity of four methods of assessing skeletal pattern (Reidel's method, Eastman correction, Ballard's method, and ‘Wits’ analysis) from cephalometric tracings have been examined, and the levels of agreement between them investigated. The possibility of the Y-axis length and SN—Y-axis angle having a bearing on the skeletal pattern was also examined. Strong correlation was found between the four methods considered. Ballard's method correlated very closely with Reidel's method, and like ‘Wits’ method, is not as unreliable as previously reported. Measurement of the SN—Y-axis angle was not found to be of benefit to the assessment of the anteroposterior dental base relationship. Reidel's method, which is the easiest to apply, is recommended as the method of choice, and routine application of the Eastman correction is not recommended.

The shear/peel and tensile/peel bond strengths of mesh-backed orthodontic brackets bonded to porcelain, using a highly filled composite and four different silane bonding agents were determined. Sites of failure were recorded for each method of testing. A method of debonding and restoring the procelain surface to its original state after debonding was also investigated. All silane bonding systems tested provided adequate bond strength for clinical use. Fusion produced significantly higher force values to failure in shear testing. There was no significant difference between the bond strengths obtained in tensile testing. Patterns of failure differed in each mode of testing, suggesting that a shear mode of debonding is more likely to cause porcelain fracture and that the possibility of porcelain fracture during function or debonding cannot be excluded. The use of a Lift-Off plier is recommended in debonding brackets from porcelain where a silane bonding agent has been used. Diamond polishing paste was better at restoring the procelain surface to its original appearance than Shofu polishing stones.

The Reflex Microscope has become a standard instrument for the precision measurement of orthodontic record models. In this study, 31 individuals with no previous experience of the microscope were assessed for their precision at identifying well defined landmarks. Considerable initial variation existed in the precision of landmark identification, but despite only a limited training period, some of the novices tested achieved a high standard of precision. Mean errors were greatest in the z axis, i.e. along the axis of the eye, and astigmatism was common amongst those recording the greatest errors in this axis. A group of individuals who performed poorly initially, were retested after additional training and practice with the microscope. Method errors were significantly reduced for the majority of those retested, but the test apparatus identified two individuals for whom further measurement with the microscope would be inadvisable.

The treatment of two patients is described in which neodymium iron boron magnets are used to assist unerupted premolars into the mouth.

A new technique is presented for the construction and use of a typodont Suitable for teaching correct bracket positioning. The advantages of the method are illustrated.

A case is presented in which two supernumerary teeth developed in the mandibular premolar region during orthodontic treatment. Their presence was only detected on a routine post-treatment radiograph. The Potential hazards of space closure with such teeth present are considered, although there were no detrimental effects in the case illustrated.

A case report is presented of a Class III malocclusion with a Class III skeletal pattern and maxillary retrusion. The patient, an 11-year-old girl, was treated with an orthopaedic face mask in conjunction with standard Edgewise mechanics.

Treatment was completed after 14 months, and proved to be stable following the active treatment and at recall 4 years later.

Some problems associated with the diagnosis of the ectopic maxillary canine are discussed. A treatment regimen is outlined for the tooth that is displaced palatally and unerupted.

Two Norfolk Terriers were used as experimental subjects to investigate the means by which human beings relate to Norfolk Terriers in maintaining their Overall dental health. The study was divided into two parts: the Hard Cheese Study (HCS) and the Oral Hygiene Study) (OHS). The difficulties in conducting experiments on this breed are highlighted and an evaluation of random error in measurements is undertaken using an Index termed Jaw Occlusions in a Kennel Environment (JOKE).