A validation of two orthognathic model surgery techniques.
In order to create an evidence-based orthognathic surgery planning protocol, an investigation of two popular model surgery techniques, the Lockwood keyspacer and the Eastman anatomically-orientated system was carried. This determined (a) the accuracy of positioning of the maxillary cast according to the prescribed treatment plan and (b) the relocation of the maxilla after a simulated Le Fort I down fracture osteotomy using the intermediate wafer as a guide. Fifteen patients-five Class II division 1, five Class II division 2, and five Class III-were included in the study. All the measurements were taken with Erickson's vertically mounted electronic caliper and variations from the treatment plan were analysed. The mean model surgery positioning errors +/- SD (mm) were: (i) vertical plane-Lockwood -0*8 +/- 1*6 and Eastman 0*00 +/- 1*0 (P = 0*0001); (ii) anteroposterior plane-Lockwood 1*2 +/- 1*8 and Eastman -0*1 +/- 1*4 (P = 0*05); and (iii) transverse plane-Lockwood 0*9 +/- 0*9 and Eastman 1*0 +/- 0*9 (P = 0*34). After the simulated osteotomy, the mean errors +/- SD were: (i) vertical plane-Lockwood -0*5 +/- 1*5 and Eastman 0*3 +/- 1*1 (P = 0*001); (ii) in anteroposterior plane-Lockwood 0*8 +/- 2*0 and Eastman 0*7 +/- 1*0 (P = 0*89); and (iii) transverse plane-Lockwood 0*8 +/- 0*6 and Eastman 0*7 +/- 0*5 (P = 0*83). The Eastman technique was relatively better especially in the vertical plane. The variations from the treatment plan were on the whole anatomically small, but in some cases could be clinically significant. (+info)
Functional occlusion: II. The role of articulators in orthodontics.
Opinion is divided on whether there is a place for the use of semi-adjustable dental articulators in orthodontics. In this review we explore the validity and reproducibility of the techniques involved in mounting study models on a semi-adjustable dental articulator. We also look at the role of articulated study models in orthodontic diagnosis and treatment planning, in the finishing stages of orthodontics and in planning for orthognathic surgery. We report that each of the many stages involved in mounting study models on a semi-adjustable articulator is a potential source of error and that only if the technique is carried out with a high degree of accuracy is it worth the additional chairside time. (+info)
The use of specific dental school-taught restorative techniques by practicing clinicians.
In 1995, a survey requesting information about the utilization of certain prosthodontic techniques was mailed to 3,544 graduates of a midwestern dental school. Responses were received from 1,455 alumni, representing a 41 percent return rate. In general, the results are consistent with international and national trends and show significant disparity in the utilization rates of certain procedures between general dentists and prosthodontists, as well as a disconnect between what is taught in the undergraduate dental educational program and what is applied in practice. For example, while prosthodontists typically apply what was taught in their educational program, utilization rates of general dentists for the facebow was 29.64 percent; the custom tray 68.48 percent; border molding 58.67 percent; altered casts 24.10 percent; custom posts 49.29 percent; prefabricated posts 67.54 percent; and semi-adjustable articulators 50.64 percent. While no solutions to this disconnect are offered the authors do pose important questions that must be addressed by the dental educational community. (+info)
The examination and recording of the occlusion: why and how.
Before presenting 'how' the examination and recording of the occlusion may be achieved, some attempt should be made to justify 'why' it is necessary. It may appear to be a strange way of justifying the need to examine the patient's occlusion, but this will initially involve a study of the influences of mandibular movements. (+info)
Good occlusal practice in advanced restorative dentistry.
In most patients the existing occlusal scheme will be functional, comfortable and cosmetic; and so if a tooth or teeth need to be restored, the most appropriate way to provide the restoration(s) would be to adopt a 'conformative' approach: that is to provide treatment within the existing envelope of static and dynamic occlusal relationships. There will, however, be situations where the conformative approach cannot be adopted, and this section aims to describe what is 'Good Occlusal Practice' in these circumstances. (+info)
Good occlusal practice in removable prosthodontics.
The loss of teeth may result in patients experiencing problems of a functional, aesthetic and psychological nature. This section addresses the very important subject of occlusal considerations for partial and complete dentures. The occlusion is particularly important given the bearing that occlusal factors have, especially on edentulous patients. (+info)
Correlation between facial morphology, mouth opening ability, and condylar movement during opening-closing jaw movements in female adults with normal occlusion.
The aim of this study was to investigate the relationship between parameters of facial morphology, maximal voluntary mouth opening ability, and condylar movements in 21 adult females, aged between 20 and 24 years. The subjects had a normal occlusion without sign or symptoms of temporomandibular joint (TMJ) dysfunction. Mandibular movements were recorded using an opto-electric jaw movement recording system with six degrees of freedom under a series of maximal mouth opening-closing movements. Maximal jaw opening and coincident condylar movement were measured three-dimensionally. The mean values of the incisor and condylar path were 41.1 +/- 3.5 mm (range 35.6-50.9 mm) and 12.8 +/- 2.8 mm (range 8.1-19.2 mm), respectively. Although the positive correlation between maximal jaw opening and facial morphology was significant, none of the variables significantly differed between the value of the condylar path and facial morphology. The length of the path of maximum incisor movement and the condylar path during mandibular movement also did not correlate. Stepwise multiple regression analysis indicated a positive association between the maximal length of the incisor path and the cephalometric value of mandibular ramus inclination (R2 value was 0.369). The results of this study suggest that facial morphology size has a limited effect on maximal voluntary mandibular opening and condylar movements in normal adult female subjects. (+info)
Condylar pathway changes following different treatment modalities.
The purpose of this investigation was to evaluate the effect of extraction and non-extraction approaches on the condylar pathways in subjects treated with fixed orthodontic appliances. The study was carried out on 70 patients (47 female, 23 male) who had undergone orthodontic treatment with fixed appliances. The mean age for the total group was 16.3 years (16.5 years for the females and 16 years for the males). Forty-seven patients were treated non-extraction and 23 with extractions. None of the patients had any temporomandibular joint (TMJ) problems before orthodontic treatment and all were treated with standard edgewise mechanics. The condylar pathway recordings were taken before and after treatment with an axiograph. The maximum opening capacity was measured and the right and left condylar pathways of each patient were recorded in protrusion and during opening movements. During treatment the left opening angle (LOA) only decreased significantly in the upper premolar extraction group. The left opening distance (LOD) decreased in all groups during treatment but was only statistically significant in the non-extraction and upper and lower extraction groups. In the small overjet group (OJ < or = 4 mm), the LOA, right opening distance (ROD) and LOD decreased significantly while there was no significant change in axiographic parameters in the large overjet group (OJ > 4 mm). In the latter group, overjet and overbite decreased while mouth opening (3 mm P < 0.05) significantly increased. These results indicate that there is no difference between the effect of different treatment protocols on the condylar pathways. (+info)