[Orthodontics in general practice 4. Impaction of maxillary front teeth]. / Orthodontie in de algemene tandartspraktijk 4. Eruptieproblemen in het bovenfront.

Eruption failures in the maxillary frontal region occur during the mixed dentition period. Dislocation and impaction of central incisors are diagnosed during or at the end of the early mixed dentition stage. These failures can be caused by crowding, premature loss of deciduous teeth, trauma or supernumerary teeth. Occasionally, a preventive orthodontic treatment is desirable to release the obstructed eruption path of a canine. Sometimes, a surgical intervention may be indicated to expose an obstructed central incisor and to remove supernumerary teeth. Retention and impaction of canines are generally discovered late in or after the late mixed dentition stage. In the agenesis of the lateral incisors or peg-shaped teeth, there is frequently impaction of the canines. General dental practitioners must be alert for possible deviations in the pattern of change in dentition right from the early mixed dentition period. Conventional two-dimensional radiographs can sometimes unjustifiably suggest a bad prognosis of an impacted tooth. Cone-beam CT scanning, which gives a three-dimensional image, can provide important additional diagnostic information.

[Orthodontics in general practice. 2. Treatment of eruption failures]. / Orthodontie in de algemene tandartspraktijk. 2. Behandeling van eruptieproblemen.

Since the introduction of composites and bonding in orthodontics, the possibilities of aligning impacted teeth into the dental arch after a surgical intervention, have remarkably increased. There are 4 important treatment techniques. The closed-eruption technique includes bracket-bonding to and ligating of the exposed tooth, followed by repositioning of the mucosal flap. The disadvantage of the method is the uncontrollable orthodontic force on the non-visible tooth during orthodontic extrusion. The open-eruption technique aims at keeping the exposed tooth visible, followed by spontaneous eruption. However, the exposure appears often as a radical exposure with unfavourable gingival consequences. The open-eruption technique with apical positioned mucosal flap is designed to expose teeth highly buccally impacted. The mucosal graft may cause a typical thick, stretched and not aesthetically acceptable gum after orthodontic treatment, even in case of using a split-thickness graft. The modified window technique is an open-eruption technique with minimal exposure, resulting in immediate eruption. If orthodontic treatment is required, the tooth is no longer impacted. The success rates of the 4 techniques vary from 75 until 99%. Study of the literature reveals insufficient scientific evidence in favour of 1 treatment technique. However, independent of the surgical technique applied, general practitioners play a crucial role in diagnostics of eruption failures and timely referral to an orthodontist.

Kinematic and kinetic analysis of distal derotational osteotomy of the leg in children with cerebral palsy.

Patients with cerebral palsy often develop rotational deformities of the lower extremities. These deformities may be caused by abnormal muscle tone, soft-tissue contractures, or bony malalignment. When rotational deformity persists after correction of the soft-tissue components, bony-realignment procedures are warranted to improve gait in ambulatory patients. We performed a retrospective review of 10 ambulatory children with cerebral palsy and tibial torsion who underwent 13 distal tibial and fibular derotation osteotomies. Preoperative and postoperative three-dimensional gait analysis were used to determine the effect of distal tibial and fibular derotation osteotomy on tibial rotation, foot-progression angle, gait velocity, and moments about the ankle. Mean tibial rotation and foot-progression angle were significantly improved by the procedure. Gait velocity improved but not significantly. Moment data demonstrated a trend toward normal. This study demonstrates that the derotational distal tibial and fibular osteotomy stabilized with percutaneous crossed Kirschner wires is a safe, reliable, and effective procedure for correcting rotational deformities of the leg in patients with cerebral palsy.

Distal tibial/fibular derotation osteotomy for correction of tibial torsion: review of technique and results in 63 cases.

Despite a tendency for rotational abnormalities of the lower leg in children to improve spontaneously over time, some fail to correct and require corrective derotation osteotomy. In this retrospective study, we report the technique and results of the distal transverse tibial and fibular derotation osteotomy with Kirschner-wire fixation performed in 63 limbs of children with cerebral palsy, clubfoot, idiopathic tibial torsion, and myelomeningocele, as well as other less common conditions. There were no significant infections, neurologic complications, delayed or nonunions, or compartment syndromes as a result of the osteotomy. There were three (4.8%) complications, including late fracture (one), cross-union (one), and distal physeal closure (one). We conclude that transverse, same-level, distal tibial and fibular osteotomy fixated with crossed Kirschner wires is a safe, efficient, and effective surgical approach to the treatment of children with tibial torsion in a variety of clinical conditions.

[Impacted teeth]. / Geïmpacteerde elementen.

Prevention of impaction depends in many cases on the knowledge of variations in eruption sequences. However, in case of impaction, spontaneous eruption can be stimulated by exposing the tooth with the modified window-technique. Frequent communications between dentist, orthodontist and oral surgeon are required to determine the right time of intervention.

In vivo tracking of the human patella.

The purpose of this study was to describe the dynamic, in vivo, three-dimensional tracking pattern of the patella for one normal male subject. Intracortical pins were inserted into the patella, tibia, and femur. The subject performed seated and squatting knee flexion/extension, and maximum voluntary quadriceps contractions. In addition, the vastus medialis oblique was subjected to maximal electrical stimulation. Motions of the markers attached to the intracortical pins were analyzed using an automated video system. Patellar and tibial motions were determined relative to a femoral reference system. While the tibia flexed 50 degrees from full extension (seated condition), the patella flexed 30.3 degrees, tilted laterally 10.3 degrees, and shifted laterally 8.6 mm. In general, these results show qualitative agreement with the data collected from cadaveric specimens [van Kampen and Huiskes, J. orthop. Res. 8, 372-382 (1990)]. The differences present may reflect different passive constraints to patellar motions, and different relative loading of the individual quadriceps components, in our study compared to the cadaveric study. Only small differences were found between patellar motions in the seated and squatting conditions. Differences in patellar displacements produced by (1) maximal electrical stimulation of the vastus medialis oblique, and (2) maximum voluntary quadriceps contraction, at 30 degrees knee flexion and full extension, may reflect the dominant influence of passive constraints, and the vastus lateralis, on normal patellar motions. Further in vivo study of patellar tracking seems warranted to evaluate surgical and conservative interventions for patellofemoral disorders.

[Impacted maxillary cuspid. III. Orthodontic aspects]. / De geïmpacteerde cuspidaat in de bovenkaak. III. Orthodontische aspecten.

Delayed eruption of impacted canines in more or less guaranteed by using the modified window technique. A decision for futher treatment can be made afterwards. If orthodontic treatment is required, fixed appliance is recommended for uneventful orthodontic positioning of these teeth.

[Impacted maxillary cuspid. IV. Periodontal aspects]. / De geïmpacteerde cuspidaat in de bovenkaak. Deel IV. Parodontale aspecten.

Treatment goal of the maxillary impacted cuspid should include health periodontal end results. This clinical and radiographic study reveals in 75% of the cases a satisfying periodontal condition.

[Impacted maxillary cuspid. I. Etiology and diagnosis]. / De geïmpacteerde cuspidaat in de bovenkaak. I. Etiologie en diagnostiek.

Attention is paid to the normal and disturbed eruption of the upper cuspid. Genetic factors seem to play the most important role in impaction or delayed eruption. The dentist needs to be aware of the diagnostic and roentgenological features of this phenomenon.

[Impacted maxillary cuspid. II. Releasing by means of a modified fenestration technique]. / De geïmpacteerde cuspidaat in de bovenkaak. II. Vrijleggen door middel van de gemodificeerde venstertechniek.

A review of the treatment of the impacted upper cuspid is presented. A description of a modified exposure technique is given. Up to the present day more than 400 impacted cuspids have been treated with this technique.

Strengthening the Montreal protocol: does it cool down the greenhouse?

Strengthening of the Montreal Protocol is recently being negotiated in London in 1990 in order to achieve further reductions of the regulated CFCs and to include possibly more substances. In this article the implications of different policies with respect to control of ozone depleting substances for climate change are analysed, including the proposed substitution by HCFCs and HFCs, carbon tetrachloride and methylchloroform. A special halocarbon module was developed within the framework of RIVM's Integrated Model to Assess the Greenhouse Effect (IMAGE). IMAGE is a parameterized science based policy model and has been developed to give policy agencies a concise overview of the quantitative aspects of the greenhouse problem, to evaluate various policy options concerning climate change and to serve as a means of communication. It is concluded, from simulations with the halocarbon module, that it is of primary importance to achieve a further reduction of the regulated CFCs compared to the Montreal Protocol with compliance by as many countries as possible. From the perspective of the greenhouse effect the inclusion of longer lived halocarbons, such as carbon tetrachloride and HCFC-22 in the protocol comes second. The application of methylchloroform, halons and HCFCs and HFCs with lower global warming potentials (GWPs) than HCFC-22 contributes only marginally to the greenhouse effect in comparison with the much more important greenhouse gases carbon dioxide, methane, ozone and nitrous oxide. Especially if further growth of the total production of HCFCs after complete replacement of the present CFCs can be avoided by using these alternatives with a lower GWP, these substances could therefore be tolerated in a transition period, from the perspective of global warming.