British Journal of Orthodontics

ISSN: 0301-228X (Print) (Online) Journal homepage:

British Society for the Study of Orthodontics Report of the Meeting held on lOth February 1992 S. Wigglesworth & R. Nashed To cite this article: S. Wigglesworth & R. Nashed (1992) British Society for the Study of Orthodontics Report of the Meeting held on lOth February 1992, British Journal of Orthodontics, 19:4, 355-356, DOI: 10.1179/bjo.19.4.355 To link to this article:

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Meeting Report


Meeting Report British Society for the Study of Orthodontics Report of the Meeting held on lOth February 1992 Mr Harry Orton, the President, welcomed members and guests to the February meeting of the BSSO. He Was pleased to announce that Professor D. Foster, ~r J. Graveley and Mr G. Rose had been elected as hfe members of the Society. He then presented Mr lain Ha thorn, the previous meetings secretary, with ~silver salver and the BSSO Special Service Award tn recognition for his services to the Society. Or Roland Smith then gave his Chapman Prize winning essay entitled 'The Effect of Upper Second Molar Extractions'. The extraction of these teeth has long been popular in the treatment of mild crowding and to facilitate the distal movement of the upper first molars. However, there is an area of controversy in the literature surrounding the possibility of over eruption of the lower second molars When their opponents are removed. The aims of the study were to quantify the vertical Positions of the lower second molars, following the extraction of upper second molars. Study models of an experimental group of 44 cases were examined and compared with a suitably matched control group. Measurements were made of the vertical Positions of the marginal ridges and relative eruptive height of the lower second molars and upper third molars, using a travelling microscope. He found that the distal marginal ridge of the lower second molar was significantly higher in the experimental group than in the control. However, he also found that the relative height of the lower second molar was partly determined by the position of its opposing upper first molar. The further distally the upper first molar is placed, the less the second molar over erupts at its mesial marginal ridge, but the distal margin ridge is even higher. The upper third molars had no significant effect on the over eruption of the lower second molars since they erupt so much later. Their final position, however, is not often good. He showed that 41 out of the 81 third molars examined were not in an ideal relationship to their adjacent first molars. The clinical implication of this treatment to the temporomandibular joint, the functional occlusion and the periodontum were addressed. The only finding of significance related to the periodontal health of the upper first molars. This was found to be worse in the

experimental group due to poor oral hygiene. which was worse in the experimental group. He suggested a useful modification to the Hawley retainer with acrylic blocks extending distal to the upper first molars to occlude with the lower second molars, and prevent their over eruption. The second paper of the evening was given by Professor Hans Pancherz and was entitled, 'The Herbst Appliance-A Fixed Functional Appliance for Class II Treatment'. This appliance was first described as a fixed bitejumping appliance by Kingsley in 1877. Herbst in 1905 developed the appliance further and in 1934 wrote a series of articles on it which were largely ignored until 1977 when Professor Pancherz started to use the appliance. The advantages of the Herbst appliance over other functional appliances are that it is worn full-time, no co-operation is required and treatment time is short. It consists of a telescopic mechanism which keeps the mandible protruded and is cemented to the teeth by Cobalt/Chromium splints, these having replaced the bands previously used. It allows opening, closing and lateral movements of the mandible. He analysed 150 cases treated by the Herbst appliance, 70 of which have now been followed up for between five and ten years. The records taken include study casts, lateral skull radiographs, hand radiographs, height measurements, EMG recordings and temporomandibular joint radiographs. Professor Pancherz first addressed the effects of the appliance on the dento-facial complex by examining 42 cases with an initial ANB angle greater than 4 degrees. The molar correction of6·7 mm was achieved by both dental (57%) and skeletal (43%) movement. Of the latter, 37% was as a result of the mandible coming forward and 6'Yo the maxilla moving backwards. The average overjet reduction was 5·2 mm. This was reduced by a similar combination of skeletal movement making up 56% ofthe change and dental movement 44%. A significant number of cases relapse and a further study showed that 90% of the post-treatment relapse occurred in the first six months. This was mostly dental in origin and was assumed to be due to the occlusion settling. Over the longer term,

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greater than five years out of retention, identifiable factors were sought as to why a certain number of cases were unstable. The upper first molars were found to have moved mesially in the relapse group and an atypical swallowing pattern was felt to be the main contributory factory. The appliance did not result in an increased growth of the mandible. Changes were examined from five different aspects. Although the initial changes were encouraging, the net changes were insignificant. Professor Pancherz accepted that over the long term follow-up period, there is a merging of the growth charts of those treated by the Herbst appliance with those in the control group. Examination of the temporomandibular joints of 19 cases, using tomograms, showed normal condyl to fossa relationships, and only l out of the 19 showed any structural change in the bony components. The effects of the appliance on the maxilla were to give a high-pull headgear effect, and its greatest contribution was in molar distalisation and intrusion. However, these effects were only temporary.

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The general indications for the use of the Herbst appliance were in the treatment of Class 11 patients with retrognathic mandibles, who were growing and where a 2 to 3 step treatment approach was indicated. However, he suggested that there were a number of specific indications for its use and these were that patients should be in the permanent dentition, mouth breathers, and with a history of poor co-operation, having had no previous response to a removable fundtional appliance. Treatment being delivered in the late period of growth tended to reduce the treatment time, the retention time and the risk of post-treatment relapse. The result was retained with an Andreason activator which held the tooth position and also trained the muscles to adapt to their new positions. Perhaps Professor Pancherz' most illuminating admission was that he only uses this approach to treatment in 5'% of cases, where all else has failed. S. WIGGLESWORTH R. NASHED

British Society for the Study of Orthodontics. Report of the meeting held on 10th February 1992.

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