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This article presents a modified activator for treatment of open bite cases. The intermaxillary acrylic of the lateral occlusal zones is replaced by elastic rubber tubes. By stimulating orthopaedic gymnastics (chewing gum effect), the elastic activator intrudes upper and lower posterior teeth. A noticeable counterclockwise rotation of the mandible was accomplished by a decrease of the gonial angle. Besides the simple fabrication of the device and uncomplicated replacement of the elastic rubber tubes, treatment can be started even in mixed dentition when affixing plates may be difficult.

Tooth transposition is a positional interchange of two adjacent teeth. The most commonly transposed tooth is the permanent canine with either the first premolar or lateral incisor. The records of 54 subjects with transposed canines, both maxillary and mandibular, were collected. Pretreatment study models of these subjects were matched with a similar number of models from unaffected individuals. Bucco-lingual and mesio-distal tooth widths, arch depth and arch width were measured on each model. Thirty-four subjects (63 per cent) were female. Thirty-seven (68.5 per cent) of the cases involved the maxillary arch and thirty-three (89.2 per cent) of these upper arch transpositions were of the canine and first premolar. In cases involving the lower arch the canine was invariably transposed with the lateral incisor. Peg-shaped lateral incisors, supernumerary and/or congenitally absent teeth occurred in 19 subjects. There were some small, but significant differences in the dimensions of some teeth, however there were no statistically significant differences in arch depths, arch widths and most tooth dimensions in subjects with and without transposed canines. These factors do not appear to be related to the development of canine transposition.

The problem of late mandibular incisor crowding is a well established phenomenon, the cause of which has been the substance of considerable debate over the years. A central issue is the possible role of the third molars though no definitive conclusions have been consistently drawn. This prospective study was designed to investigate the effects of randomly assigned early extraction of third molars on late crowding of the mandibular incisors. One-hundred-and-sixty-four patients entered the study from 1984 following completion of retention after orthodontic treatment. Seventy-seven patients (47%) returned for records up to a mean of 66 months later, and their start and finish study casts were digitized on a reflex microscope to determine Little's index of irregularity, intercanine width and arch length. Forty-four of the patients had been randomized to have third molars removed. There was no evidence of responder bias. Where third molars were extracted the mean increase in lower labial segment irregularity was reduced by 1.1 mm from a mean of 2.1 mm for the group where third molars were retained (P = 0.15, not statistically significant). This difference was also not considered to be clinically significant. The principal conclusion drawn from this randomized prospective study is that the removal of third molars to reduce or prevent late incisor crowding cannot be justified.

The prevalence of occlusal features in 939 children, aged 6-13 years, belonging to an ultra-orthodox community of Jewish Ashkenazi descent living in Jerusalem was studied clinically. Sexual dimorphism was found for overjet, overbite, and habit practising. About one-quarter of the sample exhibited some degree of occlusal mutilation due to caries, thus creating a 'caries-affected' subgroup, the rest forming the 'caries-free' subgroup. In the latter set, normocclusion was scarce (7.4 per cent), Class I being the most frequent malocclusion (49.1 per cent). Caries had a significant effect on the symmetry of bilateral occlusal relationships, lower dental midline deviation, and on crowding/spacing conditions in the mixed dentition stage (except for the maxilla in late mixed dentition). The low prevalence of normocclusion can be attributed to genetic background, environmental influences and the definition attached to normal occlusion.

A mathematically determined technique which seemed to be valid for the calculation of crowding and spacing in arches with acceptable alignment, was tested on a series of arches with varying degrees of crowding and irregularity. Upper and lower study casts of 30 individuals with sufficient malalignment and crowding to warrant orthodontic treatment with fixed appliances were examined. Models were measured by three operators, using a reflex microscope interfaced to an IBM compatible PC and a customized calculation program. The degree of crowding was compared with a "clinical' assessment of each arch, in which the irregularity was measured directly using a steel ruler. Both the computer calculated and clinical values varied between observers, but the agreement between observers was better using the reflex microscope. Correlation coefficients ranged from 0.92 to 0.96 for the reflex microscope, and between 0.86 and 0.91 for the clinical assessment. Inter-observer agreement for the three operators was high: 0.93 for the reflex microscope and 0.87 where a ruler was used. This suggests that the computer program used to calculate the crowding was valid for the crowded arches under consideration.

This study was designed to test the accuracy of measurement methods for assessment of force and tooth movement in orthodontic procedures. Daily in vivo measurements of the force produced by activated archwires showed that the initial force declined substantially (by 20 per cent of mean value) within 3 days. Both the 'trueness' (validity) and precision of the force measurements, obtained with a strain gauge, were found to be high (SD values were 1.0 cN and 0.4 cN, respectively). Horizontal tooth movements were measured with three different instruments: a slide calliper, a co-ordinate measuring machine, and laser measuring equipment based on holograms. There was a good level of agreement between these methods. This was also confirmed by calibration data. The precision of the methods was (SD values) 0.06, 0.07, and 0.13 mm, respectively. The benefits of the use of the co-ordinate measuring machine are obvious, since it can measure tooth movements in relation to reference planes in all directions.

Skeletal and dental morphology, and related growth changes during a 3-year period following second permanent molar eruption, were compared in a group of 21 subjects who had no increase in lower arch crowding, with another group of 21 subjects whose lower arch crowding had increased by 1.0 mm or more during the same period. The crowding group showed a significantly greater increase in M3 space, forward movement of the second permanent molar and increase in the inter-incisal angle than the non-crowding group. None of the other parameters examined differed significantly.

A method of cephalometric analysis is presented in which molar and overjet corrections are seen as the algebraic sum of facial skeletal growth and tooth movement relative to basal bone. The steps of superimposition and measurement are described, and a means of summarizing these changes--the 'pitchfork diagram'--is suggested.

A simplified, mathematically determined technique for calculating arch perimeter (the overlap method) is described and its validity in determining an accurate assessment of crowding is tested. Indices, expressed in millimetres of crowding or spacing, were computed for both the whole arch and the labial segment alone. Study casts of 36 individuals with clinically acceptable lower arches were used to validate the method. The degree of crowding or spacing calculated was compared with a "clinical' assessment of each arch, in which the irregularity was measured directly using a steel ruler. Various calculation schemes were tested. Depending on exactly how the overlap was determined, the results varied slightly. Although the arches showed acceptable alignment, it was preferable to include a strategy for normalizing the positions of any rotated teeth before the overlaps were calculated. Repositioning any bucco-lingually displaced teeth into the line of the arch, however, was not useful. For the complete arch good agreement with the clinical assessment was reached on 31 occasions and for the labial segment, all but one appraisals were within 0.5 mm of each other. In the remaining instances (five complete arches and one labial segment), the degree of crowding or spacing was between 0.5 and 1 mm of the clinical assessment. Considering that clinical measurement of minor degrees of crowding and spacing cannot be precise, these results were considered acceptable. The method was easy to use, relying only on the recording of mesio-distal tooth widths and was acceptably reproducible. The technique would therefore appear to provide a valid yet simple research tool with which to record the degree of crowding. Its ability to cope with irregular and crowded arches will be the subject of a subsequent review.

The purpose of this study was to examine changes in lower incisor alignment at various developmental stages, from the time of eruption to the established permanent dentition and to try to predict the degree of crowding in the permanent dentition from that observed at earlier developmental stages. Forty-eight subjects (20 male, 28 female) with intact mandibular arches were selected from the Belfast growth study records. The lower incisor space condition was measured at each of four developmental stages: (1) initial eruption of the lower permanent incisors; (2) initial eruption of the permanent canines; (3) initial eruption of the second molars; (4) 3 years after eruption of the second molars. Differences in lower incisor space condition between each developmental stage were investigated and correlation analyses between the space conditions at each stage were carried out. On average, crowding of the lower incisors decreased to a statistically significant degree (- 0.9 mm) between stages 1 and 2, and increased between stages 3 and 4 (0.4 mm). Significant correlation coefficients between space condition at each developmental stage were found, but were considered unreliable as predictors of lower incisor crowding in the mature dentition.

This study examined the effectiveness of three different aesthetic ranking systems. The Aesthetic Component of the Index of Orthodontic Treatment Need (10 photographs), a numerical scale illustrated with three photographs and a numerical scale with only two photographs were assessed. Ten general dental practitioners ranked the attractiveness of dentitions using each aesthetic scale. A greater tendency to underscore was detected when the dentists used the two-photograph scale. Reducing the number of photographs in the aesthetic scale did not significantly improve the dentists ability to rank dental aesthetics.

The aim of the present long-term follow-up study of orthodontically-treated patients (mean: 15.7 years) was to analyse post-retention changes and to reveal factors which may play a role as predictors for long-term prognosis. Pretreatment, end-of-treatment, and post-retention models of 226 cases with all types of anomaly were used to measure intercanine and intermolar width, arch length, and sum of the mesiodistal dimension of the incisors, Irregularity Index, crowding, molar and canine relationship, overjet, and overbite. In order to assess the influence of sex, initial and end-of-treatment alignment, type of therapy, amount of tooth movement, and presence of third molars on the extent of post-retention changes, the total sample was divided into subgroups. Findings indicated that post-retention crowding and incisor irregularity increased more frequently in the mandible than in the maxilla. Pretreatment variables such as increased mesiodistal incisor dimension, severe crowding and incisor irregularity, arch length deficiency, arch constriction, and increased overbite as well as post-treatment spacing, arch expansion, increased arch length, and residual Class II or III molar relationships were found to be associated factors in the process of post-retention increase of crowding and incisor irregularity. 'Overexpansion' was found to be a factor in mandibular incisor relapse.

In the Begg Technique, factors controlling the anterior intrusive force provided by the archwire have yet to be fully clarified. The rationale for bite opening with very light forces, the effect of Class II elastics on intrusive force magnitude and the intrinsic quality of 'Australian' wire in bite opening are examined in this paper. A formula is presented which allows the intrusive force that archwires exert in different individuals to be predicted. The values derived from the formula were compared with case model measurements. It was found that the intrusive force of the archwire was affected by the length of the individual dental arch. The magnitude of this intrusive force was seen to increase gradually during the period of bite opening and appeared to be related to the use of Class II elastics. The study revealed factors which affected the magnitude of the intrusive force.

The Index of Orthodontic Treatment Need was applied clinically to a group of patients and later to study models and photographs taken at that same visit. Examiner reliability and agreement between the information obtained clinically and from diagnostic models was high. There was however, poor agreement for the Aesthetic component scored from photographs, when compared with scores recorded clinically or from models.

Three children suffering from facial asymmetry were observed annually using facial stereophotogrammetry before, during, and after their general skeletal adolescent growth spurt. Stereophotogrammetry allows accurate three-dimensional measurements between identifiable facial landmarks. Five pairs of bilateral parameters connecting external canthi and angles of the mouth to alae and tip of nose, and to each other, allowed a positive sign (right-side larger) or a negative (left-side larger) assessment of parameter asymmetry. Their total, taking sign into account, assessed mid-facial asymmetry. Serial observation showed that: (1) in patient no. 1 suffering from post-traumatic condylar hypoplasia, the facial asymmetry resolved; (2) in patient no. 2 suffering from unilateral facial hypoplasia, the asymmetry, which was severe, reduced with adolescence, but did not resolve; (3) in patient no. 3 suffering from fibro-osseous dysplasia of left maxilla, the asymmetry was reduced by surgery, but the full effects of the surgery were not measurable until over 1 year after operation; subsequently, the asymmetry began to increase again.

Thirty-four children with lower premolar crowding were treated by extraction of second molars. Thirteen cases had mechanical lower arch treatment started not less than 6 months after extractions. The remainder had no treatment in the lower arch. The change in premolar crowding was measured, and the reasons why spontaneous alignment occurred in some cases and not in others were examined.

The subjective need and demand for orthodontic treatment amongst 955 12-year-old Sheffield children has been assessed using the aesthetic component of the Index of Orthodontic Treatment Need and by a fixed choice questionnaire. When answering the questionnaire a greater proportion of females perceived themselves as having less attractive dentitions and greater treatment need despite any objective evidence to support this view. Of the children at the attractive end of the aesthetic component scale 84.5 per cent were prepared to accept orthodontic treatment of an unspecified nature.

An epidemiological investigation involving 765 Glasgow schoolchildren aged nine, twelve, and fifteen years was undertaken to assess the severity of malocclusion, the need for orthodontic treatment, and the proportion of children in each age group who had previously received treatment. An index termed the Malocclusion Severity Index (MSI) was developed to establish objectively the severity of malocclusion in each individual. Fifty sets of orthodontic study models and six orthodontists assessed the reproducibility and validity of the index. Although there was a significant reduction in the proportion of children in need of orthodontic treatment between 9 and 15 years of age, a considerable number were still in need of treatment; crowding of their dentitions being responsible for the majority of the treatment requirement. The MSI was found to be as precise and valid as previously developed occlusal indices, for estimating the treatment needs of sample populations.

During the study of two-hundred orthodontic cases under treatment in the General Dental Service, four clinicians showed only moderate agreement using the British Standard Classification of Incisor Malocclusion. Cohen's Kappa statistic was used to measure the inter-examiner agreement. The 35 cases in which there was high disagreement between the examiners were scrutinized to determine the source of this disagreement. Following discussion, revised definitions were produced which included the introduction of a Class II-intermediate group. After an interval of 2 months these 35 cases were reclassified using the new definitions. Increased inter-examiner agreement was found. Four examiners (three of whom were common to the original study) then used the modified classification to describe the incisal relationship of 100 cases referred for treatment at Bristol Dental Hospital. The inter-examiner and the intra-examiner agreement were both found to be good. It is recommended that the Incisor Classification of Malocclusion be extended to include a Class II-intermediate group.

This is the last of a three-part series examining the results of orthodontic treatment in a consecutive sample of malocclusion from a Welsh town. The cephalometric changes are compared for the different treatment regimes which were employed. Where the variables being examined were common to both radiographs and study cast records the treatment changes observed for the regimes were similar. Only limited 'skeletal' change, interpreted as a change in a few cephalometric measurements, was found to occur during treatment. Perhaps of most interest was the consistent reduction of 'A' point in the full fixed appliance group.

The Eastman Standard values for cephalometry were first described almost 40 years ago and their derivation is not clear. The present study examines the rationale for the Standard and considers the way it was originally described. Based on a sample of 30 cases of Class I occlusions with normally related skeletal bases the mean incisor angulations were found to be exactly on the Eastman Standard, which, therefore, still remains appropriate as a basis for assessment and treatment planning in orthodontics.

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.

An analysis is presented of the errors and variations in the Wits analysis and the angle ANB, using computer simulation. The method is applicable to any index where the identification errors have been established for the points and planes used in its derivation. A standard deviation may be determined for the index produced and the statistical distribution of values for any number of observations.

This study compares the results of cephalometric analyses using manual and interactive computer graphics methods. Results are statistically in favour of the interactive computer system. This study provides a basis for ongoing research into alternative methods of cephalometric analyses, such as digitization and automatic landmark identification using sophisticated computer vision systems.

Orthodontic treatment change was examined for 106 consecutively referred patients using serial lateral cephalometric radiographs and study cast records. The 2-D and 3-D measurement systems used to assess the changes were compared for five variables common to both sets of records. No statistical differences were found between the study cast and radiographic records for these variables. The 3-D measurement with the Reflex Metrograph showed marginally better precision in the measurement of the treatment changes examined. However, the main advantage was that it allowed a more thorough and accurate assessment of both individual incisor position and measurement error.

In a further study of serially treated cases from a Welsh town, the results achieved for crowding, tooth alignment, residual spacing, tooth rotation, arch dimension, and centre line discrepancy are examined. The initial stability of the treatment change in these variables is also presented.

Residual lower first premolar extraction space was examined in 43 subjects, 16 male and 27 female, 5 years after extraction; 16 subjects were treated mechanically, 27 had no active treatment. Forty per cent of extraction sites had residual spaces averaging 0.62 mm left and 0.71 mm right. Various parameters were measured to try to establish reasons for non-closure of spaces. These included buccal space condition and incisal space condition measured on the pre-extraction models, and alveolar atrophy assessed on final models. The angulation of second premolars and canine to the maxillary plane and molar space were measured on 60 degrees cephalograms. Changes in these three parameters were measured after superimposing a tracing of the pre-extraction film on the final film. Angulation of lower incisors to the maxillary plane was measured on pre-extraction 90 degrees cephalograms, and change in lower incisor angulation and position measured after superimposing a tracing on the final 90 degrees film.

For more than 35 years, research in the Department of Orthodontics, University of Washington has focused on a growing collection of over 600 sets of patient records to assess stability and failure of orthodontic treatment. All had completed treatment a decade or more prior to the last set of data. Evaluation of treated premolar extraction cases, treated non-extraction cases with generalized spacing, cases treated by arch enlargement strategies, and untreated normal occlusions demonstrate similar physiological changes. 1. Arch length reduces following orthodontic treatment, but also does so in untreated normal occlusions. 2. Arch width measured across the mandibular canine teeth typically reduces post-treatment whether the case was expanded during treatment or not. 3. Mandibular anterior crowding during the post-treatment phase is a continuing phenomenon well into the 20-40 age bracket and likely beyond. 4. Third molar absence or presence, impacted or fully erupted, seems to have little effect on the occurrence or degree of relapse. 5. The degree of post-retention anterior crowding is both unpredictable and variable and no pretreatment variables either from clinical findings, casts, or cephalometric radiographs before or after treatment seem to be useful predictors.

The technique of medial axis transformation of the outline form was used for the specific analysis of mandibular shape. When used to compare mandibular shape derived from lateral cephalographs between three equal samples of 30 female patients aged 12-15 years, marked overall similarity was noted between patients with Classes I, II and III occlusions. There were however subtle contrasts including the degree of coronoid and condylar separation and orientation of the ramus relative to the corpus. Such constancy of mandibular form derived from this technique of investigation was marked contrast to the data of traditional cephalometric studies which combine both size and shape parameters together. This study therefore demonstrated that shape appears less variable than size.

A case report is presented of a set of monozygotic twins aged 14 years, one of whom sucked her thumb and one who did not indulge in the habit. The thumb sucker had a wider lower arch and a narrower upper arch than the non-thumb sucker. The thumb sucker also appeared to have a more forward position of her premaxilla on cephalometric analysis together with an increased overjet. Superimposed outlines of the tongue showed that the thumb sucker was adopting a lower position of the dorsum of the tongue at the time of initial examination.

Thirty bimaxillary protrusion cases, who had four first premolars extracted were compared with thirty Class I malocclusion cases who, likewise, had similar extractions and treatment. The changes, both in incisor relationships and the concurrent soft tissue profiles are documented. During treatment, the inter-incisal angle was increased by 20 degrees and relapsed by 4 degrees post-treatment. The protuberance of the soft tissue profile was significantly reduced by 4 degrees concurrently (Holdaway Angle). It is concluded that worthwhile treatment objectives can be achieved in these cases.

In order to investigate both the relationship between perioral muscular activity and tooth position and also the clinical indicators of this activity, two quantitative EMG studies were carried out. The first investigated the reproducibility of the method in 16 adults. Subsequently, a study employing the same protocol was conducted on 41 subjects with untreated malocclusions. Activity was measured during speech, whilst chewing biscuit, swallowing saliva, resting, and in those subjects with incompetent lips, during lip-seal. In addition to the EMG recordings, measurements were taken from study models, lateral skull radiographs and of the clinical lip heights. In general between visits random variability was sufficiently small for the method to be applied experimentally. The results suggest that the effects of perioral muscular activity are determined by the presence or absence of competent lips. This was despite similar levels of activity in both groups except during chewing. Resting activity did influence incisor position in subjects with competent lips but the intermittent activity from chewing, speaking and swallowing, did not. No clinical indicators of the level of perioral activity were found.

Recognition by a parent or child of an occlusal abnormality is one of the many factors which may influence a desire for orthodontic treatment. Non-orthodontists may not estimate the severity of malocclusion reliably and may use different criteria from orthodontists for the process. The present study therefore sought to examine the reliability of parents' and children's perceptions of the children's own malocclusions with rating scales under two anchoring conditions and to test the discrepancy between their estimates and those of a panel of orthodontists. The children's and parents' assessments had limited test-retest reliability but instead of making guesses about the severity of their malocclusions they consistently gave low estimates. These effects were not influenced by the additional anchoring stimuli.

The skeletal morphology of bimaxillary dental protrusion has been investigated in a comparative cephalometric study. Because this is considered a subset of Class I malocclusions, the null hypothesis is that there should be no significant skeletal differences between this group and a Class I control group. There were 30 Caucasians in each group with no bias for age and sex differences between them. Eighteen radiographic landmarks were identified from which 33 skeletal, dental and soft tissue parameters were computed. The bimaxillary group had an average interincisal angle of 115 degrees versus the controls 135 degrees, and showed the following morphological features which persisted over a 5-year growth period: A shorter posterior cranial base. A longer and more prognathic maxilla. Similar mandibular dimensions and prognathism. A mild Class II skeletal pattern. A smaller upper and posterior face height. Diverging facial planes. A procumbent soft tissue profile with a low lip line. These findings indicate that there is a distinctive difference between the underlying skeletal patterns found in the two groups.

The lateral cephalometric radiographs of 56 adults with Angle Class II/2 malocclusion and of 81 persons with normal Class I occlusion are compared. The statistical analysis includes the calculation of the mean value, standard deviation and the determination of differences (Wilcoxon rank-test). Group characteristics are tested by stepwise discriminant analysis. The following statements regarding Angle Class II/2 as compared with normal Class I result from this study. The upper incisors are in a retruded position. The B-point is significantly retropositioned, whereas the pogonion is in a more normal position. The length of the mandibular corpus and the total length of the mandible are slightly diminished only. Normal values result for the size and position of the maxilla, the inclination of the mandibular corpus (angle between mandibular plane and NSe) and the gonion angle.

Two groups of subjects who demonstrated unilateral maxillary canine impaction were examined, a Caucasian group and an Oriental group. It was found that there are significant differences between the groups for sex of patients seeking treatment, site of impaction (buccal/palatal), and arch form. The Oriental group was significantly more crowded in the canine area than the Caucasian group. In almost all cases the dimensions of the lateral incisor on the side of impaction were smaller than the non-impacted side, although five subjects from the Caucasian female sub-group did not conform to this pattern, and for the Oriental male sub-group the mesiodistal crown width was larger on the impacted side.

A retrospective cephalometric study of Class II Division 1 malocclusions was carried out. Sixty patients with complete overbites were compared with another group of 60 matched in every respect, with the exception of having incomplete overbites. All patients were in the permanent dentition stage and aged between 10 and 14 years. An incomplete overbite was related to vertical variation in the skeletal pattern. This was demonstrated by greater anterior lower facial height, greater gonial angle, and steeper mandibular plane inclination. Incisor alveolar heights and molar heights did not vary between the groups. No differences between groups were noted for the degree of overjet reduction achieved during treatment, or in post retention relapse of overbite and overjet.

In cephalometric radiography, two angles have been commonly used, the saddle angle (NSAr) and the SNA angle. The former has been regarded as the cranial base angle, the latter as an indicator of the antero-posterior relation of the maxilla to the cranial base. In this study, a sample of 138 lateral skull radiographs of untreated orthodontics patients aged 7-15 years and analysed. The sample consisted of Angle's Class I, Class II, and Class III malocclusion cases. Means and standard deviations of the NSAr and SNA angles and the S-N and S-Ar lines for different malocclusion groups were estimated, and for each malocclusion group, the model of linear regression (y = bx + a) between the SNA and NSAr angles was computed. The mean of the NSAr angle was significantly larger in the Class II malocclusion group than in the Class III malocclusion group (p less than 0.05). The computed regressions indicated that about 14-40 per cent of the variation of the SNA angle in different malocclusion groups and about 24 per cent in the whole sample could be explained by the variation of the NSAr angle. Because at least a part of the correlation between the NSAr and SNA angles had a topographical causation, the main cause of this topographical correlation probably being the rotation of the S-N plane, the SNA angle was regarded as an unreliable indicator, the use of which can lead to considerable errors.

The case of a patient presenting with bilateral supplemental lateral incisors is reported. The upper lateral and supplemental on one side of the arch had a questionable prognosis due to extensive caries and at their removal the supplemental from the other side was successfully transplanted across the arch.

There is no widely accepted quantitative method for assessing occlusion. The wide variation in epidemiological studies is due to the use of quantitative terms, which are subjective and allow a broad range of interpretation. A new, simple reproducible and valid quantitative method of assessing occlusion which is suitable for epidemiological and clinical use is described. Four instruments are used for direct measurement of occlusal traits. An overbite gauge has been devised and three other measuring instruments have been modified to measure overjet and crowding of the teeth. Each dental arch is divided into three segments, an incisal segment and two buccal segments. Each segment is assessed in terms of intra-arch alignment and inter-arch relationship (in occlusion). The method has been field tested and proved to be practical and valid.

In the course of a multi-disciplinary investigation of 1018 children, standardized dental photographs and study casts were obtained. It has been shown that panel ratings of dental attractiveness from standardized photographs have good validity, high intra- and inter-judge reproducibility and to be representative of lay judgement. However, such ratings compound an appraisal of cleanliness, tooth colour and gingival health in addition to purely orthodontic features. In order to isolate the latter, attractiveness ratings of study casts were made by a three person panel using visual analogue scales.

Basic descriptive cephalometric data are presented for 30 individuals with untreated Class II Division 1 malocclusions, 15 males and 15 females. Two radiographs of each subject were examined, the mean age for the first being 12 years one month, and for the second 17 years five months, thus spanning the period during which orthodontic treatment is usually carried out. Mean values for 38 bony and dentoalveolar parameters were calculated, and the male and female groups were compared. There was a tendency on average to a mild skeletal II pattern, with mild mandibular retrognathism. The mean increase in many of the linear measurements in the males was up to three times that seen in the females, and the females had a more downwards and backwards pattern of mandibular growth rotation than the males.

Lateral skull radiographs of 66 subjects with Class III malocclusion, characterized by lingual occlusion of the upper incisors and a degree of overbite, taken before and after treatment were compared with a Control Group of similar mean age and interval between films. Vertical, Horizontal and Oblique measurements were made to establish the part played by overclosure and anterior displacement of the mandible in the aetiology of Class III malocclusion. The results suggest that both may play a part but that the former is of more general significance than the latter.