An assessment of surgical and 10-year follow-up vertical changes after contemporary Class II and III orthognathic surgery.

INTRODUCTION: There has been little quantification of long-term vertical facial changes that might occur after contemporary orthognathic surgery. The aim was to assess ≥10-year follow-up vertical facial changes in patients after Class II and III orthognathic surgery. METHODS: Sequential lateral cephalograms of 162 former orthognathic patients had been gathered during routine clinical follow-up before any consideration was given to this current project. For this study, facial patterns were classified according to the Frankfort-mandibular plane and ANB angles and the horizontal distance from the pogonion to the nasion-perpendicular line. Chosen Class II and III groups were divided into longer and shorter-face subgroups on either side of the average FMP angle (longer face >25°). The assessment was made from already-available lateral cephalograms taken before treatment, at debanding, and ≥10-year clinical follow-up. RESULTS: After obvious improvement with orthodontics and orthognathic surgery, mean FMP angles seemed to move back toward the preexisting vertical dimensions in both Class II and III longer and shorter-face groups over the next decade. However, there was considerable individual variation around the means. Similar posttreatment changes were seen with the ANB angle and the distance from pogonion to the nasion-perpendicular line. Significant correlations were found between the amount of preexisting discrepancy for these variables and their changes during and after treatment. CONCLUSIONS: Significant planned vertical mandibular changes are achieved with Class II and III surgery. However, in the longer term, it would seem that, in general, there is a tendency for postsurgical vertical facial proportions to revert somewhat toward the pretreatment proportions. Wide individual variation in posttreatment musculoskeletal behavior should be expected. Despite these changes, it does not necessarily mean that there should be an expectation of long-term dentofacial collapse after such treatment.

Three-dimensional computed tomographic assessment of mandibular muscles in growing subjects with different vertical facial patterns.

AIM: The present study was undertaken to assess the relationship between the mandibular muscles and dentofacial skeletal morphology in children with different underlying vertical facial patterns, using three-dimensional computed tomography (3D-CT). METHOD: Thirty children (mean age 12.24 ± 1.57 years) underwent cranial CT examination for diagnostic purposes. 3D-CT images were reconstructed for the evaluation of the cross-sectional size, volume, and spatial orientation of the masseter and medial pterygoid muscles. These muscle parameters were also assessed in relation to the vertical facial pattern, gender and skeleto-dental form. RESULTS: Significant differences were found in muscular angulation for subjects with different underlying patterns. Greater masseter volumes were associated with increased facial width. Greater intermolar widths were found in brachyfacial subjects, with less acute muscular angulations in relation to horizontal reference lines, compared with dolichofacial subjects. This was also more obvious in the maxillary arch. CONCLUSION: Clinicians should note the likely differences in masseter and medial pterygoid orientation and volume in subjects with different underlying vertical facial patterns and that these differences may, in turn, be related to both facial skeletal width and naturally-occurring transverse dental arch dimensions.

The Herbst appliance and the Activator: influence of the vertical facial pattern.

AIM: To compare the effects of the Herbst appliance and the Activator at the completion of two-phase treatment, with respect to the vertical facial pattern (VFP) and to identify possible predictors of treatment effect. MATERIALS AND METHODS: Pretreatment, post-treatment and overall cephalometric change data were used to assess the dental and skeletal effects. Results for the change in mandibular length were also compared with changes reported for an untreated external control group. RESULTS: Clinically significant dental and skeletal changes (including mandibular incisor proclination and overjet reduction) were characteristics of both treatment methods. Any increases in mandibular length and chin prominence were not greater than those expected following natural growth. The pretreatment VFP remained essentially unaltered, while mean changes as a result of treatment were similar for brachyfacial, mesofacial, and dolichofacial subjects. No predictive factors were identified. CONCLUSIONS: Clinicians are advised to expect significant overlet reduction and mandibular incisor proclination with either treatment method. Significant skeletal change may be observed in growing subjects; however, any increase in mandibular length or chin projection is not likely to be beyond the limit set by nature. While there will be some individual variation, no significant long-term alteration in the pretreatment vertical facial pattern should be expected with either treatment. Long faces will remain long and short faces will remain short.

Expression of neural crest markers by human embryonic stem cells: an introductory project.

INTRODUCTION: Neural crest cells make up a transient migratory population of cells found in all vertebrate embryos. Great advances have been made over the past 20 years in clarifying the molecular basis of neural crest induction and, although much still remains unclear, it appears that it is a process involving several factors acting at different stages of embryogenesis. In the future, an understanding of the precise mechanisms involved in orofacial development, even at the earliest stages, may well be of use to all clinicians interested in the management of these tissues. AIM: The present study was designed to determine if the early addition of noggin (a bone morphogenetic protein lBMP) antagonist) and/or the late addition of BMP4 would increase the expression of the transcription factors: Msx-1, Snail, Slug and Pax-7. METHOD: This involved an assessment of the effects of early addition ( Days 0 to 3) of noggin and/or the late addition ( Days 4 to 7) of BMP4 on2the expression of the neural crest markers by human embryonic stem cells, co-cultured for eight days on a feeder layer of mouse PA6 cells. RESULTS AND CONCLUSIONS: The expression of the neural crest markers Pax-7, Msx-1, Slug, and Snail by human embryonic stem cells is likely to be affected by the addition of noggin and BMP4. Not all of these effects will necessarily be significant. The late addition of BMP4 is likely to significantly increase the expression of Pax-7 by human embryonic stem cells (hESCs), when compared with the effects of co-culturing with stromal cell-derived inducing activity, alone. The early addition of noggin and the late addition of BMP4 are likely to significantly increase the expression of Msx-1 by hESCs, when compared with the late addition of BMP4, alone. The hESC results support those from animal ESC studies that the late addition of BMP4, especially, may result in the differentiation of neural crest precursors.

Arch-dimensional changes in non-extraction cases with finishing wires of a particular material, size and arch form.

AIM: This study was undertaken to assess pre- and post-treatment upper and lower arch dimensions, and changes occurring in those dimensions, during orthodontic treatment without premolar extractions, when finishing wires of a particular material, size and arch form had been used. METHODS: The records of 58 patients (31 male and 27 female) with a mean age of 13.52 (±1.60) years were selected for this study, with ethics approval gained from the Departmental Human Ethics Advisory Group of the University of Melbourne (DHEAG no: 1033997.1). All patients had been treated with fixed appliances (0.018 inch, pre-adjusted edgewise) in the early permanent dentition, without premolar extractions, by one experienced orthodontist. Pre- and post-treatment upper and lower arch dimensions were measured from study casts. Correlation coefficients were calculated between these measurements as well as pretreatment cast and vertical cephalometric measurements, gender and the amount of crowding that had been relieved. RESULTS: Despite the use of finishing archwires of the same material, size and arch form (0.016 x 0.022 inch, heat-treated cobalt-chromium), there was considerable variation in dimensional changes that occurred during treatment within the total sample and its various subgroups, and in the final arch dimensions. All arch width changes were found to be strongly correlated with the amount of pretreatment crowding. Post-treatment arch dimensions and changes in those dimensions were also strongly correlated with pretreatment dimensions, suggesting that the final post-treatment arch dimensions were significantly influenced by other factors rather than simply the material, size and arch form of the finishing wires. In this treated sample, no statistically significant differences were found in the resultant arch widths and arch width changes occurring in the different vertical pattern sub-groups. CONCLUSION: The placement of finishing wires of a particular material, size and arch form is unlikely to result in exactly matching end-of-treatment arch forms and dimensions in all orthodontic patients. Instead, whether using a 0.018 or a 0.022 inch slot system, the clinician should expect considerable individual variation in final arch form and dimension, despite the placement of apparently very similar wires. The main determinants of final arch form and dimension appear to be the original muscular and occlusally-related arch form and dimension and the amount of crowding to be relieved. Final arch forms and dimensional changes with treatment are unlikely to be directly related to patient gender, age or underlying vertical pattern. The findings indicate that clinicians must decide whether they will accept the considerable lateral and antero-posterior expansion that is likely to occur when crowding is to be relieved in the permanent dentition without premolar extractions.

Effects of the Herbst appliance in growing orthodontic patients with different underlying vertical patterns.

INTRODUCTION: The present study involved an assessment of the effects of the Herbst appliance used for Class II correction in subjects with different vertical facial patterns. METHODS: Pre- and post-treatment lateral cephalograms of 91 growing Class II patients were divided into three vertical facial groups on the basis of mandibular plane angulation. All received a Herbst appliance and dental and skeletal changes were assessed in relation to pretreatment incisal overbite, overjet and the stage of cervical maturity. RESULTS: Herbst appliance treatment was accompanied by changes in the angulation of the upper and lower incisors, overjet reduction and an increase in mandibular length. In general, the rotational facial changes occurring during treatment were minimal, so that dolichofacial patterns remained long and brachyfacial patterns remained short. CONCLUSION: Herbst appliance treatment can be expected to result in considerable Class II dental correction. It is unlikely, however, that its use will be associated with clinically significant forward rotation in dolichofacial subjects. Since dolichofacial patterns are likely to remain long-faced, even after considerable Class II dental correction, orthognathic surgery may still be a consideration if normal facial proportions, without excessive facial convexity and lip strain, are treatment aims.

A study of Class III treatment: orthodontic camouflage vs orthognathic surgery.

AIM: To evaluate the differences in pretreatment and post-treatment characteristics of Class III patients treated with orthodontic camouflage or orthognathic surgery, and to compare the range of skeletal, dental and soft tissue changes that are likely to occur with treatment, with particular reference to the influence of extractions on the resultant incisor angulations. METHOD: Pretreatment and post-treatment cephalograms of 31 Class III orthodontically-camouflaged patients and 36 Class III surgical patients (without genioplasty) were obtained from one specialist practice. From the surgical group, 26 pre-surgical lateral cephalograms were also obtained. Inclusion criteria for the two groups were at least three of the following: (1) an ANB angle of 1 degree or less, (2) a Wits appraisal less than -4 mm, (3) an incisal overjet ≤ 0 mm, and (14) a Class III molar relationship. All lateral cephalograms were traced and digitised and a number of skeletal, dental and soft tissue variables were measured. The camouflage and surgical groups were also divided into premolar extraction and non-extraction subgroups to allow for a specific analysis of extraction effects. RESULTS: Before treatment, the surgical group demonstrated, on average, a more severe skeletal discrepancy and increased dental compensations, compared with the orthodontically camouflaged group. After treatment, the mean SNA angle was greater, the ANB angle was more positive, the Wits appraisal was closer to ideal and the lower incisors were less retroclined in the surgery group. There was a small mean reduction in horizontal chin projection in the surgery group compared with a small increase in the camouflage group. The mentolabial fold and the lower lip curve were deeper, on average, and the lips less retrusive after surgery. There was a mean increase in upper incisor proclination during treatment in both the surgical and camouflage groups with a greater increase in the camouflage group. There was a significant reduction in upper incisor proclination and a subsequent greater increase in the ANB angle associated with upper premolar extractions in the surgical group compared with the non-extraction group. Lower premolar extractions in the camouflage group resulted only in a deeper mentolabial fold compared with those treated without lower extractions. CONCLUSIONS: Class III patients selected for surgical treatment are likely to have more severe pretreatment dental and skeletal discrepancies than those selected for camouflage treatment. Surgical treatment is associated with significant decompensation of the lower incisors but, ultimately, not the upper incisors. Class III patients treated with either camouflage or surgery treatment are likely to finish with slightly proclined upper incisors. Generally, surgical treatment results in greater skeletal change, involving normalisation of the skeletal base relationship, a reduction in chin prominence, fuller lips, and a more favourable lip and chin contour.

Skeletal effects of the alteration of masseter muscle function.

AIM: To investigate the effects of muscle denervation and the introduction of the ß2-adrenoceptor agonist, formoterol, on the relationship between muscles and underlying skeletal growth. METHOD: Thirty-one (4-week-old) male Sprague-Dawley rats were assigned to four groups: Surgical Sham; Denervated; Denervated + ß2-agonist; and ß2-agonist only. The Surgical Sham group had the left masseteric nerve exposed but not sectioned. Both of the denervated groups had the left masseteric nerve exposed and sectioned. The groups receiving the ß2-agonist had formoterol directly injected into the left masseter muscle every three days for eight weeks. Sixteen angular and linear skeletal measurements were assessed in the overall craniofacial region and the mandible via standardised digital radiography in three views: lateral head, submento-vertex and right and left disarticulated hemi-mandibles. RESULTS: The findings indicated that, following surgical denervation of the masseter muscle, there were significant changes in the muscle and in the subsequent development of the underlying skeletal structures. The post-surgical changes were largely offset by the administration of a ß2-agonist, formoterol, which attenuated muscle atrophy. However, the administration of the ß2-agonist only, without surgical denervation, did not lead to changes in skeletal facial form. CONCLUSIONS: Denervation atrophy of the masseter muscle results in statistically significant changes in the development of the underlying skeleton. The changes, however, are localised to areas of muscle attachment. The administration of the ß2-agonist, formoterol, despite its effect on muscle anabolism, does not have a significant effect on underlying skeletal growth.

Maxillary arch width and buccal corridor changes with orthodontic treatment. Part 2: attractiveness of the frontal facial smile in extraction and nonextraction outcomes.

INTRODUCTION: This study was designed to assess the influence that the buccal corridor might have on the frontal facial attractiveness of subjects who had received orthodontic treatment with or without 4 premolar extractions. METHODS: Posttreatment full-face frontal smiling photographs of 30 premolar extraction and 27 nonextraction patients were evaluated by 20 orthodontists, 20 dentists, and 20 laypeople using a visual analog scale. The ratings were analyzed according to rater group, rater sex, and number of years in practice for orthodontists and dentists to search for any statistically significant differences in the ratings on the basis of treatment groups, subject sex, and buccal corridor widths and areas. RESULTS: Orthodontists and dentists gave higher mean overall frontal facial attractiveness scores than did laypeople. There were no significant differences in how men and women rated the study subjects. The number of years in practice did not affect how the orthodontists rated, but it did affect the ratings of the dentists. Female subjects were consistently rated as significantly more attractive than male subjects. There was no difference in ratings for the extraction and nonextraction subject groups. The buccal corridor widths and areas did not affect the frontal facial attractiveness ratings. CONCLUSIONS: If treatment has been carried out with thorough diagnosis and careful planning, neither the choice of extraction or nonextraction treatment, nor the resulting buccal corridor widths or areas appeared to affect the subjects' frontal facial attractiveness.

Maxillary arch width and buccal corridor changes with orthodontic treatment. Part 1: differences between premolar extraction and nonextraction treatment outcomes.

INTRODUCTION: In this retrospective study, we examined and compared the pretreatment and posttreatment arch widths and buccal corridor changes in subjects who had received orthodontic treatment either with or without premolar extractions. METHODS: Pretreatment and posttreatment casts, frontal smiling photographs, and lateral cephalograms of 30 extraction and 27 nonextraction patients were analyzed to determine any significant differences in arch widths, buccopalatal inclinations of the teeth, and buccal corridor widths and areas, both within and between the 2 groups. Relationships between buccal corridor measurements and corresponding arch widths and buccopalatal inclinations of the teeth were also examined. RESULTS: There was a significant increase in the posttreatment maxillary intercanine width in the extraction group but not in the nonextraction group. Both the pretreatment and posttreatment arch widths between the maxillary first molars and at the level of the posterior rugae were greater in the nonextraction group than in the extraction group. There were no significant differences in any buccal corridor widths or areas measured between the extraction and nonextraction subjects. CONCLUSIONS: Because they reflect different morphologies, there are likely to be significant differences in average maxillary anterior and posterior posttreatment arch widths in those treated with or without extractions. However, these arch width differences are not likely to be discernible in extraction and nonextraction patients as differences in the buccal corridor widths and areas.

In-vitro study of the effect of casein phosphopeptide amorphous calcium fluoride phosphate on iatrogenic damage to enamel during orthodontic adhesive removal.

INTRODUCTION: White-spot lesions (WSL) might be susceptible to mechanical damage during orthodontic bracket and adhesive removal. The aims of this in-vitro study were to investigate enamel loss on bracket and adhesive removal when the brackets were surrounded by WSL and to determine the effect of remineralizing these lesions with a 1% (w/v) casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP) solution before bracket and adhesive removal. METHODS: Precoated metal mandibular incisor brackets were centrally bonded onto polished third molars and WSL produced by exposure to a demineralization buffer for 4, 12, and 30 days (n = 20 per group). Half of the demineralized window was covered with acid-resistant nail varnish, and the specimens were then subjected to remineralization with 1% CPP-ACFP. Brackets and residual adhesive were removed, and enamel damage was assessed by digital photography, profilometry, and scanning electron microscopy. Lesion depth, mineral loss, and remineralization were measured by transverse microradiography. RESULTS: WSL enamel around the bracket was more susceptible to iatrogenic damage at adhesive removal compared with sound enamel. Remineralization of lesions with 1% CPP-ACFP before adhesive removal significantly (P <0.002) reduced the area and depth of damage. CONCLUSIONS: Remineralizing WSLs with CPP-ACFP before adhesive removal reduced iatrogenic enamel damage.

Sagittal mandibular changes with overbite correction in subjects with different mandibular growth directions: late mixed-dentition treatment effects.

INTRODUCTION: This study involved the assessment of pretreatment and posttreatment lateral cephalograms from late mixed-dentition patients with Class II Division 1 and Division 2 malocclusions with mild mandibular crowding. All were selected before treatment began. METHODS: Combined growth and treatment effects were compared with changes in untreated subjects. The study was designed specifically to determine whether anteroposterior mandibular dentoalveolar and skeletal changes associated with reduction of deep incisal overbites, by using a particular late mixed-dentition treatment approach, are influenced by the direction of mandibular growth during treatment. RESULTS: In mesofacial and brachyfacial subjects, significantly greater forward movements were found at Point B after deep overbite correction than in dolichofacial subjects. This apparently enhanced effect compared with the untreated controls was not seen at pogonion. CONCLUSIONS: Clinicians should expect considerably greater forward movement of the mandibular dentoalveolus with normal mandibular growth after incisal bite opening in mesofacial and brachyfacial patients. As a consequence, less maxillary retraction might be necessary in growing mesofacial and brachyfacial Class II Division 1 and Division 2 patients than in dolichofacial patients. On the other hand, one should not expect enhancement of basal sagittal mandibular growth, regardless of the underlying vertical facial pattern.

Incisal and soft tissue effects of maxillary premolar extraction in class II treatment.

OBJECTIVE: This retrospective study was designed to show likely upper incisal and soft tissue lip changes accompanying Class II fixed appliance treatment with only two upper premolar extractions and to assess whether the lips, especially, are predictably and directly affected with such treatment. MATERIALS AND METHODS: Pretreatment and posttreatment lateral cephalograms and study casts from 61 growing Class II patients (aged 11 to 18 years; 39 division 1 and 22 division 2) were assessed. Upper and lower lip curve depths, nasolabial angle, and upper incisal position and angulation were all assessed and compared with changes in other cephalometric variables. RESULTS: A wide range of individual response in both lip and upper incisor behavior were noted. The observed soft tissue lip changes were most likely to be related to the preexisting morphology of the lips themselves, while upper incisal changes were mainly related to their own pretreatment positions and changes occurring with treatment in the underlying bony structures. CONCLUSION: Orthodontic treatment involving the extractions of only two upper premolars is likely to result in a wide range of variation in lip and upper incisor behavior. The preexisting soft tissue morphology is likely to be the greatest determinant of lip behavior.

Effects of surface treatment on orthodontic bonding to amalgam.

AIM: This study aimed to compare the shear bond strengths of metal brackets bonded to amalgam surfaces. METHODS: One hundred and fifty amalgam samples were fabricated and either polished, roughened with a diamond bur or sandblasted with 50 mm aluminium oxide. Following thermocycling the shear bond strengths were tested and compared with control samples bonded to etched enamel. RESULTS: Concise resin composite, Metal Primer/Concise resin composite and All-Bond II/Concise resin composite bonded to sandblasted amalgam gave the highest mean shear strengths and were statistically similar to the etched enamel/Concise resin composite controls. CONCLUSION: One would expect sandblasted amalgam surfaces to be associated with higher shear bond strengths than diamond bur roughened or polished amalgam surfaces.

Myosin heavy chain isoform composition of human masseter muscle from subjects with different mandibular plane angles.

AIM: To investigate the presence of myosin heavy chain isoforms in human masseter muscle and to describe any differences in orthognathic surgery patients with different mandibular plane angles. METHOD: Biopsies were obtained from the anterior border of the superficial masseter muscle in 18 patients undergoing various orthognathic procedures. Myosin heavy chain isoforms were isolated and analysed by SDS-PAGE gel electrophoresis. Steiner's mandibular plane angles were measured from pretreatment lateral cephalometric radiographs and used to classify the vertical dimension of each subject. RESULTS: Despite the fact that there was wide individual variation, there appeared to be no direct association between the presence of myosin heavy chain isoforms and specific vertical facial patterns. Type I myosin heavy chain isoform was the most common isoform found in all subjects. More Type IIA myosin heavy chain isoforms were observed in dolichofacial subjects. There were no differences between genders in myosin heavy chain expression. CONCLUSION: A wide variation of myosin heavy chain isoforms exists in the masseter muscle of individuals with different mandibular plane angles. Further investigations involving larger sample sizes and the incorporation of bite-force measurements may help to clarify the relationship between mandibular muscle characteristics and the vertical facial dimension.

Growth and treatment changes distal to the mandibular first molar: a lateral cephalometric study.

This study examined space changes occurring distal to the mandibular first molar in growing patients treated using two different approaches. Two groups of 50 patients were selected for the study. The patients in group I were treated with the extraction of mandibular second premolars, whereas those in group II were treated without mandibular premolar extractions, by holding E-spaces with utility arches. Lateral cephalograms taken before and after treatment were used to measure space changes within the mandible. Follow-up written treatment records and radiographs were also examined to ascertain whether the mandibular third molars were ultimately extracted or retained. A greater mean space increase between Xi point and the mandibular first molar was found in boys and girls treated with second premolar extractions. The mean space increase between Xi point and the mandibular first molar, as well as the average increase in total mandibular length, was greater in boys than in girls for both treatment modalities. This reflects a greater amount of growth in boys during the treatment period. The greater mean space increase in the groups treated with second premolar extractions could be attributed to the fact that the first molar generally moved further mesially during treatment in the extraction subjects, whereas in the E-space subjects, the first molars were perhaps held back. It was noted that the mandibular third molars were ultimately more likely to have been extracted in the E-space groups than in the second premolar extraction groups within this sample.

Lip curve changes in females with premolar extraction or nonextraction treatment.

Changes in lip curvature resulting from treatment have been largely ignored in orthodontic literature. The focus instead has been primarily directed at retraction of the vermilion border and changes in the nasolabial angle. This study, therefore, was designed to retrospectively analyze changes in the upper and lower lip curves associated with growth and treatment. The lateral cephalometric records of 137 female orthodontic patients were digitized. Sixty-two were treated with premolar extractions and 75 without extractions. The overall extraction group was further divided into subgroups on the basis of the chosen extraction sequence, which included extraction of 4/4, 4/5, or 5/5. Statistical analysis revealed no significant differences in changes in lip curve depth between the two overall samples, relative to either of the two reference lines. This would suggest that an appropriately selected plan, whether extraction or nonextraction, should allow treatment to be carried out without negative effects on the curvature of the lips. Calculation of correlation coefficients and regression analysis suggested that the inherent properties and morphology of the soft tissues themselves are probably the greatest determinants of lip curve behavior with treatment. The midface soft tissues appear to be less dependent on changes in the underlying hard tissues than do the lower face soft tissues. Pretreatment upper and lower incisor positions and angulations and the underlying vertical facial dimension appear to play more significant roles in the behavior of the lower lip than the upper lip.

Facial aesthetics and the divine proportion: a comparison of surgical and non-surgical class II treatment.

OBJECTIVE: This study was designed to compare selected divine or golden proportions in Class II division 1 patients treated either during the growth phase with an activator and fixed appliances or after the completion of growth with fixed appliances and orthognathic surgery; and to determine the associations between divine facial proportions and perceived facial attractiveness. METHODS: The material consisted of subjects with Class II division 1 malocclusions treated either with upper and lower fixed appliances and orthognathic surgery or with activators followed by fixed appliances. There were 23 females and 9 males in the surgical group (Mean age: 23.5 years; SD: 9.6 years) and 17 females and 11 males in the non-surgical group (Mean age: 10.8 years; SD: 1.1 years). The divine relationships of the subjects were assessed on pre- and post-treatment lateral cephalometric radiographs, and on lateral and frontal facial photographs. In addition, the attractiveness of the subjects was scored by a panel of judges using a visual analogue scale. Facial aesthetic scores were then correlated with the presence of particular divine facial proportions. RESULTS: On average, few ratios fitted the divine proportion, either before or after treatment in either treatment group. There was, however, significant individual variation in the presence or otherwise of these divine proportions, as there were with changes in the proportions with treatment. Regardless of the treatment method, ratios in some patients moved toward the divine proportion, while those in others moved away from it. A comparison of the two treatment groups both before and after treatment showed that the mean group values for some of the proportions differed. These differences could largely be explained by differences in growth status and treatment method. CONCLUSION: Neither treatment method was more likely to result in a greater number of divine proportions, and the achievement of divine proportions seemed to have little, if any, influence on overall aesthetic outcomes.

Lip curve changes in males with premolar extraction or nonextraction treatment.

AIM: This retrospective study was designed to compare the responses of the upper and lower lip curves in young growing males, to orthodontic treatment involving either four premolar extractions or the holding of the E-spaces without premolar extractions. METHOD: Pre- and post-treatment lateral cephalograms of 67 premolar extraction and 30 nonextraction patients were assessed. The results were subjected to analysis of variance to search for statistically significant differences amongst the pretreatment variables and changes in depths of lip curves. Pearson's correlation coefficients were also calculated and stepwise regression analysis undertaken. RESULTS: A wide range of lip curve behaviour was seen in individual patients within all groups. No significant differences were found in the change in depth of lip curve amongst the various extraction and nonextraction groups. The inherent morphology of the soft tissues appeared to be the greatest determinant of lip curve behaviour with treatment. CONCLUSIONS: It would appear that neither premolar extraction nor nonextraction treatment, if based on appropriate diagnostic criteria and followed with competent clinical management, will necessarily lead to direct effects on lip curvature.

Tooth and lip responses to three commonly prescribed premolar extraction sequences: a review of recent research findings.

AIM: To review and discuss the dental and lateral profile soft tissue effects of orthodontic treatment involving three different premolar extraction patterns (4/4, 4/5, 5/5). METHOD: The results of three previously reported studies were compared and discussed. RESULTS: Wide ranges of individual variation were found for the amounts of forward molar movement and incisor retraction, and for changes in the depths of upper and lower lip curves within all three premolar extraction pattern groups. The amount of pretreatment crowding and the residual space following initial alignment were the two factors most likely to influence changes in tooth positions during treatment. Treatment changes in the curvature of the lips were influenced by the pretreatment thickness of the lips at the vermilion level. CONCLUSION: Factors other than simply the choice of premolar extraction pattern influence positional changes in the molars, incisors and lips during orthodontic treatment.