The technical reliability of superimposition on cranial base and mandibular structures

Bias in the superimposition of lateral cephalograms in adult patients with anterior open bite

INTRODUCTION

Anterior open bite malocclusion can be treated nonsurgically using fixed appliances, clear aligners, or temporary anchorage devices (TADs). Proponents of clear aligners and TADs often attribute bite closure to molar intrusion and counterclockwise rotation of the mandibular plane. These changes may be supported by superimpositions. However, the process of creating a superimposition is subjective and may be influenced by practitioner bias.

METHODS

The initial and final lateral cephalograms from 30 adult anterior patients with open bite were used in this study. Ten patients were treated with fixed appliances, 10 with clear aligners, and 10 with TADs. We asked 6 orthodontic graduate students and 6 orthodontic practitioners to complete superimpositions using these radiographs in 3 separate sessions. In the first session, the raters were told that all patients only received treatment with fixed appliances. In the second session, the raters were told that all patients were treated with clear aligners only, and in the third session, they were told all patients were treated with fixed appliances and TADs. Superimpositions were performed using Dolphin software, and each superimposition was saved as a Portable Document Format image. Change in the mandibular plane was the primary outcome and was assessed categorically (closed, no change, opened). Cephalometric values were measured and used to investigate the dental and skeletal changes associated with treatment.

RESULTS

Although the raters demonstrated a slight tendency toward the mandibular plane closing or staying the same when told the treatment was clear aligners or TADs, these differences were not statistically significant. A high degree of intrarater and interrater variability in the mandibular plane change was present in all 3 superimposition sessions. The measurements from the lateral cephs showed significant changes for overbite and incisor vertical and angular movements. Almost no change was observed in anterior facial height, mandibular plane angle, or vertical movement of the first molars.

CONCLUSIONS

This study did not observe a significant amount of superimposition bias. However, there was considerable intrarater and interrater reliability. This suggests that the same initial and final cephs may be interpreted very differently on the basis of the subjective superimposition of the raters.

Sagittal and Vertical Growth of the Maxillo-Mandibular Complex in Untreated Children: A Longitudinal Study on Lateral Cephalograms Derived from Cone Beam Computed Tomography

The aim of this longitudinal study was to evaluate the sagittal and vertical growth of the maxillo–mandibular complex in untreated children using orthogonal lateral cephalograms compressed from cone beam computed tomography (CBCT). Two sets of scans, on 12 males (mean 8.75 years at T1, and 11.52 years at T2) and 18 females (mean 9.09 years at T1, and 10.80 years at T2), were analyzed using Dolphin 3D imaging. The displacements of the landmarks and rotations of both jaws relative to the cranial base were measured using the cranial base, and the maxillary and mandibular core lines. From T1 to T2, relative to the cranial base, the nasion, orbitale, A-point, and B-point moved anteriorly and inferiorly. The porion moved posteriorly and inferiorly. The ANB and mandibular plane angle decreased. All but one subject had forward rotation in reference to the cranial base. The maxillary and mandibular superimpositions showed no sagittal change on the A-point and B-point. The U6 and U1 erupted at 0.94 and 1.01 mm/year (males) and 0.82 and 0.95 mm/year (females), respectively. The L6 and L1 erupted at 0.66 and 0.88 mm/year (males), and at 0.41 mm/year for both the L6 and the L1 (females), respectively.

Transverse Growth of the Maxillo-Mandibular Complex in Untreated Children: A Longitudinal Cone Beam Computed Tomography Study

The aim of this study is to evaluate the longitudinal transverse growth of the maxillo-mandibular complex in untreated children using the Cone Beam Computed Tomography (CBCT). Two sets of scans on 12 males (mean 8.75 years at T1 and 11.52 years at T2) and 18 females (mean 9.09 years at T1 and 10.80 years at T2) were analyzed using Dolphin 3D imaging. The transverse widths of various maxillary and mandibular skeletal landmarks and the dentoalveolar and dental landmarks at the level of first molars were measured. Overall, there were greater increases in the transverse dimension in the posterior than anterior portions of the maxilla and mandible. The increase in intergonial width of the mandible seems to be primarily due to the lengthening of the mandibular body. The dentoalveolar process at the first molar level increases at an equal rate corono-apically and is independent to the changes in molar inclination. When comparing maxillary dentoalveolar changes with that of the mandible, greater increases were noticed in the maxilla, which might be explained by the presence of sutural growth in the maxilla. Moreover, the first molars maintain their coordination with each other despite the differential increase in the maxillary and mandibular dentoalveolar processes.

A predictive model of "favorable" and "unfavorable" anteroposterior skeletal relations among Class Is and Class IIs

OBJECTIVES

To validate the use of the sagittal distance between ANS and Pg (ANSPg) as a measure of favorable and unfavorable anteroposterior skeletal relations and to identify multivariate cephalometric measures that could be used to predict favorable and unfavorable relations at 15 years of age.

MATERIALS AND METHODS

This longitudinal study included 226 untreated adolescents evaluated at 10 and 15 years of age. Patients were grouped as "favorable" or "unfavorable" based on the ANSPg (measured parallel to S-N -7°) at 15 years of age (ANSPg15). ANSPg15 was validated based on its correlation with changes in ANSPg between 10 and 15 years of age, as well as its relationships with established measures of growth potential. Multiple regression and discriminant analyses were performed to predict ANSPg15 from measures at 10 years of age.

RESULTS

ANSPg15 and the change in ANSPg between 10 and 15 years of age were significantly correlated (R= -0.661; P ≤ .001), with 77% of patients in whom relationships improved (ie, distance decreased) exhibiting favorable relationships at 15 years of age. Established measures of growth potential were significantly (P < .001) correlated with ANSPg15 and showed significant differences between patients with favorable and unfavorable relations. Multiple regression showed that the Y-axis, ANS-N-Pg, and symphyseal angle measured at 10 years explained approximately 60% (R = 0.78) of the variation in ANSPg15. Based on these three variables, discriminant function correctly predicted favorable or unfavorable relations of ANSPg15 77% of the time.

CONCLUSIONS

ANSPg15 was a valid measure for determining favorable and unfavorable anteroposterior skeletal relationships that could be predicted with moderately high levels of accuracy.

Assessment of methods used for 3-dimensional superimposition of craniofacial skeletal structures: a systematic review

Background

So far, several techniques have been recommended for the assessment of craniofacial changes through skeletal tissue superimposition, but the evidence that supports them remains unexplored. The purpose of the present study is to assess the available literature on skeletal-tissue superimpositions of serial craniofacial CT or CBCT images used to detect morphological changes.

Materials and Methods

Medline (via Pubmed), EMBASE, Google Scholar, Cochrane Library, Open Grey and Grey Literature Report were searched (last search: 17.11.2019) using specific terms that fulfilled the requirements of each database in the context of the study aim. Hand searches were also performed. The outcomes of interest were the accuracy, precision, or agreement between skeletal-tissue superimposition techniques to assess changes in the morphology of craniofacial structures. Studies of any design with sample size ≥3 were assessed by two authors independently. The study protocol was registered in PROSPERO (ID: CRD42019143356).

Results

Out of 832 studies, fifteen met the eligibility criteria. From the 15 included studies, 12 have shown high total risk of bias, one low risk of bias, and two studies have shown unclear risk of bias. Thirteen out of the 15 studies showed high applicability concerns, two unclear and no study had low applicability concerns. There was high heterogeneity among studies regarding the type of participants, sample size, growth status, machines, acquisition parameters, superimposition techniques, assessment techniques and outcomes measured. Fourteen of them were performed on Cone Beam Computed Tomography (CBCT) and one on Computed Tomography (CT) derived 3D models. Most of the studies (eleven) used voxel-based registration, one landmark-based registration and three studies compared different registration techniques, which include the surface-based registration. Concerning the area of interest, nine studies focused on the anterior cranial base and certain facial structures, four on maxillary structures and four on mandibular structures. Non-growing participants were included in six studies, growing in eight, whereas one study had both.

Conclusion

Most of the available studies had methodological shortcomings and high applicability concerns. At the moment, certain voxel-based and surface-based superimpositions seem to work properly and to be superior to landmark-based superimposition. However, further research in the field is required to develop and properly validate these techniques on different samples, through high quality studies with low applicability concerns.

Surgical Management and Evaluation of the Craniofacial Growth and Morphology in Cleidocranial Dysplasia

Cleidocranial dysplasia (CCD, MIM 119600) is a rare autosomal dominant disorder affecting bone, cartilage, craniofacial growth, and tooth formation leading to supernumerary teeth. Few reports delineate the genotype-phenotype correlations related to the variations in craniofacial morphology and patterning of the dentition and the complexity of treating patient's malocclusion. Successful management of the craniofacial deformities in patients with CCD requires a multidisciplinary team of healthcare specialists. Approximately 70% of patients are due to point mutations in RUNX2 and <20% due to copy number variations with the remainder unidentified. There is no literature to date, describing the orthognathic management of CCD patients with deletion in one of the RUNX2 alleles. The purpose of this study was to evaluate the craniofacial morphology and dental patterning in a 14-year-old Caucasian female with CCD resulting from a novel microdeletion of RUNX2 in 1 allele. The CCD patient with RUNX2 haploinsufficiency due to microdeletion had decreased craniofacial bone and ankyloses in the permanent dentition. An altered extraction protocol of supernumerary teeth was followed in this patient. Craniofacial growth and morphologic analysis demonstrated atypical skull shape, persistent metopic suture, and decreased mandibular size.

Radiographic evaluation of orthodontic treatment by means of four different cephalometric superimposition methods

INTRODUCTION:

Despite discussion on the merit of various cephalometric superimposition methods, there remains a need to assess which one can be used in daily practice with reasonably accuracy and less working time.

OBJECTIVE:

The aim of this study was to investigate four methods of cephalometric superimposition by means of assessing the longitudinal changes in craniofacial morphology caused by growth and response of adolescents with Class I malocclusion to orthodontic treatment involving first premolar extraction.

METHODS:

Pretreatment (T₁) and post-treatment (T₂) standardized lateral cephalometric radiographs of 31 adolescents (20 females and 11 males), with Angle Class I malocclusion and indication of premolar extraction, participated in this study. Radiographs were digitized, traced and had structures identified by means of a cephalometric software. Four superimposition methods were used: Björk structural method, Steiner/Tweed SN line, Ricketts N-Ba line at N-point and Ricketts N-Ba line at CC-point. Positional changes were quantified by horizontal and vertical linear changes in the following cephalometric landmarks: anterior/posterior nasal spine (ANS and PNS), gnathion (Gn), Gonion (Go), Pogonion (Pog), A-point and B-point. Differences between T₁ and T₂ in horizontal and vertical positional changes for all superimposition methods were assessed by one-way analysis of variance (ANOVA) and Bonferroni correction (p < 0.05).

RESULTS:

There were no statistically significant differences among the cephalometric superimposition methods or when patients' sex was considered.

CONCLUSION:

Björk structural method, Steiner/Tweed SN line, Ricketts N-Ba line at N-point and Ricketts N-Ba line at CC-point methods were reliable and presented similar precision when the overall facial changes due to active growth and/or orthodontic treatment were examined.

Evaluation of 3-dimensional superimposition techniques on various skeletal structures of the head using surface models

Objectives

To test the applicability, accuracy, precision, and reproducibility of various 3D superimposition techniques for radiographic data, transformed to triangulated surface data.

Methods

Five superimposition techniques (3P: three-point registration; AC: anterior cranial base; AC + F: anterior cranial base + foramen magnum; BZ: both zygomatic arches; 1Z: one zygomatic arch) were tested using eight pairs of pre-existing CT data (pre- and post-treatment). These were obtained from non-growing orthodontic patients treated with rapid maxillary expansion. All datasets were superimposed by three operators independently, who repeated the whole procedure one month later. Accuracy was assessed by the distance (D) between superimposed datasets on three form-stable anatomical areas, located on the anterior cranial base and the foramen magnum. Precision and reproducibility were assessed using the distances between models at four specific landmarks. Non parametric multivariate models and Bland-Altman difference plots were used for analyses.

Results

There was no difference among operators or between time points on the accuracy of each superimposition technique (p>0.05). The AC + F technique was the most accurate (D<0.17 mm), as expected, followed by AC and BZ superimpositions that presented similar level of accuracy (D<0.5 mm). 3P and 1Z were the least accurate superimpositions (0.79<D<1.76 mm, p<0.005). Although there was no difference among operators or between time points on the precision of each superimposition technique (p>0.05), the detected structural changes differed significantly between different techniques (p<0.05). Bland-Altman difference plots showed that BZ superimposition was comparable to AC, though it presented slightly higher random error.

Conclusions

Superimposition of 3D datasets using surface models created from voxel data can provide accurate, precise, and reproducible results, offering also high efficiency and increased post-processing capabilities. In the present study population, the BZ superimposition was comparable to AC, with the added advantage of being applicable to scans with a smaller field of view.

Mandibular growth comparisons of Class I and Class II division 1 skeletofacial patterns

OBJECTIVE

To determine class and sex differences in mandibular growth and modeling.

MATERIALS AND METHODS

A mixed-longitudinal sample of 130 untreated French-Canadian adolescents, 77 (45 boys and 32 girls) with Class I (normal or abnormal) occlusion and 53 (26 boys and 27 girls) with Class II division 1 malocclusion, was used. Based on eight landmarks, eight traditional measurements were used to compare the anteroposterior position of the maxilla and mandible, relationship between the jaws, and mandibular size. Mandibular superimpositions were used to compare the horizontal and vertical changes of condylion, gonion, and menton.

RESULTS

While there were no differences in maxillary position based on the SNA angle, Class IIs had more retrognathic mandibles than did Class Is. Total mandibular length was greater in Class Is than in Class IIs at 15 years of age. Superior and total growth and modeling changes at condylion and gonion, respectively, were greater for Class Is than Class IIs. Boys were more prognathic than girls; they had larger mandibles and exhibited greater size increases and growth changes than girls did.

CONCLUSIONS

There are both class and sex differences in mandibular growth and modeling.

How does tooth eruption relate to vertical mandibular growth displacement?

INTRODUCTION

Our objectives were to investigate the eruptive patterns of the mandibular teeth and assess their associations with mandibular growth displacements.

METHODS

Cephalograms for a mixed-longitudinal sample of 124 French-Canadian girls were evaluated between 10 and 15 years of age. Vertical mandibular displacement and mandibular eruption were evaluated by using cranial and mandibular superimpositions, respectively. Multilevel modeling procedures were used to estimate each subject's growth change over time. Stepwise multiple regressions were used to determine the amount and relative magnitudes of variations in mandibular eruption explained by mandibular growth displacement, controlling for vertical maxillary tooth movements.

RESULTS

Cubic polynomial models explained between 91% and 98% of the variations in eruption and vertical growth displacement. All curves showed acceleration of eruption until approximately 12 years of age, after which eruption decelerated. The eruption of the mandibular teeth demonstrated greater relative variability than did vertical mandibular growth displacements. Independent of the overall movements of the maxillary molars, inferior mandibular growth displacement explained approximately 54% of the variation in mandibular molar eruption between 10.5 and 14.5 years of age.

CONCLUSIONS

Inferior mandibular growth displacement and dental eruption followed similar patterns of change during adolescence. Based on their associations and the differences in variability identified, mandibular eruption appears to compensate for or adapt to growth displacements.

Sistema Decodify®: cefalometria como mensuração de risco e ferramenta administrativa para clínica ortodôntica

INTRODUÇÃO: a cefalometria pode ter uso clínico limitado em Ortodontia por demandar interpretação subjetiva. Um sistema de Inteligência Artificial (IA), o sistema Decodify®, foi desenvolvido para prover uma avaliação quantitativa individualizada de dados cefalométricos contextualizados. Nesse artigo, o sistema é testado como ferramenta administrativa em consultórios de Ortodontia. MÉTODOS: o desenvolvimento de algoritmos incluiu a modelagem de normas e desvios-padrão de dados cefalométricos brasileiros, medidos em radiografias laterais. Para testar o sistema, cefalogramas iniciais de 60 pacientes ortodônticos de dois consultórios diferentes (30 casos cada) foram processados e reprocessados por três técnicos diferentes. A reprodutibilidade e a confidencialidade intraexaminador e interexaminadores foram testadas de modo pareado. O risco em cada caso ortodôntico, produto da análise eletrônica, foi comparado por matrizes de covariância e coeficientes de confiança. RESULTADOS: os níveis de correlação pareada interexaminadores (contra padrão-ouro) para 23 pares de variáveis foram de 0,68 (distância S-Go) a 0,98 (distância Na-Me) em uma clínica ortodôntica (JU) e de 0,66 (ângulo L1.APg) a 0,98 (distância S-Go) em outra clínica ortodôntica (SP). Os níveis de correlação pareada intraexaminadores para 23 pares de variáveis foram de 0,52 (ângulo L1.APg) a 0,98 (distâncias S-Go e Na-Me) em uma clínica (JU) e de 0,55 (ângulo U1.Na) a 0,92 (distância Wits) em outra (SP). Todas as correlações foram significativas em nível de p<0,001. A média dos coeficientes de confiança dos riscos mensurados foi 0,78 para uma clínica (JU) e 0,75 para outra (SP). Os coeficientes de confiança foram significativos em nível de p<0,0001. CONCLUSÕES: os resultados dessa pesquisa suportam que as análises providas pelo sistema Decodify® são reprodutíveis e confiáveis. Assim, o sistema pode ser aplicado para contextualizar medidas cefalométricas convencionais e gerar índices de risco individualizados. O sistema pode ser usado pelo ortodontista como uma ferramenta administrativa em suas avaliações profissionais diárias.

Comparison of hand-traced and computer-based cephalometric superimpositions

OBJECTIVE

To determine the ability to produce comparable superimpositions using hand tracing and digital methods (Dolphin v10). In addition, if the two methods were comparable, we wanted to determine if a difference existed between the best-fit cranial base superimposition and S-N superimpositions using the digital method.

METHODS AND MATERIALS

Sixty-four initial (T(1)) and final (T(2)) cephalometric film radiographs were obtained. Cranial base and regional superimpositions were completed independently for each pair of radiographs by either hand tracing and digital methods. To quantitatively evaluate the differences between the two methods, the hand and digital superimpositions were digitized to obtain x-y coordinates of routine cephalometric landmarks at T(2). Linear distance between multiple corresponding (hand and digital) T(2) cephalometric landmark locations (e.g., A point) were measured and defined as the T(2) landmark distance (T(2) LD). Additionally, 61 patient records were used to compare the digital method for best-fit cranial base superimpositions versus S-N superimpositions. A Friedman test was applied to examine for differences.

RESULTS

The upper 95% confidence limit for the mean of the T(2) LD for hand and digital superimposition methods was <1 mm for all landmarks except maxillary incisor tip and apex. The upper 95% confidence interval for best-fit vs S-N was >1 mm for most landmarks.

CONCLUSION

This study validates the use of superimpositions produced by Dolphin Imaging version 10 and is a necessary step forward toward widespread acceptance of digital superimpositions.

Comparison of hand-traced and computerized cephalograms: landmark identification, measurement, and superimposition accuracy

INTRODUCTION

The purposes of this study were (1) to investigate the variations of landmark identification between film and digital cephalometric tracings, (2) to compare the ability of Quick Ceph 2000 (Quick Ceph Systems, Inc, San Diego, Calif) to measure the linear and angular measurements with the hand-traced method, and (3) to compare Quick Ceph 2000 superimpositions to the hand-traced method of superimpositions that are currently accepted by the American Board of Orthodontics (ABO).

MATERIALS

We used 30 sets of serial cephalometric radiographs of growing patients from 1 orthodontic office. Fiduciary x- and y-axes were drawn in pencil on the T1 radiographs in the regions of the cranial base, the maxilla, and the mandible. The fiduciary lines were transferred to the digital and film serial cephalograms by regionally superimposing the tracings as described in the ABO Phase III examination handbook. A Mann-Whitney test was done to compare the median and Delta of the T1 and T2 values for each measurement acquired by hand and by Quick Ceph.

RESULTS AND CONCLUSIONS

There was no difference in the identification of cephalometric landmarks made manually vs digitally with Quick Ceph 2000. There was no difference in acquiring consistent cephalometric values for the measurements required by the ABO for the Phase III clinical examination manually vs digitally by using Quick Ceph 2000. There was no difference in the regional superimpositions of the mandible, the maxilla, and the cranial base, manually vs digitally with Quick Ceph 2000.

A comparison of the stability of single-piece and segmental Le Fort I maxillary advancements

This study retrospectively evaluated the stability of Le Fort I maxillary advancements and compared segmental and one-piece maxillary osteotomy procedures. A cephalometric analysis was performed on 26 cases of maxillary advancement. The sample comprised 11 cases of one-piece and 15 cases of segmental maxillary procedures. The tracings were superimposed and digitized by computer software, and the skeletal changes were analyzed before surgery, immediately after surgery, and at a minimum of 1 year of follow-up. Different values were compared by the paired and nonpaired t tests and were correlated by the Pearson correlation test. The significant value was set at a 95% confidence interval. The maxilla was advanced by a mean of 5.0 +/- 1.6 mm (P < 0.001), and the anterior maxilla was repositioned inferiorly by a mean of 1.5 +/- 3.3 mm (P < 0.05). The maxilla relapsed posteriorly by a mean of 0.6 +/- 1.2 mm (P < 0.05) and superiorly at the anterior maxilla by a mean of 0.8 +/- 1.1 mm (P < 0.001). Overjet and overbite did not significantly change (P > 0.05). It was concluded that maxillary advancement using rigid fixation and interpositional bone grafting in both groups was a stable procedure, particularly in the horizontal plane. In the one-piece group, there was a significantly higher relapse in the vertical plane than in the segmental group (P < 0.05), however. Minor skeletal relapse was compensated for by postoperative tooth movement, and segmental procedures are recommended when required to enhance occlusal results.

Changes in the craniofacial complex from adolescence to midadulthood: a cephalometric study

The purpose of the present study was to evaluate cephalometrically the craniofacial growth changes and adjustments that occur from late adolescence to midadulthood in persons who had no previous history of orthodontic treatment. Serial lateral cephalograms from 58 subjects from the University of Michigan Elementary and Secondary Growth Study recalled on average in their late 40s were examined. Fifteen of the patients also had cephalograms taken in early adulthood (early 30s). Statistically significant growth changes occurred; mandibular and midfacial lengths as well as posterior and lower anterior facial heights had increased significantly for males and females over both time intervals. The pattern of expression of these changes was different in the two genders: males showed an anterior rotation of the mandible, whereas females demonstrated a posterior rotation of the mandible. Soft tissue changes also were somewhat different between genders. In males, the nose and chin grew downward and forward, with the lips generally moving straight downward. In contrast, females had nasal growth that progressed downward and forward, and there was a slight retrusion of the lips over time. Continued tooth eruption was noted in both genders as well.

Condylar growth and glenoid fossa displacement during childhood and adolescence

This study evaluated age and gender differences in the growth of the mandibular condyle and displacement of the glenoid fossa. The results pertain to longitudinal samples of untreated French Canadians, including 118 children and 155 adolescents. Childhood and adolescent growth were described for girls aged between 6 and 10 years and 9 and 13 years, respectively, and for boys aged between 8 and 12 years and 11 and 15 years, respectively. Four-year growth changes of the cephalometric landmarks condylion and articulare were evaluated. Mandibular and cranial/cranial base structural superimpositions were used to assess condylar growth and fossa displacement, respectively. The results showed that the condyle grew between 0.8 and 1.3 mm posteriorly and between 9.0 and 10.7 mm superiorly over the 4-year periods; the articulare landmark showed significantly more posterior and less superior growth than the condylion landmark. Relative to the cranial base reference structures, the fossa was displaced between 1.8 and 2.1 mm posteriorly and between 1.0 and 1.8 mm inferiorly. The articulare showed significantly more inferior movement than the condylion. Boys showed significantly greater superior condylar growth during adolescence than during childhood. The glenoid fossa demonstrated greater posterior and inferior displacement during adolescence than during childhood.

Timing for effective application of anteriorly directed orthopedic force to the maxilla

Class III malocclusion with retrusive maxilla can be orthopedically corrected in the deciduous and mixed dentition, with reverse-pull headgear in combination with rapid palatal expansion. The literature recommends this procedure be carried out before the patient is 8 years old to obtain the optimal orthopedic result. This statement, however, has not been supported by scientific data. The current study examined the treatment effects of patients younger than 8 years old (5 to 8 years) and patients older than 8 years old (9 to 12 years). Thirty patients treated with maxillary protraction and expansion in the Department of Children's Dentistry and Orthodontics, University of Hong Kong were included in this study. Cephalometric radiographs were taken 6 months before the initiation of treatment (T(0)), at the initiation of treatment (T1), and after 6 months of treatment (T2). In this way, (T(2)-T1) represented cephalometric changes during the treatment period and (T1-T0) represented 6 months of growth changes without treatment. Experimental subjects served as their own control in this study. A grid system consisting of maxillary occlusal plane (OL) and a line perpendicular to OL through sella (OLp) was used for linear measurements. A total of 15 linear and 3 angular cephalometric measurements were made. A multivariate analysis of variance (MANOVA), which used age and treatment time as its factors, was used to determine effect of age and/or treatment on each cephalometric parameter. Results indicated strikingly similar therapeutic response between the younger and older age groups. These data suggest that similar skeletal response can be obtained when maxillary protraction was started either before age 8 (5 to 8 years) or after age 8 years (8 to 12 years).

Cephalometric A point changes during and after maxillary protraction and expansion

The purpose of this study was to analyze the treatment and posttreatment maxillary changes achieved with maxillary protraction therapy. The cephalometric records of 25 consecutively treated Chinese children with Class III malocclusions (mean age 8.4 years) were analyzed for cephalometric A point changes, which were then compared with an untreated, age and sex matched Class III control sample. A cephalometric maxillary superimposition technique was used to differentiate between the skeletal and the local contributions to the total A point change. Results showed that 6 months of maxillary protraction therapy produced a mean A point advancement of 2.4 mm compared with 0.2 mm in the control group. Of this advancement, 75% was found to be due to skeletal maxillary advancement and 25% was attributed to local remodeling. Significantly less downward movement of A point was found with treatment compared with the controls, which could be related to the direction of force application. No significant differences were found in the horizontal and the vertical movements of A point between the treatment and the control groups during the 12-month posttreatment period, indicating stability of early maxillary protraction in patients with Class III malocclusions.

Longitudinal shape changes of the nasal dorsum

This investigation quantifies childhood and adolescent growth changes of the upper and lower nasal dorsum and evaluates various aspects of the persons' morphology that relate to shape changes of the dorsum. A longitudinal sample of 37 French-Canadian girls, each having cephalograms at 6, 10, and 14 years of age, was evaluated. The 6- to 10-year interval was chosen to represent childhood growth; the 10- to 14-year interval represented adolescent growth. The upper dorsum rotates upward and forward (counterclockwise) approximately 10 degrees between 6 to 14 years of age. The lower dorsum shows both downward and backward (clockwise) and upward and forward (counterclockwise) rotation average childhood and adolescent changes in angulation were not significant. The results clearly indicate that changes in the nasal dorsum are most closely related to angulation changes of the lower dorsum, particularly during adolescence. The lower dorsum rotates downward and backward in persons who show greater vertical and less horizontal growth changes. Rotational changes of the lower dorsum are most closely related with vertical changes at pronasale.

A preliminary study of craniofacial classification

Cephalographic evaluations often hinge on univariate statistical analyses of their component dimensions. These analyses generally depict a progressive increase in cephalometric form with age. Such analyses are, however, complicated by the varied inter-dimensional correlations. But when the cephalometric dimensions were combined together in cluster analysis, complex associations between various age groups were noted in the 1-18 year range. Such multivariate analyses revealed far more complex craniofacial age changes than traditionally envisaged. These data therefore indicated the need for further investigation of such "normocephalic gold standards" before their value in craniofacial evaluation can be established.

Mandibular rotation and angular remodeling during childhood and adolescence

Using the structural method of superimposition, childhood and adolescent rates of mandibular rotation and remodeling are described. The results pertain to a longitudinal sample of French-Canadian children, including 42 females with records at 6, 10, and 14 years of age and 39 males with records at 7, 11, and 15 years of age. There are no sex differences in rates of mandibular rotation and remodeling. Childhood rates of true rotation and angular remodeling are significantly greater than adolescent rates. Children whose first permanent molars had not erupted at the time of the first observation showed significantly greater rates of angular remodeling than children whose molars had already erupted. Over the eight year period, there were approximately 4.8 degrees of forward true rotation, between 5.2 and 6.4 degrees forward angular remodeling, and less than 1 degree of backward apparent rotation. During adolescence and the primary dentition stage, associations are strongest between true and apparent rotation. During the mixed dentition stage, true rotation is most closely correlated with angular remodeling. © 1992 Wiley-Liss, Inc.

Computerized digital enhancement in craniofacial cephalometric radiography

Application of digital radiologic imaging techniques to cephalometric assessment of the craniofacial skeleton is presented. Digital-enhanced and standard cephalometric radiographs were compared by osseous and soft tissue landmark analysis. Although both radiographic methods exhibited comparable accuracy at identifying bony landmarks, digital enhancement was consistently superior at delineating soft tissue relationships.

A method for structural mandibular superimpositioning

Structural mandibular superimpositioning on stable natural references has gained wide acceptance in the orthodontic literature. However, accurate instructions that provide a simple step-by-step procedure are not readily available. Considering the specific method described here and assuming stability of the natural reference structures, a reliable procedure for marking two artificial references (simulating "implants") on mandibles in a longitudinal series of cephalograms appears to be possible. In essence, the method is based on the construction of a template, drawn on a small auxiliary tracing sheet, which contains only information relevant for structural mandibular superimpositioning plus error checks. This template is subsequently superimposed on the radiographs in a longitudinal series by the structural method, which permits the transference of two fiducial points. These fiducial points consequently replace the images of metallic implants and thus facilitate local superimpositioning of mandibles. It is a convenient method for longitudinal growth research as well as for any two successive records in the clinical situation.

The reliability of mandibular radiographic superimposition

Using tracings from thirty pairs of serial cephalometric radiographs, the reliability of three outlines, commonly used for mandibular superimposition, was investigated. There were sizeable errors associated with all three groups, but tracings involving Björk's mandibular structures were found to be the least reliable. Despite the greater validity of the Björk structures for assessment of growth changes, in certain cases the use of the mandibular outline may be of greater value for the superimposition of tracings, especially when the time interval between the radiographs is short, or the patient has passed maturity and the growth rate has declined to a negligible level.