Prediction of mandibular growth rotation

Comparisons of soft tissue chin thickness in adult patients with various mandibular divergence patterns

OBJECTIVE

To evaluate the association between soft tissue at the chin (STC) thickness and mandibular divergence.

MATERIALS AND METHODS

Nongrowing patients seeking orthodontic treatment (n  =  190; 113 women and 77 men), who had an average age of 26.94 years (range  =  18.10-53.50 years), were stratified in four subgroups based on cephalometric mandibular plane inclination to anterior cranial base (MP/SN): low  =  MP/SN ≤ 27° (n  =  48); medium-low  =  27° < MP/SN ≤ 32° (n  =  60); medium-high  =  32° < MP/SN < 37° (n  =  37); and high  =  MP/SN ≥ 37° (n  =  45). The STC thicknesses were measured at pogonion (Pog), gnathion (Gn), and menton (Me). Group differences were evaluated with two-way analysis of variance and Student's t-test. The Pearson product moment correlation gauged associations between parameters.

RESULTS

The STC values were greater in men than women (P < .02) and were smaller in the high group (7.47 ± 2.42 mm) than in all other groups at Gn (mean values  =  9.00 mm < STC < 9.58 mm; P < .001) and at Me (high group  =  6.30 ± 1.89 mm; other groups  =  7.15 mm < STC< 7.57 mm; P  =  .011).

CONCLUSION

The STC is thinner at Gn and Me in hyperdivergent facial patterns, apparently in contrast to Pog. This differential thickness warrants focused research as it implies that it is possible (1) to vertically grow hard tissues impinging on the inferior soft tissue envelope in patients with severe hyperdivergence and (2) to plan for genioplasty in such patients when more advancement of the chin might be needed to compensate for the increased vertical height.

Etiological factors in second mandibular molar impaction

OBJECTIVES

The impaction of the second mandibular molar (MM2) has recently become more prevalent. Several etiological hypothesis have been proposed to investigate the association between skeletal features and impaction of MM2. The aims of this study were to analyze the skeletal features in patients with MM2 impaction and the association between arrested eruption of MM2 and the presence of the third mandibular molar (MM3).

STUDY DESIGN

In this retrospective study 48 subjects from 3,530 Caucasian orthodontic patients with MM2 impaction were included in a study group (SG) and compared to a control group (CG) of 200 subjects without MM2 impaction. Panoramic radiographs evaluated the presence or absence of the MM3 germ. Cephalometric analysis was performed to evaluate linear and angular skeletal values. For the statistical analysis, descriptive statistics, Student's t-test, χ2 test and odds ratio (OR) were used.

RESULTS

The paired comparisons between SG and CG showed in cephalometric analysis both a reduced mandibular gonial angle (ArGoMe) and lowered Jarabak's polygon value with a statistically significant difference (P≤ 0.05). MM3 was statistically significant associated (P≤ 0.05) with MM2 impaction but it is not a risk factor (OR 0.817).

CONCLUSIONS

Subjects with MM2 impaction show a vertical condylar growth direction. MM3 is not a risk factor for MM2 impaction. Key words:Impacted mandibular second molar, skeletal features, orthodontic.

Comparative evaluation of cephalometric occlusal characteristics between the long face pattern and pattern I

OBJECTIVE

To compare the cephalometric and intraoral characteristics between Long Face pattern and Pattern I patients, besides evaluating associations between subjective facial patterns, cephalometric facial patterns and the intraoral characteristics.

METHODS

Through evaluation of frontal and right side extraoral photographs, three previously calibrated and experienced examiners selected 30 Long Face patients (Group 1) and 30 Pattern I patients (Group 2), aged between 9 and 19 years, of both genders. The cephalometric characteristics were assessed by the following variables: SN.GoGn, NS.Gn, AIFH, SNA, SNB, ANB, 1.1, 1.NA,1-NA, 1.NB, 1-NB, NA.Po, nasolabial angle and H-Nose. Clinical evaluations were also performed to determine the presence of posterior crossbite, anterior open bite and type of Angle's malocclusion. The cephalometric data were compared by independent t test. The chi-square test was used to evaluate the association between qualitative variables.

RESULTS

Significant differences were observed between groups regarding the variables SN.GoGn, NS.Gn, AIFH, ANB, NA.Pog, 1-NA, 1.NB and 1-NB, with an increase of these measures in Group 1. There were also significant differences between groups on variable 1.1, being lower in Group 1 than in Group 2.

CONCLUSIONS

The Long Face was associated to Angle Class II malocclusion, to the presence of posterior crossbite and to anterior open bite. The Long Face subjective facial pattern was associated to dolichofacial cephalometric pattern.

Variation in timing, duration, intensity, and direction of adolescent growth in the mandible, maxilla, and cranial base: the Fels longitudinal study

There is considerable individual variation in the timing, duration, and intensity of growth that occurs in the craniofacial complex during childhood and adolescence. The purpose of this article is to describe the extent of this variation between traits and between individuals within the Fels Longitudinal Study (FLS). Polynomial multilevel models were used to estimate the ages of onset, peak velocity, and cessation of adolescent growth, the time between these ages, the amount of growth between these ages, and peak velocity. This was done at both the group and individual levels for standard cephalometric measurements of the lengths of the mandible, maxilla, and cranial base, the gonial angle, and the saddle angle. Data are from 293 untreated boys and girls age 4-24 years in the FLS. The timing of the adolescent growth spurt was, in general, not significantly different between the mandible and the maxilla, with each having an earlier age of onset, later age of peak velocity, and later age of cessation of growth as compared to the cranial base length. Compared to lengths, angles had in general later ages of onset, peak velocity, and cessation of growth. Accurate characterization of the ontogenetic trajectories of the traits in the craniofacial complex is critical for both clinicians seeking to optimize treatment timing and anatomists interested in examining heterochrony.

Changes in longitudinal craniofacial growth in subjects with normal occlusions using the Ricketts analysis

Objective

This study was designed to define the Korean norm values for the Ricketts analysis.

Methods

In this longitudinal study, lateral cephalograms of 31 subjects with normal occlusion were taken biennially from ages 9-19 years. Cephalometric measurements were performed. Parameters for which the 10-year change did not exceed one standard deviation were defined as unchanged. The means and standard deviations for the measured parameters were determined for each age group.

Results

No significant changes in growth were observed in the molar relationship, incisor overjet, incisor overbite, mandibular incisor extrusion, interincisor angle, lower incisor tip (B1) to A point-Pogonion (A-PO) plane, upper incisor tip (A1) to A-PO plane, B1 inclination to A-PO, A1 inclination to A-PO, B1 inclination to Frankfurt plane (FH), convexity, lower facial height, facial axis, maxillary depth, maxillary height, palatal plane to FH, cranial deflection, ramus Xi position, or porion location. Continual changes over the 10 years of growth were observed in the maxillary first molar distal position to pterygoid true vertical plane, facial depth, mandibular plane to FH, anterior cranial length, mandibular arc, and corpus length.

Conclusions

Clinicians can apply the Korean norms at age 9 as determined in this study when using the Ricketts analysis. The patient's age at the beginning of treatment and their sex should be taken into consideration when drawing visual treatment objectives.

Three-dimensional evaluation of the relationship between jaw divergence and facial soft tissue dimensions

OBJECTIVE

To evaluate the relationship between mandibular divergence and vertical and transverse dimensions of the face.

MATERIALS AND METHODS

A sample was recruited from the orthodontic clinic of the University of Otago, New Zealand. The recruited participants (N  =  60) were assigned to three different groups based on the mandibular plane angle (hyperdivergent, n  =  20; normodivergent, n  =  20; and hypodivergent, n  =  20). The sample consisted of 31 females and 29 males, with a mean age of 21.1 years (SD ± 5.0). Facial scans were recorded for each participant using a three-dimensional (3D) white-light scanner and then merged to form a single 3D image of the face. Vertical and transverse measurements of the face were assessed from the 3D facial image.

RESULTS

The hyperdivergent sample had a significantly larger total and lower anterior facial height than the other two groups (P < .05), although no difference was found for the middle facial height (P > .05). Similarly, there were no significant differences in the transverse measurements of the three study groups (P > .05). Both gender and body mass index (BMI) had a greater influence on the transverse dimension.

CONCLUSIONS

Hyperdivergent facial types are associated with a long face but not necessarily a narrow face. Variations in facial soft tissue vertical and transversal dimensions are more likely to be due to gender. Body mass index has a role in mandibular width (GoGo) assessment.

On the variability of the Dmanisi mandibles

The description of a new skull (D4500) from the Dmanisi site (Republic of Georgia) has reopened the debate about the morphological variability within the genus Homo. The new skull fits with a mandible (D2600) often referred as 'big' or 'enigmatic' because of its differences with the other Dmanisi mandibles (D211 and D2735). In this report we present a comparative study of the variability of the Dmanisi mandibles under a different perspective, as we focus in morphological aspects related to growth and development. We have followed the notion of modularity and phenotypic integration in order to understand the architectural differences observed within the sample. Our study reveals remarkable shape differences between D2600 and the other two mandibles, that are established early in the ontogeny (during childhood or even before) and that do not depend on size or sexual dimorphism. In addition, D2600 exhibits a mosaic of primitive and derived features regarding the Homo clade, which is absent in D211 and D2735. This mosaic expression is related to the location of the features and can be explained under the concept of modularity. Our study would support the possibility of two different paleodemes represented at the Dmanisi site. This hypothesis has been previously rejected on the basis that all the individuals were constrained in the same stratigraphic and taphonomic settings. However, our revision of the complex Dmanisi stratigraphy suggests that the accumulation could cover an undetermined period of time. Even if "short" in geological terms, the hominin accumulation was not necessarily synchronic. In the same line we discard that the differences between D2600 and the small mandibles are consequence of wear-related dentoalveolar remodeling. In addition, dental wear pattern of D2600 could suggest an adaptation to a different ecological niche than the other Dmanisi individuals.

BOS MOrth cases prize 2011

This paper describes the orthodontic treatment of two cases awarded the prize by the British Orthodontic Society for best treated cases submitted for the Membership in Orthodontics. The first case reports on the treatment of a class III malocclusion with increased vertical lower anterior facial proportions and dentoalveolar compensation that was treated with orthodontic camouflage. The second case reports on the treatment of a class II division II malocclusion with reduced vertical lower anterior facial proportions and an overbite complete to the palate, which was treated with orthodontic camouflage.

Epigenetic influence of KAT6B and HDAC4 in the development of skeletal malocclusion

INTRODUCTION

Genetic influences on the development of malocclusion include heritable effects on both masticatory muscles and jaw skeletal morphology. Beyond genetic variations, however, the characteristics of muscle and bone are also influenced by epigenetic mechanisms that produce differences in gene expression. We studied 2 enzymes known to change gene expressions through histone modifications, chromatin-modifying histone acetyltransferase KAT6B and deacetylase HDAC4, to determine their associations with musculoskeletal variations in jaw deformation malocclusions.

METHODS

Samples of masseter muscle were obtained from subjects undergoing orthognathic surgery from 6 malocclusion classes based on skeletal sagittal and vertical dysplasia. The muscles were characterized for fiber type properties by immunohistochemistry, and their total RNA was isolated for gene expression studies by microarray analysis and quantitative real-time polymerase chain reaction.

RESULTS

Gene expressions for fast isoforms of myosins and contractile regulatory proteins and for KAT6B and HDAC4 were severalfold greater in masseter muscles from a patient with a deepbite compared with one with an open bite, and genes related to exercise and activity did not differ substantially. In the total population, expressions of HDAC4 (P = 0.03) and KAT6B (P = 0.004) were significantly greater in subjects with sagittal Class III than in Class II malocclusion, whereas HDAC4 tended to correlate negatively with slow myosin type I and positively with fast myosin gene, especially type IIX.

CONCLUSIONS

These data support other published reports of epigenetic regulation in the determination of skeletal muscle fiber phenotypes and bone growth. Further investigations are needed to elucidate how this regulatory model might apply to musculoskeletal development and malocclusion.

Vertical facial height and its correlation with facial width and depth: Three dimensional cone beam computed tomography evaluation based on dry skulls

Introduction

The aim of the present study was to evaluate how vertical facial height correlates with mandibular plane angle, facial width and depth from a three dimensional (3D) viewing angle.

Methods

In this study 3D cephalometric landmarks were identified and measurements from 43 randomly selected cone beam computed tomography (CBCT) images of dry skulls from the Weisbach collection of Vienna Natural History Museum were analyzed. Pearson correlation coefficients of facial height measurements and mandibular plane angle and the correlation coefficients of height-width and height-depth were calculated, respectively.

Results

The mandibular plane angle (MP-SN) significantly correlated with ramus height (Co-Go) and posterior facial height (PFH) but not with anterior lower face height (ALFH) or anterior total face height (ATFH). The ALFH and ATFH showed significant correlation with anterior cranial base length (S-N), whereas PFH showed significant correlation with the mandible (S-B) and maxilla (S-A) anteroposterior position.

Conclusions

High or low mandibular plane angle might not necessarily be accompanied by long or short anterior face height, respectively. The PFH rather than AFH is assumed to play a key role in the vertical facial type whereas AFH seems to undergo relatively intrinsic growth.

Functional and morphological correlates of mandibular symphyseal form in a living human sample

Variation in recent human mandibular form is often thought to reflect differences in masticatory behavior associated with variation in food preparation and subsistence strategies. Nevertheless, while mandibular variation in some human comparisons appear to reflect differences in functional loading, other comparisons indicate that this relationship is not universal. This suggests that morphological variation in the mandible is influenced by other factors that may obscure the effects of loading on mandibular form. It is likely that highly strained mandibular regions, including the corpus, are influenced by well-established patterns of lower facial skeletal integration. As such, it is unclear to what degree mandibular form reflects localized stresses incurred during mastication vs. a larger set of correlated features that may influence bone distribution patterns. In this study, we examine the relationship between mandibular symphyseal bone distribution (i.e., second moments of area, cortical bone area) and masticatory force production (i.e., in vivo maximal bite force magnitude and estimated symphyseal bending forces) along with lower facial shape variation in a sample of n = 20 living human male subjects. Our results indicate that while some aspects of symphyseal form (e.g., wishboning resistance) are significantly correlated with estimates of symphyseal bending force magnitude, others (i.e., vertical bending resistance) are more closely tied to variation in lower facial shape. This suggests that while the symphysis reflects variation in some variables related to functional loading, the complex and multifactorial influences on symphyseal form underscores the importance of exercising caution when inferring function from the mandible especially in narrow taxonomic comparisons.

Tooth wear and dentoalveolar remodeling are key factors of morphological variation in the Dmanisi mandibles

The Plio-Pleistocene hominin sample from Dmanisi (Georgia), dated to 1.77 million years ago, is unique in offering detailed insights into patterns of morphological variation within a paleodeme of early Homo. Cranial and dentoalveolar morphologies exhibit a high degree of diversity, but the causes of variation are still relatively unexplored. Here we show that wear-related dentoalveolar remodeling is one of the principal mechanisms causing mandibular shape variation in fossil Homo and in modern human hunter-gatherer populations. We identify a consistent pattern of mandibular morphological alteration, suggesting that dental wear and compensatory remodeling mechanisms remained fairly constant throughout the evolution of the genus Homo. With increasing occlusal and interproximal tooth wear, the teeth continue to erupt, the posterior dentition tends to drift in a mesial direction, and the front teeth become more upright. The resulting changes in dentognathic size and shape are substantial and need to be taken into account in comparative taxonomic analyses of isolated hominin mandibles. Our data further show that excessive tooth wear eventually leads to a breakdown of the normal remodeling mechanisms, resulting in dentognathic pathologies, tooth loss, and loss of masticatory function. Complete breakdown of dentognathic homeostasis, however, is unlikely to have limited the life span of early Homo because this effect was likely mediated by the preparation of soft foods.

Association of dentoskeletal morphology with incisor inclination in angle class II patients: a retrospective cephalometric study

Introduction

The purpose of this study was to identify possible dentoskeletal parameters associated with variation of anterior tooth inclination in Angle Class II subdivisions.

Methods

Pre-treatment lateral radiographs of 144 Class II patients (68 males, 76 females) aged 9 to 17 years were classified for upper incisor inclination into three groups (proclined, normally inclined, retroclined) homogeneous for gender and skeletal jaw relationship. The effect of age on the 22 cephalometric variables was controlled by covariance analysis.

Results

Multivariate analysis of the cephalometric parameters indicated significant inter-group differences. Systematic associations with incisor inclination were revealed using rank correlation: Lower incisor proclination, Wits appraisal and gonial angle significantly decreased (0.04 ≥ p ≥ 0.002), while intercisal angle, mandibular total and corpus length and nasolabial angle increased (0.04 ≥ p ≥ 0.001) with decreasing incisor proclination.

Conclusions

Clear-cut classification criteria and control of confounding effects may clarify conflicting previous findings on dentoskeletal differences between Class II subdivisions in the mixed dentition. Only minor dentoskeletal differences appear to be associated with incisor inclination. The increased interincisal and nasolabial angle in Class II division 2 subjects are due to reclination of both upper and lower incisors. Jaw positions and chin prominence are not significantly different between the subdivisions. However, Wits appraisal is decreased in Class II division 2. The increased mandibular length observed in Class II division 2 requires further scrutinization.

The inclination of mandibular incisors revisited

OBJECTIVE

To reassess the inclination of lower incisors and evaluate possible associations with gender, age, symphyseal parameters, and skeletal pattern.

MATERIALS AND METHODS

Twelve hundred and seventy-two (605 females, 667 males) cephalograms of untreated subjects of a craniofacial growth study (age: 8-16 years) were evaluated. Correlations between the angulation of the lower incisors and age, symphyseal distances (height, width, and depth), symphyseal ratios (height-width, height-depth), and skeletal angles (divergence of the jaws and gonial angle) were investigated for all ages separately and for both sexes independently.

RESULTS

The inclination of lower incisors increased over age (8 years: girls = 93.9° [95% CI, 92.3°-95.7°], boys = 93.3° [95% CI, 91.8°-94.9°]; 16 years: girls = 96.1° [95% CI, 94.1°-98.2°], boys = 97.1° [95% CI, 95.6°-98.6°]). Inclination of lower incisors correlated with the divergence of the jaws for all ages significantly or highly significantly, except for boys and girls 9 years of age and girls 11 and 12 years of age, for which only a tendency was observed. Similarly, a strong correlation to gonial angle could be observed. No correlation could be found between the inclination of lower incisors and any symphyseal parameters (absolute measurements and ratios), except for symphyseal depth.

CONCLUSION

Lower incisor inclination is linked to the subject's sex, age, and skeletal pattern. It is not associated with symphyseal dimensions, except symphyseal depth. Factors related to natural inclination of lower incisors should be respected when establishing a treatment plan.

Mandibular symphysis morphology and dimensions in different anteroposterior jaw relationships

OBJECTIVE

To assess the morphology and dimensions of mandibular symphysis (MS) in different anteroposterior jaw relationships and to investigate whether craniofacial parameters have any correlation with its shape and/or dimensions.

MATERIALS AND METHODS

Lateral cephalograms of subjects with Class I, Class II, and Class III skeletal relationships were traced. Several craniofacial and MS parameters were measured. MS parameters were compared between the three groups using analysis of variance and were correlated with the craniofacial parameters using the Pearson correlation coefficient.

RESULTS

Larger angle of concavity of the chin, more inclination of the alveolar bone toward the mandibular plane, and larger MS dimensions and area (P < .001) were found with a Class III skeletal relationship compared to Class I and Class II relationships. The Pearson correlation coefficient between Id-Me and AFH was r  =  0.83 and between Id-Me and LAFH it was r  =  0.81.

CONCLUSIONS

The dimensions and configuration of MS in the Class III relationship were different than those in Class I and Class II relationships; the alveolar part of MS compensated for the skeletal relationship in the Class III pattern. MS dimensions were strongly correlated to anterior facial dimensions.

Postnatal changes in the growth dynamics of the human face revealed from bone modelling patterns

Human skull morphology results from complex processes that involve the coordinated growth and interaction of its skeletal components to keep a functional and structural balance. Previous histological works have studied the growth of different craniofacial regions and their relationship to functional spaces in humans up to 14 years old. Nevertheless, how the growth dynamics of the facial skeleton and the mandible are related and how this relationship changes through the late ontogeny remain poorly understood. To approach these two questions, we have compared the bone modelling activities of the craniofacial skeleton from a sample of subadult and adult humans. In this study, we have established for the first time the bone modelling pattern of the face and the mandible from adult humans. Our analyses reveal a patchy distribution of the bone modelling fields (overemphasized by the presence of surface islands with no histological information) reflecting the complex growth dynamics associated to the individual morphology. Subadult and adult specimens show important differences in the bone modelling patterns of the anterior region of the facial skeleton and the posterior region of the mandible. These differences indicate developmental changes in the growth directions of the whole craniofacial complex, from a predominantly downward growth in subadults that turns to a forward growth observed in the adult craniofacial skeleton. We hypothesize that these ontogenetic changes would respond to the physiological and physical requirements to enlarge the oral and nasal cavities once maturation of the brain and the closure of the cranial sutures have taken place during craniofacial development.

Mandibular third molar impaction: review of literature and a proposal of a classification

Objectives

The purpose of present article was to review impacted mandibular third molar aetiology, clinical anatomy, radiologic examination, surgical treatment and possible complications, as well as to create new mandibular third molar impaction and extraction difficulty degree classification based on anatomical and radiologic findings and literature review results.

Material and Methods

Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandibular third molar, impacted mandibular third molar, inferior alveolar nerve injury third molar, lingual nerve injury third molar. The search was restricted to English language articles, published from 1976 to April 2013. Additionally, a manual search in the major anatomy and oral surgery journals and books was performed. The publications there selected by including clinical and human anatomy studies.

Results

In total 75 literature sources were obtained and reviewed. Impacted mandibular third molar aetiology, clinical anatomy, radiographic examination, surgical extraction of and possible complications, classifications and risk factors were discussed. New mandibular third molar impaction and extraction difficulty degree classification based on anatomical and radiologic findings and literature review results was proposed.

Conclusions

The classification proposed here based on anatomical and radiological impacted mandibular third molar features is promising to be a helpful tool for impacted tooth assessment as well as for planning for surgical operation. Further clinical studies should be conducted for new classification validation and reliability evaluation.

Changes in soft-tissue profiles after treatment of class II/1 patients with bite-jumping appliances

We performed this study to describe changes in the soft-tissue profile after orthodontic treatment with Tränkmann's bite-jumping appliances. A total of 69 patients thus treated were compared to a control group of 36 age-matched patients based on cephalograms. Statistical analysis included mean values, standard deviations, t-tests, and Pearson's correlation testing. Highly significant (p<0.001) changes in total profile angle (N'-Ns-Pog') were observed over the course of treatment. Furthermore, a mildly significant (p<0.05) correlation with SNA angles was noted. Changes in the soft-tissue profile angle (N'-Sn-Pog') were moderately significant (p<0.001). The profile angles of the upper lip (Sn-SS-Ls) and lower lip (Pog'-Sm-Li) did not reveal significant changes. We observed highly significant (p<0.001) findings in the esthetic line (NsPog') advancement relative to the Ls and Li landmarks and in increases in lower-face height. Midface heights remained unchanged. Our results indicate that treatment with bite-jumping appliances results in increased facial convexity, advancement of the esthetic line, and increased lower-face height. The cumulative effects of growth and treatment do not, however, appear pronounced enough to result in a preference for or against treatment with a bite-jumping appliance.

Female adolescent craniofacial growth spurts: real or fiction?

The purpose of the study is to determine whether the various aspects of the craniofacial complex exhibit female adolescent growth spurts. Multilevel polynomial models were used to estimate the growth curves of a mixed-longitudinal sample of 111 untreated females 10-15 years of age. To evaluate the horizontal and vertical movements of the individual landmarks relative to stable structures, the tracings were superimposed on the natural reference structures in the anterior cranial base. The horizontal and vertical growth changes of four landmarks and the changes of three traditional linear measurements were evaluated. Posterior nasal spine (PNS) moved posteriorly at a constant rate of approximately 0.12mm/year. Five measures showed changes in growth velocity (i.e. quadratic growth curves) but not adolescent growth spurts, including the anterior movements of anterior nasal spine (ANS) and pogonion (Pg), the inferior movements of gonion (Go), and the increases in ANS-PNS and condylion to pogonion (Co-Pg). Five measurements, including the inferior movements of ANS, PNS and Pg, the posterior movements of Go, and the increases of Go-Pg exhibited adolescent growth spurts. Peak growth velocities were attained between 11.4 and 12.8 years of age, approximately 0.7-1.4 years earlier in the maxilla than mandible. While the vertical aspects of craniofacial growth exhibit distinct female adolescent growth spurts, with peak rates occurring earlier in the maxilla than mandible, most horizontal aspects of craniofacial growth do not exhibit an adolescent spurt.

Assessment of the reliability and repeatability of landmarks using 3-D cephalometric software

The aim of this study was to analyze the reliability and repeatability of identification landmarks using 3-D cephalometric software. Ten orthognathic patients were selected for this study and underwent the following protocol: 1. radiographic evaluation (CBCT technique); 2. stone casts; 3. photos; and 4. 3-D cephalometric evaluation. Twenty-one hard tissue landmarks and 14 cephalometric measurements were taken three times (T1, T2, and T3) on each patient, with an interval of one week by two experts in orthodontics (A, B). Standard deviation and Pearson's correlation coefficient were calculated to evaluate intra- and inter-observer repeatability. The results showed a strong correlation for both intra- and inter-observer Pearson's correlation coefficient (>0.7). The current preliminary study showed that the reliability and repeatability of the identification landmarks were very high if the 3-D cephalometric landmarks are defined correctly in the three planes of the space. Further evaluation is necessary to better define the 3-D cephalometric system.

Inclination of the infraorbital canal studied on dry skulls expresses the maxillary growth pattern: a new contribution to the understanding of change in inclination of ectopic canines during puberty

OBJECTIVE

The purpose of this study was to analyze the correlation between direction of the infraorbital canal and maxillary width on frontal radiographs of dry human skulls.

MATERIAL AND METHODS

Forty-two symmetrical, dry human skulls (late adolescence and adult) with no dental or skeletal anomalies. Frontal radiographs were taken of each skull placed in the Frankfort horizontal plane, with a radiopaque marker in the infraorbital canal. The maxillary transversal growth pattern was expressed as the infraorbital transversal angle (IOt) formed between a line through the contour of the bilateral orbita (lo) and a line parallel to the infraorbital marker. Three cephalometric widths were measured on the skulls, two anteriorly (the width of the piriform aperture (AP) and the interorbital width (IO)) and one posteriorly (the palatal width (PW)). A general linear model was used for statistical analysis.

RESULTS

The direction of the infraorbital canal (66.08°, 95% CI: 62.53-69.64) depended on the transversal growth: an increased PW of 1 mm resulted in a decreased IOt of 1.84° (p=0.041); an increase in IO of 1 mm resulted in an increased IOt of 2.24° (p=0.017); and an increased AP of 1 mm resulted in a decreased IOt of 3.30° (p=0.066).

CONCLUSIONS

The study indicates that the direction of the infraorbital canal in frontal view reflects the transversal growth of the maxilla. A wide maxilla posteriorly resulted in a small infraorbital transversal angle. These findings might explain the different inclination of ectopic canines.

Mandibular rotation during the transitional dentition

Objective:

To determine whether dentoalveolar changes or vertical condylar growth is more closely related to the true forward rotation of the mandible during the transition between the late primary and early mixed dentition stages of development.

Materials and Methods:

The sample included 50 subjects (25 males and 25 females) with Class I (N  =  25) and Class II (N  =  25) molar relationships. They were selected based on the availability of lateral cephalograms at two developmental stages: T1: last film with complete primary dentition (5.8 ± 0.4 years) and T2: first film with permanent incisors and permanent molars fully erupted (8.0 ± 0.2 years). Seventeen landmarks were identified and 22 measurements were calculated. The mandibles at T1 and T2 were superimposed using natural reference structures in order to measure true mandibular rotation.

Results:

The mandible underwent −2.4° ± 2.6° of true rotation, 1.9° ± 2.4° of remodeling, and −0.6° ± 1.8° of apparent rotation. There were no significant sex or Class differences in true rotation, remodeling, and apparent rotation. There was a moderate correlation (r  =  0.76) between true rotation and remodeling and a moderately low correlation (r  =  0.40) between true rotation and apparent rotation. There was a weak correlation between true rotation and SNA (r  =  0.28). True rotation was most closely associated with the increases in U1/S-N (r  =  −0.34), increases in U1/PP (r  =  −0.36), and decreases in Id-Me (r  =  0.36).

Conclusions:

Independent of sex and Class, the true mandibular rotation that occurred between the late primary and early mixed dentition was mostly masked by angular remodeling, resulting in limited amounts of apparent rotation. True rotation was significantly related to anterior dentoalveolar changes but not to the vertical growth changes that occurred.

Mouth breathing children and cephalometric pattern: does the stage of dental development matter?

OBJECTIVE

To test the hypothesis that there is no difference in the cephalometric pattern between mouth breathing children with primary dentition and mixed dentition.

METHODS

Cephalometric measurements of 126 mouth breathing children (MB) were compared to 126 nasal breathing controls (NB). Both groups were divided into deciduous dentition (mean age 4 years, 8 months) and mixed dentition (mean age 7 years, 9 months) groups.

RESULTS

A statistically significant difference was observed in the dentofacial patterns of MB children compared to NB children. The total length of the mandible was smaller in MB compared to NB children. However, this difference was found only in subjects with mixed dentition. The length of the mandibular corpus is similar in MB and NB children, although older MB children with mixed dentition had significantly smaller measurements. The lower anterior facial height was higher in MB compared to NB children, but this difference was evident only in younger children with primary dentition. Mandibular plane angle, Y-axis angle and lower anterior facial height to total anterior facial height ratio were greater, and posterior facial height to total anterior facial height ratio was smaller in MB than NB children, indicating that mouth breathers had a more vertical facial growth pattern. However, no differences were found in the vertical growth pattern associated with the stage of dental development. The ANB angle was not associated with the maturational status of occlusion. Linear measurements and the gonial angle were significantly different between children with primary and mixed dentition, but such differences were associated with normal vertical growth.

CONCLUSIONS

The present investigation rejected the null hypothesis and showed significant cephalometric differences between primary and mixed dentition MB children. Mouth breathing children in the mixed dentition have a smaller mandible (in terms of total length and corpus length) than nasal breathers. In children with primary dentition, the lower anterior facial height is higher in MB than in NB children. There was no significant association between the stage of dental development of mouth breathing children (either in the primary or mixed dentition) and the other cephalometric patterns.

Treatment of skeletal open-bite malocclusion with lymphangioma of the tongue

Lymphangioma of the tongue causes massive tongue enlargement, leading to difficulties in swallowing and mastication, speech disturbances, airway obstruction, and skeletal deformities such as open-bite malocclusion. Early reduction of tongue volume improved the excessive open bite in a young girl, but it was not sufficient to redirect the original hyperdivergent growth pattern. Orthodontic camouflage treatment was therefore rendered. Long-term evaluation after tongue-reduction surgery and orthodontic treatment is presented.

[Cervical vertebrae: Mandibular growth dynamism indicators?]

A study of mandibular growth maturation was performed on a population of 103 patients during orthodontic treatment (69 girls and 34 boys) from 11 to 16 years, having initially a Class II skeletal discrepancy. The relationship between wrist maturation indices and the cervical vertebrae maturation was studied by Lamparski classification. Significant correlations were found between Björk stages, MP3=, MP3 cap and MP3 U and respectively Lamparski stages as CVS 2, CVS 3-4 and CVS 5-6. This retrospective longitudinal study identified three mandibular variables at three different maturation stages according to Björk classification and to the six stages of Lamparski classification. The relationships between these different maturation stages and a quantitative mandibular response permit to estimate optimal time for our orthodontic therapy. The results indicate a significant increase in mandibular length between CVS 4 and CVS 5, suggesting the persistence of a condylar response to a stimulation therapy after CVS3 or CVS 4 stages (MP3 cap). Mandibular growth seems to continue after MP3 U stage or CVS 5 stage.

Evaluation of mandibular morphology in different facial types

The purpose of this study was to evaluate mandibular morphology in different facial types using various parameters. This study was conducted on lateral cephalograms of a total of 110 subjects, which included 55 males and 55 females between the age of 18-25 years having a mean of 22.3 years for males and 21.5 years for females. The sample was divided into normodivergent, hypodivergent, and hyperdivergent subgroups based on Jarabak's ratio. Symphysis height, depth, ratio (height/depth) and angle, antegonial notch depth, ramal height and width, mandibular depth, upper, lower, and total gonial angle, and mandibular arc angle were analyzed statistically and graphically. It was found that the mandible with the vertical growth pattern was associated with a symphysis with large height, small depth, large ratio, small angle, decreased ramus height and width, smaller mandibular depth, increased gonial angle, and decreased mandibular arc angle in contrast to mandible with a horizontal growth pattern. Sexual dichotomy was found with mean symphysis height and depth in the female sample being smaller than in the male sample, but symphysis ratio was larger in the female sample; males having greater ramus height and width, mandibular depth than females. The mandible seemed to have retained its infantile characteristics with all its processes underdeveloped in hyperdivergent group.

Three-dimensional longitudinal evaluation of palatal vault changes in growing subjects

OBJECTIVE

To evaluate palatal vault change in children and to assess the reliability of two palatal parameters in assessing growth modifications.

SUBJECTS AND METHODS

A group of 26 healthy white children aged 5.3 ± 0.3 years (15 boys, 11 girls) were randomly selected. Impressions of the upper dental arches were obtained at baseline and at 12, 18, and 30 months follow-up. Three-dimensional digital images of study casts were obtained using a laser scanning device. Palatal surface area and palatal volume were measured on the digital study casts at each time point. Effect size (ES) coefficients were calculated for both parameters as indices of diagnostic reliability in individual subjects when at least equal to 1.0.

RESULTS

Significant increases in palatal surface area and volume were seen over the observation period (P < .001). ES coefficients for palatal surface area were greater than those for palatal volume. However, even for the former parameter, only the value taken at 30 months was above the threshold.

CONCLUSIONS

Growth of the palatal vault was significant during the observation period, which coincides with primary and mixed dentition stages. Palatal surface area appears to be more reliable than palatal volume in assessment of growth modifications in individual subjects.

Associations between alveolar heights and vertical skeletal pattern in Moroccan adults: a cephalometric study of 127 clinical cases

The aim of our study was to investigate vertical dentoalveolar compensation in untreated patients, in search of an association between vertical facial pattern and alveolar heights. This study involved the participation of 127 untreated Moroccan adults from the patient population of the ODF (Dentofacial Orthopedics) Department at the Center for Dental Treatment and Consultation (CCTD) in Rabat. Full adult dentition was the only criterion for inclusion. Patients with major syndromes and patients with facial clefts were excluded from the study. For the purposes of this analysis, we used profile teleradiography to measure vertical and sagittal skeletal variables as well as vertical dentoalveolar variables in the anterior and posterior maxillary and mandibular regions. We also measured the incisor axes. Analyses and statistical tests were performed with SPSS(®) statistics software (version 9.5 for Windows). Results indicate that: (i) upper posterior alveolar height (UPAH) does not correlate with skeletal variables of facial divergence, but correlates strongly with anterior facial height (AFH) and moderately with posterior facial height (PFH); (ii) lower anterior alveolar height (LAAH) correlates negatively with facial height index (FHI), positively with the FMA and AFH, but does not correlate with PFH; (iii) lower posterior alveolar height (LPAH) does not correlate with skeletal variables of facial divergence; (iv) upper anterior alveolar height (UAAH) changes inversely with FHI, correlates positively with the FMA and does not correlate with PFH.

Spring-loaded bite-blocks for early correction of skeletal open bite associated with thumb sucking

Skeletal open-bite malocclusion is frequently discussed in orthodontics. Diagnosis, treatment, and retention can be difficult because this malocclusion has numerous correlated etiologic factors. The earlier this malocclusion is corrected, the better the prognosis will be, especially when the problem is skeletal. This article presents a patient with a skeletal open bite and a thumb-sucking habit who was treated in the mixed dentition with an orthodontic appliance that included an acrylic occlusal splint along with spring-loaded blocks to guide the vertical force against the posterior teeth and the alveolar process. The usefulness of the appliance as a habit-breaking therapy is also highlighted.

Molar height and dentoalveolar compensation in adult subjects with skeletal open bite

OBJECTIVE

To evaluate the skeletal and dentoalveolar components in adult subjects with skeletal open bite in the presence or absence of dental compensation.

MATERIALS AND METHODS

The study sample included 69 adult female subjects who belonged to three groups according to skeletal vertical relationships and overbite. A total of 15 variables (5 angular, 10 linear) were evaluated. Values in the dentally compensated open bite group (COBG), the dentally noncompensated open bite group (NCOBG), and the control group with normal vertical skeletal relationships and overbite (CG) were compared by means of parametric statistics.

RESULTS

The COBG and the NCOBG showed significantly greater incisor and molar heights in both jaws than the CG. No significant difference in upper or lower molar height was found between COBG and NCOBG. Incisor height was significantly greater in COBG than in NCOBG. Elongation in the incisor region was accompanied by significant narrowing of the lower anterior alveolar process in both skeletal open bite groups. Proclination of the upper incisors was significantly smaller in the COBG than in the other groups.

CONCLUSIONS

Dentoalveolar components consisting of incisor elongation and inclination play a significant role in compensating for skeletal open bite configuration in adult subjects. Increased molar height is a common finding in adults with skeletal open bite.

Chin development as a result of differential jaw growth

INTRODUCTION

During facial growth, the maxilla and mandible translate downward and forward. Although the forward displacement of the maxilla is less than that of the mandible, the interarch relationship of the teeth in the sagittal view during growth remains essentially unchanged. Interdigitation is thought to provide a compensatory (tooth movement) mechanism for maintaining the pattern of occlusion during growth: the maxillary teeth move anteriorly relative to the maxilla while the mandibular teeth move posteriorly relative to the basilar mandible. The purpose of this study was to investigate the hypothesis that the human chin develops as a result of this process.

METHODS

Twenty-five untreated subjects from the Iowa Facial Growth Study with Class I normal occlusion were randomly selected based on availability of cephalograms at T1 (mean = 8.32 yr) and T2 (mean = 19.90 yr). Measurements of growth (T2 minus T1) parallel to the Frankfort horizontal (FH) for the maxilla, maxillary dentition, mandible, mandibular dentition, and pogonion (Pg) were made.

RESULTS

Relative to Pg (a stable bony landmark), B-point moved posteriorly, on average 2.34 mm during growth, and bony chin development (B-point to Pg) increased concomitantly. Similarly, the mandibular and maxillary incisors moved posteriorly relative to Pg 2.53 mm and 2.76 mm, respectively. A-point, relative to Pg, moved posteriorly 4.47 mm during growth.

CONCLUSIONS

Bony chin development during facial growth occurs, in part, from differential jaw growth and compensatory dentoalveolar movements.