Vertical Skeletal Relationships Research Articles

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

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

Dentofacial characteristics of women with oversized mandible and temporomandibular joint internal derangement

To analyze dentofacial characteristics of temporomandibular joint internal derangement (TMJ ID) in orthodontic patients with oversized mandible (skeletal Class III pattern). The sample consisted of 66 women whose mandibular body length to anterior cranial base ratio is greater than 1.12. They were divided into three groups based on magnetic resonance images of bilateral TMJs: bilateral normal disk position (BN), bilateral disk displacement with reduction (DDR), and bilateral disk displacement without reduction (DDNR). Thirty-five cephalometric variables regarding their lateral cephalograms were analyzed by Kruskal-Wallis test to evaluate differences in dentofacial morphology among the three groups. Subjects with TMJ ID had a clockwise rotation of the ramus, with backward position of mandible, labial tipping of mandibular incisors, and protrusion of upper and lower lips. However, TMJ ID did not significantly influence vertical skeletal relationships. Most of the significant dentofacial changes were found between BN and DDR, and dentofacial changes between DDR and DDNR were minimal. This study suggests that dentofacial changes associated with TMJ ID begin to appear when TMJ ID develops to DDR from BN in patients with oversized mandible.

Effetti dentoscheletrici di un dispositivo intraorale per la distalizzazione dei molari e confronto sistematico con apparecchi alternativi

Objective The aim of the present study was to evaluate the dentoskeletal effects produced by an intraoral appliance for the unilateral or bilateral distalization of the upper first molars. Materials and methods We analyzed the pre- and post-distalization cephalometric films of 17 patients (10 males and 7 females) with class II malocclusion treated with the First Class appliance. The mean age at the start of treatment was 13 years and 4 months. Bilateral class II molar relationships were corrected within 2.4 months on average. Results Seventy percent of the space created anterior to the first molars was the result of maxillary molar distalization; the remaining 30% was due to reciprocal loss of anchorage by the maxillary second premolars. The maxillary first molars showed significant distalization of 4.0 mm, associated with a significant distal inclination of 4.6 degrees and a significant extrusion of 1.2 mm. As for loss of anchorage, the second premolars exhibited significant mesial movement of 1.7 mm and significant mesial inclination of 2.2 degrees. In the anterior region, significant mesial movement of the maxillary incisors of 1.3 mm was associated with significant incisor proclination (2.6 degrees) and a significant increase in the overjet (1.2 mm). No significant changes in either sagittal or vertical skeletal relationships were observed. Conclusions The results suggest that the intraoral appliance can produce efficient distalization of the maxillary permanent first molars comparable to that offered by other intraoral distalization devices.

Comparison of cephalometric norms between Mongolian and Korean adults with normal occlusions and well-balanced profiles

Objective: The purposes of this study were to establish cephalometric norms of Mongolian adults, which have not previously been reported in orthodontic journals, and to compare them with cephalometric norms of Korean adults. Methods: Lateral cephalometric radiographs of 74 Mongolian adults (35 men, 39 women) and 95 Korean adults (52 men, 43 women) with normal occlusions and well-balanced lateral profiles were obtained. The subjects were chosen by orthodontists of the same ethnic background. Forty craniofacial variables were measured, and groups were compared by analysis of covariance. Results: The cephalometric norms for male and female Mongolian and Korean adults with normal occlusions and well-balanced lateral profiles were established. Sexual dimorphism was found in linear skeletal measurements and vertical skeletal relationships. Compared with Korean adults, Mongolian adults had shorter anterior facial height, more prominent chins, and more upright upper incisors. There were few differences in soft tissue measurements. The differences were statistically significant, but their clinical importance may be limited. Conclusions: Cephalometric differences can be considered, but little difference may exist in the orthodontic diagnosis and treatment planning of Mongolian and Korean adults. (Korean J Orthod 2011;41(1):42-50)

Midpalatal miniscrews for orthodontic anchorage: Factors affecting clinical success

The purpose of this study was to investigate the success rate of midpalatal miniscrews used for orthodontic anchorage and the factors affecting clinical success. One hundred twenty-eight consecutive patients (101 female, 27 male; mean age, 23.4 years), who received a total of 210 miniscrews in the midpalatal suture area, were examined. Success rates were determined according to 10 clinical variables. The overall success rates were 88.20% for the total number of patients and 90.80% for the total number of miniscrews. There were no significant associations among success rate and sex, total period of treatment with miniscrews, diameter of miniscrews, types of tooth movements, and variables that represent sagittal and vertical skeletal relationships (ANB, FMA, and Sn-GoGn). The operator's learning curve, patient's age, area (midpalatal or parapalatal), and splinting significantly influenced the success rates. After adjusting for other variables, only 1- splinting-showed a significant effect on the success rate. The joining of 2 miniscrews by splinting, placement of the miniscrew in the midpalatal suture, patient's age (especially >15 years), and operator's skill were factors influencing the clinical success of orthodontic miniscrews in the palate.

Classification of the skeletal variation in normal occlusion.

The aims of this study were to classify normal occlusion samples into specific skeletal types and to analyze the dentoalveolar compensation in a normal occlusion in order to provide the clinically applicable differential diagnostic criteria for an individual malocclusion patient. Lateral cephalograms of 294 normal occlusion samples, who were selected from 15,836 adults through a community dental health survey, were measured. Using a principal component analysis, two factors representing the anteroposterior and vertical skeletal relationships were extracted from 18 skeletal variables. Cluster analysis was then used to classify the skeletal patterns into nine types. Nine types of polygonal charts with a profilogram were created. Discriminant analysis with a stepwise entry of variables was designed to identify several potential variables for skeletal typing, which could be linked with computerized cephalometric analysis for an individual malocclusion patient. Discriminant analysis assigned 87.8% classification accuracy to the predictive model. It was concluded that because the range of a normal occlusion includes quite diverse anteroposterior and vertical skeletal relationships, classifying the skeletal pattern and establishing an individual dentoalveolar treatment objective might facilitate clinical practice.

Standards of soft tissue Arnett analysis for surgical planning in Turkish adults

The aims of this study were (1) to establish standards for Arnett soft tissue cephalometric analysis of Anatolian Turkish young adults and (2) to identify possible gender differences between males and females. After analysing the cephalometric radiographs of 350 individuals, 133 subjects (67 males, mean age 22.6 +/- 2.2 years, and 66 females, mean age 22.1 +/- 2.6 years) with normal antero-posterior and vertical skeletal relationships were selected. The true vertical line was established. The landmarks were marked and soft tissue facial analysis was performed. For statistical evaluation, an independent-samples t-test was used. The lower lip thickness of the Turkish population was lower and menton thickness was greater than Arnett's norms. Turkish subjects have depressed orbital rims, cheek bones, subpupils, upright and thin upper and lower lips, retruded incisors, and pogonion and point B. Most of the Turkish mean harmony values were within the range of Arnett's harmony standards. Soft tissue thicknesses were greater and facial lengths, except upper incisor exposure, were longer in Turkish males than females. These differences between ethnic groups should be taken into consideration when formulating orthodontic/orthognathic treatment plans for patients with dentofacial deformity.

Glenoid fossa position in Class III malocclusion associated with mandibular protrusion

Our aim in this study was to investigate the position of the glenoid fossa in subjects with Class III malocclusion associated with mandibular protrusion to better clarify the role of this craniofacial component in Class III skeletal disharmony. A sample of 30 subjects, aged 8 years +/- 6 months, with skeletal and dental Class III malocclusion associated with mandibular protrusion, normal skeletal vertical relationships, and normal mandibular dimensions, was compared with a control group of 33 subjects with skeletal and dental Class I relationships. The comparisons between the Class III group and the control group on the cephalometric measures for the assessment of glenoid fossa position were performed with the Mann-Whitney U test at P <0.05. Subjects with Class III malocclusion had a significantly more mesial position of the glenoid fossa, when compared with the control group as measured with 3 parameters. An anterior position of the glenoid fossa is a possible diagnostic anatomic feature of Class III malocclusion associated with mandibular protrusion. An effective measurement to evaluate glenoid fossa position in craniofacial relationships is the cephalometric distance from the glenoid fossa to the frontomaxillary-nasal suture.

Simultaneous 3-Dimensional Le Fort I/Distraction Osteogenesis Technique: Positional Changes

This preliminary study assesses the positional changes of the maxilla after simultaneous 3-dimensional Le Fort I osteotomy and distraction osteogenesis (3D-LFI/DO). The records of 18 patients, 17.7 years of age (range, 12-38 years) at the time of surgery, manifesting transverse maxillary deficiencies and variable sagittal/vertical deformities were evaluated presurgically and 3 years postsurgery (range, 1 to 10 years). All patients underwent midsagittal 2-piece Le Fort I osteotomies. The planned sagittal and vertical positional changes were immediately performed by the Le Fort I surgery. After a latency period of 5 to 7 days, maxillary expansion was slowly achieved by distraction osteogenesis using a Hyrax appliance activated 1-mm/day. Once the planned transverse expansion had been attained, the Hyrax device served as a retention appliance for 8 to 12 weeks, after which the distraction gap was orthodontically closed. The morphological changes were assessed by comparing standardized preoperative and postsurgical models, posterior-anterior radiographs, and lateral cephalograms. Class I canine and molar relationships, along with satisfactory sagittal and vertical skeletal relationships, were observed at follow-up. The maxilla was advanced (1.5-1.8 mm) and positioned either superiorly or inferiorly (1.2-2.9 mm), depending on the original deformity. The arch perimeter increased 5.4 mm and the arch width increased between 4.2 and 6.6 mm. The maxillary expansion was nonparallel, greater anteriorly and inferiorly. The 3D-LFI/DO can be used to simultaneously and selectively widen, lengthen and vertically reposition the maxilla, producing acceptable post-treatment skeletal and dental relationships, without healing problems observed clinically.

O.099 Nasal form following secondary alveolar bone grafting

Introduction: The aim of this study was to investigate the effectiveness of a quad-helix/crib (Q-H/C) appliance in a group of growing subjects with thumb-sucking habits and both dental and skeletal open bites. Methods: The records of 23 subjects treated with Q-H/C appliances were compared with a control group of 23 untreated subjects with similar vertical relationships. Lateral cephalograms were analyzed before treatment (T1; mean age, 8.4 ± 1.4 years) and immediately after treatment (T2; mean age, 9.9 ± 1.5 years). Mean duration of treatment was 1.5 ± 7 months. The T2-T1 changes in the 2 groups were compared with a nonparametric test for independent samples (Mann-Whitney U test). Results: The average increase in overbite during Q-H/C therapy (3.6 mm more than the control group) overcorrected the amount of anterior open bite at T2. However, 4 of 23 subjects did not show positive overbites at T2. Both the maxillary and mandibular incisors had significantly greater lingual inclinations (about 4.0°) associated with greater extrusion (1.4 and 1.0 mm, respectively) in the Q-H/C group than in the control group. In addition, the treated group showed a greater downward rotation (1.2°) of the palatal plane than did the control group. This change was associated with a greater increase in upper anterior facial height (0.7 mm) and a clinically significant reduction in the palatal plane-mandibular plane angle (−1.7°) in the Q-H/C group with respect to the controls. The upper and lower lips showed significant tendencies toward retraction relative to the E-plane in the treated group (2.6 and 2.9 mm, respectively) compared with the controls. Conclusions: The Q-H/C appliance was effective in correcting the dental open bite in 90% of growing subjects with thumb-sucking habits and dentoskeletal open bites. The Q-H/C protocol produced a clinically significant improvement in the vertical skeletal relationships because of downward rotation of the palatal plane.

Glenoid Fossa Position in Class II Malocclusion Associated with Mandibular Retrusion

To assess the position of the glenoid fossa in subjects with Class II malocclusion associated with mandibular retrusion and normal mandibular size in the mixed dentition. A sample of 30 subjects (16 male, 14 female), age 9 years +/- 6 months, with skeletal and dental Class II malocclusion associated with mandibular retrusion, normal skeletal vertical relationships, and normal mandibular dimensions, was compared with a matched group of 37 subjects (18 male, 19 female) with skeletal and dental Class I relationships. The comparisons between the Class II group and the control group on the cephalometric measures for the assessment of glenoid fossa position were performed by means of a nonparametric test for independent samples (Mann-Whitney U-test, P < .05). Subjects with Class II malocclusion presented with a significantly more distal position of the glenoid fossa, when compared with the control group as measured by means of three parameters (GF-S on FH, GF-Ptm on FH, and GF-FMN). A posteriorly displaced glenoid fossa is a possible diagnostic feature of Class II malocclusion associated with mandibular retrusion. An effective cephalometric measurement to evaluate glenoid fossa position is the distance from the glenoid fossa to the frontomaxillonasal suture (GF-FMN).

A method for defining targets in contemporary incisor inclination correction

Different craniofacial properties require individual targets in incisor inclination. These requirements are mostly scheduled on the basis of cephalometric diagnosis, but, however, performed using straightwire appliances, which refer to third-order angles and not to cephalometric data. The objective of this study was to analyze the relationship between incisor third-order angles, incisor inclination, and skeletal craniofacial findings in untreated ideal occlusion subjects with natural dentoalveolar compensation of skeletal variation, in order to link the field of cephalometric assessment of incisor inclination with that of contemporary orthodontic incisor inclination correction. This study utilized lateral cephalograms and corresponding dental casts of 69 untreated Caucasians (21 males and 48 females between 12 and 35 years of age) with neutral (Angle Class I) molar and canine relationships and an incisor relationship that was sagittaly and vertically considered as ideal by three orthodontists (i.e. well supported by the antagonistic teeth and without the need for either deep or open bite correction). Upper (U1) and lower (L1) axial incisor inclinations were assessed with reference to the cephalometric lines NA and NL, and NB and ML, respectively. Sagittal and vertical skeletal relationships were classified using SNA (SNB) and NSL-ML (NSL-NL) angles. Third-order angles (U1TA and L1TA) were derived from direct dental cast measurements using an incisor inclination-recording appliance. The relationships between cephalometric and third-order measurements evaluated by calculating Pearson product-moment correlation coefficients (a = 0.05) showed strong correlations between cephalometric axial inclination data (U1NA/deg, L1NB/deg, U1NA/mm, L1NB/mm, U1NL, and L1ML) and sagittal-skeletal data, but no significant relationship between skeletal-vertical findings and incisor inclination. The mean U1TA was 4.9 (standard deviation [SD] 5.85) and the mean L1TA -3.0 (SD 6.9) degrees. Regression analyses were used for axial inclination (ANB angle designated as the independent variable) and for third-order data (U1NA, L1NB, U1NL, and L1ML designated as independent variables). Based on the correlations found in this study, a novel method for defining targets in upper and lower incisor third-order correction according to natural standards is presented. As a consequence, third-order movements can be adapted to cephalometric diagnosis with enhanced accuracy.

Early orthodontic treatment of skeletal open-bite malocclusion with the open-bite bionator: A cephalometric study

This study was designed to evaluate the effectiveness of the open-bite bionator in growing subjects with increased vertical dimensions. The records of 20 subjects with high-angle skeletal relationships (MPA > or =25 degrees) were examined. Cephalometric measurements were compared with those obtained from 23 sets of records of an untreated group matched according to age, sex, vertical skeletal relationships, and time intervals between records. Lateral cephalograms were analyzed before the start of treatment (mean age; 8.3 years) and after therapy and retention, with a mean period of observation of 2.5 years. The treated group had a significantly smaller palatal plane-mandibular plane angle (-1.9 degrees) and a greater overbite (+1.5 mm) associated with a significantly smaller overjet when compared with the control group. Based on the analysis of this sample, early treatment of skeletal open bite with the open-bite bionator appears to produce a modest effect that mainly consists of significant improvement in intermaxillary divergence. No favorable effects on the extrusion of posterior teeth were found.

Treatment and Posttreatment Effects of Quad-Helix/Crib Therapy of Dentoskeletal Open Bite

To investigate the effects of the quad-helix/crib (Q-H/C) appliance in subjects with thumb-sucking habits and dentoskeletal open bite at 2 years after the end of active treatment. The records of 21 subjects treated with the Q-H/C appliance were compared with a control group of 21 untreated subjects with similar vertical relationships. Lateral cephalograms were obtained before treatment (T1; mean age 8.4 +/- 1.4 years) and at about 2 years after treatment (T2; mean age 11.7 +/- 1.9 years) and analyzed. Mean treatment duration was 1.5 years +/- 7 months. The T2-T1 changes in the two groups were compared with a nonparametric test for independent samples. The mean increase in overbite during Q-H/C therapy (4.1 mm) represented an overcorrection of the amount of anterior open bite at T2. Both the maxillary and mandibular incisors showed significantly greater extrusion in the Q-H/C group than in the control group. The treated group showed a greater downward rotation (1.8 degrees ) of the palatal plane than did the control group. This change was associated with a clinically significant reduction in the palatal plane/mandibular plane angle (-2.5 degrees ) in the Q-H/C group. The upper lip showed significant retraction relative to the E-plane in the treated group (3.6 mm) compared with the controls. The Q-H/C appliance was effective in correcting dental open bite in 85% of the growing subjects with thumb-sucking habits and dentoskeletal open bites. Correction of anterior open bite was associated with a clinically significant improvement in maxillomandibular vertical skeletal relationships.

Treatment effects of the bionator and high-pull facebow combination followed by fixed appliances in patients with increased vertical dimensions

The purpose of this study was to evaluate the effectiveness of a first phase of bionator and high-pull facebow treatment followed by a second phase of fixed appliance therapy in growing subjects with increased vertical dimensions. The records of 24 subjects with high-angle skeletal relationships (mean MPA value approximately 30 degrees) treated consecutively with this protocol were examined. Cephalometric measurements were compared with those obtained from 23 sets of records of an untreated group matched according to age, gender, vertical skeletal relationships, and time intervals between records. The matched group of patients was from the University of Michigan Elementary and Secondary School Growth Study. Lateral cephalograms were analyzed prior to the start of treatment (T1, mean age 9.1 years), at the start of phase 2 treatment (T2, mean age 11.9 years), and after phase 2 treatment (T3, mean age 14.7 years). The total treatment duration (phase 1, retention, and phase 2) for the treated group was 5.5 years, whereas the control group total time interval averaged 5.6 years. As to sagittal relationships, no significant differences were found between treated subjects and controls at the end of the 2-phase treatment for all measurements. Counterintuitively, the bionator and high-pull headgear combination worsened the hyperdivergent facial pattern at a clinically significant level, as shown by analysis of final facial forms. The treated group exhibited a significantly larger MPA value than controls (2.5 degrees) as well as a larger inclination of the Frankfort horizontal to the occlusal plane (2.8 degrees ). Based on the analysis of this sample, the examined therapeutic protocol does not appear to be a recommendable option for treatment of subjects with increased vertical dimensions.

Comparison between skeletal, and facial measurements of vertical dimension in edentulous patients

Background: The use of dots on the nose, and chin as markers for measuring occlusal vertical dimension is common in complete denture construction. Therefore, it is important to evaluate the accuracy of facial measurements while assessing occlusal vertical dimension in edentulous patients. Materials and methods: The study was carried out on 28 edentulous patients. Occlusion rims were constructed, a central bearing-screw attached to the lower occlusion rim, and a central-bearing plate was attached to the upper occlusion rim. Then the occlusal vertical dimension was increased at predetermined amount (3, and 5 mm) by counting the number of flutes of the central bearing screw, and the corresponding facial measurements recorded by the use of a caliper device to the nearest 0.1 mm. Results: It was found that 3 mm increase in skeletal height corresponded to mean facial increase of 1.81 mm and ranged between 1-3.5 mm, while 5 mm increase in skeletal height, correspond to mean facial increase of 3.56 mm and ranged between 2.1-5.3 mm. Conclusions: Alteration of vertical skeletal relationships is corresponding with less alteration in facial movement between reference marks above, and below the mouth. This suggests that depending on facial marks when assessing occlusal vertical dimension is not very accurate.

Treatment effects of a modified quad-helix in patients with dentoskeletal open bites

The aim of this study was to investigate the effectiveness of a quad-helix/crib (Q-H/C) appliance in a group of growing subjects with thumb-sucking habits and both dental and skeletal open bites. The records of 23 subjects treated with Q-H/C appliances were compared with a control group of 23 untreated subjects with similar vertical relationships. Lateral cephalograms were analyzed before treatment (T1; mean age, 8.4 +/- 1.4 years) and immediately after treatment (T2; mean age, 9.9 +/- 1.5 years). Mean duration of treatment was 1.5 +/- 7 months. The T2-T1 changes in the 2 groups were compared with a nonparametric test for independent samples (Mann-Whitney U test). The average increase in overbite during Q-H/C therapy (3.6 mm more than the control group) overcorrected the amount of anterior open bite at T2. However, 4 of 23 subjects did not show positive overbites at T2. Both the maxillary and mandibular incisors had significantly greater lingual inclinations (about 4.0 degrees) associated with greater extrusion (1.4 and 1.0 mm, respectively) in the Q-H/C group than in the control group. In addition, the treated group showed a greater downward rotation (1.2 degrees) of the palatal plane than did the control group. This change was associated with a greater increase in upper anterior facial height (0.7 mm) and a clinically significant reduction in the palatal plane-mandibular plane angle (-1.7 degrees) in the Q-H/C group with respect to the controls. The upper and lower lips showed significant tendencies toward retraction relative to the E-plane in the treated group (2.6 and 2.9 mm, respectively) compared with the controls. The Q-H/C appliance was effective in correcting the dental open bite in 90% of growing subjects with thumb-sucking habits and dentoskeletal open bites. The Q-H/C protocol produced a clinically significant improvement in the vertical skeletal relationships because of downward rotation of the palatal plane.

Cephalometric standards for Slovenians in the mixed dentition period

The aim of this study was to develop standard cephalometric values for Slovenians in the period of the mixed dentition. Eighty-eight children were included in the study (46 girls and 42 boys, mean age 9.31 +/- 1.52 years). The selection criteria were: in the mixed dentition, a score of the modified Eismann method for an objective assessment of malocclusion of less than 15 points, the absence of aplasia and supernumerary teeth, no congential anomalies and no previous orthodontic treatment. Twenty-five cephalometric measurements were performed twice to analyse the size and shape of the craniofacial complex. The reliability of the measurements was assessed by correlation coefficients, regression, and analysis of inter-subject differences; satisfactory results were obtained. The differences between boys and girls and between those in the early and late mixed dentition period were tested with a two-way analysis of variance. The most pronounced changes between the early and late mixed dentition were observed in the vertical skeletal relationships: a decrease in mandibular inclination, interbasal angle and gonial angle, and an increase in anterior and posterior face height. Sagittal skeletal relationships remained constant from the early to the late mixed dentition. No significant differences were found between the observed developmental stages. Significant differences between genders were found only for anterior and posterior face height, with boys showing larger values (P </= 0.001). As there were no significant differences between the early and late mixed dentition, the mean measurement values of the total sample can be used as cephalometric standards for Slovenians in the mixed dentition period.

Simultaneous functional and fixed appliance therapy for growth modification and dental alignment prior to prosthetic habilitation in hypohidrotic ectodermal dysplasia: A clinical report

This clinical report describes the simultaneous use of functional and fixed appliances to modify the pattern of dentofacial development and align teeth in preparation for prosthodontic habilitation of a growing child with hypohidrotic ectodermal dysplasia. The treatment objective was to create a more favorable starting point for the prosthodontic phase of habilitation by improving the sagittal and vertical skeletal relationships and facial esthetics. This was accomplished through growth modification with functional appliances conducted simultaneously with eruption of maxillary and mandibular molars, dental arch expansion, alignment, and space management using fixed orthodontic appliances. Orthodontic retention was accomplished by means of removable partial dentures. A second phase of orthodontics conducted closer to the age of skeletal maturation will aim at definitive tooth alignment in preparation for dental implant-supported restorations.

Postpubertal assessment of treatment timing for maxillary expansion and protraction therapy followed by fixed appliances

In this cephalometric investigation, we evaluated the correction of Class III malocclusion in subjects who had attained postpubertal skeletal maturity and considered whether treatment timing influenced favorable craniofacial modifications. All subjects (n = 50) were treated with an initial phase of rapid maxillary expansion and protraction facemask therapy, followed by a second phase of preadjusted edgewise therapy. The treated sample was divided into an early treated group (early mixed or late deciduous dentition, 33 subjects) and a late treated group (late mixed dentition, 17 subjects). Mean treatment duration times were 7 years 2 months for the early treatment group and 4 years 5 months for the late treatment group. The treated patients were matched to untreated controls (early control group, 14 subjects; late control group, 10 subjects) on the basis of race, sex, mean age at first observation, mean age at second observation, mean observation intervals, and type of malocclusion. A modified version of Johnston's pitchfork analysis, with additional angular and linear measures for mandibular size and shape and for vertical skeletal relationships, was performed. Analysis of variance was used to evaluate the difference in means for each cephalometric variable in the treated groups compared with the corresponding control groups. The findings showed that orthopedic treatment of Class III malocclusion was more effective when it was initiated at an early developmental phase of the dentition (early mixed or late deciduous) rather than during later stages with respect to untreated Class III control groups. Patients treated with rapid maxillary expansion and facemask therapy in the late mixed dentition, however, still benefited from the treatment, but to a lesser degree. Early treatment produced significant favorable postpubertal modifications in both maxillary and mandibular structures, whereas late treatment induced only a significant restriction of mandibular growth. Significant changes in mandibular size were associated with significant changes in mandibular shape only in early treated subjects. The main contribution to overall occlusal correction was related to skeletal modifications rather than dental changes in both early and late treated groups.