Forward Mandibular Growth Research Articles

Factors Affecting Mandibular Growth and Displacement and Their Effect on Treatment Outcome

Orthodontists often have difficulty distinguishing between growth and displacement when it comes to the mandible and often the two are merged into one and referred to as just mandibular growth. It is clinically important to distinguish between the two as it can greatly affect the choice of treatment protocol and mechanics. In this review we shall attempt to clarify the issue with clinical examples in the hope of bringing more understanding to the problem. Controlling the factors that are involved in determining the outcome of orthodontic treatment in a growing patient can often be a difficult task and is affected by the stage of maturation. This is particularly problematic if the patient is in a slow growth phase. In some instances, this has led to the unfortunate conclusion that early or interceptive treatment is a waste of time and not only has it caused frustration for the clinician and family but also as it may result in extra cost when two phases of treatment may be needed to correct the malocclusion. With a better understanding of the factors that determine growth and displacement of the mandible better choices of treatment time and mechanics can be made and the correction of a particular malocclusion can be more successful. In the following we shall discuss the factors that affect mandibular displacement and how growth and orthodontic tooth movement affect the outcome. We shall show examples of patients where the lack of adequate condylar growth results in unfavorable displacement of the chin and others where pronounced forward displacement of the chin is the result of excessive condylar growth. We shall further discuss the role of vertical control in cases where the inherited mandibular growth pattern does not favor forward mandibular growth.

Orthosurgical management of severe class III malocclusion - A case report

Class III malocclusions are the result of insufficient forward growth of the maxilla, excessive forward mandibular growth or a combination of both. For patients whose orthodontic problems are so severe that neither growth modification nor camouflage offers a solution, surgery to realign the jaws or reposition dentoalveolar segments is the only possible treatment. Dramatic progress in recent years has made it possible for combined surgical orthodontic treatment to be carried out successfully for patients with a severe dentofacial problem. This case report highlights the successful management of a 19-year-old male with skeletal class III relationship with compromised esthetics and poor functional adaptation with combined orthodontic and surgical line of treatment. Patient's malocclusion was decompensated first by pre-surgical orthodontics with extractions of four pre molars followed by orthognathic surgery to achieve structural balance, acceptable esthetics and stable functional occlusion. Keywords: Skeletal Class III malocclusion, Orthognathic surgery, Decompensation.

Early treatment of Class III malocclusion by maxillary protraction facial mask: effects on craniofacial structures and upper airway dimensions

The aim of our study was to evaluate the effect of treatment with a maxillary protraction appliance on the development of the craniofacial structures and to describe the correlation between the skeletal changes and the sagittal airway dimension associated with tongue, soft palate, and hyoid bone position in skeletal Class III children. A total of 40patients with Class III malocclusions were evaluated by the use of lateral cephalograms. Pretreatment and posttreatment cephalometric radiographs were analyzed; linear and angular measurements were performed by the same orthodontist. The effect of treatment with a maxillary protraction appliance on the development of the craniofacial structures were evaluated by Student's T test and the correlation between treatment changes in craniofacial morphology and those in upper airway, tongue, soft palate, and hyoid position was evaluated by Pearson's correlation test. A significant increase in maxillary forward growth, inhibition of mandibular forward growth, and clockwise rotation of the mandible were observed. The statistical analysis revealed that maxillary growth had a significant positive effect on the superior upper airway sagittal dimension. The nasopharyngeal airway dimensions can be improved in the short term with maxillary protraction in skeletal Class III children.

Forward Mandibular Growth after Correction of Deep Bite in Growing Patient with Skeletal Class II

Forward Mandibular Growth after Correction of Deep Bite in Growing Patient with Skeletal Class II

Treatment outcomes of Class II malocclusion cases treated with miniscrew-anchored Forsus Fatigue Resistant Device: A randomized controlled trial.

To evaluate the skeletal, dental, and soft tissue effects of the Forsus Fatigue Resistant Device (FRD) used with miniscrew anchorage and compare them with those of the conventional Forsus FRD. This study was carried out on 38 patients. These patients were randomly allocated into three groups. The 14 patients in group 1 (aged 12.76 ± 1.0 years) were treated with the FRD appliance. In group 2, the 15 patients (aged 12.52 ± 1.12 years) received treatment with FRD using miniscrew anchorage, and the 9 patients in group 3 (aged 12.82 ± 0.9 years) received no treatment as a control group. Linear and angular measurements were made on lateral cephalograms before and immediately after Forsus treatment. Data were analyzed statistically using paired t-, ANOVA, and Tukey tests. Class I molar relationship and overjet correction were achieved in both treatment groups. Although mandibular growth was statistically nonsignificant, there was a significant headgear effect on the maxilla. Mandibular incisor proclination, maxillary incisor retroclination, and distalization of maxillary molars were significant in both treatment groups. However, no significant differences were found between the treatment groups. Class II correction was mainly dentoalveolar in both treatment groups. Use of miniscrews with Forsus did not enhance mandibular forward growth nor prevent labial tipping of the mandibular incisors.

Class II young adult treatment with Twin Force Bite corrector: 10-year follow-up

One of the most preferred compliance free fixed functional appliances in nongrowing patients is Twin Force Bite corrector (TFBC). The aim of this case report is to evaluate the effectiveness of TFBC in the treatment of an adult Class II case. A 16-year 1-month-old boy having skeletal and dental Class II relationship was selected. Roth 0.018 × 0.025 inch slots brackets were attached; a fixed lingual arch in the mandibular dental arch and a Nance appliance in the maxillary dental arch were used to increase anchorage. The TFBC therapy used for sagittal activation and stimulation of forward mandibular growth lasted for 3 months. The post-TFBC treatment lasted 6 months and the total treatment time was 9 months. Treatment of a young adult Class II malocclusion with TFBC resulted in a Class I molar occlusion, an ideal overjet, overbite, and incisor angulation in a short time and maintained in the 10-year follow-up.

Growth modification of the face: A current perspective with emphasis on Class III treatment.

A summary of the current status of modification of jaw growth indicates the following. 1. Transverse expansion of the maxilla is easy before adolescence, requires heavy forces to create microfractures during adolescence, and can be accomplished only with partial or complete surgical osteotomy after adolescence. Transverse expansion of the mandible or constriction of either jaw requires surgery. 2. Acceleration of mandibular growth in preadolescent or adolescent patients can be achieved, but slower than normal growth afterward reduces or eliminates a long-term increase in size of the mandible. Restraint of maxillary growth occurs with all types of appliances to correct skeletal Class II problems. For short-face Class II patients, increasing the face height during preadolescent or adolescent orthodontic treatment is possible, but it may make the Class II problem worse unless favorable anteroposterior growth occurs. For those with a long face, controlling excessive vertical growth during adolescence is rarely successful. 3. Attempts to restrain mandibular growth in Class III patients with external forces largely result in downward and backward rotation of the mandible. Moving the maxilla forward with external force is possible before adolescence; moving it forward and simultaneously restricting forward mandibular growth without rotating the jaw is possible during adolescence with intermaxillary traction to bone anchors. The amount of skeletal change with this therapy often extends to the midface, and the short-term effects on both jaws are greater than with previous approaches, but individual variations in the amount of maxillary vs mandibular response occur, and it still is not possible to accurately predict the outcome for a patient. For all types of growth modification, 3-dimensional imaging to distinguish skeletal changes and better biomarkers or genetic identification of patient types to indicate likely treatment responses are needed.

Hypothetical Evaluation of Stress and Displacement of the Mandible with Chin Cup Therapy Using Various Force Vectors (Finite Element Study)

Introduction: Early orthodontic treatment is recommended, since the morphologic pattern of the prognathic face associated with excessive forward mandibular growth is most likely established early in life. The chin cup is the preferred orthopedic appliance for growing children with mandibular prognathism and a normal maxilla. Aims Of Study: Evaluation of the stress and displacements in the mandible from various chin cup force vectors, using three-dimensional finite element model. Materials And Methods: Three-dimensional model of the mandible was modeled and analyzed. Chin cup with 800 g force was applied on the pogonion of the mandible. The direction of the loading vectors were 150, 200, 250, 300, 350, 400 and 900 relative to x axis, then, the mechanical responses in terms of displacement and Von Mises stresses are evaluated. Results: The highest stress levels observed in the condylar, posterior ramus regions and inferior sigmoid notch, and increased as the force vector was transferred away from the condyle. The mandible was displaced in downward and backward direction with the vector passing below and through the condyle (with angles 150, 200 and 250) forward and upward displacement was recorded as the force vector move away from the condyle (within 300, 350, 400 and 900). Conclusions: With the limitations of modeling, boundary conditions, and solution assumptions, chin cup applied in various directions produce different force vectors, which induce different stress and displacements. The force vector is an important determinant of the orthopedic effects of the chin cup and therefore should be carefully considered.

Stability of early Class III orthopedic treatment

The objective of the article is to determine the stability of early Class III orthopedic treatment in the primary and early mixed dentitions. A total of 23 patients with Class III malocclusion in the primary or early mixed dentition (mean age=6.2 ±1.5 years, CVM=1) were treated consecutively by one of the investigators (T.K.) using maxillary expansion and protraction appliances. The average treatment time was 9.1 ± 2.3 months. For each patient, a lateral cephalogram was taken at pre-treatment (T1), post-treatment (T2), and 2 years post-treatment (T3). Each patient served as his/her own control. Cephalometric analysis described by Bjork (1947) and Pancherz (1982) was used. Sagittal and vertical measurements were made along the occlusal plane (OLs) and the occlusal plane perpendicular (Olp), and superimposed on the mid-sagittal cranial structure. Data were analyzed using paired t -test. All patients in the study were treated to Class I or overcorrected to Class II dental arch relationships. Overjet and sagittal molar relationships improved by an average of 4.1 and 1.8mm, respectively (T2–T1). This was a result of 2.6mm of forward maxillary growth, .7mm of forward mandibular growth, 1.2mm of labial movement of maxillary incisors, 1.0mm of lingual movement of mandibular incisors, and .1mm of greater mesial movement of mandibular than maxillary molars. The mean overbite reduction was .9mm. The maxillary and the mandibular molars were erupted occlusally by 1.5 and 1.0mm, respectively. The mandibular plane angle was increased by .9° and the lower facial height by 3.2mm. Overall, 2 years follow-up observation (T3–T2) revealed a decrease in the overjet and the molar relationship by .3 and .2mm, respectively. This was contributed by 2.2mm of excess forward mandibular growth that was compensated by 1.9-mm dentoalveolar compensation. Overall, the changes in the overjet and the molar relationship were 3.8 and 1.5mm, respectively. The overbite reduction was .6mm. Significant overjet and overbite corrections can be obtained with maxillary protraction in the primary or early mixed dentition. Overjet and molar relationship corrections were stable 2 years post-treatment. A combination of dentoalveolar compensation and skeletal changes accounted for this stability.

Dentoskeletal Effects of 2-Phase Treatment Versus 1-Phase Treatment With Extraction of 4 First Premolars in Nonhypodivergent Class II Patients

The aim of this study was to compare the effectiveness of 2-phase (a first phase with Twin Block therapy immediately followed by a second phase with fixed appliance therapy with nonextraction) and 1-phase (fixed appliance therapy with extraction of 4 first premolars) treatment of class II division 1 malocclusion. Two groups of successfully treated subjects, aged 10 to 14 years with class II division 1 malocclusion, were evaluated: 2-phase group (n = 70) and 1-phase group (n = 76). Pretreatment and posttreatment lateral cephalograms were traced manually and subjected to Student t test. In the 2-phase group, the forward positioning of the mandible (Pg-Olp) was less than that of the extraction group. The sagittal mandibular forward growth (Pg-Olp) was, on average, 2.39 ± 0.4 mm in the 2-phase group and 4.56 ± 2.51 mm in the 1-phase group (P = 0.008, P < 0.05). In the vertical plane, the increases in lower facial height and mandibular plane angle were greater in the 2-phase treatment. In the 2-phase group, the lower anterior teeth proclined (Ii-MP) by 7.3 ± 2 degrees, and in the extraction treatment group, it changed -4.1 ± 3.6 degrees. The 1-phase group contributed more sagittal orthopedic effects than did the 2-phase group. The proclination of the mandibular incisors in the 2-phase group might restrain the mandibular bone from growing enough and cause the backward and downward rotation of the mandible.

Correlation between skeletal changes by maxillary protraction and upper airway dimensions

To describe the correlation between the skeletal changes induced by maxillary protraction treatment and the sagittal airway dimension associated with tongue, soft palate, and hyoid bone position in skeletal Class III children. Twenty Class III patients (5 boys, 15 girls; mean age, 9.4 ± 1.8 years) treated with a maxillary protraction appliance were included in this study. Pretreatment and posttreatment cephalometric radiographs were analyzed; linear and angular measurements were performed by an expert orthodontist. The correlation between treatment changes in craniofacial morphology and those in upper airway, tongue, soft palate, and hyoid position was evaluated by Pearson's correlation analysis. A significant increase in maxillary forward displacement, inhibition of mandibular forward growth, and clockwise rotation of the mandible were observed. Simultaneously, nasopharyngeal airway measurements PNS-ad1 and PNS-ad2 significantly increased by 1.4 mm and 1.9 mm, respectively. A correlation analysis revealed that maxillary protraction had a positive relationship with PNS-ad1 and PNS-ad2. The nasopharyngeal airway dimensions can be improved in the short term with maxillary protraction in skeletal Class III children.

Prediction of mandibular third-molar impaction in adolescent orthodontic patients

The purpose of this study was to identify risk factors for mandibular third-molar impaction in adolescent orthodontic patients. Radiographs made before (T1) and after (T2) treatment and at least 10 years postretention (T3) of 134 patients that allowed accurate diagnosis of impaction vs eruption of at least 1 mandibular third molar were evaluated. Univariate logistic regression analyses at T1 showed that the decision to extract premolars (P <.05), an increase of 1 mm in mesial molar movement (P <.05), and an increase of 1 mm in eruption space measured from second molar to Xi point (centroid of the ramus) (P <.01) reduced the risk of impaction by 63%, 22%, and 30%, respectively. An increase of 1 degrees in mandibular third-molar angulation relative to the occlusal plane increased the risk of impaction by 11% (P <.01). Multivariate logistic regression analyses at T1 showed that reduced eruption space (P <.01), signs of forward mandibular growth rotation (P <.01), and female sex (P <.05) increased the risk of impaction. However, association tests documented increased frequencies of extractions and more mesial molar movement in female patients with erupted third molars. Univariate logistic regression analyses at T2 showed that every millimeter of increase in eruption space measured from the second molar to the anterior border of the ramus and to Xi point reduced the risk of impaction by 29% and 22%, respectively (P <.01), whereas every degree of increase in the angle between the occlusal surface and the occlusal plane increased the risk of impaction by 11% (P <.01). Multivariate logistic regression analyses at T2 showed that increased eruption space reduced the risk of impaction (P <.05), whereas increased mesial angulation of the third-molar bud (P <.01) and signs of forward growth rotation (P <.05) increased the risk of impaction.

Effects of maxillary protraction on craniofacial structures and upper-airway dimension.

This study was conducted to examine the effect of treatment with a maxillary protraction appliance on the development of the craniofacial structures and upper-airway dimensions. A total of 25 patients (mean age: 9.8 years) with Class III malocclusions were evaluated by the use of lateral cephalograms. A significant increase in maxillary forward growth, inhibition of mandibular forward growth, and clockwise rotation of the mandible were observed. The maxillary incisors were significantly proclined and the mandibular incisors significantly retroclined. A multiple-regression analysis revealed that maxillary growth had a significant positive effect on the superior upper-airway dimension. These findings indicate that the superior upper-airway dimension can be altered during maxillary protraction.

Dentoalveolar changes related to mandibular forward growth in untreated Class II persons.

The purpose of this study was to investigate dentoalveolar changes related to mandibular forward growth in persons with Class II malocclusions. The longitudinal cephalometric films of 40 subjects with untreated Class II malocclusions from mean age 8.8 to 17.8 years (before and after pubertal growth) were analyzed and compared with the Bolton norms. There was no statistically significant difference in mandibular growth between the Class II samples and the Bolton norms upon cross-sectional comparison. In the Class II subjects, forward growth of the mandible was greater than that of the maxilla by 4.36 mm on average; the dentoalveolar complex moved forward relative to the maxillary basal bone (point A) 2.16 mm and moved backward relative to the mandibular basal bone (pogonion) 2.28 mm; a strong linear relationship (almost a 1:1 ratio) existed between mandibular forward growth and dentoalveolar complex movement (r = 0.881; y = 0.976 x + 0.183). Results indicated that the effect of forward growth of the mandible, which could potentially bring the lower dentition forward, vanished into the adaptation movements of the dentoalveolar complex through intercuspal locking. Disarticulating the occlusion to minimize the effects of the adaptive mechanism and taking advantage of normal mandibular forward growth could be fundamental biological bases in treating Class II malocclusions in growing patients.

Individual growth in Class III malocclusions and its relationship to the chin cap effects

Individual growth characteristics of the maxilla and the mandible in Class III malocclusions were investigated in terms of growth amount, growth direction, and timing of growth; chin cap effects were considered in the context of growth characteristics of the jaws. Longitudinal cephalograms of six untreated Japanese Class III subjects were used for the analysis of jaw growth from 8 to 14 years of age. The facial patterns were classified into the five groups with different effects of therapy by discriminant functions derived from our previous chin cap study. The results obtained were as follows: (1) Among the six subjects, inhibition of maxillary forward growth was found in four subjects at ages before the maximum pubertal growth in body height occurred, resulting from occlusal interference of anterior cross bite. The growth potential of the jaws appeared genetically normal, and the facial patterns were classified into groups in which chin caps have been found to be effective to some extent. (2) A subject with growth characteristics of strong mandibular downward growth was classified in a group showing backward growth of the mandible by chin caps. (3) One of the remaining sample showing the strongest mandibular forward growth was classified in a group where chin caps are not effective. (4) It was concluded that effects of chin cap therapy are closely related to growth characteristics of the mandible in Class III treatment. (Am J Orthod Dentofacial Orthop 1998;114:337-46.)

Longitudinal changes in the skeletal pattern of deciduous anterior crossbite.

Some patients who have an anterior crossbite in the deciduous dentition lose the crossbite during the transitional stage to permanent anterior teeth without orthodontic and/or orthopedic treatment. We observed 220 anterior crossbite patients at regular intervals and identified three groups of patients: in group N (n = 16) the crossbite corrected when the central incisors erupted; in group R1 (n = 16) the crossbite was within [formula: see text] and remained unchanged following the eruption of the permanent central incisors; in group R2 (n = 12) the crossbite extended over [formula: see text] and remained following the eruption of the permanent central incisors. The purpose of this study was to determine whether any differences existed among the above three groups at the initial examination, or if differences arose during eruption of the teeth. The findings indicate that the mandibular position in group N was more posterior than in groups R1 and R2, and the lengths of Pog'-Go and Gn-Cd in group N were smaller. Tooth axis of the lower incisors in groups R1 and R2 showed lingual tipping, and the maxilla in group R2 was underdeveloped. The findings of the longitudinal changes indicated that the maxillary length in group N increased and mandibular forward growth was suppressed. The initial maxillary position in groups R1 and R2 remained much the same until the permanent central incisors erupted.

Treatment effects of the Herbst appliance

The purpose of this study was to examine the results of treatment with a modified Herbst appliance. The pretreatment and posttreatment cephalometric and dental cast records of 32 consecutively treated Class II, Division 1 cases were evaluated. Results showed that the skeletal Class II correction was achieved by an average 1.5 mm of greater than normal forward mandibular growth in conjunction with a minimal “headgear” effect inhibiting maxillary growth. Dental Class II correction was achieved by significant amounts of distal bodily movement and tipping of the maxillary first molars combined with bodily forward movement of the mandibular first molars. Significant increases were seen in maxillary arch length and maxillary intercanine and intermolar widths, while the mandibular arch demonstrated few changes. Slight forward movement of the mandibular incisors was noted with no significant change occurring in the maxillary incisors.

The Begg light wire technique and dentofacial development.

The purpose of this paper is to demonstrate the application of the Begg technique in achieving specific treatment objectives in relation to facial type. Emphasis is placed on both the control of incisor position and the vertical position of the mandible. In order to meet these objectives the site of extractions can be varied, as well as components of the Begg system, such as the use of intermaxillary elastics and arch wire modification. In brachyfacial types with forward mandibular growth rotation, treatment objectives may include incisor intrusion and backwards rotation of the mandible using a non-extraction technique. In contrast, in dolichofacial types with forward mandibular growth rotation, intrusion of incisors and a stable vertical mandibular position may be the primary treatment objectives. In these cases extraction of the four first premolars is usually necessary. The objective is a final tooth position which is in harmony with the facial profile, and compatible with subsequent occlusal maturation.

An evaluation of combination second molar extraction and functional appliance therapy

The purpose of this study was to examine the results of a treatment regimen involving the extraction of four second molars followed by a combination of sagittal, Bionator, and fixed appliance therapy. The pretreatment and posttreatment cephalometric and dental cast records of 30 consecutively treated Class II, Division 1 cases were evaluated. Results showed that the Class II skeletal correction was achieved by a “headgear” effect inhibiting maxillary growth in conjunction with normal forward mandibular growth. No significant distal bodily movement or tipping of either maxillary or mandibular first molars was found. Significant increases were seen in maxillary arch length, maxillary intercanine and intermolar width, and mandibular intermolar width as a result of treatment. Maxillary third changes were more variable.

The Begg light wire technique and dentofacial development

The purpose of this paper is to demonstrate the application of the Begg technique in achieving specific treatment objectives in relation to facial type. Emphasis is placed on both the control of incisor position and the vertical position of the mandible. In order to meet these objectives the site of extractions can be varied, as well as components of the Begg system, such as the use of intermaxillary elastics and arch wire modification. In brachyfacial types with forward mandibular growth rotation, treatment objectives may include incisor intrusion and backwards rotation of the mandible using a non-extraction technique. In contrast, in dolichofacial types with forward mandibular growth rotation, intrusion of incisors and a stable vertical mandibular position may be the primary treatment objectives. In these cases extraction of the four first premolars is usually necessary. The objective is a final tooth position which is in harmony with the facial profile, and compatible with subsequent occlusal maturation.