Anteroposterior Discrepancy Research Articles

Skeletal anteroposterior discrepancy and vertical type effects on lower incisor preoperative decompensation and postoperative compensation in skeletal Class III patients

To determine the initial compensation, preoperative decompensation, and postoperative compensation of the lower incisors according to the skeletal anteroposterior discrepancy and vertical type in skeletal Class III patients. The samples consisted of 68 skeletal Class III patients treated with two-jaw surgery and orthodontic treatment. Lateral cephalograms were taken before preoperative orthodontic treatment (T0) and before surgery (T1) and after debonding (T2). According to skeletal anteroposterior discrepancy/vertical type (ANB, criteria = -4°; SN-GoMe, criteria = 35°) at the T0 stage, the samples were allocated into group 1 (severe anteroposterior discrepancy/hypodivergent vertical type, N = 17), group 2 (moderate anteroposterior discrepancy/hypodivergent vertical type, N = 17), group 3 (severe anteroposterior discrepancy/hyperdivergent vertical type, N = 17), or group 4 (moderate anteroposterior discrepancy/hyperdivergent vertical type, N = 17). After measurement of variables, one-way analysis of variance with Duncan's multiple comparison test, crosstab analysis, and Pearson correlation analysis were performed. At T0, groups 3 and 2 exhibited the most and least compensated lower incisors. In group 2, good preoperative decompensation and considerable postoperative compensation resulted in different values for T0, T1, and T2 (IMPA, T0 < T2 < T1; P < .001). However, group 3 did not show significant changes in IMPA between stages. Therefore, groups 2 and 3 showed different decompensation achievement ratios (P < .05). Group 3 exhibited the worst ratios of decompensation and stability (24% and 6%, respectively, P < .001). Anteroposterior discrepancy/vertical type (ANB: P < .01 at T0 and T1, P < .001 at T2; SN-GoMe: P < .01, all stages) were strongly correlated with relative percentage ratio of IMPA to norm value. Skeletal anteroposterior discrepancy/vertical type results in differences in the amount and pattern of initial compensation, preoperative decompensation, and postoperative compensation of lower incisors in Class III patients.

Motor coordination of masseter and temporalis muscle during mastication in mice

PURPOSE: Mice have been increasingly used to study the stomatognathic function, since genetically modified mice are expected to enhance our understanding of neural and motor disorders of the craniomandibular system. However, fundamental characteristics of jaw movements in mice have not been fully understood. In the present study, the jaw movement of mice during chewing foods of different textures was analyzed in relation to the coordination of the masseter and the temporalis. MATERIAL AND METHODS: At 11 weeks of age, electrodes were placed in the masseter and the temporalis for electromyography (EMG) recording, and jaw movement was measured using a three-dimensional jaw-tracking system. Hard food and soft food were tested. RESULTS: The jaw movement trajectories of mice in the sagittal plane showed antero-posterior excursions unlike those of human or other animals. Larger antero-posterior discrepancies between the opening and the closing paths were observed when chewing hard food, especially at the late-closing phase. The average amplitude of the temporalis was significantly larger at the late-closing phase when chewing hard food than soft food. Conclusion: Characteristic masticatory jaw movements in mice which include the divergence between jaw-opening and jaw-closing paths may be due to the earlier onset of the temporalis activity than that of the masseter. Also, anatomic factors such as the orientation of closing muscles and the shape of the temporomandibular joint may be attributed to the jaw trajectories specific to mice. During hard food chewing, the jaw closes at a more posterior position, which could extend the grinding path at the occlusal phase followed by anterior excursion, and consequently, the efficiency of grinding of food would be increased.

Traitement interceptif de classe III : une étude de cohorte à long terme

The aim of this comparative retrospective short- and long-term study was to evaluate the interceptive treatment in Class III malocclusion in daily orthodontic practice. The sample was composed of 69 children divided into two groups according to the interceptive treatment applied: 31 children in group F (facial mask) and 38 in group M (interceptive fixed appliance). A Pancherz cephalometric analysis was carried out on the lateral head films at the start of the study (t(0), after the active treatment (t(1) and 29 months after t(1) (t(2). The two groups were compared at the beginning of the study by t-test and chi-squared test: there were no difference between groups M and F except for facial divergence, which was greater in group M. Long-term comparison (interceptive and post-interceptive stage i.e. six years) showed that (i) overjet was corrected in each group: molar discrepancy was stable in both groups, (ii) alveolar discrepancy was stable and (iii) antero-posterior discrepancy was not improved in either group. At t(2) there were no differences, either qualitative or quantitative between groups M and F. In the end, more than 80% of the children did not need an orthognathic surgery.

Class II malocclusion occlusal severity description

ObjectivesIt is well known that the efficacy and the efficiency of a Class II malocclusion treatment are aspects closely related to the severity of the dental anteroposterior discrepancy. Even though, sample selection based on cephalometric variables without considering the severity of the occlusal anteroposterior discrepancy is still common in current papers. In some of them, when occlusal parameters are chosen, the severity is often neglected. The purpose of this study is to verify the importance given to the classification of Class II malocclusion, based on the criteria used for sample selection in a great number of papers published in the orthodontic journal with the highest impact factor.Material and MethodsA search was performed in PubMed database for full-text research papers referencing Class II malocclusion in the history of the American Journal of Orthodontics and Dentofacial Orthopedics (AJO-DO).ResultsA total of 359 papers were retrieved, among which only 72 (20.06%) papers described the occlusal severity of the Class II malocclusion sample. In the other 287 (79.94%) papers that did not specify the anteroposterior discrepancy severity, description was considered to be crucial in 159 (55.40%) of them.ConclusionsOmission in describing the occlusal severity demands a cautious interpretation of 44.29% of the papers retrieved in this study.

Class III subdivision malocclusion corrected with asymmetric intermaxillary elastics

Correcting a Class III subdivision malocclusion is usually a challenge for an orthodontist, especially if the patient's profile does not allow for any extractions. One treatment option is to use asymmetric intermaxillary elastics to correct the unilateral anteroposterior discrepancy. However, the success of this method depends on the individual response of each patient and his or her compliance in using the elastics. The objectives of this article were to present a successful treatment of a Class III subdivision patient with this approach and to illustrate and discuss the dentoskeletal changes that contributed to the correction.

Correction of Anterior Open Bite and Facial Profile by Orthognathic Surgery– A Case Report

This case report describes the treatment of a severe anterior open bite, Class III malocclusion with a history of digit sucking. An 18 years-old male presented with a significant anteroposterior and vertical discrepancy of face. The patient’s face was concave with procumbent lips. He had an anterior open bite of 11 mm, a reverse overjet of 8 mm, and a transverse maxillary deficiency on right side. The orthognathic surgery was elected as an option of treatment to correct the anterior open bite with improvement of facial profile. Keywords: Anterior open bite; Transverse maxillary deficiency; Vertical excess; Orthognathic surgery. DOI: 10.3329/bsmmuj.v3i1.5512 BSMMU J 2010; 3(1): 31-34

Miniscrew-assisted nonsurgical palatal expansion before orthognathic surgery for a patient with severe mandibular prognathism

A transverse maxillary deficiency in an adult is a challenging problem, especially when it is combined with a severe anteroposterior jaw discrepancy. The demand for nonsurgical maxillary expansion might increase as patients and clinicians try to avoid a 2-stage surgical procedure-surgically assisted rapid palatal expansion followed by orthognathic surgery-and detrimental periodontal effects and relapse. In this regard, a miniscrew-assisted rapid palatal expansion was devised and used to treat a 20-year-old patient who had severe transverse discrepancy and mandibular prognathism. Sufficient maxillary orthopedic expansion with minimal tipping of the buccal segment was achieved preoperatively, and orthognathic surgery corrected the anteroposterior discrepancy. The periodontal soundness and short-term stability of the maxillary expansion were confirmed both clinically and radiologically. Effective incorporation of orthodontic miniscrews for transverse correction might help eliminate the need for some surgical procedures in patients with complex craniofacial discrepancies by securing the safety and stability of the treatment, assuming that the suture is still patent.

Variáveis relevantes no tratamento da má oclusão de Classe II

Os resultados do tratamento da má oclusão de Classe II podem ser influenciados por características que são inerentes ao paciente - como a idade, a severidade da má oclusão e o grau de colaboração - ou, ainda, por fatores relacionados à conduta do profissional - como a escolha do protocolo de tratamento. Basicamente, o tratamento da Classe II pode ser realizado sem extrações ou com extrações de dois ou quatro pré-molares. Contudo, uma maior proporção de sucesso do tratamento pode ser esperada com extrações de dois pré-molares superiores, independentemente do padrão facial e da relação maxilomandibular. Considerando esta revisão, pôde-se concluir que os resultados oclusais do tratamento da Classe II são fortemente influenciados pelo protocolo de tratamento, enquanto o padrão facial não parece exercer uma influência significativa.

Má oclusão Classe II, divisão 1, de Angle com discrepância ântero-posterior acentuada

A má oclusão Classe II de Angle é caracterizada por uma discrepância dentária ântero-posterior, que pode ou não estar associada a alterações esqueléticas. Além do comprometimento estético, o fato de vir associada a um overjet acentuado faz com que o paciente fique mais exposto a traumas dentários. Este caso foi apresentado à Diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), representando a categoria 4, ou seja, uma má oclusão com discrepância ântero-posterior acentuada, Classe II com ANB maior ou igual a 5º, como parte dos requisitos para a obtenção do título de Diplomado pelo BBO. Possui uma característica incomum, que é a ausência congênita de um incisivo inferior.

The effect of mandibular setback or two-jaws surgery on pharyngeal airway among different genders

Cephalometric studies show significant gender differences in the size of the pharyngeal airway space. This study aimed to investigate and compare morphologic changes after mandibular setback or two-jaws surgery on the pharyngeal airway in men and women using computed tomography (CT). The sample included 34 women and 13 men diagnosed with Class III skeletal deformities, who had been treated by mandibular setback or bimaxillary surgery (maxillary advancement and mandibular setback). Anteroposterior, lateral and cross-sectional area dimensions of the airway, at the level of soft palate and base of tongue, were measured pre- and postoperatively on CT images. In the mandibular setback group, the anteroposterior and cross-sectional area of the pharyngeal airway at the level of the soft palate and base of tongue were significantly reduced for men or women (P<.05). In the two-jaws surgery group, only midsagittal anteroposterior dimensions at the same levels were significantly decreased for men or women (P<.05). The difference between any values measured between men and women who received bilateral sagittal split ramus osteotomy setback surgery or two-jaws surgery for the treatment of class III anteroposterior discrepancy were not statistically significant (P>.05). This study suggests that oropharyngeal airway measurements, important for airway patency, do not demonstrate sex dimorphism.

Má oclusão Classe III de Angle com discrepância ântero-posterior acentuada

A má oclusão Classe III de Angle é caracterizada por uma discrepância dentária ântero-posterior, que pode ou não estar acompanhada por alterações esqueléticas. Em geral, o aspecto facial fica bastante comprometido, sendo justamente esse fator, na maioria das vezes, que motiva o paciente a procurar pelo tratamento. Este caso foi apresentado à Diretoria do Board Brasileiro de Ortodontia e Ortopedia Facial (BBO), representando a categoria 4, ou seja, uma má oclusão com discrepância ântero-posterior acentuada, Classe III, com ANB menor ou igual a -2º, como parte dos requisitos para a obtenção do título de Diplomado pelo BBO.

Occlusal and cephalometric Class II Division 1 malocclusion severity in patients treated with and without extraction of 2 maxillary premolars

The purpose of this study was to compare the initial occlusal and cephalometric severity of Class II Division 1 malocclusion patients treated with and without extraction of 2 maxillary premolars. Dental study models and cephalograms of 62 patients were selected. Those in group 1 (n = 42) were treated without extractions, and those in group 2 (n = 20) were treated with 2 maxillary premolar extractions. Grainger's treatment priority index (TPI) was used to assess the final and the initial occlusal status of each subject. Variables such as overjet and overbite were also evaluated. Independent t tests were used to compare the occlusal variables at the posttreatment stage, the occlusal and cephalometric variables at the pretreatment stage, and the improvement in TPI values between the groups. Patients treated with 2 maxillary premolar extractions had greater initial occlusal TPI values, overjets, cephalometric apical base anteroposterior discrepancies, maxillary incisor protrusions, and anteroposterior molar discrepancies than those treated without extractions. For patients with more severe anteroposterior discrepancies, an extraction plan provides more effective treatment with less need for patient compliance.

Class II Malocclusions: Diagnostic and Clinical Considerations With and Without Treatment

Class II malocclusions are of interest to the practicing orthodontists since they constitute a significant percentage of the cases they treat. In individuals with normal occlusion and skeletal relationship, the amount of maxillary and mandibular growth is synchronized and the result is a well-balanced and esthetically pleasing profile. In individuals with Class II malocclusions, there is an anteroposterior discrepancy between the maxillary and mandibular dentitions, which may or may not be accompanied with a skeletal discrepancy. In growing individuals, the success of treatment is dependent, to a great extent, on the ability of the clinician to influence the relative growth changes in the maxilla and mandible. The purpose of this article is to provide a perspective on the characteristics, development, etiology, and broad treatment considerations in Class II malocclusions.

Espessura do processo alveolar da região anterior da maxila e mandíbula em pacientes com discrepância óssea ântero-posterior

O presente estudo teve como objetivo avaliar a espessura do processo alveolar da região anterior da maxila e mandíbula em pacientes portadores de discrepâncias ântero-posteriores. Após a seleção de telerradiografias laterais de cinqüenta e dois pacientes entre idades de sete e 13 anos, mediu-se a espessura do processo alveolar da região anterior da maxila e mandíbula. Todos os pacientes apresentavam o ângulo do plano mandibular entre vinte e trinta graus e discrepância óssea ântero-posterior entre maxila e mandíbula. Após a análise estatística (teste qui-quadrado) observou-se que não houve dependência entre a espessura do processo alveolar da maxila e mandíbula e a idade do paciente. Todavia houve dependência entre o tipo de má oclusão e a espessura de osso vestibular na região anterior da maxila. Os pacientes portadores de má oclusão de Classe III apresentaram maior porcentagem de redução de osso vestibular da região anterior da maxila quando comparados aos pacientes Classe II. Os pacientes com tendência ao crescimento vertical apresentaram a dimensão reduzida de osso lingual da maxila e osso vestibular da mandíbula.

Outcome assessment of Invisalign and traditional orthodontic treatment compared with the American Board of Orthodontics objective grading system

This treatment-outcome assessment objectively compares Invisalign (Align Technology, Santa Clara, Calif) treatment with braces. This study, a retrospective cohort analysis, was conducted in New York, NY, in 2004. Records from 2 groups of 48 patients (Invisalign and braces groups) were evaluated by using methods from the American Board of Orthodontics Phase III examination. The discrepancy index was used to analyze pretreatment records to control for initial severity of malocclusion. The objective grading system (OGS) was used to systematically grade posttreatment records. Statistical analyses evaluated treatment outcome, duration, and strengths and weaknesses of Invisalign compared with braces. The Invisalign group lost 13 OGS points more than the braces group on average, and the OGS passing rate for Invisalign was 27% lower than that for braces. Invisalign scores were consistently lower than braces scores for buccolingual inclination, occlusal contacts, occlusal relationships, and overjet. Invisalign's OGS scores were negatively correlated to initial overjet, occlusion, and buccal posterior crossibite. Invisalign patients finished 4 months sooner than those with fixed appliances on average. P < .05 was used to determine statistically significant differences. According to the OGS, Invisalign did not treat malocclusions as well as braces in this sample. Invisalign was especially deficient in its ability to correct large anteroposterior discrepancies and occlusal contacts. The strengths of Invisalign were its ability to close spaces and correct anterior rotations and marginal ridge heights. This study might help clinicians to determine which patients are best suited for Invisalign treatment.

Ranking facial attractiveness

The first aim of this investigation was to assemble a group of photographs of 30 male and 30 female faces representing a standardized spectrum of facial attractiveness, against which orthognathic treatment outcomes could be compared. The second aim was to investigate the influence of the relationship between ANB differences and anterior lower face height (ALFH) percentages on facial attractiveness. The initial sample comprised standardized photographs of 41 female and 35 male Caucasian subjects. From these, the photographs of two groups of 30 male and 30 female subjects were compiled. A panel of six clinicians and six non-clinicians ranked the photographs. The results showed there to be a good level of reliability for each assessor when ranking the photographs on two occasions, particularly for the clinicians (female subjects r = 0.76-0.97, male subjects r = 0.72-0.94). Agreement among individuals within each group was also high, particularly when ranking facial attractiveness in male subjects (female subjects r = 0.57-0.84, male subjects r = 0.91-0.94). Antero-posterior (AP) discrepancies, as measured by soft tissue ANB, showed minimal correlation with facial attractiveness. However, a trend emerged that would suggest that in faces where the ANB varies widely from 5 degrees, the face is considered less attractive. The ALFH percentage also showed minimal correlation with facial attractiveness. However, there was a trend that suggested that greater ALFH percentages are considered less attractive in female faces, while in males the opposite trend was seen. Either of the two series of ranked photographs as judged by clinicians and non-clinicians could be used as a standard against which facial attractiveness could be assessed, as both were in total agreement about the most attractive faces. However, to judge the outcome of orthognathic treatment, the series of ranked photographs produced by the non-clinician group should be used as the 'standard' to reflect lay opinion.

A new way of analyzing occlusion 3 dimensionally

This article introduces a new method for 3-dimensional dental cast analysis, by using a mechanical 3-dimensional digitizer, MicroScribe 3DX (Immersion, San Jose, Calif), and TIGARO software (not yet released, but available from the author at hayasaki@dent.kyushu-u.ac.jp ). By digitizing points on the model, multiple measurements can be made, including tooth dimensions; arch length, width, and perimeter; curve of Spee; overjet and overbite; and anteroposterior discrepancy. The bias of the system can be evaluated by comparing the distance between 2 points as determined by the new system and as measured with digital calipers. Fifteen pairs of models were measured digitally and manually, and the bias was evaluated by comparing the variances of both methods and checking for the type of error obtained by each method. No systematic errors were found. The results showed that the method is accurate, and it can be applied to both clinical practice and research.

Pharyngeal airway changes following mandibular setback surgery

Treatment of dentofacial deformities with jaw osteotomies has an effect on airway anatomy and therefore mandibular setback surgery has the potential to diminish airway size. The purpose of this study was to evaluate the effect of mandibular setback surgery on airway size. 8 consecutive patients were examined prospectively. All patients underwent mandibular setback surgery. Cephalometric analysis was performed preoperatively and 3 months post operatively with particular attention to pharyngeal airway changes. Pharyngeal airway size decreased considerably in all, patients thus predisposing to development of obstructive sleep apnea. Therefore, large anteroposterior discrepancies should be corrected by combined maxillary and mandibular osteotomies.

Unusual orthodontic retreatment

This case report describes the retreatment of a patient with a Class II Division 1 malocclusion; she had the same anteroposterior discrepancy after undergoing fixed appliance treatment with extraction of 4 first premolars. (Am J Orthod Dentofacial Orthop 2003;123:468-75)

Cephalometric and in vivo measurements of maxillomandibular anteroposterior discrepancies: a preliminary regression study.

One of the aims of the present investigation was to assess three-dimensionally the anteroposterior discrepancy of dental bases using a noninvasive direct procedure. A second aim was to verify the relationship of three-dimensional soft-tissue measurement to the well-established two-dimensional cephalometric assessments of anteroposterior discrepancy. Dental and facial landmarks were directly digitized on 20 orthodontic and maxillofacial surgery patients aged 8 to 26 years using an electromagnetic three-dimensional computerized digitizer. The anteroposterior maxillomandibular discrepancy was measured by calculating the linear distances between the projections of subnasal and sublabial landmarks on the occlusal plane, subnasal and sublabial landmarks on Camper's plane, and insertion of maxillary and mandibular median labial frenula on the occlusal plane. From lateral cephalograms of the same patients, the following measurements were obtained: subspinale point-nasion-supramentale point (ANB) angle; corrected ANB angle that compensates for the position of the maxilla and rotation of the mandible relative to the cranial base; Wits appraisal; MM-Wits, linear distance between the projections of points A and B on the bisector of the palatal plane to mandibular plane angle; and soft-tissue Wits, linear distance between the projections of soft-tissue points A and B on the bisecting occlusal plane. The best two-dimensional vs three-dimensional linear regression (r = 0.91) was found between Wits appraisal and the linear distances between the projections of maxillary and mandibular median labial frenula on the occlusal plane (Wits = -1.05 x 3D measurement - 3.75). The three-dimensional evaluation of the sagittal discrepancy of the jaws directly performed in vivo may allow a more complete analysis of a patient's soft-tissue drape together with the underlying hard-tissue structure.