Movement of the lateral and medial poles of the working condyle during mastication in patients with unilateral posterior crossbite

A Novel Imaging Technique for Analyzing Condylar Movement During Mastication in Patients With Jaw Deformities: Four-Dimensional Computed Tomography

OBJECTIVE

This study aimed to reveal characteristic condylar movements in patients with jaw deformities.

STUDY DESIGN

Thirty patients with jaw deformities before surgery were enrolled and instructed to chew a cookie during 4-dimensional computed tomography (4DCT). The distance between the most anterior and posterior positions of the bilateral condyles on 4DCT images was measured and compared among patients with different skeletal classes. Correlations between the condylar protrusion and cephalometric values were also determined.

RESULTS

The distances of condylar protrusion during mastication were significantly greater in the skeletal class II group than in the skeletal class III group ( P =0.0002). Significant correlations were found between the distances of condylar protrusion during mastication and the sella-nasion-B point angle ( r =-0.442, P =0.015), A point-nasion-B point angle ( r =0.516, P =0.004), sella-nasion plane to ramus plane angle ( r =0.464, P =0.01), sella-nasion plane to occlusal plane angle ( r =0.367, P =0.047), and condylion-gonion length ( r =-0.366, P =0.048).

CONCLUSION

Motion analysis with 4DCT images revealed that condylar movement in patients with retrognathism was larger than in patients with mandibular prognathism. Skeletal structure was therefore correlated with condylar movement during mastication.

Alterations of oral functions and dental malocclusions in adolescents: a cross-sectional population-based study

This article aims to assess whether alterations of oral functions (AOF) are associated with malocclusion (MO)'s type and severity. Cross-sectional study of a representative sample of 332 adolescents aged 12 years in São Luís-MA, Northeastern Brazil. MO criteria included Angle's classification, Dental Aesthetic Index, and other morphological problems. The AOF were evaluated by breathing, phonation, chewing, and swallowing. Odds ratios (OR) and 95% confidence intervals (95%CI) were calculated using logistic and multinomial regression analyses (α=5%). Mouth breathing was associated with defined (OR=3.84; 95%CI=1.45-10.12), disabling (OR=4.34; 95%CI=1.99-9.49), and class III (OR=4.15; 95%CI=1.19-14.54) MO. Phonation problems were associated with defined (OR=2.01; 95%CI=1.02-4.39), disabling (OR=3.04; 95%CI=1.55-5.96), and Class II (OR=2.02; 95%CI=1.28-3.18) MO. Chewing disorders were associated with posterior crossbite (PCB) (OR=2.32; 95%CI=1.12-4.82). Swallowing disorders were associated with Class III MO (OR=5.66; 95%CI=1.35-23.71), PCB (OR=6.13; 95%CI=2.76-13.62), and posterior open bite (OR=4.53; 95%CI=1.72-8.92). Breathing and phonation alterations are associated with MO in anterior arch segments, while chewing and swallowing disorders, in the posterior segments.

The Law of Minimum Vertical Dimension: Evidence for Improvement of Dental Occlusion

The law of minimum vertical dimension (MVD) states that “when the mandible moves to reach the maximum intercuspal position, this always involves bringing the mandible and maxilla as close together as possible.” Therefore, after the first occlusal contact is made, the MIP will be reached through reduction of the vertical dimension. Our objective of this study, through an integrative review of the literature review, was to determine whether ignoring this law is a factor that contributes to malocclusion, temporomandibular joint dysfunction, and recurrences of functional orthodontic and orthopedic treatments.We conducted a search of the literature in five of the main electronic scientific databases. The following medical subject heading terms were used in our search: centric relation, dental occlusion, malocclusion, vertical dimension, and mastication. We cross-referenced the descriptors in the following four groups: centric relation and maximum intercuspation; occlusal plane and malocclusion; neuro-occlusal rehabilitation; and vertical dimension and unilateral chewing. From this, we selected 277 potentially eligible articles. Out of these, 209 were excluded in accordance with the exclusion criteria already described. Thus, 65 studies were included in the qualitative synthesis.The articles were also classified according to their impact factor and degree of recommendation, in conformity with the table of the Oxford Centre for Evidence-Based Medicine. The scientific interest in the scope of the articles was also assessed by using three charts developed according to year and country of publication and the percentage of publication. Unilateral chewing creates a vicious cycle of damage that leads to an ever-increasing masticatory deficiency. Most of the articles chosen for this review confirmed that noncompliance with law of MVD was a predisposing factor in cases of relapse, in functional orthodontic and orthopedic treatments, as well as a causal factor in malocclusion and in functional and morphological TMJ dysfunctions.

Vertical contact tightness of occlusion comparison between orofacial myalgia patients and asymptomatic controls: a pilot study

OBJECTIVE

The association between occlusal contact and orofacial pain remains unclear. The aim of this study was to detect occlusal contact tightness by using a new method and to compare differences between patients and asymptomatic controls.

METHODS

Fifteen female patients with orofacial myalgia and fifteen age- and sex-matched asymptomatic controls were enrolled. Occlusal contacts were recorded by making bite imprints. The numbers, sizes, and distributions of the contacts were detected by making photos of bite imprints after biting. The Mann-Whitney U test and ANOVA were used for statistical analysis.

RESULTS

In myalgia patients, impact contacts at the molar regions were more frequent, larger in number and area size, and were distributed more on guiding cusps, compared with impact contacts in asymptomatic controls.

CONCLUSION

Our new method revealed more prevalent and more severe impact contacts in orofacial myalgia patients, compared with asymptomatic controls.

Temporomandibular joint articulations on working side during chewing in adult females with cross-bite and mandibular asymmetry

Influence of mandibular asymmetry and cross-bite on temporomandibular joint (TMJ) articulation remained unknown. This study aimed to investigate whether/how the working-side condylar movement irregularity and articular spaces during chewing differ between patients with mandibular asymmetry/cross-bite and control subjects. The cross-bite group and the control group consisted of 10 adult female patients and 10 adult female subjects, respectively. They performed unilateral gum-chewing. The mandibular movements were recorded using a video-based opto-electronic system. The 3D articular surface of the TMJ for each individual was reconstructed using CT/MRI data. For local condylar points, the normalised jerk cost (NJC) towards normal direction to the condylar surface, the angle between tangential velocity vector and condylar long axis and intra-articular space were measured. Three rotatory angles at centre of the condyle were also measured. During closing and intercuspation, (i) movements of posterior portion of the deviated side condyle showed significantly less smoothness as compared with those for the non-deviated side and control subjects, (ii) the rotations of the condyle on the deviated side induced greater intra-articular space at posterior and lateral portions. These findings suggest that chewing on the side of mandibular deviation/cross-bite may cause irregular movement and enlarged intra-articular space at posterior portion of the deviated side condyle.

Extraction treatment of a class II division 2 malocclusion with mandibular posterior discrepancy and changes in stomatognathic function

This case report describes the successful extraction treatment of a Class II division 2 malocclusion with mandibular posterior discrepancy and a congenitally missing maxillary lateral incisor on the left side. The posterior space in the mandibular arch was small, and the mandibular second molars were impacted, with distal tipping. The discrepancies in the maxillary and mandibular arches were resolved by extraction of the maxillary lateral incisor on the right side and the mandibular second premolars on both sides. The mesial movement of the mandibular first molars occurred appropriately, with the second molars moving into an upright position. A lip bumper was used with a preadjusted edgewise appliance in the maxillary dentition to reinforce molar anchorage and labial movement of the retroclined incisors. Despite the extraction treatment, a deep bite could be corrected without aggravation as a result of the lip bumper and utility arch in the mandibular dentition. Thus, an Angle Class I molar relationship and an ideal overbite were achieved. The occlusal contact area and masticatory muscle activities during maximum clenching increased after treatment. The maximum closing velocity and the maximum gape during chewing increased, and the chewing pattern changed from the chopping to grinding type. The findings in the present case suggest that the correction of a deep bite might be effective for improving stomatognathic function.

Influence of temporomandibular disorder on temporal and masseter muscles and occlusal contacts in adolescents: an electromyographic study

Background

The aim of the present study was to analyse the influence of temporomandibular disorder (TMD) on electromyographic activity in the masseter and temporal muscles of adolescents and investigate a possible association with the number of occlusal contacts.

Methods

The Helkimo Index was administered for the diagnosis of TMD and classification of the adolescents into three groups: without TMD; with mild TMD; and with moderate/severe TMD. Carbon paper was used for the determination of occlusal contact points. A standardised electromyographic evaluation was performed on the masticatory muscles at rest, during habitual chewing and during maximum voluntary clenching. The readings were normalised to maximum voluntary clenching. Statistical analysis involved the chi-squared test and Fisher’s exact test. The Kruskal-Wallis test and one-way analysis of variance with Dunn’s post hoc test were used to compare differences between groups. Pearson’s correlation coefficients (r) were calculated for the determination of correlations between the number of occlusal contacts and RMS values.

Results

Electromyography revealed significant differences in the right and left masseter and temporal muscles at rest and during chewing among the three groups. These differences were not observed during maximum voluntary clenching. No statistically significant differences were found between the groups with and without TMD regarding the number of occlusal contacts.

Conclusion

Electromyographic activity in the masseter and temporal muscles was greater among adolescents with moderate to severe TMD.

Treatment response and stability of slow maxillary expansion using Haas, hyrax, and quad-helix appliances: a retrospective study

INTRODUCTION

In this retrospective study, we evaluated the short- and long-term effects of slow maxillary expansion with Haas, hyrax, and quad-helix appliances on posterior crossbite (PXB) correction stability, and maxillary intermolar width and angulation, in the deciduous or early mixed dentition.

METHODS

The inclusion criteria were models and treatment notes of patients with PXB at the start of treatment (T1), after PXB correction (T2), and at least 2 years posttreatment (T3). Exclusion criteria were craniofacial anomalies, fixed appliance use, or more than 1 expander type. From 312 consecutive expansion patients, 74 Haas, 41 hyrax, and 45 quad-helix subjects were evaluated regarding PXB correction, intermolar width, and angulation and compared with published norms to separate treatment effects from growth. The mean ages at T1, T2, and T3 were 8, 9, and 13 years.

RESULTS

There were no significant differences in PXB correction stability or treatment response at T2 and T3 among the 3 expanders. Expansion increased intermolar width by 5 mm and tipped each molar by 2.3 degrees. At least 2 years after expander removal, molar width decreased by 1.3 mm, and the molars uprighted by 6 degrees. Compared with noncrossbite norms, PXB subjects had narrower intermolar width before treatment and greater width after expansion, and were slightly wider at least 2 years posttreatment. Both younger age at T1 and retainer use resulted in statistically greater intermolar width at T3.

CONCLUSIONS

Eighty-four percent of PXB correction remained with about one third of the initial expansion lost; retainer use and early treatment provided increased intermolar width. Haas, hyrax, and quad-helix appliances were equally effective. Slow maxillary expansion altered the PXB patients' maxillary widths from narrower to slightly wider than the widths of the noncrossbite norms.

[Diagnosis and therapy of adult patients with facial asymmetry]

The goal of orthodontic treatment is to improve the patient's life by enhancing dental and jaw functions and dentofacial esthetics [Graber TM, et al., Orthodontics current principles and techniques. 4(e) ed. St Louis: Elsevier, 2005.]. Harmonious occlusion is achieved following improvements of malocclusion via orthodontic treatment [Ehmer U and Broll P, Int J Adult Orthod Orthognath Surg 1992;7:153-159. Throckmorton GS, et al., J Prosthet Dent 1984;51:252-261.]. Perfect facial symmetry is extremely rare, and normal faces have a degree of asymmetry. Patients with dentofacial deformity more frequently have asymmetry of the face and jaws. There was a relationship between the type of malocclusion and the prevalence of asymmetry; 28% of the Class III group, but 40% to 42% of the Class I, Class II and long face groups respectively, were asymmetric [Severt TR and Proffit WR, Int J Adult Orthod Orthogn Surg 1997;12:171-176.]; therefore, facial asymmetry is a common complaint among orthodontic patients. Treatment of severe facial asymmetry in adults consists mainly of surgically repositioning the maxilla or the mandible [Bardinet E, et al., Orthod Fr 2002;73:243-315. Guyuron B, Clin Plast Surg 1989;16:795-801. Proffit WR, et al., Contemporary treatment of dentofacial deformity. 2003. St Louis: Mosby, 2003:574-644.], however, new methods, i.e. orthodontic tooth movement with implant anchorage, have recently been introduced [Costa A, et al., Int J Adult Orthod Orthognath Surg 1998;3:201-209. Creekmore TD and Eklund MK, J Clin Orthod 1983;17:266-269. Miyawaki S,et al., Am J Orthod Dentofacial Orthop 2003;124:373-378. Park HS, et al., J Clin Orthod 2001;35:417-422. Roberts WE, et al., Angle Orthod 1989;59:247-256.], and various treatment options can be chosen in patients with facial asymmetry. In this article, we describe the diagnosis and treatment of adult patients with facial asymmetry.

Mastigação e atividade eletromiográfica em crianças com mordida cruzada posterior

OBJETIVO: investigar a preferência mastigatória e o comportamento dos músculos mastigatórios, em crianças de 6 a 9 anos, com mordida cruzada posterior. MÉTODOS: 30 crianças foram selecionadas num serviço de Ortodontia de uma universidade pública. Após a concordância na participação no trabalho, foi realizada entrevista com a criança e seu responsável, para investigação de disfunção temporomandibular; análise da preferência mastigatória, por meio de registros em vídeo e avaliação eletromiográfica (EMG) dos músculos masseter e temporal anterior, durante a mastigação solicitada, direita e esquerda, de uma goma de marcar. RESULTADOS: houve diferença significante na atividade EMG dos músculos masseter e temporal anterior entre os lados de trabalho e balanceio, porém não houve diferença estatística quando foram comparadas as atividades EMG entre os lados de mordida cruzada e não cruzada, tampouco entre os lados de preferência e não preferência mastigatória. CONCLUSÃO: na amostra estudada não se verificou assimetria funcional muscular estabelecida.

Orthodontic Treatment Combined with Mandibular Distraction Osteogenesis and Changes in Stomatognathic Function

We performed an orthodontic treatment combined with mandibular distraction osteogenesis in a 15-year-old patient who wanted a correction of a chin deficiency and a protruding upper lip. The patient had an Angle Class II division 1 malocclusion with mandibular retrusion, a low mandibular plane angle, and scissors bite. First, a quad-helix appliance was applied to the mandibular dentition to correct the scissors bite in the bilateral premolar region. Later, a preadjusted edgewise appliance was applied to the maxillary and mandibular teeth. After 3 days, a mandibular distraction osteogenesis was performed. During and after the distraction, the open bite between the upper and lower dental arches was corrected using up and down elastics. The total treatment time with the edgewise appliance was 14 months. A skeletal Class I apical base relationship, good facial profile, and optimum intercuspation of the teeth were achieved with the treatment. The jaw-movement pattern on the frontal view did not change during gum chewing. However, the maximum gap without pain increased. The electromyographic (EMG) activity of the masseter and anterior temporalis muscles, and maximum occlusal force increased. The present case report suggests that an orthodontic treatment combined with mandibular distraction osteogenesis in a patient with mandibular retrusion in the late growth period might be effective for improving stomatognathic function.

Influence of forward head posture on condylar position

There are several reports suggesting that forward head posture is associated with temporomandibular disorders and restraint of mandibular growth, possibly due to mandibular displacement posteriorly. However, there have been few reports in which the condylar position was examined in forward head posture. The purpose of this study was to test the hypothesis that the condyle moves posteriorly in the forward head posture. The condylar position and electromyography from the masseter, temporal and digastric muscles were recorded on 15 healthy male adults at mandibular rest position in the natural head posture and deliberate forward head posture. The condylar position in the deliberate forward head posture was significantly more posterior than that in the natural head posture. The activity of the masseter and digastric muscles in the deliberate forward head posture was slightly increased. These results suggest that the condyle moves posteriorly in subjects with forward head posture.

A dynamic model of jaw and hyoid biomechanics during chewing

Our understanding of human jaw biomechanics has been enhanced by computational modelling, but comparatively few studies have addressed the dynamics of chewing. Consequently, ambiguities remain regarding predicted jaw-gapes and forces on the mandibular condyles. Here, we used a new platform to simulate unilateral chewing. The model, based on a previous study, included curvilinear articular guidance, a mobile hyoid apparatus, and a compressible food bolus. Muscles were represented by Hill-type actuators with drive profiles tuned to produce target jaw and hyoid movements. The cycle duration was 732 ms. At maximum gape, the lower incisor-point was 20.1mm down, 5.8mm posterior, and 2.3mm lateral to its initial, tooth-contact position. Its maximum laterodeviation to the working-side during closing was 6.1mm, at which time the bolus was struck. The hyoid's movement, completed by the end of jaw-opening, was 3.4mm upward and 1.6mm forward. The mandibular condyles moved asymmetrically. Their compressive loads were low during opening, slightly higher on the working-side at bolus-collapse, and highest bilaterally when the teeth contacted. The model's movements and the directions of its condylar forces were consistent with experimental observations, resolving seeming discordances in previous simulations. Its inclusion of hyoid dynamics is a step towards modelling mastication.

Análise da mastigação em indivíduos que apresentam mordida cruzada unilateral na faixa-etária de 07 a 12 anos

OBJETIVO: analisar a função de mastigação relacionada à mordida cruzada posterior unilateral em crianças na faixa etária de sete a doze anos. MÉTODOS: dez indivíduos de ambos os sexos com mordida cruzada unilateral posterior sem intervenção ortodôntica. Na avaliação fonoaudiológica os itens considerados foram: corte do alimento, lado da mastigação, ritmo, postura labial, escape de alimentos, movimento de mandíbula, participação exagerada da musculatura perioral, acúmulo de alimento no vestíbulo da boca, posição e tamanho do bolo alimentar. RESULTADOS: dos dez indivíduos avaliados, 80% apresentaram mastigação unilateral do mesmo lado da mordida cruzada posterior unilateral e 20% mastigação bilateral. Dos oito indivíduos analisados com mastigação unilateral, os resultados encontrados foram: corte anterior, sem escape de alimentos e movimentos rotatórios 100%; ritmo lento 50% e rápido 50%; lábios fechados 75%; participação exagerada da musculatura perioral 62,5%; sem acúmulo de alimentos 87,5%; bolo alimentar centralizado 75%; tamanho do bolo pequeno 62,5%. CONCLUSÃO: dos casos avaliados, observou-se que 80% confirmam a relação entre mastigação unilateral e mordida cruzada posterior unilateral. Na mastigação, não foram evidenciadas quaisquer outras alterações que possam estar relacionadas à mordida cruzada posterior unilateral e mastigação unilateral.

Desempenho mastigatório em adultos relacionado com a desordem temporomandibular e com a oclusão

TEMA: desordem temporomandibular e mastigação. OBJETIVO: comparar sujeitos com desordem temporomandibular a um grupo controle quanto à mastigação e analisar as variáveis relacionadas. MÉTODO: 20 sujeitos com desordem temporomandibular (grupo com DTM) e 10 do grupo controle, ambos selecionados de acordo com o exame clínico e anamnese, responderam sobre a sua auto-percepção de severidade de dor e sons nas articulações temporomandibulares, dor nos músculos, sintomas otológicos, cefaléia e dificuldade para abrir a boca. Foram também submetidos ao exame clínico, considerando o número de elementos dentários presentes e a análise funcional da oclusão - medidas de abertura bucal, excursão lateral da mandíbula, interferências oclusais e contatos oclusais do lado de trabalho e balanceio. A mastigação foi avaliada quanto ao tempo para ingerir, ao número de golpes mastigatórios e ao tipo mastigatório (unilateral ou bilateral), usando um biscoito recheado, cuja força máxima para quebrá-lo no primeiro momento foi de 4341,8g, como verificado com o auxílio do Texture Analyser TA-XT2 (Stable Micro Systems). Os grupos foram comparados por análise de variância e as correlações entre as variáveis foram calculadas pelo teste produto-momento de Pearson. RESULTADOS: a maioria dos sujeitos do grupo controle apresentou tipo mastigatório bilateral, enquanto que no grupo com DTM houve tendência ao tipo mastigatório unilateral. No grupo controle foram estatisticamente maiores os escores do tipo mastigatório e as medidas de lateralidade. No grupo com DTM foram maiores as médias de idade, o tempo de mastigação, o número de golpes mastigatórios e a severidade da DTM. O tempo e o tipo mastigatório foram correlacionados, respectivamente de modo positivo e negativo, à severidade da DTM e ao número de interferências oclusais. CONCLUSÃO: no grupo com DTM a mastigação diferiu do padrão fisiológico normal. O número de interferências oclusais e a severidade da DTM foram as variáveis correlacionadas à mastigação.

Skeletal Class III oligodontia patient treated with titanium screw anchorage and orthognathic surgery

This article reports the successful treatment of a patient, aged 15 years 8 months, with a Class III malocclusion and oligodontia; a titanium screw was used for absolute anchorage during treatment. The patient had a concave profile because of mandibular excess and asymmetric spaces in both arches. Titanium screws were implanted in the retromolar area during intraoral vertical ramus osteotomy combined with LeFort I osteotomy. Absolute anchorage was provided with anchorage wires extending from the screws to the left canine and the right lateral incisor. After orthodontic space closure, the mandibular molars were moved mesially without lingual tipping of the mandibular incisors. A good interincisal relationship was achieved. Our results suggest that titanium screws and anchorage wires in the retromolar area are useful for the mesial movement of mandibular molars.