Dynamic analysis of the effects of upper lip pressure on the asymmetry of the facial skeleton in patients with unilateral complete cleft lip and palate.

OBJECTIVE: Our purpose was to assess quantitatively the effect of increased upper-lip pressure on asymmetry of the facial bones in patients with unilateral complete lip-alveolar-palatal clefts. METHODS: We collected computed tomographic images from 16 patients with unilateral complete lip-alveolar-palatal clefts and classified them into two groups based on absence/presence of alveolar bone grafting. We categorized eight patients (9.6 +/- 2.0 years old) who had not been treated with alveolar bone grafting as the ABG(-) group and the other eight patients (9.3 +/- 1.6 years old) who had received alveolar bone grafting as the ABG(+) group. After producing a computer-aided design model for each patient, we applied a uniform load on the anterior aspects of the maxilla, alveolus, and teeth of the model to simulate the upper-lip pressure. Then we calculated the degree of distortion each model presented using the finite element method. We compared the distortion pattern between the ABG(-) and ABG(+) groups. RESULTS: In the ABG(-) patients, asymmetry of distortion between the cleft and noncleft sides was present in wide areas involving the orbit, nasal bone, piriform margin, and anterior wall of the maxillary sinus. In the ABG(+) patients, asymmetry of distortion was limited to rather small areas. CONCLUSIONS: In unilateral complete lip-alveolar-palatal clefts patients, the upper-lip pressure works to dislocate the cleft-side segment to a more posterior position than the noncleft-side segment. This finding implies that the increased lip pressure exacerbates facial asymmetry of these patients. The exacerbating effect on facial asymmetry is alleviated by alveolar bone grafting.

Alveolar bone grafting for patients with unilateral complete alveolar and palatal clefts improves the bony structure of the nose.

OBJECTIVE: This is a retrospective study regarding the effect of alveolar bone grafting (ABG) on morphological changes in the bony structure of the nose in alveolar and palatal cleft patients. METHODS: Sixty-five randomly selected adults were included in the present study. Of the 65 subjects, 21 had no congenital anomaly and were designated as the control group (n = 21; mean age 22.4 +/- 4.3 years). Forty-four had unilateral complete clefts of the alveolus and palate on the left side. The patients with clefts were further divided into two subgroups based on presence or absence of ABG in their histories. These groups were termed the ABG(+) group (n = 24; mean age 20.3 +/- 2.5 years) and the ABG(-) group (n = 20; mean age 32 +/- 4.5 years), respectively. An anatomical structure that constitutes the bony component of the nose was defined. This structure, composed of the nasal bones and part of the frontal process of the maxilla, was termed the BSEN (bony structure of the external nose). The symmetry of the BSEN was assessed quantitatively by performing morphological measurements on computerized tomographic images of each patient's skull, and these measurements were compared among the control, ABG(+), and ABG(-) groups. RESULTS: The BSEN presented more symmetric features in the ABG(+) group patients than in the ABG(-) group patients. CONCLUSION: ABG improves symmetry of the BSEN. This finding justifies ABG in terms of cosmetic improvement of the external nose in patients with unilateral complete alveolar and palatal clefts.

The dynamics in implantation for patients with clefts.

OBJECTIVE: To investigate the stresses and strains of an endosseous dental implant in patients with different types of cleft palate in a finite element model. MATERIALS AND METHODS: Seven three-dimensional (3D) maxillary models were designed on a personal computer according to computed tomography slice data obtained from seven dry skulls. Next, computer-aided modification was performed on each model to produce three other 3D models with different cleft patterns. Thus, four model types with different cleft patterns were designed and termed NORM (without cleft), ALVEOLAR (only alveolar cleft), PALATAL (only palatal cleft), and COMPLETE (complete cleft). An implant was embedded into the molar region of each model, and a 300-N vertical load and 50-N horizontal load were applied to simulate mastication. Under these conditions, the stresses occurring at the implant-bone interface were calculated by finite element analysis. RESULTS: Different stress patterns were observed between the models with a palatal cleft (PALATAL and COMPLETE) and those without palatal cleft (NORM and ALVEOLAR). Regarding vertical load application, greater stresses occurred in PALATAL and COMPLETE types than in NORM and ALVEOLAR types. On application of a horizontal load, though the stresses did not show quantitative difference, their vector patterns differed. CONCLUSION: In patients with palatal clefts, characteristic stress patterns occur on the bone-implant interface during mastication. This should be taken into consideration when performing an implant treatment in patients with clefts.

Changes in orthodontic cephalometric reference points on application of orthopedic force to jaw: three-dimensional finite element analysis.

The present study investigated the effects of two orthodontic appliances on changes in the cephalometric reference planes using the three-dimensional finite element method. We simulated the use of a headgear and an orthopedic facial mask, two devices for the application of orthodontic force to the jaw. Using a finite element model of the skull, orthodontic force was applied to the maxillary first molar in a posterior or anterior direction. Changes in the maxilla, mandible and cephalometric reference planes were ascertained by the three-dimensional finite element method. The results showed that posterior force caused a slight posterior displacement and clockwise rotation of the reference planes, while anterior force caused anterior displacement and counterclockwise rotation. Since the maxilla was displaced and rotated in the same direction, the degrees of cephalometric displacement and rotation of the maxilla were smaller than the actual values.

Correlation between facial patterns and function of the masticatory muscles in girls and women.

The relationship between maxillo-facial patterns and function of the masticatory muscles was evaluated using electromyography, in 16 women with functional normal occlusion and 16 girls with chronological normal occlusion half of them had the dolico facial pattern and the others had the brachyo facial pattern by Ricketts analysis. For the electromyography, loads of 1, 2, 3, 4, and 5 kg were applied to the mandible, and muscular activity waves were obtained from the masseter muscle and the anterior belly of the temporal muscle during isometric contraction by surface electrode induction. The median frequency value (MFV) in a frequency curve obtained by high-speed Fourier transform of the electromyographic waves was set to the evaluation index. The MFV at each applied load was higher in the adult brachyo facial pattern group than in the adult dolico facial pattern group in both the masseter and temporal muscles, whereas the differences in the MFV were slight in the child group at a 5% significance level. The child group showed approximately half the incidence of significant correlation coefficients in comparison with the adult group and a large standard deviation without marked differences in the facial patterns due to their individual differences in growth with a 5% significant level. The adult brachyo facial pattern group showed a high regression coefficient of the MFV in the masseter muscle according to the increase in the amount of the applied load. Although differences in the cooperative contraction patterns similar to those in the adult group were observed in both the child dolico and brachyo facial pattern groups, no marked significant differences were observed in the child group, who had large individual differences due to their immature growth.

Orthodontic treatment for jaw deformities in cleft lip and palate patients with the combined use of an external-expansion arch and a facial mask.

Patients with cleft lip and palate can suffer from contraction of the maxillary arch and anterior cross-bite accompanied by skeletal growth retardation. We use an appliance called an external-expansion arch and induce maxillary protraction using a facial mask in order to correct the anterior cross-bite and maxillary retrusion. In this paper, the method of application of these appliances and the effects of this therapy are reported here. The external-expansion arch consists of a labial wire, bands and a sectional arch. The 0.045-inch stainless steel wire extends along the maxillary dental arch. Hooks are soldered immediately distal to the lateral incisor and the distal leg of the vertical loop. The brackets are bonded to the maxillary anterior teeth, and a 0.016 x 0.016 inch sectional arch is set. The external-expansion arch is inserted into the headgear tube and ligated with the sectional arch using elastic thread. The maxillary bone is pulled by use of the facial mask and the elastic band. For traction, the force is about 300 g on each side, applied parallel to the occlusal plane or slightly downward. The duration of use is 8 to 12 hours per day. The external-expansion arch has several advantages: it can be applied from the early period of Hellman's dental age IIIA or IIC to improve anterior cross-bite. As it is easy to expand the anterior teeth and move individual teeth to the labial and buccal sides, establishment of a dental arch from severe collapse is not difficult. When an expanding device such as the Quad-helix is incorporated, lateral expansion becomes easier. Furthermore, it is easy to control the teeth vertically, and patient compliance is not necessary. Hence, this method is effective as a phase 1 treatment for orthodontic patients with cleft lip and palate characterized by maxillary retardation.