Electric Charge Dependence of Controlled Dye-Release Behavior in Glass Ionomer Cement Containing Nano-Porous Silica Particles.

We investigated in controlled dye-release behavior of nanosized silica particles containing nanocavities (Nanoporous silica, NPS). To determine this, NPS were mixed with glass ionomer cement (GIC), which is a medical material used as a matrix. The dye-release behavior was observed using a UV-visible spectrometer. After cationic dye was charged into GIC pellet containing NPS, the pellet could gradually release cationic dye for up to two weeks. To understand the dependence of electric charge on the dye-release behavior, three types of dyes with different charge were also investigated. Dyes having a neutral or negative electric charge were quickly released from the pellet within a couple of days. These results suggest that the nanocavities present in NPS can selectively bind cationic dyes and allow for their gradual release. This result reveals the excellent sustained dye-release property of NPS.

Assessment of hypoxic lip training for lip incompetence by electromyographic analysis of the orbicularis oris muscle.

INTRODUCTION: The aims of this study were to determine the difference in electromyography (EMG) of the orbicularis oris muscles between subjects with lip incompetence and lip competence and to elucidate the effectiveness of hypoxic lip training with EMG. METHODS: Twenty-five subjects (14 men, 11 women; mean age, 24.5 ± 2.6 years) were divided into 2 groups by sealed lip ratio: 13 subjects with lip incompetence (LI) and 12 subjects with lip competence (LC). Integral values of EMG for the orbicularis oris muscle during lip closing were estimated (baseline, T1). Then the subjects in the LI group performed the hypoxic lip training every day for 4 weeks. The EMG recordings were repeated during the training (T2), immediately after the training (T3), 4 weeks after the training (T4), and 8 weeks after the training (T5). RESULTS: In the LI group, the EMG values during lip closing were significantly higher than those of the LC group, and the values of EMG during lip closing at T3 were significantly lower than those at T1. In the posttraining period, the values of EMG at T4 and T5 were significantly lower than those at T1. The results suggested that subjects with lip incompetence need greater orbicularis oris muscle activity to keep their lips closed. CONCLUSIONS: The suggested standardized lip training could be used as a training method for patients with lip incompetence.

Genome-wide association study for mandibular prognathism using microsatellite and pooled DNA method.

INTRODUCTION: The purpose of this study was to extend an association study from chromosome 1 to the whole genome (genome-wide association study) to find susceptibility loci of mandibular prognathism. METHODS: Two hundred forty patients diagnosed with mandibular prognathism and 360 healthy controls of Japanese descent were recruited. The typing of microsatellites covering the whole genome was conducted using a pooled DNA method. Upon completion of the first and second screenings with pooled DNA, the positive microsatellite markers from both the first and second typings were retyped using individual-subject DNA samples to confirm the significance of allele frequency. RESULTS: Six microsatellites (D1S0411i, D1S1358i, D3S0810i, D6S0827i, D7S0133i, and D15S0154i) showed differences between allele frequencies of the subjects and controls at P <0.001. D1S0411i, D1S1358i, D3S0810i, D6S0827i, D7S0133i, and D15S0154i were located on chromosomes 1p22.3, 1q32.2, 3q23, 6q23.2, 7q11.22, and 15q22.22, respectively. SSX2IP, PLXNA2, RASA2, TCF21, CALN1, and RORA were suggested as candidate genes. CONCLUSIONS: The genome-wide association study using microsatellites suggested that 6 loci (1p22.3, 1q32.2, 3q23, 6q23.2, 7q11.22, and 15q22.22) were susceptibility regions of mandibular prognathism. The locus 1p22.3 was supported by a previous linkage analysis, and the other 5 were novel loci.

Evaluation of the effectiveness of intermittent mechanical pressure with short loading duration: new type of intermittent force for orthodontic treatment.

Background: Since it is difficult to precisely control the magnitude of force in orthodontic practice, controlling the duration of force is expected to prevent tissue damage. The use of an actuator as an appliance for intermittent force application is a possible solution for controlling the duration. However, effectiveness of an actuator for controlling the duration is still not clear. Aim: To determine whether a short loading duration of intermittent force has the potential to maintain a sound condition of the capillaries and induce dilation of capillaries, which is a requisite phenomenon for orthodontic tooth movement. Materials and methods: Six-week-old male hamsters with a dorsal skinfold chamber attached to an intermittent loading device were used. In three experimental groups, application of intermittent pressure that involved repetition of loading and unloading was performed. The durations of loading/unloading were 1 second/9 seconds (group T10), 1 second/19 seconds (group T20), and 1 second/29 seconds (group T30). Vessels were examined using a fluorescence microscope and a stereomicroscope for 5 days. Results: Widths of capillaries in groups T10 and T20 increased significantly (P < 0.01). In contrast, widths of capillaries in group T30 showed no significant difference from those in the control group. Only group T10 showed bleeding, obvious destruction of vessels, and a significant increase in the rate of disappearance of vessels. Conclusion: In the epidermis, although conditions are limited, a short loading duration of intermittent force maintains a sound condition of the capillaries at the tissue level and induces dilation of capillaries.

RANKL regulates differentiation of microfold cells in mouse nasopharynx-associated lymphoid tissue (NALT).

Murine nasopharynx-associated lymphoid tissue (NALT), located at the base of the nasal cavity, serves as a major site for the induction of mucosal immune responses against airway antigens. The follicle-associated epithelium (FAE) covering the luminal surface of NALT is characterized by the presence of microfold cells (M cells), which take up and transport luminal antigens to lymphocytes. Glycoprotein 2 (GP2) has recently been identified as a reliable marker for M cells in Peyer's patches of the intestine. However, the expression of GP2 and other functional molecules in the M cells of NALT has not yet been examined. We have immunohistochemically detected GP2-expressing cells in the FAE of NALT and the simultaneous expression of other intestinal M-cell markers, namely Tnfaip2, CCL9, and Spi-B. These cells have been further identified as M cells because of their higher uptake capacity of luminal microbeads. Electron microscopic observations have shown that GP2-expressing cells on the FAE display morphological features typical of M cells: they possess short microvilli and microfolds on the luminal surface and are closely associated with intraepithelial lymphocytes. We have also found that the receptor activator of nuclear factor kappa-B ligand (RANKL) is expressed by stromal cells underneath the FAE, which provides its receptor RANK. The administration of RANKL markedly increases the number of GP2(+)Tnfaip2(+) cells on the NALT FAE and that of intestinal M cells. These results suggest that GP2(+)Tnfaip2(+) cells in NALT are equivalent to intestinal M cells, and that RANKL-RANK signaling induces their differentiation.

Photophysical properties and biocompatibility of Photoluminescent Y2O3:Eu nanoparticles in polymethylmetacrylate matrix.

In this study, we produced europium-doped yttoria (Y2O3:Eu) nanoparticles and investigated their photoluminescent properties and biocompatibility. The Y2O3:Eu nanoparticles showed excellent photoluminescent properties and cytocompatibility. We also analyzed the photophysical properties of the nanoparticles in PMMA films. When the Y2O3:Eu nanoparticles were incorporated in the polymer film, they showed a strong red emission spectrum, similar to that seen with the particles alone. Energy dispersive X-ray spectroscopy (EDS) measurements indicated that the particles were distributed homogeneously in the PMMA film. Such materials could be applied not only to optoelectronic devices but also to biomedical applications such as bioimaging tools or luminescent medical/dental adhesive materials.

Microsatellite genome-wide association study for mandibular prognathism.

INTRODUCTION: Attempts have been made to identify susceptibility genes of mandibular prognathism by genome-wide linkage studies, but the results of susceptibility loci are inconsistent. There has been no genome-wide association study of mandibular prognathism. Our objective was to perform a genome-wide association study using 23,465 microsatellite markers to detect mandibular prognathism susceptibility regions. METHODS: The study was based on the pooled DNA method, including 2 steps of screening on the whole genome and subsequent individual genotyping, with 240 experimental subjects and 360 control subjects from the Japanese population. RESULTS: Two suggestive associations on chromosomes 1q32.2 (D1S1358i: P = 4.22 × 10(-4)) and 1p22.3 (D1S0411i: P = 6.66 × 10(-4)) were shown, and PLXNA2 and SSX2IP were suggested to be candidate genes; 1p22.3 flanked the region indicated by previous linkage analysis. CONCLUSIONS: The results of the genome-wide association study showed that 2 loci (1q32.2 and 1p22.3) are likely to be susceptibility regions of mandibular prognathism: 1p32.2 is a novel locus, and identification of 1p22.3 supports the results of previous linkage analysis.

Overjet, overbite and dental midline shift as predictors of tooth size discrepancy in a Bangladeshi population and a graphical overview of global tooth size ratios.

OBJECTIVES: This study aimed to measure and compare tooth size ratios in a Bangladeshi population across the following groups: those with normal occlusion, crowding or spacing; those with normal, increased or decreased overjet; those with normal, increased or decreased overbite; those with or without dental mid-line discrepancy; and those with or without lip competence. It also presents a graphical overview of the anterior and overall ratios from the study and using available global data. MATERIALS AND METHODS: This study was performed on dental casts of 260 Bangladeshi individuals, comprising 114 males and 146 females (age range, 18-24 years, mean age = 20). The Bolton anterior ratio and overall ratio were determined for the following groups: those with normal occlusion, crowding or spacing; those with normal, increased or decreased overjet; those with normal, increased or decreased overbite; those with or without dental mid-line discrepancy; and those with or without lip competence. RESULTS: There were statistically significant differences in the anterior tooth size ratios between those with or without dental mid-line discrepancy, with a mean value of 78.83% and 80.05%, respectively. Statistically significant differences were also found in overall tooth size ratios between those with normal, increased or decreased overjet and also between those with normal, increased or decreased overbite. Graphical presentations of anterior and overall ratios from the present study and using global data showed variations between populations. CONCLUSION: In the Bangladeshi population, increased tooth size ratios in subjects with dental mid-line discrepancy (anterior ratio) and also in those with decreased overjet or decreased overbite (overall ratio) may be predictors of tooth size discrepancies. The graphical overview also suggests that different international ethnic groups display unique Bolton ratios.

Congenital and postnatal factors inducing malocclusions in Japanese unilateral cleft lip and palate patients-determination using logistic regression analysis.

Objective : To assess the congenital and postnatal factors that affect degree of malocclusion in patients with unilateral cleft lip and palate using multivariate statistical analysis. Design : Retrospective study. Patients : All information on 135 subjects with unilateral cleft lip and palate was obtained from an oral examination and radiograph at the initial examination at an orthodontic clinic and from surgical records. Plaster models were taken before orthodontic treatment. The ages of the subjects ranged from 5 to 8 years with a mean age of 6.9 years. All primary surgeries for the patients were performed at a university hospital. Main Outcome Measures : The GOSLON Yardstick was used to assess the dental arch relationships (degree of malocclusion) in patients. Family history of Class III, degree of cleft, and congenitally missing upper lateral incisor on the cleft side were chosen as congenital factors inducing malocclusion. Presurgical orthopedic treatment, cheiloplasty, and palatoplasty were chosen as postnatal factors. Associations between various factors and dental arch relationships were assessed using logistic regression analysis. Results : According to adjusted odds ratios, family history of Class III is associated with a significantly worse dental arch relationship. Palatoplasty using push-back alone correlated to a dental arch relationship that was significantly worse than palatoplasty using push-back with a buccal flap. Conclusions : Multivariate analysis shows evidence that a positive family history of Class III and palatoplasty using push-back alone are associated with worse malocclusion of unilateral cleft lip and palate patients.

Three-dimensional craniomaxillary characteristics of the mouse with spontaneous malocclusion using micro-computed tomography.

The aim of this study was to clarify the morphological characteristics of craniomaxillary deviations in BALB/c-bm/bm mice with a spontaneous malocclusion (incisal transverse crossbite) using three-dimensional (3D) morphological measurements. Sixty female mice aged 13 and 25 weeks were divided into the following groups: control (BALB/c-+/+ mice, n = 20), norm (BALB/c-bm/bm mice with a normal occlusion, n = 20), and mal (BALB/c-bm/bm mice with a malocclusion, n = 20). Various points in the skull were selected and the distances between two points were measured using 3D micro-computed tomography (CT) images. Statistically significant differences in measurement values among the three groups were evaluated by one-way analysis of variance with a probability level of P < 0.05 considered statistically significant. At both ages, the lengths of almost all measurements in the norm and mal groups were significantly shorter than those in the control group. Comparison between the shifted and non-shifted sides in the mal group showed that significant lateral deviation at the maxilla and nasal bone had occurred. Using 3D micro-CT images, the results of this study quantitatively showed that the craniomaxillary complex of BALB/c-bm/bm mice was significantly smaller than that of BALB/c-+/+ mice and that BALB/c-bm/bm mice have a spontaneous transverse crossbite due to lateral deviation of the maxilla and nasal bone.

Relationship between degree of malocclusion and occlusal interference in mice that spontaneously develop anterior transverse crossbite.

INTRODUCTION: Mice with brachymorphism (bm) have defective chondrogenesis, including abnormal growth of the spheno-occipital synchondrosis. Malocclusion (anterior transverse crossbite) sometimes spontaneously occurs in inbred BALB/c-bm/bm mice, before the mandibular incisors erupt and make contact with the maxillary incisors. The aim of this study was to determine whether functional lateral loads to incisors promote anterior transverse crossbites in BALB/c-bm/bm mice. METHODS: BALB/c-bm/bm mice with normal occlusion (normal group), BALB/c-bm/bm mice with malocclusion in which the incisors were not cut (mal group), and BALB/c-bm/bm mice in which the incisors had been cut to eliminate the functional lateral load during continued growth (mal-cut group) were used. We examined the amounts of shift of the maxillary and mandibular incisors in each group using radiographic images. RESULTS: The amount of shift of the maxillary incisors in the mal group was significantly greater than that in normal group. The total amount of shift from the maxilla to the mandible in the mal group was significantly greater than in the normal and mal-cut groups. CONCLUSIONS: The results suggest that a continuous functional lateral load to the incisors is strongly related to promoting and worsening anterior transverse crossbite in BALB/c-bm/bm mice.

Interleukin-1beta levels, pain intensity, and tooth movement using two different magnitudes of continuous orthodontic force.

This study aimed to determine the optimum orthodontic force from a broader perspective. Interleukin (IL)-1ß levels in human gingival crevicular fluid (GCF), pain intensity, and the amount of tooth movement were measured during canine retraction using different magnitudes of continuous orthodontic force. Sixteen subjects (two males and 14 females), aged 18-24 years, diagnosed with Class I bimaxillary protrusion and treated with first premolar extractions participated in this study. The upper canines were retracted with continuous forces of 50 or 150 g using nickel-titanium coil springs on segmented archwires. One of the lower canines was used as a control. GCF was collected from the distal site of each tooth at specific time points. IL-1ß concentrations, pain intensity, using the visual analogue scale (VAS), and the amount of tooth movement were evaluated. One-way analysis of variance, Friedman, and paired t-tests were used for comparisons of IL-1ß in GCF, the plaque and gingival indices, and the efficiency of tooth movement on pain perception, respectively. IL-1ß concentration in the 150 g group showed the highest level at 24 hours and 2 months with significant differences compared with the control group (P < 0.05). The mean VAS score of pain intensity from the 150 g force was significantly greater than from the 50 g force at 24 hours (P < 0.01). However, no significant difference in the amount of tooth movement was found between these two different magnitudes of continuous force at 2 months. A 50 g force could effectively induce tooth movement similar to 150 g with less pain and less inflammation.

Orthodontic treatment of cleft lip and alveolus using secondary autogenous cancellous bone grafting: a case report.

AIM: This paper concerns orthodontic alignment of the maxillary lateral incisor on the cleft side of a lip and alveolar cleft patient after a secondary autogenous cancellous bone graft at the late stage of mixed dentition. SUBJECT AND TREATMENT: The patient was a Japanese girl 9 years 7 months of age who presented at the authors' clinic with a repaired lip and alveolar cleft and an incisor crossbite. At 12 years of age, a secondary bone graft of the alveolar ridge was performed using bone harvested from the iliac crest. At 14 years 7 months of age, a conventional fixed appliance was placed. RESULTS: The lateral incisor on the cleft side was brought to the line of occlusion by orthodontic alignment. A Class I molar relationship on both sides and a satisfactory facial profile were achieved. After a 2-year retention period, the occlusion and esthetics were maintained. Five years after grafting, however, a satisfactory bone level was not achieved due to positioning of the root of the lateral incisor, which was not completely upright in the bone graft area due to root tipping.

Whole-exome sequencing in a Japanese pedigree implicates a rare non-synonymous single-nucleotide variant in BEST3 as a candidate for mandibular prognathism.

Mandibular prognathism is a phenotype of facial deformity seen in populations around the world, but with higher incidence among East Asian populations. Five genome-wide nonparametric linkage analyses and a genome-wide association study to identify susceptibility loci of the phenotype have shown inconsistent results. To explore variants related to mandibular prognathism, we undertook whole-exome sequencing in a Japanese pedigree. The pedigree was ascertained as mandibular prognathism. The pedigree comprised 15 individuals from 4 generations. Four affected individuals across 2 generations and 5 unaffected individuals were chosen for whole-exome sequencing. Five non-synonymous single-nucleotide variants (SNVs) of UBASH3B, OR6M1, OR8D4, OR8B4, and BEST3 genes were detected in all 4 affected individuals, but in none of the 5 unaffected individuals. A non-synonymous SNV of the BEST3 gene, Chr12(GRCh37):g.70048878G>T, NM_032735.2:c.1816C>A, p.(L606I), was identified as rare missense variant. BEST3 is located on chromosome 12q15 and encodes bestrophin 3 from the bestrophin family of anion channels. The 4 other non-synonymous SNVs of UBASH3B, OR6M1, OR8D4, and OR8B4 were not considered plausible candidates for mandibular prognathism. Our whole-exome sequencing implicates a rare non-synonymous SNV of BEST3 as a candidate for mandibular prognathism in the Japanese pedigree.

Airway M Cells Arise in the Lower Airway Due to RANKL Signaling and Reside in the Bronchiolar Epithelium Associated With iBALT in Murine Models of Respiratory Disease.

Microfold (M) cells residing in the follicle-associated epithelium of mucosa-associated lymphoid tissues are specialized for sampling luminal antigens to initiate mucosal immune responses. In the past decade, glycoprotein 2 (GP2) and Tnfaip2 were identified as reliable markers for M cells in the Peyer's patches of the intestine. Furthermore, RANKL-RANK signaling, as well as the canonical and non-canonical NFκB pathways downstream, is essential for M-cell differentiation from the intestinal stem cells. However, the molecular characterization and differentiation mechanisms of M cells in the lower respiratory tract, where organized lymphoid tissues exist rarely, remain to be fully elucidated. Therefore, this study aimed to explore M cells in the lower respiratory tract in terms of their specific molecular markers, differentiation mechanism, and functions. Immunofluorescence analysis revealed a small number of M cells expressing GP2, Tnfaip2, and RANK is present in the lower respiratory tract of healthy mice. The intraperitoneal administration of RANKL in mice effectively induced M cells, which have a high capacity to take up luminal substrates, in the lower respiratory epithelium. The airway M cells associated with lymphoid follicles were frequently detected in the pathologically induced bronchus-associated lymphoid tissue (iBALT) in the murine models of autoimmune disease as well as pulmonary emphysema. These findings demonstrate that RANKL is a common inducer of M cells in the airway and digestive tracts and that M cells are associated with the respiratory disease. We also established a two-dimensional culture method for airway M cells from the tracheal epithelium in the presence of RANKL successfully. This model may be useful for functional studies of M cells in the sampling of antigens at airway mucosal surfaces.

Growth and development of the cranial base in mice that spontaneously develop anterior transverse crossbite.

INTRODUCTION: Homozygous brachymorphic (bm/bm) mice are characterized by disproportionately short stature. Anterior transverse crossbite sometimes develops spontaneously in inbred BALB/c-bm/bm mice that produce undersulfated glycosaminoglycans. The reason for inferior growth of the craniofacial structures of BALB/c-bm/bm mice has not been clarified. We focused on the spheno-occipital synchondrosis (SOS)-the growth site of the cranium-and investigated the growth pattern in the SOS of the BALB/c-bm/bm mice. METHODS: The BALB/c-+/+ mice and BALB/c-bm/bm mice without malocclusion were used. Sagittal sections of the cranial bases were stained with hematoxylin and eosin, observed histologically, and used to measure the anteroposterior length and the percentage of active bone volume around the SOS. RESULTS: In the histologic study, compared with the cartilage in the BALB/c mice, a bipolar column was not seen in the cartilage of the SOS in the BALB/c-bm/bm mice. The histomorphometric study showed that the anteroposterior length of the posterior cranial base was significantly shorter and the percentage of active bone volume was significantly smaller in the BALB/c-bm/bm mice than in the BALB/c mice. CONCLUSIONS: The results suggested that normal endochondral growth is disturbed in the synchondrosis of the posterior base of the skull in BALB/c-bm/bm mice.

PLXNA2 identified as a candidate gene by genome-wide association analysis for mandibular prognathism in human chondrocytes.

In a previous genome-wide association study, plexin A2 (PLXNA2) was suggested as one of the candidate genes for mandibular prognathism. PLXNA2 encodes plexin A2, a member of the plexin-A family of semaphorin co-receptors. Semaphorin 3A (sema3A) exerts an osteoprotective effect. However, to the best of our knowledge, there have been no previous studies examining the role of sema3A or plexin A2 on human chondrocytes. The objectives of the present study were to examine the function of sema3A and its receptor, plexin A2, in human chondrocytes. Normal human chondrocytes were cultured in media with either a high (100 ng/ml) or a low (1 ng/ml) concentration of sema3A, or without sema3A as a control. Cells and extracellular matrices were assayed for concentrations of protein and parathyroid hormone-related peptide receptor 1 (PTH-R1) using a bicinchoninic acid assay and an enzyme immunoassay, respectively. At culture day 7, the high and low concentrations of exogenous sema3A significantly increased the protein content compared with the control (P=0.0008 and 0.00002, respectively). At culture day 14, a high concentration of exogenous sema3A significantly increased the protein content and decreased the concentration of PTH-R1 compared with the control (P=0.002). The present study revealed novel results that exogenous sema3A suppresses the expression of PTH-R1 in human proliferative chondrocytes and suggested that sema3A may affect human chondrocytes via its receptor, plexin A2.

Expression and Dynamics of Podoplanin in Cultured Osteoblasts with Mechanostress and Mineralization Stimulus.

This study investigates the significance of the expression and dynamics of podoplanin in mechanostress and mineralization in cultured murine osteoblasts. Podoplanin increased in osteoblasts subjected to straining in non-mineralization medium, suggesting that the mechanostress alone is a podoplanin induction factor. In osteoblasts subjected to vertical elongation straining in the mineralization medium, the mRNA amounts of podoplanin, osteopontin, and osteocalcin were significantly larger than those in cells not subjected to straining, suggesting that mechanostress is the cause of a synergistic effect in the expression of these proteins. In osteoblasts in the mineralization medium, significant increases in osteocalcin mRNA occurred earlier in cells subjected to straining than in the cells not subjected to straining, suggesting that the mechanostress is a critical factor to enhance the expression of osteocalcin. Western blot and ELISA analysis showed increased podoplanin production in osteoblasts with longer durations of straining. There was significantly less mineralization product in osteoblasts with antibodies for podoplanin, osteopontin, and osteocalcin. There was also less osteopontin and osteocalcin produced in osteoblasts with anti-podoplanin. These findings suggest that mechanostress induces the production of podoplanin in osteoblasts and that podoplanin may play a role in mineralization in cooperation with bone-associated proteins.

RANKL expression in rat periodontal ligament subjected to a continuous orthodontic force.

OBJECTIVES: This study investigated longitudinal changes in receptor activator NF kappa B ligand (RANKL) expression in periodontal ligament (PDL) cells subjected to a continuous orthodontic force. DESIGN: Fifty-five-day-old male Wistar rats were divided into experimental and control groups. The experimental group had the first molars laterally expanded by a continuous orthodontic force. In each group, the horizontal section specimens were embedded in OTC compound and frozen at 0, 1, 3 and 7 days after the expansion. Sections were observed by immunostaining with anti-RANKL and the tartrate-resistant acid phosphatase (TRAP) staining. RESULT: Immunoreaction of RANKL and TRAP-positive cells were observed in the distal region of the controls and on the compressed side of the expansion group in the 3 and 7 days. Immunoreaction of RANKL was also observed after 1 day on the compression side of the expansion group, but here TRAP-positive cells were few. CONCLUSIONS: The experiments have showed that PDL cells are continuously producing RANKL on the PDL pressure side of rats subjected to mechanical stress with a continuous orthodontic force, there was no noticeable the excessive appearance of osteoclasts however. Considering this, it is expected that not only RANKL production but also other cytokines play an important role in the balancing adjustment in the alveolar bone remodeling.

Biomechanical rationale for surgically facilitated expansion of the maxilla in the cleft palate patient.

AIM: To evaluate in vitro the biomechanical effects of surgically assisted rapid palatal expansion in a photoelastic unilateral cleft palate analog by observing stresses produced during appliance activation. METHODS: A photoelastic analog of an adult skull with unilateral cleft palate was fabricated using birefringent materials to simulate bone and teeth. A customized hyrax appliance was applied to the anchor teeth and incrementally activated. Resulting stress patterns on both the cleft side and the intact side were observed and recorded photographically in the field of a circular polariscope. Subsequently, the pterygomaxillary junctions were sequentially cut, the appliance activations repeated, and the resulting stresses recorded. RESULTS: With intact pterygomaxillary junctions, the highest stresses were localized at the zygomaticomaxillary and zygomaticofrontal sutures, with higher intensity on the intact side. Stresses concentrated in the pterygoid plates evidenced resistance to the expansion forces of the hyrax appliance. On separating the defect pterygomaxillary junction, increased stresses were located from the zygomaticomaxillary suture to the zygomaticofrontal suture and at the zygomatic arches on both sides, as well as the pterygomaxillary junction of the non-defect side. After cutting both the pterygomaxillary junctions, decreased stress was located from the zygomaticomaxillary suture to the zygomaticofrontal suture, the zygomatic arch, and the frontonasal sutures on both sides. CONCLUSIONS: The pterygomaxillary junctions acted as the main resistive elements to expansion forces generated by a hyrax appliance. Separating the pterygomaxillary junctions assisted the bodily displacement of the lateral maxillary segment, which would facilitate correction of maxillary arch constrictions in the adult unilateral cleft lip patient.