Evaluation of oral function using a composite sensor during maximum lip closure and swallowing in normal children and adults

BACKGROUND

There is growing interest in the development of objective methods for assessing lip-closing function in children.

OBJECTIVE

To obtain normative data for healthy children in the developmental stages of lip closure function, we quantitatively evaluated oral movements associated with lip closure in children and adults using a composite sensor (CS).

METHODS

Twenty-five normal children (11 boys, 14 girls) aged 8.8 ± 1.6 years and 25 young adults (13 men, 12 women) aged 27.4 ± 3.9 years were asked to perform test movements, maximal lip closure and swallowing of 3 mL of water. Lip-closing pressure (LP), intraoral baro-pressure (IP) and electromyographic (EMG) activity of the upper orbicularis oris muscle were simultaneously recorded using the CS.

RESULTS

EMG activity of the upper orbicularis oris muscle during closure was significantly greater in adults than in children. There were significant positive correlations between integral values of LP and EMG for closure in adults (r = .527, p = .008) but not in children, and significant positive correlations between integral values of LP and IP for swallowing in children (r = .508, p = .010) but not in adults.

CONCLUSIONS

The CS may provide an effective tool for evaluating lip function in children acquiring oral function. For the combination of maxillary orbicularis oculus contraction and formation of intraoral negative pressure, EMG activity of the upper orbicularis oris muscle involvement in LP and IP involvement in LP may differ between children and adults.

Oral Function and Feeding Management in a Child with Alpha Thalassemia X-Linked Intellectual Disability Syndrome

Alpha-thalassemia X-linked intellectual disability (ATR-X) syndrome affects males and is associated with profound developmental delay, facial dysmorphism, genital abnormalities, and alpha thalassemia. Appropriate oral health management for affected patients is important. The purposes of this report are to describe a case involving six years of oral health management, including training in eating, drinking and swallowing, for a patient with ATR-X syndrome, and to discuss the morphological and functional oral characteristics of this disorder. The patient's oral dysfunctions were incompetent lip-closing, inappropriate tongue protrusion, deviation of chewing acquisition, and incompetent oral and pharyngeal bolus propulsion. Other problems included inappropriate ingestion posture, low interest in meals, and poor oral hygiene. A stable oral intake and an improved eating posture were achieved through an intervention; however, the patient's inappropriate tongue protrusion, deviation of chewing acquisition, and incompetent bolus propulsion remained unchanged.

Lip-closing strength in children is enhanced by lip and facial muscle training

Objectives

Weakening of lip‐closing strength (LCS) associated with an incompetent lip seal (ILS) may affect the oral balance between the lip and tongue pressures. The purpose of this study was to evaluate the effects of lip‐closing training in children with lower LCS and/or abnormal habits across different age groups and to compare its effects on increasing LCS in children with malocclusion and/or oral habits.

Material and Methods

Lip‐closing training was performed by 154 Japanese children aged 3–12 years using a specialized training device at home for 3 months. Children with oral habits and/or exhibiting less than standard LCS were included. LCS was measured using a digital strain force gauge at a dental clinic at the beginning (T0) and after each month (after 3 months: T3).

Results

Children had higher LCS responses after lip‐closing training. The first month of lip‐closing training was more effective than the subsequent months. With lip‐closing training, the LCS increased from an average of 6.2 N (T0) to 11.4 N (T3) in Group I, 7.9 N (T0) to 12.8 N (T3) in Group II, and 6.8 N to 11.4 N in Group III. Anterior cross bite, including reverse bite, open bite, and tongue thrusting, significantly reduced training effects.

Conclusion

Our findings showed that lower LCS in children with ILS resulted in greater responses to lip‐closing training in a short period, but oral dysfunction, such as abnormal habits, inhibited the positive effects of training. Our results suggest that less detrimental effects of malocclusion and abnormal oral habits lip‐closing training enhances LCS in younger children.

The effects of reducing the root length by apicoectomy on dental pulp revascularization following tooth replantation in mice

BACKGROUND/AIM

Root length is a critical factor for dental pulp regeneration following tooth replantation. The aim of this study was to analyze the effects of reducing the root length by apicoectomy on the pulp healing process using a model for tooth replantation.

MATERIAL AND METHODS

After extraction of the upper first molars (M1) of 3-week-old mice, the roots from the experimental group (EG) were shortened to half to two-thirds of their length before replantation, whereas in the control group (CG) the extracted teeth were immediately repositioned into their alveolar sockets. To determine the effects of root resection on the survival of inherent pulp cells, this study included tooth transplantation with root resection using wild-type (WT) and green fluorescent protein (GFP) transgenic mice. The M1 of GFP transgenic mice were transplanted into the alveolar socket of the M1 of WT mice. The roots of the right M1 were shortened (EG), whereas the left M1 remained untreated (CG).

RESULTS

Apoptotic cells in the EG significantly decreased in number compared with the CG at day 3. Cell proliferative activity in the EG was significantly higher than that in the CG in the root pulp during days 3-5, and nestin-positive odontoblast-like cells began to arrange themselves along the pulp-dentin border in the cusp area at day 5 in the EG but not in the CG. At week 2, tertiary dentin had formed throughout the pulp in the EG, whereas the combined tissue of dentin and bone occupied the pulp space in 60% of the CG. Root resection also positively affected the survival of inherent pulp cells to differentiate into odontoblast-like cells as demonstrated by transplantation using GFP transgenic mice.

CONCLUSIONS

Reducing the root length accelerated pulp regeneration following tooth replantation due to the better environment for revascularization.

Lip-closing pressure during food intake from a spoon in normal children

BACKGROUND

Understanding the refinement of self-feeding skills is useful for the assessment of oral functional development in children.

OBJECTIVES

To determine normative data on lip closing during food intake in the development of independent spoon-feeding in normal children, we tested the hypothesis that lip-closing pressure and spoon operation differ depending on food type.

METHODS

Fifteen normal children (eight boys, seven girls; mean age: 6.5 years) were asked to eat test foods (2, 3 and 5 g of yogurt and cream cheese) freely with a spoon. Lip-closing pressures and kinematic data on spoon operation were recorded simultaneously with a strain gauge transducer embedded in the spoon and Vicon motion analysis, respectively.

RESULTS

In the most common lip-pressure pattern, only positive pressure was generated. In the second most common pattern, negative pressure occurred first, followed by positive pressure; this pattern was seen infrequently. Positive pressure (P < .001), pressure duration (P < .001) and spoon intra-oral time (P < .05) during intake of cream cheese (an adhesive food) were significantly greater than those during intake of yogurt (a non-adhesive food). Pressure onset occurred at the beginning of the spoon withdrawal period or at the turning point from spoon insertion to withdrawal, depending on the food.

CONCLUSIONS

Lip-closing force and spoon operation varied depending on food type in preschool and early elementary school children. Our findings suggest the need to consider the importance of food diversity and to pay attention to the spoon withdrawal period when assessing the development and maturation of lip function.

Prevalence of an incompetent lip seal during growth periods throughout Japan: a large-scale, survey-based, cross-sectional study

BACKGROUND

Systemic and local factors may lead to disruption of craniofacial growth and development, causing an imbalance between the orofacial skeleton, muscle and soft tissue, dental occlusion, and the dental arch during growth periods. We aimed to reveal whether the prevalence of incompetent lip seal (ILS) varies with age and region, as well as to clarify the factors related to an ILS, in a national, large-scale epidemiological study.

METHODS

We surveyed 3399 children, from 3 to 12 years of age, visiting 66 pediatric dental clinics throughout Japan. For this survey, we employed a questionnaire consisting of 44 questions regarding daily health conditions and lifestyle habits. We evaluated the differences in ILS prevalence by age and region (using a Cochran-Armitage test for trend and a Kruskal-Wallis test), and the relationship between ILS and factors investigated in the questionnaire (using Spearman's rank correlation coefficient).

RESULTS

We observed that 30.7% of Japanese children exhibited an ILS and that the ILS rate increased with age (p < 0.001). There were no regional differences in the rate of ILS in Japanese children (p = 0.506). We revealed that 12 of 44 survey items exhibited a statistically significant correlation with ILS (p < 0.001), using Spearman's rank correlation coefficient. These items involved orofacial morphology, mouth breathing, and possibly, allergic rhinitis.

CONCLUSION

The rate of ILS seems to increase with age in children, throughout Japan. Therefore, this disorder may not self-correct during the growth periods in these children. Guidelines are required for pediatric dentists to recognize ILS among children aged 3-12 years.

Drug-Induced Naïve iPS Cells Exhibit Better Performance than Primed iPS Cells with Respect to the Ability to Differentiate into Pancreatic β-Cell Lineage

Pluripotent stem cells are classified as naïve and primed cells, based on their in vitro growth characteristics and potential to differentiate into various types of cells. Human-induced pluripotent stem cells (iPSCs, also known as epiblast stem cells [EpiSCs]) have limited capacity to differentiate and are slightly more differentiated than naïve stem cells (NSCs). Although there are several in vitro protocols that allow iPSCs to differentiate into pancreatic lineage, data concerning generation of β-cells from these iPSCs are limited. Based on the pluripotentiality of NSCs, it was hypothesized that NSCs can differentiate into pancreatic β-cells when placed under an appropriate differentiation induction condition. We examined whether NSCs can be efficiently induced to form potentially pancreatic β cells after being subjected to an in vitro protocol. Several colonies resembling in vitro-produced β-cell foci, with β-cell-specific marker expression, were observed when NSC-derived embryoid bodies (EBs) were induced to differentiate into β-cell lineage. Conversely, EpiSC-derived EBs failed to form such foci in vitro. Intrapancreatic grafting of the in vitro-formed β-cell foci into nude mice (BALB/c-nu/nu) generated a cell mass containing insulin-producing cells (IPCs), without noticeable tumorigenesis. These NSCs can be used as a promising resource for curing type 1 diabetes.

Repeated human deciduous tooth-derived dental pulp cell reprogramming factor transfection yields multipotent intermediate cells with enhanced iPS cell formation capability

Human tissue-specific stem cells (hTSCs), found throughout the body, can differentiate into several lineages under appropriate conditions in vitro and in vivo. By transfecting terminally differentiated cells with reprogramming factors, we previously produced induced TSCs from the pancreas and hepatocytes that exhibit additional properties than iPSCs, as exemplified by very low tumour formation after xenogenic transplantation. We hypothesised that hTSCs, being partially reprogrammed in a state just prior to iPSC transition, could be isolated from any terminally differentiated cell type through transient reprogramming factor overexpression. Cytochemical staining of human deciduous tooth-derived dental pulp cells (HDDPCs) and human skin-derived fibroblasts following transfection with Yamanaka’s factors demonstrated increased ALP activity, a stem cell marker, three weeks after transfection albeit in a small percentage of clones. Repeated transfections (≤3) led to more efficient iPSC generation, with HDDPCs exhibiting greater multipotentiality at two weeks post-transfection than the parental intact HDDPCs. These results indicated the utility of iPSC technology to isolate TSCs from HDDPCs and fibroblasts. Generally, a step-wise loss of pluripotential phenotypes in ESCs/iPSCs occurs during their differentiation process. Our present findings suggest that the reverse phenomenon can also occur upon repeated introduction of reprogramming factors into differentiated cells such as HDDPCs and fibroblasts.

Streptococcus pyogenes CAMP factor promotes calcium ion uptake in RAW264.7 cells

Streptococcus pyogenes is a bacterium that causes systemic diseases such as pharyngitis and toxic shock syndrome. S. pyogenes produces molecules that inhibit the function of the human immune system, thus allowing growth and spread of the pathogen in tissues. It is known that S. pyogenes CAMP factor induces vacuolation in macrophages; however, the mechanism remains unclear. In the current study, the mechanism by which CAMP factor induces vacuolation in macrophages was investigated. CAMP factor was found to induce calcium ion uptake in murine macrophage RAW264.7 cells. In addition, EDTA inhibited calcium ion uptake and vacuolation in the cells. The L-type voltage-dependent calcium ion channel blockers nifedipine and verapamil reduced vacuolation. Furthermore, the phosphoinositide 3-kinase inhibitors LY294002 and wortmannin also inhibited the vacuolation induced by CAMP factor. Fluorescent microscopy revealed that clathrin localized to the vacuoles. These results suggest that the vacuolation is related to calcium ion uptake by RAW264.7 cells via L-type voltage-dependent calcium ion channels. Therefore, it was concluded that the vacuoles induced by S. pyogenes CAMP factor in macrophages are clathrin-dependent endosomes induced by activation of the phosphoinositide 3-kinase signaling pathway through calcium ion uptake.

Prevalence of molar incisor hypomineralization and regional differences throughout Japan

Background

Molar incisor hypomineralization (MIH) frequently occurs in children worldwide. However, MIH prevalence throughout Japan has not yet been investigated. The purpose of this study was to clarify MIH prevalence rates and to consider potential regional differences throughout Japan.

Methods

A total of 4496 children aged 7–9 years throughout Japan were evaluated in this study. MIH prevalence rates among children were evaluated in eight regions throughout Japan. A child’s residence was defined as the mother’s residence during pregnancy. The localization of demarcated opacities and enamel breakdown was recorded on a standard code form using a guided record chart. Logistic regression analysis was used to evaluate whether MIH prevalence rates differed among age groups, sex, and regions.

Results

The overall prevalence of MIH in Japan was 19.8%. The prevalence of MIH was 14.0% in the Hokkaido region, 11.7% in the Tohoku region, 18.5% in the Kanto Shin-Etsu region, 19.3% in the Tokai Hokuriku region, 22.3% in the Kinki region, 19.8% in the Chugoku region, 28.1% in the Shikoku region, and 25.3% in the Kyushu region. These regional differences were statistically significant. Moreover, MIH prevalence rates decreased with age. No significant sex differences in MIH prevalence rates were demonstrated.

Conclusions

To our knowledge, this is the first MIH study carried out in several regions throughout Japan. Regional differences existed in MIH prevalence rates; particularly, MIH occurred more frequently in children residing in southwestern areas than those in northeastern areas of Japan.

An exploratory study of the factors related to mouth breathing syndrome in primary school children

OBJECTIVE

Mouth breathing syndrome (MBS) is defined as a set of signs and symptoms that may be completely or incompletely present in subjects who, for various reasons, replace the correct pattern of nasal breathing with an oral or mixed pattern. It is important to identify the relevant factors affecting MBS in order to diagnose its cause since breathing obstructions can result from multiple factors. The purpose of this study is to clarify the relevant factors and the interrelationships between factors affecting MBS among children.

DESIGN

We surveyed 380 elementary school children from 6 to 12 years in age. The questionnaire consisted of 44 questions regarding their daily health conditions and lifestyle habits and was completed by the children's guardians. A factor analysis was performed to classify closely related questions into their respective factors and to examine the strength of the correlation between the newly revealed factors.

RESULTS

Twenty-six out of the 44 questions were selected, and they were classified into seven factors. Factors 1-7 were defined as "Incompetent lip seal", "Diseases of the nose and throat", "Eating and drinking habits", "Bad breath", "Problems with swallowing and chewing", "Condition of teeth and gums", and "Dry lips", respectively. There were also correlations between these factors themselves.

CONCLUSION

MBS was categorized according to 7 major factors. Because Factor 1 was defined as "Incompetent lip seal", which was representative of the physical appearance of mouth breathers and correlated with other factors, we suggested that MBS should consist of 7 factors in total.

Isolation and characterization of lymphoid enhancer factor-1-positive deciduous dental pulp stem-like cells after transfection with a piggyBac vector containing LEF1 promoter-driven selection markers

OBJECTIVE

Lymphoid enhancer-binding factor-1 (LEF1) is a 48-kD nuclear protein that is expressed in pre-B and T cells. LEF1 is also an important member of the Wnt/β-catenin signaling pathway that plays important roles in the self-renewal and differentiation of embryonic stem cells. We speculated that LEF1 might function in the stem cells from human exfoliated deciduous teeth (SHED). In this study, we attempted to isolate such LEF1-positive cells from human deciduous dental pulp cells (HDDPCs) by genetic engineering technology, using the human LEF1 promoter.

DESIGN

A piggyBac transposon plasmid (pTA-LEN) was introduced into HDDPCs, using the Neon^® transfection system. After G418 selection, the emerging colonies were assessed for EGFP-derived fluorescence by fluorescence microscopy. Reverse transcription polymerase chain reaction (RT-PCR) analysis was performed using RNA isolated from these colonies to examine stem cell-specific transcript expression. Osteoblastic or neuronal differentiation was induced by cultivating the LEF1-positive cells with differentiation-inducing medium.

RESULTS

RT-PCR analysis confirmed the expression of several stem cell markers, including OCT3/4, SOX2, REX1, and NANOG, in LEF1-positive HDDPCs, which could be differentiated into osteoblasts and neuronal cells.

CONCLUSIONS

The isolated LEF1-positive HDDPCs exhibited the properties of stem cells, suggesting that LEF1 might serve as a marker for SHED.

Tissue-Specific Stem Cells Obtained by Reprogramming of Non-Obese Diabetic (NOD) Mouse-Derived Pancreatic Cells Confer Insulin Production in Response to Glucose

Type 1 diabetes occurs due to the autoimmune destruction of pancreatic β-cells in islets. Transplantation of islets is a promising option for the treatment of patients with type 1 diabetes that experience hypoglycemic unawareness despite maximal care, but the present shortage of donor islets hampers such transplantation. Transplantation of insulin-producing cells derived from the patients themselves would be one of the most promising approaches to cure type 1 diabetes. Previously, we demonstrated that insulin-producing cells could be produced by transfecting murine pancreatic cells with Yamanaka’s reprogramming factors. Non-obese diabetic (NOD) mice are naturally occurring mutant mice defective in insulin production due to autoimmune ablation of pancreatic β-cells. In this study, we showed that glucose-sensitive insulin-producing cells are successfully generated by transfecting primary pancreatic cells from NOD mice (aged 6 months old) with a plasmid harboring the cDNAs for Oct-3/4, Sox2, Klf4, and c-Myc. Transfection was repeated 4 times in a 2 day-interval. Sixty-five days after final transfection, cobblestone-like colonies appeared. They proliferated in vitro and expressed pluripotency-related genes as well as Pdx1, a transcription factor specific to tissue-specific stem cells for the β-cell lineage. Transplantation of these cells into nude mice failed to produce teratoma unlike induced pluripotent stem cells (iPSCs). Induction of these cells to the pancreatic β-cell lineage demonstrated their capability to produce insulin in response to glucose. These findings suggest that functional pancreatic β-cells can be produced from patients with type 1 diabetes. We call these resultant cells as “induced tissue-specific stem cells from the pancreas” (iTS-P) that could be valuable sources of safe and effective materials for cell-based therapy in type 1 diabetes.

Streptococcus pyogenes CAMP factor attenuates phagocytic activity of RAW 264.7 cells

Streptococcus pyogenes produces molecules that inhibit the function of human immune system, thus allowing the pathogen to grow and spread in tissues. It is known that S. pyogenes CAMP factor increases erythrocytosis induced by Staphylococcus aureus β-hemolysin. However, the effects of CAMP factor for immune cells are unclear. In this study, we investigated the effects of CAMP factor to macrophages. Western blotting analysis demonstrated that all examined strains expressed CAMP factor protein. In the presence of calcium or magnesium ion, CAMP factor was significantly released in the supernatant. In addition, both culture supernatant from S. pyogenes strain SSI-9 and recombinant CAMP factor dose-dependently induced vacuolation in RAW 264.7 cells, but the culture supernatant from Δcfa isogenic mutant strain did not. CAMP factor formed oligomers in RAW 264.7 cells in a time-dependent manner. CAMP factor suppressed cell proliferation via G2 phase cell cycle arrest without inducing cell death. Furthermore, CAMP factor reduced the uptake of S. pyogenes and phagocytic activity indicator by RAW 264.7 cells. These results suggest that CAMP factor works as a macrophage dysfunction factor. Therefore, we conclude that CAMP factor allows S. pyogenes to escape the host immune system, and contribute to the spread of streptococcal infection.

Choice of Feeders Is Important When First Establishing iPSCs Derived From Primarily Cultured Human Deciduous Tooth Dental Pulp Cells

Feeder cells are generally required to maintain embryonic stem cells (ESCs)/induced pluripotent stem cells (iPSCs). Mouse embryonic fibroblasts (MEFs) isolated from fetuses and STO mouse stromal cell line are the most widely used feeder cells. The aim of this study was to determine which cells are suitable for establishing iPSCs from human deciduous tooth dental pulp cells (HDDPCs). Primary cultures of HDDPCs were cotransfected with three plasmids containing human OCT3/4, SOX2/KLF4, or LMYC/LIN28 and pmaxGFP by using a novel electroporation method, and then cultured in an ESC qualified medium for 15 days. Emerging colonies were reseeded onto mitomycin C-treated MEFs or STO cells. The colonies were serially passaged for up to 26 passages. During this period, colony morphology was assessed to determine whether cells exhibited ESC-like morphology and alkaline phosphatase activity to evaluate the state of cellular reprogramming. HDDPCs maintained on MEFs were successfully reprogrammed into iPSCs, whereas those maintained on STO cells were not. Once established, the iPSCs were maintained on STO cells without loss of pluripotency. Our results indicate that MEFs are better feeder cells than STO cells for establishing iPSCs. Feeder choice is a key factor enabling efficient generation of iPSCs.

Smoothness of molar movement during gum chewing in children with primary dentition

The purpose of this study was to test the null hypothesis that molar movement during gum chewing in children with primary dentition is as smooth as in adults. Twenty-two healthy children with primary dentition and 23 healthy adult females participated in this study. Mandibular movement during gum chewing was recorded using an optoelectronic analysis system with six degrees-of-freedom at 100 Hz, and 10 cycles were selected for analysis. Normalized jerk cost (NJC) at the incisors and working and balancing molars were calculated in each phase (i.e., opening, closing and occlusal level phases) for each chewing cycle. The NJC of the working side molar in children was larger than in adults in both the opening and occlusal phases. Inter-individual variances of the NJC in each phase in children and adults were smaller than corresponding intra-individual variances, except for the NJC during the occlusal phase of adults for the working and balancing side molars. The inter- and intra-individual variances of the NJC during the closing phase were the smallest in each phase for both children and adults. This indicates that the jaw movements of children with primary dentition are more variable, less smooth, and faster than that of adults.

STO Feeder Cells Are Useful for Propagation of Primarily Cultured Human Deciduous Dental Pulp Cells by Eliminating Contaminating Bacteria and Promoting Cellular Outgrowth

STO feeder cells, a line established from mouse SIM embryonic fibroblasts, have been frequently used for establishing embryonic stem cells and maintaining them in an undifferentiated state. There are some reports demonstrating that fibroblastic cells have the ability to phagocytose Gram-positive bacterium (e.g., streptococci and staphylococci). In this study, we examined the possibility that STO cells could phagocytose Streptococcus mutans (a bacteria causing tooth decay), which always contaminates cultures of primarily isolated human deciduous dental pulp cells (HDDPCs). Simple cultivation of the primary HDDPCs in the absence of STO cells allowed S. mutans to massively propagate in the medium, thus leading to an opaque medium. In contrast, there was no bacterial contamination in the cultures containing mitomycin C (MMC)-inactivated STO cells. Furthermore, STO cells indicated bacterial phagocytic activity under fluorescent microscopy with the dye pHrodo. Besides removal of contaminating bacteria, STO feeder cells allowed the HDDPCs to spread out. These data suggest that MMC-treated STO cells can be useful for propagation of HDDPCs by eliminating contaminating bacteria and by promoting cellular outgrowth.

Tongue posture improvement and pharyngeal airway enlargement as secondary effects of rapid maxillary expansion: a cone-beam computed tomography study

INTRODUCTION

Rapid maxillary expansion (RME) is known to improve nasal airway ventilation. Recent evidence suggests that RME is an effective treatment for obstructive sleep apnea in children with maxillary constriction. However, the effect of RME on tongue posture and pharyngeal airway volume in children with nasal airway obstruction is not clear. In this study, we evaluated these effects using cone-beam computed tomography.

METHODS

Twenty-eight treatment subjects (mean age 9.96 ± 1.21 years) who required RME treatment had cone-beam computed tomography images taken before and after RME. Twenty control subjects (mean age 9.68 ± 1.02 years) received regular orthodontic treatment. Nasal airway ventilation was analyzed by using computational fluid dynamics, and intraoral airway (the low tongue space between tongue and palate) and pharyngeal airway volumes were measured.

RESULTS

Intraoral airway volume decreased significantly in the RME group from 1212.9 ± 1370.9 mm(3) before RME to 279.7 ± 472.0 mm(3) after RME. Nasal airway ventilation was significantly correlated with intraoral airway volume. The increase of pharyngeal airway volume in the control group (1226.3 ± 1782.5 mm(3)) was only 41% that of the RME group (3015.4 ± 1297.6 mm(3)).

CONCLUSIONS

In children with nasal obstruction, RME not only reduces nasal obstruction but also raises tongue posture and enlarges the pharyngeal airway.

Improvement of nasal airway ventilation after rapid maxillary expansion evaluated with computational fluid dynamics

INTRODUCTION

Rapid maxillary expansion is known to improve nasal airway ventilation. However, it is difficult to precisely evaluate this improvement with conventional methods. The purpose of this longitudinal study was to use computational fluid dynamics to estimate the effect of rapid maxillary expansion.

METHODS

Twenty-three subjects (9 boys, 14 girls; mean ages, 9.74 ± 1.29 years before rapid maxillary expansion and 10.87 ± 1.18 years after rapid maxillary expansion) who required rapid maxillary expansion as part of their orthodontic treatment had cone-beam computed tomography images taken before and after rapid maxillary expansion. The computed tomography data were used to reconstruct the 3-dimensional shape of the nasal cavity. Two measures of nasal airflow function (pressure and velocity) were simulated by using computational fluid dynamics.

RESULTS

The pressure after rapid maxillary expansion (80.55 Pa) was significantly lower than before rapid maxillary expansion (147.70 Pa), and the velocity after rapid maxillary expansion (9.63 m/sec) was slower than before rapid maxillary expansion (13.46 m/sec).

CONCLUSIONS

Improvement of nasal airway ventilation by rapid maxillary expansion was detected by computational fluid dynamics.

Do occlusal contact areas of maximum closing position during gum chewing and intercuspal position coincide?

OBJECTIVE

Occlusal contact area (OCA) is most important during the occlusal phase when food particles are being pulverized. OCA is most easily measured statically at the maximum intercuspal position (ICP). However, the assumption of coincidence between dynamic maximum closing position (MCP) and statically determined ICP has not been previously tested. The purpose of this study is to introduce a method of quantifying OCA of all teeth during dynamic mastication to determine whether the OCA at the dynamic MCP during chewing is similar to the statically determined maximum possible OCA.

DESIGN

Thirteen healthy females participated in this study. Morphologic tooth shape data were measured from dental models using an automatic 3D digitizer. Mandibular movement during gum chewing was recorded using an optoelectronic analysis system with 6 degrees of freedom, and ten cycles were selected for analysis. The dynamic OCA was estimated with a measurement system combining 3D tracking of mandibular movements with 3D digitization of tooth shape.

RESULTS

The estimated mean 3D difference between the incisor position at ICP and MCP was 0.129 mm. At the dynamic MCP, the maximum OCA was 98.5% (68.42 mm(2)) of the maximum possible contact area in the static ICP (69.46 mm(2)). Both between-subject and within-subject variation were least at the dynamic MCP.

CONCLUSION

The maximum OCA during chewing is nearly identical to statically determined maximum possible OCA.

Evaluation of upper airway obstruction in Class II children with fluid-mechanical simulation

INTRODUCTION

The purpose of this study was to test the null hypothesis that dolichofacial and brachyfacial children with Class II malocclusion do not differ in upper airway obstruction. Furthermore, the ability of fluid-mechanical simulation to detect airway obstruction within the limitations of simulation was examined.

METHODS

Forty subjects from 7 to 11 years of age with Class II malocclusion participated and were divided into 2 groups, dolichofacial and brachyfacial, based on their Frankfort mandibular plane angles. Cone-beam computed tomography images supplied the shape of the entire airway. Two measures of respiratory function, air velocity and pressure, were simulated by using 3-dimensional images of the airway. The images and simulations were compared between the 2 facial types.

RESULTS

The size of the upper airway did not differ statistically between facial types; however, the simulated maximal pressure and velocity of the dolichofacial type were significantly higher than those of the brachyfacial type.

CONCLUSIONS

Airway obstruction differs with the Frankfort mandibular plane angle, even though the depth and cross-sectional area of the airway do not. The fluid-mechanical simulation system developed in this study detected differences in airway obstruction that were not apparent from morphologic studies.

Mandibular open-close motion in children with anterior crossbite occlusion

Anterior crossbite (ACB) malocclusions are frequent; however, its characteristic functional features have not been fully described. The purpose of this study was to determine the characteristics of habitual mandibular open-close motion in children with ACB of their primary dentition. Two groups of children were selected for study; 17 with ACB (eight boys and nine girls; four years one month to seven years one month) and 19 with normal occlusion (eight boys and 11 girls; four years six months to six years seven months). The motion was recorded using an optoelectronic analysis system with six degrees-of-freedom. Mandibular incisor and condylar motion were analyzed by measuring their three-dimensional ranges and trajectories. Also estimated incisor and condylar pathways of the two groups were compared. Patients with ACB opened wider with more anterior-posterior condylar translation and more mandibular rotation. Although between-subject (inter-individual) variance of all variables in children with ACB was larger, they had less within-subject variance at the condyles. These results indicate that open-close mandibular motion in children with ACB is completely different from that of children with normal occlusion. The different motions might be related to morphological differences between the two groups.

Jaw motion during gum-chewing in children with primary dentition

This study was undertaken to characterize jaw motion during mastication in children with primary dentition and to compare jaw motion with that in adults. The means and the variances of the traditional parameters for the chewing cycle, i.e., duration, excursive ranges and 3-D distances of travel at the lower incisor, molars and condyles were analyzed and compared in 23 children and 25 female adults. The duration of opening in children was significantly shorter than that of adults. Significant differences between children and adults were observed in lateral and vertical excursion of the incisor, lateral excursion at the molars, and vertical excursion at the condyles. Many of these measurements had larger between-subject and between-cycle variances in children than adults, suggesting that chewing motion in children has not yet matured. The results of this study indicate that chewing motion in children is different from that of adults.

Oropharyngeal airway in children with Class III malocclusion evaluated by cone-beam computed tomography

INTRODUCTION

Upper airway size is increasingly recognized as an important factor in malocclusion. However, children with Class III malocclusion are somewhat neglected compared with those with a Class II skeletal pattern. Therefore, the purpose of this study was to establish the characteristic shape of the oropharyngeal airway (OA) in children with Class III malocclusion.

METHODS

The sample comprised 45 children (average age, 8.6 +/- 1.0 years) divided into 2 groups: 25 with Class I and 20 with Class III malocclusions. OA size of each group was evaluated by cone-beam computed tomography. Cluster analysis, based on OA shape, redivided the subjects into wide, square, and long types. The distributions of Class I and Class III subjects were compared among the types.

RESULTS

The Class III group showed statistically larger OA area and width compared with the Class I group. Area was positively correlated with Class III severity. The square type included 84% of the Class I malocclusions but only 30% of the Class III malocclusions, indicating that the OA in Class III malocclusion tends to be flat.

CONCLUSIONS

The Class III malocclusion is associated with a large and flat OA compared with the Class I malocclusion.

Relationship of nasal and skeletal landmarks in lateral cephalograms of preschool children

The purpose of this study was to investigate the relationship between cephalometric nasal and skeletal landmarks in preschool children. Lateral cephalograms of 80 Japanese preschool children (40 boys, mean age 5.4+/-0.3 years; 40 girls, mean age 5.2+/-0.1 years; total mean age 5.3+/-0.3 years) were traced, and 22 skeletal and 3 soft-tissue nasal points were digitized. The coordinates from each subject were transformed to a standardized plane using a custom-made program written in Microsoft Visual C++. In this standard plane, sella was the origin, Frankfort Horizontal (FH) plane was parallel to the X-axis, and all 25 points were rotated to match this reference plane. The three nasal landmarks used in this investigation were: (1) rhi', the intersection point of a line parallel to the FH plane at rhinion and the facial line; (2) pronasale (Prn), the most anterior point on the nose; and (3) subnasale (Sn), the most posterior-superior point where the columella met the upper lip. An independent-groups t-test was used to test for sex differences of coordinates of the nasal landmarks and their related skeletal landmarks. Significance was set at p<0.05. A stepwise regression analysis determined how combinations of skeletal landmarks explained the location of the nasal landmarks. Only one skeletal coordinate (N(X)) and no nasal coordinates showed a significant difference between boys and girls. The coordinates of rhi contributed significantly to the location of rhi' and Prn (except for the Y-coordinate of girls). Moreover A-point and ANS contributed to the location of Prn and Sn. For Sn, the X- and Y-coordinates of girls and the Y-coordinate of boys were related to lower incisor or dentoalveolar structure of the mandible. It appears that the nasal landmarks in preschool children can be predicted from selected skeletal landmarks, and there are no sex differences for the nasal landmarks in children.

Dentigerous cyst in primary dentition: case report of a 4-year-old girl

The purpose of this case report is to describe the treatment outcome of a 4-year-old girl with a dentigerous cyst on the primary mandibular right second premolar of her caries-free mouth. Her primary predecessor was extracted and the lesion decompressed by using a removable appliance with a resin projection. The succeeding premolar had not developed further 8 months later, however, and had to be extracted. Crown formation of the succeeding premolar might have been interrupted by the presence of the cyst. To our knowledge, this is the earliest reported asymptomatic dentigerous cyst in the mandibular premolar region with a vital primary second molar.

The P561T polymorphism of the growth hormone receptor gene has an inhibitory effect on mandibular growth in young children

P561T heterozygous missense mutation in the growth hormone receptor (GHR) is a candidate genetic polymorphism (single-nucleotide polymorphism) for human mandibular growth. The purpose of this study was to assess whether this mutation affects mandibular growth during early childhood. The difference in mandibular growth between P561T heterozygous and wild-type individuals was analysed by cephalometric measurements during childhood. The subjects included 33 children with mandibular protrusion (aged 3-12 years, 16 males and 17 females) and 27 normal children (aged 3-13 years, 14 males and 13 females). Genomic DNA extracted from buccal epithelial cells was genotyped for the P561T heterozygous mutation with a molecular analysis (polymerase chain reaction--restriction fragment length polymorphism method). Two of the patients with normal occlusion and five with mandibular protrusion were heterozygous for the mutation. Chi-square analysis showed that the frequency of this mutation did not differ statistically between the normal and mandibular protrusion subjects. Multilevel model analysis of the 101 cephalograms showed that the mutation reduced the linear measurements of the mandible. These findings suggest that P561T heterozygous mutation affects mandibular growth during early childhood, and this mutation in the GHR gene is hypothesized to function as an inhibitory factor in the process of mandibular growth.

Cross-sectional growth changes in skeletal and soft tissue cephalometric landmarks of children

In order to provide standard values for craniofacial growth of normal children, we evaluated the growth changes of skeletal and soft tissue cephalometric landmarks from lateral cephalograms of 180 Japanese children. They were divided into three groups: primary dentition, mixed dentition, and permanent dentition. Specific skeletal angles and distances showed significant gender differences with increasing age. The only significant soft tissue gender difference was nose height in the oldest group. Upper pharynx dimension and nose height differed significantly among the groups in both genders. Positions of both the upper and lower lip changed significantly between the intermediate and oldest groups of both genders. Nasolabial angle did not change significantly with growth. The results of this study should be useful for predicting craniofacial growth and development or determining the effect of orthodontic treatment.

Correlations between incisor and condyle motion during protrusion in children with primary dentition

The purpose of this study was to investigate the relationship between incisor and condyle movement during protrusion in children with primary dentition. Subjects were categorized into two age groups. A primary dentition group consisted of 20 children, and a permanent dentition group consisted of 25 women. The occlusion and TMJ in both groups were normal, with no history of orthodontic treatment. Three orthogonal excursive ranges, linear distance and curvilinear distance of the incisal and condylar points; sagittal angle of condylar rotation; and correlations between incisor and condyle distances during protrusion were estimated by using multilevel statistical models. Protrusion in children with primary dentition was characterized by: 1. significantly smaller superior-inferior ranges for incisal and condylar points in children than in adults; 2. strong positive correlations between incisor and condylar anterior-posterior ranges and linear distances, a pattern similar to that in adults.

A local GABAergic system within rat trigeminal ganglion cells

We investigated the GABAergic system within the Sprague-Dawley rat (2-3-weeks old) trigeminal ganglion (TG). Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed expression of glutamate decarboxylase (GAD) 65 and GAD67 mRNAs and mRNAs encoding GABA(A) receptor subunits alpha1-6, beta1-3, gamma1-3, and delta. In situ hybridization revealed that GAD65 and GAD67 mRNAs were expressed in neuronal cell bodies but not satellite cells. Immunohistochemical analysis showed that only GAD65 was expressed in all neuronal cell bodies, and approximately 70% of all neurons exhibited GABA immunoreactivity. Satellite cells were strongly immunopositive for GABA. GABA(A) receptor alpha1, alpha5, beta2/3 and gamma1/2/3 subunit immunoreactivities were observed in the majority of neurons, but no immunoreactivity for alpha2 was observed. Two types of cells were identified in TG based on cell size and morphology, type A and B. The percentage of cells expressing alpha3, alpha4, alpha6, and delta subunits appeared to be dependent on cell size, as delta and alpha6 expression were only observed in small (B-type) neurons. In whole-cell patch clamp experiments, GABA application induced inward Cl- currents in all neurons examined. The EC50 for GABA varied from 5.3 to 240 microm, and the Hill Coefficient (nH) varied between 0.98 and 2.6 at -60 mV. We found that GABA was released from TG cells by increasing extracellular K+ concentration to 100 mm. We speculate that GABA acts as a nonsynaptically released diffusible neurotransmitter, which may modulate somatic inhibition of neurons within the TG.

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.

Incisal paths during habitual mouth opening and closing movements of children with anterior reverse bite in the early mixed dentition

The purpose of this study was to investigate whether the pathways of habitual mouth opening and closing in children with anterior reverse bite in the early mixed dentition differed from those of children with normal occlusion. The two subject groups for this study were composed of ten children with anterior reverse bite (reverse bite group) and twelve children with normal occlusion (normal occlusion group), respectively. These movements were measured by an optoelectronic analyzing system with six degrees of freedom. Movements of the incisal point were projected on the sagittal plane to characterize the paths, and sagittal angles between the incisal path and the horizontal plane were calculated and compared. Opening and closing sagittal angles in the reverse bite group were almost equal over the entire pathway, indicating that the pathways of habitual mouth opening and closing were similar. In contrast, all opening and closing sagittal angles in the normal occlusion group were different, especially close to maximum intercuspation, indicating that their pathway of habitual mouth opening differed from their mouth closing pathway. In conclusion, children with anterior reverse bite in the early mixed dentition have different patterns of habitual mouth opening and closing movements than children with normal occlusion.

Characteristics of the gum chewing occlusal phase in children with primary dentition

Understanding of the growth and development of mandibular function is indispensable to the diagnosis of functional disturbances during childhood. The purpose of this study was to clarify the characteristics of the occlusal phase during gum chewing in children with primary dentition. Chewing motion at the working molar of 14 children with primary dentition and 28 female adults was recorded optoelectrically, and the frontal and sagittal angles of their closing and following opening strokes were measured and compared. In children the closing strokes were entered more vertically and anteriorly than in adults, and the opening strokes shifted to the non-working side in adults but moved to the working side in children. The degree of variance also differed between the two groups; the variance of the frontal angle was larger than that of sagittal angle in adults, but the opposite was true in children. These results suggested that the chewing pattern in children during the occlusal phase is distinctly different from adults and the chewing movement in children is not always less stable than in adults.

Masticatory motion after surgical or nonsurgical treatment for unilateral fractures of the mandibular condylar process

PURPOSE

We sought to compare mandibular motion during mastication in patients treated in either an open or a closed fashion for unilateral fractures of the mandibular condylar process.

PATIENTS AND METHODS

Eighty-one male patients with unilateral condylar process fractures were treated either with (n = 37) or without (n = 44) surgical reduction and rigid fixation of their condylar process fractures. At 6 weeks, 6 months, 1 year, and 2 years after treatment, the subjects' chewing cycles were recorded using a magnetic sensor array (Sirognathograph; Siemens Corp, Bensheim, Germany) while chewing Gummi-Bears (HARIBO, Bonn, Germany) unilaterally on the same side as the fracture and on the opposite side. The chewing cycles were analyzed using a custom computer program, and the duration, excursive ranges, and 3-dimensional cycle shape were compared between the 2 treatment groups at each time interval using multilevel linear modeling statistics.

RESULTS

The 2 treatment groups did not differ significantly for any measure of cycle duration or any excursive range (except lateral excursions at 1 year post-treatment) at any of the time intervals. However, the 3-dimensional cycle shapes of the 2 groups did differ significantly at all time intervals.

CONCLUSION

Surgical correction of unilateral condylar process fractures has relatively little effect on the more standard measures (duration and excursive ranges) of masticatory function. However, surgical correction better normalizes opening incisor pathways during mastication on the side opposite the fracture.

Occlusal contact area of mandibular teeth during lateral excursion

PURPOSE

This study observed occlusal contacts and determined their areas on the mandibular teeth, especially the molars, during voluntary lateral excursions.

MATERIALS AND METHODS

Occlusal contact areas were estimated with a measurement system combining 3-D tracking of mandibular movements with 3-D digitization of tooth shape. Sixteen women with sound permanent dentitions participated.

RESULTS

At the intercuspal position, estimated occlusal contact areas of the first and second mandibular molars were on average 12.6 mm2 and 9.0 mm2, respectively. However, after 3.0 mm of lateral excursion, their areas were sharply reduced to 2.2 mm2 and 1.5 mm2 on the working side, and 0.4 mm2 and 1.1 mm2 on the nonworking side, respectively.

CONCLUSION

These results suggest that the occlusal contact areas on working- and nonworking-side molars differ from each other as lateral excursion proceeds.

Jaw kinematics during mastication after unilateral fractures of the mandibular condylar process

This study compared the mandibular kinematics during mastication of patients treated for unilateral fractures of the mandibular condylar process with those of control subjects. We used a Sirognathograph (Siemens, Bensheim, Germany) to record the chewing cycles of 81 male patients with unilateral condylar process fractures while they chewed a constant bolus unilaterally on the same side as the fracture and on the opposite side. Recordings were made at 6 weeks, 6 months, 1 year, and 2 years after treatment. Similar chewing cycles were recorded for 15 male controls (Class I dental and Class I skeletal occlusion) without fractures of the condylar process. The chewing cycles of both groups were analyzed with a custom computer program, and the duration, excursive ranges, and 3-dimensional cycle shape were compared at each time interval with multilevel linear modeling statistics. Fracture patients had significantly slower chewing cycles, with significantly less maximum excursion toward the working side during the closing phase and significantly greater excursion toward the balancing side during the opening phase than the controls. The opening pathway of the incisors showed greater differences between patients and controls than the closing pathways. Differences in chewing cycle shape persisted for up to 2 years, especially when chewing was on the side opposite the fracture. Unilateral condylar process fractures produce long-lasting changes in chewing cycle duration and chewing cycle shape of adults.

Longitudinal observation of basic mandibular movements: report of a case

Sound development of mandibular function during childhood is indispensable to establishing healthy function in adults. To examine this developmental process, longitudinal recordings of basic mandibular movements were done using an optoelectronic analysis. Mandibular movements were recorded on five separate occasions in one boy, from an age of six years and five months to 14 years and five months. The incisor pathways during protrusion and lateral excursion were initially shallow, with more anterior than inferior movement, but as he grew the amount of inferior movement and the amount of rotation both increased. Similarly, at his first recording there was very little hinge-like rotation during mouth closing, but rotation increased markedly after eruption of his permanent second molars. These findings suggest that mandibular movements change from being relatively simple with more translation in younger children to more complex movements with more rotation once the permanent dentition is established.

Length of the occlusal glide during chewing in children with primary dentition

Chewing is one of the most important functions of the mandible, but, to date, there are very few studies of this function in children. The purpose of this study was to quantify the length of the occlusal glide at the lower incisal point during gum chewing in children with primary dentition. Eleven girls with primary dentition were selected for this study. Mandibular excursions with occlusal contacts and gum chewing movement were measured using an optoelectronic system that can measure mandibular movement with six degrees-of-freedom at a sampling frequency of 100 Hz. A curved mesh diagram of incisor coordinates during mandibular excursions was established to calculate the length of the occlusal glide for each subject. The occlusal glide lengths of children were compared with previously reported results for adults. The estimated length of the occlusal glide during closing was significantly shorter in children than in adults, contrary to that during opening. This result suggests that children have a characteristic chewing pattern that differs from adults.