Ability to control directional lip-closing force in skeletal class III patients.

BACKGROUND: The relationship between the maximum lip-closing force (LCF) and malocclusion has long been studied. Recently, a method to measure the ability to control directional LCF from eight directions (upper, lower, right, left and the four directions in between) during lip pursing was established. OBJECTIVE: It is considered important to evaluate the ability to control directional LCF. The aim of this study was to investigate the ability of skeletal class III patients to control directional LCF. METHODS: Fifteen skeletal class III patients (mandibular prognathism group) and 15 people with normal occlusion (normal occlusion group) were recruited. The maximum LCF and the accuracy rate (the ratio of the matched time in which the participant was able to keep the LCF in the target range over a total time of 6 s) were measured. RESULTS: The maximum LCF was not significantly different between the mandibular prognathism group and the normal occlusion group. The accuracy rate in the mandibular prognathism group was significantly lower in all six directions than that in the individual normal occlusion group. CONCLUSION: As the accuracy rate in all six directions was significantly lower in the mandibular prognathism group than that in the normal occlusion group, occlusion and craniofacial morphology might influence lip function.

Age-related differences in maximum voluntary lip-closing force and ability to control lip-closing force.

OBJECTIVES: Deterioration of lip function in the elderly is a form of oral hypofunction. It is important to understand age-related changes in lip function to improve oral health. This study aimed to quantitatively compare the maximum lip-closing force (LCF) and the ability to control LCF during voluntary lip-pursing movements between elderly and young adults and clarify the influence of aging on both measurements. METHODS: Using a multidirectional LCF measurement system, we measured six-directional maximum LCFs (upper, upper right, lower right, lower, lower left, upper right) of 20 healthy elderly men (69.6 ± 4.2 years) and 20 healthy young men (25.1 ± 3.8 years). The ability to control the LCF in each direction was assessed based on the accuracy rate. The directional LCF and the ability to control LCF were compared between the elderly and young adults. RESULTS: The maximum directional LCF in the elderly adults was significantly smaller than that in the young adults in three directions from the lower lip; moreover, the accuracy rate of the elderly adults was significantly lower than that of young adults in five of the six directions. CONCLUSIONS: Our findings suggest that the influence of aging on the accuracy of LCF may be different from that on muscle strength. Hypofunction of the lips due to aging may result not only from decreased muscle strength but also from reduced LCF accuracy.

Ability to control directional lip-closing force during voluntary lip pursing in healthy young adults.

BACKGROUND: It is considered important to evaluate the ability to control lip-closing force (LCF). OBJECTIVE: This study aimed to investigate the ability to control directional LCF. METHODS: The experimental system included an apparatus developed to measure LCF during lip pursing in eight directions (upper, lower, right, left and the four directions in between) and a display showing the exerted LCF and a target value in each direction in real time. Twenty subjects (10 men and 10 women) were instructed to maintain the LCF at a specific target value using visual feedback. Based on our preliminary experiments, the target value was set as 50% of the maximum LCF, and the range was set at the target value ±8%. The accuracy rate was defined as the ratio of the matched time, in which the subject was able to keep the LCF in the target range, to the total 3 seconds. RESULTS: The accuracy rate of men was higher than in women in the lower, lower left and lower right directions. The accuracy rate of the directional LCF differed significantly depending on the direction. In assessing the accuracy rate for each directional LCF, the rates of upper and lower directional LCF were significantly higher than those of oblique directional LCF. No significant relationship was observed between the accuracy rate and the maximum LCF except for one direction in men subjects. CONCLUSIONS: Our findings suggest that the ability to control directional LCF is affected by sex and the force direction.

Establishment of a prediction method for the mid-facial region of unknown human Mongoloid skeletal remains.

Forensic facial approximation is a technique used to estimate the antemortem facial features of unknown skeletal remains. In recent years, many researchers have reported nasal tip predictions with positive results. However, the morphological nasal features of the skull can vary widely, and it is hard to obtain accurate values using facial approximation techniques. We assumed that these variations are due to an over-dependence on the values obtained from a single distance metric factor in an anatomical area. Measurements were acquired using cephalometric radiographic images obtained from 190 Japanese individuals (90 men, aged 18-36 years and 100 women, aged 18-46 years). Soft tissue and skeletal features were traced onto acetate sheets. The orbitale (Or), porion (Po), and the Frankfurt Horizontal Plane (FHP) were plotted in addition to the rhinion (Rhi), anterior nasal spine (ANS), subnasale (Sn), prosthion, and point-A (A). From these, the following were measured: a length from rhinion to prosthion; b length from rhinion to the intersection of a line perpendicular to the anterior nasal spine; c length from the prosthion to the intersection of a line perpendicular to the anterior nasal spine; g the proportion of d/b; and f the proportion of c/b. A calculation was generated from these measurements and from proportions of a-h, and applied to the samples. An R-squared (RSQ) test and standard error (SE) were used to compare the actual and predicted values. The errors observed between the predicted and actual values were not greater than 5mm in any of the samples; 91.3% and 71.2% of predicted Sn had an error lower than 2.5 and 1.5mm respectively, from the actual. Reliable results were obtained using the method in the present study. In addition, in the process of obtaining the measurements, we found reliable proportional differences between the sexes in the piriform and axillary alveolar regions.

Morphological changes in the temporomandibular joint after orthodontic treatment for Angle Class II malocclusion.

OBJECTIVE: The aim of this study was to examine the morphological temporomandibular joint (TMJ) changes that occur after orthodontic treatment in patients with Angle Class II malocclusion. METHODS: The post-treatment changes in TMJ morphology were analyzed, based on TMJ cephalometric laminographs in 19 patients with Angle Class II malocclusion and labial inclination of the upper incisors after premolar extraction. RESULTS: The condylar pass angle, articular eminence to the Frankfort horizontal plane angle, and total, upper, and lower heights of the articular fossa increased significantly on both sides after treatment and retention. The anteroposterior width of the articular fossa decreased significantly on both sides after treatment and retention. DISCUSSION: These results suggest that adaptive bone remodeling of the TMJ occurs during the correction of occlusion with labial inclination of the upper incisors by orthodontic treatment after premolar extraction in patients with Angle Class II malocclusion.

Pilot study to establish a nasal tip prediction method from unknown human skeletal remains for facial reconstruction and skull photo superimposition as applied to a Japanese male populations.

Skull-photo superimposition is a technique used to identify the relationship between the skull and a photograph of a target person: and facial reconstruction reproduces antemortem facial features from an unknown human skull, or identifies the facial features of unknown human skeletal remains. These techniques are based on soft tissue thickness and the relationships between soft tissue and the skull, i.e., the position of the ear and external acoustic meatus, pupil and orbit, nose and nasal aperture, and lips and teeth. However, the ear and nose region are relatively difficult to identify because of their structure, as the soft tissues of these regions are lined with cartilage. We attempted to establish a more accurate method to determine the position of the nasal tip from the skull. We measured the height of the maxilla and mid-lower facial region in 55 Japanese men and generated a regression equation from the collected data. We obtained a result that was 2.0±0.99mm (mean±SD) distant from the true nasal tip, when applied to a validation set consisting of another 12 Japanese men.

Facial soft tissue thickness differences among three skeletal classes in Japanese population.

Facial reconstruction is used in forensic anthropology to recreate the face from unknown human skeletal remains, and to elucidate the antemortem facial appearance. This requires accurate assessment of the skull (age, sex, ancestry, etc.) and thickness data. However, additional information is required to reconstruct the face as the information obtained from the skull is limited. Here, we aimed to examine the information from the skull that is required for accurate facial reconstruction. The human facial profile is classified into 3 shapes: straight, convex, and concave. These facial profiles facilitate recognition of individuals. The skeletal classes used in orthodontics are classified according to these 3 facial types. We have previously reported the differences between Japanese females. In the present study, we applied this classification for facial tissue measurement, compared the differences in tissue depth of each skeletal class for both sexes in the Japanese population, and elucidated the differences between the skeletal classes.

Morphological changes in the temporomandibular joint before and after sagittal splitting ramus osteotomy of the mandible for skeletal mandibular protrusion.

Changes of temporomandibular joint (TMJ) morphology were analyzed in 21 patients with mandibular protrusion corrected using bilateral sagittal split ramus osteotomy (SSRO) and mini-plate fixation with TMJ cephalometric laminographs. The condylar pass angle, eminence to the FH plane angle, and total height of fossa and lower height of fossa in both left and right sides, significantly decreased after surgery. The width of the condyle, in both left and right sides, significantly increased after treatment. However, in the joint spaces, there were no significant differences before and after treatment. The amount of change in the eminence to the FH plane angle, total height of fossa and lower height of fossa, before and after surgery, showed significant positive correlations with that of SNB, before and after surgery. These results suggest that adaptive bone remodeling of the TMJ might occur due to the correction of occlusion and craniofacial morphology by SSRO in patients with mandibular protrusion.

Facial soft tissue thickness in Japanese children.

Facial reconstruction techniques used in forensic anthropology are based on mean soft tissue thickness measurements. Numerous studies of facial tissue thickness in adults have been published on a range of subjects from different ancestral backgrounds. Data on facial thickness in children derive primarily from Caucasoid, African-American, and Hispanic subjects. There are limited data from the few studies of Japanese children (male: skeletal class I only; female: all skeletal classes). The author has previously reported facial tissue thickness data for Japanese girls and boys with skeletal class I and for all three skeletal classes in Japanese girls. The present study reports facial soft tissue thickness data in Japanese children of all skeletal classes, within age subsets. With parental informed consent, diagnostic lateral cephalometric X-ray images were obtained from 339 Japanese children aged 7-18 years (male: 162; female: 177) who attended the Matsumoto Dental University Department of Orthodontics to undergo orthodontic treatment. Soft tissue and skeletal features were traced onto acetate sheets from the X-ray images, and 10 anthropological landmarks on the midsagittal line were measured. Means, SDs, and ranges were then calculated. Differences between male and female measurements in six age groups were compared using t-tests. Significant differences were observed at some landmarks in each age group. The findings were compared with data from other juvenile populations.

Pilot study of facial soft tissue thickness differences among three skeletal classes in Japanese females.

Facial reconstruction is a technique used in forensic anthropology to estimate the appearance of the antemortem face from unknown human skeletal remains. This requires accurate skull assessment (for variables such as age, sex, and race) and soft tissue thickness data. However, the skull can provide only limited information, and further data are needed to reconstruct the face. The authors herein obtained further information from the skull in order to reconstruct the face more accurately. Skulls can be classified into three facial types on the basis of orthodontic skeletal classes (namely, straight facial profile, type I, convex facial profile, type II, and concave facial profile, type III). This concept was applied to facial tissue measurement and soft tissue depth was compared in each skeletal class in a Japanese female population. Differences of soft tissue depth between skeletal classes were observed, and this information may enable more accurate reconstruction than sex-specific depth alone.

Autotransplantation of 28 premolar donor teeth in 24 orthodontic patients.

OBJECTIVE: To test the null hypothesis that premolar autotransplantation is not successful for orthodontic patients. MATERIALS AND METHODS: In the present study, 28 premolar transplants from 24 orthodontic patients were associated with orthodontic treatment. At a routine 3-month appointment, patients underwent a dental radiograph and a chair-side observation for periodontal problems. Three sets of dental radiographs were taken by one dental assistant using a custom holder at: preoperation (T0), 2 year postoperation (T1), and retention (T2) (4- to 14-year follow-up observation) stages. All transplants were conducted in a one-phase operation by one operator (Dr Inoue). Recipient sites were: ten for missing maxillary canines, nine for maxillary centrals and laterals, eight for lower second premolar, and five for other missing premolar sites. All recipients maintained the retained primary tooth with a socket. RESULTS: The success ratio of all 28 transplants was 100%, although four transplants shorter than a 4-year period of observation were omitted. Two transplant patients, one with a medical history of histiocytosis and the other with a history of osteomyelitis of the maxilla without a recipient socket, were also excluded from this study. Eleven of 22 premolar transplants had a root canal treatment (RCT), four of which had RCT within 2 years after the operation. CONCLUSIONS: The null hypothesis was rejected. The success ratio of premolar transplants was 100%.

Histomorphometric study on the effects of age on orthodontic tooth movement and alveolar bone turnover in rats.

The aim of this study was to investigate, in a rat model, the effects of age on the amount of tooth movement and concomitant changes in alveolar bone turnover activity adjacent to orthodontically treated tooth roots. Rats (n = 48) of four different age groups (10, 30, 50, and 80 wk of age) were used in the experiment. Maxillary first molars were tipped mesially with a nickel titanium alloy coil-spring for 2 wk by a continuous force of 10 cN. Forty-eight age-matched untreated rats were used as controls. The changes in alveolar bone turnover were assessed histomorphometrically. Two weeks after the start of tooth movement, the amount of tooth movement was found to decrease with age and was significantly different among the four age groups. The histomorphometric study demonstrated that, in all experimental groups, turnover of alveolar bone increased significantly compared with that of each age-matched untreated group. However, the rate of increase decreased in an age-related manner. These results suggest that the age-dependent decrease in alveolar bone turnover activity, in response to mechanical forces, may negatively affect the amount of tooth movement.

Facial soft tissue thickness in skeletal type I Japanese children.

Facial reconstruction techniques used in forensic anthropology require knowledge of the facial soft tissue thickness of each race if facial features are to be reconstructed correctly. If this is inaccurate, so also will be the reconstructed face. Knowledge of differences by age and sex are also required. Therefore, when unknown human skeletal remains are found, the forensic anthropologist investigates for race, sex, and age, and for other variables of relevance. Cephalometric X-ray images of living persons can help to provide this information. They give an approximately 10% enlargement from true size and can demonstrate the relationship between soft and hard tissue. In the present study, facial soft tissue thickness in Japanese children was measured at 12 anthropological points using X-ray cephalometry in order to establish a database for facial soft tissue thickness. This study of both boys and girls, aged from 6 to 18 years, follows a previous study of Japanese female children only, and focuses on facial soft tissue thickness in only one skeletal type. Sex differences in thickness of tissue were found from 12 years of age upwards. The study provides more detailed and accurate measurements than past reports of facial soft tissue thickness, and reveals the uniqueness of the Japanese child's facial profile.

Effect of age on alveolar bone turnover adjacent to maxillary molar roots in male rats: A histomorphometric study.

OBJECTIVE: The effect of age on alveolar bone turnover adjacent to maxillary molar roots of male rats was assessed histomorphometrically with special focus on bone formation and resorption. DESIGN: A total of 110 male Wistar rats ranging in age from 6 to 100 weeks were used for this study. Histomorphometric parameters were measured in fluorescence-labeled undecalcified ground and paraffin-embedded decalcified sections of the alveolar wall around the disto-lingual roots of the maxillary first molars. Bone formation was measured statically by determining the percentage of the bone surface that was double-labeled surface (dLS/BS), bone formation rate (BFR/BS), and mineral apposition rate (MAR). Bone resorption was quantified statically in terms of the number of osteoclasts (N.Oc/BS) and the percentage of the bone surface covered with osteoclasts (Oc.S/BS). RESULTS: For the total surface of the alveolar wall, the values obtained for all parameters of both bone formation and resorption decreased with advancing age. All these values rapidly decreased during the early part of the life span, from 6 to 30-40 weeks of age, of the rats. A site-specific difference between the distal and mesial sides of the alveolar wall was found for each age group. dLS/BS and BFR/BS were significantly greater (p < 0.0001) on the mesial side than on the distal one. On the other hand, the distal side showed significantly greater (p < 0.0001) value for N.Oc/BS and Oc.S/BS did the mesial one. However, there were no significant age-related changes in dLS/BS and BFR/BS on the distal side or in N.Oc/BS and Oc.S/BS on the mesial side throughout observation period. CONCLUSION: The results of the present study demonstrate that alveolar bone turnover of male rats decreased rapidly with advancing age but that in order to maintain the integrity of the tooth function mechanical stress may still have participated in bone formation and resorption of the alveolar wall even in rats 100-week old.

Chincup therapy for a young woman with anterior displacement and obtuse angle of the mandible in Class I malocclusion.

INTRODUCTION: Dolichofacial skeletal patterns are a challenge for the orthodontist. Even when treatment for a long-face patient begins before the adolescent growth spurt, excellent compliance is generally needed. The patient whose care is presented here started treatment at age 14. RESULTS: The extraction of 4 premolars, rapid palatal expansion, and excellent compliance wearing a combination occipital and vertical-pull chincup over a 2-year period led to good results at age 16, with minimal dental or skeletal relapse at age 18 years 5 months.

Scanning electron microscopy of the three different types of cementum in the molar teeth of the guinea pig.

The aim of this study was to observe the three-dimensional distribution and structural characteristics of the three different types of cementum in the molar teeth of guinea pig by means of scanning electron microscopy. Twenty-five 4-week-old male guinea pigs were used in this study. Using decalcified and undecalcified specimens with or without NaOH maceration, we examined the mandibles, maxillae and extracted molars by scanning electron microscopy. Guinea pig molars consist of two longitudinal, deeply folded lamina cores covered by enamel on all surfaces, except the buccal surface of the upper molars and the lingual surface of the lower molars. In the regions without enamel, we observed continuous thin belt-like layers of conventional acellular cementum on the dentin surface. On the enamel-covered surfaces, two different types of coronal cementum were found: small circular islands of coronal cementum called cementum pearls, which were distributed widely at almost regular intervals on the peripheral enamel surface from the apical fifth to the occlusal surface; and cartilage-like cementum, which occupied almost all of the occlusal half of the two longitudinally folded grooves. The present study demonstrated the unique distribution pattern of the three different types of cementum in guinea pig molars. These cementum types may contribute to the requirements for many different functions such as mastication, anchorage and continuous tooth eruption.

A morphological study of the relationship between arch dimensions and craniofacial structures in adolescents with Class II Division 1 malocclusions and various facial types.

INTRODUCTION: The objective of this study was to evaluate dental arch forms associated with various facial types in adolescents with Class II Division 1 malocclusions by using mathematical functions to describe the arch form at clinical bracket points. METHODS: Pretreatment lateral cephalograms and dental study casts of 73 white Brazilians were divided into 3 groups according to facial type: 17 brachyfacial, 24 mesofacial, and 32 dolichofacial. Fifteen landmarks on each dental cast were digitized. Computer-generated mathematical arch forms (fourth-degree polynomial equation and beta function) were used to evaluate arch form differences by superimposition. RESULTS: The constant term related to dental arch depth of the brachyfacial subjects was significantly greater than that of the mesofacial subjects in the maxillary arch (P = .004). Superimposition of maxillary arch analysis showed that the posterior segment width of the mathematically computed arch form tended to increase from dolichofacial type to brachyfacial type. The arch forms drawn by the 2 equations coincided at the incisal and molar regions. CONCLUSIONS: The beta function is appropriate for predicting the finishing arch form, and the polynomial equation is appropriate for the analysis (diagnosis) of various Class II malocclusions, including ovoid, tapered, and square arch forms and dental arch asymmetry.

Chin cup treatment outcomes in skeletal Class III dolicho- versus nondolichofacial patients.

This study examines cephalometric differences and sex differences in the long-term outcome of chin cup treatments of Class III subjects with two facial patterns. Seventeen nondolichofacial and 16 dolichofacial Class III male patients and 16 nondolichofacial and 16 dolichofacial female patients were treated by either bicuspid extraction or nonextraction. Rapid palatal expansion without maxillary protraction was performed on 11 male cases and 15 female cases. The borderline between the two groups was drawn either at 39 degrees mandibular plane angle or 132 degrees (male subjects) or 130 degrees (female subjects) gonial angle. Dolichofacial subjects were treated with either an occipital or a high-pull chin cup force during the first two years, followed by high-pull force during night-time wear for the subsequent three years. All treated cases showed excellent results in the retention records with acceptable posterior occlusion as well as excellent skeletal and soft-tissue profiles. In addition, patient compliance was excellent. The treatment outcomes of the two groups showed significant improvement of the skeletal Class III malocclusion. This study indicated that the treatment period and wear time of the chin cup appliance in nondolichofacial (mostly mesiofacial pattern) patients could be shorter than those of dolichofacial patients. Although all subjects showed significant improvement in the Class III malocclusion, the treatment outcome in the two groups maintained the original characteristic skeletal morphology at retention.