Factors influencing dental arch form.

Dental arch length, bilateral intermolar distance, morphology of the anterior teeth, and bilateral intercanine distance have been reported as factors influencing the determination of dental arch form. However, studies evaluating the factors that influence the determination of the above-mentioned components are limited. Therefore, to verify these points, the present study aimed to examine factors influencing the determination of dental arch form using statistical methods.Data obtained from sample dental casts were analyzed using principal component and cluster analyses. By principal component analysis, 23 sets of information were summarized into three components for the maxilla and four for the mandible. As a result of cluster analysis using principal component scores, the maxillary and mandibular dental arches were classified into four forms, respectively.Dental arch length is an important indicator of dental arch size and is influenced by the bilateral interincisor distance of the maxilla and mandible, and the mesiodistal crown width of the incisors and premolars. In the mandible, canine width also affects dental arch length. Dental arch width also influences the determination of dental arch form. However, the distance between the anterior teeth and the distance between the molars are independent and have no effect on each other.

Compliance with infection control practices when taking dental x-rays: Survey of a Japanese dental school.

The aim of this study was to assess knowledge, attitude, behavior, and compliance concerning infection control among dental practitioners in a dental university hospital in Japan. A 12-item questionnaire about infection control during radiographic procedures was distributed to 686 dental personnel working at Osaka Dental University. The questionnaire collected information on occupation and the use of gloves, holders, door handles, control panels, dental chairs, protectors, tube head, tube arms, tube cones, and keyboards for personal computers. To identify misunderstandings about, and thus noncompliance with, current infection control practices, the percentage of correct answers (PCA) was calculated. Understanding and compliance with the current practices was considered low when <75% and high when ≥75%. In addition, contaminated objects in the clinical setting were examined using black light. PCA was low for one question on using gloves in film positioning and high for three questions on using protective film barriers, regardless of the respondents' occupation. PCA was generally high for three questions on practicing hand hygiene before putting on gloves, methods to protect film holders, and methods to protect radiographic equipment, but was low among some subjects. PCA was generally low for four questions on using film protective barriers, developing images from unprotected films, practicing hand hygiene after removing gloves, and awareness of a procedures manual for taking intraoral x-rays, but was high among some subjects. Saliva contamination of radiographic equipment was confirmed by direct visualization using black light. Awareness was low of infection control measures to be used during intraoral projection. This study indicates the need for additional education and training to improve infection control practices, through, for example, using a standard procedures manual for all dental practitioners and visual evidence (visualization) of contamination.

Histological Alterations from Condyle Repositioning with Functional Appliances in Rats.

OBJECTIVE: This study was designed to assess the morphological and histological alterations of the condyle of rats undergoing forward mandibular repositioning via functional appliance. MATERIALS AND METHODS: Functional appliances were mounted onto the upper jaws of rats. Morphological analysis was conducted on micro-CT images of sacrificed animals. Histological changes in condyle were examined by immunohistochemistry using proliferating cell nuclear antigen (PCNA), matrix metalloproteases (MMPs), vascular endothelial growth factor (VEGF), tissue inhibitors of matrix metalloproteinases (TIMP-1), interleukin 1b (IL-1ß), Aggrecan and Type II collagen. Osteoclast activity was identified by tartrate-resistant acid phosphatase (TRAP) staining. RESULTS: Morphological analysis confirmed the forward positioning of the condyles of rats by the appliance, but the position gradually returned to normal on days 14 after treatment. An increase in PCNA positive cells was observed in the posterior region of the condyles on days 7, whereas PCNA positive cells decreased in the anterior region. Aggrecan and Type II collagen localization increased in the posterior region throughout the entire period, but decreased in the anterior region on days 14. In both regions, IL-1ß and VEGF localization was significantly increased for 14 days while MMPs localization was evident throughout the entire period. The TRAP positive cells were significantly elevated on days 3 and 7. CONCLUSIONS: These results suggest that the functional appliance therapy induces significant morphological and histological changes in the anterior and posterior regions of the condyle and subsequently causes adaptive cellular functions such as chondrocyte differentiation and cartilage matrix formation.

Taste preference changes throughout different life stages in male rats.

Taste preference, a key component of food choice, changes with aging. However, it remains unclear how this occurs. To determine differences in taste preference between rats in different life stages, we examined the consumption of taste solutions and water using a two-bottle test. Male Sprague-Dawley rats of different ages were used: juvenile (3-6 weeks), young adult (8-11 weeks), adult (17-20 weeks), middle-aged (34-37 weeks), and old-aged (69-72 weeks). The intakes of the high and low concentration solutions presented simultaneously were measured. We observed that the old-aged group had lower preference ratios for 0.3 M sucrose and 0.1 M MSG in comparison with other groups. The preference ratio for 0.03 mM QHCl was higher in the middle-aged group than in the three younger groups and higher in the old-aged group than the juvenile group. The taste preferences for HCl and NaCl did not significantly differ among the age groups. The old-aged group tended to prefer high concentrations of sucrose, QHCl, NaCl, and MSG to low concentrations, indicating age-related decline in taste sensitivity. We also aimed to investigate differences between life stages in the electrophysiological responses of the chorda tympani nerve, one of the peripheral gustatory nerves, to taste stimuli. The electrophysiological recordings showed that aging did not alter the function of the chorda tympani nerve. This study showed that aging induced alterations in taste preference. It is likely that these alterations are a result of functional changes in other peripheral taste nerves, the gastrointestinal system, or the central nervous system.

A histological study of mineralised tissue formation around implants with 3D culture of HMS0014 cells in Cellmatrix Type I-A collagen gel scaffold in vitro.

We cultured HMS0014 Yub621b cells within a 3D collagen gel scaffold (Cellmatrix Type I-A) and aimed to study the fate and contribution of human bone-derived mesenchymal stem cells (MSCs) in the guided bone regeneration(GBR)-engineered tissue which has developed around the titanium (Ti) test dental implant (IP) in vitro. The light microscopy (LM) and transmission electron microscopy (TEM) results of the peri-IP tissue indicated that collagen fibrils of the Cellmatrix Type I-A gel were accumulated and fabricated to provide a 3D meshwork for proliferation and differentiation of the HMS0014 cells in the top (cell) layer; mineralisation of the GBR tissue had commenced since day 1 and became markedly deposited between days 7 and 14 of the experiment. TEM observation revealed sedimentation of cement line at the periphery of the interwoven Cellmatrix fibres and fibrils in the ECM scaffold of the GBR tissue; matrix vesicle-mediated and appositional collagen-mediated mineralisation were identified in the peri-IP ECM scaffold. The fine structure study of the plurimorphic osteoblast(Ob)-like osteogeneic cells demonstrated numerous membranous organelles related with vesicular trafficking, secretion and endocytosis in the cytoplasm; well-developed cytoskeleton networks and intercellular junctional complexes were also observed. The specimens on fluorescence immunohistochemistry (IHC) by confocal laser-scanning microscopy (LSM) showed the expression of LC3 and Cx43 associated with autophagic-lysosomal degeneration pathway and signal conduction mediated with gap junctions (GJS) in maintaining tissue homeostasis of the Ob-like cells which grew and degenerated in the 3D scaffold. Results from this in vitro study suggest that Ob-like HMS0014 cells actively regulate turnover of the peri-IP ECM to recapitulate the development and formation of osteoid tissue-engineered material which might contribute to augment osseointegration around the dental implant.

Activation of microglial cells in the trigeminal subnucleus caudalis evoked by inflammatory stimulation of the oral mucosa.

To study the inflammatory hyperplasia induced by an acute noxious stimulation of oral mucosa with 5% formalin (5%FOR), we performed an immunohistochemical study on the expression of TNFá in the intermolar region of the dorsal lingual eminence (IDLE), and Iba1 and phosphorylated (phospho)- p38 MAPK involved with central nervous system microglial activation in the trigeminal subnucleus caudalis (Vc). The present study observed significantly increased expression of TNFá at either 1h or 24h of 5%FOR nociception, as well as sustained TNFá immunoreactivity in the IDLE. On the other hand, at either 1h or 24h 5%FOR nociception, Iba1- immunoreactive (IR) cells in the Vc were significantly increased after inflammatory stimulation of the IDLE; the increase was more evident at 24h 5%FOR nociception. By using the double-label immunofluorescence technique, the findings in particular demonstrated a significant increase in the number of phospho-p38 MAPK- and Iba1-IR coexpressed cells in the Vc at 24h 5%FOR nociception. The results suggest that 24h persistent microglial activation in subnuclei zonalis and gelatinosus of the Vc is evoked by 5%FOR noxious stimulation of the IDLE oral mucosa, thereby the present study indicates that the MAPK expression plays important roles in microglial activation related with central sensitization and inflammatory hyperalgesia.

Different mandibular first molar shapes according to groove and cusp configuration in relation to suggested bracket position.

The aim of this study was to explore the shape differences in the mandibular first molars through orthographic measurements using three-dimensional (3D) virtual models, and study the possibility of new morphologic categories that require more than subjective visual inspection. A total of 164 mandibular first molars with five cusps were selected for classification. Using 3D laser scanning and reconstruction software, virtual casts were constructed. After several linear and angular measurements on the virtual occlusal plane, the teeth were clustered using the partitioning around medoids methods-an unsupervised classification. The cluster analysis presented two clusters that showed statistically significant differences in the measurements over the cusp locations and groove configurations. However, gender differences were not shown in the angular groove and cusp configurations. Two clusters were found in the population of the present study, and this result suggested the existence of a diverse morphologic trait in the mandibular molar even in the same origin and could be considered in positioning orthodontic brackets that have built-in prescriptions.

A preliminary study of the dental implant therapy--initial osteogenesis of human mesenchymal stem (HMS0014) cells on titanium discs with different surface modifications.

HMS0014 cells were GBR-engineered to proliferate and differentiate into mature osteoblast(Ob)-like cells, which initiated hard tissue matrix deposition in both monolayer and PuraMatrix 3-D cultures. Subsequently, the osteogenesis initiated with attachment/adhesion of HMS0014 cells on either Titanium (Ti) or Ti alloy discs modified with osteoconductive/ osteoinductive surface textures/substrates (e.g., Disc-AO, Disc-HA, Disc-SPI) was histologically assessed. The results obtained were as follows: 1) The HMS0014 cells actively proliferated and differentiated into mature Obs to initiate mineralisation of the ECM since day 1 in both monolayer and 3-D cultures; mineralization was prominently progressed between day 7 and day 14 of cultures. 2) The SEM of 60-minute(min)s specimens demonstrated a loose distribution of proliferating spherical-to-polygonal (10 to 40 microm in diameter, avg.) cells with a bulging cell body sending out many minute filopodia and some lamellipodia to attach with the substrate in the concavities. 3) In the 180-min specimens, the cultured HMS0014 cells actively proliferated and spread into flat, large polygonal cells with prominent lamellipodia and dendritic filopodia (30 microm x 90 microm to 100 microm x 200 microm, approx.) to employ cell-to-substrate and intercellular attachments. 4) On the other hand, the present immunohistochemistry of the attached HMS0014 cells demonstrated the co-expression of F-actin (actin filaments of the cytoskeleton) and CD51 (aV integrin) in both the 60-min and 180-min specimens. We concluded that the present GBR method enhanced HMS0014 cells to initiate an osteogenesis process with a direct bone-to-substratum contact on Ti discs which were subject to different surface modifications.

Comparison of maxillary and mandibular dental arch forms by studying Fourier series developed from mathematically estimated dentitions.

We conducted a Fourier analysis on data obtained using correlation and principal component analyses of parallel-standardized dental study models; both maxillary and mandibular dental arches were predominantly round square in shape. The present study compared and determined the contribution ratio and reproducible coefficients of amplitudes (factors affecting dental arch forms), and demonstrated that the 1st to 4th and the 1st to 6th Fourier harmonics reproduced maxillary and mandibular dental arch forms, respectively. The correlation analyses of the constant term and amplitudes demonstrated that significant differences in the 2nd harmonic amplitude was strongly correlated with the curvature of anterior teeth and the length-to-width ratio in maxillary dentitions. By comparison of the constant term and amplitudes between different arch types, we did not observe significant differences in the constant term and the 1st amplitude of maxillary dentitions and in constant term and all amplitudes of mandibular dentitions. Nevertheless, the study revealed high contribution ratios of the 1st (in mandibular dentitions) and the 2nd (in maxillary dentitions) amplitudes essentially affecting the reproducibility of arch forms. The 1st amplitudes demonstrated a bow-like arrangement of all arch types, while the 2nd amplitudes adjusted the anterior-teeth curvature and in particular demonstrated the length-to-width ratio of maxillary dentitions. The 3rd and the 4th amplitudes were also determinants of the anterior-teeth curvature of maxillary dentitions. The 6th amplitude was necessary for reproduction, but showed no difference between varying mandibular dental arch types. Collectively, we conclude that the establishment of a Fourier series significantly reproduced maxillary but not mandibular dental arch forms.

Expression of TRPV4 in the stimulated rat oral mucous membrane--nociceptive mechanisms of lingual conical papillae.

The study was supported by 2006-2007 Aid Program for Overseas Training of the Promotion and Mutual Aid Corporation for Private School of Japan and International Exchange Grant, Osaka Dental University. We studied the function of TRPV4 expression and its neuronal activation in response to noxious stimulation of oral mucosa. The intermolar region of dorsal lingual eminence (IDLE) of rats was stimulated with 10 microl of either normal saline or 5% formalin. Immunohistological studies of the TRPV4, pERK and serotonin (5HT) expression in designated regions of tongues and brainstems were performed for studying the descending pain modulatory system in response to nociception. Specimens of the experimental IDLE demonstrated a significant increase of TRPV4 activity in particular in stratum basale of conical papillae (p < 0.01). pERK-IR positive neurons were significantly increased in the RMg (p < 0.05), Sp5C (p < 0.05) and Md (p < 0.01); TRPV4-IR neurons were found to show a similar distribution with pERK-IR cells in the peripheral Sp5C (p < 0.05). A significant increase of 5HT expression was observed in the RMg (p < 0.01), RPa (p < 0.01) and ROb (p < 0.05). The results suggest that TRPV4 in the oral mucosa is nociceptor of peripheral hyperalgesia, and pERK expression in the Sp5C is closely related with central hyperalgesia of the nociception. Furthermore, pERK-IR cells of the central 5HT nervous system are activated to accelerate 5HT release for neuronal modulation of the descending pain modulatory system in response to nociception.

Human dental pulp cell culture and cell transplantation with an alginate scaffold.

Many studies on tissue stem cells have been conducted in the field of regenerative medicine, and some studies have indicated that cultured dental pulp mesenchymal cells secrete dentin matrix. In the present study we used alginate as a scaffold to transplant subcultured human dental pulp cells subcutaneously into the backs of nude mice. We found that when beta-glycerophosphate was added to the culture medium, dentin sialophosphoprotein mRNA coding dentin sialoprotein (DSP) was expressed. An increase in alkaline phosphatase, which is an early marker for odontoblast differentiation, was also demonstrated. At 6 weeks after implantation the subcutaneous formation of radio-opaque calcified bodies was observed in situ. Immunohistochemical and fine structure studies identified expression of type I collagen, type III collagen, and DSP in the mineralizing transplants. Isolated odontoblast-like cells initiated dentin-like hard tissue formation and scattered autolyzing apoptotic cells were also observed in the transplants. The study showed that subcultured dental pulp cells actively differentiate into odontoblast-like cells and induce calcification in an alginate scaffold.

Effects of peripheral inflammation on activation of ERK in the rostral ventromedial medulla.

In the present study, the activation of extracellular signal-regulated kinase (ERK) in the rostral ventromedial medulla (RVM) following the injection of complete Freund's adjuvant (CFA) into the rat hindpaw was examined in order to clarify the mechanisms underlying the dynamic changes in the descending pain modulatory system after peripheral inflammation. Phospho-extracellular signal-regulated kinase-immunoreactive (p-ERK-IR) neurons were observed in the nucleus raphe magnus (NRM) and nucleus reticularis gigantocellularis pars alpha (GiA). Inflammation induced the activation of ERK in the RVM, with a peak at 7 h after the injection of CFA into the hindpaw and a duration of 24 h. In the RVM, the number of p-ERK-IR neurons per section in rats killed at 7 h after CFA injection (14.2 +/- 1.7) was significantly higher than that in the control group (4.5 +/- 0.9) [P < 0.01]. At 7 h after CFA injection, about 60% of p-ERK-IR neurons in the RVM were serotonergic neurons. The percentage of RVM serotonergic neurons that are also p-ERK positive in the rats with inflammation (20.5% +/- 2.3%) was seven times higher than that in control rats (2.7% +/- 1.4%) [P < 0.01]. These findings suggest that inflammation-induced activation of ERK in the RVM may be involved in the plasticity in the descending pain modulatory system following inflammation.

Morphological classification of mandibular dental arch forms by correlation and principal component analyses.

To evaluate the morphology of dental arches, 53 (male: 29, female: 24) paired casts having normal dentitions and occlusion were selected from 396 (age: 18 to 26 years old; male: 257, female: 139) sets of dental study models. The mandibular dentitions were preliminarily classified as square, round-square, round and round V-shaped arches based on the conventional morphological descriptions. Midpoints of the incisor edge (I1R, I1L, I2R, & I2L), summits of the cuspids (CR & CL), buccal cusps of the premolars (P1R, P1L, P2R, & P2L), mesial buccal cusps of the first and second molars (M1R, M1L, M2R, & M2L), and the midpoint (A) of line I1R-I1L were designated as reference points. From A, let a vertical line intersected line M2R-M2L at reference point B. The line A-B intersected CR-CL at reference point E. We evaluated 1) the protrusion of the cuspids by 1. angle I2R-CR-P1R (angle R) + angle I2L-CL-P1L (angle L); 2) the curvature of the anterior teeth by 2. (A-B)/(CR-CL), 3. (180 degrees-angle(CR-A-CL), and 4. (A-E)/(CR-CL); 3) the length to width ratio of the dental arch by 5. (A-B)/(M2R-M2L); 4) the degree of roundness of the mandibular arch by estimation of 6. (rtheta5 - rtheta4)R + (rtheta5 - rtheta4)L; and 5) an item 7. for the differentiation of type I and type II round-square arches by relating the bilateral contour and position of break line P1-P2-M1-M2 (i) to line P1-M2 (ii). The data of items 1., 2., 3., 4., 5., and 6. were further standardized and summarized into three essential principal components: 1) the curvature of the anterior teeth, 2) the curvilinear contour of the dental arch, and 3) the length-to-width ratio of the dental arch. The results indicated that: 1) 36 cases (67.9%) of the mandibular dentitions were round-square arches which showed no prominent principal component. 11 cases (20.8%) were square arches and 6 cases (11.3%) were round V-shaped arches; no round arches was found in mandibular dentitions. 2) Statistical analysis indicated significant differences of items 3., 4. and 6. in various mandibular arches (Student's t-test). 3) By examination of the three principal components, significant differences of item 5. between the round V-shaped arches and square and round-square mandibular arches were evident (Student's t-test). The present study elucidated that morphology of the mandibular arch was determined by a parameters representing the curvature of anterior teeth (composed of items 2., 3. and 4., and another parameter (item 6.) representing roundness of the mandibular arch.

A morphological study on the classification of maxillary dental arches.

To evaluate the morphology of dental arches, 62 (male: 36, female: 26) paired casts having normal dentitions and occlusion were selected from 396 (age: 18 to 26 years old; male: 257, female: 139) sets of dental study models. The maxillary dentitions were preliminarily classified as square, round-square, round and round V-shaped arches based on the conventional morphological descriptions. Midpoints of the incisor edge (I1(R), I1(L), I2(R), & I2(L), summits of the cuspids (CR & CL), buccal cusps of the premolars (P1(R), P1(L), P2(R), & P2L), mesial buccal cusps of the first and second molars (M1(R), M1(L), M2(R), & M2(L)), and the midpoint (A) of line I1(R)-I1(L) were designated as reference points. From A, let a vertical line intersected line M2(R)-M2(L) at reference point B. The line A-B intersected C(R)-C(L) at reference point E. We evaluated 1) the protrusion of the cuspids by (1) angle I2(R)-C(R)-P1(R) (angle R) + angle I2(L)-C(L)-P1(L) (angle L); 2) the curvature of the anterior teeth by (2) A-B/C(R)-C(L), (3) 180 degrees - angle C(R)-A-C(L), and (4) A-E/C(R)-C(L); 3) the length to width ratio of the dental arch by (5) A-B/M2(R)-M2(L); 4) the degree of roundness of the maxillary arch by estimation of (6) (rtheta5 - rtheta4)R + (rtheta5 - rtheta4)L; and 5) an item (7) for the differentiation of type I and type II round-square arches by relating the bilateral contour and position of break line P1-P2-M1-M2 (i) to line P1-M2 (ii). The data of items (1), (2), (3), (4), (5), and (6) were further standardized and summarized into three essential principal components: 1) the curvature of the anterior teeth, 2) the curvilinear contour of the dental arch, and 3) the length-to-width ratio of the dental arch. The results indicated that: 1) 60% of the maxillary dentitions were round-square arches which showed no prominent principal component; 2) square maxillary arches distinctly showed a small (1) angle R + angle L; 3) round arches were characteristic by small (6) (rtheta5 - rtheta4)R + (rtheta5 - rtheta4)L values; and 4) round V-shaped arches had large (1), (3) and (4) values.