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[Anatomical study on the root apex in the maxillary anterior teeth].

This study was undertaken to anatomically investigate the apical portion of root canal. Teeth used in this study were thirty maxillary central incisors, thirty maxillary lateral incisors and thirty maxillary cuspids extracted from patients between the ages of 11 and 73. All of the teeth had periodontal disease, but none had periapical disease. Resorption of the root surface could not be seen with the naked eye. The results obtained were as follows: 1. Deviations of the root apex and the apical foramen. Both of the root apex and apical foramen of the central incisors and cuspids were displaced distolabially from the tooth axis. Those of the lateral incisors were displaced distolingually from the tooth axis. The coincidence between the root apex and apical foramen was found in 16.7 per cent of both the central incisors and the cuspids, and in 6.7 per cent of the lateral incisors. 2. Diameters of the apical foramen and perpendicular distances between the root apex and apical foramen. The labiolingual diameters in the apical foramen of the central incisors, the lateral incisors and the cuspids were 0.504 mm, 0.452 mm and 0.425 mm respectively. Those diameters were larger than the mesiodistal diameters in the maxillary anterior teeth. Both the labiolingual and mesiodistal diameters in the central incisors were the largest. The perpendicular distances between the root apex and the apical foramen of the central incisors, lateral incisors and cuspids were 0.450 mm, 0.440 mm and 0.510 mm respectively. Those in the cuspids were the largest. The apical foramen in the cuspids was located slightly closer to the cervical side. 3. Diameters of the apical constriction and perpendicular distances between the root apex and apical constriction. The apical constriction of the root canal was located in either cementum or dentin. The labiolingual diameters of the root canal in the apical constriction of the central incisors, the lateral incisors and the cuspids were 0.425 mm, 0.369 mm and 0.425 mm respectively. The root canal labiolingual diameters in the maxillary anterior teeth was approximately 0.050 mm larger than mesiodistal diameters. The shapes of the root canal in the apical constriction were mostly the circular, oval and ovoid, while a few irregular shapes were observed. The perpendicular distances between the root apex and the apical constriction of the root canal in the central incisors, the lateral incisors and the cuspids were 0.863 mm, 0.825 mm and 1.010 mm respectively. 4. The stricture ratio of diameter between the apical foramen and the apical constriction of the root canal.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

Mechanism of reduction of aortic valvular stenosis by percutaneous transluminal balloon valvuloplasty: report of five cases and review of literature.

Among five patients (69 to 93 years of age) in whom percutaneous transluminal balloon valvuloplasty was performed for severe aortic stenosis, fractures of cuspid calcium were observed in three, fractures and a cuspid tear in one, and no gross alterations in one. Aortic stenosis resulted from degenerative (senile) calcification of tricuspid aortic valves in two patients, calcification of congenitally bicuspid aortic valves in two, and postinflammatory (presumably rheumatic) fibrocalcific disease in one. Fractures of calcific lesions, by allowing hingelike motion along their sites, seemed to facilitate cuspid mobility and thereby provided the apparent morphologic substrate for reduction in functional stenosis. Among three cases with fused commissures (two bicuspid and one postinflammatory), however, mobility of the conjoined cusps was not achieved after valvuloplasty, despite fracture of calcific nodules in the adjacent valve pocket of one case, because the fused and calcified commissures were not split or fractured and therefore continued to act as rigid struts that impeded cuspid motion. In the current autopsy evaluation of the effects of aortic balloon valvuloplasty, greater cuspid mobility seemed to be achieved in subjects with degenerative calcific stenosis than in those with calcified bicuspid valves or distortion by postinflammatory disease.

Age Factors↗

The bonded mandibular lingual retainer.

The lower fixed retainer from cuspid to cuspid has been one of the commonly used methods of retention at the end of the orthodontic treatment. Orthodontists mostly use the lingual wire soldered to cuspid bands for the fixed lower retainer. With the advent of the new effective bonding materials many orthodontists prefer to use cuspid-to-cuspid/biscuspid-to-biscuspid bonded retainers to obtain optimal retention of lower anterior teeth both functionally and aesthetically. After experimenting with a variety of previous methods, such as the use of rubber bands, elastic threads, cotton pliers, ligature wires and silastic trays for the accurate placement and immobilization of a lower lingual retainer during the bonding, we have found that the use of two 1 to 1 1/2 inch pieces of 0.016 inch wires tack welded to lingual wire gives the best results. It is more accurate, simple, inexpensive and designed to save the orthodontist chair time.

Dental Bonding↗

[Characteristics of the enamel mineralization of the intact permanent teeth in children 6 to 14 years old].

The composition of enamel from the first permanent lower molars was studied intravitally in 140 somatically asymptomatic children with intact teeth. The contents of Ca, P and molar Ca/P ratio were determined. At the age of 10, 13 and 14 years Ca levels were higher as related to 10, 13 and 14 for cuspid and to 13 and 14 years for paracervical specimen. After 10 years, cuspid Ca content was higher than cervical. At the age of 10 to 14 cuspid P content was reduced. Age-related increase in molar Ca/P ratio was also found. The values attained those characteristic of adult intact enamel at cuspid by the age of 9, and at cervix by 12 years. The data suggest that cuspid enamel matures earlier than pericervical one.

Adolescent↗

[The etiology of canine tooth impaction--a space analysis].

The aim of this study was to examine to what extent excess space must be taken into consideration as an etiological factor in upper canine impaction with special attention paid to the role of the adjacent laterals. To clarify this question the pre- and post-treatment models of 63 patients with a total of 84 impacted cuspids were measured and the cephalograms of 116 patients having 144 impacted cuspids were analyzed. The results of this study revealed: 84.5% of the cuspids were palatally impacted while 15.5% were labially impacted. An arch deficiency was found in only 18% of the palatally impacted cuspids, whereas there was an arch-length deficiency in 46% of the buccally impacted. In 35% of the cases there was a correlation between peg shaped laterals and palatal impaction, however, such was not present in the patients with vestibular retention. Finally the cephalometric data revealed horizontal growth characteristics in 80% of the palatally impacted canines as opposed to 23% in those labially impacted.

Adolescent↗

Central representation of dental structures in the kitten, including projections to the mesencephalic trigeminal nucleus.

Horseradish peroxidase (HRP) was injected into either a single maxillary or a single mandibular primary (deciduous) cuspid tooth of 8- to 10-week-old kittens. The large apex of the primary cuspid allowed for some leakage of the HRP from the pulpal chamber to the periodontal ligament (PDL). Thus, the injection procedure resulted in the application of HRP to the PDL as well as to the pulpal tissues. The transganglionic transport of HRP resulted in discrete terminal fields within the spinal trigeminal nucleus (STN) and the main sensory nucleus (MSN). These projections were clearly somatotopically organized within the STN, but less so within MSN. Within pars oralis (PO) and pars interpolaris (PI), mandibular cuspid dental structures (MdCDS) were represented in a dorsal position relative to the maxillary cuspid dental structures (MxCDS), whereas within pars caudalis (PC) and the adjacent reticular formation the somatotopic representation was not dorsoventral, but rather mediolateral, with the MdCDS represented more medially than the MxCDS. Areas of overlap between MxCDS and MdCDS were found within MSN and to a lesser degree within the superficial laminae of PC. In addition, the fiber pathway leading to labeled somata in the mesencephalic trigeminal (Mes V) nucleus was clearly identified. The majority of the fibers traced to the Mes V nucleus exited the spinal trigeminal tract at the level of the transition from PO to the MSN and traversed the nuclear region in a position dorsal to and separate from the trigeminal motor tract. As in STN, fibers within the caudal Mes V tract appeared to be somatotopically organized, with the fibers from the MdCDS generally more dorsal than the ones from the MxCDS. Labeled fibers, some with terminal arbors, were also identified in close association with the trigeminal motor tract. The findings show a complex pattern of central representation in the immature feline central nervous system for deciduous dental structures.

Afferent Pathways↗

[Analysis of distalization of lower canine by light-segmented archwire].

OBJECTIVE: To analyze the practical effect of distalization of lower cuspiud by light-segmented archwire. METHODS: 17 cases were selected. In all cases, two lower first bicuspids were extracted and lower molars were designed as reinforced anchorage. In the first half year, lower cuspids were distalized with light-segmented archwire, and lower incisors were in the physiologic drift stage. Before the treatment, three months and six months after the treatment, cephalograms and study models were recorded respectively. The data were analyzed with SPSS 10.0. RESULTS: The distance of mesiolization of the first lower molar was 1.14 mm in half a year. The distance of distalization of the lower cuspid was 5.02 mm in half a year. No significant difference was found in LM-MP and SN-MP angle. LI-NB angle was decreased by 9.57 degrees. Crowding of lower incisors was transferred from -2.55 mm to 1.08 mm. CONCLUSION: During distalization of lower cuspid by light-segmented archwire, anchorage tooth was stable, lower cuspids were distalized effectively, and lower incisors drifted towards the ideal position automatically.

Bicuspid↗

[Strength of teeth to fracture by impact. Testing of fractural strength against impact force, using replication models of human permanent teeth].

Traumatic injury anterior teeth is often encountered clinically. A number of clinical and statistical studies have so far been undertaken for the incidences, causes and ages in terms of the site of fracture. However, little has been attempted at fundamental estimation of the fractural resistance of anterior teeth that are susceptible to fracture. This has been studied in only an erect position of eruption by Nose or Chin. Changes in resistance of teeth in a twisted position or at different angles of eruption still remain unstudied. We took an interest in the relation between physicopositional conditions of human teeth and changes in their fractural strength against impact. Determination of the resistance of teeth to a variety of experimental conditions was attempted by use of an Izod-type tester. Epoxy resin replication models of human anterior teeth were used as experimental specimens, since human teeth were considered inappropriate because of their large individual differences and an anticipated difficulty in precise reproduction of the angles of eruption and torsion. The following results were obtained; (1) In the replication models of teeth erected positioned at 90 degrees vertically to the horizontal plane, the fractural strength against impact was highest for the maxillary cuspid model and was lowest for the mandibular central incisor model. (2) In the replication models of teeth with their mesial or distal incisal margin twisted 45 degrees medially, the fractural strength was reduced for all the teeth except the maxillary central incisors. (3) In comparison of the strength between the replication models with the mesial incisal margin twisted 45 degrees medially and those with the distal incisal margin twisted likewise am marked reduction in strength was found for the maxillary cuspid model prepared in the former condition of torsion. For the mandibular cuspid model, a relatively large reduction of the strength was found in the latter condition of torsion. (4) In comparison of the strength of teeth positioned at various angles, the strength was decreased by slanting either labially or lingually for all the replication models except the maxillary and mandibular cuspid models.

Cuspid↗

Shear bond strength of Scotchbond in vivo.

The shear bond strengths of Scotchbond, HEMA/Scotchbond, and Scotchbond 2 were measured in vivo in dog canine and molar enamel and dentin. Dentin bond strengths were compared in superficial, middle, and deep dentin. The acid-etched enamel bond strengths of the three bonding systems ranged from 10 to 11 MPa and were not statistically different. Scotchbond/Silux bonds to superficial and middle cuspid and molar dentin were 3 MPa and were not statistically different. HEMA-treated dentin did not consistently improve Scotchbond strengths to either tooth type at any dentin depth. Deep dentin from either tooth type yielded significantly lower bond strengths. Scotchbond 2/Silux shear bond strengths were significantly higher (6-8 MPa) in superficial and middle cuspid dentin but were not different from Scotchbond bonds made to deep cuspid dentin or to any depth of molar dentin. The observation that molar bond strengths are lower than those made to cuspid dentin indicates that there are important substrate differences between teeth as well as within dentin as a function of depth. The dog model may be useful for the screening of new dentin bonding systems prior to clinical trials.

Animals↗

[A study of electric information monitoring in the treatment of bruxism with occlusal splint].

OBJECTIVE: An electric monitor of bruxism had been invented in order to evaluate the curative effect of cuspid occlusal upheaving splint and stabilization splint. METHODS: 20 patients with bruxism were randomly divided into two groups. A cuspid occlusal upheaving splint or a stabilization splint was fabricated respectively for patients. The vertical dimension for each splint was 0.5 mm lower than mandibular postural position. Sleeping time, bruxist time and times of bruxism were recorded with bruxism monitor that was invented for studying bruxing. RESULTS: The bruxist time and the times of bruxism were decreased obviously in patients with cuspid occlusal upheaving splint, while no significant difference was shown before and after using the stabilization splint. CONCLUSIONS: The bruxism monitor can automatically measure and record the data of bruxism with splint, which is valuable for clinic. The curative effect of cuspid occlusal upheaving splint is better than that of stabilization splint for treating bruxism.

Adult↗

The path of chewing movement before and after experimental occlusal interference.

To understand functions of the masticatory system accurate recording and analysis of mandibular movement are indispensable. The purpose of this experiment was to find functional differences in the path of masticatory movement due to experimental occlusal interference. Occlusal interference was placed on the mandibular first molar or cuspid of the habitual chewing side in seven normal subjects. While subjects were asked to masticate gum on one side at a time, jaw movements were recorded and analyzed using an automatic masticatory movement analysis system previously developed. Standard deviations (SD) of the vertical and lateral elements in the opening and closing phases were calculated and compared before and after the occlusal interference. In the opening phase the SDs increased significantly with either the interference placed on the cuspid or molar tooth. In the closing phase it generally increased with either the interference. The effect was significantly more with the cuspid interference than that of the molar tooth. The SD of the vertical element is also generally increased with either interference. However, in contrast to the lateral element, the effect of the molar interference on the vertical element was significantly more than that of the cuspid.

Adult↗

[The valvular apparatus and tissue organization of the endothelium of the thoracic duct].

The structure of ostial valves and valves located along the thoracic duct and of its branches ostial valves and right lymphatic duct ostial valves were studied in 30 experimental outbred dogs and 46 cats. Cryodestruction of thoracic duct was performed in 28 outbred cats. 1, 3, 7 and 14 days later perfusive fixation with intercellular borders impregnation was carried out with simultaneous examination of intact regions of intravalvular segments, cisterna chyli and area of thoracic duct trunks connection with valvular surfaces. Tissue organization in ageing was studied using the intervalvular segment of old animals. Specimens were studied by means of scanning electron microscopy and film preparations of endothelium. Valves, located along the thoracic duct length are bicuspid formations, while ostial ones are falciform and cuneiform respectively in 80 and 20%. Endotheliocytes of cuspids are characterized with high content of microfilaments bundles in the cytoplasm and low content of microvesicles. Cells of the valvular free margin cross the cuspid edge and have adaptive changes preventing their desquamation: fusiform shape, long basal processes and bundles of microfilaments in the cytoplasm. Peculiar "pericyte-like" cells alike with myofibroblasts lie deep in the cuspid thickness close to the sinusal venous side. Fascicles of the duct smooth myocytes reach the base of the valve. Besides, in the ostial valve stroma there is elastic membrane, better displayed along the cuspid venous side. Increased polymorphism and changes of the endotheliocytes metric characteristics were demonstrated in the zones of turbulent lymph flow. Analysis of the newly formed endothelium tissue mosaics allows to reveal mechanisms of monolayer repair: spreading and migration of endotheliocytes on the first day, their proliferation within three days, desquamation of newly formed endotheliocytes and spreading of adjacent cells on later stages.

Aging↗

Anatomical study of the root apex in the maxillary anterior teeth.

The purpose of this study was to investigate anatomically the apical portion of the root canal of human maxillary anterior teeth. Thirty maxillary central incisors, 30 maxillary lateral incisors, and 30 maxillary cuspids were used. These were teeth from patients ranging in age from 11 to 73 yr. The root apex and main apical foramen coincided in 16.7% of central incisors and cuspids and in 6.7% of the lateral incisors. The labiolingual diameter of the root canal at the apical constriction of the central incisors, lateral incisors, and cuspids averaged 0.425 mm, 0.369 mm, and 0.375 mm, respectively; and the respective vertical distances between apex and apical constriction were 0.863 mm, 0.825 mm, and 1.010 mm.

Adolescent↗

[Dental arch characteristics of the facial asymmetry].

OBJECTIVE: To study the characteristics of dental arches in the patients with facial asymmetry. METHODS: 20 facial asymmetrical patients were chosen as the study subjects. They were 8 boys and 12 girls, aged from 12-year to 16-year old. 20 normal occlusion persons without signs of facial asymmetry were chosen as control. Dental casts were measured by 3-dimension measuring machine. Dental arch asymmetry, coordination between upper and lower dental arch, and dental inclination were measured. SAS 6.03 was used in statistical analysis. RESULTS: The distance from cuspid and the first bicuspid to the median palatal raphe in the side of crossbite was larger than that of contralateral side in maxilla. The distance from cuspid, bicuspids and the first molar to the midline in the side of crossbite was smaller than that of contralateral side in mandible (P < 0.05). The dental arch width of cuspid and first premolar in maxilla was smaller than that of mandible (P < 0.05) . Significant buccal inclination of the maxillary posterior teeth coupled with lingual inclination of the mandibular posterior teeth was found on the crossbite side. In contrast, significant lingual inclination of the maxillary posterior teeth coupled with buccal inclination of the mandibular posterior teeth was found on the contralateral side (P < 0.05). CONCLUSION: The width of upper anterior dental arch was smaller, and the inclination of upper and lower posterior teeth between crossbite side and counterside was different in facial asymmetry patients.

Bicuspid↗

Contact damage as a failure mode during in vitro testing.

PURPOSE: The purpose of this study was to identify the failure mode(s) for all-ceramic crowns tested in vitro and to determine whether measured failure loads in this type of testing would be influenced by indenter radii (a classic Hertzian cone-crack variable) and specimen thickness. MATERIALS & METHODS: Fracture surfaces and failure probability data from glass-ceramic cuspids (n = 50) tested in a previous in vitro study were examined to determine their mode of failure. To further evaluate the failure mode identified for the crowns, 100 ceramic platelets (50 glass-ceramic, 50 feldspathic porcelain) were loaded to failure beneath spherical indenters (radii, 0.75-94 mm). RESULTS: Glass-ceramic cuspids failed from blunt contact damage at the point of loading (with Hertzian stress-state damage evident). Ceramic platelets exhibited failure from either the indentation surface (Hertzian cone-cracking present) or from the supported surface (ie, mimicking bending failure). Failure-loads increased with the indenter radius for both failure modes. Failure from blunt contact damage occurred at markedly higher loads than did failure from support-surface sites. CONCLUSIONS: Blunt indentation damage was identified as being the failure source for the glass-ceramic cuspid crowns and a major failure mode for both feldspathic porcelain and glass-ceramic platelets loaded beneath spherical indenters. This failure mode is not similar to that reported for clinically failed glass-ceramic crowns. Influential testing variables were contact radius, ceramic thickness, and the surface finish of both the ceramic specimen and test platen.

Analysis of Variance↗

Transverse curvature of the acoustic slowness surface in crystal symmetry planes and associated phonon focusing cusps

Conditions are derived for the existence of focusing cusps in ballistic phonon intensity patterns for propagation directions in crystal symmetry planes. Line caustics are known to be associated with lines of vanishing Gaussian curvature (parabolic lines) on the acoustic slowness surface, while cusps are associated specifically with points where the direction of vanishing principal curvature is parallel to the parabolic line. A parabolic line meets a crystal symmetry plane sigma at a right angle, and so it is the vanishing of the slowness-surface curvature transverse to sigma that conditions the existence of a cusp. A relation for the transverse curvature is derived and analyzed. It is shown that in an arbitrary symmetry plane sigma there may be up to four pairs of inversion-equivalent cuspidal points for SH (out-of-plane polarized) waves, and up to eight pairs of cuspidal points associated with the in-plane polarized (usually quasi-transverse) waves. In tetragonal crystals, the symmetry planes containing the four-fold axis can have at most two pairs of cusps for the SH waves and up to six pairs of cusps for the in-plane waves. In cubic crystals, the face symmetry planes sigma cannot have cuspidal points for SH waves, as is known, while four pairs of cusps for in-plane waves exist in sigma if and only if the outer-most slowness sheet has a concave region embracing the four-fold axis. The points of vanishing transverse curvature on the slowness surface in symmetry planes of tetragonal and cubic media are identified by concise relations, facilitating their explicit analysis.

Journal Article↗

Bilateral creeping attachment using free mucosal grafts. A case report with 4-year follow-up.

Two extensive periodontal recessive lesions in bilateral maxillary cuspid ares were treated surgically with free autogenous masticatory mucosal grafts. No attempt was made initially to achieve total root surface coverage. Evaluation of the sites during a 4-year postoperative period demonstrated unusual degrees of "creeping attachment." The maxillary left cuspid graft completely covered the root with 9 mm of gingival-equivalent tissue while the maxillary right cuspid area displayed 90% (7 mm) root surface coverage.

Adult↗