Central Teeth Research Articles

Radular ultrastructure of South American Ampullariidae (Gastropoda: Prosobranchia)

The radula of five species of South American Ampullariidae was analysed by Scanning Electron Microscope (SEM) with the purpose of enlarging new studies on the systematic of this family. The studied species were Pomacea canaliculata (Lamarck, 1822), Pomacea scalaris (d'Orbigny, 1835), Pomella (P.) megastoma (Gray, 1847), Asolene (A.) platae (Maton, 1809) and Felipponea neritiniformis (Dall, 1919). The central tooth shows different attributes which provide the means for generic determination; the analysis of the central tooth, the lateral and marginal ones by SEM adds further information for species differentiation.

A COMPARISON BETWEEN THE RAYPEX5 APEX LOCATOR AND CONVENTIONAL RADIOGRAPHY FOR DETERMINING WORKING LENGTH OF STRAIGHT AND CURVED CANALS

INTRODUCTION: The purpose of this in vitro study was to compare the accuracy of the new electronic apex locator Raypex5 with radiography for working length determination of straight and curved root canals. MATERIALS AND METHODS: Twenty straight and single canals of maxillary central teeth and twenty curved mesiobuccal canals of mandibular molar teeth were used. Access cavities were prepared and working lengths were determined by means of Raypex5 and conventional radiography then compared with actual working lengths (AWL). Data were analyzed by ANOVA with repeated measurements and Least Significant Difference (LSD) test. RESULTS: There was no significant difference between electronic and actual working length determination for straight canals (p=0.74). For curved canals the difference between electronic and actual working length was significant (p<0.0001). There was a significant difference between radiographic and actual working length determination either for straight and curved canals (p=0.024, p<0.0001). The difference between radiographic and electronic working length determination was also significant for straight canals (p=0.006). The percentage of electronic measurements within ±0.5 of AWL was 70% for straight canals and 35% for curved root canals. The percentage of radiographic measurements within ± 0.5 of AWL was 50% for straight canals and 25% for curved root canals. CONCLUSION: Raypex 5 is an apex locator that measured the tooth length within a clinically acceptable range especially in anterior straight canals.

Redescription and 3D morphology of Williamia gussonii (Gastropoda: Siphonariidae)

Since it has never been described adequately, the taxonomic status of the type species of the siphonariid genus Williamia, W. gussonii (da Costa, 1829), is unclear. A redescription with the designation of a neotype is provided in the present study. Shell, radula and soft-part anatomy are investigated in detail by light microscopy, SEM and 3D-computer reconstruction and visualization of serial sections. The most significant features of the hard parts are the freely extending periostracum at the shell edge and the radula organization, with a tiny central tooth, bicuspid lateral teeth and scale-like trapezoid lateral-marginal teeth. These characters perfectly correspond to other Williamia species. In contrast, soft-part anatomy reveals features which differ strongly from those of other Williamia species. In particular the genital system lacks a bursa copulatrix but has other accessory structures, the pallial cavity that does not extend to the left side of the body, and there is only a single pulmonary vessel. Characters are discussed with regard to their usefulness for phylogenetic consideration, with a focus on siphonariid relationships. The hard-part characters appear to be more significant than the soft -part anatomy for the phylogeny of Williamia, and it is suggested that the genus is monophyletic.

Multidisciplinary approach to the rehabilitation of a crown‐root fracture with original fragment for immediate esthetics: a case report with 4‐year follow‐up

Dental practitioners frequently encounter dentoalveolar traumas. According to the severity of the trauma, a large spectrum of complications such as isolated tooth fracture, dentoalveolar fracture or fracture at maxillofacial region may occur. If the isolated tooth fracture occurs particularly at anterior region, the rehabilitation should satisfy both esthetic and functional problems. An unrestorable tooth should be extracted and this leads to more complex treatments such as implant or conventional prosthetic rehabilitations, which will restore the function, but impair the esthetics. Recently, powerful new generation dual-cured resin composites have been produced for reattachment of original fractured fragments. In this case, we presented treatment of oblique crown-root fracture of a maxillary central tooth from enamel-cement junction by the reattachment technique. We used dual cured resin composite (Panavia F) and a self-tapping screw-post (Dentatus) for reattaching the crown fragment. Orthodontic treatment was applied for intruding and leveling the tooth. Four years after treatment, the tooth exhibited good esthetics, good periodontal health and normal function. However, minimal relapse occurred in spite of orthodontic treatment. In conclusion, the reattachment technique is an alternative method, which offers satisfactory esthetic and functional rehabilitation of the fractured teeth.

Characteristics of sensing lower-jaw-position in patients with cerebral palsy during laughing gas-induced sedation

To clarify the effects of the applied during sedation with nitrous oxide (hereafter referred to as laughing gas) on the ability of muscles attached to the lower jaw to sense lower-jaw-position and on the sensation of muscle spindles attached to the lower jaw in patients with cerebral palsy (CP) using healthy adult subjects without functional abnormalities of the jaws and oral cavities as control subjects (hereafter referred to as healthy subjects). Experiments were performed under the following conditions: for each subject, before the inhalation of laughing gas (LG) and oxygen (air-inhalation condition: referred to as without LG inhalation) and during the inhalation of LG and oxygen (inhalation condition of LG and oxygen under LG-induced sedation: referred to as during LG inhalation). Subjects in the experiments were eight CP patients and eight healthy people as controls. The ability to discriminate lowerjaw- position was estimated by asking the subjects to determine whether the diameter of a test stick was larger or smaller than that of a reference stick after performing the following tasks: a) holding a reference stick between the central teeth of their upper and lower jaws for 5 s, and b) replacing the reference stick with a test stick and holding it at the same position for 5 s, and the test stick was then removed. The following findings were obtained. 1) In comparing discrimination ability in the absence of LG-induced sedation and that during LG-induced sedation of healthy control subjects, the rate of mis-estimation (RME) was significantly larger during LG-induced sedation than in the absence of LG-induced sedation for a test stick diameter (10.5 mm or 11.0 mm) larger than the reference stick diameter (10. 0mm) ( P < 0.05). No significant differences were observed for any other test sticks ( P > 0.05). 2) In comparing discrimination ability in the absence of LG-induced sedation and that during LG-induced sedation of CP patients, RME was significantly smaller during LG-induced sedation than in the absence of LG-induced sedation, when the test stick diameter (9.5 mm) was smaller than the reference stick diameter ( P < 0.05). No significant differences were observed for any other test sticks ( P > 0.05). These results indicate that neural functions are inhibited at the upper level of the central nervous system in CP patients, leading to the attenuation of sustained increase in muscle tonus that is characteristic of CP patients. In summary, it seems that the LG has some inhibitory effect on the activity of γ-motor neurons innervating muscle spindles attached to the lower jaw via the upper level of the central nervous system and that this inhibitory effect contributes to an improvement in the discrimination ability.

Follow-up of 2 Traumatic Cases of Severely Intruded Deciduous Teeth

Two traumatic cases of severely intruded deciduous teeth were evaluated for several months. One case was a complete intrusion of the primary upper central teeth. The intruded teeth re-erupted spontaneously within a month but needed endodontic treatment after 6 months. The other case was a severe lateral intrusion of the upper central tooth, which re-erupted labially but did not reach the incisal plane even after one year. It produced no complication of the pulp but re-alignment procedure will be needed.

Effects of vibration stimulus on lower-jaw-position sensation in patients with cerebral palsy during inhalation of laughing gas

To clarify the effects of a vibration stimulus applied during sedation with nitrous oxide (hereafter referred to as laughing gas) on the ability of muscles attached to the lower jaw to sense lower-jaw position and on the sensation of muscle spindles attached to the lower jaw in patients with cerebral palsy (CP) using healthy adult subjects without functional abnormalities of the jaws and oral cavities as control subjects (hereafter referred to as healthy subjects). Experiments were performed under the following conditions: for each subject, before the application of the vibration stimulus (referred to as S pre ) and after the application of the vibration stimulus (S post ); before the inhalation of laughing gas (LG) and oxygen (air-inhalation condition: referred to as without LG inhalation) and during the inhalation of LG and oxygen (inhalation condition of LG and oxygen under LG-induced sedation: referred to as during LG inhalation). Subjects in the experiments were eight CP patients and eight healthy people as controls. The ability to discriminate lower-jaw position was estimated by asking the subjects to determine whether the diameter of a test stick was larger or smaller than that of a reference stick after performing the following tasks: a) holding a reference stick between the central teeth of their upper and lower jaws for 5 s, and b) replacing the reference stick with a test stick and holding it at the same position for 5 s, and the test stick was then removed. The following findings were obtained. 1) In comparing the ability of healthy subjects to discriminate between S pre and S post during LG inhalation using different test sticks, when the test stick diameter was 9.5 mm (smaller than the reference stick diameter), the rate of mis-estimation (RME) for Spost was significantly larger than that for Spre ( P < 0.05). No significant differences were observed for any other test sticks. 2) In comparing the ability of CP patients to discriminate between S pre and S post during LG inhalation using different test sticks, when the test stick diameter was 9.5 mm (smaller than the reference stick diameter), the RME for S post was significantly smaller than that for S pre ( P < 0.05). No significant differences were observed for any other test sticks. These results suggest the following: the combination of LG for sedation with vibration stimulus further inhibits neuronal functions at the upper level of the central nervous system in CP patients, compared with cases in which each variable is applied separately, and the combination also inhibits the sustained increase in muscle tonus, which is characteristic of CP patients. LG reduces the activity of γ-motor neurons via the upper level of the central nervous system. In addition, tonic vibration reflex (TVR) develops due to the vibration stimulus, which increases the threshold value of sensitive muscle sensation and decreases the activity of γ-motor neurons, and furthermore decreases the activity of muscle spindles attached to the lower jaw. Consequently, a tendency toward increased ability to discriminate lower-jaw position is observed.

Peroxide Penetration into the Pulp from Whitening Strips

It was observed that externally applied bleaching gels may penetrate into the pulp chamber. This study was conducted to evaluate the peroxide diffusion from two whitening strips into the pulp chamber. Twenty-four, human, extracted, maxillary central teeth were separated into three groups (n = 8). All teeth were sectioned 3-mm apical to CEJ, the intracoronal pulp tissue was removed, and the pulp chamber was filled with acetate buffer. Vestibuler crown surfaces of teeth in the experimental groups were subjected to whitening strips; the teeth in the control group were exposed only to distilled water. The acetate buffer solution in each tooth was transferred to the tube. Leuco-crystal violet and enzyme horseradish peroxidase also were added to the tube. The pulpal peroxide was determined spectrophotometrically. The results indicated that the whitening strip containing 14% hydrogen peroxide presented a higher pulpal peroxide penetration than 6.5 % hydrogen peroxide (p < 0.001).

Microeledone mangoldi n. gen. and n. sp., a deep-water pygmy octopus from the Norfolk Ridge, New Caledonia (Cephalopoda:Octopodidae)

Microeledone mangoldi n. gen. and n. sp. is described from a male specimen collected from approximately one kilometre deep on the Norfolk Ridge south of New Caledonia in the south-west Pacific Ocean. This tiny octopus is characterised by a single row of suckers that are functional to the tips of the arms, the absence of an ink sac, the presence of a pair of chitinous stylets, a UU-shaped funnel organ, a copulatory organ with distinct ligula and calamus, and a distinctive radula. The radula has seven teeth per row. The unique central (rachidian) tooth has a long, sharp mesocone with a curved and grooved tip. The remaining rows of teeth are also unique, being flattened and plate-like. Marginal plates are absent. The body is smooth, without papillae, cartilaginous tubercles, or a lateral ridge. Functional chromatophores are absent. This octopus appears related to several other genera of deep-sea octopods with a single row of suckers, namely Thaumeledone Robson, 1930, Bentheledone Robson, 1932 and Graneledone Joubin, 1918, to which the new genus is compared. Definitions of the genus Thaumeledone are reviewed.

First record of Mastophorus muris (Gmelin, 1790) (Nematoda: Spiruroidea) from a wild host in South America.

Mastophorus muris (Gmelin, 1790) (Nematoda: Spiruroidea) is reported parasitizing the grey leaf-eared mouse Graomys griseoflavus (Waterhouse, 1837) (Rodentia: Sigmodontinae) from the province of La Pampa, Argentina. The distinct position of Mastophorus (Spirocercidae: Mastophorinae) and Protospirura (Spiruridae), sometimes still confused, is again confirmed. The pattern of pseudolabial teeth (a large central tooth with smaller teeth on each side), which seems to be rather stable in all known descriptions, is here confirmed with the aid of scanning electron microscopy. The finding represents the first record of the species in Argentina, but also from a wild host in South America. This indicates an expansion of the distribution range of the species, which, in the subcontinent, was hitherto restricted to domestic rodents.

SYSTEMATIC POSITION AND TAXONOMY OF THE GENUS HIRTUDISCUS FROM COLOMBIA (GASTROPODA: SCOLODONTIDAE)

Hirtudiscus Hylton Scott, 1973 can be classified in the Scolodontidae because of the reduced jaw, the dagger-like lateral teeth with basal plates, which point away from the centre, the aulacopod foot and the elongate kidney. The minute central teeth, ovoviviparity and the course of the right ommatophoral retractor (which passes between penis and vagina) indicate that Hirtudiscus belongs to the subfamily Scolodontinae. The peculiar suture of the shell and the incision at the parietal angle of the aperture might be synapomorphies of Hirtudiscus and Drepanostomella. In addition to the type species, three species are described as new from the Cordillera Oriental in Colombia.

Sexual dimorphisms in radula of Conomurex persicus (Gastropoda: Strombidae) in the Mediterranean Sea

Dentition characters of Conomurex persicus found along the Mediterranean coasts of Turkey were analyzed. For the analyses of radula, 289 individuals (34 adult males, 140 adult females and the remainder juve- niles) were examined. Male and female individuals of the species had different numbers of radular cusps. The radula of the taenioglossate type was made up of two marginal teeth, one lateral and one central (rhachidian) tooth, each being delicate and with different numbers of cusps. The central and lateral teeth had seven cusps and five cusps, respectively, in both males and females. Outer and inner marginal teeth of males had two and one cusps, while those of females had five and six cusps, respectively. The female's radula is yellow-whitish. The male's radula is reddish dark brown.

Contribution of Raman spectroscopy to identification of biominerals present in teeth of Acanthopleura rehderi, Acanthopleura curtisiana, and Onithochiton quercinus.

Raman spectroscopic investigations of the major lateral teeth of the chitons Acanthopleura rehderi and Acanthopleura curtisiana indicate that, in addition to the magnetite of the cutting surface and a carbonated hydroxyapatite in the central tooth core, these species deposit limonite in place of the lepidocrocite reported for other members of the genus Acanthopleura. A comparison of the spectra from these species with those of Onithochiton quercinus, which also deposits limonite, indicates that the current assignment of these species to Acanthopleura may not be appropriate. Biomineralization of the major lateral teeth may be a useful parameter to include in the taxonomic classification of chiton species.

Description of Xanthocalanus quasiprofundus sp. n. from the Arctic and redescription of X. obtusus and X. kurilensis from the North Pacific (Copepoda: Calanoida: Phaennidae)

The Arctic Xanthocalanus quasiprofundus sp. n. differs from X. profundus Sars, 1907 in the larger size (7.6 vs. 6.2 mm), presence of 10 teeth on masticatory edge of Md gnathobase and of spinules near bases of central teeth, 1 very enlarged brush-like seta of distal endopodal complex of Mx2, presence of 3 sensory setae on syncoxa of Mxp and of transverse row of spinules on Re1 of P4, and some details of P5 structure. Females of X. obtusus and X. kurilensis have 1 worm-like and 7 slender brush-like sensory setae differing in lenth on distal endopodal complex of Mx2. Male of 5th copepodid stage of X. kurilensis has an additional rudimentary seta, i.e. 9 elements, on distal endopodal complex of Mx2 (number primitive for Bradfordian families). Adult male of X. kurilensis has here 1 enlarged brush-like seta, 4 very slender brush-like setae and 1 rudimentary seta. The presence of 1 and 2 worm-like sensory setae on Li3 and Mx2 is noted in all 3 examined species.

Causes of Dental Fractures in the Early Permanent Dentition: A Retrospective Study

Two hundred eight patients, who applied to the Department of Pedodontics, Dental School, Dicle University between 1995 and 1998, were evaluated in terms of permanent teeth fracture. The aim of this retrospective study was to investigate the probable causes of the trauma, the effects of age and gender on dental trauma, prevalence of fracture types, and distribution of fracture type according to arch. It was observed that the falls or collisions were the main causes. It was also determined that the age group most frequently suffering fractures was ages 9 to 11 years. The majority of the patients were male. The enamel-dentin-pulp-type fracture and those causing the tooth to become nonvital were the most prevalent, and the majority of the fractures were observed in maxillary central teeth.

Ultrasonic measurement of enamel thickness: a tool for monitoring dental erosion?

Objectives: Wear of dental hard tissues, e.g. dental erosion, is reported to be a growing problem. A non-destructive measurement of enamel layer thickness would provide the opportunity for both early diagnosis, and longitudinal measurement of progressive enamel loss. It was the aim of this study to investigate the potential of ultrasonic pulse-echo measurements for the enamel thickness measurement. Methods: Nine extracted human incisor teeth were selected and stored in physiological saline. Mesial and distal tooth parts were removed, resulting in a central tooth slice of about 2 mm thickness. Where possible three buccal, and one palatal measuring sites were selected and indicated by pencil marks on one of the section planes. Ultrasonic pulse-echo measurements were made at each site using a Panametrics 25DL thickness gauge (Panametrics, Waltham, MA, USA), using a perspex delay line transducer (15 MHz) and glycerine coupling medium. Ultrasonic measurements were validated by measuring the thickness of the enamel layer at the marked side of the tooth slices with a light stereomicroscope at 120× magnification. Two observers performed independent measurements. Results: Limits of agreement for measurements by two observers ( n=42) were −0.09 and 0.09 mm. Measurements performed at 21°C and 34°C were not significantly different, as analysed by paired Student's t-test ( p=0.19). Pearson's correlation coefficient between ultrasonic and microscopic measurements was 0.90. Analysis of all measurements from both observers at both temperatures yielded a sound velocity in enamel of 6.5×10 3 m/s (standard error 0.1×10 3 m/s). Conclusions: It was concluded that the ultrasonic measurement of the enamel thickness is feasible without enamel preparation.

Indirect evidence for ecophenotypic plasticity in radular dentition of Littoraria species (Gastropoda: Littorinidae)

In examination of radulae from all but one of the 36 species of the littorinid genus Littoraria we found extraordinary intraspecific variation in those occurring on a range of substrates. Radulae from rock showed a less well developed ‘hood’ on the rachidian tooth, a strikingly enlarged major cusp on each of the five central teeth, fewer cusps on the outer marginal teeth and the radular ribbon was longer, when compared with radulae of conspecifics from plant substrates. The radulae of species found exclusively on rock differed in similar ways from those restricted to plant substrates (mangroves, driftwood and saltmarsh). We suggest that this may be an example of phenotypic plasticity of radular form, induced by substrate and/or diet, as recently shown experimentally in another littorinid genus. The mechanism of inducible plasticity deserves further study. Ecotypic variation in the radula may be widespread in littorinids, and radular characters should therefore be used with caution in studies of taxonomy, phylogeny and adaptation.

Normal faciolingual inclinations of tooth crowns compared with treatment groups of standard and pretorqued brackets

Faciolingual inclinations of tooth crowns were measured on plaster casts of normal occlusions and posttreatment orthodontic models of treated cases. Normal anatomic occlusion, standard edgewise and Roth bracket groups of 10 subjects were examined for a change in torque values. On study models, crown inclinations of right and left central teeth to second molar in the upper and lower dental arches were measured to the functional occlusal plane and mean tooth inclinations were calculated. In normal occlusion group, upper central and lateral teeth inclined lingually, lower central teeth inclined slightly labially and lower lateral teeth inclined lingually but the standard deviations of mean values for upper and lower anterior teeth were high. Upper posterior teeth, from canine to molar, had a lingual inclination and lower posterior teeth had a progressively increasing lingual inclination from lateral to molar teeth. In treatment groups, upper central and lateral teeth had labial crown inclination and lower molar teeth had more lingual inclination as compared with the normal occlusion group. No significant variation was found between the mean torque values of standard and Roth treatment groups. (Am J Orthod Dentofac Orthop 1997;112:50-7.)

The relationship of the incisive papilla to the maxillary central incisors and canine teeth in Southern Chinese

A photographic technique was used to measure anatomic landmarks located on dental casts. The relationship of the maxillary anterior teeth to the incisive papilla in a Southern Chinese population living in Hong Kong was studied. The distances from the labial surface of the central incisors to the midpoint and the posterior border of the incisive papilla were measured. The area on the incisive papilla where the intercanine line crossed was noted. The data obtained were compared with those from previous studies of Caucasians. Results show that there is little difference between the Southern Chinese in this study and most other ethnic groups. The guidelines that use the incisive papilla as a reference for the setting of artificial teeth in denture construction recommended for Caucasians can be applied to Southern Chinese patients.

Detection of two coexisting species of Oxystele (Gastropoda: Trochidae) by morphological and electrophoretic analyses

Oxystele variegata (Anton, 1838) is one of the commonest intertidal topshells on the coast of South Africa. In this study we show that the so‐called O. variegata actually consists of two sympatric species, which differ in shell colour patterns, in the proportions of the central tooth of the radula, and in the electrophoretic mobilities of some enzymes: O. impervia (Menke, 1843) (which tends to occur higher up the shore), and O. variegata (Anton, 1838) (occurring further down the shore).The shell of O. impervia has a pattern of dark red, orange, yellow or brown maculations, on a ground colour that is red, orange, yellow or brown, respectively; that of O. variegata has a pattern of red maculations or lines on a ground colour that is either off‐white, or greenish‐grey. Both O. impervia and O. variegata exhibit an immense variety of shell colours and pattern and in both, shell colour variation is an interplay between two factors: ground colour and maculated spiral bands. By expanding the maculated spiral bands in breadth, at the expense of the ground colour, an original shell pattern of spiral bands may be transformed into one of axial or diagonal stripes.The radula of both species resemble the typical trochid pattern. They are, however, consistently different: the central tooth of the radula of O. imperial usually has a shallow base and a cusp that is slightly indented, whereas that of O. variegata usually has a deep base, and a well indented cusp.Further differences between the species were revealed by electrophoretic studies. Of six loci examined, two were found to be taxonomically diagnostic. Another two had at least one species‐specific allele at a frequency of 0·1 or greater, and significant heterogeneity in allelic frequency between the two species was found in the four non‐diagnostic loci.The differences in shell colour patterns, radular tooth structure and enzyme mobilities support the conclusion that O. impervia and O. variegata are separate but closely related species, with similar geographic distributions and an overlapping zonation.