Accessory Cones Research Articles

New insights into the retinal microstructure-diurnal activity relationship in the African five-lined skink (Trachylepis quinquetaeniata) (Lichtenstein, 1823)

BackgroundThe retinae of diurnal vertebrates have characteristics. Most lizards are strictly diurnal, and their retinal morphology is still unknown.Materials and methodsThe retina of the African five-lined skink (Trachylepis quinquetaeniata) was studied using light and transmission electron microscopy.ResultsThe retina's ten layers were all detected. The inner nuclear layer was the thickest by an average of 67.66 μm, and the inner plexiform layer was 57.564 μm. There were elliptical, long cylindrical, and spherical melanosomes (small and large) in the pigment epithelial layer of the retina. The cylindrical melanosomes had a large area on the lateral surfaces of cones to increase light scatter absorption. The photoreceptor layer of the retina had cones only. There were single and double cones, with the double cones consisting of principal and accessory cones. The cones had inner and outer segments separated by oil droplets. A spherical paraboloid body existed between the limiting membrane and the ellipsoid. All single cones had a paraboloid, and double cones had a large paraboloid in the accessory cone. The presence of paraboloids and large ellipsoids with mitochondria of varying sizes may have helped focus the light on cone segments.ConclusionThe African five-lined skink's eye was light-adapted due to a variety of retinal specializations related to the demands of its diurnal lifestyle in its environment.

Evaluation of filling ability of Guttaflow Bioseal sealer to the simulated lateral canal by scanning electron microscope

Background and objectives: Lateral canals establish a connection between the main root canal and periodontal ligament. Any necrotic tissue and bacteria residing in the lateral canals influence the efficiency of the filling of the root canal and the outcome of root canal therapy. The aim of this study was to determine which type of root canal sealer among GuttaFlow Bioseal, AH-Plus and Endosequence BC sealer provides deeper penetration into artificially prepared lateral canals. Methods: Thirty mandibular first premolars with single canals and mature roots were instrumented using Protaper universal rotary system after decoronation and standardisation of length (12mm). Three lateral canals were prepared in the coronal, middle and apical thirds in each root (at 3, 6, and 9 mm) using #15 engine-driven reamer. The specimens were divided into three groups (n = 10), according to the filling material, (I): Guttaflow Bioseal seal, (II): AH Plus sealer, (III): Endosequence Bioceramic sealer. In all groups, specimens were obturated using the corresponding Protaper universal gutta-percha and accessory cones. Specimens in each group were cross sectioned. Depth of sealer penetration was measured using a scanning electron microscope. Results: The data were subjected to ANOVA and Tukey’s HSD tests, with significance level of 5%. There was no difference among the tested sealers for filling the lateral canals. Concerning the positions of lateral canals, no differences were also found among sealer types, except for middle portion (at 7 mm from the apex); statistically there is a significant difference between three types of sealer (P value= 0.05), where GuttaFlow Bioseal showed a significantly greater penetration depth than AH Plus sealer.

Management of Traumatic Inflammatory External Root Resorption

Inflammatory external root resorption is one of the major complications after traumatic dental injury. It is characterized by the loss of mineralized dental tissue which may, ultimately, result in loss of the tooth. However, with appropriate treatment, prognosis for these teeth may be greatly improved, by preventing or arresting resorption. This is a case report of an 18-year-old male patient presented with root canal treated maxillary central incisors associated with pain; with history of trauma. Radiographic examination revealed periradicular lesion and associated pathologic resorption of the apical region of the root with respect to 11 and calcification of the root canal with inadequate obturation with respect to 21. After removal of the root canal filling, 11 was disinfected with intracanal double antibiotic paste. After 2 weeks, antibiotic dressing was removed, and apical third was sealed with mineral trioxide aggregate (MTA). Canal was obturated with custom-fit gutta-percha and accessory cones with AH plus sealer and restoration was done with composite resin. Retreatment was also done with respect to 21 and obturated with custom-fit gutta-percha. Both teeth were restored with E-max crown. No clinical symptoms were apparent, significant osseous healing of the periradicular region was observed with arrest of external root resorption with respect to 11 and no periapical changes were apparent with respect to 21 on subsequent follow-up.

Theoretical distribution of gutta-percha within root canals filled using cold lateral compaction based on numeric calculus.

This study aimed to present a new method based on numeric calculus to provide data on the theoretical volume ratio of voids when using the cold lateral compaction technique in canals with various diameters and tapers. Twenty-one simulated mathematical root canal models were created with different tapers and sizes of apical diameter, and were filled with defined sizes of standardized accessory gutta-percha cones. The areas of each master and accessory gutta-percha cone as well as the depth of their insertion into the canals were determined mathematically in Microsoft Excel. When the first accessory gutta-percha cone had been positioned, the residual area of void was measured. The areas of the residual voids were then measured repeatedly upon insertion of additional accessary cones until no more could be inserted in the canal. The volume ratio of voids was calculated through measurement of the volume of the root canal and mass of gutta-percha cones. The theoretical volume ratio of voids was influenced by the taper of canal, the size of apical preparation and the size of accessory gutta-percha cones. Greater apical preparation size and larger taper together with the use of smaller accessory cones reduced the volume ratio of voids in the apical third. The mathematical model provided a precise method to determine the theoretical volume ratio of voids in root-filled canals when using cold lateral compaction.

Management of Oehlers Type II Dens in Dente with Open Apex and Alveolar Bone Defect.

A 22-year-old male patient was referred to Department of Conser-vative Dentistry and Endodontics with a chief complain of pus discharge in upper left teeth region. Clinical examination showed oedema, sinus opening and pus discharge in relation to maxillary left central incisor, which did not respond to thermal tests (heat and cold) but responded positively to palpation and percussion [Table/Fig-1a,b]. On radiographic examination the upper left central incisor showed a bulbous root associated with open apex and periapical radiolucent area. It clearly showed that there was a tooth within a tooth extending nearly up to the root apex [Table/Fig-1c]. A clinical diagnosis of dens in dente Type II with open apex was made. The treatment options were discussed with the patient and informed consent was obtained. The treatment plan consisted of removal of dens in dente followed by root canal treatment, periapical surgery, retrograde filling of root with MTA and bone graft for regeneration of lost periodontal tissue. With rubber dam isolation the dens in dente was carefully separated and removed with help of a diamond bur and ultrasonic tips [Table/Fig-1d-f]. The canal was instrumented circumferentially and enlarged. Chlorhexidine was used as an irrigant as use of sodium hypochlorite carried the risk of extrusion into the periapical region through the open apex. Calcium hydroxide-iodoform paste (Metapex) was used as intra-canal medicament and the canal was obturated with gutta-percha cones after seven days when the patient was asymptomatic. Rest of canal was laterally condensed using accessory cones, and the access cavity was sealed with non-eugenol temporary cement (Cavit, 3M ESPE). After this under local anaesthesia, a mucoperiosteal flap was reflected and severe osseous destruction was observed on facial surface of tooth #21 [Table/Fig-2a]. After thorough debridement of the periapical osseous defect, a canal template was placed inside the canal and the defect was repaired with Resin Modified Glass Ionomer Cement [Table/Fig-2b]. Apex was sealed with MTA (ProRoot MTA, Dentsply) and the large osseous defect was filled with hydroxyapatite bone graft (G-bone, Surgiwear) covering the defect surface [Table/Fig-2c]. Flap was repositioned and sutured with 3-0 silk non-resorbable interrupted sutures [Table/Fig-2d]. Written post-operative instructions were given, antibiotics and analgesics were prescribed for one week. Patient was monitored on weekly schedule post-operatively, to ensure good oral hygiene. Sutures were removed after 10 days and tooth was restored with fiber post and nano-hybrid composite (Coltene Whaledent) [Table/Fig-3a-3e]. Oral hygiene instructions were reinforced, and patient was kept on maintenance for 3 months to re-evaluate this area. At subsequent follow-up examinations tooth was asymptomatic and post-operative radiograph after one year revealed complete healing in peri-radicular region [Table/Fig-3f,g].

New records of late Holocene tephras from Lake Futalaufquen (42.8°S), northern Patagonia

In regions with limited knowledge of the historical volcanic record, like remote areas in the Andean Southern Volcanic Zone, the definition of reliable age-depth models for lake sequences represents a valuable tool for tephra layers dating. In Lake Futalaufquen (42.8°S), Northern Patagonia, a short sedimentary sequence was extracted after the AD 2008 Chaitén eruption with the purpose to analyze the records of volcanic eruptions at these poorly studied latitudes. The sequence was dated by 210Pb, 137Cs, and 14C techniques. Five tephras were identified for the last 1600 years, restricted to the last 5 centuries. Sedimentology, morphology, and geochemical properties allowed the characterization of the tephras and their correlation with tephras recently identified proximal to the sources, mainly from Chaitén and Huequi volcanoes, and Michinmahuida accessory cones, representing the first distal records reported of these tephras. Furthermore, tephras modeled ages obtained by the sequence age-depth model shrink the ages for the volcanic events, like a potential cycle of activity from Michinmauida accessory cones during AD 1530 ± 55, one eruption from Huequi volcano at AD 1695 ± 50, and a possible recent eruption from Chaitén at AD 1775 ± 40. Additionally, the work contributes to improve the regional volcanic records knowledge, basic for volcanic hazard assessment.

Radiographic evaluation of the quality of root canal obturation of single-matched cone Gutta-percha root canal filling versus hot lateral technique

Aim: The aim of this study is to evaluate radiographically the quality of root canal filling in mesiodistal and buccolingual view when comparing matched cone condensation and warm lateral Gutta-percha condensation using system B heating instrument in a low-heat warm lateral condensation technique in0 vitro. Materials and Methods: A total of 40 mandibular premolars with straight single canals were divided into two groups with 20 each. The root canals were shaped by hand file and Revo-S rotary files to size (25, 0.06) at the end point, then they filled by Gutta-percha cone and meta-seal sealer. In group A, a single matched cone technique was used to fill the root canals. In group B, a hot lateral condensation using system B instrument at 101°C was performed. Result: The result of this study showed no significant difference in density of Gutta-percha fill in apical and coronal two-third when comparing matched cone root canal filling and hot lateral technique (P > 0.05). The only significant difference (P < 0.05) was in matched cone between buccolingual and mesiodistal view in the coronal two-third. Conclusion: Within the limitation of this study, single matched cone technique has a good density in the apical one-third as that of the hot lateral technique so it may be used for filling narrow canals. In the coronal two-third of the root canal, single matched cone technique showed inferior density of root canal filling which can be improved by using accessory cones Gutta-percha in wide canal.

Single-cone obturation technique: a literature review

The technique of single-cone obturation is a technique that uses only the master cone. There have been an increase in its use, especially by employing larger cones with larger taper sizes that best match the geometry of rotary nickel-titanium systems (NiTi), not requiring the use of accessory cones, thus reducing the time spent in endodontic obturation. Objective: To review the literature on this technique and to compare it with other existing techniques, as well as to elucidate its advantages and disadvantages. Literature review: The single-cone obturation technique enables an easier and faster endodontic obturation. However, regarding to the aspects such as the obturation quality, apical microleakage and bacterial penetration, this technique is similar to or lower than others. Conclusion: This technique has the advantage of saving time during the filling of the root canal. However, further studies are necessary to evaluate its prognosis, especially in canals with complex anatomy.

Golgi meet Cajal: coupling and feedback at retinal photoreceptors

Photoreceptors not only transduce and relay light signals, they also receive a dazzling array of synaptic input from the retinal network including electrical and chemical synaptic signals from other photoreceptors, lateral feedback from horizontal cells, and long range feedback from interplexiform cells. In this issue of The Journal of PhysiologyGao et al. (2013) quantitatively tackle the interplay between some of these circuits. Gap junction coupling in the retina is pervasive and perplexing. It starts at the first cell layer, the photoreceptors, and is observed in every cell type as visual signals travel through this network. In a tissue designed for acuity, photoreceptor coupling could blur images and dampen signals. Instead, evidence indicates that coupling reduces noise and leads to an increase in both gain and dynamic range: an engineering marvel (Attwell et al. 1987). Coupling can be either homotypic (rod–rod, cone–cone) or heterotypic (rod–cone). Rods are high sensitivity, low resolution light detectors where strong homotypic coupling has clear advantages in improving dim light communication. Furthermore, heterotypic coupling allows rods to pass signals through the cone circuitry with a shift in sensitivity that expands the dynamic range of rod vision (Bloomfield & Dacheux, 2001). Gao et al. (2013) have now presented detailed measurements of this heterotypic coupling in salamander retina. Studies over several decades, often emanating from this laboratory, have made this animal a model system. In addition to the previously described strong heterotypic coupling of a subset (∼20%) of salamander rods, there is also coupling of variable strength with all cone subtypes. The coupling is linear and symmetrical. The rod–cone coupling is less than rod homotypic coupling, ranging from approximately half in the strongly coupled rod subset to about 10% in principal double cones. Surprisingly, the coupling is not under circadian control, unlike fish or rodents, although it is altered by background illumination. But in addition to sign-conserved coupling, Gao et al. (2013) explore the unidirectional ‘sign-inverting’ synapse from rods to cones (Attwell et al. 1983). They found that this feedback, generated by B-type horizontal cells, affects all but accessory cones (these receive A-type horizontal cell feedback). Surprisingly, the horizontal input to cones induces a chloride current, mediated by a glutamate transporter. A similar glutamate-gated channel has been described in bipolar cells, where it is an autoreceptor that suppresses transmitter release (Veruki et al. 2006). At the photoreceptor feedback synapse the mechanism may be more complex because it has to compete with glutamate release from photoreceptors and the potential stimulation of metabotropic receptors. The synaptic calcium channel that induces photoreceptor glutamate release is also under the direct control of horizontal cells. A further complication is that the chloride reversal potential sits slightly below the cone's dark membrane potential, instead of the more negative potential in bipolar cell terminals. Thus, while horizontal cell depolarization linked to surround responses hyperpolarizes and/or reduces transmitter release from cones, this B-type horizontal cell pathway may depolarize cones. The horizontal cell input would occur at light offset and oppose the effect of rod–cone coupling. As the authors suggest, horizontal cell lateral pathways are diverse and involve activation of multiple mechanisms. There is no shortage of candidates, including feedback by pH, GABA and ephaptic synapses (Thoreson & Mangel, 2012). And if unexpectedly glutamate is the transmitter, what role does this leave for GABA found in B-type horizontal cells? The report of Gao et al. (2013) fills in many of the gaps, but (Gao et al. 2013) the saga of horizontal cell feedback continues and you know that with the introduction of a new set of characters the story will not end soon.

Effect of disinfectant solutions on gutta‐percha and resilon cones

The aim of this study was to evaluate the effects of the 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and MTAD solutions on the surface of gutta-percha and Resilon cones by using atomic force microscopy (AFM). Accessory cones were washed and dried. The cones were randomly divided into six groups: gutta-percha immersed in NaOCl, CHX, and MTAD, and Resilon immersed in NaOCl, CHX, and MTAD. AFM images of the same area were made in different periods of time. JPK™ Image Processing Software was used to evaluate the images. The parameters used to evaluate the changes were RMS and line profiles. No statistically significant change was observed in the RMS values. The line profiles detected changes only for gutta-percha surfaces after immersion in NaOCl and MTAD solutions. In conclusion, 5.25% NaOCl and MTAD are associated with local changes in surface roughness of gutta-percha cones. No change was observed when 2% CHX was used. The use of all tested solutions did not produce any changes on Resilon surface.

Comparison of apical sealing ability of laterally compacted gutta percha versus single cone compaction technique using nickel titanium rotary system - An in vitro study

Objective - To study, measure and compare the apical sealing ability of laterally compacted gutta percha using 2% gutta percha with 2% accessory cones , 6% gutta percha with 2% accessory cones with single cone compacted ProTaper gutta percha point corresponding to ProTaper preparation, using fluorescent dye penetration technique. Study Design: 79 extracted human mandibular premolars were collected and disinfected. They were divided into 25 teeth each in 3 experimental groups and 2 teeth each in positive and negative control group. Biomechanical preparation was done using ProTaper rotary system. Group I and II were obturated with 2% and 6% gutta percha cones along with 2% accessory cones using lateral compaction technique. In group III single cone compaction with ProTaper gutta percha cone was done. 2 teeth instrumented but not obturated were used as positive control whereas 2 teeth obturated and sealed completely with nail varnish served as negative control. All the specimens were immersed in Rhodomine 6G fluorescent dye for 48 hours, and then teeth were sectioned longitudinally. Apical leakage was measured under a fluorescent microscope. Results - Data obtained was subjected to statistical analysis using Anova Test and Tukey's HSD test, it showed statistically significant difference in apical leakage among the single cone obturated ProTaper gutta percha points and the laterally compacted 2% and 6% gutta percha points, with no statistically significant difference seen between laterally compacted 2% and 6% gutta percha. Conclusion - Under the limitations of the present study single cone compaction using ProTaper gutta percha points corresponding to its respective preparation provided a better apical seal than the laterally compacted 2% and 6% gutta percha.

Temperature Changes in Gutta-Percha and Resilon Cones Induced by a Thermomechanical Compaction Technique

Introduction The aim of this study was to assess temperature changes in conventional gutta-percha, thermoplastic gutta-percha, and Resilon cones by using thermomechanical compaction technique. Methods The root canals of extracted human teeth were placed in resin blocks and sectioned. After root canal preparation, cavities perforating the lingual wall were prepared at 4 and 8 mm from the apex, and K-type thermocouples coupled to a digital temperature meter were inserted until reaching the root canal. After placement of the main cone and accessory cones of each material assessed, a #45 thermomechanical compactor was used at 10,000 rpm. Data were analyzed by using analysis of variance and Tukey test for paired comparisons ( P < .05). Results A significant difference was observed between initial and maximum temperatures (mean increase, 5°C–8°C) with all materials ( P < .05). The 3 materials showed similar temperature changes ( P > .05). Changes in the apical third were higher when compared with the cervical third ( P < .05). Conclusions Our results suggest that gutta-percha and Resilon present similar temperature changes during thermomechanical compaction.

Morphological changes in the retina in Pacific ocean salmon Oncorhynchus masou fry in response to neutralization of the geomagnetic field in conditions of normal illumination

The studies reported here provide the first demonstration that retinal responses in both the fry of the migratory salmon trout Oncorhynchus masou and the dwarf form of this species changed in conditions of experimental neutralization of the geomagnetic field (GMF); migratory salmon trout fry and dwarves showed different changes. The responses of different types of retinal photoreceptor in migratory salmon trout fry to neutralization of the GMF differed: while rods and double cones perceived neutralization of the GMF as the onset of darkness (the scotopic reaction), single (generally blue-sensitive) cones responded to neutralization of the GMF both as presentation of blue light or (very rarely) ultraviolet irradiation. The retina of dwarf male salmon trout responded to neutralization of the GMF with a double response: rods showed a light (photopic) response, while double (red/green-sensitive) cones produced dark (scotopic) responses. Single (blue-sensitive) cones responded to neutralization of the GMF as bright blue light. Thus, the morphological picture of the retina in dwarf male salmon trout in these experimental conditions corresponds to the perception of blue light. The initial conditions were different--normal diffuse daylight with a brightness of about 7.5 Lx. It is likely that neutralization of the magnetic field had no effect on rods, while double, red-green, cones responded as to darkness, i.e., the fish did not perceive red or green light in the visible spectrum, but perceived only blue and, possibly, ultraviolet light by means of central blue-sensitive and accessory cones. Thus, these experiments demonstrated that in conditions of normal daylight illumination, retinal photoreceptors in salmon fry respond to changes in the earth's magnetic field, i.e., objectively function as magnetoreceptors.

Isolation of chick retina cones and study of their diversity based on oil droplet colour and nucleus position

The chick retina has four morphological cone types that differ not only in shape, but also in the visual pigment in the outer segment, in the colour of the oil droplet in the inner segment and in synaptic connectivity. Neither the type of droplet nor the visual pigment has been definitively established for the four cone types. The main aim of the present work has been the isolation of entire live photoreceptors in order to study the oil droplet colour in each cone type and to quantify each type. We have improved an earlier retinal cell isolation method and obtained large numbers of entire cones. Principal cones (27% of the cones) possess a yellow or colourless droplet. Accessory cones (27% of the cones) all contain a small pale green droplet. Straight cones (44% of the cones) have a red, orange, yellow, or colourless droplet. Oblique cones (1.66% of the cones) all have a colourless droplet. We have found that straight cones with a red, orange, or yellow droplet differ in terms of the position of the nucleus and their percentage and conclude that they are distributed in three rows in the outer nuclear layer (ONL) of the central retina. Our study of 4,6-diamidino-2-phenylindole-stained retinal sections has revealed three rows of nuclei instead of the two currently thought to form the ONL. Together, our results show a larger cone diversity than previously known, suggest a larger functional diversity and provide an efficient method for isolating entire chick photoreceptors.

Comparison of first accessory cone penetration after using stainless-steel and ni-ti spreaders in curved resin blocks.

The purpose of this study was to compare first accessory gutta-percha penetration after the use of nickel-titanium (Ni-Ti) or stainless-steel spreaders in curved resin blocks. Forty resin blocks with 30º and 45º curvatures (20 blocks for each) were prepared and #30 master cones were placed in canals. In part one, under 20 Newton pressure, Ni-Ti or stainless-steel spreaders were placed alongside the master cone and their penetration was measured with a millimeter ruler. In part two, after removing the spreader, one of the accessory cones (#15, #20 or MF) was substituted in the canal and its penetration was measured. The Mann-U Whitney test was used for the final evaluation. In both curvatures, the penetration of Ni-Ti spreaders were significantly more than stainless-steel spreaders (p<0.005). Penetration of the first accessory cones (#15 and MF) in Ni- Ti spreader group were also significantly more than stainless-steel group (p<0.05) (in both curvature groups). This study showed that Ni-Ti spreaders and #15 accessory cones penetrated deeper in curved canals than stainless spreaders and #15 accessory cones. Therefore, the use of NiTi spreader in lateral condensation technique is suggested for better results.

Sealing properties of two contemporary single‐cone obturation systems

To compare the sealing of root canals filled with two single-cone obturation systems and a warm vertical compaction technique. Forty-two single-rooted teeth were decoronated to obtain 17-mm-long root segments. The root canals were cleaned and shaped to size 40, 0.06 taper and filled with: (i) warm vertical compaction with AH Plus (control); (ii) ActiV GP and (iii) GuttaFlow with single master cones. Leakage was evaluated by fluid filtration at 10 psi before root resection, and after 3, 6, 9 and 12 mm apical resections. Repeated measures anovas on ranks and Dunn's multiple comparison tests were performed to examine differences in fluid flow rates amongst different resection lengths for each filling technique. The surface and interior aspects of glass-ionomer filler-coated ActiV GP gutta-percha cones was evaluated with SEM. No statistical difference amongst the filling techniques was seen at 0 and 3 mm root resections. ActiV GP and GuttaFlow exhibited more leakage than AH Plus at 6, 9 and 12 mm resections. AH Plus recorded the best overall results. A nonhomogeneous coating of glass-ionomer fillers on the surface of ActiV GP cones was detected. The two single-cone techniques examined are as effective in sealing the apex as AH Plus when the latter was used with warm vertical compaction. It is further hypothesized that the inferior coronal seal of these single-cone techniques may be improved with the placement of accessory cones to reduce sealer thickness or an immediate coronal adhesive restoration.

Improving the Performance of EndoREZ Root Canal Sealer With a Dual-cured Two-Step Self-etch Adhesive. II. Apical and Coronal Seal

This study tested the hypothesis that the seal of EndoREZ may be improved with an adhesive-modified technique. Instrumented single-rooted teeth were filled with: (a) Warm vertical compaction with AH Plus (control); (b). EndoREZ with master cones and passive application of accessory cones; (c) Application of Clearfil Liner Bond 2V before EndoREZ and gutta-percha condensation. Leakage was assessed by fluid filtration at 10 psi before root resection and after 3 to 12 mm apical resections. Statistical analyses revealed significant differences in filling technique and resection lengths. EndoREZ exhibited significantly higher overall leakage, while no difference was found between AH Plus and the adhesive-modified EndoRez technique. Apical resection of EndoREZ to 12 mm exhibited more leakage than all other interactions, but was not significantly different from the same material resected to 9 mm. Although EndoREZ exhibited an acceptable apical seal, its coronal seal may be improved with the use of a dual-cured self-etch adhesive.

Putative ultraviolet-photosensitivity in the retina of 1-year-old nibbler Girella punctata: Based on molecular and histological evidences

Ultraviolet (UV) photosensitivity in 1-year-old nibbler Girella punctata, which inhabits the coastal reefs of Japan, was investigated, based on retinal histology and visual pigment cDNA cloning. The retinal cone mosaic of the nibbler showed a square-shaped arrangement of double cones with a central single cone and accessory corner cones, which are representative putative UV-photoreceptors, at each corner of the square. Six cDNA fragments encoding putative visual pigment of nibbler were isolated and sequenced. Its deduced amino acid sequences were classified into five classes of opsin: UV, blue, green (one gene each), red (two genes), and rod (one gene) by comparison with other teleost opsins and phylogenetic analysis. Possible contributions of UV-sensitivity in nibbler was discussed regarding homing, feeding, and schooling.

The effect of using an inverted master cone in a lateral compaction technique on the density of the gutta-percha fill.

We sought to measure and calculate the percentage of the gutta-percha-filled area in the apical root canal after the use of a standardized or inverted master cone in cold lateral compaction.Study design Two groups of extracted mandibular premolars with a single canal were instrumented with instruments of the same size; furthermore, they were obturated with laterally compacted gutta-percha cones with AH26 used as a sealer. In the first group, a standardized master cone was used with its narrow end in an apical position, whereas in the other group, an inverted master cone was used with its wide end in an apical position. The 2 master cones had the same apical diameter and fit in the apical canal. After lateral compaction, horizontal sections were cut at a level 3 and 5 mm from the apex of each filled tooth. Photographs of the sections were taken by using a microscope equipped with a digital camera; the photos were then scanned as tagged-image file format images. The cross-sectional area of the canal and the gutta-percha were measured by using an image-analysis program. The percentage of gutta-percha-filled area was calculated. At both levels, the inverted master cone produced a significantly higher percentage, statistically, of gutta-percha-filled area than did the standardized master cone (P =.001 at 3 mm; P =.012 at 5 mm). The use of an inverted master cone in cold lateral compaction may facilitate the apical placement of accessory cones, significantly increasing the volume of gutta-percha while reducing the volume of sealer in the apical root canal.

Lateral Condensation in Canals Prepared with Nickel Titanium Rotary Instruments: An Evaluation of the Use of Three Different Master Cones

Forty-five single-rooted teeth were instrumented with ProFile ISO .06 nickel-titanium rotary instruments and obturated with lateral condensation using three different master cones: an ISO-standardized gutta-percha cone (group A), a Dia-ISO(GT).06 gutta-percha cone (group B), and a size medium gutta-percha cone (group C). Obturation efficiency in each group was evaluated by recording the number of accessory cones utilized. To evaluate obturation quality in the three groups, a cross-sectional observation of the ability of the gutta-percha in each group to obliterate the prepared canal space was carried out. Results showed that obturation efficiency was significantly greater in groups B and C than in group A. There was no significant difference in obturation quality between any of the three groups.