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PubMed2004

Wide faces or large canines? The attractive versus the aggressive primate.

Hominids display marked body size dimorphism, suggestive of strong sexual selection, yet they lack significant sex differences in canine size that are commonly associated with intrasexual competition in primates. We resolve this paradox by examining sex differences in hominoid facial morphology. We show that chimpanzees, but not gorillas, exhibit clear sexual dimorphism in face width, over and above that expected based on sex differences in body size. We show that this facial dimorphism, expressed as an index, is negatively correlated with canine dimorphism among anthropoid primates. Our findings suggest that a lack of canine dimorphism in anthropoids is not owing to weak sexual selection, but rather is associated with strong sexual selection for broader face width. Enlarged cheek-bones are linked with attractiveness in humans, and we propose that the evolution of a broad face and loss of large canines in hominid males results from mate choice.

Animals↗
PubMed2003

Evolution, climatic change and species boundaries: perspectives from tracing Lemmiscus curtatus populations through time and space.

To provide empirical evidence of species boundaries and the role of climatic change in affecting evolution, we documented evolution of the sagebrush vole, Lemmiscus curtatus, through hundreds of thousands of years by following populations from the middle Pleistocene to the present. We found that: (i) extant representatives of the species culminate a morphological transition that was initiated within an unusually arid and warm interglacial period, perhaps related to the shift from glacial-interglacial cycles dominated by a 41,000 year periodicity to those dominated by a 100,000 year rhythm; and (ii) sympatry of extant and extinct morphotypes persisted for more than 800,000 years. This exceptionally detailed tracing of extinct populations into extant ones suggests that species such as the one we studied are real entities in space, that their boundaries become fuzzy (although potentially diagnosable) through time and that unusual climatic warming may initiate significant evolutionary change manifested at the morphological level.

Animals↗
PubMed2005

Morphological evolution, ecological diversification and climate change in rodents.

Among rodents, the lineage from Progonomys hispanicus to Stephanomys documents a case of increasing size and dental specialization during an approximately 9 Myr time-interval. On the contrary, some contemporaneous generalist lineages like Apodemus show a limited morphological evolution. Dental shape can be related to diet and can be used to assess the ecological changes along the lineages. Consequently, size and shape of the first upper molar were measured in order to quantify the patterns of morphological evolution along both lineages and compare them to environmental trends. Climatic changes do not have a direct influence on evolution, but they open new ecological opportunities by changing vegetation and allow the evolution of a specialist like Stephanomys. On the other hand, environmental changes are not dramatic enough to destroy the habitat of a long-term generalist like Apodemus. Hence, our results exemplify a case of an influence of climate on the evolution of specialist species, although a generalist species may persist without change.

Analysis of Variance↗
PubMed2004

Climate change and size evolution in an island rodent species: new perspectives on the island rule.

As stated by the island rule, small mammals evolve toward gigantism on islands. In addition they are known to evolve faster than their mainland counterparts. Body size in island mammals may also be influenced by geographical climatic gradients or climatic change through time. We tested the relative effects of climate change and isolation on the size of the Japanese rodent Apodemus speciosus and calculated evolutionary rates of body size change since the last glacial maximum (LGM). Currently A. speciosus populations conform both to Bergmann's rule, with an increase in body size with latitude, and to the island rule, with larger body sizes on small islands. We also found that fossil representatives of A. speciosus are larger than their extant relatives. Our estimated evolutionary rates since the LGM show that body size evolution on the smaller islands has been less than half as rapid as on Honshu, the mainland-type large island of Japan. We conclude that island populations exhibit larger body sizes today not because they have evolved toward gigantism, but because their evolution toward a smaller size, due to climate warming since the LGM, has been decelerated by the island effect. These combined results suggest that evolution in Quaternary island small mammals may not have been as fast as expected by the island effect because of the counteracting effect of climate change during this period.

Animals↗
PubMed2004

A comparison between clearing and radiographic techniques in the study of the root-canal anatomy of maxillary first and second molars.

AIM: To compare a clearing technique with conventional radiography in studying certain features of the root-canal system of maxillary right first and second molars. A secondary aim was to assess interexaminer agreement for these features using radiographs. METHODOLOGY: Eighty-three recently extracted permanent maxillary right first molars and 40 recently extracted maxillary right second molars from an Irish population were included. Standard periapical radiographs were taken from a buccolingual and mesiodistal direction. The specimens were then decoronated, demineralized in 10% hydrochloric acid for 8 days and then cleared using methyl salicylate. The cleared teeth were examined using a dissecting microscope (x20), and data relating to number of roots, canal type following Vertucci's classification, presence of lateral canals, presence of transverse anastomoses and position/number of apical foramina were collected. The radiographs were examined by two independent trained endodontists using an X-ray viewer and a magnifying lens (x2) in a dark room for the same features studied using the clearing technique. RESULTS: The Kappa values for the agreement between the radiographic examiners A and B and the clearing technique and between the two examiners for the number of roots were 0.60, 0.64 and 0.53; for the root-canal type, 0.37, 0.41 and 0.42; for the number of roots with lateral canals, 0.21, 0.18 and 0.14; and for the transverse anastomoses, 0.29 for radiographic Examiner A. Radiographic Examiner B did not feel capable of accurately recognizing transverse anastomoses from the radiographs. For the position/number of apical foramina, the Kappa values were 0.33 and 0.24, respectively. In general, the Kappa values were low to modest for all comparisons. CONCLUSIONS: It is concluded that the agreement between the two radiographic examiners and the agreement between either radiographic examiner and the clearing technique were poor to moderate, indicating the limited value of radiographs alone when studying certain aspects of the root-canal system.

Dental Pulp Cavity↗
PubMed2004

The accuracy of electronic working length determination.

AIM: To determine in vivo the accuracy of two impedance quotient apex locators under clinical conditions. METHODOLOGY: Electronic working length determination was carried out before extraction in 79 human teeth with 93 root canals. In 51 root canals, the determination was performed using the apex locator Justy II(R) (Hager & Werken, Duisburg, Germany); in 42 canals, the apex locator Endy 5000(R) (Loser, Leverkusen, Germany) was used. A root canal instrument was fixed at working length with composite material prior to extraction followed by the exposure of a radiograph. After histological preparation of the apical region, the teeth were examined under a light microscope. The distance of the file tips to the target intervals 'minor foramen - major foramen' and 'apical canal constriction' was determined. These values were compared with the calculated working lengths, determined by radiographic assessment. The data were statistically analysed by a paired t-test. RESULTS: For both apex locators and both target intervals, no significant differences between the electronic and radiographical assessments were recorded. The probability of determining the area between minor and major foramen was 82.4% for Justy II and 81% for Endy 5000. However, accurate determination of the apical constriction was only successful in 51% (Justy II) and 64.3% (Endy 5000) of canals. Variation of the inaccurate measurements was higher for Endy 5000 than for Justy II. CONCLUSIONS: Under clinical conditions, it is possible to determine the region between the minor and major apical foramen with electronic length measuring devices (ELD). However, use of these devices does not result in precise determination of the apical constriction.

Adult↗
PubMed2004

Accuracy of the Justy II Apex locator in determining working length in simulated horizontal and vertical fractures.

AIM: To study the effectiveness of an electronic apex locator (EAL; Justy II; Yoshida Dentcraft, Tokyo, Japan) in locating simulated horizontal and vertical fractures in single roots. METHODOLOGY: An EAL was used to measure the distance within the canal of horizontal (n = 31) and vertical (n = 31) fractures, created with a disk in single-rooted teeth. Accuracy of the EAL was evaluated by comparing the measurements with those made using a size 10 file. Data were analysed with the non-parametric Passing and Bablok method. RESULTS: For simulated horizontal fractures, the EAL measured exactly the same length as a size 10 file, without constant or proportional errors. In vertical simulated fractures, the EAL measured (on average) with a constant error of 7.5 mm shorter than the size 10 file; the difference had a wide confidence interval (-72.3 to 2.6 mm). CONCLUSIONS: In this laboratory study, the Justy II EAL was able to determine accurately the position of simulated horizontal fractures, but was unreliable when measuring simulated vertical fractures.

Dental Instruments↗
PubMed2004

Toxicity of concentrated sodium hypochlorite used as an endodontic irrigant.

AIM: To present a clinical case that illustrates the toxicity of concentrated sodium hypochlorite (NaOCl) on vital tissues. SUMMARY: The severe clinical consequences of extruding concentrated NaOCl into the periradicular tissues during root canal irrigation are described. After diagnosis of external resorption in tooth 34, endodontic treatment was initiated. Following irrigation with a concentrated NaOCl solution, a rapidly developing swelling and haematoma were visible. During the next few days, an extensive bruise and local necrosis of the oral mucosa developed. After healing of the involved tissues, the canal was prepared and obturated. At this time, no clinical symptoms remained. KEY LEARNING POINTS: * The use of concentrated NaOCl as a root canal irrigant might cause severe clinical problems when extruded into vital tissues. * The present report confirms the known toxicity of NaOCl to soft tissues following inadvertent extrusion. * To avoid extrusion, it is always prudent to confirm the length and integrity of the root canal system before irrigating with concentrated solutions.

Dental Pulp Cavity↗
PubMed2004

Influence of orthodontic movement on root length of autotransplanted immature third molars.

The aim of this study was to investigate the influence of orthodontic extrusion or derotation on final root length and root length increment in 75 autotransplanted immature third molars. Depending on the condition of the recipient site and the root morphology, transplants had to be placed in extreme rotated or infra-occluded position. Three to six months after transplantation, these transplants were derotated to a correct position in the dental arch (derotation group, n = 19) or extruded to the occlusal plane (extrusion group, n=18). Thirty-eight transplants with no orthodontic treatment need served as controls (control group). Transplants were followed clinically and radiologically for a mean period of 4.0 yr. No statistically significant differences were observed between the extrusion and the control groups or between the single-rooted transplants in the different groups. In contrast, multi-rooted transplants in the derotation group showed a statistically significantly shorter final root length than multi-rooted transplants in the extrusion and the control groups. However, as these differences may be considered to be of minor clinical importance (<1 mm), it can be concluded that the effect of orthodontic movement on root development of transplanted immature third molars is of only negligible clinical significance.

Adolescent↗
PubMed1992

Variables affecting electronic root canal measurement.

This study was conducted in two parts. In the first part, 20 single-rooted teeth that had been scheduled for extraction were investigated. The electronic root canal lengths were measured in vivo with a Dental Sono-Explorer type Y-III, and the actual canal lengths were measured after extraction of the teeth. The rate of agreement of the two measurements was 77.5% within a range of +/- 0.5 mm, while it was 100% at +/- 2.0 mm, which is acceptable clinically. In the second part, there were 19 simulated canals whose lengths and apical foramen sizes were known beforehand. Experiments revealed a negative correlation between the areas of the apical foramina and the difference between the electronic and the actual root canal lengths. This relationship was shown by the linear regression equation: ŷ = 0.6-1.6x. With the exception of the smallest areas of foramina, electronic root canal length measurements were less than the actual lengths.

Analysis of Variance↗
PubMed1992

Comparison of three imaging techniques for assessing endodontic working length.

The accuracy of endodontic working length estimation was investigated using three imaging techniques: radiography (Rd), Xeroradiography (Xr) and Radiovisiography (RVG positive and negative prints). An in-vitro model of extracted single straight roots, mounted in wooden blocks with wax, was employed in the study. Optimum exposures were established for each of the imaging techniques. The magnification of the images was measured and the resolution of the RVG images was also investigated. Comparable Rd (D-speed film), Xr,RVG positive and RVG negative images were made of five roots with size 10 files in situ. Images of 10 standard files were made, ranging from 2.0 mm through the root apex to 2.5 mm short of the apex, resulting in 200 images. Six observers each assessed the working distance on 100 images, measuring the distance from the apical foramen to the file tip. After allowing for the magnification of the images, these results were compared with the 'true' file tip to apical foramen (measured with the aid of a reflex microscope). The inaccuracy of working distance estimations was considered to be of clinical significance (> 0.5 mm) in 6% of measurements made from Rd and Xr, 19.2% of measurements from RVG negative and 32.3% from RVG positive images. In addition, 14% of RVG images were too poorly defined to be assessed. The first-generation RVG system was used in this study. It was therefore concluded that the most accurate estimates of working distance were made from Xr and Rd images, and that RVG images, particularly the RVG positive images, were the least accurate and most difficult to read.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗