SciCombinator

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Concept: Incisor

271

Multi-level fission-fusion societies, characteristic of a number of large brained mammal species including some primates, cetaceans and elephants, are among the most complex and cognitively demanding animal social systems. Many free-ranging populations of these highly social mammals already face severe human disturbance, which is set to accelerate with projected anthropogenic environmental change. Despite this, our understanding of how such disruption affects core aspects of social functioning is still very limited.

Concepts: Human, Species, Sociology, Mammal, Primate, Complex number, Hippopotamus, Incisor

177

The aim of the study was to test the hypothesis that the gene defect causing congenital absence of maxillary lateral incisors also causes narrowing of the dentition. A total of 81 patients with one or two congenitally missing lateral incisors were retrieved; 52 (64.2 per cent) patients presented bilateral agenesis, whereas 29 (35.8 per cent) had unilateral agenesis. The control group consisted of 90 consecutively treated patients. The largest mesiodistal crown dimension for all teeth, except for the maxillary second and third molars, was measured on plaster casts using a digital caliper to the nearest 10th of a millimetre. Statistical testing was performed using the analysis of variance model (P < 0.05) to test for differences in the mesiodistal dimension between the sample and the control group. Significance has been assessed using a P-value threshold level of 5 per cent. Agenesis of maxillary lateral incisors was found to be a significant predictor of tooth size. Patients who were missing maxillary lateral incisors had smaller teeth compared to control subjects, except for the maxillary right and left first molars. This finding was true for both unilateral and bilateral lateral incisor agenesis. Interaction between maxillary lateral incisor agenesis and gender was not significant. Patients with congenitally missing lateral incisors have narrower teeth than patients without any dental anomalies, except for maxillary first molars. A higher prevalence of microdontic contralateral incisors was found in patients with unilateral agenesis with respect to the control group.

Concepts: Teeth, Analysis of variance, Molar, Incisor, Maxillary central incisor, Canine tooth, Maxillary lateral incisor, Mandibular lateral incisor

138

The first histological study of an entire hadrosaurid dental battery provides a comprehensive look at tooth movement within this complex structure. Previous studies have focused on isolated teeth, or in-situ batteries, but this is the first study to examine an entire dental battery of any dinosaur. The absence of direct tooth-to-tooth contact across the entire battery and a unique arrangement of the dental tissues in hadrosaurids led us to compare their teeth with the ever-growing incisors of mammals. The similarity in the distributions of tissues along the incisor, coupled with continuous eruption, make for helpful comparisons to hadrosaurid teeth. The mammalian ever-growing incisor can be used as a model to extrapolate the soft tissue connections and eruptive mechanisms within the hadrosaurid dental battery. Serial sections across the adult dental battery reveal signs of gradual ontogenetic tooth migration. Extensive remodeling of the alveolar septa and the anteroposterior displacement of successive generations of teeth highlight the gradual migration of tooth generations within the battery. These eruptive and ontogenetic tooth movements would not be possible without a ligamentous connection between successive teeth and the jaws, underscoring the dynamic nature of one of the most unique and complex dental systems in vertebrate history.

Concepts: Tissues, Mammal, Tissue, Rodent, Teeth, Incisor, Dinosaur, Hadrosaurid

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Background: Topography and fascicular arrangement of the inferior alveolar nerve (IAN) can provide critical information for the estimation of damage to IAN based on patient symptoms, or conversely to evaluate the symptoms resulting from injury to the IAN. Purpose: The fascicular composition and organization of the IAN were determined to confirm the microarchitecture of the IAN bundles into each of the mandibular teeth, including the composition of the mental nerve. Materials and Methods: The IAN within the mandibular canal (MC) was examined in 30 hemifaces of embalmed Korean cadavers. Results: The most common patterns of nerve fascicle innervation to the mandibular teeth could be grossly classified into three: (1) the superior buccal portion of the IAN innervating the molars, (2) the superior portion innervating the premolars, and (3) the superior lingual or the superior lingual and inferior lingual portions in the posterior MC and the lingual portions in the anterior MC, innervating the incisors and canine. The buccal two-thirds portion of the IAN was composed of the mental nerve. Conclusion: The IAN had distinctive fascicular organizations, which make it possible to forecast the degree, location, and extent of nerve damage according to presenting symptoms.

Concepts: Cranial nerves, Teeth, Mandibular nerve, Incisor, Canine tooth, Inferior alveolar nerve, Mandibular canal, Mental nerve

29

Abstract Objective. The purpose of this study was to evaluate the effect of mechanical and chemical surface treatment methods on the bond strength of resin cement to fiber post. Materials and methods. The roots of 36 maxillary central incisor teeth were mounted in auto polymerized acrylic resin blocks (10 × 15 mm) and the root canals were enlarged with the drills of post system (2.1 mm width, 12 mm length). Thirty-six fiber posts were randomly assigned to one of the following surface conditioning methods: silane coupling agent, methylene chloride etching, 24% hydrogen peroxide etching, air abrasion with 50 µm Al(2)O(3), 1-3 µm synthetic diamond particles and silica coating with 30 µm SiO(x). Fiber posts were cemented to the root canals with adhesive resin cement (Panavia F 2.0). Three slices of 1.5 mm thick were obtained from each root. Push-out tests were performed with a universal testing machine. The data were analyzed with one-way analysis of variance (ANOVA) and Tukey HSD tests (α = 0.05). The effect of the surface treatments were examined under a scanning electron microscope (SEM) and surface roughness were evaluated with a profilometer. Results. Surface pre-treatment methods affected the bond strength (p < 0.05). The highest bond strengths were obtained by air abrasion with synthetic diamond particles, the lowest bond strength were obtained by etching with methylene chloride (p < 0.05). Conclusion. Mechanical surface pre-treatment methods showed higher bond strength values than chemical methods. Synthetic diamond particles may be an alternative method to increase resin cement bonding on the quartz fiber post surfaces.

Concepts: Electron, Oxygen, Materials science, Analysis of variance, Scanning electron microscope, Tests, Incisor, Maxillary central incisor

28

Skulls (n = 1,205) of southern sea otters were examined macroscopically according to defined criteria. The museum specimens, acquired from strandings, varied in age from juvenile to adult, with an equal sex distribution. The results from all young adult and adult specimens were pooled according to tooth type. Ninety-two percent of teeth were available for examination, with 6.5% artifactually absent, 0.6% deemed absent due to acquired tooth loss and 0.03% deemed congenitally absent. All teeth were normal in morphology, except for three pairs of fused teeth, including two instances of fused maxillary first incisor teeth. Supernumerary teeth were associated with 97 normal teeth (most commonly maxillary canine teeth) in 68 specimens. At least one persistent deciduous tooth was present in six skulls, two of which were from adults. The majority (94.6%) of alveoli, either with or without teeth, were not associated with bony changes consistent with periodontitis; however, the majority (74.4%) of specimens did have at least one tooth associated with mild periodontitis. The mesial root of the mandibular third premolar tooth was the most common location at which periodontal hard tissue lesions were observed (56.6%). Ten sea otters had lesions consistent with focal enamel hypoplasia. Approximately half of the teeth (52.0%) were abraded; almost all adult specimens (98.1%) contained at least one abraded tooth, while fewer young adults were affected (76.4%). Tooth fractures were uncommon, affecting 1,343 teeth (4.5%). Periapical lesions were associated with 409 teeth (1.3%) in a total of 176 specimens, and these would likely have caused considerable morbidity while the animals were alive.

Concepts: Teeth, Tooth development, Incisor, Canine tooth, Maxillary lateral incisor, Premolar, Sea otter, Deciduous teeth

27

External cervical resorption is the loss of dental hard tissue as a result of odontoclastic action; it usually begins on the cervical region of the root surface of the teeth. This case report demonstrates an external cervical resorption in a maxillary central incisor of a 24-year-old male patient. After surgical intervention and root canal treatment, the resorption was subsequently sealed with mineral trioxide aggregate. The 18 months follow-up demonstrates no pathological changes on clinical and radiographic examination. This case report presents a treatment strategy that might improve the healing outcomes for patients with external cervical resorption.

Concepts: Hospital, Mammal, Teeth, Endodontic therapy, Endodontics, Incisor, Maxillary central incisor, Maxillary lateral incisor

27

Objective: The purpose of this case report is to introduce a minimally invasive microsurgical technique for the treatment of the necrotic, immature apex tooth in adult patients and to provide treatment recommendations. Method and Materials: A 43-year-old male patient was diagnosed with chronic apical periodontitis associated with a necrotic, immature apex of the maxillary central incisor. A minimally invasive microsurgical approach was applied for the treatment of the periapical disease. The crown of the immature apex tooth was left intact. Results: The 1-year follow-up radiograph revealed uneventful healing of the periradicular lesion while soft tissue healing was optimal. Conclusion: The minimally invasive microsurgical technique may provide a viable solution for the survival of challenging necrotic, immature apex tooth cases in adults. Proper case selection is mandatory for the success of this technique.

Concepts: Scientific method, Medical terms, Tissues, Minimally invasive, Case study, Soft tissue, Teeth, Incisor

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OBJECTIVE: Determine the differences in skeletal and dental maxillary expansion as evidenced by the degree of dental tipping and if this is symmetrical or not. METHODS: Sixty-two patients who were diagnosed as requiring maxillary expansion treatment were recruited over an 18-month period. Patients were randomly allocated into three groups where a total of three to four cone-beam computerized tomographies (CBCT) were obtained throughout a one-year period depending on the group allocated. Landmarks used were from the first and second molars and premolars of the maxilla. For each of the eight teeth, three landmarks were identified: the root apex, alveolar bone and pulp chamber. Statistical analysis consisted in the use of MANOVA and after significant overall effects were detected, the univariate repeated measures results were analyzed along with separate ANOVA for each variable at each of the four time points. RESULTS: There was strong overall significance for time, group, and time*group. The first and second molars saw both bone- and tooth-anchored treatment groups with significantly different dental inclination than the control group. For the second premolars, only the tooth-anchored group was significantly different from control. The tooth-anchored group was also significantly different than the control group in the first premolar measurements. For the analysis of asymmetry in dental inclination, no significant time, group, or time*group effects were seen overall. CONCLUSION: The analysis provided evidence that dental tipping does occur in the molars for both RME treatments, while the premolars showed increased tipping in the tooth-anchored, but not the bone-anchored group.

Concepts: Scientific method, Symmetry, Teeth, Analysis of variance, Incisor, Canine tooth, Premolar, Maxillary first premolar

27

- Primary tooth impaction is a rare phenomenon when compared to permanent teeth impaction. The purpose of this report is to present a 5-year-old Chinese girl who exhibited impaction of tooth 51, its unusual consequence on the permanent successor tooth and its comprehensive management. Her parents revealed that at 6 months of age, the patient had fallen from her bed and struck her face on the floor; however, there were no teeth present in the oral cavity. The intraoral examinations identified a bony-like projection on the buccal aspect of the alveolus in the 51 region. Radiographic examination revealed that tooth 51 exhibited an unfavourable orientation, with the crown directed towards the palate. Therefore, the impacted tooth 51 was surgically removed, and two years later tooth 11 erupted into the oral cavity with an indentation on its incisal aspect, which resembled the crown of the primary teeth, thus giving the appearance of a tooth within a tooth or ‘dens in dente’. Subsequently, enameloplasty and composite resin build-up was performed on tooth 11 for aesthetic reasons. It is very unusual to have the clinical crowns of both primary and permanent teeth in such close proximity within the alveolar bone, and the present case is a good example to emphasize that trauma to the primary teeth is of considerable importance due to the close proximity of the primary teeth to permanent tooth germs.

Concepts: Teeth, Incisor, Maxillary central incisor, Canine tooth, Maxillary lateral incisor, Deciduous teeth, Permanent teeth