Lingual Face Research Articles

Intraoral Radiographic Study of the Pulp Cavity of the Shortfin Mako Shark (Isurus Oxyrinchus).

The shortfin mako shark (Isurus oxyrinchus) is a large pelagic predator that inhabits coastal and ocean waters. It has several teeth arranged in rows that run from the rostral to the lingual face. These teeth are in several stages of maturation, where the teeth closest to the rostral face are more mature and functional and the teeth closest to the lingual face are still in development. The tooth supply of the shark is unlimited throughout its life. The mechanism of tooth replacement follows that, when the front teeth are discarded physiologically, the posterior teeth replace it. This study us used a head and dental arch of I. oxyrinchus. Intraoral radiographs were obtained with the aim to show details of the pulp cavity. The study concluded that the pulp diameter varies according to the stage of dental maturation.

Dento-alveolar trauma rehabilitation using fixed prosthesis: clinical case report

Dental trauma is an unexpected, accidental event and requires immediate emergency attention. There are several etiological factors and almost any collision between the face and an object can result in a dental trauma. Objective: The objective of this study is to report a case of dento-alveolar trauma and its dental management, promoting the patient's well-being, restoring health, function and aesthetics. Case report: A 20-year-old male patient came to the dental clinic of CEUNI - FAMETRO complaining of dissatisfaction with his broken tooth after a sports collision. Intraoral clinical examination revealed a large coronary loss below the gingival level in element 15, leaving only the buccal and lingual faces. In the initial radiographic examination, it was verified the presence of an endodontic treatment already performed, but endodontic retreatment was necessary, due to exposure and contamination of the filling material. The treatment plan proposed to the patient consisted of rehabilitation with an intraradicular retainer and then the cementation of a ceramic crown. Conclusion: The study concluded that the rehabilitation with the use of an intraradicular retainer, the fiberglass pin and the metal-free ceramic crown also obtained good results. Thus, it was observed that these materials were able to return the functionality of the tooth, oral health and aesthetics with a natural aspect to the element, the patient reported that he was very satisfied with the final result of his treatment.

A new janassid (Chondrichthyes, Petalodontiformes) from the Late Mississippian of Alabama, USA

ABSTRACT Teeth from the late Mississippian Bangor Limestone, Monteagle Limestone, and Pride Mountain Formation (early to middle Chesterian = late Viséan–early Serpukhovian) of northern Alabama, USA, are designated as Cavusodus whitei, gen. et sp. nov. The species is similar to Cypripediodens cristatus Duffin and Ward, known only from the Eyam Limestone Formation (Mississippian, late Viséan) of Derbyshire, England. Cypripediodens cristatus, the only species of the genus, is distinguished by teeth having an elongate crown, an apical cusp having a nearly circular cross-section, a secondary cusp on the lingual face, and several cristae on the lingual heel. Cavusodus whitei teeth resemble those of Cypripediodens cristatus but differ in lacking the secondary cusp, in having a more labiolingually compressed apical cusp, in possessing more robust lingual cristae, and in possessing a longitudinal groove on the labial face. The genera comprising the Janassidae are reconsidered. It is proposed that only Janassa, Cholodus, and Cypripediodens be retained, in addition to the new genus. urn:lsid:zoobank.org:pub:DB68190C-E9E6-48C7-B5A7-8A72D174CBCE

Un nouveau cas de façonnage dentaire intentionnel au Néolithique pour le dolmen A4 de la nécropole de Chenon (Charente, France)

We report the case of a new type of dental shaping practiced post-mortem on two lower canines belonging to an individual who had been deposited in the main corridor of the double megalithic monument called A4 passage-grave of the Neolithic Necropolis at Chenon (Charente, France). The main purpose of the present study based on ESEM microscopic observation of human teeth was to examine the trimming process used to shape these teeth. The ESEM observations were performed at different magnifications (30X, 100X, 200X, 500X) on the fractured lingual face, near the CEJ, near the pulp cavity and on the edge of the crown. The tooth shaping was done symmetrically on the two canines, from top to bottom of the lingual side, halfway up the crown, from the mesial face to the distal face, descending a little lower than the CEJ under the gum. A polishing of the exposed surface completed the proceeding. This type of teeth shaping has not been listed until now within the classifications of canine shaping. Known trimmed canines are either pyramid-shaped or L-shaped and observed from Neolithic period to Iron age in Spain.

Tratamento cirúrgico de frenectomia lingual: Relato de caso

Anquiloglossia, também conhecida popularmente como ¨língua presa¨ é uma anomalia congênita, definida como uma prega mediana localizada no dorso da língua e próximo ao assoalho bucal, que se estende até face lingual da crista alveolar. É constituído por pregas da membrana mucosa, tecido conjuntivo rico em fibras colágenas e elásticas, tecido gorduroso e fibras musculares, além de vasos sanguíneos protegidos por tecido epitelial pavimentoso estratificado. Tem a função de auxiliar na movimentação tridimensional da língua, deglutição, dicção e sucção. Nos casos de alterações congênitas, observa-se limitações dos movimentos linguais, interferências periodontais, ortodônticas, protéticas, além da socialização. A indicação cirúrgica geralmente é diagnosticada por dentistas, fonoaudiólogos e pediatras, podendo ser tratada cirurgicamente em qualquer idade através de técnicas convencionais e outras técnicas descritas na literatura, com auxílio de lâminas frias, eletrocautérios ou laser cirúrgico. O objetivo desse trabalho é relatar o caso de frenectomia lingual de um paciente do gênero masculino de 15 anos de idade.

Correlation between the transverse dimension of the maxilla, upper airway obstructive site, and OSA severity.

Acquiring a better comprehension of obstructive sleep apnea physiopathology can contribute to improving patient selection for surgical treatments. We hypothesize that maxillary transverse deficiency restricts the space available for the tongue, leading to upper airway obstruction during sleep. Our primary hypothesis was that maxillary transverse deficiency increases the prevalence of tongue collapse during drug-induced sleep endoscopy (DISE). The secondary hypothesis was that maxillary transverse deficiency will also increase the prevalence of circumferential collapse at the velopharynx. The exploratory hypothesis was that maxillary transverse deficiency is associated with increased obstructive sleep apnea severity. The objectives of this study were to correlate maxillary morphometric measurements with (1) the anatomic level of obstruction during DISE and (2) the apnea-hypopnea index on polysomnography. We made a cross-sectional analysis of patients with obstructive sleep apnea undergoing DISE in search of positive airway pressure alternative treatment. Maxillary measurements were collected from a computed tomography scan (interpremolar distance, intermolar distance [IMD] and sella-nasion A point angle), findings from DISE, and sleep study variables from polysomnography. Correlation between computed tomography, DISE, and polysomnography data was assessed using Pearson's correlation, and receiver operating characteristic curves were determined for each facial measurement. Sixty-nine patients were included in the study. The group with velopharyngeal circumferential collapse had mean IMD = 26.30 mm (25.5-31.45), and the group with anteroposterior collapse had mean IMD = 29.20 mm (26.8-33.10; P = .040). The group with complete tongue-base obstruction had mean interpremolar distance = 26.40 mm (25.1-28) and IMD = 26.30 mm (25.6-28.4), and the group without obstruction had mean interpremolar distance = 28.7 mm (27.2-30; P = .003) and IMD = 34.06 mm (32.1-37; P < .001). The receiver operating characteristic curve determined an IMD cutoff of 29.8 mm for predicting tongue-base obstruction. The maxillary transverse deficiency, identified by reduction in interpremolar distance and IMD, predicted the occurrence of complete tongue-base obstruction, complete concentric collapse at the velopharynx, and multilevel obstruction during DISE. We did not find an association between the maxillary measurements and obstructive sleep apnea severity. These associations hold some promise in ultimately supplanting insights previously available only through DISE.

Archaeogaia macachaae gen. et sp. nov., one of the oldest Notoungulata Roth, 1903 from the early-middle Paleocene Mealla Formation (Central Andes, Argentina) with insights into the Paleocene-Eocene south American biochronology

In this contribution, we report the discovery of Archaeogaia macachaae gen. et sp. nov., one of the oldest notoungulate recovered from the upper section of Mealla Formation in the Tonco Valley (Northwestern Argentina, Salta Province). The new material consists on a left mandibular fragment with damaged m1 and complete m2-3. Archaeogaia macachaae is characterized by the following combination of features: m1 slightly shorter than m2 and both larger than m3; brachydont molars; talonid mesio-distally shorter than trigonid; metaconid slightly taller than protoconid and distally placed; reduced paraconid in m2; metalophid straight in m2–3, but it runs mesially forming a slightly obtuse angle in the labial edge in m2, whereas it is more transverse in m3; transverse entolophid; mesial cingulid extending from the middle to the lingual face of molars; and distal cingulid connecting the hypoconulid with the mesial face of the entoconid on m2–3. We perform a phylogenetic analysis based on a data matrix composed of 147 craniodental characters and 70 taxa. The analysis yields 6104 most parsimonious trees of 423 steps each. In the strict consensus previously well-supported clades collapse into a polytomy; and Archaeogaia is positioned within the order Notoungulata based on two synapomorphies: a) presence of a transverse entolophid, and b) lower cheek teeth with short mesio-distal protolophid, transverse metalophid and mesio-distal hypolophid slightly convex labially. The former character was recovered as a synapomorphy for Notoungulata in several previous studies. According to the reduced consensus, Archaeogaia occupies different positions within the order; these fluctuating locations could be the result of the presence of plesiomorphic features in the holotype, and the absence of the structures that define the notoungulate clades in which the new taxon is located. The paleomagnetic data indicates that the Mealla Formation was deposited during Chron 27r to the base of Chron 26r (latest Danian-earliest Selandian). In this context, we discuss the finding of Archaeogaia, and the age of Mealla Formation in the South American biochronology.

Skeletal Anatomy, Phylogenetic Relationships, and Paleoecology of the Eocene Urolophid Stingray Arechia Crassicaudata (Blainville, 1818) from Monte Postale (Bolca Lagerstätte, Italy)

ABSTRACT In this paper we re-examine the taxonomy and systematic position of the Eocene stingrays from Bolca Lagerstätte which are traditionally assigned to Urolophus crassicaudatus (Blainville). The analysis of their tooth morphology supports an assignment to the Eocene stingray genus Arechia Cappetta, a taxon known from isolated teeth from the Ypresian-Lutetian of northern and western Africa. The teeth of the Bolca specimens differ from the type species A. arambourgi in some characters (i.e., labial face with concave profile just below the crest, convex lower down; lingual face slightly more developed than the labial, with convex profile in its upper part and a concave profile in its mid-lower region) that justify the recognition of a second species within the genus, i.e., A. crassicaudata. This taxon also shows a unique combination of features (e.g., pectoral disc large and rhomboid; tail short, 44–52% of total length; ca. 238 vertebral centra; distal segment of propterygia located between mouth and antorbital cartilage; mesopterygium single, not fused to radials; 100–117 pectoral radials; 15–17 pelvic-fin radials; elongated caudal fin of aplesodic type) that supports its sister-group relationship with the living urolophids Urolophus and Trygonoptera. Arechia was a typical inhabitant of the near coastal and warm habitats that characterize the Monte Postale paleoenvironment. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

Influence of different restorative material and cement on the stress distribution of ceramic veneer in upper central incisor.

Considering new ceramic systems, doubts about the appropriate combination of ceramics and cement are common. To evaluate the influence of the elastic modulus (E) of cement agents associated with different indirect veneers on the stress distribution using finite element analysis. The finite element analysis was applied to evaluate the stress distribution on the structures. For that, a computer-aided design software was used for a three-dimensional (3D) modeling of an upper central incisor with preparation for an indirect veneer. The model was imported into the analysis software in STEP (Standard for Exchange of Product data) format. Tetrahedral elements formed the mesh. Solids were considered isotropic, linearly elastic, homogeneous, and with ideal contacts. Load application (100N, 45°) occurred on the lingual face. Cement agents have their E classified as low, intermediate, and high. The ceramic materials used were a hybrid ceramic, a zirconia reinforced lithium silicate and a lithium disilicate. It was observed that none of the factors significantly influenced the stress concentration in dentine. Groups with high E cementing agent showed the highest stress peaks. The E of restorative material was significant for the stress generated in the veneer, and groups with hybrid ceramic presented more homogeneous stress results. The higher E of the cement agent and the ceramic, the higher the stress concentration, suggesting that hybrid ceramic associated with low elastic modulus resinous cement has superior biomechanical behavior.

ATYPICAL FIBROUS DYSPLASIA—CASE REPORT

MJC, 56-year-old woman with melanoderma, attended the clinic of stomatology to evaluate the increase of volume in the jaw discovered in routine examination. The intraoral examination found a volume increase in mandible body region of molars in the lingual face, which was painless and covered by an integrated and normochromic mucosa. The diagnostic hypotheses were fibro-osseous lesion and osteoma. A cone beam computed tomography was performed, where a mixed-aspect image with expansion and preservation of the cortical bone was observed. It was also possible to observe that the base of bone implantation of the lesion was pediculated. An incisional biopsy was performed with osteoplasty. The fragments were sent for histopathologic examination. The report was of fibrous dysplasia, with an extremely atypical clinical and radiographic aspect. The patient continues to be clinically and radiographically asymptomatic, with no complaints, signs of exacerbation of the condition, or involvement of other skeletal bones.

Efficacy of virginiamycin for the control of periodontal disease in calves

ABSTRACT: Periodontal diseases are multifactorial infectious processes caused by complexes of microorganisms, with damage to health, production, and animal welfare. The aim of the present study was to evaluate the efficacy of virginiamycin in the prevention and control of two early forms of periodontal disease: gingivitis and necrotizing gingivitis. Ten weaned calves, aged four to six months, were permanently kept in a single lot under the same rotational grazing regime in a newly reformed area of Panicum maximum. Five of the calves were orally administered 340mg of virginiamycin (Virginiamycin Group) daily for a period of 18 weeks, while the remaining five calves (Control Group) remained under the same food management but did not receive virginiamycin. During this period, animals underwent 18 weekly evaluations regarding periodontal health, with monitoring and recording of clinical parameters of the eight deciduous incisor teeth on the labial and lingual faces. At approximately two-week intervals, nine collections of subgingival sulcus material from five sites of the four right incisor teeth of each animal were performed and subjected to microbiological evaluation using polymerase chain reaction with primers of 25 microorganisms considered potentially pathogenic. After 1440 periodontal clinical evaluations of incisor teeth of the 10 calves, a total of 395 episodes of gingivitis were recorded, of which 267 occurred in the Control Group and 128 in the Virginiamycin Group. Similarly, 89 episodes of necrotizing gingivitis were recorded; 58 in the Control Group and 31 in the Virginiamycin Group. Comparison of between-group means found significant differences for teeth with gingivitis and necrotizing gingivitis (t test; p&lt;0.05). The total number of teeth with gingivitis (p&lt;0.01) and necrotizing gingivitis (p&lt;0.01) in Control Group was significantly higher than that of gingivitis (p&lt;0.01) and necrotizing gingivitis (p&lt;0.05) in the Virginiamycin Group. There was a positive correlation between total occurrence of gingivitis and necrotizing gingivitis in the Virginiamycin Group by Pearson’s test. Virginiamycin had a protective effect on treated animals compared with the Control Group (OR = 0.36: CI (95%) = 0.27-0.43). In the Control Group, Actinomyces israelli (4.74%), domain Archaea (1.58%), Eikenella corrodens (1.05%), Fusobacterium nucleatum (27.37%), class Mollicutes (5.26%); Porphyromonas endodontalis(5.26%); Porphyromonas gulae(0.53%), Prevotella buccae (6.32%), Prevotella loescheii (3.68%), Prevotella nigrescens (8.42%), Prevotella oralis (1.58%), Tannerella forsythia (0.53%), and Treponema denticola (4.21%) were detected at healthy sites, and gingivitis or necrotizing gingivitis samples. In the Virginiamycin Group, A. israelli (3.41%), domain Archaea (0.98%), F. nucleatum (9.27%), class Mollicutes(4.39%), P. endodontalis (4.39%), P. gulae (0.49%), P. buccae (8.29%), P. loescheii (6.83%), P. nigrescens (15.61%), P. oralis (1.46%), Selenomonas sputigena (0.49%), T. forsythia (0.49%), and T. denticola (2.44%) were detected. In conclusion, virginiamycin administered at a dosage of 340mg/animal/day significantly reduced the occurrence of gingivitis and necrotizing gingivitis in cattle maintained on reformed pastures, and was revealed to have action against periodontal bacterial microbiota considered to be potentially pathogenic.

Prolagostomus amplus Ameghino is a Junior Synonym of the Patagonian Rodent Pliolagostomus notatus Ameghino (Chinchillidae; Early Miocene, Santa Cruz Formation)

Chinchillidae is a group of caviomorph rodents that includes the extant Chinchilla, Lagidium and Lagostomus. The latter genus, with a single living species (Lagostomus maximus), is grouped in the subfamily Lagostominae together with the extinct Eoviscaccia (Early Oligocene-Early Miocene), Prolagostomus (Early-Middle Miocene) and Pliolagostomus (Early-Middle Miocene). The Lagostominae are represented in the Santa Cruz Formation (late Early Miocene of Santa Cruz Province, Argentina) by Pliolagostomus notatus and eight species of Prolagostomus. One of these species of Prolagostomus, “Prolagostomus amplus”, was originally characterized by having all lower cheek teeth of the same size. The holotype and referred material of “Prolagostomus amplus” do not show some of the characters commonly used to distinguish Prolagostomus from other lagostomines (e.g. molars with sinuous hypoflexus/hypoflexid, anterior and lingual face of the lower molars not forming a marked angle, laminar third lobe of the M3 posteriorly or posterolingually oriented), instead, they share with Pliolagostomus notatus the presence of straight hipoflexus/hipoflexid in all cheek teeth, anterior and lingual face of the lower molars forming a marked angle, third lobe of the M3 subtriangular and lingually oriented, mental foramen dorsolaterally located. Therefore, we consider that “Prolagostomus amplus” is a synonym of Pliolagostomus notatus.

Influence of 10% sodium ascorbate gel application time on composite bond strength to bleached enamel

Objective To analyze bond strength to bleached enamel following application of 10% sodium ascorbate gel. Material and methods Forty third molars were allocated into five groups (n = 8): GP – unbleached specimens restored with composite resin; GN – specimens restored immediately after bleaching; and G15; G30 and G60 (test groups) – bleached specimens treated with 10% sodium ascorbate gel for 15, 30 and 60 min before restoration. The teeth were sectioned and the buccal and lingual faces were restored. After storage in distilled water (37 °C/24 h), sticks of ±0.8 mm2 were tested in tensile (0.5 mm/min). Fractures were observed and classified. Data (in MPa) were analyzed with one-way ANOVA and Tukey tests (α = 0.05). Results No differences were found among GP (26 ± 6.0), G15 (23 ± 7.3), G30 (25 ± 6.1) and G60 (25 ± 5.1), with GN (15 ± 5.5) showing the lowest bond strength (p < 0.0001). Conclusion The application of 10% sodium ascorbate gel for 15 min after bleaching with 37.5% hydrogen peroxide restored the bonding to enamel.

Record of &lt;em&gt;Carcharocles megalodon&lt;/em&gt; in the Eastern Guadalquivir Basin (Upper Miocene, South Spain)

Tortonian diatomites of the San Felix Quarry (Porcuna), in the Eastern Guadalquivir Basin, have given isolated marine vertebrate remains that include a large shark tooth (123.96 mm from apex to the baseline of the root). The large size of the crown height (92.2 mm), the triangular shape, the broad serrated crown, the convex lingual face and flat labial face, and the robust, thick angled root determine that this specimen corresponds to Carcharocles megalodon . The symmetry with low slant shows it to be an upper anterior tooth. The total length estimated from the tooth crown height is calculated by means of different methods, and comparison is made with Carcharodon carcharias . The final inferred total length of around 11 m classifies this specimen in the upper size range of the known C. megalodon specimens. The palaeogeography of the Guadalquivir Basin close to the North Betic Strait, which connected the Atlantic Ocean to the Mediterranean Sea, favoured the interaction of the cold nutrient-rich Atlantic waters with warmer Mediterranean waters. The presence of diatomites indicates potential upwelling currents in this context, as well as high productivity favouring the presence of large vertebrates such as mysticetid whales, pinnipeds and small sharks (Isurus). These large vertebrates recorded in the Eastern Guadalquivir Basin were potential prey of C. megalodon .

Rotation axis of the maxillary molar and maximum tooth movement according to force direction

Aim: To evaluate the correlation between the maxillary molar rotation center and the direction of the maximum tooth movement according to the force direction using three-dimensional finite element analysis (3D-FEA). Methods: Computed tomography of a human tooth was used to build a finite element model, which comprised the cancellous and cortical bones, the periodontal ligament and the tooth. After applying lateral and posterior boundary conditions, a 1 N force was applied to the mesial and lingual faces of the maxillary molar to simulate buccal and distal tipping forces on the tooth. Results: The initial displacement of the maxillary first molar was greater for distal tipping than for buccal tipping. The rotation axis for distal tipping in this simulation was located on the furcation of the first molar. For buccal tipping this axis was on the cervical and middle third of the buccal roots of the maxillary first molar. Conclusions: The applied movement interferes in molars Cres location. Higher molar tipping is expected when distal movement is applied rather than buccal movement thanks to the close distance between Cres and location of the force applied to this movement.

Evaluation of the fracture resistance of remaining thin-walled roots restored with different post systems

The purpose of this work was evaluating the fracture strength of bovine roots weakened experimentally, restored with two different techniques: internal reinforcement of root canal walls with composite resin and a cast metal post and core or anatomic post (glass fiber post associated with composite resin). Thirty bovine lower central incisive were selected and transversally sectioned, remaining 14 mm of root in order to approximate to the human maxillary central incisive. A sequence of standardized wear was used to weak the root until the walls remaining achieved from 0.5 to 0.7 mm of thickness at the cervical edge. Two groups were separated randomly (n=15) in order to test the roots reinforced with composite resin associated with cast metal post and core (CMP), or roots restored with composite resin associated to the glass fiber post (GFP). The test were applied in a Universal Test Machine (EMIC) with tangential compressive loading focused on the lingual face of core in an angle of 135° with the long axis of the tooth at a crosshead speed of 0.5 mm/min until failure occurred. The results showed that the fracture strength of remaining roots with weakened walls was influenced by the restorative technique, and the higher values of strength fractures were observed in the group of roots reinforced by composite resin associated with CMP (p&lt;0.001) when compared to the group of roots restored with anatomic post.

Description of a New Species of the Family Echinorhinidae (Chondrichthyes, Elasmobranchii) from the Upper Cretaceous Himenoura Group in Kumamoto Prefecture, Southwestern Japan

Abstract. Many species of the family Echinorhinidae are reported from the Cenozoic, but from the Cretaceous only a few species have been reported. In this paper, a new species, Echinorhinus wadanohanaensis of the family Echinorhinidae, is described from the Upper Cretaceous (Santonian) Hinoshima Formation of the Himenoura Group at Ryugatake-machi in Kumamoto Prefecture, Japan. The species differs from other congeners in having a distally inclined main cusp, the distally directed cusp apex not extending beyond the distal demarcation of the distal heel, no lateral cusplets (basal cusplets), a large principal cusp, no vertical groove in the root, few grooves below the boundary of the enameloid on the lingual face, and being markedly large in size. This is the first report of the family Echinorhinidae from the Santonian as well as the first report of the family Echinorhinidae from the Cretaceous of Japan.

Effects of threaded post placement on strain and stress distribution of endodontically treated teeth

The aim of this study was to evaluate the effect of parallel and tapered threaded post placement on the strain and stress distribution of endodontically treated teeth. Fifteen bovine incisors were sectioned 15 mm from their apices, endodontically treated, and divided into three groups (n=5) according to three different threaded posts: parallel threaded post (Radix-Anker, RA); tapered threaded post (Euro-Post, EP) and tapered threaded post (Reforpost II, RII). A strain-gauge was fixed on the proximal surface perpendicular to the long root axis, 2 mm from the cervical limit. Strain generated during post placement was recorded and compared using one-way ANOVA and Tukey's test (α=.05). A scanning electron microscope was used to examine the longitudinal root sections. Stress was evaluated for each group in a two-dimensional finite element analysis. The models were meshed with tetrahedron elements and loaded with 2 N at an angle of 135° to the lingual face. The equivalent Von Mises stress was calculated. The one-way ANOVA showed significant difference among the groups. The RA group (150.0±12.2 A) produced higher external strain than the RII (80.0±12.2 B) and the EP (70.0±6.1 B) groups. The inner strain was approximately five times greater than the external dentin strain. High stress concentrations in each thread of the posts were observed. Scanning electron micrographs showed cracks that started in the threads of the posts. The threaded post placement induced root strain mainly on the parallel side post. Root strain and stress concentration on the post threads tended to create cracks in the inner root canal dentin.

An early juvenile specimen of Bolong yixianensis (Ornithopoda: Iguanodontia) from the Lower Cretaceous of Ningcheng County, Nei Mongol, China

We describe an early juvenile specimen (ZMNH M8812) of Bolong yixianensis from the Yixian Formation (Lower Cretaceous) of Ningcheng County, Nei Mongol, China. The specimen consists of an almost complete skeleton preserved two-dimensionally on a slab. The short and deep skull proportions and unfused neurocentral sutures in most preserved vertebrae suggest that the ZMNH M8812 is a juvenile individual. Osteohistological study confirms a very early developmental stage. The study reveals the ontogenetic changes of Bolong for the first time. The specimen revealed one additional autapomorphy for Bolong yixianensis: the lingual face of the maxillary crown is bounded by thickened mesial and distal margins and bisected by a prominent median principal ridge. The study revealed the following ontogenetic trends of Bolong: increased tooth rows in both maxilla and dentary, increased robustness of the jugal and scapula, the radius and ulna become more robust and shorter relative to the hindlimb and the metatarsals become proportionally shorter. ZMNH M8812 represents the first juvenile non-hadrosaurid iguanodontian specimen described from the Lower Cretaceous of eastern Asia.

Finite element analysis of stress distribution in anchor teeth in surgically assisted rapid palatal expansion

The treatment of a transverse maxillary deficiency in skeletally mature individuals should include surgically assisted rapid palatal expansion. This study evaluated the distribution of stresses that affect the expander's anchor teeth using finite element analysis when the osteotomy is varied. Five virtual models were built and the surgically assisted rapid palatal expansion was simulated. Results showed tension on the lingual face of the teeth and alveolar bone, and compression on the buccal side of the alveolar bone. The subtotal Le Fort I osteotomy combined with intermaxillary suture osteotomy seemed to reduce the dissipation of tensions. Therefore, subtotal Le Fort I osteotomy without a step in the zygomaticomaxillary buttress, combined with intermaxillary suture osteotomy and pterygomaxillary disjunction may be the osteotomy of choice to reduce tensions on anchor teeth, which tend to move mesiobuccally (premolar) and distobuccally (molar).