Anatomia, Histologia, Embryologia

ORIGINAL ARTICLE

Radiography, Computed Tomography and Magnetic Resonance Imaging of Craniofacial Structures in Pig 1, L. Stehlık4, S. Odehnalova´5 and M. Buchtova 1,2* M. Kyllar1, J. Sˇtembırek2,3, I. Putnova

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Addresses of authors: 1Department of Anatomy and Histology and Embryology, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno, Palackeho 1/3, 612 42, Brno, Czech Republic; Institute of Animal Physiology and Genetics, v.v.i., Academy of Sciences of Czech Republic, Veveri 97, 602 00 Brno, Czech Republic; Department of Oral and Maxillofacial Surgery, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava-Poruba, Czech Republic; Department of Diagnostic Imaging, Small Animal Clinic, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno, Palackeho 1/3, 612 42 Brno, Czech Republic; Sevaron s.r.o., Palackeho 163a, 612 00 Brno, Czech Republic

*Correspondence: Tel.: +420 532 290 157; fax: +420 541 212 988; e-mail: [email protected] With 14 figures Received September 2012; accepted for publication October 2013 doi: 10.1111/ahe.12095

Summary The pig has recently become popular as a large animal experimental model in many fields of biomedical research. The aim of this study is to evaluate the basic anatomical structures in the head region of the pig to lay the groundwork for its practical clinical usage or pre-clinical research in the future. We used three different diagnostic imaging methods: radiography, computed tomography (CT) and magnetic resonance imaging (MRI). The analysis showed that radiographic imaging is suitable only for general evaluation of the facial area of the pig skull. CT images showed excellent spatial definition of bony structures of the whole craniofacial area, and MRI images revealed fine soft tissue details. Radiography is preferentially suited to general assessment of bone structures of the facial skeleton; however, the thick layer of adipose tissue in the craniofacial region of the pig makes the imaging of some parts difficult or even impossible. CT is useful for revealing morphological details of mineralized tissues, whereas MRI is more suitable for soft tissue analysis and the detection of subtle pathologic changes in both bone and soft tissues. Therefore, before using pigs as an experimental model in craniofacial research, it is necessary to evaluate the suitability and disadvantages of potential imaging methods and how appropriate they are for accurate visualization of desired structures.

Introduction The pig has become a favourite biomedical model for human research over the past decade (Bustad and McClellan, 1965, 1966; Bustad, 1966; Millikan et al., 1974; Bermejo et al., 1993; Jacobi et al., 2005; Blagbrough and Zara, 2009; Zheng et al., 2009; Sasaki et al., 2010; Papadaki et al., 2010). Pig oral mucosa were used to study the process of scar-free wound healing (Mak et al., 2009; Larjava et al., 2011) and to understand the drug permeability through individual layers of mucosa (Campisi et al., 2008). Pig models have served to identify regenerative processes after periodontal stem cell application © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

(Sonoyama et al., 2006), dental implantations (Nkenke et al., 2005a,b) or bone renewal (Sun et al., 2010). There are many effective ways to use pig in craniofacial research and detailed information has recently been summarized (Stembirek et al., 2012). Knowledge of diagnostic imaging of porcine anatomy is imperative to characterize abnormal conditions both in clinical and research settings. However, there are few publications on the use of radiography, computed tomography (CT) and magnetic resonance imaging (MRI) in the pig, and they focus on only a few structures (Bustad and McClellan, 1965; Millikan et al., 1974; Wang et al., 1998; Zheng et al., 2009). Here, we describe craniofacial

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Fig. 1. Radiographs of pig skull. (a) Dorsoventral projection, (b) Laterolateral projection. 1 – ramus mandibulae; 2 – processus paracondylaris; 3 – arcus zygomaticus; 4 – corpus mandibulae; 5 – vomer; 6 – bulla tympanica; 7 – os rostrale; 8 – sinus maxillaris; 9 – sinus frontalis rostralis; 10 – sinus frontalis caudalis; 11 – os pterygoideum; 12 – sinus sphenoidalis; 13 – caninus.

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Fig. 2. 3D reconstruction of porcine skull; 2a – rostral view of surface anatomy; 2b – rostral view of the paranasal sinuses; 2c – lateral view of surface anatomy. 1 – os rostrale; 2 – foramen infraorbitale; 3 – foramen supraorbitale; 4 – processus zygomaticus ossis frontalis; 5 – processus frontalis ossis zygomatici; 6 – arcus zygomaticus; 7 – protuberantia occipitalis; 8 – foramina mentalia; 9 – sinus frontalis rostralis medialis; 10 – sinus frontalis rostralis lateralis; 11 – sinus maxillaris; 12 – sinus frontalis caudalis; 13 – ramus mandibulae; 14 – processus coronoideus mandibulae; 15 – foramen lacrimale; 16 – condylus mandibulae; 17 – processus paracondylaris; 18 – condylus occipitalis.

structures and how they can be viewed by different imaging methods, with the aim of filling in this basic missing knowledge.

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Radiographic evaluation is the most common method of diagnostic imaging. The main advantage of this method is its general availability and low cost. Contrain-

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Fig. 3. Transverse computed tomography images of porcine skull – rostral part. (a–c) Transverse sections at the level of vestibulum nasi, (d–e) transverse sections at the level of dens caninus, (f–h) transverse sections from the first to the third premolar 1 – plica alaris; 2 – os incisivum; 3 – os nasale; 4 – concha nasalis ventralis; 5 – processus nasalis ossis incisivi; 6 – symphysis mandibulae; 7 – vomer; 8 – dens caninus; 9 – processus conchalis maxillae; 10 – plica recta; 11 – meatus nasi dorsalis; 12 – meatus nasi medius; 13 – meatus nasi ventralis; 14 – palatum durum; 15 – sinus frontalis rostralis medialis; 16 – canalis mandibulae; 17 – septum nasi; 18 – concha nasalis dorsalis; 19 – second premolar; 20 – sinus maxillaris; 21 – ductus lacrimalis; 22 – third premolar.

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Fig. 4. Transverse computed tomography images of porcine skull – caudal part. (a–b) Transverse sections from the fourth premolar to the third molar tooth, (c–f) transverse sections from last molar tooth to the level of temporomandibular joint: 1 – fourth premolar; 2 – canalis mandibulae; 3 – septum nasi; 4 – canalis infraorbitalis; 5 – maxillary sinus; 6 – sinus frontalis caudalis; 7 – sinus frontalis rostralis lateralis; 8 – sinus lacrimalis; 9 – bulla tympani; 10 – meatus nasopharyngeus; 11 – labyrinthus ethmoidalis; 12 – second molar; 13 – condylus mandibulae; 14 – arcus zygomaticus; 15 – calvaria; 16 – cerebrum; 17 – os temporale – processus zygomaticus; 18 – ramus mandibulae; 19 – os zygomaticum – processus temporalis; 20 – sinus sphenoidalis; 21 – os pterygoideum.

dications associated with its use are few. In humans, small animal and equine practice, it is used as the main noninvasive diagnostic technique for the detection of trauma, metabolic or oncological changes in mineralized craniofacial tissues. However, the situation is different in the pig. Radiographic examination used to be the method of choice for the diagnosis of atrophic rhinitis in pigs (Rhinitis atrophicans suum). Recently, simpler and less invasive methods such as PCR, serological techniques or loop-mediated isothermal amplification of Pasteurella multocida and Bordetella bronchiseptica were introduced to screen for this disease and radiography has become less utilized (Register and DeJong, 2006; Sun et al., 2010). CT enables the visualization of tissues in diverse layers and projections with the differentiation of soft and hard tissues, including joints. Furthermore, it allows the 3D reconstruction of bony structures. CT belongs to the group of diagnostic methods that are widely used in human medicine and, in the last few years, in veterinary medicine as well (Lee et al., 2011). In pig, computed tomography has been used for the evaluation of abdominal fat (McEvoy et al., 2009; Chang et al., 2011), for the assessment of tooth root lesions (Kumar et al., 2011), bone quality (Hohlweg-Majert et al., 2011) and peri-implant defect diagnosis (Mengel et al., 2006). However, craniofacial structures of pig with their possible use in research have not been reviewed using computed tomography. MRI is a method with high soft tissue contrast without any undesirable side effects. It is effective in discerning soft tissue detail. MRI is also capable of detecting minor pathological changes including minor degenerative changes in the bone or joints. Synovial and subsynovial tissues can be visualized as well. Many studies have considered MRI as the method of choice for visualizing soft tissues such as salivary glands, paranasal sinuses mucosa, joints or muscles (Matteson et al., 1996; Tvrdy, 2007). In veterinary medicine, MRI is readily used in small animal practice and with some limitations in equine practice (Garrett et al., 2009; Rodriguez et al., 2010). The routine use of MRI diagnostics in pig medicine has been limited, mainly due to the cost. However, its use in pigs can be helpful in biomedical research, as was shown recently for brain development (Winter et al., 2011).

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Craniofacial research has advanced significantly over the last decade, mainly due to the advances in stem cell research. An accurate knowledge of different imaging modalities of porcine head anatomy is imperative for the correct interpretation of research results. This study aimed to identify and label the most important craniofacial structures in the pig using three different imaging methods (radiography, CT and MRI) and prepare references for further biomedical research using the pig as an experimental model, in accordance with the new EU directive (2010/ 63/eu) on the protection of animals used for scientific purposes. Furthermore, we demonstrate here anatomical slices of frozen pig heads in the transverse and sagittal planes for easier orientation in individual craniofacial areas. Materials and Methods The heads of 24-month-old (n = 7) pigs were obtained from a slaughterhouse and from the animal facility of the Institute of Animal Physiology and Genetics in Libechov (strain LiM – Libechov Minipig). Only females were used for this study to make imaging conditions consistent. The animals were euthanized by intravenous injection of thiopental or captive bolt pistol. All procedures were conducted following a protocol approved by the Animal Research Committee of the Institute of Animal Physiology and Genetics, v.v.i. (Libechov, Czech Republic, approval n. 67985904). Radiography and CT examination of pig heads were performed at the Department of Diagnostic Imaging, Small Animal Clinic, University of Veterinary and Pharmaceutical Sciences Brno (Brno, Czech Republic). Scout images for planning the CT examination were used instead of classic radiographic examination due to the large size of an adult animal’s head. The CT scans were taken using a 16 multislice CT scanner (LightSpeed; GE Healthcare, Milwaukee, WI, USA). The scanning protocol was as follows: 140 kV, 50–283 mAs (auto mA function), helical mode with slice thickness 0.625 mm, pitch 0.5625 and high frequency reconstruction algorithm (bone). The display field of view was 47.9 cm. The MRI analysis was performed in the Institute for Clinical and Experimental Medicine, Praha (Magnetom Trio Tim 3T; Siemens, Erlangen, Germany), on pig heads

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(24 months old). Forty-eight transverse and sagittal T1weighted images were using. Basic parameters were as follows: sequence name fl2dl, field of view 160 9 160 mm,

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Fig. 5. Transverse sections of the porcine head. (a) The level of first incisor, (b) the level of interalveolar space, (c) the level of first premolar tooth, (d) the level of second premolar tooth, (e) the level of second molar tooth, (f) the level of temporomandibular joint. 1 – septum nasi; 2 – plica alaris; 3 – os incisivum; 4 – os nasale; 5 – plica recta; 6 – concha nasalis ventralis; 7 – vomer; 8 – symphysis mandibulae; 9 – dens incisivus (I2); 10 – maxilla; 11 – palatum durum; 12 – meatus nasi medius; 13 – meatus nasi ventralis; 14 – m. levator labii superioris; 15 – m. caninus; 16 – m. depressor labii superioris; 17 – sinus frontalis; 18 – os temporale; 19 – m. temporalis; 20 – processus conchalis maxillae; 21 – lingua; 22 – brain; 23 – meatus nasi communis; 24 – os frontale; 25 – sinus sphenoidalis; 26 – labyrinthus ethmoidalis; 27 – orbit; 28 – sinus maxillaris; 29 – arcus zygomaticus; 30 – meatus nasopharyngeus; 31 – dens molaris (M2); 34 – m. genioglossus; 33 – canalis mandibulae; 35 – corpus mandibulae; 32 – m. buccinator; 36 – m. masseter; 37 – m. pterygoideus medialis; 38 – ramus mandibulae; 39 – condylus mandibulae.

slice thickness 2.0 mm, spacing between slices 2.2 mm, echo time 6.15 ms, repetition time 750 ms, flip angle 70°, rows 448 and columns 448.

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Fig. 6. Sagittal computed tomography images of porcine skull; 6a – sagittal image of the labial aspect of mandible; 6b – sagittal image of the oral aspect of the mandible; 6c – median image; 6d – paramedian image through the palatum durum. 1 – os rostrale; 2 – canalis mandibulae; 3 – sinus maxillaris; 4 – sinus frontalis rostralis lateralis; 5 – sinus frontalis caudalis; 6 – sinus sphenoidalis; 7 – condylus mandibulae; 8 – sinus frontalis rostralis medialis; 9 – concha nasalis ventralis.

Results Radiography Lateral radiographic projections of the porcine head discerned all bony structures in the facial area well. Bones of the neurocranium and temporomandibular joint (TMJ) did not visualize well in detail due to the superimposition of bones, muscles and adipose tissue. The nasal cavity of the pig is typically elongated, and all bony parts of the nasal cavity were discerned in radiograph (Fig. 1a). The dorsal nasal concha (concha nasalis dorsalis) was only lightly distinguishable in the dorsal part of the nasal cavity, followed by the clear medial concha (concha nasalis media) and underlined by distinct ventral nasal concha (Fig. 1b). Bone structures that follow the ethmoi-

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dal bone caudally lost radiographic detail due to the superimposition of different tissues in this area (Fig. 1). The paranasal sinuses in the pig are represented by large maxillary and frontal sinuses and smaller palatine, sphenoid and lacrimal sinuses (Fig. 1b). All paranasal sinuses were well discerned on radiography except the lacrimal sinuses. The maxillary sinus is characterized by medial, lateral and dorsocaudal extensions; however, these were not visualized on radiographs. The floor of the maxillary sinus extends ventrally to the level of the facial crest (Fig. 1b). Rostrally, the sinus ends in the infraorbital foramen. The frontal sinuses can be separated into two entities: the rostral and caudal frontal sinuses (Fig. 1b). The caudal frontal sinus represents the largest of the frontal sinuses and excavates the parietal, occipital, frontal

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and temporal bones. However, these excavations were not visualized on the radiographic projections. Communicating openings between different paranasal sinuses were also not visible using radiography. The orbit, due to its location on the border between the facial and neurocranium, was not recognized easily on the radiographs. Only the supraorbital margin and zygomatic arch could be fully identified (Fig. 1a). Teeth were visualized effectively on all radiographs, with their shapes and locations in the jaw and alveolus discernible (Fig. 1b). The dental formula of pig permanent dentition is 3I 1C 4P 3M in all dental quadrants. The maxilla, together with the infraorbital canal and its opening, was readily apparent on the lateral radiographic view. Furthermore, the mandible was easily identified with its two main parts: the ramus and the body of the mandible (Fig. 1b). Computed tomography

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Fig. 7. Sagittal sections of the porcine head. (a) Median section, (b) Sagittal section at the level of molars, (c) Sagittal section through palatum durum 1 – os rostrale; 2 – septum nasi – pars cartilaginea; 3 – sinus frontalis; 4 – sinus sphenoidalis; 5 – os nasale; 6 – lingua; 7 – rugae palatinae; 8 – mandible; 9 – epiglottis; 10 – m. genioglossus; 11 – os incisivum; 12 – sinus maxillaris; 13 – m. pterygoideus lateralis; 14 – m. pterygoideus medialis; 15 – gl. mandibularis; 16 – m. masseter; 17 – concha nasalis ventralis; 18 – plica alaris; 19 – basihyoideum; 20 – os occipitale; 21 – os frontale; 22 – os rostrale; 23 – concha nasalis dorsalis; 24 – concha nasalis media; 25 – os occipitale; 26 – labyrinthus ethmoidalis; 27 – plica basalis; 28 – meatus nasopharyngeus; 29 – tonsilla veli palatini; 30 – os hyoideum – basihyoideum.

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A series of transverse, sagittal and horizontal images was collected to visualize different structures through the porcine head (Figs 2–11). The selection of slices included the whole facial part of the head continuing to the level caudally behind the TMJ. All structures that were identified on radiographs could be identified on CT images as well. For easier orientation in CT images, we included here sections through frozen head in both transverse (Fig. 5) and sagittal planes (Fig. 7). The elongated nasal cavity (Fig. 10a–c) was clearly identifiable with detail of all bony structures including the spatial orientation of the conchae and bones forming the roof and floor of the nasal cavity (Fig. 3 compared with Fig. 5, Fig. 6 compared to Fig. 7). The thickness of the mucosal layer covering different parts of the nasal cavity could be assessed (Fig. 3e compare with Fig. 5b). Transverse sections clearly showed the meatus of the nose forming between individual conchae (Fig. 3f compare with Fig. 5c). Ventral to the medial nasal concha, and occupying the major part of the nasal cavity, is the ventral nasal concha (concha nasalis ventralis, Fig. 3e compared with Fig. 5b), which is broad and flat caudally and tapers rostrally into the alar fold (plica alaris). All parts of the paranasal sinuses were identifiable, including their communications, spatial orientation and the thickness of the mucosal lining (Figs 2b, 3 and 4; for details see Fig. 8). Ventral to the shelf of the dorsal nasal concha (Fig. 3h), in the lateral part of the wall, is the nasofrontal aperture (apertura nasofrontalis), which extends dorsally into the frontal sinus (sinus frontalis), and the nasomaxillary aperture (apertura nasomaxillaris), which expands laterally into the maxillary sinus (sinus maxillaris). © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

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Fig. 8. Detail computed tomography images of paranasal sinuses. (a–b) Sagittally reconstructed CT images of paranasal sinuses, (c) transversal CT image at the level of the third premolar tooth, (d–f) dorsally reconstructed CT images of paranasal sinuses 1 – labyrinthus ethmoidalis; 2 – sinus ethmoidalis; 3 – sinus frontalis rostralis medialis; 4 – sinus frontalis caudalis; 5 – sinus conchae nasalis dorsalis; 6 – meatus nasi medius; 7 – concha nasalis ventralis; 8 – concha nasalis dorsalis; 9 – sinus maxillaris; 10 – meatus nasi communis; 11 – meatus nasi ventralis; 12 – meatus nasi medius; 13 – meatus nasi dorsalis; 14 – third premolar; 15 – bulla tympani; 16 – sinus sphenoidalis; 17 – sinus frontalis rostralis lateralis; 18 – sinus lacrimalis; 19 – meatus nasopharyngeus.

The maxillary sinus is represented by medial, lateral and dorsocaudal extensions (Figs 4 and 8). Broad, low ridge or septal (corresponding to the infraorbital canal) projection from the osseous floor incompletely divides this sinus into medial and lateral compartments (Fig. 4b). Caudally, the maxillary sinus extends to a transverse level, passing through the last molar tooth (Fig. 6b,c). Both the rostral and caudal parts of the frontal sinus could be distinguished (Figs 3, 4 and 6). The sinuses of the right and left sides are separated by a median septum (Fig. 3g). They are connected with the nasal cavity through the nasofrontal opening (apertura nasofrontalis) into the labyrinthus ethmoidalis, which occurs at the level of the last molar tooth (Fig. 8a). The caudal sinus is extensively excavated, resulting in thin outer and inner bone lamellae (Fig. 4). This hollowed structure is greatly strengthened by its numerous incomplete bony lamellae (lamellae intrasinusiales), which form compartments communicating with each other (Fig. 4a). The rostral frontal sinus is © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

divided by the septum into the rostral medial frontal sinus and the rostral lateral frontal sinus (Fig. 3h). The rostral medial frontal sinus communicates rostrally with the dorsal nasal concha and extends rostrally into the caudal part of the nasal bone and caudally to the level of the medial wall of the orbit (Fig. 3h). The rostral lateral frontal sinus is caudolateral to the rostral medial frontal sinus and expands into the medial wall of the orbit, excavating the processes of the frontal bone (Fig. 6). The sphenoid sinus (sinus sphenoidalis) is a paired sinus (right and left side) divided by a septum (Fig. 4e). It is located in close proximity to the chiasma opticum (data not shown). It elongates rostrally into the pterygoid process of the basisphenoid bone, and laterally and dorsally it excavates into the squamous part of the temporal bones, reaching into the zygomatic process (Fig. 4e). The orbit of the pig is surrounded rostrally by the lacrimal and zygomatic bones and dorsally by the frontal bone (Fig. 2a,c). Its bony margin is incomplete caudolat-

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Fig. 9. Detail computed tomography images of teeth. (a–c) Sagittally reconstructed CT images of lower and upper jaw, (d) dorsally reconstructed CT image of the lower jaw with focus on tooth roots, (e–i) transverse CT images of the individual teeth 1 – canalis mandibulae; 2 – vomer; 3 – concha nasalis ventralis.

erally, and orbital ligament fills this margin (Fig. 2c). The zygomatic bone continues caudally with the processus temporalis, which, together with the processus zygomaticus of the temporal bone, forms a thick dorsally convex zygomatic arch (Figs 2c and 4c). Individual teeth and their location are identifiable on the individual CT slides (Figs 2 and 4a–c; for details see Fig. 9). Alveoli, their structures and shapes were clearly discernible (Fig. 9). The incisor teeth of the pig are

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curved so that the medial teeth are situated rostrally to the lateral teeth (Fig. 3a). They are separated by large areas (spatia interdentalia) from each other as well as from the large canines (Fig. 10d). The canine roots are long, round and deeply implanted in both jaws (Fig. 3e). The canine tooth is well developed in males with the root projecting caudodorsally/caudoventrally above the root of the second premolar tooth (data not shown). Root projection is shorter in females (Fig. 6a). The cheek teeth © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

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Fig. 10. Dorsally reconstructed computed tomography images of porcine skull. (a–d) dorsal reconstructions of the upper jaw, (e–f) dorsal reconstructions of the lower jaw. 1 – processus paracondylaris; 2 – bulla tympani; 3 – ramus mandibulae; 4 – arcus zygomatius; 5 – sinus maxillaris; 6 – sinus frontalis rostralis lateralis; 7 – sinus frontalis rostralis medialis; 8 – concha nasalis dorsalis; 9 – os rostrale; 10 – meatus nasopharyngeus; 11 – foramen infraorbitale; 12 – sinus conchae ventralis; 13 – vomer; 14 – rugae palatinae; 15 – maxillary caninus; 16 – os pterygoideum; 17 – maxillary incisors; 18 – maxillary molar (M3); 19 – canalis mandibulae; 20 – mandibular molar (M3); 21 – margo interalveolaris; 22 – corpus mandibulae.

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increase in size from the rostral to caudal positions (Fig. 9a). The first premolar in each jaw is small and simple (Fig. 9a,c). The margo interalveolaris is localized between the canine and the first premolar in both jaws (Fig. 10d). In the upper jaw, the first and second premolars possess two roots, the third premolar three roots, and the fourth premolar five roots (data not shown). The upper molars have up to six roots. In the lower jaw, the third premolar has two roots and the fourth premolar has three roots (Fig. 9d). The first and second molars have four roots, and the third molar possesses five roots (Fig. 9d). © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

The maxilla was easily assessed on transverse sections including its structure and shape (Fig. 3g,h). The roof of the infraorbital canal serves as the floor of the maxillary sinus (Fig. 3h). The floor of the maxilla, on the other hand, is formed by alveoli of the premolar and molar teeth (Fig. 3g,h). The mandible or lower jaw was also well visualized using CT scans, and all major parts were identified (Figs 3 and 4). The mandible consists of the body and the ramus (Figs 2–4). Both parts are joined at the symphysis and each narrows significantly rostrally (Figs 2c and 3b). The molar part of the body is very thick and strong (Figs 2c and 4c). The alveolar border is thin

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Fig. 11. Detailed dorsally reconstructed computed tomography images of temporomandibular joint. (a) proximal plane, (b) middle plane, (c) distal plane 1 – condylus mandibulae; 2 – processus paracondylaris; 3 – bulla tympani; 4 – sinus sphenoidalis; 5 – squama ossis temporalis; 6 – arcus zygomaticus; 7 – sinus frontalis caudalis; 8 – processus coronoideus mandibulae.

rostrally and widens caudally, parallel with that on the opposite side (Fig. 2c). The TMJ (articulatio temporomandibularis) of a pig is a simple incongruent joint (Fig. 4f, for details see Fig. 11), where the convex surface of the mandibular condyle (condylus mandibulae) articulates with the articular surface of the temporal bone (facies articularis squama ossis temporalis). The articular surface of the temporal bone, which is obscured by the zygomatic arch in the lateral view (Fig. 4f compare with Fig. 5f), is composed of transversely elongated shallow articular tubercles (tuberculum articulare ossis temporalis) and a shallow triangular mandibular fossa (fossa mandibularis ossis temporalis) caudal to it (Fig. 9). Magnetic resonance imaging A series of transverse as well as sagittal sections was used for MRI analysis (Figs 12–14). On the selected images, detailed structures of the nasal cavity and paranasal sinuses similar to the CT scans could be identified (Fig. 13). Bones and bony structures could be identified, but their detail was not easily discernible (Fig. 14). Soft tissue structures such as the mucosal covering of the conchae, as well as detailed structures of the ectoturbinalia and endoturbinalia of the labyrinthus ethmoidalis, were shown in clear detail (Fig. 13).

Large salivary glands were recognizable on both sagittal and transverse sections of MRI images (Figs 12–14). The parotid gland (glandula parotis) is a large triangular structure that extends for a short distance over the caudal part of the masseter muscle and along the whole course of the ramus mandibulae (Fig. 12a–d). The dorsal angle of the parotid gland reaches and covers the vertical part of the ear canal (Fig. 12b). The parotid duct arises on the deep face of the parotid gland and follows the angle and corpus of the mandible medially to the level of the incisura vasorum facialium (data not shown). Here, it crosses the body of the mandible ventrally onto the lateral side where it follows the anterior edge of the masseter muscle. The mandibular gland (glandula mandibularis) is small and oval in shape (Fig. 12e–h). It is located caudomedially from the angle of the mandible and covered by the parotid gland (Fig. 12d,e). Muscles, as an important structure of the head, were easily identified, including their origin and attachment (Figs 12–14). Primarily, masticatory musculature was identified. There are five main masticators in pigs: the masseter, temporal muscle, medial pterygoid, lateral pterygoid and digastricus. The masseter (musculus masseter) consists of two heads (Fig. 14c–e). The superficial head, or pars superficialis, originates on the zygomatic arch (Fig. 14c) and is inserted in the mandibular angle (angulus mandibulae, Fig. 14b). The deep head, or pars profun-

Fig. 12. Magnetic resonance of pig head in sagittal plane (T1-weighted sequence) from the level of musculus masseter (a–d) to the level of bulbus oculi (e-h). 1 – m. masseter; 2 – gl. parotis; 3 – meatus acusticus externus (vertical part); 4 – m. zygomaticotemporalis; 5 – m. cutaneus faciei; 6 – m. digastricus; 7 – m. temporalis; 8 – m. sternomastoideus; 9 – ln. parotideus; 10 – mandible; 11 – gl. mandibularis; 12 – bulbus oculi; 13 – articulatio temporomandibularis; 14 – condylus mandibulae; 15 – squama ossis temporalis; 16 – m. pterygoideus medialis; 17 – basihyoideum; 18 – m. mylohyoideus; 19 – meatus acusticus externus; 20 – m. buccinator; 21 – sinus maxillaris; 22 – thyrohyoideum; 23 – corpus mandibulae; 24 – m. depressor labii superioris; 25 – rostrum; 26 – m. trapezius; 27 – m. longissimus capitis; 28 – m. levator labii superioris.

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Fig. 13. Magnetic resonance of pig head in sagittal plane (T1-weighted sequence) from the level of dental arches (a,b) to the median plane of the head (c,d). 1 – lingua; 2 – rostrum; 3 – m. caninus; 4 – sinus maxillaris; 5 – labyrinthus ethmoidalis; 6 – sinus frontalis (pars rostralis); 7 – sinus frontalis (pars caudalis); 8 – m. digastricus; 9 – m. cutaneus faciei; 10 – m. genioglossus; 11 – bulla tympanica; 12 – cellulae mastoidae; 13 – m. trapezius; 14 – m. splenius capitis; 15 – m. sternomastoideus; 16 – concha nasalis ventralis; 17 – concha nasalis dorsalis; 18 – sinus sphenoidalis; 19 – m. longus capitis; 20 – m. hyoglossus; 21 – sinus conchae dorsalis; 22 – canalis incisivus; 23 – cavum laryngis; 24 – epiglottis; 25 – m. thyroglossus; 26 – rugae palatinae.

da, originates on the posterior part of the zygomatic arch and is inserted in the masseteric fossa (Fig. 14b–e). The temporal muscle (musculus temporalis) originates in the temporal fossa or planum parietale and is inserted in the internal side of the coronoid process of the mandible (Fig. 12c–g). The pterygoid muscle (musculus pterygoideus) consists of two parts (Figs 13 and 14). The medial pterygoid (musculus pterygoideus medialis) originates from the pterygoid fossa on the medial surface of the lateral pterygoid plate of the sphenoid and is

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inserted in the interior medial surface of the angle of the mandible (Fig. 14f). The lateral pterygoid (musculus pterygoideus lateralis) has two heads (Fig 14d–f). The superficial head originates from the inferior surface of the greater wing of the sphenoid, and the deeper head originates from the lateral surface of the lateral pterygoid plate of the sphenoid. Both heads unite and are inserted in the anterior surface of the neck of the mandibular condyle and the pterygoid fovea (data not shown). The digastricus muscle (musculus digastricus) is composed of two contin-

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Fig. 14. Magnetic resonance of pig head in transverse plane (T1-weighted sequence) of pig head from the level of bulbus oculi (a,b) to the level of cerebellum (f). 1 – labyrinthus etmoidalis; 2 – bulbus oculi; 3 – choana; 4 – upper molar (M2); 5 – lingua; 6 – corpus mandibulae; 7 – sinus lacrimalis; 8 – m. buccinator; 9 – sinus frontalis rostralis; 10 – apertura nasofrontalis; 11 – sinus maxillaries; 12 – m. masseter pars superficialis; 13 – m. geniohyoideus; 14 – m. masseter pars profunda; 15 – arcus zygomaticus; 16 – m. temporalis; 17 – palatum durum; 18 – lamellae intrasinusiales; 19 – m. pterygoideus lateralis; 20 – ramus mandibulae; 21 – m. digastricus; 22 – sinus sphenoidalis; 23 – m. pterygoideus medialis; 24 – bulla tympani; 25 – condylus mandibulae; 26 – articulatio temporomandibularis; 27 – auris externa; 28 – discus articularis; 29 – squama ossis temporalis.

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uous heads that originate on the paracondylar process of occipital bone and are attached to the medial side of the mandible (Fig. 14e). The soft tissues of the TMJ were also well delineated (Figs 12E and 14F). The articular disc (discus articularis) is biconcave in the sagittal view (data not shown). The reflections of the anterior bundle of collagen fibres form the anterior capsule where the lateral pterygoid muscle is found (musculus pterygoideus lateralis, Fig. 14f). Discussion Domestic and miniature pigs are widely used in medical research, either as a general medium-sized model that is larger than a rodent or as a special model (Nomori et al., 2005; Pemberton et al., 2005), based upon specific © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

anatomical and physiological characteristics. Currently, to our knowledge, there are no reports regarding diagnostic imaging anatomy in the pig. Therefore, we focused our attention on the craniofacial region to provide a description of the normal anatomy of the pig’s head and compare the usability of different imaging methods in experimental research. Imaging techniques in large animals bridge the gap between pre-clinical and clinical research. It is possible to use the same scanners to image large laboratory animals as humans, and with few modifications, the same scanning protocols can also be used. Moreover, medical hypotheses and problems addressed in human clinics or human investigations can be tested and studied on large animals using various imaging techniques (Olsen et al., 2007; Puchalski et al., 2009). However, for researchers

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who are not veterinarians, it is necessary to know the main anatomical structures in the porcine head to be able to perform a comparison with the corresponding features in human. Therefore, our aim was to prepare basic visual material for such use. For that purpose, we selected diagnostic imaging methods that are commonly used in human medicine such as radiographic evaluation, CT and MRI. Each of these designated methods has advantages and disadvantages to their use in the pig model. Radiography is the cheapest and most widespread method in clinical and experimental settings for visualization of soft and hard tissues. However, there is one limiting factor that restricts its use in the pig. This is the thick layer of adipose tissue localized in the craniofacial region of the adult pig, which makes imaging of some parts difficult or even impossible, especially in older animals. The superimposition of the great thickness of bones, soft tissues such as muscles and fat disguise the whole neurocranium. Only the frontal sinuses, due to their hollow spaces, can be well visualized. Structures of research interest, such as the TMJ or middle ear, are not suitably visible on radiographs. This finding is in agreement with most studies dealing with radiography of the skull in different species of domestic animals (Thrall et al., 1989; Codner et al., 1993). However, radiographs of the nasal cavity and teeth resulted in acceptable visualization for assessing these structures, in contrast with some studies in different animal species (Thrall et al., 1989; Codner et al., 1993; Arencibia et al., 2000). Based on our study, we conclude that radiography is a suitable diagnostic tool in assessing the rostral facial skeleton and main paranasal sinuses in the pig. CT is less frequently used in veterinary medicine compared with radiography; however, its widespread use is becoming more common, especially in small animal practice (Losonsky et al., 1997; Arencibia et al., 2000). The cost of CT scans prevents it from being routinely used in clinical or experimental settings (De Rycke et al., 2007). On the other hand, it is possible to generate CT scans on different planes, thus providing the investigator with detailed anatomical information and spatial orientation. CT scans provide an observer with superior quality of bone structures including structures of the neurocranium, which are obscured on radiographic views. Excellent visualization of bony structures of the temporomandibular joint, orbit and middle ear were achieved compared with radiographs. Lower quality pictures were gathered for soft tissue detail; however, it was still possible to assess the thickness of the mucosal linings of the nasal cavity and paranasal sinuses. It was not possible to distinguish individual muscles, salivary glands, nerves or vessels. This could be accomplished using contrast enhanced CT imaging (Wang et al., 2007; Puchalski et al., 2009). Three dimensional reconstruction imaging software is

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another advantage of CT scans, which allows the investigator to visualize the spatial orientation of the head. On the other hand, it is limited to just the bony parts of the skull. MRI is becoming more available in small animal and equine practice at the present time (Losonsky et al., 1997; Arencibia et al., 2000). Spatial resolution and definition of soft tissue detail were superior in quality to both radiography and CT images. MRI images proved to be superior for the visualization of fine details of soft tissues such as muscles, vessels, lymph nodes and large salivary glands. MRI of the pig head provided excellent anatomical contrast correlation and allowed the identification of the most clinically relevant structures, including the size and thickness of nasal and paranasal mucosa. High-quality visualization of soft and mineralized tissues was evident in MRI images. The palatine and infraorbital nerves, salivary glands and muscles had higher signal intensities because of the short relaxation times. The nasal cavity, paranasal sinuses and teeth, on the other hand, had lower signal intensity due to shorter relaxation times. In our study, we used T1-weighted imaging, which has previously been confirmed to be more suitable for providing good spatial resolution and better anatomical distinctions in contrast to T2-weighted images that are more appropriate for the detection of fluid or oedema, and therefore for the detection of pathological changes (De Rycke et al., 2007). In conclusion, MRI of the porcine head provides good quality visualization of many structures of the craniofacial region. It remains a well-adapted technique because of its good spatial resolution, superior soft-tissue contrast and ability to detect subtle pathologic changes in the tissues. CT imaging is advantageous in providing excellent spatial resolution and superior contrast of bone structures. The disadvantage of these two techniques is the relative lack of availability of the equipment and relatively high cost. Radiography is only suitable for the general evaluation of the facial area of the porcine head; however, its use is still preferred due to the low cost and ease of availability. We hope that accurate knowledge of porcine craniofacial anatomy coupled with understanding of the different imaging modalities will help to improve researchers’ ability to distinguish normal from abnormal anatomical features and assess research outcomes. Acknowledgements I. Putnova was supported by the Grant Agency of the University of Veterinary and Pharmaceutical Sciences Brno (Grant 28/2010/FVL), and M. Buchtova was supported by the Czech Science Foundation (Grant 304/08/ P289). The laboratory runs under IPAG (RVO:67985904). © 2013 Blackwell Verlag GmbH Anat. Histol. Embryol. 43 (2014) 435–452

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References Arencibia, A., J. M. Vazquez, R. Jaber, F. Gil, J. A. Ramirez, M. Rivero, N. Gonzalez, and E. R. Wisner, 2000: Magnetic resonance imaging and cross sectional anatomy of the normal equine sinuses and nasal passages. Vet. Radiol. Ultrasound 41, 313–319. Bermejo, A., O. Gonzalez, and J. M. Gonzalezm, 1993: The pig as an animal model for experimentation on the temporomandibular articular complex. Oral Surg. Oral Med. Oral Pathol. 75, 18–23. Blagbrough, I. S., and C. Zara, 2009: Animal models for target diseases in gene therapy-using DNA and siRNA delivery strategies. Pharm. Res. 26, 1–18. Bustad, L. K., 1966: Pigs in the laboratory. Sci. Am. 214, 94–100. Bustad, L. K., and R. O. McClellan, 1965: Use of pigs in biomedical research. Nature 208, 531–535. Bustad, L. K., and R. O. McClellan, 1966: Swine in biomedical research. Science 152, 1526–1530. Campisi, G., C. Paderni, R. Saccone, M. G. Siragusa, L. Lo Muzio, C. Tripodo, L. I. Giannola, and A. M. Florena, 2008: Carbamazepine transbuccal delivery: the histo-morphological features of reconstituted human oral epithelium and buccal porcine mucosae in the transmucosal permeation. Int. J. Immunopath. Pharmacol. 21, 903–910. Chang, J., J. Jung, H. Lee, D. Chang, J. Yoon, and M. Choi, 2011: Computed tomographic evaluation of abdominal fat in minipigs. J. Vet. Sci. 12, 91–94. Codner, E. C., A. G. Lurus, J. B. Miller, P. R. Gavin, A. Gallina, and D. D. Barbee, 1993: Comparison of computed tomography with radiography as a noninvasive diagnostic technique for chronic nasal disease in dogs. J. Am. Vet. Med. Assoc. 202, 1106–1110. De Rycke, L. M., J. H. Saunders, I. M. Gielen, H. J. van Bree, and P. J. Simoens, 2007: Magnetic resonance imaging, computed tomography, and cross-sectional views of the anatomy of normal nasal cavities and paranasal sinuses in mesaticephalic dogs. Am. J. Vet. Res. 64, 1093–1098. Garrett, K. S., J. B. Woodie, R. M. Embertson, and A. P. Pease, 2009: Diagnosis of laryngeal dysplasia in five horses using magnetic resonance imaging and ultrasonography. Equine Vet. J. 41, 766–771. Hohlweg-Majert, B., M. C. Metzger, T. Kummer, and D. Schulze, 2011: Morphometric analysis – cone beam computed tomography to predict bone quality and quantity. J. Craniomaxillofac. Surg. 39, 330–334. Jacobi, U., R. Toll, H. Audring, W. Sterry, and J. Lademann, 2005: The porcine snout-an in vitro model for human lips? Exp. Derm. 14, 96–102. Kumar, V., L. Gossett, A. Blattner, L. R. Iwasaki, K. Williams, and J. C. Nickel, 2011: Comparison between cone-beam computed tomography and intraoral digital radiography for assessment of tooth root lesions. Am. J. Orthod. Dentofacial Orthop. 139, 533–541.

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Larjava, H., C. Wiebe, C. Gallant-Behm, D. A. Hart, J. Heino, and L. Hakkinen, 2011: Exploring scarless healing of oral soft tissues. J. Can. Dent. Assoc. 77, b18. Lee, S., J. Jung, J. Chang, J. Yoon, and M. Choi, 2011: Evaluation of triphasic helical computed tomography of the kidneys in clinically normal dogs. Am. J. Vet. Res. 72, 345–349. Losonsky, J. M., L. C. Abbott, and I. V. Kuriashkin, 1997: Computed tomography of the normal feline nasal cavity and paranasal sinuses. Vet. Radiol. Ultrasound 38, 251–258. Mak, K., A. Manji, C. Gallant-Behm, C. Wiebe, D. A. Hart, H. Larjava, and L. Hakkinen, 2009: Scarless healing of oral mucosa is characterized by faster resolution of inflammation and control of myofibroblast action compared to skin wounds in the red Duroc pig model. J. Dermatol. Sci. 56, 168–180. Matteson, S. R., S. T. Deahl, M. E. Alder, and P. V. Nummikoski, 1996: Advanced imaging methods. Crit. Rev. Oral Biol. Med. 7, 346–395. McEvoy, F. J., M. T. Madsen, M. B. Nielsen, and E. L. Svalastoga, 2009: Computer tomographic investigation of subcutaneous adipose tissue as an indicator of body composition. Acta Vet. Scand. 51, 28. Mengel, R., B. Kruse, and L. Flores-de-Jacoby, 2006: Digital volume tomography in the diagnosis of peri-implant defects: an in vitro study on native pig mandibles. J. Periodontol. 77, 1234–1241. Millikan, L. E., J. L. Boylon, R. R. Hook, and P. J. Manning, 1974: Melanoma in Sinclair swine: a new animal model. J. Inv. Derm. 62, 20–30. Nkenke, E., M. Fenner, E. G. Vairaktaris, F. W. Neukam, and M. Radespiel-Troger, 2005a: Immediate versus delayed loading of dental implants in the maxillae of minipigs. Part II: histomorphometric analysis. Int. J. Oral Maxillofac. Implants 20, 540–546. Nkenke, E., B. Lehner, M. Fenner, F. S. Roman, U. Thams, F. W. Neukam, and M. Radespiel-Troger, 2005b: Immediate versus delayed loading of dental implants in the maxillae of minipigs: follow-up of implant stability and implant failures. Int. J. Oral Maxillofac. Implants 20, 39–47. Nomori, H., Y. Imazu, K. Watanabe, T. Ohtsuka, T. Naruke, T. Kobayashi, and K. Suemasu, 2005: Radiofrequency ablation of pulmonary tumors and normal lung tissue in swine and rabbits. Chest 127, 973–977. Olsen, A. K., D. Zeidler, K. Pedersen, M. Sørensen, S. B. Jensen, and O. L. Munk, 2007: Imaging techniques: CT, MRI, and PET scanning. In: Swine in the Laboratory. Surgery, Anesthesia, Imaging, and Experimental Techniques. (M. M. Swindle, ed.). Boca Raton, FL: CRC Press. pp. 387–395. Papadaki, M. E., M. J. Troulis, J. Glowacki, and L. B. Kaban, 2010: A minipig model of maxillary distraction osteogenesis. J. Oral Maxillofac. Surg. 68, 2783–2791. Pemberton, J., X. Li, T. Karamlou, C. A. Sandquist, K. Thiele, I. Shen, R. M. Ungerleidere, A. Kenny, and D. J. Sahn, 2005: The use of live three-dimensional Doppler echocardiography in the measurement of cardiac output: an in vivo animal study. J. Am. Coll. Cardiol. 45, 433–438.

451

Craniofacial Structures in Pig

Puchalski, M. S., D. L. Galuppo, P. C. Drew, and E. R. Wisner, 2009: Use of contrast-enhanced computed tomography to assess angiogenesis in deep digital flexor tendonopathy in a horse. Vet. Radiol. Ultrasound 50, 292–297. Register, K. B., and K. D. DeJong, 2006: Analytical verification of a multiplex PCR for identification of Bordetella bronchiseptica and Pasteurella multocida from swine. Vet. Microbiol. 117, 201–210. Rodriguez, M. J., A. Agut, M. Soler, O. Lopez-Albors, J. Arredondo, M. Querol, and R. Latorre, 2010: Magnetic resonance imaging of the equine temporomandibular joint anatomy. Equine Vet. J. 42, 200–207. Sasaki, R., Y. Watanabe, M. Yamato, S. Aoki, T. Okano, and T. Ando, 2010: Surgical anatomy of the swine face. Lab. Anim. 44, 359–363. Sonoyama, W., Y. Liu, D. Fang, T. Yamaza, B. M. Seo, C. Zhang, H. Liu, S. Gronthos, C. Y. Wang, S. Wang, and S. Shi, 2006: Mesenchymal stem cell-mediated functional tooth regeneration in swine. PLoS One 1, e79. Stembirek, J., M. Kyllar, I. Putnova, L. Stehlik, and M. Buchtova, 2012: The pig as an experimental model for clinical craniofacial research. Lab. Anim. 46, 269–279. Sun, D., J. Wang, R. Wu, C. Wang, X. He, J. Zheng, and H. Yang, 2010: Development of a novel LAMP diagnostic

452

M. Kyllar et al.

method for visible detection of swine Pasteurella multocida. Vet. Res. Comm. 34, 649–657. Thrall, D. E., I. D. Robertson, D. A. Mcleod, G. L. Heidner, P. J. Hoopes, and R. L. Page, 1989: A comparison of radiographic and computed tomographic findings in 31 dogs with malignant nasal cavity tumors. Vet. Radiol. Ultrasound 30, 59–66. Tvrdy, P., 2007: Methods of imaging in the diagnosis of temporomandibular joint disorders. Biomed. Pap. 151, 133–136. Wang, S. L., J. Li, X. Z. Zhu, K. Sun, X. Y. Liu, and Y. G. Zhang, 1998: Sialographic characterization of the normal parotid gland of the miniature pig. Dent. Maxill. Fac. Rad. 27, 178–181. Wang, S., Y. Liu, D. Fang, and S. Shi, 2007: The miniature pig: a useful large animal model for dental and orofacial research. Oral Dis. 13, 530–537. Winter, J. D., S. Dorner, J. Lukovic, J. A. Fisher, K. S. St Lawrence, and A. Kassner, 2011: Noninvasive MRI measures of microstructural and cerebrovascular changes during normal swine brain development. Pediatr. Res. 69, 418–424. Zheng, Y., Y. Liu, C. M. Zhang, H. Y. Zhang, W. H. Li, S. Shi, A. D. Le, and S. L. Wang, 2009: Stem cells from deciduous tooth repair mandibular defect in swine. J. Dent. Res. 88, 249–254.

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Radiography, computed tomography and magnetic resonance imaging of craniofacial structures in pig.

The pig has recently become popular as a large animal experimental model in many fields of biomedical research. The aim of this study is to evaluate t...
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