Nestin and dental pulp stones - a case report-driven hypothesis.

The dental pulp stem cells (DPSCs) are mesenchymal stem/stromal cells (MSCs) with multilineage potential of differentiation. Different studies investigated dental pulp stones (PS), the calcified masses in the dental pulp, in regard to their prevalence, topography and structure. The etiology of PS is still unclear and, to our knowledge, the DPSCs were not attributed yet specific roles in PS formation. We report here an immunohistochemical study of a PS-embedding dental pulp from an impacted third mandibular molar of an adult patient, in which we used antibodies against CD34, Ki67, glial fibrillary acidic protein (GFAP), α-smooth muscle actin (α-SMA) and nestin. While endothelial cells expressed CD34 and pericytes or vascular smooth muscle cells expressed α-SMA, DPSCs and the osteoblasts coating the PS were exclusively labeled with nestin antibody. Stromal networks of nestin-expressing DPSCs were regarded as in situ providers of osteogenic progenitors involved in PS formation. Further experimental studies, with larger lots of tissue samples, as well as extended panels of markers, are needed in order to elucidate the DPSC hypothesis in the PS etiology.

A glimpse of past, the temporo-buccinator band of Hovelaque, or the buccotemporal fascia of Zenker.

Only a few studies published until now have described the fascial-tendinous complex between the temporal and the buccinator muscles, which will be reviewed here. In 1957, the "temporo-buccinator band" (TBB) was described by Gaughran, who gave credit to Hovelaque for its first description in 1914. Zenker coined it in 1955 as the "buccotemporal fascia" (BTF). A buccal extension of the temporal muscle tendon extends from the temporal crest of the mandible to insert within the buccinator muscle, anterior to the pterygomandibular raphe, and posterior to the parotid duct that perforates the buccinator. That tendinous expansion is embedded within the buccotemporal fascia, which is oriented antero-infero-medially and joins the buccopharyngeal fascia, forming the TBB/BTF, above which we find the buccal fat pad. The buccal nerve and artery cross this anatomical structure. The TBB/BTF is an additional layer closing the pterygomandibular space anteriorly, and its knowledge is needed for practitioners performing inferior alveolar nerve blocks.

The mandibular incisive foramen, a false mental foramen.

BACKGROUND: The mandibular incisive foramen (MIF) is an opening on the external surface of the dentate mandibular body, medial to, and facing the mental foramen (MF). There is actually scarce evidence of such MIF. CLINICAL PRESENTATION: A retrospective Cone Beam CT (CBCT) study of the archived files of a 56 y.o. male patient was documented anatomically for dental medical purposes. In the 2nd premolar region of the left hemimandible were found two adjacent foramina facing one each other: the distal one was opened medially, while the medial one was oriented distally. On axial CBCT slices the mandibular canal was detected to open at the distal foramen in the outer cortical plate of the mandible. The medial foramen in that cortical plate served as entrance to the mandibular incisive canal, thus being a MIF. CONCLUSION: CBCT accurately distinguishes the canals opening on the outer cortical plate of the mandible thus is of use to differentiate a MIF from a MF. Such adjacent foramina expose at risk not just the mental nerve, as in cases with true multiple MF, but also the IAN and the mandibular incisive nerve.

The unusually lower position of the mandibular foramen and the canal of the neck of mandible.

BACKGROUND: The inferior alveolar nerve (IAN) courses through the mandibular foramen (MF) to enter the first segment of the mandibular canal (MC) in the mandibular ramus, to further supply with trigeminal fibers the lower teeth of that hemimandible. As the IAN also supplies the mylohyoid nerve, it is a mixed nerve. METHODS: Unusual morphologies of the mandibular ramus were encountered during a retrospective study of archived CBCT files. RESULTS: A previously unreported anatomic variation was found bilaterally in an edentulous mandible, consisting of a lowered position of the MF, with seemingly compensatory lengthening and enlargement of the sulcus colli, thus shortened MCs. Also, a rare neurovascular canal of the neck of the mandible was incidentally found unilaterally in another case and is reported here. CONCLUSIONS: Such possibilities of variation could justify the individual effect of the IAN block.

A rare anatomic variation: Triple mental foramina.

Multiple mental foramina (MF) are rarely found in the human mandible. We report on the case, as documented using cone beam computed tomography (CBCT), of the triple MF that were identified on the right hemimandible of a 28-year-old female patient. The distal foramen was located on the mandible between the apices of the second premolar root and the first molar mesiovestibular root, being reached by a thin canal that left the mandibular canal. A pair of mesial foramina were identified between the apices of the premolar teeth. Thus, the three foramina corresponded to a surface area of 23.49mm2 of the mandible. On the opposite side, a single mental foramen had a surface area of just 13.25mm2. On each side, retromolar canals that opened into the retromolar fossae were also found. The anatomic possibility of multiple MF increases the surface area at risk during surgical procedures, increases the risk of neurovascular damage and obscures the common tooth-related location of the mental foramen. Practitioners should, therefore, consider a personalised and imaging-documented approach so as to avoid treatment failure.

Infraorbital canal bilaterally replaced by a lateroantral canal.

The infraorbital canal (IOC) normally courses above the maxillary sinus in the orbit floor. During a retrospective study of cone beam computed tomography (CBCT) scans, we found a previously unknown variant of the IOC. The IOCs were absent, being replaced by lateroantral canals coursing around and not above the maxillary sinus to open at infraorbital foramina which were located above the second upper premolar teeth. On coronal multiplanar reconstructions, the lateroantral canals were located anatomically at the outer limit of the zygomatic recess of each maxillary sinus, while the upper wall of the sinus was devoid of any canal. Such rare variant should be kept in mind by dental practitioners and surgeons, as it can determine modifications of common procedures. In this regard, the anatomy of maxilla, as well as mandible, should be evaluated in CBCT on a case-by-case basis.

Human adult dental pulp CD117/c-kit-positive networks of stromal cells.

Dental pulp tissue was collected from 6 healthy adult patients, prior to prosthetic treatments, in order to evaluate the in situ phenotype of dental pulp stromal cells and compare with that of dental pulp stem cells. A CD34-/CD44+/CD105-/CD117+/CD146-/nestin- phenotype of stromal cells in the dental pulp core was found. Cells with a similar phenotype, but CD44-, were found in the cell richzone. Dental pulp stromal networks (DPSNs) were found CD117+/CD44+ in the pulp core, but CD117+/CD44- in the cell rich zone. The c-kit-positive DPSNs were contacting pulp nerves and were, in this regard only, comparable to interstitial Cajal cells. Stromal signalling in dental pulp needs further evaluation, in normal tissue as well as a possible cause of persisting pain after endodontic treatments.

Possible role of apoptosis in the pathogenesis and clinical evolution of radicular cyst: an immunohistochemical study.

AIM: To investigate whether the apoptotic cascade is activated through the extrinsic pathway in epithelial lining and connective tissue of radicular cysts. METHODOLOGY: Fifteen radicular cysts were fixed in formalin, embedded in paraffin wax and processed for immunohistochemistry to evaluate the expression of polyclonal antibodies against Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), DR5 and caspase-3. Immunocomplexes were treated with the secondary antibodies and finally detected using the avidin-biotin-peroxidase complex. Immunoreactivity was visualized by development with 3,3'-diaminobenzidine. Data were analysed using the Mann-Whitney U-test; P < 0.05 was considered significant. RESULTS: The three antibodies were detected in connective tissue fibroblasts of all radicular cysts; TRAIL and DR5 immunoexpression was significantly greater (P < 0.05) compared with that of caspase-3. The three antibodies were also expressed in almost all epithelial layers and in endothelial cells of newly formed vessels. CONCLUSION: The involvement of apoptosis in the pathogenesis of radicular cysts, demonstrated by the immunoexpression patterns of TRAIL, DR5 and caspase-3 in lining epithelium and connective tissue, may explain their bland clinical aggressiveness and slow, benign evolution.

The "sand watch" mandible.

The lingual surface of the mandible's body is commonly indicated as presenting the submandibular and sublingual fossae, which are separated by the mylohyoid line. The mylohyoid line attaches to the mylohyoid muscle (MM). Less attention has been paid to the 'mylohyoid boutonnières', which allow the 'sublingual buttons' to pass through the mylohyoid muscle in the submandibular space. The cone-beam computed tomography files of patients were routinely examined for anatomical studies. Two cases were found with unexpected morphologies of the mandible's body - the mylohyoid lines were incomplete anteriorly, and herniated sublingual tissue determined an additional fossa inferior to that line in the premolar region. That fossa was termed the 'accessory submandibular fossa'. It determined on coronal slices a 'sand watch' contour of the mandible's body. With such a peculiar morphology, the mandible is more prone to fracture. Moreover, when inserting endosseous implants, the procedure should be carefully personalised in such rare cases.

The extramandibular inferior alveolar nerve in cases with severely atrophic lower jaws.

There are very few evidences on the extramandibular course (EMC) of the inferior alveolar nerve (IAN). We report here two such cases. The first one was encountered at dissection, in a human adult female cadaver where the right IAN terminal division was identified in the premolar region, above a severely atrophied mandibular body. The second case was a patient evaluated by cone-beam CT, who presented with an extremely atrophic mandible with bilateral extramandibular courses of the IANs. Such severe atrophy of the mandible may be considered as residual ridge class 7 along with the existing Atwood classes. EMCs of the IAN may not only occur in extreme mandibular atrophy, but also in dentate mandibles. In edentulous mandibles, an extramandibular IAN may complicate local surgical procedures or hamper denture wearing.

Transantral intraseptal sinuous canal.

The sinuous canal is an anatomically well-defined intramural canal of the maxillary sinus (MS) folded within the antral walls. Commonly, its first, infraorbital part, courses within the antral roof, while its second, transverse facial part courses below the infraorbital foramen within the anterior antral wall. While retrospective files of patients that were scanned in cone-beam computed tomography (CBCT) for different dental medical purposes were observed randomly, a peculiar variant of the sinuous canal was noticed and further documented. The respective canal origin was far posterior in the infraorbital groove and the canal coursed through the MS embedded within an incomplete oblique septum dividing the antrum into anterosuperior and posteroinferior chambers. Then the sinuous canal continued with the transverse facial segment. As the sinuous canal contains the superior anterior alveolar nerve and artery, major suppliers of the frontal teeth, it is recommended to document in CBCT a possible transantral, and not intramural, course of it, especially when surgical or endoscopic corridors through the MS are planned.

Altered anatomy in a case with a buccally impacted maxillary canine tooth.

Bilateral dissections of maxilla were performed in a human adult cadaver head, male, aged 53 years. After the en block removal of the soft tissues in the oral and infraorbital regions, the antero-lateral surface of maxilla was exposed and also the vestibular aspect of the upper alveolar process. An oblique labially impacted right upper canine was evidenced, completely submucosal: its apex was tangent to the maxillary sinus floor, while the superior side of the apical part of the root was in close relation with the floor of the laterally expanded inferior nasal meatus. Superior and adjacent to the neck of that impacted canine a follicular cyst was evidenced and the antral wall presented distally to the apex of the impacted canine a dehiscent area, where the antral mucosa was only covered by an incomplete thin bony lamella. The incisors on that side were present but no resorption was identified at their level. Within the anterior border of the wall separating the maxillary sinus, small, and the inferior nasal meatus, the nerve for that impacted canine was coursing; the nerves for the upper incisors were initially located within the antero-lateral wall of the inferior nasal meatus. Although small, the maxillary sinus presented a supero-medial recess above the enlarged inferior nasal meatus and lateral to the normally-sized middle nasal meatus.

The temporomandibular joint: pneumatic temporal cells open into the articular and extradural spaces.

The pneumatisation of the articular tubercle (PAT) of the temporal squama isa rare condition that modifies the barrier between the temporomandibular joint(TMJ) space and the middle cranial fossa. During a routine examination of thecone-beam computed tomography (CBCT) files of patients who were scannedfor dental medical purposes, we identified a case with multiple rare anatomicvariations. First, the petrous apex was bilaterally pneumatised. Moreover, bilateraland multilocular PAT were observed, while on one side it was further found thatthe pneumatic cells were equally dehiscent towards the extradural space and thesuperior joint space. To the best of our knowledge, such dehiscence has not previouslybeen reported. The two temporomastoid pneumatisations were extendedwith occipital pneumatisations of the lateral masses and occipital condyles, thelatter being an extremely rare evidence. The internal dehiscence of the mandibularcanal in the right ramus of the mandible was also noted. Additionally, doublemental foramen and impacted third molars were found on the left side. Suchmultilocular PAT represents a low-resistance pathway for the bidirectional spreadof fluids through the roof of the TMJ. Further, it could add to a morphologicalpicture of hyperpneumatisation of the posterior cranial fossa floor, which couldsignify the involvement of the last four cranial nerves in the clinical picture of TMJpain.

New radiopaque acrylic bone cement. II. Acrylic bone cement with bromine-containing monomer.

Bromine-containing methacrylate, 2-(2-bromopropionyloxy) ethyl methacrylate (BPEM), had been used in the formulation of acrylic radiopaque cements. The effect of this monomer incorporated into the liquid phase of acrylic bone cement, on the curing parameters, thermal properties, water absorption, density, compression tests and radiopacity was studied. A decrease of maximum temperature and an increase of the setting time were observed with the addition of the bromine-containing monomer in the radiolucent cement composition. Adding BPEM in radiolucent acrylic bone cements composition results in the decrease of glass transition temperature and increase of its thermal stability. Acrylic bone cements modified with bromine-containing comonomer are characterized by polymerization shrinkage lower than the radiolucent cement. Addition of bromine-containing comonomer in radiolucent acrylic bone cement composition determines the increase of compressive strength. Acrylic bone cements modified with bromine-containing comonomer proved to be radiopaque.

The anatomy of a horizontally impacted maxillary wisdom tooth.

A completely horizontally impacted upper third molar was revealed after routine dissection of a 62-year-old human cadaver of a Caucasian male. The molar was penetrating into the maxillary sinus and there was antral dehiscence of its bony alveolus. The bony alveolus was immediately in front of the greater palatine canal contents, and the bottom of the alveolus was dehiscent towards the greater palatine foramen. Within the greater palatine canal and foramen the greater palatine artery was duplicated and the nerve was found. Such antral relations of an impacted upper third molar predispose to oroantral communications if extraction is performed, while the close neurovascular relations represent a risk factor for postextractional haemorrhage and neurosensory disturbances and must be borne in mind when deciding on or performing the extraction.

Endothelial expression of c-kit and CD68 in dental follicles of human impacted third molars.

BACKGROUND: Periodontal tissue remnants of odontogenesis constitute the dental follicle (DF) which is actually considered a stem niche in adults. However, potentialities of local endothelia within this niche seem overlooked. We thus aimed at testing the endothelial cells expression of c-kit, the progenitor cells marker, and CD68, commonly regarded as a monocyte/macrophage marker, in human DFs. MATERIALS AND METHODS: We performed an immunohistochemical study using these two markers which were applied on samples collected from ten adult patients. RESULTS: The markers were positively expressed in endothelial cells, as well as in spindle-shaped stromal cells of the DF. CONCLUSIONS: The origin of DF stem or progenitor cells needs reviewing in the light of these findings, as endothelium could be a donor site for niche inhabitants.

Combined anatomical variations: The mylohyoid bridge, retromolar canal and accessory palatine canals branched from the canalis sinuosus.

The study of anatomical variations is important not only for collecting anthropometric data, but also for improving clinical protocols and understanding why a particular clinical procedure sometimes does not yield the expected results. We report the case of a 74 year-old patient, in which we observed combined anatomical variants of the mandible and maxillary bone. One of these was the unilateral mylohyoid bridge (MB) of the uncommon, lingular type. This MB extended posteriorly to the spine of Spix, over the sulcus colli behind the spine. It thus formed a common mandibular canal (MC) which further divided into a retromolar canal and the MC proper. This combination of variants in the mandible has not, to our knowledge, previously been reported, at least in studies using cone beam computed tomography (CBCT). Additionally we found multiple accessory canals (ACs) deriving from the canalis sinuosus, which opened opposite to each frontal tooth, presumably carrying either dental fibers of the palatine nerves, or palatine fibers of the anterior superior alveolar nerve. Although the ACs in the anterior palate are well established anatomical variants, the MB appears in publications rather as an anthropological identifier. However, when present, it can impede anaesthesia of the lower teeth and thus deserves to be included in anatomical descriptions. The evaluation of patients in CBCT should observe the anatomical features on a case-by-case basis and it also provide data for studies of MB prevalence in large numbers of patients.

Toll-like receptor 4 expression in the epithelium of inflammatory periapical lesions. An immunohistochemical study.

Toll-like receptors (TLR) are essential for the innate immune response against invading pathogens and have been described in immunocompetent cells of areas affected by periapical disease. Besides initiating the inflammatory response, they also directly regulate epithelial cell proliferation and survival in a variety of settings. This study evaluates the in situ expression of TLR4 in periapical granulomas (PG) and radicular cysts, focusing on the epithelial compartment. Twenty-one periapical cysts (PC) and 10 PG were analyzed; 7 dentigerous non-inflamed follicular cyst (DC) served as control. TLR4 expression was assessed by immunohistochemistry. TLR4 immunoreaction products were detected in the epithelium of all specimens, with a higher percentage of immunostained cells in PG. Although TLR4 overexpression was detected in both PG and PC, there were differences that seemed to be related to the nature of the lesion, since in PG all epithelial cells of strands, islands and trabeculae were strongly immunoreactive for TLR4, whereas in PC only some areas of the basal and suprabasal epithelial layers were immunostained. This staining pattern is consistent with the action of TLR4: in PG it could promote formation of epithelial cell rests of Malassez and in epithelial strands and islands the enhancement of cell survival, proliferation and migration, whereas in PC TLR4 could protect the lining epithelium from extensive apoptosis. These findings go some way towards answering the intriguing question of why many epithelial strands or islands in PG and the lining epithelium of apical cysts regress after non-surgical endodontic therapy, and suggest that TLR4 plays a key role in the pathobiology of the inflammatory process related to periapical disease.

Immunohistochemical analysis of matrix metalloproteinase-13 in human caries dentin.

The immunoexpression profile of matrix metalloproteinase-13 was investigated for the first time in dentin of human caries and healthy teeth. Twelve permanent premolars (10 caries and 2 sound) were decalcified in ethylenediaminetetraacetic acid and processed for embedding in paraffin wax. Sections 3-4 µm in thickness were cut and processed for immunohistochemistry. A mouse monoclonal anti-metalloproteinase-13 antibody was used for localisation using an immunoperoxidase technique. Dentinal immunoreactivity was detected in all teeth; it was weak in sound teeth and strong close to the caries area. These in vivo findings suggest a role for metalloproteinase-13 in the development and progression of adult human dental tissue disorders.

Dental pulp as a stem cell reservoir.

Currently, much information is provided regarding the presence and the roles in tissue regeneration of stem cell niches residing in post-natal dental pulp. So far, three types of adult stem cells have been isolated from dental pulp. Correct evaluation of these cells is important in order to determine their potential use in clinical fields. The present study aims to review the origins and immunophenotype of these cells. The particularities of interstitial cells of the stem cell niches are also debated.