Bovine and Ovine Teeth as a Substitute for the Human Teeth: An Experimental Study.

Statement of the Problem: Although various kinds of research have been conducted to compare the physical and chemical properties of dentin and enamel in animal and human samples, proving the ability of animal dentin material as a good substitute for human specimens is always a challenge for experimental studies. Purpose: The aim of the present study is to investigate whether the changes in the dentin microhardness of animal samples are similar to those of human samples or not. Materials and Method: In this in vitro study, sixty single-rooted human, bovine, and ovine teeth (n=20 in each group) were decoronated at CEJ. The remaining roots were embedded in acrylic resin and a cross-section cut was made in the middle of the samples in order to achieve dentin disks. All of the 120 samples were randomly assigned to three control (n=20 for each group) and three experimental groups (n=20 for each group). In the experimental groups, calcium hydroxide with a creamy consistency was prepared and the disks were embedded in dishes containing calcium hydroxide. Control groups were embedded in physiological saline. The samples were incubated for seven days at the 37oC and Vickers microhardness test was performed immediately. The average of three yielded values was considered as the final value of microhardness. Data were analyzed using two-way ANOVA, one-way ANOVA, and Tukey's post hoc tests. Results: In the control group, the human samples showed the highest microhardness value, while the bovine teeth had the lowest microhardness value (p< 0.001). In the calcium hydroxide group, the human samples showed the highest microhardness value in comparison to bovine and ovine to teeth. However, no significant difference was observed between the bovine and ovine samples in microhardness value. Conclusion: Based on our research, substituting bovine and ovine samples with human samples in experimental studies is not recommended. Nevertheless, more studies are needed in this regard.

Foreign Bodies of Dental Iatrogenic Origin Displaced in the Maxillary Sinus - A Safety and Efficacy Analysis of a Retrospective Study.

Introduction: Foreign bodies (FB) of the paranasal sinuses are an uncommon clinical entities with the maxillary sinuses being those most frequently affected. According to the literature, 60% of paranasal sinus FB are of iatrogenic origin, while 25% are of traumatic origin. This article aims to present an iatrogenic origin series of cases of FB displaced or projecting into the maxillary sinus. Materials and Methods: In this retrospective study, the presence of the foreign body was revealed with radiologic methods and confirmed during the operation with macroscopic or later with histopathologic examination. All cases were treated with osteoplasty with vascularised pedicled bone flap or through minimally invasive intraoral procedure. Results: A total of 27 patients were included in our study, 14 men and 13 women. The age range was 18-65 years with mean age of 46.14 (standard deviation = 10.35) years. Foreign body was displaced fragments of teeth in 11 patients (40.27%), complete teeth in four patients (14.81%), dental implants in five patients (18.51%), dental impression material in 2 cases (7,40%), gutta percha cone in two patients (7.40%), endodontic sealer associated with aspergillosis in two patients (7.40%), and dental burr in one patient (3.7%). The time between dental foreign body displacement and the surgical intervention for its removal was critical for the occurrence of sinusitis. All operated patients remained asymptomatic during a follow-up of at least 1 year. Discussion: Prompt intervention for removal of FB eliminates the risk for chronic inflammation of the affected maxillary sinus and reduces the odds for sequelae.

Patterns of variation in canal and root number in human post-canine teeth.

Descriptive morphology of tooth roots traditionally focuses on number of canals and roots. However, how or if canal and root number are related is poorly understood. While it is often assumed that canal number is concomitant with root number and morphology, in practice canal number and morphology do not always covary with external root features. To investigate the relationship between canal and root number, fully developed, adult post-canine teeth were examined and quantified from computerized tomography scans from a global sample of 945 modern humans. We tested the hypotheses that root and canal number do not follow a 1:1 ratio, that canal to root ratios differ between teeth, and that canal to root ratios differ across major human geographical groups. Results indicate that not only is root number dependent on canal number, but that this relationship becomes more variable as canal number increases, varies between individual teeth and by major geographical group, and changes as these groups increase in geographical distance from Sub-Saharan Africa. These results show that the ratio of canal number to root number is an important indicator of variation in dental phenotypes.

Acid Dentin Lysate Failed to Modulate Bone Formation in Rat Calvaria Defects.

Autogenous tooth roots are increasingly applied as a grafting material in alveolar bone augmentation. Since tooth roots undergo creeping substitution similar to bone grafts, it can be hypothesized that osteoclasts release the growth factors stored in the dentin thereby influencing bone formation. To test this hypothesis, collagen membranes were either soaked in acid dentin lysates (ADL) from extracted porcine teeth or serum-free medium followed by lyophilization. Thereafter, these membranes covered standardized 5-mm-diameter critical-size defects in calvarial bone on rats. After four weeks of healing, micro-computed tomography and histological analyses using undecalcified thin ground sections were performed. Micro-computed tomography of the inner 4.5 mm calvaria defects revealed a median bone defect coverage of 91% (CI: 87-95) in the ADL group and 94% (CI: 65-100) in the control group, without significant differences between the groups (intergroup p > 0.05). Furthermore, bone volume (BV) was similar between ADL group (5.7 mm3, CI: 3.4-7.1) and control group (5.7 mm3, CI: 2.9-9.7). Histomorphometry of the defect area confirmed these findings with bone area values amounting to 2.1 mm2 (CI: 1.2-2.6) in the ADL group and 2.0 mm2 (CI: 1.1-3.0) in the control group. Together, these data suggest that acid dentin lysate lyophilized onto collagen membranes failed to modulate the robust bone formation when placed onto calvarial defects.

Automatic tooth roots segmentation of cone beam computed tomography image sequences using U-net and RNN.

BACKGROUND: Automatic segmentation of individual tooth root is a key technology for the reconstruction of the three-dimensional dental model from Cone Beam Computed Tomography (CBCT) images, which is of great significance for the orthodontic, implant and other dental diagnosis and treatment planning. OBJECTIVES: Currently, tooth root segmentation is mainly done manually because of the similar gray of the tooth root and the alveolar bone from CBCT images. This study aims to explore the automatic tooth root segmentation algorithm of CBCT axial image sequence based on deep learning. METHODS: We proposed a new automatic tooth root segmentation method based on the deep learning U-net with AGs. Since CBCT sequence has a strong correlation between adjacent slices, a Recurrent neural network (RNN) was applied to extract the intra-slice and inter-slice contexts. To develop and test this new method for automatic segmentation of tooth roots using CBCT images, 24 sets of CBCT sequences containing 1160 images and 5 sets of CBCT sequences containing 361 images were used to train and test the network, respectively. RESULTS: Applying to the testing dataset, the segmentation accuracy measured by the intersection over union (IOU), dice similarity coefficient (DICE), average precision rate (APR), average recall rate (ARR), and average symmetrical surface distance (ASSD) are 0.914, 0.955, 95.8% , 95.3% , 0.145 mm, respectively. CONCLUSIONS: The study demonstrates that the new method combining attention U-net with RNN yields the promising results of automatic tooth roots segmentation, which has potential to help improve the segmentation efficiency and accuracy in future clinical practice.

GREMLIN 2 Mutations and Dental Anomalies.

Isolated or nonsyndromic tooth agenesis or hypodontia is the most common human malformation. It has been associated with mutations in MSX1, PAX9, EDA, AXIN2, EDAR, EDARADD, and WNT10A. GREMLIN 2 (GREM2) is a strong bone morphogenetic protein (BMP) antagonist that is known to regulate BMPs in embryogenesis and tissue development. Bmp4 has been shown to have a role in tooth development. Grem2(-/-) mice have small, malformed maxillary and mandibular incisors, indicating that Grem2 has important roles in normal tooth development. Here, we demonstrate for the first time that GREM2 mutations are associated with human malformations, which include isolated tooth agenesis, microdontia, short tooth roots, taurodontism, sparse and slow-growing hair, and dry and itchy skin. We sequenced WNT10A, WNT10B, MSX1, EDA, EDAR, EDARADD, AXIN2, and PAX9 in all 7 patients to rule out the effects of other ectodermal dysplasias and other tooth-related genes and did not find mutations in any of them. GREM2 mutations exhibit variable expressivity even within the same families. The inheritance is autosomal dominant with incomplete penetrance. The expression of Grem2 during the early development of mouse teeth and hair follicles and the evaluation of the likely effects of the mutations on the protein structure substantiate these new findings.

Dental root size in bats with diets of different hardness.

The relationship between tooth roots and diet is relatively unexplored, although a logical relationship between harder diets and increased root surface area (RSA) is suggested. This study addresses the interaction between tooth morphology, diet, and bite force in small mammals, phyllostomid bats. Using micro computed tomography (microCT), tooth root morphology of two fruit-eating species (Carollia perspicillata and Chiroderma villosum) and two insect-eating species (Mimon bennettii and Macrotus californicus) was compared. These species did not differ in skull or estimated body size. Food hardness, rather than dietary classification, proved to be the strongest grouping factor, with the two insectivores and the seed-processing frugivore (C. villosum) having significantly larger RSAs. Bite force was estimated using skull measurements; bite force significantly correlated with tooth RSA but not with body size. Although the three durophagous species did exhibit larger crowns, the area of the occlusal surface did not vary among the four species. There was a linear relationship between root size and crown size, indicating that the roots were not expanded disproportionately; instead the entire tooth was larger in the hard diet species. MicroCT allows the nondestructive quantification of previously difficult-to-access tooth morphology; this method shows the potential for tooth roots to provide valuable dietary, behavioral, and ecological information in small mammals. J. Morphol. 276:1065-1074, 2015. © 2015 Wiley Periodicals, Inc.

Osterix regulates tooth root formation in a site-specific manner.

Bone and dentin share similar biochemical compositions and physiological properties. Dentin, a major tooth component, is formed by odontoblasts; in contrast, bone is produced by osteoblasts. Osterix (Osx), a zinc finger-containing transcription factor, has been identified as an essential regulator of osteoblast differentiation and bone formation. However, it has been difficult to establish whether Osx functions in odontoblast differentiation and dentin formation. To understand the role of Osx in dentin formation, we analyzed mice in which Osx was subjected to tissue-specific ablation under the control of either the Col1a1 or the OC promoter. Two independent Osx conditional knockout mice exhibited similar molar abnormalities. Although no phenotype was found in the crowns of these teeth, both mutant lines exhibited short molar roots due to impaired root elongation. Furthermore, the interradicular dentin in these mice showed severe hypoplastic features, which were likely caused by disruptions in odontoblast differentiation and dentin formation. These phenotypes were closely related to the temporospatial expression pattern of Osx during tooth development. These findings indicate that Osx is required for root formation by regulating odontoblast differentiation, maturation, and root elongation. Cumulatively, our data strongly indicate that Osx is a site-specific regulator in tooth root formation.

Wntless regulates dentin apposition and root elongation in the mandibular molar.

Wnt signaling plays an essential role in the dental epithelium and mesenchyme during tooth morphogenesis. However, it remains unclear if Wnt ligands, produced from dental mesenchyme, are necessary for odontoblast differentiation and dentin formation. Here, we show that odontoblast-specific disruption of Wntless (Wls), a chaperon protein that regulates Wnt sorting and secretion, leads to severe defects in dentin formation and root elongation. Dentin thickness decreased remarkably and pulp chambers enlarged in the mandibular molars of OC-Cre;Wls(CO/CO) mice. Although the initial odontoblast differentiation was normal in the mutant crown, odontoblasts became cuboidal and dentin thickness was reduced. In immunohistochemistry, Wnt10a, ß-catenin, type I collagen, and dentin sialoprotein were significantly down-regulated in the odontoblasts of mutant crown. In addition, roots were short and root canals were widened. Cell proliferation was reduced in the developing root apex of mutant molars. Furthermore, Wnt10a and Axin2 expression was remarkably decreased in the odontoblasts of mutant roots. Deletion of the Wls gene in odontoblasts appears to reduce canonical Wnt activity, leading to inhibition of odontoblast maturation and root elongation.

A new technique to make transparent teeth without decalcifying: description of the methodology and micro-hardness assessment.

Diaphanisation and other in vitro endodontic models (i.e., plastic blocks, micro-CT reconstruction, computerised models) do not recreate real root canal working conditions: a more realistic endodontic model is essential for testing endodontic devices and teaching purposes. The aim of this study was to describe a new technique to construct transparent teeth without decalcifying and evaluate the micro-hardness of so treated teeth. Thirty freshly extracted teeth were randomly divided into three groups as follows: 10 non-treated teeth (4 molars, 3 premolars, 3 incisors; control group - G1), 10 teeth were diaphanised (4 molars, 4 premolars, 2 incisors - G2) and 10 teeth were treated with the new proposed technique (2 molars, 6 premolars, 2 incisors - G3). Vickers hardness tester (MHT-4 and AxioVision microscope, Carl Zeiss, 37030 Gottingen, Germany - load=50 g, dwell time=20s, slope=5, 50× magnification) was used to determine microhardness (Vickers Hardness Number - VHN). Statistical analysis was performed using the Intercooled Stata 8.0 software (Stata Corporation, College Station, TX, USA). Only groups 1 and 3 could be tested for hardness because diaphanised teeth were too tender and elastic. Differences in enamel VHN were observed between G1 (mean 304.29; DS=10.44; range 283-321) and G3 (mean 318.51; DS=14.36; range 295.5-339.2) - (p<0.05); differences in dentine VHN were observed between G1 (mean 74.73; DS=6.62; range 63.9-88.1) and G3 (mean 64.54; DS=5.55; range 51.2-72.3) - (p<0.05). G3 teeth presented a slightly lower VHN compared to G1, probably due to some little structural differences among groups, and were dramatically harder than the diaphanised teeth. The described technique, thus, can be considered ideal for testing endodontic instruments and for teaching purposes.

In vitro macroscopic and endoscopic analysis of three-rooted maxillary premolars and two-rooted mandibular premolars in the same individual: a case report / Análisis macroscópico y endoscópico in vitro de premolares maxilares trirradiculares y mandibulares birradiculares en un mismo individuo: un reporte de caso

The recent addition of endoscopy in dental practice has enabled clinicians to have an excellent view of the operative field, yielding highly successful visualization of anatomical structures that are difficult to access, both in oral surgery and endodontics. The purpose of this report is to provide an in vitro macroscopic, radiographic, and endoscopic description of the anatomic variation of the roots of maxillary and mandibular first premolars in the same patient. A 22-year-old patient was referred by an orthodontist for the extraction of all the first premolars. Once extracted, the premolars were examined macroscopically and then analyzed radiographically after trepanation and filled root canal systems. Subsequently, a diaphanization process was carried out and the samples were sectioned at the middle and apical third for observation by endoscope. It was found that both the maxillary first premolars had three roots, and mandibular first premolars had two roots, all with complete root formation. Apical deltas or accessory canals were not identified in the radiographic images; however, through endoscope at the middle third, it was possible to observe an accessory canal to the first maxillary and mandibular right premolars. Thus, it can be concluded that the view through the endoscope allows better identification of accessory canals than X-rays.

La reciente incorporación del endoscopio a la práctica odontológica ha permitido al clínico, contar con una excelente visualización del campo operatorio, consiguiendo resultados altamente exitosos en la visualización de estructuras anatómicas de difícil acceso, tanto en cirugía oral como en endodoncia. El propósito de este reporte de caso es realizar una descripción in vitro macroscópica, radiográfica y endoscópica de las variables anatómicas de las raíces de los primeros premolares maxilares y mandibulares en un mismo paciente. Una paciente de 22 años es derivada por un ortodoncista para exodoncia de los primeros premolares. Una vez extraídos, los premolares fueron analizados en un principio macroscópicamente, para luego ser analizados radiográficamente una vez trepanados y obturados los sistemas de conductos radiculares. Posterior a esto, se sometieron a un proceso de diafanización y se les realizaron cortes a nivel del tercio apical y medio para ser observados mediante endoscopio. Se detectó que ambos primeros premolares superiores presentaban 3 raíces, y los inferiores 2 raíces, todos con formación radicular completa. No se identificaron deltas apicales ni conductos accesorios en las imágenes radiográficas; sin embargo, fue posible mediante el endoscopio a nivel del tercio medio, un conducto accesorio para los primeros premolares derechos inferiores y superiores situación que no se pudo identificar radiográficamente. Finalmente, la visualización a través del endoscopio permite una mejor identificación de conductos accesorios que las radiografías.

Variaciones anatómicas radiculares y sistemas de canales / Tooth root and pulp canal anatomical variations

El desarrollo dentario resulta de una complicada interacción entre el epitelio oral y el tejido mesenquimático subyacente durante la Odontogénesis. La interacción anormal de estos tejidos podría resultar en el desarrollo y/o erupción de un diente anómalo, ectópico o con variación anatómica. El presente reporte muestra tres casos de variaciones anatómicas radiculares y al sistema de canales: un canino mandibular, un premolar mandibular y un primer premolar maxilar. El diagnóstico en los tres casos se efectuó por medio del análisis de radiografías. El canino y premolar mandibular presentaron dos raíces y dos canales, el premolar maxilar presentó tres raíces y tres conductos. Dada la presencia de una caries penetrante en este último, fue derivado a un especialista en endodoncia para su tratamiento y posterior rehabilitación. Idealizar el sistema de canales como una entidad simple es un error, por lo que es importante considerar estas variaciones anatómicas especialmente ante presencia de dientes con patologías que requieran tratamientos de endodoncia o cualquier procedimiento al interior del sistema de canales, ya que la oportuna y adecuada indicación de exámenes complementarios permite pesquisar y diagnosticar variaciones anatómicas de este tipo, para minimizar la ocurrencia de accidentes durante el tratamiento.

Teeth development results from a complicated interaction between oral epithelium and underlying mesenchematic tissue during odontogenesis. Abnormal interaction between this tissues could result in development and eruption of an ectopical, anomalous teeth or with an anatomical variation. This report shows three cases of teeth with anatomical variations at root and pulp canal in mandibular canine and bicuspid, and maxillary first bicuspid. Diagnosis of these cases was performed through radiographical analysis. Mandibular canine and bicuspid shown two root and two pulp canals, maxillary first bicuspid presented three roots and three pulp canals. Considering that maxilar tooth showed caries closer to pulp chamber, patient was derived to an endodontic specialist to perform an endodontic treatment and rehabilitation. Idealizing root canal as a simple and invariable structure is a mistake. Clinicians always ought to take into consideration potential anatomical variations in teeth, especially in those that require endodontic treatments or any kind of procedure inside root canal system. Timely and adequate indication of imagenological complementary exams allow an adequate diagnosis of anatomical variations that will decrease chances of accidents during treatment.