Split Teeth Research Articles

Differentiation of the structure of dentinal tubules and dentinal canaliculi in human teeth of different ages

The dentinal tubules are designed to protect the odontoblast processes, which leave behind a cytoplasmic process during tooth development. Around the cytoplasmic process, a dentin matrix is deposited, which eventually mineralizes. However, the question of the role and structure of the cytoplasmic process of the odontoblast in each dentinal tubule after dentin has completely finished the formation process remains an unresolved issue. We investigated the dentinal tubules of 20 permanent teeth (premolars and molars) of people of different ages using a scanning electron microscope. The occlusal surfaces and longitudinal fracture planes of both decalcified and non-decalcified native tooth preparations were examined. In longitudinally split teeth at the periphery of the pulp chamber of a young human premolar, odontoblasts can be seen forming a continuous layer adjacent to the parapulpal dentin. Each of the odontoblasts has a separate process that penetrates into the dentinal tubule. More peripheral parts of the dentinal tubules were either empty or contained cylindrical structures that were better visualized after acid etching on longitudinally split samples. Etched split dentinal tubules in the outer dentin more often contained cylindroid tubular structures. In each individual dentinal tubule, the odontoblast processes are arranged in the form of thin-walled tubules, which, with the help of a supporting fibrillar framework, occupy a central position. On the occlusal surface of a mature human molar, the intertubular dentin has the appearance of a smooth-surfaced structure. Practically all dentinal tubules contain more or less preserved dentinal canaliculi, indicating their fairly pronounced resistance to adverse factors. Inside the lumen of the dentinal tubules, three different types of structures are observed: odontoblast processes, cylindrical structures, and collagen fibers. Odontoblast processes are visualized both along the entire length of the dentinal tubules and only in the parapulpal parts of the dentinal tubules. Their peripheral parts were either empty or contained cylindrical structures that likely correspond to the laminae limitantes. Collagen fibers often form a fibrillar network that on one side intertwines into the dentinal canaliculus, and on the other side is connected to the walls of the dentinal tubules due to perpendicular microtubules for anchoring fibrils. Collagen fibers are most numerous in the parapulpal parts of the dentinal tubules. This study only partially explained certain aspects of the dentin microstructure, but further in-depth studies of dentin ultrastructure are necessary to more fully understand the pathology of hard tooth tissues in people of different ages and the possibilities for its treatment and prevention.

A Novel Counter-Rotating AFPM Machine Based on Magnetic-Field Modulation for Underwater Propulsion System

The underwater propulsion system (UPS) with two counter-rotating propellers is very popular now. In tradition, it needs two electric machines or additional gears, which greatly increases the volume and weight of the system. Therefore, a novel counter-rotating axial-flux permanent magnet (AFPM) machine based on magnetic-field modulation (MFM) for the UPS is proposed. It contains a more pole (MP) rotor and a less pole (LP) rotor on two sides. The MFM is achieved through the split teeth on the stator. Based on the MFM, the two rotors can rotate in opposite directions. The principle of MFM and the relationships of rotary speeds between two rotors are analyzed. Furthermore, the effects of split tooth shape and dimensions on the performances of the proposed machine are also evaluated. The triangular skew fan-shaped split teeth are adopted in the counter-rotating AFPM machine. Finally, the prototype is manufactured and an experiment is conducted to validate the performance. The results show the consistency of analysis and experiment.

Antimicrobial efficacy of sodium hypochlorite and hyper-pure chlorine dioxide in the depth of dentin tubules in vitro

ObjectivesThe study aimed to compare the antibacterial effect of a novel disinfectant, hyper-pure chlorine dioxide (hClO2) to sodium hypochlorite (NaOCl) in various depths of dentin tubules.Materials and methodsThe distal root of the extracted lower molars was infected artificially with Enterococcus faecalis. The control group was rinsed with saline, and the test groups were irrigated with either 5% NaOCl or 0.12% hClO2. The longitudinally split teeth were stained by viability stain. The coronal third of the root was scanned with a confocal laser scanning microscope. The fluorescent intensities were measured, and the percentage of dead bacteria was calculated at depths up to 950 μm along the dentin tubules. The effect of penetration depth, irrigants, and their interaction on antimicrobial efficacy was determined by the linear mixed model.ResultsThe percentage of dead bacteria was higher both in the NaOCl (45.1 ± 2.3%, p < 0.01) and in the hClO2 (44.6 ± 3.8%, p < 0.01) irrigant groups compared to saline (23 ± 4.5%); however, there was no difference between them. The percentage of killed bacteria was not correlated with the depths in any group (p = 0.633).ConclusionsOur results suggest that the functional penetration depth of NaOCl is at least 2–3 times more than published to date. There is no difference in disinfection effectiveness along the dentin tubules between NaOCl and hClO2 until at least the measured 950 μm. However, both were only able to eradicate the intratubular bacteria partially.Clinical relevanceHyper-pure ClO2 could be used as an alternative or final adjuvant irrigant in endodontic treatment.

Analysis of Synergistic Stator Permanent Magnet Machine With the Synergies of Flux-Switching and Flux-Reversal Effects

Dual permanent magnet (PM) machines have attracted numerous interests due to the high torque density and compact volume <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</i> This article investigates a synergistic PM machines with the synergies of flux switching and flux reversal effects. The flux-reversal and flux-switching PM (FSPM) flux paths circulate from two sides of the split teeth separately, which avoid the over-saturation with dual PM excitations. The preferred stator and rotor pole number is derived from a simplified analytical model and the influence of leading parameters is analyzed as design guidelines. Furthermore, the synergistic stator PM machine is optimized and compared with FSPM machines. It is revealed that the synergistic stator PM machine exhibits ∼20%, ∼10%, and ∼17% higher torque density than conventional FSPM machine, C-core FSPM machine, and E-core FSPM machine, respectively. Besides, good flux weakening capability is achieved with a larger inductance than conventional FSPM machine, and higher efficiency is obtained at both low-speed and high-speed operations. Finally, an experimental prototype is fabricated to validate the proposed concepts.

A New Hybrid Magnet Dual Stator Field Modulation Machine With Different Split Ratios of Stators

A new type of hybrid magnet dual stator field modulation machine with different split ratios of stators (DSR-HMDSFMM) is proposed in this article, which has the merit of high torque density. The split teeth of stator sever as modulators to modulate air gap flux density based on the magnetic gearing effect for high torque production. The total split tooth number of inner stator is equal to that of outer stator because the pole pair numbers of armature reaction and permanent magnet (PM) excitation on rotor are equal. Furtherly, the inner and outer stators with different split ratios and same split tooth number are employed to increase torque production because armature windings with high winding factor and high turn number can be used. In addition, the employment of hybrid magnet excitation can increase space utilization and enhance the air gap flux density with low harmonic distortion. Therefore, the proposed DSR-HMDSFMM can achieve high torque production with the same volume and PM usage. In order to find the optimal split ratio match of stators, several DSR-HMDSFMMs with different combinations of split ratios are proposed and calculated. The configuration and operating principle are illustrated, together with electromagnetic performances of the proposed machines analyzed using finite element analysis (FEA). The FEA-predicted results show that the proposed HMDSFMM exhibits high air-gap flux density with low harmonic distortion and high torque density, which is promising for the direct-drive applications.

Analysis and Reduction Methods of Cogging Torque in Dual PM Vernier Machines With Unevenly Distributed Split Teeth

This article investigates the source and reduction methods of cogging torque in dual PM Vernier machines (DPVMs), especially for the ones with unevenly distributed split teeth (UDST). At first, the increase of no-load back electromotive force in DPVMs with UDST is illustrated through the analysis of airgap working flux harmonics. The reason for largely increased cogging torque of DPVMs with UDST is then analyzed, and main flux harmonics that contribute to cogging torque are identified. To reduce cogging torque and torque ripple, several effective methods are introduced in this article, which are mainly based on the reduction or offset of corresponding airgap flux harmonics. The cogging torque reduction effects and torque performances of these methods are compared. Among them, newly proposed N/S-parts offset method is proved to be superior to other methods in DPVMs. A new DPVM prototype with UDST and N/S-parts offset structure is built and tested. Experimental results show that through the N/S-parts offset method, cogging torque of the machine is largely decreased from 9 to 0.3 N·m, which validates the analysis and simulation results.

Red fluorescence for assessing longitudinal tooth fractures

BackgroundThis study was designed to determine whether autofluorescence emitted from longitudinal tooth fractures (LTFs) differs between fracture types, with the aim of determining which clinical factors are related to red fluorescence at the fracture line. MethodsThirty-three extracted teeth were classified into cracked teeth, split teeth, and root fractures using LTF types according to the American Association of Endodontists classification. The types of LTFs were identified using an operating microscope. LTF autofluorescence was captured using a fluorescence technique. Clinical examinations were performed using the preoperative factors from clinical and radiographic findings. ResultsRed fluorescence was identified in 82% and 83% of cracked and split teeth, respectively. None of the vertical root fractures exhibited red fluorescence (p<0.001). When red fluorescence was identified on the outer tooth surface, it penetrated into the crack line, but fluorescence that was not red at the tooth surface did not penetrate the fracture line. Among the examined preoperative clinical factors, differences between the presence and absence of red fluorescence were identified for sinus tract formation (p = 0.021), and radiographic features (p = 0.027). Regression analysis revealed a significant factor related to the red fluorescence, with sinus tract formation having a negative effect on red fluorescence (odds ratio [OR]=0.09). The presence of comprehensive periradicular lesions in radiography had a positive effect on red fluorescence (OR=5.04). ConclusionsCracks originating from tooth crowns in certain types of LTFs were associated with red fluorescence, and cracks with red fluorescence were associated with extensive periodontal bone resorption around the teeth roots.

Comparative Study of Dual PM Vernier Machines

In this paper, two types of dual permanent magnet (PM) machines, i.e., stator slot dual-PM (SSDPM) machine and split-tooth dual-PM (STDPM) machine, are investigated and compared. Both machines have consequent pole structure with Halbach array PMs. Their difference lies in the position of stator PM. The SSDPM machine has Halbach array PMs in the stator slots, while the STDPM machine has PMs between the split teeth. Torque characteristics, i.e., average torques and torque ripples, of different slot/pole number combinations of the two machines are compared. The 24 stator slots/20 rotor slots/4 armature pole pair (24S20R4Pa) SSDPM machine with distributed windings and the 24 stator slots/10 rotor slots/4 armature pole pair (12S20R4Pa) STDPM machine with concentrated windings are compared under both open-circuit and on-load conditions. The results show that the SSDPM machine is more competitive by delivering higher torque density and higher power density.

Analysis of Split-Tooth Stator Slot PM Machine

In this article, split-tooth stator slot permanent magnet (PM) machines, which have high fault-tolerant capability, are proposed. Compared with the existing 12-slot 10-pole (12S10P) stator slot PM machine, the torque can be improved by 66% by properly choosing the split tooth number and other geometric parameters. It is found that two split teeth stator slot PM machine (ST2) shows the best torque characteristics among the stator slot PM machines with different split tooth number. To further illustrate the merits and demerits of ST2, a conventional 6S4P surface mounted PM machine (SPMM) and a 6S4P variable flux reluctance machine serve as the benchmarks to compare with the 6S11P ST2, at both open circuit condition and load condition. The 6S11P ST2 shows 68% higher torque over the 6S4P VFRM. Although the torque of the 6S11P ST2 is around half of the 6S4P SPMM, the former has 70% higher torque per PM volume than the latter. Furthermore, demagnetization analyses under three-phase short-circuit and pure d-axis currents show that the 6S11P ST2 has much better demagnetization withstand capability over the 6S4P SPMM. A Prototype is manufactured and tested to validate the theoretical analyses.

Fractographic Analysis of a Split Tooth Presenting Radiographically as a Horizontal Root Fracture in an Unrestored Mandibular Second Molar

IntroductionSpontaneously catastrophic fracture of intact unrestored molar teeth is not common. Nevertheless, cracks do occur that progress apically, resulting in the complete splitting of the tooth and root. This report describes a catastrophic fracture that occurred in an unrestored mandibular second molar resulting in a previously unreported combination of a longitudinal and horizontal root fracture, appearing radiographically as a single horizontal root fracture. MethodsTooth fragments were examined clinically, stereoscopically, and by scanning electron microscopy. Fractographic analysis was used to investigate the dynamics involved in fracture initiation, structural resistances encountered during progression of the fracture, and reasons for direction changes culminating in the unusual radiographic appearance. ResultThe uniqueness of this report is that it describes fractographic evidence of factors contributing to the initiation and progression of an in vivo crack. It shows fracture markings that are evidence of the energy dissipation mechanisms. The topographic location of these markings confirmed that cracks occur in vivo in stages with different rates of progression. ConclusionThis analysis helps to explain why split teeth are uncommon and highlights some of the multitude of factors that have to coincide for a tooth to catastrophically fracture. The report describes the mechanism of fracture and should stimulate clinicians and researchers to investigate cracking of teeth by undertaking fractographic analysis of extracted cracked teeth.

Etching Treatment Effect on Surface Morphology of Dental Structures

This study examined and compared surface of human dentine after acidic etching with hydrogen peroxide, phosphoric acid liquid and gel. Surface demineralization of dentin is necessary for a strong bond of adhesive at dental surface. Split human teeth were used. After application of mentioned substances at dentin level measures of the contact angle and surface morphology were employed. Surface morphology was analyzed with the help of scanning electron microscopy and atomic force microscopy. Liquid phosphoric acid yielded highest demineralization showing better hydrophobicity than the rest, thus having more contact surface. Surface roughness are less evident and formed surface micropores of 4 �m remained open after wash and air dry providing better adhesive canalicular penetration and subsequent bond.

Automatic detection of tooth cracks in optical coherence tomography images.

PurposeThe aims of the present study were to compare the image quality and visibility of tooth cracks between conventional methods and swept-source optical coherence tomography (SS-OCT) and to develop an automatic detection technique for tooth cracks by SS-OCT imaging.MethodsWe evaluated SS-OCT with a near-infrared wavelength centered at 1,310 nm over a spectral bandwidth of 100 nm at a rate of 50 kHz as a new diagnostic tool for the detection of tooth cracks. The reliability of the SS-OCT images was verified by comparing the crack lines with those detected using conventional methods. After performing preprocessing of the obtained SS-OCT images to emphasize cracks, an algorithm was developed and verified to detect tooth cracks automatically.ResultsThe detection capability of SS-OCT was superior or comparable to that of trans-illumination, which did not discriminate among the cracks according to depth. Other conventional methods for the detection of tooth cracks did not sense initial cracks with a width of less than 100 μm. However, SS-OCT detected cracks of all sizes, ranging from craze lines to split teeth, and the crack lines were automatically detected in images using the Hough transform.ConclusionsWe were able to distinguish structural cracks, craze lines, and split lines in tooth cracks using SS-OCT images, and to automatically detect the position of various cracks in the OCT images. Therefore, the detection capability of SS-OCT images provides a useful diagnostic tool for cracked tooth syndrome.

Functional tooth restoration utilising split germs through re-regionalisation of the tooth-forming field.

The tooth is an ectodermal organ that arises from a tooth germ under the regulation of reciprocal epithelial-mesenchymal interactions. Tooth morphogenesis occurs in the tooth-forming field as a result of reaction-diffusion waves of specific gene expression patterns. Here, we developed a novel mechanical ligation method for splitting tooth germs to artificially regulate the molecules that control tooth morphology. The split tooth germs successfully developed into multiple correct teeth through the re-regionalisation of the tooth-forming field, which is regulated by reaction-diffusion waves in response to mechanical force. Furthermore, split teeth erupted into the oral cavity and restored physiological tooth function, including mastication, periodontal ligament function and responsiveness to noxious stimuli. Thus, this study presents a novel tooth regenerative technology based on split tooth germs and the re-regionalisation of the tooth-forming field by artificial mechanical force.

Analysis of split tooth as an unstudied reason for tooth extraction.

BackgroundSplit tooth is an unstudied reason for tooth extraction. The purpose of this study was to determine and analyze split tooth as a reason for extraction in a dental clinic in Benin City.MethodsThe prospective study was carried out on 669 patients having tooth extraction between May, 2005 and December, 2012. Over the period of the study, diagnosis and tooth extraction were done by three dentists of more five years practice experience. The indications for tooth extraction were noted with specific interest on those diagnosed as split tooth without restoration. Data was entered into Microsoft excel, sorted and transported into SPSS (SPSS version 16.0, Chicago, IL, USA).ResultsSplit teeth constituted for 39 (5%) of extracted teeth. This 39 extractions were done in 38 patients meaning that two split teeth were extracted on separate occasions from same patient. The majority 23 (61%) of extracted split tooth were done in patients in the fifth decade of life. More of the split tooth extraction were performed in males 28 (72%) than females 11 (28%). Overall mandibular teeth were more affected than the maxillary teeth and the most affected teeth were mandibular second molars 23 (59%) while the least affected were the mandibular first premolars 1 (3%) and the third molars 1 (3%). The reported masticatory accident as aetiology, were biting on stone 21 (53%) or piece of bone 10 (26%) while eating. A few 3 (8%) were suspected bruxists. The majority 25 (65%) visited the dental clinic 3–6 months after the incident and onset of symptoms.ConclusionSplit tooth constitute a reasonable common reason for tooth extraction and this was most common in the fifth decade of life. It is therefore important to improve early diagnosis of a cracked tooth in order to prevent the progression of the crack tooth to split tooth.

A SEM evaluation of dentinal adaptation of root canal obturation with GuttaFlow and conventional obturating material

The aim of this in-vitro study was to compare dentinal adaptation of conventional obturating material and GuttaFlow in young permanent teeth of child patients. Ten young permanent anterior teeth with closed foramen were selected for the study. Root canal preparations were carried out using a step back technique. The canal was alternately irrigated with 5.25% sodium hypochlorite solution and 17% EDTA and normal saline. After root canal preparation specimens were randomly divided into two groups (n=5). GROUP "A": Obturated with zinc-oxide eugenol sealer and gutta-percha cone using cold lateral obturation technique. GROUP "B": Obturated with GuttaFlow as per the manufacturer's instruction. The teeth were split into two halves. Five randomly chosen longitudinal split teeth samples each from Group "A" and Group "B" was observed under scanning electron microscope to access the interface between obturating material and dentin at the level of 2 mm from the apex. On statistical analysis the dentinal adaptation (μm) of Group A was observed with a mean of 0.52 and standard deviation 0.15, while the value of mean and standard deviation were noted 0.12 and 0.02 for Group B. The "t" value on comparison of Group A and Group B is 5.79 with "P " value of <0.001, which is highly significant. From result of the study it can be concluded Group B samples showed significantly superior seal when compared with Group A. Complete seal was not observed in any of Group A samples.

Crown cementing strategy for naval divers

Background: A large number of personnel working in hyperbaric environment such as divers and submariners during escape drills report to the out patient department with split teeth, displacement of restoration and pain during ascent after diving. These symptoms are probably attributable to dental barotraumas. Therefore, a need was felt to undertake a study in this area, with a specific interest for treating these patients. Methods: Sixty extracted single rooted premolar teeth were prepared and full cast crowns were cemented. Out of these, 20 were prepared with zinc phosphate, 20 with glassionomer and 20 with resin cement. After seven days of storage, each of the teeth in experimental group was pressure cycled 15 times to 3 atmospheres after which the force required to dislodge the crowns was tested on an Instron testing machine. Result: A significant difference was found (student's t test p value<0.01) between the force required to dislodge the crowns with zinc phosphate cemented control group (141.70 ± 38.62) and experimental group (16.92 ± 10.13). Similarly a significant difference was observed in the glassionomer cemented control group (184.33 ± 25.33) and experimental group (90.50 ± 34.07). On the other hand, no difference was found between the resin cemented control group (289.15 ± 81.48 ) and experimental (279.43±87.48) group. Conclusion: Within the limitations of this study and based on the results, it was concluded that environmental pressure cycling affected the retention of crowns cemented with zinc phosphate and glassionomer cement. Panavia resin cement used in this study appeared to be unaffected by environmental pressure cycling. On the basis of the results of this study, dental surgeons should consider cementing fixed prosthesis with resin cements for patients who are exposed to marked variations in environmental pressure, such as divers and submariners during escape drills.

Morphological Deformities in Chironomus Riparius Meigen Larvae after Exposure to Cadmium over Several Generations

In order to test the potential of chironomiddeformities for biomonitoring, induction of morphologicaldeformities in Chironomus riparius larvae was assessed afterchronic exposure (static with renewal) of eggs and subsequentinstars to sublethal nominal cadmium concentrations of 0, 3 (NOEC),9 (intermediate) and 27 (chronic LC50) μg Cd l-1 during 7to 10 generations. Deformities which could be associated with anindirect or direct cadmium effect were split medial mentum teeth(more frequent in 9 and 27 μg Cd l-1) and premandibledeformities (especially in 3 μg Cd l-1). The controlcontained more larvae with additional teeth in mentum and mandiblethan the metal-exposed conditions. In the 9 μg Cd l-1 condition the frequencies of larvae with split medial mentumteeth increased in the last four generations, to reach 40%. Theunpredictability of fluctuations of deformity frequencies over thegenerations was associated with parental effects and experimentalmanipulation. The deformity percentages correlated positively withthe mortalities and could be related to the induction of toleranceto cadmium, as was concluded on the basis of life cycle analysis ina previous paper. This experiment demonstrated a concentration-response relationship between deformities and sublethal levels ofcadmium. However, the observed generation fluctuations caution for(1) the use of single-generation experiments for definingecotoxicological threshold values, and (2) experimentally inducedgenetical drift in multi-generation experiments.

Traumatic Dental Disease and Soft Tissue Injuries of the Oral Cavity

Trauma to the oral cavity can result in an array of injuries affecting teeth, bone, and soft tissue. A thorough examination of the oral cavity is often facilitated by employing a full-mouth speculum after the horse has been tranquilized. Identification of broken, loose, or split teeth; fractures of the premaxilla or mandible; and avulsion or laceration of soft tissue structures such as the lips or tongue is usually straightforward. Treatment options vary depending on the structure involved; however, appropriate treatment generally results in a functional and cosmetically acceptable end result.

Subsurface morphologic changes of ND:YAG laser‐etched enamel

Background and Objective Etching the enamel surface with a Nd:YAG dental laser produces impact craters with cavities, micropores, and microfissures. This in vitro SEM study examined laser-etched enamel to determine the pattern and extent of subsurface changes. Study Design/Materials and Methods The facial surface of 10 maxillary central incisor teeth were coated with a black initiator and laser-etched with a pulsed Nd:YAG laser (1.06λ, 75 mJ, 15 Hz, 320 μm fiber, 94 J/cm2 fluence). The facial surface of five teeth were plastic-embedded under a low vacuum, then demineralized in 10% formic acid. The other teeth were split inciso-apically. All samples were prepared for SEM. Results Examination of the plastic impressions showed a delicate interlacing pattern of thin partitions and small knob-like expansions. Examination of the split teeth showed the penetration of microfissures into the enamel estimated at 10 μm. Conclusion These subsurface alterations may provide space for the infiltration and mechanical retention of dental resin. Lasers Surg. Med. 21:193–197, 1997. © 1997 Wiley-Liss, Inc.

Subsurface morphologic changes of ND:YAG laser-etched enamel.

Etching the enamel surface with a Nd:YAG dental laser produces impact craters with cavities, micropores, and microfissures. This in vitro SEM study examined laser-etched enamel to determine the pattern and extent of subsurface changes. The facial surface of 10 maxillary central incisor teeth were coated with a black initiator and laser-etched with a pulsed Nd:YAG laser (1.06 lambda, 75 mJ, 15 Hz, 320 microns fiber, 94 J/cm2 fluence). The facial surface of five teeth were plastic-embedded under a low vacuum, then demineralized in 10% formic acid. The other teeth were split incisoapically. All samples were prepared for SEM. Examination of the plastic impressions showed a delicate interlacing pattern of thin partitions and small knob-like expansions. Examination of the split teeth showed the penetration of microfissures into the enamel estimated at 10 microns. These subsurface alterations may provide space for the infiltration and mechanical retention of dental resin.