Radiological estimation of interradicular space of primary molar teeth

Radiological estimation of interradicular space of primary molar teeth has been performed. Radiograms taken from the department's archives on which primary molar teeth without dental caries were visible have been used for the purposes of the examinations. Roentgenograms had been made for exposition conditions required for endodontic therapy needs. Periodontium, lamina dura of the alveolus, bone texture of the interradicular space and disposition of permanent tooth buds have been estimated according to the radiograms. From the examination results it followed that proper estimation of interradicular space of primary molar teeth according to radiograms made for endodontic therapy needs is not possible. Radiological image of interradicular space of primary molar teeth in various both with reference to bone structure and disposition of permanent tooth buds. In most cases the interradicular space of primary molar teeth demonstrates thin bone structure on radiograms that should be considered to be physiological state when the continuity of lamina dura of the alveolus is preserved.     

Interradicular Root Canals in Mandibular First Molars: A Literature Review and Ex Vivo Study

Introduction

Successful endodontic treatment vastly depends to a high degree on an accurate knowledge of root canal system morphology. It is a prerequisite to be aware of all possible reservoirs where bacteria and/or toxins can persist, compromising the surrounding tissues; such knowledge results in endodontic success.

How Does the Pulpal Floor of a Molar Tooth Develop?

Development of the pulpal floor was reviewed from both macroscopic and microscopic perspectives, and relations between individual variation in tooth roots and their development are considered. It has been thought that the pulpal floor of a molar tooth is formed as a continuation of the coronal dentine in rodents. In humans, the interradicular dentine develops from a separate mineralization center or centers (subpulpal lobe), and only later does it unite with the coronal dentine. The subpulpal lobe appears in the tooth germ of some mammals other than humans, but it is absent in mice. The molars of Suncus have a large pulpal floor, and are useful as a model of the development of the bifurcation area. The calcified process of the pulpal floor in Suncus is divided into two stages : (1) the primary subpulpal lobe appears, and (2) a secondary subpulpal lobe forms aggregated by the small calcified centers. The number of secondary subpulpal lobes determines the root number. The connecting line among the subpulpal lobes on the completed tooth becomes a ridge (interradicular crista) on the external surface, and a groove (isthmus) on the internal surface. The pattern of the interradicular crista seems to depend on the number of roots. We addressed the following three macroscopic variants and these developments ; (1) three-rooted mandibular molar, (2) enamel projection, and (3) gutter-shaped root. These structures relate to developmental events.     

The crystallinity of human deciduous teeth in hypophosphataemic vitamin D-resistant rickets

Five teeth were obtained from three patients with hypophosphataemic vitamin D-resistant rickets (HVDRR) and five corresponding sound teeth from five healthy children. According to powder X-ray diffraction analysis, the half-peak breadths of (310) and (002) reflections of HVDRR dentine were smaller than those of normal dentine. Splitting fractions obtained from i.r. spectral analysis of HVDRR dentine powder were larger than those of normal. Microbeam X-ray diffraction analysis showed that the relative half-peak breadths of globular dentine in ground sections of HVDRR teeth were smaller than those of normal circumpulpal dentine. Transmission electron microscopy demonstrated that the hydroxyapatite crystals of globular dentine in HVDRR teeth were larger than those of normal dentine. Thus the crystallinity of deciduous tooth dentine in HVDRR was greater than that of normal dentine, mainly because of the large hydroxyapatite crystals in HVDRR globular dentine.     

Age-related changes in hardness and modulus of elasticity of dentine

OBJECTIVES: Little knowledge has been clarified about the relationship between the morphological and physical changes of dentine during aging. The purpose of this study was to clarify the modulus of elasticity and hardness related to the morphological changes of dentine by aging using a transmitted light microscope (TLM) and a nano-hardness tester (NHT). METHODS: Aged human molars and young third molars were used. The dentine morphology was observed under a TLM. The hardness and Young's modulus of elasticity related to the morphologic study were evaluated with an NHT. RESULTS: The thickness of mantle dentine and globular dentine of aged teeth were less than that of young teeth. Transparent dentine was observed only underneath the attrition of young teeth. Reactionary tertiary dentine formed and a "dark zone" was found at the junction between physiologic secondary and reactionary dentine only in aged teeth. At the mantle dentine, hardness and modulus of elasticity of aged dentine were higher than those of young dentine. The reactionary dentine in aged teeth and newly developed secondary dentine in young teeth demonstrated lower modulus of elasticity and hardness than those of other circumpulpal dentine. Relatively low modulus of elasticity and hardness were observed at the zone between secondary and reactionary dentine. CONCLUSIONS: Changes in dentine due to aging resulted in transformation of morphological features causing changes to their hardness and modulus of elasticity at the explicit areas such as the increase of hardness and modulus of elasticity at mantle dentin and the reduction of these properties at the "dark zone" that found in aged teeth.     

Morphological characterization and permeability of attrited human dentine

OBJECTIVE: Dentine is a vital tissue that can be changed by physiological and pathological condition. The purpose of this study was to clarify the morphology and permeability of dentine that changed by wearing process. METHODS: Twenty extracted human molars with enamel attrition and dentine was exposed and 20 intact human extracted third molars that had not reached occlusion were used. Ten teeth per each group were observed under light microscope (LM) and transmission electron microscope (TEM). Remaining 10 teeth per each group were subjected for evaluation of dentine permeability. RESULTS: Under LM, the transparent dentine and reactionary dentine were found in the attrition group but were not found in the group unaffected by attrition. When the transparent dentine were examined under the TEM, it was found that dentinal tubules were partially or completely occluded by growth of peritubular dentine or by precipitation of needle-like or rhombohedral crystals in transparent dentine. In reactionary dentine, tubular dentine structures that were comparable to those in secondary physiologic dentine were observed whereas atubular dentine demonstrated occlusion of tubules by high mineral substances or by peritubular dentine under the TEM. Permeability of dentine from worn teeth was less than those from unoccluded teeth significantly. CONCLUSION: Change in dentine by wear resulted in the formation of reactionary dentine and transparent dentine that illustrated various types and degrees of tubular occlusion. These decrease the dentine permeability.     

锥形束CT对微螺钉前牙根间植入区骨量的分析

目的 通过对微螺钉种植支抗前牙根间植入区骨量进行三维测量分析,为前牙根间植入位点的选择提供参考.方法 对36名成人患者的上、下颌前牙区行锥形束CT扫描及三维重建,分别测量U/L11(上/下颌中切牙根间),U/L12(上/下颌中切牙和相邻侧切牙根间),U/L23(上/下颌侧切牙和相邻尖牙根间)距上、下前牙釉牙骨质界3mm、5 mm、7 mm及9mm水平的根间距(D1)和牙槽骨宽度(D2).采用SPSS 17.0软件进行单因素方差分析和Duncan法进行两两比较.结果 相邻两牙根间最小距离D1:从大到小依次为U11＞U23＞L23＞L11＞U12＞L12,所有牙位越往根尖方向D1越大,其中只有U11,U23分别距离釉牙骨质界5mm和7mm根间距大于3mm,相邻两牙根间唇舌向牙槽骨宽度D2为:U11＞L11,U12＞L12,L23＞U23,不同水平D2值在3.82～6.62mm之间.结论 上、下颌前牙区,上颌中切牙之间及上颌侧切牙和尖牙之间的根间区是植入微种植体较理想的部位.     

The relationship of interradicular width and alveolar bone loss. A radiometric study of a periodontitis population

Contrasting data exist on the relationship between interproximal width and loss of marginal bone in a periodontitis susceptible population. Reports of clinical observations suggest that the prognosis of teeth with minimal interradicular width should be downgraded in periodontal patients. Others indicate a higher prevalence of intrabony lesions in wider interproximal spaces. Radiographs of 114 adult patients with evidence of bone loss consistent with periodontitis were examined. Measurements of interradicular width and the location of the bone margin from the cementoenamel junction were made at 811 interproximal sites using an optical digitizer at 3X magnification. The relationship between bone loss and interradicular width was investigated. The results indicate that as the interradicular width increases, the interproximal bone margin tends to be in a more apical location. No findings supported the contention that bone in a narrow interradicular space is at greater risk in patients who have had periodontitis.     

Dentine hypersensitivity

Based on the hydrodynamic theory for stimulus transmission across dentine, it would be logical to conclude that teeth exhibiting the clinical symptoms referred to as dentine hypersensitivity should have dentinal tubules open at the root surface and patent to the pulp. With the exception of studies on cut dentine, there is little direct evidence to support this conclusion. In this study, caries-free teeth with exposed cervical root areas scheduled for extraction which were classified as non-sensitive or hypersensitive after suitable stimulation were examined by scanning electron microscopy. Hypersensitive teeth showed highly significantly increased numbers of tubules per unit area (approximately 8 X) compared with non-sensitive teeth. Tubule diameters were significantly wider (approximately 2 X) in hypersensitive compared to non-sensitive teeth. The number of teeth showing the penetration of methylene blue through the zone of exposed cervical dentine was larger and the depth of penetration greater in hypersensitive teeth compared to non-sensitive teeth. The results provide further evidence that stimulus transmission across dentine in hypersensitive teeth is mediated by a hydrodynamic mechanism. An understanding of factors which open dentinal tubules would seem important if attempts to prevent or treat dentine hypersensitivity are to be successful.     

Comparison of resin-dentine interface in primary and permanent teeth for three different durations of dentine etching

Hybridization of dentine is identified as a basic bonding mechanism between resin and dentine, hence studying the micro morphology of hybrid layer may explain lower bond strength that has been observed in primary teeth. The aim of the present study was to compare the thickness and micromorphology of Hybrid layer formed in primary and permanent teeth for 3 different durations of dentine etching time (5, 10 and 15 sec) with 10% phosphoric acid as etchant. Thickness and micromorphology of hybrid layer was observed on SEM photographs obtained at 750X. Results indicated that primary teeth presented with a significantly thicker hybrid layer compared to permanent teeth at 10 sec (P<0.05) and 15 sec (P<0.01) of dentine etching. It was concluded that owing to the high reactivity of primary teeth to etchants, the etchants be applied for shorter period on primary dentine compared to permanent dentine for better performance of composite restoration in primary dentition.     

Swine teeth as potential substitutes for in vitro studies in tooth adhesion: a SEM observation

Animal teeth are routinely used in studies that test dental materials; however, no studies have yet proposed the use of swine teeth in laboratory tests. The purpose of this study was to compare the effects of acid etching on the dentine and enamel of human and swine teeth, aiming at the use of swine teeth as substitutes for human teeth in adhesion tests. Four human molars and four swine molars free of caries were used. For the study of enamel, two human and two swine teeth were longitudinally sectioned with a dental handpiece and a carborundum disk. For evaluation of dentine, the remaining teeth had the occlusal third of their crowns removed using a low speed diamond saw. All specimens underwent acid etching with 37% phosphoric acid for 30s. The etched surfaces were then washed with air/water spray for 10s. The specimens were then prepared for analysis in a Sterioscan 440 scanning electron microscope. It was observed a similar morphology in human and swine teeth, despite swine enamel was thinner than human enamel. Acid etching of swine enamel promoted a demineralization similar to that observed in human enamel in which the three types of Silverstone's patterns were observed. Acid etching of dentine exposed the opening of dentinal tubules in both swine and human teeth. Peritubular dentine was removed by phosphoric acid, while collagen fibrils appeared discernible in intertubular dentine. Thus, this study showed that enamel and dentine from swine and human teeth share many structural similarities after acid etching.     

Calbindin D-28k distribution in odontoblasts underneath tertiary dentine in human carious teeth

OBJECTIVE: The aim of this study was to examine the calbindin D-28k immunoreactivity in carious teeth to know whether this protein may have a function in tertiary dentine formation. METHODS: Human extracted teeth with or without carious lesions were immersion-fixed with Zamboni fixative, demineralized in 4.13% EDTA solution (pH 7.4), frozen-sectioned, and processed for calbindin immunoreactivity and hematoxylin-eosin stain. The intensity of the immunostaining was evaluated by quantitative densitometry. RESULTS: In intact teeth, numerous odontoblasts were aligned underneath the secondary dentine and their cell bodies showed the immunoreactivity. In carious teeth, tertiary dentine had poor- or rich tubular patterns under the carious lesion. Underneath the tubule-poor tertiary dentine, distinct odontoblasts could not be seen at the central site. However, some cells with a flat appearance were located at this site and were immunonegative for calbindin D-28k. On the other hand, columnar odontoblasts were seen at the peripheral site, and their cell bodies and processes showed strong immunoreactivity. Underneath the tubule-rich tertiary dentine, columnar odontoblasts were abundantly distributed, and the strong immunoreactivity was observed in their cell bodies and processes. The immunoreactivity in odontoblasts underneath the tertiary dentine with poor or rich tubular pattern was more intense than that for the secondary dentine in intact teeth (P<0.05). On the other hand, the intensity of the immunoreactivity in odontoblasts was similar underneath the secondary dentine in intact and carious teeth. CONCLUSIONS: The present study demonstrated that calbidin D-28k was actively synthesised by odontoblasts under the carious lesion. These findings may suggest that this protein plays an important role in the tertiary dentine formation.     

Dentine hypersensitivity

Studies of extracted teeth have shown that teeth exhibiting dentine hypersensitivity have larger numbers of widened dentinal tubules at the dentine surface compared to non-sensitive teeth. Many compounds used in the treatment of dentine hypersensitivity are thought to achieve therapeutic benefit by tubule occlusion, but there has been almost no attempt to prove such action in vivo. These studies systematically determined whether the dentine surface could be evaluated non-invasively, by a scanning electron microscopic replica technique. Employing a silicone rubber impression method in vitro, the surface detail of dentine could be accurately replicated, with surface scratches, tubules and intratubular structures on the original reproduced on the replica. With attention to method, similar accuracy was achieved in vivo, particularly when tubules were open on the dentine surfaces of the original. The method would appear useful for the study of the dentine surface in cases of dentine hypersensitivity and could prove the first objective method of studying the effects of treatment agents used in the treatment of this painful condition.     

Stress–strain response in human dentine: rethinking fracture predilection in postcore restored teeth

Abstract –  In this study, the biomechanical perspective of fracture predilection in post-core restored teeth is investigated using computational, experimental, and fractographic analyses. The computational finite element analysis and the experimental tensile testing are used to evaluate the stress–strain response in structural dentine. The fractographic evaluations are conducted using laser scanning confocal microscopy and scanning electron microscopy to examine the topography of dentine from experimentally fractured specimens, and clinically fractured post-core restored teeth specimens. These experiments aided in correlating the stress–strain response in structural dentine with cracks and catastrophic fractures in post-core restored teeth. It was observed from these experiments that the inner dentine displayed distinctly high strains (deformations), while the outer dentine demonstrated high stresses during tensile loading. This implies that the energy fed into the material as it is extended will be spread throughout the inner dentine, and there is less possibility of local increase in stress at the outer dentine, which can lead to the failure of dentine structure. During post-endodontic restoration with increase in loss of inner dentine, the fracture resistance factor contributed by the inner dentine is compromised, and this in turn predisposes the tooth to catastrophic fracture.     

Interradicular dentin dysplasia associated with amelogenesis imperfecta

Very few reports are available on the occurrence of dysplasia of both enamel and dentin. This report concerns a rare association of amelogenesis imperfecta with a dysplasia of dentin in the interradicular area in sisters of Japanese descent who have no other morphologic anomalies. Retarded tooth eruption was also a clinical feature in both sisters. Histologic examination of several teeth revealed that the anomalous interradicular dentin consisted of a mass of small, onion-like calcified bodies. The absence of any dental abnormalities in both parents, who are related as first cousins, supports the concept of autosomal recessive inheritance for this trait.     

Adenosine triphosphate in normal and carious human dentine.

Adenosine triphosphate (ATP) levels were quantitatively measured in various layers of freeze-dried human dentine. Developing, intact, fully-formed, carious and gangrenous teeth were studied. ATP was extracted from the dentine powder with 0.1 M perchloric acid solution. Using a liquid scintillation counter, the amount of ATP (pmole/mg dentine) was determined from 10-mg samples of dentine by means of the luciferase reaction. The highest ATP level in hard dentine was observed in coronal and apical peripulpal areas of developing teeth (2. 0 pmole/mg dentine). In coronal hard dentine, ATP concentration decreased towards the dentine-enamel junction, where practically no ATP could be observed. In intact teeth, the corresponding peripulpal values were statistically lower (0. 4 pmole/mg dentine). ATP levels of 1.7 pmole/mg dentine were observed in coronal peripulpal dentine under an incipient caries lesion. When the hard dentine became soft and carious, 5–8 times higher ATP values were measurable (8.7–14.5 pmole/mg dentine).     

Quantitative microradiography of intact and worn human coronal dentine

The mineral content of the incisai part of the coronal dentine of intact and worn teeth per unit volume was determined by means of quantitative contact microradiography. In the buccal to lingual direction, a zonated pattern of mineralization was evident. In the intact teeth, the highest values for the mineral content were at the central streak between the incisal tip of the dentine and the pulp horn (50 per cent). A narrow zone of dentine adjacent to the central streak contained about 45 per cent minerals and the bulk of dentine about 48 per cent, whereas the mineral content of the mantle dentine averaged 42 per cent. Only small variations in the degree of mineralization were found in this area of the coronal dentine between teeth at various age levels.In the worn teeth, an increase in the mineral content of the incisai dentine was evident at all levels between the exposed surface and the pulp horn. Centrally in the worn dentine, the increase was about 4 per cent whereas laterally the increase averaged 2 per cent.     

The permeability of natural dentine caries before and after restoration: An in vitro study

OBJECTIVES: The objectives of this experiment were to determine in vitro the permeability of teeth exhibiting a range of natural dentine caries and the effects of caries excavation and subsequent restoration on the dentine permeability of extracted teeth. METHODS: Forty-five human permanent molars with obvious occlusal caries were selected and coronal dentine permeability was measured before (baseline) and after caries excavation, as well as after acid etching the prepared cavity and finally, after restoration. RESULTS: The small permeability values for all teeth made statistical testing between the different stages of specimen preparation both meaningless and inappropriate. An alternative means of examining the data was to calculate the percentage of teeth which had exhibited permeability values greater than zero at each of the four specimen preparation stages. The percentage of teeth with permeability greater than zero remained unchanged before and after cavity preparation (23%). Removal of the smear layer, however, increased substantially the percentage of teeth demonstrating permeability greater than zero, to 72%. None of the restored teeth demonstrated measurable permeability. CONCLUSION: The teeth chosen exhibited a range of dentine caries and, surprisingly, demonstrated either low or no measurable permeability. This experiment highlighted the need for more investigation into the quality of carious-affected dentine and the properties of the smear layer produced from such dentine.     

In vitro effectiveness of a chemo-mechanical method for caries removal.

AIM: The aim of the study was to assess the efficacy of chemo-mechanical method for caries removal based on histological analysis and scanning electron microscopy of dentine samples. METHODS: Forty-five freshly extracted human deciduous and permanent teeth with dentinal caries were used in this in vitro study. The teeth were allocated to two different technique groups. Chemo- mechanical caries removal using Carisolv was performed in 30 teeth and in 15 teeth caries was removed using conventional rotary instruments. The caries status of dentine was judged according to clinical criteria (probing and visual inspection). After caries removal had been completed, teeth were sectioned through the prepared cavities and the two halves of each tooth were processed for light microscopy and scanning electron microscopy. Light microscope was used to examine the specimens for the presence of bacteria in dentine tubules. Scanning electron microscope was used to determine surface characteristics of the cavity floor after caries removal. RESULTS: All examined dentine surfaces were clinically caries free. Regarding the presence of bacteria, 53% of chemo- mechanically prepared teeth and 87% of conventionally prepared teeth were bacteria-free (p>0.05). Efficacy of both methods was confirmed using scanning electron microscope, but different dentine topography was recorded after chemo-mechanical and conventional caries removal. Conclusion: Based on histological and scanning electron microscope analyses it could be concluded that this chemo-mechanical method is efficient in the removal of carious dentine.     

A (3H)-proline autoradiographic study of dentine bridge formation in transplanted mouse molar teeth.

A dentine bridge invariably forms across the cervical pulp of transplanted mouse molar isografts. Autoradiographic study demonstrated that bridge formation occurred in two phases. Firstly during post-operative degeneration cellular dentine was formed by non-polar secretion from degenerating cells. Cellular dentine formation was also observed in allografts. Secondly, as isografts recovered, tubular secondary dentine was formed by cuboid pre-odonto-blasts and then by fully differentiated odontoblasts. Similarities were noted between reparative dentinogenesis in transplanted teeth and in teeth in situ. These similarities suggest that reparative dentinogenesis is an identical process irrespective of the stimulus for formation and that the capacity for repair of transplanted teeth resides within the donor tissue. These experiments also demonstrate the remarkable inherent healing capacity of the dental pulp.