Human root caries: histopathology of arrested lesions.

The histopathology of arrested root caries lesions was examined in extracted human teeth. The main structural characteristics of arrested lesions were the completely mineralized surface area and the formation of a distinct sclerosis of the dentinal tubules. Intertubular dentin was, with the exception of the dentinal tubules, fully mineralized up to the surface. Dentinal tubules near the surface were either filled with ghosts of microorganisms or with crystals of different shapes. Sclerosis of the dentinal tubules was characterized by the presence of three different patterns of intratubular mineralization that occur in distinct regions of the zone of tubular sclerosis. The patterns were distinguishable by the type of crystals and their association with organic structures such as collagenous fibrils or odontoblast processes. It is suggested that arrested lesions are based on (1) the formation of an inner barrier that interrupts the diffusion of substrata from the pulp to invaded bacteria, (2) the formation of an outer barrier by a compact, highly mineralized surface region which blocks the diffusion of products of bacterial metabolism into dentin, and (3) an area of mineralization which extends from the outer barrier toward the root canal within demineralized dentin. The present study demonstrates the considerable potential of caries lesions in dentin to become arrested, and subsequently partially remineralized. These phenomena seem to depend on the severity of an active lesion and its location on the root surface. This should be taken into account when diagnosing root caries lesions. The potential of root caries lesions to become arrested indicates that the treatment concept of active root caries lesions should be reconsidered.     

Ultrastructural study on human root caries

Superficial root caries lesions of incisors and premolars of 24 patients aged 52-60 years were studied by scanning electron microscopy and transmission electron microscopy. In the predominantly gram-positive bacteria of the root dental plaque, a great number of corncob configurations were observed. Bacterial infiltration into cementum occurred without any gradient of demineralization and mainly followed the borders between calcified cementum bundles as well as incremental lines. The narrow channels which were filled initially by a single row of gram-positive bacteria broadened progressively with simultaneous destruction of the apatite minerals and the collagenous matrix. Root dentin invasion showed great similarities to coronal dentin with an important gradient of demineralization. In the deep layers, sclerosed tubules contained sometimes rhombohedral crystals. In more superficial layers, bacterial invasion occurred initially in still partially sclerosed tubules. Tubular lumens as well as lateral side branches which had lost their peritubular dentin were filled with gram-positive microorganisms. An important diffuse destruction of the apatite minerals was observed at this stage in the intertubular dentin which still presented typical cross-banded collagen fibrils. The confluence of enlarged dentinal tubules filled by numerous microorganisms led to large bacterial zones with complete destruction of root dentin.     

Micromorphological and micronanalytical characterization of stagnating and progressing root caries lesions

Root caries is the predominant disease of the tooth tissues in the elderly population and differs in progression and micromorphology from coronal dentin caries. Therefore, different clinical concepts are needed for the treatment of these progressing and arrested lesions. It was the aim of this study to investigate the three-dimensional structure and volume of stagnating and progressing root caries lesions and to determine the mineral composition of the different lesion zones to achieve a better understanding of the natural history of root caries lesion formation. Of 21 extracted human teeth of patients between 42 and 77 years of age with stagnating and progressing root caries lesions serial sections were cut and investigated with polarized light and scanning electron microscopy. From the polarized light micrographs 3D reconstructions were made to determine the volumes of the lesion zones and their relations expressed in a demineralization index (DI). With increasing size of the demineralizing zone the DI increased indicating an increase in the size of the translucent zone. The 3D reconstructions showed distinct differences between stagnating and progressing root caries lesions. In the hypermineralized translucent dentin not all dentin tubules were obliterated by intratubular dentin and within the translucent dentin scattered dead tracts were found. Electron dispersive X-ray (EDX) analysis showed that the intertubular dentin of the translucent dentin was also demineralized to a certain extent. The results indicate distinct morphological differences between progressing and stagnating root caries lesions which may have consequences for treatment strategies.     

Transmission electron microscopic characterization of hypersensitive human radicular dentin

Transmission electron microscopy (TEM) and x-ray microanalysis (XMA) were used for the study of the ultrastructure of the lumens of dentinal tubules in superficial layers of dentin specimens obtained by use of a new biopsy technique from both hypersensitive and naturally desensitized areas of exposed root surfaces, in vivo. The TEM images showed clearly that the lumens of most of the tubules were occluded with mineral crystals in naturally desensitized areas, but such lumens were empty and surrounded with peritubular and intertubular dentin in hypersensitive areas. Moreover, electron-dense structures that lined peritubular dentin were observed in the empty lumens of dentinal tubules.     

Interfacial morphology of an adhesive composite resin and etched caries-affected dentin.

The interfacial structure between an adhesive composite resin and dentin after caries removal and acid conditioning was investigated. The hybrid layer between the adhesive resin and surface-demineralized dentin was found to be wider in the area of empty tubules compared with that of the occluded tubules, and was found to be the thinnest at the lateral walls of the cavity where the dentinal tubules run parallel to the cavity surface. Thus, the extent of demineralization by acid conditioning as well as impregnation of resin into the intertubular dentin forming the hybrid layer is probably related to the degree of closure and direction of the dentinal tubules.     

In vitro surface analysis of active and arrested dentinal caries using a pH-imaging microscope

This in vitro study evaluated the pH value of active and arrested caries lesions in deep dentinal caries using a pH-imaging microscope (SCHEM-100, HORIBA Ltd, Kyoto, Japan). Buccal-lingual cut sections of extracted human teeth that had either active or arrested dentinal caries lesions were placed on the pH-imaging sensor of the microscope. The pH values were compared statistically by one-way ANOVA and Fisher's PLSD test (p<0.05). In addition, both types of caries lesions were compared with a caries detector solution for this pH-imaging characterization. For both active and arrested lesions in dentin, the lowest pH values in the caries lesions (range from 5.3 to 6.6) were lower than that of intact dentin (range from 6.8 to 7.4). There were statistical differences between the lowest pH value within the active lesion (range from 5.3 to 5.8) and the arrested lesion (range from 6.3 to 6.6) (p<0.05). Although the arrested lesion was unstainable and impermeable to the dye, there was a close relationship between dye staining and pH-imaging characterization within the active lesion from visual inspection.     

氯化钠溶液对人牙根面牙本质早期龋再矿化作用的影响

目的：探讨单纯用氯化钠（NaCl)溶液处理人牙根面牙本质早期龋后，提高根面早期龋再矿化作用的可行性，方法：在人牙根面上形成早期人工龋，将标本分组，分别用0．5mol/L,NaCl溶液和0．5mol/L EDTA二钠盐溶液浸泡后，用再矿化液处理，扫描电镜下观察比较早期龋矿化前牙根表面形态及矿化后牙根表面矿物盐沉积情况，显微X线照像及其图像分析比较矿化后矿物含量的不同。结果：人牙根面早期龋表面用NaCl溶液浸泡前后无明显改变，早期龋用EDTA二钠盐溶液浸泡后表面见大量牙本质小管开放，再矿化后，前者比后者表层明显增厚，表层阻射度明显增强。结论：用NaCl溶液处理人牙根面早期龋以后，再矿化效果明显增强，NaCl溶液对早期龋表面无不良影响。     

Demineralization of caries-affected transparent dentin by citric acid: an atomic force microscopy study.

OBJECTIVES: This study determined recession rates of peritubular dentin and intertubular dentin in citric acid solution (0.018M, pH=2.5) for caries-affected transparent dentin, one of the major components of dentin substrate as altered by caries, with comparisons made with non-carious dentin. METHODS: Transparent dentin was identified by sagittally sectioning five obviously carious teeth. Sections were then cut through the transparent dentin area perpendicular to the course of the dentinal tubules. Polished dentin samples of the transparent dentin and non-carious dentin were prepared with an internal reference layer and studied at specific intervals for citric acid etching in an atomic force microscope (AFM). RESULTS: At baseline, transparent dentin was identified by dentinal tubules that were largely occluded with mineral deposits that on etching proved to be acid resistant. Peritubular dentin etched rapidly and linearly over time until it could no longer be measured, yielding etching rates for transparent dentin that could not be distinguished from normal dentin. The normal and transparent intertubular dentin surfaces began etching at nearly the same rate, but then surface recession stabilized after less than 1 microm depth change for both dentin types. SIGNIFICANCE: Most previous studies have focused on demineralization and bonding to normal dentin, although many bonding procedures involve altered dentin substrates, such as those modified by caries. In this study, peritubular and intertubular dentin from normal and caries-affected dentin exhibited similar behavior. The major difference was the presence of acid resistant mineral in most of tubule lumens in the transparent dentin.     

Human root caries: histopathology of advanced lesions

The histopathology of human root caries was examined in extracted teeth. The present study details several stages of advanced carious lesions in root dentin. Lesions of different severities were assessed by different optical methods. Four major root caries patterns were defined and significant differences between coronal and root caries elucidated. The patterns were distinguishable by (1) their location at the exposed root surface, (2) their mode of spreading towards the root canal and over the root surface, (3) their mode of bacterial spreading in dentin and (4) the role of dentinal defense mechanisms. In addition, a comparison of clinical and histological classification of lesions revealed that the carious process extended much deeper towards the root canal and had a higher degree of both bacterial infection and dentin demineralization than could be predicted by clinical examination.     

SEM investigations on the human sclerosed dentinal tubules

Sclerotic changes of dentinal tubules appeared in the dentin beneath the carious, attrition and abrasion lesions and in the transparent root dentin were investigated using the scanning electron microscopy. 1) Shape of crystal-like substances appeared in the dentinal tubules could not be closely related to kinds of dentin destruction. 2) In the dentinal tubules beneath the carious lesions, cuboidal or rhomboid-shaped, short rod-like, long rod-like, plate-like and droplet-like crystals were mainly observed. Combination of cuboidal or rhomboid-shaped and short rod-like crystals or that of long rod-like and plate-like crystals were most frequently observed. 3) In the dentinal tubules beneath attrition and abrasion lesions, cuboidal or rhomboid-shaped, short rod-like and droplet-like crystals were mainly observed, however, the size of cuboidal or rhomboid-shaped crystal was usually smaller than that observed beneath carious lesion and they deposited compactly within the tubules. 4) In the sclerosed dentinal tubules in the transparent root dentin, compact deposition of rhomboid-shaped and irregular sand-like crystals were usually observed. Size of rhomboid-shaped crystal is smaller than that observed beneath carious lesion. The deposit of sand-like crystal in the tubules was easily discriminated from the matrix of peritubular dentin. 5) In any case, the kinds of crystals and pattern of deposition were not necessarily same between the neighboring tubules. However, in a tubule, they were almost same in shape and mode of deposition throughout the entire length of tubule from the outer side to the pulpal side. These facts seem to indicate that mineral deposition within the tubule due to sclerosis is performed under individual condition. 6) Finding showing biological control of mineral deposition within the dentinal tubules by the odontoblasts could not be observed.     

Density of dentinal tubules affects the tensile strength of root dentin.

OBJECTIVES: The aim of this study is to count the dentinal tubules in the coronal and middle-apical third of root dentin of teeth extracted due to the progression of periodontal disease, and to compare the Ultimate Tensile Strength (UTS) of the same areas. The research hypothesis was that root dentin areas with different densities of dentinal tubules would also show different UTS values. METHODS: From 10 caries free maxillary central, lateral incisors and canines, extracted for periodontal reasons from three patients, cylindrical specimens approximately 10 mm long were prepared parallel to the long axis of the root and then divided into two parts using a low speed diamond saw one from the coronal third of the root, (Group 1) and one from the middle-apical third of the root (Group 2). The density of the dentinal tubules of the specimens of the two groups was measured by means of a scanning electron microscope and the UTS of the specimens was measured by a microtensile test. One way ANOVA was used to assess the effect of specimen location (coronal specimens vs. middle-apical specimens) on UTS. The differences in the density of dentinal tubules between coronal and middle-apical specimens were also subjected to statistical analysis using one-way ANOVA. RESULTS: UTS values of middle-apical specimens were found to be significantly (p < 0.05) higher than those of coronal specimens. The results of the one-way analysis of variance showed that the number of dentinal tubules of the samples from the coronal part of the root groups was significantly higher than that of samples from the middle-apical part (p < 0.05). SIGNIFICANCE: These results suggest that high values of tensile strength of the dentin are associated with low densities of dentinal tubules and that apical areas of root dentin are more resistant to tension than coronal ones.     

根龋封闭治疗后的细菌学和病理学研究

目的:研究根龋封闭治疗后,发生的龋病静止效应。方法:采用封闭剂治疗活动根龋前(基线),封闭后6个月的龋性牙本质样本进行细菌培养计数;选择活动根龋封闭1年后需拔除的患牙制作牙本质切片用作病理观察。结果:17例活动性根龋牙封闭治疗后半年,涂膜下存活细菌总量及特异致龋菌数量均大幅度降低(P<0.0001);病理学观察发现活动根龋封闭1年后,龋病静止,涂膜下龋性牙本质表层有再矿化区带形成。结论:封闭剂治疗根龋,有望把活动件龋损转化为静止龋,这可能为老年根龋防治提供新的途径。     

人工龋树脂牙本质粘接界面拟生态矿化的定量评估

目的 探讨人工龋拟生态再矿化的定量评估方法和效果.方法 通过脱矿/再矿化液的pH 循环法建立人工龋模型,使用全酸蚀粘接剂Single Bond Plus（SB 组）、One-Step（OS 组）和自酸蚀粘接剂Adper Prompt L-Pop（LP 组）进行树脂粘接,在含聚丙烯酸（PAA）和聚乙烯膦酸（PVPA）的模拟体液/硅酸盐水门汀系统中诱导矿化,采用显微计算机X 线断层摄影术（micro CT）定量评估再矿化效果.结果 矿化诱导4 个月后SB 组、OS 组和LP 组样本病损深度均有降低,由矿化前的300 滋m 分别减少至47、53 和87 滋m,矿化率分别为73.76%、81.39%和74.54%.结论 micro CT 是定量评估人工龋树脂牙本质粘接界面矿化程度的一种有效方法.含PAA 和PVPA 的模拟体液/硅酸盐水门汀系统可诱导树脂渗透脱矿牙本质再矿化（P ＜ 0.05）,且不同的粘接剂对人工龋拟生态再矿化效率无显著性影响.     

Tissue response to dental caries

Abstract Caries still represents the most widespread human disease. The pulp tissue sequelae of den tin caries are of utmost importance, because prevention of pulpal damage considerably reduces the need for extensive restorations and endodontic therapy. There is, however, considerable disagreement in the literature regarding how early the pulpal response to caries can be detected. The material in this article, gathered from the author's and his coauthors' earlier investigations, deals with pulp reactions from initial caries to increasingly extensive caries; caries in combination with attrition; the effect of carious den tin in experimental cavities of intact dentin; the effect of medicaments, restorative procedures and materials, and indirect pulp capping in the treatment of deep caries; microbiologic aspects of dentin caries; diagnosis criteria for treatment; light and electron microscopic study of teeth with carious exposure; periodontal disease and root caries in the geriatric population; pulp biopsies of teeth with periapical lesions, and the breakdown of the remaining pulp and its periapical sequelae. Pulpal reactions to initial caries detected as early as bacteria reach the dentinal tubules arc also discussed. As in medium and deep caries, this can be reversible following the removal of the infected dentin, except for irritation dentin and calcifications on the canal walls or free in the lumen. Bacteria remaining in dentinal tubules combined with iatrogenesis may be the reason for pulpal disintegration under deep restorations. Indirect pulp capping is not an acceptable procedure. Pain (or lack thereof) is not a predictable indicator of the inflammatory stage of the pulp. Root caries must be treated early to prevent pulpal destruction. Vital pulp tissue can be found in the roots of teeth with periapical radiolucencies that will ultimately show the presence of bacteria.     

Relationship between the color of carious dentin with varying lesion activity, and bacterial detection

OBJECTIVES: To investigate the relationship between the color of carious dentin with varying lesion activity, and bacterial detection in the lesions. METHODS: In 26 extracted human molars with coronal dentin caries and four extracted sound human molars, dentin was removed by a round bur every 150 microm from the dentin surface, in the direction of the pulp chamber. Before and after removal, images of nine-color samples and the dentin surface stained with a caries detector dye (1% acid red in propylene glycol) were taken simultaneously by a charge-coupled device (CCD), and dentinal tissue samples were taken with a new round bur. From the images, corrected L*, a* and b* values (CIE 1976 L*a*b* color system) of the dentin surfaces were calculated from the color changes of the nine-color samples. Bacterial DNA in the dentinal tissues was detected by polymerase chain reaction. RESULTS: Before removal of dentin, the L* of sound molars (L*>50) was significantly larger than that of carious molars (L*<50) (ANOVA, Scheffe's F-test, P<0.05). In addition, the carious molars were divided into type I (a*>20, characteristics of active caries) and type II (a*<20, characteristics of arrested caries), and there was a significant difference in the a* value (P<0.05). For both carious types, the area under the receiver operating characteristic curve of L* was significantly larger than that of a* or b* (univariate Z score test, P<0.05), and the rate of bacterial detection decreased as the L* of dentinal tissue increased, and bacterial DNA was not detected when L* was >60. CONCLUSIONS: Sound and types I and II carious dentin were discriminated by the combination of L* and a* values of dentinal tissue stained with the caries detector dye before removal of dentin. In carious lesions, the a* values of carious dentin stained with the dye were related to the carious lesion activity before removal of carious tissue, and the L* values were related to the degree of caries progression.     

Relationship between large tubules and dentin caries in human deciduous tooth

The purpose of this study was to elucidate the relationship between large tubules and dentin caries by using human deciduous incisors that showed various levels of attrition but no macroscopical lesions resulting from caries. The teeth were cut longitudinally in the mesio-distal direction and the exposed surfaces observed with a high-resolution field emission scanning electron microscope. The inside of each large tubule showed dense collagen fibers running parallel to its long axis and small spherical bodies of aggregated crystals, but no marked attrition. In teeth where attrition had exposed dentin at the incisal edge, oral bacteria had infiltrated the large tubules. Furthermore, in teeth with advanced attrition, it was difficult to distinguish between the large tubules and the surrounding dentin matrix, and numerous bacteria were observed in both areas. These findings support the hypothesis that large tubules play a role in the pathway of caries formation in coronal dentin when incisal dentin is exposed by attrition. This suggests that early treatment of exposed dentin surfaces might be effective in preventing dental caries.     

葡萄籽提取物促进早期牙本质龋损再矿化作用的体外研究

目的评价葡萄籽提取物（GSE）对人工牙本质龋的再矿化作用和显微结构的影响。方法制备60个人牙本质标本,采用化学法形成人工牙本质龋损,将样本随机分为4组,分别用10%GSE溶液、1 mg/L NaF溶液、10%GSE+ 1 mg/L NaF溶液和去离子水（DDW）处理,进行体外pH循环。采用显微硬度计测定处理前、后各样本的显微硬度值,扫描电镜观察pH循环后各组牙本质显微结构的变化,并用X线能谱仪分析牙本质元素百分含量。采用SPSS17.0软件包对数据进行统计学分析。结果显微硬度结果显示,GSE组牙本质的显微硬度获得百分比（SMHR）为40.87±9.92,NaF组为44.60±12.48,GSE+NaF组为48.54±9.27,去离子水组为15.98±8.33。与去离子水组相比,3个实验组的SMHR值均显著提高（P<0.05）,但相互之间无显著差异。扫描电镜显示,GSE组、NaF组和GSE+NaF组牙本质小管大部分呈封闭状态,而去离子水组牙本质小管呈开放状态。元素分析结果显示,3个实验组的Ca、P百分含量均显著高于去离子水组（P<0.05）。结论GSE能显著促进人工牙本质龋的再矿化作用,抑制牙本质龋的进展。     

Effects of plaque control on the patency of dentinal tubules: an in vivo study in beagle dogs

BACKGROUND: The aim of this in vivo study was to evaluate the effects of plaque control on the patency of dentinal tubules using vital teeth of beagle dogs. METHODS: Class V cavities were prepared on the cervical areas of the mandibular and maxillary molars in each dog with a diamond point. To simulate the state of dentinal hypersensitivity, the teeth were etched with 50% citric acid for 2 minutes to obtain patent dentinal tubules. Plaque control was achieved by brushing the left-side teeth every day, whereas no plaque control was performed for the right-side teeth. A dentin biopsy was performed after 1, 2, and 3 weeks using the cylindrical diamond point to obtain dentin specimens. RESULTS: In the plaque control group, some of the dentinal tubules were occluded with precipitate (Ca/P=1.49), and the diameter of the dentinal tubules decreased from 2.42+/-0.33 microm (mean+/-SD) to 1.11+/-0.51 microm after 7 days, although most of the dentinal tubules remained open. In contrast, no precipitate was observed in the dentinal tubules of the non-plaque control group. Also, the diameter of the dentinal tubules increased from 2.42+/-0.33 to 2.9+/-0.49 microm, due to the demineralization of the peritubular and intertubular dentin. CONCLUSION: Plaque control plays a key role in reducing the patency of dentinal tubules and, therefore, might promote the natural repair of dentinal hypersensitivity.     

Ultrastructural and microbiological analysis of the dentin layers affected by caries lesions in primary molars treated by minimal intervention

PURPOSE: The purpose of this in vivo study of primary teeth was to analyze the ultrastructure and microbiology of dentin layers affected by caries lesions before and after restorations with resin-modified glass ionomer. METHODS: Samples of carious dentin from primary teeth removed prior to restoration placement (baseline-0 day) were compared with samples taken after 30 and 60 days. Dentin from 8 primary molars was analyzed by scanning electron microscopy (SEM) and dentin from 22 primary molars was examined microbiologically to compare bacteria (total of viable counts, Streptococcus spp, Streptococcus mutans, Lactobacillus spp, and Actinomyces spp) before and after treatment (30 and 60 days). RESULTS: Baseline caries samples had enlarged dentinal tubules with bacteriol invasion. SEM samples after treatment suggest better tissue organization, with more compact collagen fibers arrangement and narrower dentinal tubules. The number of bacteria decreased in all samples at both 30 (98%) and 60 (96%) days, with all bacteria species showing similar trends. CONCLUSIONS: The minimal intervention approach is very effective to promote beneficial changes in the lesion environment and favorable conditions for the healing process in primary teeth.     

Evaluation of active and arrested carious dentin using a pH-imaging microscope and an X-ray analytical microscope

A pH-imaging microscope was tested on carious teeth to examine the acid-base characteristics of active and arrested carious dentinal lesions and compared with an assessment of mineral loss in carious affected lesions using an x-ray analytical microscope. Extracted human molars, 22 active and 83 arrested carious teeth, were sliced vertically to maximize the presence of visible carious lesions. The pH change on the dentin surface was measured with a pH-imaging microscope, and the mineral loss was measured with an x-ray analytical microscope. The pH value of intact dentin and active and arrested carious dentinal lesions showed 7.0 (n=105), 5.8 (n=22) and 6.6 (n=83), respectively (analyzed by Kruskal-Wallis). The mineral loss was distinguishable in active dentinal lesions (4.92 times as much as intact dentin), while arrested lesions showed a slight mineral loss (2.19 times as much as intact dentin). The changes in pH value and mineral loss were significantly correlated (Pearson's correlation coefficients r=-0.8024) in active carious dentin lesions and weakly correlated (r=-0.1480) in arrested carious dentin lesions. Changes in tooth substance with the progression of the active carious process were reflected in a reduction in pH value and an increase in the amount of mineral loss.