Histomorphologic Characterization of Noncarious and Caries-Affected Dentin/Adhesive Interfaces

PURPOSE: The purpose of this study was to compare the dentin/adhesive interfacial characteristics when bonding to noncarious as well as caries-affected dentin. MATERIALS AND METHODS: Seven extracted, unerupted, third molars were sectioned into halves. Artificial caries was created on one-half of each tooth, leaving the other half as a control. Dentin surfaces were treated with UNO adhesive according to the manufacturer's instructions for the wet-bonding technique and under environmental conditions present in the oral cavity. Dentin/adhesive interface sections of each half-tooth were stained with Goldner's trichrome, a classic bone stain, and examined using light microscopy. The width of exposed collagen was measured directly from photomicrographs, and adhesive penetration was analyzed qualitatively. RESULTS: The degree and extent to which the adhesive encapsulated the demineralized dentin matrix were reflected in the color difference in the stained sections with the noncarious dentin sections showing a degree of collagen encapsulation superior to that of the caries-affected dentin sections. The overall mean widths of exposed collagen were significantly (p < or = .05) greater at the caries-affected dentin/adhesive interface, 8.6 (1.7) microm, as compared with those at the noncarious dentin/adhesive interface, 6.0 (1.5) microm. CONCLUSIONS: The morphologic characteristics of the caries-affected dentin/interface suggest an increase in the exposed collagen zone and a decrease in the quality of the adhesive infiltration when compared with noncarious dentin. The evidence suggests that dentin substrate characteristics have a significant effect on the dentin/adhesive interface structure.     

Scanning electron-microscopic study of pellicle and plaque formation on tetracyclineimpregnated dentin

Abstract — Previous experiments have shown that tetracyclinecs may react with hydrosyapatite, e.g. in enamel and dentin, without losing their antimicrobial capacity. The present paper examines the pattern of pellicle and plaque formation on doxycycline-treated dentin by the use of scanning electron microscopy (SEM). From newly extracted human teeth were prepared standardized dentin slabs, half of which were soaked in aqueous solutions of doxycycline HC1, 10 mg/ml (pH 2.5) for 10 min. Seven volunteers carried doxycycline-impregnated specimens ligated to the buccal surface of a maxillary molar for 2 h, 8 h, 24 h and 120 h, respectively. Untreated control specimens were ligated to the contralateral teeth. After removal from the oral cavity, the dentin slabs were briefly rinsed in water, allowed to air dry and processed for SEM. SEM assessment of the specimens showed that doxycycline-impregnation resulted in a superficial etching of the dentin, a reduced rate of pellicle formation as well as an impairment of pellicle adhesion, and a retarded bacterial plaque formation on the dentin surfaces.     

The Maillard reaction in demineralized dentin in vitro

The Maillard reaction between carbohydrate and protein has been proposed as a cause of the browning of carious lesions. The aim of the present investigation was to determine the occurrence of this reaction in bovine dentin collagen in vitro and to establish the effect of the reaction on the proteolytic degradation of bovine dentin collagen in vitro. Slices of demineralized bovine dentin were incubated with 0.2 M glucose or buffer for 10 weeks at 37°C. The formation of initial (furosine) and advanced (pentosidine) products of the Maillard reaction in dentin exposed to glucose was confirmed by HPLC. After reduction with NaBH₄ to prevent intermediate Maillard products from further reaction, slices were either degraded with collagenase for fluorescence measurement or incubated with trypsin or pepsin to assess enzymatic degradation. Fluorescence characteristic for the Maillard reaction increased in glucose-exposed slices. Degradation of collagen by pepsin, but not by trypsin, was greatly depressed following glucose pretreatment. This may indicate an altered sensitivity to proteolytic degradation; the Maillard reaction thus has a potential role in caries arrestment.     

Multiple internal resorptions in deciduous teeth: a case report

We report a case of rare multiple internal resorptions. Etiology of multiple internal resorptions is unknown. Interestingly, the patient had an atopic dermatitis, which is possibly related to multiple and rapid internal resorptions.     

The effect of apical foramen patency on condensation stresses

Abstract Mathematical models and computer-based engineering tools were used to evaluate the effect of a patent or closed apical foramen on stresses that are produced within gutta-percha during condensation. We examined a mathematical model of a tapered canal with a definite constriction and compared the results when the apical foramen was closed or open. When the canal was closed an almost constant stress was seen throughout the gutta-percha. When the foramen was open a sharp increase in lateral stress was observed in the apical portions of the canal. The constriction near the foramen caused the gutta-percha to be squeezed together and the stress was increased. This increases the likelihood that the gutta-percha is well adapted to the apical constriction. However, the stresses are also transferred to the surrounding dentin, resulting in a stress concentration near the apical foramen where the bulk of dentin is minimal.     

Immunocytochemistry of keratan sulfate proteoglycan and dermatan sulfate proteoglycan in porcine tooth-germ dentin

Keratan sulfate proteoglycan and dermatan sulfate proteoglycan have been reported to inhibit collagen fibrillogenesis. We investigated their distribution in order to evaluate the role of proteoglycan in dentinogenesis. Specimens of porcine tooth-germ dentin and erupted teeth were the materials on which antibodies to keratin sulfate and dermatan sulfate proteoglycan were used. Predentin was found to be positive for both antibodies and the reaction ceased in the calcification front. Uniformly thick collagen fibrils (30-70 nm in diameter) were distributed in the predentin matrix, which would become intertubular dentin in the future. Both antibodies reacted positively along these fibrils. In contrast, along the surface layer of dentin in the tooth germ and that in erupted teeth, collagen fibrils of 10-300 nm in diameter were noted occasionally in dentinal tubules whose odontoblastic processes had disappeared and these heterogeneous fibrils were negative for both antibodies. Our findings suggest that keratan sulfate proteoglycan and dermatan sulfate proteoglycan distributed in the predentin inhibit calcification of collagen fibrils in the uncalcified matrix and disappear in the calcification front. It is further suggested that keratan sulfate proteoglycan and dermatan sulfate proteoglycan distributed along collagen fibrils in the predentin matrix maintain uniform thickness, whereas collagen fibrils in dentinal tubules varied in thickness because of the absence of involvement of both proteoglycans. Therefore, keratan sulfate proteoglycan and dermatan sulfate proteoglycan were thought to be involved in both calcification and matrix formation.     

Intertubular growth in pure seminomas: associations with poor prognostic parameters

Clinical stage I seminomas are effectively treated with surgery raising concerns as to when to give adjuvant radiation therapy given the risk of secondary malignancies. A recent randomized trial found tumor size and rete testis invasion to be the strongest predictors of relapse in clinical stage I seminomas. These 2 parameters may be surrogate measures of tumor volume. Intertubular seminoma (ITS) of the testis describes the presence of neoplastic germ cells within the interstitium of the testis. These cells are detected away from the main macroscopic mass. Because ITS can infiltrate in a 3-dimensional fashion, it may also represent a measure of tumor volume not usually noted in standard pathology reporting. The goal of this study was to determine the incidence of ITS in pure seminomas and its association with other prognostic parameters. One hundred twenty consecutive pure seminomas surgically removed between 1998 and 2003 were evaluated. ITS was defined as the presence of an interstitial or intertubular growth pattern of tumor cells, which was noncontiguous with the main tumor and present at least 3 high-power fields away from the tumor mass. The average tumor size was 3.4 cm. Of the entire cohort of patients, which included pathological stages T1 through T3, 11% had invasion through the tunica albuginea, 51% had rete testis invasion, 51% had lymphovascular invasion, 93% had associated intratubular germ-cell neoplasia, and 36% had ITS. ITS was significantly associated with rete testis invasion ( P = .001). Logistic regression analysis looking at ITS, tumor size, patient age, and lymphovascular invasion revealed that only ITS was associated with rete testis invasion (RR, 4.1, P < .0001). ITS is present in a significant proportion of pure seminomas and has a significant association with rete testis invasion. The presence of ITS may therefore be an important prognostic factor, not only because it alters the calculated size of the tumor but also because it has an association with rete testis invasion.     

Scanning electron microscopy of teeth in dominant osteogenesis imperfecta: Support for genetic heterogeneity

Scanning electron microscopic studies were performed on 25 deciduous and permanent teeth from members of 7 kindreds with dominant nonlethal osteogenesis imperfects (OI). Two families had normal teeth on clinical and radiological examination; five familes had blue or brown opalescent teeth with specific radiologic findings. Enamel surfaces and prism organization were normal on all teeth. On fractured surfaces, the dentin tubules of normal teeth from patients with OI were evenly distributed and coursed regularly to the dentin-enamel junction. Opalescent teeth had few tubules and those present were short, narrow, and tortuous. Dentin calcification fronts of normal teeth were composed of many nodules with regularly spaced openings on their surfaces. Calcification fronts of opalescent teeth were composed of irregularly spaced, small nodules, which varied greatly in size and the nodules lacked tubule openings on their surfaces. The results of this study support the concept that at least two dominant forms of OI exist – one in which all individuals with IO have normal teeth, and the other in which all with OI have blue or brown opalescent teeth with characteristic changes on SEM.     

人前磨牙牙髓牙本质复合体层粘连蛋白的免疫组织化学研究

目的　研究层粘连蛋白在牙髓牙本质复合体内的表达 ,探讨其分布与功能的关系。　方法　收集不同年龄新鲜健康人前磨牙 6 0颗 ,固定 ,脱钙 ,石蜡包埋 ,层粘连蛋白免疫组织化学染色。　结果　层粘连蛋白免疫反应性 ( IR)普遍存在于牙髓、前期牙本质和成熟牙本质小管与成牙本质细胞突起之间 ,以牙髓的神经与血管周围最为丰富 ,冠髓较根髓密集。　结论　层粘连蛋白 IR不仅见于牙髓与前期牙本质 ,而且也见于成熟牙本质 ,它对支持、固定牙髓牙本质复合体各结构的正常位置、形态可能发挥了重要作用