小鼠牙胚裸鼠体内移植的形态学观察

目的:观察小鼠牙胚裸鼠体内移植后的形态学变化。方法:将出生后5天的小鼠的下颌第一磨牙牙胚异位移植到成年裸鼠背部肌层中,在移植后第7天和第14天分别取出植入的牙胚,常规制片,HE染色,显微镜下观察。另取出生后12天和19天的小鼠各1只,常规制片,HE染色,作移植后不同时间的对照。结果:肉眼观察发现,移植后牙胚生长于肌浅层,组织相容性好,表面有丰富的毛细血管;组织学观察表明:移植后的牙胚可继续发育,但比正常发育的牙胚速度减慢。牙本质层较薄,移植后形成大量牙本质小管、排列不规则的牙本质。虽然上皮根鞘位置变化不明显,但牙根可继续根向延伸。髓室底形成,髓腔缩小,根部钙化程度明显增强。移植后第7天,牙胚内外均有炎细胞浸润;但移植后第14天的牙胚,均未见明显的炎症现象。结论:小鼠牙胚裸鼠肌浅层移植后有一定的发育趋势,可以短期用于牙根发育的研究。     

A radiologic analysis of dentigerous cysts and odontogenic keratocysts associated with a mandibular third molar

OBJECTIVE: The purpose of this study was to discriminate radiographically between dentigerous cysts (DCs) and odontogenic keratocysts (OKCs) associated with a mandibular third molar. STUDY DESIGN: The material consisted of panoramic radiographs of dentigerous cysts (44 patients, 45 cysts) and odontogenic keratocysts (15 patients, 16 cysts), all of which were related to a mandibular third molar. The radiographic images were analyzed with reference to the patients' ages and symptoms. RESULTS: The mean age of patients in the OKC group was less than that of patients in the DC group. The mean area of the cysts in the OKC group was larger than that of those in the DC group. The mean distance from the second to the third molar in the DC group was greater than that in the OKC group. Although there was a significant correlation between the area and distance in the DC and OKC groups, the patients' ages did not significantly correlate to the area and distance of either cyst. CONCLUSIONS: The OKCs had a tendency toward rapid growth in the patient's youth but short movement of a third molar compared with the DCs. The DCs and OKCs do not appear to develop gradually from the period when follicles or dental lamina were formed but arise at various periods randomly.     

Fate of fluoride-induced subameloblastic cysts in developing hamster molar tooth germs

White opacities and pits are developmental defects in enamel caused by high intake of fluoride (F) during amelogenesis. We tested the hypothesis that these enamel pits develop at locations where F induces the formation of sub-ameloblastic cysts. We followed the fate of these cysts during molar development over time. Mandibles from hamster pups injected with 20 mg NaF/kg at postnatal day 4 were excised from 1 h after injection till shortly after tooth eruption, 8 days later. Tissues were histologically processed and cysts located and measured. Cysts were formed at early secretory stage and transitional stage of amelogenesis and detected as early 1 h after injection. The number of cysts increased from 1 to almost 4 per molar during the first 16 h post-injection. The size of the cysts was about the same, i.e., 0.46 ± 0.29 × 10⁶ μm³ at 2 h and 0.50 ± 0.35 × 10⁷ μm³ at 16 h post-injection. By detachment of the ameloblasts the forming enamel surface below the cyst was cell-free for the first 16 h post-injection. With time new ameloblasts repopulated and covered the enamel surface in the cystic area. Three days after injection all cysts had disappeared and the integrity of the ameloblastic layer restored. After eruption, white opaque areas with intact enamel surface were found occlusally at similar anatomical locations as late secretory stage cysts were seen pre-eruptively. We conclude that at this moderate F dose, the opaque sub-surface defects with intact surface enamel (white spots) are the consequence of the fluoride-induced cystic lesions formed earlier under the late secretory–transitional stage ameloblasts.     

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由于颌骨内的成牙组织常可作为囊肿和肿瘤的组织来源,因此颌骨是人类骨骼中最好发上皮性囊肿和肿瘤的部位。这类牙源性病损好发于年轻人,可造成颌骨及邻近组织的破坏,导致口腔颌面部外形改变,某些侵袭性病损具有较高的复发倾向,可对患者的生存质量及心理健康造成严重影响。本文着重讨论几种常见的牙源性囊肿与牙源性肿瘤的病理学诊断。     

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牙源性囊肿与牙源性肿瘤是口腔颌面部较为常见的疾病。由于临床表现的多样性,易与其他类型的颌面部囊肿或肿瘤相混淆,而且不同类型的牙源性囊肿和肿瘤其治疗方案也有所区别,所以牙源性囊肿及肿瘤的术前诊断对于其治疗方案的选择起着关键的作用,而在其诊治的过程中,影像学检查起到了非常重要的作用;不同类型的牙源性囊肿及肿瘤的影像学表现也各具特征。本文对常见的牙源性囊肿(牙源性角化囊肿等)及肿瘤(成釉细胞瘤、恶性成釉细胞瘤等)的影像学表现结合实际的影像学图片作简单的介绍,比较各种影像学检查在上述疾病诊断中所具有的优点,以期望能将CT、MRI及全景片等影像学检查手段更好的运用于上述疾病的诊治中。     

Notch1在小鼠下颌第一磨牙牙胚发育中的表达

目的探讨Notch1在小鼠下颌第一磨牙胚胎发育过程中的组织学分布。方法制作ICR小鼠下颌第一磨牙不同发育阶段的冰冻组织切片,对小鼠下颌第一磨牙自牙胚发育起始期至出生后2天不同发育阶段组织的Notch1分布情况进行免疫组织化学染色。结果 Notch1在小鼠下颌第一磨牙牙胚发育起始期和蕾状期牙板上皮上方或其包绕的口腔上皮中表达,在牙板上皮中没有表达。自帽状期至钟状期,Notch1在牙胚的中间层表达,而在内釉上皮中无表达。至牙釉质和牙本质分泌期,Notch1仍在颈环部位的中间层表达。此外,Notch1还在牙胚发育不同时期的间充质、牙乳头和早期牙髓中表达。结论 Notch1可能在小鼠下颌第一磨牙发育过程中的牙上皮特别是内釉上皮的细胞分化,以及牙囊和牙乳头细胞分化及分化完成后的牙髓干细胞的稳定性方面有重要作用。     

Ultrastructure of odontogenic jaw cysts

The epithelial ultrastructure of six radicular cysts, four follicular cysts, and five keratocysts was studied with special attention to the epithelium-connective tissue junction, Inflammation was found to cause widened interepithelial cell spaces which often harbored inflammatory cells in the radicular and follicular cysts. The characteristic structures at the epithelium-connectivc tissue junction (plasma membrane, lamina lucida and basal lamina) were not affected by inflammation. Fibrous structures were seen to connect the basal lamina to the underlining collagenous connective tissue The keratocyst specimens, however, showed juxtaepithelial collagenolysis that was not associated with the degree of inflammation. Desmosomes were rare in the inflamed keratocysts' spinous layer but the cell-to-cell interactions still appeared close. Inflammatory cells were not detected within epithelium of the keratocyst specimens.     

Neoplastic potential of odontogenic cysts

Odontogenic cysts and tumors are distinct entities and quite a common occurrence in the jaw bones. The lining of odontogenic cysts shows a potential for neoplastic transformation to non odontogenic malignancies like squamous cell carcinoma and mucoepidermoid carcinoma, and odontogenic tumors like ameloblastoma and adenoamatoid odontogenic tumor (AOT). AOT is a benign, epithelial odontogenic tumor, common site being the anterior maxilla. Its origin from a dentigerous cyst and in the mandible is rare. A case of an AOT arising from a dentigerous cyst associated with an impacted permanent mandibular left lateral incisor is reported.     

Ultrastructure of odontogenic jaw cysts

The epithelial ultrastructure of six radicular cysts, four follicular cysts, and five keratocysts was studied with special attention to the epithelium-connective tissue junction. Inflammation was found to cause widened interepithelial cell spaces which often harbored inflammatory cells in the radicular and follicular cysts. The characteristic structures at the epithelium-connective tissue junction (plasma membrane, lamina lucida and basal lamina) were not affected by inflammation. Fibrous structures were seen to connect the basal lamina to the underlining collagenous connective tissue. The keratocyst specimens, however, showed juxtaepithelial collagenolysis that was not associated with the degree of inflammation. Desmosomes were rare in the inflamed keratocysts' spinous layer but the cell-to-cell interactions still appeared close. Inflammatory cells were not detected within epithelium of the keratocyst specimens.