鼠哺乳期二(噁)英暴露对子代牙槽骨生长发育的影响

目的 研究鼠哺乳期二(噁)英类物质2,3,7,8-四氯二苯对二(噁)英暴露对大鼠仔鼠牙槽骨生长发育的影响.方法 60天龄2,3,7,8-四氯二苯对二(噁)英暴露组和对照组仔大鼠被处死,将其带有磨牙的上颌骨行树脂包埋,制备硬组织磨片并在荧光显微镜下观察,对两实验组牙槽骨的组织形态、荧光标记情况及组织形态计量学参数进行比较.结果 与对照组相比,二(噁)英暴露组牙槽骨骨小梁结构较为疏松,荧光标记较紊乱.实验组与对照组骨小梁宽度分别为(52.5±5.2)μm及(59.4±6.6)μm,二者差异有统计学意义(P<0.05);骨小梁数目分别为(3.27±0.23)mm-1及(3.75±0.29)mm-1,差异有统计学意义(P<0.01);骨小梁分离度分别为(217.3±37.6)μm及(177.6±33.8)μm,差异有统计学意义(P<0.05);矿化沉积率分别为(0.68±0.08)μm/d及(0.95±0.12)μm/d,差异亦有统计学意义(P<0.05).结论 二(噁)英类物质哺乳期暴露显著降低了大鼠仔鼠牙槽骨的质、量,并影响其空间构型.     

Is there a lower threshold value of bone density for early loading protocols of dental implants?

This clinical study aimed to determine the bone density in dental implant recipient sites using computerized tomography (CT) and to establish a lower threshold value of bone density for early loading protocols. The study group was composed of 100 early loaded implants in 42 patients. A total of four groups were established according to the loading time and implant sites. The bone density of each recipient site for implant placement was determined using CT. The maximum insertion torque values were recorded with torque controlling machine. Implant stability measurements were performed with resonance frequency analyser. The bone density values varied from 528 to 1231 HU. It was found that mean bone density, insertion torque and resonance frequency analysis values were 887 +/- 180 HU, 41.2 +/- 6 Ncm, and 73.7 +/- 4 ISQ, respectively. Strong correlations were found between these three parameters. CT may be a useful tool for assessing the bone density of recipient areas before implant placement, and the early loading of dental implants may be possible in the implant sites where bone density is over 528 HU.     

Histologic evaluation of the buccal and lingual bone plates in anterior dog teeth: possible influence on implant dentistry

Background: Recent studies in animals have shown pronounced resorption of buccal bone plate after immediate implantation. The sectioning of experimental material for histologic evaluation of the bone plates could provide valuable information about the possible effect of bone exposure in periodontal and implant surgeries. Methods: Twenty‐four incisors were collected from dogs. After decalcification, the blocks were immersed in paraffin and bucco‐lingual histologic sections were examined under light microscope. Some sections were reserved for immunohistochemical analysis. Results: The bone density, the width of the bone plates, and the percentage of vessels presented in the periodontal ligament and periosteum were analyzed in the buccal and lingual bone plates, which were divided corono‐apically into thirds. The buccal bone plates showed statistically higher bone density compared to the lingual bone plates in the coronal thirds. The width of both bone plates increased from the coronal to the apical third, but all the buccal thirds were significantly thinner compared to the lingual thirds. No statistically significant differences were found between the bone plates for the percentage of area occupied by the blood vessels in the periodontal ligament or periosteum. Conclusion: It is reasonable to conclude that the higher bone density, represented by the lower number of marrow spaces, in association with the thinner aspect of the buccal bone plates made them more fragile to absorb compared to the lingual bone plates, especially during mucoperiosteal procedures.     

Profiling of bacterial flora in crevices around titanium orthodontic anchor plates

OBJECTIVES: The aims of this study were to characterize the microflora in crevices around titanium orthodontic anchor plates using anaerobic culture and molecular biological techniques for bacterial identification, and to compare the microbial composition between crevices around anchor plates and gingival crevices. MATERIAL AND METHODS: Samples from crevices around titanium anchor plates and healthy gingival crevices of 17 subjects (aged 20-29) were cultured anaerobically, and isolated bacteria were identified by 16S rRNA sequencing. RESULTS: The average logarithm colony-forming units/ml were 6.84, 7.51 and 8.88 in healthy anchor plate crevices, inflamed anchor plate crevices and healthy gingival crevices, respectively, indicating that the bacterial density of anchor plate crevices was lower than that of healthy gingival crevices. Of 184 strains isolated from healthy anchor plate crevices of seven subjects, 108 (59%) were anaerobic bacteria, while 73 (40%) were facultative bacteria. Predominant isolates were Gram-negative rods, such as Campylobacter (12%), Fusobacterium (10%) and Selenomonas (10%), and Gram-positive facultative bacteria, such as Actinomyces (17%) and Streptococcus (8.2%). Of 133 strains isolated from inflamed anchor plate crevices of three subjects, 110 (83%) were anaerobic bacteria, while predominant isolates were Gram-negative rods, such as Prevotella (47%), Fusobacterium (33%) and Campylobacter (16%). On the other hand, of 146 strains isolated from healthy gingival crevices of seven subjects, 98 (67%) were facultative bacteria, while 45 (31%) were anaerobic bacteria. Predominant isolates were Gram-positive facultative bacteria, such as Actinomyces (37%) and Streptococcus (20%). CONCLUSIONS: These results suggest that the environment in crevices around titanium orthodontic anchor plates is anaerobic and supportive of anaerobic growth of bacteria, which may trigger inflammation in the tissue around the plates.     

Bone health and oral health

BACKGROUND: Low bone mass in the skeleton, which increases the risk of osteoporotic fracture, also may be associated with periodontal bone loss and tooth loss. Osteoporosis and periodontal disease share several common risk factors, including older age, smoking and perhaps insufficient dietary intakes of calcium and vitamin D. CONCLUSION: Research supports the idea that osteoporosis independently influences alveolar bone height loss. Strategies for reducing osteoporosis risk also may help retard alveolar bone loss. Meeting dietary intake recommendations for calcium and vitamin D is one strategy that is appropriate for a broad segment of the population. CLINICAL IMPLICATIONS: A healthy lifestyle has multiple benefits for the mouth and throughout the body. Dental professionals can play a role in preventing osteoporosis by reinforcing this message.     

半坡博物馆馆藏六千年前人牙槽骨水平状况分析

目的:调查距今六千年前新石器时期古人牙齿的牙槽骨水平状况,以探求牙周病的罹患及发展趋势。方法:观察记录并统计了西安半坡博物馆馆藏76例古人牙槽骨水平情况,用SPSS 12.0软件对全部的884个牙齿进行了统计学分析。结果:①有64个个体的500个牙齿患有牙周病,占观察牙齿总数的57.08%,该人群牙周病的平均患病率为86.49%。②36~55岁年龄组牙周病患病率(96.55%)>24~35岁年龄组(86.67%)>23岁以下年龄组(61.54%)。③牙周病的罹患累及各个牙位,第一磨牙的牙周病患病率最高,切牙及第三磨牙的患病率低,其大小顺序为:M1>M2>P1>P2>C>I2>I1>M3。④性别在牙周病患病率方面无显著性差异(P>0.05)。结论:本研究旨在了解六千年前古人牙槽骨水平的一般状况,有助于人们推断牙周疾病在人类进化过程中的变化规律,并为认识当时人类社会生产与生活情况提供间接的证明。     

Assessment of correlation between computerized tomography values of the bone, and maximum torque and resonance frequency values at dental implant placement

summary The aim of this study was to determine the bone density in the designated implant sites using computerized tomography (CT), the fastening torque values of dental implants, and the implant stability values using resonance frequency analysis. Further aim was to evaluate a possible correlation between bone density, fastening torque and implant stability. Eighty‐five patients were treated with 158 Brånemark System implants. CT machine was used for preoperative evaluation of the jawbone for each patient, and bone densities were recorded in Hounsfield units (HU). The fastening torque values of all implants were recorded with the OsseoCare equipment. Implant stability measurements were performed with the Osstell machine. The average bone density and fastening torque values were 751·4 ± 256 HU and 39·7 ± 7 Ncm for 158 implants. The average primary implant stability was 73·2 ± 6 ISQ for seventy implants. Strong correlations were observed between the bone density, fastening torque and implant stability values of Brånemark System TiUnite MKIII implants at implant placement (P < 0·001). These results strengthen the hypothesis that it may be possible to predict and quantify initial implant stability and bone quality from pre‐surgical CT diagnosis.     

Contribution of the periosteum to bone formation in guided bone regeneration. A study in monkeys

The periosteum has been referred to as a protective barrier in the regeneration of bone defects. The objective of this study was to determine the contribution of periosteum as a natural barrier to bone formation in guided bone regeneration. Mucoperiosteal flaps were elevated bilaterally on the buccal aspect of the mandibular angle in 5 cynomolgus monkeys. Bleeding was induced by perforating the cortical bone. A hemispherical titanium mesh was fixed over the areas thus creating a void 5 mm in height between the mesh and the bone surface. One one side the mesh was covered with an ePTFE membrane (test side). The contralateral side did not receive further treatment (control side). After 4 month healing, histomorphometric analyses were used to determine the percentage of new bone in the void underneath the mesh, and the ratio between mineralized tissue and marrow spaces in new and old bone. The mean percentage of new bone tissue was 77.2 +/- 7.5% for the test sides and 68.6 +/- 8.4% for the control sides (P = 0.018, t-test). This new bone contained 80.0 +/- 3.6% mineralized tissue in the test group and 82.5 +/- 5.0% in the control group (P > 0.05, t-test). In both groups the newly formed bone exhibited significantly less mineralized tissue than the old bone (P < 0.05, t-test). It is concluded from this study that new bone formation was enhanced by the additional use of an ePTFE membrane under a periosteum-lined mucoperiosteal flap when space maintenance was excluded as a critical factor.     

VDR deficiency affects alveolar bone and cementum apposition in mice

Objective

To compare the mineralisation density (MD), morphology and histology of alveolar bone and cementum amongst VDR +/+, VDR −/−, and VDR −/− groups supplemented with a diet TD 96348, containing 20% lactose, 2.0% calcium and 1.25% phosphorous.

Methods

Four groups of mice (6 mice/group) were identified by genotyping: VDR +/+ mice (VDR wild type), VDR −/− mice (VDR deficient), VDR −/− offsprings derived from VDR −/− parents receiving a supplemental diet (early rescued), and VDR −/− mice fed with a supplemental diet beginning at age one month (late rescued). All mice were sacrificed at age 70.5 days. Micro-CT was used to compare MD and morphology of alveolar bone and cementum. H–E and Toluidine blue staining was used to examine the ultrastructure of the alveolar bone and cementum at matched locations.

Results

In VDR −/− group, alveolar bone and cementum failed to mineralise normally. Early rescue increased MD of alveolar bone in VDR −/− mice with excessive alveolar bone formation, but which not observed in late rescue group. MD and morphology of cementum–dentine complex in both early and late rescue groups were comparable with VDR +/+ group when feeding with high-calcium rescue diet.

Conclusions

VDR affects alveolar bone mineralisation and formation systemically and locally. However, cementum apposition and mineralisation is mainly regulated by calcium concentrations in serum.