Assessment of aging characteristics of female condylar trabecular structure by cone-beam computed tomography

Objectives

This study was performed to analyze the aging-related changes of the female condylar bone mineral density (BMD) and trabecular structure by cone-beam computed tomography (CBCT), and determine whether the condylar structure shows obvious changes after menopause.

Methods

The CBCT images of 160 female patients who met the inclusion criteria for the study were collected and divided into four groups by age (20–29 years, 30–39 years, premenopausal, and postmenopausal groups). Computer processing software CT-Analyser (Version 1.15.2.2+; SkyScan, Antwerp, Belgium) was used to measure the condylar BMD and related indexes, namely the bone volume/tissue volume ratio (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular structure model index (SMI), and bone surface area/volume ratio (BS/BV). SPSS 12.0 (SPSS Inc., Chicago, IL, USA) was used to analyze the radiographic findings and statistical differences.

Results

No significant differences were found between the bilateral condyles in each group (P?>?0.05). BV/TV, Tb.N, and Tb.Th of the condyle decreased with age, and the postmenopausal group showed significantly different values for each index compared with the other groups (P?<?0.01). Tb.Sp, SMI, and BS/BV of the condyle increased with age, and the postmenopausal group showed significantly different values for each index compared with the other groups (P?<?0.01).

Conclusions

With increasing age, the female condylar bone volume decreases, the Tb.N and Tb.Th decrease, the gap between the trabecular bone increases, and plate-like trabecular bone gradually transforms into a rod-like form. These changes are much more obvious in postmenopausal women.

     

Microcomputed tomographic analysis of bone microarchitecture after sinus augmentation with hyaluronic matrix: a case–control study

Background

The aim of this study was to analyze trabecular microarchitecture of augmented sinuses with hyaluronic matrix and xenograft by microcomputed tomography, and to investigate whether hyaluronic matrix has an effect on the newly formed bone quality.

Materials and methods

Thirteen patients undergoing maxillary sinus augmentation were included in this split-mouth study. Right and left sinus sites were randomly assigned to test and control group. In test group, the sinus was grafted with hyaluronic matrix and xenograft; in control group, only with xenograft. Four months after augmentation, bone samples were harvested during implant placement and analyzed for the following trabecular microarchitecture parameters using microcomputed tomography: bone volume (BV), total volume (TV), bone volume fraction (BV/TV), bone surface (BS), specific bone surface (BS/BV), bone surface density (BS/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular pattern factor (Tb.Pf), and fractal dimension (FD).

Results

There was statistically significant difference only for BS/TV parameter between two groups. BS/TV was higher in hyaluronic matrix group compared with control group.

Conclusions

Addition of hyaluronic matrix to xenograft may enhance bone quality in terms of bone surface density. However, more research investigating the microstructural variation of augmented sinuses is needed with a greater sample.

     

Bone microarchitecture and turnover in the irradiated human mandible

ObjectivesThe aim of this study was to assess the microarchitecture and turnover in irradiated cancellous mandibular bone and the relation with radiation dose, to elucidate the effects of radiotherapy on the mandible.Patients and methodsMandibular cancellous bone biopsies were taken from irradiated patients and controls. Micro-CT scanning was performed to analyze microstructural bone parameters. Bone turnover was assessed by histomorphometry. Local radiation dose at the biopsy site (Dmax) was estimated from radiotherapy plans.ResultsTwenty-seven irradiated patients and 35 controls were included. Osteoid volume (Osteoid Volume/Bone Volume, OV/BV) [0.066/0.168 (median/interquartile range (IQR), OV/BV; %), P < 0.001], osteoid surface (Osteoid Surface/Bone Surface, OS/BS) [0.772/2.17 (median/IQR, OS/BS; %), P < 0.001] and osteoclasts number (Osteoclasts per millimetre bone surface, Ocl/mmBS; mm²) [0.026/0.123 (median/IQR, Ocl/mmBS; mm²), P < 0.001] were decreased; trabecular number (Tb.N) was lower [1.63/0.63 (median/IQR, Tb.N; 1/mm⁻¹), P = 0.012] and trabecular separation (Tb.Sp) [0.626/0.24 (median/IQR, Tb.Sp; μm), P = 0.038] was higher in irradiated mandibular bone. With higher Dmax, trabecular number increases (Spearman's correlation R = 0.470, P = 0.018) and trabecular separation decreases (Spearman's correlation R = −0.526, P = 0.007). Bone mineral density (BMD, milligrams hydroxyappetite per cubic centimetre, mgHA/cm³) [1016/99 (median/IQR, BMD; mgHA/cm³), P = 0.03] and trabecular separation [0.739/0.21 (median/IQR, Tb.Sp; μm), P = 0.005] are higher whereas connectivity density (Conn Dens) [3.94/6.71 (median/IQR, Conn Dens), P = 0.047] and trabecular number [1.48/0.44 (median/IQR, Tb.N; 1/mm⁻¹), P = 0.002] are lower in Dmax ≤50 Gy compared to controls.ConclusionsRadiotherapy dramatically impairs bone turnover in the mandible. Deterioration in microarchitecture only affects bone irradiated with a Dmax of <50 Gy. The 50 Gy value seems to be a critical threshold to where the effects of the radiation is more detrimental.     

The correlation of different methods for the assessment of bone quality in vivo: an observational study

Different methods for the assessment of bone quality were evaluated in this study. Sixty alveolar bone areas were investigated. Peri-apical and panoramic radiographs were obtained with an aluminium scale to assess optical density. The Lekholm and Zarb (L&Z) classification was determined through radiographic analysis and the surgeon’s tactile perception. A trephine was used to obtain a bone biopsy for assessment by micro-computed tomography (micro-CT) and histomorphometry. Primary stability of the implants was assessed using insertion torque (IT) and the implant stability quotient (ISQ). The optical density on peri-apical radiographs was correlated with IT, ISQ, and micro-CT (BV, BV/BT, Tb.Th, Tb.N, BS/BV, Tb.Pf, and SMI) (rho ≤ 0.471, P ≤ 0.028). Panoramic radiography showed a correlation only with bone surface (BS) and bone surface/volume ratio (BS/TV) (rho ≤ 0.290, P ≤ 0.031). IT showed a correlation with ISQ, histometry, and micro-CT (BV, BS/TV, Tb.Th, Tb.N, BS/BV, Tb.Pf, Tb.Sp, BV/BT) (rho ≤ 0.550, P ≤ 0.022). ISQ did not show any correlation with micro-CT. The L&Z classification showed correlations with the optical density obtained in the peri-apical radiographs, histometry, osteocyte count, IT, and micro-CT (BS/BV, Tb.Sp, Tb.Pf, BV, BS/TV, Tb.Th, Tb.N) (rho ≤ 0.344, P ≤ 0.042). The L&Z bone classification and IT are reliable methods, peri-apical radiographs and ISQ are acceptable, and panoramic radiography is not a reliable method for the assessment of bone quality.     

Microcomputed tomography analysis of particular autogenous bone graft in sinus augmentation at 5 months: differences on bone mineral density and 3D trabecular structure

Objectives

This study investigated the effects of gender on the three-dimensional (3D) bone mineral density (BMD) and micromorphology of the trabeculae of matured autogenous bone grafts after sinus floor augmentation, and compared them to those of adjacent native bone.

Materials and methods

Ten bone biopsy samples were removed from the implant placement areas of patients who had received second-stage sinus floor augmentation, and analyzed by microcomputed tomography. BMD phantoms with two calcium hydroxyapatite densities (0.25 and 0.75 g/cm³) were used to determine the BMD of the grafted and native bone samples. The 3D structural parameters of the trabeculae, including percentage of bone volume (bone volume/tissue volume, BV/TV), trabecular thickness (Tb.Th), trabecular number, trabecular separation, trabecular pattern factor (Tb.Pf), and structure model index, were analyzed between males and females and between grafted bone and native bone.

Results

No significant gender-specific differences in BMD and 3D trabecular structure of either native or grafted bone were found (P?>?0.05). Compared to the adjacent native bone, the autogenous grafted bone exhibited lower BV/TV and Tb.Th as well as a higher Tb.Pf (P?<?0.05). Additionally, there was a weak positive correlation between the Tb.Th values of grafted and native bone (R ²?=?0.58).

Conclusions

In the maxillary sinus, autogenous grafted bone exhibited lower BV/TV, Tb.Th, and trabecular connectivity than the adjacent native bone. No significant gender-specific differences were found for either the BMD or 3D trabecular structure of grafted bone.

Clinical relevance

After bone remodeling, autogenous grafted bone revealed different 3D trabecular structure as compared to native bone.     

Microarchitecture of medication-related osteonecrosis of the jaw (MRONJ); a retrospective micro-CT and morphometric analysis

Medication-related osteonecrosis of the jaw (MRONJ) is a severe side effect of antiresorptive (AR) drugs such as bisphosphonates (BP) and denosumab (Dmab). Although several risk factors are described, the etiology of MRONJ is still not fully elucidated. Bone-strengthening is the primary aim of antiresorptive therapy; however, overly increased bone mass and microcrack accumulation are also discussed in MRONJ etiologies. The aim of this study is to evaluate the microarchitecture of jaw bones with micro?computed tomography (micro-CT) in AR-treated patients with or without MRONJ.Human jaw bone samples of AR-treated patients were separated into 11 groups by AR treatment bisphosphonate (BP), denosumab (Dmab), both (M) and control groups. Subgroups were divided according to the clinical localization as AR-exposed vital jaw bone (BP_exp, Dmab_exp, M_exp), osteonecrosis–margin of a sequestrum (BPO_mar, DmabO_mar, MO_mar) and osteonecrosis–sequestrum (BPO_seq, DmabO_seq, MO_seq). Healthy jaw bone (C_HB) and osteoporotic jaw bone (C_OP) represent control groups. Samples underwent retrospective micro-CT and morphometric analysis in representative units by bone volume fraction (BV/TV), bone surface density (BS/BV), trabecular thickness (Tr.Th.), trabecular number (Tr.N.), trabecular space (Tr.Sp.), Euler characteristic for bone connectivity, bone mineral density (BMD) and tissue mineral density (TMD).A total of 141 samples from 78 patients were analyzed. BV/TV of M_exp group (mean: 0.46 ± 0.27) was significantly higher than in the C_OP group (mean: 0.14 ± 0.05; p = 0.0053). Tr.Th. differed significantly between the BP_exp group (mean: 0.32 ± 0.15) and the M_exp group (mean: 0.57 ± 0.20; p = 0.0452) as well as between the BPO_seq group (mean: 0.25 ± 0.10) and the MO_seq group (mean: 0.39 ± 0.18; p = 0.0417). Signs of trabecular thickening and unorganized trabecular microarchitecture from AR-exposed- to sequestrum groups, were analyzed in 3D reconstructions. However, BS/BV, Tr.N., and Tr.Sp. showed no significant differences. Euler characteristic of the BPO_seq group (median: 7.46) doubled compared to that of the BP_exp group (median: 14.97; p = 0.0064). Mineralization parameters BMD and TMD were similar in all groups.Findings show evidence of enhanced bone mass and suspect microarchitecture in some AR-treated jaw bone compared to osteoporotic jaw bone. Despite increased bone mass, some MRONJ samples showed decreased trabecular connectivity by Euler characteristic compared to AR-treated jaw bone. These samples may indicate extensive ossification and ineffective bone mass with superficially higher bone mass without existing or even reduced mechanical stability, indicated by connectivity loss. This result might also suggest a high risk to microcrack accumulation. At some point, possibly some kind of over-ossification could lead to under-nourishment and microarchitectural weakness, creating instability, subsequently increasing vulnerability to MRONJ.     

Preliminary Clinical Study to Evaluate the Relationship between Systemic Bone Turnover and the Microstructure of the Alveolar Bone

The objective of this study was to assess the possibility of developing a clinical minimally invasive and standardized method to evaluate the relationship between the microstructure of the jaw bone and systemic bone turnover. For this purpose, we performed standardized bone biopsy of the alveolar bone, and compared the 3D bone microstructure using micro-computed tomography (micro-CT) with bone mineral density (BMD) of the lumbar spine and biochemical markers of bone turnover. We evaluated a total of 9 samples taken from 6 patients by standardized biopsy using a trephine bur. BMD was evaluated using dual energy X-ray absorptiometry (DXA). Regarding the biochemical markers of bone turnover, serum bone-specific alkaline phosphatase (BAP) and serum osteocalcin (OC) were used as bone formation markers, and urinary cross-linked N-telopeptides of type I collagen (NTx) and urinary deoxypyridinoline (DPD) were selected as bone resorption markers. We scanned micro-CT images of these samples. Bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular spacing (Tb.Spac), fractal dimension, trabecular bone pattern factor (TBPf) and node-strut (Nd.Nd/TV, TSL/TV) were measured. Regarding the correlations between the parameters of bone microstructures, TB/TV, Tb.N, fractal dimension, and node-strut seemed to be positively correlated and Tb.Spac and TBPf seemed to be negatively correlated with each other, but Tb.Th seemed to have a low correlation with other parameters. OC and/or BAP showed a significantly high correlation with many structural parameters (p < 0.05%). In conclusion, some microstructural parameters may change according to the systemic bone turnover.     

不同方式处理犬下颌磨牙区即刻种植间隙的效果评价

目的: 探讨在犬下颌磨牙区即刻种植中,不同方式处理拔牙窝与种植体之间的间隙后的新骨形成情况。方法: 选择 6 条 1.5~2.0 岁的拉布拉多犬作为实验对象,在每条犬下颌骨中拔除两侧的第四前磨牙和第一磨牙,分别植入 4 颗牙种植体（Astra Tech^®,4.0 mm × 10 mm）。种植体和拔牙窝骨壁之间的近远中间隙分别进行3种处理,分为空白组（NN组）、胶质银明胶海绵（Gelatamp） 组（EN组）和 Gelatamp + 可吸收胶原膜（CM）组（EG 组）。术后12周收集标本,进行显微CT 扫描和组织学分析。采用SPSS 25.0软件包进行统计学分析。结果: 牙种植术后 12 周存活率为 100%。显微CT 扫描结果显示,新骨高度、骨矿物质密度（BMD）、骨体积分数 （BV/TV）、骨表面积骨体积比（BS/TV）、骨小梁厚度（Tb.Th）、骨小梁数（Tb.N）和骨小梁间距（Tb.Sp）等指标,组间无显著差异。组织学分析结果显示,新骨形成面积和种植体与骨接触面积（BIC）在组间无统计学差异。结论: 使用不同方式处理种植体与拔牙窝之间的间隙后的12周内,与空白对照组相比,单独放置 Gelatamp 或与 CM 联合使用,对种植体周围新骨形成、BIC、BMD、BV/TV、BS/TV、Tb.Th、Tb.N 及 Tb.Sp 等均无显著影响。     

Early bony changes associated with bisphosphonate-related osteonecrosis of the jaws in rats: A longitudinal in vivo study

ObjectiveTo evaluate early bony changes in an animal model of Medication-Related Osteonecrosis of the Jaw (MRONJ) at the side of the local trauma and at the contralateral side, comparing with a control group. Bony changes were evaluated by Microcomputed Tomography (MicroCT) at three times points: at baseline (T0), after drug administration (T1) and after dental extraction (T2).DesignTwo groups were compared: the experimental group in which zoledronic acid (ZA) was administered (17 rats) and the control group (13 rats). Dental extractions of the lower left first molars were performed in all animals. The left side was considered as the supposed affected area in the ZA group, and the right side was considered as the unaffected area. In these areas, the following structural microtomographic bone parameters were calculated: Bone Mineral Density (BMD), Trabecular Thickness (Tb.Th), and Bone Volume Proportion (BV/TV). The comparison of quantitative bone parameters among the different sides and experimental phases of both studied groups were performed by ANOVA-factorial.ResultsNone of the animals of the control group developed MRONJ. In the ZA group, 76% presented bone exposure. From T0 to T1, Tb.Th and BV/TV increased, and in T2, the mean values were higher in ZA group than in the control group. BMD increased throughout the different phases of both groups.ConclusionsStructural bony changes occurred in the ZA group at both mandibular sides before the dental extraction (T1). Tb.Th and BV/TV should be further investigated as potential early bone markers of MRONJ.     

不同去势时间对大鼠牙槽骨微结构影响的比较研究

目的 比较不同去势时间对大鼠牙槽骨微结构的影响,探讨牙槽骨骨质疏松大鼠模型建立成功的参数。方法 24只6月龄雌性SD大鼠,随机分为4组：（1）对照组1（Sham1）;（2）去势组1（OVX1）;（3）对照组2（Sham2）;（4）去势组2（OVX2）。分别在全麻下行假手术和双侧卵巢去势术。于术后3个月和4个月处死各组大鼠,取双侧上颌骨标本,通过Micro-CT扫描、HE染色、抗酒石酸酸性磷酸酶（TRAP）染色、Van Gieson染色、荧光双标观察并分析牙槽骨微结构的变化。结果 去势3个月后OVX1组与Sham1组大鼠相比,体重增加25.09%（P<0.01）;牙槽骨骨体积分数（BV/TV）、骨小梁数目（Tb.N）、骨小梁分离度（Tb.Sp）,牙骨质界-牙槽嵴顶（CEJ-ABC）距离无改变（P>0.05）,骨小梁宽度（Tb.Th）降低了12.44%（P<0.05）,破骨细胞数量增加了40.12%（P<0.01）;骨形成沉积率（MAR）无明显改变（P>0.05）;去势4个月后OVX1组与Sham1组大鼠相比,体重进一步增加了26.25%（P<0.01）,BV/TV、Tb.Th、MAR分别降低了11.15%、17.22%和38.45%（P<0.01）,Tb.Sp和破骨细胞数量分别增加了81.89%和35.67%（P<0.01）,Tb.N和CEJ-ABC距离无变化（P>0.05）,HE和Van Gieson染色均表明OVX2组大鼠牙槽骨骨量降低,骨髓腔面积增加,骨小梁微结构破坏、变细,部分区域发生断裂。结论 6月龄雌性SD大鼠去势4个月后,牙槽骨发生明显骨质疏松,可作为合适的牙槽骨骨质疏松大鼠模型参数的理论依据。     

Relationships between bone strength and bone quality: three-dimensional imaging analysis in ovariectomized mice

Objectives Low-energy trauma resulting in fractures of the distal femur is often observed in elderly patients with osteoporosis; such fractures are often associated with treatment difficulties and poor prognosis. The purpose of this study was to clarify the factors that affect the bone strength of the distal femur.Methods We used ovariectomized mice to demonstrate bone quality factors associated with deterioration of the strength of the distal femur. Ten-week old ICR-strain mice were ovariectomized or sham-ovariectomized. Total bone mineral density (BMD), total bone area, cortical BMD, cortical thickness, and trabecular BMD were measured by peripheral quantitative computed tomography in the distal metaphyseal region of the femora. As three-dimensional architectural parameters, the trabecular number, trabecular thickness (Tb.Th), trabecular separation, and connectivity density were measured in the same region by microcomputed tomography. The maximum load measured by compression testing of the distal metaphyseal region was regarded as the bone strength of each sample.Results No significant differences in total bone area or in cortical BMD were found between the groups. Bone strength showed the closest relationship with total BMD (r = 0.834). Multiple regression analysis demonstrated that total BMD greatly depended on cortical thickness. The addition of Tb.Th to trabecular BMD markedly reflected bone strength (R = 0.857), suggesting that Tb.Th affected bone strength more significantly than trabecular BMD.Conclusions These findings suggested that deterioration of bone strength of the distal femur (metaphysis) was not caused by a reduction in cortical BMD, but was related to reduced cortical thickness, which reduced total BMD, and to trabecular BMD and architecture, in particular to reduced Tb.Th.     

增材制造Ti-6Al-4V钛合金种植体骨结合的动物实验研究

目的探讨增材制造Ti-6Al-4V（TC4）钛合金种植体动物体内的骨结合和成骨效果,为进一步临床应用提供实验依据。 方法选择健康雄性新西兰兔42只,以兔双侧后腿股骨髁部为种植体植入区,将实验兔先分为2周（A组）、8周（B组）2个大组,每组21只;每大组中再分为3个亚组,分别为A1组、A2组、A3组和B1组、B2组、B3组,每小组7只。A1组和B1组实验兔双侧后腿股骨髁部分别植入原始表面和表面改性TC4钛合金种植体各1枚;A2组和B2组实验兔植入原始表面TC4钛合金种植体和钛骨种植体各1枚;A3组和B3组实验兔植入表面改性TC4钛合金种植体和钛骨种植体各1枚;使2周、8周均含有3种种植体各14枚。术后2、8周观察并比较分析3种种植体的植入成功率和骨结合情况,观察指标为：骨体积分数（BV/TV）、骨小梁面积密度（BS/BV）、骨小梁厚度（Tb.Th）、骨小梁数量（Tb.N）和骨小梁间隔（Tb.Sp）。对各组不同时段种植体骨界面骨密度指标,使用SPSS 21.0软件包对数据进行双因素方差分析,验证不同表面、不同时间对种植体骨结合水平的影响,并采用Tukey′s多重比较检验分析组间统计学差异。 结果3种种植体不脱钙组织切片、骨块微CT扫描及光学显微镜观察显示,随着植入后的时间进展,3种种植体表面骨组织的量逐渐增多,分布逐渐变密。2周时,表面改性TC4钛合金种植体组的BV/TV、Tb.N显著高于原始表面和钛骨组,差异有统计学意义（P<0.05）;Tb.Th显著高于钛骨组（P<0.05）;BS/BV、Tb.Sp显著低于钛骨组,差异有统计学意义（P<0.05）。8周时,3种种植体的BV/TV、BS/BV、Tb.Th、Tb.N和Tb.Sp差异均无统计学意义（P>0.05）。 结论表面改性TC4钛合金种植体2周时即能形成更多的骨组织,骨小梁的分布更密集,骨结合能力更强,有望成为口腔种植体的优选材料。     

Assessing Bone Type of Implant Recipient Sites by Stereomicroscopic Observation of Bone Core Specimens: A Comparison With the Assessment Using Dental Radiography

Background: The aim of the study is to determine if bone quality evaluation of surgically obtained bone core specimens using a stereomicroscope is reliable for determining bone quality at implant recipient sites. Methods: Bone quality was presurgically assessed in 122 edentulous ridges obtained from 62 patients using periapical radiographs and categorized according to the Lekholm and Zarb classification. During surgery, bone specimens were trephined, and bone types were immediately classified using a stereomicroscope. Microarchitectural characteristics of bone cores were evaluated after being scanned using microcomputed tomography (micro‐CT). Results: Bone types of implant sites categorized from radiography and stereomicroscope had statistically similar distribution but poor interrater agreement. Using micro‐CT, maxillae and mandibles showed significant differences in microarchitectural characteristics of bone cores. Bone volume (BV), total volume (TV), and trabecular thickness (Tb.Th) increased, whereas bone surface density (BS/BV) and open porosity (Po.[Op]) decreased in mandibular bone cores compared with those in maxillary bone cores. Moreover, micro‐CT values of BV/TV and Po.(Op) statistically correlated with bone types assessed by stereomicroscopy, particularly in mandibles (adjusted means of BV/TV of Type 2 to 4 versus Type 1 decreasing from ?9.88%, ?15.09%, ?29.31%; those of Po.(Op) ranged from 9.77%, 15.06%, 29.52% in an upward trend). However, such correlations were not found in maxillae or when bone types were classified using periapical radiographs. Conclusions: Caution is needed when using presurgical periapical radiographs to predict bone quality at implant recipient sites. Surgically preserved bone core specimens, whenever obtainable, might offer additional information to accurately assess bone quality, particularly at mandibular implant sites.     

Chronological changes in the microstructure of bone during peri-implant healing: a microcomputed tomographic evaluation

Our objectives were to examine the titanium-bone interfaces chronologically and to clarify the process of osseointegration using microcomputed tomography (microCT). The mandibular premolars of 3 dogs were extracted and 12 weeks later 2 Straumann dental implants were installed in each quadrant. The microstructural changes at the bone-implant interface at the first, fourth, and eighth weeks after installation were evaluated by microCT and a 3-dimensional image was constructed. The microstructural measurements at the bone-implant interface, including the trabecular number (Tb.N), bone volume fraction (BV/TV), structure model index (SMI), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp) and connectivity density (Conn.D), were measured. Experimental outcomes were analysed for correlations between time and microstructural variables of trabecular bone. Tb.N increased significantly during the eighth week compared with that during the first and fourth week (p = 0.001, 0.002). BV/TV increased generally with time and there were significant differences (p = 0.003) between each time group. While Tb.Sp decreased with time and changed significantly during the eighth week compared with that during the first week (p = 0.021), differences in SMI, Tb.Th and Conn.D did not differ significantly according to time of implant. The significant increase in the Tb.N and BV/TV during the eighth week after insertion of implants indicates that the formation of new bone before the eighth week is the key to osseointegration.     

The influence of altered functional loading and posterior bite-blocks on the periodontal ligament space and alveolar bone thickness in rats

Objectives: Posterior bite-blocks are resin-based structures elevating the occlusion and creating intrusive force on the posterior teeth. Bite-blocks were applied to the molars of growing rats and a hard and soft diet was used to create altered functional masticatory forces. The aim of the present investigation was to study the effect of this appliance on the periodontal ligament space and alveolar bone thickness when combined with altered masticatory forces.

Material and methods: Fifty-two four-week-old rats were divided into two groups, hard and soft diet. Two weeks later, half of them received a bite-block appliance, creating four groups: control hard (CH), control soft (CS), bite-block hard (BH) and bite-block soft (BS). All were sacrificed at age of 10 weeks. Their heads were scanned by micro-CT and periodontal ligament space (PDL) width, cross-sectional alveolar socket surface and alveolar bone thickness were measured. Analysis of variance (ANOVA) was used to compare the groups.

Results: The PDL was 9.2% thinner in the CS group (p?p p?=?0.018) in the CS group, 10.7% in the BH group (p?p?Conclusions: Young rats wearing posterior bite-blocks have narrower PDL space and thinner alveolar bone compared to controls. When fed a soft diet, the alveolar bone is even thinner but the PDL showed no difference.     

Effects of chitosan oligosaccharides on the femur trabecular structure in ovariectomized rats

Objectives Drugs used to treat osteoporosis are taken long-term and ideally have no adverse effects. Recent interest has focused on chitosan oligosaccharides as a bone-inducing substance for use as bone graft material. The present study was designed to investigate the effects of chitosan oligosaccharides on the femur trabecular structure in ovariectomized rats by three-dimensional imaging analysis using micro-computed tomography (CT).Methods Female 12-week-old Wistar rats were divided into three groups, which underwent ovariectomy (two groups) or sham surgery (one group). After 12 weeks, rats of one of the ovariectomized groups began treatment with chitosan oligosaccharides (500 mg/kg bodyweight) three times per week for 8 weeks. Then, the femurs of all rats were resected for bone analysis by micro-CT, and three-dimensional images of the femur were reconstructed from the axial CT images to evaluate the following parameters: bone volume/tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.sp), trabecular bone pattern factor (TBPf), structure model index (SMI), number of nodes per unit tissue volume, number of termini per unit tissue volume, and the total strut length per unit tissue volume.Results The BV/TV, Tb.Th, and Tb.N were significantly higher in the ovariectomized and treated (OVX + C) group versus the ovariectomized, untreated (OVX) group. Tb.Sp, TBPf, and SMI were significantly lower in the OVX + C group versus the OVX group.Conclusions Our findings demonstrate that chitosan oligosaccharides prevent decreases in bone volume, trabecular number, trabecular thickness, and trabecular connectivity in the femurs of ovariectomized rats.     

Micro X-ray computed tomography analysis for the evaluation of asymmetrical condylar growth in the rat

Authors– Nakano H, Watahiki J, Kubota M, Maki K, Shibasaki Y, Hatcher D, Miller AJ Objectives – To investigate the influence of forced lateral bite on mandibular growth, micro X‐ray computed tomography (CT) was used for the purpose evaluating condylar cartilage and cancellous bone formation in 10 male Wister rats (3 weeks of age). Settings and sample population – The rats were divided into two groups – experimental and control. In experimental group, an inclined crown was cemented onto the maxillary incisors to produce 2.5 mm shift toward the left side during mastication. Right–left differences in whole mandibular length, mandibular height, condylar size, trabecular structure of the condylar head and three‐dimensional (3‐D) finite element analysis were assessed using 3‐D images reconstructed from micro X‐ray CT scans when the mice had reached 21 weeks. Measurements and Results – Asymmetrical growth was found in the experimental group, in which the left condylar head became thicker and shorter than the right condylar head during development. When comparing the left and right condyles of the experimental animals, histomorphometric analysis from micro X‐ray CT showed that the bone volume (BV) of the cancellous bone, the surface area of the cancellous bone (BS), the BS/BV ratio, the BV fraction (BV/TV), and the trabecular thickness and trabecular number were less for the right condyle than for the left condyle. Conclusions – These findings suggested that artificial changes in the mastication do influence the growth of condylar head, condylar bone trabecular structure, and mineralization.     

Analysis of mandible trabecular structure using digital periapical radiographs to assess low bone quality in postmenopausal women

PurposeTo analyze the quality of mandibular trabecular structure in postmenopausal women using periapical radiographs. Postmenopausal women are subjected to low bone quality; hence, early detection methods are needed. In addition to bone mineral density (BMD), trabecular architecture must be assessed to determine bone quality. The mandible represents bone quality and allows the assessment of trabecular structure from periapical radiographs.Material and MethodsLumbar (BMDL) and femoral BMD (BMDF) examinations were performed using dual-energy X-ray absorptiometry (DXA) in 31 postmenopausal women and divided into normal, osteopenia, and osteoporotic groups. Periapical radiographs were taken at both posterior sites of the mandible. The region of interest was taken 2 mm from the apical root of the first molar. Trabecular parameters consisting of trabecular thickness (Tb.Th) and bone percentage (BA/TA) were measured using BoneJ.ResultsBoth trabecular parameters were significantly correlated with BMDF [BA/TA ​​(r = 0.3796; p < 0.05) and Tb.Th (r = 0.508; p < 0.05)]. BA/TA and Tb.Th were significantly different between the osteoporosis and normal groups (p < 0.05) contrast to osteopenia and normal groups (p > 0.05).ConclusionChanges in mandibular trabeculae structure in postmenopausal women can be assessed using periapical radiographs.     

Guided tissue regeneration using rigid absorbable membranes in the dog model of chronic furcation defect

Abstract

Objective. Absorbable membranes are used to promote the regeneration of periodontal defects by Guided Tissue Regeneration (GTR). However, their collapse into the defect is commonly reported, impairing regeneration. Therefore, absorbable but rigid membranes aiming at preventing such collapse were developed and analyzed in periodontal regeneration. Materials and methods. Membranes were analyzed in class II furcation defects in dogs; procedures included periodontal disease induction, prophylaxis and GTR (treated groups) or open flap debridement alone (control group). For GTR, the membranes were made of either 25% hydroxyapatite (HA) in polyhydroxybutyrate matrix (PHB) or 35% HA in PHB. Animals were clinically evaluated for gingival recession, clinical attachment level (CAL) and biopsies were collected at 60 and 120 days. Bone volume, trabeculae number, trabecular thickness and trabecular separation were quantified by micro-computed tomography, followed by histology. Results. Membrane exposure was observed in both treated groups (25 and 35% HAP) from the 8^th day after surgery, continuously progressing until 120 days. Mean CAL for all groups remained above normal values for dogs. Bone volumetric values were not significantly different. Partial formation of bone, cementum and periodontal ligament was observed in treated groups. An inflammatory infiltrate was observed in the dense connective tissue that partially filled the center of the treated defects with active osteoclasts on bone surface. Conclusion. Although partial regeneration of the defect was observed, it was limited by wound contamination. Consequently, rigid absorbable membranes made of HA and PHB failed to improve the regeneration of class II furcation defects in dogs.     

A Longitudinal Study of the Effect of Experimental Osteoporosis on Bone Trabecular Structure in the Rat Mandibular Condyle

Abstract

The authors performed a longitudinal study of the microstructural changes occurring in the mandibular condyle during osteoporosis using the findings obtained from micro-CT. The subjects used in this study were eight Sprague-Dawley rats. Among them, five were administered the immunosuppressant drug FK506 by injection for five weeks, while the other three were administered saline solution in the same manner. Micro-CT images were taken of the bilateral mandibular condyle, hip, and knee joints in all animals on days 1, 8, 15, 22, 29, and 36 following injection. Six indices of morphometric analysis were compared between the two groups. Significant differences were observed in BV/TV, Tb.Th, Tb.N, and Tb.Sp in the mandibular condyle, while trabecular bone density appeared to decrease in the immunosuppressant group on three-dimensional (3D) imaging. And, in comparison with the mandibular condyle and femur, they were similar. These results suggested that osteoporosis affects not only the femur, but also the mandibular condyle.