Effect of ovariectomy on the local residual ridge remodeling

RNA Extraction from Cartilage: Issues, Methods, Tips

The increase in degenerative diseases involving articular cartilage has pushed research to focus on their pathogenesis and treatment, exploiting increasingly complex techniques. Gene expression analyses from tissue are representative of the in vivo situation, but the protocols to be applied to obtain a reliable analysis are not completely cleared through customs. Thus, RNA extraction from fresh samples and specifically from musculoskeletal tissue such as cartilage is still a challenging issue. The aim of the review is to provide an overview of the techniques described in the literature for RNA extraction, highlighting limits and possibilities. The research retrieved 65 papers suitable for the purposes. The results highlighted the great difficulty in comparing the different studies, both for the sources of tissue used and for the techniques employed, as well as the details about protocols. Few papers compared different RNA extraction methods or homogenization techniques; the case study reported by authors about RNA extraction from sheep cartilage has not found an analog in the literature, confirming the existence of a relevant blank on studies about RNA extraction from cartilage tissue. However, the state of the art depicted can be used as a starting point to improve and expand studies on this topic.

Osteogenesis Differences Around Titanium Implant and in Bone Defect Between Jaw Bones and Long Bones

The aim of this study is to evaluate the osteogenesis around titanium implant and in bone defect or fracture in jaw bones and long bones in ovariectomized (OVX) animal models. The literature on the osteogenesis around titanium implant and in bone defect or fracture in jaw bones and long bones was reviewed with charts. Fourty-eight rats were randomly divided into OVX group with ovariectomy and SHAM (sham-surgery) group with sham surgery. Titanium implants were inserted in the right mandibles and tibiae; bone defects were created in the left mandibles and tibiae. Two-week postoperatively, mandibles and tibiae of 8 rats were harvested and examined by hematoxylin and eosin staining and histological analysis; 4-week postoperatively, all mandibles and tibiae were harvested and examined by Micro-CT and histological analysis. A total of 52 articles were included in this literature review. Tibial osteogenesis around titanium implant and in bone defect in OVX group were significantly decreased compared with SHAM group. However, osteogenesis differences in the mandible both around titanium implant and in bone defect between groups were not statistically significant. OVX-induced osteoporosis suppresses osteogenesis around titanium implant and in the bone defect or fracture in long bones significantly while has less effect on that in the jaw bones.

The effect of experimental osteoporosis on bone regeneration: Part 1, histology findings

OBJECTIVES

To histologically define the healing events occurring in calvarial critical size defects (CSDs) following treatment with a collagen barrier for guided bone regeneration (GBR) and a particulate graft in healthy and osteoporotic conditions.

MATERIAL AND METHODS

Thirty-six 10-month-old, female, Wistar rats were used in this study. Half of them were ovariectomized (OVX) and fed with a low-calcium diet to induce an osteoporotic-like status. In each animal of both groups, two 5-mm CSDs were created, one in the centre of each parietal bone, and they were treated with a deproteinized bovine bone mineral (DBBM) particulate graft and a bi-layer collagen membrane. Six OVX and six healthy control rats were randomly euthanized at 7, 14 and 30 days. One defect per animal was randomly processed for decalcified histology. Three central sections were used for qualitative histology and histomorphometric analysis.

RESULTS

No significant difference in terms of percentage of newly formed bone was detected between the two groups at the different healing periods. However, a trend towards less bone formation and of poorer quality, expressed as reduced bone maturation, was detected in the OVX animals at 30 days.

DISCUSSION

According to this study, GBR with a collagen barrier and a DBBM graft can be successfully obtained also in osteoporotic-like conditions. Future studies considering longer healing periods and controlling for the confounding factors arising from the use of a particulate graft are needed to confirm these data.

Resorption of mandibular alveolar bone following loss of molar teeth and its relationship to age at death in a human skeletal population

Estimating adult age at death in skeletal remains is problematic, particularly in older adults. Molar wear is arguably the most reliable ageing technique for palaeopopulations, but many older adult skeletons have lost their molar teeth ante mortem, precluding its application. Resorption of the alveolar process occurs following tooth loss, and this appears to continue for a prolonged period. The current work investigates the relationship of this process to individual age in a nineteenth century AD European archaeological skeletal series of known age at death (N = 92 individuals), and discusses its potential as an age indicator. Mandibular corpus height was measured at the different molar positions. In females, reduction of corpus height with age was found at molar positions showing ante mortem loss. In both sexes, a relationship was found between age and a simple composite measure of corpus height in the molar region in those showing ante mortem loss of one or more mandibular molars. The correlation was stronger in females (r = -0.74) than in males (r = -0.49), appeared approximately linear, and continued into the ninth decade, the oldest age group in the study material. The results suggest that investigation of height of the posterior part of the mandibular corpus as a skeletal age indicator for individuals that have lost one or more molar teeth is merited in other palaeopopulations.

Loss of molar occlusion and mandibular morphology in adults in an ancient human population consuming a coarse diet

The purpose of the study is to investigate the link between number of molar teeth retained in occlusion and mandibular morphology in adults in an ancient, high dental wear human population. The study material comprises skeletons from Mediaeval Wharram Percy, England (N = 50 female, 69 male adults). It was hypothesized that adults retaining fewer occluding molars would show reduction in mandibular dimensions, particularly in the ascending ramus and gonial regions where the main muscles of mastication have their insertions. Molar occlusal status is assessed using the concept of functional units. Mandibular morphology is assessed using a suite of ten linear measurements plus the mandibular angle. Results show no evidence for any association between number of molars retained in occlusion and mandibular angle. There was an association between mandibular size and number of molars retained in occlusion, with smaller mandibular dimensions in those retaining fewer occluding molars. Some measurements were affected more than others so that there was also some shape alteration. Alteration of mandibular dimensions was more clearly demonstrable in females than in males. Only in females could significant reduction in the ascending ramus and gonial regions be demonstrated. Reasons for the apparent difference in response to loss of molar occlusion between male and female mandibles are unclear, but sex differences in bony metabolism mediated by hormonal factors may be implicated. Results suggest that care should be exercised when including mandibles from individuals showing loss of molar occlusion in morphological studies.

Diabetes mellitus and corticotherapy as risk factors for alendronate-related osteonecrosis of the jaws: a study in Wistar rats

BACKGROUND

The purpose of this study was to investigate the influence of diabetes and corticotherapy on the development of osteonecrosis of the jaws associated with sodium alendronate.

METHODS

Rats were allocated into 4 groups of 11 animals each, representing different treatments: (1) alendronate; (2) alendronate and corticotherapy; (3) alendronate and diabetes; and (4) control. Tooth extractions were performed in all animals, and histological analysis was performed by hematoxylin and eosin staining and immunohistochemistry using anti-bone morphogenetic protein (BMP)-4 and anti-matrix metalloproteinase (MMP)-13 antibodies.

RESULTS

On hematoxylin and eosin analysis, proportions of inflammatory infiltrate, microbial colonies, and osteonecrosis were significantly greater in the diabetes group. BMP-4 expression in connective tissue was higher in the corticosteroid group than the alendronate group. There were no significant differences between the other groups. MMP-13 expression did not differ between the groups analyzed.

CONCLUSION

Diabetes but not corticotherapy is associated with jaw osteonecrosis in rats undergoing alendronate therapy and subjected to tooth extractions.

Osteocalcin immunolabeling during the alveolar healing process in ovariectomized rats treated with estrogen or raloxifene

The influence of an estrogen-deficient state was evaluated in this study and also its treatments with estrogen (E(2)) or with raloxifene (RLX) on the expression of osteocalcin during the periods of the chronology of the alveolar bone healing process (7, 14, 21, 28 and 42 post-extraction days) by means of immunohistochemistry reactions and histomorphometric analysis. Rats (200-220 g) with oestrus cycles normal were either OVX or sham-operated and divided into four groups: sham, OVX control (OVX/O), estrogen (OVX/E(2); 17 beta-estradiol, 400 microg/mo) and raloxifene (OVX/RLX; 1 mg/kg bw/d) groups. Histomorphometric analysis showed the sham group presented the highest mean value of bone formation post-extraction. The reaction of immunohistochemistry for osteocalcin presented stronger expression of osteocalcin with predominance at 14 and 21 days on sham group. The OVX/RLX group presented better results than OVX/E(2), considering the expression of osteocalcin in osteoblastic lineage cells, but still inferior than the sham group. It was concluded that ovariectomy decreases the mineralization process and the osteocalcin expression during the chronology of the alveolar healing process that is not totally recovered with estrogen replacement or raloxifene treatment.

Ovariectomy delays alveolar wound healing after molar extractions in rats

PURPOSE

This study was conducted to investigate the morphological effects of the absence of estrogen on alveolar wound healing of young female rats after tooth extraction.

MATERIALS AND METHODS

A total of 60 4- to 6-week-old female rats underwent bilateral ovariectomy (OVX) or sham operations. Three weeks later, the first mandibular molars were extracted. Subsequently, the animals were killed by cervical dislocation 3, 5, 7, 14, 21, or 28 days after tooth extraction. The mandibles were removed, and serial transversal sections of mesial alveolus of the first mandibular molars were obtained for histometric analysis.

RESULTS

OVX sockets showed significant increases in fibroblasts and collagen content 3 and 5 days after the extractions, followed by significant decreases in these parameters in the subsequent periods. In accordance with the decreased collagen content in the latest period of healing, new bone formation was significantly reduced in the OVX animals.

CONCLUSION

These findings suggest that the initial molecular changes observed in the absence of estrogen lead to delayed alveolar wound healing.

A review of the association between osteoporosis and alveolar ridge augmentation

OBJECTIVE

Because of increasing life expectancy and popularity of dental implants, surgeons face a larger number of osteoporotic patients who require bone augmentation. Relationship between low bone density/osteoporosis and bone graft success is still not clear. The purpose of this article is to review and summarize the literature regarding the success of alveolar bone augmentation in osteoporosis.

STUDY DESIGN

The study design includes a literature review of relevant preclinical and clinical articles that address the association between osteoporosis and alveolar bone augmentation.

RESULTS

Increased rate of complications such as resorption of bone graft, non-integration of bone graft, delayed healing time, and implant failure in augmented bone especially in the maxilla may be associated with compromised bone health.

CONCLUSIONS

Despite the decreased success rate, osteoporosis is not an absolute contraindication for bone augmentation and dental implant placement. The modifiable risk factors for osteoporosis should be eliminated before surgery.

Smoking may affect the alveolar process dimensions and radiographic bone density in maxillary extraction sites: a prospective study in humans

PURPOSE

Loss of ridge width and height typically occur after tooth extraction. This study aimed to investigate whether smoking would effect alveolar ridge remodeling after tooth extraction.

MATERIALS AND METHODS

Twenty-one individuals (11 nonsmokers, 10 smokers) requiring a nonmolar extraction in the upper jaw were selected. Radiographs were taken 7 and 180 days after surgery, and the following parameters obtained: alveolar process height (AH), alveolar process width (AW), radiographic bone density in the postextraction socket (BDS), and in the pre-existing bone apically (BDPB).

RESULTS

Six months after surgery, intragroup analysis showed that both groups presented a significant reduction in AH, while only smokers had a significant reduction in AW, BDS, and BDPB (P < .05). Furthermore, intergroup analysis showed that smokers presented lower BDS (91.45 pixels +/- 26.62 and 59.53 pixels +/- 19.99, for nonsmokers and smokers, respectively; P = .006) and continued to present lower BDPB (129.34 pixels +/- 42.10 and 89.29 pixels +/- 29.96, for nonsmokers and smokers, respectively; P = .023). Additionally, smokers presented a tendency for lower AH and AW than nonsmokers, but this was not statistically significant.

CONCLUSION

Within the limits of the present study, smoking may lead to a more significant dimensional reduction of the residual alveolar ridge and postpone postextraction socket healing.

Bone healing in osteoporotic female rats following intra-alveolar grafting of bioactive glass

We have investigated the effect of ovariectomy combined with a low Ca diet on bone healing following the implantation of bioactive glass into extraction sockets, in rats. Ovariectomized rats received a low Ca diet from the day of surgery until sacrifice while sham-operated animals were fed a standard laboratory chow. Two weeks after surgery the upper incisors were extracted and the alveolar sockets in both groups were partially filled with a particulate bioglass (PerioGlas). The animals were killed 1, 2, 3 and 9 weeks after tooth extraction and the relative volume fraction of the healing components (bone trabeculae, connective tissue and coagulum remnants) was estimated in histological paraffin sections by a histometric differential point-counting method. The bioglass particles persisted inside the socket for all the experimental periods and, as bone repair proceeded, they were progressively enclosed in newly formed bone trabeculae which in some cases established a close contact with their surface. The volume fraction of neoformed bone trabeculae relative to the volume fraction of connective tissue and coagulum remnants was greater in the sockets of ovariectomized animals implanted with bioglass than in those of the overiectomized non-implanted groups.

Comparison between two experimental protocols to promote osteoporosis in the maxilla and proximal tibia of female rats

The effects of two experimental protocols (ovariectomy associated or not with a low calcium diet) used to promote osteoporosis in the rat maxilla and proximal tibia were compared 5 and 11 weeks after surgery. Female Wistar rats were ovariectomized or sham-operated. Half of the ovariectomized rats were fed a low Ca++ diet (ovx*) and the remaining ovariectomized (ovx) and sham animals received a standard chow. At sacrifice, the proximal metaphysis was excised from the tibia and the molars were extracted from the hemi-maxilla. Dry (60 degrees C overnight) and ash (700 degrees C/14 h) weights were measured and the ashes were used for Ca++ measurement by means of a colorimetric method. After 5 weeks, ovx caused no alteration while ovx* decreased proximal metaphysis (17%) and maxilla (35%) bone mass. After 11 weeks, ovx caused a 14% bone mass reduction in the proximal metaphysis but not in the maxilla, while ovx* caused a comparable bone mass reduction (30%) in both bone segments. Calcium concentration was not altered in any experimental condition. The results show that estrogen deficiency is insufficient to cause maxillary osteoporosis in rats over an 11-week period and a long-term ovariectomy is needed to exert deleterious effect on proximal metaphysis bone mass. When a low Ca++ diet is associated with estrogen deficiency, however, a relatively precocious harmful effect is observed, twice as pronounced in the maxilla than in the proximal metaphysis. On a long-term basis, ovariectomy associated with a low Ca++ diet seems to be equally injurious to both proximal metaphysis and maxilla.

Bone mineral density of the mandible in ovariectomized rats: analyses using dual energy X-ray absorptiometry and peripheral quantitative computed tomography

INTRODUCTION

Although previous studies have shown that maxillary molar extraction in ovariectomized (OVX) animals causes mandibular loss of bone, it is still questionable as to whether estrogen deficiency affects mandibles with functional occlusion.

MATERIALS AND METHODS

To answer this question, 13-week-old female Sprague-Dawley rats were bilaterally OVX or sham-operated. After 109 days, the bone mineral density (BMD) of the femurs and mandibles was measured using dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computed tomography (pQCT).

RESULTS

In DEXA analysis, although the BMD of the total mandible of the OVX rats was similar to that of the sham-operated rats, the BMD of the condylar region in the OVX rats had decreased by 12.5%. In pQCT analysis, decrease in trabecular BMD of the mandibular bone was detectable but low in the molar region (maximal 13%), whereas no difference was seen in cortical BMD. In the femurs, the trabecular bone prominently decreased in OVX rats (30% decrease in pQCT analysis) as previously reported.

CONCLUSION

This study revealed regional differences in the mandibular bone decrease in OVX rats. Although the mechanism of low susceptibility of the mandible to estrogen-deficient conditions remains unknown, it is likely that mechanical stress derived from functional occlusion is preventing bone loss in this pathological condition. Furthermore, this study demonstrated the advantage of pQCT in analyzing rat mandibular bone.

Effects of oestrogen deficiency on osteoclastogenesis in the rat periodontium

This study was designed to investigate quantitative changes in osteoclast generation in rat periodontium following ovariectomy. Wistar rats, aged 9 weeks, were subjected to either ovariectomy (OVX) or sham surgery. Osmotic pumps were implanted in 24 rats and either 17beta-oestradiol or vehicle solution were infused continuously. The rats were assigned to one of the following groups: (1) OVX+vehicle; (2) sham+vehicle; or (3) OVX+ 17beta-oestradiol. On the days 7 and 14 after surgery, four rats in each group were killed. Mandibles were demineralized and embedded in paraffin. Frontal sections of alveolar bone in the region of the first molar were cut for enzyme histochemistry and immunohistochemistry. On day 7, there was no significant difference in the number of tartrate-resistant acid phosphatase (TRAP)-positive cells located on bone surfaces in either group. However, the number of TRAP-positive mononuclear cells that were separated from the bone surface was significantly higher in group 1 than in groups 2 and 3. On the day 14, the number of TRAP-positive cells in group 1, which were attached to the bone surface, was significantly higher than had been apparent on day 7. There were also significant increases in the number of nuclei of TRAP-positive cells attached to the bone in group 1 compared with groups 2 and 3 on day 14. These findings demonstrate that oestrogen deficiency induces of osteoclastogenesis in the rat periodontium and that quantitative changes in osteoclastogenesis could be prevented by E2 infusion.

Ovariectomy hinders the early stage of bone-implant integration: histomorphometric, biomechanical, and molecular analyses

Postmenopausal osteoporosis is a contributing factor to alveolar bone atrophy associated with tooth loss in the elderly. The use of dental titanium implants has been increasingly adapted to treat these edentulous patients. This study examines whether female gonadal hormone deficiency interferes with the critical integration process between bone and implants. Two types of experimental titanium implants with acid-treated surfaces were placed in the femurs of ovariectomized (ovx) and sham-operated control rats: T-cell implants with a hollow chamber for histomorphometric and steady-state mRNA expression assays, and unthreaded cylindrical implants for biomechanical push-in tests. At week 2, less bone area was found in the ovx-implant group (p = 0.0495) than in the sham-implant group. The implant push-in test showed that the ovx-implant group had approximately half of the withstanding value of the sham-implant group (p = 0.009). However, these differences between the ovx and sham groups became diminished at week 4. Total RNA samples were examined by a reverse transcriptase-polymerase chain reaction assay for col1a1, col3a1, bone sialoprotein (bSP) II, osteonectin, osteopontin, osteocalcin, integrin beta1 and integrin beta3. In untreated bones and in created bone defects without implant placement, ovx did not affect the steady-state levels of the mRNAs tested. When implants were placed, significant upregulation of these genes was observed in the sham-implant group; however, only osteocalcin and integrins were upregulated in the ovx-implant group. The results suggest a biphasic effect of female gonadal hormone deficiency that may temporarily interfere with the early implant-tissue integration process, and which may be associated with a failure to upregulate a selected set of bone extracellular matrix genes. Once established, however, functional bone-implant integration can be achieved even in ovx rats.

Effects of ovariectomy and/or dietary calcium deficiency on bone dynamics in the rat hard palate, mandible and proximal tibia

The effects of ovariectomy and/or dietary calcium deficiency on bone dynamics were examined by comparing the histomorphometric changes in these bones. Five groups of rats were studied, (1) unoperated basal controls; (2) sham-operated, fed on a normal-calcium diet; (3) ovariectomized, fed on a normal-calcium diet; (4) sham-operated, fed on a calcium-deficient diet; (5) ovariectomized, fed on a calcium-deficient diet. The basal controls were killed at 6 weeks of age, and the remaining groups were killed at 18 weeks of age. The hard palate, mandible and proximal tibia were processed undemineralized for quantitative bone histomorphometry. Bone volume, eroded surface, osteoid surface and bone-formation ratio were calculated. A significant age-related increase in bone volume and a significant decrease in bone formation were observed in the hard palate and mandible, whereas no significant age-related increase in bone volume could be found in the tibia. In the hard palate, ovariectomy neither inhibited age-related increases in bone volume nor affected bone dynamics, while both the combined ovariectomy and dietary calcium deficiency and dietary calcium deficiency alone led to bone loss and increased bone turnover. In contrast, in the mandible and proximal tibia, ovariectomy alone as well as dietary calcium deficiency led to bone loss and increased bone turnover. Ovariectomy, therefore, produced no significant changes in the hard palate, but affected bone dynamics in the mandible and tibia. However, dietary calcium deficiency induced bone loss and increased bone turnover in the hard palate, mandible and proximal tibia, independently of ovariectomy.

Mandibular bone formation rates in aged ovariectomized rats treated with anti-resorptive agents alone and in combination with intermittent parathyroid hormone

Anti-resorptive agents--including estrogen (E), calcitonin (CT), and bisphosphonates--are established in the treatment of osteoporosis. Intermittent administration of parathyroid hormone (PTH) stimulates bone formation and is a possible therapeutic agent for the restoration of bone mass. The purpose was to determine the effects of the anti-resorptive agents alone and in combination with intermittent PTH on bone formation in the mandible and a long bone in the aged ovariectomized (Ovx) rat. Female rats were ovariectomized or sham-operated. One year later, groups of Ovx rats were treated with E, CT, or the bisphosphonate, Risedronate (NE). Additional groups of Ovx rats were treated with each of these agents in combination with human PTH for 10 weeks. Estrogen treatment suppressed most indices of bone formation in the humerus and mandible, while NE decreased some indices of formation at the endocortical and endosteal surfaces of the mandible and humerus. Increased double-labeled surface and mineral apposition rates were observed only on the mandibular endosteal surfaces following CT treatment. When the anti-resorptive agents were combined with intermittent PTH, most indices of bone formation at all skeletal sites were substantially greater than those of the untreated Ovx controls as well as the E-, CT-, and NE-treated groups, respectively. These results provide additional evidence that established and emerging therapies for osteoporosis affect osseous tissues in the oral cavity, and this may influence the progression of diseases and/or aging changes at this site.

Current perspectives in residual ridge remodeling and its clinical implications: a review

PURPOSE

This article reviews the current understanding of the biology of tooth extraction wound healing and residual ridge remodeling.

METHODS

The review of the biology of tooth extraction wound healing involves a discussion of the different cells populating the tooth extraction wound, the matrix formation, and the control of the repair process in the short-term. Defects in socket matrix formation or cellular activity will lead to stalled healing. The review of residual ridge remodeling describes the long-term result of tooth extraction and formation of residual ridges, in which the quantity of bone tissue continuously decreases. This may suggest that any potential regulatory factors of residual ridge resorption should have an adverse effect either on the increased catabolic activity by osteoclasts or on the decreased anabolic activity by osteoblasts. Both short-term tooth extraction healing and long-term residual ridge remodeling processes are interdependent. Furthermore, any potential genetic and environmental regulatory factors can affect the quality and quantity of bone by altering the gene expression events taking place in bone cells.

RESULTS

The intent of this article was to review the current progresses of biologic research on residual ridge remodeling and to relate the changes at molecular, cellular, and tissue levels. The understanding of residual ridge remodeling may provide a sound scientific basis for improved restorative and therapeutic treatments of the edentulous population.