Bone microarchitecture and turnover in the irradiated human mandible.

OBJECTIVES: The 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 METHODS: Mandibular 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. RESULTS: Twenty-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. CONCLUSIONS: Radiotherapy 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 irradiated human mandible: A quantitative study on bone vascularity.

OBJECTIVES: Hypovascularisation is thought to play an important role in the pathogenesis of osteoradionecrosis. The objective of this study was to assess the microvascular system in the irradiated mandibular bone marrow. MATERIALS AND METHODS: Mandibular bone biopsies were taken from 20 irradiated patients and 24 controls. Blood vessels were visualized using CD34 antibody stain to detect endothelial cells. The vascular density (VD) and vascular area fraction (VAF) were measured. Mean vessel lumen area, perimeter and diameter of the vessels were calculated for each vessel. A distinction was made between large and small vessels (cut-off point <400 µm2). RESULTS: Vascular density and vascular area fraction were lower in the irradiated group. The mean vascular perimeter and mean vascular diameter were higher in samples with a local radiation dose of ≥50 Gy, whereas the percentage of small vessels was lower. Larger vessel perimeter is associated with higher radiation dose. A longer interval between biopsy and radiotherapy is associated with a larger mean vessel perimeter and a lower percentage of small vessels. CONCLUSIONS: Radiation dosages higher than 50 Gy mainly affect the smaller vessels. With increased time after irradiation, the share of smaller vessels in the mandibular bone marrow seems to decrease. In search of the exact mechanisms of irradiation damage and osteoradionecrosis of the mandible, the role of the microvascular system in the mandibular bone marrow should be further explored.

[A phd completed. The effect of radiotherapy on oral mucosa cell morphology.] / Serie: Hora est. Het effect van radiotherapie op de morfologie van de orale mucosa.

The treatment of oral cancer usually consists of surgical removal of the tumour, possibly followed by radiotherapy. The purpose of this dissertation research was to investigate the effects of radiotherapy on the oral tissues, in particular the superficially positioned epithelial cells in the oral mucosa. Earlier studies with electron microscopy revealed that unradiated oral mucosa cells, when observed at high magnification, contain microplicae (ridges or folds). Together with various saliva components, these microplicae form a protective layer that offers defence against, for instance, microorganisms. Radiotherapy damages these microplicae and may even destroy them altogether. Studies have shown that this effect of radiation can be observed in animals as well as in humans. As the radiation dose increased (50 Gy or more) the destruction of the microplicae was more severe. With a dose of 60 Gy or more the microplicae completely disappeared. This process may play an important role in the occurrence of osteoradionecrosis in the jaw and failure of dental implants placed after radiotherapy.

[A woman with a painful and enlarged tongue]. / Een vrouw met een pijnlijk vergrote tong.

A 53-year-old woman presented with painful macroglossia and periorbital papules. Based on this clinical features and biopsies the diagnosis of nodular amyloidosis was established. Further analysis revealed that multiple myeloma was the underlying hematological disorder.

Bone augmentation followed by implant surgery in the edentulous mandible: A systematic review.

Long-standing loss of natural teeth in the mandible can lead to severe jaw atrophy and even mandibular fracture. There is no consensus on the best pre-prosthetic surgical treatment to reconstruct the atrophic edentulous mandible. The purpose of this review was to provide an overview of the existing literature and to give an evidence-based recommendation for bone grafting and future research. This systematic review was conducted according to the PRISMA statement. A literature search was performed in online databases Pubmed and Cochrane library for articles published between January 1980 and September 2017. The search was conducted using Medical Subject Heading terms: alveolar ridge augmentation; mouth, edentulous and mandible. Eligible articles were included according to in- and exclusion criteria and assessed on quality. Dental implant survival and bone stability were the primary outcomes. Secondary outcomes were complications. Twenty-four text articles matched the criteria and were included. Eleven articles were assessed to be of adequate quality for analysis. Graft stability seems to be higher in vertical distraction and tent-pole grafting, but as the dental implant survival is high (91.7% or higher) regardless of the procedure used for bone augmentation, this is of no clinical relevance. The survival rate of dental implants is high, regardless of the bone augmentation procedure used. High-quality clinical trials are needed to support the current evidence and guidelines on pre-implant bone grafting. Reporting of future research should include proper baseline characteristics and treatment description, as well as uniform outcome rendering.

The use of a biphasic calcium phosphate in a maxillary sinus floor elevation procedure: a clinical, radiological, histological, and histomorphometric evaluation with 9- and 12-month healing times.

BACKGROUND: This study evaluates the clinical, radiological, histological, and histomorphometric aspects of a fully synthetic biphasic calcium phosphate (BCP) (60% hydroxyapatite and 40% ß-tricalcium phosphate), used in a human maxillary sinus floor elevation (MSFE) procedure with 9- and 12-month healing time. METHODS: A unilateral MSFE procedure, using 100% BCP, was performed in two series of five patients with healing times of 9 and 12 months respectively. Clinical and radiological parameters were measured up to 5 years postoperatively. Biopsy retrieval was carried out during dental implants placement. Histology and histomorphometry were performed on 5-µm sections of undecalcified bone biopsies. RESULTS: The MSFE procedure with BCP showed uneventful healing in all cases. All dental implants appeared to be well osseointegrated after 3 months. Radiological evaluation showed less than 1 mm tissue height loss from MSFE to the 5-year follow-up examination. No signs of inflammation were detected on histological examination. Newly formed mineralized tissue was found cranially from the native bone. The BCP particles were surrounded by connective tissue, osteoid islands, and newly formed bone. Mineralized bone tissue was in intimate contact with the BCP particles. After 12 months, remnants of BCP were still present. The newly formed bone had a trabecular structure. Bone maturation was demonstrated by the presence of lamellar bone. Histomorphometric analysis showed at 9 and 12 months respectively an average vital bone volume/total volume of 35.2 and 28.2%, bone surface/total volume of 4.2 mm2/mm3 and 8.3 mm2/mm3, trabecular thickness of 224.7 and 66.7 µm, osteoid volume/bone volume of 8.8 and 3.4%, osteoid surface/bone surface (OS/BS) of 42.4 and 8.2%, and osteoid thickness of 93.9 and 13.6 µm. CONCLUSIONS: MFSE with BCP resulted in new bone formation within the augmented sinus floor and allowed the osseointegration of dental implants in both groups. From a histological and histomorphometric perspective, a 9-month healing time for this type of BCP may be the optimal time for placement of dental implants.

Regulation of CYP27B1 mRNA Expression in Primary Human Osteoblasts.

The enzyme 1α-hydroxylase (gene CYP27B1) catalyzes the synthesis of 1,25(OH)2D in both renal and bone cells. While renal 1α-hydroxylase is tightly regulated by hormones and 1,25(OH)2D itself, the regulation of 1α-hydroxylase in bone cells is poorly understood. The aim of this study was to investigate in a primary human osteoblast culture whether parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), calcitonin, calcium, phosphate, or MEPE affect mRNA levels of CYP27B1. Our results show that primary human osteoblasts in the presence of high calcium concentrations increase their CYP27B1 mRNA levels by 1.3-fold. CYP27B1 mRNA levels were not affected by PTH1-34, rhFGF23, calcitonin, phosphate, and rhMEPE. Our results suggest that the regulation of bone 1α-hydroxylase is different from renal 1α-hydroxylase. High calcium concentrations in bone may result in an increased local synthesis of 1,25(OH)2D leading to an enhanced matrix mineralization. In this way, the local synthesis of 1,25(OH)2D may contribute to the stimulatory effect of calcium on matrix mineralization.

Complications and Risk after Mandibular Reconstruction with Fibular Free Flaps in Patients with Oral Squamous Cell Carcinoma: A Retrospective Cohort Study.

Background We retrospectively analyzed the incidence and types of postoperative complications after mandibular continuity reconstructions with fibular free flaps (FFF) in patients with oral squamous cell carcinoma (OSCC) and identified potential risk factors for postoperative complications. Methods Data were retrieved from the medical records in the Department of Oral and Maxillofacial Surgery/Oral Pathology, VU University Medical Center/Academic Centre for Dentistry Amsterdam (ACTA), Amsterdam, The Netherlands from April 1995 to September 2013, and were statistically analyzed. Results In this study, 85 patients were included in whom 86 FFFs were used for mandibular reconstruction. Thirty-seven patients (43%) developed ≥ 1 surgical complication and 9 patients (10.5%) developed ≥ 1 systemic complication. Three patients (3.5%) developed total flap failure and six patients (7.0%) developed partial flap failure. Surgical complications were correlated with tobacco use, partial glossectomy, type of mandibular defect, and anatomic staging. Systemic complications were associated with age > 60 years and Charlson comorbidity index > 2. Hospitalization > 30 days was associated with type of mandibular defect. Conclusions The use of the FFF for reconstructing mandibular continuity defects in OSCC patients may be associated with postoperative complications. Patients with coexisting medical conditions and anterior mandibular defects have an increased risk for developing complications. Patients who undergo segmental mandibular resection including a partial glossectomy could have a reduced risk for complications.

Mechanical loading and the synthesis of 1,25(OH)2D in primary human osteoblasts.

The metabolite 1,25-dihydroxyvitamin D (1,25(OH)2D) is synthesized from its precursor 25-hydroxyvitamin D (25(OH)D) by human osteoblasts leading to stimulation of osteoblast differentiation in an autocrine or paracrine way. Osteoblast differentiation is also stimulated by mechanical loading through activation of various responses in bone cells such as nitric oxide signaling. Whether mechanical loading affects osteoblast differentiation through an enhanced synthesis of 1,25(OH)2D by human osteoblasts is still unknown. We hypothesized that mechanical loading stimulates the synthesis of 1,25(OH)2D from 25(OH)D in primary human osteoblasts. Since the responsiveness of bone to mechanical stimuli can be altered by various endocrine factors, we also investigated whether 1,25(OH)2D or 25(OH)D affect the response of primary human osteoblasts to mechanical loading. Primary human osteoblasts were pre-incubated in medium with/without 25(OH)D3 (400 nM) or 1,25(OH)2D3 (100 nM) for 24h and subjected to mechanical loading by pulsatile fluid flow (PFF). The response of osteoblasts to PFF was quantified by measuring nitric oxide, and by PCR analysis. The effect of PFF on the synthesis of 1,25(OH)2D3 was determined by subjecting osteoblasts to PFF followed by 24h post-incubation in medium with/without 25(OH)D3 (400 nM). We showed that 1,25(OH)2D3 reduced the PFF-induced NO response in primary human osteoblasts. 25(OH)D3 did not significantly alter the NO response of primary human osteoblasts to PFF, but 25(OH)D3 increased osteocalcin and RANKL mRNA levels, similar to 1,25(OH)2D3. PFF did not increase 1,25(OH)2D3 amounts in our model, even though PFF did increase CYP27B1 mRNA levels and reduced VDR mRNA levels. CYP24 mRNA levels were not affected by PFF, but were strongly increased by both 25(OH)D3 and 1,25(OH)2D3. In conclusion, 1,25(OH)2D3 may affect the response of primary human osteoblasts to mechanical stimuli, at least with respect to NO production. Mechanical stimuli may affect local vitamin D metabolism in primary human osteoblasts. Our results suggest that 1,25(OH)2D3 and mechanical loading, both stimuli of the differentiation of osteoblasts, interact at the cellular level.

Microplicae--Specialized Surface Structure of Epithelial Cells of Wet-Surfaced Oral Mucosa.

The surface structure of the superficial cells of the oral mucosa is decorated with numerous membrane ridges, termed microplicae (MPLs). The MPL structure is typical of the epithelial surfaces that are covered with protective mucus. Cell membrane MPLs are no longer seen as passive consequences of cellular activity. The interaction between MPLs and the mucins has been demonstrated, however the role of MPL structure seen on the upper surface of the oral epithelial cells is speculative. The cell surface is of potentially great significance, as it harbors many markers for refined prognosis and targets for oral mucosal diseases and cancer therapy. With these aspects in mind, we conducted the present review of the MPL structure and function in order to form the basis for further studies of MPLs of the oral epithelial cells.

Growth factor gene expression profiles of bone morphogenetic protein-2-treated human adipose stem cells seeded on calcium phosphate scaffolds in vitro.

The secretome of stem cells strongly determines the outcome of tissue engineering strategies. We investigated how the secretome of human adipose stem cells (hASCs) can be affected by substrate, BMP-2 treatment, and degree of differentiation. We hypothesized that as differentiation progresses, hASCs produce increasingly more gene products associated with processes such as angiogenesis and bone remodeling. Human ASCs were treated for 15 min with BMP-2 (10 ng/ml) to enhance osteogenic differentiation, or with vehicle. Subsequently, hASCs were seeded on plastic or on biphasic calcium phosphate (BCP) consisting of 60% hydroxyapatite and 40% ß-tricalcium phosphate. A PCR array for ~150 trophic factors and differentiation-related genes was performed at day 21 of culture. A limited set of factors was quantified by qPCR at days 0, 4, 14 and 21, and/or ELISA at day 21. Compared to plastic, BCP-cultured hASCs showed ≥2-fold higher expression of ~20 factors, e.g. cytokines such as IL-6, growth factors such as FGF7 and adhesion molecules such as VCAM1. Expression of another ~50 genes was decreased ≥2-fold on BCP vs. plastic, even though hASCs differentiate better on BCP than on plastic. BMP-2-treatment increased the expression of ~30 factors by hASCs seeded on BCP, while it decreased the expression of only PGF, PPARG and PTN. Substrate affected hASC secretion of Activin A and seemed to affect P1NP release. No clear association between hASC osteogenic differentiation and growth factor expression pattern was observed. Considering our observed lack of association between the degree of differentiation and the expression of factors associated with angiogenesis and bone remodeling by hASCs, future bone regeneration studies should focus more on systematically orchestrating the secretome of stem cells, rather than on inducing osteogenic differentiation of stem cells only. Short incubation with BMP-2 may be a promising treatment to enhance both osteogenic differentiation and environmental modulation.

[Rapid prototyping: a very promising method]. / Rapid prototyping: een veelbelovende methode.

Rapid prototyping is a method which makes it possible to produce a three-dimensional model based on two-dimensional imaging. Various rapid prototyping methods are available for modelling, such as stereolithography, selective laser sintering, direct laser metal sintering, two-photon polymerization, laminated object manufacturing, three-dimensional printing, three-dimensional plotting, polyjet inkjet technology,fused deposition modelling, vacuum casting and milling. The various methods currently being used in the biomedical sector differ in production, materials and properties of the three-dimensional model which is produced. Rapid prototyping is mainly usedforpreoperative planning, simulation, education, and research into and development of bioengineering possibilities.

Periosteal ossification of the vascular pedicle after reconstruction of continuity defects of the mandible and the maxilla with fibular free flaps: a retrospective study.

Periosteal ossification of the vascular pedicle of a fibular free flap after reconstruction of mandibular and maxillary continuity defects has been thought to be rare. The purpose of this study was to evaluate its incidence and contributory factors to its development.

[Notes concerning an overdenture on 2 implants as the standard for treating an edentulous mandible]. / Kanttekeningen bij een overkappingsprothese op 2 implantaten als gouden standaard voor de behandeling van een edentate onderkaak.

Patients with an edentulous mandible often have difficulty retaining conventional dentures. It was formerly the case that, as a rule, 4 implants were placed in the interforaminal area of the mandible in order to provide retention for the mandibular denture. A large body of research, however, revealed good results with 2 implants with various mesostructures. The 2 implant overdenture in the mandible has since become standard for edentulous patients. Research results indicate that this treatment should be the primary option under certain conditions. The appropriate types of care which are indicated by these conditions should, however, be carefully distinguished. Under certain anatomical conditions, such as a low and narrow alveolar ridge, exposed mandibular nerves, very low density alveolar bone (Class IV bone) and very sensitive mucous membranes, 4 implants are indicated. Patients who are less manually dextrous might be better served with 2 implants and a single mesostructure.

The use of Straumann Bone Ceramic in a maxillary sinus floor elevation procedure: a clinical, radiological, histological and histomorphometric evaluation with a 6-month healing period.

OBJECTIVES: In this study, we evaluated the quality and quantity of bone formation in maxillary sinus floor elevation procedure using a new fully synthetic biphasic calcium phosphate (BCP) consisting of a mixture of 60% hydroxyapatite and 40% of beta-tricalcium phosphate (Straumann Bone Ceramic). MATERIAL AND METHODS: A unilateral maxillary sinus floor elevation procedure was performed in six patients using 100% BCP. Biopsy retrieval for histological and histomorphometric analysis was carried out before implant placement after a 6-month healing period. RESULTS: In this study, the maxillary sinus floor elevation procedure with the use of BCP showed uneventful healing. Radiological evaluation after 6 months showed maintenance of vertical height gained immediately after surgery. Primary stability was achieved with all Straumann SLA dental implants of 4.1 mm diameter and 10 or 12 mm length. The implants appeared to be osseointegrated well after a 3-month healing period. Histological investigation showed no signs of inflammation. Cranial from the native alveolar bone, newly formed mineralized tissue was observed. Also, osteoid islands as well as connective tissue were seen around the BCP particles, cranial from the front of newly formed mineralized tissue. Close bone-to-substitute contact was observed. Histomorphometric analysis showed an average bone volume/total volume (BV/TV) of 27.3% [standard deviation (SD) 4.9], bone surface/total volume (BS/TV) 4.5 mm(2)/mm(3) (SD 1.1), trabecula-thickness (TbTh) 132.1 mum (SD 38.4), osteoid-volume/bone volume (OV/BV) 7.5% (SD 4.3), osteoid surface/bone surface (OS/BS) 41.3% (SD 28.5), osteoid thickness (O.Th) 13.3 mum (SD 4.7) and number of osteoclasts/total area (N.Oc/Tar) 4.4 1/mm (SD 5.7). CONCLUSIONS: Although a small number of patients were treated, this study provides radiological and histological evidence in humans confirming the suitability of this new BCP for vertical augmentation of the atrophied maxilla by means of a maxillary sinus floor elevation procedure allowing subsequent dental implant placement after a 6-month healing period. The newly formed bone had a trabecular structure and was in intimate contact with the substitute material, outlining the osteoconductive properties of the BCP material. Bone maturation was evident by the presence of lamellar bone.

Incidence of venous thromboembolism in oral and maxillofacial surgery: a retrospective analysis.

This study retrospectively investigates the incidence and risk factors for venous thromboembolism (VTE) in patients undergoing maxillofacial surgery. Data were obtained from patients treated between January 2005 and June 2006. Patients' records were reviewed for complaints and information relating to deep venous thrombosis (DVT) and pulmonary embolism (PE). All patients completed a questionnaire on complaints relating to DVT and PE. The patients were classified according to risk and the incidence of reported DVT and PE was calculated. The study population comprised 411 patients with a mean age of 32 (+/- 17) years. The median postoperative follow-up period was 53 (23-639) days. None of the patients received thromboembolism prophylaxis. The incidence of VTE in the study group was 0.5%. Logistic regression analysis demonstrated a relationship between body mass index and hospital stay with thromboembolism (p<0.05). Patients undergoing pre-implant surgery with bone graft proved to be at risk (p=0.07). The incidence of VTE in oral and maxillofacial surgery seems to be low, but thromboembolism prophylaxis may be justified in patients with clear potential risk factors.

[Reconstruction after surgical treatment of head and neck cancer: surgical and prosthetic possibilities]. / Reconstructie na chirurgische tumorbehandeling in het hoofd-halsgebied. Chirurgische en prothetische mogelijkheden.

Soft and hard tissue defects in the head and neck region after benign or malignant tumour resection, can be reconstructed by surgical techniques, such as tissue transplantation, and/or prostheses. The aim of reconstruction is to restore the original esthetics and functions of the bone and soft tissues that have been resected. The introduction of free vascularized osteomyocutaneous fibula and iliac crest flaps improved the surgical possibilities of reconstructing the mandible and the maxilla. With respect to oral rehabilitation, a reconstruction of the mandible and the maxilla should be carried out in such a way that it provides an adequate base for inserting endosseous implants, which will retain a removable or fixed prosthesis This requires good interdisciplinary planning, in which the plan for prosthetic treatment determines, in part, the choice of reconstruction method.

[Surgical dilemmas. Sinus floor elevation]. / Chirurgische dilemma's. De sinusbodemelevatie.

Limited alveolar bone height prevents the placement of dental implants. Sinus floor elevation is an internal augmentation of the maxillary sinus that allows implants to be placed. The principle of this surgical procedure is the preparation of a 'top hinge door', that is raised together with the Schneiderian membrane in the cranial direction. The space which created under this lid is filled with a bone transplant. Autogenous bone is the standard transplant material, despite the fact that a second surgery site is necessary. Under certain circumstances bone substitutes can be used, with a longer healing phase. If sufficient alveolar bone height is available to secure implant stability, simultaneous implantation and sinus floor elevation are possible. Considering the significant anatomical variation in the region of the maxillary sinus, a sound knowledge of the anatomy is of great importance.