Michael Stiller

Effect of β-tricalcium phosphate particles with varying porosity on osteogenesis after sinus floor augmentation in humans

This study examines the effect of two beta-tricalcium phosphate (TCP) particulate bone grafting materials with varying porosity on bone formation and on osteogenic marker expression 6 months after sinus floor augmentation. Unilateral sinus grafting was performed in 20 patients using a combination (4:1 ratio) of beta-TCP particles with 35% porosity (TCP-C) or 65% porosity (TCP-CM) and autogenous bone chips. At implant placement cylindrical biopsies were sampled and processed for immunohistochemical analysis of resin embedded sections. Sections were stained for collagen type I (Col I), alkaline phosphatase (ALP), osteocalcin (OC) and bone sialoprotein (BSP). Furthermore, the area fraction of newly formed bone as well as the particle area fraction were determined histomorphometrically first, apically close to the Schneiderian membrane and second, in the center of the cylindrical biopsies. In the TCP-CM patient group a larger amount of bone formation and particle degradation was observed in the apical area and thus at the largest distance from the crestal bone compared to the TCP-C group. Good bone bonding behaviour was observed with both materials. This was accompanied by expression of ALP, Col I, BSP and OC in the newly formed bone and osteogenic mesenchym in contact with the degrading particles. Both TCP materials supported bone formation in the augmented sinus floor. Six months after implantation of both types of beta-TCP particles, bone formation and matrix mineralization was still actively progressing in the tissue surrounding the particles. Consequently, a greater porosity appears to be advantageous for enhancing bone formation and particle degradation.

Primary and secondary Sjögren’s syndrome in children – a comparative study

Abstract Sjögren’s syndrome is a chronic inflammatory systemic autoimmune disease mainly affecting the exocrine and, particularly, the salivary and lacrimal glands. The condition usually occurs in adults. In 1994, the criteria for this syndrome were redefined in a multicenter European study. In children, Sjögren’s syndrome is a rare and probably underdiagnosed disease. To date, Sjögren’s syndrome in children has only been described in case reports and in the comparative presentation of various study results. So far, no study of a comparative classification into primary and secondary Sjögren’s syndrome has been carried out in a patient population of any size. Sjögren’s syndrome should be considered in the differential diagnosis of children with recurrent parotitis, keratoconjunctivitis sicca, or pronounced and early tooth decay associated with xerostomia. In this study of 23 children and adolescents under the age of 16 with the clinical symptoms and laboratory findings of Sjögren’s syndrome, we differentiate between primary and secondary Sjögren’s syndrome. The value of the individual methods of assessing the oral and the ophthalmological components and the manifestation of the underlying rheumatic condition are discussed on the basis of the EULAR criteria. The EULAR diagnostic criteria are of limited applicability in children because reliable anamnestic data are frequently lacking. Another problem in diagnosing Sjögren’s syndrome is the short-term detection of serological alterations and clinical symptoms. Even if young patients do not completely fulfill the required criteria, Sjögren’s syndrome can be assumed or confirmed in the presence of positive testing for oral and ocular manifestations and recurrent salivary gland enlargement.

A method for immunohistochemical detection of osteogenic markers in undecalcified bone sections

To evaluate the osteogenic potential of novel implant materials, it is important to examine their effect on osteoblastic differentiation. Characterizing the tissue response at the bone-biomaterial interface in vivo at a molecular level would contribute significantly to enhancing our understanding of tissue integration of endosseous implant materials. We describe here a new technique that overcomes difficulties commonly associated with performing immunohistochemistry on undecalcified sawed sections of bone. Sheep mandible specimens were fixed in an ethanol based fixative to maintain adequate antigenicity of the tissue. As a result, it was possible to omit antigen retrieval at high temperature for recovery of antigenicity, and detachment of sections from the slides was avoided. Following dehydration and infiltration, the specimens were embedded in a resin composed of polymethylmethacrylate and polybutylmethacrylate. Polymerization was achieved by adding benzoylperoxide and N,N-dimethyl-toluidine. This resin was selected because it maintained the antigenicity of the tissue, provided adequate properties for cutting 50 µm thick sections, and it facilitated deacrylizing the sawed sections. Acid-resistant acrylic slides were glued to the blocks using an epoxy resin based two-component adhesive to avoid detachment of the slides during the deacrylation procedure. Samples were stained for alkaline phosphatase, type I collagen, osteonectin, osteopontin, osteocalcin and bone sialoprotein. The EnVision + ™ dextran polymer conjugate two-step visualization system was applied for immunohistochemical detection of these bone matrix proteins. This procedure yielded positive staining for the osteogenic markers in cells and matrix components. The protocol described here facilitates the use of immunohistochemistry on resin embedded sawed sections of bone and provides a convenient and reliable method that can be used routinely for immunohistochemical analysis of hard tissue specimens containing implant materials.

Quantification of bone tissue regeneration employing β-tricalcium phosphate by three-dimensional non-invasive synchrotron micro-tomography — A comparative examination with histomorphometry

PURPOSE This methodical study presents a novel approach to evaluate the validity of two-dimensional histomorphometric measurements of a bone biopsy specimen after sinus floor elevation by means of high contrast, high resolution, three-dimensional and non-destructive synchrotron micro-tomography (SCT). The aim of this methodical description is to demonstrate the potential of this new approach for the evaluation of bone biopsy samples. MATERIALS AND METHODS Unilateral sinus grafting was carried out exemplarily in two patients using a combination of beta-tricalcium phosphate (beta-TCP) and autogenous bone chips. For the first patient a beta-TCP with 35% porosity and in the second with 60% porosity was used. At implant placement, 6 months after sinus grafting, a cylindrical specimen was biopsied from the augmented area. Subsequent to the histological embedding in resin the specimens were imaged using a SCT facility resulting in three-dimensional (3-D) images with approximately 4 microm spatial resolution (1.5 microm pixel size) for each patients specimen. Subsequent to the SCT acquisition, tissue sections were prepared for histomorphometric analysis. RESULTS Bone area fractions determined by two-dimensional (2-D) quantitative histomorphometry and by analysis of the corresponding 2-D slice from the SCT volume data were similar. For the first biopsy specimen (beta-TCP with 35% porosity), the bone area fractions were 53.3% and 54.9% as derived by histomorphometry and by analyzing a SCT slice, respectively. For the second biopsy specimen (beta-TCP with 60% porosity) the bone area fractions were 38.8% and 39% respectively. Although the agreement between the 2-D methods was excellent, the area fractions were somewhat higher than the volume fractions computed by 3-D image analysis on the entire SCT volume data set. The volume fractions were 48.8% (first biopsy specimen) and 36.3% (second biopsy specimen). CONCLUSION Although the agreement between the 2-D methods is excellent in terms of computing the area fractions, the structural 3-D insight which can be derived from classical 2-D methods, including histomorphometric analysis is considerably limited. This fact is emphasized by the discrepancy between the measured areas and volume fractions.

In vitro synchrotron-based radiography of micro-gap formation at the implant–abutment interface of two-piece dental implants

Micro-radiography using hard X-ray synchrotron radiation is the first potential tool to allow an evaluation of the mechanical behavior of the dental implant–abutment complex during force application, thus enabling the enhancement of the design of dental implants which has been based on theoretical analysis to date.

Diagnostic value of sialography with both the conventional and digital subtraction techniques in children with primary and secondary Sjo ̈gren’s syndrome ☆ ☆☆

OBJECTIVE The application of anamnestic data on siccative symptoms required for classifying adult Sjögrens syndrome is limited in childhood. Instrumental test procedures are therefore necessary for objectively recording the oral and ophthalmologic manifestations of the disease. The aim of this study was to clarify the sialographic changes that occur in Sjögrens syndrome in children. STUDY DESIGN A total of 23 sialograms were obtained with both conventional and digital subtraction techniques in 21 children with primary (10 girls and 1 boy) or secondary Sjögrens syndrome (10 girls). The films were assessed by 3 physicians and submitted for a consensus analysis if necessary. RESULTS The pathologic features observed in the children varied from a slightly narrowed ductal system to multiple peripheral ductal ectasias and completely destroyed parenchyma. Sialographic examinations demonstrate that, with progressing disease, regression of acinar dilatations and rarification of the ductal system occur. CONCLUSION The results show that the spectrum of sialographically recordable lesions in Sjögrens syndrome in children is greater than is described thus far in the literature.

Craniosynostosis in cherubism

Cherubism is a rare autosomal dominant fibro-osseous disorder that affects almost exclusively maxilla and mandible. Extracranial skeletal involvement is rare. We report on three affected males in three generations. The youngest affected relative was examined at age 4 months. He also had craniosynostosis. His affected father and grandfather had cherubism and clubbing of the fingers. Cherubism was mapped to region 4p16. Because of the associated cranio-synostosis, we excluded the FGFR3 gene as a candidate gene for cherubism.

A Comparative Study of the Biodegradability of Calcium-Alkali- Orthophosphate Ceramics in vitro and in vivo

Introduction Bioactive calcium phosphate ceramics have been widely used for bone regeneration.However, depending on the clinical application, these materials need to exhi bit varying degrees of biodegradability. For example,inclinical applications inwhi chimplants are tobe insertedintothe regeneratedsite,rapidbiodegradability is more important comp aredtoapplications inwhichthis is not the case.Therefore, there have been numerous efforts todev elop novel materials witha higher solubilitycomparedtotricalcium phosphate(TCP).Amongthevariouscalc ium phosphatematerials whichare currently clinically available,TCP possesses the highest solubility andbiodegradability. The most reliable methodfor evaluatinga bone substitute mat erial’s capability to degrade and promote bone formation and osseous regeneration is by performing hist omorphometric measurements onex vivospecimens from animal experiments.Anim al studies,however,are very cost-intensive.Furthermore,due toanincreasing focus onanimal ethic s,there has beenanongoingsearchfor alternative in vitromethods whichcancontribute toreduc ing the number of animal experiments.Consequently,this study compares aninvitromethodfor evaluating the biodegradability of novel calcium-alkali-orthophosphate ceramic particulates - by using solubility measurements - tohistomorphometric evaluationof the biodegradability of these materials by determining the decrease of particle size inhistological sections whichwer e obtainedsubsequent toimplantationinvivousingasheepmodel. Material and Methods Three novel calcium-alkali-orthophosphate ceramic bone substitute materials were studied. These materials are glassy-crystalline materials witha higher solubility thanβ-tricalcium phosphate [1-3].The compositionof these materials is rather similar, since their maincrystalline phase is the new phase Ca

In Vivo Osteogenesis Assessment of a Tricalcium Phosphate Paste and a Tricalcium Phosphate Foam Bone Grafting Materials

Calcium phosphates (CaPs) are synthetic bone grafting materials. CaPs are an alternative to overcome the drawbacks present with autologous bone grafting and/or xenograft materials. Among the CaPs, tricalcium phosphate (TCP) stands out as a good candidate due to its physicochemical properties. The clinical performance of β-TCP has already been proven and established. Nevertheless, the format in which TCP is delivered is also important in terms of clinical handling. This work assessed the in vivo performance of TCP-based bone grafting materials with different formats. Materials studied were a TCP paste (TCP-P), a TCP foam (TCP-F) and TCP granules (TCP-G). A sheep scapula model was used to evaluate the osteogenic performance of these bone grafting materials. All materials performed well in terms of bone regenerative capacity and material resorption. However, TCP-P and TCP-F displayed a more pronounced initial material resorption and also exhibited better handling properties compared to TCP-G. TCP-based materials with improved handling properties, such as TCP-P and TCP-F, which at the same time possess the advantageous properties of β-TCP are suitable bone substitute materials for grafting and reconstruction of bone defects in numerous clinical applications.

Dental Graft Materials

Owing to the significant increase in dental implants placements and in alveolar ridge augmentation procedures over the last two decades, there has been an ever-increasing demand for adequate bone grafting materials. Consequently, numerous bone grafting materials have been investigated. This includes calcium phosphate-based grafting materials such as synthetic and coralline or bovine-derived hydroxyapatites, tricalcium phosphate ceramics, biphasic hydroxyapatite tricalcium phosphates, calcium carbonates, bioactive glasses and glass ceramics, and demineralized freeze-dried bone allografts. More recently, injectable and mouldable cements as well as scaffolds for craniofacial bone tissue engineering have been developed. Furthermore, the combination of grafting materials with growth factors has been explored. However, compared to the bone substitute materials, which are currently clinically available, there is a significant need for bone substitute materials that degrade more rapidly but at the same time stimulate osteogenesis. This has initiated an ever-increasing search for bioactive rapidly resorbable bone grafting materials that exhibit good bone-bonding behavior by stimulating enhanced bone formation at the interface in combination with a high degradation rate. Furthermore, current research efforts include the optimization of resorbable bone grafting cements as well as of scaffolds and concepts for various tissue engineering approaches.