Effect of bone conditioning on primary stability of FRIALIT-2 implants.

BACKGROUND: Primary stability is crucial to implants used for orthodontic anchorage. Bone condensing to enhance primary stability is controversial. MATERIAL AND METHODS: Fourteen Frialit-2-stepped screw and cylinder implants were placed in the median palatine sutures of 22 cadaveric human heads. In half of both types, the implant bed was prepared using a Frialit Bone Condenser. Primary implant stability was evaluated using non-invasive resonance frequency analysis. Moreover, the bone-implant contact area was examined histomorphometrically and radiographically. RESULTS: Bone condensing yielded a slightly, yet not significantly increased implant stability quotient compared with a conventional technique. In spongy bone, a significant histomorphometric increase of bone-implant contact (P<0.0001) and a significant increase of radiographic density was revealed for both implant types, while no significant changes were observed within the compact area. CONCLUSION: The study shows that bone condensing yields an improved histologic implant-bone contact only in spongy bone, which was paralleled by radiographic-densitometric findings.

The ultrastructure and processing properties of Straumann Bone Ceramic and NanoBone.

The ultrastructure, fundamental chemistry, and processing modes of fully synthetic bone grafting materials are relevant to the reconstruction of osseous defects. Rapid progress in the profitable market of biomaterials has led to the development of various bone substitutes. Despite all these efforts, an ideal and full substitute of autologous bone is not yet in sight. With regard to anorganic calcium phosphate ceramics, Straumann Bone Ceramic and NanoBone are compared. These have a similar composition and are osteoconductive, which indispensably requires contact with well-vascularised bone.

Bone graft substitutes in periodontal and peri-implant bone regeneration.

Regenerative medicine provides different therapy alternatives alongside gold standard autogenous grafts for the treatment of periodontal or peri-implant osseous defects. Continuing progress in the field of alloplastic bone substitutes has yielded promising solutions to the appropriate indications with the membrane technique either alone or in combination with enamel matrix derivatives. Their clinical outcomes, however, still require critical discussion.

Histological and fluorescence microscopic examination of the bone/implant interface in orthodontic miniscrews (Mondeal).

The temporary nature of orthodontic implants demands optimisation of size and design in order to minimise damage and risk to the patient. Slender and shorter miniscrews offer the advantage over conventional implants of easier and more ubiquitous positioning with minimised risk of injury to neighbouring anatomical structures such as tooth roots, nerves or vessels. The question is raised, however, as to what extent these advantages are gained at the price of diminished stability or a more unfavourable bone interface. In order to evaluate the screw/bone interface, 14 orthodontic miniscrews (Mondeal Medical Systems, diameter: 1.5 mm, length: 9 mm) were inserted into the right and left mandibles of 7 pigs (Sus scrofa domestica). Bone fluorochromes were administered in a defined order for polychrome sequencing. The samples gathered after 70 days were analysed using histological techniques and fluorescence microscopy. The lower part of the self-tapping thread displayed undisturbed bone apposition. Fluorescence microscopy revealed remodelling and bone apposition within the thread grooves.

The use of ceramic drills on a zirconium oxide basis in bone preparation.

The favourable mechanical properties and high biocompatibility of the newly developed mixed ceramics composed of zirconium oxide and aluminium oxide have continuously extended the scope of their application. Rotating instruments on a zirconium oxide basis are regarded as superior to metal burs in dentoalveolar surgery in terms of favourable temperature effects on the surrounding bone tissue and the economic advantage that they wear slowly, enabling them to be used repeatedly. In this study ten round burs made of zirconium oxide and aluminium oxide mixed ceramics were used for typical dental-alveolar preparation types on an explanted pig jaw. Prior to the first and following the tenth application a scanning electron microscopic (SEM) analysis of possible wear signs was conducted. However, this revealed no evidence of wear or resulting loss of sharpness.

Bacterial colonisation of interior implant threads with and without sealing.

Premature loss of dental implants is due, apart from mechanical factors, to germrelated inflammation. Gaps and hollow spaces within the implant system, for example the gap between implant and abutment in the two-part implant system, may provide a bacterial reservoir causing or maintaining inflammation. The bacterial spectrum involved is similar to that found in periodontitis. This in vitro study aimed to scrutinise the capability of Porphyromonas gingivalis (DSM 20709), the bacterium blamed for inducing peri-implantitis, to pass the implant/abutment gap in titanium implant systems used for orthodontic anchorage and to remain vital in the interior. Additionally, the in vitro effectiveness of gutta percha for gap sealing was examined. Twelve titanium implants (Straumann, diameter: 3.3 mm, length 5.5 mm) were provided with abutments at a defined torque (20 Ncm), six of which were sealed with gutta percha before screwing in the abutment. Subsequently the implants were placed in a nutrient solution (thioglycolate boullion with haemin-menadione solution) that contained Porphyromonas gingivalis. Microbiological specimens were sampled from the implant interiors after 24 and 72 hours and analysed using culture methods. There was evidence that penetration of the periodontal pathogen Porphyromonas gingivalis to the implant interior may occur as early as after 24 hours. Microbes were also detected in the interior of implants sealed with gutta percha. The abutment/implant interface in vitro provides a microbiological leakage for the prospective peri-implantitis-inducing bacterium Porphyromonas gingivalis. Survival of the bacterium is possible in the interior, so that development of a bacterial reservoir is assumed. This in vitro trial produced no evidence that sealing with gutta percha is an effective means to prevent secondary bacterial colonisation in the implant interior.

The survival and proliferation of fibroblasts on orthodontic miniscrews with different surface treatment: an in vitro study.

It is of fundamental importance for prosthodontic and orthodontic applications that there is a short osseointegration time of dental implants without inflammation of the surrounding tissue. In addition to the chemical properties of the implant material, the surface morphology is an equally critical parameter. The objective of this work was to study the effect of two simple surface treatments on the survival and proliferation of fibroblasts. Three groups of orthodontic miniscrews (Mondeal) were used. One group was given an airflow (EMS, Schweiz) treatment, the second was sand-blasted in the area of the threading and a third group served as a control. After preparation sterilised screws were cultured in vitro with fibroblasts (L-929). The metabolic cell activity on the implant surface was determined after 24, 48 and 120 hours using the alamarBlue assay and a count of DAPI labelled fibroblasts was performed with a fluorescence microscope. After 24 hours, but not at 48 hours and 120 hours, the metabolic activity of the fibroblasts was slightly decreased for the airflow screw group. Generally, no significant difference was found regarding metabolic activity and proliferation of fibroblasts within the different groups.

The application of bone graft substitutes for alveolar ridge preservation after orthodontic extractions and for augmentation of residual cleft defects.

The use of bone substitute materials in orthodontics is to be considered prior to orthodontic space closure after tooth extraction during the treatment of marked crowding as well as for treatment of residual defects in cleft-lip-and-palate children. In both cases the common objective is structure preservation or augmentation of the alveolar ridge. The demands to be made on the synthetic bone graft substitute comprise not just complication-free and safe use but also the chance of early tooth movement into the treated defect area with sufficient stability of the new tooth position.

The clinical application of a new synthetic bone grafting material in oral and maxillofacial surgery.

A novel bone formation material based on hydroxyapatite-xerogel is presented. With the use of the innovative sol-gel technology this material is produced in the low-temperature range by the addition of silicon dioxide; in its structure it mimics to a great extent the natural bone matrix. This results in high osteoconductivity and an osteoprotective effect as well as in complete biodegradation corresponding to bone formation in the course of natural bone remodelling. Two case reports are presented.

Wound management after the application of bone grafting substitutes in the orofacial region.

Surgical dressing after the application of bone grafting material depends on the type and size of the defect. A complete and tension-free wound closure has proved to be successful. In this context the infection problem needs special attention. Bone graft substitutes with an adequate surface structure, porosity and chemical properties, in combination with sufficient blood circulation, hold osteoconductive potential. They serve as a guide rail for the osteoblast-induced formation of new bone tissue, which at best may lead to complete replacement of the grafting material.

Requirements and infection prophylaxis for internally cooled implant drills.

Implant site preparation is crucially important to long-term success. Heat generation during drilling is unfavourable, since bone is relatively susceptible to heat, depending on its vascularisation and microstructure. Numerous factors such as drilling pressure, number of revolutions, drill design, wear and material, drilling depth and cooling influence heat generation. Internally cooled drills are, therefore, increasingly used, even though the improved cooling effect compared to conventional externally cooled drills is controversial. Internally cooled drills may have the disadvantage of a germ reservoir developing in the cooling channel. This study aimed to examine the effects of disinfection and sterilisation of internally cooled drills. After contamination of the cooling channel with suitable bioindicators (Enterococcus faecium, ATCC 6057 and spores of Bacillus stearothermophilus, ATCC 7953), the drills were disinfected (disinfection solution ID 220, Dürr Dental) and autoclaved (Webeco, E5S90, 134 degrees C, 2.6 bar, 5 min). Disinfection was not completely effective except after pre-cleaning. By means of sterilisation all spores of Bacillus stearothermophilus were completely killed. Internally cooled drills can be successfully disinfected by means of this hygienic procedure routinely used in dental practice and no source of infection is created.

The in vitro viability and growth of fibroblasts cultured in the presence of different bone grafting materials (NanoBone and Straumann Bone Ceramic).

Different clinical applications, including dentistry, are making increasing demands on bone grafting material. In the present study we have analysed the viability, proliferation and growth characteristics of fibroblasts cultured in vitro together with two different bone grafting materials, NanoBone and Straumann Bone Ceramic, over a period of 24 and 28 days respectively. Viability was measured at least every 72 hours by using the alamarBlue assay, a test that measures quantitatively cell proliferation and viability but does not require cell fixation or extraction. After one week of culture fibroblast viability was as high as in controls for both grafting materials and remained high (> 90%) for the duration of the experiment. Cell growth was evaluated microscopically. Scanning electron microscopy revealed a dense fibroblast growth at the surface of both bone grafting materials after three weeks of in vitro culture. Generally, our in vitro analyses contribute to further insights into cell - scaffold interactions.

The biodegradation of hydroxyapatite bone graft substitutes in vivo.

Hydroxyapatite (HA) ceramics are widely used for bone reconstruction. They are osteoconductive and serve as structural scaffolds for the deposition of new bone. Generally, scaffold materials should be degradable as they affect the mechanical properties of the reconstructed bone negatively. Degradation by osteoclasts during the bone remodelling process is desirable but often does not take place. In the current study we analysed by light microscopy the degradation of two granular HA implants in critically sized defects in the mandibula of Goettingen mini-pigs five weeks after implantation. Bio-Oss consists of sintered bovine bone and NanoBone is a synthetic HA produced in a sol-gel process in the presence of SiO2. We found that both biomaterials were degraded by osteoclasts with ruffled borders and acid phosphatase activity. The osteoclasts created resorption lacunae and resorptive trails and contained mineral particles. Frequently, resorption surfaces were in direct contact with bone formative surfaces on one granule. Granules, especially of NanoBone, were also covered by osteoclasts if located in vascularised connective tissue distant from bone tissue. However, this usually occurred without the creation of resorption lacunae. The former defect margins consisted of newly formed bone often without remnants of bone substitutes. Our results show that the degradation of both biomaterials corresponds to the natural bone degradation processes and suggest the possibility of complete resorption during bone remodelling.

The morphological and clinical relevance of mandibular and maxillary bone structures for implantation.

Tooth loss, which interrupts the biocybernetic feedback circuit of the masticatory system, changes the structures of the jaw bone: such changes are termed "inactivity atrophy". The mandible is subject to vertical atrophy and the maxilla is primarily subject to horizontal atrophy. The mandible possesses more compact bone, the maxilla more spongy; the resorption directions also differ (mandible: towards the oral aspect; maxilla: towards the vestibular). An implant helps to restore the biocybernetic feedback system. The amount of available bone, bone structure, and topographic conditions are crucial factors influencing implant success. Osseointegration is performed at an early stage (which includes bleeding, granulation tissue, foreign-body recognition, interactions) and at a late stage (so-called osseous bridging, development of fibrous and lamellar bone).

The manufacture of synthetic non-sintered and degradable bone grafting substitutes.

A new synthetic bone grafting substitute (NanoBone, ARTOSS GmbH, Germany) is presented. This is produced by a new technique, the sol-gel-method. This bone grafting substitute consists of nanocrystalline hydroxyapatite (HA) and nanostructured silica (SiO2). By achieving a highly porous structure good osteoconductivity can be seen. In addition, the material will be completely biodegraded and new own bone is formed. It has been demonstrated that NanoBone is biodegraded by osteoclasts in a manner comparable to the natural bone remodelling process.

Bone functions and the requirements for bone grafts and substitutes in the orofacial region.

Bone is the largest calcium storage, has distinctive plasticity and adaptability and is part of the supporting tissue. An adequate composition is thus necessary. The bone matrix consists of organic and anorganic structures. Osteoblasts, osteoclasts and osteocytes are responsible for bone formation, resorption and metabolism. The periosteum, endosteum and bone tissue are a functional unit and provide protection, nutrition and growth. Bone is subject to continuous remodelling.

Critical considerations on the diagnostic appraisal, adaptation and remodelling of bone graft substitutes.

The diagnostic assessment of skeletal defects has a long-standing tradition. As a result of the development of new bone grafting materials, the demands on diagnostic assessment have also increased. The mode and quality of diagnostic appraisal are crucial to further clinical use and outcome prediction. Alongside traditional clinical and biological techniques, molecular biological methods have gained a broad scope of application and will be used even more frequently in the future.