Nano-crystalline diamond-coated titanium dental implants - a histomorphometric study in adult domestic pigs.

Promising biomaterial characteristics of diamond-coatings in biomedicine have been described in the literature. However, there is a lack of knowledge about implant osseointegration of this surface modification compared to the currently used sandblasted acid-etched Ti-Al6-V4 implants. The aim of this study was to investigate the osseointegration of microwave plasma-chemical-vapour deposition (MWP-CVD) diamond-coated Ti-Al6-V4 dental implants after healing periods of 2 and 5 months. Twenty-four MWP-CVD diamond-coated and 24 un-coated dental titanium-alloy implants (Ankylos(®)) were placed in the frontal skull of eight adult domestic pigs. To evaluate the effects of the nano-structured surfaces on bone formation, a histomorphometric analysis was performed after 2 and 5 months of implant healing. Histomorphometry analysed the bone-to-implant contact (BIC). No significant difference in BIC for the diamond-coated implants in comparison to reference implants could be observed for both healing periods. Scanning electron microscopy revealed an adequate interface between the bone and the diamond surface. No delamination or particle-dissociation due to shearing forces could be detected. In this study, diamond-coated dental titanium-alloy implants and sandblasted acid-etched implants showed a comparable degree of osseointegration.

Preclinical animal model for de novo bone formation in human maxillary sinus.

OBJECTIVES: Up to now the effect of bone-substitute materials on de novo bone formation has been tested in a variety of preclinical animal models. We hypothesized that there is no significant difference in bone regeneration after application of autogenous bone (AB) and bone substitutes in a porcine calvarial monocortical defect model and in human maxillary sinus. STUDY DESIGN: Twenty-four weeks after application of ss-tricalcium phosphate (betaTCP), hydroxyapatite (HA), and AB in each of 3 defects on the sculls of 6 adult pigs (N = 54) and the application in 44 sinus floor elevations (11x betaTCP, 6x HA and 24x AB) in 41 patients, bone regeneration rates where compared microradiographically. Wilcoxon rank-sum test was used for statistical analysis. RESULTS: Comparing the human with the animal specimens microradiographically, no significant difference of the mineralization rate could be found. CONCLUSION: The chosen porcine model is a valuable method for preclinical testing of bone-substitute materials in maxillofacial surgery.

Antibiotic-containing collagen for the treatment of bone defects.

Recent studies have explored the use of biodegradable implants that incorporate antibiotics for the treatment of bone infections. In this study, a biodegradable composite containing bovine collagen and teicoplanin (Targobone) was used for the treatment of mandibular nonunion defects. Patients with mandibular nonunion defects subsequent to osteosynthesis were treated with Targobone (n = 9) or with autologous bone grafts (n = 12). Clinical and radiological evaluations were performed preoperatively, immediately postoperatively, and 4 and 24 weeks postoperatively. Bone regeneration was defined relative to the original defect area in the panoramic radiograph by using image analysis software. In the Targobone group, the defect area decreased to 78% (SD +/- 21.8%) of the preoperative area within 4 weeks and to 21% (SD +/- 9.7%) of the preoperative area within 24 weeks. In the autologous bone graft group, the defect area decreased to 69% (SD +/- 32.4%) of the preoperative area within 4 weeks and to 4.7% (SD +/- 5.6%) of the preoperative area within 24 weeks. Thus, Targobone is a promising option for the treatment of bone defects.

Changes of mineralization of free autogenous bone grafts used for sinus floor elevation.

For augmentations before implant placement in areas of minor bone quantity, autogenous bone is considered the reference to all bone substitutes used alternatively. Autogenous bone transplants originate from various donor areas and can be prepared in different ways before augmentation. They may either be used as block grafts or may be milled to granules that can be used solitarily or in combination with a bone substitute. In a prospective study, 61 patients of the Maxillofacial Surgery Department of our University receiving two-stage sinus floor elevation because of insufficient bone supply were randomly selected. At first-stage surgery, the local augmentation procedure, monocortical probes were obtained on the site of bone harvesting. At second-stage surgery, the implant insertion 6 months after the elevation procedure, bone cores were harvested in the areas of implant placement. Donor regions were the following three areas: the posterior (N=28) and anterior pelvic region (N=15) and the chin region (N=18). The implanted bone in all three groups was particulated to granules of 2-3 mm(2) using a bone mill. All biopsies were analyzed by means of microradiography. The anterior pelvic bone grafts showed a mineralized tissue grade of 35.1+/-7.6% before milling and augmentation. The posterior pelvic bone grafts exhibited a mineralization of 30.7+/-9.5% and the chin bone grafts 74.6+/-8.6%. At second-stage surgery after 6 months, the mineralization was 36.1+/-7.59% in the areas where bone grafts from the anterior pelvic crest were used. Probes harvested from sites with posterior pelvic bone augmentations showed a mineralization rate of 34.5+/-6.5%, and sites were chin bone grafts were applied expressed a mineralization of 54+/-8.6% (P=0.003 compared with the pre-operative value). The comparison of the microradiographical results demonstrated significant differences in the mineralization grades depending on the origin of the graft. The origin of the grafts and their remodeling influenced the mineralization rates found at 6 months. How these data may influence the long-term clinical outcome considering implant survival and bone resorption has to be examined in further long-term studies.

Expression of bone matrix proteins during the osseus healing of topical conditioned implants: an experimental study.

OBJECTIVES: Osseointegration of implants depends on time and local bone conditions regarding quality and quantity. This led to the bone classification by Lekholm et al. The aim of the present study was to follow the expression of bone matrix proteins during the phase of osseointegration after conditioning of the bone bed by means of immunohistochemistry. METHODS: In the porcine frontal skull, implant beds of identical size were created. Before placement of the implants (Ankylos 4 x 3.5 mm), the implant beds were conditioned using bone condensation (cond), an osteoinductive collagen (Co) and platelet-rich plasma (PRP). These conditioning methods were compared with standard procedure. The animals were sacrificed after 2, 4 and 8 weeks. The specimens were then analyzed by light microcopy and immunohistochemistry for expression of bone morphogenic proteins (BMP)2, procollagen I and osteocalcin (OC). RESULTS: Light microscopy revealed an initial effect of condensation and the bovine collagen at 2 weeks in comparison with the standard group. The PRP did not achieve a significant effect. At 8 weeks, the results of the standard, bone condensation and the bovine collagen group had aligned. The PRP group showed a significantly lower bone-implant contact (BIC) (P=0.003) compared with the standard group. BMP2 expression was significantly higher in all evaluated test groups at 4 and 8 weeks, as well as at 2 weeks in the condensation group. The procollagen I expression at 2 weeks was significantly increased for PRP and lower in the collagen and condensation group compared with standard procedure. Values for 4 and 8 weeks were slightly higher than in the standard group. No significant differences were obvious in the OC group at any time. CONCLUSIONS: During the initial healing phase, an effect of the evaluated methods of topical bone conditioning can be demonstrated by differences in the expression of BMP2 and procollagen I. These findings had leveled at 8 weeks and were, in contrast, not detectable in the expression of OC or by means of light microscopy.

Lack of beneficial effects of platelet-rich plasma on sinus augmentation using a fluorohydroxyapatite or autogenous bone: an explorative study.

BACKGROUND: Maxillary sinus augmentation is frequently necessary before placement of dental implants in the posterior maxilla. Besides autogenous bone graft, various bone substitutes have been used, with favourable results. Although platelet-rich plasma (PRP) has been used in the field of oral and maxillofacial surgery for years, its beneficial effects on osseous regeneration still remain unclear. The aim of this study was to evaluate the short and long time effects of PRP on single-stage sinus augmentation using autogenous bone or a fluorohydroxyapatite (Algipore) in a randomized prospective animal study. METHODS: After extraction of maxillary premolars of sixteen minipigs, the wounds were allowed to heal for 2 months. Then, sinus augmentations were performed bilaterally using one of the following grafting materials: autogenous bone and Algipore with or without PRP. Three dental implants (Ankylos) were installed in each sinus simultaneously. Four animals were euthanized at each period of observation (1, 2, 8 and 12 months). Implant-bearing specimens were sectioned bucco-lingually along the long axis of implants and undecalcified ground specimens were prepared. The bone-implant-contact (BIC) was measured by means of microradiographic examination. For histological evaluation, the specimens were stained with toluidin blue, and the percentage of the newly formed bone and the remaining bone substitute were evaluated. RESULTS: The grafting materials chosen showed increasing levels of BIC and newly formed bone throughout the period of observation in both PRP and non-PRP groups. Adding PRP resulted in lower BIC and newly formed bone compared with autogenous bone grafts or Algipore alone. However, a statistical significance was not found. The percentages of the remaining bone substitute in both the PRP and non-PRP groups were closely comparable in all observation periods. CONCLUSIONS: The application of PRP could not reveal significant beneficial effects on the BIC, the percentage of the newly formed bone and the remaining bone substitute in this study.

Influence of platelet-rich plasma on a bioglass and autogenous bone in sinus augmentation. An explorative study.

Platelet-rich plasma (PRP) has been introduced to the field of oral and maxillofacial surgery for a decade, but its beneficial effects on maxillary sinus augmentation remain unclear. The aim of this study was to evaluate the short- and long-term effects of PRP on osseointegration following single-stage sinus augmentation in a randomized prospective animal study. The maxillary premolars of 24 minipigs were extracted bilaterally and allowed to heal for 2 months. Consecutively all animals underwent bilateral sinus floor elevation using autogenous bone, Biogran as well as a combination of the materials with PRP. Three dental implants (Ankylos, Dentsply Co., Mannheim, Germany) were installed in each sinus simultaneously. Four animals were sacrificed at each period of observation (1, 2, 8 and 12 months). Microradiographic images of the specimens were made for quantitative evaluation of the bone-implant contact (BIC) and light microscopic images were made for qualitative analysis. An increment of the BIC during the observation time could be seen over the observation time in all groups. Autogenous bone exhibited a level of BIC from 25.1 +/- 9.96% at 1 month to 55.1 +/- 13.10% at 12 months; on adding PRP, the BIC ranged from 28.4 +/- 4.64% to 52.5 +/- 17.06%. Biogran with and without PRP led to BIC levels from 16.3 +/- 4.64% to 37.6 +/- 16.40% and 21.7 +/- 4.33% to 46.6 +/- 19.37%, respectively. The results of this study did not show a significantly positive effect of PRP on the BIC following sinus augmentation in both groups.

Neurophysiological monitoring of alveolar nerve function during sensor-controlled Er:YAG laser corticotomy in rabbits.

BACKGROUND AND OBJECTIVES: The sensor-controlled Er:YAG laser system may be a potent tool for tissue specific cutting in surgery. In order to investigate the impact of the laser on neural tissues, inferior alveolar nerve (IAN) function was monitored by the jaw-opening reflex (JOR) during specific corticotomy in rabbits. STUDY DESIGN/MATERIALS AND METHODS: Laser jaw corticotomy was performed in 13 anesthetized rabbits. During and after specific corticotomy the JOR was evoked by electric intraoral stimulation to monitor effects on IAN function. RESULTS: The JOR permanently abolished in one case and transiently failed immediately after surgery but largely recovered within days in another rabbit. In one experiment JOR threshold increased 7 days after corticotomy. Histology did not prove any objective nerve pathology. CONCLUSIONS: Monitoring IAN function by the JOR demonstrated the relatively low risk of nerve damaging during sensor-controlled laser corticotomy.

The bone-metal interface of defect and press-fit ingrowth of microwave plasma-chemical vapor deposition implants in the rabbit model.

PURPOSE: The histological differences between the defect and contact areas of the implant surface to bone were tested in 35 New Zealand White rabbits in a standardized model. Microwave plasma chemical vapor-coated implant probes were tested in control and uncoated materials. MATERIAL AND METHODS: In each femur of 35 rabbits, cylindrical implant rods with a planed side were inserted. Three groups, divided in coated and uncoated material at half, were observed 42, 84 and 168 days. The probes were examined histologically for bone-implant contact in the curved and plane (defect area) sides. RESULTS: Generally the bone-implant contact seems to be nearly constant in time in the curved area of coated and uncoated probes. Here the implant was inserted in the press-fit mode. Diamond-coated probes showed similar bone-implant contact (51.9% (42 days), 62.5% (84 days), 56.1% (168 days)) compared to uncoated material (56.2%, 65.4%, 62.9%). The defect area (plane side) had no bone-implant contact at the time of insertion and showed increasing values on longer observation times with only significant differences in the 42-day group between coated (17.85%, 35.2%, 47.7%) and uncoated materials (35.5%, 40.55%, 51.81%). CONCLUSION: The evaluation of the curved side of the implant probe showed no great variation of bone-implant contact within the described observation times. This model simulates the usual implant insertion situation. The diamond-coated material becomes osseointegrated at a later time point. The bone-implant contact was only statistically relevant in one group in comparison to uncoated material.

Clinical trial of modified ankylos implants for extraoral use in cranio- and maxillofacial surgery.

PURPOSE: Epithetic solutions in the maxillofacial region are indicated if plastic surgery reconstruction is not a valid option for an extensive defect. The purpose of this study was to examine whether the extraoral implants used provided sufficient retention to be used as anchoring aids. MATERIALS AND METHODS: Between November 1999 and September 2002, 33 identical modified Ankylos implants for extraoral anchorage were placed in 10 patients for the fixation of various epitheses in the midfacial (eye, nose) and ear regions in the course of a clinical trial. RESULTS: Over a follow-up period of 2 to 34 months, all implants remained osseointegrated (as confirmed radiographically), and the implants and epithetic restorations were clinically stable. DISCUSSION: The results demonstrated that the lasting retention of maxillofacial epitheses provided by implants assures patients that their epitheses are securely fixed. CONCLUSION: The demonstrated extraoral implant system not only achieved sufficient osseointegration but also showed good clinical handling and easy fixation possibilities for epithetic anchorage.

Sensor-based laser ablation for tissue specific cutting: an experimental study.

The interaction of laser light and tissue causes measurable phenomenons. These phenomenons can be quantified and used to control the laser drilling within a feedback system. Ten halves of dissected minipig jaws were treated with an Er:YAG laser system controlled via a feedback system. Sensor outputs were recorded and analyzed while osteotomy was done. The relative depth of laser ablation was calculated by 3D computed tomography and evaluated histologically. The detected signals caused by the laser-tissue interaction changed their character in a dramatic way after passing the cortical bone layer. The radiological evaluation of 98 laser-ablated holes in the ten halves showed no deeper ablation beyond the cortical layer (mean values: 97.8%). Histologically, no physical damage to the alveolar nerve bundle was proved. The feedback system to control the laser drilling was working exactly for cortical ablation of the bone based on the evaluation of detected and quantified phenomenon related to the laser-tissue interaction.

Reconstruction of skull bone defects using the hydroxyapatite cement with calvarial split transplants.

PURPOSE: We sought to present a new method for primary reconstruction of traumatic or tumor calvarial defects. PATIENTS AND METHODS: Forty-one patients underwent reconstruction of calvarial bone defects between October 1998 and December 2001. Among them were 19 patients who needed reconstruction of the calvaria due to traumatic bone loss. Five of these trauma cases had insufficient primary reconstruction of the calvaria. Tumor resection caused calvarial defects in 22 patients. For primary reconstruction of the skull bone defects, calvarial split grafts were used to cover the defect as accurately as possible. The monocortical layers of the calvaria were fixed with titanium miniplates. Irregular defects surrounding the transplanted regions were filled with hydroxyapatite cement. In one case of posttraumatic bone loss, hydroxyapatite cement alone was sufficient to reconstruct the defect. RESULTS: The follow-up of each patient was at least 6 months; the longest period was 38 months. Evaluated clinical and radiologic results are stable, showing no measurable side effects. CONCLUSION: Hydroxyapatite cement alone or in combination with calvarial split grafts gave clinically and aesthetically stable results in the reconstruction of skull bone defects. The cement can be used for many reconstruction possibilities in craniofacial surgery.

Er:YAG laser osteotomy directed by sensor controlled systems.

BACKGROUND: Great efforts have been taken in the past to develop laser systems suitable for bone cutting. Laser systems emitting light in the infrared spectrum (2.9, 3.0 microm) have been found to be ideal for efficient bone ablation with very little carbonization. AIM: To evaluate a new laser bone cutting system enabling the automatic detection of different tissue qualities by an integrated sensor to avoid damage to sensitive structures such as blood vessels or nerves. MATERIAL: An Erbium:YAG laser containing an integrated closed-loop control system, was constructed and tested on dissected bone. Process emissions such as resonance changes caused by the interaction of laser light and various tissue structures can be used for a controlled system. Sensor signals from a photodiode and a piezo-electric accelerometer were received and processed to guide the laser osteotomy. METHODS: Tests were performed on dissected bone specimens from rabbit femur (14) and minipig jaw (6). After laser application, the bone specimens were evaluated macroscopically and histologically. RESULTS: The specimens were evaluated histomorphometrically for the depth of cortical bone ablation when the closed-loop control system switched off the laser. Mean courses of 97.45% (pig) and 97.83% (rabbit) showed that the systems work with precision. CONCLUSION: After penetrating the cortical bone layer, the laser beam was promptly interrupted due to extreme changes of the signal character received by the sensor system. The in vitro tests of this new laser closed-loop control system were successful.

Hydroxyapatite cement (BoneSource) for repair of critical sized calvarian defects--an experimental study.

AIM: In an experimental study the hydroxyapatite cement BoneSource was tested for the ability in relation to the defect size and for its resorption properties. MATERIAL AND METHODS: In an animal study, BoneSource was applied to repair bicortical defects of different sizes in frontal bones of six Goettingen minipigs. The area was evaluated radiographically and histologically 12, 18 and 40 weeks postoperatively. RESULTS: After 40 weeks approximately 90% of the hydroxyapatite cement had been resorbed and replaced with bone. After 12 weeks, approximately 30% had been degraded, and 40% after 18 weeks. In small bone defects, the mucosa of the frontal sinus lined the bone substitute (BoneSource). In the reconstruction of large areas, a membrane was used to stabilize the material. Despite this membranous support, BoneSource material prolapsed into the frontal sinus. DISCUSSION: Hydroxyapatite cement is for the repair of bone defects. It can be moulded to shape the reconstruction. Its use is limited by the defect size and the need for a dry bed. CONCLUSION: BoneSource is well suited to repair small defects with proven high biocompatibility. However, in large defects, the material is not sufficiently stable.

Intraoperative Image-Guided Surgery of the Lateral and Anterior Skull Base in Patients with Tumors or Trauma.

The aim of this investigation was to evaluate the suitability and usefulness of the Stealth Stationtrade mark intraoperative guiding system (Medtronic Sofamor Danek, Memphis, TN) in a variety of indications. Eleven intraoperative image-guided procedures were performed for anterior or lateral skull base lesions. The most common neurosurgical approaches included frontal, coronal, and parietotemporal access. Neuronavigation reliably allowed the extent of tumor configuration and risk zones (e.g., blood vessels) to be visualized. Thus, gross tumor resection was achieved in 6 of 7 patients and facilitated reconstruction by the maxillofacial surgeon, resulting in radiologically symmetrical and clinically satisfying results. Postoperatively, one patient was blind from a continuity defect of the optic nerve caused by a bone fragment. Despite destruction of anatomical landmarks related to tumor invasion or intraoperative bone removal, neuronavigation proved helpful in the reconstruction of bony structures. Overall, the use of neuronavigation in interdisciplinary surgery for complicated tumors or trauma of the anterior or lateral skull base allows more radical resection associated with less morbidity.

Examination of the bone-metal interface of titanium implants coated by the microwave plasma chemical vapor deposition method.

PURPOSE: Diamond layers can be plated with microwave plasma chemical vapor deposition (MWP-CVD) treatment on metal bases such as titanium-aluminum-vanadium alloy (Ti-6Al-4V). The bonding strength of the diamond layer to the metal base is very high, so that no fissures and partial loss of coating take place-well known phenomena that may occur with other coatings in tribologic material testing. In an experimental study using 40 New Zealand White rabbits, a new method for coating implant material was tested for stability of the bone-metal interface. MATERIALS AND METHODS: The results of histomorphometric and biomechanical evaluation of coated and uncoated probes implanted in the distal femur of 40 rabbits were compared. The animals were divided into 3 groups, with observation times of 42, 84, and 168 days. RESULTS: The bone-implant contact was 5% to 18% less in coated than in uncoated probes. Only the early group, with 42 days healing time showed significant differences. Values for the pull-off force of uncoated material were about 3 to 4 times higher than coated material (diamond layer = 2.7 microm). The force increased 2 to 3 times when 200-nm coatings were tested. Electron microscopy detected undercuts of the rough surface that were obturated by diamond when the coating was too thick. DISCUSSION: Diamond-coated material seems to have no corrosion problems in contrast to all other known implant material. CONCLUSION: An inert diamond layer on a metal base can become osseointegrated. Biomechanical stability increased by thinning the diamond coating.