Philipp Stockmann

Panoramic radiograph, computed tomography or magnetic resonance imaging. Which imaging technique should be preferred in bisphosphonate-associated osteonecrosis of the jaw? A prospective clinical study

It was the aim of the present study to find out which radiological imaging techniques allow assessing the extent of bisphosphonate-associated osteonecrosis of the jaw (BONJ) in an adequate way. Twenty-four patients suffering from BONJ were included in the study. Before surgery, each patient was examined with panoramic radiograph, contrast-enhanced magnetic resonance imaging (MRI) and non-enhanced computed tomography. The detectability of BONJ was assessed for the three imaging techniques. The extent of the jaw region affected by BONJ was determined in MRI and CT scans and compared to the intra-operative situation. The detectability of BONJ lesions was 54% for panoramic radiographs, 92% for MRI scans and 96% for computed tomography (CT) scans. The intra-operatively assessed extent of BONJ correlated significantly with the measurements on CT scans (p = 0.0004) but did not correlate significantly with the measurements in MRI scans (p = 0.241). The intra-operatively measured extent of BONJ differed significantly from the CT measurements (p = 0.00003) but not from the MRI data (p = 0.137). Although MRI as well as CT have a high detectability for BONJ lesions that exceeds that of panoramic radiographs by far, both techniques show problems with the exact assessment of the extent of BONJ lesions in the individual patients. Therefore, the relevance of MRI and CT for the preoperative assessment of the extent of BONJ lesions is limited. Future research should focus on the identification of imaging techniques that allow assessing the extent of BONJ lesions with a higher accuracy.

The effect of load on heat production, thermal effects and expenditure of time during implant site preparation – an experimental ex vivo comparison between piezosurgery and conventional drilling

OBJECTIVES Piezoelectric surgery (PS) is meant to be a gentle osteotomy method. The aim of this study was to compare piezosurgical vs. conventional drilling methods for implant site preparation (ISP) - focusing on load-dependent thermal effect on hard tissue and the expenditure of ISP time. MATERIALS AND METHODS Three hundred and sixty ISP were performed on ex vivo pig heads using piezosurgery, spiral burs (SB) and trephine burs (TB). The load applied was increased from 0 to 1000 g in 100-g intervals. Temperature within the bone was measured with a thermocouple, and duration was recorded with a stop watch. Thermal effects were histomorphometrically analysed. Twelve ISPs per technique were performed at the lateral wall of the maxillary sinus. RESULTS PS yields the highest mean temperatures (48.6 ± 3.4°C) and thermal effects (200.7 ± 44.4 μm), both at 900-1000 g. Duration is reduced with a plus of load and significantly longer in either case for PS (P < 0.05). There is a correlation of the applied load with all other examined factors for PS and TB. Temperature and histological effects decrease for SB beyond 500 g. CONCLUSIONS PS yields significantly higher temperatures and thermal tissue alterations on load levels higher than 500 g and is significantly slower for ISP compared to SB and TB. For ISP with PS, a maximum load of 400 g should be maintained.

Diabetes mellitus negatively affects peri-implant bone formation in the diabetic domestic pig

AIM Diabetes mellitus is classified as a relative contraindication for implant treatment, and higher failure rates have been seen in diabetic patients. The aim of the present study was to investigate the effect of diabetes on peri-implant bone formation in an animal model of human bone repair. MATERIALS AND METHODS Diabetes was induced by an intra-venous application of streptozotocin (90 mg/kg) in 15 domestic pigs. Implants were placed after significant histopathological changes in the hard and soft tissues were verified. The bone-implant contact (BIC), peri-implant bone mineral density (BMD), and expression of collagen type-I and osteocalcin proteins were qualitatively evaluated 4 and 12 weeks after implantation. Fifteen animals served as healthy controls. RESULTS Diabetes caused pathological changes in the soft and hard tissues. The BIC and BMD were significantly reduced in the diabetic group after 4 and 12 weeks. Collagen type-I was increased in the diabetic group at both time points, whereas osteocalcin was reduced in the diabetic group. CONCLUSIONS Poorly controlled diabetes negatively affects peri-implant bone formation and bone mineralization. These findings have to be taken into consideration for diabetic patients with an indication for implant therapy.

Resorbable versus titanium osteosynthesis devices in bilateral sagittal split ramus osteotomy of the mandible — the results of a two centre randomised clinical study with an eight-year follow-up

BACKGROUND This study was conducted to compare the long-term clinical outcome of patients with jaw disproportion who had had fixation with resorbable polylactic acid containing positioning screws with those who had had titanium positioning screws in bilateral sagittal split ramus osteotomy of the mandible (BSSO). PATIENTS AND METHODS Sixty-six patients with isolated mandibular jaw disproportion were included and divided randomly into two treatment groups (resorbable and titanium). Patients were followed for 8 years postoperatively using a standardised protocol. Material-specific complications, functional problems and clinical findings within the former operation field were documented. Treatment stability was determined by occlusion criteria. RESULTS Thirty-four patients (54%) were followed until the end of the study. No significant differences were observed in the outcomes of patients in the two groups related to the materials used for osteosynthesis or the long-term treatment stability. During the study, no foreign body reactions were observed. CONCLUSION This study showed that resorbable and titanium positioning screws were equally effective as fixation devices in sagittal split osteotomy. Complete resorption of the resorbable screws could not be verified because of the absence of histological examination, however, the use of resorbable positioning screws can be considered as an alternative osteosynthesis material to conventional titanium osteosynthesis devices in sagittal split osteotomy.

Osteocutaneous free flap including medial and lateral scapular crests: technical aspects, viability, and donor site morbidity.

The aims of the present study were to check for metabolism of the bony segments of osteocutaneous free flaps that included lateral as well as medial scapular crests by 18F-fluoride positron emission tomography (PET)/computed tomography (CT) examinations and to assess donor site morbidity. Twenty patients were included in the study. In 10 patients, osteocutaneous free flaps were harvested that included lateral as well as medial scapular crests. Seven days after surgery, an 18F-fluoride PET/CT examination was performed to assess the metabolism and viability of the bony segments. In the additional 10 patients, flaps were harvested that only included the lateral scapular crest. All patients were asked to fill in the disabilities of the arm, shoulder, and hand (DASH) questionnaire 1 and 6 months after surgery. In the 10 free flaps that included lateral as well as medial scapular crests, 18F-fluoride PET/CT examinations revealed metabolism and viability of both bony segments. The DASH scores for the two patient groups did not differ significantly at 1 and 6 months after surgery (p(1 month) = 0.520, p(6 months) = 0.545). It seems that scapular osteocutaneous free flaps adopting lateral as well as medial scapular crests are a viable option for mandibular reconstruction and may be an alternative to the fibular double barrel.

Influence of residual alveolar bone height on implant stability in the maxilla: an experimental animal study

AIMS/BACKGROUND Empirically, for implant placement associated with sinus floor augmentation, a minimum of five mm of residual crestal bone height has been recommended in order to achieve sufficient initial implant stability. It has been the aim of the study to test this assumption in an experimental animal trial. MATERIAL AND METHODS In eight mini pigs, three premolars and two molars were removed on one side of the maxilla. Three months later the animals were assigned to four groups of two animals each. A cavity was created at the base of the alveolar process so that the residual bone height was reduced to 2, 4, 6 and 8mm, respectively. The coronal part of the alveolar crest remained unchanged. An inlay augmentation procedure was carried out using a particulated autogenous bone graft from the iliac crest, and six implants (Xive, diameter 3.8mm, length 13mm) were placed. Implant stability was assessed by resonance frequency analysis at the time of implant placement (T0), after 6 months of unloaded healing (T1) and after 6 months of functional loading (T2). RESULTS During follow-up, two implants were lost in sites with a residual alveolar bone height of 2mm. At the time of implant placement, resonance frequencies were 6754.4 +/- 268, 6500.3 +/- 281.5, 6890.3 +/- 255.4 and 7877.9 +/- 233.7 Hz for residual bone heights of 2, 4, 6 and 8mm, respectively. At stage-two surgery and after 6 months of functional loading, resonance frequencies were 6431.7 +/- 290.8, 6351.8 +/- 437.6, 6213.4 +/- 376.2 and 6826.8 +/- 458.9 Hz vs. 6171 +/- 437.4, 6047 +/- 572.4, 6156.7 +/- 272.6 and 6412.8 +/- 283.5 Hz. Statistical analysis revealed an association of residual alveolar height and implant stability at T0 and T1 only (P<0.01), while bone height was not found to influence implant survival. CONCLUSION The results of the present trial demonstrate an association of alveolar bone height and implant stability at the time of implant placement and stage-two surgery. Yet the assumption that 5mm of residual crestal bone height is a relevant threshold for simultaneous implant placement and sinus floor augmentation is not supported from an experimental point of view.

Msx-1 is suppressed in Bisphosphonate exposed jaw bone- analysis of bone turnover related cell signalling

OBJECTIVES Bone-destructive disease treatments include bisphosphonates and antibodies against receptor activator for nuclear factor κB ligand (aRANKL). Osteonecrosis of the jaw (ONJ) is a side-effect. Aetiopathology models failed to explain their restriction to the jaw. The osteoproliferative transcription factor Msx-1 is expressed constitutively only in mature jaw bone. Msx-1 expression might be impaired in bisphosphonate-related ONJ. This study compared the expression of Msx-1, Bone Morphogenetic Protein (BMP)-2 and RANKL, in ONJ-affected and healthy jaw bone. MATERIAL AND METHODS An automated immunohistochemistry-based alkaline phosphatase-anti-alkaline phosphatase method was used on ONJ-affected and healthy jaw bone samples (n = 20 each): cell-number ratio (labelling index, Bonferroni adjustment). Real-time RT-PCR was performed to quantitatively compare Msx-1, BMP-2, RANKL and GAPDH mRNA levels. RESULTS Labelling indices were significantly lower for Msx-1 (P < 0.03) and RANKL (P < 0.003) and significantly higher (P < 0.02) for BMP-2 in ONJ compared with healthy bone. Expression was sevenfold lower (P < 0.03) for Msx-1, 22-fold lower (P < 0.001) for RANKL and eightfold higher (P < 0.02) for BMP-2 in ONJ bone. CONCLUSIONS Msx-1, RANKL suppression and BMP-2 induction were consistent with the bisphosphonate-associated osteopetrosis and impaired bone remodelling in BP- and aRANKL-induced ONJ. Msx-1 suppression suggested a possible explanation of the exclusivity of ONJ in jaw bone. Functional analyses of Msx-1- RANKL interaction during bone remodelling should be performed in the future.

Which region of the median palate is a suitable location of temporary orthodontic anchorage devices? A histomorphometric study on human cadavers aged 15–20 years

INTRODUCTION Endosseus implants can provide a reliable anchorage during orthodontic treatment. The midpalatal structures around the sutura palatina mediana (SPM) are of special interest due to increasing placement of orthodontic implants in this area. Knowledge about the osseous conditions at this site is necessary to predict the expected degree of implant osseointegration. METHODS The upper jaws of 10 human cadavers, aged 15-20 years, were decalcified, and cross-sectional specimens were obtained from four anterior-to-posterior palatal regions for histomorphometric analysis. The analyses focused on the amount of bone and the width of the SPM to determine the anatomical requirements for reliable insertion of palatal implants. RESULTS Bone density [bone-volume (BV)/ tissue-volume (TV)] in all measured areas was 40-60%. The maximum density was measured at the level of the first premolars (54.9+/-5.9%) and the least values (44.2+/-9.6%) were measured at the level of the interconnecting line of the canines. The mean width of the SPM varies from 1.2 to 0.3 mm in different sections of the palate. In the median sagittal plane, the mean values of bone height to nasal cavity reached >5 mm as far as the level distal of the second premolars. Bone height 2 mm paramedian to the SPM decreased consistently from anterior (4.3+/-0.9 mm) to posterior (2.5+/-0.8 mm). CONCLUSIONS Our results indicate that the amount and quality of bone along the anterior palatal midline in 15-to-20-year olds is sufficient for orthodontic implantation. Even implantation posterior to the recommended first premolar level, at which orthodontic implants are most often placed, may be suitable. There are some limitations, however, due to small number of samples and variations of anatomical structures.

Increased human defensine levels hint at an inflammatory etiology of bisphosphonate-associated osteonecrosis of the jaw: An immunohistological study

BackgroundHuman β-defensins (hBD) are antimicrobial peptides that are an integral part of bone innate immunity. Recently, it could be shown that expression of hBD-1, -2 and -3 were upregulated in cases of osteomyelitis of the jaws. In order to gain insight into the possible impairment of hBD metabolism in bisphosphonate-associated osteonecrosis of the jaws (BONJ), the present exploratory study was designed so as to determine the qualitative and quantitative expression of afore mentioned hBDs in BONJ and infected osteoradionecrosis (ORN), both of which represent inflammatory bone diseases.MethodsBone samples were collected from patients with BONJ (n = 20) and ORN (n = 20). Non-infected healthy bone samples (n = 20) were included as controls. Immunohistological staining in an autostainer was carried out by the (Strept-ABC)-method against hBD-1,-2,-3. Specific positive vs. negative cell reaction of osteocytes (labeling index) near the border of bony resection was determined and counted for quantitative analysis. Number of vital osteocytes vs. empty osteocytes lacunae was compared between groups.ResultshBD-1,-2 and -3 could be detected in BONJ as well as ORN and healthy bone samples. Immunoreactivity against hBD-2 and -3 was significantly higher in BONJ than in ORN and healthy jaw bone samples. Number of empty osteocyte lacunae was significantly higher in ORN compared with BONJ (P = 0.001).ConclusionUnder the condition of BONJ an increased expression of hBD-1,-2,-3 is detectable, similarly to the recently described upregulation of defensins in chronically infected jaw bones. It remains still unclear how these findings may relate to the pathoetiology of these diseases and whether this is contributing to the development of BONJ and ORN or simply an after effect of the disease.

Establishment of a streptozotocin‐induced diabetic domestic pig model and a systematic evaluation of pathological changes in the hard and soft tissue over a 12‐month period

OBJECTIVE The number of diabetic patients in need of medical treatment is growing steadily. Therefore, a diabetic animal model with high degree of similarities with humans, which is suitable for the systematic evaluation of biomaterials and medical devices, is needed. MATERIALS AND METHODS Twenty domestic pigs were used for the study. Fifteen received Streptozotocin (STZ) to induce diabetes mellitus. Internal parameters were measured and bone as well as soft tissues biopsies were taken after 0, 6 and 12 months and evaluated qualitatively and quantitatively by means of scanning electronic microscopy, light microscopy and microradiography. RESULTS The results of the clinical internal parameters, determined by the American Diabetes Association for the definition of diabetes mellitus could be fulfilled. Pathological changes of the skin vasculatures were already visible after 6 months with a significant wall thickening in the diabetic group. The bone mineralization was lower in the diabetic group after 6 months and with a significant difference after 12 months. CONCLUSION From the present results, it can be concluded that a STZ dosage of 90 mg/kg body weight in the domestic pig is suitable for the induction of an apparent diabetes, leading to histolopathological changes in the hard and soft tissues already after 6 months. The high degree of similarities with humans makes it an interesting diabetic animal model for biomaterial research in a compromised animal model.