Navigational exploration of bony defect mimicking a solid lesion of the mandible compared to conventional surgery by young professionals.

INTRODUCTION: The aim of the current study was to evaluate the accuracy of resection a solid lesion in an acrylic lower jaw by young professionals using a dynamic computer-assisted surgical system comparted to conventional surgery technique. MATERIAL AND METHODS: Twenty students performed the removal of the lesion conventionally and twenty students did the operation with a dynamic computer-assisted surgical system. Both groups were compared regarding the defect size, operation time, and surgical complications. RESULTS: The defect size in the jaw was significant smaller with the navigated surgery (p < 0.001). Operation time was shorter without navigation system, but no significance was found (p = 0.137). Without navigation system three young professionals perforated the lingual cortex. DISCUSSION: Navigated surgery can immediately be used by young professionals and support young surgeons in everyday clinical practice, especially in operations with difficult anatomic situations.

Screening for Platelet Dysfunction and Use of Prophylactic Tranexamic Acid in Patients Undergoing Deep Brain Stimulation: A Retrospective Analysis of Incidence and Outcome of Intracranial Hemorrhage.

INTRODUCTION: The rate of intracranial hemorrhage (ICH) after deep brain stimulation (DBS) is between 1.5 and 6.1%, with prolonged deficits occurring in 0.4-2.5% of the patients. This retrospective study investigates whether the prophylactic administration of tranexamic acid (TA) to patients with abnormal platelet function detected preoperatively by platelet function analyzer (PFA) lowered the risk for an ICH event. METHODS: We performed a systematic review of the medical records of 485 consecutively admitted patients who underwent bilateral DBS surgery in a single-center university hospital setting between 2009 and 2018. The cohort was split into two groups. In one group, preoperative PFA screening was performed (n = 156, patients recruited from 2014 to 2018), and TA was administered if platelet function was abnormal. No preoperative PFA was performed in the second group (n = 359, patients recruited from 2009 to 2013). Both cohorts were analyzed for the occurrence of ICH, defined by (i) detection of ICH in routine postoperative magnetic resonance/computed tomography imaging or (ii) in non-routine imaging for the onset of new neurological symptoms. RESULTS: Fourteen of the 156 screened patients (9%) showed reproducible PFA-100 closure abnormalities (3 with von Willebrand disease, 11 with no identifiable cause of platelet dysfunction). Two of the 156 patients (1.3%) in this cohort revealed an ICH on imaging, 1 of whom (0.6%) exhibited a prolonged neurological deficit as a result of ICH. In the cohort without platelet testing, 11 of the 329 patients (3.3%) demonstrated ICH on imaging, of whom 5 (1.5%) suffered from a prolonged neurological deficit. CONCLUSION: In this retrospective study, the screening and the administration of TA appeared to lower the risk of an ICH by 1.8%. One patient with von Willebrand disease suffered an ICH despite TA treatment. A prospective study is needed to clarify the impact of platelet testing and TA administration on the of incidence ICH.

Scaffold implantation in the omentum majus of rabbits for new bone formation.

Restoration of the mandible after defects caused by ablative surgery remains challenging. Microvascular free flaps from the scapula, fibula or iliac crest remain the 'gold standard'. A drawback of these methods is donor-side morbidity, availability and the shape of the bone. Former cases have shown that prefabrication of a customized bone flap in the latissimus dorsi muscle may be successful; however, this method is still associated with high donor-side morbidity. Osteogenesis in the omentum majus of rabbits by wrapping the periosteum into it was confirmed recently and is particularly interesting for bone endocultivation. Twelve adult male New Zealand white rabbits were used. In each, two hydroxyapatite blocks were implanted in the greater omentum with autologous bone or autologous bone + rhBMP-2. Bone density measurements were performed by CT scans. Fluorochrome labelling was used for new bone formation detection. The animals were sacrificed at week 10, and the specimens were harvested for histological and histomorphometric analysis. In histological and fluorescence microscopic analysis, new bone formation could be found, as well as new blood vessels and connective tissue. No significant differences were found regarding the histological analysis and bone density measurements between the groups. It could be demonstrated that the omentum majus is a practical way to use one's own body as a bioreactor for prefabrication of tissue-engineered bony constructs. Regarding the influence and exact dose of rhBMP-2, further research is necessary. To establish and improve this method, further large-animal experimental studies are also necessary.

Microdialysis in postoperative monitoring of microvascular free flaps: Experiences with a decision algorithm.

BACKGROUND: Reconstruction with free flaps has become a usual practice in maxillofacial surgery. Clinical monitoring is still the standard approach for postoperative follow-up, but can be difficult or impossible with intraorally situated or buried flaps. Microdialysis is a sampling technique that offers the possibility to monitor the metabolism of flaps continuously. It is a reliable method for early diagnosis of ischemia. MATERIALS AND METHODS: 48 microvascular free flaps applied following oral cancer resection were monitored with a microdialysis (MD) catheter, placed in the flap. Glucose, lactate, and lactate/pyruvate ratio were monitored using a bedside analyser for 5 days. 48 free flaps served as controls and were assessed (refill, flap temperature, and color) by clinical monitoring (CM). RESULTS: 12 flaps monitored by MD showed abnormal metabolism and underwent revision. Eight flaps were saved and four were lost within the first 5 days postoperatively. In addition, two flaps were lost at days 15 and 30 postoperatively, without previous complications. Four flaps assessed by CM developed complications, underwent revision, and were saved. In addition, five flaps were lost between the 8th and 23rd days postoperatively, without revision, due to missing previous clinical signs. CONCLUSION: Postoperative monitoring of free flaps using a microdialysis decision algorithm allows early diagnosis of anastomotic complications. It is a clinically feasible and sensitive monitoring method for microvascular flaps, allowing surgical revision to be undertaken before clinical alteration takes place.

Do Adaptors Shorten the Battery Life of Nonrechargeable Generators for Deep Brain Stimulation?

OBJECTIVE: Generators implanted for deep brain stimulation must be replaced after several years. If a Kinetra generator is replaced by the Activa-PC, an adaptor will be required to attach it to the original extension cables. On the basis of our clinical impression that the battery life of the Active-PC generator was shorter when an adaptor was used, we performed this retrospective study. METHODS: We determined the battery lifetimes of deep brain stimulation generators that had been implanted in our department. The inclusion criterion was the initial implantation of a Kinetra generator that was later replaced by an Activa-PC with adaptor, which itself was subsequently also replaced. These patients were compared with an Activa-PC control group without an adaptor but identical with regard to number of battery exchanges, disease, and target. RESULTS: There were 28 patients in the study group and 14 in the control group. Battery lifetime of the Activa-PC with adaptor (32.4 ± 7.7 months) was significantly shorter than that of the Kinetra (53.5 ± 15.7 months, P = 0.000006). The battery life of Activa-PC without an adaptor (35.3 ± 8.2 months) did not differ significantly from that of the Activa-PC with an adaptor (P = 0.333). CONCLUSIONS: The battery lifetime in a replacement Activa-PC is shorter than that in the original Kinetra generator. Adaptors have no significant effect on battery life. Patients should be informed that the battery in their new generator must be checked more frequently than before.

Bone tissue engineering in the greater omentum is enhanced by a periosteal transplant in a miniature pig model.

AIM: Reconstruction of bone defects with autologous grafts has certain disadvantages. The aim of this study is to introduce a new type of living bioreactor for engineering of bone flaps and to evaluate the effect of different barrier membranes. MATERIALS & METHODS: Scaffolds loaded with bone morphogenetic proteins and bone marrow aspirate wrapped with either a collagen membrane or a periosteal flap were implanted in the greater omentum of miniature pigs. RESULTS: Both histological and radiographic evaluation showed proven bone formation and increased density after 8 and 16 weeks, with an enhanced effect of the periosteal transplant. CONCLUSION: The greater omentum is a suitable bioreactor for bone tissue engineering. Endocultivation is both an innovative and promising approach in regenerative medicine.

Complications of Impulse Generator Exchange Surgery for Deep Brain Stimulation: A Single-Center, Retrospective Study.

BACKGROUND: Nonrechargeable deep brain stimulation impulse generators (IGs) with low or empty battery status require surgical IG exchange several years after initial implantation. The aim of this study was to investigate complication rates after IG exchange surgery and identify risk factors. METHODS: We retrospectively analyzed complications following IG exchange surgery from 2008 to 2015 in our department. Medical records of all patients who underwent IG exchange surgery were systematically reviewed. The shortest follow-up time was 19 months. RESULTS: From 2008 to 2015, 438 IGs were exchanged in 319 patients. Overall complication rate was 8.90%. Infection developed in 12 patients (2.74%). Six patients (1.37%) experienced local wound erosions. Hardware malfunctions were present in 11 patients (2.51%), and local hemorrhage was observed in 3 cases (0.68%). Repeated fixation of the IG was required in 2 patients (0.46%). Traction of the connecting cables necessitated surgical revision in 2 patients (0.46%). In 2 cases (0.46%), the IG was placed abdominally or exchanged for a smaller device owing to patient discomfort resulting from the initial positioning. One 80-year-old patient (0.23%) had severely worsening heart failure and died 4 days after IG exchange surgery. CONCLUSIONS: IG exchange surgery, although often considered a minor surgery, was associated with a complication rate of approximately 9% in our center. Patients and physicians should understand the complication rates associated with IG exchange surgery because this information might facilitate selection of a rechargeable IG.

Determination of VEGF, collagen type 1 and versican in the discus articularis of the temporomandibular joint in relation to dental status.

The aim of this study was the investigation and comparison of the presence of vascular endothelial growth factor (VEGF), collagen type 1 and the proteoglycan versican in the discus articularis in relation to dental status (full dentition [1], partial dentition [2] and edentulous [3]). The right disci articulares were removed from 17 donated bodies (6 with full dentition, 5 with partial dentition and 6 edentulous). The specimens were immunohistochemically stained for VEGF, collagen type 1 and versican. Semiquantitative analysis of the disci was conducted within the groups based on the intensity of immunoreactivity of VEGF, collagen type 1 and versican. In addition, a pairwise comparison was carried out between the three experimental groups. The results revealed significantly higher immunoreactivity for VEGF and versican in groups 2 and 3 than in group 1. Conversely, determination of immunoreactivity was significantly higher in group 1 for collagen type 1 than in the other two groups. These results indicate an elevated presence of the proteoglycan versican and the neoangiogenesis factor VEGF when the occlusal supporting zone has been lost. By contrast, detection of collagen type 1 is reduced. The loss of collagen type 1 and rise in versican and VEGF suggest increasing degeneration when the supporting zone is lost due to the loss of teeth.

* Endocultivation of Scaffolds with Recombinant Human Bone Morphogenetic Protein-2 and VEGF165 in the Omentum Majus in a Rabbit Model.

The reconstruction of defects in the mandible are still challenging. Despite several adequate microvascular bone reconstruction techniques, there is a need for ectopic bone endocultivation without drawbacks by donor-site morbidity. The omentum majus is described as a good vascularized fleece with undifferentiated cells with potential for bone culturing. In the omentum majus of six rabbits, two hydroxyapatite blocks were incorporated for 12 weeks each. The blocks were prepared with recombinant human bone morphogenetic protein-2 (rhBMP-2) or VEGF165 + rhBMP-2 and wrapped into the omentum. For ectopic bone endocultivation observation computed tomography (CT) scans were performed, and fluorescence markers were applied. After harvesting the block, histological sections were performed with hematoxylin and eosin and toluidine blue staining. In the CT scans, the Hounsfield units of the blocks increased within the trail. In some sections, new bone formation was observed within the hydroxyapatite blocks, however, the histological staining showed soft-tissue invasion only, no gross bone formation was observed. The ectopic bone endocultivation in the omentum majus is technically a good approach. An adequate mixture of osteoinductive proteins is still missing.

Deficiency of the DSPP-cleaving enzymes meprin α and meprin ß does not result in dentin malformation in mice.

Formation of dentin requires the maturation of procollagen I and the proteolytic processing of the dentin sialophosphoprotein (DSPP). These cleavage events can be facilitated by the metalloproteinases meprin α and meprin ß as well as by bone morphogenetic protein 1 (BMP-1). All three enzymes have been shown to play important roles during collagen I maturation in vivo and their potential in cleaving DSPP was demonstrated in vitro. Hence, it has been discussed whether meprin α, meprin ß, BMP-1 or all three are crucial factors in the onset and progression of dentin-related diseases and this issue is addressed here. In this study, we compare the incisors and molars of meprin α (Mep1a -/-)- and meprin ß (Mep1b -/-)-deficient mice with wild-type (WT) controls on the macroscopic and microscopic level. The dentin was evaluated towards the bone mineral density, dentin volume, calcification and collagen matrix integrity. Using immunohistochemistry, we could identify meprin ß, BMP-1 and DSPP/DSP in the pre-dentin of WT mice. Nevertheless, no significant dentin malformation was observed in Mep1b -/- or Mep1a -/- deficient mice.

No deficit in neurocortical information processing in patients with cleft lip and palate.

BACKGROUND: Cleft lip and palate (CLP) represents the most common malformation of the midfacial region worldwide. It can be suggested that the facial stigmatization, the speech impediment, and the long-standing pressure of treatment cause a range of life stressors. Neurocortical information is influenced by physiological and psychological factors and varies significantly in patients suffering from chronic stress, anxiety, depression, or other psychopathological conditions following maladaptation. The aims of the present study were to investigate the neurocortical information processing of patients with CLP using the contingent negative variation (CNV) paradigm and to evaluate secondary psychopathology, anxiety, and depression. MATERIALS AND METHODS: Twenty-five adults with CLP and 25 healthy volunteers, matched in age and gender, were investigated using recordings of the CNV. Initial CNV (iCNV), late CNV (lCNV), and total CNV (tCNV) as well as habituation slope of the iCNV were determined in each subject. Additionally, each participant had to complete the hospital anxiety and depression questionnaire (HADS) and the Symptom Checklist-90-R (SCL-90-R). RESULTS: Individuals with CLP did not differ significantly from healthy subjects according to any of the CNV parameters investigated. No correlations could be revealed between the measured items and the confounding factors age and gender. Additionally, there were no differences between the groups regarding depression and SCL-90-R; however, anxiety showed significant group differences on a subclinical level. CONCLUSIONS: These data suggest that subjects with CLP show normal neurocortical information processing. It seems likely that CLP and its treatment have no impact on psychosocial functioning and neurophysiological mechanisms of attention. CLINICAL RELEVANCE: The specific living conditions of patients with CLP do not result in disease-specific neurophysiological changes.

Secondary cleft nose rhinoplasty: Subjective and objective outcome evaluation.

INTRODUCTION: Secondary rhinoplasty in cleft lip and palate (CLP) is commonly the last step in a set of surgical procedures that result in a variable but typically intensive change in facial appearance. However, there is evidence that the sentiment about the aesthetic and functional outcomes between patients and surgeons is different. The present study aimed to evaluate the subjective and objective outcomes of secondary rhinoplasty in patients with CLP. MATERIAL AND METHODS: Secondary rhinoplasty was performed in 10 patients with repaired unilateral CLP via a standardized open approach. For the subjective evaluation, the patients completed the rhinoplasty outcome evaluation (ROE) questionnaire. Pre- and postoperative photographic documentation served as the basis for the objective evaluation, which included the following: (1) assessment by five specialists at craniofacial malformation consultation appointments and by three doctors in continuing education using the Asher-McDade aesthetic index (AMAI) rating, and (2) metric facial analysis to determine the nasofrontal angle and the nasolabial angle. RESULTS: Patient satisfaction was high, based on the evaluation of the ROE questionnaire. The analysis of the AMAI rating questionnaire showed no significant differences between the positive ratings of the 'experienced' and 'inexperienced' doctors. In contrast, there was an obvious and significant difference between the 'preoperative' and 'postoperative' time points for questions 1-3. The metric analysis showed statistically significant improvements of the nasolabial angle and the nasofrontal angle. The subjective and objective outcome evaluations were descriptively congruent. CONCLUSIONS: The data suggest that standardized secondary rhinoplasty in CLP leads to both a subjective and a statistically significant objective improvement of facial appearance and thus may support the psychosocial rehabilitation of affected patients. Furthermore, our results showed that the subjective and objective outcome evaluations of secondary rhinoplasty were largely compatible.

Mechanical properties of collagen membranes: are they sufficient for orbital floor reconstructions?

INTRODUCTION: The most common reconstruction materials for orbital floor fractures are PDS (polydioxanone) foil and titanium meshes. These materials have advantages and disadvantages. Therefore, new materials are needed to improve surgical outcomes. MATERIALS AND METHODS: Three resorbable collagen membranes (Smartbrane(®), BioGide(®), Creos(®)) were tested for their mechanical properties (puncture strength) in mint and artificially aged (3, 6, 8 weeks) conditions and were compared to PDS foil, titanium meshes (0.25 mm, 0.5 mm) and human orbital floors (n = 7). RESULTS: The following puncture strengths were evaluated: human orbital floor, 0.81 ± 0.49 N/mm(2); 0.25 mm titanium mesh, 5.36 ± 0.25 N/mm(2); 0.5 mm titanium mesh, 16.08 ± 5.17 N/mm(2); Smartbrane, 0.74 ± 0.31 N/mm(2); BioGide, 1.65 ± 0.45 N/mm(2); and Creos, 2.81 ± 0.27 N/mm(2). After artificial aging, the puncture strengths were significantly reduced (p ≤ 0.05) at 3, 6 and 8 weeks as follows: Smartbrane, 0.05 ± 0.03 N/mm(2), 0.03 ± 0.02 N/mm(2), and 0.01 ± 0.01 N/mm(2), respectively; BioGide, 0.42 ± 0.06 N/mm(2), 0.41 ± 0.12 N/mm(2), and 0.32 ± 0.08 N/mm(2), respectively; and Creos, 2.02 ± 0.37 N/mm(2), 1.49 ± 0.42 N/mm(2), and 1.36 ± 0.42 N/mm(2), respectively. CONCLUSION: The tested materials showed sufficient puncture strength for orbital floor reconstruction in mint condition. Moreover, after artificial aging, the Creos and BioGide membranes showed sufficient resistance, while Smartbrane showed equivocal data after eight weeks. Therefore, collagen membranes have adequate properties for further in vivo investigations for orbital floor reconstructions.

Increased infection rates of sinus floor elevations after the use of a bone filter.

OBJECTIVES: The collection of bone debris during the preparation of sinus floor augmentations is a commonly used technique for avoiding autologous bone transplants and thereby reducing donor site morbidity. However, the collected bone debris has a higher risk of bacterial contamination. The aim of this retrospective study was to analyse whether the use of a bone filter had an impact on the infection rates after sinus floor augmentation. MATERIALS AND METHODS: A retrospective analysis was conducted of 340 sinus floor elevations (136 using a bone filter) in 249 patients. The sinus floor elevations were performed with the lateral approach. RESULTS: Localised infection occurred in 7.0 % (24 of 340) of the sinus floor elevations. In 40.0 % of the cases, a bone filter was used, and in this group, the infection rate was 13.0 %. In the control group, the infection rate was 4.0 %. One hundred one patients received bone transplants from the iliac crest, and these patients had a lower infection rate of 2.0 %. Stepwise factor reduction, according to Akaike, showed the use of a bone filter to be the most relevant factor for postoperative infection. CONCLUSIONS: To reduce the amount of bacteria, full-mouth disinfection with chemical agents and a strict aspiration protocol should be used when a bone filter is applied. Antibiotic prophylaxis should be prescribed to reduce the risk of postoperative infections further. CLINICAL RELEVANCE: In use of a bone filter, there is the possibility of higher infection rates of sinus floor augmentations.

Highly porous hydroxyapatite with and without local harvested bone in sinus floor augmentation: a histometric study in pigs.

OBJECTIVE: Sinus floor augmentation with autologous bone is an accepted treatment option in dental implantology. In this study, an entirely synthetic, nano-structured, hydroxyapatite-based bone substitute material (SBSM, NanoBone(®); Artoss, Rostock, Germany) was supplemented with a mixture of locally harvested bone to enhance osteogenesis. METHODS: Bilateral sinus augmentation procedures were performed in eight domestic pigs using the lateral window technique. On the right side (control), 2.6 ml of SBSM was used, and on the left side (test), 2.6 ml of SBSM with additional 15% (390 µl) autologous bone was used. At the time of augmentation, a titanium implant (ITI(®)) was inserted from a laterocaudal direction. After 3 months, the sites of augmentation were removed and examined in non-decalcified sections by microradiography and fluorescence microscopy of sequentially labelled specimens and histometry. RESULTS: On both sides, a significant amount of newly formed bone was observed. However, a statistically significant difference in the bone-implant contact was observed in the control group (median, 28.9%) compared with the test side with the additional autologous bone (median, 40.6%) (P = 0.01). Different bone density was achieved from the coronal to apical surfaces (medians, 54.6%, 9.6%, and 27.5%) compared with the test side (medians, 55.2%, 40.6%, and 44.2%). The median of augmentation height was 8.6 mm on the control side and 11.5 mm on the test side (P = 0.01). Bone apposition was observed in both groups after 15 days. CONCLUSION: The SBSM shows acceptable results in sinus floor augmentation. The additional use of locally harvested autologous bone enhances bone density and osseointegration of the implants.

Leakage of fluid around endotracheal tube cuffs: a cadaver study.

BACKGROUND: The aim of the study was to evaluate the leakage of liquid past the cuffs of tracheal tubes in fresh frozen human heads. METHODS: Six truncated fresh frozen heads were used and intubated with 8.0 mm endotracheal tubes. The intracuff pressures tested were 30 and 100 cmH2O. Subsequently, 20 ml of each of two oral antiseptic rinses (0.2% chlorhexidine and octenidine [octenidol®, Schülke & Mayr GmbH, Norderstedt, Germany]) was applied for thirty seconds in the mouth. During the trial, leakage of the cuffs was examined. RESULTS: The sealing between the tracheal cuff and tracheal wall was leakage-proof for all tested intracuff pressures and all tested antiseptic rinses. However, approximately 5.6 ml and 1.8 ml leaked into the esophagus and remained as a cuff-puddle, respectively. CONCLUSIONS: The sealing between an endotracheal tube cuff with an intracuff pressure of 30 cmH2O and the tracheal wall is leakage-proof during oral care with antiseptic rinsing. An increase of intracuff pressure to 100 cmH2O does not appear to be required.

Forces affecting orbital floor reconstruction materials--a cadaver study.

INTRODUCTION: The objectives of this study were: (i) to evaluate the applied force and the displacement of the orbital contents after orbital floor reconstruction using artificially aged reconstruction materials in fresh frozen human heads and (ii) to analyze the puncture strength of the materials. MATERIAL AND METHODS: Six fresh frozen human heads were used, and orbital floor defects in the right and left orbit were created by 3.0 J direct impacts on the globe and infraorbital rim. The orbital floor defect sizes and displacements were evaluated after a Le-Fort-I osteotomy. RESULTS: The orbital floor defect sizes were 208.3(SD, 33.4) mm(2) for the globe impacts and 221.8(SD, 53.1) mm(2) for the infraorbital impacts. The forces on the incorporated materials were approximately 0.003 N and 0.03 N for the PDS-foil and collagen membrane, respectively. The displacements of the materials were +0.9 mm and +0.7 mm for the PDS-foil and collagen membrane, respectively. The puncture strengths of the PDS-foil and collagen membrane decreased from approximately 70 N and 12 N at week 1 to approximately 5 N and 1.5 N at week 8 of artificial aging. CONCLUSION: The force applied to the orbital content is minimal, and the puncture strengths of the artificially aged materials are more than sufficient for the measured forces.

Increased intraosseous temperature caused by ultrasonic devices during bone surgery and the influences of working pressure and cooling irrigation.

PURPOSE: The purpose of this study was to investigate the increases in intraosseous temperature generated by a modern ultrasonic device for bone surgery (UDBS) and the influences of working pressure and cooling irrigation on this temperature. MATERIALS AND METHODS: Twenty human mandibular bone specimens (20x15x5 to 7 mm) were used; three vertical cuts were performed for a duration of 12 seconds per cut. Each bone specimen was machined with a different combination of working pressure (1.5, 2.0, 3.0, 4.0, or 6.0 N) and cooling irrigation (0, 30, 60, or 90 mL/min), and intraosseous temperatures were measured. Harmful temperature development was defined as an increase of more than 10°C for the 75th percentile and/or a maximum increase of more than 15°C. Cutting performance was also measured. RESULTS: Harmless intraosseous temperature development was identified for working pressures of 1.5 N and 2.0 N with cooling irrigations of 30, 60, and 90 mL/min and for 3.0 N at 90 mL/min. The maximum temperature observed was 72°C (6.0 N with 60 mL/min). The mean cutting performance values were 0.21±0.02 mm/s for 6.0 N, 0.21±0.06 mm/s for 3.0 N, 0.20±0.01 mm/s for 4.0 N, 0.11±0.05 mm/s for 1.5 N, and 0.08±0.03 mm/s for 2.0 N. CONCLUSIONS: To prevent tissue damage in dental bone surgery, a minimum coolant amount of 30 mL/min is recommended. The working pressure should be chosen with great care because of its significant influence on intraosseous temperature. Doubling of the working pressure from 1.5 to 3.0 N requires a tripling of the coolant (30 to 90 mL/min) to prevent tissue damage. A working pressure above 3.0 N did not result in improved cutting performance.

Maximum forces applied to the orbital floor after fractures.

The objective of this study was to measure the force on and displacement of completely detached intraorbital tissue from the bony orbit, as a worst-case scenario after orbital trauma, to preserve the maximum load and predict the necessary strength of reconstruction materials. Six fresh-frozen human heads were used, and orbital floor defects in the right and left orbits were created by the direct impact of 3.0 J onto the globe and infraorbital rim. The orbital floor defect sizes and displacements were evaluated after performing a Le Fort I osteotomy. In addition, after the repositioning of the completely detached intraorbital tissue, the forces and displacements were measured. The mean orbital floor defect sizes were 208.3 (SD, 33.4) mm2 for globe impacts and 221.8 (SD, 53.1) mm2 for infraorbital impacts. The mean intraorbital tissue displacement after the impact and before repositioning was 5.6 (SD, 1.0) mm for globe impacts and 2.8 (SD, 0.7) mm for infraorbital impacts. After repositioning, the displacements were 0.8 (SD, 0.5) mm and 1.1 (SD, 0.7) mm, respectively. The measured forces were 0.10519 (SD, 0.00958) N without the incorporation and approximately 0.11128 (SD, 0.003599) N with the incorporation of reconstruction materials. The maximum forces on the completely detached orbital tissue were minimal (∼0.11 N) and suggest the use of collagen membranes as reconstruction materials for orbital floor defects, at least in medium-sized fractures.

Forces charging the orbital floor after orbital trauma.

The objectives of this study were (i) to evaluate different fracture mechanisms for orbital floor fractures and (ii) to measure forces and displacement of intraorbital tissue after orbital traumata to predict the necessity of strength for reconstruction materials. Six fresh frozen human heads were used, and orbital floor defects in the right and left orbit were created by a direct impact of 3.0 J onto the globe and infraorbital rim, respectively. Orbital floor defect sizes and displacement were evaluated after a Le Fort I osteotomy. In addition, after reposition of the intraorbital tissue, forces and displacement were measured. The orbital floor defect sizes were 208.3 (SD, 33.4) mm(2) for globe impact and 221.8 (SD, 53.1) mm(2) for infraorbital impact. The intraorbital tissue displacement after the impact and before reposition was 5.6 (SD, 1.0) mm for globe impact and 2.8 (SD, 0.7) mm for infraorbital impact. After reposition, the displacement was 0.8 (SD, 0.5) mm and 1.1 (SD, 0.7) mm, respectively. The measured applied forces were 0.061 (SD, 0.014) N for globe impact and 0.066 (SD, 0.022) N for infraorbital impact. Different fracture-inductive mechanisms are not reflected by the pattern of the fracture. The forces needed after reposition are minimal (~0.07 N), which may explain the success of PDS foils [poly-(p-dioxanone)] and collagen membranes as reconstruction materials.