P. Maurer

Risk factors for a bad split during sagittal split osteotomy

One of the operative complications during sagittal split osteotomy (SSO) in orthognatic surgery is a bad split, meaning an undesired fracture of the mandible during osteotomy. The aim of this study was to find out if there is a relation between the occurrence of bad splits during SSO and the presence of third molars, the patients age, or the surgeons experience. Clinical notes of 110 consecutive patients who had had a total of 220 SSOs using the Obwegeser/Dal Pont technique were evaluated and divided into three groups: 1 missing third molar (n=168); 2 retained or impacted third molar that was removed during the SSO (n=23); and 3 third molar left in place during SSO (n=29). There were a total of 12 (6%) bad splits. 9 (5%) in group 1, two (9%) in group 2, and one (3%) in group 3. There were no significant differences between groups 1-3, in particular the surgeons qualification had no influence on the incidence. Older patients seemed more at risk of a bad split than younger ones.

Scope and limitations of methods of mandibular reconstruction: a long-term follow-up

Surgical treatment of cancers of the oral cavity often requires resection of the mandible, which sacrifices continuity, thereby implying considerable loss of function and aesthetics. The aim of the present study was to compare different methods of mandibular reconstruction for long-term results, complications, and factors associated with failure. During the 10-year period (1995-2005), 102 patients (73 men and 29 women, mean age 55 years, range 11-83) had a continuity resection of the mandible as described by Jewer et al. as follows: lateral continuity defect (n=53), central/lateral continuity defect (n=24), lateral/central/lateral continuity defect (n=14), central continuity defect (n=6), hemimandibular continuity defect (n=4) and central/hemimandibular continuity defect (n=1). The gap in the mandible was bridged with a titanium reconstruction plate in 73 patients, four of whom required a temporomandibular joint prosthesis. In 29 patients the mandibles were reconstructed with free autologous bone grafts fixed with miniplates. The overall 1-year success rate was 64%; 66% for the 73 patients who had miniplate/bone fixation and 63% in the 29 whose defects were bridged with a reconstruction plate. Complications were associated with the reconstruction plate in 39%. The most common complications were extraoral exposure (16%), intraoral exposure (10%), loose osteosynthesis screws (5%), fractures of the reconstruction plate (5%), and extra/intraoral exposure (1%). All fractures were noted at least 6 months postoperatively. There was no increased risk (p=0.67) depending on the osteosynthesis device used (miniplate or reconstruction plate). The risk of failure of the reconstruction plate was significantly higher in men (p=0.002) and smokers (p=0.004), whereas no increased risk was apparent for the anatomical site of the defect. Radiation reduced the 1-year success rate from 64% to 45% but not significantly so (p=0.67). There were no significant differences between the reconstruction methods. Alloplastic reconstruction devices are the treatment of choice for many patients.

Canalicular Network Morphology Is the Major Determinant of the Spatial Distribution of Mass Density in Human Bone Tissue: Evidence by Means of Synchrotron Radiation Phase-Contrast nano-CT

In bone remodeling, maturation of the newly formed osteonal tissue is associated with a rapid primary increase followed by a slower secondary increase of mineralization. This requires supply and precipitation of mineral into the bone matrix. Mineral delivery can occur only from the extracellular fluid via interfaces such as the Haversian system and the osteocyte pore network. We hypothesized that in mineralization, mineral exchange is achieved by the diffusion of mineral from the lacunar‐canalicular network (LCN) to the bone matrix, resulting in a gradual change in tissue mineralization with respect to the distance from the pore‐matrix interface. We expected to observe alterations in the mass density distribution with tissue age. We further hypothesized that mineral exchange occurs not only at the lacunar but also at the canalicular boundaries. The aim of this study was, therefore, to investigate the spatial distribution of mass density in the perilacunar and pericanalicular bone matrix and to explore how these densities are influenced by tissue aging. This is achieved by analyzing human jawbone specimens originating from four healthy donors and four treated with high‐dosage bisphosphonate using synchrotron radiation phase‐contrast nano‐CT with a 50‐nm voxel size. Our results provide the first experimental evidence that mass density in the direct vicinity of both lacunae (p < 0.001) and canaliculi (p < 0.001) is different from the mean matrix mass density, resulting in gradients with respect to the distance from both pore‐matrix interfaces, which diminish with increasing tissue age. Though limited by the sample size, these findings support our hypotheses. Moreover, the density gradients are more pronounced around the lacunae than around the canaliculi, which are explained by geometrical considerations in the LCN morphology. In addition, we speculate that mineral exchange occurs at all interfaces of the LCN, not only in mineralization but also in mineral homeostasis.

Micromorphometrical analysis of conventional osteotomy techniques and ultrasonic osteotomy at the rabbit skull.

OBJECTIVES The ultrasonic osteotome, which was recently introduced, is an alternative to conventional methods of osteotomy. The aim of the present study was to establish the differences between three osteotomy techniques and to perform a quantitative roughness analysis of the osteotomized bone surfaces. MATERIALS AND METHODS Fresh bony samples of standardized size were taken from the rabbit skull. The techniques used were as follows: reciprocate micro-saw, Lindemann bur, ultrasonic osteotome with the two insert tips OT6 (rough) and OT7 (fine). The prepared surfaces were examined by light microscopy, environmental surface electron microscopy (ESEM) and by confocal laser scanning microscopy (CLSM). RESULTS It was difficult to distinguish between cortical and cancellous bone after using the conventional osteotomy technique. The ultrasonic technique preserved the original structure of the bone. The values observed for superficial roughness were as follows: 3.97 microm (micro-saw), 5.7 microm (Lindemann bur), 2.48 microm (OT7) and 3 microm (OT6). There were statistical differences between the values of the bur and insert tip OT6 (P=0.015) as well as between the bur and insert tip OT7 (P=0.003). CONCLUSIONS In the present study micromorphological differences after using various osteotomy techniques could be clearly identified.

Comparative evaluation of two osteosynthesis methods on stability following sagittal split ramus osteotomy.

INTRODUCTION The aim of this study was to employ the finite element method (FEM) to compare the stability of 2.0 mm titanium screws in a triangular configuration with that of a 2.0 mm titanium miniplate as osteosynthesis material following bilateral sagittal split osteotomy. MATERIAL A model of the mandible was produced, consisting of 19,854 elements and 4285 nodes. The mechanical parameters of the materials investigated were taken from the literature and notified by the manufacturer. RESULTS On condition that the materials were subjected only to their respective ultimate tensile stress, it was possible to neutralise a masticatory force of 1246 N (Newtons) with the miniplate and of 1675 N with the bicortical triangular screw configuration. The strain limit was determined by the peri-implant bone and not the osteosynthesis material. CONCLUSION The finite element method (FEM) appears to be suitable for simulating complex mechanical stresses in the maxillofacial area, as also confirmed by the agreement between our data and those in the literature, and with clinical experience. It should enable considerable savings to be made in terms of time, material and animal experiments in the future development of osteosynthesis materials and techniques.

Functional and radiographic long-term results after bad split in orthognathic surgery

Bilateral sagittal split osteotomy (BSSO) is a standard procedure in orthognathic surgery. The aim of the present study was to perform a matched pair analysis (bad sagittal split versus regular sagittal split) regarding the functional and radiographic long-term results after BSSO. Of 110 cases of mandibular hypoplasy treated with BSSO, 7 cases of bad sagittal splits (Group A) were selected, clinically examined and matched to 7 cases where no bad split occurred (Group B). The Research Diagnostic Criteria for Temporo Mandibular Disorders (RDC/TMD), condylar morphology scale (CMS) and ramus height measurements using orthopantomograms were carried out in the follow-up period to observe the clinical and functional status and condylar resorbtion or remodelling. The mean follow-up time was 28.6 months. The RDC/TMD examination did not show a higher incidence of temporomandibular dysfunction, including pain or clicking in the bad split group. Patients without a bad split showed statistically significant (p<0.05) better mouth opening. The CMS measurements were comparable in both groups. When compared with regular splits, bad splits, if treated in an appropriate manner, have a good chance of functional success, although, some mandibular movements can be compromised.

Computer assisted chewing power in patients with segmental resection of the mandible

BACKGROUND Surgical treatment of tumors of the oral cavity often requires a segmental resection of the mandible. This always implies a considerable loss in function and aesthetics. The aim of the present study was to measure the chewing force obtained by patients after mandibular resection. PATIENTS AND METHODS In a group of 20 patients (twelve males, eight females, average age 59 years), chewing force were registered by means of a computerized measurement device. In 16 patients, the defect was bridged by a reconstruction plate, in three with an iliac bone graft stabilized by miniplates, and in one patient with only two miniplates. RESULTS The maximum value in the molar region was 186 N und the minimum was 28 N. The average bite force in the molar region reached 81.1 N (+/-46.1) with 42.9 N (+/-35.7) in the front region. The highest value was registered in a patient with an iliac bone graft without soft tissue defect. The lowest was found in patients with bony chin defects. CONCLUSION Based on these results, a reduction of 76% in the molar region and 59% in the incisor region was observed. These values might be helpful in providing a more realistic definition of the functional loadings found in patients after mandibular resection, which in turn may help in the development of new reconstruction devices.

Computergestützte Kaukraftanalyse bei Patienten mit Unterkieferkontinuitätsresektionen

BACKGROUND Surgical treatment of tumors of the oral cavity often requires a segmental resection of the mandible. This always implies a considerable loss in function and aesthetics. The aim of the present study was to measure the chewing force obtained by patients after mandibular resection. PATIENTS AND METHODS In a group of 20 patients (twelve males, eight females, average age 59 years), chewing force were registered by means of a computerized measurement device. In 16 patients, the defect was bridged by a reconstruction plate, in three with an iliac bone graft stabilized by miniplates, and in one patient with only two miniplates. RESULTS The maximum value in the molar region was 186 N und the minimum was 28 N. The average bite force in the molar region reached 81.1 N (+/-46.1) with 42.9 N (+/-35.7) in the front region. The highest value was registered in a patient with an iliac bone graft without soft tissue defect. The lowest was found in patients with bony chin defects. CONCLUSION Based on these results, a reduction of 76% in the molar region and 59% in the incisor region was observed. These values might be helpful in providing a more realistic definition of the functional loadings found in patients after mandibular resection, which in turn may help in the development of new reconstruction devices.

Alterations of mass density and 3D osteocyte lacunar properties in bisphosphonate-related osteonecrotic human jaw bone, a synchrotron µCT study.

Osteonecrosis of the jaw, in association with bisphosphonates (BRONJ) used for treating osteoporosis or cancer, is a severe and most often irreversible side effect whose underlying pathophysiological mechanisms remain largely unknown. Osteocytes are involved in bone remodeling and mineralization where they orchestrate the delicate equilibrium between osteoclast and osteoblast activity and through the active process called osteocytic osteolysis. Here, we hypothesized that (i) changes of the mineralized tissue matrix play a substantial role in the pathogenesis of BRONJ, and (ii) the osteocyte lacunar morphology is altered in BRONJ. Synchrotron µCT with phase contrast is an appropriate tool for assessing both the 3D morphology of the osteocyte lacunae and the bone matrix mass density. Here, we used this technique to investigate the mass density distribution and 3D osteocyte lacunar properties at the sub-micrometer scale in human bone samples from the jaw, femur and tibia. First, we compared healthy human jaw bone to human tibia and femur in order to assess the specific differences and address potential explanations of why the jaw bone is exclusively targeted by the necrosis as a side effect of BP treatment. Second, we investigated the differences between BRONJ and control jaw bone samples to detect potential differences which could aid an improved understanding of the course of BRONJ. We found that the apparent mass density of jaw bone was significantly smaller compared to that of tibia, consistent with a higher bone turnover in the jaw bone. The variance of the lacunar volume distribution was significantly different depending on the anatomical site. The comparison between BRONJ and control jaw specimens revealed no significant increase in mineralization after BP. We found a significant decrease in osteocyte-lacunar density in the BRONJ group compared to the control jaw. Interestingly, the osteocyte-lacunar volume distribution was not altered after BP treatment.

The importance of temporomandibular function for patient satisfaction following orthognathic surgery.

Aim:From the patients point of view, the main reasons for undertaking orthognathic surgical treatment are esthetic improvements in dentofacial appearance. The aim of this study was to analyze various factors that influence patient satis faction regarding treatment results.Patients and Methods:A total of 102 (f = 67, m = 35) patients were examined after an average follow-up of 47 months. The average age at surgical intervention was 24.3 years. We evaluated the answers to a patient-satisfaction questionnaire, the Helkimo Index findings, nerve function parameters, and the frequency of intra- and post-operative complications.Results:91% of the patients were satisfied or very satisfied with the result. Answers to the questionnaire revealed that 80 (79%) patients would undergo treatment again, and 22 (21%) patients would not. There were no significant differences between the two groups concerning age, gender, type of surgical intervention, diagnosis, nerve function and complications. Statistically-significant differences were found in the Helkimo Index D 0 – D III, and pain reported in joints and movements (chi2-test, p < 0.05).Conclusions:We demonstrate that treatment results were influenced by the craniomandibular functional status. More pronounced symptoms of craniomandibular dysfunction correlated with lower patient satisfaction.ZusammenfassungZiel:Aus Sicht des Patienten stehen meist ästhetische Wünsche im Vordergrund, um eine aufwendige kieferorthopädisch-kieferchirurgische Behandlung zu beginnen. Ziel dieser Studie war es, die verschiedenen Faktoren zu analysieren, die die Patientenzufriedenheit beeinflussen.Patienten und Methodik:Insgesamt 102 (w = 67, m = 35) Patienten wurden im Mittel 47 Monate nach dem Eingriff untersucht. Das durchschnittliche Alter zur Zeit der Operation betrug 24,3 Jahre. Es wurden folgende Befunde erhoben: Fragebogen zur Zufriedenheit, Helkimo-Index, Nervenfunktionsprüfung, Erhebung der intra- und postoperativen Komplikationen.Ergebnisse:Zufrieden und sehr zufrieden mit dem Ergebnis waren 91% der Patienten. Die Frage, ob der Patient die Behandlung erneut beginnen würde, wurde von 80 (79%) Patienten bejaht und von 22 (21%) verneint. Zwischen diesen beiden Gruppen bestanden keine signifikanten Unterschiede für Alter, Geschlecht, Operation, Diagnose, Nervenfunktionsstörungen und Komplikationen. Für den Helkimo-Index D 0 – D III, den Gelenk- und Bewegungsschmerz fanden sich statistisch signifikante Unterschiede (Chi2-Test, p < 0,05).Schlussfolgerungen:Es konnte gezeigt werden, dass den temporomandibulären Funktionsbefunden ein großer Stellenwert für den Behandlungserfolg beizumessen ist. Deutlich ausgeprägte Symptome einer temporomandibulären Dysfunktion korrelieren mit einer geringeren Patientenzufriedenheit.