Intramandibular course of the mandibular nerve; clinical significance for distraction and implantology.

OBJECTIVE: Loss of teeth is accompanied with loss of function and therefore reduction of alveolar bone height. Insufficient bone height can jeopardize the anchorage of implants or surgical procedures such as distraction osteogenesis, because of possible mandibular nerve damage. The goal of this investigation was to determine the exact course of the intramandibular nerve in edentulous mandibles. MATERIAL AND METHOD: The study samples included 37 dry human edentulous mandibles. A dental CT scan analysis was performed and four cross sectional views were investigated for each mandible. The Cawood classification was used to assess the grade of atrophy. Implantation simulation was performed in every case. RESULTS: There was no bilateral symmetry in edentulous mandibles, whatever the cross-section studied. A rate of 38.7% were classified Cawood class IV, the most common group in edentulous patients. Our study results led us to place the distraction osteogenesis device in the posterior edentulous mandible. Implant placement was not possible in every case. DISCUSSION: Our findings allow better understanding from the pathway of the mandibular canal close to the first and second molar in edentulous mandibles. This anatomical data and surgical techniques such as implant insertion and distraction osteogenesis allow finding solutions for "mandibular edentulism". Distraction is essential for a successful implantology.

Osteogenic uni- or bilateral form of the guided rapid maxillary expansion.

Surgically assisted rapid palatal expansion is an important treatment procedure in patients with constricted maxillae. Several surgical methods have been proposed to expand the maxilla bilaterally. A new technique was developed for performing a symmetric or asymmetric maxillary expansion guided by the stability of the mid-palatal area employing two osteotomy cuts on either side of mid-palatal suture. A Hyrax-type expansion device was used post-operatively. Seventeen patients were included in the study (9 males, 8 females) with a mean age of 30.7 years. Inter-canine and inter-molar widths were evaluated at three assessment intervals: before treatment (T1), immediately after appliance removal (T2) and at six months follow-up (T3). Between T1 and T2, a mean expansion of 7.1 and 9.9mm was achieved at the canine and molar areas, respectively. The amount of relapse measured between T2 and T3 was minimal (a mean value of 0.35 and 0.8mm at the canine and molar areas, respectively). Asymmetric expansion was performed in 6 patients who exhibited unilateral skeletal constriction at the initial assessment and these cases appeared stable at T3. The surgical approach described in the current study enabled rapid maxillary expansion of unilateral and bilateral skeletal constriction cases effectively and with good stability.

3D-FEM and histomorphology of mandibular reconstruction with the titanium functionally dynamic bridging plate.

Biomechanical investigation of the mandible is difficult due to the complex geometrical structure. A three-dimensional finite element model of the mandible and masticatory muscles was produced with approximately 23,000 hexahedral elements. On this model, mesial and distal portions of the jaw were resected and bridged with a buccal and/or caudally positioned bridging plate. The plate was fixed caudal or buccal to the mandible. The defect was left as it was or reconstructed with an exactly fitting transplant defined as bone. The jaw was loaded at a predefined point. The changes in stresses and deformations of bone, the transplant and the bridging plate were analysed. In the caudally positioned bridging plate, finite element analysis showed lesser stresses around the fixation screws of the bridging plate. During reconstruction of the lateral defect, the buccal (ramus)-caudal (corpus) position of the bridging plate showed fewer stresses and deformations than purely buccal positioning. The caudal position of the bridging plate has biomechanical advantages and facilitates fixation of the plate, and fixation of a bone graft on the jaw stumps. Histomorphological investigations, 12 weeks and 7 years after reconstruction, show partial osseous integration or transformation of autologous iliac crest transplants.

The Endo-Distractor for preimplant mandibular regeneration.

OBJECTIVE: A simple practical device for a new technique of vertical distraction osteogenesis was developed. The Endo-Distractor Krenkel was originally intended for the anterior regeneration of highly atrophic mandibles. The Endo-Distractor features several novelties. Placement is made intraosseously in the basal cortical bone. The distraction screw length may be adapted to the depth of chin soft tissues. The quality of anchorage in the basal cortical bone guarantees the stability of the distraction vector. The endobuccal emergence is that of an artificial crown, and does not cause any patient discomfort. The device can easily be removed without secondary surgery. All kinds of implants may be placed after the retention time. This study's objective was to evaluate the use of the Endo-Distractor Krenkel in edentulous patients with highly atrophic mandibles. MATERIAL AND METHOD: This new device was used on 18 patients, between January 2000 and September 2004, who were then followed-up for at least 36 months. Mandibular atrophy was measured with a lateral cephalogram, then classified according to Atwood's modified classification. The studied criteria included the amplitude of distraction, its duration, the distractor's lingual tilt, the number and outcome of implants, and complications. RESULTS: The sex ratio was 17 female for one male patient. The mean patient age was 56 years (43 to 66 years). The mean distraction amplitude was 11.3mm (8 to 14 mm). The mean retention time was 186.8 days (37 to 309 days). The distractor's mean lingual tilt was 4.3 degrees (0 to 23 degrees ). Two mandibular fractures occurred 6 weeks after placing the Endo-Distractor. The first one was treated medically, and the second one required removing the Endo-Distractor and osteosynthesis. An average of four interforaminal implants were placed for a total of 24 Brånemark and 51 Straumann implants. Four implants were lost in a patient due to infection. All other implants were osseointegrated. No bone loss was detected at follow-up after functional loading. DISCUSSION: These results show that alveolar distraction is possible on severely atrophic mandibles. The quality of bone and gum reconstruction is satisfactory both for functional and esthetic results. Surgical difficulty and rate of complications were lower than with conventional distraction techniques.

[Acatalasemia--Takahara's disease]. / Akatalasämie--Morbus Takahara.

The case of a 30 year old man with acatalasemia is presented. The congenital disorder is charaterized by a lack or major reduction of catalase, an enzyme that catalyzes the decomposition of hydrogen peroxide to oxygen and water. The defect is inherited in an autosomal recessive fashion. Occasionally the defect manifests as progressive oral gangrene or Takahara's, disease.

2D-finite element analyses and histomorphology of lag screws with and without a biconcave washer.

For osteosynthesis and for bone transplant fixation in particular, a lag screw with a biconcave washer, the so called "Anchor Screw" (AS) has been introduced in maxillo-facial surgery. Using 2D-finite element analysis (FEA), the v. Mises and the circumferential stresses induced in underlying bone by this AS are analysed and compared to those under a conventional lag screw. The stress distributions below the biconcave washer of the AS were correlated with histomorphological bone reactions after AS osteosynthesis in two tumor patients, retrieved 12 weeks and 19 months after tumor surgery, respectively. Depending on the thickness of cortical bone, the v. Mises stress concentrations below the biconcave washer were lower than under the head of the conventional lag screw (CLS), but with a higher stress maximum concentrated around the rim of the washer. The circumferential stresses were only half as high around the AS, and thus the deformation of bone was reduced. As predicted by FEA, histology showed microcrack formation, but then after minimal resorption, remodelling of bone below the biconcave washer. Stable osteosynthesis could be demonstrated by bony union already after 12 weeks, and, while bone remodelling continued in the healed osteotomy, it had decreased around the screws after 19 months. It can be concluded from the biomechanical principles and the histomorphological findings that the AS appears superior to the CLS.

Treatment of mandibular-condylar fractures.

Particularly with true dislocation fractures, nonoperative treatment with maxillomandibular fixation followed by physiotherapeutic exercises leads to poor results, as was proved with axiography and clinical examinations. The main reason for this is the shortening and scarring of the condyloid process and the lack of function of the lateral pterygoid muscle. The condyle with its insertion of the muscle is usually displaced medially and anterially and nearly in touch with the origin on the pterygoid process so that protrusion by the muscle is no longer possible. The physiologic relationship of the lateral pterygoid muscle is restored after reduction of the condyle and osteosynthesis of the condylar neck fracture and the original distance between origin and insertion of the muscle is re-established and is a fundamental necessity for regaining function (Fig. 40). The anchor screw osteosynthesis is a most effective technique with low limitations for its indication. A comparison with plates shows this technique to be very economic because one anchor screw has the effect of at least one five-hole plate with five plating screws. That means a reduction of osteosynthesis implants of up to 80%, which saves a lot of money. On the other hand, the sophisticated technique of an anchor screw osteosynthesis needs some training on the part of the surgeon to get the best results possible. In general, we could realize that the anchor screw osteosynthesis gives a perfect adaptation of the fracture ends with compression also on the inner cortical layer, which with plates is only possible in rare cases. After an osteosynthesis of mandibular condyle neck fractures with an axial anchor-screw there are a few cases with an absorptive process in the fracture interface where the screw migrates in an axial direction with loosening of the osteosynthesis. This effect can be compared with the effect of a dynamic hip screw, which leads to compression of the callus, which speeds up bony union at the expense of shortening the bone. When the same absorption happens using a plate, the fracture ends cannot become sintered and the plate is in danger of fracturing as a result of metal fatigue. Ceipek evaluated 136 patients with mandibular condylar neck fractures treated with axial anchor screw osteosynthesis. Thirty-six of these screws showed signs of migration, but only 3.7% for more than 4 mm. For the migration process there are some important risk factors: difficult repositioning of the proximal fragment, dorsal luxation fracture, indirect method of anchor screw osteosynthesis, narrow condyle neck, no intercuspation in the molar region, no compliance, and disturbance of bone healing. Another stable technique of osteosynthesis should be used if patients show more risk than one risk factor.

[Functional dynamic bridging plate and its use in the mandible]. / Die funktionsdynamische Uberbrückungsplatte und ihre Anwendung im Unterkiefer.

The principle of the functionally dynamic bridging plate can be compared with the construction of a double bridge. The first bridge, which performs a protective function, is established by means of a plate which extends from one stump of the mandible to the other. The homogeneous, square-sectioned, central bar of the plate tolerates micromovements when stressed and demonstrates no predetermined breaking points. The second bridge ist established with the aid of the primary or secondary bone transplants, which are fixed to each other separately and to the stumps of the mandible with supplementary gracile implants. An adequate degree of functional stress on the bone transplant, i.e. the transmission of functional dynamical forces, is essential for the remodelling of the bone and must extend from one resected stump to the other. The choice of a square cross-section for the functionally dynamic bridging plate bar simplifies the three-dimensional bending and shaping of the plate on a template or the bone, thereby stressing the plate material uniformly and protecting it accordingly. This considerably facilitates the intraoral fixation of the plate. The functionally dynamic bridging plate system has proved successful in cases of partial mandibular resections, after tumour resections or in cases of defects following traumas and inflammations. It is suitable for cases with or without immediate bone reconstruction. It can be placed on the buccal side of the mandible, the caudal side or a combination of both. Positioning bone transplants can thus be carried out by a direct approach without obstruction and is consequently technically simpler.(ABSTRACT TRUNCATED AT 250 WORDS)

Axial 'anchor' screw (lag screw with biconcave washer) or 'slanted-screw' plate for osteosynthesis of fractures of the mandibular condylar process.

Almost a quarter of all mandibular fractures are located in the condylar neck region and generally lead to disturbances of occlusion. Because they still possess active growth centres, children and adolescents can take advantage of the joint's remodelling capacity following conservative treatment of these fractures. Fractures with displacement of the condylar head in adults can interfere with function if they are not surgically reduced (Krenkel and Strobl, 1989). In addition, a compensatory overloading of the non-fractured side, which originally goes unnoticed, can bring about disc pathology and chronic pain years later. For this reason, a surgical technique was developed for the management of mandibular condylar neck fractures. A new axial/oblique-axial lag screw (anchor screw) with biconcave washers (anchor washer) makes it possible to carry out standardized osteosynthesis in the region of the thin mandibular condyle neck. Functional exercises can be initiated immediately after the operation. There are three operative procedures using an extraoral approach (1-3) and two using an intraoral approach (4-5), depending on the type and severity of the fracture: 1. Direct anchor screw osteosynthesis with closed gliding hole. 2. Indirect anchor screw osteosynthesis with open gliding groove and safety plates. 3. Osteosynthesis with a 'slanted-screw' plate for longer oblique fractures. 4. Intraoral anchor screw method. 5. Intraoral anchor screw method with intraoral 'slanted-screw' plate. The functional long-term results of conservatively and surgically treated mandibular condylar neck fractures were objectively documented by means of mechanical and electronic axiography. The functional long-term results of the condylar neck fractures treated surgically were significantly better than those treated conservatively.(ABSTRACT TRUNCATED AT 250 WORDS)

The caudal mandibular reconstruction plate: a radiographic and histologic study of an autopsy specimen.

During autopsy, a reconstructed partial mandibular resection was recovered and subjected to histological examination. The mandible had been reconstructed 12 weeks earlier with a caudal plate and autologous cancellous bone from the iliac crest. Undecalcified microsections showed that the plate was firmly anchored by screws on both sides and on one side there was bony union. However, most of the free transplant bone had undergone 'unreplaced resorption.' Nevertheless, this method offers advantages over the conventional method of seating the plate on the buccal aspect and has interesting potential for further development.

[Cephalometric analysis of Class III patients after surgery]. / Kephalometrische Analyse von Patienten aus dem progenen Formenkreis nach operativer Korrektur.

The University of Innsbruck, Department of Dentistry, analysed the cephalograms of 23 prognathic patients whose dysgnathia was corrected by an osteotomy of the mandible only. The obtained results were compared with an analysis of the respective models. Documentation was obtained prior to surgery, post-operatively and during follow-up examinations over a period of at least six years. Evaluation of the results focused on occlusion and the WITS-appraisal. Prior to surgery 21 patients presented with a macromandibulosis which in 50 percent of the cases was combined with a micro- or retromaxillosis. As a rule, there were also dento-alveolar compensations with retrusion of the lower front teeth and protrusion of the anterior maxillary teeth. Surgical results remained stable in 14 cases, three patients incurred a slight partial relapse while six patients had a significant relapse, though the original extend of the malocclusion with anterior crossbite reoccurred in two cases only. It was possible to prove the relationship between relapse and the existence of myofunctional disturbances. Consequently, safe long-term results may only be obtained by means of interdisciplinary planning and treatment.

[Long-term outcome of functional treatment for high double-sided condylar fractures]. / Spätfolgen einer funktionell behandelten, doppelseitigen hohen Kollumfraktur.

The conservative procedures widely used to treat fractures of the condylar neck seem to provide positive short-term benefits, but on long-term observation the results sometimes are not consistent with the early prognosis. We observed a patient (adult female) from the time of the accident for a period of 7 years. The patient suffered from a high double-sided fracture of the condylar neck combined with a multiple fracture in the frontal region of the mandible. The treatment plan was: 1. primary osteosynthesis of the fracture in the frontal-region, 2. intermaxillary fixation for 14 days, 3. functional post-operative treatment using monoblock. Up to the first month it looked like a normal recovery. However, after three months the expected recovery became questionable. After 7 years it was obvious that the recovery had reached its peak between 3 months and 1 year after the operation. The patient experienced chronic pain and progressive loss of function. Such results are unsatisfactory and new operative procedures using osteosynthesis have to be developed.

[Effects of myofunctional disorders on occlusion following surgery for mesial bite]. / Die Auswirkungen myofunktioneller Störungen auf die Okklusion mach Progenieoperationen.

In a follow-up study of 24 patients with mesial bite operated on at the Department of Oral and Maxillofacial Surgery, University of Innsbruck Medical School, relations between the outcome of sagittal splitting and myofunctional disorders were investigated. Orofacial imbalances of variable extent were found to be present in 16 of the patients followed up. Effects of myofunctional factors on occlusal position, occlusion, overbite and overjet are reviewed. Five patients with particularly severe myofunctional disorders underwent detailed logopedic and myofunctional evaluation. Results are presented. As myofunctional factors may profoundly affect the late results of surgery, it is concluded that patients with myofunctional disorders should undergo adjuvant myofunctional rehabilitation before or at least after surgery in order to prevent relapses.

[Experience with evacuable maxillary sinus endothesis for orbital and maxillary trauma]. / Erfahrungen mit der evakuierbaren anatomischen Kieferhöhlenedothese beim Orbita- und Oberkiefertrauma.

Results with a deflatable anatomically designed Endothesis for the reduction of fractures of the antral walls, especially the orbital floor. For the treatment of the fractures of the antral walls, especially of the extended fractures of the orbital floor, after repositioning through the maxillary sinus, treatment is necessary which supports the maxillary sinus and which, being effective in all directions, protects the ciliated epithelium and guaranties the drainage of secretions. After anatomical preexaminations three differently large hollow models for the maxillary sinus made of thin-walled silicon were developed. These "Endotheses" were implanted through a facial window into the maxillary sinus and are to be filled by way of nasal drain with contrast fluid. 51 patients were subjected to clinical, x-ray and, in selected cases, endoscopic post-control.

The mandibular condyles in the submentovertex projection--their morphology and topographical relationship to the foramina spinosa.

On conventional radiographs, the morphology and position of the condyles in an axial view are best seen in the submentovertex projection. The foramina spinosa, which are used by the middle meningeal arteries as passages and are clearly outlined in this view, serve as landmarks for a co-ordinate system that permits precise measurements of various angles and distances. One hundred and twenty-six submentovertex views were used for measuring the condyles. Results presented as means and standard deviations suggest condylar variables to be related to the function of the stomatognathic system. Practical applications include surgical, orthodontic or prosthetic manipulations of the mandible resulting in transverse or sagittal displacement of the condyles.