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Biomedical subjects

H A Merten

Publications and source records attributed to H A Merten.

At least 37 records · Page 2Linked to original sources
PubMed2000

Introduction of "vario plates" for retention after mandibular distraction osteogenesis.

This report introduces a new removable orthodontic appliance called "vario plates" for retention following distraction osteogenesis of the mandible. The "vario plates" consist of removable orthodontic appliances in the maxilla and the mandible. These are fabricated out of self-curing resin with typical wire elements. They are connected with telescoping maxillomandibular guidance rods, which have a smoothly variable length, from the maxillary molar region to the mandibular premolar region on each side. The telescope on both sides is adjustable in this length by means of a protrusion nut. Thus, it is possible to move the mandible forward an exactly controlled amount. The "vario plates" are in function for 24 hours a day in the patient for the first 6 months after mandibular distraction osteogenesis and subsequently only at night. The application of the plates is demonstrated in a patient with Goldenhar syndrome. Application of "vario plates" after distraction osteogenesis makes it possible to hold the mandible in a stable position. The combination of maxillofacial surgery with distraction osteogenesis and orthodontic treatment and retention leads to an improvement in therapy of patients with severe dentofacial anomalies.

Adult↗
PubMed1999

[Roentgenologic, endoscopic and ultrasound evaluation of the maxillary sinus after sinus lift with simultaneous endosseous implantation].

X-ray, ultrasound, and endoscopy were used in follow-up after sinus floor augmentation. In 23 out of 63 patients, healing was uneventful. Water's view revealed opacification of the maxillary sinus 1 week postoperatively in 40 patients, and opacification persisted in four patients. In these patients, endoscopy showed inflammatory reactions of the mucosa. Ultrasound proved to be a valuable tool in follow-up. Sinusitis occurred in three patients and was due to migration of bone chips in two of these. Out of 132 inserted implants, eight were lost during the healing period and three more during the loading period.

Alveolar Bone Loss↗
PubMed1999

[Clinical studies on the pathophysiology of odontogenic abscesses].

In 26 patients with abscesses in the maxillofacial area, the electrolyte concentrations, pH and osmotic and hydrostatic pressures of the pus fluid were measured and calculated. The main cations identified were sodium (134 +/- 38 mmol/l) and potassium (37 +/- 16 mmol/l) and as anions chloride (183 +/- 46 mmol/l) and bicarbonate (10 +/- 4 mmol/l). The pH value of the pus liquid was 6.164 +/- 0.233. The calculated mean osmotic pressure of the pus liquid was 7910 +/- 1455 mm Hg, whereas the measured physical pressure inside the abscess was 49 +/- 13 mm Hg. Both pressure types show time-dependent pressure curves. With time, the real pressure inside the abscess cavity increases, whereas the osmotic pressure decreases. There was no relationship between the two pressure types and the different species of microorganisms responsible for the inflammation. The results of the study reveal that abscesses can be regarded as osmotically active systems, and the mechanism by which the abscess is formed might be as follows. After penetration of virulent microorganisms into the tissue space, the area of acute inflammation is walled off by the collection of inflammatory cells. Destruction of tissue by products of the polymorphonuclear leucozytes takes place and results in liquefactive necrosis and a hypertonic abscess cavity. The inwards-directed flow of tissue fluids into the cavity via the abscess membrane causes volume expansion and generates pressure, two facts that can explain the swelling dynamics and typical symptoms of abscesses in the maxillofacial area.

Humans↗
PubMed1999

[Diagnostic and therapeutic concepts of canine fossa abscess. Evaluation of a multicenter study of 55 German-speaking departments of oromaxillofacial surgery].

A possible complication of fossa canina infections is reactive thrombosis of the vena angularis, which can lead to cavernous sinus phlebothrombosis. According to the literature there are different opinions about the treatment protocol of fossa canina abscesses. Therefore a multicentre study was undertaken in which 55 departments of oral surgery were interviewed using a standardized questionnaire about their procedures. The basis of diagnosis consists of clinical examination (100%), antibiogram (77.1%) and radiography (97.1%). A total of 28.6% use additional imaging procedures. Sonography is used by 20.0% and is found to be helpful in the diagnosis of vena angularis thrombosis. The painful palpation of the medial angle of the eye is of major diagnostic importance (100%) although anatomic variations of the vena angularis have to be considered. Extraoral incisions are not used in most cases (25.7% in exceptional cases) as well as ligations of the vena angularis in case of thrombosis (8.6% in exceptional cases). There is an agreement in the use of antibiotics (elective administration in 14.3%, obligatory administration in 85.7%); 77.1% don't use heparin to treat thrombosis of the vena angularis. In heparin therapy risks such as bleeding complications and thrombocytopenia have to be considered.

Cavernous Sinus Thrombosis↗
PubMed1999

[Biodegradable miniplates (lactosorb) in cranio-osteoplasty--experimental results with the rapidly maturing, juvenile minipig].

As a passive intracranial transmission (PIT- effect) has been described for metallic osteosyntheses materials in the infant growing skull. Thereby the use of resorbable plates and screws might be an alernative fixation device in infant craniofacial surgery. For evaluating the biological behaviour, craniotomies were performed in the frontoorbital region of four infant minipigs, six weeks of age and 6.1 kg of weight. After turning and orthotopical repositioning the full thickness bone graft were fixed with resorbable plates and screws made of LactoSorb on the left side after epiperiosteal, on the right side after subperiosteal preparation. The animals were sacrificed after 3, 6, 9 and 18 months. Histologically, a PIT- effect was detected similar to metallic microplates and screws being significant diminished after epiperiosteal preparation and plate positioning. The biodegradation was not affected by intraosseous translocation. Even in case of intrasinuidal transmission no inflammatory reactions werde observed. No contraindications for the clinical use of this specific PLLA-PGA copolymer could be found when implanted in the rapidly growing craniofacial bone surfaces.

Animals↗
PubMed1999

[Animal experiments on the frontal sinus development after craniofacial surgery on the frontal bone in Göttingen miniature pigs].

According to the literature, the development of the frontal sinus is a result of the active immigration of cells from the ethmoidal complex into the os frontale. This migration theory is in contrast to the results in patients with Apert's syndrome. When front-orbital advancement at the age of a few months is performed in these patients--at a time when the frontal suture is not yet closed--a sinus developed despite the distance between nasal root and os frontale, being up to 2 cm. In order to investigate the development of the frontal sinus, an animal study in 12 juvenile Goettingen minipigs (age 5-6 weeks) with histologically pronen un-developed frontal sinus was performed. To exclude the emigration of ethmoidal complex cells into the frontale bone an orthotopical transposition of the frontale bone into the os occipitale was performed. Histologically the development of a frontal sinus in the frontal bone was excluded before transplantation. The macro- and microscopic comparison with a control group revealed that in the orthotopical transplants in the os occipitale an epithelium-lined sinus developed beginning from the 35th week. Based on our histomorphological results, a development scheme for the genesis of the sinus frontalis and a model is drawn.

Animals↗
PubMed1999

The resorbable miniplate system Lactosorb in a growing cranio-osteoplasty animal model.

In the surgical treatment of craniosynostosis and craniofacial dysostosis in the growing child, passive intraosseous translocation (PIT effect) with intracranial displacement of metal plates and screws may be a problem. In an animal experiment, a possible PIT effect using resorbable PLA/PGA miniplates (Lactosorb, W. Lorenz, FL, USA) following cranio-osteoplasty were investigated in four young Göttingen minipigs. In addition to the mechanical properties, the processes of degradation and of sub- vs supraperiosteal application of the miniplates were evaluated. During degradation the resorbable PLA/PGA miniplates performed like metal plates as they also displayed passive intraosseous translocation in the growing animal model. However, in the experimental PLA/PGA miniplating the internal calvarial bone was not affected. Degradation took 12-18 months and was not delayed by bony incorporation. Mechanical properties proved to be sufficient in craniofacial surgery. Supraperiosteal plating delayed the PIT effect during the first 3 months after surgery. In the growing skull resorbable plates seem to be a promising therapeutic approach. However, prior to a general recommendation results of long-term clinical studies have to be evaluated.

Absorbable Implants↗
PubMed1999

What is the best possible design of temporary anterior mandibular osteotomy? A histomorphological animal study.

When squamous cell carcinomas in the oral cavity have advanced to the size of T2 to T3 or when they start to encroach on the middle, occasionally it is necessary to divide the mandible at the parasymphysis and swing the hemimandible away from the midline for intraoral exposure of tumor resection. The osteotomy is usually performed in either a straight vertical cut, in a step-cut fashion, or in a dove-tail geometric configuration. The design of the geometric pattern of the osteotomy determines whether or not the postoperative period is prolonged. The authors analyzed the best possible design of temporary anterior mandibular osteotomy. In an animal study of 12 Goettingen minipigs (GMPs) the authors investigated the best possible design of geometric pattern of mandibular osteotomy and the fragment healing process. Their primary interest was directed at the histomorphological bone-healing process after straight vertical bone cut, step-cut fashion, and dove-tail osteotomy of the mandible, and rigid fixation with an osteosynthesis plate. From this study it can be concluded that the dove-tail osteotomy of the mandible is the best possible design of temporary anterior mandibular osteotomy in preventing pseudoarthrosis due to the mainly primary bone contact and gap healing process.

Animals↗
PubMed1999

Single lag screw fixation for malar fracture (type B) fixation: reduction of hardware treatment costs.

In an attempt to define the most simple and inexpensive method of achieving postreduction stability in zygomatic fractures, the authors compared two different methods of internal rigid fixation of the frontozygomatic suture line in one group with miniplates and in another group with Panfix lag screws. The randomized study protocol consisted of a control group of 20 patients and 40 patients with laterally displaced body fractures of the zygoma. Statistical differences were not seen between the control subjects and the patients who required open reduction and internal fixation either with one osteosynthesis plate at the frontozygomatic suture line or a lag screw osteosynthesis. Lag screw fixation in malar type B fractures could lower hardware treatment costs and is an alternative method that provides sufficient stability in indicated patients.

Bone Plates↗
PubMed1998

Degradation of and intraosseous reactions to biodegradable poly-L-lactide screws: a study in minipigs.

In 20 minipigs an osteotomy of the lumbar spine was done at L3 and fixed with resorbable implants (plate and screws) made of poly-L-lactide. For 24 months postoperatively the cancellous bone surrounding the screws was examined histologically. Specimens from the body of lumbar spine L2 and L4, carrying the screws, were fixed in a series of ethanol immersions and then embedded in methylmethacrylate. Longitudinal and transverse sections were cut with a microtome at 4-5 microns and stained by the Masson-Goldner and Giemsa method for light microscopy. Our investigation confirmed a long degradation period of poly-L-lactide and little inflammatory reaction within the bone during the whole period of observation. For poly-L-lactide the degradation time exceeded the longest follow-up time in this study, 24 months. Polymorphonuclear granulocytes and mononuclear round cells were scarce in all follow-up groups. Osteolytic changes or the emergence of seroma was not observed. Textured bone was evident early close to a thin fibrous capsule surrounding the screws. The remodelling of the bone close to the screws ensues by the formation of osteons.

Absorbable Implants↗
PubMed1998

Significance of the periosteum in onlay craniofacial augmentation.

In the quest for bioinert, easily applicable, and individually adaptable alloplastic materials, hydroxyapatite (HA) has gained a new application in onlay craniofacial augmentation. On the basis of clinical and experimental proof that intraosseous translocation of HA occurs after HA onlay augmentation, we conducted an animal study on 16 adult Goettingen minipigs in which HA, as blocks or granular, was implanted for a maximum time of 72 weeks. Our aim was to study the difference between periosteal and subperiosteal onlay augmentation of two different HA forms by comparing HA-bone interface on the intact frontal bone treated with a block form of HA versus granular HA, with special emphasis on the periosteum. Within a few weeks after subperiosteal augmentation, subimplant changes in the grafted bone became evident to such an extent that within 72 weeks the granules migrated into the frontal sinus. In contrast, in epiperiosteal HA onlay augmentation, no intraosseous migration of HA particles was observed, regardless of the type of HA implants. The HA particles were integrated within the connective tissue, and the connective tissue infiltrated the interstitial spaces. For the most part, the location and the shape of the implant remained stable. The periosteum assumed the function of a limiting membrane. We recommend that epiperiosteal onlay augmentation with HA be performed only if previous studies have proven that shape and location are stable. The periosteum should be preserved because it functions as a limiting membrane, retaining the HA and preventing it from migrating into the subimplant bone.

Animals↗
PubMed1998

Avoidance of implicit hazards: the realignment of maxillary and mandibular arches in comminuted and facial fractures.

The authors introduce an attempt to elevate the problem of proper realignment of the maxillary and mandibular arches to achieve an exact transversal width of the lower third of the face with an index of the sum of the maxillary and mandibular central incisors, together with a new Artex-Callotte System (Karl Storz GmbH, Tuttlingen, Germany). This allows individual and anatomically correct restoration of the dental arches. This is especially helpful if either a large number of teeth or portions of dental alveolar processes have been lost in comminuted panfacial fractures. In addition, a sequential, step-management concept of comminuted panfacial fractures is described and illustrated. The goals of treatment with this method are to reestablish the midfacial height and projection and the occlusion, and reestablish the integrity of the nose, the orbit, and the transversal dimension of the lower jaw. This simple method is not yet well appreciated.

Adult↗
PubMed1997

[Multi-point contact (MPC) osteosynthesis plate. 1: Animal experiment histomorphologic studies in the Göttingen minipig].

Based on the results of clinical and animal studies as reported in the literature, the subimplant cortex becomes porous underneath conventional osteosynthesis plates with a flat surface. To solve this problem, we developed an implantable plate which creates multiple contact points between plate and bone, called the multi-point contact or MPC plate. In an experimental animal study conducted on 16 Göttingen minipigs we investigated the bone reaction beneath 2 different types of osteosynthesis plates: the conventional type with a flat interface versus the multi-point contact type. Both epiperiostal and subperiostal plating was performed on pig's intact tibiae. After an implantation period of 16 weeks, the results were documented and compared. It was shown that the osteal remodeling activity of the cortical bone adjacent to the plate increased under both plates up to the twelfth week, but declined towards the end of the study period. Compared to the MPC plate, a conspicuous remodeling front accompanied by porosis of the cortical bone adjacent to the plate was found underneath the conventional osteosynthesis plates with a flat surface-to-bone interface. The different subimplant reactions between the 2 plates can be best explained by the fact that intracortical implant-induced viscoelastic osteocyte diffusion is better under the MPC plate, whereas it is impaired under the conventional flat plate.

Animals↗
PubMed1997

Hemifacial microsomia: extraoral appliance for the early treatment of an infant. Literature review and case report.

In this report a description of the different features of hemifacial microsomia is given and a new way of early treatment of concomitant respiratory problems is presented. An extraoral appliance was developed for the treatment of an infant affected with this syndrome. The purpose was to temporarily minimize the child's repeated respiratory disturbances, which were probably caused by glossoptosis, until an autologous costochondral graft in the mandibular ramus could be performed. An improvement of respiration, of facial asymmetry and even a stimulation of mandibular growth was observed. It is claimed that the use of this appliance can help to avoid tracheotomy in many severe cases of uni- or bilateral facial microsomia with glossoptosis and apnea. This treatment should be considered as temporary until the general condition of the patient has improved and grafting is possible.

Combined Modality Therapy↗
PubMed1997

Scanning electron microscopic study of primary fracture healing.

Scanning electron microscopy was used to study primary bone healing. This technique, essential for a three-dimensional description, has provided excellent visualization and revealed new aspects of the micromorphology of primary bone healing. Calcifying collagen bundles were responsible for the first mechanical stability, bone healing took place later in fracture vaults generated by compressed fracture fragments which were partially nonvital. A direct bridging of the fracture fragments by sprouting osteons was not observed.

Animals↗