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Biomedical subjects

H Terheyden

Publications and source records attributed to H Terheyden.

32 records · Page 2Linked to original sources
PubMed2000

Acoustic rhinometry: validation by three-dimensionally reconstructed computer tomographic scans.

The aim of the present study was a validation of acoustic rhinometry (AR) by computed tomography (CT). Six healthy subjects were examined by CT and AR. The CT data were processed in a computer program (AutoCAD), and a virtual three-dimensional model of each nasal cavity was constructed. This model permitted an individual prediction of the center line of the sound wave propagation through the air volume of the nasal cavity with the cross-sectional areas oriented perpendicularly to this line. The area-distance curves derived from AR and CT were compared. Linear regression analysis revealed a reasonable agreement of AR and CT in the anterior nose below a mean of 6 cm distance from the nostrils [r = 0.839, P < 0.01, m = 1.123, b = -0.113 (AR = m x CT + b)]. The measuring accuracy using CT as gold standard revealed a mean error at the nasal valve of <0.01 cm(2) (4.52%) and at the nasal isthmus of 0.02 cm(2) (1. 87%). Beyond 6 cm, the correlation decreased (r = 0.419), and overestimation of the true area occurred (>100%). In conclusion, the measurements were reasonably accurate for diagnostic use up to the turbinate head region. Certain factors induce an overestimation of the true areas beyond this region. However, these factors are constant and reproducible in a single subject, and intraindividual comparative measurements are possible beyond the turbinate head region.

Acoustics↗
PubMed1999

Experimental computer-assisted alloplastic sandwich augmentation of the atrophic mandible.

PURPOSE: This study evaluated the effectiveness of a technique that combined computer-aided surgery with alloplastic augmentation and implant-borne prosthodontic rehabilitation of the atrophic mandible. MATERIALS AND METHODS: Computed tomographic (CT) data from an atrophic cadaver mandible were transferred to a computer-aided design (CAD) system that prepared an anterior sandwich osteotomy. The cranial segment was moved upward and backward to provide an ideal alveolar relationship, and the geometry of the intermediate space was used to design a titanium implant. Furthermore, a surgical template was derived for the osteotomies, and insertion of dental implants was planned to stabilize both the transposed bone and the intermediate implant on the bony base. An identical implant for augmentation was also fabricated from poly-D,L-lactide in a mold as a possible resorbable carrier for osteoinductive proteins. RESULTS: The experimental surgery was successfully performed with maximum precision on the dried mandible. The fabrication of an implant made out of poly-D,L-lactide for the same purpose was also possible. CONCLUSIONS: This preliminary experiment showed that it is possible to use CAD/computer-aided manufacturing (CAM) technology to prepare a prefabricated template and a corresponding titanium implant for mandibular augmentation with a high degree of exactness. Dental implants could be planned and integrated in this procedure as well. The fabrication of a mold using this method also provided the opportunity to give a complex shape to possible carriers of osteoinductive substances.

Alveolar Bone Loss↗
PubMed1999

The self adapting washer for lag screw fixation of mandibular fractures: finite element analysis and preclinical evaluation.

Besides rigid fixation, lag screws have distinct advantages compared with plates in appropriate indications in mandibular fractures. However, in current lag screw systems, the relatively small area of the screw head has to transfer the tensile force which can exceed 1000 N in the symphysis, to the thin cortical bone plate. Countersinking, which is obligatory in most systems, will weaken the cortical plate. Finite element analysis (FEA) revealed that load in this situation can exceed the normal tensile strength of metal and bone. Consequently, a new washer was constructed which both increased the supporting surface and did not require countersinking. The washer is self adapting (SAW) to the cortical plate in a defined position, forming a ball and socket joint with the screw head. Using the FEA model, a ten-fold reduction in load on bone and metal was observed with the new washer. In a miniature pig mandibular symphysis fracture model, the clinical applicability and a favourable histological reaction were demonstrated, compared with conventional lag screw designs.

Alloys↗
PubMed1999

Self-adapting washer system for lag screw fixation of mandibular fractures. Part II: In vitro mechanical characterization of 2.3 and 2.7 mm lag screw prototypes and in vivo removal torque after healing.

The aim of this study was to mechanically characterize self-tapping 2.3 and 2.7 mm titanium lag screw prototypes which are part of the newly developed 'self-adapting washer' maxillofacial lag screw osteosynthesis system. In vitro in a screw testing machine the insertion torque, maximum locking torque and axial force and the ultimate torsional strength were assessed. In vivo in six miniature pigs using a mandibular symphyseal fracture model, the removal torques after 3 and 6 months of healing were measured. Additionally the bone-metal contact (BMC) of the screws was assessed histometrically. The maximum insertion torque (0.185 Nm) was far below the mechanical limits of the screws (2.3 mm = 0.96 Nm, 2.7 mm = 1.6 Nm). A tightening of the 2.7 mm screw with an axial force of 1000 N and of the 2.3 mm screw with 500-550 N leaves a safety margin of approximately one-third on the ultimate torsional strength. Clinically these values permit the use of two 2.3 mm lag screws or one 2.7 mm lag screw in mandibular symphysis fractures since 1000 N tensile axial force are required in this indication. During screw removal after 6 months healing, torque levels close to the mechanical limits of the screws were recorded and screw failures were observed. This failure rate may have been due to the BMC of 49.8% which was in the range of titanium dental implants. Accordingly the screw heads were reinforced to prevent fractures.

Animals↗
PubMed1999

Sinus floor augmentation with simultaneous placement of dental implants using a combination of deproteinized bone xenografts and recombinant human osteogenic protein-1. A histometric study in miniature pigs.

Maxillary sinus floor augmentation with autogenous bone has become a widely accepted procedure in implant dentistry. The use of osteoconductive bone substitutes in this indication is controversial, since their use can lead to a prolonged healing time, inhomogenous ossification, foreign body reaction, migration of particles and low bone-implant contact (BIC). The purpose of this study was to examine whether the combination of an osteoinductive protein (recombinant human osteogenic protein-1 (rhOP-1 = bone morphogenetic protein-7) with natural bovine bone mineral (BioOss) would improve ossification and the bone-implant contact (BIC) in a sinus floor augmentation with simultaneous placement of implants. In this study, the maxillary sinus floors in 5 miniature pigs were augmented with 3 ml BioOss containing 420 micrograms rhOP-1 on the test side and 3 ml BioOss alone on the control side. At the time of augmentation a titanium implant (ITI) was inserted from a laterocaudal direction. After 6 months of healing the sites of augmentation were removed and examined in non-decalcified sections by microradiography, fluorescence microscopy of sequentially labelled specimens and by histometry. On both sides, significant amounts of newly-formed bone were observed. However, on the test sites, the percentage of BIC in the augmented area was 80.0% versus 38.6% on control sites. It can be concluded that the application of bone morphogenetic proteins caused a more rapid and enhanced osseointegration of simultaneously placed implants when compared to the bone substitute alone. Therefore recombinant human osteogenic protein-1 delivered by natural bone mineral has the potential to become a clinical alternative for autogenous bone grafts in sinus floor augmentation.

Animals↗
PubMed1999

Decisive diagnosis of infected mandibular osteoradionecrosis with a Tc-99m-labelled anti-granulocyte Fab'-fragment.

The accepted golden standard for detection of inflammatory bone disease is conventional three-phase bone scanning. Hyperperfusion, a high blood-pool activity and elevated bone metabolism are typical signs for an acute osteomyelitis. However, in case of subacute, chronic inflammation, neither elevated blood flow nor high blood-pool activity may be seen. This may cause difficulties in differentiating such cases from neoplastic or postoperative changes. This case report verifies the possible advantage of immunoscintigraphy with Tc-99m-labelled anti-granulocyte Fab'-fragments (LeukoScan) in a patient with infected mandibular osteoradionecrosis, who had equivocal clinical symptoms and questionable radiographic results. LeukoScan is shown to be more sensitive in case of subacute bone inflammation compared with three-phase bone scanning. However, acquisition of delayed images after 24 hours including SPECT is inevitable in case of negative scans during the first hours of investigation.

Aged↗
PubMed1999

Mandibular reconstruction in miniature pigs with prefabricated vascularized bone grafts using recombinant human osteogenic protein-1: a preliminary study.

A new technique of prefabrication of vascularized bone grafts in the latissimus dorsi muscle of miniature pigs, using recombinant human osteogenic protein-1 (rhOP-1) and xenogenic bone mineral as a carrier, is presented. The grafts were used to reconstruct a mandible using microsurgical anastomosis of the thoracodorsal vessels of the flap with a branch of the external carotid artery and the external jugular vein. The technique provided enough bone to reconstruct a mandible. The bone marrow stayed viable after transplantation, demonstrated by fluorescence microscopy and scintigraphy. Compared with identical defects of the contralateral side, which were treated with directly applied rhOP-1/bone mineral, a significantly better result was obtained with the prefabrication technique. The prefabrication technique may provide a means to treat irradiated patients with bone grafts produced by osteoinductive proteins and has a potential to become a clinical alternative to conventional vascularized bone grafts.

Animals↗
PubMed1997

Recombinant human osteogenic protein 1 in the rat mandibular augmentation model: differences in morphology of the newly formed bone are dependent on the type of carrier.

Recombinant human osteogenic protein 1 (rhOP1), also known as bone morphogenetic protein 7, was investigated in a newly developed experimental model, the rat lateral mandibular augmentation model. Algipore and Bio-Oss Block were applied as carrier materials. Extensive induction of newly formed bone was demonstrated on the test side containing rhOP1 and did not occur on the control side without rhOP1. The interstitial bone formation was limited to the augmented area and was not observed in the surrounding masseter muscle. The morphology of the newly formed bone differed in both carrier systems, which may be an important characteristic for the clinical indication of carrier systems in combination with bone morphogenetic proteins.

Animals↗
PubMed1996

[Position of the disc in collum mandibulae fractures--a magnetic resonance tomography study].

39 condylar mandibular fractures were examined by magnetic resonance imaging (MRI) within the first 12 hours after trauma prior to therapy. A new classification has been applied on the traumatic disc displacements. Three types A, B, C can be distinguished. Type A means no displacement in relation to the condylar fragment and the fossa. Type B means a displacement in the transversal plane exceeding the physiologic range of movement. Type C means displacement in the sagittal as well as in the transversal plane which exceeds the physiologic range of movement of the disc. The classified type of displacement could not be correlated exactly with dislocation and position of the bony fragments. Therefore the type of displacement cannot be predicted from conventional radiographs. Three cases of evident rupture of the disc in the biconcave zone could be shown by MRI. This kind of displacement has not been represented in the classification yet. In a presented case a rupture of the disc had been depicted preoperatively and the disc could be repaired via an preauricular approach. By means of MRI surgeons in future are able to pay more attention to the traumatology and reconstructive surgery of the temporomandibular disc.

Fracture Healing↗
PubMed1995

[Long-term follow-up of tooth transplantation from the functional and periodontal viewpoint].

The outcome of 81 of 99 patients being treated from 1980 to 1993 by transplantation of autologous teeth was investigated. The overall transplant survival rate was 91% after 1 year, 81% after 5 years and 70% after 9 years. The early loss of transplanted teeth was due to healing disorders. The long-term losses were due to caries and replacement resorption. Caries in tooth transplants has to be treated very early, because deep caries or deep drilling leads to an infection of the nutrient canals of the osteodentine. If the pulp chamber of a transplant is once obliterated by osteodentine, endodontic treatment can no longer be performed in many cases. The periodontal condition of the transplants did not differ from that of normal teeth. In 23% there was a decreased tooth mobility, caused by ankylosis of the transplant. 51% of the transplants showed occlusal disturbances but none of the patients had signs of occlusal traumatization of the teeth or of the temporomandibular joint. In comparison to success rates taken from the literature it is pointed out that tooth transplantation has a better long-term prognosis than endodontic treatment. Therefore, in young patients requiring root canal treatment, tooth transplantations should be considered.

Adolescent↗
PubMed1994

[Indication for and effectiveness of fluconazole in oral candidiasis].

From 1991 until 1993 we used fluconazole in 56 cases of oral candidosis which could not be managed by local therapy only. In seven cases there was no clinical improvement. A mycological cure was seen in 44 cases. In cases of oral candidosis which do not respond to local therapy fluconazole has proven a success especially in the follow up of patients with oral cancer and in cases of oral precancerous lesions with mycotic colonization.

Candidiasis, Oral↗
PubMed1991

[Problem of anesthetic failure].

Failure of local anesthetics is a common problem in dentistry. A sample of 210 dental practitioners was chosen at random and asked to evaluate the significance of anesthesia failure, comparing different injecting techniques. A standardized questionnaire, including a visual analogue scale for quantitative data, was distributed among the participants. The frequency of failure was indicated by most of the participants at 2% to 5% total. Considerably higher assessments were apparent in endodontics and abscess incisions. Rates of failure were said to be low in infraorbital nerve block, average in infiltration anesthesia and high in mandibular nerve block. These preliminary results indicate that a reliable anesthetic in dental treatment cannot always be provided.

Anesthesia, Dental↗
PubMedDate not supplied

Growth and transplantation of a custom vascularised bone graft in a man.

BACKGROUND: A major goal of research in bone transplantation is the ability to avoid creation of secondary bone defects. We aimed to repair an extended mandibular discontinuity defect by growth of a custom bone transplant inside the latissimus dorsi muscle of an adult male patient. METHODS: Three-dimensional computed tomography (CT) scanning and computer-aided design techniques were used to produce an ideal virtual replacement for the mandibular defect. These data were used to create a titanium mesh cage that was filled with bone mineral blocks and infiltrated with 7 mg recombinant human bone morphogenetic protein 7 and 20 mL of the patient's bone marrow. Thus prepared, the transplant was implanted into the latissimus dorsi muscle and 7 weeks later transplanted as a free bone-muscle flap to repair the mandibular defect. FINDINGS: In-vivo skeletal scintigraphy showed bone remodelling and mineralisation inside the mandibular transplant both before and after transplantation. CT provided radiological evidence of new bone formation. Postoperatively, the patient had an improved degree of mastication and was satisfied with the aesthetic outcome of the procedure. INTERPRETATION: Heterotopic bone induction to form a mandibular replacement inside the latissimus dorsi muscle in a human being is possible. This technique allows for a lower operative burden compared with conventional techniques by avoiding creation of a secondary bone defect. It also provides a good three-dimensional outcome.

Activin Receptors, Type I↗