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Biomedical subjects

J Beumer

Publications and source records attributed to J Beumer.

At least 19 recordsLinked to original sources
PubMed2005

Abutment load transfer by removable partial denture obturator frameworks in different acquired maxillary defects.

STATEMENT OF PROBLEM: Excessive stress on abutment teeth adjacent to a maxillary resection defect during loading of partial denture obturator frameworks may shorten the life of the teeth. PURPOSE: The aim of this study was to photoelastically compare the forces exerted on the supporting structures of abutment teeth in 3 differently sized surgical resections with removable partial denture designs used to restore such maxillectomy defects. MATERIAL AND METHODS: Composite photoelastic models were constructed of a human maxilla that had undergone each of 3 maxillectomies: partial, radical, and radical involving the contralateral premaxilla. The abutment teeth included all remaining anterior teeth, the first premolar, and second molar, except the radical maxillectomy, which included the contralateral premaxilla where all remaining teeth were used as abutment teeth. All abutment teeth were restored with complete metal crowns, and removable partial denture frameworks were fabricated. Loading zones were selected according to the resection, and a 10-lb load was applied at each load point. The resulting stresses were observed and recorded photographically in a circular polariscope. The 2 teeth adjacent to the resection were then splinted, and the loading regimens were repeated. RESULTS: Without splinting, loads closer to the defect produced lingual tipping of the teeth adjacent to the resection and a mesial tipping tendency of the second molar. The tipping effects were greatest in the model with the largest resection. Splinting reduced tipping of the teeth adjacent to the resection and produced more uniform stress around these 2 abutment tooth roots for all of the models. CONCLUSION: The results of this in vitro study suggest that splinting the 2 teeth adjacent to a resection defect improves stress distribution around the roots during loading. This could increase the clinical life of the abutment teeth.

Birefringence↗
PubMed1999

Restoration of partially edentulous patients using customized implant abutments.

The ideal placement of implants is not always possible in partially edentulous patients. The diverse and unique implant positions that occur in clinical practice may be difficult or impossible to restore through the use of conventional abutments. Customized abutments permit the fabrication of aesthetic restorations that correct deficiencies in implant angulation, alignment, and position. These abutments also enhance the soft tissue emergence profile of the restorations and allow the prosthetic margins to be properly positioned in all dimensions. Additional benefits include ease of treatment delivery and comparative expense.

Dental Abutments↗
PubMed1998

Restoration of irradiated patients using osseointegrated implants: current perspectives.

STATEMENT OF PROBLEM: The success rates of osseointegrated implants used to restore patients who were irradiated for head and neck tumors are influenced by radiation-induced changes in the hard and soft tissues. PURPOSE: This article examined, by review of the literature, current perspectives on the restoration of irradiated patients using osseointegrated implants. RESULTS: In published reports that investigated both intraoral and extraoral applications, irradiation decreased implant success rates and the amount of reduction was dependent on the location within the craniofacial skeleton. The limited number of implants and patients in these studies precludes definitive conclusions regarding the efficacy of placing implants into irradiated tissues. The implants placed into the irradiated anterior mandible have demonstrated an acceptable implant success rate of 94% to 100% with a minimal risk of osteoradionecrosis. The efficacy of implants in the posterior mandible has not been examined. Implant success rates ranged from 69% to 95% in the irradiated maxilla for intraoral applications. Extraoral applications demonstrated excellent implant success rates in the temporal bone (91% to 100%). The rates in the anterior nasal floor have varied from 50% to 100%. The implant success rates in the frontal bone decreased as the length of the studies increased (96% to 33%). The long-term efficacy of implants in the irradiated frontal bone is poor.

Animals↗
PubMed1998

Implants in the partially edentulous patient: restorative considerations.

Restorative considerations are critical to the long-term success of fixed implant-supported prostheses, especially in the posterior quadrants of the partially edentulous patient. The parafunctional habit of bruxism must be identified and addressed. The restoration should dictate implant placement. Control of forces directed upon the prosthesis and implants is critical to long-term success. Anatomic limitations to implant placement and surgical procedures to correct these deficiencies must be considered for their impact on the prosthetic restoration. Nonaxial forces or bending moments should be minimized by the use of an adequate number, position and alignment of implants; by control of the occlusion; and by design of the prosthesis. The patient must understand the risks, limitations, costs and time commitments of implant restorations prior to treatment.

Dental Implantation, Endosseous↗
PubMed1997

An implant-supported fixed-removable prosthesis with a milled tissue bar and Hader clip retention as a restorative option for the edentulous maxilla.

Restoration of the edentulous maxilla with implant retained and supported prosthesis is challenging because of inherent anatomic limitations present after the loss of teeth. A fixed-removable prosthesis is one treatment choice for restoration of the edentulous maxilla with implants. This prosthesis meets the requirements for esthetics, phonetics, comfort, and hygiene, as well as favorable biomechanical stress distribution to the implants. This article presents a procedure for fabrication of a fixed-removable prosthesis with a precision milled bar, Hader clip attachments, and a superstructure prosthesis. The criteria for patient selection and the advantages and disadvantages of this prosthesis are discussed.

Centric Relation↗
PubMed1997

Clinical evaluation of implants retaining edentulous maxillary obturator prostheses.

PURPOSE: Fabricating a maxillary obturator can be challenging. Placement of implants can have a dramatic effect on the stability and retention of the prosthesis in the edentulous maxillectomy patient. This article provides clinical retrospective analysis of osseointegrated implants used to retain maxillary obturators. MATERIAL AND METHODS: Patient charts and radiographs were reviewed to determine implant status, bone loss patterns, and implant survival rates. Twenty-six patients were included with 102 implants placed, from which there were 19 intact withdrawals (implants lost because of recurrent disease or patient death), five implants with unknown status, 24 implant failures, and 54 functional implants. RESULTS: The overall survival rate for implants in this patient population was 69.2%. The percent implant survival rate was 63.6% for the irradiated group (67.0% before radiation, 50.0% after radiation) and 82.6% for the nonirradiated group. Implants located in anterior sites demonstrated statistically significant differences in annual bone height changes compared with posterior sites. CONCLUSIONS: The majority of implant failures (18 of 24) occurred either at stage II surgery or before loading. Implants placed during tumor resection, implants placed within the maxillectomy defects, and implants receiving postoperative radiation demonstrated low survival rates.

Adult↗
PubMed1997

Reconstructed mandibular defects: fibula free flaps and osseointegrated implants.

Twenty patients with microvascular fibula flap reconstruction of oromandibular defects were selected for implant-retained prosthodontic rehabilitation. A total of 71 osseointegrated implants were placed within the grafted fibulas. Four patients had immediate implant placement at the time of their reconstructive surgery, and the remaining 16 patients had implants placed secondarily. One patient received postoperative radiation therapy (5910 cGy) 6 weeks following reconstruction and immediate implant placement. No implants were placed in previously irradiated flaps. A minimum 6-month period of osseointegration was allowed prior to second stage surgery. Fifty-four of the 71 implants were uncovered; 46 of these implants were functional, and 3 were in the process of being restored. Among the 54 implants (15 patients) that were uncovered, only 1 failed to osseointegrate, 2 implants were reburied, and 2 were removed. The follow-up period ranged from 1 to 49 months since second stage surgery. Although a number of prosthodontic designs were used, 11 of the 15 patients were restored with removable overlay prostheses. Only those implants exposed to postoperative radiation demonstrated radiographic bone loss following functional loading.

Adult↗
PubMed1997

Implants in the partially edentulous patient: restorative considerations.

Restorative considerations are critical to the long-term success of fixed implant-supported prostheses, especially in the posterior quadrants of the partially edentulous patient. The parafunctional habit of bruxism must be identified and addressed. The restoration should dictate implant placement. Control of forces directed upon the prosthesis and implants is critical to long-term success. Anatomic limitations to implant placement and surgical procedures to correct these deficiencies must be considered for their impact on the prosthetic restoration. Nonaxial forces or bending moments should be minimized by the use of an adequate number, position and alignment of implants; by control of the occlusion; and by design of the prosthesis. The patient must understand the risks, limitations, costs and time commitments of implant restorations prior to treatment.

Bicuspid↗
PubMed1994

Restoration of oral function after maxillectomy with osseous integrated implant retained maxillary obturators.

This study assesses the success rate of osseous integrated implantation in assisting the prosthetic obturation of maxillectomy defects. Twenty-three patients received a total of 85 osseous integrated implants used for retaining maxillary obturators between 1985 and 1993. Defects include 13 radical maxillectomies, 5 premaxillary resections, 4 subtotal maxillectomies, and 1 soft-palate resection. Thirteen patients (50 implants) received a radiation dose ranging from 5,040 to 7,940 cGy. Implants can be placed at the time of ablation or subsequently. Efforts were made to spare uninvolved segments of the maxilla, especially premaxillary segments and tuberosities, at the time of ablation. Following a 6-month period of integration, implants were uncovered and utilized in prosthetic rehabilitation. Specific implant sites reveal variable success rates, with the anterior maxilla being 86% successful compared with the posterior maxilla being 57% successful. Radiation reduces the success rate from 80% to 55%, although it does not eliminate a patient from being a candidate for implantation. Prosthetic rehabilitation of large maxillary defects can be greatly facilitated with the use of osseous integrated implants in the remaining midfacial skeleton.

Alveolar Bone Loss↗
PubMed1994

Surgical planning using three-dimensional imaging and computer modeling.

The acquisition, processing, and use of three-dimensional (3D) imaging provide new insights into normal and abnormal craniofacial anatomy. In this article, characteristics of CT and MRI scanning are reviewed along with the methods used to delineate tissues and produce 3D patient displays, including contouring, shaded surface, and volumetric processing. The use of 3D model fabrication for surgical planning is discussed with examples of the production of a custom CT-based auricle model and the use of rapid prototyping technology to create models for custom alloplastic implant surgery. The review concludes with some speculation about the future of 3D medical imaging as it will influence surgical training and practice over the coming decades.

Diagnostic Imaging↗
PubMed1993

Surgical considerations for endosseous implants in the craniofacial region: a 3-year report.

From 1987 to 1990, 28 patients were treated with titanium implants (Brånemark flange fixtures) in the craniofacial area for the support of craniofacial prosthesis or anchorage of bone-conduction hearing aids in the Orofacial Implant Center at the University of California, Los Angeles (UCLA). A total of 88 implants were placed, of which 22 were placed in previously irradiated areas. Twenty-three of the implants were placed in the orbital area, 37 in the mastoid area, 20 in the nasal area, and eight in various other craniofacial regions. Seven implants were lost in four different patients. The proper location and positioning of implants in specific areas of the craniofacial regions, as well as soft-tissue complications and management, are discussed.

Adolescent↗
PubMed1992

Histomorphometry of bone apposition around three types of endosseous dental implants.

Three different types of commercially available dental implants (Nobelpharma, IMZ, and Integral) were implanted in the edentulous mandibles of seven adult mongrel dogs. Twenty-one implants were harvested with block sections after 12 weeks and embedded in polymethyl methacrylate resin. Undecalcified sections were prepared with the sectioning-grinding technique. The percentage of bone contacting the implant surface was measured with a self-designed histomorphometry method using a millimeter grid in a stereomicroscope. The results demonstrated a significantly higher percentage of bone along the hydroxyapatite-coated implant than that seen with the titanium-surfaced implant types.

Alveolar Process↗
PubMed1990

Gravity-induced stresses by an obturator prosthesis.

Recontruction after surgical resection of tumors of the maxillae and paranasal sinuses is difficult. In addition to the intermittent forces encountered during function, the prosthesis is subjected to the constant force of gravity. This investigation photoelastically studies the gravity-induced stresses transmitted to the remaining oral structures by various obturator prosthesis framework designs. Frameworks which used I-bar and circumferential retainers with buccal retention were most severe, while the swinglock and light wire retainers were intermediate in generated stress.

Bite Force↗