The International Journal of Oral & Maxillofacial Implants, 05/1993

Eleven patients who had undergone surgical treatment for head and neck cancer and had titanium implants placed for skin-penetrating prostheses were irradiated postimplantation. The absorbed doses of irradiation to the implant region varied between 50 and 80 Gy. The time interval between implant surgery and irradiation varied from 4 to 60 months. Of 32 fixtures placed, 2 were removed as part of extended tumor surgery and 2 were lost in conjunction with induced chemotherapy. Five of the patients showed skin dehiscences around 9 implants after completed irradiation. Osteoradionecrosis developed in three of the patients after radiotherapy. If irradiation is to be performed in areas where titanium implants have been placed, it is recommended that all prostheses, frameworks, and abutments be removed before irradiation; the fixtures should be allowed to remain intact but should be covered with skin or mucosa. Keywords: backscatter effects, irradiation, osseointegration, prosthetic reconstruction, titanium implants

Titanium screw taps and titanium fixtures were investigated by SEM before and after experimental use. Peri-implant bone surfaces were examined immediately after surgery and 5 months after implantation by SEM using the SE mode, backscattered electron imaging, and EDX analysis to detect titanium contamination of the bone specimens. The Ti content of the livers, kidneys, and lungs of six Göttingen minipigs, which had received two screw implants each, was determined using flameless atomic absorption spectroscopy and compared to a control group with no implants. Results showed that Ti particles were abraded and deposited on the bone surface during the preparation of implant beds. Five months after placement, particles were no longer observed on the bone surface next to the implants. Determination of the Ti concentration of the inner organs showed that the lungs contained the highest amount of titanium. The Ti content of the kidneys and livers was much lower. All values differed significantly from those of the control group (P .01). Keywords: SEM analysis, surface changes, titanium implants

An engineering model of maxillary single anterior implants was developed to calculate the force-moment systems resulting from occlusal contacts. Analysis of a clinical example showed that flattening the incisal guidance and/or placing the implant in a more upright position reduced the moment and the labial component of the force but increased the intrusive component. The calculations are applicable to the design of implants and may help in the long-term evaluation of clinical success. Keywords: biomechanics, dental implants, implant failure, prosthodontics

A method for restoring the posterior portion of the maxilla with a simultaneous composite alloplastic sinus lift graft and placement of press-fit implants is presented. Sinus grafting is needed because of minimal remaining alveolar bone. The composite graft material uses a combination of demineralized freeze-dried cortical bone and Interpore 200 hydroxyapatite. Since 1987, 45 sinus grafts with simultaneous placement of 111 root-form implants have been performed for 27 patients. None of the 76 restored implants have been lost. Complications were encountered in 2 patients (4 sinuses) who were heavy smokers. Antibiotics were administered, symptoms subsided, and the implants integrated. Keywords: composite graft material, demineralized freeze-dried cortical bone, hydroxyapatite, root-form implants, simultaneous graft and implant placement, sinus lift graft

The composition and thickness of the oxide formed on commercially pure titanium disks were analyzed after the disks were subjected to one of four surface treatments: (1) cleaning with the initial Brånemark regimen, (2) Brånemark regimen and autoclaving, (3) Brånemark regimen and radiofrequency glow discharge (RFGD) treatment for 5 minutes, and (4) Brånemark regimen and RFGD treatment followed by storage for 30 days. Electron spectroscopy for chemical analysis showed titanium dioxide to be the prominent oxide; no significant differences in the thickness of the oxide layers were found. Keywords: oxide, radiofrequency glow discharge, sterilization, surfaces, titanium

This paper reports histologic and histomorphometric results concerning bone healing around 13 pure titanium screw-shaped root-form implants that were placed in three mongrel dogs immediately after extraction of maxillary and mandibular premolars. Osseous healing around the implants showed a great deal of variability depending on the arch in which the implant was placed and on the original anatomy of the implant site. Implants placed in the mandible showed the greatest amount of bone apposition, with a mean total bone of 60.3%. Implants placed in the maxilla showed less bone and greater variability both visually and statistically, with a mean total bone of 46.3%. The values obtained for bone after 5 months of healing of the control sites were consistent with the values obtained for bone approximating the implants after the same time period. This was true for both arches. It was impossible to visually or statistically discriminate between sham surgical control sites and routine control sites or between implant sites and either of the control sites. Implant surgical procedures and implant placement seemed to have little effect on the tabulated values beyond tooth extraction alone. This research suggests that immediate implants have the potential for developing good bone apposition depending on the area of implantation. Keywords: animal, bone, dog, endosseous implant, extraction, healing, histology, histomorphometry, morphometry

This study was conducted to determine the effect of abutment angulation on the stress field near a specific dental implant. Photoelastic resin was cast directly to five 3.8 × 10-mm Steri-Oss implants in 50 × 70 × 13-mm molds. One additional model was fabricated with a strain gauge rosette embedded in the resin to allow precise determination of normal stresses. Zero-degree, 15-degree, and 20-degree abutments were assembled on each of the six implants, subjected to 178 N load, and viewed with a circular polariscope. Observed fringe patterns were photographed for all six models, and strain indicator readings were recorded for the strain gauge model. Numerical data from the strain gauges produced results that agreed with the visual interpretation of the isochromatic fringes. Strain gauge data were also used to calculate the principal stresses and strains. Although a statistically significant increase in stress and strain was found for each increase in abutment angulation, all three abutments produced principal strains that appear to be within the physiologic zone for bone. All values for stress and strain were determined at the location of the rosette, approximately 4 mm from the implant. Higher stresses and strains exist in regions closer to the fixture. Keywords: angled implant abutments, photoelastic resin, strain gauges, stress analysis

A passive threshold determination was carried out on 31 patients subdivided into four test groups according to different prosthesis types supported by osseointegrated implants. They were compared to a control group of 10 patients with nonrestored natural test teeth. Forces were generated by a solenoid-driven stimulating device, which was placed in contact with the implant or tooth prior to the actual force rise to avoid impact forces. The findings indicate that the threshold level of implants is 50 times higher than that of natural teeth when tapping is avoided, which might otherwise trigger distant receptors. Bone deformation triggering the periosteal mechanoreceptors is the most logical explanation for the sensation reported. Keywords: oral implants, perception, periodontal receptors, tactile threshold

The field of dental implantology has expanded treatment options available to patients with incomplete dentitions. With the use of regenerative techniques and periodontal plastic surgery procedures, the periodontium and its surrounding tissues can be modified in an attempt to re-create normal function and esthetics. This article describes a combination of surgical procedures, including the placement of endosseous dental implants, guided tissue regeneration, and periodontal plastic surgery, used to restore function and esthetics in the maxillary anterior region. Keywords: anterior maxilla, endosseous implants, esthetics, periodontal surgery

When five to six implants are used in a fixed reconstruction, it is desirable to place the most distal implant as close to the mental nerve as possible. This allows the cantilever of the fixed prosthesis to be extended posteriorly as much as is biomechanically feasible. Forty-seven mental nerve regions were dissected on cadavers to determine the exact relationship between the mental foramen, the inferior alveolar nerve, and its two terminal branches - the incisive and mental nerves. The most anterior position in which the mental nerve was encountered was 1 mm forward or mesial to the most anterior aspect of the mental foramen. Based upon this finding, it is likely that damage to the mental nerve can be avoided if the distal surface of the most posterior implant is 1 mm anterior to the anterior border of the mental foramen. Keywords: anatomical relationship, dental implant, mental nerve

Masticatory improvement obtained by the use of osseointegrated implants (Brånemark System) was analyzed through questionnaires collected from 22 Japanese patients. The questionnaires were designed to assess mastication of different Japanese foods. The postoperative score of masticatory function obtained by analysis of the questionnaires was 90.9, as opposed to the preoperative score of 43.9. A multiple regression analysis indicated that the number of placed implants has no signiiScant effect on the improvement of masticatory function, whereas preoperative performance does. Further, the degree of masticatory improvement showed variation according to the condition of the dental arch opposing the implant prostheses. The group having implant prostheses in the opposing arch showed the highest improvement. Keywords: masticatory function, osseointegrated implants

A method has been developed to examine the relationships between titanium implants in bone and the immune and hemopoietic cell populations in the adjacent bone marrow; it involves the use of miniaturized implants in the diaphysis of mouse femurs. After surgical placement of the implants, mice were sacrificed and the femurs were either embedded directly in Epon for preparation of ground sections or were decalcified in EDTA, embedded in Epon, subjected to a fracture technique to remove the implant, and sectioned for light and electron microscopy. Scanning electron microscopy revealed that the surfaces of implants removed in this way were virtually free of tissue remnants. Ground sections showed bone in direct contact with the implant surface, providing the first evidence of osseointegration in mice. In addition, an extensive surface of the implant interfaced directly with regenerated bone marrow, a condition that persisted for at least 18 weeks. Some bone marrow cells forming an incomplete layer in contact with the titanium interface had morphologic characteristics of macrophages and giant multinucleated cells. The results demonstrate a long-term integration between titanium implants and cellular elements of bone marow and provide an experimental model to examine the possible implications of this interaction on the processes of Iymphopoiesis and hemopoiesis. Keywords: bone marrow, giant cells, hemopoietic microenvironment, mice, titanium implant

Lingual paresthesia following the surgical placement of implants does not occur frequently. When it does occur, a serious problem may result for the practitioner, especially if the patient has not been informed of the risk before surgery. This report emphasizes the importance of practitioner experience and competence. It also addresses the need for knowledge of the course of the lingual nerve and preoperative planning of implant placement in the mandible. Keywords: implantology, lingual nerve, mandible, paresthesia