The International Journal of Oral & Maxillofacial Implants, 04/1992

The Nd:YAG dental laser has been recommended for a number of applications, including the decontamination or sterilization of surfaces of dental implants that are diseased or failing. The effects of laser irradiation in vitro (1) on the surface properties of plasma-sprayed titanium and plasma-sprayed hydroxyapatite-coated titanium dental implants, and (2) on the potential to sterilize those surfaces after contamination with spores of Bacillus subtilis have been examined. Surface effects were examined by scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction after laser irradiation at 0.3, 2.0, and 3.0 W using either contact or noncontact handpieces. Controls received no laser irradiation. Melting, loss of porosity, and other surface alterations were observed on both types of implants, even with the lowest power setting. For the sterilization study, both types of implants were first sterilized by exposure to ethylene oxide and then contaminated with spores of B subtilis. After laser irradiation, the implants were transferred to sterile growth medium and incubated. Laser irradiation did not sterilize either type of implant. The spore-contaminated implants in the control group were successfully sterilized with ethylene oxide. Keywords: implant, Nd:YAG dental laser, surface alteration, sterilization

Using the finite element method, this study modeled a 4.0 × 13.0-mm IMZ implant, restored with a cast gold crown, to examine the influence of the polyoxymethylene (POM) intramobile element (IME) on the transmission of vertical and oblique forces. Stress concentrations in the bone and in components of the implant system were much greater under a 30-degree load than under an equal vertical load. Stress transmission to bone occurred chiefly in the crestal region, and these stresses were not reduced when the IME was modeled in POM rather than in titanium. Maximum stress concentrations occurred in the fastening screw. Keywords: biomechanics, computers, implant-supported prosthesis, intramobile element, stress analysis

Although the first and second molars usually are lost first in a partially edentulous maxilla, titanium implants are seldom placed more distally than at the second premolar site because of the poor quality of bone often found in the posterior maxilla. The present series encompasses 72 Brånemark implants placed in the third molar-tuberosity area with a success rate of 93% and an average follow-up after loading of 21.4 months. Moreover, two of the failed implants were in patients who had a simultaneous successful implant contralaterally. Keys to this high success rate include the meticulous identification and correction of all pathoses, modification of the drilling sequence to maximize initial implant stabilization, achievement of bicortical fixation whenever possible, gentle handling of the soft tissues and periosteum, and elimination or minimization of transmucosal occlusal loading during osseointegration and of nonaxial loading after connection. Keywords: maxillary tuberosity, osseointegrated implants

To consistently provide passively fitting implant superstructures, an understanding of the accuracy and precision of all phases of fabrication and connection is required. The initial phase of fabrication, ie, impression making and cast forming, was investigated in an earlier report for a mandibular five-implant model. The current study evaluates the accuracy of working casts produced from impressions using two different transfer copings in a 15-degree divergent two-implant posterior mandibular model. While the indirect method is less cumbersome to use, it was found to be less accurate in the prior study. The purpose of this study was to see if the direct method is more precise for this clinical situation. A transfer was deemed effective in producing experimental casts if distances between specified points on the cast agreed with the corresponding distances on the master cast. The absolute value of the difference in distances between experimental and master casts was compared for the two techniques (two-sample t tests). No significant differences were noted (P > .05), and the power of the tests ranged from 0.70 to 0.96 against the one-sided hypothesis that the direct method had a smaller mean absolute difference in distance than the indirect method. This suggests no clear advantage in using the direct method in similar clinical situations. Comparison of these findings to other impression accuracy studies is made. Keywords: direct coping, impression transfer method, indirect coping, partially edentulous

Over a 78-month period from 1983 to 1990 at the Mayo Clinic, 353 patients involving 407 jaws were restored with 1,778 Brånemark system implants supporting prostheses. Complications involved loss of implant anchorage, soft tissue problems, or mechanical problems. The most predominant complication involved soft tissues. There were 152 patients with loaded prostheses who had no complications and 37 with only one occurrence. Those seen in 160 patients with more than one occurrence were all conservatively managed, so that prosthesis use was only permanently discontinued in 4 patients, who returned to the use of a maxillary complete denture. Keywords: complications, tissue-integrated prosthesis

Hydroxyapatite-coated and titanium-coated IMZ dental implants were investigated in an animal study. The implants were placed in the distal femurs of rabbits. Six months after placement, histomorphometric evaluation of the bone-to-implant contact was conducted. The hydroxyapatite-coated specimens demonstrated significantly more direct bone contact compared to the titanium-coated controls. Keywords: coatings, histomorphometry, hydroxyapatite, implants, titanium

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. Keywords: experimental study, histomorphometry implant surface, machined commercially pure titanium, plasma flame-sprayed hydroxyapatite, plasma flame-sprayed titanium

This study investigated the undecalcified bone and enveloping tissues supporting commercially pure titanium one-stage and two-stage endosseous dental implants placed into the mandibles of adult mongrel dogs. Correlative light microscopy, transmission electron microscopy, and high-voltage transmission electron microscopy demonstrated a dynamic bone interface to the implants. Mineralized tissue was routinely observed within 20 to 50 nm from the implant interface, separated from the implant interface only by an electron-dense deposit. The densely mineralized collagen fiber matrix was oriented parallel to the implant interface, as were osteocytes that were found close to the interface. Osteocytic projections progressed through canaliculi, often directly to the implant interface. Unmineralized areas that appeared to have the potential for mineralization were also identified. Keywords: bone, dental implants, high voltage electron microscopy, in vivo interface, mandible, osteocytes, titanium

This report describes one phase of a long-term comparative implant investigation involving 20 of 120 endosseous implants placed in 30 adult mongrel dogs. Fixed prostheses involving 16 of the 20 (4 control implants) two-stage ceramic endosseous implants have been provided using routine prosthodontic procedures and the limited prosthetic components available for the Bioceram Series II implant system. The prostheses have proven to be functional with minimal maintenance. To date, after 1 year of follow-up, 2 of the two-stage implants have exhibited problems caused by fracture of the hexagonal collar. None of the implants to date has been lost and none of the fixed prostheses has required re-cementation or any other type of maintenance other than normal hygiene. Clinical evaluation suggests continued implant and prosthesis serviceability after 1 year in function. Keywords: ceramic implant, endosseous implant, root-form implant

Nine clinical centers participated in a prospective study of overdentures supported by Brånemark implants in the maxilla or mandible. The study initially comprised 133 patients provided with 117 implants placed in the maxilla and 393 implants placed in the mandible. The preliminary results indicate a success rate in the mandible comparable with the reports on fixed prostheses. Conversely, overdenture treatment in the maxilla seems to be less favorable than previous reports of fixed restorations. The differences between the fixed and the present overdentures in the maxilla were mainly based on differences in patient selection and bone quality. A total of 32 implants was mobile and removed and another 29 implants were lost to follow-up because of patient dropout up to the first annual checkup after denture placement. A higher implant failure rate occurred in the maxilla. Mucosal reactions were also more unfavorable around implants placed in the maxilla. Keywords: Brånemark implants, multicenter study, overdentures

This investigation was conducted to evaluate osseointegrated skin-penetrating facial titanium implants used for anchoring facial prostheses over a 5-year period and to recommend guidelines for the use of osseointegrated implants in the restorative treatment of auricular and orbital defects. The total success rate for implant survival was 95.6% in the auricular defects and 67.2% in the orbital defects. Approximately 10% of the patients will have some skin problems, whereas the remaining 90% will have no or minimal problems. The possibility of achieving osseointegration around an orbital defect is not as good as in the mastoid process. Success criteria for the use of implants in the craniofacial region are given. Keywords: facial prosthesis, osseointegration, titanium fixture

When residual ridge atrophy of the edentulous mandible and maxilla is accompanied by a skeletal Class III jaw relationship, surgical correction is necessary for optimal functional, phonetic, and esthetic results whenever implant-supported prostheses are to be placed. A method is described in which a single procedure combines the endosseous placement of nonsubmerged titanium implants in appropriate prosthetically predetermined locations with defined advancement of the maxilla. Preoperative diagnostic examinations, cast simulation, and transfer of the latter to the site of surgery are of the utmost importance. Keywords: Class III edentulous patient, Le Fort I osteotomy, nonsubmerged implants, one-stage procedure, residual ridge atrophy

A buccal plate destroyed by the inflammatory process as a result of a longitudinal root fracture was completely restored by the combined use of an IMZ implant placed in the alveolus of the fractured maxillary central incisor and the principles of guided tissue regeneration. A Gengiflex membrane was used to cover the implant, and porous hydroxyapatite was used as grafting material. At the 6-month reentry, the defect around the implant was completely filled by mineralized tissue. Keywords: Gengiflex, guided tissue regeneration, IMZ implant, porous hydroxyapatite

This case report demonstrates that severe disuse atrophy of an edentulous mandible can be changed to reparative bone growth through restoration of function and masticatory ability using an osseointegrated implant-supported fixed prosthesis. In 8 years,bone height in the retroforaminal area nearly doubled and a new bony layer remodeled the cranial roof of the mandibular canal. Keywords: atrophic mandible, bone growth, implants, osteogenesis