The International Journal of Oral & Maxillofacial Implants, 01/1993

The aim of the present study was to experimentally induce peri implant bone defects around three different types of implants by plaque accumulation and to determine whether new bone formation can occur on previously contaminated dental implants. Dental implants were placed into the mandibles of beagle dogs. Gross plaque accumulation around the implants was undisturbed for 3 months, which resulted in circumferential peri-implant bone defects. Bony defects surrounding the hydroxyapatite implants were significantly greater than those around the titanium implants. Surgical treatment consisted of granulation tissue removal, preparation of the implant surface, and the placement of an e-PTFE membrane over each test implant. Before the flap was closed to cover the implants, perforations were made into the cancellous bone. Each control implant received identical treatment, but without placement of a membrane. Surgical exposure after an uneventful submerged healing period showed evidence of closure of the peri-implant bone defects. Corresponding histologic examination of 2-month sections demonstrated large amounts of rapidly formed lamellar bone beneath the membrane. Some areas of the previously contaminated implant surface showed evidence of e-osseointegration. These preliminary results support the hypothesis that plaque-induced peri-implant bone defects can be successfully treated by a submerged membrane technique in the dog model. Keywords: bone regeneration, dental implants, experimental breakdown, e-osseointegration, surface preparation

Force distribution with natural teeth depends on micromovement induced by the periodontal ligament. The location and cusp inclination of the tooth qualitatively alter the force pattern. Osseointegrated implants do not have micromovement associated with force distribution. Force distribution to the osseointegrated implant interface is completely different than with natural teeth. Alterations in tooth location and cusp inclination are suggested to limit implant overload. Force distribution in splinted natural teeth and osseointegrated prostheses are compared. The mechanism of interface force distribution and the consequences of poor interface fit are interrelated. The differential mobility of splinted natural teeth affects diagnosis and treatment. However, combining natural teeth with an osseointegrated prosthesis requires new design principles. Keywords: differential mobility, force distribution, impact area, interface force distribution, micromovement, micron movement, modulus of elasticity

Dental implants obtained from four suppliers were analyzed by electron spectroscopy for chemical analysis and scanning electron microscopy. Three of the implants were delivered in a sterilized condition, while the fourth implant was delivered in a plasma-sprayed condition. The covering oxide layer consisted mainly of TiO2. Divalent and trivalent states of titanium were also detected, showing that TiO and Ti2O3 layers occurred. The thickness of the oxide formed on the plasma-sprayed implant was 3.4 nm. The oxide thicknesses of the sterilized implants were 4.6 ± 0.4 nm. The surfaces of all samples were covered with organic contaminants. A strong fluorine signal was obtained from one sample, indicating that the supplier etches the implants in hydrofluoric acid. Calcium and zinc were found on the surfaces of all samples from one supplier, while calcium and silicon were found on the surfaces of the implants from another supplier. It is suggested that inorganic contaminants should be avoided because these species can possibly provoke the dissolution of titanium. Keywords: cleanliness, dental implant, oxide thickness, surface analysis, titanium

Four patients who had undergone combined surgical and radiotherapeutic treatment for maxillofacial cancer had osseointegrated titanium implants placed in the bone of the treated region at various intervals after irradiation. Preoperatively and postoperatively, hyperbaric oxygen therapy was administered to the patients at the level of 2 or 3 atmosphere absolute (ATA). Of the 21 fixtures placed, one was lost because of lack of osseointegration, rendering the survival rate 92.3%. Hyperbaric oxygen therapy seemed be a viable method to improve the survival rate of fixtures in irradiated bone tissue. Keywords: hyperbaric oxygen therapy, osseointegrated implant, radiation

A combination of horseshoe-shaped iliac bone grafts and Brånemark implants was used in 30 patients with severely resorbed maxillary alveolar ridges. All patients were followed clinically for 2 years and evaluated with regard to prosthesis stability, fixture survival, wound healing complications, and soft tissue conditions. Surgery was performed by the same oral surgeons using identical procedures, and the prosthetic treatment was performed by the same prosthodontist. The development group included the first 10 patients and the routine group included the following 20. Fixture survival in the development group was 54.4%, whereas 88.3% of the fixtures in the routine group have survived after 2 years. The average fixture survival in the study was 77.4%. Three patients in the development group lost all fixtures, primarily the result of trauma to the grafted region. With respect to the difficult situation many of these patients experienced, the survival rate should be considered most acceptable. Keywords: Brånemark implants, bone graft, maxilla

Many completely and partially edentulous patients experience advanced xerostomia and have considerable difficulty wearing tissue-supported prostheses. A conservative, maximum bone preservation approach to immediate implant placement is presented. The surgical and prosthetic considerations for treating a patient with Sjögren's syndrome are reviewed and discussed. Keywords: immediate implant placement, Sjögren's syndrome, xerostomia

The simultaneous use of autogenous bone grafts and osseointegrated implants has opened up new possibilities in the reconstruction of large tissue defects in the oral-maxillofacial region. In this paper, the successful rehabilitation of a patient who lost the premaxilla following a segmental osteotomy is described. The resulting oronasal communication and bony defect were restored by placing a bone graft from the iliac crest that was stabilized with two osseointegrated implants. A fixed prosthesis was fabricated to replace the missing anterior teeth. Esthetic and functional criteria were fulfilled. Keywords: autologous graft, osseointegrated implants, premaxillary necrosis

Two hydroxyapatite-coated IMZ implants, extracted for psychiatric reasons, were prepared using a cutting-grinding system and studied with scanning electron microscopy and laser scanning microscopy. The examination showed tissue integration with a very intimate bone-implant contact. Laser scanning showed the presence of a layer of dark staining material, resembling a reversal line of bone tissue, at the bone-implant interface, which could be the result of a film of organic material deposited on the bone and hydroxyapatite surfaces. Keywords: bone-implant interface, hydroxyapatite, hydroxyapatite-coated implants, laser scanning microscope

The bone response to two hydroxyapatite (HA) products (Osteogen and Alveograf) and a porous methacrylate resin material (HTR) in rats was compared. Fifty rats had four holes drilled in each iliac crest. The three alloplasts were placed in separate cavities and the fourth cavity was left empty as an absolute control. The survival times varied. The results were evaluated by subjective and histomorphometric analysis. Data were analyzed with ANOVA. There was a statistical difference in bone apposition between HTR and the HA products. The HTR was less osteoconductive, while HA consistently showed dense bone formation. The HA products are generally associated with greater bone formation, suggesting that HA is a better material for bone replacement than HTR. Keywords: alloplasts, bone formation, hydroxyapatite, methacrylate resin

Alternating use of the original method of internal drill cooling with manual external cooling, one IMZ implant was placed in the diaphysis (compact bone) and metaphysis (spongy bone) of the left distal tibia in each of six sheep. After polyfluorochrome sequential labeling, two animals survived for 4, 8, and 16 weeks without functional loading of the implants. The drill holes and bone-implant reactions were evaluated in undecalcified ground sections and microradiographs, using computer-aided histomorphometry. At least 30% of all drill holes were incongruent, but up to 25% of the implant surfaces had primary bone contacts. Four weeks after implantation, distinct differences in the bone reactions could be determined between the experimental conditions. After both cooling methods, osteoclastic resorption had extended up to 0.5 mm into peri-implant compact bone and up to 0.18 mm into spongy bone. Based on the percentage of newly formed bone-to-implant contacts, external cooling proved superior at all superficial drill hole levels in compact bone and in all spongy bone beds, while internal cooling was only better at the deeper drill hole levels in compact bone. After 8 and 16 weeks, peri-implant bone remodeling led to further increased new bone-implant contacts, irrespective of incongruent drill holes or cooling methods. At all time periods, abraded titanium particles were observed within interfacial foreign body cells. Conclusions are: (1) additional external cooling seems beneficial for any internal cooling, particularly in compact bone; (2) spongy bone apparently tolerates drilling heat better and reacts with more and earlier new bone formation; (3) the IMZ drill set cannot guarantee a congruent drill hole; (4) the titanium plasma-sprayed coating is endangered by mechanical abrasion. Keywords: bone structure, drill cooling, endosseous implant, histomorphometry

A total of 68 patients, 26 men and 42 women, aged 21 to 86 years, were treated with 204 endosseous implants (TPS, ITI, Bonefit, or Biolox) from 1985 to 1990. They were examined at their latest recall visit approximately 22.5 months after surgery, the range varying greatly between the implant systems used (from 4 to 60 months). Fourteen implants were lost during the observation period because of failures in osseointegration. There were no statistically significant differences in success rates between the implant systems during the observation period. The Periotest values, however, differed between the Bonefit and ITI implants in maxillae (P .001) and mandibles (P .01), and between successful and failed TPS implants (P .001, unpaired t test). In four of the failures, all ITI implants, the prosthetic restorations (fixed dentures and single crowns) had been lost. All other failures were treated by using the previous complete denture. Possible causes of failure included advanced age and poor general health of the patient, complications in the surgical procedures, and compromised oral hygiene. Keywords: complications, oral implants, Periotest

In 1988, a 54-year-old edentulous patient received a cranial bone onlay graft with the immediate placement of five dental implants. Treatment procedures and early results of restoration are described. Keywords: alveolar atrophy, cranial bone onlay graft, dental implants