J. Lindström

Osseointegrated Titanium Implants: Requirements for Ensuring a Long-Lasting, Direct Bone-to-Implant Anchorage in Man

A total of 2895 threaded, cylindrical titanium implants have been inserted into the mandible or the maxilla and 124 similar implants have been installed in the tibial, temporal or iliac bones in man for various bone restorative procedures. The titanium screws were implanted without the use of cement, using a meticulous technique aiming at osseointegration--a direct contact between living bone and implant. Thirty-eight stable and integrated screws were removed for various reasons from 18 patients. The interface zone between bone and implant was investigated using X-rays, SEM, TEM and histology. The SEM study showed a very close spatial relationship between titanium and bone. The pattern of the anchorage of collagen filaments to titanium appeared to be similar to that of Sharpeys fibres to bone. No wear products were seen in the bone or soft tissues in spite of implant loading times up to 90 months. The soft tissues were also closely adhered to the titanium implant, thereby forming a biological seal, preventing microorganism infiltration along the implant. The implants in many cases had been allowed to permanently penetrate the gingiva and skin. This caused no adverse tissue effects. An intact bone-implant interface was analyzed by TEM, revealing a direct bone-to-implant interface contact also at the electron microscopic level, thereby suggesting the possibility of a direct chemical bonding between bone and titanium. It is concluded that the technique of osseointegration is a reliable type of cement-free bone anchorage for permanent prosthetic tissue substitutes. At present, this technique is being tried in clinical joint reconstruction. In order to achieve and to maintain such a direct contact between living bone and implant, threaded, unalloyed titanium screws of defined finish and geometry were inserted using a delicate surgical technique and were allowed to heal in situ, without loading, for a period of at least 3--4 months.

Intra-Osseous Anchorage of Dental Prostheses:I. Experimental Studies

An investigation of factors controlling healing and long term stability of intra-osseous titanium implants to restore masticatory function in dogs revealed that an integrity of the good anchorage of the implant requires: (1) Non-traumatic surgical preparation of soft and hard tissues and a mechanically and chemically clean implant. (2) Primary closure of the mucoperiosteal flap, to isolate the implant site from the oral cavity until a biological barrier has been reestablished. (3) Oral hygiene to prevent gingival inflammation. Provided these precautions are taken, it is possible to subject dental prostheses, connected to the implants, to unlimited masticatory load. With these precautions such implants were found to tolerate ordinary use in dogs for periods of more than 5 years without signs of tissue injury or other indications of rejection phenomena.Macroscopic clinical investigation, stereomicroscopy, roentgenography and light microscopy of the implant site in situ and after removal from the body showed...

An experimental and clinical study of osseointegrated implants penetrating the nasal cavity and maxillary sinus

Implants were inserted in the upper jaw of three dogs in such a way that they penetrated the bone wall of the nasal cavity. The dogs were killed one year later, and the hard and soft tissues around the penetrating implants were analyzed. Radiographic and histologic examinations did not show any signs of adverse tissue reaction. The implants were all integrated in bone without fibrous tissue formation in the interface. A total of 139 implants, which pierced the bone of the sinus or nasal cavity, were inserted in the upper jaws of 101 patients. Forty-four sinus- and 47 nasal-penetrating implants were observed for five to ten years. The success rates were 70% and 72%, respectively. For 25 sinus- and 23 nasal-penetrating implants that were observed for two to five years, the success rates were 88% and 96%, respectively. The implant losses in nearly all clinical cases occurred during the first two years of function.

FIVE-YEAR EXPERIENCE WITH SKIN-PENETRATING BONE-ANCHORED IMPLANTS IN THE TEMPORAL BONE

A method for stable integration of titanium-implants in bone tissue has been developed at the University of Gothenburg, Sweden. Screw shaped implants have been inserted in the temporal bone using a delicate surgical technique. After healing-in of the implants it is, in a later séance, possible to penetrate the skin to establish a reaction-free percutaneous passage. An up to 5-year clinical follow-up has shown the possibilities of this new method in the treatment of patients with e.g. certain hearing disorders or facial defects after tumour surgery.

Reconstruction of the Defective Mandible

In a clinical material consisting of 31 cases of mandibular defects, caused by tumour resection or by trauma, reconstruction has been carried out by means of a stabilizing titanium splint and autologous bone and marrow transplantation, the longest period of observation being 9 years. The functional results obtained are assessed with reference to the cause of resection. Different technical procedures are described and the objectives and the planning of reconstruction of the lower jaw are discussed.

Analysis of the Mechanical Impedance of Bone-Anchored Hearing Aids

Some patients who need hearing aids are unable to use an apparatus which transmits the sound via the external ear canal and have to use a bone conduction hearing aid. The bone vibration transducer of this aid is applied to the skin over the mastoid process and the sound is transmitted via the soft tissue and bone to the cochlea. The pressure needed to apply the transducer often gives the patient discomfort and the damping effect of the soft tissue gives poor quality of the sound transmitted. Advances in the ability to permanently implant foreign material in the body and perform permanent skin penetration has made it possible to develop a bone-anchored hearing aid. Fourteen patients have been equipped with such hearing aids. To be able to give these patients the best hearing aid, a new transducer has to be constructed to match the new situation. The impedance of the bone-anchored titaniumscrew/skull has been studied and the resistance and reactance of the mechanical impedance have been measured. The influence of a damping soft tissue layer over the bone has been analyzed. The difference between the impedance of the skull and the impedance of the soft tissue + skull was in the order of 10 to 25 dB depending on the frequency.

Five years' experience with bone-anchored auricular prostheses.

A prosthetic device might be indicated in craniofacial reconstruction when plastic surgery is impossible or when the final cosmetic result is unsatisfactory. However, the attachment of a prosthesis is often very difficult. Bone-anchored, skin-penetrating titanium implants have been used for retention of auricular prostheses in 38 patients. The patients have been followed up for 1 to 5 years. No patient has been lost to follow-up. Only 1 implant out of the 159 inserted was found to have failed to integrate. Two skin-penetrating abutments have been removed because of inflammation where they penetrated the skin. The surgical procedure as well as the manufacture of the prostheses and the attachment is presented in detail.

Mandibular Reconstruction Using the Preformed Autologous Bone Graft

Preformed bone grafts (PBG) were inserted in large jaw bone defects in 5 patients. The grafts in all cases healed-in rapidly. Two patients died of metastatic sarcoma 1 year after grafting. The other patients are healthy with excellently functioning grafts 3, 5 and 8 years after transplantation, respectively. The preformation of bone grafts is, however, regarded as a resource consuming technique that should be used only in selected cases of mandibular reconstruction. Particularly in young individuals, the better results achieved with PBG, in comparison with other types of grafts, seem to justify the more complicated surgical procedure. Apart from a description of the preformation technique, the present paper also introduces advice as how to minimally traumatize the hard tissues in bone graft surgery.

Verrucous Squamous Cell Carcinoma of the Larynx: Evidence for Increased Metastatic Potential after Irradiation

Verrucous squamous cell carcinoma is a rare type of well-differentiated squamous cell carcinoma with a characteristic morphologic appearance and specific clinical behavior. It has been claimed that this tumor may undergo dedifferentiation after radiotherapy; this will result in a more aggressive behavior. From 1968 to 1980, we have diagnosed and treated 569 squamous cell carcinomas of the larynx. Fourteen of them were reported to exhibit verrucous features macroscopically. These tumors were histopathologically reexamined. All 569 cases were stratified with regard to tumor stage (≤T2 N0 M0) and treatment (irradiation). Six patients of 340 were then diagnosed as having verrucous squamous cell carcinomas, according to the Ackerman criteria. The patients were followed for at least 5 years and regional metastases of poorly differentiated carcinoma developed in at least two patients in the verrucous carcinoma group within 2 1/2 years after full-dose irradiation. Among the patients with nonverrucous carcinoma, this frequency was estimated to be 3%. This study provides evidence that metastatic spread that occurs after irradiation is approximately 10 times more frequent (p < 0.05) for T1–2 laryngeal verrucous carcinomas, as compared to the common type of squamous cell carcinoma.

Repair of Defects in Mandible

In an experimental series in dogs large mandibular and tibial defects were reconstructed by using a titanium splint to re-establish skeletal continuity and autologous grafts of spongious bone and marrow compensating for the bone removed. The results of this experimental investigation were used to design a method for repair of mandibular defects in man. With the aid of titanium splints and autologous bone and marrow grafts the anatomy of the mandible could be restituted and immediate function achieved. The results of application of these principles for repair of mandibular defects in 10 cases are reported.