The International Journal of Oral & Maxillofacial Implants, 05/1995

A common problem associated with dental implant restorations is loosening of screws that retain the prosthesis to the implant. A method was developed to determine initial preload on UCLA-type abutment screws by measuring elongation after applying known tightening torques with a digital torque gauge. Loosening torque was also measured after tightening to 32 N-cm torque for gold alloy abutment screws and 20 N-cm for titanium ahutment screws. Gold alloy and titanium abutment screws were each used to secure a gold UCLA hexed abutment to a titanium implant. Stresses and forces were calculated from the elongation measurements for three regions of each screw. Elongation of the screws after applying the manufacturer's recommended tightening torques were within the elastic range. Induced stresses were 57.5% and 56% of the yield strengths for gold alloy and titanium, respectively. Tightening of screws beyond recommended levels may be possible without producing plastic deformation. At manufacturer's recommended torques, mean preload was 468.2 (± 57.9) N using gold alloy screws and 381.5 (± 72.9) N with titanium screws. Keywords: biomechanics, elongation, implant, preload, screws

Premolar teeth were extracted from dogs and the remaining alveolar bone was surgically reduced to produce Class III ridge defects. Following 2 months of healing, a new technique using allogeneic cortical columns to prop up the raised mucoperiosteal flaps and create space for developing tissue was employed to create space for regeneration of the ridges. In the control sites, the cortical columns alone were used to prop up the mucoperiosteal flap; whereas in the experimental sites, barrier membranes (expanded polytetrafluoroethylene or bone membranes) were interposed between the flaps and the projecting cortical columns. In alternate sites, decalcified allogeneic freeze-dried particulate bone was added to fill the voids between the cortical columns, the underlying host bone, and the membranes. Variations of the new approach that were based on the principles of guided tissue regeneration provided the most significant gains in ridge width, with a mean aggregate gain of 3.31 mm. Histologically, all variations of the basic technique were seen to have augmented the surgically reduced ridges. Osseous regeneration was observed only where the barrier membranes were used. The addition of particulate bone filler did not appear to offer any advantage. This new approach to ridge augmentation meets the requirements for alveolar ridge regeneration. Keywords: bone membranes, cortical columns, guided bone regeneration, regeneration requirements, ridge augmentation, ridge regeneration

From April 1986 to September 1993, 134 implants (97 immediate implants, 26 early secondary immediate implants, and 11 late secondary implants) were placed in 20 patients following extraction of all residual teeth. After a mean follow-up period of 27.1 months, the implants were analyzed with regard to peri-implant soft tissue parameters and bone resorption. When the examination was performed, 131 implants (97.7%) were found to be functioning successfully. The mean pocket depths varied between 1.3 and 2.6 mm, and the peri-implant bone resorption showed values between 0.5 and 1.3 mm. Fixed and removable prostheses revealed equal results with regard to the parameters examined. The results of the present study indicate that serial immediate implantation can be considered to be a very promising implant treatment modality for serial teeth extraction, if specific parameters are taken into account. Keywords: immediate implantation, serial teeth extraction

A narrow edentulous alveolar ridge, less than 6 mm in the buccopalatal aspect, can prevent restoration by means of endosseous implants. A widening technique using alveolar ridge splitting and interpositional autogenous bone grafting is described. Accurate imaging of the alveolar bone shape and size was assessed with computerized tomography in a 1:1 scale. Following 6 months of healing, osseointegrated Brånemark implants were placed in the grafted sites. Keywords: alveolar ridge widening technique, computerized tomography, interpositional bone grafting, osseointegrated dental implants

Craniofacial implants have been used successfully for the retention of facial prostheses. However, complications occur that can lead to the loss of implant integration. One such complication is infection possibly resulting from crevicular microflora activity. As part of an ongoing study, samples from crevicular sites surrounding 17 craniofacial implants were collected and submitted for microbiological assay. The results demonstrated the presence of opportunistic pathogens in many sites regardless of subjects' hygiene efforts. The significance of the findings is reviewed. Keywords: craniofacial implants, implant infection, percutaneous space

Few methods have been described that can quantitatively evaluate masticatory function. This study investigated the usefulness of a low-adhesive color-developing chewing gum system for the evaluation of patients with implant-supported prostheses. Fifteen dentate subjects and 22 patients with dental implants participated in this study. The color developed in the gum after chewing reflects masticatory function and is evaluated quantitatively with a color-analyzing system. The results indicate that this system can be used to evaluate occlusal function, and they confirm the importance of stable prostheses for higher masticatory function. Keywords: chewing gum, dental implant, masticatory function

The visor-sandwich osteotomy augmentation and onlay bone grafts are among the various methods for rehabilitating the lower third of the face and restoring oral function. However, these methods have provided unpredictable results. When sufficient bone is available for reconstruction of atrophic jaws with endosseous implants, this can be the treatment of choice. In patients with insufficient bone available for conventional implant treatment, the use of an adjunctive inferior border graft may be considered. Keywords: Brånemark implants, cadaver mandible, mandibular reconstruction, Procera prosthesis, severe mandibular atrophy

A retrospective follow-up study was undertaken to assess the clinical condition, complications, and prosthodontic aftercare of two different implant systems over a long period. Thirty-six patients treated with a total of 135 ITI type F endosseous implants, and 37 patients treated with the transmandibular implants and a total of 146 transmandibular posts, were studied during a mean follow-up period of 70 months and 44 months, respectively. The choice of implant type was mainly influenced by a change in financial support by the National Health Insurance Company in The Netherlands in 1987. Cumulative success rates were calculated using the Kaplan-Meier product limit method. In the analysis, the risk for failure of the implants was adjusted for differences in mandibular bone height. There were no differences between the two treatment groups with regard to age, gender, period of edentulousness, and mandibular bone height. During the follow-up period, plaque, bleeding, and hyperplasia scores demonstrated no significant differences between the two groups. The ITI type F group showed significantly more recession, and the transmandibular implant group demonstrated significantly increased Periotest values. After adjusting for differences in bone height, patients treated with ITI type F implants had a lower risk of failure (relative risk, 0.55; 95% confidence interval 0.32 to 0.95). However, neither of the implant systems fulfilled Albrektsson's criteria of success. Keywords: follow-up, implant, overdenture, superstructure

The restoration of four missing maxillary incisors with implants and custom-made abutments is described. Acetal was used to fabricate the custom-made abutments, instead of the conventional metals. This material is resistant to wear, and it is biocompatible and white in color. Acetal meets esthetic requirements, particularly when restoring the anterior region of the dental arches. The white post does not give a grayish appearance to the surrounding soft tissues, and the possible gingival recession around the post will not compromise esthetics. The presented case report indicates excellent esthetic and functional results. Keywords: acetal, custom-made abutment, implant abutment

Placement of immediate implants is a routine clinical procedure. However, certain clinical conditions, especially the presence of infected sites, are considered to be contraindications for the immediate implant. Based on clinical experience, it is proposed that if certain preoperative and postoperative steps are carefully followed and meticulous debridement of the alveolus is done during the surgical procedure, immediate implants can be successfully placed into chronically infected sites. The advantages of this procedure are discussed. Keywords: Gengiflex membrane, guided bone regeneration, immediate implants, infected site

When carrying out restorations supported by dental implants, it is advisable to have a temporary method that offers the possibility of evaluating and/or creating a proper emergence profile, peri-implant health, occlusion, esthetics, acceptable phonetic response, and hygiene, as well as one that facilitates progressive loading of the implants during the bone maturation period. To maintain osseointegration it is essential that a prosthesis fit with total passivity, since the lack of a periodontal ligament renders the implant unable to modify its position. Gold cylinders for EsthetiCone abutments, which were modified following a previously reported technique, were used so that provisional prostheses could be fixed to the cylinders in the mouth by means of an alternative cementing technique. By this way, a provisional prosthesis with total circumferential fit, maintaining the option of retrieval, could be routinely obtained. Keywords: interim prostheses, osseointegration, passive fit