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Statement of Problem: The replacement of missing teeth with implant-associated restorations has become a widely used treatment modality in recent years. The length of dental implants may be a critical factor in achieving and maintaining osseointegration. Purpose: The aim of this study was to evaluate the survival rate and bone loss of dental implants with different lengths Materials and Methods: A retrospective cohort study was performed on 60 ITI-system implants, evenly distributed into three groups including 8, 10 and 12 mm high implants in the posterior segments of both jaws. Demographic information, oral hygiene, cigarette smoking, implant length, duration of implant placement (at least 24 months), bleeding on probing index and pocket probing depth were recorded for all participants. Bone loss was calculated using pre- and post-operative panoramic radiographs. Results: The mean rate of bone loss was different among the three groups and were found to be 0.21 (0.45), 0.3 (0.41) and 0.43 (0.55) mm in the 8, 10, and 12 mm high implants, respectively. Neither mean bone loss nor bleeding on probing index showed significant differences with implant length. A significant correlation was found between implant length and pocket probing depth (P

The Polymer Expansion Implant System, which is a system for the substitution of missing dental roots in natural or surgical alveolus, has been developed by the author. The polymer used is poly (methyl methacrylate) (PMMA). A material is sought that has three of the basic physical and mechanical qualities of human dentine: low modulus of elasticity, thermal and electrical passiveness, and ideal porosity. In addition it should be resistant, easily worked, biocompatible, and of low cost. Of the biomedical polymers, PMMA has these qualities, and it can be used as a substitute for dental roots. The design of bodies to be implanted as substitutes for dental roots requires: anatomical measurements of the maxilla and sockets; methods of retention by the bone tissue; and methods of insertion. The formation of lamina dura around an implanted body is a reply of the organism to the forces acting on it and a demonstration of the good interaction of the porosity of the material, the peri-implant collagenous fibers and bone. X-rays that demonstrate the behavior of bone to a PMMA implant are shown.

Eighty-seven blade implants have been inserted either in the maxilla or mandibles of patients. The technique of construction of the implants requires a study cast and radiographs for measurements. During surgery, the individualized implant can be molded to fit the curvature of the alveolar ridge. These implants use a substantial amount of bone for support, and immediate stabilization of the implant is not necessary. However, because of the possibility of resorption of the implant, an alternate shoulderless design has been developed.

Numerous types of implants for use fol­ lowing enucleation or evisceration have been described. Descriptions of the more popular ones, usually carrying the designer's name, may be found in papers by Mules, Wheeler, Ruedemann, Cutler, Berens, Hughes, Dimitry, and Durham. Dimitry gave an excellent account of the history of enuclea­ tion and evisceration up to 1944. Since all types have their advantages and their champions, it would appear desirable to decide on the criteria which should determine the choice of implant in any particular case.

This is a preliminary report regarding a technique combining a subperiosteal metal implant and a marrow-bone graft. The purpose of this procedure is to restore the mandibular bone, which covers and protects the exposed mandibular canal and nerve, and to augment this graft procedure by a metal implant. The metal implant acts as a tray or crib to hold the bone graft in position and to protect it during initial healing period. Following this period, the implant will then receive the major part of the occlusal forces and will transmit them directly to the bone rather than against the mucosa. The implant posts are made so they can be removed to allow for the initial healing of the bone graft without communication with the oral cavity. Small screws are placed in position for about four weeks during healing to prevent bone from closing the screw holes. The postoperative course was uneventful, and results from the standpoint of function and comfort (Fig. 19) are excellent. There is no evidence of pressure paresthesia which was previously present when the patient used a soft tissue-borne mandibular denture. The marrow-bone graft is remodeling excellently, and in many areas, bone completely covers the metal implant. Clinical evaluations in three other patients as well as research on animals are currently being successfully conducted to investigate all aspects of this combination procedure. After 14 months, the initial clinical use of the technique has been most encouraging.

Titanium implants have been designed which utilize a solid core and porous exterior. The technique for implants containing posts utilizes a cast chromium-cobalt splint for fixation and the buried implants are held in place by the overlying gingiva until tissue growth into the porosity results in stabilization. Clinically successful post implants with apparent bone ingrowth and healthy gingiva surrounding the post have been achieved for periods up to three months.