Research shows that the same anaerobic, gram-negative pathogens are present in the periodontal and implant pocket or crevice. The implants in a partially edentulous case are probably more at risk due to the bacteria being more pathogenic and a seeding mechanism from the tooth pocket to the implant crevice. In the face of a normal microbial flora, retrograde periimplantitis or radiographic bone loss without gingival changes may be due to trauma because of overloading, loading too soon, and/or loading in a lateral direction. Finally, the combination of an infective process (periimplantitis) and noninfective or traumatic process (retrograde periimplantitis) will result in rapid osseous destruction and, possibly, loss of the implant fixture(s).
Hydroxylapatite (HA) coatings have shown promise due to the enhanced integration of osseous tissues to coated implant surfaces, particularly in sites where bone quality or quantity is compromised. This promise has resulted in a dramatic increase in clinical utilization of HA-coated implants. In spite of encouraging clinical findings, the long-term stability of the hydroxylapatite/bone interface has been challenged. Microbiologically, the HA-coated implant surface may be more susceptible to the formation of bacterial plaque. Additionally, critical variations exist between implant coatings that may affect long-term survival. Despite such concerns, after eight years of clinical utilization, the hydroxylapatite-coated implant surface has not been shown to be predisposed to increased long-term failure.
Root form implants may be either cylindrical or threaded, metal or calcium-phosphate-ceramic (CPC) coated. Biological and mechanical principles dictate a preference for threaded implants, and a retrospective study comparing surface characteristics reveals a marked preference for HA-coated threaded implants, at least in the short-term period of observation.
Retrievability is the major advantage of screw-retained implant restorations compared to cement retention; however, implant screw loosening continues to be a frequently cited disadvantage of this technique. This paper describes the factors involved in maintaining a stable screw joint assembly by maximizing preload on the retaining screw while minimizing joint-separating forces. Practical clinical solutions to minimize this clinical problem are suggested. Readers are cautioned to address both the occlusal and biomechanical etiologies of screw loosening.
Implant dentistry has made great advances since its inception several decades ago. As a result, predictability and success have reached high levels. Nonetheless, efforts continue to further refine implant design, materials, and techniques to reduce even the small percentage of failures that still occur. As part of this effort, the authors for the past six years have conducted clinical trials of Steri-Oss threaded titanium implants and HA-coated implants. The results have been consistent with the body of implant research reported since the 1970s. Optimum implant performance is realized when a well-designed system such as those tested is utilized in association with astute clinical judgment.
Placement of implants in the dental alveolus crest of the mandible and maxilla is limited by the height of bone between the alveolar crest and the maxillary sinus, floor of the nose, and the inferior alveolar canal. This paper discusses three surgical grafting procedures--the sinus lift and graft, the split cortical (or sandwich) graft, and the onlay graft--these add additional bone to the anterior and posterior maxilla, and also the procedure to reposition and protect the neurovascular bundle so that endosseous implants may be placed.
A protocol for implant dentistry is presented including preoperative and postoperative planning stages. The focus is on post-second-stage-surgery restoration, understanding the currently available dental components, and the communication between the surgeon, restorative dentist, and laboratory technician. Some of the common pitfalls that occur are discussed, and six key points are described.
The safety and efficacy of HA-coated screw-type titanium dental implants was studied in an 8-year retrospective study. The results show that HA-coating clearly decreases failure rates in the posterior mandible and the anterior and posterior maxilla.
Modern digital radiographic techniques can aid the clinician in planning dental implant selection and placement before and during surgery, a well as in the long term assessment of periimplant bone support. Implant treatment planning can be facilitated using computed tomography on film-based motion tomography. During surgery, direct digital radiography allows the clinician to visualize the relationship of the osteotomy sit to important anatomic structures such as the mandibular nerve. Following placement, digital subtraction radiography permits detection of osseous changes too small to be seen by eye with an accuracy approaching 95%. Such sensitivity and specificity encourages early evaluation and, if necessary, intervention on behalf of the ailing implant.
The rationale and protocol to gradually load the implant after the initial bone interface have been established and discussed. Bone density is the most critical factor in determining the amount of healing time between first and second-stage surgeries and also between the five appointments for prostheses which are cement-retained.
Early techniques in implant dentistry utilized immediate impression-taking and loading of endosseous implants. Because these techniques became associated with an unacceptably high incidence of complications and failures in early implant dentistry, many dental professionals came to look upon the procedures with disfavor. This disregard overlooked the fact that in many cases the utilization of immediate impression-taking and loading was successful. This presentation suggests to the clinicians to reconsider the issue of immediate loading from two contemporary perspectives. First, the author's research indicates that the benefits of single-stage implant treatment can be realized with a two-stage implant. Second, even when single-stage treatment is not elected, the advantages of faster, more convenient (and therefore more acceptable) treatment for the patient can be realized by taking an impression at the time of implant placement with the use of a new insertion tool/impression pin currently in clinical trials and described in this paper.
This article discusses the "implant team" concept as it is actually carried out in an implantology practice. The restorative dentist is designated to function as the head of the team, directing each stage of the treatment. He is the first one the patient consults, he refers the patient to the surgeon, and he consults other specialists, if necessary. Excellent communication between the members of the team is stressed throughout.
The inevitable loss of alveolar bone following tooth loss deserves a prophylactic approach from the dental profession. By preserving bone through regenerative procedures, the patient option and likelihood of successful future dental implant treatment are enhanced. The use of fascia lata similarly extends surgical and restorative options to patients who otherwise might not be candidates for dental implants. A variety of materials is available for these procedures, but whichever are selected, it is imperative that the dental implant professional operate as a member of a team of interrelated disciplines if the results of dental implant treatment are to be optimized.
Controversy has recently arisen regarding hydroxylapatite (HA) coatings and HA-coated implants. The frequent absence of information about relevant scientific parameters in critical articles and presentations makes it difficult for clinicians to accurately assess the validity of these reports and/or the quality of the products being reported. In order to make informed decisions regarding HA-coated products, clinicians need to familiarize themselves with the critical variables of HA crystallinity, purity, density, bond strength, and dissolution rate. Clinical and histological studies indicate that when high standards are observed for these five parameters, HA coatings and HA-coated products provide a reliable component of the clinical armamentarium.
The use of implants with fixed partial dentures requires that the restorative dentist address a new set of concerns when planning treatment. This paper presents some important issues and evaluates the advantages and disadvantages of each choice, including the decision whether to treat the patient as a totally implant-supported or as a combination case. The special problems of posterior restorations include occlusion, rigid versus nonrigid coupling mechanisms, root intrusion, and screw versus cement retention.
