Impressions at Surgical Placement and Provisionalization of Implants

From the earliest attempts to successfully design and place dental implants, immediate loading and function have been hallmarks of treatment. Abundant failures in the early developmental stages of implants were commonplace and often occurred immediately or after a short period of functional loading. In many cases, patients were left with clinical problems more severe than their original edentulism. Although those early failure rates were unacceptable by today’s standards, many cases did survive and provide long-term support for functioning prostheses. Retrospective analysis of those early, immediately, or provisionally loaded implants allows us to now understand why so many of those cases were successful and why others were not. For example, the successful biologic use of metals was highly limited until the development of clean surgical techniques and antibiotics in the nineteenth century. Early experimentation with various implant materials showed that the necessary characteristics of tissue compatibility, corrosion resistance, and strength could not be entirely met in all metals. Gold, silver, and platinum were tissue compatible and corrosion resistant, but lacked strength under high stress. Metals that provided better strength, such as brass, copper, and steel, had poor tissue compatibility and corrosion resistance. During the 1930s, the fi rst surgical implants were stainless steel alloyed with 18% chromium and 8% nickel, which had good corrosion resistance and strength and were well tolerated by the body. Molybdenum, added later, improved corrosion resistance and formed the basis of an alloy (i.e., Type 316L) commonly used today for orthopedic implants. During the same decade, an alloy used for casting dental appliances, cobalt chromium-molybdenum, was also used for surgical implants. Corrosion or mechanical failure, such as wear, fretting, and fatigue of coatings, can release particulate debris capable of eliciting both local and systemic biologic responses. Metals are usually not tolerated in large amounts by the body. The ideal implant material would have to be passive to prevent an immunologic response and inert to resist corrosion that could harm local tissues and organs and compromise the long-term functioning of an implant in the biologic environment. Furthermore, the ideal implant material should not yield during insertion, fracture, or fatigue or otherwise fail during in vivo use. Therefore, an implant material’s intrinsic properties of elasticity, yield point, ultimate tensile strength, compressive strength, fatigue strength, hardness, and corrosion behavior must be appropriate for the function it is called to perform. In 1940, Bothe et al. experimented with the surgical use of titanium and fi rst reported its extreme biocompatibility. It was not until the 1950s, however, that research by Gottlieb and Leventhal and Clarke and Hickman documented titanium’s superior ability to withstand corrosion and remain relatively inert in the body. In the mid-1960s, Branemark et al. reported that ordered, living bone forms a direct structural and functional connection with a load-carrying titanium implant in the process that we now call “osseointegration.” The modern understanding of biomaterials, implant surface textures, bone physiology, biomechanical loading and/or function, and the systemic health of patients thus enables clinicians to achieve high survival rates and long-term predictability in implant placement. Armed with this knowledge, selecting patients appropriate for immediate functional implants offers advantages, including shorter total treatment time, improved stabilization of hard and soft tissue anatomy, fewer patient visits, and an overall increase in patient comfort and function over a traditional two-stage approach. Today, with the use of exceptional diagnostic information and sophisticated radiographs, such as CT scanning and computerized analysis programs, the unknowns of the anatomy and bone quality are no longer left to assumptions. Reformed three-dimensional views, anatomic models, surgical guides, and presurgical prosthetics can help ensure that implants placed into immediate functional loading are able to achieve aesthetic results and long-term survival rates that equal or surpass implants placed according to the standard, two-stage surgical approach.