From the onset of his journey to write this book, the author and contributors were committed to provide an evidence-based publication for all levels of clinical expertise. The primary focus is to understand the “Zero Bone Loss Concepts” in regards to crestal bone stability. The interplay between biology, biomechanics, surgical, and prosthetic factors is very well documented. Furthermore, he highlights the distinction between clinical practice and scientific research and how these disciplines can be integrated. The hierarchy of evidence serves as the backbone for the manuscript that consists of 2 major parts: surgical and prosthetic.
Section I: Surgical Concepts
A fundamental understanding of bone biology is emphasized in this chapter to allow clinicians to distinguish between zero bone loss, stable remodeling, progressive bone loss, bone demineralization/mineralization, corticalization, and bone growth. Building on this knowledge, it is accepted that crestal bone loss is multifactorial. The challenge is separating and balancing the impact of various factors to achieve desired outcomes. Because the crestal bone loss variables are vast and exceed the scope of this book, a selective approach was taken. First, implant design factors include the presence or absence of a polished implant neck and the implant soft-tissue thickness and attached gingiva.
There are multiple implant designs available on the market. It is the clinician's responsibility to have an in depth knowledge of the particular features and design concepts of the selected system for each treatment. In regards to crestal bone stability, 2 primary components are discussed in details: the implant polished collar and the microgap. It is very well documented that a polished implant collar/neck does not integrate and presents a potential liability for further bone loss if it is positioned below the crestal bone level. On the other hand, the microgap is even more complex. Three major factors in a microgap design must be managed: (1) bacterial contamination, (2) location of the microgap, and (3) micromovements. All 3 are detrimental to bone loss. However, the conical connection and platform switching can reduce or prevent this loss by controlling bacterial leakage and enhancing the implant–abutment stability.
The implant placement depth is a critical variable in the zero bone loss concepts. Therefore, a clinician' selection of an implant for a particular therapy must depend on the understanding of the implant design and its impact on the crestal bone. There are 2 primary philosophies in regards to implant design: (1) tissue-level implants and (2) bone-level implants with and without platform switching. The bone-level implants with platform switching can be placed at or below the bone level depending on the stability of the implant–abutment connection. However, bone-level implants without platform switching should have a machined collar approximately 1 mm and must be placed supracrestally to compensate for the location of the microgap and potential bacterial leakage. Tissue-level implants must keep the polished collar above the bone crest and must take into considerations the soft-tissue thickness to avoid restorative complications.
The author and his team embarked on several clinical trials that will be highlighted in the following chapters. As promised in the beginning of the book, “It is this marriage of science and practice” that is the foundation of every study that they have conducted. The primary focus of this chapter is the vertical soft-tissue thickness and how it is measured. A thorough literature review of the biologic width, its importance in understanding the volumetric soft-tissue requirements around implants, and that the bone loss occurs as a protective biologic mechanism against bacteria serves as a guideline for the clinical studies. Many clinicians believe that the conical connection and platform switching are absolute remedies in preventing bone loss. However, it has been demonstrated in this chapter that in the presence of thin vertical soft tissue, bone loss will still take place. It is well defined now that vertical soft tissue is a new biologic factor that must be taken into considerations and must be measured before implant placement. Based on the studies presented in this chapter, at least 3 mm of vertical soft-tissue thickness must be present to avoid crestal bone loss during the formation of the biologic width around implants.
Chapters 5, 6, and 7
These chapters are combined for the purpose of the book review to deliver a more complete assessment of the issues affecting crestal bone stability. Several protocols and clinical techniques are presented in regards to crestal and subcrestal implant placement based on clinical trials conducted by the author and his team. As discussed earlier, the clinician must follow the manufacturer's recommendations to determine the implant placement depth and take into consideration the available bone between the crest and anatomical structures. The subcrestal implant placement is a widely accepted method to compensate for the lack of vertical soft-tissue thickness. However, the clinician must select an implant system with a conical connection and a platform switching. Another method to aid in increasing the vertical soft-tissue volume is flattening of the alveolar ridge. This is definitely helpful in situations with a short clinical crown. However, if the 2 previous methods are contraindicated, the tent-pole technique can represent a potential alternative. This approach is more technical and requires much higher surgical skills because the soft-tissue release is the most important and difficult variable to control.
The primary and crucial requirement for zero bone loss has been defined, by the author, as a vertical soft-tissue thickness or volume. One must remember it is not the only variable that must be controlled to achieve success or the defined concept at hand. The deficient soft tissue can be corrected by vertical soft-tissue augmentation using a variety of graft sources, a technique that is widely around natural teeth and implants. A series of studies reflecting real clinical situations are presented. Allografts and xenografts can be used as connective tissue substitutes or alternatives. The most widely used is porcine-derived. A minimum of 2 mm gain in vertical augmentation can be achieved. However, in the event that the gain is greater, we should consider that beyond 5 mm can be problematic. The selection of a single- or two-stage approach is clinician-dependent.
The clinician must distinguish between adequate and acceptable vertical soft-tissue thickness and attached gingival tissues around dental implants. One cannot substitute for the other. They are both necessary determining variables for achieving crestal bone stability. It has been defined that a minimum of 2 mm on the buccal and lingual aspect of implants is a requirement. Similar to the vertical soft-tissue augmentation, allografts and xenografts seem to gain great popularity. These substitutes eliminate the need for a secondary surgical site to harvest autologous grafts and provide an unlimited supply.
The previous chapters served to define the problems associated with crestal bone stability as well as presenting a sequence of studies to offer potential solutions based on accurate diagnoses. This chapter is a practical guide for various clinical situations previously presented with excellent step-by-step illustrations, side by side with clinical cases. This is an outstanding summary.
Section II: Prosthetic Concepts
Section I focused on the vertical soft-tissue thickness as a singular variable. It became very evident that there are multiple other factors that must be taken into consideration from a surgical perspective. Now, that we have defined that the crestal bone stability is multifactorial, the multiple prosthetic options will come into play and further influence how zero bone loss can be achieved. Rather than a top–down approach, the author selected the reverse. Regardless of this change in the sequence, the prosthetic variables must be examined thoroughly. Cement- or screw-retained restorations, abutment selection, emergence profile and biomaterial selection will influence our clinical decision-making and judgment.
The available data in the literature can be confusing and conflicting regarding the “best” type of therapy when it comes to the selection of the type of restoration. Once again, the author is very methodical in his approach. He defines the problem through clinical evidence, designs a series of clinical studies, and presents the results as a guideline or a decision tree for clinicians. Cemented restorations with standard abutments can be very challenging for cement removal regardless of the technique. Clinicians must adhere to a strict protocol, using custom abutments with supragingival margins to ensure removal of cement remnants. All other methods do not guarantee complete cement removal and predispose patients to potential peri-implantitis.
Because the concept of cement restoration can be beneficial in achieving passive fit and creating an interface between implant–abutment restoration, a modification is required to minimize complications. The hybrid cement/screw retention with titanium-base abutment is an excellent alternative. There are various clinical and laboratory steps that are necessary to fabricate such a prosthesis. It is mandatory not to treat the titanium base with airborne particles to maintain maximum retention and to use resin cement for chemical bonding. The hybrid cement/screw restoration and traditional cement restoration have a similar clinical behavior.
The previous chapters featured the different modalities in treating a single-tooth restoration. The fixed partial denture represents a higher level of complexity. The selection of impression coping and abutment is different. The clinician must be comfortable with the open-tray impression techniques. It is possible to combine hexed and nonhexed components for the final restoration. This treatment modality requires segmentation of the case and therefore will require additional implants. There are several clinical cases presented in the chapter to demonstrate all the necessary steps to manage this type of advanced therapy.
The abutment selection criteria seem to focus on materials and design. However, many other variables must be considered such as anterior or posterior, cement or screw retained, and soft-tissue thickness, etc. The cement-retained restoration for the posterior implants, zirconia custom abutments with supragingival margin location are the recommendations of the author and what is widely accepted in today's clinical practice. The anterior implants require different steps from a design perspective. A margin verification abutment replica is used to accurately and intraoraly determine the desired margin location. The screw-retained restorations can be used anteriorly depending on the 3 dimensional implant placements. For all anterior treatments, the clinician must be adept at impression techniques that allow duplication of exact soft-tissue topography after provisionalization.
The emergence profile and restoration contour impact the crestal bone response and stability. As previously seen, the author supports his study design by clinical manifestation of a problem. He attempted to continue on this path in this chapter and selected cases to support the narrative. It should be noted that some of the cases selected, based on radiographic evidence, are not clinically acceptable, and therefore, the bone loss was expected. It is evident that if the angle of the restoration exceeds 25°, the crestal bone will not be stable in the long term. The laboratory does not have radiographic data; it is the responsibility of the clinicians, for implants in the subcrestal position, to select the appropriate titanium base gingival height.
Chapters 17 and 18
These chapters are combined for the purpose of the book review; they are both addressing the concerns related to prosthetic materials and selection. Dental implants can be restored with a variety of materials. The clinician and the laboratory technician must work very closely to select and more importantly to distinguish the differences in subgingival and supragingival material requirements. The impact on cellular adhesion and plaque control takes center stage for the subgingival material of choice. At the present time, zirconia is the most biocompatible, followed by titanium and polished lithium disilicate. The least compatible is veneering ceramics. Clinicians should follow a cleaning protocol for abutments and prostheses.
Chapter 19 and 20
Clinically, subgingival and supragingival materials must respond to different needs. However, it is impossible to analyze these components separately because they will have to be integrated together, to deliver a final restoration. To maximize the biocompatibility benefits of zirconia, the sub-gingival portion is polished. It cannot be glazed or veneered with ceramics. The supragingival zirconia is glazed and colored. At times, when considering combining zirconia with other materials, clinicians and laboratory technicians need to weigh the functional and aesthetic for long-term success. Clinicians can combine zirconia with lithium disilicate for strength and zirconia with feldspathic veneering for great aesthetics.
Zero Bone Loss Concepts are presented with excellent details from a clinical point of view. Tomas was focused and delivered a very comprehensive book addressing the complex world of crestal hard- and soft-tissue stability. I understood the author's goal from his introduction. The references are expansive, current, and support the clinical narrative. Very high-quality clinical documentations showcase the team’s skills and commitment. My only concern is that the radiographic data were not standardized and its interpretation could be challenged. Regardless, this text is clinically relevant and a must have in every implantologist's library.