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General Principles of Augmentation Surgery

Information has never been as widely available as it is today. This is especially true for dental implantology, which is still very much in flux many decades after its establishment. In the dynamic interplay between product developers and clinicians, new biomaterials and augmentation procedures enter the practice almost daily. There are countless publications and tempting continuing education courses on everything. The art of the (dental) practitioner is to correctly classify the amount of innovations and information for the benefit of the patient. What is good and what is bad for my patient? What is risky and what is predictable? What is effective and what is unnecessary? What pays off and what only costs? What is fashionable and what is enduring? The basis of judgment is experience and profound knowledge.

Dentistry has traditionally been strongly influenced by material sciences, because until a few years ago it took place predominantly outside the better ectodermal envelope of the body. Through implantology, among other things, the spectrum of dental treatment has expanded into the interior of our patients’ bodies. This requires better: a broadened theoretical basis for dentistry, which is derived from biology and medicine. The performance of the surgeon in augmentations depends not only of the correct technical execution, but above all the correct therapeutic recommendations under consideration of numerous influencing factors. This book is intended to help the practitioner build self-confidence and critical judgment in making good decisions and to provide some joy when the biology behind one’s clinical observations becomes apparent and sustained success is achieved.

1.1 Bone as a Success Factor in Implantology

The opportunity for functional and biological tissue regeneration is a privilege of dentistry compared to most other branches of medicine. Today, bone regeneration techniques allow dentists to accept almost no deviation in the shape of the jaw bone as a given, whether acquired by accident, tumor, or atrophy of the alveolar ridge after tooth loss or as the result of congenital lack of dentition.

This also applies to corrections of the occlusal relation and vertical dimension of the jaws. The foundations for surgical correction of the bone and the overlying soft tissues in preparation for tooth replacement treatment were largely laid by specialists in preprosthetic surgery in the 1970s and 1980s.¹ Bone augmentation is a safe procedure in the long term. Data from prospective 10-year studies exist today for major techniques.

Fig 1-1 The fate of the implant is decided by the first millimeter. Roughened implant parts must not come into contact with the bacteria of the sulcus. Augmentation is required here.

The fate of the implant is decided on the first millimeter² (Fig 1-1). A circumferential ring of bone covering all roughened portions of the implant on all sides can prevent downgrowth of the junctional epithelium and thus pocket formation³ and supports a good long-term prognosis for lasting implant health.⁴ Circumferential bone of at least 1-mm but preferably 2-mm thickness supports a good long-term prognosis and the basis for a soft tissue sealing apparatus. Sufficiently thick bone creates a natural gingival color by preventing a discoloration by the dark titanium of the dental implants (Fig 1-2). Bone is generally the basis of esthetics as it defines the height of the gingiva (Fig 1-3) and anchors the facial soft tissues. The alveolar process must be sufficiently wide to accommodate a stable implant with sufficient material thickness that will not deform or even fracture under mastication. In addition, the bone height should be sufficient to avoid long dental crowns and interdental plaque retention. Bone should be present within the prosthetic and functional loading axis of the restoration. This allows the prosthesis to be more delicate and esthetic (Figs 1-4 to 1-6).

Fig 1-2 Photo superimposition. Replacement of the maxillary lateral incisors with titanium implants. A gray discoloration by titanium should be prevented by sufficiently thick bone and soft tissue.

1.2 Aims of Bone Augmentation: Function – Esthetics – Prognosis

The aforementioned guidelines result in the following goals of bone augmentation:

• Function
• Esthetics
• Prognosis

Implantology has masticatory rehabilitation as its primary medical goal. With good function, good esthetics often results automatically. In addition, esthetics is becoming more important as a therapeutic goal. The position of the bone shoulder determines the position of the overlying soft tissue and thus the gingival (pink) esthetics. These relationships are summarized in the English rhyme:

The tissue is the issue,

but the bone sets the tone,

and the clue is the screw. (D. Garber, Atlanta)

Fig 1-3 The soft tissue height (biologic width) is composed of the following elements: connective tissue attachment, junctional epithelium, and sulcus depth or free gingiva. It is the same for teeth and implants, averaging about 3 mm. Because the soft tissue height is a constant, it can be planned in advance by augmenting the bone height.

Fig 1-4 In implant-retained prosthetic restoration of the maxilla, the implants can be placed intersinusoidally in the anterior region, avoiding sinus floor augmentation. In this case, however, the prosthesis must be an overdenture or otherwise made very solidly to avoid fracture. With augmentation, the support polygon is large, allowing the placement of 6 to 8 implants and the use of a removable prosthesis that can be designed much more delicately because the risk of breakage is low.

Fig 1-5 Maxillary restoration without augmentation. a. Overdenture for the maxilla with intersinusoidally placed implants, avoiding augmentation. b. Lack of salivary irrigation underneath the overdenture leads to reddening of the palate (ie, denture stomatitis, candidiasis) and gingival hyperplasia at the implants with pseudo-pocket formation. The masticatory load-bearing capacity is relatively low due to the lack of abutment spread.

Fig 1-6 Maxillary restoration with augmentation. a. Sinus floor augmentation allowed the placement of more implants, providing a greater number of abutments. b. Panoramic image after sinus floor augmentation on both sides. c. Prosthetic restoration with a delicately crafted removable and prosthesis that allows for irrigation and interdental cleaning (Prof. Dr. M. Kern, Kiel). d. Galvano-telescopic copings. e. Intraoral frontal view of prosthesis. f. Extraoral appearance of the lips with natural esthetics.

1.3 Atrophy of the Alveolar Process

In contrast to the jaw base, the alveolar process in the maxilla and mandible is not embryologically endochondrally preformed. The alveolar process bone is formed via intramembranous ossification alongside the eruption of teeth to the occlusal plane. Accordingly, this bone also disappears after the teeth are lost. Alveolar ridge atrophy therefore is physiologic and not a disease; however, the consequences, ie, loss of masticatory function and the inability to wear dentures, can lead to disease, especially since the atrophy progresses very rapidly in some patients. Resorption of alveolar bone begins at the buccal bone lamella and later involves the oral bone lamella. The resorption of the maxillary alveolar process is also explained by the principle of bundle bone (Fig 1-7). This type of bone consists of the calcified insertions of ligaments. In the alveolar process, these are the insertions of Sharpey fibers (after William Sharpey, anatomist in London). After tooth extraction, the periodontal ligament disappears as does, inevitably, the bundle bone, which can make up the entire facial lamella of the dental compartments. Loss of the alveolar process is accelerated by, among other things, marginal periodontitis, traumatic tooth extraction, unstable overdentures, and generalized osteoporosis. Particularly severe atrophy with formation of a flappy ridge and irritation fibromas is seen in combination syndrome (Fig 1-8) in the anterior maxilla when hard mandibular residual dentition or mandibular dental implants occlude against a maxillary full denture supported only by soft tissues. As atrophy occurs, there is also decreased blood flow to the jaws, which can cause a reverse flow in the mental artery. The risk of fracture increases due to the reduction in the cross-section of the mandible.

Since the teeth and the alveolar process in the maxilla are physiologically inclined buccally and there is a narrow apical base, height reduction of the bone results in a shift of the ridge center inward, ie, centripetal atrophy of the maxilla (Fig 1-9

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