Concepts of ridge augmentation

Editor's Notes

• #3: Mark M. Ravitch said this
• #4: After the loss of teeth atrophy of the alveolar processes occurs in a vertical as well as a horizontal plane. The term atrophy is defined in the dictionary as “a wasting away; a diminution in the size of a cell, tissue, organ, or part”. This process is starting and continuous throughout life because of the lack of stimuli (disuse atrophy) seen on alveolar process of the jaws. A classification of the edentulous jaws has been developed based on a randomised cross-sectional study from a sample of 300 dried skulls. It was noted that whilst the shape of the basalar process of the mandible and maxilla remains relatively stable, changes in shape of the alveolar process is highly significant in both the vertical and horizontal axes. In general, the changes of shape of the alveolar process follows a predictable pattern.
• #5: Different views of sites of a dry mandible. a. cross section through an empty alveolar socket of a mandibular canine tooth; the red line represents the expected bone contour that would be established had the tooth been removed; note that the buccal wall contains exclusively cortical bone. b. cross section through an empty alveolar socket of a mandibular premolar tooth; note that the buccal wall contains exclusively cortical bone in spite of its being relatively thick c. cross section through an empty alveolar socket of a mandibular canine tooth; the red line represents the expected bone contour that would be established had the tooth been removed; note that the buccal wall is extremely thin ("paper thin") and contains exclusively cortical bone d. cross section of an edentulous inter-radicular site a few months after tooth loss; there is less bone loss in this area compared with extraction socket sites. e. upper view of an empty socket of the lower second molar showing the cribriform alveolar bone proper f. clinical view of the anterior segment of an edentulous mandible 1 year after extraction; severe disuse atrophy is noted
• #6: Healing of the extraction socket with and without socket grafting. When socket grafting is not adopted, major alveolar ridge resorptionoccurs.Inafirstphase,initiallythebloodclot,subsequentlythegranulationtissueandlatertheprovisionalmatrixandthewoven bone fill up the alveolus. The bundle bone is completely resorbed causing a reduction in the vertical ridge. In a second phase, the buccal wall and the woven bone are remodeled causing the horizontal and further vertical ridge reduction. When socket grafting is adopted, the first phase and vertical bone reduction still occur, however, the second phase and the horizontal contraction are reduced.
• #8: Atwood evaluated the resorption process in the postextraction anterior ridge of the edentulous mandible in several clinical and cephalometric studies [11-13]. Atwood and Coy divided the factors affecting the rate of resorption into four categories: anatomic, metabolic, functional and prosthetic. Anatomic factors included the thickness of the mucosa covering the ridge, the ridge relationship, the depth of the socket, the number of sockets present, the size, shape, and density of the ridges. Metabolic factors influence the cellular activity of osteoblasts and osteoclasts by way of nutritional, hormonal, and other metabolic facets. Functional factors involved the intensity, duration, frequency, and direction of forces applied to bone. These factors affected cellular activity, bone formation or resorption, depending upon a patient’s resistance to the forces. Primarily, prosthetic factors concerned the type of prostheses involved and the materials and principles used to obtain a restorative goal. All categories as described by A
• #10: In 1983, Seibert classified alveolar crestal defects:[1] Class I: buccolingual loss of tissue with normal apicocoronal ridge height Class II: apicocoronal loss of tissue with normal buccolingual ridge width Class III: combination-type defects (loss of both height and width) Seibert in 19832 and later modified by Allen in 1985Allen further quantified the loss of ridge dimension into mild (<3 mm), moderate (3–6 mm) and severe (>6 mm).
• #18: Part 1: Orientation of the defect H: horizontal V: vertical C: combined S (or +S): sinus area Part 2: Reconstruction needs associated with the defect 1: low: < 4 mm 2: medium: 4-8 mm 3: high: > 8 mm Part 3: Relation of augmentation and defect region i: internal, inside the contour e: external, outside the ridge contour
• #38: L-PRF membranes are not comparable to resorbable collagen or non-resorbable ePTFE membranes, they belong to a completely different category of membrane [145]. However, the difference between GTR and NTR is not only the replacement of the various heterologous membranes used in GTR by a new kind of natural autologous membrane: it is also a true evolution of the concept behind. Indeed, L-PRF membranes are optimized blood clot, and therefore their interactions with the tissues do not follow strictly the core principles of GTR: GTR membranes had to stabilize the blood clot and to create a cell-proof barrier against soft tissue invagination, a NBR membrane is the blood clot itself (therefore rich in cells) and is only a bioactive competitive barrier. While other membranes are considered as foreign bodies by the host tissues and interfere with the natural tissue healing process, a L-PRF membrane is as natural as the host tissue: it is a blood clot prepared in an optimized form and that can be easily handled by a surgeon. mThe use of L-PRF membranes during the treatment of periodontal intrabony defects was called NTR and represented an alternative technique to GTR. Logically GBR can evolve into a new form of bone regeneration using L-PRF membranes, called Natural Bone Regeneration (NBR). NBR is based on the same principles than NTR described previously, the main difference being that NBR only targets to regenerate bone (and not the periodontal ligament and gingival attachment on the teeth), and consequently also to regenerate the gingival tissue covering this bone: in the NBR core concept, like in NTR, hard and soft tissues can not be considered separately.
• #41: The survival rate of the 31 implants was 100% and the prosthesis success rate was 96.8%.
• #44: If buccal vertical releasing incisions and periosteal fenestrations do not provide enough flap advancement to achieve tensionless primary closure, it is necessary to cut deeper into the sub mucosa. This is done only when necessary as the patient experiences increased morbidity with regard to swelling, hemorrhage, and discomfort.
• #52: Chemical composition of bone consists of 65% mineral, mostly hydroxyapatite, 25% organic matrix (90% collagen, 10% proteoglycan and noncollagenous protein), and 10% water. Bone is formed by osteoblast. Bone formation starts with the deposition of osteoid, which subsequently mineralized. Woven bone formed at faster rate than lamellar bone. The mineralization of woven bone is initiated by matrix vessicle pinched off from the cytoplasmic process. It is able to form struts and bridges and its apposition rate depends on osteoblast recruitment. Woven bone grew at rapid rate and the interval between deposition and mineralization is only from 1 to 3 days. Lamellar bone grows about 1 to 2 micron per day. The interval between deposition and mineralization is 10 days. Mineralization of lamellar bone occurred with some basic criterias: an adequate concentration of calcium and phosphate ions, the presence of a calcifiable matrix and nucleating agens, and the control by regulators (promoters and inhibitors). Collagen is thought to have a major role in being a nucleator. Study of the repair of bony of bony defects of various diameters have shown that when the diameter of the bony defect is .2mm in diameter or less, we will have a new perfect osteon growth. When the defect is approaching .5mm in diameter, osteon like compartment resulted from branching vessel will form. When the defect is 1.0mm or more in diameter, blood vessel could not traverse the area and thus the result is the incomplete healing of the defect. The distance of which the blood vessel can branching and allow complete healing of the defect is called the osteogenic jumping distance (Harris 1983). It indicates that bone is not able to cross gaps wider than 1mm by one single jump. Thus in the case of the defect which is greater than 1.0mm in diameter, we have exceeds the osteogenic jumping distance. The osteogenic jumping distance is species specific (Rat has high osteogenic jumping distance and therefore experiment with rat should allowed for creation of greater defect). The distance of which the blood vessel can branch and allow complete bridging by woven bone healing of a defect is called the “osteogenic jumping distance” 46. The osteogenic jumping distance is around 1 mm for rabbit cortical bone and is species specific. Larger gaps or holes will take longer time to complete repair. Bone filling of larger defects is facilitated by osteoconduction, ie, by offering a framework or scaffold for bone deposition. There are certain conditions that will influence the osteoconduction: 1) Biocompatibility of the scaffold and 2) The external and internal structure of the scaffold should favor tissue ingrowth and bone deposition
• #59: Leo Tolstoy, Anna Karenina