INDEX
1 INTRODUCTION 4
Consequences of the loss of teeth 6
Modifications of the jaw as a result of edentulism 7
The classes of bone atrophy 9
Classification of bone quality 10
Aesthetic changes as a result of total edentulism 12
2 RECONSTRUCTIVE SURGERY 14
The Bone Grafts 14
Osteoconduction 15
Osteoinduction 16
Osteogenesis 16
Biology of non-vascularizated bone grafts 17
Iliac Crest graft 19
Graft surgery managment 20
3. IMPLANTOLOGY 22
Osseointegration 22
4. THE AIM OF THE THESIS 25
5. MATERIALS E METHODS 26
Surgical methods 26
Post Operative treatment 28
Implant surgery 30
Data collections 31
Method of calculation of volumes and surfaces 32 Measured quantities, derivatives, procedures fitting and interpolation 37
Statistucal analysis 40 6. RESULTS 41 7. DISCUSSION 48 8. CONCLUSIONS 52 9. APPENDICES 53 Appendix A 53 Appendix B 67 Appendix C 70 Appendix D 94 Appendix E 95 Appendix F 111 10. BIBLIOGRAFY 112
INTRODUCTION
The oral rehabilitations functions supported by osseointegrated implants have become very important in the rehabilitation techniques both for totally edentulous arches that for those who are only partially edentulous
1,2,3.
In jaws, an inadequate volume often does not allow for the immediate placement of dental implants; this because it is the natural process of resorption of the alveolar crest after dental extractions. In more the remodeling process is continuous, then, especially for edentulous patients for many years, they can cause serious alveolar bone resorption, especially if the patient was suffering of untreated periodontal disease 4.
However, even in the jaws that have undergone a process of severe atrophy of edentulous ridges, the implant-prosthetic rehabilitation can be made before bone augmentation; such reconstructive procedures ranging from vascularized bone graft 5, non vascularized bone graft 6, or by tissue
regeneration techniques 7.
Regarding not vascularized bone grafts sampling sites are various both intraoral, including the jaws 8, both extraoral such iliac crest 9, tibia 10 and
calvaria 11. If for the intervention of bone reconstruction is required only a
modest amount of autologous material, it is usually taken intraorally, from chin or preferably from mandibular branch 12,13,14. The benefits are various,
such as intraoral access, low morbidity, reduced recovery time, minimal bone resorption and maintaining of the original density of the graft; may still arise, in the patient, post surgical compliances of a sensorial nature due to the type of sampling technique made 15.
If the increase of alveolar crest is necessarily extended in volume, the calvaria or iliac crest donor sites are the most chosen 16,17,18; the iliac crest,
provides a good amount of autologous material, even if the picking operation is not without risks: injury may occur venous-arterial, nerve damage, injuries to noble structures such as the ureter, can occur hernias, pelvic fractures, or problems of an infectious, aesthetic defects and incidents of chronic anxiety, and of course also extensive bruising 19. In this
regard the levy calvaria, severe complications are extremely rare, as long as the surgeon receive appropriate training 20.
The unpredictable nature of the resorption of the bone graft is the biggest difficulty encountered by the surgeon that comparisons with bone reconstruction in maxillofacial surgery. To try to solve this problem numerous studies have related bone resorption with the embryological origin (EC Endochondral intramembranoso or IM) and with the micro-architecture of bone (cortical or cancellous bone). Some autors refers that the dominant process of resorption was the embryological origin of the graft, highlighting that the autogenous graft intramembranoso retained its volume better than they did the grafting Endochondral 21,22, others were
convinced that the driving factor the resorption process was the micro-architecture; Indeed Hardesty & Marsh speculated that the differences in the conservation of the volume of the bone graft taken from the cortical thick calvaria and iliac crest (taking cortico-cancellous), which were due more to their embryological origin, three-dimensional bone architecture 23.
Other authors have demonstrated below that graft survival it is primarily determined by the composition in the cortical and cancellous bone 24, while
others have shown that the factor which drives the volumetric stability is the micro-architecture of the coupling 25.
numerous studies that tried to quantify numerically the process of resorption, both in terms simply through the use of two-dimensional planar x-rays 26, both in terms of three-dimensional, analyzing volume and density
of the graft 16,27,28. The calculation of the volume of the bone graft has to
pass through a measurement that takes into account the three dimensions of space, and therefore for diagnostic techniques for three-dimensional images, suited to the morphology of hard tissues, or scans, computed tomography (CT scan ).
Resorption of the grafts in reconstructive purpose of the alveolar ridges, taken from the iliac crest, appears to be greater than the remodeling of those taken from calvaria, and this is reported by different authors 16,27,29.
In that regard, vascularized bone grafts, they are characterized by a more rapid and an almost complete incorporation which allows an immediate structural support, from the immediate ability to produce new bone (thanks to the integral transplantation of living cells) and by a sudden blood supply from part of the receiver 30. This provides an easily understandable because
the remodeling of the grafts is less vascularized than non-vascularized 31.
Consequences of the loss of teeth
The loss of teeth as well as having psychological effects of various levels on the patient, because the loss of stomatognathic functions, phonetics, chewing and aesthetics. The tooth loss is often associated with anatomical changes characteristic of senescence, with structural and functional changes in soft tissue and hard tissue. Also they change the biomechanics of the TMJ and intermaxillary relations. With the loss of teeth (edentulous intercalated) creating a free space in the arch that is gradually closed by the adjacent teeth. The teeth antagonists no longer having a stop occlusal extrude. These typical tooth movement, interfere with any rehabilitation
therapies, as causing the loss of the space required for the placement of the prosthetic elements.
We will focus on the processes of absorption in the bones and the maxillary soft tissue alterations, turning to look mainly to those changes that occur at the level of the maxillary frontal edentulous ridges, a site of the treatment.
Modifications of the jaw as a result of edentulism
Bone is a living tissue constantly subject to phenomena of neoapposizione and resorption and its dimensional and structural stability is the result of constant balance between these two processes, we can speak of stability of dynamic type. When one of the two phenomena prevails observed structural changes and morphological bone. Several studies and several theories have followed over the years to explain and investigate the elements responsible for the processes of bone resorption and remodeling. Next to factors uniquely recognized influential, such as gender, hormones, metabolism, and parafunctions inadequate prosthesis, considerable interest was studies and related theories that see the shape and the bone tropism given and maintained by the stimulation exerted by the anatomical structures related to it .
According to the theory of Moss, shape and volume of bone are determined not only genetically but also by functional stimuli exerted on the bone from other tissues that he calls "functional matrix". The fabrics that constitute the functional matrix; muscles, vessels and nerves, act on
Roberts et al. They argue that the bone must be constantly stimulated to stay healthy and that this favors the equilibrium phenomena apposition and resorption 33.
The teeth transmit compressive forces to the alveolar bone and the tensile (piezoelectric potential) sufficient to keep it in a situation trophic; when you lose your tooth is less stimulation exerted by this alveolar bone and consequently the alveolar atrophies.
It is good to distinguish the basal bone, which is formed in the fetal period and which possesses most of the muscle insertions, alveolar bone that is formed instead following the eruption decay. The close relationship between alveolar bone and teeth remains constant for the whole life so that no recess is formed in the case of agenesis and the loss of the teeth follows the atrophy of the alveolar bone. We can now say in the light of what the literature shows that the alveolar atrophies because most stressed by the element tooth. The basal bone does not undergo a substantial modification of its morphology as a result of the loss of teeth, since in it remain the muscle attachments to stimulate it. Only in cases of severe bone atrophy, favored by the action of traumatic prosthesis incongruous or by the absence of trophic muscle linked to it, typical of aging, we are witnessing a resorption which however never goes beyond the ad muscle. The extent of remodeling varies from sector to sector and maxillary changes depending on the individual. Individual variability is influenced by systemic factors that regulate bone metabolism such as calcitonin and parathyroid hormone. Several systemic diseases can affect bone metabolism and particularly osteoporosis (senile, post-menopause, hyperparathyroidism and Cushing's syndrome), osteomalacia and taking medication (corticosteroids, anticonvulsants). There are also local factors able to promote the remodeling as facial morphology. The dolichocephalics retain more bone than brachycephalic and this is due to the different distribution of
masticatory forces in the two skeletal types. Traumatic extraction techniques and inadequate favor greater absorption, prolonged use of removable dentures can cause ischemia and periosteal then promote bone loss. From the clinical point of view the reshuffle of edentulous jaws proceeds according to predictable patterns and can be differentiated according to the various sectors concerned. In the upper jaw the resorption process has generally in a horizontal centripetal type both in the front and in the rear sector. In the mandible you have a horizontal resorption area interforaminal, while the rear is mostly vertical, overall it is centrifugal. The changes they face the edentulous jaws, causing an alteration of intermaxillary relationships with a tendency to pseudo third skeletal class in the sagittal and transverse cross bite. In figure 1 are indicated the structural alterations of the edentulous jaws compared with the original situation in the presence of dental elements.
The classes of bone atrophy
will refer to the classification of Cawood and Howell 34 which is currently the most cited in the literature. The authors formulated their classification studying the changes of the morphology of the edentulous jaws on skulls dry and documenting the use of points defined and easily reproducible bone resorption despite the diversity of individual follows patterns repeatable and predictable. They came to the conclusion that the resorption was different according to the place where was manifested and substantially centrifugal and centripetal for the mandibular jaw resulting change in relations interarch. The classification for the atrophy involves 6 classes and 6 classes mandibular jaw broken in turn for the anterior and posterior. In detail:
• Class I teeth present
• Class II alveolar post-extraction immediate
• Class III alveolar post-extraction with late reossification dell'alveolo post-extraction alveolar process and rounded but adequate height and thickness
• Class IV ridge with adequate height but insufficient thickness, defined in "knife edge"
• Class V flat crest, insufficient both in height and in thickness • Class VI crest depressed, with baseline bone atrophy
Classification of bone quality
Another important change in load of edentulous jaws is that of decreased bone density due to the loss of the stimulus functional teeth in the arch. The ability to classify the bone quality is important for professionals because of the tool to predict the chances of success of therapies and reconstructive implant, influenced as we shall see, the bone quality. The authors Lekholm and Zarb proposed a classification of bone quality that is based on the ratio of the component medullary than cortical 35. This
classification has been revised and expanded by Misch 36. The author
divides the types of bone density in the following:
D1
dense cortical bone and cancellous poorD2
bone with thick cortical and cancellous meshedD3
bone with cortical and cancellous bone thin-meshedD4
bone with thin cortical and cancellous bone to meshD5
immature bone, demineralizedThe bone of D1 is typical of the region baseline symphysis. It's a little bone indicated for placement of plants and for fixing a graft because it has a poor blood supply that significantly slows the re-formation of bone, are difficult techniques of site preparation, because the density of the tissue requires a torque to rotating instruments with excessive risk of bone necrosis from overheating. The bone of type D2 bone quality is optimal and is present in the body and jaw in the frontal area of the jaw. The cortex
characteristics are comparable to that of class D2 even if with a lower vascularization of the cancellous bone. The bone type D4 is a soft bone that remains poorly suited to any surgery. Its cortex is very thin and does not allow an adequate primary stability of the inserted implants.
The clinical data of bone density can be detected accurately by means of computed tomography data analyzed with specific programs for dentistry like Denta-scan and Maxiscan. The oblique sections of the jaws can be distinguished visually from the cortical bone marrow and then bind the type to a class of Misch. The data TAC assign each voxel a number that is dependent on the average density of the tissues in that specific unit volume. This number which can be put in evidence on the radiographic areas of interest (ROI) is part of a scale of the density of Hounsfield (Hu). It can take values between -1500 and +2595 and combines the density of water to 0 while the air to values close to -1500. The bony structures are included in the scale values between +150 and +1000 Hu. Is possible to relate the data in units HU with the classification of Misch as follows:
Misch
D1
HU> 1250Misch
D2
850 < HU ≤ 1250Misch
D3
350 < HU ≤ 850Misch
D4
150 < HU ≤ 350Aesthetic changes following total edentulism
The remodeling of the jaw following dental extractions causes, as seen in the previous paragraphs, bone volume modifications, intermaxillary relations changes and also soft tissue alterations. All these muscular and skeletal changes cause a modification in facial morphology that the slow
establishment are not caught by the patient. This aspect should be taken into account when they're going to reconstruct the maxillary bone volumes of introducing changes in facial appearance to which the patient must be properly prepared. Mandibular resorption of the alveolar process causes superficializzation of the mandibular neurovascular bundle. The insertions of the on the buccal and lingual mandibular masticatory muscles become more superficial inreduction of the vestibule. The band of attached gingiva tends to decrease gradually and in cases where bone resorption has been particularly rapid creating the so-called mucosal ridges furniture (flabby ridges). The maxillary bone loss is associated with a flattening of the vault of the palate and the palatine neurovascular bundle is positioned at the edentulous ridge. Aesthetic consequences that are associated to the total edentulism and are countless and all associated with a senile age. It has a decrease in facial height caused by loss of the vertical dimension. The chin becomes protruding forward giving a prognatic aspect (pseudo third class). The orbicularis muscle is no longer supported by the bony structures and dental loses tone causing a narrowing of the lips. The corners of the mouth turn down giving the patient look "unhappy". Increase wrinkles that surround the upper lip, you approfonda the nasolabial groove, there is the disappearance of the angle lip mental, increases the angle filter-columellar.
RECONSTRUCTIVE SURGERY
To solve the deficit that is created in patients following partial or total loss of alveolar bone, the first half of the '900 to date have been designed numerous methods of reconstructive surgery, associated or not with the use of multiple grafting materials . Calcium crystals, glass-ceramics, bone derived from cattle, horses, human cadavers and treated with various methods of freeze drying, freezing and demineralization, these are some of the materials most often used as a bone substitute in clinical practice. None of these resources used for the reconstruction of atrophic maxillary equated, in terms of predictability of success and retention volume grafted, the results obtained from the bone autograft.
Those benefits have been slow to show off in the scientific literature, as long as the use of autologous bone graft was associated with traditional prosthetics procedures (ie removable dentures); Only with the advent of the prosthesis on osseointegrated endosseous titanium implants, this material "noble" was able to highlight its particular characteristics regenerative.
Since then research has centered its scope on the study of the biology of autologous bone grafts, in order to obtain guidelines for their correct and beneficial use.
The Bone grafts
The grafts to increase the amount of bone available are classified according to their origin in:
• AUTOLOGOUS grafts: from the same individual
• SYNGENIC grafts: from an individual genetically identical (identical
• ALLOGENIC grafts: from individuals of the same species but different
• XENOGENIC grafts: from organisms of a different species (cattle,
pigs, horses ...)
• ALLOPLASTIC implants: are exclusively synthetic and
biocompatible.
The ideal characteristics sought in a graft material are: 1. Biocompatibility
2. Osteoconductive 3. Osteoinduction 4. Osteogenesis
5. Allow the osteosynthesis
6. Get a revascularization in the shortest possible time
7. To be removed from the body and replaced by new bone recipient of excellent structural qualities
8. Easy availability
9. Good cost / benefit ratio
Osteoconduction
It is the ability grafted bone to provide structural scaffold for new bone formation. The graft is flooded with chips that provide vascular progenitor bone cells from the periphery to the inside, favoring a gradual replacement with new bone graft itself ("creeping substitution").
Osteoinduction
It is the ability of the graft to stimulate the differentiation of mesenchymal cells from the totipotent receiving site or from the vascular bed in osteoblasts. This attitude is the presence and the liberation by the graft, biochemical messengers of inducing the differentiation of bone, in particular morphogenetic proteins (BMB) 37. The osteoinductive materials most frequently used are allogenic and autogenous bone. The allogenic bone is taken from cadavers and processed and stored in various forms. In literature there are controversial opinions on the osteoinductive capacity of allogeneic grafts and the discrepancy of results is likely to be attributed to different concentration of BMB present.
Osteogenesis
It is the ability of the graft to form new bone by the proliferation of viable cells contained in it. The autogenous bone is the only material that possess this property that can be maintained at high levels by adopting techniques for sampling and preservation atraumatic and grafting the bone collected as soon as possible into the bone receiver. The cells of the graft shipping, survived in variable quantities depending on the trauma suffered, they will be maintained viable by passive diffusion of nutrients from the surrounding tissues. For this purpose they play an important role, at the same conditions at the receiving site, the microarchitecture of the graft and the amount of viable cells present. In particular it was noted that the structure of cancellous bone compared to cortical bone structure has more features rigenerative38 because it is more easily perfused in depth as a nutrient, has a higher concentration cell and undergoes a more rapid revascularization.
Evidently, this is the only autologous bone graft material to possess all the
characteristics described (osteoconduction, osteoinduction and
osteogenesis) and is therefore to be considered, at the time, the "gold standard" for bone reconstructive surgery.
Biology of not vascularized bone grafts
After transplantation of the bone at the recipient site starts healing, characterized by a succession of a number of biological processes that lead final engraftment of the graft. These biological phases 39 can be
summarized as follows:
1. Formation of a hematoma around the graft caused by the bleeding of the surgical wounds of the receiving site. At this early stage only a small amount of grafted cells, peripheral, remain viable through imbibition plasma to the early revascularization.
2. Around the fifth, seventh day appears an inflammatory response around the graft that is being reorganized into a dense fibrovascular stroma.
3. Between the tenth and the fifteenth day is a progressive vascular invasion with trend centripetal namely from the periphery of the graft in its interior. Necrotic tissue derived From the autolysis cell is removed from macrophages, and time slots are filled with tokens vascular leading primitive mesenchymal cells with osteogenic potential.
4. In the areas reached by the tokens neoformed vascular enter the phase of bone deposition. Osteoblasts and osteoclasts in the graft
revascularization and neoapposizione. These events are influenced by phenomena of osteoconduction, osteoinduction and osteogenesis that act in various ways in the early stages of healing and persist until there is complete revascularization and bone replacement graft. 5. The graft is completely replaced by new bone is subject to the
phenomenon of remodeling. It is due to the influence of mechanical stress of the environment surrounding the graft, as already affirmed in 1892 Wolff ("form follows function").
The ultrastructural features graft seem to affect these biological steps. The medullary bone graft (Figure 2a) is revascularized completely and more rapidly than the cortical bone since the presence of large spaces between the bone trabeculae without resistance all'insinuarsi of newly formed blood vessels. The gradual revascularization of cancellous grafts by vessels from the recipient bed is normally completed within a few weeks and after the first few hours the nutrition of grafted cells is guaranteed even in the depth of the phenomenon of perfusion. At the same time the invasion vascular graft arrive undifferentiated mesenchymal cells lining the trabecular bone, differentiate into osteoblasts and osteoid depositing a layer around a central core of necrotic bone. Necrotic areas trapped in the newly formed bone are gradually absorbed the activity osteoclastic and also replaced completely by new bone 37. The cortical bone graft (Figure 2b) is revascularized rather
more slowly and sometimes incompletely. Revascularization is limited by dense lamellar structure and the newly formed vessels can penetrate into connection only through the existing channels of Volkmann and Havers, from the periphery of the graft to the inside. It is not known penetration of vessels during the first week and the complete revascularization can require several months or not completed ever. The cortical graft repair the activity begins with early osteoclast resorption systems Haversian peripheral necrotic followed by resorption of the inner cortex. Where he had bone
Fig 2b. Gli innesti di osso corticale presentano una rivascolarizzazione più lenta e incompleta, a causa della loro densa struttura lamellare. I vasi sanguigni devono penetrare attraverso i canali di Havers e Volkmann.
resorption appear osteoblasts that deposit osteoid matrix. The start of the stage in the graft cortical apposition occurs before the necrotic bone is properly removed. These necrotic areas surrounded by a halo of bone resorption and peripheral newly formed take the form of seizures bone. The graft cortical loses about 60% of the normal resistance to several months after its positioning as the repair process starts with osteoclastic resorption that increases its internal porosity 37.
Iliac Crest graft
The first authors to describe the use of bone grafts for purposes implant from the iliac crest were Kratochvil & Boyne 40 and Breine & Brånemark 41
after experiencing a technique of positioning of grafts from the crest and installations in a single phase, with the clinical data unsatisfactory, they developed an intervention divided into two halves with the placement of
Fig 2a. Gli innesti di osso spongioso presentano una rivascolarizzazione più rapida e completa, a causa della presenza nella loro architettura di ampi spazi aperti che facilitano l’invasione vascolare
presents the advantage of a good surgical accessibility. The harvested bone has features cortico-medullary bone marrow with predominant component, which give a fair plasticity and easy adaptability to the receiving site. In contrast, there is the disadvantage of increased morbidity, need for hospitalization and operate on the patient under general anesthesia, the need to rig operators simultaneously two fields one for the withdrawal at the crest level and the other for the graft in the oral, there is the impairment of gait for at least one month and permanence, even if modest in size, of a cutaneous scar. In some cases they were found changes in thermal sensitivity and pain of the skin surface 42.
The iliac crest is the top edge of the hip bone, part of the pelvic bones, originated before the anterior superior iliac spine and goes back to the posterior superior iliac spine. On ASIS fit muscles sartorius, tensor fascia lata and the inguinal ligament. The outer lip of the ridge are insertion muscles gluteus medius and gluteus minimus.
The inner lip fit the internal oblique muscles, transversus abdominis muscle and the iliac. As for vascular structures, the arterial circulation of the basin is ensured from the iliac external and internal. In the donor site there are no large-caliber vessels and arterial trunks of surgical interest are represented dall'arteria circumflex iliac deep and shallow. The nerves of surgical
interest are the inguinal-ileum nerve, ileo-hypogastric and lateral femoral cutaneous thigh. The seats iliac pickup can be localized in ileum front or rear. The most used is the area medial iliac front (Figure 3).
Grafting techniques
The placement of the graft within the receiving site is closely linked to the type of bone defect and the need to restore a height and a thickness
Fig 3. principale area di prelievo da cresta iliaca
adequate to ensure the primary implant stability. Depending on the position the grafts are divided into:
IMPLANTS OF ENDORSEMENTS: "ONLAY grafts"
Grafts Onlay Veneer (grafts affixing horizontal): this type of grafts are indicated in the correction of edentulous ridges thin (less than 6 mm), but high enough for the implant (at least 10 mm between the crestal margin and anatomical structures in risk). Local fundamental requirement is the presence of soft tissue and well vascularized with a sufficient amount of keratinized mucosa.
Onlay Grafts Occlusal (grafts affixing vertical): these grafts are indicated in the ridges of suitable thickness (> 6 mm), but of insufficient height (<10 mm) to the positioning of installations of adequate length, defects in post-traumatic or post- oncologic resection edge alveolar jawbone and in cases of increased distance interarch. They are contraindicated in case of insufficient quantity or quality of the soft tissues of the recipient bed.
IMPLANTS FOR INTERPOSITION: "INLAY grafts"
The grafts of this type are used in small bone defects to restore the profile and the required bone volume to the placement of the implants 43.
SADDLE Grafts
These grafts are indicated in case it is necessary to restore in a same bone defect both the height and thickness adequate for the implant placement, or rather when requesting a ridge augmentation both vertical and horizontal. Also in this case the graft fixation will be done via rigid fixation can prevent it have movements during the healing period 43.
IMPLANTOLOGY
Modern implantology is a discipline that provides dental-surgical rehabilitation of the edentulous patient through the positioning in the jaws of biocompatible titanium implants able to osseointegrate. They serve as an anchor point for the dental prosthesis. Like many other discoveries also osseointegration, the principle underlying the current oral implantology, was made randomly. The credit goes anyway to Professor Branemark, orthopedic of the Swedish University of Gothenburg, and his research group. In 1952 he was studying the microbiological characteristics of bone healing of rabbit femurs were surgically inserted in which the cylinders of titanium. At the time of the removal, a few months after placement, he realized that it was no longer possible to extract them, as appeared to be welded to the bone. This new phenomenon was called osseointegration and was described as a process by which you get a rigid fixation of alloplastic material, clinically asymptomatic during functional loading. Scientific research is therefore proposed to investigate the main requirements for optimal osseointegration and in 1981 Albrektsson et coll. defined these prerequisites:
• biocompatibility of the implant material • Shape the plant
• Terms of implant surface • State of the implant site
• Surgical technique for implant placement • Load conditions imposed after
Osseointegration
Osseointegration is defined histologically as a direct contact between bone and alloplastic material evaluated resolution limit of optical microscopy.
This definition can not be used in clinical practice for the evaluation of the therapeutic success can not for obvious reasons take samples for histological microscopic analysis. In dental practice assessing osseointegration indirectly, through its clinical correlate that is manifested by:
• Lack of mobility implant
• No pain application of torsional forces
If you experience these conditions we can rule out fibrointegration, synonymous with treatment failure. In fibrointegration forms of fibrous connective interface between bone and implant that being soft consistency and presenting innervation gives the system mobility and tenderness to mechanical stimulation. The fibrous tissue is also not suitable to withstand masticatory loads since these will cause an inflammation followed by bone resorption. The osseointegration however, is not to be considered as a phenomenon which manifests itself as "all or nothing". The histological data show quite an event that partially affects the implant surface, in "patchwork", with the degree of contact between bone and implant more than 60% in cases of therapeutic success.
The osseointegration is a healing process of a wound that does not take place eventually, but only when it has been complied with all the guidance that years of research have provided, most of them are influenced by several factors including:
1. Biocompatibility of implant materials
2. Adequate implant shape: plants can be classified according to the shape (cylindrical, screw and mixed), the type of surface treatment
suitable for the maintenance of primary stability, surface treatments that extend the surface, favoring and increase osseointegration and a shape and size suitable to distribute chewing loads traumatize the bone without excessively.
3. Characteristics of the implant surface: the greater bone-implant interface allows an increase of osseointegration and a better secondary stability.
The surface roughness can be achieved by various means that can be classified in the following way:
• Surfaces treated by addition of material • Surfaces treated for removal of material • Surfaces machined
4. Condition of the implant: the evaluation of the space available bone is an important point in the planning of therapy, because the osseointegrated implant has a size that requires an adequate bone volume to receive him, as to give an optimal primary and secondary stability. The trend in treatment plans is to choose the implant with the maximum size suitable for the surgical site and with a length of at least 10 mm.
5. Surgical technique Implant: the purpose of implant surgery is to insert an intraosseous implant in a position suitable to be used as a prosthetic support. It's good to follow protocols to ensure standardized surgical implant just inserted characteristics essential for success:
• Primary implant stability 44
• Maintaining the viability of tissue in close contact with the plant 45
THE AIM OF THE THESIS
Creating a method for measuring the volume and surface of autogenous bone graft taken from non-vascularized headquarters extraoral (iliac crest) using DICOM files (The Digital Imaging and Communications in Medicine) obtained by CT scan (CT scan) at various time intervals.
Evaluation of bone remodeling of the bone-implant system and prediction of bone resorption by morphological analysis is that grafted bone of the recipient site.
MATERIALS AND METHODS
In this study we were examined frontal areas with severe jaw bone atrophy horizontal that would not allow a prosthetic rehabilitation by inserting osseointegrated dental implants.
All patients were edentulous at the anterior maxilla associated with bone atrophy framed in a class IV Cawood & Howell 34.
Was carried out a case study based on an intra- and extra-oral clinical examination, evaluation of surgical and prosthetic using the wax and a CT scan performed with an individual template for radiological and surgical support. In no case it was observed a bone quantity sufficient to ensure the positioning of implants.
The bone atrophy was the result of a condition of edentulous ongoing for several years treated by means of a removable prosthesis, of an alveolar bone loss due to periodontal disease or major trauma. No patient underwent resection of bone as part of a cancer treatment.
The increase horizontal bone was necessary in those cases in which the width of the ridge residual bone was less than 6 mm 47, even though adequate height. The surgery of horizontal autologous bone graft was performed according to the procedure described by Triplett & Schow 43.
Subsequently, in a second surgery, from 3 to 5 months after the step of reconstructive surgery, to all patients were positioned titanium dental implants in rebuilt areas. The choice of a deferred implant placement is
required to compensate for any unpredictable remodeling and bone 48 and
because this method greatly improves the osseointegration implant 49.
Surgical methods
Reconstructive surgery was realized under general anesthesia with nasotracheal intubation accompanied by local infiltration of anesthetic and
vasoconstrictor to achieve hemostasis to the surgical approach. The antibiotic coverage was ensured by an administration one hour prior to surgery of 2 g. of amoxicillin in combination with clavulanic acid intravenously.
Many autors have been described different techniques of surgical approach for bone harvesting from the medial surface of the anterior iliac crest. These differ substantially for the location of the osteotomic incisions, and the avaiability of cortico-midollary bone. Have also been described minimally invasive sampling techniques with trephine drills, indicated when we want to perform a graft into particulate and there is a great need for bone. In these cases the levy hipbone is carried denuding only the area crestal and running on this different core samples, varying in number to the quantity of bone request 50. will focus the attention on the sampling
technique described by Politi in block 51 which constitutes a modification
of the technique osteotomy proposal from Grillon 9.
The skin in the iliac designated pickup are plotted in advance by the surgeon two or three elective lines that identify the natural course of the skin folds. Their identification is done with the patient standing and leaning forward with the torso. One of these lines will then be chosen during surgery as the incision line for access to the drawing. It is then more lines repere and in particular the position of the anterior superior iliac spine and the course of the iliac crest. The ASIS is an impassable limit surgery to avoid the risk of damaging the superficial circumflex iliac artery, the lateral femoral cutaneous nerve, the inguinal ligament. Choosing the line elective at a safe distance from the anterior superior iliac spine, we proceed along
dissection allows better healing of the wound by preventing the formation of a scar full thickness capable of provoking adhesions). The engraving of the aponeurotic muscle plane to the bone is made along the ridge for a length proportional to the amount of bone to be taken. It proceeds to the skeletonization of the pickup in the direction anteromedial with detachment of the abdominal muscles and iliac. The phase osteotomy described by Politi 51 provides the realization of a lid crestal bone with side
hinge (trap-door) to below which runs the levy en block cortico-medullary. The lid is then repositioned going to restore normal morphology crestal with less discomfort for the patient. The cover is made with chisels and / or reciprocating cutters with three lines osteotomic, two perpendiculars to the crest and one, with connectors, along the lip medial ridge. Leveraging with chisels inserted into the incision joining flips the door sideways. The fourth side suffers a fracture without dislocation of green wood parts, held together by the persistence of the periosteum. Drilling holes where to pass the wire osteosynthesis for the repositioning of the door. It will rely on two lateral steps made by reducing the size of the levy respect to the cover. Osteotomies delimiting the block are realized with chisels and / or reciprocating saws in the cortex of the crestal medial face, with extension of the lines beyond their meeting point, in order to avoid the formation of dangerous cracks bone during the final stage of the drawing which takes place with the 'insertion of chisels in depth, in the bone marrow exposed by tilting the door. This technique provides a bone marrow primarily because the greater amount of cortical component, provided in the door crestal, is not retrieved. After repositioning the cover with wire osteosynthesis proceed to suture the wound with absorbable suture, separate stitches and carried out plans for up to one skin. It may be useful to the application of a drainage if the bleeding in the surgical steps has proved plentiful.
A mucoperiosteal flap with crestal incision is prepared for access to the outer portion of the vestibular wall of the maxillary anterior. After exposure of the cortical bone, which is on the vestibular lingual / palatal of the alveolar ridge, the graft, already drawn down, it must be modeled and adapted to the recipient bed (the cortical bone is positioned buccally in the majority of cases); It prepares the recipient site with multiple perforations to promote the penetration vascular graft during engraftment. The bone grafts en block, (type of cortico-medullary taken from the iliac crest), once positioned at the onlay buccal wall of the edentulous ridge so treated (technique Triplett 43), are fixed to ensure direct contact graft-recipient site ,
by means of screws from osteosynthesis (length from 7 to 15 mm and diameter 2 mm) with technical lag-screw 52.
Release of the mucoperiosteal flap, with periosteal incision (plastic Rehrman) to eliminate tensions of the flap and on the graft with suture points "U" (or Donati) 43. After about three / four months reopening to
remove the means of synthesis and placement of the implants 53.
Postoperative
The patients were given antibiotic therapy for at least five days associated with anti-inflammatories and painkillers. Patients, within twenty days, was prescribed a liquid and semi-liquid diet and forbidden to wear dentures. Oral hygiene was maintained with rinses of chlorhexidine digluconate 0.2%. The patients followed a gradual course of rehabilitation that foresaw the use of the two crutches for ambulation in the second day after surgery and for one week, the abandonment of a crutch in the second week and both in the third.
Implant surgery
About 3-4 months after reconstructive surgery was performed a CT scan of the toothed upper jaw with a new template for the study radiological-surgical placement of dental implants.
After an healing time of 4 months from reconstructive surgery, the patients were subjected to a new surgical procedure under general anesthesia for the removal of screws from osteosynthesis and the placement of dental implants in accordance with the method described by Adell et al. 54. The
size of the implant was planned in advance of data denta CT scan, while the placement was led during the operation by radiological-surgical template. The implants have always been placed with submerged technique. After about four months was provided to the clinical evaluation of osseointegration and the positioning of the gingiva by mucotomie, at the implant site, under local anesthesia with infiltration Carbocaine with adrenaline 1:50000. After about four weeks, necessary for the rehabilitation of the peri-implant soft tissue, could start the prosthetic phase. The rehabilitation protocol is summarized in the diagram below.
All dental implants were placed endosseous, cylindrical screw, with external hexagonal connection (out-Link® PRO-Link® Sweden & Martina, Due Carrare, Italy PD), and were functionalized with dentures fixed type.
RECONSTRUCTIVE SURGERY TIME 3-4 WKS IMPLANT SURGERY 4 MONTHS 4 MONTHS HEALING SCREWS PROSTHETHIC REABILITATION
Data collection
The collected data (time T0) beginning at the time of scanning Computed Tomographic, realized in the study phase, if possible just prior to surgery of bone reconstruction. The subsequent time-points were established just prior to the implant placement (T1), and one year after implant surgery (T2), and subsequently every year by the latter, T3, T4, ect ...
T0 CT denta scan pre-‐GRAFT osseo 4 MONTHS TIME RECONSTRUCTIVE SURGERY IMPLANT SURGERY T1 CT denta scan post-‐GR T2 CT denta scan control 1 YEAR
Radiographic examination
As described in the previous section, all patients underwent a CT scan denta (High Speed double detector CT scanner, General Electric Medical Systems, Milwaukee, WI, USA).
For proper acquisition of data, it is essential the correct positioning of the patient's head. Referring maxillary arch, position the patient's head so that the axial scans are parallel to the hard palate.
The technique involves the execution of axial scans very contiguous, with a thickness of 1 mm, the matrix of execution is 512 x 512 voxels, extended to cover the entire height of the arch studied, while the FOV (Field Of View) is variable from 138 to 170 mm, sometimes even square.
Method of calculation of volumes and surfaces
During the protocol data acquisition, positioning the patient's head is entrusted exclusively to the technical manual; it is therefore very difficult that such positioning results in two scans, layer by layer, even comparable. Our aim is not only to compare these axial scans but even overlap or better fonderle55, as is usually done with files obtained through different techniques of diagnostic imaging, for example by melting matrices resulting from PET with those obtained with CT instruments. The overlap of the matrices CT, 512 x 512 x n (where n is the number of axial), will be by a reallocation of the array of voxels. The original DICOM files have been altered so that all those belonging to the same patient T0, T1 and T2 have the same value of FOV.
This operation was made possible by using the listing resize (in Appendix A) platform MATLAB 7.0.1, which uses a scaling matrix 512 x 512 xn type "bilinear". The three-dimensional matrix to 12 bits of the original file is also converted into a 16-bit matrix, so that they are easier the more changes.
For a perfect overlap of two matrices obtained from two scans at different times it is necessary a re-allocation of the voxel space obtained by an alternative method to that of quaternion 56. The technique of quaternions involves too many operations that would slow down the process of reformatting. It was here exploited the method of the minimum distances of a point from the three Cartesian axes (mutually orthogonal). For each patient is built according to three bony anatomical landmarks (anterior nasal spine and the two hooks pterygoid - Appendix B) a plan maxillary (z plane): on it were built a plane x, which is orthogonal to it and that steps for the anterior nasal spine and the midpoint between the hooks, and a plan y, orthogonal to the two planes cited supra and passing through the midpoint of the three anatomical landmarks.
Fig 4. Resize from FOV 137,78 mm to FOV 160,69.
Using the listing reformat (in Appendix C) on the platform MATLAB 7.0.1 each matrix of voxels is re-allocated spatially in a manner that the three points of reference anatomical bone have, for the same patient, the same spatial arrangement (Figure 5). The listing reformat uses the file TRIPLANE4.m for the construction of the reference planes and for the calculation of the distances that each voxel has by the latter according to the equation in appendix (D). If necessary, for the voxel that after the procedure re-allocamento found to nil, it uses the file ordfilt2.m that replaces the null value the average value of the voxel proximal.
In this way a matrix 512 x 512 16-bit xna on or at time T1 or T2, can be
fused with the matrix 512 x 512 with 16-bit xn relative to T0 latter made
only by voxel value ≥ 200 Hu in unison which is associated with the value expressed in Hounsfield relation to air (-1500 Hu).
The merger of the two matrices, with dominance of the matrix at T0, is realized with the listing union (Appendix E) platform MATLAB 7.0.1, which converts the resulting matrix again in 12-bit and saves it in the
DICOM format so that it can be accessed by the program SimPlant Pro 10.1 (Platform V10.0.1.6, from 1992 to 2006 Materialise nv). They were saved as DICOM also reformats the three T0, T1 and T2.
Looking to denta scan the resulting file we note that the orientation of the axial scans has been rotated 90 degrees counterclockwise, this in order to easily distinguish the changed files from the original ones. We specify that although the voxel have been re-allocated was not corrected their direction, steps that would have slowed the process of reformatting a factor 3.
Through the program SimPlant Pro 10.1 were created masks relating to voxels with intensity ≥ 200 Hu. In this way it was possible to calculate the volume of the bone graft and its surface at time T1 (obtainable from the DICOM files resulting from the fusion procedure, apex fus), respectively, and the time and T2, respectively, and. They were also calculated the volume and surface relative to file.dcm reformatted the time T0 and T1
(peak ref) respectively, and related to masks that they had obtained from the voxel intensity and Hu ≥ 200 that are located within sections radial line of cross-sectional theoretically below the bone graft itself.
Measured quantities, derivatives, procedures fitting and interpolation
Percentage of grafted bone that redidua to T2 or R%, given by equation 1,
which expresses the percentage of bone from the time T1 (100% bone) is
preserved at the time T2:
fus fus 1 2 T T V V 100 R%= ⋅ (1)
The external surface of 1 T
ES , obtained by subtracting from the total value
of the graft surface contact (
1 1
1 T T
T S CS
ES = fus − ).
It was also measured the volume of the receiving site at time T1 or by calculating only the radial section (that is, placing as the outer limits of the cross-sectional sections that did not appear the graft) below the graft and technically equivalent to rif
0 T
V . A correlation between the measured and
R% was searched.
Were calculated to three derived values, expressed through three indexes, so that it could be sought a correlation between more than two variables. A correlation has been sought between R%, and at the same time the volumes and of the bone graft and the bone portion receiving the graft itself at time T1; The study of this correlation has forced the development of an index of volume or indexV, calculated as ratio Trai two volumes, one portion of the bone receiver (BBT1) and graft (Equation 3).
fus 1 1 T T V BB indexV = (3)
A further correlation was also sought between R% and a sort of "height graft" at time T1, calculated by the ratio between the value of the volume of the graft at the time T1 and the surface area of contact at time T1. This index or indexH expressed in Equation 4, indications for the note about the thickness of the graft, when viewed in a cross-sectional image.
1 1 T T CS V indexH fus = (4)
For the analysis of correlation between R% and what is a "form" of the graft was drafted third index, or indexs, obtained from the ratio of the volume of the graft and its outer surface at time T1 ( Equation 5).
1 1 T T ES V indexS fus = (5)
The quantities measured and those derived who have had at least an average correlation (both positive and negative, -40 <corr <+40) with R% have been used for the construction of a scatter plot in two dimensions (R% vs SIZE) and It was created a linear fitting.
An interpolation procedure was performed using the values of R% and those of the indexes that have shown at least an average correlation with the percentage of residual bone at time T1. This interpolation was represented as a color image, in which color represents the value R% (resorption: red = minimum, blue = maximum).
The interpolation process was conducted with the listing in Appendix F of platform MATLAB 7.0.1
Statistical analysis
Given the nature of the data that are discrete and asymmetrical distribution, to evaluate the significance of the measures volumetric and surface grafting at time T1 and time T2 is tested using the Wilcoxon signed rank test for paired data that calculates the probability relative to the hypothesis that two independent samples come from distributions with equal medians (with a significance level of 5%).
For the construction of the correlation matrix in pairs, between all the measured and derived, it has been applied to the method of Spearman; in that the array are comprised both the correlation coefficients (ρ) that the significance (Sig.) regarding these coefficients (with a significance level of 5%).
RESULTS
The reconstructed areas were distributed in 6 patients, of which 3 females of average age 51.5 (± 7.6) and 3 males of average age 47.3 (± 13.3) (Table 1), that between September 2001 and October 2004 were subjected to an intervention reconstructive bone surgery, with autologous non-vascularized bone grafts to the maxilla, using technique incremental horizontal bone.
Total Females Males
n° patients 6 3 3
Age ±sd 49.4(±12.1) 51.5(±7.6) 47.3(±13.3)
Age range 32.5-58.7 43.6-58.7 32.5-58.3
Smokers 2 1 1
Non smokers 4 2 2
Table 1. Age (mean (), standard deviation (sd) and range expressed in years), gender distribution and smoking at the time of surgery incremental.
None of the patients examined presented systemic diseases or contraindications to surgery. Prerequisites to access the surgical procedure were the presence of good oral hygiene, the absence or the moderate consumption of cigarettes.
Between reconstructive surgery and the implant surgery it was asked patients to not make any prosthetic loading the reconstructed areas.
We observe that the bone graft at time T1 had an average volume and average area amounting to 2,169 (± 1949) mm3 and 2933 (± 1098) mm2,
Ac
r
T
yp
e
Type of graft horizontal
Position fus 1 T V (mm3) fus 2 T V (mm3) fus 1 T S (mm2) fus 1 T S (mm2) Rem% Ma xi lla
Iliac Crest FRONTAL
2169 (±1949) 1467 (±2008) 2933 (±1098) 2594 (±1149) 57.9
Table 2. Average size (expressed in mm2 ± sd) and average volume (in mm 3 ± sd) measured at time T1 and the time T2 and the average proceeds of R%.
Compared Groups Wilcoxon test significance Ma sc el la Iliac
crest FRONTAL horizontal
fus 1 T V vs VTfus2 0.318 fus 1 T S vs STfus1 0.691
Table 3. Significance of the Wilcoxon test and ANOVA; I am here compared the different values of volumes and areas relating to the times T1 and T2.
The values relating to the volumes and areas are presented in Figure 8 and 9.
Figure 8. Plot relative to the average volume (in mm 3 ± sd) measured at time T1 and time T2.
An analysis of the correlation coefficients (Table 4) revealed the existence of an average level of negative correlation between R% and the index of volume (indexV), while between R% and indexH was highlighted an average positive correlation. All other variables showed a low correlation with R%. All correlations between R% and various sizes were not statistically significant. R% 1 T CS 1 T ES 1 T
BB indeV indexH indexS
R% ρc. coefficient 1 -0.1786 0.3214 -0.3214 -0.4643 0.5714 -0.1429 Sig. (two-tailed) 0.7131 0.4976 0.4976 0.3024 0.2000 0.7825 N 7 7 7 7 7 7 7 1 T CS ρc. coefficient -0.1786 1 0.7857 0.7500 -0.2500 0.1429 0.6071 Sig. (two-tailed) 0.7131 0.0480 0.0663 0.5948 0.7825 0.1667 N 7 7 7 7 7 7 7 1 T ES ρc. coefficient 0.3214 0.7857 1 0.3571 -0.7500 0.6786 0.6071 Sig. (two-tailed) 0.4976 0.0480 0.4444 0.0663 0.1095 0.1667 N 7 7 7 7 7 7 7 1 T BB ρc. coefficient -0.3214 0.7500 0.3571 1 0.3214 -0.4286 0.1071 Sig. (two-tailed) 0.4976 0.0663 0.4444 0.4976 0.3536 0.8397 N 7 7 7 7 7 7 7 indexV ρc. coefficient -0.4643 -0.2500 -0.7500 0.3214 1 -0.9643 -0.5714 Sig. (two-tailed) 0.3024 0.5948 0.0663 0.4976 0.0028 0.2000 N 7 7 7 7 7 7 7 indexH ρc. coefficient 0.5714 0.1429 0.6786 -0.4286 -0.9643 1 0.3929 Sig. (two-tailed) 0.2000 0.7825 0.1095 0.3536 0.0028 0.3956 N 7 7 7 7 7 7 7 indexS ρc. coefficient -0.1429 0.6071 0.6071 0.1071 -0.5714 0.3929 1 Sig. (two-tailed) 0.7825 0.1667 0.1667 0.8397 0.2000 0.3956 N 7 7 7 7 7 7 7
Table 4. Spearman ρ coefficients between all the measured and derived ( CST1,EST1,BBT1,
Statistically significant correlations were found for couples - and indexV-indexH. Although the two scatter plot of% R and the index as a function of volume (indexV) and the index of Height (indexH) seemed linear, the values of R2 obtained by fitting have revealed that the data are not mathematically functions rectilinear (Figure 10-11).
Figure 11. Plot the percentage graft residual T2 as a function of the index relative to the bone volume of the receiving site (indexV); the R2 value obtained by linear fitting is equal to 0.5438.
y = -11,447x + 89,663 R2 = 0,5438 -60 -40 -20 0 20 40 60 80 100 120 0 2 4 6 8 10 indexV y = 11,488x + 10,001 R 2 = 0,4977 -40 -20 0 20 40 60 80 100 120 % o f t he g ra ft ed a re a a t T 0 % o f t he g ra ft ed a re a a t T 1
So, given the correlation found between these factors, a procedure interpolation of the percentage of residual graft at the time T2 according to the two indices just presented has been realized. (Figure 12)
The data relating to interpolation were used for the construction of a two-dimensional graph in which each bone graft is represented by a colored dot; the planar arrangement of this point is guaranteed by the two indices used as coordinates [xy], respectively [indexV indexH], while the color represents the percentage of residual graft at time T1 (= graft preserved red, blue = graft resorbed: Figure 12)
Such interpolation is based on Delaunay tessellation that provides a group of simplices with the only property that the unambiguous circumference that circumscribes each simplex does not contain data points. Given that in a space of two dimensions the simplex is a triangle ,. any polygon can be broken down into a minimum number of triangles. Each of the three vertices of each triangle will have different intensity of color. Each point of the surface of each triangle can be interpolated based on the distance that it has by the three vertices of the triangle itself.
Each point in the plane of the indices (or plan indicial) will have a different distance with respect to each data point. The interpolation is based on the principle that the more a data point is distant from each point of the plan indicial much less influence (in relation to the inverse distance interpolation). It was thus obtained a representation of matrix resorption.
Fig 14. interpolation 3-D data to vary the index of volume (indexV) and the index of height (indexH). The color bar indicates the value of R%.
6.67 5.33 4.00 2.67 1.33 0 1.25 2.5 3.75 5 6.25 30 40 50 60 70 80 90 indexV R% in d exH ( m m )
DISCUSSION
Among all autologous bone grafts considered in the literature, that seems to be the best from calvaria to extensive reconstructions of the alveolar ridge 57,58. At least as it regards the level of bone resorption engaged in
animal studies this appears to be true; Donovan et al, comparing the resorption of grafts from calvaria and iliac crest in pigs have shown a conservation respectively of 91.2% and 52.5% to a 12-month controlled. For more histological evaluation shows that the couplings from the calvaria are characterized by a minimum degree of inflammation, while in those from iliac crest inflammatory response is impressive in the first 4 months and probably related to loss of volume.
In clinical studies, only one author has so far presented results on the absorption volume of autologous bone grafts from calvaria used in alveolar reconstruction. The study is to Smolka 27, which presents a graft resorption
at 12 months equal to 19.1%, a value very similar to that relative to previous data obtained from animal studies. At about withdrawals from the iliac crest Johansson and his collaborators 16 by CT scans, they measured
the volume of the graft from the iliac crest after reconstruction of the maxilla of 10 patients and found resorption relative to onlay grafts amounted to 49.5% in six months.
For more resorption not only cause a reduction in volume but also softening and reducing the share of trabecolar bone 28. Although this effect
can be evidenced by a decrease in the intensity of bone graft, we believe that more information might come from observing the different rates of resorption relative to both the cortical portion of the graft that its spongy part.
In the study we have shown that although the resorption volumetric average is related to the data of the remodeling of grafts from the iliac
crest, that is, of 57.9% against 49.5% Johansson (which, however, analyzed the remodeling Pre-implant, and that is the opposite of what that we do), otherwise observing the correlation of bone resorption in respect of various magnitudes presented, we note that the percentage of grafting residue at T2 has well-defined relations with at least two of the indices
(indexV and indexH) for which it was calculated a correlation average (negative and positive indexV indexH). The linear dependence appears to the index of the contact surface (indexH); the more this index increases, the more the percentage of resorption appears to decrease. The index connected to the contact surface, dimensionally is expressed in mm, and can be roughly imagined, if viewed in a cross-sectional image, such as the
thickness of the bone grafted. So the thicker bone grafted at time T1 and
lower its reabsorption. The other index that seems to affect the resorption of the graft is connected to the volume of basal bone (indexV); the dependency also in this case seems linear. Recall that this index is obtained from the ratio between the volume basal bone and the implant, whereby the more this index increases, the more it means that the recipient site has been grafted a minor quantity of bone being equal basal bone, or that for the same volume of the grafted bone radial portion of bone receiver is greater. Now bone resorption seems more just to grow to such an index, thereby increasing the volume of the bone graft (being equal basal bone) should be placed at a disadvantage its reabsorption.
Regarding all other sizes, they seem to have no influence on the bone remodeling of the grafts from the iliac crest in the areas horizontal front jaw, at least this is clear from the analysis of correlation coefficients which,
