Part 1- The history and concept of implant

Chapter 1 Dental implants
The Institute of Clinical Materials

Haruyuki Kawahara
Dai Kawahara

I. Definition of implants
The social recognition of implants in dentistry has shown a dramatic increase in recent years and inJapan the term “implant” has come to represent dental implant. However, the definition of a dental
implant: “artificial material that is inserted into the jawbone or the periosteum by an invasive method,and one that can be used as a substitute for teeth”, is vague, and has not been strictly defined. An
appropriate name for a dental implant that would be most suited to current practice would be the term,“artificial root”.
This definition may cause slight confusion. In searching the term “implant” in the PubMed database,46,575 medical papers were extracted at the time of writing (5.2.2008). In comparison, 9,768 papers wereextracted with the keyword “dental implant”, a mere 20 percent of the former search result, thus
suggesting that the term “implant” is not uncommon in the field of medicine. That is to say, it is
impossible to identify “an implant as a dental implant”; it is therefore necessary to write the words“dental implant” to achieve more specificity.
The term “implant” itself remains ambiguous. According to the “Glossary of Oral and Maxillofacial
Implants”, which was compiled by W. R. Laney who served for a long time as the Editor in Chief of theInternational Journal of Oral and Maxillofacial Implants (JOMI), an implant is defined as “an artificial
material or tissue that shows biocompatibility upon its surgical implantation”. This is inclusive of
implants that are removed afterwards for diagnostic or experimental purposes.
This definition has been authorized by four academic groups: the Academy of Osseointegration, theAmerican Academy of Periodontology, the American College of Prosthodontists, and the European
Association for Osseointegration. The use of this definition, however, would indicate that dental implants
include composite resins and crowns, and cover allografts in the terminology.
If the term implant is to be re-defined in the context of current practice, it should be defined as follows:“an artificial material that is inserted into the jawbone as a replacement for a tooth”. As we, having comethis far, have no intention of causing confusion, the term “dental implant” will also cover the following:
implants for correction, membranes used for guided tissue/bone regeneration (GT/BR), and materials forosseous implants including autologous bone. Further, a more specific definition should be given formaterials such as artificial roots, for example, “artificial material that is inserted into or onto the jawbone
for the purpose of replacing teeth”.

1II. History of the implant
As shown in Table 1-1-1, the history of the dental implant goes back to 3000 B.C., to the period when theancient Egyptian civilization prospered. In this book, we will cover the history of dental implants from thetime of Allen’s report1), which in 1687 was the first to mention dental replantation and transplantation,and from the 1800s, the period where the practice of modern surgery started, along with the concepts ofsterilization and disinfection. This was the time when medical information started to be written down
and be provided in paper form.

Table 1-1-12)-6)
Reports of Dental Implants until the 17th Century
During the period from the 1500s to the beginning of the 1800s, teeth were bought off from theresurrectionists which were collected from the poor or the corpses for purposes of allotransplantation5).
This method, which was most common in Europe, has since disappeared for various reasons, particularly
due to the common onset of secondary infections such as syphilis and tuberculosis7).
It is most probable that the first person to publish a description of the technique of modern dental
implants was a French dentist, Maggiolo J. According to M.E. Ring, Maggiolo describes a method toimplant 18-karat gold alloy, with three branches into the jawbone, and to install a porcelain crown as asuperstructure in his book: “Le Manuel de l’Art du Dentiste” (1809) 6). By 1886, the process of2

intraoperative sterilization had undergone vast improvements, in which time, Harris had constructed asocket in the jawbone to insert a column made of porcelain. Interestingly, this porcelain was coated with arough layer of lead in order to increase the supporting strength. A porcelain crown was placed as thesuperstructure, and this is the approach that is thought to have continued for 27 years6).
In a similar manner, in the latter half of the 1800s, Berry constructed a root-form implant that was
lead-free. Following this trend, Pajime used silver, and Bonwil, gold and iridium as the material, each ofwhich were implanted for single tooth replacement or for support of a complete denture7).
Entering the 20th century, Scholl made a root-form, porcelain implant in 1905 that consisted ofcorrugated structure. He also proposed a design in which a wire was initially incorporated within the
superstructure for forming a connection with the remainder of the original tooth7).
Most of the surgical methods for dental implants in the past had involved immediate implantation.
However, surgical tools such as the drilling systems used in present practice were developed andimproved by Greenfield, who also introduced trephine bur and dental implants with a hollow cylindricaldesign. He was also the first to report the failure of implant treatment due to infection, and thus his
contributions to the history of dental implants are immeasurable6).
In 1937, Vitallium®, a cobalt-chromium-molybdenum alloy was developed which was used on patients by
Stock at Harvard University. Some of these cases were followed-up for 15 years until Stock’s death7).
Meanwhile, in 1940, Dahl was the first to attempt subperiosteal implant, but this approach did not
become common before being employed by Gershkoff and Goldberg in 1948.
In 1951, the Academy of Implant Dentures was established, which is presently known as the American
Academy of Implant Dentistry9).
Reflecting back on the dental history in Japan around this time, the late Dr. Toshio Yamane set up the
Yamaguchi Plastic Dental Society in 1956, which later became the driving force for Artificial root researchin Japan. Dr. Yamane established an independent institute to experiment on animals, which produced
many experts in the field of artificial roots. The institute is currently known as the Japan Institute forAdvanced Dentistry10).
The oldest academic report in Japan is a collection of consecutive reports by Dr. Toshitaka Kaketa
constituting a series of reports that were published in the academic journal of the Japan Prosthodontic
Society. In retrospect, it is no exaggeration to say that his achievements in the 1950s–1960s weremonumental, particularly in the time when the opportunity to report the use of artificial roots waslimited and this kind of practice were not kindly perceived11)-19).
The Japanese Society of Dental Implants was established in 1972, however, due to a series of difficulties,
it was not until 1978 for the academic journal to see the light of day. Later, it merged with the Japan
Society of Dental Implant Research becoming the present Japanese Society of Oral Implantology (JSOI)
20).

Meanwhile in the area of basic research, Haruyuki Kawahara, one of the authors of this text, haddiscovered that the cell proliferation was unaffected by the presence of titanium or zirconia and tissue
proliferation was found to be more effective on the surface of these metals than on the glass plate. At thetime, however, the extent and the nature of biocompatibility of each of these metal materials had not yet
been defined. The topic of biological characteristics of dental materials as a whole became a theme worth
investigating. The results of such researches were summarized and published in the International Dental
3

Journal in 1968. This in turn triggered extensive researches into the biological properties of dental
materials as a whole, and the results of these studies have appeared temporarily21).
The story that the discovery by Brånemark in Europe 1950 that titanium can be integrated with bone, led
to the concept of osseointegration, advocated in 196922) that is still applicable in current practice, isinfamous. This has come to be known as Brånemark’s theory and the concept of osseointegration
flourished rapidly in the 1980s, which brought about a defining moment in the clinical field of implants.
In Sweden at the time, the concept of dental implants was perceived with skepticism; therefore the term
“fixture” was used instead to soften criticism.
Around the same period, in the United States, Linkow was developing the first screw-type implant called
Ventplant, which was completed in 1963. This implant is currently referred to as self-tapping implant,
which is covered with screw threads with an open-cage design. Cobalt-chromium alloy was used as themetallic material, but is said to have been replaced by titanium due to the results of Brånemark’s
research22).
During the period of 1960s to the 1970s, surgical methods of bone regeneration, like those used today, had
not yet become widespread, as the use of screw-type implants was avoided in narrow bone structures suchas the jawbone, and the blade implant was considered “mainstream”. Therefore, the Ventplant
disappeared before it saw the light of day. Although this trend was also seen in Japan, Kawahara andKyocera Co. Ltd. succeeded in the formation of monocrystalline alumina in 1975. Bioceram, which is the
product name, became the first implant made in Japan for both domestic and overseas use. It has been
said that the Bioceram was implanted in over 60,000 patients and was the most pervasive andwell-researched implant among the dental implants manufactured in Japan.
In 1978, the Harvard Consensus Conference was held to establish consensus on the use of implants at
Harvard University, and the standard for a successful implant was settled on whether the implantremained embedded and functional for five years. This standard may seem extremely short, but it
illustrates what the expectations of implant treatments were at the time.
In the 1980s, Professor Zarb of the University of Toronto played a central role in holding the Toronto
Conference on Osseointegration in Clinical Dentistry, where Brånemark presented the results of his
research over 30 years and his clinical practice for nearly 20 years. With this Conference as a turning
point, the Brånemark Regimen spread over North America. The typical Brånemark regimen during thisperiod consisted of implanting four to six fixtures into the mental foramen of the lower jaw, with thesubsequent placement of bilateral cantilever as the standard prosthesis. Brånemark also insisted that,after implantation, the fixture should be left for four to six months and be isolated from any kind of
external force. This was when the surgical two-stage technique became widespread throughout the world,
starting in North America, followed by the spread of the submergible design. Many clones of this design
were produced and are still in use today.
Towards the late 1980s, the revolutionary movement of the Brånemark regimen swept over Japan in thesame way, and a surge in implant research took place. This movement was a different kind seen with
Linkow’s Blade-type or the Bioceram that had its struggles, and has continued its uses to this day.

III. Types and characteristics of the implant
Implants can be classified into several types, such as subperiosteal, endosseous, and transosteal implant,4but, in this book, we will avoid mentioning implants other than endosseous implants, taking into
consideration the types of implant that are currently used in clinical practice. Moreover, the endosseous
implant can be classified roughly into blade-type and root-form according to its shape, but, in this book,we will only mention the root-form implant for the same reason as before, and classify these as shown in
Table 1-1-2. The root-form implant can largely be divided into one-stage type and two-stage type, in
accordance with the operative methods used. It is possible to use the two-stage implant as a one-stage
implant and such usage has been increasing in recent years.

Type

Typical products

Similar products which are on
the market at present

AQB implant
One stage implant

Two stage implant(One stage implant)

Table 1-1-2 Classification of the Root-Form Implants

A. One-Piece TypeThe most primitive design is the one-piece type, and the AQB Implant that was developed in Japan is atypical example. At the time, the design of the AQB Implant was deemed retrograde as it was placed on
the market in the golden age of the two-stage type of implant. However, even large enterprises such as
Nobel Biocare and Zimmer Inc. have adopted this style. The major advantage of this type of implant is theabsence of a microgap in between the abutments. In addition, it does not require any prosthetic
procedures for implant placement, so there are no problems commonly associated with prosthetics. This
type of implant seems to be the simplest and the easiest to use among the three types, however, it may bedifficult to prepare the prosthesis when the major axis of the implant and the tooth axis of the prosthetic
tooth differ significantly. This type of implant is unsuitable for cases where initial fixation is not adequate.
Here, a large area of the implant is exposed in the mouth at the time of implantation, and thus is easily
affected by external forces.

B. One-Stage Type
5

The Straumann Standard Implant is the most prominent one-stage type and is widely known by its old
name, the “ITI Implant”. In addition to its advantage of requiring surgery only once, as the implant iscommunicated with the oral cavity from the time of implant placement, it is more resistant to theexternal forces than the one-piece type because the area exposed in the mouth is small, and it
micromotion can be minimized. The positioning of the crown can be adjusted to some extent at theabutment level if the major axis of the implant and the tooth axis are not fitted correctly, as the crown isstructurally separate but problems such as those listed in Fig. 1-1-1 can occur in the portions related tothe abutments.

Fig. 1-1-1 Example of a rupture that occurred in the Octa®
abutment of a Straumann Standard Implant

C. Two-Stage Type
This type is the most commonly produced of the two types, and in many cases, its design is adopted fromthe standard Brånemark regimen that act to minimizes micromotion by closing the wound after
implanting the fixture. It is thus often used in cases where micromotion must be avoided in cases of poor
initial fixation or in cases where bone is grafted to the periphery of the fixture. In principle, uncovering
surgery that exposes the implanted fixture takes place after a period of several months, to allow
subsequent placement of the transmucosal abutment that penetrates through the mucous membrane.
There are more variations to the abutments than with the one-stage type, therefore it is possible to adjust
the location of the crown more freely at the abutment level, but a considerable number of problems havebeen reported with the use of this type of implants (Fig.1-1-2).

Fig. 1-1-2
Contamination around the screw that resulted fromthe loosening of the abutment screw

6Many companies have adopted the two-stage design, however, there has also been recent development ofa method known as “immediate loading,” where the transmucosal abutment is attached in a similarmanner to the one-stage type, at the time of insertion of the fixture.

IV. Style of the interface between the implant and bone
Extensive research into the interface between the implant and bone in terms of surface chemistry andmorphology is continued to this day. Implants with various surface treatments have developed in
response to the results of research. This book reports the observed surface chemical characteristics6 of
the interface between titanium and the bone, in consideration to its morphological aspects.
A.

Interaction between titanium and calcium phosphate compounds

It has been shown that phosphorus and calcium diffuse into the oxidative layer on the surface of titanium,by immersing it in “pseudo-body fluid” that includes calcium and phosphate ions. The elemental ratio ofphosphorus and calcium in this oxidized layer approaches that of hydroxyapatite, 1.67, as the duration of
immersion increases. This property was discovered by Dr. Takao Hanawa (Professor of Tokyo Medical and
Dental University), who is one of the contributors to this text, and discovered that the calcium phosphate
compound present on the titanium surface is hydroxyapatite, using Ultra-sensitive Fourier-Transform
Infrared (FT-IR) Spectroscopy 23).
Previously, titanium was believed to be inactive in organisms as it was covered by an oxide layer that was
stable in the atmosphere. However, it was found here that titanium is microscopically an active material,
and that this phenomenon (which can be observed in pseudo-body fluid) is also seen on the surface oftitanium removed from the living body. This was a monumental finding that unraveled thecharacteristics of the interface between titanium and bone at the atomic level, and that unmasked thenature of osseointegration, a biomaterial research result that Japan can be proud of. This finding alsofueled the development of implants with a variety of improved titanium surfaces. As classic examples offormation of the oxidized layer, methods of immersing titanium in a solution that already contains
calcium ion24), or infusing calcium ions25) are used. Both methods have been shown to accelerate theproduction of calcium phosphate effectively in pseudo-body fluids, and this phenomenon has also been
confirmed to occur in animal experiments.
Other methods including alkaline treatments that immerse titanium in sodium hydroxide solution withthe application of heat26), or hydrogen peroxide treatment27) have also been reported as methods forsurface reformation that accelerate the production of calcium phosphate. With regards to the alkaline
treatment, there have been many reported examples in the field of orthopedics, and bone induction has
also been observed in muscle28).

B. Interaction between Titanium and Biopolymers
In an electrolytic solution, it takes several weeks for calcium and titanium to grow into HA on the surfaceof titanium, but in an organism, hematogenous biopolymers such as fibrinogen and fibronectin rapidly
adsorb and orientate on the titanium surface, and subsequently mediate the biological reaction(Fig. 1-1-3).
Fibrinogen is converted into fibrin which polymerizes to form a biological mesh. The subsequent
7

biological processes of wound healing are regulated by cell growth factors such as PDGF released by theplatelets that were trapped by the fibrin mesh. As a result of this release, the proteins involved inossification, such as osteocalcin, osteopontin, and osteonectin have been shown to be up-regulated30).
Recent research has used osterix, a transcription regulation factor involved in the differentiation of theosteoblast, as a marker. It was found by Masaki et al. and Guo et al. that a hydrofluoric acid-treatedimplant shows a higher expression of osterix than those with SLA or SLActive treated surfaces 31),32).

Fig. 1-1-3
Quantitative adsorption kinetics measured for the proteins human serum albumin (HSA), fibrinogen, andfibronection on Tio2 covered optical wave guide tips, using optical waveguide lightmode spectroscopy(OWLS). Protein concentration: 160 µg/ml. Flow rate: 1ml/h 29)

C. The Dynamic Interface between Titanium and Bone
Based on the analysis of titanium and calcium phosphate with respect to the inorganic surface chemistry
or using biological markers as an indicator, titanium and bone can be found to be interacting and be
integrated with one another. However, the results from animal experiments do not always reflect these
inorganic research results. Fig. 1-1-4 shows an electron micrograph of the results of application of a load
after the initial implantation in a monkey33). Fig. 1-1-4-a shows that no space between the fixture and thebone can be seen even with 1000 × magnification. Fig. 1-1-4-b shows that distribution of calcium can beobserved along the surface of the fixture. However, in Fig. 1-1-4-c, it can be observed that the distributionof phosphorus is not concurrent with that of calcium and there is a phosphorous-deficient layer of roughly
10 µm.
Morphologically, these findings seem to suggest that, although the bone appears to be interacting withthe fixture, in actual fact, it is not the bone, but special tissues lacking phosphorus that are interactingwith the fixtures instead. That is to say, the term osseointegration only refers to a morphologicalobservation, and even the implants that have not shown clinical mobility can be supported by specifictissue that is biochemically distinct from the bone. Unfortunately, whether this observation is continuous
throughout the osseointegration process or whether it is limited to a specific period is not yet clear, but it
can at least act as evidence that the bone and implant form a dynamic interface 34).

8

a

b

c

Fig.1-1-4-a,b,c
Atomic spectroscopy of the structures surrounding the fixture buried in monkey 33). The image, takenwith electron microscope, featuring the interface between the surfaces of titanium and the bone (Fig.
1-1-4-a). A localized image featuring calcium atom, under the same magnification (Fig. 1-1-4-b). A
localized image of the phosphate atom under the same magnification (Fig. 1-1-4-c).

D. Interface between Hydroxyapatite and BoneIn response to the clinical demands, the means in which to accelerate the incorporation of calcium andphosphate at the interface between the bone and the implant had became the subject of research. One of
the most typical examples is the method of HA coating on the surface of the titanium metal. Once thehydroxyapatite (HA) and bone interact, integration at a crystalline level is not an impossible task, as has
been reported by Kato 35).
HA does not show any toxicity or tendency to induce local or systemic inflammation. Regardless of its
shape, whether it is in the form of a block or granules, it has been found not to give rise to inflammatory
or foreign-body reactions.
Furthermore, fibrous encapsulation does not appear; in fact, it is known that direct interaction with thebone occurs instead. Both HA blocks and granules gave satisfactory outcome in experiments using dogs,
rabbits, rats, and primates in the fields of orthopedics and dentistry. There were no local or systemic side
effects reported. With these findings, HA was considered an ideal material for implants. Nevertheless,results of clinical trials of HA implants were dismal, as it fractured or fell out within a short period oftime. A swift change was incorporated with the construction of two-stage implants, but no improvements
in prognosis could be achieved, and its use rapidly declined. However, the researchers did not relinquish;
with clinically proven adhesiveness of HA to bone36), the idea was developed to cover the titanium with
HA in order to reinforce mechanical strength. After the report of Duchyne’s group was published,technology to coat titanium or its alloy flourished37), however, the method used to spray on HA at hightemperatures, known as the plasma spray method, resulted in breakdown of HA with conversion into
amorphous calcium phosphate (ACP). This resulted in liquefaction of the HA38).
In addition, from the analysis of sintered or coated HA, HA is known to lose its hydroxyl group in theprocess of sintering or plasma spraying.
Therefore, the emergence of a “real” HA coating had been long-awaited39). In order to avoid the loss of thehydroxyl group, ADVANCE CO., Ltd. and a research group from the Institute for Medical and Dental
9

Engineering, Tokyo Medical and Dental University, published a method of spraying calcium phosphate(β-TCP) onto the titanium surface with the plasma spray method, as the raw material, followed by ahydrothermal treatment to coat highly crystalline HA onto the titanium surface 40). Clinical trials of this
HA-coated implant began at the Mitsui Memorial Hospital in 1988 41) and, owing to this technique,properties such as its excellent biocompatibility and osteoconduction of HA were able to be revived. As
shown in Fig. 1-1-5, the bone tissues connect with HA over the complete surface area showing a higher
contact rate than any other titanium implant materials. Furthermore, its osteoconduction has been
observed to be much faster than that of the titanium surface, and the contact area is much larger than
SLA as shown in the SLA Surface Study by Buser et al., which has often been cited for this type of
research 42).

Fig. 1-1-5
Image of the bone tissue, which is strongly interacting with the HA coating layer.

V. Current situation and future trends for implants
A. Varieties of Implant and their Prognoses
A significant number of manufacturing companies produce significant variety of implants. According to asystematic review that evaluated clinical results of various types of implants, some research shows thatthe marginal bone loss associated with the cylindrical IMZ Implant is greater than that of the Brånemark
System or the Straumann ITI. Concerning implants with smooth surfaces (machined surface), the risk ofperi-implantitis is 22% lower than implants with rough surfaces. There have not yet been any specificimplants with which its excellence proven over a long duration of time, or confirm that the failure toconcentrates in a given type of implant.
This review was based on the results of a few randomized clinical trials, the number of people who took
part in these studies was limited, and the assessment period were short, therefore, the results carry therisk of being biased. In order to draw accurate conclusions, a set of randomized clinical trials performed
for a longer period are thus necessary, conducted in a sufficient number of patients to gain significance43).
Surveying these articles that describe implant prognosis, it becomes clear that most of the authors ofthese papers are from university hospitals or from well-equipped institutions, where the pre-operative
examination and diagnosis can be presumed to be conducted under the supervision of experienced
surgeons. Therefore, it is not rational to directly apply the results of these studies to those of general
10practitioners, and equal success in treatment should not be expected.

B. Surgical Simulation and Surgical Navigation
The foundation that supports surgical simulation and surgical navigation comprises computed
tomography (CT) and computer-aided design/computer-aided manufacturing systems (CAD/CAM
systems). The CT scan has a long history, but CT only assumed a prominent position with the publicationof the DICOM standard in 1993 44), and with improvements in the speed of data transmission over theInternet and the processing capacity of personal computers that occurred in the late 1990s. Handling ofdata for three-dimensional reconstruction became possible with personal computers, which in turnenormously improved both the precision of the preoperative medical examination and diagnosis.
Alongside the expansion of capacity of the personal computer that occurred at an exhilarating speed,
many companies developed CAD/CAM systems. This in turn allowed not only medical examination anddiagnosis but also preoperative preparation of a surgical stent capable of controlling the drilling direction
most suitable for the bone surface, the remaining teeth, and the basal surface, even avoiding critical partsin the bone. Furthermore, we have entered a period that permits the construction of prosthetic
superstructures before surgery, and some companies have already announced their implementation ofthese systems.
Fig.1-1-6 shows a conceptual scheme that combines on computer the scanned images of the basal surface
and the remaining teeth as three-dimensional information, and information about the bone structure
obtained from the CT scan. By re-constructing and combining these two sets of 3D information on thecomputer, a surgical index can be created that defines the direction of drilling in compliance with theremaining teeth and basal surface, and avoids more vulnerable parts of the bone, such as the lower
alveolar canal.
Fig. 1-1-7-a is a picture of a plaster cast and Fig.1-1-7-b is an imaging index that complies with the toothplane and basal surface by scanning the plaster cast. To prepare a surgical index (Fig. 1-1-7-c) compatible
with the mucosal membrane and plane of the remaining teeth, the imaging index is used to check the
intraosseous information gained from CT scan against the basal surface and tooth plane by making use of
the relief surface on the front side of the imaging index.
The use of a surgical index that was constructed by combining details of preoperative soft tissuemorphology and the bone tissue with CAD/CAM on computer, improves very significantly the safety of the“flapless fixture” surgical procedure, which in the past relied on intuition and prior experience45). This is amethod whereby the implant is installed without detachment of the mucoperiosteal flap.
Fig. 1-1-8 is an overlapped image of the preoperative and postoperative CT scans.

Fig.1-1-6
By compounding the 3D structure of the jawbone gained
from scan of the plaster cast, and the 3D CT data on thecomputer, a surgical navigation can be created that
corresponds well with the mucus plane and the dental
plane to facilitate the regions of high risk.
11

Fig.1-1-7-a The plaster castFig.1-1-7-b

Fig.1-1-7-c

The index for photography

The surgical index

Fig. 1-1-7-a, b, c
The index for photography (Fig. 1-1-7-b) that was produced to fit the plaster cast (Fig.1-1-7-a), and thesurgical index that suits the completed base. It is possible to control the orientation of the drilling byapplying the surgical index on the surface of the mucosa and the remaining teeth for the preparation for
the implantation in its flapless form.

Fig.1-1-8
The superposition of the preoperative and the
postoperative CT scan images. The cylinder
structures shown in blue indicate the simulation of
the preoperative simulation.

C. Immediate placement and immediate loading
In reflecting on current implant treatment in terms of material technology, the major advances in thisfield were recognition of the clinical significance of the HA coating, and the various reforms of thetitanium surfaces. The most substantial among these was that the Standard Brånemark Regimen
became an entrenched standard in the field of dental implants.
It gradually became clear that osseointegration would occur regardless of the use of two-stage surgery, or
whether load was exerted immediately on the implant. This led to the concept of immediate loading. Thisis the clinical technique that was followed by practitioners such as Linkow46), Cherchève47) and
Ledermann48) for a long time, however, its presence as a clinical technique has become more relevant withadvances in the materials used on the implant surface, and now that quality control has been instituted.
The number of reports related to immediate loading has increased substantially since 2000; these havedemonstrated the anticipated value of the technique. From a critical point of view, the two-stage methodthat was advocated by Brånemark involved a detour, however, it is still of clinical significance in thehistory of dental implants as it provided us with a precise surgical method.
In addition, the method known as immediate placement became a popular technique. This method is also
12one that opposes the idea proposed by Brånemark, but it is clear that, reflecting on past history, theoriginal implant was installed immediately into the hole left by the removed tooth.
With awareness of infection, and the implementation of antibiotics, immediate placement became
possible in an environment that is as clean as possible. The implementation of both immediate placement
and immediate loading methods has been proven to be ideal for clients (patients), and systems now exist
that employ this concept. Well-represented examples are Novum™ and All-On-Four™ which have been
proposed by NobelBiocare. The former has already disappeared from the product lineup on the website ofNobelBiocare, with only a few reports. According to De Smet, Novum™ and other implants that aredesigned to be inserted in distal positions carry a great risk if loaded immediately 49). On the other hand,the use of All-On-Four™ in Japan has become more prevalent in 2007, and there have not been any major
problems reported thus far. Progress has been smooth, however, the period of observation in several of theclinical trials facilities was not very long and careful surveillance therefore still needs to be maintained 50),
51).

VI. What is expected of the AQB implant?
At the first academic clinical presentation of the 1998 IAI Conference, two novel properties of the AQB
implant were reported and demonstrated these with clinical examples. First, early loading of implants,
where the secondary surgery can be conducted two weeks after the initial implant installation, andsecond, the fact that the movement of the fixture is not an irreversible phenomenon and recovery fromthis was shown with a clinical example52). These presentation were given in the midst of dental dogma of
the Standard Brånemark regimen, however, the present practice of dental implants such as immediate
installation of implants following tooth extraction, immediate loading, and immediate restoration, provesthat the actual clinical results are much stronger than theoretical arguments.
There is a great number of clones and derivatives of the two-stage and one-stage types, but the model forthe twenty-first century clones and derivatives of the single-stage type can be said to be those of AQB
implant (Fig. 1-1-9).
More than a decade has passed since the AQB implant was introduced, during which time there havebeen significant advances in both the methods of assessment and surgery. From now on, what is expectedof the AQB implant is simplification of the navigation systems that have been implemented for use ofdata reconstructed from CT scanning, and establishment of a method of implant surgery that is highly
reliable.
The substantial number of clinical results of the AQB implant that have been accumulated by a large
number of dental clinicians should not be confined to the limits of this country but spread worldwide; but
this has not yet taken place. This could be because we have been pursuing practicality over fame; it ishardly likely that I alone am disappointed by this.

13

Fig. 1-1-9
Many clones or the modifications of the two-stage type implant represented by the Zimmer and Nobel
Biocare (left), and the one-stage type implant represented by the Straumann System (center), have beenplaced on the market. The single-stage type AQB Implants (right) were also derived from the Nobel
Biocare and the Zimmer models.

References
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25.
3) Coleman A. I. A syllabus in the study of history of dentistry. USC COD, LA. 1970: 5,12.
4) Atilla G. A rare find in Anatolia - A tooth implant (mid-sixth century B.C.). J Oral Implant 1993; XIX:
54-57.
5) Asbell M B. Dentistry: A historical perspective. Bryn Mawr, Penn. Dorrance-Company, Inc. 1988: 45,
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