CHAPTER THREE: THE PRACTISE OF ORAL IMPLANTOLOGY USING MOSTDIS

CHAPTER THREE: THE PRACTISE OF ORAL IMPLANTOLOGY USING MOSTDIS

BASIC INFORMATION ON MOSTDIS

OSSEOINTEGRATION  IN THE USE OF MINI-IMPLANTS

Mini-implants, narrow diameters, small diameters, reduced diameters, MOSTDIs are all made from titanium and they all osseointegrate, just like conventional sized dental implants. Mini-implants, due to their smaller diameter and minimally invasive placement technique results in a much smaller healing challenge to the body and therefore probably integrate even faster. In addition, they are usually placed up to a torque of 50 ncm as compared to 30 ncm in the case of conventional. This can be done because minis are solid one piece implants and are actually stronger in resisting fracture than conventionals that have a hole within the fixture which weakens it considerably and does not allow the driver to apply a high torque to it. Thus minis can and are torqued to a higher level than conventionals, giving it a stronger primary stability that allows immediate loading and faster finishing than conventionals.

RETRIEVABILITY IN MINI- IMPLANTS

The ongoing debate in oral dentistry is whether or not a prosthesis should be screwed on or cemented. In his landmark lecture in 1982 in TORONTO, CANADA, Professor Branemark showed successful cases of endosseus screw titanium dental implants, all of which were of the two piece design with the prosthesis screwed on. The screwed on technique was designed to enable retrievability so that if any complication like a fracture or infection occurs, the prosthesis can be removed by unscrewing the connecting screw. The implant could then be examined and remedial action may be taken with direct visual information.

Over the years, it has been observed again and again that in general, oral implants have an average success rate of up to 95%. Therefore, as argued by some practitioners, since there is only a 5% to 10% failure rate, the prosthesis ought to be screwed on so that they can be retrieved when necessary in order to treat the oral implants directly. This advantage, they feel, offsets the disadvantage of loose screws, broken screws, the need for high precision, the resulting microgap, and the high costs of manufacturing and maintenance of such small precision components.

The other school of thought feels that the combined disadvantages do not justify the advantage of ease of retrievability that is gained with a screw retained prosthesis. After all, if worse comes to worse, the prosthesis can be cut off with a high speed air rotor or a diamond disc with a guard.  In addition, dental practitioners have been cementing crowns and bridges for years over natural teeth, even though after 10 years, almost 30% of crowns and bridges that are built on natural teeth fail for one reason or another. The logic therefore is that if we insist on cementing on our crowns and bridges even though there is a 30% failure rate after 10 years, then based on the same logic, there is even greater justification in cementing on our crowns and bridges over dental implants instead of screwing them on.

One solution to this problem is to use a temporary cement like temp-bond and even dycal to cement the implant prosthesis on. Thus if necessary, the prosthesis can be removed with minimal guided force. Temporary cements with its weak bonding strength works over implants because implants are osseointegrated, i.e. ankylosed to the bone and does not move. Natural teeth are attached to the bone via the periodontal ligament which allows the natural teeth to move in tandem with the applied forces, much like the suspension of a car. Therefore, if a temporary cement is used, the cement bond is broken easily especially when there are eccentric forces acting on the prosthesis.

Another school of thought is that when in doubt, use a screw, and when you are very sure of your implant fixtures, cement them in. This philosophy can often cause a crisis of choice when the time to fix the prosthesis comes.

The ideal system seems to be one that would allow easy retrievability without the accompanying disadvantages of a screw retained system. Currently, because of the numerous inherent disadvantages of screwing on the prosthesis, the trend is more and more towards cementation with temporary cement. And after a period of time, if the temporary cement fails, then a permanent cement to fix on the prosthesis is used, the logic being that adequate time has been allowed to ensure the health and stability of the implant.

In the case of mini-implants, retrievability have always been a problem since most crowns and bridges were cemented on permanently. Temporary cements may be a solution but because of the smaller size of the implant head as compared to conventional implants, the prosthesis tends to become unstuck more often. A prosthodontic solution for mini-implants may be to use prefabricated abutments that fit over the small implant head. The resulting abutment is then larger and less likely to fracture in the lab and easier to build a prosthesis on. In addition, the depth of porcelain used will not be so thick as to compromise its ability to resist fracture. The prosthesis can then be cemented permanently on to the abutment and then cemented with temporary cement over the small implant’s head. In this case, the prosthesis can be removed when necessary with a crown remover, thus solving the problem of retrievability. A corresponding technique is to cement the abutments permanently on the MOSTDIs and the final prosthesis can be cemented on the abutment with temporary cement.

The success of oral implantology has been built on the solid advances of crown and bridge prosthodontics that began in earnest since the early 20^th century. Initially, crown and bridgework were frowned upon because they were poorly constructed and paid little heed to hygiene, maintenance and material biocompatibility to oral tissues.

However, since the middle of the 21^st century with rapid advances in infection control and materials science, crown and bridgework has had unprecedented success in function, aesthetics and maintenance. But the bugbear of having to cut and injure vital teeth proved to be an ongoing problem. Crown and bridgework after 10 years on the average has up to 30% failures, very often due to sequelae and as a result of cutting abutment teeth all the way to dentine. No matter how much cooling water spray we apply, once we cut to the dentine, the pulp undergoes an inflammatory response showing that there is acute damage done to it. Most of the time, the tooth repairs and defends itself successfully. However, there is a substantial percentage of such teeth that undergoes chronic inflammatory changes that later becomes acute if there is bacterial invasion. With the advent of oral implantology, the necessity of cutting vital teeth has become increasingly obsolete. Now crowns and bridges can be built totally on non-vital artificial screw titanium implants. But it is to be recognized that without the advanced development of crowns and bridges on vital teeth, oral implantology will not enjoy the outstanding success it has today.

PROSTHODONTICS FOR CONVENTIONAL  2 PIECE DENTAL IMPLANTS

Since Professor Braunemark’s landmark presentation on his 15 year studies on large two piece titanium screw dental implants in 1982, most implant manufacturers have basically copied his precedents.

The precedents were:-

(1) The use of titanium

(2) Root sized screws

(3) Atraumatic placement

(4) Two piece screw dental implants

(5) Waiting 3-6 months for osseointegration of the fixture before connecting the second piece called the abutment

(6) Building the crowns and bridges on the abutment and screwing them on for the sake of retrievability

Abutments are usually screwed on to the implant proper, usually called the fixture. The abutment itself may have a threaded part that can be used to screw it on or it may have a separate screw to connect it to the fixture. Some implant abutments are designed to fit into the fixture and just tapped on and held there basically by frictional forces. Some abutments may also be cemented onto the fixture.

Crowns and bridges may be screwed on as advocated by Professor Branemark and his followers. Increasingly, many practitioners cement in the prostheses. The rationale for cement over screwing them on are many, the top of which is since we have all along cemented on crowns and bridges event though they have only a 70% success rate after 10 years, what is wrong with cementing on crowns and bridges on oral implants whose success rate is 90% after 10 years.

However, Professor Branemark has an important point in requiring retrievability for his implants. That was why he advocated that the prosthesis should be screwed on rather than cemented on. The additional problem in screw retained prosthesis is the need for passive fit and therefore a very high precision fitting, failing which the improperly fitting prosthesis will give rise to screws loosening or fracturing or implants losing osseointegration. Cementation requires less precision because the gaps can be filled up with cement.

Some practitioners solve the problem of retrievability by using temporary cement. The prosthesis can easily be removed whenever necessary by using a crown remover. Temporary cement works on implants indefinitely because implants are osseointegrated/ ankylosed to the bone and move very little in relationship to other implants since they are all osseointegrated to the same bone. Temporary cement does not work on teeth because teeth can move much more independently of each other and this movement will break the temporary cement and cause the bridge to come loose after a short time.

PROSTHODONTICS FOR ONE PIECE SMALL DENTAL IMPLANTS AND THE QUESTION OF RETRIEVABILITY

There are several problems encountered in building a prosthesis over small dental implants. The issue of whether small dental implants are strong enough to bear crowns and bridges will be addressed in another chapter. This chapter will address mainly the prosthodontic restoration of small dental implants.

The several problems are:-

(1) The abutment portion of the SDI is small. The diameter is usually between 2.0mm to 2.5mm. The small abutment when cast in a model can break easily and thus be problematic to the dental technician.

(2) Building a crown or bridge over a small 2.5mm diameter abutment will result in large amounts of metal or porcelain used. If permanent cement is used and one day the crown or bridge has to be removed for one reason or other, it would be a very tedious process to cut through the thick metal and porcelain.

(3) The small abutment results in very thick porcelain supported by a small metal core. Such porcelain can fracture more easily.

(4) The large surface area interface between the mucosa and the crown or bridge may allow collection of food debris that can give rise to foul smells and infection,

(5) Because of the small diameter of the implant, a good emergence profile cannot be achieved. As such, aesthetics from the anterior teeth may be a problem.

Some of the solutions used so far for the above problems are:-

(1) Prefabricated copings are made. These are precision made to fit over the head of the SDI. They may be connected to the implant and prepared like for a crown or a bridge. Impressions are taken, models are cast and the crown and bridge built in the lab. The copings can also be placed and the impression taken with the copings coming off with the impression. Implant analogues are inserted into the copings stuck in the impression. The casting will have the analogues in place. The copings are replaced and the crowns and bridges built over them.

(2) Composite or glass ionomer material may be bonded on to the implant head and then prepared like for a crown or bridge. The problem in this case is a smooth surface of the composite or glass ionomer in its interface with the mucosa cannot be obtained. The use of a rubber dam or some kind of film will leave a tiny space that may serve as a food trap.

(3)In place of the emergence profile for the anteriors, the anterior crowns are built directly on to the mucosa surface, the surface around the SDIs or the models are relieved generously from 0.5mm to 1.0mm to give the crowns and bridges a slight compression on the mucosa surface resulting in a reasonable emergence profile. This technique has been used very successfully on anterior pontics of bridges. There is hardly any food debris or plaque under the pontics if properly constructed.

TREATMENT PLANNING

TREATMENT PLANNING

There are three broad areas in treatment planning, namely:-

1. The patient’s expectations and budget:  Firstly, ask the patient what are his/her expectations and hopes, and then listen very carefully. It is the patient who is paying for the treatment and it is the patient who has to live with it. The ability to meet and even exceed the patient’s expectations is vital to the success or failure of  any treatment plan. Then ask the patient concerning their budget that they have in mind for the cost of the treatment, and then try to work reasonably within the budget.

2. The medical and oral condition of the patient: The general medical condition of the patient should be assessed and written down. This can often be done easily with the help of a questionnaire. Based on the questionnaire, the dentist can ask further questions that will help in the treatment planning. Then the oral condition must be checked carefully and then written down.

3. The dentist’s expertise and materials available:  The dentist should then assess honestly and diligently whether the treatment required is within his capacity. This will determine whether the dentist should go ahead with the treatment, refer the patient to someone who has the expertise, or work together with a fellow dentist who has the expertise. The materials that the dentist have available are important because the particular demands of the case may require certain materials and  certain characteristics of the implant system used, and the dentist should determine this before proceeding.

CHAPTER TWO: THE THEORY AND PRACTISE OF ORAL IMPLANTOLOGY USING MOSTDIS

                     

CHAPTER TWO: THE THEORY AND PRACTISE OF ORAL IMPLANTOLOGY USING MOSTDIS

GENERAL THEORY

The basic requirements of successful oral implantology is caricatured as follows:-

(a) Titanium: It has been proven through the years that titanium is eminently biocompatible to the human body. The surface layer of titanium dioxide is able to form an intimate bond with living bone in the right circumstances. This bond may be either biological or mechanical or both.

(b) Sterilility:  The implant must be sterile when placed to prevent infection and to allow an intimate bone implant contact to develop.

(c) Atraumatic Placement: The less trauma to the bone, the smaller the inflammatory response and the more likely osseointegration will take place uneventfully.

(d) Covered Healing: Again this will decrease the possibility of infection.

(e) Retrievability: The principle of retrievability was achieved by using screws to retain the crown and bridges. Screws were used so that the bridges and crowns were easily retrieved by exposing the screws and unscrewing them. Retrievibility was emphasized by the professor during that pioneering period so that if any complications arose around the implants, the crowns and bridges would be swiftly and reversibly removed in order to eyeball the complications and treat them. Briefly, it was to prevent the implants from being hot, hidden and hazardous. Thus, the dental implants and its immediate surrounding tissues were made cool, accessible and therefore safe.

With the advent of mini implants, the principle of retrievability became a problem. The mini-implant was too small to fix a screw on and cementation would mean great difficulty in removing the crowns and bridges. Temporary cementation usually resulted in the crowns and bridges coming loose in a short time. Permanent cementation would mean having to cut through the thick metal of the crowns and bridges if there arises a need to retrieve them. The metal is thick because the mini-implants have small diameters and therefore a lot of metal and porcelain had to be used to bulk up the prosthesis to the correct sizes.

HISTORY AND PROGRESS OF MINI DENTAL IMPLANTS

Mini-implants alias small dental implants alias reduced diameter implants alias MOSTDIs were first used to stabilize dentures and transitionals while waiting for implants to osseointegrate. In recent years however, they are increasingly used very successfully in supporting crowns and bridges. If the trend continues, minis will become the main work horse in dental implantology. It is not inconceivable that in 10 years or so, dental implantology especially MOSTDIs will become a regular part of undergraduate dental training. (MOSTDIs stand for Minimized Osseointegrated Titanium Screw Dental Implants and for the purposes of this book we will mainly use this term from hereon)

This is because of the realization that dental implantology has so revolutionized every field of dental treatment, be it restorative, prosthodontic, endodontic, orthodontic, oral surgery, etc. Optimal dental care would not be complete without including dental implantology into the treatment planning. With MOSTDIs, dental implantology has become simpler, cheaper and with a much smaller learning curve than conventional sized dental implants, which we will refer from now on as COSTDIs. It must be added that MOSTDIs are also much more forgiving when complications arise because they are small and once removed, the bone and mucosa grow back much more rapidly than in the case of COSTDIs. (COSTDIs  stand for Conventional Osseointegrated Screw Titanium Dental Implants).

The change will speed up considerably as prosthodontic solutions designed especially for MOSTDIs are invented and disseminated. In this book, I will present in some detail the possible prosthodontic solution for MOSTDIs that will keep the critical margins of soft and hard tissues around the neck of the implants cool, accessible and safe as opposed to hot, hidden and hazardous. This will also help to overcome the challenge of retrievability of crowns and bridges when MOSTDIs are used.

HARD TISSUE

Hard tissue in implant dentistry refers to the bone. Generally, the bone in the maxilla is softer than the bone in the mandible. The hardness of the bone also varies within the same arch. The bone in the anterior of the maxilla is usually harder than that of the posterior and vice versa in the mandible. Hardness of the bone depends on bone density, i.e. the degree of calcification of the bone. Bone is divided into cortical bone that forms the outermost layer of bone which is hard and cancellous bone which is the bone encased by the cortical bone and is softer. The cancellous bone also varies in hardness within the same jaw. For the practical purposes of preparing the bone hole or osteotomy for receiving a dental implant, bone quality is classified into D1, D2, D3 and D4 bone, in descending hardness. The hardest is D1 and the softest is D4. The hardest will be more difficult to drill and must therefore be drilled slower with plenty of irrigation to prevent overheating the bone. The harder the bone will require the size of the bone hole to be closer to the size of the final implant, whereas in soft bone, the bone hole can be smaller.

SOFT TISSUE

Soft tissue in the mouth for the purpose of placing dental implants will refer mainly to the mucosa overlying the alveolar ridge where the missing tooth or teeth were. This mucosa will be usually attached mucosa in that the epithelium is directly attached to the periosteum of the bone. Attached mucosa is where it is advised that the dental implant should be placed so that it will most simulate the natural tooth and will be easier to clean. Unattached  mucosa will be loose as there is a layer of connective tissue between the epithelium of the mucosa and the periosteum. A dental implant emerging through unattached or loose mucosa is thought to be more prone to plaque formation and more difficult to keep clean.

OCCLUSION

A preliminary assessment of the patient’s occlusion is paramount to the long term success of dental implants. Is the occlusion overclosed, open, deviating, have premature contacts? Is the patient suffering from bruxism. All these have to be considered together with the final treatment plan. The more teeth the patient has lost, the more important this process of treatment planning is.

THE BASIS FOR USING MINI DENTAL IMPLANTS

THE BASIS FOR USING MINI DENTAL IMPLANTS

While I would like spend a lot of time reading up all the journals I can lay my hands on and including all their references as part of this book, I realize as a clinician with a busy practice and a large family commitment, my time has to be prioritized carefully.

However, the need for this book cannot wait. There is a huge debate currently on whether or not mini implants or small dental implants or as I prefer to call them MOSTDIS (Minimised Osseointegrated Screw Titanium Dental Implants) should or should not be used for the long term fixation of crowns and bridges.

In the last few years, there has been a widespread concession that mini-implants can be used for denture stabilization. I use the word “concession” as (opposed to “consensus”) because previous to that, mini-implants were frowned upon as transitionals pretending to be “genuine” implants. Historically, mini-implants were used as transitionals that were placed between the conventionally sized dental implants to hold the temporary prosthesis while waiting for the conventional implants to osseointegrate. When the time came to remove the temporary prosthesis, some of the transitionals were found to have osseointegrated  and were impossible to unscrew. Often, the head of such osseointegrated mini-implants were cut off and the endosseous part left in situ. Over time, it occurred to some practitioners that transitories or mini-implants can be used in a more permanent or long term manner.

Initially, mini-implants were used more for denture stabilization. Subsequently, some practitioners tried cementing crowns and then bridges on top of the mini-implants and more often than not were found to be successful, especially in the mandible. Such practices were frowned upon and even condemned by oral implantologists because of several reasons:-

(1) Mini-implants were considered too small in diameter and therefore its ability to withstand masticatory forces over long periods of time were doubtful.

(2) Mini-implants were used originally as transitories and therefore should remain so.

(3) The surface area of mini- implants compared to a conventional implant is too small and therefore the amount of osseointegration is insufficient to withstand masticatory forces.

(4) Mini- implants do not osseointegrate.

(5) It goes against the original tenets laid down by Professor Branemark where it is accepted wisdom that the size of the implant fixture should imitate the size of the root of the tooth that it is replacing.

(6) The emotional element also comes into play, as in, “How can oral implantology be so simple and easy to do?” Emotionally it is difficult to accept that a previously complex procedure can be bypassed with a simple approach.

(7) How can you load mini-implants so routinely when conventional implants usually cannot be loaded immediately, and when done so, only progressively?

These reasons why can be readily addressed when the facts are laid down clearly:-

(1) Mini- implants are made of titanium alloy, i.e. is size for size, 1.6 times stronger than commercially pure titanium. The diameter of mini- implants range between 2.0mm to 3.0mm. Mini- implants are actually less prone to fracture because it is solid. Conventional implants are more prone to fracture because they consist of 2 pieces with a connecting screw in between. If a conventional implant is 4.0mm in diameter and the abutment with the connecting screw together is 2.0mm in diameter. The thickness of the remaining wall of the implant fixture is only 1mm. Compare this to the mini implant which is 2.5mm in diameter or thickness, which is stronger? The mini- implant…… believe it or not is stronger than the conventional implant! It is less prone to fracture than the conventional implant.

(2) Additionally, the 2 piece conventional implant is connected by a screw which has a tendency to come loose and even fracture. Also, there is a microgap between the 2 pieces of the conventional implant which harbour microorganisms that causes bone resorption and sometimes peri-implantitis. Such a chronic source of pathogens in the body may cause coronary artery disease with the accompanying sequelae.

(3) Just because mini implants were designed to be transitionals should not mean that they cannot be used permanently. Many mini- implants have been used for crowns and bridges in the last 10 years successfully. The concept that an implant root should imitate the root size of the tooth it is replacing is largely an assumption by the pioneers of implantology. The basis should have been a study of how much osseointegrated surface is required to withstand the masticatory forces of a particular tooth. It should be reasonable to assume that the surface area of osseointegration can be designed to be less than the surface area of the periodontal ligament of the tooth to be replaced , since osseointegration square mm to square mm is much stronger a bond than the bond of the periodontal ligament, although without the shock-absorbing ability of the periodontal ligament. It is much more easier to extract a tooth than an osseointegrated implant. In fact, you cannot extract an osseointegrated implant. It is reasonable again therefore, to assume that an implant that is half the size of a tooth root will give sufficient surface area of osseointegration to carry the tooth and support it’s masticatory functions.

(4)  Actually, it is the titanium oxide layer on both pure titanium and titanium alloy that is biocompatible and integrates and not pure titanium. Titanium, whether pure or alloy is covered with a layer of titanium oxide immediately on exposure to air. It follows then that both titanium and its alloy will osseointegrate.

(5) The whole world of surgery is moving relentlessly towards minimal invasiveness as shown by the rapid change towards laporoscopy and closed surgery as far as possible. Why should’nt we, as responsible professionals, not make oral implantology less invasive and as simple as possible?  This will not only lower costs, it would decrease clinical time for the doctor and recovery time for the patient. On top of it, such procedures have  proven to be relatively pain free and heals rapidly.

(6) One reason why mini- implants can be loaded immediately as a matter of routine is because there is minimal trauma to the bone. As such, the process of osseointegration begins immediately on implantation. There is no transitional margin of necrosis between the implant and bone which is found in conventional implant placement. Also, because the mini-implant is small, the healing challenge to the surrounding tissue is correspondingly small, the tissue heals rapidly. The healing challenge to the surrounding tissue in the case of the conventional implant is much more and therefore requires a longer time, thus immediate loading of conventional implants often is less successful.

(7) The actual surface area of minis are actually comparable to the surface area of conventional size dental implants. This is because minis are usually placed deeper and therefore longer than conventionals, thus increasing the effective surface area available for osseointegration.

• A conventional sized dental implant 4mm diameter and 10mm long has a surface area of about 125 sq mm.
• A reduced diameter dental implant 2.5mm diameter and 10mm long has a surface of about 80sq mm.
• A reduced diameter dental implant 2.5mm diameter and 13mm long has a surface of about 100sq mm.
• A reduced diameter dental implant 2.5mm diameter and 16mm long has a surface of about 125 sq mm.
• A reduced diameter dental implant 2.5mm diameter and 19mm long has a surface of about150 sq mm.

Note: The actual surface area for all threaded screw implants will be 30 to 50% more than the figures above, taking into consideration that the surface of the threads will be more than that of a simple cylindrical surface.

Thus  a mini that is 2.5mm diameter and 16mm long in its threaded area has a surface area equivalent to a conventional sized dental implant 4mm diameter and 10mm long.

In my experience, this length is one of the most common mini used and very often 2 minis are used to restore one molar. Two minis 2.5mm diameter and with the threaded part 10mm long has a surface area of 160 sq mm! This is more than that of a conventional 4mm diameter and 10mm long. Two minis 10mm long is more than adequate for one molar since very often one molar is restored by a conventional that has a surface area of only 125 to 150sq mm.

How I Got Hooked

Before I could bring myself to place in the first dental implant into my patient’s jaw, I had to overcome the difficult mental block of believing that it is actually possible for a missing tooth to be replaced by an artificial implant.

Throughout my dental school training and into my subsequent years of treating various types of dental diseases, the incessant mantra that was emphasized again and again and again was the need to prevent inflammation of the tissues in the mouth, especially the soft tissue. Time and time again, I observed how vulnerable teeth can become once the gums have become inflamed. Inevitably, the inflammation was associated with foreign elements like pathogenic bacteria in plaque attached to teeth and fillings and prostheses. The idea of a foreign element being embedded into the gums and bones, sticking out into the mouth, then expecting them to stay there and undergo continued stress and hoping that they will be maintained there for years was considered a pipe dream.

In order to overcome the mental block, I decided to read as much about dental implants as possible. I paid special attention to the landmark discoveries and writings of Professor Branemark of Sweden.  I spent a small fortune buying his books and others like it and reading them all. This intellectual exercise helped me to substantially overcome the deep seated skepticism that I felt towards dental implants to the point that I felt that I was ready to take on my first patient. Having convinced my first patient to have dental implants placed in her mouth, I proceeded to do a sinus lift simultaneously with 3 conventional implants placed on the upper left maxilla! I planned carefully and worked down all the steps required and read up all I could to prepare for my first implant surgery.

Then I followed the steps faithfully and stitched up the wound. Four months later I placed in some healing caps and a week later removed them. The sight of a well formed crater in the gums lined by healthy-looking pink mucosa, at the bottom of which I could see the shiny surface of the titanium fixture was something I can never forget. There was little or no inflammation and no bleeding. It struck me convincingly and clearly that titanium is biocompatible with the bone and mucosa of the human body.

From that moment on, I was hooked. Dental implants work!

TYPES OF DENTAL IMPLANTS: COSTDIS AND MOSTDIS

TYPES OF DENTAL IMPLANTS: COSTDIS AND MOSTDIS

Dental implants may be divided into 2 main types of implants, namely COSTDIs and MOSTDIs. COSTDIs stand for Conventional Osseointegrated Screw Titanium Dental Implants. MOSTDIS stand for Minimized Osseointegrated Screw Titanium Dental Implants. The main difference between the 2 are the difference in diameter. Generally, anything below 3mm in diameter are considered MOSTDIs and anything 3mm and above in diameter is considered COSTDIS. We will focus on MOSTDIS in this book.

A BRIEF HISTORY OF DENTAL IMPLANTS CONTINUATION

THE HISTORICAL BACKDROP

The Chinese might have pulled it off, except that soon after the voyages of Admiral Cheng Ho, they fell into the “Middle Kingdom” mindset that closed off the rest of the world, having decided that they had nothing to learn from the rest of the world. From that point onwards, it was a steady decline.

During the rise of Islamic Civilization, great learning in every field of science ranging from medicine, mathematics , astronomy etc. developed, and the Europeans and many others from the then known world came to learn from them. But this rise of learning and discovery somehow  also faltered.

The Europeans went through their dark ages when most thinking and ideas were dictated by their political and religious leaders. The Renaissance brought about a renewed surge and determination to use reason and logic to tackle every field of knowledge and endeavour. And we are still feeling the effects today.

So “the dream come true” has emerged from the great upsurge of logical thought and reasoned understanding of Mother Nature. Science has enjoyed a heavy emphasis since then and in the last century has been diligently applied to the science of healing of the mouth, teeth and body. The dream of mankind to replace a lost tooth with something as good as before if not better was pursued with renewed vigor and enthusiasm, this time with a reasoned, logical and scientific approach.

Dental implants stumbled from one material to another, stainless steel screws, porcelain inserts, glass, ivory, bone, stone etc. were all tried and used. The mainstay in ideas and design seemed to be the use of metals like gold, chrome cobalt and steel of various types with all types of designs ranging from screws and cylinders and spikes and frameworks that rest intimately on the surface of the bone.

INNOVATORS IN DENTISTRY

Historically, innovators in dentistry like in most other disciplines were practitioners who pushed the limits of treatment. But those who dare to try something not tried before has always been frowned upon. And rightly so, since we are treating human beings and  not inanimate objects. Those who want to do new things must approach it with care, compassion and with all the science available at the time and place.

When fixed partial dentures [read bridges] were introduced in the 1900s, it was vehemently opposed by the profession. They caused innumerable health problems because they were poorly made and placed. Not until decades later, when anatomic form, occlusion, physiologic principles and ceramics were introduced did they become as successful as it is today. The idea was excellent, but the supporting science was inadequate. All it required was a corresponding improvement of applied science before it proved to be viable and successful. And this success has laid the groundwork for the success of oral dental implants today.

Proponents of implant dentistry also ran through the same gauntlet, and just barely 20 to 30 years ago, the mention of the word “implant” alone was stared at with deep frowns by the conservatives of the day. And rightly so, because conservatives have their uses and radicals have their uses. Liberals, leftists and even extremists give check and balance and allow the whole behemoth of the world of dentistry to wobble forward steadily and surely. Linkow and Branemark, now feted as heroes of dentistry were during their days of pursuing their vision and experimentation, labeled as mad and crazy and even irresponsible.

With this perspective in mind, while examining every innovation with a careful, analytical, and critical scientific mind, we should also at the same time discipline ourselves not to jump to conclusions and make premature judgments on a procedure or innovation that may eventually prove successful and a boon to many.

THE DEVELOPMENTS

Archaelogical diggings have revealed the presence of crude tooth implants made of bone or stone stuck to the lower jaw of homo sapiens. Records have shown that the ancient Chinese, Egyptians, Incas all practice some form of root form implants dating back to 4 to 5 thousand years ago.

Strock in 1939 used vitallium screws as dental implants. Dahl of Germany in 1943 developed button inserts for stabilizing full upper dentures. These were intramucosal inserts. Goldberg and Gershkoff in 1946 designed and used a metal framework that rested intimately on the surface of the bone and were called subperiosteal implants which proved to be reasonably successful giving up to 90% success at 5 years but fell to 65% after 10 years. Behrman and Egan in 1953 used magnets implanted into the jaws to hold the dentures in place. Sollier and Chercheve in  1953 used transosseous implants for the lower anterior jaw that went from the lower border of the mandible upwards right through to emerge in the upper border of the edentulous mandible in order to hold the dentures. Linkow in 1969 reported his results in using blade implants that basically formed a type of false periodontal ligament made up of scar tissue that worked for as long as they did not get infected! Roberts and Roberts in 1970 gave their results using the ramus frame implant that inserted into the mandible at three points: the mandible symphysis and the left and right retromolar areas.

THE DEFINING MOMENT

The defining moment for the dream to come true came in Toronto, Canada. In May 1982, Professor Per-Ingvar Branemark of Sweden, with great trepidation, presented the results of his systematic long term prospective studies of what he called “osseointegration” especially in relation to replacing a lost tooth almost as good as new. It has to be recorded that at the last minute, he became so distraught and fearful of a hostile response that he almost pulled out of the conference completely. Thankfully, he did not. The significance of his presentation in Toronto caused at first a ripple in the global dental community. When the implications set in, it began a massive alteration of how we do dentistry especially in our treatment planning and our standards of care in oral rehabilitation of a compromised mouth and teeth. Today, we are witnessing a tsunami of oral implant manufacturers and products and realizations that the way we should do dentistry has changed radically and irreversibly as a result of osseointegration! Texts on the various disciplines of dentistry ranging from oral surgery to orthodontics etc. have to be rewritten substantially as a result. Though there has been various claims as to who really did discover osseointegration and  the use of root shaped implants, the credit has to be given to Branemark for systematically documenting and experimenting on the concept for two decades or more before publishing and sharing his prospective studies  to all and sundry. His published findings gave dentists everywhere the confidence and scientific basis to develop and use dental implants to the level that we see today. And still the industry is growing by leaps and bounds globally . Osseointegration has integrated into mainstream dentistry and is here to stay. The promise of tooth germ implants will take a while yet before it can become as practical as osseointegrated titanium dental implants has already become today.

THE SIGNIFICANCE

The  significance of Branemark’s revelations become even more clear when compared against  the “Harvard Consensus on Dental Implants of 1978”.  The National Institutes of Dental Research in the USA brought together clinicians, researchers and professors of dentistry who decided together that in order for a dental implant to be considered successful, it should provide functional service for 5 years in 75% of cases. The objective criteria developed then were:-

• Bone loss no greater than one-third of the vertical height of the implant
• Good occlusal balance and vertical dimension
• Gingival inflammation amenable to treatment
• Mobility of less than 1mm in any direction
• Absence of symptoms and infection
• Absence of any damage to adjacent teeth
• Absence of paraesthesia or anesthesia or violation of the mandibular canal, maxillary sinus, or floor of the nasal passage
• Healthy collagenous tissue

We can see now that these esteemed professionals had far underestimated what human ingenuity can do! Today, all these criteria has been surpassed and not only that , the success of osseointegration has raised the benchmark of what constitutes a successful dental implant . The wonderful thing is dentists today routinely meet and exceed all these criteria when using and dispensing dental implants to patients all over the world.

CONCLUSION

While we do want to trumpet ourselves as one of possibly only two elite groups of health professionals[the other being the opthalmologists who routinely place lens implants successfully]  who has succeeded routinely to replace an important organ[tooth] almost as good as new with a synthetic substitute and without the need to mess around with trying to suppress the immune system to prevent rejection and so on, we need to caution ourselves to practice this discipline of dental implantology responsibly and ethically and always pushing the envelope of excellence and economy as optimally as possible especially in the context where we are. The day is fast approaching when dental implants will be placed routinely in every dental clinic just as routinely as we do a filling.

Dr. Chow Kai Foo   21^st May 2007

REFERENCES

1. Contemporary Implant Dentistry  by Carl E. Misch

2. Dental Implantology  Tufts University Open Course Ware

3.  A Matter of Balance by Elaine Williams

EVIDENCE BASED MEDICINE

EVIDENCE BASED MEDICINE:

A HISTORICAL AND REALISTIC APPRAISEMENT

SO THAT WE KNOW WHAT ACTUALLY WE ARE TALKING ABOUT

Evidence Based Medicine has been bandied about for some time, usually whenever a specialist wants to put a generalist in his/her place. Recently, I was at the receiving end of it when I stood up at a meeting to speak on behalf of a treatment modality that I feel would benefit the common person no end if only the generalists would learn to use it. Even though I felt that I was correct, the result was that I was passed over as not being scientific enough. As a result, I have read up and here I have given a synopsis of my conclusions. One of the firsr revelations is that EBM does not mean that only irrevocable scientific research can justify a treatment modality. This misconception is in most minds whenever the term Evidence Based Medicine is used. As a result one is made to feel guilty when one cannot immediately quote the scientific evidence for our choice of treatment. The truth is that EBM is actually the subjective result of a combination of different types of both objective and subjective evidences, ranging from random controlled trials to clinical cases and anecdotes. While recognizing that this synopsis is not a final statement on it, nevertheless it is a helpful note on what EBM actually means and how we should use it practically.

All medicine and dentistry are based on evidence to a greater or lesser extent. The perennial question to be asked should always be what type of evidence and how good is it? The following is a basic timeline of the modern development of the term Evidence Based Medicine.

1. Professor Archie Cochrane, a Scottish Epidemiologist in his retirement years wrote a book entitled, “Effectiveness and Efficiency: Random Reflections on Health Services” in 1972.

2. It had a landmark effect on the health profession because the question of how really effective are our curative procedures was an issue that had not been addressed aggressively for some time. Historically, it is a question that has always been in the mind of the deliverers of treatment to help them to decide on a hopefully successful course of treatment. I am of course referring to serious, ethically inclined practitioners and not charlatans who are just out for a fast buck. Ancient medical texts usually have at its basis some amount of logic, passed down assumptions and usually common sense with an occasional dash of magic and illogicality.

Modern western based medicine has progressed ever since they came out of the dark ages (with a heavy push from the indomitable Martin Luther of the Renaissance and Reformation fame). Logic and rationale were applied seriously to cures and treatment of diseases, and thus western based medicine proceeded to dominate the world scene because many of their treatments work somewhat and sometimes spectacularly, and is based on some rational commonsense. However, along the years, thinking had stagnated somewhat so that by the time Professor Cochrane offered up his book, it met a crying, but unspoken felt need.

3. Professor Cochrane’s work currently is honored and propagated in centres of evidence-based medical research called “Cochrane Centers”.

4. The term “Evidence Based Medicine” or EBM for short was first coined and used in a published medical article by Guyatt et al in 1992.

5. Professor David Sackett in the 1996 editorial of the British Medical Journal defined EBM as, “EBM is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients.” Let me paraphrase, “Evidence based medicine is the wise use of current research in curing individual patients.” The original philosophy of EBM does not mean pitting research evidence against clinical experience and individual patient values. Instead, it is the integrating of these three, namely research evidence, clinical experience and individual patient values in order to come out with a suitable and balanced course of treatment.

6. Strength of evidence can be generally divided as follows:

            Level 1 :  Random Controlled Trial

            Level 2 :  Controlled Trial

            Level 3 :  Clinical Experience

            Level 4 :  Hearsay

7. One more consideration to take into account in deciding on a treatment modality for a patient should be the question, “ What is the purpose and intention of using the principle of EBM in the treatment of patients?”

            Is it for the patient’s sake to cure?

Or        Is it for the doctor’s sake to justify their conscience or for monetary gain?

Or        Is it for the administration’s sake to streamline operations?

The answer, I believe often lies and should lie somewhere between these considerations.

By:

Dr Chow Kai Foo

BDS Singapore

FDSRCS England

Academy of Medicine Malaysia

July 2012

Cognitive schema and naturalistic decision making in evidence-based practices. Department of Psychiatry, Yale School of Medicine, CMHC, 34 Park Street, Room 144, New Haven, CT 06508, USA. paul.falzer@yale.edu

J Biomed Inform. 2004 Apr;37(2):86-98

The Internet Journal of Allied Health Sciences and Practice

Evidence Based Practice: Misconceived perceptions and warped realities

Dr Saravanan Kumar  Volume 8 Num 4

Evidence Based Medicine Wikepedia

Evidence Based Practice and the Principles of Effective Practice by The Open University

A BRIEF HISTORY OF DENTAL IMPLANTS:    a dream come true

Dr. Chow Kai Foo

BDS Singapore

FDSRCS England

Cert. of Implantology  Germany

A PRECOCIOUS CENTURY

We are now into the 21^st Century. The previous century, the last century of the millenium, the 20^th Century was a precocious century. Precocious because it has superceded the previous 50 centuries of recorded human history and civilization in terms of the accumulation of knowledge. In one quantum leap of a single century, we increased many many times more than all the raw knowledge accumulated in the previous 50 centuries of recorded  history. Today, we can no longer master a subject in a few short years of intense study like in the 19^th century backwards. We can only launch ourselves into the beginning of a lifetime of learning, focusing on the subject or profession of our choice constantly looking out for the sudden breakthrough that may  rearrange all our past knowledge of the subject.. Because knowledge has become so vast and increasing so fast continuously, we cannot afford to stay still, but to keep on and on learning.

A DREAM COME TRUE

In the field of dentistry, it is fitting that the dream of its practioners for thousands of years have at last come to pass in the last century, the audacious century, or some might want to call it the precocious century. Today, a dentist can replace a lost tooth at will and almost as good as new! As dentists, or stomatologists, which is a more accurate term, we are extremely fortunate to be practicing today.

“The goal of modern dentistry is to return patients to oral health in a predictable fashion. The goal of modern dentistry is to restore the patient to normal contour, function, comfort, esthetics, speech and health, regardless of the atrophy, disease, or injury of the stomatognathic system.”     Carl E. Misch

While it remains fresh in my mind may be the best reason why I must blog this particular portion in. At the ITI meeting in Kuching/Malaysia on Thursday May 24th 2012, I was listening to Dr Chatchai Kunavisanut from Thailand speaking on the topic, "Reduced diameter implant: A solution for a narrow ridge", and then giving his opinion on it. He duly showed a case where the lower anterior ridge was very narrow, and he placed two minis to replace two incisors in an "experiment"!?!!  It was a clear contradiction against his own advice not to use minis. On his final slide, he showed pictures of two mini implant cases in which he casually pointed out that they are bound to fail. The conclusion then was, "do not use mini dental implants!".

One look at the two pics and I immediately recognized them to be from my blogspot: smalldentalimplants.blogspot.com.  When it came to discussion on what had been shown, I stood up and readily confessed that those were my cases, one on the upper right and one showing the lower left molars built on mini dental implants. I duly informed the speaker and the audience that contrary to them failing, they were still in my patients' mouths when I last saw them barely a few months ago and after at least 3 years after the minis were placed!!! After checking my blog:

http://smalldentalimplants.blogspot.com/2010/05/blog-post.html

http://smalldentalimplants.blogspot.com/2010/08/bone-climbing-up-mini-dental-implant.html,

I must correct myself, it was the lower right molar, not the lower left.


The mistake that I made was that I went on and on elaborating on why we should not judge minis prematurely and that all serious implant dentists should treatment plan with both minis and conventionals in mind...... and so on.  I should have just set down and let the dear doctor defend what he just said. It was already the end of the meeting and the moderator was pointing at his watch. When I sat down, Dr. Stephen Chen from Australia insisted on replying to what I said. He said that treatment should be evidence based and not anecdoctal and basically challenged me for the studies that can support the wider use of minis and if so proven, he will be one of the first to start using them! In addition, they will even give me a slot in Bangkok to speak at the ITI Congress South East Asia in Bangkok Thailand in May 16-17 2013. I immediately took up the challenge and said that I will get the retrospective study from my own practice and also from the practices of some of my colleagues in Malaysia. Yap, a multi-centre retrospective study! Challenge thrown, challenge taken and the study is going to be ready. Check out the link below as well to read the debate over narrow diameters with an initial query from Carl Misch himself and a final closing comment from yours truly here.

http://www.osseonews.com/narrow-diameter-implants-are-there-absolute-contraindications/

How I Got Hooked.

Before I could bring myself to place in the first dental implant into my patient’s jaw, I had to overcome the difficult mental block of believing that it is actually possible for a missing tooth to be replaced by an artificial implant.

Throughout my dental school training and into my subsequent years of treating various types of dental diseases, the incessant mantra that was emphasized again and again and again was the need to prevent inflammation of the tissues in the mouth, especially the soft tissue. Time and time again, I observed how vulnerable teeth can become once the gums have become inflamed. Inevitably, the inflammation was associated with foreign elements like pathogenic bacteria in plaque attached to teeth and fillings and prostheses. The idea of a foreign element being embedded into the gums and bones, sticking out into the mouth, then expecting them to stay there and undergo continued stress and hoping that they will be maintained there for years was considered a pipe dream.

In order to overcome the mental block, I decided to read as much about dental implants as possible. I paid special attention to the landmark discoveries and writings of Professor Braunemark of Sweden.  I spent a small fortune buying his books and others like it and reading them all. This intellectual exercise helped me to substantially overcome the deep seated skepticism that I felt towards dental implants to the point that I felt that I was ready to take on my first patient. Having convinced my first patient to have dental implants placed in her mouth, I proceeded to do a sinus lift simultaneously with 3 conventional implants placed on the upper left maxilla! I planned carefully and worked down all the steps required and read up all I could to prepare for my first implant surgery.

Then I followed the steps faithfully and stitched up the wound. Four months later I placed in some healing caps and a week later removed them. The sight of the healthily pink and well healed gingiva, like a well formed crater in the gums at the bottom of which I could see the shiny surface of the titanium fixture was something I can never forget. There was little or no inflammation and no bleeding. It struck me convincingly and clearly that titanium is biocompatible with the bone and mucosa of the human body.

From that moment on, I was hooked. Dental implants work!

                                          

Why shouldn’t we, as responsible professionals make oral implantology less invasive and as simple as possible? This will not only lower costs, it would decrease clinical time for the doctor and recovery time for the patient. On top of it, such procedures have been proven to be relatively pain free.

(6) One reason why mini- implants can be loaded immediately as a matter of routine is because there is minimal trauma to the bone. As such, the process of osseointegration begins immediately on implantation. There is no transitional margin of necrosis between the implant and bone which is found in conventional implant placement. Also, because the mini- implant is small, the healing challenge to the surrounding tissue is correspondingly small and the tissue heals rapidly and almost immediately.

The healing challenge of the surrounding tissue in the case of the conventional implants is much more and requires a longer time, thus immediate loading of conventional implants often is less successful.

(7) The actual surface area of minis are actually comparable to the surface area of conventional size dental implants. This is because minis are usually place deeper and therefore longer than conventionals, thus increasing its effective surface area available for osseointegration.

• A conventional sized dental implant 4mm diameter and 10mm long has a surface area of about 125 sq mm.
• A reduced diameter dental implant 2.5mm diameter and 10mm long has a surface of about 80sq mm.
• A reduced diameter dental implant 2.5mm diameter and 13mm long has a surface of about 100sq mm.
• A reduced diameter dental implant 2.5mm diameter and 16mm long has a surface of about 125 sq mm.
• A reduced diameter dental implant 2.5mm diameter and 19mm long has a surface of about150 sq mm.

Thus  a mini that is 2.5mm diameter and 16mm long in its threaded area has a surface area equivalent to a conventional sized dental implant 4mm diameter and 10mm long.

In my experience, this length is one of the most common mini used and very often 2 minis are used to restore one molar. Two minis 2.5mm diameter and 10mm long has a surface area of 160 sq mm! This is more than that of a conventional 4mm diameter and 10mm long. Two minis 10mm long is more than adequate for one molar since very often one molar is restored by a conventional that has a surface area of only 125 to 150sq mm.