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