Editorial - Saudi Dental Journal

ISSN (Print) 1013-9052
EISSN 1658-3558

The Saudi Dental Journal,
P.O. Box 52500,
Riyadh 11563,
Kingdom of Saudi Arabia

Tel.	966-1-467-7328
Fax.	933-1-467-7308 / 966-1-467-7534
Email	saudidj@ksu.edu.sa

Editorial

Implants: Clinical Reports vs Scientific Criteria

Recently, hundreds of clinical reports have been published showing success rates of dental implant modalities of between 90 and 100% over long period of time ranging from 5-15 years. Yet, the most recent official position of the USA's National Institute of Dental Research (NIDR) Consensus on Dental Implants as formulated by the most informed, experienced and responsible group of scientists and clinicians representing almost every type of dental implant is "none of the present implant systems meets the scrutiny of scientific criteria".
The practicing dentist being continuously per suaded by the commercial sector to purchase and use their implant system and, hopefully, is also exposed to the academic sector which is emphasizing care and caution, has become con fused. To use or not to use dental implants; that is the question. A dental implant as is perceived by the profes sion is a device that is capable of replacing the func tions of the natural tooth or teeth.
To attempt to answer the above question in the light of that perception, and resolve the wide dis parity between the NIDR's consensus and the pub lished clinical reports, let's go back to basics and examine a situation familiar to us over several gen erations of dental practice; the child who comes to the office with a permanent central incisor in his hand stating that this fill out from his mouth few hours ago after suffering a blow to the face. Tooth is carefully treated endodontically, tooth and soc ket are methodically prepared, tooth is replaced in socket and stabilized, tooth is relieved from occlu sion and child is instructed not to use the tooth for a while. Assuming best success, the tooth will become ankylosed with direct bony attachment to its socket within 6 months.
Physiologic compatibility of any dental implant material can hardly reach that of dental cementum. But let's be generous enough to state that we now have several materials with tissue compatibility equal to that of dental cementum. Accordingly, when the root portion of the best of implants is sub merged in bone for 3-6 months, unloaded and undisturbed, the implant root will also ankylose to bone. The ankylosed state is a much more better anchorage level than the osseointegrated state
since the former is bony anchorage at any micro scopic or analytic level while the latter is only at "the optical microscopic level" and has been reported to be only 50% bone in both maxilla and mandible. But, to avoid the accusation of being excessively strict, we will say that up to this point the implant root is attached to the jaw as well as is the ankylosed tooth; no one dares to disagree and states that the implant will be better attached than the tooth.
In the case of the ankyiosed tooth we congratu late the patient and let him use his tooth in normal function. Five to ten years from that date, the crown of the tooth falls off because the root has been resorbed. The chances that such a tooth will last beyond 10 years is very small.
In the case of the implant, we expose the bone and attach to it the appropriate core and a suitable crown. The patient is instructed to use it in normal functions and methodically returns periodically for cleaning. Now we are being told by the clinical reports that such an implant, functioning normally, lasted so far more than 15 years and continues to serve effectively and in excellent condition and that the chances for such success rate is greater than 90%.
As such we, as a profession, are being told that while the natural tooth anchored by ankylosis has no chance to last more than ten years, the implant anchored by less than ankylosis will last more than twenty years. When a dentist, attending a meeting where such a report is made, raises his hand, fear fully to question the speaker who was just intro duced as an "expert" and asks how could that be, the latter authoritatively and victoriously answers "here are the reports of all of these distinguished scientists and universities". Our dear colleague the dentist who is totally absorbed by his patients, practice, expenses, etc. just sets down. There is not much the dentist can do, he did not read enough about the subject, since his job is principally to treat the patient and he expects to learn from the "ex pert" who has just told him that the implant is far better than the ankylosed natural tooth. It is to this dentist, my teacher, my colleague and my student, that this editorial is dedicated.
The naked truth, my friend, lies not in physiolog ical compatibility and how much the implant remained well held in its position, but in mechani cal (functional) compatibility and how much real function did the implant render over its life.
In the ankylosed tooth, the patient uses his tooth normally, he bites strongly as always, he brushes his teeth once or twice a day as always, and sub jects his teeth to ordinary mandibular excursions and daily trauma as always. The result of all such activity is that he is applying a good amount of compressive forces (pressure) on his teeth. That compression, thanks to PDL and Lamina Dura (LD), is converted to tension (pulling, bone depositing) in the supporting alveolar bone of all teeth except that of the ankylosed one, since it does not have PDL or LD. Therefore, the compressive functional loads falling on the ankylosed tooth are transmitted as compressive forces to the supporting alveolar bone, inducing osteoclastic activity. Osteoclasts will eat away calcified tissue, either the bone of the alveolus of the ankylosed tooth or the cementum and dentin of the tooth itself. For reasons beyond this editorial, the osteoclasts eat away the root of the ankylosed tooth and keep at it until the whole root is devoured and the crown just falls off. The extremely important role of PDL fibers held to some kind of LD to the real success of implants is well supported by a 1990 article by Buser et al.
If we generously accept that the implant is anchored to its site by, at best, ankylosis, then under normal function, osteoclastic activity must also occur. In this case the osteoclasts do not like to eat away Ti, Ti-V-AL, Co-Cr, Fe-Cr, AL203, single crystals, or whatever material from which the implants is made, so they eat away the bone sur rounding the implant. The lost bone is replaced by fibrous tissue and the implant becomes loose. That is exactly what have been happening since 1912 and should be happening until today and will con tinue to happen until one of two things happen. The introduction of a smart implant capable of con verting the compressive biting force in the mouth to tensile stresses (osteoblastic activity inducing) in the supporting bone, as is the case with the natural tooth, is one alternative. We hastily state that no such implant is available at this time. The second possible solution is to find a way to prevent the compressive biting force from reaching the sup porting bone all together or to minimize its mag nitude. Decreasing the resorbing effect of the biting force can be achieved also in one of two ways; either by placing a shock absorber in the implant or by designing the prosthesis on the implant such that it receives decreased biting loads.
So far as shock absorbing is concerned, some people have thought of that and designed implants with various springs and other gadgets in them as far back as 35 years ago. I am not aware of the availability of any of such implants at this time. Other people decided to place some other kind of shock-absorber in their implant and there is at least one of these available at this time. None of these implants, so designed, will convert the compressive biting stresses to tensile stresses in the bone, but they will reduce the magnitude of compressive stresses in the bone and will slow down the bone resorption.
So far as designing the prosthesis on the implant such that it receives decreased biting loads, hence, transmits decreased compressive stresses to the supporting bone and slows down the resorption process, several such implants are available today. These constitute the several implant modalities generally called the cylinderical or the osseointeg-rated implants. The long term clinical success of these implants can not be explained, even by their own manufacturers, except by the fact that the bit ing forces transmitted to the implant supporting bone must have been reduced through special prosthesis design. The manufacturers of these implants call such prosthesis design as "impecca- ble". The fact is that, even our prosthesis design terminology is also being changed since the word "impeccable" here is to mean narrow and short occlusal table (bicuspidization), very low angle cusp inclinations (zero degree or close), position ing of the prosthesis relative to the supporting bone where the patient can not exert maximum biting force, and the use of acrylic (very low rigidity) to form the crowns. Another "impeccable" thing done is to build the occlusion so that when the upper and lower teeth meet freely there is minimum contact. While in natural teeth such light contact will continually increase by the natural ten dency of teeth to erupt, with implants one does not have to worry. Implants are rarely opposed by nat ural teeth, generally they are opposed by a pros thesis, either dentures or implant supported dentures, neither of which erupts. In addition, the patient is intensively instructed as to careful use of his/her implants and to the fact that unless he/she is extremely cooperative the implants will fail. The patient who was lead to believe that he/she is receiving the most recent advance in dental care, worked on by an expert team of surgeons, pros thodontists and periodontists, have suffered through the surgical trauma; given the impression that he/she was among the very fortunate ones; and in many places, have paid much of his life savings to receive another set of "his own teeth", dedicates himself to caring for these implants. The patient has been so prepared psychologically that he will do anything to protect these implants including eating the softest of foods and brushing and flossing many times a day and reporting back to his dentist promptly. In other words, the patient is placed in a psychological frame of mind to serve the implants instead of being served by them.
Had we done all of these bite force reducing steps and care inducing methods to our patient with ankylosed natural tooth, the tooth would have lasted many more years than just ten. If our fully dentulous patients give their natural teeth the level of care an implant recipient gives to his implants, we would rarely have to extract, endodontically treat, or even extensively restore a tooth.
There is no other explanation available in the lit erature as to why should these non- shock absorb ing and non stress-converting implants last longer than the natural ankylosed tooth, other than pros thesis designs that reduce the biting force. Statisti cally, these special designs in the prosthesis are called confounding factors. If these confounding factors are eliminated, the adjusted statistical reports should show that the success rates of these cylinderical implants will, at best, be equal to or less than those of the ankylosed tooth since the biomechanical compatibilities of the two situation are, at best, equal. This position is well supported by eleven years of research and 29 contributions to the literature by this author et al and 33 invited pre sentations world wide, on the subject of biomedi cal compatibility of dental implants alone. Adell, in Branemark et al, 1985 states "It appears that any undue force in relation to the local bone properties may lead to microfractures which may heal with non-mineralized connective tissue. This is likely to occur if the excessive load is of a repetitive nature as are occlusal forces. The requirement for impecc able prosthodontics - to optimize stress distribution via the prosthesis to the supporting bone - cannot be overemphasized". This statement further sup ports our explanation. If the manufacturers of these implants wish to present, other reason as to why these implants would perform better than the natu ral ankylosed tooth, we will be happy to receive it, and if addresses the issue, directly and scientifi cally, will publish it in this space.
In summary, there has been some progress, especially relative to surgical techniques and ter minology, in the science of implantology, but there has been no breakthroughs. Once the confound ing factors are eliminated, the reported success rates will be just a few percentage points higher than those for the better blade implants, likely not 90% and not more than 75 % over five years either. This conclusion, however, does not mean we should not use implants. The writer, despite his research findings, has been an advocate of implant use whenever necessary as evidenced by his serv ing as past President and member of the Board of Directors of one of the largest implant groups in the world and one which is reputed for strongly foster ing the placement of implants.
We should place implants when we have no other conventional dental practice alternatives. When we do so, the patient must be well informed of the risk. So called good selection of patients who receive implants is a heresy. We place implants for a patient who truly and absolutely needs them, we do not select candidates to receive them. The treat ment plan, general health of the patient and his means psychologically, physically and financially will dictate the use or no use of implants. The healthy, strong, cooperative, edentulous patient with ample bone support, selected usually to receive implants, is most likely in no need for implants. The young person with a few missing teeth, does not need implants, either. As of today, dental implantology is not a conventional dental procedure and the above argument states that it is not a proven procedure either. It is a young grow ing science and the noisy clinical reports can only harm its badly needed further progress severely. If we indeed have over 90% success rate, over 20 years period of normal function then we do not need to do any more research to attain the true replacement of the natural tooth system. Had this been the case, Buser and Stick of Switzerland, Warrer of America's Harvard and Karring of Denmark (1990) will not need to seek a means to develop a PDL attachment system to the implant, especially when the implant used in their experi ments is one of the cylinderical-osseointegrated types and has every reason to be capable of also presenting success rates greater than 90% over a twenty years period. Clearly, they are not satisfied with clinical reports either. The choice must be made by the profession, do we change all the prin ciples of a functional prosthesis design to enhance the success rates of dental implants through the introduction of many confounding factors to our statistics? or, do we continue with our research progress to introduce the smart implant that will truly replace the functions of the natural tooth? Since we can't elect the first choice as it introduces a real heresy to our dental science, it is our profes sional ethical responsibility to opt to the latter alter native. [Heresy is defined by Belloc in Bork (1990) as the dislocation of some complete and self sup porting scheme by the introduction of a novel denial of some essential part therein].
In the meantime, what implant should you use when absolutely necessary? Use the implant that suites the situation at hand and with adequate train ing. Use a cylindrical design, use a shock absorbing design, use a blade design, use a subperiosteal design or a transosteal design. They all will serve with almost equal success rates provided that they all receive or not receive, the same number of con founding factors, surgical care of placement and frequent maintenance.

H. Mohammed -Al Tahawi, DDS,MScD,PhD,FICD,DICOI,FADM

Group Editor, Editorial Board

Recently, hundreds of clinical reports have been published showing success rates of dental implant modalities of between 90 and 100% over long period of time ranging from 5-15 years. Yet, the most recent official position of the USA's National Institute of Dental Research (NIDR) Consensus on Dental Implants as formulated by the most informed, experienced and responsible group of scientists and clinicians representing almost every type of dental implant is "none of the present implant systems meets the scrutiny of scientific criteria".
The practicing dentist being continuously per suaded by the commercial sector to purchase and use their implant system and, hopefully, is also exposed to the academic sector which is emphasizing care and caution, has become con fused. To use or not to use dental implants; that is the question. A dental implant as is perceived by the profes sion is a device that is capable of replacing the func tions of the natural tooth or teeth.
To attempt to answer the above question in the light of that perception, and resolve the wide dis parity between the NIDR's consensus and the pub lished clinical reports, let's go back to basics and examine a situation familiar to us over several gen erations of dental practice; the child who comes to the office with a permanent central incisor in his hand stating that this fill out from his mouth few hours ago after suffering a blow to the face. Tooth is carefully treated endodontically, tooth and soc ket are methodically prepared, tooth is replaced in socket and stabilized, tooth is relieved from occlu sion and child is instructed not to use the tooth for a while. Assuming best success, the tooth will become ankylosed with direct bony attachment to its socket within 6 months.
Physiologic compatibility of any dental implant material can hardly reach that of dental cementum. But let's be generous enough to state that we now have several materials with tissue compatibility equal to that of dental cementum. Accordingly, when the root portion of the best of implants is sub merged in bone for 3-6 months, unloaded and undisturbed, the implant root will also ankylose to bone. The ankylosed state is a much more better anchorage level than the osseointegrated state
since the former is bony anchorage at any micro scopic or analytic level while the latter is only at "the optical microscopic level" and has been reported to be only 50% bone in both maxilla and mandible. But, to avoid the accusation of being excessively strict, we will say that up to this point the implant root is attached to the jaw as well as is the ankylosed tooth; no one dares to disagree and states that the implant will be better attached than the tooth.
In the case of the ankyiosed tooth we congratu late the patient and let him use his tooth in normal function. Five to ten years from that date, the crown of the tooth falls off because the root has been resorbed. The chances that such a tooth will last beyond 10 years is very small.
In the case of the implant, we expose the bone and attach to it the appropriate core and a suitable crown. The patient is instructed to use it in normal functions and methodically returns periodically for cleaning. Now we are being told by the clinical reports that such an implant, functioning normally, lasted so far more than 15 years and continues to serve effectively and in excellent condition and that the chances for such success rate is greater than 90%.
As such we, as a profession, are being told that while the natural tooth anchored by ankylosis has no chance to last more than ten years, the implant anchored by less than ankylosis will last more than twenty years. When a dentist, attending a meeting where such a report is made, raises his hand, fear fully to question the speaker who was just intro duced as an "expert" and asks how could that be, the latter authoritatively and victoriously answers "here are the reports of all of these distinguished scientists and universities". Our dear colleague the dentist who is totally absorbed by his patients, practice, expenses, etc. just sets down. There is not much the dentist can do, he did not read enough about the subject, since his job is principally to treat the patient and he expects to learn from the "ex pert" who has just told him that the implant is far better than the ankylosed natural tooth. It is to this dentist, my teacher, my colleague and my student, that this editorial is dedicated.
The naked truth, my friend, lies not in physiolog ical compatibility and how much the implant remained well held in its position, but in mechani cal (functional) compatibility and how much real function did the implant render over its life.
In the ankylosed tooth, the patient uses his tooth normally, he bites strongly as always, he brushes his teeth once or twice a day as always, and sub jects his teeth to ordinary mandibular excursions and daily trauma as always. The result of all such activity is that he is applying a good amount of compressive forces (pressure) on his teeth. That compression, thanks to PDL and Lamina Dura (LD), is converted to tension (pulling, bone depositing) in the supporting alveolar bone of all teeth except that of the ankylosed one, since it does not have PDL or LD. Therefore, the compressive functional loads falling on the ankylosed tooth are transmitted as compressive forces to the supporting alveolar bone, inducing osteoclastic activity. Osteoclasts will eat away calcified tissue, either the bone of the alveolus of the ankylosed tooth or the cementum and dentin of the tooth itself. For reasons beyond this editorial, the osteoclasts eat away the root of the ankylosed tooth and keep at it until the whole root is devoured and the crown just falls off. The extremely important role of PDL fibers held to some kind of LD to the real success of implants is well supported by a 1990 article by Buser et al.
If we generously accept that the implant is anchored to its site by, at best, ankylosis, then under normal function, osteoclastic activity must also occur. In this case the osteoclasts do not like to eat away Ti, Ti-V-AL, Co-Cr, Fe-Cr, AL203, single crystals, or whatever material from which the implants is made, so they eat away the bone sur rounding the implant. The lost bone is replaced by fibrous tissue and the implant becomes loose. That is exactly what have been happening since 1912 and should be happening until today and will con tinue to happen until one of two things happen. The introduction of a smart implant capable of con verting the compressive biting force in the mouth to tensile stresses (osteoblastic activity inducing) in the supporting bone, as is the case with the natural tooth, is one alternative. We hastily state that no such implant is available at this time. The second possible solution is to find a way to prevent the compressive biting force from reaching the sup porting bone all together or to minimize its mag nitude. Decreasing the resorbing effect of the biting force can be achieved also in one of two ways; either by placing a shock absorber in the implant or by designing the prosthesis on the implant such that it receives decreased biting loads.
So far as shock absorbing is concerned, some people have thought of that and designed implants with various springs and other gadgets in them as far back as 35 years ago. I am not aware of the availability of any of such implants at this time. Other people decided to place some other kind of shock-absorber in their implant and there is at least one of these available at this time. None of these implants, so designed, will convert the compressive biting stresses to tensile stresses in the bone, but they will reduce the magnitude of compressive stresses in the bone and will slow down the bone resorption.
So far as designing the prosthesis on the implant such that it receives decreased biting loads, hence, transmits decreased compressive stresses to the supporting bone and slows down the resorption process, several such implants are available today. These constitute the several implant modalities generally called the cylinderical or the osseointeg-rated implants. The long term clinical success of these implants can not be explained, even by their own manufacturers, except by the fact that the bit ing forces transmitted to the implant supporting bone must have been reduced through special prosthesis design. The manufacturers of these implants call such prosthesis design as "impecca- ble". The fact is that, even our prosthesis design terminology is also being changed since the word "impeccable" here is to mean narrow and short occlusal table (bicuspidization), very low angle cusp inclinations (zero degree or close), position ing of the prosthesis relative to the supporting bone where the patient can not exert maximum biting force, and the use of acrylic (very low rigidity) to form the crowns. Another "impeccable" thing done is to build the occlusion so that when the upper and lower teeth meet freely there is minimum contact. While in natural teeth such light contact will continually increase by the natural ten dency of teeth to erupt, with implants one does not have to worry. Implants are rarely opposed by nat ural teeth, generally they are opposed by a pros thesis, either dentures or implant supported dentures, neither of which erupts. In addition, the patient is intensively instructed as to careful use of his/her implants and to the fact that unless he/she is extremely cooperative the implants will fail. The patient who was lead to believe that he/she is receiving the most recent advance in dental care, worked on by an expert team of surgeons, pros thodontists and periodontists, have suffered through the surgical trauma; given the impression that he/she was among the very fortunate ones; and in many places, have paid much of his life savings to receive another set of "his own teeth", dedicates himself to caring for these implants. The patient has been so prepared psychologically that he will do anything to protect these implants including eating the softest of foods and brushing and flossing many times a day and reporting back to his dentist promptly. In other words, the patient is placed in a psychological frame of mind to serve the implants instead of being served by them.
Had we done all of these bite force reducing steps and care inducing methods to our patient with ankylosed natural tooth, the tooth would have lasted many more years than just ten. If our fully dentulous patients give their natural teeth the level of care an implant recipient gives to his implants, we would rarely have to extract, endodontically treat, or even extensively restore a tooth.
There is no other explanation available in the lit erature as to why should these non- shock absorb ing and non stress-converting implants last longer than the natural ankylosed tooth, other than pros thesis designs that reduce the biting force. Statisti cally, these special designs in the prosthesis are called confounding factors. If these confounding factors are eliminated, the adjusted statistical reports should show that the success rates of these cylinderical implants will, at best, be equal to or less than those of the ankylosed tooth since the biomechanical compatibilities of the two situation are, at best, equal. This position is well supported by eleven years of research and 29 contributions to the literature by this author et al and 33 invited pre sentations world wide, on the subject of biomedi cal compatibility of dental implants alone. Adell, in Branemark et al, 1985 states "It appears that any undue force in relation to the local bone properties may lead to microfractures which may heal with non-mineralized connective tissue. This is likely to occur if the excessive load is of a repetitive nature as are occlusal forces. The requirement for impecc able prosthodontics - to optimize stress distribution via the prosthesis to the supporting bone - cannot be overemphasized". This statement further sup ports our explanation. If the manufacturers of these implants wish to present, other reason as to why these implants would perform better than the natu ral ankylosed tooth, we will be happy to receive it, and if addresses the issue, directly and scientifi cally, will publish it in this space.
In summary, there has been some progress, especially relative to surgical techniques and ter minology, in the science of implantology, but there has been no breakthroughs. Once the confound ing factors are eliminated, the reported success rates will be just a few percentage points higher than those for the better blade implants, likely not 90% and not more than 75 % over five years either. This conclusion, however, does not mean we should not use implants. The writer, despite his research findings, has been an advocate of implant use whenever necessary as evidenced by his serv ing as past President and member of the Board of Directors of one of the largest implant groups in the world and one which is reputed for strongly foster ing the placement of implants.
We should place implants when we have no other conventional dental practice alternatives. When we do so, the patient must be well informed of the risk. So called good selection of patients who receive implants is a heresy. We place implants for a patient who truly and absolutely needs them, we do not select candidates to receive them. The treat ment plan, general health of the patient and his means psychologically, physically and financially will dictate the use or no use of implants. The healthy, strong, cooperative, edentulous patient with ample bone support, selected usually to receive implants, is most likely in no need for implants. The young person with a few missing teeth, does not need implants, either. As of today, dental implantology is not a conventional dental procedure and the above argument states that it is not a proven procedure either. It is a young grow ing science and the noisy clinical reports can only harm its badly needed further progress severely. If we indeed have over 90% success rate, over 20 years period of normal function then we do not need to do any more research to attain the true replacement of the natural tooth system. Had this been the case, Buser and Stick of Switzerland, Warrer of America's Harvard and Karring of Denmark (1990) will not need to seek a means to develop a PDL attachment system to the implant, especially when the implant used in their experi ments is one of the cylinderical-osseointegrated types and has every reason to be capable of also presenting success rates greater than 90% over a twenty years period. Clearly, they are not satisfied with clinical reports either. The choice must be made by the profession, do we change all the prin ciples of a functional prosthesis design to enhance the success rates of dental implants through the introduction of many confounding factors to our statistics? or, do we continue with our research progress to introduce the smart implant that will truly replace the functions of the natural tooth? Since we can't elect the first choice as it introduces a real heresy to our dental science, it is our profes sional ethical responsibility to opt to the latter alter native. [Heresy is defined by Belloc in Bork (1990) as the dislocation of some complete and self sup porting scheme by the introduction of a novel denial of some essential part therein].
In the meantime, what implant should you use when absolutely necessary? Use the implant that suites the situation at hand and with adequate train ing. Use a cylindrical design, use a shock absorbing design, use a blade design, use a subperiosteal design or a transosteal design. They all will serve with almost equal success rates provided that they all receive or not receive, the same number of con founding factors, surgical care of placement and frequent maintenance.

H. Mohammed -Al Tahawi, DDS,MScD,PhD,FICD,DICOI,FADM
Group Editor, Editorial Board