DENTAL IMPLANTS - PART 4
CONSIDERATIONS.....
For dental implant procedures to work, there must be enough bone in the jaw, and the bone has to be strong enough to hold and support the implant. If there is not enough bone, more may need to be added with a bone graft procedure discussed earlier. Sometimes, this procedure is called bone augmentation. In addition, natural teeth and supporting tissues near where the implant will be placed must be in good health.
In all cases careful consideration must be given to the final functional aspects of the restoration, such as assessing the forces which will be placed on the implant. Implant loading from chewing and parafunction (abnormal grinding or clenching habits) can exceed the biomechanic tolerance of the implant bone interface and/or the titanium material itself, causing failure. This can be failure of the implant itself (fracture) or bone loss, a "melting" or resorption of the surrounding bone.
The dentist must first determine what type of prosthesis will be fabricated. Only then can the specific implant requirements including number, length, diameter, and thread pattern be determined. In other words, the case must be reverse engineered by the restoring dentist prior to the surgery. If bone volume or density is inadequate, a bone graft procedure must be considered first. The restoring dentist may consult with the oral surgeon, periodontist, endodontist, or another trained general dentist to co-treat the patient. Usually, physical models or impressions of the patient's jawbones and teeth are made by the restorative dentist at the implant surgeons request, and are used as physical aids to treatment planning. If not supplied, the implant surgeon makes his own or relies upon advanced computer-assisted tomography or a cone beam CT scan to achieve the proper treatment plan.
Computer simulation software based on CT scan data allows virtual implant surgical placement based on a barium impregnated prototype of the final prosthesis. This predicts vital anatomy, bone quality, implant characteristics, the need for bone grafting, and maximizing the implant bone surface area for the treatment case creating a high level of predictability. Computer CAD/CAM milled or sterolithography based drill guides can be developed for the implant surgeon to facilitate proper implant placement based on the final prosthesis' occlusion and aesthetics.
Treatment planning software can also be used to demonstrate "try-ins" to the patient on a computer screen. When options have been fully discussed between patient and surgeon, the same software can be used to produce precision drill guides. Specialized software applications such as "simplant" (simulated implant) or "NobelGuide" use the digital data from a patient's CBCT to build a treatment plan. A data set is then produced and sent to a lab for production of a precision-in-mouth drilling guide.
SUCCESS RATES....
Dental implant success is related to operator skill, quality and quantity of the bone available at the site, and the patient's oral hygiene. The consensus is that implants carry a success rate of around 95%.
One of the most important factors that determine implant success is the achievement and maintenance of implant stability. The stability is presented as an ISQ (Implant Stability Quotient) value. Other contributing factors to the success of dental implant placement, as with most surgical procedures, include the patient's overall general health and compliance with post-surgical care.
FAILURE....
Failure of a dental implant is often related to failure to osseointegrate correctly. A dental implant is considered to be a failure if it is lost, mobile or show peri-implant (around the implant) bone loss of greater than 1.0mm in the first year and greater than 0.2mm a year after.
Dental implants are not susceptible to dental caries but they can develop a condition called peri-implantitis. This is an inflammatory condition of the mucosa and/or bone around the implant which may result in bone loss and eventual loss of the implant. The condition is usually, but not always, associated with a chronic infection. Peri-implantitis is more likely to occur in heavy smokers, patients with diabetes, patients with poor oral hygiene and cases where the mucosa around the implant is thin.
Currently there is no universal agreement on the best treatment for peri-implantitis. The condition and its causes is still poorly understood.
Risk of failure is increased in smokers. For this reason implants are frequently placed only after a patient has stopped smoking as the treatment is very expensive. More rarely, an implant may fail because of poor positioning at the time of surgery, or may be overloaded initially causing failure to integrate. If smoking and positioning problems exist prior to implant surgery, clinicians often advise patients that a bridge or partial denture rather than an implant may be a better solution.
Failure may also occur independently of the causes outlined above. Implants like any other object suffers from wear and tear. If the implants in question are replacing commonly used teeth, then these may suffer from wear and tear and after years may crack and break up, although this is a very rare occurrence. The only way to minimize the risk of this happening is to visit your dentist for regular reviews.
In the majority of cases where an implant fails to integrate with the bone and is rejected by the body the cause is unknown. This may occur in around 5% of cases. To this day we still do not know why bone will integrate with titanium dental implants and why it does not reject the material as a "foreign body". many theories have been postulated over the last five decades. A recent theory argues that rather than being active biological tissue response, the integration of bone with an implant is the lack of a negative tissue response. In other word for unknown reasons the usual response of the body to reject foreign objects implanted into it does not function correctly with titanium implants. It has further been postulated that an implant rejection occurs in patients whose bone tissues actually react as they naturally should with the "foreign body" and reject the implant in the same manner that would occur with most other implanted materials.
CONTRAINDICATIONS....
There are few absolute contraindications to implant dentistry. However, there are some systemic, behavioral and anatomic considerations that should be assessed.
Particularly for mandibular (lower jaw) implants, in the vicinity of the mental foramen (MF), there must be sufficient alveolar bone above the mandibular canal also called the inferior alveolar canal or IAC (which acts as the conduit for the neurovascular bundle carrying the inferior alveolar nerve or IAN).
Failure to precisely locate the IAN and MF invites surgical insult by the drills and the implant itself. Such insult may cause irreparable damage to the nerve, often felt as a paresthesia (numbness) or dysesthesia (painful numbness) of the fum, lip and chin. This condition may persist for life and may be accompanied by unconscious drooling.
Uncontrolled type II diabetes is a significant relative contraindication as healing following any type of surgical procedure is delayed due to poor peripheral blood circulation. Anatomic considerations include the volume and height of bone available. Often an ancillary procedure known as a block graft or sinus augmentation are needed to provide enough bone for successful implant placement.
There is new information about intravenous and oral bisphosphonates (taken for certain forms of breast cancer and osteoporosis, respectively) which may put patients at a higher risk of developing a delayed healing syndrome called osteonecrosis. Implants are contraindicated for some patients who take intravenous bisphosphonates.
The many millions of patients who take an oral bisphosphonate (such as Actonel, Fosamaz and Boniva) may sometimes be advised to stop the administration prior to implant surgery, then resume several months later. However, current evidence suggests that this protocol may not be necessary. As of January, 2008, an oral bisphosphonate study reported in the February 2008 Jornal of ORal and Maxillofacial Surgery, reviewing 115 cases that included 468 implants, concluded "There is no evidence of bisphosphonate-associated osteonecrosis of the jaw in any of the patients evaluated in the clinic and those contacted by phone or e-mail reported no symptoms.
For dental implant procedures to work, there must be enough bone in the jaw, and the bone has to be strong enough to hold and support the implant. If there is not enough bone, more may need to be added with a bone graft procedure discussed earlier. Sometimes, this procedure is called bone augmentation. In addition, natural teeth and supporting tissues near where the implant will be placed must be in good health.
In all cases careful consideration must be given to the final functional aspects of the restoration, such as assessing the forces which will be placed on the implant. Implant loading from chewing and parafunction (abnormal grinding or clenching habits) can exceed the biomechanic tolerance of the implant bone interface and/or the titanium material itself, causing failure. This can be failure of the implant itself (fracture) or bone loss, a "melting" or resorption of the surrounding bone.
The dentist must first determine what type of prosthesis will be fabricated. Only then can the specific implant requirements including number, length, diameter, and thread pattern be determined. In other words, the case must be reverse engineered by the restoring dentist prior to the surgery. If bone volume or density is inadequate, a bone graft procedure must be considered first. The restoring dentist may consult with the oral surgeon, periodontist, endodontist, or another trained general dentist to co-treat the patient. Usually, physical models or impressions of the patient's jawbones and teeth are made by the restorative dentist at the implant surgeons request, and are used as physical aids to treatment planning. If not supplied, the implant surgeon makes his own or relies upon advanced computer-assisted tomography or a cone beam CT scan to achieve the proper treatment plan.
Computer simulation software based on CT scan data allows virtual implant surgical placement based on a barium impregnated prototype of the final prosthesis. This predicts vital anatomy, bone quality, implant characteristics, the need for bone grafting, and maximizing the implant bone surface area for the treatment case creating a high level of predictability. Computer CAD/CAM milled or sterolithography based drill guides can be developed for the implant surgeon to facilitate proper implant placement based on the final prosthesis' occlusion and aesthetics.
Treatment planning software can also be used to demonstrate "try-ins" to the patient on a computer screen. When options have been fully discussed between patient and surgeon, the same software can be used to produce precision drill guides. Specialized software applications such as "simplant" (simulated implant) or "NobelGuide" use the digital data from a patient's CBCT to build a treatment plan. A data set is then produced and sent to a lab for production of a precision-in-mouth drilling guide.
SUCCESS RATES....
Dental implant success is related to operator skill, quality and quantity of the bone available at the site, and the patient's oral hygiene. The consensus is that implants carry a success rate of around 95%.
One of the most important factors that determine implant success is the achievement and maintenance of implant stability. The stability is presented as an ISQ (Implant Stability Quotient) value. Other contributing factors to the success of dental implant placement, as with most surgical procedures, include the patient's overall general health and compliance with post-surgical care.
FAILURE....
Failure of a dental implant is often related to failure to osseointegrate correctly. A dental implant is considered to be a failure if it is lost, mobile or show peri-implant (around the implant) bone loss of greater than 1.0mm in the first year and greater than 0.2mm a year after.
Dental implants are not susceptible to dental caries but they can develop a condition called peri-implantitis. This is an inflammatory condition of the mucosa and/or bone around the implant which may result in bone loss and eventual loss of the implant. The condition is usually, but not always, associated with a chronic infection. Peri-implantitis is more likely to occur in heavy smokers, patients with diabetes, patients with poor oral hygiene and cases where the mucosa around the implant is thin.
Currently there is no universal agreement on the best treatment for peri-implantitis. The condition and its causes is still poorly understood.
Risk of failure is increased in smokers. For this reason implants are frequently placed only after a patient has stopped smoking as the treatment is very expensive. More rarely, an implant may fail because of poor positioning at the time of surgery, or may be overloaded initially causing failure to integrate. If smoking and positioning problems exist prior to implant surgery, clinicians often advise patients that a bridge or partial denture rather than an implant may be a better solution.
Failure may also occur independently of the causes outlined above. Implants like any other object suffers from wear and tear. If the implants in question are replacing commonly used teeth, then these may suffer from wear and tear and after years may crack and break up, although this is a very rare occurrence. The only way to minimize the risk of this happening is to visit your dentist for regular reviews.
In the majority of cases where an implant fails to integrate with the bone and is rejected by the body the cause is unknown. This may occur in around 5% of cases. To this day we still do not know why bone will integrate with titanium dental implants and why it does not reject the material as a "foreign body". many theories have been postulated over the last five decades. A recent theory argues that rather than being active biological tissue response, the integration of bone with an implant is the lack of a negative tissue response. In other word for unknown reasons the usual response of the body to reject foreign objects implanted into it does not function correctly with titanium implants. It has further been postulated that an implant rejection occurs in patients whose bone tissues actually react as they naturally should with the "foreign body" and reject the implant in the same manner that would occur with most other implanted materials.
CONTRAINDICATIONS....
There are few absolute contraindications to implant dentistry. However, there are some systemic, behavioral and anatomic considerations that should be assessed.
Particularly for mandibular (lower jaw) implants, in the vicinity of the mental foramen (MF), there must be sufficient alveolar bone above the mandibular canal also called the inferior alveolar canal or IAC (which acts as the conduit for the neurovascular bundle carrying the inferior alveolar nerve or IAN).
Failure to precisely locate the IAN and MF invites surgical insult by the drills and the implant itself. Such insult may cause irreparable damage to the nerve, often felt as a paresthesia (numbness) or dysesthesia (painful numbness) of the fum, lip and chin. This condition may persist for life and may be accompanied by unconscious drooling.
Uncontrolled type II diabetes is a significant relative contraindication as healing following any type of surgical procedure is delayed due to poor peripheral blood circulation. Anatomic considerations include the volume and height of bone available. Often an ancillary procedure known as a block graft or sinus augmentation are needed to provide enough bone for successful implant placement.
There is new information about intravenous and oral bisphosphonates (taken for certain forms of breast cancer and osteoporosis, respectively) which may put patients at a higher risk of developing a delayed healing syndrome called osteonecrosis. Implants are contraindicated for some patients who take intravenous bisphosphonates.
The many millions of patients who take an oral bisphosphonate (such as Actonel, Fosamaz and Boniva) may sometimes be advised to stop the administration prior to implant surgery, then resume several months later. However, current evidence suggests that this protocol may not be necessary. As of January, 2008, an oral bisphosphonate study reported in the February 2008 Jornal of ORal and Maxillofacial Surgery, reviewing 115 cases that included 468 implants, concluded "There is no evidence of bisphosphonate-associated osteonecrosis of the jaw in any of the patients evaluated in the clinic and those contacted by phone or e-mail reported no symptoms.
