The treatment planning has to be meticulously executed during the surgery and proper surgical technique is vital as failure can occur in many ways as described.
1) Placement of implant with improper axial angulation
Surgical placement of the implant improperly can lead to a prosthetic rehabilitation that compromises esthetics and the distribution of loads. In cases when the available bone is less the best way is to graft the site and obtain an ideal biomechanical scenario. The use of implant in an angulated direction (to place the implant as dictated by bone and not the future restoration) leads to the creation of offset loads.Endosseous implants are best suited to distribute occlusal forces in an axial direction and the shear forces are highly damaging to the implant structure and supporting bone and causes implant failure and therefore any offaxial angulation should be limited to about 25 degrees.The use of angulated abutment only upto 25 degrees is recommended in the anterior region
1) Placement of implant with improper axial angulation
Surgical placement of the implant improperly can lead to a prosthetic rehabilitation that compromises esthetics and the distribution of loads. In cases when the available bone is less the best way is to graft the site and obtain an ideal biomechanical scenario. The use of implant in an angulated direction (to place the implant as dictated by bone and not the future restoration) leads to the creation of offset loads.Endosseous implants are best suited to distribute occlusal forces in an axial direction and the shear forces are highly damaging to the implant structure and supporting bone and causes implant failure and therefore any offaxial angulation should be limited to about 25 degrees.The use of angulated abutment only upto 25 degrees is recommended in the anterior region
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| Off axis placement of implant |
2) Less than ideal Primary Stability
Faulty osteotomy (a bigger osteotomy than required for the selected diameter of implant) can result when excessive force is used to disengage a locked drill during the implant site osteotomy preparation, due to faulty hand positioning of the surgeon during drilling or threading or poor bone quality where there is less resistance to the drill.. Bone cell injury with subsequent necrosis and elliptical preparation of the site with subsequent soft tissue encapsulation around the implant are the resultant effects.
Literature has shown that gaps in the range of 0.25 mm around the implant healed albeit with lesser bone implant contact, and the increase of the gap from 0.7 to 1.7 mm led to a thin soft tissue layer around the implant. The presence of micromotion of greater amplitude in implants with poor primary stability leads to failure of osseointegration. It is imperative that the osteotomy preparation be precise.
3) Impaired Healing and Infection Because of Improper Flap Design
The oral field in itself is a contaminated area due to the presence of the normal oral microflora. Improper flap design can lead to ischemic tissue breakdown and could lead to an early infection at the implant site which would jeopardize the implant status. Basic surgical principles need to be followed with care for the flap design to ensure blood supply, visibility and access and primary closure without tension.Also the presence of systemic conditions like diabetes mellitus and anaemia, in the patient may increase the impairment of wound healing.
4) Overheating the bone and exerting too much pressure
Minimal temperature elevation during surgical drilling of the bone is a key factor in atraumatic surgical technique. Bone cell death occurs at a temperature of 47 degrees Celsius and higher when drilling is performed for one minute. Because of bone cell damage, a connective tissue interface is formed between the implant and the viable bone thus leading to loss of integration. It is recommended therefore, that a speed of no more than 2000 rpm with a copious irrigation, graded drilling (with graded series of drill sizes) with minimal application of pressure be used.
5) Minimal space between implants and implant and adjacent tooth
It is important to maintain a distance of at least 1.5 to 2 mm between an implant and adjacent tooth and a distance of at least 3 mm between two implants. This is imperative in order to preserve the vitality of bone by having an adequate blood supply and any compromise in this leads to bone loss.
Schematic diagram depicting the minimal distance between tooth and implant and between adjacent implants
Faulty osteotomy (a bigger osteotomy than required for the selected diameter of implant) can result when excessive force is used to disengage a locked drill during the implant site osteotomy preparation, due to faulty hand positioning of the surgeon during drilling or threading or poor bone quality where there is less resistance to the drill.. Bone cell injury with subsequent necrosis and elliptical preparation of the site with subsequent soft tissue encapsulation around the implant are the resultant effects.
Literature has shown that gaps in the range of 0.25 mm around the implant healed albeit with lesser bone implant contact, and the increase of the gap from 0.7 to 1.7 mm led to a thin soft tissue layer around the implant. The presence of micromotion of greater amplitude in implants with poor primary stability leads to failure of osseointegration. It is imperative that the osteotomy preparation be precise.
3) Impaired Healing and Infection Because of Improper Flap Design
The oral field in itself is a contaminated area due to the presence of the normal oral microflora. Improper flap design can lead to ischemic tissue breakdown and could lead to an early infection at the implant site which would jeopardize the implant status. Basic surgical principles need to be followed with care for the flap design to ensure blood supply, visibility and access and primary closure without tension.Also the presence of systemic conditions like diabetes mellitus and anaemia, in the patient may increase the impairment of wound healing.
4) Overheating the bone and exerting too much pressure
Minimal temperature elevation during surgical drilling of the bone is a key factor in atraumatic surgical technique. Bone cell death occurs at a temperature of 47 degrees Celsius and higher when drilling is performed for one minute. Because of bone cell damage, a connective tissue interface is formed between the implant and the viable bone thus leading to loss of integration. It is recommended therefore, that a speed of no more than 2000 rpm with a copious irrigation, graded drilling (with graded series of drill sizes) with minimal application of pressure be used.
5) Minimal space between implants and implant and adjacent tooth
It is important to maintain a distance of at least 1.5 to 2 mm between an implant and adjacent tooth and a distance of at least 3 mm between two implants. This is imperative in order to preserve the vitality of bone by having an adequate blood supply and any compromise in this leads to bone loss.
Schematic diagram depicting the minimal distance between tooth and implant and between adjacent implants
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| Schematic diagram depicting the minimal distance between tooth and implant and between adjacent implants |
6) Placing the Implants in Immature Grafted Sites
One of the most common causes of prosthetically related implant failure is believed to be the too rapid loading of the implant supported prosthesis. When the implants are to be placed in grafted bone sites, the timing of the surgery is of utmost importance. Failure is ensured if the implant is loaded before the surrounding bone matures from woven bone into lamellar. Woven bone is only partly mineralized and is immature bone with an unorganized structure that is unable to withstand full scale stresses. The waiting period mandatory for implant survival in cases of grafted bone sites ranges from 6-9 months.
7) Placement of the Implant in an Infected Socket or a Pathologic Lesion
Dental implants may fail due to:
1) Placement of the implant fixture into an infected socket (during immediate implant placement).
2) Placement of the implant fixture into an existing pathology like cyst.
3) Migration of infection from a neighbouring tooth via the narrow space. The implant during the early stages of osseointegration is especially sensitive to any adjacent infection e.g. Endodontic lesion in adjacent tooth.It is therefore very important that the correct planning of the implant procedure is done after a thorough diagnosis and any existing lesions are treated prior to the surgical placement of implants.
8) Contamination of the Implant Body before Insertion
The implant may be contaminated by manufacturing error, by the operator, from non titanium instrumentation and by the bacteria of the oral cavity. Contaminated handling of the implant prior to insertion, dropping it, is poor surgical protocol and it ensures failure. It is advocated to handle implants with titanium instruments and prior to surgery washing the gloved hands with saline after donning the gloves to prevent any contamination with glove powder.
One of the most common causes of prosthetically related implant failure is believed to be the too rapid loading of the implant supported prosthesis. When the implants are to be placed in grafted bone sites, the timing of the surgery is of utmost importance. Failure is ensured if the implant is loaded before the surrounding bone matures from woven bone into lamellar. Woven bone is only partly mineralized and is immature bone with an unorganized structure that is unable to withstand full scale stresses. The waiting period mandatory for implant survival in cases of grafted bone sites ranges from 6-9 months.
7) Placement of the Implant in an Infected Socket or a Pathologic Lesion
Dental implants may fail due to:
1) Placement of the implant fixture into an infected socket (during immediate implant placement).
2) Placement of the implant fixture into an existing pathology like cyst.
3) Migration of infection from a neighbouring tooth via the narrow space. The implant during the early stages of osseointegration is especially sensitive to any adjacent infection e.g. Endodontic lesion in adjacent tooth.It is therefore very important that the correct planning of the implant procedure is done after a thorough diagnosis and any existing lesions are treated prior to the surgical placement of implants.
8) Contamination of the Implant Body before Insertion
The implant may be contaminated by manufacturing error, by the operator, from non titanium instrumentation and by the bacteria of the oral cavity. Contaminated handling of the implant prior to insertion, dropping it, is poor surgical protocol and it ensures failure. It is advocated to handle implants with titanium instruments and prior to surgery washing the gloved hands with saline after donning the gloves to prevent any contamination with glove powder.
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