How are Implants Fitted?
Dental implants are usually completed in two phases:
phase 1-Surgical
During the first stage of treatment. The actual implant is placed. This process is generally performed in our office with light sedation to help make the patient more comfortable. Using precise gentle surgical techniques. The implant is placed into the jaw bone for 2 to 3 months while osseointegration (bonding to bone) takes place. This helps ensure a strong, solid foundation for replacement teeth.
phase 2-Restorative
In the second stage of treatment, we must create and attach the new tooth or teeth to the anchored implant(s) in your jaw. Dental implants can replace a single tooth, several teeth or complete denture.
Today the implant procedure may be performed with a tooth crown in place directly after implant placement or within a few days. The procedure is easy and very efficient as in one appointment is not only surgery performed but a provisional crown is also in place.
To help the surgeon position the implants, A guide is made (usually out of acrylic) to show the desired position and angulation of the implants.
• Sometimes the final position and restoration of the teeth will be simulated on plaster models to help determine the number and position of implants needed.
• CT scans can be loaded to CAD/CAM software to create a simulation of the desire treatment.
Virtual implants are then placed and a stent created on a 3D printer from the Data.
Planning for dental implants focuses on the general health condition of the patient, the local health condition of the mucous membranes and the jaws and the shape, size, and position of the bones of the jaw, adjacent and opposing teeth.
There are certain conditions that can increase the risk of failure.
Those with poor oral hygiene, heavy smokers and diabetics are all at greater risk for a variant of gum disease that affects implants called peri-implantitis, increasing the chance of long-term failures.
Long term steroid use, osteoprosis and other disease that affect the bones can increase the risk of early failure of implants.
It has been suggested that radiotherapy can negatively affect the survival of implants.
Bisphosphonate drugs
The use of bone building drugs, like bisphosphonates and anti-RANKL drugs require special consideration with implants, because they have been associated with a disorder called Medication-Related Osteonecrosis of the Jaw (MRONJ).
The drugs change bone turnover, which is thought to put people at risk for death of bone when having minor oral surgery.
At routine doses, the effects of the drugs linger for months or years but the risk appears to be very low.
The long-term success of implants is determined, in part, by the forces they have to support.
As implants have no periodontal ligament, there is no sensation of pressure when biting so the forces created are higher. To offset this, the location of implants must distribute forces evenly across the prosthetics they support. Concentrated forces can result in fracture of the bridgework, implant components or loss of bone adjacent the implant.
The ultimate location of implants is based on both biologic and mechanical factors.
A-Basic implant surgical procedure
Most implant systems have five basic steps for placement of each implant:
1. Soft tissue reflection:
An incision is made over the crest of bone, splitting the thicker attached gingiva roughly in half so that the final implant will have a thick band of tissue around it. The edges of tissue, each referred to as a flap are pushed back to expose the bone.
2. Drilling at high speed:
After reflecting the soft tissue, and using a surgical guide or stent as necessary, pilot holes are placed with precision drills at highly regulated speed to prevent burning or pressure necrosis of the bone.
3. Drilling at low speed:
The pilot hole is expanded by using progressively wider drills (typically between three and seven successive drilling steps, depending on implant width and length).
Care is taken not to damage the bone cells by overheating. A cooling saline or water spray keeps the temperature low.
4. placement of the implants:
The implant screw is placed and can be self-tapping, otherwise the prepared site is tapped with an implant analog. It is then screwed into place with a torque controlled wrench at a precise torque so as not to over load the surrounding bone.
5. tissue adaptation
The gingiva is adapted around the entire implant to provide a thick band of healthy tissue around the healing abutment.
This technique is called “one stage-surgery”
In contrast, an implant can be buried, where the top of the implant is sealed with a cover screw and the tissue is closed to completely cover it.
After an integration period, a second surgery is required to reflect the mucosa and place a healing abutment.
This method is called “two-stage surgery”
In the early stages of implant development (1970-1990), implant systems used a two-stage approach, believing that it improved the odds of initial implant survival.
Subsequent research suggests that no difference in implant survival existed between one-stage and two-stage surgeries, and the choice of whether or not to “bury” the implant in the first stage of surgery became a concern of soft tissue management.
The choice of one or two-stages, now centers on how best to reconstruct the soft tissues around lost teeth.
B-Flapless surgery
Flapless surgery is an alternate technique, where a small punch of tissue is removed for implant placement rather than raising flaps.
There are different approaches to placement dental implants after tooth extraction. The approaches are:
1. Immediate post-extraction implant placement.
2. Delayed immediate post-extraction implant placement. (two weeks to three months after extraction).
3. Late implantation. (three months or more after tooth extraction)
There are also various options for when to attach teeth to dental implants, classified into:
1. Immediate loading procedure.
2. Early loading (one week to twelve weeks)
3. Delayed loading (over three months)
For an implant to become permanently stable, the body must grow bone to the surface of the implant (osseointegration).
Based on this biologic process, it was thought that loading an implant during the osseointegration period would result in movement that would prevent osseointegration, and thus increase implant failure rates. As a result, two to four months of integrating time (depending on various factors) was allowed before placing the teeth on implants (restoring them).
However, later research suggests that the initial stability of the implant in bone is a more important determinant of success of implant integration, rather than a certain period of healing time. As a result, the allowed to heal is typically based on the density of bone the implant is placed in and the number of implants splinted together, rather than a uniform amount of time.
When implants can withstand high torque (35 Ncm) and are splinted to other implants, there are no meaningful differences in long-term implant survival or bone loss between implants loaded immediately, at three months, or at six months. Even in solid bone, require a period of no-load to minimize the risk of initial failure.
An increasingly common strategy to preserve bone and reduce treatment times includes the placement of a dental implant into a recent extraction site.
On the one hand, it shortens treatment time and can improve aesthetics because the soft tissue envelope is preserved. On the other hand, implants may have a slightly higher rate of initial failure.
For an implant to osseointegrate, it needs to be surrounded by a healthy quantity of bone. In order for it to survive long-time, it needs to have a thick healthy soft tissue (gingiva) envelope around it. It is common for either the bone or soft tissue to be so deficient that the surgeon needs to reconstruct it either before or during implant placement.
A- Hard tissue (bone) reconstruction
Bone grafting is necessary when there is a lack of bone. While there are always new implant types, such as short implants, and techniques to allow compromise, a general treatment goal is to have a minimum of 10 mm in bone height, and grade from A to O (A- 10+ mm of bone, B=7-9 mm, C= 4-6 mm and O=0-3 mm) where an implants likelihood of osseointegrating is related to the grade of bone.
To achieve an adequate width and height of bone, various bone grafting techniques have been developed.
The most frequently used is called guided bone graft augmentation (GBR) where a defect is filled with either natural (harvested or auto graft) bone or allograft (donor bone or synthetic bone substitute), covered with a semi-permeable membrane and allowed to heal. During the healing phase. Natural bone replaces the graft forming a new bony base for the implants.
The common procedures are:
1. the sinus lift
With a “sinus lift” bone can be grafted under the sinus membrane increasing the height of bone.
Maxillary sinus floor augmentation termed “sinus lift” is a surgical procedure which aims to increase the amount of bone in the posterior maxilla (upper jaw bone), in the area of the premolar and molar teeth, by lifting the lower schneidrian membrane (sinus membrane) and placing a bone graft.
When a tooth is lost the alveolar process begins to remodel and causes a loss in both height and width of the surrounding bone. In addition, when a maxillary molar or premolar is lost, the maxillary sinus pneumatizes in this region which further diminishes the thickness of the underlying bone.
Overall, this leads to a loss in volume of bone.
The goal of the sinus lift is to graft extra bone into the maxillary sinus, so more bone is available to support a dental implant.
For a sinus lift there is two techniques:
a-closed
A closed sinus lift is performed in case there is only need for a small addition of bone. The method includes performing a hole in the palate, through which we insert the desirable amount of bone. The insertion of the dental implant may be combined within this dental implantation treatment.
b-open
For a open sinus lift, after creating a lateral window and elevating the sinus membrane, mineralized cortical cancellous Allograft blend will be hydrated and inserted into the sinus cavity.
A Resorbable collagen membrane will be used to cover the lateral windows, and the site will be sutured.
2. Lateral alveolar augmentation
Lateral bone grafting is an oral surgery procedure used in patients whose jaw bones are insufficient in width to support dental implants. Bone grafting is performed as an in-office procedure, often as on integral step in the dental implants process.
When a greater amount of bone is needed, it can be taken from another site and transplanted to the implant site
There are some method and different materials for lateral alveolar graft:
a- Inlay graft (Block bone graft)
Block bone graft is a procedure in which the patient own bone is harvested (autogenous graft) to replace the deficient area of the jaw bone.
b- GBR (Guided Bone Regeneration)
It is dental surgical procedures that use barrier membrane to direct the growth of new bone at sites with insufficient volumes of bone for proper function or esthetics. In this procedure, are commonly used some bone graft such as autogenous (the patient’s own bone), xenograft (harvested from animals) or Allograft (harvested from human body) under the membrane.
3. Vertical alveolar augmentation
Increase in the height of a site
4. Socket preservation
After tooth extraction and debridement, allograft particulate was inserted into the tooth sockets and gently compacted. A membrane was placed over the grafting material, and the site was sutured and allowed to heal.
Mineralized cortical cancellous Allograft Blend provides a scaffold for cell growth and acts as a guide for rapid bone regeneration.
B- Soft Tissue (gingiva) reconstruction
The gingiva surrounding a tooth has a 2-3 mm band of bright pink, very strong attached mucosa, then a darker larger area of unattached mucosa that folds into the cheeks.
When replacing a tooth with an implant, a band of strong attached gingiva is needed to keep the implant healthy in the long-term.
This is especially important with implants because the blood supply is more precarious in the gingiva surrounding an implant, and is theoretically more susceptible to injury because of a longer attachment to the implant than on a tooth.
When an adequate band of attached tissue is absent, it can be recreated with a soft tissue graft.
there are four methods that can be used to transplant soft tissue:
1- Reposition of palatal roll
A roll of tissue adjacent to an implant in palatal side can be moved towards the Buccal side (lip side)
2-Free Gingiva Graft (FGG)
Gingiva from the palate can be transplanted
3- Connective Tissue Graft
Deeper connective tissue from the palate can be transplanted.
4- Pedicle graft
A finger of tissue based on a blood vessel in the palate or the other site of gingiva can be repositioned to the area.
The prosthetic phase begins once the implant is well integrated or has a reasonable assurance that it will integrate and an abutment is in place to bring it through the mucosa.
An abutment is selected depending on the application.
In many single crown and fixed partial denture scenarios, custom abutments are used.
The abutment is seated on the implant, a screw passes through the abutment to secure it to an internal thread on the implant (lag-screw).
There are variations on this, such as when the abutment and implant body are one piece or when a prefabricated abutment is used.
The platform between the implant and the abutment can be flat (buttress) or conical fit.
In conical fit abutments, the collar of the abutment sits inside the implant which allows a stronger junction between implant and abutment and a better seal against bacteria into the implant body. To improve the gingival seal around the abutment collar, a narrowed collar on the abutment is used, referred to as platform switching.
The combination of conical fits and platform switching gives marginally better long term periodontal conditions compared to flat-top abutments.
Regardless of the abutment material or technique, an impression of the abutment is then taken and a crown secured to the abutment with dental cement. (cement type)
Another variation on abutment / crown model is when the crown and abutment are one piece and the lag-screw traverses both to secure the one-piece structure to the internal thread on the implant. (screw-retained)
There does not appear to be any benefit, in terms of success for cement versus screw-retained prosthetics, although the latter is believed to be easier to maintain and the former offers high esthetic performance.
When a removable denture is worn, retainers to hold the denture in place either custom made or “off-the-shelf” abutments.
However, the same four implants angled in such a way to distribute occlusal forces may be able to safely hold a fixed denture in place with comparable costs and number of procedure giving the denture wearer a fix solution.
After placement, implants need to be cleaned (similar to natural teeth) with a periodontal scaler to remove any plaque. Because of the more precarious blood supply to the gingival, care should be taken with dental floss. Implants will lose at a rate similar to natural teeth in the mouth but will otherwise last.
The porcelain on crowns should be expected to discolour, fracture or require repair approximately every ten years,
Where implants are used to retain a complete denture, depending on the type of attachment, connections need to be changed or refreshed every one to two years.
An oral irrigator may also be useful for cleaning around implants.
A-During Surgery
Placement of dental implants is a surgical procedure and carries the normal risks of surgery including infection, excessive bleeding and necrosis of the flap of tissue around the implant.
Nearby anatomic structures, such as the inferior alveolar nerve, the maxillary sinus and blood vessels, can also be injured when the osteotomy is created or the implant placed.
Even when the lining of the maxillary sinus is perforated by an implant, long term sinusitis is rare.
An inability to place the implant in bone to provide stability of the implant (referred to as primary stability of the implant) increases the risk of failure to osseointegration.
B-First Six Months
a– Primary implant stability
Primary implant stability refers to the stability of a dental implant immediately after implantation. The stability of the titanium screw implant in the patient’s bone tissue post-surgery may be non-invasively assessed using resonance frequency analysis.
Sufficient initial stability may allow immediate loading with prosthetic
reconstruction, though early poses a higher risk of implant failure than conventional loading.
The relevance of primary implant stability decreases gradually with regrowth of bone tissue around the implant in the first weeks after surgery, leading to secondary stability.
Secondary stability is different from the initial stabilization, because it results from the ongoing process of bone regrowth into the implant (osseointegration).
When this healing process is complete, the initial mechanical stability becomes biological stability. Primary stability is critical to implantation success until bone regrowth maximizes mechanical and biological support of the implant. Regrowth usually occurs during the 3-4 weeks after implantation.
Insufficient primary stability, or high initial implant mobility, can lead to failure.
b– Immediate post-operative risks
1. Infection
Pre-op antibiotics reduce the risk of implant failure by 33 percent but do not affect the risk of infection.
2. Excessive bleeding
3. Flap breakdown (less-than 5%)
c-Failure to integrate
An implant is tested between 8 and 24 weeks to determine if it is integrated.
There is significant variation in the criteria used to determine
implant success, the most commonly cited criteria at the implant level are the absence of pain, Mobility, infection, gingiva bleeding, radiographic lucency or peri-implant bone loss greater than 1.5 mm.
Dental implant success is related to operator skill, quality and quantity of the bone available at the site. And the patient’s oral hygiene, but the most important factor is primary implant stability.
The approximate values of failure rate are 1% – 6%.
– Integration failure is rare. Particularly if a dentist’s instructions are followed closely by the patient.
– Immediate loading implants may have a higher rate of failure.
– More often, osseointegration failure occurs when a patient is either too unhealthy to receive the implant or engages in behavior that contraindicates proper dental hygiene including smoking or drug use.
C-Long Term
The long-term complications that result from restoring teeth with implants relate, directly, to the risk factors of patient and the technology.
There are the risks associated with appearance including:
– A high smile line
– Poor gingival quality
– Missing papillae
– Uncommon shapes of teeth
– Bone missing & bone atrophy
– Poor oral hygiene
The risks can be related to biomechanical factors such as:
– The geometry of the implant does not support the teeth like the natural teeth did.
– Grinding of the teeth
– Lack of bone
– Low diameter implants
There are some technological failure risks:
– Fixture fracture
– Screw fracture
– A loss of retention to the teeth they are intended to support
Long-Term failures are due to either loss of bone around the tooth and / or gingival due to peri-implantitis or a mechanical failure of the implant.
Long-term (5-10 years) survival of dental at 93-98 percent depending on their clinical use.
There is more risk for peri-implantitis in cement-retained compare to screw-retain due to cement can escape from under the crown during cementation to get caught in the gingiva.
Also in two stage implants between the fixture and the abutment are gaps and cavities into which bacterial can penetrate from the oral cavity, later these bacteria will return into the adjacent tissue and can cause peri-implantitis.
The most commonly cited criteria for success are function of at least five years in the absence of pain, mobility, radiographic lucency and peri-implant bone loss of greater than 1.5mm on the implant, the lack of suppuration or bleeding in the soft tissue and occurrence of technical complications / prosthetic maintenance, adequate function, and esthetics in the prosthetic. In addition, The patient should ideally be free of pain, paraesthesia, able to chew and taste and be pleased with the esthetics.