Peri-implantitis is an infection around the implant. It affects the gum and the bone. It entails progressive bone loss which can, in some cases, lead to loss of the implant.
Today an implant is considered to have failed when bone height representing more than half of the implant length has been lost, i.e. when more than half of the implant is no longer encased in bone.
The decision of whether or not to fit a new implant depends on the patient’s health, on whether there is sufficient remaining bone to fit a shorter implant, on whether the patient is in pain or not, etc.
At our San Sebastian clinic we are specialists in dental implants, a solution which can last for decades.
The amount of bone loss depends on different factors
More or less bone will be lost depending on the implant surgery technique used, the characteristics of the patient’s health and habits, of the bone, of the implant itself and of the prosthesis fitted to the implant.
- The Surgery
- The Patient
- The Implant Bed
- The Implant Characteristics
- The Prosthesis
1. The Surgery
Location of the implant
The prognosis varies depending on the position of the implant in the mouth. If the gum is thin and moves in this area, there is a greater risk of peri-implantitis.
Milling and drilling
To fit an implant the bone must be shaped using a milling cutter or drill. Care must be taken to avoid heat as this prevents osseointegration, i.e. joining to the bone. The cutter must therefore be very carefully irrigated.
The implant must be fixed solidly in place, with no movement. This primary stability is necessary for the bone to graft to the implant. But care must also be taken not to screw it in too hard as this would cut off the blood supply and hinder the bone from bonding with the implant.
The surgical technique depends on the density and anatomy of the bone into which the implant is inserted.
Contrary to appearances, there is a greater chance of loss when the bone is very hard or cortical (bone type I) than when it is less dense or spongy (bone type IV).
The bone bed to which we fix the implant can have different bone densities. Knowing its biology thanks to scanning means that we can use the correct technique for every situation.
Traditionally, 2mm are left between the implant and the adjacent natural tooth to ensure that there is enough bone for the implant to bond without damaging the root of the tooth.
In cases where there is no other option, this can be reduced to 1.5mm. Any less means that the implant could be lost, causing peri-implantitis.
Minimum distance between implants
When two or more implants are fitted, 3mm of bone width is required between them to prevent subsequent bone loss in the area.
In the back of the mouth, the implant must be placed in the middle of the socket. This more complicated to the front of the mouth, particularly in the upper jaw since the implant must be positioned axially to the tooth, carrying out the process from the palate. This enables access to the screw without affecting the aesthetics, which we would do if we were to work from the front of the tooth.
After tooth extraction, bone in the incisive area recedes from front to back; also, on fitting the axial implant, the tip of the implant is sometimes exposed, showing two or three threads. To prevent this, we are currently using shorter implants, with good results.
When fitted to the lower teeth, the depth is less important, given that the height of the area where the tooth joins the implant is not of any particularly aesthetic importance since it is not visible when speaking or smiling.
In the upper front teeth, the implant must be fitted 2mm higher than the amelocemental junction of the adjacent teeth. We come out at the top to ensure that the soft tissue surrounding the implant head is thick and will not recede or expose the implant head.
Number of surgical phases
This depends on whether the healing abutment is fitted in place from the beginning or not, given its repercussion on marginal bone loss at a later stage. It seems that fitting an abutment in one or two phases has an influence on osseointegration, but not on marginal bone loss.
2. The Patient
Diseases and Habits
Diabetes. Patients with diabetes suffer more infections and have greater difficulty healing.
Osteoporosis. This is not a contraindication for fitting implants, provided that the patient is not taking bisphosphonates.
Alcohol and tobacco. These have a hugely negative effect on bone loss and implant survival. The extent of their use is also a factor.
All of us have saprophytic bacteria, which can be found in the case of both healthy patients and those with health issues.
Bacteria do not, in themselves, cause peri-implantitis.
Bacteria turn into pathogens when the host is susceptible, i.e. when they suffer stress, smoke, drink, have poor hygiene or suffer from some kind of systemic disease.
In these susceptible patients, several kinds of bacteria come together, enter the epithelium around the implant, thereby reducing the immune response of both the cells and the complement system.
3. The Implant Bed
An implant will have a greater or lesser capacity of osseointegration, and therefore of keeping the bone in place over time, depending on:
The bone can have more or less density (from type I to V), and there can be different types of bone around a same implant. It is important to use the adequate surgical technique.
The implant will behave better if the bone is native to the implant placement area than if it is a bone graft from another part of the mouth or body (pelvis or cranium).
Type of defect
It is not the same if we are dealing with a bone surface requiring perforation to fit the implant, or a space missing one or two walls which require filling with the patient’s own bone or biomaterials.
Types of bone-filling biomaterial
Biomaterials come in different types. Each biomaterial has its own properties and, therefore, different indications.
When using biomaterials for bone filling, we add some of the bone obtained from the patient when drilling; this stimulates osteogenesis.
The proportion most used is 20% of autologous bone 80% of Bio-Oss. The latter does not reabsorb, while the autologous bone does, but only after formation of the bone filling has been stimulated.
On other occasions, autologous bone and Bio-Oss are used 50-50%. This means higher bone production. Bio-Oss increases the support and prevents reabsorption of the filling.
Different materials will produce different bone qualities, meaning that behaviour will differ with respect to peri-implantitis.
4. The Implant Characteristics
When choosing an implant that will last over time with no bone loss, we must consider different properties:
This involves increasing the attraction of osteocytes to the implant surface. To do this, Astra adds fluoride to the surface, while the BTI implants contain hydroxyapatite. This is important during the first four weeks of osseointegration.
The porcelain crown connection or other prosthetic abutments in the implant must be sealed. If micromovement exists, a microgap or groove appears in which bacteria nest, eventually leading to bone loss.
It is therefore essential that both the implant and the prosthetic abutments are of very good quality and made by a recognised brand which applies strict quality controls.
Design of the implant surface
The existence on the implant of macro- or micro-threads and the way the surface is worked is essential to osseointegration, i.e. joining to the bone. It does not have as much influence on potential subsequent bone loss.
The head of the implant must be surrounded by thick, stable epithelium, sealing the peri-implant groove to prevent germs from entering. This is the most important characteristic of the implant with a view to preventing peri-implantitis and marginal bone loss.
It is achieved by means of the Switch Platform concept, i.e. where the first millimetres of the implant must be wider than the platform connecting to the prosthesis. This forms a thick epithelial ring which seals the implant.
5. The Prosthesis
Bone loss can occur on connecting the crown to the implant. That’s why it is important to use a transepithelial abutment of two or more mm in height to prevent marginal bone loss. Also, on taking impressions to make the prosthesis, the peri-implant epithelium will suffer less, maintaining the epithelial seal.