Zero bone loss concept: quick clinical answer
“Zero bone loss” is a tissue-preservation objective, not a guaranteed outcome for every implant. Crestal stability depends on patient risk, three-dimensional implant position, surgical handling, hard- and soft-tissue volume, connection and restorative design, cleansable contours, plaque control and maintenance. Evaluate outcomes with standardized radiographs where indicated and corresponding clinical findings over time.
- Dr Nupur ShriraoAbstract
Bone loss during dental implant placement is still a major issue that dentists encounter, but it is a complication that can be prevented. The ‘zero bone loss concept’ is new idea by Dr. Tomas Linkevičius and this article is an attempt at providing a reader’s summary and brief overview of the many factors involved in this concept. Different strategies are presented that can be used to achieve zero bone loss years after treatment. Further reading of the same is suggested by the author before clinical implementation.Introduction
The outcome of implant treatment relies on the stability of the crestal bone, and that is the key factor that will determine whether treatment will succeed or fail. But many of the implant cases we perform have some degree of bone loss. Implant success criteria suggested by Albrektsson et al in 1986, states that 1.5 mm of bone loss within the first year of loading can be considered a success, if later bone loss does not exceed 0.2 mm annually. However, implants used in contemporary dentistry have superior designs and surfaces that results in more success and bone stability. Therefore, some recent studies have questioned this accepted success criteria.
The ‘zero bone loss’ concept
Zero bone loss(a term introduced by Tomas Linkevičius ), or crestal bone stability, is when the bone has not receded or been lost for any reason whatsoever. When zero bone loss concepts are implemented, the chance to develop peri-implantitis is the lowest.There may be an ideal clinical situation—sufficient bone height and width, 2 mm or more of attached tissues, and implant placement in the correct 3D position—but crestal bone loss still occurs. Why and how to prevent this? We can prevent it by developing the ‘zero bone loss concept.’It can be divided into: -
- Surgical factors of the zero bone loss concept
- Prosthetic factors of the zero bone loss concept
Surgical factors of the zero bone loss concept
- Implant designs
- Implant placement depth
- Vertical soft tissue thickness
- Attached gingiva around dental implants
- If positioned below the bone level, the polished collar of an implant neck does not osseointegrate and will cause bone loss.
- The microgap (connection between implant and abutment) is detrimental to bone because of bacterial leakage and micromovements of the abutment inside the implant.
- Platform switching (abutment or suprastructure with a diameter that is smaller than the implant diameter at the implant-platform level) shifts the microgap inward in a horizontal direction, keeping bacterial leakage away from the bone.
- A conical connection provides stability of the implant-abutment junction, but this stability alone does not guarantee that there will be no bone loss.
- Bone-level implants without platform switching should have a machined collar approximately 1 mm in height and should be positioned slightly supracrestally to keep the microgap and associated bacteria away from the bone.
- Tissue-level implants (implant with a polished collar of 1.8 mm or greater) must be placed so that the polished implant neck is completely out of the bone as otherwise, the polished collar can cause bone loss.
- Implants with platform switching can be placed at the bone level and below. The depth depends on the stability of the implant-abutment connection.
- Current knowledge shows that at least 3 mm of vertical (crestal) soft tissue thickness must be present to avoid any crestal bone loss during formation of the biological width around implants.
- Platform switching and a conical connection do not prevent crestal bone loss if implants are placed in thin vertical soft tissues.
- At least 2 mm of attached tissue should be present on the buccal and lingual aspects of implants.
- Connective tissue grafts as well as porcine-derived xenografts can be used to establish adequate immobile mucosa.
Prosthetic factors of the zero bone loss concept
- Cement- or screw-retained restoration
- Emergence profile of the restoration
- Subgingival implant restoration materials
- Supragingival implant restoration materials
- Cement/screw-retained restorations with titanium bases can be used for prosthetic rehabilitation of implants.
- A titanium base abutment, which has multiple undercuts for retention, differs from a regular titanium abutment, which has a more even surface.
- Biomechanically, cement/screw-retained restorations behave like cemented restorations because the finished crown is cemented on a titanium base abutment.
- Cement remnants act as a predisposing factor for peri-implantitis development and are more likely to cause peri-implant disease in patients with a history of periodontitis.
- In patients without periodontal involvement, cement remnants may not cause infection for a long time or infections may be less severe.
- The only reliable way to ensure complete removal of cement remnants is to use custom abutments, without any undercut and with supragingival margins. This allows cement to be seen and easily removed.
- The deeper the position of the cementation margin, the more cement remnants will be left over.
- Techniques such as the use of rubber dam, replica abutments, and retraction cord can be used, but they do not guarantee that all cement remnants will be removed.
- A wide titanium base with a short gingival height may cause bone loss for subcrestally placed implants but may not cause any problems for implants placed at the bone crest.
- When implants are placed subcrestally, the gingival height of the titanium base should correspond to the depth of subcrestal implant placement.
Free for members
Keep reading — it's free
The rest of this article is open to DentalReach members. Create a free account, or sign in, and every article on the site opens in full.