|Year : 2021 | Volume
| Issue : 2 | Page : 65-67
Bone loss around implants: Is it inevitable, preventable, irreversible, or untreatable?
ProSmile Dental Clinic and Implant Centre, Dr. L H Hiranandani Hospital, Powai, Mumbai, Maharashtra, India
|Date of Submission||07-Dec-2021|
|Date of Decision||07-Dec-2021|
|Date of Acceptance||07-Dec-2021|
|Date of Web Publication||14-Dec-2021|
Dr. Sharat Shetty
ProSmile Dental Clinic and Implant Centre, Dr. L H Hiranandani Hospital, Powai, Mumbai, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Shetty S. Bone loss around implants: Is it inevitable, preventable, irreversible, or untreatable?. J Dent Implant 2021;11:65-7
Marginal bone loss has been associated with dental implants ever since its first use and slow loss (0.2 mm per year) has been the accepted norm of success. However, clinicians have been flummoxed with various rates of bone loss in spite of following accepted protocols. This is due to the inadequate data regarding the cause-effect understandings and controversies around them. Furthermore, various disciplines have put forth their theories to substantiate them such as the inflammatory model, infection model, material corrosion model, implant-abutment connection model, and occlusal overload model and their varying combinations. Besides, there is a strong correlation between clinicians' and patients' factors. As the regeneration of bone is questionable and in most instances not possible, it is imperative to review all variable etiologies in a specific case and control them judiciously for minimizing the rate of loss over a long period and achieve maintainable success. One needs to differentiate the responses from periodontal ligament-tooth interface and implant-bone interface as they are not similar as the former has good blood and nerve innervations bolstering the innate defense and being more forgiving.
| Causes of Bone Loss|| |
Polished machined collars
There is enough evidence that the smooth surface does not encourage bone adhesion and results in bone resorption around machined surfaces till the beginning of the rough surface. Hence, implant designs with microrough surfaces and grooves promote good bone adaptation and can be placed equicrestally or subcrestally, whereas smooth surface should be placed supracrestally as soft tissues show good attachment with smooth surfaces. The corrosion products due to the release of metal ions (metallosis) into the surrounding tissues, especially bone is also known to cause resorption.
Heterogeneous surface and microgeometry of the implant collar
External coatings of implants with hydroxyapatite materials and macrodesigns in the coronal part of the implants resulted in the separation of the coatings and larger rough surfaces promoting bacterial invasion and faster bone loss. Hence, these are discontinued and replaced by microgeometrical designs.
Location of implant-abutment junction
Implant-abutment junction when close to the bone margin could induce bone loss due to pumping of the microbes and their byproducts directly into the bone margin and causing resorption. Moving it away from bone margin vertically (supracrestal or subcrestal), especially in implant matched abutment connections or horizontally by platform switching will not disturb the labile bone margin and maintain the current level of bone.
Microgap between implant and abutment
The quantum of the movement of the components and the size of microgap can significantly influence bone loss. Although there is not enough evidence about the type of internal connection's contribution to more marginal loss, the tighter fit of conical connection merits some advantage. Besides, the tissue level implants and one-piece implants pose a greater advantage to reduce the limitations of microgaps but have esthetic compromises.
Current periodontal disease
Fulminating existing periodontal infections have the potential to colonize the surfaces of freshly placed implants, especially in immediate placement protocol and leads to the risk of early marginal bone loss.
Clinical handling during surgery
Initial bone loss on placement of implant could be attributed to surgical trauma to heat generation of drilling process, high speeds, blunt drill bits, inadequate irrigation, inherent poor bleeding in the site and higher bone densities and not enough crestal widening. Also, flapped protocols allow extended exposure of the bone and may contribute to bone loss.
Residual bone width after osteotomy
Minimal circumferential width of 1 mm bone around implants is required for its survival. Thin bone <1 mm are vulnerable to thermal, pressure, and bacterial insults and undergo microfractures as they become more devoid of defense and regenerative cells. Judicious interventions by clinicians respecting the bone, especially in poor quality and reduced bone quantity are essential for minimal bone resorption.
Distance between two adjacent implants
A minimum distance of 3 mm has been suggested between two implants to avoid compromise of vital in-between bone. The use of precisely designed surgical guides ensures this distance and prevents subsequent bone loss.
Inadequate biologic width
Survival of bone and especially with a foreign body (implant-abutment) exiting at its crest needs a good minimal healthy soft tissue (three-dimensional biologic width) of >3 mm. This also tolerates the varying vagaries of the oral environment.
Inherent and acquired
Barring the unchangeable genetic bone conditions and patients' systemic disorders if not controlled, unwanted oral habits, parafunction, and inadequate home care add to risks of bone resorption postimplant therapy. These need early detection and corrective interventions whenever possible.
Literature is abundant with the negative effects of smoking on the healing and marginal bone loss around implants. The probable explanations are the heat, toxic irritant chemicals of tobacco, drying actions of the smoke, reduced local blood supply, altered immune responses, and reduced resistance to infections. Cessation protocols and patient compliance should be ensured to achieve the long-term success of implant rehabilitation.
This factor if not well-controlled contributes more to the marginal bone loss as bone being labile is sensitive to the strain applied. The amount, direction, and duration of time of the load largely depend on the design of the prosthesis and compliance with instructions by the patient. The rigidity and stability of the connections of various components also play an important role. Clinicians should hence customize the implant-abutment-prosthesis assembly to suit individual patients. The number of implants, their location, and splinting to reduce overload need to be carefully understood and implemented. Functional loading of immediately placed implants has the potential for inducing bone loss and hence avoided.
Excess cement in the soft-tissue sulcus
Poor attachment of soft tissue around the collar of abutment cannot tolerate the provocation by the residual cement of the luted implant restorations. These promote mechanical irritation, bacterial colonization, and further attachment loss leading to peri-implantitis and marginal bone loss. These can be managed with supragingival margin placement or substituting with screw-retained option whenever possible.
| Significance of Marginal Bone Loss|| |
Continuous marginal loss will expose the rough surfaces of implants to the oral cavity and further favoring microbial growth and loss of attachments. And extensive loss of bone will result in failing or failed implant and may warrant its removal sooner and compromised future solutions. The goal of the clinician is to give the benefits of the implant treatment over a long period of time before it fails even if it is inevitable.
| Identifying Marginal Bone Loss|| |
As marginal bone loss is an unwelcome outcome, and since it has many patient and treatment variables, its continuous monitoring and identification are mandatory. Standardized radiographic assessments at various times of treatment and regularly after that need to done to evaluate the loss and its rate at the earliest so that corrective interventions can be instituted. The reasonable time of radiographic evaluations is 6 months. This will also determine the expected and missed risk factors.
| Prevention and Management Strategies|| |
To minimize the marginal bone loss, it is essential to understand as many causative factors as possible in an individual patient, and the clinician should customize implant treatment plan and not use a mathematical model for all patients.
Identify and select patients for implant treatment by understanding the absolute or relative contraindications to ensure a high survival rate and reduce the negative influences to slow down the marginal bone loss
Material characteristics of the chosen implant system with regards to their diameter, surface characteristics, connection types need to be recognized and should be optimally used. Zirconia abutments show better tissue responses than titanium and could also replace titanium implants in future.
Preventing peri-implantitis should be perpetually in mind while placing implants. These include respecting native bone for their quality and quantity, early placement than delayed, atraumatic surgical manipulations, and controlling all predisposing biological factors.
Loading of dental implants with occlusal forces should be designed to favorably minimize marginal bone loss. These comprise correct angulations and number of implants, avoiding early functional loading and splinting in case of compromised biomechanical designs of the implant-abutment-prosthesis complex.
Abutment to implant connections does play a major role to avoid bone loss. Choosing an appropriate platform switching model with adequate rigidity and durability of the connection can decrease microgap-induced bone loss considerably.
Nonirritational prosthetic planning is the clinicians' best option to avoid or minimize bone loss. Choosing a one-time abutment concept, judicious choice and handling of cemented or screw-retained restorations, attaining a favorable occlusal contact relationship, and regularly monitoring the tissue-restorations interfaces go a long way to maintain the integrity of crestal bone,
Timely continuing professional development by the clinician is necessary for preventing and managing crestal bone loss. These advanced solutions will aid in finding a balance for achieving biological, functional, and esthetic success in implant rehabilitation for a long period of time.
”Without change there is no innovation, creativity, or incentive for improvement. Those who initiate change will have a better opportunity to manage the change that is inevitable.”-William Pollard