A bone to pick

Martin Wanendeya looks at the importance of the quality and quantity of bone when placing dental implants

A strong foundation, metaphorically or literally, is highly influential on long-term success. This truism very much applies to dental implants, where the foundation – bone tissue – must be of sufficient quality and quantity, or else they may not successfully osseointegrate enough to prove viable in the long term (Juodzbalys and Kubilius, 2013).

Osseointegration

Osseointegration is the process by which the bone surrounding the surface of a load-bearing implant knits to it. Stability is critical to the success of this process. While primary stability is attained from the mechanical adhesion of the implant, secondary stability is contingent on primary stability, and is the result of the osseointegration process.

Where primary stability is lacking, the bone remodelling process will be adversely affected, leading to more fibrous bone and a weaker implant-bone interface. Micromotion, due to a lack of stability, can ultimately lead to localised bone resorption (Javed et al, 2013).

Successful osseointegration is reliant on numerous factors, including, but not limited to, the health of the patient, smoking status, the design and material composition of the implant, differences in surgical method and execution, and hormones. Two of the major factors governing the long-term success of the osseointegration process is the quality and quantity of the bone the implant is inserted into (Goutam et al, 2013).

Bone quality

Not all bone is created equal. It varies in density, vascularity, and so on. Generally speaking, primary stability increases with greater bone density, and this, in turn, can improve secondary stability (by facilitating the osseointegration process).

The anatomical location of the bone influences its density. For example, the anterior mandibular bone is denser than the posterior maxillary bone. As we might expect, implants in the former are reportedly more successful (Ayranci et al, 2017).

Some bone has more potential to regenerate, as is the case with predominantly trabecular (type III) bone. In contrast, densely-compact, homogenous (type I) bone features a comparatively low rate of cell proliferation, alongside minimal collagen deposition and no mineralisation. Consequently, in type I bone, the tissues do not sufficiently stiffen, resulting in the level of strain induced by the implant remaining high. High-strain provokes the formation of fibrous tissue, which is far from ideal (Li et al, 2017).

Because primary stability can be significantly influenced by bone quality, some researchers recommend using imaging technologies like computerised tomography (CT) or cone beam CT (CBCT) to assess the bone during treatment selection and planning, in order to more reliably evaluate it and better factor it into the design choice of the implant (Howashi et al, 2014).

Insufficient bone density can also increase the chances of an iatrogenic injury, particularly if unexpected. This can lead to the surgeon placing too much pressure on the drill, relative to what is required – resulting in over-penetration and potentially a nerve injury. These types of errors can be better avoided through careful preoperative planning and assessment (Steinberg and Kelly, 2015).

Bone quantity

Dental implants require sufficient bone to provide structural stability, and to withstand the forces exerted upon it. Where bone quantity is insufficient, and/or the bone has defects, osteoplasty and hard or soft tissue augmentation can be necessitated.

The quantity of bone required depends on the anatomical location, the design of the implant(s), and the structure of the bone (Juodzbalys and Kubilius, 2013). Aesthetics are another consideration, as the shape of the bone can have a significant effect on the patient’s profile – generally speaking a reduced gumline is associated with an older appearance.

Osteoporosis

Osteoporosis is a relatively common condition that results in a reduction of bone quality and quantity. Furthermore, through several mechanisms, the condition reduces the osteogenic capacity of the bone – it impairs bone regeneration and healing (Alghamdi, 2018).

While osteoporosis is theorised to increase the risk of dental implant failure and is associated with higher rates of implant loss across a number of studies, there is disagreement across the available literature on the subject as to whether it is a contraindication to treatment, and to the degree of risk it represents (Giro et al, 2015). It is advisable that longer healing times are allowed for in patients with osteoporosis (Merheb et al, 2016).

It should also be noted a small subset of patients (0.1%) receiving bisphosphonate treatment for osteoporosis develop bisphosphonate related osteonecrosis of the jaw. For those predisposed, invasive dental treatment often acts as a catalyst, with studies finding that tooth extraction was a precipitating factor in 38% to 80% of cases (MacLean et al, 2017; Palaska et al, 2009).

Expertise

For clinicians that lack the confidence, expertise or facilities to treat dental implant patients with inadequate quantity and quality of bone, it is always worth referring to a trusted clinic like Ten Dental+Facial.

The award-winning team is led by highly experienced implant dentists, Drs Nikhil Sisodia and Martin Wanendeya, who offer a seamless referral service for both simple or complex cases.

With careful case assessment and treatment planning, dental implants are a fantastic treatment modality for many edentulous and partially edentulous patients. Many factors must be considered to ensure long-term success and minimise complications, not least the patient’s bone structure.

It is important to have a good understanding of the health and pharmacological status of patients undergoing any surgical procedure, particularly as many patients seeking implants are elderly and, therefore, more likely to present factors that may increase the chance of complications – osteoporosis among them.

References

Alghamdi H (2018) Methods to improve osseointegration of dental implants in low quality (type-iv) bone: an overview. Journal of Functional Biomaterials 9(7): 7

Ayranci F, Sivrikaya E, Omezli M (2017) Is bone density or implant design more important in implant stress formation in patients with bruxism? Biotechnology & Biotechnological Equipment 31(6): 1221-1225

Giro G, Chambrone L, Goldstein A, Rodrigues J, Zenóbio E, Feres M, Figueiredo L, Cassoni A, Shibli J (2015) Impact of osteoporosis in dental implants: a systematic review. World Journal of Orthopedics 6(2): 311-315

Goutam M, Chandu G, Mishra S, Singh M, Tomar B (2013) Factors affecting osseointegration: a literature review. Journal of Orofacial Research 3(3): 197-201

Howashi M, Tsukiyama Y, Ayukawa Y, Isoda-Akizuki K, Kihara M, Imai Y, Sogo M, Koyano K (2014) Relationship between the CT value and cortical bone thickness at implant recipient sites and primary implant stability with comparison of different implant types. Clinical Implant Dentistry and Related Research 18(1): 107-116

Javed F, Ahmed H, Crespi R, Romanos G (2013) Role of primary stability for successful osseointegration of dental implants: factors of influence and evaluation. Interventional Medicine & Applied Science 5(4): 162-167

Juodzbalys G, Kubilius M (2013) Clinical and radiological classification of the jawbone anatomy in endosseous dental implant treatment. Journal of Oral & Maxillofacial Research 4(2): e2

Li J, Yin X, Huang L, Mouraret S, Brunski J, Cordova L, Salmon B, Helms J (2017) Relationships among bone quality, implant osseointegration, and Wnt signaling. Journal of Dental Research 96(7): 822-831

MacLean F, Mason R, Downie J, Watt I, Gallagher A, Gallacher S, Hinnie J (2017) The incidence of bisphosphonate related osteonecrosis of the jaw (BONJ) in patients treated with oral bisphosphonates for osteoporosis. Endocrine Abstracts 50: 55

Merheb J, Temmerman A, Rasmusson L, Kübler A, Thor A, Quirynen M (2016) Influence of skeletal and local bone density on dental implant stability in patients with osteoporosis. Clinical Implant Dentistry and Related Research 18(2): 253-260

Palaska P, Cartsos V, Zavras A (2009) Bisphoshonates and time to osteonecrosis development. The Oncologist 14: 1154-1166

Steinberg M, Kelly P (2015) Implant-related nerve injuries. Dental Clinics of North America 59(2): 357-373

For more information, visit www.tendental.com or call 020 33932623.