Are You a Borderline Candidate for Implants? The Real Assessment Factors

Very few people are told outright that implants are impossible. Rather more are told something vaguer — that they "might not have enough bone", or that it "would be complicated" — and leave without understanding what that actually means for them.

The reality is that implant suitability sits on a spectrum. There is a group of clearly straightforward cases, a much smaller group where implants genuinely are not advisable, and a substantial middle where the answer depends on planning, preparation, and how much the patient is willing to change beforehand.

Being in that middle group is not a rejection. It usually means there is work to do first.

What tips a case from straightforward into borderline?

Usually one or more of: reduced bone volume or poor bone quality at the intended site; a medical condition or medication that affects healing or bone metabolism; a history of periodontitis, particularly if it is not currently stable; smoking; anatomical structures such as the sinus or the nerve canal sitting close to where the implant needs to go; heavy grinding; or limited mouth opening. None of these is automatically disqualifying. Each changes the risk profile and the planning.

The most common issue, and the one most often mentioned to patients.

Bone begins resorbing as soon as a tooth is removed, and the greatest loss happens in the first year. Someone who lost a tooth two decades ago has a very different ridge from someone who lost one last month — which is the argument for ridge preservation at the time of extraction.

Volume is height and width. An implant needs bone around it in all directions, and a knife-edge ridge may have adequate height but insufficient width.

Quality matters independently. Dense cortical bone in the lower jaw gives excellent initial stability. The softer bone often found in the upper posterior region gives less, which affects the healing protocol and sometimes the technique used.

What can be done. Bone grafting to build width or height; sinus augmentation to create height in the upper back region; narrower or shorter implants where appropriate; angled placement to make use of available bone, as explained in our article on angled implant biomechanics; or approaches designed for reduced density, covered in our article on treatment where bone density is low.

Assessment requires a CBCT scan. A two-dimensional radiograph shows height reasonably but cannot show width or the true position of anatomical structures.

Diabetes. Well-controlled diabetes is not a barrier and outcomes are broadly comparable to those in non-diabetic patients. Poorly controlled diabetes impairs healing and raises infection risk. Control, not diagnosis, is what matters.

Bone-modifying medication. Bisphosphonates and related drugs, particularly by injection or at higher doses, carry a risk of impaired jaw bone healing. This must be disclosed — including drugs taken years ago, since some persist in bone.

Immunosuppression, whether from disease or medication, affects healing and infection risk.

Radiotherapy to the head or neck significantly alters bone healing and requires careful, individually tailored planning.

Anticoagulants. Usually managed rather than a barrier, but they need discussing in advance.

Cardiovascular disease, autoimmune conditions and thyroid disorders may influence planning and healing.

Give a complete medical history including supplements. Something you consider irrelevant may not be.

Patients who have lost teeth to periodontitis are at higher risk of peri-implantitis. The bacteria involved are similar, and susceptibility often reflects individual immune response as much as cleaning.

Crucially, this does not rule out implants. It means:

• Gum disease must be treated and stable before implants are placed, through gum disease treatment

• Remaining pockets should be resolved, since they act as a reservoir

• Home cleaning needs to be genuinely good, not merely intended

• Maintenance intervals will be shorter than standard

• Long-term monitoring is essential

Placing implants into an actively diseased mouth is a poor idea regardless of how good the bone looks.

The single most significant modifiable factor. Smoking reduces blood flow to healing tissue, impairs the immune response and interferes with the early healing phase described in our article on what happens biologically after implant placement.

Studies consistently show higher failure rates and higher peri-implantitis rates in smokers. Risk is dose-related, and stopping — even for a defined period around surgery — improves the picture. Some clinicians will decline to place implants in heavy smokers who are unwilling to stop, and that is a legitimate clinical position rather than a moral one.

If you smoke and want implants, this is the conversation worth having first.

• Maxillary sinus. After upper molar loss, the sinus often expands downwards, reducing available height. Sinus augmentation can address this

• Inferior alveolar nerve. Runs through the lower jaw and must be avoided, with a safety margin. Shorter implants or altered positioning may be needed

• Mental foramen in the lower premolar region

• Adjacent tooth roots, which may need orthodontic movement to create space

• Thin gum tissue, which can allow greyness to show through and is more prone to recession — sometimes addressed with a soft tissue graft

• Limited mouth opening, which restricts access for surgical instruments

CBCT imaging and digital planning make most of these manageable, but they add complexity and cost.

Arrange an assessment if:

• You have a missing tooth or teeth

• A tooth is failing and you want to plan replacement before extraction

• You have a loose adult tooth

• You have been told previously you have insufficient bone

• Your denture is loose or uncomfortable

• You have a bridge that is failing

• You have been declined for implants elsewhere and want the reasoning explained

A proper assessment includes full medical history, clinical examination of teeth and gums, periodontal charting, CBCT imaging, bite assessment, and a written treatment plan with costs. If any of those is missing, ask about it.

Much of what makes a case borderline can be improved:

• Stop smoking. The highest-impact change available

• Get gum disease under control and demonstrate stability

• Improve diabetic control and discuss targets with your GP

• Establish excellent daily cleaning before treatment, not after

• Address grinding with a night guard

• Consider bone grafting where volume is the limiting factor

• Review medications with your GP where relevant

• Preserve the ridge at extraction if a tooth is still to be removed

• Attend hygiene appointments consistently in the run-up

Our dental implants page sets out the treatment pathway.

• Implant suitability is a spectrum, not a binary

• Bone volume and quality are the most common limiting factors, and CBCT is needed to assess them

• Controlled medical conditions are usually manageable; uncontrolled ones are the issue

• A history of gum disease raises peri-implant risk but does not preclude treatment

• Smoking is the most significant modifiable risk factor

• Anatomical obstacles usually add complexity rather than making treatment impossible

• Several borderline factors can be improved before a decision is made

The NHS guide to dental implants covers what treatment involves and who may be suitable.

Borderline is not a verdict. It is a description of where you currently are, and most of the factors that put people there can be moved.

If you have been told implants might not be possible, the useful next question is not "can I have them?" but "what specifically is the obstacle, and what would change it?"

To arrange an implant assessment, arrange an appointment at 22 Wimpole St, London W1G 8GQ, or call 020 7183 0692.

Dental symptoms and treatment options should always be assessed individually during a clinical examination.

This article is for general educational information only and is not professional dental advice, diagnosis, or a treatment recommendation. Information here is general and cannot replace an in-person assessment by a qualified, GDC-registered dental professional. Symptoms, suitability, fees, timelines, and outcomes vary according to individual clinical circumstances. If you have pain, swelling, or other concerning symptoms, seek prompt professional dental care. Always request a written treatment plan and cost estimate before proceeding with treatment.

Written Date: 1 September 2026 Next Review Date: 1 September 2027