Managing cases

Implant dentistry is now well established as a field, and is experiencing its ‘mature period’. However, the reputation of the discipline is in danger because of over-marketing and too much commercialism, lack of scientific evidence for many implant types and biomaterials, as well as new clinical methods, and above all, an increasing rate of complications and failures.

One well-recognised cause of failures (apart from technical failures) is insufficient buccal bone:

• an exposed micro-rough implant surface and lack of bone and/or keratinised and firmly attached peri-implant mucosa are proven risk factors for the development of peri-implantitis
• poor implant positioning and unfavourable local anatomy are the most frequent risk factors for mucosal recession, leading to aesthetic failures
• insufficient bone anchorage (especially when buccal bone is lacking) is a causal factor of de-osseointegration, together with mechanical overload factors (bruxism, occlusion, etc.)

An appropriate implant design should be selected and positioned, and should be surrounded by bone and keratinised mucosa. A recent experimental study (Monje et al. in review) showed that the buccal wall at healed sites should be at least 1.5mm at the day of surgery.

“A recent experimental study showed that the buccal wall at healed sites should be a least 1.5mm”

Buccal bone plays a significant role in implant complications and failures. Most peri-implant infections originate at sites of insufficient buccal bone.

Thin buccal cortical walls will be lost during bone healing due to avascular necrosis. The rough surface of the implant then becomes exposed – in general, the rougher the surface, the worse the effect – and a pocket is created which facilitates the colonisation of biofilms.

“Buccal bone plays a significant role in implant complications and failures.”

From this point of view, there are a number of arguments in favour of using implants with a hybrid design with a machined neck and a rough bony
area.

At this point, the speaker highlighted some take-home messages:

• do not compromise on the thickness of the buccal and lingual bone walls
• the walls must be at least 1.5mm thick at the day of implant placement
• use a hybrid design with a smooth surface in the soft tissue area
• locate the micro-rough surface at least 1mm below the crest

The speaker also described a protocol for ‘early placement with contour augmentation’ which has been used for twenty years at the University of Bern to treat cases involving two-wall defects in post-extraction sites. This approach has been well documented in the long-term (Chappuis et al. 2018). The implant is placed 4–8 weeks after the extraction and the buccal contour is rebuilt by guided bone regeneration (GBR) using a 2-layer composite graft, a collagen membrane and tension-free primary wound closure.

In healed sites with horizontal atrophy, a staged approach is necessary. First, ridge augmentation is done with an autologous block graft, covered with a thin layer of DBBM granules and a collagen membrane. This technique has been documented since 1990, with the last publication in 2017 (Chappuis et al. 2017).

“In healed sites with horizontal atrophy, a staged approach is necessary.”

Soft tissue grafting is indicated in cases with a lack of keratinised mucosa (usually after aesthetic implant failures); when there is a lack of convexity of the buccal ridge contour; or in case of metallic tattoos in the mucosa.

The speaker drew the following conclusions:

• buccal bone is crucial for achieving long-term stability of dental implants
• the implant should be inserted deep enough to avoid the rough surface being exposed in the peri-implant sulcus after healing
• in posterior zones, a hybrid design with a machined neck is strongly recommended
• in cases involving thin or missing buccal wall, or when contour augmentation is required, rebuild it using GBR (in the vast majority of situations this can be done simultaneously)
• soft tissue grafting is not used routinely (less than 10% of cases)

“Buccal bone is crucial for achieving long-term stability of dental implants”