What do we need – bone or soft tissue?
When preparing a treatment plan, the clinician must decide if the case is suitable for bone augmentation or soft-tissue grafting. In some cases, both procedures – or neither – are required. It is often the case that everyday solutions cannot be concluded directly from documented evidence, as individual cases can vary greatly, and so we need to listen to the experts for their recommendations.
“In some cases, both procedures – or neither – are required.”
The chair presented three cases which are representative of those typically encountered in daily practice to be discussed during the session (Figures 1–3):
- case 1: the patient presented with a lack of horizontal dimension in the posterior mandible
- case 2: the patient’s upper right incisor had to be extracted and presented mucosal recession, periodontal inflammation, insufficient papillae, apical fistula and damaged vestibular bone
- case 3: involving a soft tissue complication in an eight-year-old implant which had suffered marginal recession
When is buccal bone mandatory?
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
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”
Chappuis V, Cavusoglu Y, Buser D, von Arx T. Lateral Ridge Augmentation Using Autogenous Block Grafts and Guided Bone Regeneration: A 10-Year Prospective Case Series Study. Clin Implant Dent Relat Res. 2017 Feb;19(1):85-96. doi: 10.1111/cid.12438. Epub 2016 Jul 31.
Chappuis V, Rahman L, Buser R, Janner SFM, Belser UC, Buser D. Effectiveness of Contour Augmentation with Guided Bone Regeneration: 10-Year Results. J Dent Res. 2018 Mar;97(3):266-274. doi: 10.1177/0022034517737755. Epub 2017 Oct 26.
Monje A, Chappuis V, Monje-Gil F, Muñoz F, Urban I, Wang HL, Buser D: The critical buccal bone thickness revisited: An experimental study in the Beagle Dog. Int J Oral Maxillofac Implants (accepted)
Soft tissue approach for implant installation
Dehiscence around a dental implant is usually caused by poor implant positioning. The use of soft tissue grafting to treat this kind of complication is documented in a study with five-year results (Zucchelli et al. 2018) (Figure 1). The speaker outlined the steps involved in this procedure:
- switch to an abutment with the smallest diameter possible to allow the tissue to grow around it
- raise a partial thickness flap to keep the papilla intact and move it coronally to displace it
- treat the implant surface (only if exposed/probable before surgery)
- anchor a connective tissue graft to the de-epithelialised papilla and ensure it is completely covered by the flap
“Dehiscence around a dental implant is usually caused by poor implant positioning”
The aim is to increase the soft tissue thickness at the transmucosal level. The speaker pointed out that the soft tissue margin can continue to grow following this treatment, and tends to ‘creep’ down onto the crown. This can be observed by comparing the ‘before and after’ photos (Figure 2). A critical point for the success of this approach is that the loss of bone is only on the buccal aspect and is not interproximal. This technique is suitable for well osseointegrated implants without any signs of peri-implantitis.
The speaker went on to describe the five-year outcomes of this approach for prosthetic and soft tissue management. Despite the poor implant positioning and absence of buccal bone in the patients include in the study, they achieved a mean coverage of 97.2% of the level of the adjacent teeth and complete coverage in 79% of the cases. Patients were highly satisfied with this treatment (especially considering that the alternative was implant removal). The most impressive outcome reported was the continued increase of soft tissue volume (‘creeping’) over time.
“The aim is to increase the soft tissue thickness at the transmucosal level.”
The same technique was used in one of the cases presented by the chair at the start of the presentation. The case involved an implant which still had connective tissue adhering to the surface, but no buccal bone covering it. The speaker illustrated how the technique fulfilled the treatment objectives to not only mask the transparency, but also increase soft tissue thickness in the absence of buccal bone and even also replace the suprabony component of the soft tissue (or so-called ‘transmucosal area’) (Figure 3).
The speaker explained that the increased thickness achieved by this approach maintains the integrity of the margin, preventing the inner inflammatory area from becoming thicker than the remaining healthy portion. The ‘soft tissue approach for implant installation’ (Zucchelli. in press) is a protocol to prevent aesthetic complications based on the following principles:
- delayed approach
- correct 3D-guided positioning of the implant
- split thickness flap advanced coronally
- soft tissue graft to increase the thickness of the transmucosal zone
- immediate temporary crown to support the displaced flap and prevent its collapse
“Increased thickness maintains the integrity of the margin”
From an aesthetic point of view, the speaker said it makes more sense to increase the thickness 3–4mm coronal to the margin – the transmucosal area – than to augment the bone in a more apical area. Buccal bone does not have a significant influence either on aesthetics or on stability, provided that a soft tissue graft has been performed to compensate for the insufficient bone in the buccal crest.
Soft tissue augmentation also improves the emergence profile, which in turn makes it easier for the patient to clean the area and minimise plaque accumulation.
One of the questions addressed by the speaker was: ‘Is it possible to follow this protocol in the case of immediate implant placement?’ His answer was yes. But because the papillae are smaller, the graft should be applied to the inner face of the flap and then the flap should be displaced coronally.
“Soft tissue augmentation also improves the emergence profile”
The same protocol can be successfully used in the molar region, where it has been shown that peri-implant crestal bone loss is associated with mucosal thickness (Linkevicius et al. 2009; Stefanini et al. 2016). Recently, the literature has highlighted the beneficial effects of soft tissue augmentation procedures in mainting peri-implant health (Thoma et al. 2018; Giannobile et al. 2018).
Some conclusions can be drawn about the ‘soft tissue’ approach:
- it is ideal for treating peri-implant mucosal dehiscence
- in the aesthetic zone, this approach is critical for successful aesthetic outcomes
- in the posterior area, the approach is recommended for improving patient maintenance and peri-implant health
Giannobile WV, Jung RE, Schwarz F; Groups of the 2nd Osteology Foundation Consensus Meeting. Evidence-based knowledge on the aesthetics and maintenance of peri-implant soft tissues: Osteology Foundation Consensus Report Part 1-Effects of soft tissue augmentation procedures on the maintenance of peri-implant soft tissue health. Clin Oral Implants Res. 2018 Mar;29 Suppl 15:7-10. doi: 10.1111/clr.13110.
Linkevicius T, Apse P, Grybauskas S, Puisys A. The influence of soft tissue thickness on crestal bone changes around implants: a 1-year prospective controlled clinical trial. Int J Oral Maxillofac Implants. 2009 Jul-Aug;24(4):712-9.
Stefanini M, Felice P, Mazzotti C, Marzadori M, Gherlone EF, Zucchelli G. Transmucosal Implant Placement with Submarginal Connective Tissue Graft in Area of Shallow Buccal Bone Dehiscence: A Three-Year Follow-Up Case Series. Int J Periodontics Restorative Dent. 2016 Sep-Oct;36(5):621-30. doi: 10.11607/prd.2537.
Thoma DS, Naenni N, Figuero E, Hämmerle CHF, Schwarz F, Jung RE, Sanz-Sánchez I. Effects of soft tissue augmentation procedures on peri-implant health or disease: A systematic review and meta-analysis. Clin Oral Implants Res. 2018 Mar;29 Suppl 15:32-49. doi: 10.1111/clr.13114.
Zucchelli G, Felice P, Mazzotti C, Marzadori M, Mounssif I, Monaco C, Stefanini M. 5-year outcomes after coverage of soft tissue dehiscence around single implants: A prospective cohort study. Eur J Oral Implantol. 2018;11(2):215-224.
Zucchelli G, Mazzotti C. Soft tissue guided implant therapy. Quintessenza Edition, in press
In the first case described by the chair, a good approach could be to perform soft tissue augmentation first, and then during a second procedure place the implant and perform GBR simultaneously.
Zucchelli thought that a simultaneous sub-marginal connective tissue graft could be simpler and better for the patient. Buser said he would perform GBR and implant placement simultaneously, achieving primary closure and covering the implant with the membrane. Then he would re-evaluate the case at the time of implant uncovering. It was suggested that the minimum width of keratinised mucosa would be 3mm. If there was any less, the case couldn’t be solved in one surgery. Zucchelli insisted on the importance of soft tissue thickness to prevent future recessions. There was some doubt as to whether an average doctor could successfully perform Zucchelli’s technique to obtain the same results as him.
“Zucchelli insisted on the importance of soft tissue thickness to prevent future recessions”
A flapless procedure could also be a good option for the patient, and wouldn’t interfere with the crestal vascular supply. It may be the best choice (provided that the site has adequate bone and soft tissue dimensions). However, Zucchelli pointed out that by ‘going flapless’, the soft tissue thickness can’t be improved and, consequently, future recession cannot be prevented.
“A flapless procedure could also be a good option for the patient”
The second case was not considered a good candidate for immediate implant placement. Buser said he would prefer early placement (4–6 weeks), after soft tissue healing will have provided extra connective tissue to cover the GBR graft, and would simultaneously place the implant. Buser said that decisions would be made about additional soft tissue procedures at the re-evaluation stage (when uncovering the implant). Zucchelli said he would wait six months for total healing and would then perform the ‘soft tissue approach’ described in his presentation. Roccuzzo revealed that the method he chose was socket grafting for alevolar ridge preservation (ARP), in order to give himself a better opportunity to instruct the patient in oral hygiene. According to both speakers the problem with socket grafting in case of a missing buccal bone wall is that biomaterials are in contact with soft tissue and are not integrated with bone. For the past five years, Buser has used socket grafting much more frequently, in particular in elderly patients. This helps to reduce the morbidity for patients by using a flapless implant placement technique after four to six months, and eliminates the need for a bone augmentation procedure.
Buser uses socket preservation mainly in cases involving elderly patients with reduced mobility as a simpler approach with flapless surgery, using narrow diameter implants and without augmentation. Zucchelli only recommends this approach when primary stability cannot be obtained.
“Buser uses socket preservation mainly in cases involving elderly patients with reduced mobility”
In the third case, Buser’s preferred approach was resective: implantoplasty to eliminate the rough surface and re-adaptation of the flap (since there are no aesthetic concerns in this particular case). Zucchelli emphasised that something had to be done before mucositis set in, since the best time to treat dehiscence is before the rough surface is exposed and contaminated. In this case, he recommended his ‘soft tissue approach’ to prevent future problems.