Implants in the aesthetic zone

17 September, 2014
 

Tooth replacement using endosseous implants has provided predictable and stable results with good long-term implant survival rates. However, the goal of implant treatment has evolved from achieving purely osseous fixation to providing an aesthetic, long-lasting restoration that seamlessly blends with the existing dentition. Therefore, factors such as the appearance of soft tissue are of utmost importance in order to achieve success, especially in the aesthetic zone.

All implant placements have hard and soft tissue components, and correct management of these tissues during treatment planning will avoid a simple case becoming a complex case.

Soft tissue management can be separated into:

  • Pre-implant placement – often overlooked
  • With implant placement – all implant placements involve some component
  • Post-implant restoration – most often reactionary in nature.

Pre-implant soft tissue management is generally the most simple approach and yet the most difficult treatment to sell to the patient. Pontic or implant site development surgery can help to produce excellent results but adds to treatment duration. It requires the patient to accept the concept of delayed placement when treatments are advertised in the general media as ‘immediate’.

Soft tissue assessment and keratinised mucosa

It is good practice to document the pre-operative soft tissue situation, not only to manage patient expectations but also to avoid potential litigation if there is disagreement over the position of the final gingival margin.

Important factors include: patient biotype; papillae height; pocketing; marginal height relative to adjacent teeth; and the patient’s smile line in relation to the soft tissues.

The minimum amount of keratinised gingivae required has been a controversial topic. Clinical evidence suggests that if good oral hygiene is performed, then little to no keratinisation is required to maintain fixation.

However, clinical experience over clinical evidence suggests that having thick keratinised tissue at the gingival margin makes the biological seal around the implant more effective and reduces long-term tissue recession.

Pre-implant placement soft tissue management

Tissue augmentation should be considered at the treatment planning stage. Starting with the ideal soft tissue improves the predictability of hard tissue augmentation, as well as implant health. It is better to have too much tissue early that can be manipulated, rather than have to replace it when there is a deficit post-operatively.

Tooth extrusion

In cases where the tooth is still present, orthodontic tooth extrusion may be appropriate to advance not only the soft but hard tissues, including the problematic interdental height (Mantzikos, 1997). Classic fixed arch orthodontics are very effective however, novel use of adhesive bridge work can advance the tissues coronal prior to extraction. (Figs 1a-d)

Extraction techniques/socket preservation

Socket preservation should be discussed with all patients prior to any extraction. At this stage, the condition of the hard and soft tissues and temporisation techniques has a significant effect on the final aesthetic and functional outcome around implants.

In cases where immediate placement is not appropriate, preserving the architecture of the underlying hard and soft tissues is paramount. Wherever possible, extractions should be bone preserving using a combination of periotomes, elevators and gentle rotation rather than expansion. Multi-rooted teeth should be divided and piezo surgery used to remove palatal or lingual bone to facilitate extraction. Alternatively, the ‘furrowing’ technique should be employed to avoid buccal plate trauma.

The socket should be cleaned and debrided to remove macroscopic infection as far as possible and encouraged to bleed. It is good practice to map the buccal plate for deficiencies with a periodontal probe at this stage. Using the natural tooth crown as a pontic can be an effective solution to maintain the soft tissue structure. (Fig 2a-c)

In the presence of significant apical pathology, we maintain the soft tissue using collagen cones retained in the socket with a horizontal criss-cross mattress suture, promoting clot stabilisation and preventing ingression of soft tissue into the bony socket. This is normally left for six to 12 weeks before additional surgical procedures are carried out.

If it is believed that the majority of any apical pathology has been removed, augmentation of the remaining socket can be conducted using bone particulate material. Collagen cones are inserted into the socket and flattened underneath the margins of the socket and sutured into place, again with retaining horizontal mattress sutures to encourage epithelial growth across the socket and limit ingression into the graft. (Fig 3a-c)

In addition, if there is a significant lack of keratinised tissue prior to extraction or at presentation, it may be necessary to perform soft tissue augmentation prior to any hard tissue or implant procedure. A connective tissue graft (CTG) with split thickness flap may be used to increase keratinisation volume and allow tension-free primary closure if significant bony defects are to be repaired. (Figs 4a-c)

With implant placement/pre-restorative

Implant design

It is important that clinicians are aware of how the design features of the selected implant influence implant position, and hard and soft tissue outcomes. It has been accepted that most two-piece bone level implants will cause some hard tissue loss if placed at the level of the crest. However, some provisional evidence suggests that both macro- and microscopic design features may reduce, if not completely prevent, crestal bone loss.

There has also been evidence of direct connective tissue attachment to the implant neck, which will redefine the tissue compartments of the biological width around dental implants and create a soft tissue biological supra-crestal seal for the bone that previous implant designs lacked. (Fig 5a) There is also scope to utilise tissue level implants to protect the crestal bone.

Ideal 3D placement

The final implant position within the arch relative to the neighbouring dentition has a significant effect on the long-term outcome and stability of the overlying soft and hard tissue form. Buser (2004) has described the ideal biological envelope that a bone level implant must sit on so as not to cause further bone and soft tissue resorption, while Tarnow (2003) details the expected papillary position relative to the interdental bone. (Fig 5b)

The final 3D position of the implant is far more predictable if placed using a restorative-focused surgical stent. This can be simplified further if a radiopaque restorative trial is captured intraorally using CBVT, so that both surgical and restorative approaches can be combined into a CBVT guided surgical stent.

Flap design

It is the authors’ belief that, if there is adequate form and function of both hard and soft tissue prior to placement, consideration must be given to performing flapless surgery or immediate implant placement to maintain the soft tissue support. The flapless approach or using tissue punches have the advantage of reducing morbidity and speeding up soft tissue healing.

Additionally, as no bone is exposed and periosteal blood flow is not compromised, it can lead to reduced bony resorption and minimal soft tissue scar formation. The major drawback of this technique is poor surgical site visualisation and potential disposal of useful keratinised soft tissue.

Where the buccal plate requires visualisation, the choice is to preserve or lift the adjacent interdental papillae. Sclar (2003) describes the papillae preservation flap that allows for the adjacent papillae to remain over the inter-dental bone, with the relieving incisions curved and changing direction within the mucogingival border to disguise post-operative scar tissue.

When significant ridge grafting is required, larger soft tissue flaps involving one or more adjacent teeth may be employed. Generally with large flaps, relieving incisions are made distal to the anterior teeth. Care must be taken with these large flaps to minimise papillae recession post-operative bone resorption caused through tissue acidosis. Furthermore, significant flap advancement can result in transposition of unkeratinised sulcular epithelium over the neck of the implant, requiring corrective surgery later.

There are many more novel solutions to flap design that are case specific, such as the ‘aesthetic buccal flap’ described by Steigman (2008). In cases where periodontal bone support is poor but soft tissue architecture is favourable, access to the buccal plate can be made through an incision in the mucogingival border without the need to interrupt or cut circumferential gingival fibres at the cervical margin.

Surgical staging, temporisation and immediate placement

As discussed, if hard and soft tissue is optimised pre-extraction, and if there is no infection or occlusal issues, then consideration can be given to immediate implant placement with immediate
provisionalisation.

It is difficult to provide a truly non-functional implant-retained temporary crown or bridge; however, a customised healing collar offers sufficient support to the facial and interdental soft tissues where loading is a concern. Surface modification on healing collars and abutments (Laser-Lok, BioHorizons) can also maintain soft tissue compartmentalisation by reducing apical migration of the junctional epitheilium,
allowing direct connetive attachment to the collar/abutment itself (Nevins, 2010).

In cases of keratinisation deficiency, a submerged approach can be used to increase soft tissue bulk, allowing an attached connective tissue roll graft procedure during second stage surgery. In addition, submerging healing collars can allow for additional soft tissue ‘dead space’, as described by Salama (1995), facilitating soft tissue manipulation at the restorative stages to guide tissue regeneration.

Care must be taken when removable temporisation is employed, due to the lack of papillary support and possible tissue compression of the gingival architecture. If possible, adhesive temporary bridgework is preferable over an acrylic denture to replace bound saddles of less than four units. If a removable prosthesis cannot be avoided, the functional compressive elements of pontic design overlying the implant must be sympathetically handled. Both removable and fixed solutions can help with pontic site development of soft tissue guidance prior to restoration.

Soft tissue augmentation

During placement, the opportunity can be taken to augment the facial tissues to reduce repeated surgical intervention and morbidity by performing a free CTG from either the patient or cadaver sources.

Post-restorative management

Post-restorative soft tissue correction is the most common and least predictable soft tissue intervention. The restoration can be removed and soft tissue bulk improved if the implant position is favourable. CTG can be employed to ‘biotype boost’ deficient soft tissue, although there is little evidence to support the long-term results of such reparative procedures.

Free gingival grafting, coronally advanced flap and other root coverage concepts can also be employed. However, none are ideal in nature and almost always result in a compromised outcome.

The final solution sadly, is to use pink restorative material to disguise the form of the underlying soft tissue. It has the advantage that repeated surgical intervention is not required to create the illusion of soft height and bulk.

However, blending with adjacent soft tissue can be difficult and the ‘ridge lap’ creates major issues cleaning the prosthesis, which can result in further hard and soft tissue loss.

Conclusions

Although there are numerous approaches to managing soft tissues at various stages of implant treatment, it is best that soft tissue is optimised as early as possible in the treatment plan.

Furthermore, it is the authors’ belief that immediate implant placement can be considered only if the gingival tissues are in the desired form and function pre-treatment.

When soft tissues do require correction, it is suggested that a delayed or submerged approach is considered to increase soft tissue bulk, allowing further tissue manipulation and a wider margin for error.


About the authors

Donald Morrison, owner and partner of Quadrant Dental Practice, gained his BDS from Dundee University in 1997. He has trained extensively with experts worldwide, as well as holding a Master’s in Aesthetic Implant Dentistry from the University of Lancashire. Donald takes great pleasure in working with ground-breaking dental techniques to provide excellence in treatment for patients using a gentle and caring approach that is second to none.

Peter Byrne, owner and partner of Quadrant Dental Practice, qualified from Glasgow Dental School. He too has trained extensively with experts around the globe and also holds his Master’s degree in Aesthetic Implant Dentistry. His work ranges from single tooth replacements to complex full-mouth rehabilitations, involving implants and cosmetic dentistry using metal free-restorations.

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