Regeneration: New lease of life for periodontally affected teeth

Modern microsurgical instruments, novel flap designs, site specific suturing techniques and the use of magnification, have all contributed to the concept of periodontal regeneration.

Whilst resective procedures remain a viable tool in the periodontist’s armamentarium, a more conservative approach reduces morbidity and improves aesthetic outcomes. Guided Tissue Regeneration (GTR) aims to restore damaged or lost tissues to their previous form and function. In periodontitis, GTR refers to the formation of new cementum, a functionally orientated periodontal ligament, alveolar bone and gingival attachment.

New attachment can only be formed if cells of the periodontal ligament colonise the root surface during cementogenesis (Melcher 1976). If epithelial cells migrate into that area, new attachment cannot occur. In the same way, if cells from the lamina propria migrate into the area immediately coronal to the bone crest, no coronal regeneration of the alveolar bone can be expected.

The proof-of-principle study demonstrated that true regeneration could be achieved using a Millipore filter. The space provided by the filter allowed new periodontal ligament regrowth as epithelial cells were prevented from repopulating the wound, thereby creating the initial principles of guided tissue regeneration (Nyman et al. 1982).

Advances

In the last two decades, flap designs have changed dramatically following the development of new biomaterials and instruments. Minimally invasive surgery (Harrel 1999, Harrel & Rees 1995 and Trombelli et al. 2012), papilla preservation techniques such as the modified or simplified papilla preservation (Takei et al. 1989, Cortellini et al. 1995, Cortellini et al. 1999) and microsurgical approaches (Cortellini & Tonetti 2001 and 2005) have been introduced to improve the outcomes of GTR.

Local factors that influence bone infill

The size of the bony defect and the number of walls (1-3 walls/circumferential defects), plays an important role in the regenerative potential of the site, providing wound stability and maintaining space.

In cases of unfavourable architecture, for example wide defects (>37 degrees) or one wall defects, the additional use of allogenic graft materials or synthetic bone biomaterials has been suggested to prevent collapse the barrier and maintain the necessary space (Polimeni et al. 2005, Cortellini & Tonetti 1999). Tooth mobility can also influence outcomes and peri–operative management.

New Materials

A number of growth factors and bone morphogenic proteins have also been used in an attempt to enhance the innate regenerative potential. Platelet-derived growth factors have demonstrated regenerative potential of the periodontal ligament cells and osteoblast enhancing regeneration of the periodontal attachment in in-vitro studies (Ojima et al. 2003) and multicentre randomised control trials (Nevins et al. 2005).

Enamel matrix derivatives have been widely tested offering positive results at one year follow up in a systematic review showing mean attachment gain and probing depth reduction of 1.1 mm and 0.9 mm respectively (Esposito et al. 2009).

Suturing

Irrespective of the materials used, the stability of the fibrin clot adhering to the root surface at the initial phase of healing is critical to the outcome. During early healing, the structural integrity of the wound relies principally on suture closure.

Passive adaptation and approximation of the wound margins require mattress-suture techniques to evenly distribute tensile forces and deflect plaque accumulation away from the incision line, favouring primary intention healing. The suture material itself should allow adequate tensile strength during the critical period of healing of the initial 7 to 10 days (Burkhard & Lang 2015).

Conclusions

Regeneration is the ultimate goal for periodontal therapy. However, GTR remains a challenging procedure and is highly technique sensitive.

Prudent case selection, clinical assessment of the defect site (depth and configuration of the defect, width and volume of keratinised gingiva) , the potential for regeneration and selecting the most appropriate techniques and materials are essential. Precise surgical management of the wound (i.e. flap design and manipulation, space provision, wound stability and primary intention healing), has a direct impact on healing and level of success.

GTR is a well-documented and established procedure to induce regeneration in infrabony defects and Class II furcation defects (Tonetti et al. 2002). Such periodontal sites with persistent pocketing following initial therapy should therefore be considered for GTR. In selected cases, GTR can improve the prognoses of teeth significantly, enhancing longevity and stability for teeth previously regarded as having ‘poor’ prognoses.

Chong Lim:GDC Number: 70007, BDS (National U. of Singapore), MSc in Periodontics (Eastman Dental Inst., UCL), MSc (Distinction) in Dental Implantology (U. of Bristol). Chong heads the Perio & Implant DRC near Richmond Bridge. He is also involved with providing post graduate education for the ITI, Eastman Dental Institute & University of Bristol.