Dental Membranes

Which came first – Bone graft or Membrane?

What membrane materials exist? How do they compare?

Before implant restoration became widespread Guided Tissue Regeneration (GTR) procedures were offered which utilised dental membranes to exclude gingival tissue from occupying a periodontal pocket giving bone periodontal tissues the space and time to regenerate. The first barrier membranes (expanded ptfe AKA GoreTex) created the required healing compartment, yet required a second procedure to remove. These materials were associated with a high incidence of dehiscence and infection prompting the development of bioresorbable matrix barriers by Gottlow and co-workers in the late 1980s.

Image shown:

Guidor bioresorbable matrix barrier

Guided Bone Regeneration (GBR) membranes

As Dental Implant restoration increased the materials used for GTR were revised to meet the needs of GBR, especially so the requirement for them to be resorbing. Guidor bioresorbable matrix barrier (as shown) was an early example of a resorbing GTR barrier adapted for GBR procedures. Despite excellent clinical results the technical challenge of production limited its supply creating the demand for alternative resorbing materials. Resorbing collagen appeared as an alternative at the same time as general dental practitioners were emerging as alternative providers to specialists such as periodontologists and Oral Maxillo facial surgeons promoting its uptake.

All barrier membranes require surgical skills such as flap management and fixation which were not well taught in the general dental community. Additionally, one of the challenges when using collagen membranes is the collapse into the defect which occurs if a space-filling material is not used underneath. These factors led to the emergence of proprietary bone graft scaffolds and bone void fillers which gained popularity in GBR alone and in combination with barrier membranes.

Today, due to the development of more advanced proprietary bone graft materials many implantologists report the regeneration of excellent new bone without the need for a dental membrane. One such material is Powerbone Dental Putty.

WHEN IS A BARRIER MEMBRANE NEEDED?

Barrier membranes carry three key functions:

• To create a healing space for bone and periodontal tissue to regenerate.
• To reduce micromovements inherent in particulate bone grafts. Movement between the particles will delay healing.
• To help exclude soft tissue invasion during the healing phase.

WHAT TYPE OF DENTAL MEMBRANES EXIST TODAY?

Dental barrier membranes can be resorbable or non-resorbable. Non-resorbable membranes are better at creating space yet require a second procedure for removal with the disadvantages of time and trauma. Fully resorbing barrier membranes offer the advantages of a single procedure in exchange for reduced space maintenance.

Non-resorbable Dental Membranes

Titanium Mesh
Ti-mesh maintains space in a predictable way making it ideal for the reconstruction of the severely deficient alveolar ridge. Ti-mesh can be shaped to match the defect and allows an unimpeded blood supply from the periosteum due to its holes (pores). Standard Ti-mesh is available in rectangles which are ideal for delayed (two-stage) regeneration and implant surgery. Standard Ti-Mesh is fixed in place with stainless bone screws or tack.

Customised Ti-Mesh is ideal for simultaneous bone grafting and dental implant placement due to the ease of fixation around the implant collar.

Sometimes titanium mesh is used to reinforce a PTFE (poly-tetra fluoroethylene) polymer membrane such as the original GoreTex brand. The original expanded PTFE was shown to be susceptible to microorganism transfer – especially so after exposure to the oral environment (dehiscence) which increases when wound closure is sub-optimal. High-density polymers of PTFE with a nominal pore size of less than 0.3 microns have replaced e-PTFE types for this reason. Studies report that surgical removal is easier for d-PTFE membrane than e-PTFE with less disturbance to the regenerated tissue below.

Nevertheless, reinforced PTFE still requires removal promoting the re-formulation of the original polymer materials for GBR with Powerbone Barrier Membrane and Tisseos emerging as licensed variants. (See below)

Titanium Foil

Titanium Foil is a unique material produced from pure titanium that is placed after extraction to preserve and regenerate hard tissue. Titanium foil produced by Bionnovation is bio-electrically neutral thanks to electrochemical passivation which results in extremely low biofilm retention meaning that Titanium foil can be used where closure cannot be achieved or could be aesthetically undesirable. Because titanium foil is extremely thin it can be removed through a micro incision.

Resorbable Dental Membranes

Fully resorbing dental barrier membranes can be distinguished by their origin and the time frame in which the barrier function is maintained.

Animal origin

Collagen is a protein that makes up the structure or framework in connective tissue, skin, tendons, bones, and cartilage. The collagen used in resorbable dental membranes is sourced from the pericardial or peritoneal areas of pigs or cows. Pericardial collagen presents a higher mechanical strength than peritoneal collagen. The original bovine peritoneal collagen (Geistlich Bio-Gide) is less stiff and more prone to collapse into the wound promoting the development of extended-function collagen materials.

Function time and cross-linking.

Functional resorption time is different from complete resorption time as non-functional remnants will remain long after the barrier function is compromised. Because native collagen is a protein it can resorb quickly. If exposed to saliva this dissolution can be rapid. This resorption time directly impacts function and is a limiting factor for the use of native collagen membranes in dental bone graft procedures. It is one reason Geistlich recommends two layers for its Bio-Gide despite the obvious disadvantages this brings.

Methods to extend the resorption time of collagen membranes include chemical and physical processing. Processing with chemicals such as glutaraldehyde successfully extends the resorption time for a collagen membrane. Unfortunately, products cross-linked with glutaraldehyde increase inflammatory response and are reported to be toxic in higher concentrations.

Cross-linking via process development

For these reasons, methods to physically modify the collagen were developed such as dehydrothermal (DHT) treatment. When applied to porcine pericardial sourced collagen DHT treatment produces a membrane that exhibits high tensile strength, resistance to degradation with reduced inflammatory responses. One such material is T-Gen (also called Ossguide).

Polymer (synthetic) origin

The polymer materials of polylactic, (PLA), polyglycolic (PGA), and poly(lactic-co-glycolic) acid (PLGA) are widely used in various medical applications, e.g. as biodegradable implants in surgery, as raw materials for wound closure stitches or as carrier substances for the delivery of pharmaceuticals. They present excellent biocompatibility and adjustable degradation rate and are non-toxic in humans. (1) and were the first resorbable materials used for GTR and GBR with high tensile strength and excellent space maintenance.

ENHANCED FUNCTION, DIFFERENT CHARACTERISTICS

Clinicians familiar with PTFE will find the application of Powerbone Resorbing Synthetic similar. Clinicians transitioning from Resorbable Collagen such as T-Gen should be aware of certain material and performance variances and allow a short time to adapt their technique to gain maximum benefit.

Preparation and Fixation.

Resorbable synthetic membranes are often stiffer than their collagen counterparts. This stiffness makes them less pliable and less drapable. It is also the reason why when adapted resorbing synthetic membranes create space better and are a more substantial barrier.

To achieve this we recommend warming the membrane beforehand so that it can better flex to the defect shape. Fixation is mandatory to ensure defect continuity. Simple membrane tacks are ideal. These can be left in place or removed after the procedure via a tiny micro-incision.

In summary

BROWSE AND PURCHASE

Resorbable and non-resorbable membranes and fixation tools can be browsed and purchased online from Regen store HERE.

References

1. Sharma. PLA/PLGA nanoparticles prepared by nanospray. Journal of Pharmaceutical Investigation volume 49, pages 405–426 (2019.