“Biomimetics in dentistry”
Biomimetics is a term coined by Otto Schmitt in the 1950’s, while studying the nerves in a
squid. He attempted to copy and design an artificial device that could replicate the same
process of synaptic impulse.
It literally means to mimic life. It is considered the study of natural structural processes to try
to mimic or replicate it artificially in an attempt to restore the same function or aesthetics. It
is synonomous with biomimicry, biomechanics and biomimesis.
Age, disease and traditional restorations can cause further problems to the existing tooth
structure. As teeth have no natural method of repair, biomimetic principles should be used to
artificially repair the tooth to its natural functions and aesthetics. There are two aspects to
biomimetics in Dentistry. The lost or missing dental tissue is restored, leading to the full
return of function and aesthetics to the tooth. Or the material used can regenerate, replicate or
mimic the missing dental tissue closely.
Restorative Dentistry
The physiological performance of intact teeth is the result of intimate and balanced
relationships between biological, mechanical, functional and esthetic parameters. Natural
teeth, through the optimal combination of enamel and dentin, constitute the perfect and
unmatched compromise between rigidity, strength and resilience (Magne, 2002)1.
Therefore a biomimetic approach to restorative dentistry would mean aesthetic and functional
restorative materials similar to the natural tooth and its individual layers of dentine and
enamel. This would exclude amalgam and other precious and non precious metal-based
materials as they do not mimic the natural tooth in terms of aesthetics or properties. In 2006
Magne said “The goal of biomimetics in restorative dentistry is to return all of the prepared
dental tissues to full function by the creation of a hard tissue bond that allows functional
stresses to pass through the tooth, drawing the entire crown into the final functional biologic
1
2
and esthetic result The intact tooth in its ideal hues and shades, and perhaps more importantly
in its intracoronal anatomy, mechanics and location in the arch, is the guide to reconstruction
that determines success.”6,10.
In 1956 Vale tested the biomechanics of posterior teeth. He deduced that teeth which were
prepared to a certain degree became less resistant to occlusal forces2. In 1971 Grimaldi tested
teeth which were unrestored, prepared and restored to see how they functioned and the
biomechanics of the teeth. There have been other authors since who have investigated the
biomechanics/biomimetics of teeth and restorations345. According to Magne and Douglas in
1999, teeth have a good equilibrium of strength, flexure and stiffness. They are resistant to
fracture and flex to a certain degree. Dental disease, age and restorations weaken these
factors6. There are certain types of restorations that can restore these factors to a better degree
than other types of restorations7.By 2007 Pascal Magne did the same as Vale, but using new
technology in virtual computer programming8,9.
As previously mentioned, according to Magne,“the goal of biomimetics in restorative
dentistry is to return all of the prepared dental tissue to full function by creating a hard tissue
bond that allows functional stress to pass through the tooth, drawing the entire crown into the
final functional and esthetic result”6,10.
Therefore there is a large element of biomimetics on the preparation of the tooth, chemical
bonding to the tooth and materials used to restore the tooth, but also the relationship between
the materials.
Materials
We are aware that there may be some regeneration or stimulation of dentine with certain
dental materials11. There are also materials that can actually remineralise acid etched
dentine12. These materials would be classified as being “biomimetic”. There are still long
term studies on going with the regeneration of tooth substance. Other biomimetic materials
are materials used to restore the tooth which closely mimic enamel and dentine.
As previously mentioned the tooth structure itself is used as a guide to reconstruct the
diseased or missing parts to its original strength and properties. Adhesive bonds, glass
ionomers, composites and ceramics are utilised to reconstruct and replicate these features in a
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natural tooth. The table below demonstrates the similarity of these artificial materials to
natural tooth substance.
Materials
Table 1
From the table we can see that feldspathic ceramics are the closest to mimic enamel and
hybrid composites are the closest to mimic dentine. However it is has been also advised to
use composites131415 for small loss in tooth tissue and Glass ionomer cements (GIC) as a base
layer161718.
Magne also demonstrated that anterior teeth deform and flex more than posterior teeth. The
loss of tooth substance and the properties of the tooth in anterior and posterior teeth can be
restored by good bonding of porcelain to the tooth. Magne demonstrated that the porcelain
not only bond well and restores the aesthetics but also restores and strengthens the teeth with
porcelain veneers and adequate bonding techniques6,7,8,9,19,35. The restored tooth even behaves
like the natural tooth with catastrophic testing1.
Composite resins are now displaying favourable properties and longevity on par to
amalgam2021. The technique involves minimal preparation22 decreasing pulpal involvement
and decreasing the prognosis of fractures2324. It therefore preserves tooth substance and
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vitality. Some authors argue that composite can actually strengthen the remaining tooth
structure when placed well with reduced c-factors and shrinkage2526. Small to moderate sized
restorations should be restored with composite6.
Glass Ionomer Cements (GIC) is considered to be useful in deep class I or II cavities to fill up
the base as lining material6. They are also useful as buccal class V cavities. Composite can
then be bonded over as a closed sandwhich technique. GIC can also be used to fill any
undercuts for preparation of indirect restorations6. GIC releases fluoride, is bacteriacidal,
stimulates sclerotic dentine and also has properties similar to dentine. As such would fit the
definition of biomimetic27. However as their tensile strength is poor they are not advocated in
use of high occlusal stress and force. Biodentine is a new material that may replace GIC as a
liner in deep fillings28, but further research is needed. GIC is currently being the main tool for
advocates of minimum invasive dentistry293031 which is under the umbrella of biomimetic
restorative dentistry.
Magne argues that porcelain bonded to metal and other substances like amalgam6,32 which do
not follow biomimetic principles and do not attempt to restore the tooths natural properties.
He also argues that gold is excessively stiff, thereby also not following biomimetic
principles33. As these materials also are not bonded with the existing tooth structure there is a
higher likelihood of cracks, leakage and bacterial invasion causing further deterioration19,25.
This is then repaired with the same materials which fail again but with less tooth substance
leading to tooth loss. Biomimetics prevents and stops the repair-replace-repair cycle of
destruction and deterioration.
Magne and other authors argue that the occlusal stresses of the tooth should pass through the
whole tooth with a strength bond21,22. Without this bond the restoration will not be
successful34,35,36. Therefore producing high strength bonds from tooth to restoration and /or
restoration to restoration is the key.
Bonding technology and bond strengths have increased tremendously since it began.
Buonocore started in 195537 and since then techniques and materials have developed. There is
self etch, total etch, all in one bonding systems and a mixture of the different types. We know
that the strongest bonds are in the total etch system with separate etch, prime and bond38,39.
As such we can now be more confident in bonding composite to dentine and enamel. Dentine
bonding agents (DBA) are now bonding porcelain and composite restorations to a similar
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way that enamel is bonded to dentine at the Dentinoenamel junction40. Magne has
incorporated Immediate Dentine Sealing (IDS) as the technique advocated in bonding
indirect porcelain restorations32. IDS is essentially a total etch technique immediately after
preparation of the tooth.
IDS has a number of advantages:1 It bonds to freshly cut dentine which produces the strongest bonds414243.
2 There is precuring of the DBA after tooth preparation and before final impressions, which
increases bond strength44,45,46,47,48.
3 IDS allows maturation of the bond without occlusal stress, improving strength of the
bond49,50.
4 IDS protects against bacterial leakage during temporisation which could contaminate the
bond51.
IDS should be used in conjunction with proper preparation of the fitting surface of the
porcelain (etching and silanisation of porcelain).
There are some disadvantages with IDS and the total etch technique. Both are very technique
sensitive. It has been noted that it works well in expert hands but less so in less experienced
operators. It has the potential to contaminate the impression material and the DBA during the
temporisation. The DBA may actually bond to the temporary restorations themselves. There
is also separate session to prepare the porcelain fitting surface32.
Current practices of preparation of the tooth by the modern dental drill can cause further
harm to the tooth. Drilling the tooth can cause fractures, and heat which can make repair
more difficult. Other more biomimetic methods to prepare teeth are being investigated, such
as laser, air abrasion etc that may do less harm and preserve more tooth tissue. But currently
nothing is comparable in terms of popularity, versatility and costs than the modern dental
drill.
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Outside Prosthetic Dentistry
Biomimetic dentistry also includes regeneration of the periodontium and alveolar bone
surrounding the teeth. One of the most common techniques used is bone grafts for alveolar
defects. This is utilised in oral surgery, periodontics and endodontics and is sometimes called
guided bone regeneration (GBR). These grafts may be animal or human bone grafts which
lay down bone matrix resulting in new bone. These grafts have osteogenic features. Other
graft material may be artificial which signals the host to stmulate bone growth in that area.
These are osteoinducive materials. These materials can be classed as allografts (human
donor), autogenous (from the patient), alloplast (synthetic) and xenografts (animal).
Sometimes bony healing cannot occur due to connective tissue growth into the bony defect.
This can be prevented by the use of barrier membranes in conjunction to the bone graft
material to prevent cells that form connective tissue into the defct, thereby allowing just cells
that form periodontium and alveolar bone to form. Barrier membrane come in various
different materials but are classified as resorbable (Alpha-hydroxyacids, Amino acid based
polymers, Natural or synthetic types), or non resorbable (EPTFE, Ceramic, Titanium mesh)52.
As well as regeneration of bone there are techniques to regenerate gingival tissues. This will
allow gingival coverage in gingival recession areas. They are sometimes called Guided
Tissue Regeneration (GTR). This Allows more aesthetic, functional and natural gingival
tissue which would otherwise cause aesthetic and functional problems such as sensitivity and
loss of attachment. Such techniques include free gingival grafts and connective tissue grafts
(autogenous and artificial which increase attached gingivae) and a variety of root coverage
techniques53.
Recombinant human bone morphogenetic protein (BMP) 2, BMP 7 AND BMP 4 has been
known to induce new dentine formation in exposed pulpal tissue54 The pulpal tissue actually
changes into odontoblasts. The BMP have also been used to produce alveolar bone and
cementum on teeth in baboon studies55. This is a exciting propect and could change the
practice of endodontics, periodontics and oral surgery. However there is still a lot more
research needed and currently it has been performed on canine and ape studies.
Platelet rich plasma (PRP) is being researched in animal and human studies. PRP is made
from the patient’s own blood and certain factors are separated to use on the patient. Other
factors include platelet-derived growth factor, transforming growth factor, insulin-like growth
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factor, and epidermal growth factor. These factors help speed recovery, haemostasis and
wound healing56.
There has been a large number of studies and research developing in other specialities of
dentistry and medicine. There are a number of materials being investigated and studied that
can regenerate human dental and gingival tissue, but further research is needed before
application in routine dentistry.
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