The Protocols of Biomimetic Restorative Dentistry:

2002 to 2017
Increase the longevity of restorations with the biomimetic approach
David Starr Alleman, DDS | Matthew A. Nejad, DDS | Capt. David Scott Alleman, DMD

During the last 15 years, the restorative approach has steadily evolved, progressing from
mechanical retention to advanced adhesion. This transition was fostered by a wealth of
scientific publications, improvements in adhesive materials, and most importantly, worldwide
dissemination of the science and techniques of advanced adhesion. Collectively, the science,
principles, and techniques of advanced adhesive dentistry are known as biomimetic dentistry.
At its core, the biomimetic approach respects the simple philosophy that, to adequately
restore teeth, we must “mimic life” and understand the natural tooth in its entirety.
1-3

Logically, conserving more of the intact tooth is paramount to this approach, which pairs
perfectly with adhesion. Similar to the intact natural tooth, an adhesively-restored tooth is
better able to handle and manage functional stresses. As a result, the biomimetically-restored
tooth eliminates gaps under restorations and cracks into dentin that develop as a result of
deformation and stress concentrations, reducing or eliminating postoperative pain and
sensitivity and preserving vitality, as bacteria are not able to invade and kill the pulp. The
4,5

natural flexibility and fracture resistance of a tooth are also enhanced when it is hydrated by
the vital pulp. 4,6

The biomimetic protocols of today are founded on the “silent revolution” of adhesive dentistry
that developed during the 80s and 90s. This revolution was advanced by Japanese
7-9

researchers who identified two different layers of carious dentin that had two different
characteristics of dentin adhesion. These researchers were able to predictably bond to dentin
by using the novel technology of a caries detecting dye, which allowed an ideal caries removal
end-point to be visualized in the all important “peripheral seal zone.”6 On a dentin surface free
of denatured collagen, a bond to dentin could be established using newly developed
polymerizable monomers that were both hydrophilic and hydrophobic. With these two
technological breakthroughs, Dr. Takao Fusayama and his team of researchers at the Tokyo
Medical and Dental University began the quest for conservative, long-lasting adhesive
restorations. For the next two decades, continued advances in materials and techniques
10

allowed for more extensive dental defects to be restored in both the anterior and posterior
regions of the mouth. 3,11-1 3

Fast-forwarding to 2002, a landmark book was published that advanced major concepts in
biomimetic dentistry, including new information regarding the properties of natural teeth and
their behavior under function, preparation design principles, and the all important foundational
biomimetic concept of immediate dentin sealing. In the same year, a technique to reduce the
1,2

effects of polymerization shrinkage stress was published, referred to as a stress-reduced

direct composite, which allowed a biomimetic approach to a direct composite restoration. 14-

This article outlines the biomimetic paradigms and protocols that are supported by these and
16

other scientific publications and practiced by biomimetic dentists around the world.
Biomimetic Paradigms
Biomimetic restorative dentistry is founded on these four basic paradigms:

1. Maximum bond strength. Reducing polymerization stress to the developing hybrid layer
results in a 300% to 400% increase in bond strength. Dentin bond strengths in the range of
17-2 0

30 MPa to 60 MPa are in the same range as the tensile strengths of enamel, the
dentinoenamel junction, and dentin. This strong bond allows the biomimetically restored tooth
21

to function and handle functional stresses like an intact natural tooth.

2. Long-term marginal seal. A strong and secure bond allows for a long-term marginal seal to
be established and maintained during functional stresses. 3,22-25

3. Increased pulp vitality. By maintaining a highly bonded seal, the restoration will provide
long-term function without recurrent decay, dental fractures, or pulp deaths. A vital tooth is
3,16,26,2 7

also three times more resistant to fracture. 28

4. Decreased residual stress. Residual stress, while hard to visualize, leads to cuspal
deformation, debonding, gaps, cracks, pain and sensitivity, and recurrent decay. Reducing
residual stress while maintaining the maximum possible bond strength is the ultimate goal of
any biomimetic restorative technique. 29,30

Biomimetic Protocols
The biomimetic restorative protocols used to produce these results can be divided into two
groups: stress-reducing protocols and bond-maximizing protocols.

Stress-Reducing Protocols
The first group includes 10 key stress-reducing protocols, which promote stress reduction to
the developing hybrid layer as it is formed and throughout the life of the restoration under
function:3,25
1. Use indirect or semi-direct restorations for the occlusal and interproximal enamel
replacements. An indirect technique is the most stress-reduced technique. It reduces the
volume of shrinking restorative material.3,11,22This also reduces residual stress.22,29,30
2. Decouple with time. This protocol states that polymerization shrinkage stress to the
developing dentin bond of the hybrid layer should be minimized for a certain period of time (ie
5 to 30 minutes) by keeping initial increments to a minimum thickness (ie less than 2mm). This
minimal thickness prevents the connection, or “coupling,” of deep dentin to enamel or
superficial dentin before the hybrid layer is matured and close to full strength. This procedure
neutralizes the “Hierarchy of Bondability,” which states that the shrinkage of composite
moves toward (or “flows” toward) the walls of the preparation that are the most mineralized
and dry and flows away from the walls of the preparation that are the most moist and
organic.20,31-33
3. Restore the dentin with thin horizontal layers of composite that are 1mm or less. This 14,20

ensures that decoupling with time is properly achieved and that the flow of the composite is
not moving away from the deep dentin during the early stage of horizontal layer development.
This is the solution to the problem of a preparation’s complex geometry and the resulting
configuration stresses, which are known as “C-Factor” stresses. Small volume increments
34,35

are always associated with small ratios of bonded to unbonded surface areas; thus, high C-
Factor stresses can be reduced to “micro C-Factor” stresses. This is the basic protocol of the
stress-reduced direct composite technique.14,15
4. For large restorations, place fiber inserts on pulpal floor and/or axial walls to minimize
stress on the developing bond strength of the hybrid layer.24,36 The fiber nets allow the
composite on either side of the net to move in different directions via micro shifting of the
woven fibers. The polymer network is still highly connected, but the polymerization shrinkage
does not stress the hybrid layer.37
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5. Use slow start and/or pulse activation polymerization techniques.14-16,26,38
6. Use dentin replacing composites with shrinkage rates of less than 3% and with a modulus
of elasticity between 12 GPa and 20 GPa.1-3,12,38

7. When restoring pulp chambers in non-vital teeth, use dual cure composite with the
chemical cure mode active for the first five minutes.39 The volume of composite is not as
critical for chemically cured composites because the chemical initiation of the polymerization
is very slow (4 minutes to 5 minutes).34,35 This slow polymerization allows sufficient time for
the dentin bonding system to mature into a strong hybrid layer.

8. Remove dentin cracks completely within 2mm of the dentinoenamel junction. This area is
referred to as the “peripheral seal zone.” Remove all dentin cracks inside of the peripheral
seal zone to a depth of 5mm from the occlusal surface and to a depth of 3mm interproximally
from the axial wall.6 If cracks into dentin are left under the restoration, micro-movements
under function will allow the cracks to get longer (ie crack propagation).4,5,40 Larger cracks
propagate with smaller forces than shorter cracks; therefore, it is recommended to remove as
much of the cracked dentin as possible without exposing the pulp.
9. Limit onlay cusps to thinner than 2mm after removal of decay and cracked dentin.1-3 This
will change the forces on the hybrid layer from predominantly tensile to predominantly
compressive, which helps reduce bond fatigue.25,41
10. Verticalize occlusal forces to reduce tensile stress to the restoration and the cervical
region of the tooth.41 This can be done by restoring anterior guidance with bonded composite
to the lingual surface of maxillary cuspids and/or the facial surfaces of mandibular cuspids.

Bond-Maximizing Protocols
The second group includes eight key bond-maximizing protocols, which, when implemented,
can help achieve the maximum possible bond strengths attainable when employing the
stress-reducing protocols:

1. Establish a caries-free peripheral seal zone. Achieve a caries-free zone 2mm to 3mm
circumferentially around the cavity without exposing the pulp. Inside of the peripheral seal
zone, caries excavation should be limited to a depth of 5mm, measured on the long axis from
the cavo-occlusal surface. Measuring from the proximal tooth, the depth of excavation should
be limited to 3mm from the cavo-proximal surface.6
2. Air abrade surfaces. Air abrade composite surfaces for bonding/cementation. This will
increase bond strength to both normal and carious dentin.19,42 It will also change the failure
mode to eliminate failures in the hybrid layer.19 When bonding to the composite base of a
biomimetic restoration, air abrasion will maximize the composite-to-composite bond.12,43
3. Bevel enamel. Bevel enamel across enamel rods to increase bond strength.44
4. Deactivate matrix metalloproteinases. This prevents 25% to 30% of bond strength from
being degraded.45 Deactivation can be achieved by using a 30 second treatment with 2%
chlorhexidine (eg Consepsis, Ultradent), benzalkonium chloride (eg Micro-Prime B, Danville or
Etch 37, Bisco), or a dentin bonding system with the MDPB monomer (eg SE Protect,
Kuraray).6
5. Employ gold standard bonding systems. Use a gold standard dentin bonding system that
can achieve a microtensile bond strength of 25 MPa to 35 MPa on enamel and 40 MPa to 60
MPa on flat dentin surfaces. The available data indicates that three-step total etch dentin
bonding systems and two-step self-etch dentin bonding systems offer the best clinical
performance.19,46
6. Utilize immediate dentin sealing. The application and polymerization of dentin bonding
agents at the time of preparation (and before an impression is taken) has numerous
advantages and will ultimately increase the microtensile bond strength by 400% when
compared to the traditional approach of bonding the dentin at the cementation
appointment.17,18 This is fundamental to achieving maximum bond strength.
7. Resin coat the immediate dentin sealing. This can be done with a flowable resin or a lower
viscosity restorative composite with a modulus of elasticity of around 12 GPa (ie the same as
deep dentin). This ensures that the dentin bonding system is fully polymerized even if the
pressure of pulpal fluid transudation (in conjunction with the air-inhibited layer) has made the
adhesive too thin to be polymerized due to air-inhibition. Once the dentin bonding system is
resin coated and the resin coating is light polymerized, the air inhibition and transudation
stop. This step also creates a “secure bond,” which means that if the onlay was ever
dislodged from the resin coating, the resin coating would stay bonded to the sealed dentin.13,47-
49 A few dentin bonding systems have thicker and highly filled adhesives (ie around 80

microns). These dentin bonding systems can act like a resin coating. Examples include
OptiBond FL (Kerr), All Bond 3 (Bisco), and PQ1 (Ultradent).
8. Achieve deep margin elevation. A sub-gingival box margin needs to be bonded and raised
to a supra-gingival position to obtain a biomimetic microtensile bond strength greater than 30
MPa. This deep margin elevation, in conjunction with immediate dentin sealing, resin coating,
and the composite “dentin replacement,” is referred to as the “bio-base”—a term used by the
Academy of Biomimetic Dentistry for the stress-reduced, highly bonded foundation that the
indirect or semi-direct inlay or onlay will be bonded to.50,51

Case Presentation
In this case, which would present problems for dentists who perform treatments without
biomimetic restorative protocols, the caries are deep and the structure of the tooth is
compromised (Figure 1 through Figure 10). For a traditional, full-coverage treatment, much of
the intact tooth would have to be sacrificed. However, employing biomimetic restorative
protocols can solve many of these problems by conserving tooth structure and promoting
healing of the pulp. By combining the stress-reducing and bond-maximizing protocols,
biomimetic restorative dentistry is able to reconnect all parts of the tooth with all parts of the
restoration while maintaining a lifelike tensile/cohesive strength in the 30 to 50 MPa range.
Lifelike Longevity

These two semi-direct biomimetic restorations (Figure 11) on teeth #3 DOLF inlay/onlay and
#4 full onlay (mirror reversed) are more than
15 years old now. The onlay on the bicuspid
and the inlay/onlay on the molar were
restored using most of the protocols
presented in this article with the exception of
fiber placement for stress reduction and deep
margin elevation on the bicuspid. There is a
slight ditching of the flowable cementing resin
on the molar, but no leakage is present. The
onlays were fabricated out of Z-100 (3M, St
Paul, MN).

This 10-year-old stress-reduced direct composite

restoration (Figure 12) included fiber placement for
stress relief. Only the cracks into the dentin were
removed. The cracks into the enamel were stabilized
with biomimetic protocols to re-establish a tensile
cohesive strength from side to side, front to back,
and top to bottom. As a whole, the tooth is now
functioning again like a natural tooth. The occlusal
surface was restored with Majesty Posterior
(Kuraray, Okayama, Japan).

These Empress inlay and Empress onlay restorations

(Figure 13) are 17 years old. Replacing occlusal and
interproximal enamel, they are bonded to stress
reduced bio-bases consisting of immediate dentin
sealing, resin coating, and dentin replacement with a
composite (AP-X, Kuraray) with a modulus of
elasticity similar to dentin (16.7 GPa). The modulus
of elasticity of the ceramic enamel (Empress, Ivoclar)
is around 80 GPa. This number is a little higher than
the enamel that it replaces, which has a modulus of
elasticity of around 60 GPa. Composites with a
modulus of elasticity of 20 GPa, such as Z-100 and Majesty Posterior, have also been
functioning biomimetically for 10 to 20 years without breaking down.3
Conclusion
When performing a biomimetic restoration, it is vital to visualize the accomplishment of the
protocols. Magnification in the 5X to 8X range is highly recommended when performing a
biomimetic restoration. The use of a surgical microscope or high-powered loupes makes
6

treatment very predictable.

Beyond the biomimetic paradigms, stress reducing protocols, and bond maximizing
protocols, there are other principles that are related to biomimetic restorative dentistry.
Minimally-invasive dentistry, structural analysis of existing tooth structure, and polymerization
dynamics of composites are important topics that fully-trained biomimetic restorative dentists
need to understand.34,35,40,52
The purpose of using biomimetic restorative concepts and protocols is to increase the
longevity of restorative dental treatments and to reduce or eliminate future cycles of
retreatment. In addition, conservation of tooth structure prevents periodontal complications
and pulp death.27 Dentists and patients who choose biomimetic dentistry enjoy these benefits
every day.

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About the Authors

David Starr Alleman, DDS
Co-Director
Alleman-Deliperi Centers for Biomimetic Dentistry
South Jordan, Utah and Cagliari, Sardinia, Italy
Co-Director
Biomimetic Dentistry CE
Beverly Hills, CA
Matthew A. Nejad, DDS
Co-Director
Biomimetic Dentistry CE
Beverly Hills, CA
Adjunct faculty
Herman Ostrow School of Dentistry
University of Southern California
Los Angeles, California
Capt. David Scott Alleman, DMD
Instructor
Alleman-Deliperi Centers for Biomimetic Dentistry
South Jordan, Utah and Cagliari, Sardinia, Italy
US Army Dental Corps
Seoul, Republic of Korea