Tải bản đầy đủ - 0trang
1 Biologics: Delivering Abutments Without Introducing Potentially Harmful Foreign Materials
14 Delivery of the Definitive Abutment/Prosthesis
Fig. 14.2 (a) Radiograph, highlighting the excess cement associated with a failing implant. (b)
Abutment retrieved from implant seen in radiograph. The excess residual cement is clearly visible,
indicating poor clinical use of cement
with lubricant and oxide layers can be produced during the laboratory work flow,
and adsorbed contaminants can be accumulated during the delivery.
Abutment cleaning procedures such as cleansing with decontaminates such as alcohol, soaps, or steam vapor at the end of the laboratory phases should be routinely carried out. The effectiveness of such methods has been questioned as impurities may still
be detected on the abutment surface. It is considered that under certain circumstances,
this exogenous material can trigger soft and hard tissue inflammatory responses.
To date, no clear cleaning protocols exist, and as such the introduction in the
clinical practice of cleaning technologies able to maintain or even positively affect
host cell response constitutes a very important area of research. In this context, cold
plasma technology represents an efficient clinical option. Plasma is defined as a
partially or wholly ionized gas with a roughly equal number of positively and negatively charged particles. Two types of plasma exist: high and low temperature. Only
the last one (ionized gases generated at pressures between 13 and 266 Pa and temperature below 60 °C) could be considered for clinical purpose such as surface
modification and organic cleaning.
With appropriate plasma parameters, argon plasma removes all chemical traces
from former treatments, in effect producing cleaner and more well-controlled surfaces than with conventional preparation methods.
As mentioned, plasma cleaning produces two notable effects:
1 . Cleaning and corrosion protection
2. Increasing the surface energy
It has been demonstrated that this procedure can produce a cleaning effect on
customized abutments after 12 min comparable with the one after 45 min in an
ultrasonic bath. At the same time, it was demonstrated to increase the surface energy
(wettability), showing in vitro cell adhesion both to the abutment and implant
C. P. K. Wadhwani et al.
Advantages of plasma cleaning were demonstrated in vivo to enhance the soft
tissue response during prosthetic implant phases. Such a modified surface, unlike
traditional machined-polluted surface abutment, might provide improved opportunities for a direct fibro-collagenous attachment, preventing soft tissue downgrowth.
From a clinical point of view, these favorable events may result in a long-term hard
and soft tissue stability. Early data suggest significantly improved preservation of
the bone at 5 years with the use of argon plasma to clean abutments prior to
Work by Wilson and others has demonstrated a positive relationship between excess
cement and peri-implant disease. This foreign material may cause serious implant
heath issues with an etiology, though not fully understood, considered to be multifactorial. Cement type, abutment design, cement application amount, and margin
position have all been studied, illustrating that each may have a positive or negative
effect on the implant.
The excess cement issues related to cement materials are likely derived from the
bacterial interaction, chemical effects, host response, and sensitization producing
negative tissue responses.
Few cements have ever been tested for their antibacterial effects as they relate to
the microbes implicated in peri-implant disease. Many claims are made about antibacterial properties simply because the cement may contain chemicals such as triclosan. Without proper bacterial tests being made, these claims should be ignored,
and the manufacturers held to a higher standard whereby they truly understand the
products they sell. Dental cements for teeth are frequently tested for their antimicrobial activity against caries-producing bacteria; surely implant cements and the bacteria associated with diseases specific to implants need to be considered.
The first study to evaluate the response of peri-implant-related, Gram-negative
microbes was conducted by Raval in 2012. His work suggested that Temp-Bond
(Kerr) with eugenol inhibited both planktonic and biofilm growth of A. actinomycetemcomitans, P. gingivalis, and F. nucleatum. Although a rudimentary study
design, it gave some indication of the need for such studies. The results of this study
indicated that zinc oxide with eugenol appeared to be a very effective antibacterial
material especially against the “specially formulated” implant cements.
Further negative effects of cements used with implant restorations have been
reported. Cement particles have been found in soft tissue biopsies of failed removed
implants, initially reported by Ramer and then by Burbano. The cement may be a
result of the cementation process itself or be a result of fragments breaking off after
the cement has fully set. In the authors’ opinion, it is possible that the cement is
being implanted within the soft tissues during the final cementation process. The
sulcular tissue around the implant is very different compared to that around the
tooth. The attachment is easily stripped away; it also shows high permeability and
has a poor blood supply, which reduces the ability to repair. Some cements also
14 Delivery of the Definitive Abutment/Prosthesis
Fig. 14.3 (a) A square piece of PTFE yellow tape, cut and a hole punched in the center using a
rubber dam punch. (b) The PTFE piece placed over the abutment, checking that it will not be
caught in the connection of the implant site (by seating an analog over the connection allows this
to be confirmed). (c) Model showing how the barrier PTFE works, again it must not encroach onto
the margin area, or it will be trapped during cementation. (d) PTFE barrier in place as the crowns
are being seated with finger pressure first. The barrier protects the vulnerable soft tissues from
have very thin film thickness which allows them to be pushed directly into the tissues. Although it does not seem logical that materials can penetrate soft tissues,
any clinician that has ever encountered an amalgam tattoo will understand that this
occurs commonly. Allergic response to the chemicals used by cement manufactures is also a cause for concern. Most, if not all, material substance data sheets
(MSDS) warn that the cements must be handled with care, often recommending
gloves to protect the skin. The skin tissue has been shown to be multiple times less
permeable than mucosa, and protection of the peri-implant soft tissues is almost
never considered. This can be readily achieved by using rudimentary dams made
with polytetrafluoroethylene (PTFE) tape (Fig. 14.3a–d). Finally, some cements
contain fluoride, which can become associated with hydrogen to produce hydrofluoric (HF) acid. This particular acid can result in corrosion of titanium and titanium
alloys. Not only does it roughen the surface allowing more bacteria to adhere, reactive oxidative species can be produced by the body that leads to host tissue
To date almost all cements are developed for natural teeth which have very different requirements compared to implant restorations. Currently, there is no ideal
implant cement, but selection should be based on sound clinical criteria, with the
C. P. K. Wadhwani et al.
Table 14.1 Outlines some of the differences in cement selection criteria for implant restorations
and cement properties for the natural tooth
Need for cement
Metal, ceramic, acrylic
Periodontal tissues, pulp
Caries, pulpal, periodontal
May or may not follow
scallop of the tissues
May be detrimental
Corrosion of titanium possible
Bacteria found in peri-implant
½–1 mm below anterior aesthetic sites,
often above the free gingival margins
Preparation follow gingival tissues
Absolute (prevent caries)
Similar to dentine (relatively low)
clinician understanding desirable and undesirable qualities of the selection made.
Wadhwani and Schwedhelm summarized in detail the different considerations for
material selection specific to teeth and implant-cemented restorations (Table 14.1).
Abutment design has evaluated the cement margin location, indicating this is
most critical. Linkevicius has shown that a cement margin site as minimal as 1 mm
below the soft tissues can result in excess cement extrusion into the soft tissue sulcus and recommends the margin be placed equi-gingival. Abutment modifications
that control cement flow have also been described, as have techniques to limit
cement volume and control application site. All these measures should be taken into
account when considering cementation of the implant restoration.
Cement application techniques with implants have been poorly studied. Most clinicians have never been taught how to optimize cement flow within the crown abutment system, and the authors believe that many of the problems related to residual
excess cement come from a lack of knowledge on cement materials and how they are
used. In a survey of over 400 clinicians as to where and how cement is applied, three
distinct patterns were noted. Cement was either grossly applied, applied at the margin of the crown, or painted on the intaglio walls of the crown. Apart from the application technique, most clinicians were unaware of how much cement was required
for the finite lute space between the crown and the abutment, with most applying far
in excess of what is ideally required. Cement knowledge must not be limited to
chemistry or setting characteristics; understanding the mechanics of flow is required.
Wadhwani studied this using a super computer and specialized fluid dynamic software. It was determined that the optimum site for most cements was an application
near to the cervical margin of the in the form of a circumferntial hoop. Also, speed of
seating was determined to be optimal when around 14 mm per second. Too fast and
the cement due to its inherent non-Newtonian character shear thinned and was
pushed past the margin. Too slow and the occlusal aspect was not fully filled, again
14 Delivery of the Definitive Abutment/Prosthesis
resulting in an excess of cement extrusion through the margin. Currently, all implantabutment components have little if any science behind their shape. Most are simply
machined to conform to the shape dentists have been preparing teeth for over
50 years. There is no understanding of the shape, which today defies all reasoning.
With the expense of implant abutments, we should demand their shape be made to
follow their function. With metal and ceramic abutments, there is no need to have
them conform to a tooth form—they may have vents, spiral cement spill ways, conical inserts, and many other designs that will help the clinician prevent cement excess
extrusion—all we need is to drive the science behind implant component design.
14.4 Aesthetics and Simple Implant-Abutment Modifications
Aesthetics has always been of great concern in the dental industry, with color, contour, and soft tissue emergence profiles high on our list to help satisfy both the
patient and the clinician. When implants are employed as replacements for the teeth,
there are multiple issues in trying to emulate the natural tooth. One such example is
how aesthetics and biologics may interact. For instance, the current gold standard
for implantable materials used in the dental implant industry is titanium. This silver
gray metal with excellent biocompatibility, strength, and ability to withstand the
challenges of the oral environment is used widely for the implant body, abutments,
and prosthetic components.
However, the color of titanium has become an aesthetic issue, especially when it
reflects through the gingival tissues and produces a blue/gray discoloration. Such aesthetic demands have resulted in newly developed and measured tests for color as well
as form of the peri-implant tissues. Fürhauser was the first to describe the so-called
pink esthetic score. This index compared the shape, color, and form of the implant and
restoration on the peri-implant tissues. Others added and modified the index to measure the restoration related to the existing dentition and surrounding environment.
One method of overcoming the blue/gray hue of titanium was the introduction of
zirconia-based abutments. They also provided an improved foundation base color
for all ceramic restorations used in highly aesthetic cases. However, zirconia is not
as strong as titanium, and the literature report abutment fracture issues (Fig. 14.4a,
b). Also, if the restoration requires cementation to the zirconia abutment, this is not
always predictable due to zirconia’s low adhesive properties. Finally, the interface
of zirconia with titanium implants may promote titanium particle discoloration
within the tissues as a result of dissimilar wear rates.
To overcome these issues and help with abutment aesthetics, some manufacturers of titanium abutments use a titanium nitride (TiN) coating method, producing a
yellow/gold-colored surface effect. This places a surface coating layer of dissimilar
material onto the surface of the titanium. However, case reports have suggested
patients may be allergic to this surface, and the biocompatibility of TiN does not
appear to be as sound as the titanium dioxide that spontaneously forms on titanium
metal in an oxygen environment. Some orthopedic studies have reported that the
TiN layer can crack off the surface of the titanium.
C. P. K. Wadhwani et al.
Fig. 14.4 (a) Zirconia abutment fracture at the implant-abutment connection, considered a weak
site. (b) This fracture has left some of the zirconia still within the implant itself, which can be challenging to remove
Fig. 14.5 Abutments have
been anodized using
batteries and diet soda. By
varying the voltage applied,
yellow/gold colors can be
used for the core abutment
color. Pink hues can be
produced for the abutment
beneath the tissues. Both
pink and yellow can also be
produced by selective
An improved way of coloring titanium has been described in the literature, which
uses a very different technique to provide aesthetic-colored abutments (Fig. 14.5).
Anodization is a physicochemical controlled method of thickening the titanium
dioxide surface layer. This is the same layer that naturally and sponaneously evolves
if the titanium is left in air and is the basis of the biocompatibility of titanium itself.
This is a simple, fast, and inexpensive technique for coloring the titanium that has
been described in the dental literature and can be done by anyone, using common
materials. When the titanium dioxide layer is thickened, a physical phenomenon
occurs, whereby natural white light is absorbed and reflected back as a thin film