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1 Biologics: Delivering Abutments Without Introducing Potentially Harmful Foreign Materials

1 Biologics: Delivering Abutments Without Introducing Potentially Harmful Foreign Materials

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14  Delivery of the Definitive Abutment/Prosthesis



a



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b



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

surfaces.



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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

placement.



14.3 Cements

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



a



b



c



d



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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

cement insult



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

destruction.

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



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Table 14.1  Outlines some of the differences in cement selection criteria for implant restorations

and cement properties for the natural tooth

Substructure

Biological tissue

association

Primary disease

issue

Restorations finish

line

Cement margin

Need for cement

seal

Anti-caries agents

Corrosion

Radiopacity

Microbial challenge



Implant restoration

Metal, ceramic, acrylic

Peri-implant tissues



Natural tooth

Dentine, enamel

Periodontal tissues, pulp



Peri-implant disease



Caries, pulpal, periodontal



May or may not follow

scallop of the tissues

Questionable

May be detrimental

Corrosion of titanium possible

Highly radiopaque

Bacteria found in peri-implant

sites



½–1 mm below anterior aesthetic sites,

often above the free gingival margins

Preparation follow gingival tissues

Absolute (prevent caries)

Desirable

Not applicable

Similar to dentine (relatively low)

Caries-producing bacteria



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



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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.



286



a



C. P. K. Wadhwani et al.



b



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

anodization



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



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