Breast Implant Generations       
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Dallas Plastic Surgery

Cohesive gel study Information

Breast Implant Generations

William P. Adams Jr. MD

When the generation scheme (Table I) was first proposed,
there were essentially three generations of breast
implants corresponding to products developed in the
1960s (first generation), 1970s (second generation), 1980s (third generation). 

Table I: Generations of Silicone Gel Filled Breast Implants

First-generation devices are represented
by the original silicone gel implant developed by
Cronin and Gerow. This device, the Silastic 0, was manufactured
by Dow Corning from approximately 1964 to
1968 (5). The Silastic 0 possessed a thick elastomer shell
with seams and a viscous silicone gel. Dow Corning made
several modifications to the original device, including
changes in the elastomer, creating a seamless shell, and
later making the shell much thinner. First-generation
devices overall were characterized by thick shells, a thick
viscous gel, and Dacron patches, and were produced until
the late 1970s. The most commonly reported complication
of these devices was capsular contracture.
Second-generation devices were modified in an attempt
to improve the rate of capsular contracture. These devices
were designed with a much thinner shell (0.13 mm versus
0.25 mm average thickness) and a less viscous gel, and the
Dacron patches were removed (5). The first second-generation
device was Dow Corning’s Silastic I. It was introduced
in 1972, and manufacturing of the Silastic I overlapped
with the production Silastic 0 and was produced
until 1986. It did not provide any appreciable reduction
in the incidence of capsular contracture and reportedly
had a higher incidence of rupture that was attributed to
the strength of its shell (5).
The phenomenon of gel bleed was realized in the 1970s
(5,12–14). Gel bleed is the diffusion of non-cross-linked
silicone oil from the gel across the elastomer shell into the
surrounding environment. Although the significance of
this phenomenon remains unclear today, it stimulated
manufacturing changes that are characteristic of thirdgeneration
devices. Thicker, reinforced barrier shells characterize
third-generation devices. The thickness and
strength improvements were developed out of concern for
shell failure with second-generation devices. Shell strength
was improved by reinforcing the elastomer composition
with silica (1). Creating a barrier to gel diffusion with
phenyl or triflouropropyl groups bonded to the shell surface
reduced diffusion of non-cross-linked silicone (2,3).
These properties are retained in current manufacturing
processes. It is important to keep in mind that gel bleed is
a function of diffusion of silicone oil across the elastomer.
The gel bleed does not change based on the viscosity
(degree of cohesion of the gel filler).
Saline-filled breast implants were first manufactured
in France in 1964, introduced by Arian with the goal of
being surgically placed via smaller incisions. These
devices had a high failure rate and were discontinued in
the early 1970s (5). Heyer-Schulte was the first U.S. manufacturer
of saline-filled devices. The original devices consisted
of thin shells created through a high temperature
vulcanization (HTV). These devices were prone to spontaneous
deflation (5). Modifications in the shell manufacturing
have allowed the high success rates that characterize
modern saline-filled devices. The current devices are
manufactured with thicker, room temperature vulcanized
(RTV) shells.

Implant Filler

Modifications in the characteristics of the implant filler
have also occurred. The most obvious being the change to
saline-filled devices during the “implant crisis”; however,
significant modifications have occurred in the silicone gel
characteristics. The modifications in silicone gel technology
are significant enough that many consider the modern
era gels a fourth implant generation. Since 1992, due to
increase demands to improve manufacturing processes,
current silicone gel implants are improved devices with
slightly thicker shells and more cohesive gel filler than
third-generation devices.
Because breast implants are filled with medical-grade
silicone, changes in silicone gel chemistry have centered on
the cohesive quality of the gel. All silicone gels are cohesive
but the degree of cohesiveness has clinical importance. The
degree of cohesiveness is a reflection of the elastic memory
or shape retention of the gel. Cohesiveness is produced by
the chemical cross-linking of the silicone gel molecules. The
degree of cohesiveness imparts important characteristics to
the structure and feel of the implant. Second-generation
implants produced before 1985 contained minimally
cohesive gels. Third- and fourth-generation devices evolved
to contain increasingly cohesive gels after 1985, and in
1993, form-stable cohesive gel implants were
introduced.
The fifth-generation implants are form-stable cohesive
gel implants (e.g., Inamed 410 and Mentor CPG). These are
shaped silicone gel devices with enhanced cohesion that
offer improved breast shaping and results. These implants
are currently undergoing clinical trials in the United States.
Silicone gel and saline are the only materials presently
available for use as filling material for breast implants in
the United States. Soy-filled implants (Trilucent) were marketed
for a short time period in Europe but were voluntarily
pulled from the market in 2000 by the manufacturer
(15,16). Trilucent implants contained Trilipid 6, a medicalgrade
triglyceride fat extracted from soybean oil. This material
was studied in animals and not shown to be a safety
concern. Approximately 5,000 European women and 50
U.S. women received the implants as part of European and
U.S. clinical trials. In the United States, the devices had
limited availability through an investigation device exemption
(IDE). The devices were taken out of clinical use due
to the development of inflammatory reactions resulting
from the leakage of the oil into the surrounding tissues
(17,18). The reactions resolved with removal of the devices
and did not present long-term health concerns. There are
presently no other alternative fillers available through clinical
trial.

Next time  we  will look at  implant   texture and its  clinical  significance in  breast implants.  Stay tuned!

 William P. Adams Jr. MD

 

 

William P. Adams, Jr., MD, PA

2801 Lemmon Ave. West

Suite  300

Dallas, Tx  75204

O: 214-965-9885

Fax - 214-969-0933

 

dr@dr-adams.com

www.dr-adams.com


 

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For further questions or to schedule a consultation call 214-965-9885 or email Dr. Adams.   Dallas plastic surgeon offers plastic surgery procedures - forehead lift, browlift, breast augmentation using saline breast implants, silicone breast implants, cohesive gel breast implants, Gummy-bear breast implants,  liposuction, rhinoplasty and more to Dallas, Ft. Worth, Austin, Houston and surrounding areas.                     

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