Guy LaTorre

Complications related to retained breast implant capsules

Citing evidence that breast implant-related capsules resolve uneventfully, surgeons have elected to leave the capsules in place when implants are removed because capsulectomy adds both morbidity and expense to the procedure. However, recent clinical and histopathologic evidence suggests that uneventful resolution is not always the case, and several potential problems may arise from retained capsules after removal of the implant. Retained implant capsules may result in a spiculated mass suspicious for carcinoma, dense calcifications that obscure neighboring breast tissue on subsequent imaging studies, and cystic masses due to persistent serous effusion, expansile hematoma, or encapsulated silicone filled cysts. Furthermore, retained capsules are a reservoir of implant-related foreign material in the case of silicone gel-filled implants and textured implants promoting tissue ingrowth. To avoid complications from retained capsules, total capsulectomy or postoperative surveillance should be offered to patients.

In vitro measurement of silicone bleed from breast implants.

&NA; A method to measure gel bleed from intact silicone gel‐filled breast implants was developed. This nondestructive technique permits accurate and reproducible serial measurements of silicone bleed from smooth wall breast implants (n = 10) under simulated physiologic conditions in vitro. Gel bleed rates from new low bleed gel‐filled implants and intact explants (unbarriered, low bleed, double lumen) were determined. These results demonstrate the reliability of this method to quantify silicone gel bleed and may permit a meaningful comparison of bleed rates from implants in the future. (Plast. Reconstr. Surg. 97; 756, 1995.)

Structural evolution of a porous type-VI sol-gel silica glass

The structural evolution of type-VI porous sol-gel-derived optical glasses is described. The average pore radius of the glasses studied is 30 ,A, with an exceptionally narrow pore size distribution. These glasses are particularly suited to laser surface densification. Their properties make them also attractive as matrices for impregnation of second phases and as a substrate material for the production of fully dense optical lens elements and micro-optical devices. The properties of the matrices are reported for the as-dried state to densities approaching 2.2 g/cm 3, with thermal treatments from room temperature to 1060°C. The parameters of sintering for the gel-glass transformation are measured, and the phenomena occurring for three temperature ranges are evaluated. An activation energy of 65 + 9 kcal/mol for sintering with a structure factor n = 1.0 + 0.3 was found for the initial stage sintering of the material.

Effect of long-term in vitro testing on the properties of bioactive glass-polysulfone composites.

The combination of bioactive ceramics and polymers can allow the preparation of composites with tailorable mechanical properties and bioactive behavior. In these composites, bioactive ceramics can act as a source of both reinforcement and bioactivity, while the polymer matrix can add toughness and processability to the material. On the other hand, the effect of using a highly dimensional unstable phase as a reinforcing agent on the long-term properties of the composite is a major concern regarding the lifetime of possible applications. In this work, a bioactive glass-polysulfone particulate composite was prepared by hot-pressing at 215 degrees C a mixture of polysulfone and different concentrations of bioactive glass particles (Bioglass 45S5, particle size range: 125-106 microm) to yield composites having 20 and 40 vol % of bioactive glass particles. The obtained composites were exposed to a simulated body fluid at 37 degrees C for different periods of time ranging from 1 h to 60 days. After the test, the mechanical properties of the composites were investigated by a four-point bending test, while DMS (dynamic mechanical spectroscopy) was used to identify the effect of water on the structure and behavior of the composite. The interface between glass particles and the polymer was also investigated by SEM/EDX and diffuse reflection infrared spectroscopy. The results showed that a decay in the mechanical properties of the composites within the first 20 h of test can occur. Otherwise, after this initial decay, no more pronounced reduction in properties could be noted. The analyses of the fracture surface of composites tested in vitro indicated the hydration of the surface of the particles. Therefore, it was concluded that water migration through the interface of the composite causes surface dissolution of glass particles and formation of voids, which were responsible for the observed decay in mechanical properties. Composites with modified interfaces revealed less damaged fracture surfaces than composites with untreated interfaces.

Silicone Degradation Reactions

Silicone (polydimethylsiloxane, PDMS) is generally a very stable polymer. Because of this, it is used in a wide variety of adverse environments such as those with high temperature or as electrical insulation. However, a great deal of this stability derives from the fact that hydrolysis reactions which occur are reversible and the polymer essentially heals itself. It is likely that such reversibility would not occur in the surface region where high concentrations of other components, such as water, can exist. Because of the significant concern about the fate of silicone released from breast implants in particular, it is important to understand the types of chemical changes which may occur in silicone upon exposure to physiological environments so that the data on various silicon-containing species can be correlated with other physiological studies on known compounds. Accordingly, this chapter will focus on the known silicone degradation reactions which occur within normal physiological ranges (37° and mixed aqueous environment). Various other studies will be drawn upon to evaluate the possible changes since the literature on silicone modification under physiological situations is sparse at this time. Three main reactions discussed are hydrolysis, oxidation, and addition.

The UV-visible spectrum in porous type VI silica : application and theory

The ultraviolet (UV) through visible (VIS) absorptions are determined and analyzed for porous type VI sol-gel-derived silica optical matrices. Changes in the UV-VIS spectral response are related to changes in the texture and molecular structure of the gel silica. There is a significant increase in UV cutoff as the pore size increases from 12 A to 90 A radius pores. This result is analyzed using classical scattering theory in combination with semi-empirical molecular orbital (MO) calculations. The concentration of small (three- and four-member) silica rings is a function of the processing temperature and history. As a result the UV absorption is observed to move to larger wavelengths as the number of three-member silica rings increases.

Properties of gel-silica optical matrices with 4.5-nm and 9.0-nm pores

Sol-gel processing of tetramethyl orthosilicate with HNO3 as a catalyst has been used to make optically transparent silica matrices with interconnected porosity of 1.2 to 1.4 nm radii. However, large pores are often needed for impregnation of the matrices with optically active organics. Larger pore volumes are also desirable for many applications of these optical composites. Two methods for producing larger pore matrices are compared: (1) Catalysis with dilute HF, and (2) aging in a basic NH4OH solution. Pore radii of matrices made by the HF method are 5.0 nm after thermal stabilization at 900 degree(s)C and 4.4 nm after 1000 degree(s)C. Pore volumes are 0.9 cm3/g at 900 degree(s)C and 0.7 cm3/g at 1000 degree(s)C. The ammonia aging process yields 9.0 nm radius pores at 900 degree(s)C and 8.7 nm pores at 1000 degree(s)C. Pore volumes are 1.0 cm3/g at 1000 degree(s)C. Optical properties (including UV cut-off, UV-vis-NIR transmission, IR absorption, index of refraction), bulk and structural densities of the matrices made by both methods (900 degree(s)C and 1000 degree(s)C stabilization) are compared with the 1.4 nm pore radius matrices.

Macrophage-Silicone Interactions in Women with Breast Prostheses

In order for silicone from breast implants to have an effect on the immune system, it must be demonstrated that cells with the potential for immune system function have access to silicone. It had long been thought that the fibrous capsule surrounding breast prostheses functioned as an effective barrier between the biomaterial and the host. Implants that ruptured were thought to be innocuous to the host as long as the fibrous tissue capsule surrounding the implant was intact. This was termed “contained rupture.” Thus, the capsule was thought to prevent the egress of foreign material (Bingham et al. 1988)