fda proposal (mate junior series)

8/3/2019 FDA Proposal (Mate Junior Series)

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Document No.: Revised: 05/03/12 File Name:

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Injectable Silicone Cheek Implants

Gingers and Friends

3/17/11

Rachel Bethancourt

Marissa Hill

Dillon Lynch

Robert Welsh


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Report Title: Multi Component Cheek Implants

1. ABSTRACT

The current method of chin implants involves the insertion of a solid siliconeform into the malar area via an intraoral incision. This method requires alarge incision in order to fit the implant into the zygomatic cavity. The malarregion is accessed via the mouth as to leave no unsightly scars on the facialarea, but his choice of incision location also leads to higher risk of infection.The goal of the project is to create an implant consisting of a siliconeelastomer shell and an injectable silicone rubber core. This will allow theincision site to be moved to an extraoral location, lowering the risk ofinfection, minimizing invasiveness, and expediting recovery time/ reducingpatient discomfort.

The functional requirements of the implant are to last a minimum of 15 years,to be non toxic, biocompatible, and have similar facial integration of current

solid silicone cheek implants. The silicone filler will be created with 3 varyingproportions of base to catalyst and the presence and absence of a calciumcarbonate filler to attempt to best replicate the current solid silicone implantscurrently in use. The samples will be subjected to a weighted load for 24hours and the change in thickness will be measured. The combination ofthese factors and levels with the least amount of change in thickness is themost desirable.


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Design and Development Planning

1.1. Introduction

1.1.1. The process of cheek augmentation requires an intraoralincision to place the solid silicon implants into a cavity locatedanterior to the zygomatic bone.

1.1.2. The incision location is selected to minimize the appearance ofthe resulting scar, but also increases the risk of infection due tobacteria in the mouth. The size of the implant also creates theneed for a large incision.

1.1.3. The availability of medical grade polymer shells is low and willnot be incorporated in testing. The filler alone will be tested todetermine if its properties correlate to the solid silicone implant.

1.2. Problem Statement

1.2.1. The use of solid silicone cheek implants requires too large of

an incision. A new technology needs to be created to allow fora smaller, extraoral incision.

1.3. Project Goals, Solution and Objectives

1.3.1. The goal of the project is to create an implant which can beinserted into the zygomatic region of the face through a smallerincision. This will allow the incision site to be moved to anextraoral location, lowering the risk of infection, minimizinginvasiveness, and expediting recovery time/ reducing patientdiscomfort

1.3.2. By creating an implant consisting of a silicone elastomer shell

and an injectable silicone rubber core, the implant can beinserted into the facial cavity in the form of a rolled up shell.This requires a biocompatible shell material to be obtained andan injectable polymer which can mimic the properties of currentsolid silicone implants.

1.4. Testing Justification and Overview

1.4.1. Three proportions of base to catalyst will be tested from a twopart castable silicone kit. After full curing, weights will be placedon top of the samples for 24 hours to measure the change inthickness.

1.4.2. In order to determine if the castable silicone can accuratelymatch the properties of solid silicone the elastic modulus willneed to be tested. This ensures that the new product meets thespecifications and natural abilities of the current solid siliconeimplant in place.


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1.4.3. This new method will lower the risk of infection in patients andis beneficial for them. The introduction of this technology willnot require surgeons to obtain new skills to use and will beeasily received by current surgical teams.

1.5. Important Terminology

1.5.1. Zygomatic- the cheek bone regionIntraoral- inside the mouthExtraoral- outside the mouthMaxillofacial- the upper jaw and area of face aboveMalar- the cheek, zygomatic bone, and side of the head

1.6. Organizational Responsibilities

1.6.1. Rachel Bethancourt will be responsible for obtaining thesilicone rubber mixture to test for the appropriate properties.Dillon Lynch will obtain syringes and shells for testing. Marissa

Hill will be in charge of determining testing methodology.Robert Welsh is in charge of data acquisition and organization.

1.7. Document Tracking, Deliverables and Timeline

1.7.1. Robert Welsh will be responsible for all important documents.There will be a specified folder in which all documents will befiled and it will be present at all group meetings.

1.7.2. A medical journal review will be published so that all data canbe reviewed and read by any who has interest.

1.7.3. All physical procedural tools and equipment will be obtained by

the group by the second week in February. Testingmethodology will be created to match specific materialsobtained within one week of full material acquisition. Datacollection will be completed 10 days before the finalpresentation.


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2. DESIGN INPUTS

2.1. User and Patient Needs

The surgeon responsible for the procedure is the main user of theimplant. The patient is a secondary user. The surgeon needs an

implant which they can confidently insert into the patient. The processof filling the shell cannot be too complicated as to lead to increasedrisk of patient infection or rejection. The patient needs the newimplant to mimic the natural properties of the cheek.

2.2. Performance Requirements

2.2.1. The functional requirements of the implant are to last aminimum of 15 years, to be non toxic, biocompatible, and havesimilar facial integration of current solid silicone cheekimplants.

2.2.2. The device will be placed on top of the zygomatic bone of theface. This region of the body is fairly static with the exceptionof facial expressions. The implant will be placed under themuscle, simulating a larger zygomatic bone and will not beaffected by muscle movement,

2.3. Design Input Assessment Plan

The shape, location, and outer material of this implant will be thesame as the implants currently in use. This accounts for the sameappearance superficially, environment of the implant, andbiocompatibility as in current methods. The only major change will bethe core of the implant and the insertion method. The insertion

method is known to have a lower risk of infection, but is not chosencurrently because of the scarring. The core of the material will haveno interaction with the body because it is sealed in the plastic shell.The chosen silicone elastomer is currently used in breastaugmentations. This certifies its capability to be used in the body withno harmful results.


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3. PROPOSED SOLUTION

3.1. Conceptual Design Description

In order to reduce the invasiveness of intraoral malar and submalarinsertion a process, similar to breast augmentation, will be used in

which a small shell is inserted surgically extraorally into the malarregion and filled with a solidifying silicone core . The shell will bemade from a (Silicon elastomer) must have a negligible volume but asurface are of approximately 50.6 cm2. This shell will be made of thesame elastomer as used in breast implants and therefore proven tobe leak free during filling and compatible with the human body. Thecore will be made of (silicone rubber) with will be injected in gel forminto the shell were it will undergo solidification. The volume of thesilicone core is approximately 25.75 cm3 and is nontoxic to the humanbody, though it will be completely enclosed by the shell and willtherefore not be exposed to human tissue. In order to meet the

patients needs the (silicone rubber) will have the same elasticmodulus when hardened as current implants in order to provide thesame support and feel. This procedure will allow surgeons to improvemalar and submalar augmentation with a lower chance of infectionand will allow the procedure to be completed extraorally withminiscule scarring to the face.

3.2. Design Performance

Current malar and submalar implants meet all of this procedure sperformance specifications; therefore in order to maintain the qualityof the implant those values such as volume and elastic modulus willbe reproduced. The current implants meet all FDA standards andsince there is no change in the final product just the process in whichit is surgically inserted it meets all requirements.

3.3. Patient Safety Assurance

The outer shell which will be the only part in contact with the patientsfacial tissue has been used in breast augmentation for many yearsand its biocompatibility has been shown by its history. The castablesilicone inserted into the shell should never come in contact withhuman tissue, though in the case of leak during the procedure thematerial is non-toxic and will not harm the patient. If a leak occurs,then the implant and any leaked silicone rubber will have to be

removed surgically in order to preserve the correct appearance of theface and for patient comfort.


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4. DESIGN VERIFICATION PLAN

4.1. Design of Experiment

4.1.1. The silicone epoxy was mixed at three different percentages ofcatalyst, by weight (amount catalyst/total amount), at 6%, 9%,

and 13%, with 9% being the manufacturers recommendedproportion. There was also calcium carbonate filler added to asecond batch of all three proportions. The amount of filleradded to the silicone was calculated by the equation todetermine mass fraction of matrix and filler in a compositebased on elastic modulus.

4.1.2. After all samples had properly cured they were labeled with aletter (A-F) to indicate which of the 6 treatments they hadreceived as well as the number (1-6) within each lettered groupto identify each from one another. The initial thickness of eachsample was measured at 3 locations on the sample and theaverage was calculated.

4.2. Sample Description

4.2.1. Silicone V-340 was used. It is a two part mix which can havethe proportions of the parts varied.

4.2.2. The samples were mixed during the same period of time on thesame day to reduce the possibilities of variation due touncontrollable factors such as temperature and humidity. Thesamples were mixed indoors using the same producer toprepare all samples.

4.3. Test Procedures

4.3.1. The procedures that will be used to conduct each test will be todo the compression over time test for samples A-F (A-C haveno filler with the three ratios while D-F have fillers). Thesamples numbered 1-2 for each letter A-F were placedunderneath a 45 pound weight. It was left there for 24 hours.The difference of the thickness was then evaluated. Samples 3-4 for letters A-F were then placed underneath two 10 poundweights. Each 10 pound weight had three samples underneathit in order to distribute the weight evenly throughout all

samples.4.3.2. We are assuming that the samples are the same thickness and

are evenly distributed underneath the weights to ensure equalweight is on each sample.

4.4. Equipment


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4.4.1. Square candy molds were used to create uniform 1 inch2samples. The batches of different compositions were mixed inpaper cups with wooden stirring sticks and the proportions ofbase, catalyst, and calcium carbonate filler were weighed on adigital scale. Weighted plates were used for compression of the

samples. One 45lb. weight and four 10lb. weights were used.4.5. Analytical Techniques

4.5.1. Four averages were taken for each level and factorcombination, one from each of four different samples percomposition which were given the weighted treatment.

4.5.2. A Design of Experiment analysis was performed to view themain effects and interactions. A p-value less than .05 wouldindicate a significant difference in performance betweensamples.

4.5.3. The modulus of the solid silicone implant will be chartedcompared to the tested modulus.

5. RESULTS

5.1. DOE Analysis

5.1.1. An analysis of the data was run to determine the effects of thelevels and factors alone as well as their interaction with oneanother. The following graphs were generated:

13%9%6%

0.009

0.008

0.007

0.006

0.005

0.004

NO FILLERFILLER

A

Weight % Catalyst

Mean

B

Main Effects Plot for C7

Data Means

Figure 1.


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NO FILLERFILLER

0.010

0.009

0.008

0.007

0.006

0.005

0.004

0.003

B

Mean

6%

9%

13%

A

Interaction Plot for C7

Data Means

Figure 2.

5.2. Interpretation of Analysis

5.2.1. In Figure 1, the plot on the left shows that the 9wt% catalystsamples exhibited the least amount of compression over time.The p-value for weight % catalyst was .168. In accordance to

our selected cut off of .05, this is not a significant differencebetween the different proportions. More advanced testing withmore data could show that this factor could contribute to asignificant difference in performance, but this experiment hasnot shown it to be so.

5.2.2. Also in Figure 1, the plot on the left shows the performancebased on the presence of calcium carbonate filler. The slope ofthe line is very small, but does show the absence of filler togive the least amount of compression over time. The p-valuefor this test is .744, certainly showing no significance. As withthe proportion further testing could give more certainty but the

interaction of filler with the silicone polymer has giveninconclusive results.

5.2.3. Figure 2 shows the interaction of both variables giving a moredetailed look at the results. The cause of the not-significantdifference in the filler can be attributed to the fact that 2 of theproportions showed a higher compressibility over time with the


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presence of filler, but the third, 6wt%, showed a reducedcompression over time with the presence of the filler. The fillerdid not perform the same in all samples. The interaction plotalso shows that the 9wt% sample did not exhibit the leastamount of compression over time for both filler and non filler;

the 6wt% with filler showed less compression over time thanthe 9wt% with filler. The p-value of this test is .655, showing nosignificant difference. The inconsistency of samples to performbased on filler most likely lead to this. As with all tests, moredata would need to be collected to come to a more certainconclusion.

6. DISCUSSION

6.1. Viscoelastic Polymers

6.1.1. The properties that determine the elastic deformation of apolymer are not as simple as many of the ideal models. In factsolid state deformation is time-dependent and nonlinear and soresembles some combination of elastic and viscous responses.If a material is linear and elastic then the applied stress directly proportional to the strain , however; for polymersbecause of time-dependence and nonlinearity, E is not aconstant and the term tensile modulus is used instead. Whenthe stresses are taken away from a polymeric material beforefracture, the strain recovery path is not the same as the loadingpart of the deformation cycle another difference from ideal

behaviors. Since both the deformation and recovery are time-dependent, some part of their behavior must be viscous. Mostpolymers contain a combination of elastic and viscous behaviorcalled viscoelasticity. The degree of viscoelasticity is stronglydependent upon the temperature of test, the rate at which thepolymer is deformed, degree of crystallinity, cross linking, andmolecular mass. strain are not recoverable is viscous flowtherefore when a polymers undergoes stress not all strain isable to be recovered. The amount of strain that can berecovered is largely due to the temperature under which thestress is applied. Time dependence is also a key factor, if

mechanical stress is held constant then the strain will increasewith time resulting in creep.

6.2. Reaction Effects

6.2.1. During the process of creating our implant we attempted toalter the manufactures ratio of catalyst and the base in order toresult in a silicone with different properties. We created three


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types of samples with the ideal sample percent being 9 percentcatalyst, and the other samples being 6 percent and 12percent. We predicted that the sample with a higher catalyst(12%) would react more and result in more cross linking andthus a stronger material. The 6 percent sample behaved as we

expected and resulted in a less stiff more elastic material dueto the fact not as much cross linking occurred due to the factthat the reaction was not able to complete itself. However ourprediction on the 12% sample was off base due to the fact thatat the ideal ration the reaction completes itself and with ahigher catalyst it does not continue and all that remains is someunreacted catalyst which lends the material its viscous behaviorand results in a higher viscoelasticity.

6.3. Calcium Carbonate Filler Interactions

6.3.1. During the experiment we hypothesized that filler would allowthe silicone mix to solidify more efficiently therefore resulting ina stronger viscoelasticity. We predicted that the filler wouldnthave a major effect on the amount of cross linking and would

just add its properties to the mold resulting in a stiffer piece ofsilicone. In reality however the filler had the opposite effect. Itseverely reduced the amount o f cross linking and resulted in amaterial with much lower viscoelasticity due to the fact that thelack of cross linking caused the polymer to behave in a muchmore viscous manner. This resulted in seeing a significantlyhigher amount of deformation during stress testing thereforeeliminating the samples with filler as a plausible choice for animplant.

7. CONCLUSION

Overall, we created a material that was injectable and could hypotheticallybe used as a cheek implant therefore our project was a Success. Howeverfuture study would be necessary to test the effect our implant would have onthe body. The surgical procedure would also have to be designed in order toachieve the goals we had set forth.

fda proposal (mate junior series)

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