BIOMATERIALS Maxillofacial & Skull Implants. Brendan Boyd & Stuart Mah

Transcription

1 BIOMATERIALS Maxillofacial & Skull Implants Brendan Boyd & Stuart Mah

2 Outline Of Presentation Basic Anatomy of Face and Skull Reasons/Defects responsible for maxillofacial & skull surgery History of Alloplastic Facial Implants Brief overview of Surgical Process for implantation Biomaterials Of Metal Implants Biocompatibility Of Metal Implants Biomaterials Of Plastic Implants Biocompatibility Of Plastic Implants Metal VS Plastic Implants Future Advancements Of Implants Alloplastics: Artificial implantable materials substituted for tissue grafts; e.g., plastics, silicones, metals, textiles, etc. 2

3 Anatomy of Face FRONTAL NASAL TEMPORAL SPHENOID ZYGOMATIC MAXILLA MANDIBLE 3

4 Anatomy of Skull PARIETAL FRONTAL NASAL ZYGOMATIC MAXILLA TEMPORAL MANDIBLE 4

5 Reasons for Needing Alloplastic Implants Cosmetic reasons (ie( ie.. Plastic surgery) Birth defects (ex. Cleft palate) Deconstructive disease (ie( ie.. Cancer) Sports or related injuries Accidents (ex. Car accidents) 5

6 History of Alloplastic Facial Implants Used for centuries in cosmetic and reconstructive surgery Implants in the maxillofacial area have been used in aesthetic and reconstructive practices to achieve symmetry and balance Early implantable materials included gold cleft palates and ivory nasal inlays Documented use of facial reconstructive surgery dates as far back as 800 B.C. Driving force for facial reconstructive surgery in late 1800 s and early 1900 s s was in fact war 6

7 Surgical Process for Implantations Reconstructive software Previous CT Scans New CT Scans CT scans used to analyze bone and cartilage deformities or intrusions, to allow for planning of surgery 3D volume reconstruction products offer complete 3D segmentation and manipulation Vworks 4.0 Clinic 3D by CyberMed of Seoul Combination of two technologies allows surgeons to map out and visualize how they will perform their facial reconstructive surgery 7

8 Surgical Process for Implantations Actual Surgical Process Three methods for securing metal prosthetic devices in human body 1. Press-fitting the device in the bone 2. Cementing them to an adjoining bone using an adhesive 3. Affixing them in place with screws Generally accepted method for affixing non-metallic metallic artificial facial implants is using an adhesive 8

9 Biomaterials of Metal Implants Properties Metal Tensile Strength (Mpa) Yield Strength (Mpa) Hardness Titanium Alloy (with Vanadium and Aluminum) Very Hard Gold Medium Hardness Stainless Steel Medium Hardness Tungsten Very Hard cobalt-chromium chromium alloys Titanium Low- Medium Hardness Low- Medium Hardness Ductility Medium Medium Very, Very High Low Low Very Low Corrosion Resistance Very High 4.5 Very High 4.85 Density (g/cu. cm.) Very, Very High High 8.03 High Very High

10 Tensile Strength / Density Metal Tensile Strength (Mpa( Mpa) Titanium Titanium Alloy (with Vanadium and Aluminum) Density (g/cu. cm.) Gold Gold has low tensile strength Elongation will cause improper functioning of facial parts Among the highest Density value Approx. 4.5x more dense than Titanium Causes unbalance Less comfortable when implanted 10

11 Ductility/Corrosion Metal Tensile Strength (Mpa) Yield Strengt h (Mpa( Mpa) Hardnes s Ductility Corrosion Resistance Density (g/cu. cm.) Titanium Low- Medium Hardness Medium Very High 4.5 Stainless Steel Medium Hardness Low High 8.03 Shaping to contour of bone Priority towards Cosmetics / Functionality of facial parts Makes surgical process less difficult Better stability when joined with bone Higher corrosion in stainless steel Cause pain Functional capacity reduced 11

12 Hardness Metal Hardness Ductility Density (g/cu. cm.) Titanium Low-Medium Hardness Medium 4.5 Tungsten Very Hard Low Need moderately hard substance Less physical force applied to facial area Vital and sensitive parts located in facial/skull region Tungsten not practical for maxillofacial or skull area 12

13 Why Titanium? Strong resistance to corrosion Good candidate for long term implants Has a strong oxide layer that renews itself Ease of shaping/bending compared to steel or cobalt- chromium Upon bending, Titanium reverts less than Steel No allergic reactions 13

14 Biocompatibility Of Titanium Facial Implants Completely inert to human body fluids FIGURE 1 Meets the following criteria of being biocompatible 1. corrosion-resistant resistant 2. tissue compatible 3. vital and elastic Titanium implants are tolerated for up to 13 years Much longer than other modern metallic facial implants No inflammatory response or large cell reactions (e.g. Figure 1) So far, titanium particles in tissue have no clinical significance or long-term effects 14

15 Biocompatibility Continued Success Rates Titanium plates and screws used on 54 patients with severe facial fractures Included Males and Females ranging from 5 to 74 years of age Of these patients, only 16.7% had reoperation due to cosmetic deformities or functional conflicts 15

16 Non-Metallic Implants Two main types of non-metallic artificial facial implants have been used over the past few decades: Silicone Rubber Calcium Phosphate Apatite Early implants were centralized around silastic implants Silastic is a silicone rubber composite material Virtually every artificial implant (non-metallic) was made of some composite of this material Material patented by Dow Corning Corporations 16

17 Examples of artificial implants made of silastic material: ears burr hole covers chins breast implants (responsible for lawsuits) 17

18 Implants are stable up to 90 days after insertion into body (according to chart) On Dow Corning website, they re listed appropriate time period for insertion is no more than 29 days Dow Corning sued for over 6 billion dollars due to reaction of silicon implants, mainly breast implants Lawsuits ongoing due to incompatibility of implants in the body 18

19 Calcium Phosphate Apatite (CPA) Implant Material One of the most important implantable materials Very biocompatible Usually molded to form artificial ears and chins etc., specific to the patient CPA is usually made into a composite material Composite material usually is a mixture of CPA and other biomaterials, such as Hydroxyapatite Bone is approximately 70% CPA, including some Hydroxyapatite 19

20 Biocompatibility of Modern Non-metallic implants To test biocompatibility of Hydroxyapatite,, sheets of it were surgically implanted onto skulls of patients Results No side effects were observed Implant appeared to be attached to the skull securely Hydroxyapatite adhered to skull of human 20

21 Metal vs Non-Metallic Implants Each offers its own advantages/disadvantages Metal Very strong Hard, high tensile strength Not as biocompatible Can be firmly attached to bone using screws or press- fitting E.g. Good for plates / reinforcement for bones Non-Metallic Very flexible Very biocompatible Easily formed to make natural-looking looking prosthetics Easier to manufacture Tends to become brittle over time in some cases Not nearly as strong 21

22 Future Advancements Best biocompatible metal is titanium Still causes fibrosis after 13 years Need to find more biocompatible metal One way is to coat the metal with a biocompatible material E.g. Hydroxyapatite or beta- tricalcium phosphate (TCP) Trials of coated prosthetic hips have shown promising signs of integration in the body 22

23 Another method to make titanium plates more biocompatible is to roughen the metal surface Creates a micro-porous structure through which bone is more likely to attach or grow This increases chances of osteointegration Osteointegration: : Bone growth directly adjacent to a metal implant 23

24 References Internet Resources db=pubmed&list_uids PubMed&list_uids= &dopt=Abstract db=pubmed&list_uids PubMed&list_uids= &dopt=Citation ID=63867 Book Resources Advances In Biomedical Polymers, Charles G. Gebelein,, 1987, Plenum Press, New York Advances in Biomaterials Volume 5, Ducheyne,, Van der Perre & Aubert,, 1984, Elsevier Science Publishers, Netherlands Biomaterials, A.L. Bement,, 1971, Battelle Seattle Research Center 24