Different corrosive effects on hydroxyapatite nanocrystals and - - PowerPoint PPT Presentation

Different corrosive effects on hydroxyapatite nanocrystals and amine fluoride-based mouthwashes on dental titanium brackets: a comparative in vitro study

Presented by Sean Day, Stanley Gelin, Kristin O’Connor, Chris Sullivan, and Brian Wilson

About the Authors

• Alma Mater Studiorum, University of Bologna

Department of Chemistry Bologna, Italy

– Marco Lelli – Ismaela Foltran – Giulia Montebugnoli – Massimo Marcaccio – Norberto Roveri

• University of Pisa Istituto Stomatologico Tirreno,

Lido di Camaiore, Lucca, Italy

– Olivia Marchisio – Annamaria Genovesi – Ugo Covani

Key Terms

• Fluoridated Hydroxyapatite – Fluoride

attached calcium material used in dental enamel.

• SEM – Scanning Electron Microscopy is a way

to visualize the surface roughness of the material.

• AFM – Atomic Force Microscopy is a way to

visualize the surface roughness of the material.

• Biomemetic – Any human made substance

that is meant to imitate things naturally found in the body.

History of Dental Work

• Early History

– Mummified ancients with crude metal bands wrapped around individual teeth (catgut used as wire!). – Hippocrates and Aristotle both ruminated about ways to straighten teeth.

History of Dental Work

• Important Breakthroughs

– In 1728 a French dentist used a “Bandeau” to help expand the arch – In 1757 another French dentist perfected the Bandeau – In 1819 Delabarre introduced the wire crip which marked the birth of contemporary orthodontics

History of Dental Work

• The First Metal

Mouths

– In the early 1900s

• rthodontists used

gold, platinum, silver, steel, gum rubber, and vulcanite. Why do you think titanium was eventually used over

• ther materials or other

metals?

Why use titanium?

Low thermal conductivity. Has an appropriate modulus of elasticity, which helps bone to heal when in close contact. Highly ductile and resistant to cyclic forces in the oral environment. Considered to be biocompatible

Use of Dental Fluoride

• When exposed to fluoride in a mouthwash,

the native hydroxyapatite will substitute a hydroxyl group for a fluoride ion.

• This modification promotes more enamel

formation, higher crystallinity, and stronger mechanics

• Fluoride also inhibits bacterial metabolism

in plaque formation

Alternative Treatment

• Fluoride is being replaced by biomimetic

hydroxyapatite nanocrystals.

– Hydroxyapatite that is substituted by carbonate anions and zinc to mimic native dental HA

• Have been shown to be able to produce

mineral deposition on enamel and dentin

Biomimetic CHA Images

• TEM images of zinc substituted carbonate-

hydroxyapatite nanocrystals

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Effects of Fluoride

• Fluoride has a corrosive effect on titanium
• Titanium oxide layer destroyed
• At pH <3.5 and concentrations >30 ppm,

fluoride degrades titanium and increases the surface roughness

Bracket Corrosion

• Corroding the titanium brackets changes the

topology of the biomaterial

– The extra surface area allows for more adhesion by bacteria

• This can lead to oral diseases and decrease the

effectiveness of the dental implant through

• What other methods besides modifying surface

roughness could be used to prevent bacterial accumulation?

Purpose of Study

• Compare the corrosive effects on titanium

by both fluoride mouthwash and CHA mouthwash

• Why?

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METHODS: General Outline

• Four types of titanium were considered:
• 1. Polished
• 2. Blasted
• 3. Machined
• 4. Acid-etched
• Each type 3 mm thick and 6 mm diameter
• Each type had six in vitro test samples
• Each sample was dipped in mouthwash for

60 seconds two times a day for 30 days

• Titanium plates were rinsed after treatment

Discussion Question

What do you think about the protocol that was used for dipping? Are there other variables that might make this experiment less realistic?

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METHODS: In Vitro Test

• Polished titanium bracket samples were

tested at room temperature

– A nanostructured microcrystal CHA-based mouthwash

• Composition of biomimetic CHA (active

component): Ca(-x)Znx(PO4)(6-y)(CO3)y(OH)2

• X = 0.1
• Y=0.4

– An amine fluoride F—based mouthwash

• pH between 4.3 and 5.5

METHODS: Morphological Characterization

• SEM

– Scanning Electron Microscopy – Carl-Zeiss EVO, 40 XVP (Oberkochen, Germany) with energy dispersive detector (EDAX) Inca 250 (Oxford, UL)

• Used secondary electrons at 25 KV and different

magnifications

– Uses a beam of high energy electrons to scan and produces images of a sample – Used to visualize the surface roughness of the titanium sample

METHODS: Morphological Characterization

• AFM

– Atomic Force Microscopy – Digital Instruments Nanoscope IIIa Multiomode SPM

• (Digital Instruments, Santa Barbara, CA, USA)
• Superior multitasking control for scanning probe

microscopes (SPMs)

• J scanner and silicon nitride tips (200 lm long with nominal

spring constant 0.06 N/m)

– Uses SPMs in contact mode to produce images of the surface topography of a sample

• By recording height adjustments or changes

in interatomic forces

– Used to visualize the surface roughness of the titanium sample

Discussion Question

AFM and SEM are both good topographic

• techniques. How can these be supplemented to get

chemical composition information?

RESULTS

SEM Images of Titanium Surfaces

Polished Blasted Machine Treated Acid-Etched Discussion Question Polished titanium was chosen as the more suitable plates to be utilized in this study. How do these results support this selection? How might the results have been different if a different surface was used?

SEM images of titanium surfaces after mouthwash treatment

Surface after fluoride-based mouth wash treatment Elementary analysis after fluoride-based mouth wash treatment Surface after CHA-based mouth wash treatment Elementary analysis after CHA-based mouth wash treatment

Discussion

• The zinc-substituted carbonate–

hydroxyapatite (CHA) based mouth wash had HA deposition filling the streaks on the titanium surface and therefore reducing surface roughness.

• The energy dispersive detector (EDAX)

analysis revealed the presence of calcium and phosphorus which was characteristic of the CHA present in the mouthwash.

Ca5(PO4)6(OH)2 Hydroxyapatite

Comparison of Pre and Post- Treatment SEM Images

Original, Polished Titanium F and CHA treated Titanium

AFM Analysis

10 x 10 μm Section 100 x 100 μm Section

Discussion

• The treatment with amine the

fluoride based mouthwash induced a roughness characterized by streaking with higher peaks and deeper valleys on the titanium bracket surface.

• Increased depth of the streaks

encouraged bacterial growth, promoting infection and prosthesis contamination and mobility.

Amine Fluoride

Discussion

• Treatment with the CHA-based mouthwash induced a

roughness characterized by streaking with smoothed peaks and less deep valleys on the titanium bracket surface.

• Hydroxyapatite deposition protected against the surface
• xidative process, which can damage the mechanical

behavior of the titanium brackets.

Numerical Analysis From AFM Images

Discussion Question

• Using your knowledge of biomaterial

surface properties, what are the advantages and disadvantages of using a ceramic implant?

Conclusion

• Determined the presence of F- in a mouthwash

induces mechanical weakness in the metallic dental implant and bacterial contamination.

• Found that the presence of zinc-substituted CHA in a

mouthwash prevents the deterioration of the metallic dental implant and contamination with bacteria.

Questions???