Oral Sciences n3

Braz J Oral Sci. 14(1):1-4

Original Article Braz J Oral Sci.
January | March 2015 - Volume 14, Number 1

Chemical analysis and Vickers hardness of
orthodontic mini-implants

Christiane Cavalcante Feitoza1, Guilherme José Pimentel Lopes de Oliveira2, Rafael Leonardo Xediek Consani3,
Eloisa Marcantonio Boeck1, Karina Eiras Dela Coleta Pizzol1, Nadia Lunardi1

1Centro Universitário de Araraquara – UNIARA, Department of Dentistry, Area of Orthodontics, Araraquara, SP, Brazil
2 Universidade Estadual Paulista – UNESP, Araraquara Dental School, Department of Diagnosis and Surgery, Area of Periodontology, Araraquara, SP, Brazil

3Universidade Estadual de Campinas – UNICAMP, Piracicaba Dental School, Department of Oral Rehabilitation, Piracicaba, SP, Brazil

Correspondence to:
Nádia Lunardi

Av. Maria Antonia Camargo de Oliveira,170
CEP: 14707-120, Araraquara, SP, Brasil

Phone: +55 19 991648770
E-mail: nadialunardi@yahoo.com.br

Abstract

Orthodontic mini-implants are used in clinical practice to provide efficient and aesthetically-pleasing
anchorage. Aim: To evaluate the hardness (Vickers hardness) and chemical composition of mini-
implant titanium alloys from five commercial brands. Methods: Thirty self-drilling mini-implants, six
each from the following commercial brands, were used: Neodent (NEO), Morelli (MOR), Sin
(SIN), Conexão (CON), and Rocky Mountain (RMO). The hardness and chemical composition
of the titanium alloys were performed by the Vickers hardness test and energy dispersive X-ray
spectroscopy, respectively. Results: Vickers hardness was significantly higher in SIN implants
than in NEO, MOR, and CON implants. Similarly, VH was significantly higher in RMO implants than
in MOR and NEO ones. In addition, VH was higher in CON implants than in NEO ones. There
were no significant differences in the proportions of titanium and aluminum in the mini-implant alloy
of the five commercial brands. Conversely, the proportion of vanadium differed significantly between
CON and MOR/NEO implants. Conclusions: Mini-implants of different brands presented distinct
properties of hardness and composition of the alloy.

Keywords: orthodontics; dental materials; hardness.

Introduction

In recent decades, there has been a growing demand for orthodontic treatment
in dental offices by adult patients, which required the development of an efficient
and aesthetically-pleasing anchorage system to enable and expedite treatment.
The orthodontic mini-implant is a temporary skeletal anchorage device that allows
the orthodontist to work safely because it eliminates the ensuing side effects on
teeth used as anchorage in conventional treatment and does not depend on patient
compliance1. The ease of installation and removal, possibility of insertion in
different intraoral regions, low cost, small healing time, and good patient acceptance
all contribute to the diffusion of the technique2-4.

Several studies have demonstrated the clinical efficacy of this anchorage
technique5-7, but clinical practice exposes some disadvantages such as screw
breakage during installation, the possibility of osseointegration making removal
difficult, and the lack of stability with subsequent mini-implant loss. Thus, further
studies on the efficacy of mini-implants are needed to solve these issues.

The resistance of mini-implants is determined by the interaction between
mini-implant design and chemical composition of the alloy. The alloy used for
mini-implant production should be nontoxic, biocompatible, have good mechanical

Received for publication: November 05, 2014
Accepted: January 29, 2015

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Group
SIN

NEO

C O N

R M O

M O R

Manufacturer
SIN - Sistema de

Implantes Nacional

Neodent

Conexão

Rocky Mountain
Orthodontics

Morelli

Origin
São Paulo/SP, Brazil

Curitiba/PR, Brazil

Arujá/SP, Brazil

Seoul, South Korea

Sorocaba/SP, Brazil

*ND (mm)
1.60

1.60

1.50

1.60

†NL (mm)
6.00

7.00

6.00

Profile (mm)
0.00

1.00

0.00

2.00

Shape
Cylindrical

Cylindrical

Conical

Cylindrical

Lead Thread
Single

Single

Double

Single

Table 1.Table 1.Table 1.Table 1.Table 1. Mini-implant features according to manufacturer’s specifications.

*ND = Nominal Diameter; †NL = Nominal Length

properties, and be stress, tension, and corrosion resistant8-9.
The use of orthodontic mini-implants in different bone
regions, including roots, requires that screws have reduced
size and thickness and resist higher torsional loads than those
required for insertion, in addition to orthodontic and
orthopedic forces. To meet these requirements, the titanium
alloy (Ti-6Al-4V) chosen for manufacture of mini-implants
incorporates aluminum (Al) and vanadium (V) into its
composition along with commercially pure titanium (cpTi)10.
Ti-6Al-4V alloy has higher fatigue resistance than (cpTi),
while having the same corrosion resistance and low toxicity11.
The amount of each component in the alloy, in addition to
the manufacturing quality, can alter its mechanical properties
such as hardness and resiliency, which are responsible for
the fracture resistance of the mini-implant.

Given the wide diversity of mini-implant types available
in the market, this study aimed to evaluate the chemical
composition and Vickers hardness (VH) of five orthodontic
mini-implant commercial brands to determine whether their
properties are suitable for clinical use.

Material and methods

Orthodontic mini-implants
Thirty self-drilling mini-implants were used, six each

from five commercial brands (SIN – SIN, Neodent – NEO,
Conexão – CON, Rocky Mountain – RMO, and Morelli –
MOR) with the largest number of similar characteristics to
enable comparisons (Table 1). The macrostructural aspects
of each mini-implant design are shown in Figure 1. Three
mini-implants of each brand were used for the Vickers
hardness analysis while the other three were used for the
EDS analysis.

Vickers Hardness
Vickers hardness was determined by penetration length

of the pyramidal diamond tip. A single operator previously
calibrated by the repetition process performed hardness tests
using a Shimadzu HMV-2micro hardness tester at a load of
300 gf and 4.904 N for 5 sec. The measurements were
performed over the mini-implant head, which is the region

with the highest stability for diamond penetration. Each of
the three mini-implants from the five commercial brands was
measured three times, totaling nine measurements per brand.

Energy dispersive X-ray spectroscopy (EDS)
The remaining mini-implants were used for semi

quantitative analysis of alloy components. Each mini-implant
was removed from its packaging only at the time of analysis
so that the surface was not manipulated or contaminated by
external agents, thus preserving the original characteristics.
Six surface micrographs of each mini-implant (two of the
mini-implant head, two of the body, and two closer to the
mini-implant tip) were taken in panoramic view using a
scanning electron microscope coupled with Noran Instruments
EDS detector with a Vantage digital acquisition engine. The
values for the chemical composition of the alloy were then
obtained from these measurements.

Statistical Analysis
Due to the small number of samples, non-parametric

tests were used for the statistical analysis using Bioestat 5.0
software (Belém, PA, Brazil). The Kruskall-Wallis
complemented by the post-hoc test of Dunn was used to
evaluate the statistical differences regarding the hardness

Fig. 1. Micrographic aspects of mini-implant design from five commercial brands
(18X magnification). a) SIN-SIN, b) Neodent – NEO, c) Conexão – CON, d) Rocky
Mountain – RMO, and e) Morelli – MOR

Chemical analysis and Vickers hardness of orthodontic mini-implants

Braz J Oral Sci. 14(1):1-4

33333

and the chemical composition of the alloy between the brands.
The Bioestat 5.0 software (Belém, PA, Brazil) was used for
the analysis and the significance level was set at 5% (p<0.05)
for all the tests.

Results

Vickers Hardness
There were significant differences in VH values between

commercial brands. Vickers hardness was significantly higher
in SIN implants than in NEO, MOR, and CON implants.
Similarly, VH was significantly higher in RMO implants than
in MOR and NEO ones. In addition, VH was higher in CON
implants than in NEO ones (Table 2).

Brands Vickers Hardness
1-SIN 400.66 ±35,142,3,5

2-NEODENT 337.11±4,66
3-CONEXÃO 366.11±19,572

4-ROCKMO 393.00±4,932,5

5-MORELI 342,44±14,52

Table 2.Table 2.Table 2.Table 2.Table 2. Vickers hardness values of three mini-implant
samples each from five commercial brands.

2mini-Implants with higher hardness than the Neodent mini-implants (Kruskal Wallis
with Dunn);
3mini-Implants with higher hardness than the Conexão mini-implants (Kruskal
Wallis with Dunn);
5 mini-Implants with higher hardness than the Morelli mini-implants (Kruskal Wallis
with Dunn).

GROUPS Ti A l V
1-SIN 87.10 8.51 4.06
2-NEO 86.89 8.39 4.293

3-CON 86.94 8.99 3.91
4-RMO 86.04 8.31 4.11
5-MOR 86.85 8.86 4.323

Table 3.Table 3.Table 3.Table 3.Table 3. Proportion of metal components in orthodontic
mini-implant alloys from five commercial brands determined
using energy dispersive X-ray spectroscopy (EDS).

³mini-Implants with higher proportion of vanadium than the Conexão mini-implants
(Kruskall Wallis with Dunn).

Energy dispersive X-ray spectroscopy (EDS)
There were no significant differences in the proportions

of titanium and aluminum in the mini-implant alloy of the
five commercial brands. Conversely, the proportion of
vanadium differed significantly between CON and MOR/
NEO implants. Even though the differences in mean values
between brands were small, the low proportion of vanadium
in the alloy causes small variations to be readily detectable
(Table 3).

Discussion

Vickers hardness values showed little variation within
each commercial brand except for CON implants. Conversely,

VH values differed significantly between brands, and SIN
and RMO implants exhibited the highest VH values.

Our findings are consistent with the study by Eliades et
al. (2009)12, who evaluated mini-implants from a single
commercial brand and found VH values of 342 ± 14 HV for
the body and 354 ± 16 HV for the surface. These VH values
are slightly higher than the ones found in our study, which
ranged from 337 ± 4.66 HV (NEO) to 440 ± 35.14 HV
(SIN). Moreover, the values of both studies are higher than
the value (325.0 ± 10.1 HV) found by Lima et al. (2011)13,
who evaluated implants made with the same alloy.

Energy dispersive X-ray spectroscopy (EDS) is a semi
quantitative analysis that determines the chemical elements
in the specimen and quantifies their approximate proportions.
The results of our study confirmed the presence of Ti, Al, and
V in mini-implants alloys, albeit at different proportions than
those specified by manufacturers (Ti6Al4V). Nevertheless, the
fact that we found a higher proportion of aluminum
(approximately 8%) may be an artifact of the technique.

The difference in VH among brands may be due to
differences in the proportion of titanium and vanadium in
mini-implant alloys. Even though the proportion of titanium
was similar in all commercial brands, titanium alloys can
have different amounts of alpha-phase and beta-phase
titanium, possibly due to differences in the manufacturing
process of the alloy. For instance, Cotrim-Ferreira et al.
(2010)11 showed that there were quantitative differences in
alpha-phase and beta-phase titanium in mini-implant alloys
from three commercial brands (SIN, Dewimed, and CON),
even though they were within the guidelines of the
“Technical Committee of European Titanium Producers”
described in Publication ETTC-2.

The crystalline microstructure of the alloy, i.e., the
amount of alpha and beta titanium in the alloy, is responsible
for differences in its mechanical properties. An alloy with a
higher amount of beta-phase titanium has higher tensile
strength than an alloy with a higher amount of alpha-phase
titanium, whereas alpha titanium has higher corrosion
resistance than beta titanium10,14.

The addition of vanadium (a beta stabilizer) and an
increase in temperature can both result in increased beta-
phase titanium in the alloy15. This study showed that there
were differences in the proportion of vanadium among
commercial brands. Even though these differences were not
high, because the proportion of vanadium in the alloy is
low, any small deviations are readily detectable and become
statistically significant. Thus, the differences in VH among
mini-implant brands may have been due to the proportion of
vanadium in the alloy or to differences in heating and cooling
temperatures during the manufacturing process of mini-
implants14.

The difficulty in the casting process of titanium mini-
implants may also have been responsible for the differences
in VH observed in our study. The low density of titanium,
its high melting temperature, and high chemical reactivity
with surface elements and atmospheric gases make casting
of this alloy extremely costly and laborious due to the need

Chemical analysis and Vickers hardness of orthodontic mini-implants

Braz J Oral Sci. 14(1):1-4

for special equipment to keep the titanium in a vacuum
oxygen-free environment or in the presence of inert gases16-
18. Additional tests such as X-ray diffraction are needed to
test the hypothesis that titanium phases affect alloy hardness.
The variation in alpha and beta phases of mini-implants may
occur during manufacturing of the alloy or even during the
manufacturing process of the mini-implant.

The knowledge of mini-implant hardness and
composition is vital to assist in choosing the ideal commercial
brand and model for each installation site, thus minimizing
the risk of fracture. However, tensile strength of mini-implants
is determined not only by their chemical composition and
hardness, but mini-implant design is also fundamental for
mini-implant choice since these parameters influence the
possibility of the mini-implants fracture.

Based on the results of this research it can be concluded:
1. There were significant differences in Vickers hardness
between SIN and Neodent/Morelli/Conexão; RMO and
Neodent/Morelli; and Neodent and Conexão brands; 2. The
proportion of vanadium in the alloy differed significantly
between commercial brands; 3. The effect of these differences
in the clinical practice needs to be test in clinical trials.

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