UNIVERSIDADE ESTADUAL PAULISTA

“JÚLIO DE MESQUITA FILHO”

Instituto de Ciência e Tecnologia

Campus de São José dos Campos

ORIGINAL ARTICLE DOI: https://doi.org/10.4322/bds.2024.e4375

Braz Dent Sci 2024 July/Sept;27 (3): e4375

This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in

any medium, provided the original work is properly cited.

Strain gauge evaluation of bone microstrain in full-arch implant-

supported prostheses: cobalt-chromium and ﬁberglass materials

Avaliação extensométrica de microdeformações ósseas em prótese implanto-suportada de arco completo: materiais cobalto-

cromo e ﬁbra de vidro

William Simões de OLIVEIRA1 , Mariana Simões de OLIVEIRA2 , Alinne Siqueira CARVALHO1 ,

Guilherme de Siqueira Ferreira Anzaloni SAAVEDRA3 , Marco Antonio BOTTINO3 , Lafayette NOGUEIRA JÚNIOR3 

1- Universidade Estadual Paulista, São Paulo, SP, Brazil

2- Universidade Federal de Juiz de Fora, Juiz de Fora, MG, Brazil.

3- Universidade Estadual Paulista, Departamento de Materiais Dentários e Prótese, São Paulo, SP, Brazil.

How to cite: Oliveira WS, Oliveira MS, Caravalho AS, Saavedra GSFA, Bottino MA, Nogueira Júnior L. Strain gauge evaluation of bone

microstrain in full-arch implant-supported prostheses: cobalt-chromium and berglass materials. Braz Dent Sci. 2024;27(3):e4375.

https://doi.org/10.4322/bds.2024.e4375

ABSTRACT

Objective: This study addresses the strain gauge evaluation of bone microstrain in full-arch implant-supported

prostheses using two distinct materials: Cobalt-Chromium (CoCr) and Fiber Reinforced with Composite (FRC).

Material and methods: By employing strain gauge analysis, this study compares the mechanical properties of CoCr

and FRC, noting that FRC bars exhibit signicantly smaller microstrain under load, suggesting a more balanced

strain distribution. Results: This nding may be attributed to the intrinsic material properties of each, where FRC

offers relative exibility and a modulus of elasticity closer to that of human bone tissue, promoting harmonious

integration with peri-implant tissue. Additionally, the potential toxicity of CoCr alloys is addressed, emphasizing

the importance of alternative materials that minimize health risks. Conclusion: This study contributes to the eld

of implant-supported rehabilitations, suggesting that FRC may offer signicant mechanical and biocompatible

advantages over CoCr. However, it underscores the need for further research to validate these ndings.

KEYWORDS

Cobalt-chromium alloys; Dental prosthesis, Implant-supported; Elastic modulus; Fiberglass; Osseointegration.

RESUMO

Objetivo: Este estudo aborda a avaliação do extensômetro da microdeformação óssea em próteses implanto-

suportadas de arcada completa utilizando dois materiais distintos: Cobalto-Cromo (CoCr) e Fibra Reforçada com

Compósito (FRC). Material e métodos: Ao empregar análise de extensômetro, este estudo compara as propriedades

mecânicas do CoCr e do FRC, observando que as barras do FRC apresentam microdeformação signicativamente

menor sob carga, sugerindo uma distribuição de tensão mais equilibrada. Resultados: Esse achado pode ser

atribuído às propriedades intrínsecas do material de cada um, onde a FRC oferece relativa exibilidade e módulo

de elasticidade mais próximo ao do tecido ósseo humano, promovendo integração harmoniosa com o tecido

peri-implantar. Além disso, é abordada a potencial toxicidade das ligas de CoCr, enfatizando a importância de

materiais alternativos que minimizem os riscos à saúde. Conclusão: Este estudo contribui para o campo das

reabilitações implanto-suportadas, sugerindo que a FRC pode oferecer vantagens mecânicas e biocompatíveis

signicativas sobre o CoCr. Porém, ressalta a necessidade de mais pesquisas para validar esses achados.

PALAVRAS-CHAVE

Ligas de cobalto-cromo; Próteses dentárias, Suportadas por implantes; Módulo de elasticidade; Fibra de vidro;

Osseointegração.

Braz Dent Sci 2024 July/Sept;27 (3): e4375

Oliveira WS et al.

Strain gauge evaluation of bone microstrain in full-arch implant-supported prostheses: cobalt-chromium and fiberglass materials

Oliveira WS et al. Strain gauge evaluation of bone microstrain in full-arch implant-

supported prostheses: cobalt-chromium and ﬁberglass materials

INTRODUCTION

Oral rehabilitation with implant-supported

prostheses has revolutionized treatment for

edentulous patients, offering solutions that

signicantly improve quality of life. Since the

introduction of the concept of osseointegration

by Brånemark [1], dentistry has witnessed

signicant advances in the design and selection

of materials for prostheses, aiming to optimize

their longevity and functionality. The selection of

material for prosthesis infrastructure is important,

given its direct inuence on load distribution and

structural integrity of oral rehabilitations [2,3].

The introduction of alternative materials

in the manufacturing of infrastructures for

implant-supported prostheses has been a eld

of intense research in recent years. The growing

interest in materials such as fiber-reinforced

composite (FRC) is due to its unique properties,

including excellent mechanical strength and lower

thermal conductivity compared to traditional

metals like cobalt-chromium (CoCr). Recent

studies [4] highlighted the potential of FRC in the

manufacture of prosthetic bars, demonstrating

its ability to efficiently distribute masticatory

loads while minimizing strains transmitted to

peri-implant bone.

Furthermore, biocompatibility is an

increasingly considered factor in the choice of

materials for implant-supported prostheses.

The literature shows that FRC-based materials

offer additional advantages in these aspects,

favoring a more harmonious integration with

peri-implant tissue and not undergoing oxidation

or releasing ions or byproducts into the body.

The use of FRC in prosthetic infrastructures

not only meets functional requirements but

also promotes a favorable environment for

the maintenance of peri-implant health [5],

as corroborated by Pesce et al. (2019) [6],

who demonstrated the favorable mechanical

properties and biocompatibility of ber-reinforced

composites.

The choice of material for prosthesis

infrastructure is fundamental for the success

of oral rehabilitation. Al Jabbari (2014) [7]

extensively explored the mechanical properties

and biocompatibility of CoCr alloys, noting their

exceptional strength and durability. However, the

rigidity of these materials may result in a less-

than-ideal load distribution, leading to adverse

microstrain in the surrounding bone tissue.

In contrast, Ferreira et al. (2014) [8] investigated

the use of FRC, emphasizing its ability to offer

a more favorable load distribution due to its

relative exibility and modulus of elasticity closer

to that of natural bone.

Therefore, this study aimed to evaluate bone

microstrain in edentulous jaws rehabilitated with

four internal connection Morse cone implants,

supporting hybrid prosthesis infrastructures made

of CoCr and FRC. The objective is to investigate

if there are significant differences in strain

distribution between the two different protocol

prosthesis infrastructures, hypothesizing that the

distinct material properties of CoCr and FRC will

inuence the bone microstrain.

MATERIAL AND METHODS

For this study, a synthetic bone model

simulating an edentulous jaw with mild atrophy

was used, manufactured from polyurethane and

endowed with elastic properties similar to human

bone tissue [9,10]. Four cylindrical Morse cone

implants (Torque Hard, Conexão Sistemas de

Prótese, Arujá, São Paulo, Brazil) with a diameter

of 4.0mm and length of 13mm each, were used.

Additionally, prosthetic abutments (Solid Micro

Units) manufactured by the same company, with

Morse cone connection and a transmucosal height

of 2.5mm, were employed.

The installation of the implants in the

mandible model (Polyurethane) was carried

out freehand taking care so that they were

equidistant and parallel to each other. Then,

they were fixed in the resin to simulate

osseointegration. The scanning and design phase

of the infrastructures was carried out using an

intraoral scanner and CAD software, allowing

the prosthetic infrastructures to be designed and

manufactured to t precisely to the previously

installed implants (Figure 1).

The prosthetic infrastructures included

Protocol-type bars made of CoCr (n=5) and

FRC (n=5). These infrastructures were digitally

designed using an intraoral scanner and

Computer-Aided Design (CAD) software and

subsequently manufactured using subtractive

and additive manufacturing technologies,

respectively, and had dimensions of 4.3x7x65mm

(Figure 2). The design of the bar in its bilateral

distal portion was made in an airplane wing

shape. The length of the cantilevers was 12mm.

Braz Dent Sci 2024 July/Sept;27 (3): e4375

Oliveira WS et al.

Strain gauge evaluation of bone microstrain in full-arch implant-supported prostheses: cobalt-chromium and fiberglass materials

Oliveira WS et al. Strain gauge evaluation of bone microstrain in full-arch implant-

supported prostheses: cobalt-chromium and ﬁberglass materials

The bars were screwed onto the jaw model and

the torque used was the torque suggested by the

manufacturer.

For the evaluation of bone microstrain,

strain gauges (PA-06-060BA-120-L (Excel

Sensores Ind. Com. Exp. Ltda, Taboão da Serra,

Sao Paulo, Brazil, resistance 120 Ω; gauge length:

1.5 x 1.3 mm) were xed on the surface of the

jaw model according to the spaces available

between the implants (Figure 3), and their

output channels and connection to the data

acquisition machine were identified through

colors. Red and yellow strain gauges were placed

on the distal surfaces of the posterior and anterior

implants on the right side, respectively. Green

and blue strain gauges were placed on the distal

surfaces of the posterior and anterior implants

on the left side, respectively. The prosthetic

infrastructures manufactured in CoCr and FRC

were then subjected to static vertical loads of

100N at the end of the right cantilever, near the

red strain gauge, to simulate masticatory forces.

A load application device (LAD), developed by

Nishioka et al. (2015) [11], was used (Figure 4).

The electrical cables were identified

with colored tapes according to the previous

description of the strain gauge group and

soldered to a copper electronic plate, connecting

Figure 1 - Polyurethane prototype resembling an edentulous

mandible with a ﬂat base and borders with Conexão Torque Hard

implants and prosthetic abutments installed.

Figure 2 - Top view of Cobalt-chromium and Fiberglass bars in the

ﬁnalization process.

Figure 3 - Strain gauges ﬁxed on the models.

Figure 4 - Test specimen ﬁnished with Cobalt-Chromium bar

subjected to static compression with a force of 100N on the right

cantilever end.

Braz Dent Sci 2024 July/Sept;27 (3): e4375

Oliveira WS et al.

Strain gauge evaluation of bone microstrain in full-arch implant-supported prostheses: cobalt-chromium and fiberglass materials

Oliveira WS et al. Strain gauge evaluation of bone microstrain in full-arch implant-

supported prostheses: cobalt-chromium and ﬁberglass materials

them directly to exible electrical conductors with

a diameter of 1.5 mm each, which in turn were

connected to a data acquisition machine (ADS

2000 - Lynx Tecnologia Eletrônica Ltda. - SP -

Brazil) through a base with identied connectors

to minimize manipulation to the connectors of

the Data Acquisition machine. This machine is

responsible for receiving the signals resulting

from the variation of the electric current owing

through the strain gauges, amplifying them, and

converting them into digital signals. These signals

were then sent to the computer, providing data

on the microstrain (µε/a) suffered by the test

specimen (TS), through the AqDados7.2 software

(Lynx Tecnologia Eletrônica Ltda. - SP - Brazil).

The statistical analysis of the data collected

through the strain gauges was performed using

ANOVA (Tables I and II) and Tukey’s post-

hoc test (Table III), aiming to compare the

Strain distribution between the infrastructures

manufactured from the two different materials

and determine the existence of statistically

signicant differences between them.

RESULTS

In this study, it was observed that the FRC and

CoCr bars exhibited distinct patterns of microstrain

under a static axial load of 100N. The FRC bars

demonstrated a more balanced distribution of

strain, with signicantly lower average microstrain

values compared to the CoCr bars, as evidenced

by ANOVA and Tukey’s test statistical analyses,

which revealed statistically signicant differences

between the materials (p <0.05).

Specically, the FRC bars exhibited lower

microstrain on the Yellow and Blue strain gauges,

Table I - One-way ANOVA (Fischers’s) statistical test for FRC and

CoCr bars obtained through Jamovi computer software (Version

2.3)

FRC CoCr

F 34.3 17.4

df1 3 3

df2 96 96

p <0.01 <0.01

Note: df = degree of freedom.

Table II - Descriptive table of means, standard deviation, and standard error of the tests performed on FRC and CoCr samples, obtained

through Jamovi computer software (Version 2.3)

FRC CoCr

Red Yellow Blue Green Red Yellow Blue Green

N 25 25 25 25 25 25 25 25

Mean 565.4 162.8 59.8 242.5 530.4 470.6 898.9 82.5

SD 280.2 156.1 67.3 178.3 138.0 345.4 704.3 81.3

SE 56.0 31.2 13.5 35.7 27.6 69.1 140.9 16.3

Note: Red = posterior implant on the right side; Yellow = anterior implant on the right side; Green = posterior implant on the left side; Blue =

anterior implant on the left side.

Table III - Tukey’s Post-Hoc statistical tests comparing the extensometers associated with Fiberglass and CoCr bars, obtained through Jamovi

computer software (Version 2.3)

Red-FRC Yellow-FRC Blue-FRC Green-FRC

Red-CoCr Mean diﬀerence -35.0 – – –

p-value 0.578 – – –

Yellow-CoCr Mean diﬀerence – 308 – –

p-value – <0.001 – –

Blue-CoCr Mean diﬀerence – – 839 –

p-value – – <0.001 –

Green-CoCr Mean diﬀerence – – – -160

p-value – – – <0.001

Note: Red = posterior implant on the right side; Yellow = anterior implant on the right side; Green = posterior implant on the left side; Blue =

anterior implant on the left side.

Braz Dent Sci 2024 July/Sept;27 (3): e4375

Oliveira WS et al.

Strain gauge evaluation of bone microstrain in full-arch implant-supported prostheses: cobalt-chromium and fiberglass materials

Oliveira WS et al. Strain gauge evaluation of bone microstrain in full-arch implant-

supported prostheses: cobalt-chromium and ﬁberglass materials

suggesting a better capacity for load absorption

and distribution. On the other hand, the CoCr bars

showed higher microstrain values, particularly

on the Blue strain gauge, indicating a possible

concentration of strain and a less favorable load

distribution, which may negatively inuence bone

integrity and long-term implant stability.

DISCUSSION

Long-term clinical success largely depends

on the appropriate choice of materials and

prosthetic infrastructure design, which should

optimize load distribution and minimize strains

transmitted to peri-implant bone [12].

The significant difference in microstrain

between FRC and CoCr bars can be attributed to

intrinsic material properties. FRC, with its modulus

of elasticity closer to that of human bone tissue,

allows for a more homogeneous load distribution

and reduces the risk of concentrated strain points,

which are detrimental to osseointegration and

implant stability. This nding is corroborated by

previous studies [4,13] which highlighted the

mechanical superiority and biocompatibility of

FRC in dental applications. Thus, when compared

to other bar materials like titanium and CoCr, the

ber-reinforced resin bar exhibited lower weight

and reduced approximately 25% of the generated

strains [14].

On the other hand, the greater microstrain

observed in CoCr bars can be explained by the

rigidity of this material, which, despite its strength

and durability, may lead to inadequate load

distribution. This observation is consistent with

the literature, which emphasizes the importance

of the relative exibility of the prosthetic material

for favorable load distribution [7]. Additionally,

the potential toxicity of CoCr raises additional

concerns about its biocompatibility, especially

considering the release of metallic ions into the

oral environment, which can trigger adverse

tissue reactions [15,16].

The choice between FRC and CoCr should

not be based solely on mechanical considerations

but also on biological, aesthetic, and nancial

criteria. While FRC bars have demonstrated

mechanical and biocompatible advantages in

this study, clinical experience, ease of handling,

and cost are also relevant factors in clinical

decision-making [17].

This study used the strain gauge method to

measure and analyze the biomechanical behavior

of two different material bars. It measures

localized surface strain through changes in

electrical resistance, offers high precision, and

real-time data acquisition, and is relatively

simple and cost-effective to implement [11].

Finite Element Analysis (FEA), a numerical

method that subdivides structures into finite

elements, allows for comprehensive internal

strain analysis across complex geometries and

conditions. Although highly versatile, FEA

requires sophisticated software, and signicant

computational power, and depends heavily on

model accuracy [3]. Photoelasticity employs

polarized light to visualize stress distribution

in transparent materials, providing full-field,

non-intrusive stress patterns. However, it is

predominantly qualitative and limited to specic

materials [13].

Although a single operator performed the

experimental work to ensure a standardized

process, our data must be cautiously extrapolated

to the clinical setting, as the complex biothermal

mechanical factors of the oral environment are

not considered in vitro testing.

This study contributes to the understanding

of the biomechanical implications of different

infrastructure materials in implant-supported

rehabilitations, suggesting that FRC may offer a

promising alternative to CoCr alloys. However,

additional clinical studies are needed to validate

these in vitro ndings and explore the long-term

clinical impact of these observations.

CONCLUSION

This study showed that FRC bars exhibited

significantly smaller microstrain under load

compared to CoCr. The behavior suggests

that FRC is superior in force absorption and

distribution when used for full-arch implant-

supported prostheses. However, the importance

of conducting further research, including clinical

studies, to fully understand the impact of these

results and improve oral rehabilitation techniques

using implants, is emphasized.

Author’s Contributions

WSO: Conceptualization, Methodology,

Writing – Original Draft Preparation, Writing

– Review & Editing. MSO: Writing – Original

Braz Dent Sci 2024 July/Sept;27 (3): e4375

Oliveira WS et al.

Strain gauge evaluation of bone microstrain in full-arch implant-supported prostheses: cobalt-chromium and fiberglass materials

Oliveira WS et al. Strain gauge evaluation of bone microstrain in full-arch implant-

supported prostheses: cobalt-chromium and ﬁberglass materials

Draft Preparation, Writing – Review & Editing,

Translation. ASC: Methodology, Writing –

Original Draft Preparation, Writing – Review &

Editing. GSFAS: Supervision, Writing – Review

& Editing. MAB: Supervision, Writing – Review

& Editing. LNJ: Conceptualization, Supervision,

Writing – Review & Editing.

Conict of Interest

The authors have no conicts of interest to

declare.

Funding

This research did not receive any specic

grant from funding agencies in the public,

commercial, or not-for-prot sectors.

Regulatory Statement

None.

REFERENCES

1. Brånemark PI, Hansson BO, Adell R, Breine U, Lindström J,

Hallén O,etal. Osseointegrated implants in the treatment of

the edentulous jaw. Experience from a 10-year period. Scand J

Plast Reconstr Surg Hand Surg. 1983;16(1):1-132. PMid:356184.

2. Rodriguez AM, Aquilino SA, Lund PS. Cantilever and implant

biomechanics: A review of the literature, Part 2. J Prosthodont.

1994;3(2):114-8. http://doi.org/10.1111/j.1532-849X.1994.

tb00138.x. PMid:9227107.

3. Geringer A, Diebels S, Nothdurft FP. Influence of superstructure

geometry on the mechanical behavior of zirconia implant

abutments: A finite element analysis. Biomed Eng Online.

2014;13(59):501-6. http://doi.org/10.1515/bmt-2013-0088.

PMid:25029078.

4. Bergamo ETP, Bastos TMC, Lopes ACO, de Araujo Júnior ENS,

Coelho PG, Benalcazar Jalkh EB, et al. Physicochemical and

mechanical characterization of a fiber-reinforced composite

used as frameworks of implant-supported prostheses.

Dent Mater. 2021;37(8):e443-53. http://doi.org/10.1016/j.

dental.2021.03.014. PMid:33865619.

5. Menini M, Pesce P, Pera F, Barberis F, Lagazzo A, Bertola

L,etal. Biological and mechanical characterization of carbon

fiber frameworks for dental implant applications. Mater

Sci Eng C. 2017;70(Pt 1):646-55. http://doi.org/10.1016/j.

msec.2016.09.047. PMid:27770938.

6. Pesce P, Lagazzo A, Barberis F, Repetto L, Pera F, Baldi D,etal.

Mechanical characterisationfor of multi vs. uni-directional carbon

fiber frameworks for dental implant applications. Mater Sci Eng

C. 2019;102:186-91. http://doi.org/10.1016/j.msec.2019.04.036.

PMid:31146989.

7. Al Jabbari YS. Physico-mechanical properties and prosthodontic

applications of Co–Cr dental alloys: A review of the literature.

J Adv Prosthodont. 2014;6(2):138-45. http://doi.org/10.4047/

jap.2014.6.2.138. PMid:24843400.

8. Ferreira MB, Barão VA, Faverani LP, Hipólito AC, Assunção WG.

The role of superstructure material on the stress distribution

in mandibular full-arch implant-supported fixed dentures. A

CT-based 3D-FEA. Mater Sci Eng C. 2014;35:92-9. http://doi.

org/10.1016/j.msec.2013.10.022. PMid:24411356.

9. Rodrigues VA, Tribst JPM, de Santis LR, de Lima DR, Nishioka

RS. Influence of angulation and vertical misfit in the evaluation

of micro-deformations around implants. Braz Dent Sci.

2017;20(1):32-9. http://doi.org/10.14295/bds.2017.v20i1.1311.

10. Tribst JPM, Dal Piva AMDO, Rodrigues VA, Borges ALS, Nishioka

RS. Stress and strain distributions on short implants with two

different prosthetic connections–an in vitro and in silico analysis.

Braz Dent Sci. 2017;20(3):101-9. http://doi.org/10.14295/

bds.2017.v20i3.1433.

11. Nishioka RS, Vasconcellos LG, Jóias RP, Rode Sde M. Load-

application devices: a comparative strain gauge analysis. Braz

Dent J. 2015;26(3):258-62. http://doi.org/10.1590/0103-

6440201300321. PMid:26200149.

12. Ahmed MAM, Hamdy AM, Fattah GA, Effadl AKA. Prosthetic

design and restorative material effect on the biomechanical

behavior of dental implants: strain gauge analysis. Braz Dent

Sci. 2022;25(3):e3380. http://doi.org/10.4322/bds.2022.

e3380.

13. Fayad NMEH, Bahig DE. The effect of different framework’s

material on strain induced in distal abutment in mandibular

Kennedy’s class II: an in-vitro study. Braz Dent Sci.

2023;26(3):e3775. http://doi.org/10.4322/bds.2023.e3775.

14. Zaparolli D, Peixoto RF, Pupim D, Macedo AP, Toniollo MB, Mattos

MDGC. Photoelastic analysis of mandibular full-arch implant-

supported fixed dentures made with different bar materials

and manufacturing techniques. Mater Sci Eng C. 2017;81:144-7.

http://doi.org/10.1016/j.msec.2017.07.052. PMid:28887958.

15. Tai Y, DeLong R, Goodkind RJ, Douglas WH. Leaching of nickel,

chromium, and beryllium ions from base metal alloy in an artificial

oral environment. J Prosthet Dent. 1992;68(5):692-7. http://doi.

org/10.1016/0022-3913(92)90388-Q. PMid:1403951.

16. Al-Hiyasat AS, Bashabsheh OM, Darmani H. Elements released

from dental casting alloys and their cytotoxic effects. Int J

Prosthodont. 2002;15(5):473-8. PMid:12375463.

17. Hassan NA, Elkhadem AH, Kaddah A, El Khourazaty NS.

Prosthesis and implant survival in immediately loaded full

arch restorations using fiber-reinforced versus non-reinforced

temporary frameworks: a randomized clinical trial. Braz Dent

Sci. 2022;25(3):e3251. http://doi.org/10.4322/bds.2022.

e3251.

William Simões de Oliveira

(Corresponding address)

Universidade Estadual Paulista, Av. Engenheiro Francisco José Longo,

777 - Jardim Sao Dimas, São José dos Campos, SP, Brazil

Email: drwilliamsimoes@gmail.com

Date submitted: 2024 May 15

Accept submission: 2024 July 29