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.2023.e3909

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

The eﬀects of TiO

nanotubes on bond strength and radiopacity of

a self-adhesive resin cement in self-curing mode

Os efeitos de nanotubos de

TiO

na resistência de união e radiopacidade de um cimento resinoso auto-adesivo no modo

auto-polimerizável

Leandro Edgar PACHECO

, Ana Paula Rodrigues de MAGALHÃES

, Carla Müller RAMOS-

TONELLO

, Lígia Saraiva BUENO

, Orisson Ponce GOMES

, Lucas José de AZEVEDO-SILVA

,

Adilson Yoshio FURUSE

, Paulo Noronha LISBOA-FILHO

, Carmem Silvia Costa PFEIFER

, Ana Flávia Sanches BORGES

, Paulo Afonso Silveira FRANCISCONI



1- Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Dentística, Endodontia e Materiais Odontológicos. Bauru,

SP, Brazil.

2- Universidade Paulista, Curso de Odontologia, Departamento de Dentística. Goiânia, GO, Brazil.

3 – Universidade Estadual Paulista, Faculdade de Ciências, Departamento de Física. Bauru, SP, Brazil.

4 - Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Prótese e Periodontia. Bauru, SP, Brazil.

5 - Oregon Health & Science University, School of Dentistry, Biomaterials and Biomechanics, Restorative Dentistry Department. Portland, OR, USA.

How to cite:

Pacheco LE, Magalhães A

PR, Ramos-Tonello CM, Bueno LS, Gomes OP, Azevedo-Silva LJ et al. The effects of TiO

nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode. Braz Dent Sci. 2023;26(4):e3909.

https://doi.org/10.4322/bds.2023.e3909

ABSTRACT

Objective: The aim of this in vitro study was to analyze the inuence of the titanium dioxide nanotubes in a self-cure mode polymerization of

a dual resin luting agent through push out bond strength and radiopacity tests. Material and Methods: After mixed with a commercial dual

self-adhesive resin cement, three concentrations of titanium dioxide nanotubes (0.3, 0.6, and 0.9% by weight) were analyzed in self-curing

mode. The bond strength to bovine root dentin and berglass posts was assessed with the push out bond strength test and was evaluated in

three thirds (cervical, middle and apical) (n=10), followed by failure mode analysis (SEM), and the ISO standard 9917-2 was followed for

radiopacity test (n=10). Data were statistically analyzed by one-way ANOVA test, followed by Tukey’s test (α=0.05). Results: Reinforced

self-adhesive resin cement with 0.6% titanium dioxide nanotubes showed significant difference compared to the control group for push out

test (p=0.00158). The modified groups did not show significant difference among thirds (p=0.782). Radiopacity showed higher value for

group with 0.9% titanium dioxide nanotubes in comparison with control group (p<0.001). Conclusion: The addition of titanium dioxide

nanotubes to a self-adhesive resin cement increased the bond strength to dentin and radiopacity values in the self-cure polymerization mode.

KEYWORDS

Bond strength; Dental cements; Fiber post; Nanotubes; Radiopacity; Titanium.

RESUMO

Objetivo: O objetivo deste estudo in vitro foi analisar a inuência de nanotubos de dióxido de titânio na polimerização química de um

agente cimentante resinoso dual através de testes de resistência à união e radiopacidade. Material e Métodos: Após misturado com um

cimento resinoso auto-adesivo comercial, três concentrações de nanotubos de dióxido de titânio (0,3, 0,6 e 0,9% em peso) foram analisadas.

A resistência da união para a dentina da raiz bovina e os pinos de bra de vidro foi avaliada pelo teste de push-out e avaliada em três

terços (cervical, médio e apical) (n = 10), seguido pelo análise de modo de falha (MEV) e a norma ISO 9917-2 foi seguido para teste de

radiopacidade (n = 10). Os dados foram analisados estatisticamente pelo teste ANOVA um fator seguido do teste de Tukey (α = 0,05).

Resultados: O cimento resinoso auto-adesivo reforçado com nanotubos de dióxido de titânio a 0,6% mostrou diferença significativa em

comparação com o grupo controle para teste de push-out (p=0,00158). Os grupos modificados não mostraram diferença significativa

entre os terços (p=0,782). A radiopacidade mostrou maior valor para o grupo com nanotubos de dióxido de titânio 0,9% em comparação

com o grupo controle (p<0,001). Conclusão: A adição de nanotubos de dióxido de titânio a um cimento resinoso auto-adesivo aumentou

a os valores de resistência de união à dentina e radiopacidade no modo de polimerização química do agente cimentante.

PALAVRAS-CHAVE

Resistência adesiva; Cimentos odontológicos; Pino de bra; Nanotubos; Radiopacidade; Titânio.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

INTRODUCTION

Self-adhesive resin cements are capable

of bonding to tooth without an adhesive or

etchant phase due to the presence of fillers

able to neutralize the early low pH, functional

acid monomers, and a dual polymerization

system [1,2]. The resin cement interaction

with apatite present at tooth substrate [2-4]

and with the metal oxides from the basic

acid-soluble inorganic fillers results in the

gradual neutralization of the resin cement acidity

as the reaction progress [1,2,5,6]. This is quite

significant, once self-adhesive resin cements

polymerization can be considerably delayed

by low pH via the deactivation of free radicals,

what ultimately can compromise the curing

reaction [2].

There is scarce literature on the evaluation

of self-cure mode of dual self-adhesive resin

cements when used in the absence of light-curing.

This knowledge is of crucial importance, once

decreased mechanical properties have been

demonstrated in the cement line areas where light

penetration is not sufcient [7]. In addition, in

specic cases where light penetration still results

in low intensity being delivered to the material,

studies have shown that the redox portion of the

polymerization may be jeopardized by a partially

gelled/vitried structure. That is known to lead

to lower hardness values when compared to a

material that undergoes redox by itself, where

bond strength is indirectly compromised [7].

Bond strength of self-cure mode polymerization

to dentin is still a complex issue, especially when

related to root canal areas. This chemical interaction

has but a series of factors that can inuence and

harm it of proceeding in a satisfactory way. For

fiber posts cementation cases, the smear layer

and debris created during the instrumentation,

particular characteristics of the root canal as density

and orientation of the tubules, accessibility and

variations in different depths of the same root canal,

can compromise this interaction and be a challenge

for the cementation procedure [8-11].

In order to overcome those limitations and

improve mechanical and adhesive properties,

several studies in literature reported a variability

of nanostructures being added to dental

composites, such as TiO

-nt [12-15]. Compared to

other forms and sizes, the addition of nanotubes

may lead to signicantly improved physical and

mechanical properties, in behalf of a high ratio

of surface area to volume achieved [14,16].

Positive results for a self-adhesive resin cement

enhanced by TiO

-nt were shown in literature,

including improvement in specic mechanical,

biological and physical-chemical properties [15].

These ndings, mainly about the auto-cure mode,

raise questions if other properties might also be

affected by the nanotubes inclusion.

Factors as satisfactory visualization of

cementation line, excess cement and marginal

adaptation are indispensable for a correct

diagnosis and an adequate follow-up of restorative

treatments. Accordingly, radiopacity of these

materials is not only required [17-19], but a

very effective tool to achieve suitable results,

especially considering areas where other forms

of examinations besides radiographic are not

achievable. The addition of metal oxides might

strongly interfere in this property, producing

an increase of the photoelectric cross section

interaction [20]. However, there is still a lack in

literature of radiopacity data for self-adhesive

resin cements enhanced by TiO

-nt.

Therefore, the aim of this investigation

was to determine the bond strength to bovine

root dentin and the radiopacity values of a

self-adhesive resin cement modied by TiO

-nt

at three concentrations only in self-cured

polymerization mode. The null hypothesis of the

present study was that the addition of different

concentrations of TiO

-nt would not affect bond

strength and radiopacity values of self-adhesive

dual resin cement.

MATERIALS AND METHODS

Experimental design

In this in-vitro study, different concentrations

of TiO

-nt (0.3, 0.6 and, 0.9 wt%) [14] were

added to a self-adhesive resin cement (RelyX

U200,3M ESPE, St. Paul, MN). The dual cement

was evaluated only in self-cured mode, and

specimens (sps) were tested through push-out

bond strength test (PBS) and radiopacity test (RO).

In accordance with Ramos-Tonello et al. [15], the

sps were randomly divided in four groups: (SCG)

self-adhesive resin cement, without TiO

-nt

(control group); (S03) self-adhesive resin cement

with 0.3 wt% of TiO

-nt; (S06) self-adhesive

resin cement with 0.6 wt% of TiO

-nt; (S09)

self-adhesive resin cement with 0.9 wt% of

TiO

-nt.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

Specimen preparation

The TiO

-nt were manufactured and

characterized according to the method described

by Arruda et al. [21]. Equal portions of base and

catalyst pastes of RelyX U200 were dispensed by

clicker packing on a paper pad and weighed using

a scale (Pinnacle P-214, Denver Instrument, NY).

After, pre-stablished percentages of TiO

-nt were

weighed using the same scale. TiO

-nt were mixed

by hand to the base paste for 10 s and handled

with the catalyst paste for more 10 s in a room

with ambient light, controlled temperature

(23ºC) and humidity (50%) [15].

Push-out bond strength

Forty bovine anterior teeth, with internal root

canal diameter less than 3 mm and a minimum

length of 30 mm, with not curves, were selected

according to the Animals Use Ethics Committee. The

teeth were cleaned and stored under refrigeration

in a 0.1% Thymol solution. The roots were

separated from the crows to create a standard

access to the root canal and to obtain 17mm length.

Next, the root canal shaping and cleaning were

performed with the working length established at

16 mm with nickel-titanium rotary instruments

(ProTaper Universal, Dentsply Maillefer, Ballaigues,

Switzerland) to the nal F5. After each instrument,

2.5% NaOCl solution (Rioquímica, São José do

Rio Preto, Brazil) irrigation was carried out. The

protocol to remove smear layer was followed with

1 ml 2.5% NaOCl to rinse the canals, 1 ml of EDTA

(Biodinâmica, Ibiporã, Brazil) for 30 s, in sequence

by nal irrigation with 1 ml 2.5% NaOCl and 1ml

distilled water. The root canals were dried with

paper points (Tanari, Manaus, Brazil).

The root canals were filled by lateral

condensation technique with gutta-percha points

size F5 (ProTaper Universal, Dentsply Maillefer,

Ballaigues, Switzerland) and epoxy calcium

hydroxide-based sealer (Sealer 26, Dentsply,

Petrópolis, Brazil). Roots were coronally sealed

with glass ionomer cement (Maxxion R, FGM,

Joinville, Brazil) and stored at 37 ±1ºC in 100%

humidity for 14 days to complete setting the sealer.

After that, the root canals were unsealed

up to 13 mm length using low-speed drills

(Gates-Glidden and Largo Peeso Reamer, Dentsply

Maillefer, Ballaigues, Switzerland). A low-speed

drill, provided by the posts-system manufacturer

(Whitepost DC #2, FGM, Joinville, Brazil) was

used to prepare the posts-space into the root

canals (13 mm length). After rinsed the root

canals with distilled water and dried with paper

points (Tanari, Manaus, Brazil), the glass ber

posts (Whitepost DC #2, FGM, Joinville, Brazil)

were tested in the root canals to check the position

and tting, cleaned with 70% ethanol, dried,

silanized (Silane, Angelus, Londrina, Brazil) with

microbush (Cavibrush, FGM, Joinville, Brazil) for

1 min and dried again. For the luting procedure,

one click of the clicker packing of the resin cement

was used for each post and distributed randomly

in four groups according to experimental design

(n=10). The ber glass posts were covered with

the resin cement modied or not with TiO

-nt and

inserted into the root canals as seen in Figure 1.

Figure 1 - Methods for PBS: root canal shaped (A), root canal ﬁlled with gutta-percha cones and epoxy calcium hydroxide-based sealer (B), and

root canal unsealed until 13 mm length and ﬁberglass post luted (C).

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

This stage was carried out in a room with ambient

light, controlled temperature (23ºC) and humidity

(50%) to ensure the self-cure mode, and after

30 min, the sps were stored in an oven at 37 ± 1ºC

in 100% humidity (articial saliva solution).

After 24 h, the roots were fixed on a

low-speed cutting-machine (Isomet, Buehler,

Lake Bluff, IL) and sectioned with a diamond disc,

under water-cooling, perpendicularly to the long

axis. Nine sps were obtained out of each root:

three cervical, three medial, and three apical as

seen in Figure 2. Each slice (1.0 ±0.2 mm thick)

was measured with a digital caliper (Absolute

Digimatic, Mitutoyo, Tokyo, Japan), marked with

a permanent pen on their apical side and stored

in 3 ml of articial saliva solution at 37 ±1ºC in

a container with coded identier, not disclosed

to the operator (blind trial). After 7 days, the

push-out bond strength test was performed

in a universal testing machine Instron 3342

(Instron Co., Canton, MA) with a 500 Kg (50 N)

load-cell at a cross-head speed of 0.5 mm/min in

the apical-coronal direction. Each slice was placed

on the test base with its coronal side directed to

the device, and aligned with the corresponding

perforation. A plunger compatible with the post’s

diameter (0.9 – 1.1 mm) pushed the post portion,

making no contact with the dentin.

The load failure recorded in Kgf was divided

by the area (mm

) to converted the values in MPa.

The formula A = π (R2+R1) [h

+ (R2-R1)

]

0.5

was used to nd the bonding area where π value

it is 3.14, R2 represents the fragment coronal

radius [9].

After testing, the failure modes were analyzed

with a 200 × magnication optical microscope

(Dino - Lite Plus Digital Microscope, AnMo

Eletronics Co., Taipei, Taiwan) and categorized

as: 1) A - C/D (adhesive between the cement

and the dentin); 2) A - C/P (adhesive between

the cement and the post); 3) CP (cohesive in the

post); 4) CC (cohesive in the cement); 5) Mixed

(adhesive and cohesive simultaneously). The

three more representative failures of each group

were processed for analysis in Scanning Electron

Microscopy (SEM) by variable pressure, APEX

Express (APEX Corporation, Delmont, PA) with

400 and 1000 × magnication.

Radiopacity

Forty resin cement sps were manufactured

with a split polytetrauoroethylene mold, as seen

in Figure 3A, according to ISO 9912-2:2010 [22],

by the same operator and divided in the groups

determined: SCG, S03, S06 and S09 (n=10).

Three clicks of the clicker packing resin cement

were used and the TiO

–nt were added according

to the group being prepared. The resin cement

was handled in a room with ambient light and

inserted in a single portion in the mold to slightly

overll it. After 30 min, the resin cement sps

were removed from the mold and checked with a

digital caliper to guarantee 1.0 ±0.1 mm of nal

thickness. Then, sps were stored in grade 3 water

(ISO 9912-2:2010), during 7 days.

The RO test was carried out up to 30 min

after removing the sps from deionized water.

The images were obtained by an occlusal lm

size X-ray sensor (Intraoral image plate #4,

VistaScan, Dürr Dental, Bietigheim-Bissingen,

Germany), previously calibrated for use with

single-phase dental X-ray unit with appropriate

software (VistaScan Perio Plus, Dürr Dental,

Bietigheim-Bissingen, Germany). One specimen

of each group and an aluminum step wedge were

placed on the top of the lm, as seen in Figure 3B.

This aluminum device was used to convert the

radiopacity in equivalent mm of aluminum.

Figure 2 - Methods for PBS: root with ﬁberglass post luted (A), root at the cutting machine (B), and slices of the root (specimens): tree of each third

(

– cervical third;

– medium third;

– apical third) (C).

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

Radiographic images were obtained with a

conventional dental X-ray equipment (Yoshida

Kaycor, X-707, Tokyo, Japan), at 70 kVp and 7

mA. The exposure time 30 s at a distance of 400

mm as seen in Figure 3C. Three images were

obtained of each set X-rayed, which was led

in 1070 dpi resolution, in JPG format as seen

in Figure 3D. Digital images were evaluated for

optical density by grey scale analysis software

(Adobe Photoshop CC 2017, Adobe Systems

Incorporated, CA), by the same operator. The

grey scale values for the aluminum stepwedge

(3 points in each step) and for all specimens

(5 points in each specimen) were measured and

the correspondent means were calculated.

The RO value was converted in aluminum

millimeters by the formula A × 1/B + mm/Al

immediately below RDM where A represents the

aluminum stepwedge increment immediately below

to the RDM, 1 the mm increment between each

aluminum stepwedge, B the aluminum stepwedge

immediately above to the RDM and RDM is the

radiographic density of the material [23].

Figure 3 - Methods for radiopacity: Split polytetraﬂuoroethylene mold (15.0 mm ø x 1.0 mm) (A). X-ray sensor, specimens and aluminum step

wedge (B). X-ray sensor, specimens and aluminum step wedge positioned at 400mm from the X-Ray device (C). Digital image in JPG format (D).

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

Statistical analysis

Statistical analysis was carried out with the

software Stat Soft (Statistica v10.0 Entrerprise,

TBICO Software Inc., CA). PBS and RO values

were subjected to the Kolmogorov-Smirnov and

Shapiro-Wilk normality tests and data were

normally distributed. Then, data were analyzed

by one-way ANOVA test, followed by post hoc

multiple comparisons Tukey’s test. ANOVA with

repeated measures was performed to compare

PBS per thirds at the α = 0.05 signicance level.

RESULTS

The results for PBS per root are presented

in Table I. S06 (7.12 ± 1.89 MPa) group showed

signicant difference for the SCG (4.30 ± 1.03 MPa)

(p=0.001580). For PBS per thirds, the results are

presented in Figure 4, which the modied groups

did not show signicant difference among thirds

(p=0,782). Figure 5 shows the failure distribution

(in %) for PO. The PO failure analysis - SEM images

obtained for each failure type in representative

samples from the evaluated groups are presented

in Figure 6A–E.

The RO analysis is present in Table II. The

variance of the RO values showed correlation

with the addition of TiO

-nt. All groups complied

with the minimal value established. S09 (2.27 ±

0.11) group showed signicant difference for the

SCG (2.00 ± 0.16) (p<0.001).

DISCUSSION

The null hypothesis of the present study

was rejected since it showed that adding variable

concentrations of titanium dioxide nanotubes affects

bond strength and radiopacity of self-adhesive resin

cement in self-cure mode. RelyX U200 is indicated for

the luting of berglass posts, and in fact, self-adhesive

resin cement has shown higher push-out bond

strength values than conventional resin cement in all

thirds of the root canal dentin [24,25]. However, the

dual resin cements rely on the light-curing process

to reach the highest conversion degree. As a result,

it is considered that a low conversion degree can

cause poor bond strength values, mainly in areas

where light-curing is weaker, such as root canal

apical portions [25].

According to the literature, the push-out

test chosen for this study is considered the best

simulation of clinical conditions and provides a

better assessment of the adhesion mechanism

once it evaluates the structural variations of

the dentin substrate in the root canal [8,26].

In this study, the results for PBS showed an

increase in the S06 group compared to SCG.

Table I - Means and standard deviations for PBS (per root)

Groups PBS (MPa)

SCG 4.30 (1.03)

S03 4.12 (0.99)

S06 7.12 (1.89)

S09 5.16 (2.04)

Lowercase letters show signiﬁcant statistical diﬀerences among

groups (p=0.00040).

Table II - Means and standard deviations for radiopacity (RO)

presented as follows

Groups RO

SCG 2.00 (0.16)

b,c

S03 1.96 (0.15)

S06 2.19 (0.20)

a,b

S09 2.27 (0.11)

Lowercase letters show signiﬁcant statistical diﬀerences between

lines ( p=0.000254).

Figure 4 - PBS values (mean ± standard deviation) of all groups

tested (per thirds).

Figure 5 - Values (%) failure analysis of each group tested for PBS.

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

An increased conversion can be suggested to be

the reason for that result, as previous reports

showed an enhanced degree of conversion of an

auto-adhesive resin cement with the addition of

TiO

-nt at 0.3% to 0.9 wt% [15]. Adding these

percentages may play a role in initial viscosity,

which inuences the mobility of polymerizing

species [27]. The increase in viscosity was

sufcient to decrease the rate of termination.

This fact allowed propagation to proceed to a

greater extent in conversion, but not as dramatic

to decrease the propagation rate – the net result is

likely an increase in conversion [27]. Even though

polymerization kinetics was not evaluated here,

the increase in push-out bond strength in tandem

with previously reported results [15] adds

evidence for using TiO

-nt modied materials in

clinical conditions relying predominantly on the

self-cure mode, as glass bers posts.

The decrease in bond strength at deeper

portions of the root canal is a concern that

remains in literature. Many studies exhibited

lower values of push-out strength in the apical

third when compared to the cervical and middle

thirds; this has been attributed to the difculty to

access deep and tight areas with the instruments

available, the decient elimination of the smear

layer before the luting procedure, and the low

penetration of resin cement into the dentin root

canal [8,24,28]. In addition, these regions are

far from photoactivation unit access, possibly

affecting the conversion degree of the resin

cement. It is well stablished that the use of light

activation during polymerization of dual-cured

materials leads to higher degree of conversion

values [26,29]. This study has shown promising

results in comparison per thirds, once the

result of apical thirds presented the same value

compared to the medium and cervical thirds.

These results showed no statistical difference

among the thirds for all groups evaluated,

however, an analysis of the photopolymerization

factor could respond other influence of the

modification of these cements. Besides, the

failure analysis exhibited results in accordance

with literature [24,30,31] with predominance

of adhesive failures in all thirds and all groups.

These results revealed that the cement/dentin

interface was more prevalent in the SCG, S03

and S06, while in the S09 group the cement/post

interface was the most observed, as observed in

SEM images on Figure 6.

Another crucial property for limited

light-curing access areas in cementation procedures

is radiopacity, which plays a critical role in

secondary caries diagnosis, detection of cement

excess, examination of open gingival margins or

marginal excesses [20,32-34]. The International

Organization for Standardization (ISO) for

resin-modified cements requires radiopacity

values equal to or greater than that of the same

thickness of aluminum (ISO 9912-2:2010) [22].

Figure 6 - PBS failure analysis - SEM image of each group showing failure type: Failure 1 (A-C/D) of a slice #3 of the cervical third of S03

group (A); Failure 2 (A-C/P) of a slice #2 of the cervical third of S03 group (B); Failure 3 (CP) of a slice #2 of the cervical third of S09 group (C);

Failure 4 (CC) of the slice #1 of the apical third of S03 group (D); Failure 5 (M) of a slice #2 of the cervical third of S09 group (E).

Braz Dent Sci 2023 Oct/Dec; 26 (4): e3909

Pacheco LE et al.

The effects of TiO2 nanotubes on bond strength and radiopacity of a self-adhesive resin cement in self-curing mode

Pacheco LE et al.

The eﬀects of TiO

nanotubes on bond strength and radiopacity

of a self-adhesive resin cement in self-curing mode

The radiopacity values of dentin and enamel

vary between 0.9 - 1.0 and 1.8 - 2.0 mm Al [35].

Furthermore, several studies have been carried out

using radiopaciers to modify the radiopacity of

dental cements [36,37]. Overall, groups SCG, S03,

S06, S09 complied for material radiopacity and

exceeded the radiopacity of enamel and dentin,

with values ranging between 1.90 - 2.37 mm

Al. Furthermore, S06 and S09 groups exhibited

higher values in comparison with SCG which

both demonstrated signicant difference in the

statistical analysis. These results are in accordance

with the literature, which reports TiO

-nt as a

suitable radiologic contrast agent [20], and are

interesting from a clinical point of view, enabling

more accurate follow-up of the respective cases.

It is important to understand the self-cured

reaction of the dual self-adhesive resin cements

as an element to better predict the cement

behavior in this condition. This cure mode should

be considered especially in areas with restricted

access to light as berglass posts cementation [38].

The data performed in the present study along with

the good results already presented in literature for

degree of conversion, mechanical strength, cell

viability [15]. Thus, the feasibility of use of this

modied material in the future depends on further

studies and clinical trials, in order to be grounded

in solid evidence to predict better clinical longevity

for the respective indications. Both characteristics

evaluated can benet clinical situation increasing

longevity of indirect restorative procedures, with

better adhesion of berglass posts to dentin in

regions with lower light access. Similarly, a major

radiopacity may help the diagnosis of the proper

sealing of the resin cement.

CONCLUSIONS

The addition of 0.6% and 0.9% TiO2-nt

increased the bond strength and radiopacity values

in a self-cure mode of a dual self-adhesive resin

cement, respectively. Based on the nanostructure’s

inuence on the materials’ behavior, adding TiO2

nanotubes proved to be a promising additive for

these materials, aiming to improve the adhesive

longevity of indirect restorations.

Acknowledgements

The authors thank FGM for providing berglass

posts. The authors are also grateful to Fernanda

Sandes de Lucena and Lorena de Mello Alcântara

Garrido for the contribution in this study.

Author’s Contributions

LEP: Conceptualization, Methodology,

Formal Analysis, Writing - Original Draft

Preparation. APRM, CMRT: Conceptualization

Methodology, Investigation, Formal Analysis.

LSB, OPG: Methodology, Investigation, Formal

Analysis. LJAS: Methodology, Investigation,

Formal Analysis. AYF: Formal Analysis, Writing

- Review & Editing, Visualization. PNLF and

CSCP: Formal Analysis, Writing - Review &

Editing, Visualization. AFSB: Conceptualization,

Writing - Review & Editing, Visualization, Project

Administration. PASF: Conceptualization, Writing

- Review & Editing, Visualization, Supervision,

Project Administration, Funding Acquisition.

Conict of interest

There are no conicts of interest to declare.

Funding

This study was supported in part by the

Coordenação de Aperfeiçoamento de Pessoal de Nível

Superior – Brazil (CAPES - nance code 001) and

Conselho Nacional de Desenvolvimento Cientíco

e Tecnológico - Brazil (CNPQ - #133504/2017-4).

Regulatory Statement

This study was conducted in accordance with

all the provisions of the local human subjects

oversight committee guidelines and policies of:

CEUA/FOB/USP.

The approval code for this study is: 003/2019.

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Ana Flávia Sanches Borges

(Corresponding address)

Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de

Dentística, Endodontia e Materiais Odontológicos. Bauru, SP, Brazil

Email: afborges@fob.usp.br

Date submitted: 2023 Jun 26

Accepted submission: 2023 Nov 16