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.2025.e4609

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

This is an Open Access article distributed under the terms of the Creative Commons Attribution license (https://creativecommons.org/licenses/by/4.0/), which permits

unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

Desgaste de dois sistemas de attachments diferentes em overdentures mandibulares suportadas por implantes: um estudo

clínico comparativo

Ammar Omar BELAL1 , Moataz Mostafa Bahgat ELMAHDY1 , Sayed Mohammed Mohammed ELMASRY1 ,

Mohamed Ezzat ELSAYED1 

1 - Suez Canal University, Faculty of Dentistry, Prosthetic Dentistry, Ismailia, Egypt.

How to cite: Belal AO, Elmahdy MMB, Elmasry SMM, Elsayed ME. Wear of two different attachment systems in implant supported

mandibular overdentures: a clinical comparative study. Braz Dent Sci. 2025;28(1):e4609. https://doi.org/10.4322/bds.2025.e4609

ABSTRACT

Introduction: The stud attachment is regarded as one of the most popular systems for the retention of removable

overdentures. A new type of PEEK attachment system, such as Novaloc, may have a good prognosis compared

to other systems. Aim of the study: The purpose of this clinical study is to compare two different attachment

systems, Novaloc and Locator, regarding wear resistance under implant-supported overdentures. Material and

Methods: The research sample consisted of 10 patients with complete lower and upper edentulous. A complete

lower denture was made supported by two implants, with a conventional complete denture for each patient. The

patients were divided equally into Group 1: Novaloc attachment system. Group 2: Locator attachment system.

The wear measurements were done using a digital stereomicroscope and repeated after 4, 8, and 12 months. The

data was collected, calculated, and statistically analyzed using the SPSS program. Results: According to One-way

ANOVAs and independent T-test and throughout the observation period (P-Value > 0.05). The results showed

the presence of wear in both attachment systems, but with statistically signicant differences, as the amount of

wear was greater in the Locator group compared to the Novaloc group. Conclusion: Under the circumstances

of this study, it can be concluded that the Novaloc attachment system is superior to the Locator in terms of its

resistance to wear during the observation period of 1 year when compared to the Locator system.

KEYWORDS

Attachments; Locator; Novaloc; Nylon; Overdenture; PEEK; Wear.

RESUMO

Introdução: A xação por Attachments é considerada como um dos sistemas mais populares para a retenção de

overdentures removíveis. Um novo tipo de sistema de xação PEEK, como o Novaloc, pode ter um bom prognóstico

em comparação com outros sistemas. Objetivo do estudo: O objetivo deste estudo clínico é comparar dois sistemas

de Attachments diferentes, Novaloc e Locator, com relação à resistência ao desgaste sob overdentures suportadas

por implantes. Material e Métodos: A amostra da investigação foi constituída por 10 pacientes desdentados totais

inferiores e superiores. Foi realizada uma prótese total inferior suportada por dois implantes, e uma prótese total

convencional para cada paciente. Os pacientes foram divididos igualmente em Grupo 1: Sistema de xação Novaloc.

Grupo 2: Sistema de xação Locator. As medições de desgaste foram efetuadas utilizando um estereomicroscópio

digital e repetidas após 4, 8 e 12 meses. Os dados foram recolhidos, calculados e analisados estatisticamente

utilizando o programa SPSS. Resultados: De acordo com as ANOVAs One-way e o teste T independente ao longo

do período de observação (p-valor > 0,05). Os resultados mostraram a presença de desgaste em ambos os sistemas

de xação, mas com diferenças estatisticamente signicativas, pois a quantidade de desgaste foi maior no grupo

Locator em relação ao grupo Novaloc. Conclusão: Nas circunstâncias deste estudo, pode-se concluir que o sistema

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

INTRODUCTION

Retention and stability are important factors

in the successful fabrication of a complete

denture [1,2]. Today implant-supported

mandibular overdentures retained by two

implants with unpainted systems (ring-ball-

cylindrical types) or splinted systems (bar

attachment) associated with a maxillary complete

denture have been proposed as the rst choice of

treatment for edentulous patients [3], and this

treatment seeks to provide better stability and

retention of the mandibular complete denture,

thus improving the masticatory function of

the patient and providing greater satisfaction,

better oral health-related quality of life and

comfort, therefore, knowledge of the different

attachment systems and an understanding of their

mechanical properties, such as retention and load

distribution, could help clinicians select the proper

attachment for each case [4,5]. The cylindrical

attachment systems, which were made from PEEK

material, such as the Novaloc or nylon systems

like the Locator, were created to address specic

indications, such as smaller prosthesis spaces,

because of their improved retention and smaller

size [6,7]. Due to its improved dual retention

over the last two decades, the locator has become

the most cylindrical type with the lowest prole

height. The matrix is composed of a polyethylene

retention device and a 1.2 mm internal retention

pin that can withstand an 8-degree maximum

angulation in all directions [8-10]. But like any

mechanical equipment, the locator will inevitably

develop more mechanical issues with time. The

male nylon inserts of the locator attachment have

been seen to wear out excessively and demand

more maintenance over time, which has resulted

in a loss of retention [11]. On the other hand,

the Novaloc retention device is placed in titanium

or Poly-ether-ether-ketone (PEEK) casings and is

constructed of PEEK to increase wear resistance,

which revealed encouraging ndings in a few in

vitro studies of the long-term retention of peek

retention devices [12-14]. To date of this article,

there are not many clinical studies comparing

these two types, although there was a study

by Abdelaziz et al. 2021 [15] which compares

the PEEK and nylon insert in the locator system

only. Therefore, to reduce this gap in existing

literature, this clinical study was conducted to

assess these two different attachment systems,

Novaloc and Locator, regarding wear resistance

under implant-supported overdentures.

MATERIALS AND METHODS

This clinical research was a case-controlled

trial. It was made at the Department of Prosthetics

Dentistry at the Faculty of Dentistry at Suez Canal

University, after the Scientic Research Ethics

Committee with code number: 2021-40.

The research sample consisted of ten

complete edentulous patients. The sample

size was calculated using Open-Epi version

3.01 (Emory University, USA) at a condence

interval of 95% with one ratio to compare equal

groups.

The patients were selected randomly without

regard to gender or age. All the patients had

good oral and physical health and were accepted

based on the following inclusion criteria: all

patients had maxillary and mandibular alveolar

ridges covered with healthy tissue, Sufficient

mandibular alveolar bone conrmed by CBCT,

six months at the last extraction, and sufcient

inter-jaw space, which was conrmed using the

putty index technique. Exclusion criteria were

parafunctional habits, alcoholism, a history of

radiation therapy in the head and neck region or

temporomandibular joint disorders, and systemic

diseases that can affect the success of implants.

After explaining the work and study steps to

the patients and obtaining their approval through

consent. A conventional acrylic complete upper

and lower removable denture was produced using

the standard procedures that are recognized in

the academic community. Primary upper and

lower impressions were taken as part of the

process, and a nal impression was taken using

cold acrylic cured trays after border molding to

create the wash impression. The jaw relation was

de xação Novaloc é superior ao Locator em termos da sua resistência ao desgaste durante o período de observação

de 1 ano, quando comparado com o sistema Locator.

PALAVRAS-CHAVE

Attachments, Novaloc, Locator, overdenture, Wear, PEEK, Nylon.

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

then registered using record bases, articial teeth

were arranged, try-ins were made, dentures were

waxed up, asking procedures were made, and

the outcome was made in the patient’s mouth

with any modications that were required for

the dentures.

After that, the patients were divided equally

into: Group 1: Novaloc attachment system. Group

2: Locator attachment system.

A apless implant placement approach and

conventional loading were intended. Therefore,

a surgical guide was made using the CAD-CAM to

guarantee the implant’s accurate placement and

orientation in the canine area (Figure 1).

Each patient received two bone Straumann

implants (Straumann Dental Implant System,

Switzerland), which were 3.3 mm in diameter

and 13 mm in length. (Figure 2). After three

months, and according to the conventional

loading protocol to ensure that the implants can

be loaded. Implants were assessed clinically,

showing no signs of pain or inflammation,

and a radiograph image demonstrated no

bone resorption around the implants. After

that, implants were exposed, and mounting of

the implant system smart peg. The resonance

frequency analysis system (Mega ISQ System,

South Korea) was used to evaluate the secondary

stability and readiness to be loaded based on

scientic recommendations.

After that, both Novaloc (Straumann,

Möhlin, Switzerland) and Locator (Zest Anchors,

Escondido, USA) were placed in the implants and

tightened using the driver for each attachment

and tightened using the torque ratchet wrench

according to the manufacturer’s instructions

(30 Newton). For all patients, the direct

pick-up method was applied to incorporate

Novaloc retention inserts and Locator retention

replacement males (Figure 3).

Wear measurements were done immediately

after the placement of the dentures at the

Faculty of Agriculture at Mansoura University,

utilizing a professional camera (10MP Tucsen

Figure 1. (a) Intraoral view of the upper jaw. (b) Intraoral view of the lower jaw. (c) Conventional Complete denture. (d): surgical guide design

with parallel axes.

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

Figure 2. (a) Check parallelism. (b) Straumann Dental Implant System.

Figure 3. (a) Novaloc attachments were screwed. (b) Novaloc retention inserts. (c) Locator attachments were screwed. (d) Locator retention

replacement male.

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

(Figure 4). All attachment inserts for both

groups were captured on camera under the same

conditions when shooting for documentation

to ensure that replicate experiments can be

accurately repeated. The digital photos were

loaded onto a desktop computer and analyzed

using software (Tucsen Mono Microscope

ISH1000, China) to measure dimensions. Two

perpendicular axes were used in measuring the

inside circumference of the insert (A and B) for

both groups in millimeters (mm) with a maximum

of two decimal places. In addition to two other

axes for the diameter of the central plastic core

(C and D) for the locator group (Figure 5).

The observation period was one year, so all

measurements were repeated 4, 8, and 12 months

after the rst session, and changes in attachment

sizes were noted by tracking the results (Figure 6).

The data were collected, tabulated, and

statistically analyzed using SPSS version 26.0 for

Windows, and the normality test (Shapiro-Wilk)

was used for normality, and the independent

sample t-test was used to compare the two

groups, the level of signicance (p-value) was

set at 0.05.

RESULTS

The stereomicroscope demonstrated the

surface characteristics and internal dimensions of

Novaloc retention inserts and Locator retention

Figure 4. The stereomicroscope (Olympus SZ61, Japan) beside the

camera (10MP Tucsen USB2.0 H series, ISH 1000, China).

Figure 5. Wear measurements using stereomicroscope, (a) Novaloc retention inserts. (b) Locator retention replacement male. A software

program (Tucsen Mono Microscope ISH1000, China) was used to measure the inner circumference of both Novaloc and locator (Axis A, B in

blue color, beside the plastic core of Locator Axis C, D in green color).

USB2.0 H series, ISH 1000, China) attached to

a stereomicroscope (Olympus SZ61, Japan) at

15× magnication. A stereomicroscope was used

to assess wear by measuring internal dimensions

and changes in them during observation periods

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

replacement males, but due to the difculty of

measuring surface roughness accurately, as the

microscope used was not a scanning electron

microscope (SEM), because the study was

clinical, and the difculty of coating the insert

with the gold layer necessary to show the surface,

as is the case in in-vivo studies, only dimensions

were measured.

The standard dimensions were measured

at time T0 before their functional use in the

patient’s mouth. The used Novaloc retention

inserts and Locator retention replacement males

suffered from adhesive, abrasive, and cohesive

wear after two observation periods, T1 and T2,

with a change in their dimension; however, it

was larger in the locator group, but during the

nal observation, the locator group experienced

clear surface fatigue, exhibiting clear deformation

and an increase in the outer circumference of

the retention replacement males compared to

Novaloc retention inserts, while the dimensions

of the central plastic core have decreased. The

results showed a statistically signicant difference

between the Novaloc Attachment group and the

Locator Attachment for wear along the T0 and

T3 periods using an independent sample T-test

at P<0.05. Generally, the Locator Attachment

group had higher values for wear compared

with the Novaloc Attachment group at different

periods (Table I).

Figure 6. Stereomicroscope image for diﬀerent periods of observation, with noticeable deformity and deterioration: (a, b) Novaloc retention

inserts. (c, d) Locator retention replacement.

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

DISCUSSION

This study was conducted to assess the

clinical performance of two different attachments,

Novaloc and Locator, in terms of wear-through

dimension changes on retention devices of the

attachments using a stereomicroscope [16].

According to scientific reference, the

definition of wear is the gradual removal or

deformation of material from solid surfaces

during their function, which can be attributed to

mechanical or chemical causes [17]. wear that

occurred has several potential explanations that

are associated with the clinical environment of

the two attachments, implant angulation, design,

and component wear [10]. In other words, the

observed wear can be attributed to the continuous

mechanical and thermal stimuli that attachment

systems experience within the oral cavity, which is

caused by patient manipulation of the prosthesis,

including insertion and removal, masticatory

wear, the acidity of the food eaten by the patient,

and deterioration resulting during the cleaning of

the prosthesis [18]. Although most of the research

comparing the two attachments was conducted in

a lab setting in contrast to this clinic study, oral

circumstances may vary amongst patients, such

as occlusions or mastication cycling on resorbed

alveolar ridges. This will lead to denture rotation

around the attachment, ultimately causing

retention loss because of matrix wear [19,20].

Based on several studies, found the nylon of

the Locator retention replacement male was

strongly affected by simulated mastication [14],

in addition to the effect of the act of insertion and

removing the denture or cleaning and brushing

it, which could lead to increased wear on the

attachments especially for Novaloc [21].

The other reason may be attributed to the

slight differences in the surgical guide between

the design and its manufacture [22], besides the

effect of the length of the implant; as its length

increases, the possibility of it deviating laterally

increases [23], and since the surgical guide used

was supported by mucosa, there was a greater

distance between the sleeve and the bone, a

greater error in determining the exact depth

of the implant in order to achieve symmetry,

or an occlusal height equal to the implant. On

the opposite side [24], subsequently will affect

the angulation and position of the implants

and attachments, which the clinic operators

cannot see, but their effect on wear will become

apparent later, as Misch and Resnik [25] said

about attachment complications: If one implant

is higher than the other, the prosthesis will

disengage from the lower implant during function

and rotate primarily on the higher implant.

This situation will accelerate the wear. If one

implant is farther from the midline, it will serve

as the primary rotation point or fulcrum when

the patient occludes in the posterior segments.

In such a case, the more medial the implant

attachment, the faster it will wear, and even

a small amount of angulation will cause an

undercut and raise the wear rate, this agrees

with Choi et al. [12] and Arnold et al. [26] who

showed the superiority of Novaloc over Locator

during their laboratory studies in the case of

parallel and non-parallel implants.

Regarding the design and component

factors, as is well known, the two attachments

have a cylindrical form and rely on mechanical

friction between the abutment and each inner

surface retention device to obtain uniform

retention in all undercut areas [27]. Added

retention of the locator due to the joint’s dual

retention design, which has a higher contact

surface than the Novaloc and thus higher friction;

this designation does not exist in the Novaloc, but

on the contrary, there is a side groove to expand

the Novaloc attachment during the insertion and

Table I - Comparison between Novaloc Attachment and Locator Attachment in each time.

Novaloc Attachment Group Locator Attachment group Independent

T-test p-value

mean SD mean SD

T0 2.780 0.204 4.018 0.123 16.42 <0.005

T1 2.900 0.149 4.210 0.137 20.46 <0.005

T2 2.930 0.170 4.540 0.135 23.43 <0.005

T3 3.040 0.117 4.750 0.158 27.46 <0.005

SD: standard deviation; p: P value for comparing between the studied Groups. Statistically signiﬁcant at p ≤ 0.05

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

removal of the denture, thus relieving pressure

and friction on the inner surface [12].

Used materials to make the retention device

is the other explanation. Polyethylene or nylon,

which has been employed in the locator because

of its elasticity and biocompatibility, exhibits

significant deformation and needs a lot of

maintenance. This may be explained by the low

resistance of polyethylene to scratches, despite its

exibility, but the roughness of the surface and

the disappearance of the outer layer will lead

to increased absorption of oral uids more than

PEEK in Novaloc [28], thus increasing its size

and hardness, and thus increasing the effect of

friction. Novaloc is made from PEEK, a material

with high biocompatibility, good mechanical

properties, high-temperature resistance, chemical

stability, polishability, and good wear resistance

to fatigue and tensile stress [29]. This may

explain the ndings of some laboratory studies

that showed a large drop in locator retention

compared to a decline in Novaloc throughout

the same period [12]. Although it must be noted

that within the observation period of this study.

The performance of both attachments was

satisfactory, but results are still consistent with the

study of Wakam et al. [30] and Choi [19] about

the inevitable occurrence of wear, regardless of the

type of attachment used, and also agree with de

Souza et al. [31], Passia [13], and Maniewicz [14]

on the good prognosis of Novaloc compared with

Locator, although the study by Koenig et al. [32]

linked the decreasing and aging of Novaloc’ s

ability to retain overdentures with chemical

cleaning agents.

The ndings Strengthen that clinicians might

prefer the Novaloc attachment for patients who

require implants or prosthetics expected to endure

signicant use or wear. However, given the limited

sample size and observation duration, additional

studies with larger extended follow-up periods

are recommended to conrm these ndings and

fully assess the long-term performance and patient

outcomes associated with both attachment types.

CONCLUSION

Within the limitations of this study in terms

of the sample size and duration of observation,

the following can be concluded: The Novaloc

attachment exhibited better wear resistance,

indicating that it may maintain its functional

integrity and performance over time more

effectively than the Locator attachment. This

characteristic is crucial for long-term success

in clinical applications, especially in scenarios

involving repetitive stress or loading.

LIMITATION

This study has limitations due to a

small sample size of 10 patients, affecting

generalizability and statistical power. To address

this issue, it would be recommended to use non-

parametric tests and multiple imputations to

account for missing data. While these methods

can help improve the study’s validity, they are not

a substitute for a larger sample size.

Acknowledgements

This article is part of clinical research

prepared for a doctoral degree, and it considers all

academic and ethical standards of clinical work,

with the patient’s consent to work according to

internationally recognized legal frameworks and

according to the instructions of the Faculty of

Dentistry at Suez Canal University in Egypt. All

appreciation to the supervisors who assisted in

the preparation of the research.

Data Availability Statement

All data relevant to this study are included

in the manuscript.

Author’s Contributions

AOB : Conceptualization, data curation,

Writing – Original Draft Preparation, Writing –

Review & Editing. MMBE: Supervision. SMME:

Supervision. MEE: Supervision.

Conict of interest

Regarding any product, service, and/or

company mentioned in this article, the authors

have no nancial, proprietary, or other personal

interest of any kind.

Funding

This research did not receive any specic

grant from funding agencies in the public,

commercial, or not-for-prot sectors.

Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

Regulatory Statement

This study was conducted in accordance

with all the provisions of the local human subject

oversight committee’s guidelines and policies

of the ethical committee, and according to the

instructions that are involved in the Faculty of

Dentistry, Suez Canal University. The approval

code for this study is: 2021-406, Faculty of

Dentistry, Suez Canal University.

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Braz Dent Sci 2025 Jan/Mar;28 (1): e4609

Belal AO et al.

Wear of two different attachment systems in implant supported mandibular overdentures: a clinical comparative study

Belal AO et al. Wear of two diﬀerent attachment systems in implant supported

mandibular overdentures: a clinical comparative study

Date submitted: 2024 Dec 01

Accept submission: 2025 Mar 28

Ammar Omar Belal

(Corresponding address)

Suez Canal University, Faculty of Dentistry, Prosthetic Dentistry, Ismailia, Egypt.

Email: Ammar_belal@dent.suez.edu.eg

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