1-s2.0-S188319581300131X-main

j o u r n a l o f p r o s t h o d o n t i c r e s e a r c h x x x ( 2 0 1 4 ) x x x x x x

JPOR-219; No. of Pages 8Position Paper

Clinical application of removable partial denturesusing thermoplastic resinPart I: Definition andindication of non-metal clasp dentures

Kenji Fueki DDS, PhDa,d,*, Chikahiro Ohkubo DMD, PhDb,c,e,Masaru Yatabe DDS, PhDb,d,f, Ichiro Arakawa DDS, PhDb,c,g,Masahiro Arita DDS, PhDb,c,h, Satoshi Ino DDS, PhDb,i,Toshikazu Kanamori DDS, PhDb,j, Yasuhiko Kawai DDS, PhDb,c,k,Misao Kawara DDS, PhDb,l, Osamu Komiyama DDS, PhDb,l,Tetsuya Suzuki DDS, PhDb,c,m, Kazuhiro Nagata DDS, PhDb,n,Maki Hosoki DDS, PhDb,o, Shin-ichi Masumi DDS, PhDb,h,Mutsuo Yamauchi DDS, PhDb,p, Hideki Aita DDS, PhDa,q,Takahiro Ono DDS, PhDa,r, Hisatomo Kondo DDS, PhDa,s,Katsushi Tamaki DDS, PhDa,t, Yoshizo Matsuka DDS, PhDa,o,Hiroaki Tsukasaki DDS, PhDa,u, Masanori Fujisawa DDS, PhDa,v,Kazuyoshi Baba DDS, PhDa,u, Kiyoshi Koyano DDS, PhDa,w,Hirofumi Yatani DDS, PhDx

a Japan Prosthodontic Society, Clinical Guideline Committee (20112012), Japanb Japan Prosthodontic Society, Non-Metal Clasp Denture Expert Panel (20112012), Japanc Japan Prosthodontic Society, Removable Prosthodontics Expert Panel (20112012), JapandSection of Removable Partial Prosthodontics, Tokyo Medical and Dental University, JapaneDepartment of Removable Prosthodontics, Tsurumi University School of Dental Medicine, JapanfTokyo Branch, JapangDepartment of Partial and Complete Denture, School of Life Dentistry at Tokyo, The Nippon Dental University, JapanhDivision of Occlusion & Maxillofacial Reconstruction, Department of Oral Function, School of Dentistry, Kyushu

Dental University, JapaniKanagawa Dental University, Yokohama Clinic, JapanjTohoku & Hokkaido Branch, JapankDepartment of Removable Prosthodontics, Nihon University School of Dentistry at Matsudo, JapanlDepartment of Oral Function and Rehabilitation, Nihon University School of Dentistry at Matsudo, Japanm Section of Oral Prosthetic Engineering, Tokyo Medical and Dental University, JapannComprehensive Dental Care, The Nippon Dental University Niigata Hospital, JapanoDepartment of Fixed Prosthodontics, Institute of Health Biosciences, The University of Tokushima, Graduate School,

Japan

* Corresponding author at: Section of Removable Partial Prosthodontics, Department of Masticatory Function Rehabilitation, GraduateSchool of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, 113-8549 Tokyo, Japan.Tel.: +81 3 5803 5514; fax: +81 3 5803 5514.

E-mail address: [email protected] (K. Fueki).

Available online at www.sciencedirect.com

ScienceDirect

journal homepage: www.elsevier.com/locate/jpor

1883-1958/$ see front matter # 2013 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.http://dx.doi.org/10.1016/j.jpor.2013.12.002Please cite this article in press as: Fueki K, et al. Clinical application of removable partial dentures using thermoplastic resinPart I: Definitionand indication of non-metal clasp dentures. J Prosthodont Res (2014), http://dx.doi.org/10.1016/j.jpor.2013.12.002

j o u r n a l o f p r o s t h o d o n t i c r e s e a r c h x x x ( 2 0 1 4 ) x x x x x x2

JPOR-219; No. of Pages 8pDepartment of Prosthodontics, Division of Oral Functional Science and Rehabilitation, School of Dentistry, Asahi

University, JapanqDivision of Occlusion and Removable Prosthodontics, Health Sciences University of Hokkaido, JapanrDepartment of Prosthodontics, Gerodontology and Oral Rehabilitation, Osaka University Graduate School of

Dentistry, JapansDepartment of Prosthodontics and Oral Implantology, Iwate Medical University, JapantDepartment of Oral & Maxillofacial Rehabilitation, Removable Prosthetics, Kanagawa Dental College, JapanuDepartment of Prosthodontics, Showa University, JapanvDivision of Fixed Prosthodontics, School of Dentistry, Meikai University, JapanwSection of Implant and Rehabilitative Dentistry, Division of Oral Rehabilitation Faculty of Dental Science, Kyushu

University, JapanxDepartment of Fixed Prosthodontics, Osaka University Graduate School of Dentistry, Japan

Contents

1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

2. Preparation of position paper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

3. Term and definition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

4. Indications and contraindications for NMCDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

4.1. Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

4.2. Contraindications and cases in which use requires caution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

4.2.1. Type of partially edentulous arch and occlusal relationship. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

4.2.2. Anatomical factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

4.2.3. State of oral hygiene. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5. Advantages and disadvantages of NMCDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.1. Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.1.1. Esthetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.1.2. Feel during use of NMCDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.1.3. Metal allergy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.2. Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.2.1. Discoloration and degradation of thermoplastic resin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.2.2. Difficulty of polishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.2.3. Breakage of resin clasp, difficulty of adjusting retention capacity and repair. . . . . . . . . . . . . . . . . . . . 000

5.2.4. Design of retentive parts and periodontal condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

5.2.5. Ineligibility for insurance coverage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

6. Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000

a r t i c l e i n f o

Article history:

Received 11 November 2013

Accepted 5 December 2013

Available online xxx

Keywords:

Removable partial denture

Thermoplastic resin

Non-metal clasp denture

Resin clasp

Metal allergy

a b s t r a c t

This position paper proposes a definition and naming standard for removable partial

dentures (RPDs) using thermoplastic resin, and presents a guideline for clinical application.

A panel of 14 experts having broad experience with clinical application of RPDs using

thermoplastic resin was selected from members of the Japan Prosthodontic Society. At a

meeting of the panel, non-metal clasp denture was referred as the generic name of RPDs

with retentive elements (resin clasps) made of thermoplastic resin. The panel classified non-

metal clasp dentures into two types: one with a flexible structure that lacks a metal

framework and the other having a rigid structure that includes a metal framework. Accord-

ing to current prosthetic principles, flexible non-metal clasp dentures are not recommended

as definitive dentures, except for limited cases such as patients with a metal allergy. Rigid

non-metal clasp dentures are recommended in cases where patients will not accept metal

clasps for esthetic reasons. Non-metal clasp dentures should follow the same design

principles as conventional RPDs using metal clasps.

# 2013 Japan Prosthodontic Society. Published by Elsevier Ireland. All rights reserved.Please cite this article in press as: Fueki K, et al. Clinical application of removable partial dentures using thermoplastic resinPart I: Definitionand indication of non-metal clasp dentures. J Prosthodont Res (2014), http://dx.doi.org/10.1016/j.jpor.2013.12.002

j o u r n a l o f p r o s t h o d o n t i c r e s e a r c h x x x ( 2 0 1 4 ) x x x x x x 3

JPOR-219; No. of Pages 8outside the scope of their intended use, this would be a serious

disadvantage for patients. It has also been pointed out that

depending on the material, problems including fracture of the

resin clasp, roughening of the polished surface of the denture

base, or discoloration of denture base resin may occur, and

treatment such as reline or repair may be difficult. In practice,

various problems do occur after denture fitting in at least some

patients, and while the evidence from clinical trials is limited,

there is a possibility that the inappropriate use of RPDs using

thermoplastic resin may become a social issue. If this situation

is left unaddressed, it may decrease public trust in dental

treatment and dentistry. In light of these circumstances, the

Japan Prosthodontic Society (JPS) has cautioned against the

regular clinical use of RPDs using thermoplastic resin, stating

that Although so-called non-clasp dentures have the positive

advantage of being effective in restoring external appearance,

they have the disadvantage that if they are used in the wrong

patients they may cause major damage, including abnormal

resorption of the residual ridge and increase of movement of

the abutment teeth, and their indications should be scienti-

fically verified in the future. In a clinical guideline formulated

original paper had been published based on clinical research

on RPDs using thermoplastic resin [4]. Then, a questionnaire

was sent to a panel of prosthodontists on how to formulate a

guideline (dentures to be covered, types of defect, design,

whether or not to limit them to thermoplastic resin materials).

The results revealed that most prosthodontists wanted to

formulate a guideline on the different types of thermoplastic

resin currently in use, cases in which their use is indicated,

and denture design. Given the lack of evidence, however, it

was considered that it would be difficult to formulate a

guideline for such a wide diversity of patients using standard

methods. The decision was therefore made to select an expert

panel from among JPS members who had clinical experience

with RPDs using thermoplastic resin in order to form a

consensus based on clinical experience, and to publish the

results as a position paper. The objectives of this position

paper were (1) to propose an official term and definition for

RPDs using thermoplastic resin, and (2) to provide guidelines

for prosthodontists and general dentists on points to note with

respect to the indications and contraindications, design, and

clinical use of such dentures.1. Introduction

Esthetics is a matter of great concern for patients receiving

dental treatment, especially prosthetic treatment. Therefore,

esthetic aspects must be considered to ensure patient

satisfaction with dental treatment. Patients find the sight of

the metal clasp of removable partial dentures (RPDs) in the

esthetic area undesirable for both esthetic and psychological

reasons; this is one explanation for patients disliking the use

of RPDs. Conventionally, attachments have been used in

patients who place emphasis on esthetics, but the need to

remove large quantities of tooth structure and the require-

ment for specialist skills means that at present, this is not a

generally viable choice. In the United States, since the 1950s,

polyamide resin (nylon) has been used to fabricate RPDs that

do not contain any metal elements. Since 2007, a number of

thermoplastic resins have also been approved for use as

denture bases in Japan (Table 1). The use of RPDs made either

from resin alone or a combination of resin and metal is now

rapidly gaining popularity among general dentists and is

considered to be superior to conventional metal-clasp

retained RPDs with metal clasps in terms of both esthetics

and comfort [1]. Changes in public awareness have led to

increasingly strong demands from patients with respect to

esthetic aspects when fitting prostheses, with an increasing

number of patients avoiding RPDs because they are associated

with growing old. The need for dentists to respond to this

demand from patients may be a cause of the increasing

popularity of such RPDs.

RPDs using thermoplastic resin have some limitations as

revealed by prosthodontists [2]. The first issue is that some

RPDs using thermoplastic resin do not conform to the

principles regarding the standard RPD design in Japan, and

that the use of such RPDs may seriously affect the periodontal

tissues of abutment teeth and the residual ridge. As this

procedure is simple and is not covered by national health

insurance, if patients demands and desires for a good esthetic

appearance are given precedence and such RPDs are usedPlease cite this article in press as: Fueki K, et al. Clinical application of remand indication of non-metal clasp dentures. J Prosthodont Res (2014), htin 2008, JPS stated that Application of flexible dentures solely

from the viewpoint of anterior esthetics is not recommended.

The second problem identified by prosthodontists is that

there is no set definition or name for RPDs using thermoplastic

resin, which are commonly known as flexible dentures, non-

clasp dentures, clasp-free dentures, and metal-free dentures.

Recently, non-clasp dentures has become the generally

used term, but according to the definition in the US GPT-8

Glossary of Prosthodontic Terms [3], the resin part that

extends from the denture base to include the abutment teeth

and which is responsible for retention is a structural element

that should be called a clasp, and the term non-clasp is

therefore inappropriate.

In light of this situation, the Clinical Guideline Committee

responded to a request from the Social Insurance and Dental

Service Problem Committee and considered correcting the

guideline. They first searched the literature in PubMed and

Igaku Chuo Zasshi (ICHUSHI, Japan Medical Abstracts Society)

to collect the latest clinical evidence, and found that there

were a limited number of studies: as of August 2011, only one

Table 1 Thermoplastic resins available for non-metalclasp dentures in Japan (December 2012).

Generic name Product name Manufacturer

Polyamide BIO PLAST HIGH DENTAL JAPAN

Valplast UNIVAL

Flex Star V Nippon Dental supply

BIO TONE HIGH DENTAL JAPAN

Lucitone FRS DENTSPLY International

Ultimate Ultimate

Polyester EstheShot Bright i-Cast

EstheShot i-Cast

Polycarbonate Reigning N Toushinyoukou

Reigning Toushinyoukou

JET CARBO-S HIGH DENTAL JAPAN

JET CARBO RESIN HIGH DENTAL JAPAN

Acrylic resin ACRY TONE HIGH DENTAL JAPAN

Polypropylene UNIGUM WELDENZovable partial dentures using thermoplastic resinPart I: Definitiontp://dx.doi.org/10.1016/j.jpor.2013.12.002


JPOR-219; No. of Pages 82. Preparation of position paper

The 21 members selected to serve on the expert panel for 2011

2012 were requested to complete a questionnaire, and five

members who had clinical experience with RPDs using

thermoplastic resin in several patients were included in our

expert panel. Information was then gathered from JPS

members who had at least 5 years clinical experience with

RPDs using thermoplastic resin, and an additional nine

members were selected to join the expert panel. Thus, a total

of 14 members prepared the initial draft of this position paper.

At a panel meeting in August 2012, members discussed the

official term and definition for RPDs using thermoplastic resin

and the structure of the position paper, and reached a

consensus. All the members of the expert panel were

responsible for writing different sections of the draft position

paper, and the content was corrected through Internet

discussion among the panel as a whole until a consensus

was obtained. The final document was completed after review

by the clinical guideline committee. The PubMed and ICHUSHI

online databases were used to search the literature, as well as

manual search. The selection of literature was not carried out

systematically.

3. Term and definition

Fig. 1 A non-metal clasp denture without metal elements.In 1956, the US company Valplast developed super-polyamide,

a type of nylon, as a material for use in dentures. Dentures for

which all the structural elements other than the artificial teeth

are manufactured from this thermoplastic resin without the

use of metal have been mostly known by the company name,

Valplast, but are also called flexible dentures or nylon

dentures, and have become widely used worldwide (Fig. 1)

[5,6]. In Japan, these dentures were individually imported and

used on a trial basis before they were approved by the Ministry

of Health, Labour and Welfare, and it became common to call

them by names such as non-clasp dentures or metal-free

dentures. Since their approval under the pharmaceutical

affairs law in April 2008, numerous thermoplastic resins have

been developed, and these have mistakenly been known by

the names of their manufacturer, supplier, or laboratories;

however, in general, the name non-clasp dentures has

taken root among general clinicians.

Please cite this article in press as: Fueki K, et al. Clinical application of remand indication of non-metal clasp dentures. J Prosthodont Res (2014), htAccording to the GPT-8 [3], a clasp is defined as the

component of the clasp assembly that engages a portion of the

tooth surface and either enters an undercut for retention or

remains entirely above the height of contour to act as a

reciprocating element. Generally it is used to stabilize and

retain a removable dental prosthesis. According to this

definition, a clasp is not described as being made of metal.

The resin retentive elements known as arms, fingers, and

wings may thus be regarded as genuine clasps according to

this definition, as they use undercuts to retain and stabilize

RPDs, and they are also known as resin clasps or esthetic

clasps [7,8].

This interpretation therefore indicates that the term non-

clasp dentures refers only to those that do not incorporate

clasps in any form, such as attachment dentures, milling

dentures, or telescope dentures. Thus, in this position paper,

the term non-metal clasp dentures (NMCDs) is used to refer

not only to dentures that do not contain any metal elements,

but also to dentures that incorporate a metal rest or frame-

work (Figs. 2 and 3), and is defined as the general name for

RPDs using denture base resins as the denture retentive

parts. This definition thus includes not only those dentures in

which the retentive parts and the denture base are produced

as a single whole, but also those dentures in which a resin used

for the retentive parts is different from that for denture base

(Fig. 4). In this position paper, the resin retentive part of

NMCDs is referred to as the resin clasp.

Fig. 2 A non-metal clasp denture with metal rests.4. Indications and contraindications forNMCDs

4.1. Indications

In this position paper, NMCDs have been categorized into two

types; NMCDs with/without overall rigidity according to

whether or not they include a metal structure and the elastic

modulus of the denture base resin (Table 2) and indications are

suggested in each type of NMCD. NMCDs that do not include a

metal structure and are not rigid are indicated as interim

dentures or spare dentures for patients with metal allergy,

patients with few missing anterior teeth, and patients with

few missing teeth with occlusal support, and as epitheses for

patients in whom the dentures carry no functional burden,

patients for whom esthetics must be given top priority, and

ovable partial dentures using thermoplastic resinPart I: Definitiontp://dx.doi.org/10.1016/j.jpor.2013.12.002


JPOR-219; No. of Pages 8patients who do not consent to the preparation of abutment

teeth (Fig. 5). NMCDs that include a metal structure and are

rigid are basically indicated in a wide range of cases (Figs. 24).

4.2. Contraindications and cases in which use requirescaution

Contraindications for NMCDs depend on the type of partially

edentulous arch and occlusal relationship, anatomical factors

that affect the design and fabrication of RPDs, or a state of oral

hygiene that may affect the maintenance and management of

RPD treatment.

Fig. 3 A non-metal clasp denture with a framework (Reigning N

clasp.

Fig. 4 A non-metal clasp denture using different denture base

clasp on working cast; (b) delivered denture.

Fig. 5 A non-metal clasp denture without metal framework rep

(a) Labial view on working cast; (b) palatal view on working cas

Please cite this article in press as: Fueki K, et al. Clinical application of remand indication of non-metal clasp dentures. J Prosthodont Res (2014), ht4.2.1. Type of partially edentulous arch and occlusal

relationshipNMCDs may be designed with a metal rest or framework to

control displacement of the dentures while in use, and designs

that incorporate metal may be used with almost all types of

partially edentulous arches. Their use is difficult, however, in

patients with non-vertical stop occlusion or those with few

remaining teeth, in whom good treatment results cannot be

expected even with the use of metal clasp-retained RPDs. For

patients with non-vertical stop occlusion in particular,

rotation and sinking of the denture base, changes in occlusal

position, and resorption of the residual ridge tend to occur,

W). (a) Basal surface of the denture; (b) metal rest and resin

resins for retentive elements and a denture base. (a) Resin

lacing missing maxillary bilateral frontal teeth (ValplastW).

t.


marginal gingiva, potentially causing its mechanical damage.

It has been reported that NMCDs that contain no metal

structures at all tend to sink [9], suggesting that more careful

follow-up is required for patients with metal-free NMCDs.

5. Advantages and disadvantages of NMCDs

5.1. Advantages

5.1.1. Esthetics

op

Fig. 6 Deterioration of thermoplastic resin used for non-

metal clasp denture. Polished surface of the maxillary

complete denture (left) was good, however surface of

denture base of a mandibular non-metal clasp denture

(EstheShotW) has become roughened after a year and

6-month use. Denture base of the posterior area was

repaired using a cold-cured resin (indicated with arrow).


JPOR-219; No. of Pages 8resulting in the concentration of excessive force in the resin

clasp. As there is a high risk that resin clasps may quickly

become deformed or break, they are contraindicated.

The stress on the resin clasp may also be high in patients

with few remaining teeth. Although it depends on the location

of the remaining teeth and the condition of the opposing

dentition, particular caution is required if molar occlusal

support has been entirely lost, the occlusal position is

unstable, or poor support is provided by the mucosa of

residual ridge at the edentulous area due to severe residual

ridge resorption or abnormal mucosa under the denture base.

4.2.2. Anatomical factors

As the upper margin of the resin clasp of NMCDs is designed to

be positioned on the tooth surface and the lower margin on the

gingiva, its external shape is affected not only by the crown

morphology of the abutment tooth but also by the morphology

of the alveolar part. In patients with a clinically short crown

length, in whom the distance between the survey line on the

abutment tooth and the oral vestibule is inadequate, and with

an excessive undercut in the alveolar part, it may be difficult to

design a resin clasp of appropriate shape and width. The resin

clasp may lack sufficient retention capacity and strength, and

caution is therefore required. In most NMCDs, the thermo-

plastic denture base resins cannot be chemically bound to the

artificial teeth, meaning that holes must be made to hold the

artificial teeth and they must be mechanically fixed. In

patients with a small amount of clearance with opposing

teeth at the missing area, the artificial teeth may be lost,

cracked, or fractured, and caution is therefore required.

4.2.3. State of oral hygiene

Table 2 Rigidity of non-metal clasp dentures using therm

Generic name Product name

Polyamide Valplast

Lucitone FRS

Ultimate

Polyester EstheShot Bright

EstheShot

Polycarbonate Reigning

Reigning N

a Low < 2000 MPa; high 2000 MPa.b With metal framework.Metal clasps are designed in such a way that they do not to

come into contact with the gingival margin, but the resin

clasp of NMCDs covers the tooth structure of the cervical

region of abutment teeth, the marginal gingiva, and the

labial-buccal mucosa. As a wide area around the abutment

teeth becomes unhygienic, this may cause or exacerbate

caries and periodontal disease. The need for adequate dental

plaque control has been emphasized [9], and patients with

poor oral hygiene and those who do not respond regular

repeat appointments are not suitable candidates. As the

degradation of resin materials may also increase the

adherence of dental plaque, worsening the cleanliness of

dentures, regular oral maintenance is essential. In patients

who use a NMCD with no support from a metal rest, should

the dentures sink then the resin clasp compresses the

Please cite this article in press as: Fueki K, et al. Clinical application of remand indication of non-metal clasp dentures. J Prosthodont Res (2014), htlastic resins.

Elastic modulusa Denture rigidity

Low Rigidb

Low Rigidb

Low Rigidb

Low Rigidb

High Rigid

High Rigid

High RigidDenture wearers, both men and women, are highly concerned

about the esthetic appearance. Although dental implant

treatment is effective, many patients dislike the idea of

inserting a metal implant into the bone, or are afraid of

surgical treatment. The cost is also generally high. RPDs may

be proposed as an alternative, but both patients and dentists

may hesitate at the thought of a metal clasp visible from the

outside. The esthetic appearance of RPDs may be guaranteed

by the use of magnetic or precision attachment, milling

dentures, or telescope dentures, but if the abutment tooth is a

vital tooth, such retainers may be difficult to use, and dentists

may be at a loss how to deal with this. With NMCDs, it is

possible for the retentive parts to actively utilize a vital tooth,

increasing the opportunities for both patients and dentists to

choose RPDs.


tal

sti


JPOR-219; No. of Pages 85.1.2. Feel during use of NMCDsThe resins currently in use have a lower elastic modulus

and a softer surface compared with acrylic resin [1013],

meaning that patients feel better when worn. There also

appears to be no problem with fit [14,15]. As there is a low

risk of breakage of dentures made solely of resin, which are

highly elastic and not at all rigid, the denture base can be

made thinner. This makes them lighter and thinner than

RPDs using an acrylic resin or metal framework to ensure

rigidity.

5.1.3. Metal allergyDentures that contain no metal at all eliminate concerns about

metal allergy. Historically, the first NMCDs in the 1950s were

made of polyamide resin, which was developed to deal with

the allergic reaction to residual monomers after the poly-

merization of acrylic resin [16]. This advantage has also been

utilized subsequently for avoiding metal allergy [17].

5.2. Disadvantages

5.2.1. Discoloration and degradation of thermoplastic resin

Surface roughening after a few months of denture delivery

was identified in all but a few materials [18]. As the surface is

not as hard as that of acrylic resin, the depths and the widths

of marks were greater than the acrylic resins by the scratch

Fig. 7 Deterioration of thermoplastic resin used for non-me

(ValplastW); (b) discoloration and decolorization of thermoplatest [19], thus the polished surface loses its luster. Discolora-

tion and loss of color are also seen [2022] (Figs. 6 and 7).

Candida growth is not a concern as long as denture

maintenance is possible, but if adequate cleaning cannot be

performed then more caution would be required than for

acrylic resin [23].

5.2.2. Difficulty of polishingToothbrush friction experiments (measuring the decrease in

volume) on the denture base material used in NMCDs have

shown that it loses less than one fifth of the volume lost by

acrylic resin [24]. Nevertheless, although the surface is easily

damaged, as described above, these materials are regarded as

not susceptible to surface loss even when damaged. This

property means that compared with acrylic resin they may be

difficult to polish at the chairside [25], and a special polish is

required. When the glass transition point is exceeded in the

non-crystalline portion of a polymer material, it takes on a

Please cite this article in press as: Fueki K, et al. Clinical application of remand indication of non-metal clasp dentures. J Prosthodont Res (2014), htrubbery form, and the heating effect of polishing may also be

detrimental.

5.2.3. Breakage of resin clasp, difficulty of adjusting retentioncapacity and repairNo guidelines have been indicated for the design of resin

clasps of NMCDs. Therefore, the width, thickness, and length

are designed via trial and error. Design guidelines based on

differences in materials physical properties would therefore

be desirable [26]. Frequent breakage of the retentive elements

in the early years has led to improvement in their physical

properties. Clasp wires were buried in the retentive parts with

the aim of ensuring continued retention and preventing

breakage. If the material is one that adheres to self-curing

resin, then the retentive capacity may be recovered to some

extent, but if not then it is difficult to adjust. We will address

adhesion to self-curing resin in the context of repair and reline

of different materials in Part II. Materials to which self-curing

resin does not adhere must be repaired in a laboratory.

5.2.4. Design of retentive parts and periodontal conditionIn NMCDs, the resin clasp covers the cervical area of the

abutment teeth over a wide area on both the crown and root

sides, being designed to be part of the gingiva. This means that

the area covered by the resin clasp is large, and the undercut

and relief regions may easily become dead space, with the risk

clasp dentures. (a) Loss of burnish on polished surface

c resin (Lucitone FRSW).of exacerbating periodontal conditions. Meticulous cleaning is

therefore essential.

5.2.5. Ineligibility for insurance coverageNMCDs using thermoplastic resin are not covered by national

health insurance in Japan. The cost of NMCDs consisting

entirely of resin is different from that of dentures that utilize a

metal framework for rigidity. Their ineligibility for insurance

coverage means that patients must pay a greater amount, but

as mentioned in the opening sentences of this paper, many

people prefer to use NMCDs, and this is based heavily on the

improved esthetics of RPDs.

6. Recommendations

In this position paper, within the current restricted scope,

non-rigid NMCDs cannot be recommended as definitive


[10] Sano M, lto K, Nomura A, Kohno S. Properties ofthermoplastic polymers used for non-clasp dentures. J Jpn


JPOR-219; No. of Pages 8dentures in light of current prosthetic principles, with the

exception of patients with metal allergies and some others.

NMCDs that include a metal framework to provide rigidity

may be recommended in cases in which the patient is

uncomfortable with a metal clasp running through areas that

would affect esthetic appearance. Methods of reline and

maintenance should be understood with reference to the

properties of the different materials used.

Conflicts of interest

The preparation of this position paper was funded by JPS. JPS

does not receive support from any specific group or

corporation. No funding from any group or corporation

was used for the preparation of this position paper. The

members of the expert panel and clinical guideline commit-

tee involved in the preparation of this position paper did not

receive any support from any specific group or corporation

with respect to NMCDs. Members of the expert panel who

had contributed to the development of or lectured on a

specific resin were not involved in writing about the resin

concerned.

Acknowledgement

This paper is the secondary publication of the position paper

published in the Annals of Japan Prosthodontic Society [27].

r e f e r e n c e s

[1] Suzuki T, Shimpo H, Kitano N, Sato M, Kawai Y, Kanki Y,et al. A questionnaire survey on the thermoplasticdentures. Ann Jpn Prosthodont Soc 2011;3:133 [specialissue; in Japanese].

[2] Ohkubo C, Yatabe M, Arita M. Present status and clinicalproblems of non-metal clasp denturescan it become onechoice for prosthetic rehabilitation? Ann Jpn ProsthodontSoc 2012;4:634 [special issue; in Japanese].

[3] Glossary of prosthodontic terms. 8th edition. J ProsthetDent 2005;94:185.

[4] Saito M, Oguma H. Questionnaires for patients satisfactionwith a super-polyamide denture in a clinic. J Esthet Dent2009;22:604 [in Japanese].

[5] Lowe LG. Flexible denture flanges for patients exhibitingundercut tuberosities and reduced width of the buccalvestibule: a clinical report. J Prosthet Dent 2004;92:12831.

[6] Meijer GJ, Wolgen PJ. Provisional flexible denture to assist inundisturbed healing of the reconstructed maxilla. J ProsthetDent 2007;98:3278.

[7] Kaplan P. Flexible removable partial dentures: design andclasp concepts. Dent Today 2008;27:1223.

[8] Singh JP, Dhiman RK, Bedi RP, Girish SH. Flexible denturebase material: a viable alternative to conventional acrylicdenture base material. Contemp Clin Dent 2011;2:3137.

[9] Hosoi T. Non-clasp denture. DE 2009;168:14 [in Japanese].Please cite this article in press as: Fueki K, et al. Clinical application of remand indication of non-metal clasp dentures. J Prosthodont Res (2014), htSoc Dent Products 2009;23:2834 [in Japanese].[11] Yokoyama N, Machi H, Hayashi K, Uchida T, Ono T, Nokubi

T. Physical properties of polyamide resin (nylon group) as apolymeric material for dentures: Part 2. Surface hardnessand tensile strength. J Nippon Acad Dent Technol2004;25:8792 [in Japanese].

[12] Kawara M, Suzuki H, Ishikawa S. Progress of EstheShot1 foresthetic denture report of abrasion losses-. Ann JpnProsthodont Soc 2011;3:E89 [in Japanese].

[13] Ucar Y, Akova T, Aysan I. Mechanical properties ofpolyamide versus different PMMA denture base materials. JProsthodont 2012;21:1736.

[14] Hayashi K, Yokoyama N, Machi H, Uchida T, Ono T, NokubiT. Physical properties of polyamide resin (nylon group) as apolymeric material for dentures: Part 1. Characteristics ofabsorbent and dimensional change. Journal of NipponAcademy of Dental Technology 2004;25:806 [in Japanese].

[15] Hishimoto M, Katou Y, Akita Y, Murakami Y, Iida S.Physical properties of polyester copolymer for denturematerials. J Nippon Acad Dent Technol 2008;29:196 [specialissue; in Japanese].

[16] Stafford GD, Huggett R. The use of nylon as a denture-basematerial. J Dent 1986;14:1822.

[17] Kuwahara K, Nagahama F, Kitahara K, Wada M, MakimuraS, Kimura K, et al. A case of using non-metalclasp partialdenture for the patient with metal allergy. Nichidai KokoKagaku 2004;30:1349 [in Japanese].

[18] Yatabe M. How to deal with non-clasp denture? Itsadvantages and problems. Quintessence 2010;29:208390[in Japanese].

[19] Kawara M, Iwata Y, Iwasaki M, Komoda Y, Iida T, Asano T,et al. Scratch test of thermoplastic denture base resins fornon-metal clasp dentures. J Prosthodont Res 2013;58 (thisissue).

[20] Takabayashi Y. Characteristics of denture thermoplasticresins for non-metal clasp dentures. Dent Mater J2010;29:35361.

[21] Katsumata Y, Hojo S, Ino S, Hamano N, Watanabe T, KondoN, et al. Color stability of a flexible nylon denture baseresin. J Kanagawa Odont Soc 2007;42:1405 [in Japanese].

[22] Sepu lveda-Navarro WF, Arana-Correa BE, Borges CP, JorgeJH, Urban VM, Campanha NH. Color stability of resins andnylon as denture base material in beverages. J Prosthodont2011;20:632863.

[23] Fernandes FSF, Pereira-Cenci T, Silva WJ, Filho APR,Straioto FG, Cury AADB. Efficacy of denture cleansers onCandida Spp. biofilm formed on polyamide and polymethylmethacrylate resins. J Prosthet Dent 2010;105:518.

[24] Takahashi H, Kawada E, Tamaki Y, Teraoka H, Hosoi T,Yoshida T. Basic properties of thermoplastic resins fordenture base material referred to non clasp denture. J JpnDent Mater 2009;28:1617 [in Japanese].

[25] Abuzar MA, Bellur S, Duong N, Kim BB, Lu P, Palfreyman N,et al. Evaluating surface roughness of polyamide denturebase material in comparison with poly (methylmethacrylate). J Oral Sci 2010;52:57781.

[26] Taguchi Y, Shimamura I, Sakurai K. Effect of buccal partdesigns of polyamide resin partial removable dentalprosthesis on retentive force. J Prosthodont Res 2011;55:447.

[27] Fueki K, Ohkubo C, Yatabe M, Arakawa I, Arita M, Ino S,et al. Clinical application of removable partial denturesusing thermoplastic resin (non-metal clasp dentures). AnnJpn Prosthodont Soc 2013;5:387408 [in Japanese].ovable partial dentures using thermoplastic resinPart I: Definitiontp://dx.doi.org/10.1016/j.jpor.2013.12.002

Clinical application of removable partial dentures using thermoplastic resin-Part I: Definition and indication of non-metal clasp denturesIntroductionPreparation of position paperTerm and definitionIndications and contraindications for NMCDsIndicationsContraindications and cases in which use requires cautionType of partially edentulous arch and occlusal relationshipAnatomical factorsState of oral hygiene

Advantages and disadvantages of NMCDsAdvantagesEstheticsFeel during use of NMCDsMetal allergy

DisadvantagesDiscoloration and degradation of thermoplastic resinDifficulty of polishingBreakage of resin clasp, difficulty of adjusting retention capacity and repairDesign of retentive parts and periodontal conditionIneligibility for insurance coverage

RecommendationsConflicts of interestAcknowledgementReferences

Documents

1-s2.0-S188319581300131X-main