Condition category
Oral Health
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting
Publication status
Results overdue

Plain English Summary

Background and study aims
As a result of increased life expectancy and oral health promotion, there has been a gradual shift in the amount of people who are totally edentate (lacking teeth). Advancements in the field of dentistry have provided more options for patients who have experienced tooth loss. While treatment such as the use of implants exists, removable partial dentures (RPDs) are widely used in clinical practice for their advantages in many cases. RPDs are available in a variety of types. Among them is the conventional removable partial denture (CRPDs) with metal clasps. While they are a popular option, there are drawbacks such as impairment of esthetics (looks), discomfort, and metal allergy when using them. To overcome these disadvantages, the next type, the non-metal clasp denture (NMCDs) was developed. NMCDs are made using a thermoplastic (a substance that become plastic when heated and harden on cooling) denture base resin and do not have a metal clasp. As they are increasingly being used, the application of it is mostly based on the clinician’s preference and there is limited amount of research conducted on this type of denture. In addition to these two types of dentures, there is also the shortened dental arch (SDA) which does not require restoration (repair) of the full dental arch. This concept, while having been proposed over the years, is somewhat controversial in that it attempts to prioritize functionality over complete restoration. With all of these options, it is important to properly evaluate the patient-related outcomes in situations where implants are not to be used (which is often still the case in general), for the benefit of the patient. The aim of this clinical trial is to investigate the oral health-related quality of life (OHRQoL) among participant patients who have received CRPDs, NMCDs, and SDAs.

Who can participate?
Adults aged 24 to 85 have mandibular free edge loss patient.

What does the study involve?
Participants are allocated to one of six different groups. Each group received the three types of treatment (CRPDs, NMCDs, and SDA) in one of six preset sequences. Dentures are delivered to the patients and control appointments were scheduled few days afterwards. Each type of treatment is used for two weeks. At the end of each usage, participants arerequested to answer questions to assess oral function, facial appearance, any pain, and impact. After finishing the three treatments, two options for prosthesis are presented for the patient to choose. A follow-up appointment take place three to six months for adjustments.

What are the possible benefits and risks of participating?
As far as benefits, patients have a more active role in choosing the type of prosthesis they feel is the best for them. There are no major risks because all forms of treatment are noninvasive and do not require surgery

Where is the study run from?
Nakai Dental Office (Japan)

When is the study starting and how long is it expected to run for?
January 2015 to July 2017

Who is funding the study?
Investigator initiated and funded (Japan)

Who is the main contact?
Dr Tadafumi Kurogi

Trial website

Contact information



Primary contact

Dr Tadafumi Kurogi


Contact details

1-7-1 Sakamoto
Nagasaki City

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Oral health-related quality of life of non-metal clasp dentures and shortened dental arch with unilateral mandibular distal-extension edentulism: a within-subject controlled clinical trial


Study hypothesis

The aim of this study is to investigate the Oral Health-related Quality of Life (OHRQoL) in participant patients who use various types of treatment for partial edentulism.

Study hypothesis:
There are three prosthetic options, conventional removable partial dentures (CRPDs), non-metal clasp dentures (NMCDs) and shortened dental arch (SDA), for the unilateral mandibular distal-extension edentulism will not lead to different oral health-related quality of life (OHRQOL).

Ethics approval

Ethics Committee of Nagasaki University Hospital Japan, 03/03/2015, ref: 15022313

Study design

Interventional randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting

GP practices

Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet


Oral Health-related Quality of Life (OHRQoL)


In order to ensure that the process is exactly the same so as not to include confounder, participants are allocated to one of six groups,
treated as sequences ABC, ACB, BAC, BCA, CAB and CBA. Each participant receive a written description of the experimental procedures and informed consent is obtained prior to enrollment into the study. Participants are divided and assigned to six different groups. Each group receive the three types of treatment (CRPDs, NMCDs, and SDA) in one of six preset sequences. Dentures are delivered to the patients and control appointments are scheduled few days afterwards.

This study employed crossover design, a within-subject controlled clinical trial, for the three treatment options:

1. Conventional removable partial dentures (CRPDs): The conventional removable partial denture (CRPD) is the most common type of removable partial denture. It consists of a set of artificial replacement teeth and metal framework with clasps. The clasps are thin finger-like structures usually made of thin resilient metal alloy that rest upon and wrap around the remaining natural teeth. These clasps keep the prosthesis securely in place, but still allow the user to easily take it out for cleaning and proper brushing of remaining natural teeth. Depending on the denture design which is based on mouth conditions, there may be some show of the clasp(s). This issue with esthetics, along with occasional discomfort and allergic reaction to the metal, are often cited as disadvantages of this type of denture.

2. Non-metal clasp dentures (NMCDs): The non-metal clasp denture (NMCD) was developed to rectify the disadvantages of the conventional removable partial denture with metal clasps. Instead of using metal clasps, this type of denture is fabricated using a thermoplastic denture base resin. The prosthesis is inserted by fitting itself onto the gums of the user and secures itself to the natural teeth and surrounding areas. This type of denture is known to be much more esthetically pleasing and eliminates all issues with metal allergies. While this type treatment has been gaining some popularity over the years, the application of it is based only on the individual clinician's preference.

3. Shortened dental arch (SDA): The Shortened Dental Arch (SDA) comprises of anterior and premolar teeth with missing posterior occlusal units. By focusing treatment on the replacement of teeth towards the front of the mouth, priority is placed on functionality over the restoration of the entire dental arch. This provides efficient dental care with no risk of over-treatment.

Each treatment takes two weeks. The total duration of treatment (including fabrication and adjustment) takes 11 weeks. Each type of treatment are used for two weeks. At the end of each trial, participants are requested to answer an oral health impact profile (OHIP) questionnaire to assess oral function, oro-facial appearance, any oro-facial pain, and psychosocial impact. The Oral Health Impact Profile (OHIP) is a questionnaire that organizes data on the patient rated outcome measures, developed for measuring the oral related quality of life (OHRQOL). Its validity and reliability were previously established and it has been widely used in clinical trials. In this study, the Japanese version of OHIP (OHIP-J49) is used. All treatments and interventions are conducted by one board-certified prosthodontist from the Japan Prosthodontist Society at the same centre.

After finishing the treatments, two options for prosthesis are presented for the patient to choose. A follow-up appointment is scheduled to take place three to six months post-delivery for remounting and adjustments. Treatment is concluded upon agreement between the clinician and patient to terminate.

Intervention type



Drug names

Primary outcome measure

Oral-related quality of life is measured using the oral health impact profile (OHIP) at two weeks after each treatment.

Secondary outcome measures

1. The effect of other factors (sex, age, edentulous period and the number of missing teeth) are measured using exploratory analysis at each treatment.
2. Analysis in four sub-domains of oral health impact profile (OHIP) (difference among 3 options test score using the mixed effect model). The questionnaires cover four sub-domains (Oral function, Oro-facial appearance, Oro-facial pain and Psychosocial impact).

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Mandibular free edge loss patient
2. Person in hope of the production of the denture or adjustment
3. The patient that a document agreement by the free will of a patient was provided after enough understanding after having received enough explanation on participating to this study
4. Aged between 24-85 years old

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. It is the person with the trouble for a question vote answer
2. The person who has a loss on chin face
3. Person considered that the participation in study is difficult having a systemic anamnesis
4. The person that periodontal treatment is not finished
5. In addition, the patient whom a study person in charge judged to be inappropriate as a subject

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Nakai Dental Office
724-1 Yohojimae-cho Nakagyu-ku Kyoto City

Sponsor information


Nakai Dental Office

Sponsor details

724-1 Yohojimae-cho

Sponsor type

Hospital/treatment centre



Funder type


Funder name

Investigator initiated and funded

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

I intend to analyze data and prepare the manuscript in 2017 and publish my study in JDR CTR in 2018.

IPD sharing statement:
The data sets generated during and/or analyzed during the current study will be stored privately available repository at the Nakai Dental Office (Japan).

Intention to publish date


Participant level data

Stored in repository

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

27/02/2020: The country of recruitment was corrected from United Kingdom to Japan. 26/10/2017: Internal review. 22/09/2017: Internal review