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Randomised multicentre study of prosthetic treatment options for shortened dental arch
ISRCTN ISRCTN97265367
DOI 10.1186/ISRCTN97265367
ClinicalTrials.gov identifier
EudraCT number
Public title Randomised multicentre study of prosthetic treatment options for shortened dental arch
Scientific title
Acronym SDAS
Serial number at source DFG WA 831/2-1 to 2-6
Study hypothesis Over the last 20 years a mechanistic attitude correlated with a lack of longitudinal controlled randomised trials regarding the question of prosthetic treatment after tooth loss. The need assessment considered the replacement of all missing teeth by fixed or removable partial dentures or dental implants as a necessity especially in cases of shortened dental arches. Modern prosthetic concepts distinguish between different dimensions of need (normative need, perceived need) being well aware of the fact that perceived need has been under-represented in the past. An innovative sight puts a higher emphasis to the subjective components of need assessment and outcome measurement. Generally three adverse effects of non-replacement of molars were postulated: temporomandibular joint (TMJ) disorders, tooth migration/overeruption, insufficient chewing ability. However, no evidence based on randomised trials has been provided concerning the incidence of the adverse side effects mentioned above, nor is there high-level evidence regarding a benefit of removable dentures for molar replacement. On the contrary removable partial dentures are compromised by a high incidence of adverse side effects such as plaque accumulation and peridontal breakdown.

Among therapeutic alternatives, an approach with a limited restoration goal focused on incisors, canines and premolars (shortened dental arch [SDA] concept) has been described and implemented although discussed controversially. Within this concept, fixed partial dentures are used for tooth replacement of which a superior performance compared with removable partial dentures has been reported. The multi-centre study was initiated in 2000 because evidence was lacking concerning the benefit of different therapeutic options regarding the preservation of oral health, oral health related quality of life, patients satisfaction, absence of discomfort, satisfactory chewing ability and aesthetic satisfaction. Public health aspects of the study lie in the fields of health economics, avoidance of over-treatment, and therapy guidelines on a population based level.

Two prosthetic therapy arms will be compared:
1. The replacement of posterior teeth at last up to the first molar by removable partial dentures
2. Prosthetic treatment according to the shortened dental arch concept. To avoid removable partial dentures, posterior teeth are replaced up to the second premolar by fixed restorations, if necessary. Molars are not replaced.

The aim of this trial is to test the hypothesis that the treatment outcome varies depending on the treatment concept (fixed versus removable prostheses) in the therapy of patients with missing molars.
Lay summary Not provided at time of registration
Ethics approval Ethics Committee of the Medical Faculty of the Technical University of Dresden (Ethikkommission der Medizinischen Fakultät der Technischen Universität Dresden). Date of approval: 19/04/1999 (ref: EK 260399)
Study design Multi-centre randomised controlled clinical trial.
Countries of recruitment Germany
Disease/condition/study domain Tooth loss/ molar replacement
Participants - inclusion criteria 1. Patients over 35 years of age, who requested prosthetic treatment with a minimum dentition of both canines and one premolar per side preserved in at least one jaw (Kennedy class I). A dentition including all anterior teeth up to the second premolar on both sides in one jaw was defined as maximum
2. Rejection of implant treatment by the patient
3. Patients with general health according to American Society of Anesthesiologists (ASA) classification group one ore two
4. All abutment teeth must be free of periodontal disease (pocket depth less or equal 4 mm, tooth mobility <= grade 2, mean plaque index <= grade 2, bleeding on probing at all teeth <=25 %) and caries
5. Caries free adjacent teeth
6. Sufficient treatment of the opposite jaw, extending the dentition depending on the randomized treatment option up to the second premolar or the first molar
Participants - exclusion criteria 1. Patients with alcohol or drug addiction
2. Mentally disordered patients
3. Patients with TMJ disorders
4. Dysgnathic patients with Angle class II or III
5. Patients who have received or need orthodontical treatment
6. Patients who have been already sufficiently treated
7. Patients who do not accept a removable deture
8. Patients who demand the replacement of all molars
9. Patients with general health American Society of Anesthesiologists (ASA) classification group four
Anticipated start date 01/10/2000
Anticipated end date 31/12/2010
Status of trial Completed
Patient information material Not available in web format, please use the contact details below to request a patient information sheet
Target number of participants 400
Interventions Control group (Therapy A): The molar replacement by removable partial dentures, carried out using fixed crowns and bridges as anchor for removable dentures

Intervention group (Therapy B): Restorations according to the SDA concept, with only fixed restorations or no restoration at all. The maximum extension reached up to the second premolar, and no molars were replaced. All restorations were made according to a standardized procedure (SOP) given by the study protocol.

Standard gold alloys and dental ceramics were used for fixed restorations, base metal alloys for the removable denture frameworks.
Primary outcome measure(s) Further tooth loss. Duration of follow-up: 5 years
Secondary outcome measure(s) The following will be assessed at baseline (4-8 weeks after insertion), 6 month, then annually from Year 1 to 5:
1. Clinical:
1.1. Crown/root caries
1.2. Abrasion (Index 0-4)
1.3. Interdental spacing in the anterior region (Index 0-3)
1.4. Sensibility (+/-)
1.5. Periodontitis/Gingivitis: Plaque-index (index 0-3), probing depth (6 point measurement in mm), attachment loss (6 point measurement in mm), bleeding on probing (BOP)(+/-), tooth mobility (index 0-3), mucosa lesions (California Dental Association [CDA] Criteria)
2. Clinical dysfunction index: Muscle pain via palpation (m. masseter pars profunda et superficialis, m. temporalis pars posterior et anterior, m. pterygoideus medialis et lateralis)
3. Range of movement (mm): maximal opening
4. TMJ function: Description of pain on movement/path of movement, palpation/auscultation
5. Technical (according to the CDA criteria): Treatment performance, preparation form, marginal fit, occlusion static/dynamic in µm, proximal contacts (shape/ strength)
6. Technical performance (according to the CDA criteria): Evaluation of used materials, prosthesis and bridge design, saddle extension, possibility of dental hygiene

Subjective:
9. Oral health related quality of life (OHIP-Questionnaire): Measure of self reported dysfunction, discomfort and disability attributed to oral conditions
10. Dworkin Index Axis II (questionnaire): Assessment of psychological distress and psychosocial dysfunction including questions regarding:
10.1. Graded chronic pain severity
10.2. Depression
10.3. Vegetative symptoms and somatization subscales of the SCL-90-R developed by Derogatis and others
10.4. Jaw disability checklist

The CDA Criteria are used according to the Guidelines for the Assessment of Clinical Quality and Professional Performance of the California Dental Association: http://www.cda.org/library/cda_member/policy/quality/quality.html
Sources of funding German Research Foundation (Deutsche Forschungsgemeinschaft) (grant ref: WA 831/2-1 to 2-6 ) (Germany)
Trial website http://zahnreihe.klinikum.uni-muenster.de/
Publications 1. 2010 protocol in http://www.ncbi.nlm.nih.gov/pubmed/20170481
2. 2010 results in http://www.ncbi.nlm.nih.gov/pubmed/20400723
3. 2012 results in http://www.ncbi.nlm.nih.gov/pubmed/22699671
Contact name Prof  Michael  Walter
  Address Fetscherstr. 74
  City/town Dresden
  Zip/Postcode 01307
  Country Germany
  Tel +49 351/458 2706
  Fax +49 351/458 5314
  Email Michael.Walter@uniklinikum-dresden.de
Sponsor German Research Foundation (Deutsche Forschungsgemeinschaft) (Germany)
  Address Kennedyallee 40
  City/town Bonn
  Zip/Postcode 53175
  Country Germany
  Tel +49 228/885 1
  Fax +49 228/885 2777
  Email postmaster@dfg.de
  Sponsor website: http://www.dfg.de
Date applied 26/02/2008
Last edited 26/09/2012
Date ISRCTN assigned 04/04/2008
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