PROSTHETIC REHABILITATION OF SHORT DENTAL ARCH: SYSTEMATIC REVIEW

Mostafa Saad Swedan 1 , Ahmed Y. Alqutaibi 2 , Samah K. Ezzat 3 , Radhwan S. Algabri 1 , Ahmed M. Keshk 1 and Amal Kaddah 1 . 1. Department of Prosthodontics, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. 2. Department of Prosthodontics, Faculty of Oral and Dental Medicine, Ibb University, Ibb, Yemen. 3. Depattment of Oral Biology, Faculty of Dentistry, Mansoura University, Mansoura, Egypt. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

Treatment with RPDs is the most common of these options, because it is noninvasive and inexpensive. However, patients who have missing posterior teeth frequently stop wearing RPDs [23][24][25] Furthermore, treatment with RPDs has a high "biological cost" with high caries incidence and periodontal breakdown of abutment teeth [26][27][28] . Thus, fixed restorations using CFPDs or IFPDs are recommended as alternative options for replacement of distal extension edentulous space especially in patients who have high risk for caries occurrence and periodontal disease [29][30][31][32] .
RPDPs, FDPs and implant procedures evidently operate on the premise of optimal occlusion encompassing the aesthetics, oral function, oral health and comfort created by the occluding teeth. This practice appears to have evolved empirically, with no scientific or clinical evidence to support its widespread acceptance by clinicians 14,21,22,[33][34][35][36][37] . Restoration for distal extension edentulous space using CFPDs is usually limited up to the second premolar, thus missing molars remain unrestored (premolar occlusion).
The aim of this systematic review was to identify and analyses existing clinical trials which compare the biological effect and quality of life outcomes of prosthodontic interventions used for treating shortened arches versus unrestored shortened arches in partially dentate adult patients.
The following research question addresses the aim and objectives of the study: In adult patients with shortened dental arches, what is the effect of prosthodontics interventions on the harmful effect and OHRQoL compared to having no treatment?
Review method:-A prior protocol was made for this systematic review and registered at the International prospective register of systematic reviews (PROSPERO2016: CRD42017056090). Accessible from http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42017056090.
Search Strategy:-This systematic review was conducted in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines.
An electronic search was carried out utilizing the PubMed and the Cochrane CENTRAL databases for articles published in English till the end of March 2017. The following keywords were used: "short dental arch or SDA or removable partial dentures or PPDs or cantilever fixed partial dentures or CFPDs or implant supported fixed partial dentures or IFPDs or biological complication and oral health quality of life".

90
Exclusion criteria were as follows: any clinical trial other than RCTs, In vitro studies, case reports, technical reports, studies on animals, studies on maxillofacial defects and studies in language other than English language.

data collection
The search included two stages. During the first stage titles and abstracts were monitored by two independent reviewers. Full texts were obtained if the studies meet the inclusion criteria or if the titles and abstracts are not giving obvious data to make a clear decision. In the second stage, data extraction was done separately by the same reviewers. Disagreements were discussed to reach a decision, and if not resolved a third reviewer was conferred. Data extraction from the included studies were as follows: Authors, time of publication, gender, mean of age in years, follow-up period in years, number of patients in every group and mode of treatment.

Quality assessment
Assessment of the quality of individual studies was done separately and in duplicate by the same reviewers. The criteria for quality assessment among RCTs were performed by means of Cochrane Collaboration Risk of Bias Tool 38 . This tool covers sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting (reporting bias), and other potential sources of bias. Each domain was judged as low risk or high risk otherwise, when there is deficient data to make a decision the study is rated, unclear risk.

summary measures
Meta-analysis of the included studies was done in case of similarity of comparisons and outcomes considering the patients as the statistical unit.

publication bias
In case of inclusion of 10 or more studies in the present systematic review, a funnel plot is performed. If asymmetry was shown in the plot, there is a possibility of publication bias.

search result
Search results are summarized using PRISMA flow chart ( Figure 1). 487 titles were selected from Initial search and an additional one study identified through other sources, after removal of duplicates, 313 Records screened and 294 records excluded. From 19 Full-text publications evaluated for eligibility, a11 Full-text publications were excluded with reasons, thus, an 8 full text randomized clinical trials were selected and considered eligible for inclusion ( Table  1). The reasons for study exclusion are given in (Table 2).

Characteristics of included studies
The selected eight studies were RCTs and were published between1987 to 2017. The observation period ranged from 12 months to 5 years. All of the studies were conducted in a university setting. Characteristics of included studies are listed in (Table 1). The included trials comprise the following comparisons: compare between rehabilitated of free end saddle with RPDs and CFPDs versus SDA concept. The studies were grouped according to types of interventions into the following comparisons: Comparison 1: FDPs versus RPDPs for SDAs in the lower jaw. Two included studies from the UK and Denmark assessed comparison 1 33,34,37,[39][40][41][42][43] . Comparison 2: RPDPs versus no treatment (SDA). five studies from Germany and Ireland assessed comparison 2 [44][45][46][47][48][49][50][51][52][53][54] Comparison 3: SDA versus CDA. Only one study from the Netherlands assessed comparison 3 10,55,56 . Table(4) specifies the quality assessment of the included studies and these are summarized in the "risk of bias table" and "risk of bias graph" where judgements are categorized to indicate a low, high, or unclear risk of bias following the Cochrane guidelines. Below we give a detailed explanation of these results: Sequence Generation: Three of the eight trials were reported as having been randomized. For sequence generation, two clinical trials used computergenerated numbers and a third trial used randomly permuted block randomization for generating the allocation sequence, which we judged as having a low risk of bias [39][40][41][42][46][47][48][52][53][54] .

Quality assessment of included studies:-
The Witter et al (2001) clinical trial invited subjects to join the department for a study, and no attempt was made to randomize patients, thus it is judged as having a high risk of bias [55][56][57] . The Budtz-Jorgensen and Isidor and Shoi et 91 al. (2014) trials did not mention how the sequence was generated and provided insufficient information to enable us to judge whether there was ahigh or low risk of bias, and we thus rated it as having an unclear risk of bias 33,34,37,49 .
Blinding: The Moynihan et al (2000) study was referred to as a double blinded study with the clinician blinded to allocation of intervention and statistician being blinded to treatment and thus it is judged as having a low risk of bias [39][40][41][42] . The Witter et al (2001) study can be considered as a single blinded study because evaluation of outcomes was completed by a calibrated observer at all intervals, but it was not stated as such, thus it is judged as having an unclear risk of bias [55][56][57] . Mc Kenna (2012) indicated that the researcher was not involved in the intervention allocation, making it a single-blinded study, thus it is judged as having a low risk of bias 47,48 . The Wolfart et al (2005) study indicated that it was impossible to blind the dentist and patient due to discrepancies of the treatments; thus it was judged as having a high risk of bias, whereas Budtz-Jorgensen and Isidor (1987) provided insufficient information related to blinding and it was regarded as having an unclear risk of bias 33,34,46,[50][51][52][53][54] (2012) studies were conducted on the ""intention-to-treat"" (ITT) principle; and the studies reported proportionate numbers of losses to follow-up (which were small) and some having no losses between the intervention and control [39][40][41][42][46][47][48][50][51][52][53][54] . Witter et al (2001) indicated that regression models accounted for the subjects lost during the study 56 . Thus, all 4 studies above were judged as having a low risk of bias [39][40][41][42][46][47][48][50][51][52][53][54] . On the other hand, Budtz-Jorgensen and Isidor (1987) did not indicate and specify how the analysis was completed, but all pre-specified outcomes were reported, and the number of losses to follow-up was small, thus it was judged as having a low risk of bias 33,34,37 . In the Budtz-Jorgensen and Isidor (1987) and Witter et al (2001) studies all outcomes were reported but outcomes were not prespecified as primary or secondary outcomes 33,34,37,[55][56][57] Both these studies were thus judged as having a high risk of bias. The three remaining RCTs specified the outcomes as primary and secondary and reported these as such, thus these were judged as having a low risk of bias [39][40][41][42][46][47][48][50][51][52][53][54] . Other potential sources of bias: No other sources of bias were detected with four of the five included studies. The Budtz-Jorgensen and Isidor (1987) study was judged as having high risk of bias because there were six patients who did not wear the RPDP at all during the study 33,34,37 .  41 . Similarly, Isidor and Budtz-Jorgensen (1990) observed 22 dental carious lesions in the RPDP group compared with only two lesions in the FDP group; however we could not calculate a treatment effect since the respective number of patients was not reported. Our unit of analysis was individual patients and not individual teeth 37 .
Tooth Loss: In the Isidor and Budtz-Jorgensen (1990) study, 11 teeth were extracted in the RPDP group compared with only one tooth in the FDP group during the five years of observation. However, no treatment effect could be calculated because the respective numbers of patients were not reported 37 . . They also reported that spacing remained the same in all regions over time in the SDA group 56 . No treatment effect could be calculated because the results were given per region and also because the respective number of patients were not specified in the results.
Excluded study characteristics: All non-RCTs and reviews were excluded from this SR. Other SRs and summary articles were viewed as potentially included studies, but these were however later not considered for inclusion (Table2)

Discussion:-
Studies comparing treatment outcomes within subjects before and after treatment indicated that RPD improved masticatory function, patient satisfaction and OHRQoL. However, studies that compared the outcomes between subjects found that patients with RPDs did not show significantly greater masticatory performance, patient satisfaction and OHRQoL than for those with CFPDs (premolar occlusion) or no restoration for missing molars. Furthermore, treatment with RPDs showed higher risk for caries incidence, gingival inflammation and poor oral hygiene than treatment with CFPDs. Survival rate and tooth loss in patients with CFPDs were not significantly less than in patients with RPDs, but more visits for maintenance after treatment were required in patients with RPDs. These suggest that treatment with RPDs does not have significant advantage over treatment with CFPDs. Risks for TMD and occlusal instability without restoration of missing molars were not higher than for treatment with RPDs. Therefore, the SDA concept seems to be a more favorable option than treatment with RPDs when considering a minimum intervention approach. However, it should be noted that the SDA concept may be contraindicated in 93 patients under 50 years of age and with malocclusion such as Angle"s Class III or a sever Class II relationship, evidence for parafunction, pre-existing TMD and a marked reduction in alveolar bone support for remaining teeth 59 . Budtz-Jorgensen (1987, 1990) regarding an increase in caries incidence as reported 2 and 5 years post treatment 37,41,43 . In addition, the increase in caries incidence for the RPDP group also concurred with the research of Bergman et al, (1964), cited in Budtz-Jorgensen (1990) 33 .

Jepson et al (2001) and
other studies 33,34,39,43 . For patient satisfaction, the small sample size does not allow us to generalize our results to other settings, thus it is advised to conduct these studies amongst different populations. Tooth loss as a primary outcome is questioned due to extended time periods, thus it was advised to use caries and periodontal attachment loss as outcomes instead 51 .
The Mc Kenna study (2012), which is the most recently conducted RCT; the results are similar to other RCTs completed in the past, where small sample sizes would not necessarily show a significant difference between interventions given the follow-up 47,48 . In this case, follow-up after only one month of treatment was too short to show any difference between interventions 47,48 .But the cost-effectiveness reported with this RCT has been noted as researchers and clinicians are under the impression that the cost for FDPs far outweighs that of RPDP treatment 22,47,60 . And this has been in line with the findings of the Danish study published some years ago 33,37 .
The quality of the evidence is indicative of the integrity of the study and the research conducted. With reference to the quality assessment of the included studies, this has been described in detail above. More importantly, this quality is determined by the study designs. Study designs are graded according to the quality of evidence that they provide. Systematic reviews and RCTs are considered to be designs of the highest quality 38,61 .
Only RCTs were included in this systematic review which provides stronger evidence and increases the strength of the recommendations. After completing the quality assessment (using the GRADE approach) of the included studies, it clearly showed that some of the studies had not followed the exact guidelines for RCTs, but nevertheless had the features thereof 38,61 . These can be regarded as downgraded RCTs. These downgraded RCTs did not use randomization, allocation concealment or blinding, and failed to specify the outcomes as primary or secondary. These downgraded RCTs could thus affect the quality of evidence only slightly 38,61 . For example, the Budtz-Jorgensen (1987,1990) and Witter et al (2001) studies could be regarded as downgraded CTs 10,33,34,37,[55][56][57] .

Conclusion:-
The results from this SR related to SDAs as a treatment option, it would have strengthened the recommendation of the SDA as a treatment option for partially edentulous patient.   63 Cross sectional study Armellini 64 Cross sectional study Astrand 65 Combination of natural teeth with implant Onur Cakir 66 Implant supported prosthesis Roger A. 67 Case control GONCALVES 68 Implant supported prosthesis IVAN TANASIĆ 69 In vitro study NISSAN 70 Not SDA Ohkubo 71 Pilot study Sanchez 72 Not RCT FUEKI 73 Not RCT   45 Low risk Low risk Low risk unclear unclear High Aras 44 Low risk Low risk Low risk unclear High unclear SHOI 49 97 Full-text articles excluded, with reasons (n =11)