Oral Rehabilitation

Journal of

Journal of Oral Rehabilitation 2014 41; 515--522

Management of shortened dental arches and periodontal health: 5-year results of a randomised trial
* , K . V A C H † , J . S T R U B ‡ , T M U N D T § , H . S T A R K ¶ , M. H. WALTER*, B. MARRE € TMANN**, G. HEYDECKE††, M. KERN‡‡, S. HARTMANN§§, P . P O S P I E C H * , B . W OS ¶¶ R . L U T H A R D T , J . H U P P E R T Z * * * , S . W O L F A R T † † † & W . H A N N A K ‡ ‡ ‡ *Department of Prosthetic Dentistry, Faculty of Medicine Carl Gustav Carus, Technische Universit€ at Dresden, Dresden, †Department of Medical Biometry and Statistics, University Medical Center Freiburg, Freiburg, ‡Department of Prosthetic Dentistry, Albert-Ludwig University of Freiburg, Freiburg, §Department of Prosthodontics, Gerodontology and Biomaterials, Dental School, Ernst-Moritz-Arndt University of Greifswald, Greifswald, ¶Department of Prosthetic Dentistry, University of Bonn, Bonn, **Department of Prosthetic Dentistry, Justus-Liebig University Giessen, Giessen,

††

Department of Prosthodontics, University Medical Center Eppendorf, Hamburg,

Christan-Albrechts University, Kiel,

‡‡

Department of Prosthetic Dentistry,

§§

Department of Prosthetic Dentistry, Johannes-Gutenberg University of Mainz, Mainz,

¶¶

Department of

Prosthetic Dentistry, Center of Dentistry, Ulm University, Ulm, ***Department of Prosthetic Dentistry, Julius-Maximilians University of W€ urzburg, W€ urzburg,

†††

Department of Prosthodontics and Dental Materials, RWTH Aachen University, Aachen, and

‡‡‡

Department of

Prosthodontics, Geriatric Dentistry and CMD, Charite Universit€ atsmedizin Berlin, Berlin, Germany

In a multicentre randomised trial (German Research Association, grants DFG WA 831/2-1 to 2-6, WO 677/2-1.1 to 2-2.1.; controlledtrials.com ISRCTN97265367), patients with complete molar loss in one jaw received either a partial removable dental prosthesis (PRDP) with precision attachments or treatment according to the SDA concept aiming at pre-molar occlusion. The objective of this current analysis was to evaluate the influence of different treatments on periodontal health. Linear mixed regression models were fitted to quantify the differences between the treatment groups. The assessment at 5 years encompassed 59 patients (PRDP group) and 46 patients (SDA group). For the distal measuring sites of the posterior-most teeth of the study jaw, significant differences were found for the plaque index according to Silness and L€ oe, vertical clinical attachment loss (CAL-V), probing pocket depth (PPD) and bleeding on probing. These differences SUMMARY

Introduction Although the management of shortened dental arches and the shortened dental arch (SDA) concept have © 2014 John Wiley & Sons Ltd

were small and showed a slightly more unfavourable course in the PRDP group. With CAL-V and PPD, significant differences were also found for the study jaw as a whole. For CAL-V, the estimated group differences over 5 years amounted to 0
27 mm (95% CI 0
05; 0
48; P = 0
016) for the study jaw and 0
25 mm (95% CI 0
05; 0
45; P = 0
014) for the distal sites of the posterior-most teeth. The respective values for PPD were 0
22 mm (95% CI 0
03; 0
41; P = 0
023) and 0
32 mm (95% CI 0
13; 0
5; P = 0
001). It can be concluded that even in a well-maintained patient group statistically significant although minor detrimental effects of PRDPs on periodontal health are measurable. KEYWORDS: dental prosthesis, dental plaque index, periodontal attachment loss, periodontal pocket, gingival bleeding on probing, periodontal diseases Accepted for publication 22 February 2014

been subject of numerous studies and reviews (1–6), there is still sparse evidence on the clinical performance of different treatments with removable, fixed and implant borne restorations (7). A recently doi: 10.1111/joor.12160

516

M . H . W A L T E R et al. published retrospective study showed the long-term stability of SDAs (8). Little is known about differences between the treatment modalities in terms of periodontal health (9). Irrespective of the SDA condition, limited evidence is available for a superior clinical performance of fixed compared with removable restorations in terms of periodontal health (10–12). In summary of a literature review, qualitative and quantitative changes in plaque caused by partial removable dental prostheses (PRDPs) were reported (13). The evidence on the clinical performance of distal extension PRDPs retained with precision attachments is sparse. High rates of technical and biotechnical complications were found (14). Also, crowns and fixed dental prostheses (FDPs) may have various detrimental effects on gingival and periodontal health (15) although the impact appears to be minor (16) and less significant than with removable prostheses. In a literature review, an increased incidence of advanced gingival inflammation with fixed restorations was reported (17). The randomised shortened dental arch study (RaSDA) was designed to provide clinical outcome data for non-implant treatments with and without molar replacement. For the primary outcome tooth loss, previous analyses showed no significant differences between the treatment groups (18, 19). The aim of this current analysis was to evaluate periodontal health over 5 years. The null hypothesis was that the treatments do not lead to differences in periodontal health.

Materials and methods Trial design This study is a multicentre randomised controlled clinical trial with 14 participating university dental schools. It is registered at controlled-trials.com under ISRCTN97265367 (main trial). Participants Any patient over 35 years of age who requested prosthetic treatment and exhibited the required dental status was considered for participation. All molars had to be missing in one jaw (study jaw). At least the canine and one pre-molar had to be present on each side. Treatment and data collection were carried out in dental school settings (20).

Interventions Probing pocket depths ≤4 mm and generalised bleeding on probing rates ≤25% were pre-conditions to enter the prosthetic treatment phase. In the majority of cases, this condition had to be achieved by an appropriate pre-treatment. Two treatments were carried out after a standardised protocol. In the PRDP group, molars and missing second pre-molars were replaced by a PRDP. Precision attachments (Mini SG* ) were part of a splinted crown or an FDP retainer crown on the posterior-most tooth. The rationale for this denture type was that it was/is widely used in Germany and has no aesthetic limitations as clasps that could have biased patient satisfaction. In the SDA group, no prosthetic extension of the dental arch was conducted if the second pre-molar was present. If the posterior-most tooth was the first pre-molar, the second pre-molar was replaced by a cantilever FDP. In both groups, anterior gaps were closed with FDPs. The opposing jaw had to be sufficiently restored. Supportive periodontal therapy (SPT) was administered depending on individual patient needs according to the protocol of the participating centres for reasons of practicability. Therefore, heterogeneous patient care with regards to SPT was the result as a number of patients had regular check-ups and hygiene measures conducted by their family dentists. Outcomes Tooth loss was the primary outcome (19). The following periodontal secondary outcomes were assessed for all teeth: 1 2 3 4

Plaque index (PlI) according to Silness and L€ oe (21) Probing pocket depth (PPD), Vertical clinical attachment loss (CAL-V), Bleeding on probing (BOP).

The PlI was assessed at four sites per tooth. The measurements of PPD, CAL-V and BOP were conducted with a graduated periodontal probe (PCP-12† ) to the nearest mm at six sites per tooth. The CAL-V was measured from the cementoenamel junction or crown margin.

*Cendres + M
etaux SA, Biel/Bienne, Switzerland. †

Hu-Friedy, Manufacturing C., Chicago, IL, USA. © 2014 John Wiley & Sons Ltd

PERIODONTAL HEALTH IN SHORTENED DENTAL ARCHES The outcomes were assessed after treatment (baseline), at 6 months, and annually thereafter. All clinical examinations were conducted by trained and calibrated randomly assigned external examiners, in most cases in presence of the treatment coordinator.

protocol and sent a randomisation request to the biometrical centre. After receiving the randomisations, they were forwarded to the dental clinics by the treatment coordinator. Statistical methods

Calibration Independent experts performed the initial training and calibration. This also encompassed the periodontal outcome variables. Videos demonstrating the clinical procedures were recorded and made available in the password protected area of the study group website. The calibration meetings were repeated annually (20). Sample, analyses and randomisation Sample size calculation was based on an expected tooth loss rate of 20% for RDP and 5% for SDA after 5 years. Applying a two-sided primary significance test (alpha = 5%), 70 patients per group are required to provide 75% power of detecting treatment differences of the estimated magnitude (20). This was performed using randomly permuted blocks for each dental clinic with stratification into two age groups: up to 50 years und above 50 years of age. Allocation concealment The allocation concealment was warranted because the randomisation procedure was conducted centrally (Department of Medical Informatics and Biomathematics, University of M€ unster). The generation of the randomisation list, data management and statistical analyses were performed by different personnel. The statistical analysis plan was drafted independently from information about study groups. The statistician was not blinded to the information about the treatment groups. Randomisation – implementation Eligible patients, who contacted one of the participating study centres, were approached and data forms were completed. Once a patient had given his/her informed consent, the data forms with clinical findings and treatment planning were sent to the treatment coordinator. The treatment coordinator checked the data regarding their conformity with the study © 2014 John Wiley & Sons Ltd

The statistical analyses were conducted with STATA 12.1‡. The intention-to-treat principle was not applied. Two patients who had been allocated to the SDA group but received the PRDP treatment at fault and one patient who switched from SDA to PRDP treatment immediately after insertion were not included in the analysis. Drop-outs, patients lost to follow-up and patients with loss of the posterior-most tooth were included up to their last examination. Linear mixed regression models were fitted to quantify the differences between the treatment groups relative to the change of the outcome variables over time. We assumed a separate baseline of the groups. There were variations within each centre and between the centres. Therefore, we used a model allowing each centre its own mean slope over time for each treatment group. The fitted model allowed each patient, each measuring point, each group and each centre to have a mean separate slope. The procedure was carried out for PlI, PPD and CAL-V. For BOP, variables were formed that described the rate of bleeding sites per patient, site and point in time. For all four outcome variables, separate analyses were conducted for all teeth in both jaws together, the opposing jaw alone, the study jaw alone and the disto-buccal and disto-oral sites of the posterior-most teeth of the study jaw. The rationale for the latter approach was the expected high impact of the treatment at these sites (11). In all analyses, the level of significance was set to P = 0
05.

Results Two hundred and fifteen patients were enrolled. (Fig. 1). The assessment at 5 years encompassed 59 patients in the PRDP group and 46 patients in the SDA group. Current smoking was reported in 19% (PRDP group) and 32% (SDA group), diabetes in 7% (PRDP

‡

StataCorp LP, College Station, Texas, USA.

517

M . H . W A L T E R et al. Randomized (N = 215)

Allocation

Treatment A: PRDP group

Allocated to intervention (N = 109) •Age (years), mean (SD): 59.3 (11.2) •Female N (%): 49 (45.0%) •Number of teeth, mean (SD): 15.5 (4.6)

Follow-up

Intervention

Did not receive allocated intervention (N = 28)

Analysis

518

•Refusal of randomization results (N = 6) •High costs (N = 3) •Impaired state of health (N = 3) •Disapproval by health insurance (N = 2) •Loss off eligibility through tooth loss(N = 2) •Time expenditure (N = 1) •Relocation (N = 1) •Preference of alternative restoration (N = 1) •No-show (N = 5) •Deceased (N = 1) •Unknown (N = 3)

Treatment B: SDA group

Allocated to intervention (N = 106) •Age (years), mean (SD): 59.6 (10.3) •Female N (%): 58 (54.7%) •Number of teeth, mean (SD): 14.8 (5.1)

Did not receive allocated intervention (N = 35) •Refusal of randomization results (N = 13) •High costs (N = 3) •Impaired state of health (N = 1) •Disapproval by health insurance (N = 2) •Loss off eligibility through tooth loss (N = 1) •Time expenditure (N = 1) •Relocation (N = 1) •Preference of alternative restoration (N = 4) •No-show (N = 6) •Deceased (N = 0) •Unknown (N = 3)

Received allocated intervention (N = 81) Got false intervention (N = 0) •Age (years), mean (SD): 60.4 (10.6) •Female N (%): 41 (50.6%) •Number of teeth, mean (SD): 14.8 (4.6)

Received allocated intervention (N = 69) Got false intervention (N = 2) •Age (years), mean (SD): 59.6 (10.4) •Female N (%): 41 (57.7%) •Number of teeth, mean (SD): 13.6 (5.2)

Lost to follow-up (N = 10) •Withdrew from study (N = 7) •Relocated (N = 2) •Lost interest in participation (N = 3) •Unknown (N = 2) •Deceased (N = 3) Discontinued intervention (N = 12) •Switched treatment -Poor adaptation to RDP (N = 1) •Alternative restoration after complication (N = 11)

Lost to follow-up (N = 10) •Withdrew from study (N = 8) •Impaired state of health (N = 1) •Lost interest in participation (N = 3) •Unknown (N = 4) •Deceased (N = 2) Discontinued intervention (N = 13) •Switched treatment -Instant dislike of the restoration after insertion (N = 1) -Problems with chewing and missing molars (N = 2) •Alternative restoration after complication (N = 10)

Analyzed (N = 81)

Analyzed (N = 68)

Fig. 1. Participant flow.

group) and 9% (SDA group). Related to quadrants, the posterior-most teeth in the study jaw at baseline were 161 second pre-molars and 133 first pre-molars. According to the protocol, all posterior-most teeth were crowned in the PRDP group. In the SDA group, this applied to 109 teeth (80
1%). 69 (SDA group) and 67 (PRDP group) second pre-molars had to be replaced. In 23 (SDA group) and 22 patients (PRPD

group), front teeth/incisors were replaced by an FDP. In six cases (SDA group), all pre-molars and anterior teeth were present and no restoration needed (19). The baseline mean values for PPD were 2
26 (s.d. 0
63) mm (PRDP group) and 2
27 (s.d. 0
61) mm (SDA group). The baseline mean values for CAL-V were 2
66 (s.d. 1
03) mm (PRDP group) and 2
68 (s.d. 0
96) mm (SDA group). © 2014 John Wiley & Sons Ltd

PERIODONTAL HEALTH IN SHORTENED DENTAL ARCHES

Fig. 2. Estimated increase in vertical clinical attachment loss (red line-PRDP, blue line-SDA) during the study period.

Table 1. Results of mixed linear models for plaque index and bleeding on probing. Five-year changes in the groups and group differences over 5 years (dimensionless). Ninety-five per cent confidence intervals in parentheses

Group, time interval Plaque index PRDP over 5 years SDA over 5 years Group difference over 5 years Bleeding on probing PRDP over 5 years SDA over 5 years Group difference over 5 years

All teeth

Opposing jaw

Study jaw

Distal sites of posterior-most teeth (study jaw)

0
31 (0
09; 0
52) 0
16 (0
01; 0
31) 0
15 ( 0
12; 0
04) P = 0
278

0
31 (0
06; 0
55) 0
13 ( 0
15; 0
40) 0
18 ( 0
09; 0
44) P = 0
188

0
32 (0
11; 0
54) 0
17 (0
03; 0
32) 0
15 ( 0
11; 0
41) P = 0
263

0
31 (0
10; 0
52) 0
01 ( 0
14; 0
16) 0
31 (0
06; 0
55) P = 0
015*

0
11 (0
05; 0
18) 0
07 ( 0
003; 0
14) 0
04 ( 0
05; 0
14) P = 0
375

0
13 (0
05; 0
20) 0
08 ( 0
007; 0
18) 0
04 ( 0
06; 0
15) P = 0
427

0
06 (0
04; 0
17) 0
11 ( 0
01; 0
13) 0
05 ( 0
05; 0
14) P = 0
310

0
14 (0
07; 0
21) 0
02 ( 0
08; 0
11) 0
13 (0
01; 0
24) P = 0
031*

*Significant difference.

Table 2. Results of mixed linear models for vertical clinical attachment loss and probing pocket depth. Five-year changes in the groups and group differences over 5 years in mm. Ninety-five per cent confidence intervals in parentheses

Group, time interval Vertical clinical attachment loss PRDP over 5 years SDA over 5 years Group difference over 5 years Probing pocket depth PRDP over 5 years SDA over 5 years Group difference over 5 years

*Significant difference. © 2014 John Wiley & Sons Ltd

All Teeth

Opposing jaw

Study jaw

Distal sites of posterior-most teeth (study jaw)

0
34 (0
15; 0
53) 0
12 ( 0
05; 0
29) 0
22 ( 0
2; 0
46) P = 0
073

0
37 (0
11; 0
63) 0
29 (0
07; 0
51) 0
08 ( 0
26; 0
42) P = 0
635

0
36 (0
20; 0
52) 0
09 ( 0
08; 0
26) 0
27 (0
05; 0
48) P = 0
016*

0
41 (0
27; 0
56) 0
16 (0
002; 0
32) 0
25 (0
05; 0
45) P = 0
014*

0
29 (0
15; 0
43) 0
11 ( 0
04; 0
26) 0
18 (0;0
36) P = 0
052

0
31 (0
10; 0
51) 0
26 (0
08; 0
45) 0
04 ( 0
23; 0
31) P = 0
751

0. 32 (0
18; 0
46) 0
1 ( 0
05; 0
25) 0
22 (0
03; 0
41) P = 0
023 *

0
37 (0
22; 0
52) 0
05 ( 0
11; 0
21) 0
32 (0
13; 0
5) P = 0
001*

519

520

M . H . W A L T E R et al. At 5 years, all patients of the RPDP group confirmed that the denture was worn regularly. Moderate increases over time in all secondary outcomes were found in both groups. The regression lines for CAL-V are visualised in Fig. 2. Overall, a more unfavourable course was found in the PRDP group as expressed by a number of small but significant group differences (Tables 1 and 2). All given 5-year values were calculated by multiplying the computed values per month by 60. For all teeth and the opposing jaw, no significant group differences were found. For the study jaw, significant differences were found with CAL-V and PPD amounting to 0
27 mm per 5 years and 0
22 mm, respectively. Significant differences in all outcomes were found at the distal sites of the posterior-most teeth in the study jaw. For only one of the six significant effects, we observed a variation suggesting that 15% of the centres have a negative treatment effect (a deterioration of plaque index over time in the PRDP group). This however had no significance for the differences between the treatment groups.

Discussion Basically, periodontal variables exhibited data in the range of sound values with both treatments. There was a slightly more unfavourable 5-year course of periodontal health in the PRDP group. Significant differences between the groups were found but only for the study jaw and at the distal sites of the posterior-most teeth of the study jaw. The null hypothesis had to be rejected. The external validity of the study is certainly limited by the use of precision attachment-retained PRDPs, leading to a more rigid connection compared with clasp retained dentures. Attachment-retained PRDPs are common in Central Europe and had been chosen for that reason but are less common worldwide. The rate of patients who quit because of the randomisation results was about twice as high in the SDA group. This was unavoidable but could have slightly influenced the results. The intention-to-treat principle was not applied. Bias resulting from incomplete outcome data could have been expected. However, the number of excluded patients in both study groups is nearly similar, so this aspect can be neglected. Regarding the detected differences, it can be stated that the assumed negative impact of removable dentures on periodontal health could be confirmed,

however with very low effect sizes. The validity of the results is strengthened by the finding that all periodontal variables showed changes in the same direction: they point to a slight decline/worsening of periodontal health in the PRDP group. So far, respective group differences for most other variables such as tooth loss and oral health-related quality of life could not be found (22, 23). The increase in CAL-V measured in the PRDP group was above the values from an extensive epidemiological study in Germany. In this study, mean changes of 0
10 mm over 5 years were reported in subjects aged 20 to 81 years (24). Our higher values are probably due to a higher mean age and the fact that we examined a sample of patients with a history of multiple tooth loss. The distal surface of the posterior-most teeth is known to be at particular risk (9, 11). Lower premolars serving as PRDP abutment teeth were reported to show a tendency towards a lower bone height (9). Our results confirm this susceptibility of the posteriormost teeth. Our findings also strengthen the assumption of higher plaque accumulation with PRDPs (12). In parts, this might be explained by the extracoronal location of the attachments we used. The results for PII and BOP demonstrate the need for hygiene measures at these areas (and confirm the significance of oral hygiene in general). On the whole, the extent of detrimental effects of PRDPs on periodontal health can be appropriately expressed as a slightly increased periodontal risk. It should be emphasised, however, that the vast majority of values was found to lie in the range of sound values in both groups. This is in line with the respective analyses of tooth loss (18, 19). In only four cases, compared with two in the SDA group, tooth loss in the study jaw of the PRDP group was attributed to periodontal problems (19). The causes for the worse results in the PRDP group could be a change in the microflora and/or qualitative as well as quantitative changes in plaque (13). Important factors in PRDPs that might be causal for negative changes are a higher tendency to food impaction and also a potentially more difficult cleaning. Additionally, the fact that in the PRDP group, all posterior-most and second posterior-most teeth were crowned might have had a negative impact on the periodontal variables. It remains unclear whether the observed changes will have any future impact on the incident tooth loss. © 2014 John Wiley & Sons Ltd

PERIODONTAL HEALTH IN SHORTENED DENTAL ARCHES The findings strengthen the assumption of the SDA being a stable condition in a high portion of patients (1, 2). In view of our results, no damaging effects of SDAs on periodontal health have to be expected.

Conclusions From the results it can be concluded, that even in a well-maintained patient group minor detrimental effects of PRDPs on periodontal health are measurable. However, in less well-maintained patient groups, the effects might be greater. The posterior-most abutment teeth appear to be at a particular risk. Regarding these findings, potential periodontal risks and benefits relative to quality of life and patient’s preferences have to be carefully weighed against each other. Many patients with sufficient remaining teeth might prefer the SDA approach for financial reasons. Overall, the outcome of attachment-retained PRDPs in terms of periodontal health was found to still be good. The small negative effects do not justify a rejection of PRDPs when they are indicated. Furthermore, the good clinical course regarding periodontal variables in patients with premolar occlusion adds further evidence to the clinical validity of the SDA concept and might increase the limited professional application of this concept (4).

Acknowledgments The study was approved by an ethical board (TU Dresden, EK 260399) and is registered at controlledtrials.com under ISRCTN68590603 (pilot trial) and ISRCTN97265367 (main trial). We acknowledge the contribution of the following members of the RaSDAstudy group: W. Reinhardt, F. Jahn (Department of Prosthetic Dentistry and Dental Material Science, University of Jena), T. Reiber (Department of Prosthetic Dentistry and Dental Material Science, University of Leipzig), W. Gernet (Department of Prosthetic Dentistry, Ludwig-Maximilians University Munich) and E. Busche (Department of Prosthetic Dentistry, Witten-Herdecke University) in study design, study implementation and data collection.

Funding The study was supported by the Deutsche Forschungsgemeinschaft (German Research Association), Grant DFG WA 831/2-1 to 2-6, Grant DFG WO 677/2-1.1 © 2014 John Wiley & Sons Ltd

to 2-2.1. The first author was the principal grant holder.

Conflict of interests The authors declare no potential conflict of interests with respect to the authorship and/or publication of this article.

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