Comparison of the impact of two types of removable partial dentures on the periodontal health of the remaining teeth: A prospective clinical study

Abstract Objective To evaluate and compare the impact of two removable partial dentures (acrylic removable partial denture [ARPD] and metallic removable partial denture [MRPD]) on periodontal tissues of the remaining teeth in the first 12 months of denture use. Materials and Methods This prospective clinical study included 40 patients, of which 20 received ARPDs, 20 received MRPDs, nine in the maxilla, and 11 in the mandible each. The patients were 45–65 years old; 24 were females, and 16 were males. Patients’ demographic details, clinical indicators of periodontal complications, and biochemical measurement of Hs‐C‐reactive protein (CRP) and alkaline phosphatase (ALP) were considered. One‐way analysis of covariance and Friedman were used to measure the differences in clinical periodontal parameters between the two types of dentures. Results The significant findings were: Plaque index (PLAQ) scores for abutment teeth were higher in MRPD wearers (mean = 12.15) than ARPD wearers (mean = 10.45), whereas ARPD users had significantly higher mean bleeding on probing (BOP) values (mean = 1.5) than MRPD users (mean = 0.00); mobility of abutment teeth showed no significant differences; timeline comparisons showed a significant increase in the percentage of nonabutment teeth mobility in ARPD users (p = .028) compared with MRPD users over the same follow‐up period (p = .102). Conclusions For a short‐term period of 1 year, periodontal and mobility parameters have no significant impact on the abutment and nonabutment teeth of ARPD and MRPD users. Moreover, biochemical markers (CRP and ALP) for periodontal inflammation exhibited no significant difference in both types of dentures.


| INTRODUCTION
Removable partial dentures (RPDs) are the most commonly used removable prosthodontic appliances for partial edentulism. Prosthodontic treatment with RPDs is indicated when fixed prosthodontic treatment is ruled out due to clinical or financial factors. Therefore, it is unsurprising that treatment with RPDs is generally less successful than fixed prosthodontic solutions (Vermeulen et al., 1996). The most common disadvantages of partial dentures are poor oral hygiene, negative impact on the remaining natural teeth, and limited oral comfort (Creugers & de Baat, 2009). However, the proper design of RPD can significantly reduce the incidence of such problems (Fueki et al., 2014). Metal framework dentures have certain advantages over acrylic-based dentures, for instance, providing a stable denture base and maintenance of oral hygiene (Fueki et al., 2014). Technical and biological complications due to denture wear have been called time-related issues (Tong et al., 2015). The denture base material may have a critical impact on denture-supporting tissues. However, acrylic removable partial dentures (ARPDs) may cause problems with the abutment teeth more frequently than Co-Cr bases, as acrylic is not as rigid as Co-Cr alloys, making it prone to fracture (Yoshida et al., 2011). One study has shown that ARPDs cause inflammation of gingival tissues more than metallic removable partial dentures (MRPDs) F I G U R E 1 Measurement of periodontal clinical parameters.
F I G U R E 2 Biochemical analysis: (a) venous blood withdrawal, (b) biochemical analysis, (c) overview of the results. (Bissada et al., 1974). Treatment with ARPDs may result in a rapid loss of the remaining natural teeth and can pose a higher risk for complete edentulism (Allen, 2011).
Biological complications that cause a faster deterioration of the patient's health are more often caused by removable partial dentures than fixed dental dentures (FDPs) Thomason et al., 2007). Dentists aim to diagnose periodontal changes that could compromise the long-term prognosis and therapeutic outcomes (McGivney & Castleberry, 1989). Oral hygiene is even more important for patients with RPDs than their counterparts with fixed appliances ). Since RPDs can cause harmful changes in the quality and quantity of plaque, patients must ensure the highest level of plaque control (Ghamrawy, 1976). One study established that RPDs can increase the risk of dental plaque, gingivitis, and caries but not periodontal disease (Preshaw et al., 2011). Other studies haven't observed any changes in the periodontal parameters in a group of patients with clasp-retained RPDs, which is interesting since the clasp is generally placed around abutment teeth, resulting in plaque accumulation (Bergman et al., 1995;Ellakwa, 2012).
Periodontitis is characterized by a nonspecific acute-phase response with acute-phase reactants like CRP (Chalmers et al., 2008).
It was observed that increased C-reactive protein (CRP) levels persisted among individuals with extensive periodontal diseases (Slade et al., 2000). Also, there is a strong correlation between the intensity of the inflammatory process in periodontal tissues and the level of alkaline phosphatase (ALP) activity (Ainamo et al., 1990).
Periodontal changes in abutment and non-abutment teeth in both MRPDs and ARPDs have not been assessed. Biochemical markers of periodontal inflammation (CRP and ALP) have never been used to monitor the effects of denture treatment on the human body.
Hence, this study aims to evaluate and compare the impact of two removable partial dentures (ARPD and MRPD) on the remaining teeth and periodontal tissues in the first 12 months of denture use. Note: One-way analysis of covariance test.
F I G U R E 3 Mean MPD and MAL scores for patients with MRPDs and ARPDs at three-time intervals (abutment teeth). ARPDs, acrylic removable partial dentures; MAL, mean attachment level; MPD, mean probing depth; MRPDs, metallic removable partial dentures.
F I G U R E 4 Mean PLAQ and BOP scores for patients with MRPDs and ARPDs presented at three-time intervals (abutment teeth). ARPDs, acrylic removable partial dentures; BOP, bleeding on probing; MRPDs, metallic removable partial dentures; PLAQ, plaque index.
RPDs. Twenty-four participants were females, and 16 were males.
The periodontal condition in abutment and non-abutment teeth of 40 patients was examined through mean probing depth (MPD) and mean attachment level (MAL) expressed in mm, plaque index (PLAQ), and bleeding on probing (BOP) expressed in percentage, and mobility (MOB) at Time 1 (T1), Time 2 (T2), and Time 3 (T3) of wearing RPDs (Figure 1).
-MPD was measured from the gingival margin to the base of the periodontal pocket using a periodontal probe (PCP, UNC-15, and Hu-Friedy) -The clinical attachment level (CAL) was measured from the cementoenamel junction (CEJ) to the base of the pocket.
-Mobility was evaluated using Miller's classification (Miller, 1985 Note: One-way analysis of covariance test. Abbreviations: ARPDs, acrylic removable partial dentures; BOP, bleeding on probing; MAL, mean attachment level; MPD, mean probing depth; MRPDs, metallic removable partial dentures; PLAQ, plaque index. comparison of clinical periodontal and biochemical paramteres (CRP and ALP) for the abutment and non-abutment teeth was carried out with the One-way analysis of covariance test for the two types of dentures at three different time points (T1, T2, and T3).

| RESULTS
The study was carried out on a sample of 40 patients-24 females (60%) and 16 males (40%)-with a mean age of 53.6 years (±8.60), of which 32.5% were living in rural areas and 67.5% in urban areas. The frequency distribution of the patients' education, type of denture, and antagonist jaw are presented in Table 1.
Cross-tabulation of the type of denture and antagonist jaw shows the percentage of patients with MRPDs and ARPDs that received prosthodontics treatment or had natural teeth in their antagonist jaw (Table 2).
Periodontal parameters for non-abutment teeth did not vary significantly between the two types of dentures at three different intervals. The recorded values for various periodontal parameters are in Table 4, Figures 5 and 6.
F I G U R E 5 Mean MPD and MAL scores for patients with MRPDs and ARPDs presented at three-time intervals (non-abutment teeth). ARPDs, acrylic removable partial dentures; MAL, mean attachment level; MPD, mean probing depth; MRPDs, metallic removable partial dentures.
F I G U R E 6 Mean PLAQ and BOP scores for patients with MRPDs and ARPDs at three-time intervals (non-abutment teeth). ARPDs, acrylic removable partial dentures; BOP, bleeding on probing; MRPDs, metallic removable partial dentures; PLAQ, plaque index.
In (Table 5) the percentage of mobile teeth and the percentages of time-point mobility for each type of denture (MRPDs and ARPDs) have been noted, and in (Table 6) obtained results for two kinds of dentures were compared using one-way analysis of covariance.
The percentage of mobile nonabutment teeth was calculated, and percentages of time-based mobility for each type of denture were presented (Table 7).
Hs-CRP and ALP levels were measured for both types of dentures at three different time intervals. The results for patients with MRPDs did not show any statistically significant differences in ALP values at the three-time intervals (p-value = .116) (Table 8), and similar results were obtained for CRP values (p-value = .387).
However, a post hoc analysis revealed a slightly significant increase in CRP values from 178.29 to 290.93 (p-value = .048) at T2 ( Table 9).
The One-way analysis of covariance was performed to assess the differences in ALP and CRP levels between both types of dentures after a particular time. Covariates were incorporated, and the adjusted means were compared. The mean values were adjusted according to the initial values, and the outliers were deleted from the data set. The assumption for homogeneity was checked with Levene's test for homogeneity of variance, and the interaction between the covariate and the independent variable, if any, was assessed. In all the cases, the assumption of homogeneity of regression slopes was met (Table 10).

| DISCUSSION
A removable partial denture remains the most common treatment for partially edentulous jaws or severely compromised dentition. The main goal of a prosthodontic appliance is to restore the esthetics and function of the oral cavity without further damage to the oral tissues.
In our study, analysis of periodontal parameters performed between the abutment teeth of MRPD and ARPD wearers revealed no significant difference between MPD and MAL measurements at various time intervals. A significant difference was observed between the PLAQ scores, where in MRPD patients, mean scores (mean = 12.15) were higher compared with the patients wearing an ARPD (mean = 10.45). Furthermore, a difference was observed in BOP scores where ARPD users had significantly higher values (2.55) when compared to their MRPD counterparts (2.00). These results match the study conducted in Kosovo, where there was an increase in the mean scores of BOP, PD, and plaque index on the abutment teeth three months following RPD insertion (Dula et al., 2015). Another study observed an increased prevalence of plaque, gingival recession, and gingivitis, especially on dentogingival surfaces within 3 mm proximity to the dentures (Yeung et al., 2000). Furthermore, a study by Amaral et al. (2010) concluded that plaque scores, mean probing depth, and gingival index score had increased significantly in abutment teeth compared to non-abutment teeth at a follow-up period of 3 months.
T A B L E 5 Time comparison of abutment teeth mobility in patients with MRPDs and ARPDs. Note: One-way analysis of covariance test.
Periodontitis is characterized by a pathological deepening of the gingival sulcus. Our study shows a slight increase in clinical periodontal measurements in both abutment and nonabutment teeth observed across both types of RPDs. A study showed that high plaque scores and a maintenance interval longer than 3 months were significant predictors for changes observed in the periodontium (do Amaral et al., 2010). Another concluded that in patients with removable partial dentures, the direct abutment teeth were periodontally affected compared to non-abutment teeth among regular and irregular attendants over 3 years (Qudah & Nassrawin, 2004).
It was found that patients wearing an ARPD or MRPD did not have any significant increase in mobility on their abutment teeth over 12 months. These results are concomitant with the study of Ammara et al. (2010). The results for ARPD wearers indicate a significant increase in patients' tooth mobility between T1 and T3, while MRPD wearers showed no statistical increase in tooth mobility. Similar results were seen in a study where tooth mobility was relatively unchanged in abutment teeth with a follow-up of 5 years. It was observed that non-abutment teeth showed an initial decline and then significantly improved throughout the follow-up (Qudah & Nassrawin, 2004).

| 565
The major limitation of this study is the short follow-up period.
However, this study can pave the way for future research on the complications between different dentures. It also provides tools to help monitor and analyse oral health indicators and the short-term effects of denture wear.
T A B L E 9 Pairwise time comparison with a post hoc analysis of biochemical parameters in patients with MRPDs and ARPDs.
Biochemical parameters per type of denture Note: One-way analysis of covariance.

PATIENT CONSENT
Patient's written consent was taken before administering the questionnaire and clinical examination.