Comparison of Three Prosthodontic Treatment Modalities for Patients with Periodontally Compromised Anterior Mandibular Teeth: A 2-year follow-up study

Abstract

Objectives

To prospectively assess self-perceived chewing function (CF) and oral health-related quality of life (OHRQoL) in geriatric patients after receiving three different treatment modalities in the mandible: removable partial denture (CD-RPD), complete denture (CDs), or complete overdenture supported by mini dental implants (CD-MDI). At baseline, all patients had mobile anterior teeth (1 mm or >) and missing posterior teeth in the mandible. Patients were completely edentulous in the maxilla. After treatment, patients were recalled at the 3-month and the 2-year post-treatment period.

Materials and Methods

A total of 176 patients participated (CD group, n=68; CD-RPD group, n=58; CD-MDI group, n=50). Self-reported CF was assessed using the Chewing Function questionnaire (CFQ), The OHRQoL was evaluated using the OHIP14 questionnaire, which the patients completed 1. before treatment, 2. three months after treatment, and 3. at the 2-year post-treatment stage.

Results

The OHRQoL and the self-perceived CF significantly improved in all groups after treatment (p<0.01). The highest improvement of a CF was recorded in the CD-MDI group. The OHRQoL was significantly higher in the CD-MDI group in comparison to the CDs group after treatment (p<0.01). At the 2-year post-treatment stage, self-perceived CF significantly further improved in the CD-MDI group, while it worsened in the CD and the CD-RPD groups (p<0.01). The same pattern was recorded for the OHIP14 summary scores. The highest amount of denture repairs and adjustments was recorded in the CD-RPD group, although maintenance was also demanding in the CD-MDI group.

Conclusion

Within the limitations of this study, rehabilitation with mandibular MDI retained overdenture can be considered as preferred treatment with the constant improvement of OHRQoL and a chewing function in comparison to mandibular CD or mandibular RPD option in patients with mobile anterior mandibular teeth.

Introduction

It has been well documented that prosthodontic rehabilitation improves patients' oral health-related quality of life (OHRQoL) (1-3). Treatment modalities for complete or almost complete edentulism in geriatric patients have changed over time, from complete (CDs) and removable partial dentures (RPD) to implant-supported fixed or removable constructions (1-5). Moreover, in the year 2002, a panel of experts in prosthodontics and dental implantology concluded that the restoration of edentulous mandible with conventional complete dentures was no longer the first choice prosthodontic treatment due to overwhelming evidence that a two-implant overdenture should become the first choice of treatment for the edentulous mandible (6, 7). However, many geriatric patients are not optimal candidates for placement of dental implants of standard dimensions, either due to their extensive ridge resorption and inadequate buccolingual bone volume, or due to their financial limitations, chronic diseases, or fear to undergo complicated surgical treatments, which include flap reflection, osteotomy and/or different modalities of bone augmentation (8-11).

In the past, dentists needed to compromise and maintain the remaining anterior teeth in the mandible despite their mobility and advanced periodontal disease in order to provide the patients a transient period in which the removable denture would be retained by clasps to allow better retention of removable dentures. Before dental implants had proved their usefulness for removable denture retention and stabilization, keeping teeth with mobility due to the severe bone loss was the only possible option allowing dentists to avoid a complete mandibular denture.

More than a decade ago, slim implants (mini dental implants or MDI) were released to the dental market to support and retain complete dentures. Insertion of MDIs is a quicker and simpler option than the placement of standard size implants (12-15). Most of the time there is also no need for flap reflection (12-25). In many cases, when the insertion torque is adequate (i.e., from 25 up to 45 N/cm²) the MDIs can be immediately loaded (13, 17). The MDIs also representing an advantageous option from a financial perspective in comparison to standard size implants, because they are cheaper, and there is no need to purchase abutments as MDIs are one-piece implants. Since the MDIs have been introduced, they have been confirmed as a suitable treatment option in many follow-up studies ranging from six-month to seven years (12-26). It has been proven that patients with MDIs and mandibular overdentures achieve even better or at least comparable oral health-related quality of life (OHRQoL) and satisfaction when compared to two standard dental implants (2, 12-14, 16, 20, 21). Nevertheless, long-term survival rate studies for MDIs are still lacking. The high short-term survival rates of MDIs were only recorded for mandibular overdentures, whereas for maxillary overdentures retained by the MDIs, the short-term survival rates were significantly lower, ranging from 54 to 85% (27, 28). In a study by Maryod et al., delayed loading of MDIs showed better MDI survival rate and less bone loss in comparison to immediate loading in the mandible (15). In a 5-year observational prospective clinical study of immediately loaded new mandibular overdentures on four MDIs, the patient satisfaction increased significantly over five years (13).

However, a self-reported chewing function with MDIs has not been prospectively followed up yet. It has also not been reported yet to which extent MDI-retained mandibular overdentures improve chewing function when compared to patients having CDs in both jaws, or with patients having a maxillary CD and a Kennedy Class I long saddle clasp retained RPD on anterior teeth in the mandible.

The main objective of this clinical study was to assess a self-perceived chewing function and OHRQoL in three groups of patients dependent on the type of a new mandibular denture (CD, RPD, or MDI supported mandibular overdenture (MDI-CD)). Each patient received a new maxillary CDs. The additional aim of the study was to monitor the after-treatment effects of the three prosthodontic treatment options for the mandible over time.

Materials and methods

All participating patients were informed about the study, and all of them signed the informed consent. The study received the institutional ethical board approval. The patients, who were willing to participate in the study, have been assigned to one of the three study groups and were rehabilitated at the Department of Removable Prosthodontics, School of Dentistry, the University of Zagreb from January 2013 till April 2016.

At baseline, all patients who came seeking treatment were completely edentulous in the maxilla. They had 3-5 mobile anterior teeth in the mandible due to extensive bone loss from advanced periodontal disease. The patients were assigned to three different groups. One group comprised the patients with mobile anterior teeth, which were extracted and the patients were treated with new complete mandibular dentures (CD group). The second group consisted of patients who received mandibular long saddle clasp retained RPDs on the remaining anterior mobile teeth (CD-RPD group). The third group received complete mandibular overdentures supported by four mini dental implants (CD-MDI group) following the extraction of their anterior mandibular teeth.

The selection criteria for the CD-RPD group were: a maxillary CD, mandibular Kennedy Class I status, no teeth distally from the lower canine on one side of the mandibular arch, and no teeth distally from the second incisor on the other side of the arch (i.e., Kennedy Class 1). Furthermore, the remaining teeth had at least grade 1 (less than 1 mm of perceptible mobility in buccolingual direction) or grade 2 of tooth mobility (i.e., at least 1 mm, but less than 2 mm) (29, 30). Due to their mobility, the remaining teeth were not splinted by a fixed partial denture, and therefore it was not possible to use precision or semi-precision attachments. Nineteen patients in the CD-RPD group had five remaining teeth, twenty-five patients had four remaining teeth, and fourteen patients had only three remaining teeth. The CD-RPD patients received long saddle RPDs with lingual plate major connector made of CoCr alloy to prevent fracture. Cast clasps retained the dentures.

All patients included in this study had suffered a considerable atrophy of the mandibular residual alveolar ridge as they had already been the removable denture wearers for at least five years. The initial study design was that the patients would be randomly assigned to the three groups. Nevertheless, despite the available option to receive free treatment regardless of the three treatment options, some patients refused to accept mini dental implants and were reassigned to the other two groups. Therefore, the study design was modified into the convenience sample study. All costs for MDIs were covered by a research grant (details in the Acknowledgement section). Patients who rejected MDIs for various reasons including fear of surgical procedure, pain, fear of possible medical complications, thoughts they were too old, etc. were allocated into the other two groups. All mandibular dentures were reinforced by a metal framework.

Absolute exclusion criteria for the insertion of the MDI were uncontrolled diabetes mellitus, acute malignant co-morbidity including current or recent chemotherapy, intravenous bisphosphonate intake and any history of radiotherapy to the head and neck region. Prior to the MDI placement, panoramic radiographs and/or CBCTs of the mandible were obtained from each participant in the CD-MDI group. All participants receiving MDIs had buccolingual alveolar width of less than 4.5 mm. They received four MDIs intraforaminally in the mandible implanted by a flapless technique (a total of 202 mini-dental implants were inserted, Dentium, South Korea). The implant width and length were chosen based on the residual ridge width and length.

The MDI width was 2.0 or 2.5 mm, while the MDI length varied from 8, 10, 12, up to 14 mm. The MDIs were placed following the manufacturer’s recommendation using a surgical motor unit (W&H Implantmed GmbH, Austria) with saline solution for external irrigation for drill cooling and calibrated drills at low speed after punching through the cortical bone. The depth of bone preparation was 1-2 mm less than the length of the roughened surface of implants. Implants were screwed at a torque ranging from 25 up to 45 N/cm². The two posterior mini-dental implants were inserted in the tooth location of 34 and 44 in a mature bone, while the position of the two anterior MDIs was dependent on the site of anterior tooth extraction. The implants were inserted near the extraction sites in sites with a mature bone. Only in cases when the extraction socket was very shallow, and the bone anatomy allowed choice of much longer MDIs, the implants were inserted in the extraction socket. The two anterior MDIs were sometimes placed in the sites of mandibular first or second incisors. Antibiotics were prescribed to the patients 2-6 hours prior the MDI insertion and for the following three days. Fifteen days later, when pain from surgery has subsided, impressions for new dentures were obtained. Overdentures were retained by O-ball matrices and were early loaded (6 to 8 weeks after implant insertion). After denture delivery, the patients received detailed instructions on how to maintain oral hygiene with MDIs using a soft toothbrush in the mouth and a hard toothbrush for denture hygiene. The patients who received CDs or CD-RPDs also received instructions about their oral hygiene maintenance. Prosthodontic residents supervised by a specialist of prosthodontics made all dentures. Another specialist of prosthodontics, not included in the study or in the denture manufacture, assessed the quality of all new dentures (new complete dentures in the maxilla, as well as all three types of removable dentures in the mandible). Mandibular overdentures on MDIs were assessed prior loading. Assessments were made for the denture borders, the vertical dimension of occlusion, and the artificial teeth set-up, by using the Likert scale from 1 (unsatisfactory) to 5 (excellent). Only the patients whose quality of new dentures was assessed as excellent or very good were included in the present study for patients’ self-assessment of chewing function and OHRQoL. Throughout the two years after prosthodontic rehabilitation in the mandible, all study participants from all three groups were scheduled for the regular recall visits.

The CD group comprised 68 patients (40 females, 28 males) with the mean age of 69.6±11.2 years, the CD-RPD group 58 patients (32 females, 26 males), mean age 66.0±8.0, years, and the CD-MDI group comprised 50 patients (44 females, 6 males), with the mean age of 66.7±9.3 years. All patients from the three groups were previous removable denture wearers.

The Croatian version of the OHIP14 questionnaire (31) and the chewing function questionnaire (CFQ) (32) were completed on three occasions: the first time at baseline immediately before treatment, the second time two to three months after finishing treatment (when all adjustments of new dentures had been completed), and the third time 2 years post-treatment (Fig. 1).

Fig 1.

A brief overview of questionnaires used in the study with their summary score ranges and questions (items).

For each of the OHIP14 items, the patients were asked how frequently they had experienced the impact during the previous week (33). The five categories of choice per item were never, rarely, occasionally, often, and very often; (Likert scale from 0 to 4). Zero indicated an absence of problems, while higher scores indicated more impaired oral health. When filling-in the CFQ or the OHIP14 questionnaire, the patients were asked to assess their difficulties while chewing different foods during the previous week (33). The CFQ answers were graded on the Likert scale from 0 to 4 (0 = absence of problems, up to 4 = the highest problem or inability to chew specific food). For both questionnaires, summary scores were used for statistical analysis. Summary scores for the OHIP14 questionnaire range from zero to 56, and the summary scores for the CFQ range from zero to 40.

Statistical analysis (SPSS 20 for Windows, IBM) included one sample Kolmogorov-Smirnov test for testing normality of the data distribution, descriptive statistics, paired t-test (pretreatment vs. post-treatment data), and one-way ANOVA (post hoc Scheffe’s test). The linear mixed model was also used (summary scores were dependent variables; treatment option, gender, and level of education were fixed factors; age was a covariate). P values <.05 were considered statistically significant.

Results

All summary scores were normally distributed (P>0.05). There were no statistically significant differences in age between the three study groups (F=2.42; P=0.092).

In the CD-MDI group, two mini-dental implant heads broke during insertion in two different patients. Broken implants were left as „sleeping implants“, however, the respective patients received a new MDI, each. Three additional implants were lost during the first 6-8 weeks (in three different patients) who received mandibular overdenture retained with only three MDIs (instead of four). Two additional MDIs were lost during the first year, and no MDI was lost during the second year, resulting in the 97% implant treatment survival rate. There were also no clinical signs of moderate or advanced peri-implantitis according to classification for peri-implantitis proposed by Froum and Rosen (34). No significant problems with dentures were registered in the CD-MDI group, and no fracture repairs were necessary. Four patients needed additional adjustments due to sore spots, two matrices were loosened and were remounted, and a total of 34 O-rings (17%) were changed in different patients.

In the CD-RPD group, fourteen teeth were lost in the mandible (in nine patients) and were replaced by acrylic teeth in the respective dentures. If the abutment tooth was lost, the new wire clasp was made on the adjacent tooth. Five clasps were broken in seven patients and they were repaired. Twenty-three patients reported clasp loosening several times and came to a dental office for clasp activation. Thirteen patients reported sore spots after the period of adjustment (the first three months). In the CD group, twenty-four patients required additional adjustments due to sore spots, while four patients required a mandibular denture relining. Differences between the baseline-, the after-treatment-, and the 2-year post-treatment summary scores are presented separately for the CFQ, and the OHIP14 scores (Figure 2 and Figure 3, respectively).

Fig 2.

OHIP14 summary scores (histograms) with 95% confidence intervals in complete denture wearers (CD), mandibular removable partial long saddle denture (Kennedy Class I) (CD-RPD), and in mini dental implant retained mandibular overdentures (CD-MDI). *=significant difference between patient groups for the amount of score reduction (p<0.05), +=significant differences between patient groups for the 3-month after treatment scores; Ş=significant differences between patient groups for the 1-year after treatment scores, §=significant score increase in relation to the 3-month after treatment scores.

Fig 3.

Summary Scores of the Chewing Function Questionnaire (CFQ) (histograms) with 95% confidence intervals in complete denture wearers (CD), removable partial, long saddle mandibular denture wearers (Kennedy Class I, CD-RPD), and in mini dental implant retained mandibular overdentures (CD-MDI). *=significant difference between patient groups for the amount of score reduction (p<0.05), +=significant differences between patient groups for the 3-month after treatment scores, Ş=significant differences between patient groups for the 1-year after treatment scores, §=significant score increase in relation to the 3-month after treatment scores, ‡=significant score decrease in relation to the 3-month after-treatment scores.

The treatment significantly reduced both, the OHIP14 and the CFQ scores in comparison to the baseline scores in all treatment groups (p<0.001). However, the amount of score reduction was significantly different among treatment groups (F=4.95, p=0.008 for the OHIP14; F=30.39, p<0.001 for the CFQ). The CFQ score reduction was significantly higher in the CD-MDI group than in both, the CD group (mean difference = -9.89; p<0.001, Scheffe post hoc) and the CD-RPD group (mean difference = -7.53; p<0.001, Scheffe post hoc). The OHIP14 score reduction was significantly higher in the CD-MDI group than in the CD group (mean difference = -5.49; p=0.008, Scheffe post hoc).

The three-month after-treatment (when patients were adjusted to their dentures) summary scores were significantly different among groups (F=4.84, p=0.009 for the OHIP14 questionnaire; F=7.93, p=0.001 for the CFQ). The CD-MDI group had significantly lower OHIP14 scores than the CD-RPD group (mean difference = -3.18; p=0.009, Scheffe post hoc). Moreover, the CD-MDI group had significantly lower CFQ scores than both, the CD group (mean difference = -3.34; p=0.001, Scheffe post hoc) and the CD-RPD group (mean difference = -2.31; p=0.030, Scheffe post hoc).

Multivariate analysis (linear model) analyzed the effect of variables: treatment option, gender, level of education and age on the dependent variable (Summary score) and revealed that only treatment option yielded to significant effects (p=0.030) regarding the OHIP14 summary scores, while age (p=0.203), gender (p=0.160), and level of education (p=0.340) did not. Similar results were registered for the CFQ after treatment summary scores. The only significant effect was elicited by the treatment option (p=0.002), while gender (p=0.390), age (p=0.287), and the level of education (p=0.172) yielded no significant effects.

Two years after the prosthodontic rehabilitation, the CFQ (t=12.18, p<0.001), as well as OHIP14 scores (t=7.19, p<0.001) significantly increased (more difficulties) in the CD group (p<0.001) compared to the three-month after-treatment results. In the CD-RPD group, the OHIP14 summary scores significantly increased (t=2.15, p=0.036). In the CD-MDI group, the OHIP14 scores remained stable (even slightly decreased), whereas the CFQ scores were significantly smaller compared with the post-treatment scores (t=5.609, p<0.001).

Discussion

The CD-MDI group benefited most from the treatment, compared to the CD and the CD-RPD groups. The patients in the CD-MDI group improved both, self-perceived chewing function and OHRQoL better than the other two groups. The OHRQoL and the chewing function worsened throughout the first two years in the CD and the CD-RPD groups, while in the CD-MDI group the chewing function showed further improvement.

In general, almost all prosthodontic rehabilitation options show high initial treatment effects (1, 35-37), which is in accordance with the results of this study. For the overdentures retained by the standard size implants, the excellent initial and long-term treatment effects have already been proven (1-4, 35). The CD-MDI treatment in the mandible has become a viable treatment option for patients with atrophic alveolar ridges and/or for those with financial limitations (2, 13-26). One study showed that patients with mandibular overdenture retained with four MDIs had a better OHRQoL in comparison to those with bar and locator overdentures retained by two standard size implants throughout a period of three years (2). Chewing function in patients with the MDI retained overdenture has not been assessed or compared with patients receiving other treatments yet. Therefore, we evaluated patients with three different prosthodontic rehabilitation options in the mandible considering both, OHRQoL and a self-perceived chewing function. All patients had a CD in the maxilla, and all patients were of similar age.

The long saddle mucosa born clasp-retained RPD group of patients represented a transient alternative to complete edentulism. Anterior mandibular teeth usually remain as last surviving teeth in patients' mouth (38-40). Prior dental implants utilization, dentists often preserved mobile anterior mandibular teeth in order to use them for denture retention by clasps to provide a slow transition to the complete mandibular denture. The retention of mandibular CDs depends only on factors such as interfacial surface tension, gravity, a viscosity of the saliva, anatomical and mechanical factors of a denture bearing area, and muscular coordination (40-43). Apart from keeping the last remaining teeth, a contemporary dentist has the alternative to insert dental implants to solve problems inherent to complete denture wearing. The MDI can be used in patients who would otherwise need bone augmentation, and this allows inclusion of a higher number of potential implant patients and less expensive and invasive treatment modalities.

The patients in this study were first offered to receive four MDIs, without any charge, as the research grant covered the costs of implants. Most of the patients who refused the MDI therapy explained that it was due to their fear of pain or fear of possible complications due to their old age, while some of them declined MDIs due to sufficient satisfaction with their old dentures. All patients who refused MDIs were assigned into the CD or RPD groups. The MDI overdentures in this study were early loaded, as this was reported to be a better option than the immediate loading protocol (15).

The impact of oral interventions on individually self-perceived oral health outcomes has been recognized as an important health component (1, 2, 4, 13, 23, 24, 31-33, 36-38, 40-50, 53, 58-60). We, therefore, decided to use the self-perceived measures, namely the OHIP14 and the CFQ to assess treatment outcomes. A recent study showed that self-perceived chewing ability and objective mixing ability (chewing) have been significantly inter-related (42). Although recent studies showed that the OHRQoL comprises of four dimensions (33, 34, 36-48), only the summary scores of the OHIP14 questionnaire have been assessed in this study, as it is the most frequently used questionnaire in prospective oral health-related quality of life assessment (49). Although the OHIP14 shows lower sensitivity in the edentulous patients than the OHIP-EDENT (50), it was preferred in this study, because the CD-RPD group had some anterior teeth left in the mandible and were not suitable for the OHIP-EDENT questionnaire.

As expected, all treatment options elicited significant treatment effects, which were confirmed by a significant after-treatment score reduction. However, excellent benefits of the CD-MDI treatment considering both, chewing function, and OHRQoL, in comparison to the CD and the CD-RPD group, have been proven in the study. Despite the fact that the CD-RPD group had clasps to improve denture retention and stability, the CD-MDI group revealed significantly better after-treatment chewing scores, probably due to better retention and stability of dentures provided by MDI matrices with “O” rings than by clasps on the remaining teeth in the CD-RPD group, regardless of how many teeth had been present (three, four or five) or what was their position and/or condition. Significantly better OHIP14 after treatment scores in the CD-MDI group than in the CD-RPD group could additionally be attributed to aesthetic concerns (clasp visibility in the CD-RPD group), and not solely to the self-perceived chewing function in the CD-MDI group.

However, two years after denture insertion, both OHRQoL and the chewing function worsened (i.e. confirmed by increased questionnaires scores) in the CD patients and in the CD-RPD group, which we attributed to problems inherent to removable denture wearing, such as residual ridge resorption, mucosal inflammation and/or clasp loosening (50-59). Scores of the CFQ, as well as the OHIP14 were not dependent on the position and number of the remaining teeth in the CD-RPD group. On the contrary, the OHIP14 scores slightly decreased further and the CFQ scores significantly reduced in the CD-MDI patients (revealing further improvement), which we attributed to patient's better adaptation to their dentures and subsequent increased confidence and stability while chewing at the 2-year observation stage. The results related to OHRQoL are in agreement with some other authors reporting that patient satisfaction with mini-implant retained mandibular overdentures increased significantly with time (2, 13, 22). ELsyad et al. reported that patient satisfaction with MDI treatment increased considerably with time over five years, especially for eating (hard/soft) food, the comfort of denture wearing, stability/retention of mandibular dentures, ease of oral hygiene and ease of handling the dentures (13). However, the results of a self-perceived chewing function are reported for the first time in this study for MDI retained overdenture patients.

After initial adjustments, the CD-MDI group had no significant repairs or additional adjustments through the first two years as well as no fractures due to metal skeleton reinforcement. The number of patients who asked for further adjustments was the highest in the RPD group. The respective group had the highest amount of repairs due to the extractions of some of the remaining teeth over time. Although two matrices were loosened and repaired and 17% of O-rings had to be changed after two years, which may be considered demanding maintenance, the MDI treatment option showed to be superior to other options, as it showed the highest and persistent, even improving results over time regarding the chewing function and OHRQoL. When compromised teeth due to non-treated active periodontal disease are left in the mouth for better denture retention and support, it may have a harmful effect on the systemic health of geriatric patients (56, 61). Therefore, the MDI retained mandibular overdenture can be considered a safer option than keeping teeth with active periodontal disease, specifically in geriatric patients with systemic diseases, although we need to be aware that MDI can also be affected by peri-implantitis, which can harbor infection not beneficial to this patient population.

The limitations of the study include relatively small sample size, differences in number, position, and degree of mobility of remaining teeth in the CD-RPD group, some differences regarding bone volume, i.e., residual ridge atrophy in the maxilla and in the mandible and relatively short observation period. An assessment of the patient’s personality was also not performed.

Conclusions

Patients receiving mandibular overdentures retained by mini dental implants showed the highest improvement of OHRQoL and chewing function, consistent and even improved over the period of 2 years in comparison to patients who received a complete mandibular denture or a long saddle clasp retained Kennedy class I partial removable denture on slightly mobile anterior teeth.