A 5-Year Retrospective Study Evaluating Periodontal Health and Oral Health-Related Quality of Life of Implant-Supported Overdentures With Locator and Magnetic Attachments Open Access

As noted in the McGill¹  and York consensus,²  overdentures over 2 implants, particularly in the mandible, have now become the first treatment option for toothless patients. It has been observed that retention and stability have been improved compared with conventional prostheses, with increased patient satisfaction.^3,4 

Various studies have evaluated patient satisfaction and oral health-related quality of life (OHQoL) after 2 mandibular implants supporting overdentures, and have shown that both are influenced by the degree of retention and implant stability, which were in turn affected by the attachment system used.^5–9 

Attachment systems for dental implant overdentures are divided into unsplinted and splinted (bar types).¹⁰  Unsplinted attachments, such as the ball, magnet, and Locator types, make oral hygiene easy.^10,11  However, they are limited in that implants must be placed parallel to each other and they lead to decreased stability of overdentures compared with bar-type attachments.^11–13  The Locator is often used because it has a lower profile than other types, has easily replaceable components,¹⁴  and can tolerate an implant angulation of up to 40 degrees.^13,15  Magnetic types also have a low profile, result in less horizontal stress being transferred to the implants,^15–19  protrude less than other types, and are smooth and comfortable for patients when the denture is not in the mouth.^15,20  These tend to be preferred by disabled and elderly patients because they are easier to manipulate.^19,20 

Two commercially available unsplinted attachment types were used. The fact that overdentures with Locator attachments are active only on the vertical axis during insertion and removal of the dentures, and that overdentures with magnetic attachments are continuously active on the vertical axis may suggest that magnet attachments can cause more peri-implant vertical bone loss.²¹  However, torsional forces are more dangerous for dental implants, and magnet attachments may cause less torsional force than Locator attachments because they allow movement on the horizontal axis.²²  Therefore, less vertical bone loss can be considered. No difference was found in the literature on the survival rate for either attachment system.^22,23 

This retrospective study compared peri-implant vertical bone loss, the periodontal index, and OHQoL of patients using mandibular implant-supported overdentures with 2 different attachment systems after an average of 5 years of use.

Previous studies have examined patient satisfaction or bone loss using the periodontal index.^{9,15,17,20–29}  However, in a literature review, there were no studies that have evaluated bone loss using the periodontal index plus quality of life together in patients using dentures with different attachment types. The null hypotheses of this study were as follows:

• There will be no differences in peri-implant vertical bone loss around the implant in patients using implant-supported mandibular overdentures with Locator and magnetic attachments.

• There will be no differences in periodontal health in patients using implant-supported mandibular overdentures with Locator and magnetic attachments.

• There will be no differences in OHQoL in patients using implant-supported mandibular overdentures with Locator attachments, magnetic attachments, and conventional complete dentures.

• There will be no correlation between peri-implant vertical bone loss, periodontal health, and OHQoL in patients using implant-supported mandibular overdentures with Locator attachments, magnetic attachments, and conventional complete dentures.

• There will be no differences in the maintenance of overdentures in patients using implant-supported mandibular overdentures with Locator attachments and magnetic attachments.

All the patients in the study were explained the procedure in detail prior to the commencement of study. Every patient was explained about the treatment procedure and written consent was taken for same. The study was performed in accordance with the Declaration of Helsinki and with the ethical approval from the ethics committee of Erciyes University Faculty of Medicine. Screening was performed to identify patients with conventional complete dentures and 2 dental implant-supported mandibular overdentures with magnet and Locator attachments treated at the Department of Prosthodontics Faculty of Dentistry at least 5 years previous to study recruitment. After screening, 16 mandibular overdenture patients with magnet attachments, 24 with implant-supported mandibular overdentures with Locator attachments, and 25 conventional complete denture patients were included in the study. Written informed consent was obtained from all patients. Inclusion criteria included being edentulous, having 2 implant-supported overdentures, having the prosthesis at least 5 years, not having general medical contraindications regarding surgery, not being exposed to radiotherapy in the head and neck area, no psychological problems, and no use of alcohol, tobacco, or illegal drugs.

The study was a nonrandom, conveniently sampled, limited sample, nonequivalent groups, observational, retrospective, cohort study.

Group 1 (control group) included 25 patients with conventional maxillary and mandibular dentures. Group 2 included 24 patients with a maxillary complete denture and 2 implant-supported mandibular overdenture with Locator attachments (Dentium Implants). Group 3 included 16 patients with a maxillary complete denture and 2 implant-supported mandibular overdenture with magnet attachments (Dyna Dental, Halsteren, Netherlands).

The existing dentures of all patients were evaluated by a single specialist (Z.K.), and the patients were administered the oral health impact profile-14-Turkish version (OHIP-TR-14) questionnaire, which is one of the most commonly used OHQoL instruments.³⁰  The Turkish version³¹  was used. Panoramic radiographs were taken for all patients (Planmeca Promax 2DS3). Previous complications and maintenance requirements with dentures were noted. In the last stage clinical evaluation, maintenance requirements were made for the patient's dentures, including relining requirement, fracture, loss of retention, and abutment changes.

Panoramic radiographs of all patients were taken 1 week after implant surgery and are available in the digital archive of the faculty. Anamnesis of the general health and dental records of all patients admitted to the university hospital are entered into the digital system as standard protocol. After implant placement, all patients undergoing implant treatment receive panoramic radiography and register to the same system, and patients are invited annually for an appointment for oral hygiene motivation and general evaluation as a standard procedure. During these appointments, an anamnesis is taken from the patient again and changes in the current general health and oral health are entered into the system. After 5 years, the control radiographs were taken and the sizes of the dental implants were measured from panoramic radiographs using image editing software (Image J, National Institutes of Health). The magnification of the radiographs was calculated by proportioning the implant length on the radiograph to the actual length of the implant. Then the marginal bone levels measured at the mesial and distal points were averaged with reference to the neck of the implant. The difference between the marginal bone levels obtained from both digital panoramic radiographs was noted as peri-implant vertical bone loss.

To evaluate the clinical success of dental implants, the plaque index and gingival index were measured at 6 points at the mesial and distal sides of the implants.^32,33  In addition, bleeding on probing and probing depths were measured, averaged, and recorded.

The methodology and the results of the study were reviewed by an independent statistician. Histogram and q-q plots were examined to assess the data normality. Shapiro Wilk test was used to test the data normality. Levene test was used to test the variance homogeneity. The mean, standard deviation, median, and interquartile ranges were used to summarize the continuous variables. Mann-Whitney U test was applied to compare the distribution of continuous variables between group. One-way analysis of variance and Kruskal-Wallis H tests were used when comparing more than 2 groups. Bonferroni test was applied for post hoc multiple comparisons. The relationship between the continuous variables were analyzed with Spearman correlation test. Univariate regression analysis was conducted to evaluate the effect of periodontal variables on the OHIP-TR. Significant variables at P < .25 on univariate analysis were taken into multiple model and forward stepwise selection was performed using Wald statistic at P < .10 stringency level. The threshold of statistical significance was set at P < .05. Analyzes were conducted using TURCOSA (Turcosa Analytics Ltd Co) statistical software.

The demographic and laboratory features of all groups in the study are shown in Table 1. There were no statistically significant differences between the groups in terms of total OHIP-TR-14 scores (P > .05). Although the average vertical bone resorption measured in group 2 at the end of 5 years was 1.38 mm, there was an average vertical bone loss of 1.45 mm in group 3, but this difference was not statistically significant (P > .05) (Table 2). Among the periodontal health indicators, there were no statistically significant differences in the mean values for plaque index, gingival index, probing depth, and bleeding on probing (Table 2). Regarding maintenance, a statistically significant difference was found between groups 2 and 3, and the maintenance requirement of group 3 was more than that of group 2 (Table 2). Correlation analyses for group 2 showed that there was a positive correlation between gingival index and bleeding during probing (r = 0.917, P < .001) (Table 3). In group 3, a positive correlation between bleeding during probing and gingival index was observed (r = 0.773, P < .001) (Table 3). Univariate linear regression analysis results between OHIP-TR and periodontal variables are shown in Table 4. Beta coefficients, standard errors of the coefficients, standardized β coefficients, t statistics, and P values are summarized. According to the univariate linear regression analysis between OHIP-TR and periodontal variables, for locator attachment, probing depth was found to be the only significant variable in both univariate and multiple linear regression models (s = 11.590, R² = 0.238, F = 6.868, P = .016). There were no significant variables for magnetic attachment (Table 4).

In this retrospective study, periodontal health status, peri-implant vertical bone resorption, OHQoL, and maintenance requirements of double dental implant-supported mandibular overdentures in 24 patients with Locator attachments, 16 patients with magnet attachments, and 25 patients with conventional complete dentures were evaluated after 5 years of use.

We observed that all 80 implants placed in 40 patients (group 2 = 24, group 3 = 16) using both Locator attachments and magnetic attachments continued to function successfully after 5 years.

In this study, panoramic radiographs for the evaluation of peri-implant vertical bone loss were used because the study was retrospective. In addition, orthopantomography is a reliable radiological procedure and standardized projection in the vertical plane is suitable for vertical measurements.^34,35  Panoramic radiographs have been shown to provide reliable information for determining the bone attachment point to implant grooves.³⁴  In a retrospective study that used panoramic radiographs, Geckili et al³⁴  did not find a statistically significant difference in terms of bone loss between the ball, Locator, and bar attachment systems. In the same study, the average bone loss around the Locator retaining implants after 48 months was 1.07 ± 0.16 mm.³⁴  Elsyad et al¹⁵  reported in a 1-year study that the effects of Locator and magnet attachments on peri-implant tissue were statistically greater than the vertical attachment loss around Locator attachments. They also reported a significant positive correlation between bone loss and probing depth.¹⁵ 

In this study, there were no statistically significant differences between Locator and magnet attachments after 5 years of use in terms of average bone loss, supporting the first hypothesis of the study. This result is not consistent with Elsyad et al.¹⁵  This may be due to the fact that maximum resorption of bone is seen within the first year and then there is a transition to a stable state.

Because the Locator attachment may cause more stress around an implant than magnet attachments, vertical bone resorption may be greater in the first year. In this study, the average value of peri-implant bone resorption was 1.38 mm (0.89–2.52 mm) for Locator attachments and 1.45 mm (0.64–1.81 mm) for magnet attachments. In terms of vertical bone resorption, both groups were in line with the previously reported success criteria of 1.5 mm in the first year and then 0.2 mm each year thereafter.³⁶ 

Elsyad et al¹⁵  investigated the plaque score around dental implants in mandibular overdentures with magnet attachments and Locator attachments and reported that magnet attachments had higher plaque scores after a 1-year follow-up. Another study reported that magnetic attachments could affect microorganisms and cause more plaque accumulation.³⁷  By contrast, Ceruti et al³⁸  reported that there is minimal plaque accumulation around magnetic attachments. In this retrospective study, we found no statistically significant differences in plaque index in any of the groups. Elsyad et al¹⁵  reported that the probing depth of dental implants in mandibular overdentures with magnet attachments and Locator attachments increases with time. In our study, probing depths increased in both groups over time; however, there were no statistically significant differences between the 2 groups, which is consistent with Elsyad et al.¹⁵  Increased probing depth may be associated with vertical bone loss over time and peri-implant soft tissue expansion.^15,39 

In this study, there were no statistically significant differences in the average values for the plaque index, gingival index, probing depth, and bleeding during probing between groups 2 and 3. Therefore, the second hypothesis of the study was supported.

There are many kinds of attachments on the market, such as bar, ball, and magnetic attachments with rigid or nonrigid telescopic copings and Locators.^40,41  The effects of implant supports on overdenture success, patient satisfaction, and quality of life are considered critical factors that need further investigation.^42–44 

In a study of 82 edentulous patients, Mumcu et al⁴⁵  reported that the total Oral Health Impact Profile-14 (OHIP-14) scores of patients using bar-retained overdentures were significantly lower than all other attachment types. In a study on maxillary edentulous patients, Ikbal et al⁶  found no statistically significant differences between total OHIP-14 scores of 50 patients using conventional complete dentures and 26 patients using implant-supported overdentures.

Patient satisfaction studies on implant-supported overdentures are generally performed on patients with mandibular implant-supported overdentures and mandibular complete dentures.^44,46  Kuoppala et al⁴⁷  reported that the attachment type does not affect patient satisfaction as evaluated using the OHIP-14. Another study found that the quality of life of patients using mandibular implant-supported overdentures was higher than the total scores of OHIP-14 before and after treatment in 78 patients treated with Locator attachments over double mandibular dental implants.⁴¹ 

In this study, there were no statistically significant differences in the total OHIP-TR-14 scores of patients using conventional dentures, Locator-retained implant-supported mandibular overdentures, and magnetically retained implant-supported mandibular overdentures, supporting the third hypothesis. This is consistent with Kuoppala et al.⁴⁷  This may be because the OHIP-TR-14 questions were not addressed immediately after the delivery of the dentures but rather 5 years after the end of the treatment, and the patients may have adapted to the dentures used.

In addition, it should be noted that dentures in older patients and disabled patients may require further simplification.¹⁵  Dentures with the best retention may not always be the most suitable denture for any given patient.^15–17  Retaining systems of existing dentures need to be simplified in very old and disabled patients.^15,16  For example, the use of a magnetic attachment instead of a bar or Locator attachment will improve the patient's quality of life.

In this study, a very good positive correlation was found between the gingival index and bleeding during probing in group 2. In group 3, a good positive correlation with bleeding during probing and gingival index was observed. It does not explain causation, but these results reject the fourth hypothesis of the study. In addition, according to the linear regression analysis between OHIP-TR and periodontal variables, for locator attachment, probing depth was found to be the only significant variable in both univariate and multiple linear regression models. No significant regression finding was found to show a causation between other periodontal health parameters and OHIP-TR-14.

In addition to the many advantages of implant-supported overdentures, some biological and biomechanical complications may occur during functional activities.^12,48–52  Many studies have reported that nonsplinted attachment designs require more maintenance.^53–55 

Bilhan et al⁵⁶  did not find any correlation between attachment type and the occurrence of complications. In our study, a significant difference was found between the magnetic and Locator attachments in terms of the need for maintenance. The difference between these results may be due to the fact that the previous study evaluated maintenance after 1 year of use while we considered 5 years of use.

The limitations of this study included a small patient population, In this regard, the results presented in the present investigation should be interpreted with caution due to the study design and on a rather small sample-size. In addition, other limitation included the use of OHIP-TR-14 due to the lack of a Turkish version of the Oral Health Impact Profile for edentulous patients, which was developed exclusively for edentulous patients. Also, the study was retrospective in nature, and peri-implant vertical bone resorption was evaluated with panoramic radiographs instead of periapical radiographs taken using a parallel technique. This warrants further study. This study was retrospective, and the next planned study should be planned prospective. The periodontal conditions of the patients can be recorded and evaluated immediately after delivery of the prosthesis, and compared with the periodontal conditions of the patient in recallings. In addition to these, periapical radiographs taken with parallel technique can be used to measure vertical bone loss more reliably. In addition, new studies can be made by including other attachment types such as ball or ring. The sample size can be expanded by including splinted and nonsplinted attachments.

Within the limitations of the study, according to the results of the study, there are no differences in peri-implant vertical bone loss in mandibular overdentures with Locator and magnet attachments, in periodontal health in mandibular overdentures with Locator and magnet attachments, or between the OHQoL of patients using mandibular overdentures and conventional complete dentures, Locators, and magnetic attachments. In addition, magnetic attachments require more maintenance than Locator attachments in the results of the study. From a clinical perspective, further prospective studies and more sample sizes are needed to evaluate the periodontal health and OHQoL of implant-supported overdentures with Locator and magnetic attachments.

OHIP:

oral health impact profile

OHIP-TR-14:

oral health impact profile-14-Turkish version

OHQoL:

oral health-related quality of life

The authors thank Dr Gözde Ertürk Zararsiz from the department of Biostatistics at Erciyes University, Kayseri, Turkey for their assistance with the statistics in this study.

Ikbal Leblebicioglu Kurtulus, Duygu Kilic, Ravza Eraslan, Zeynep Karacalar and Kerem Kılıc state that there are no conflicts of interest. No support or grant was taken for this study.