The effect of 2 versus 4 implants on implant stability in mandibular overdentures: A randomized controlled trial

Mandibular overdentures retained by 1 or 2 implants: a 5-year randomized clinical trial on implant stability and peri-implant outcomes

AIM

This is a report of the 5-year results of a two-group parallel randomized clinical trial comparing longitudinal implant stability, and clinical and radiographic peri-implant outcomes of mandibular overdentures retained by one (1-IOD group) or two (2-IOD group) implants.

METHODS

All participants received 4.1 mm diameter tissue-level implants (Straumann® Standard Plus - SLActive®, Institut Straumann AG), installed in the mandible midline (1-IOD; n = 23) or the lateral incisor-canine area bilaterally (2-IOD; n = 24), and loaded after 3 weeks. Implant Stability Quotient (ISQ) was measured using a resonance frequency device (Osstell® Mentor, Integration Diagnostics) at implant placement, after three weeks (loading), and at the 6-month, 1-, 3-, and 5-year follow-ups. Marginal bone loss and clinical implant outcomes (plaque, calculus, suppuration and bleeding) were assessed periodically up to 5 years after loading.

RESULTS

Only minor changes in marginal bone level were observed after 5 years (mean = 0.37; SD = 0.44 mm), and satisfactory and stable peri-implant parameters were observed throughout the 5-year follow-up. No significant differences between groups were found. Overall, the mean primary implant stability was considered high (> 70) for the two groups (1-IOD = 78.1 ± 4.5; 2-IOD = 78.0 ± 5.8). No noticeable changes were observed between implant insertion and loading. A marked increase was observed from insertion to the 6-month follow-up - the mean difference for the 1-IOD group was + 5.5 ± 5.5 (Effect size = 1.00), while for the 2-IOD group, the mean difference was + 6.0 ± 5.6 (Effect size = 1.08). No relevant changes were observed throughout the follow-up periods up to 5 years. Linear mixed-effect model regression showed no influence of the bone-related variables (p > 0.05) and the number of implants (p = 0.087), and a significant effect of the time variable (p < 0.001).

CONCLUSION

Satisfactory peri-implant outcomes and stable secondary stability suggest good clinical performance and successful long-term osseointegration of the implants for single and two-implant mandibular overdentures. Using a single implant to retain a mandibular overdenture does not seem to result in detrimental implant loading over the five years of overdenture use.

CLINICAL RELEVANCE

This study corroborates the use of a single implant to retain a mandibular denture.

Impact of adding zirconium oxide nanoparticles to the 3D printable acrylic resin base material for implant-retained overdentures: A clinical comparative parallel study

STATEMENT OF PROBLEM

Three-dimensionally (3D) printed acrylic resin base materials have been adopted in prosthetic dentistry. However, their mechanical and biological properties require improvement.

PURPOSE

The purpose of this clinical study was to evaluate the effect of adding zirconium oxide nanoparticles to a 3D printable acrylic resin base material for a 2-implant-retained complete mandibular overdenture in terms of peri-implant tissue health, surface roughness, and biofilm formation.

MATERIAL AND METHODS

Twenty edentulous patients were enrolled in this clinical parallel study. All patients received maxillary complete dentures opposing a 2-implant-retained mandibular overdenture. The participants were randomly divided into 2 equal groups according to the mandibular overdenture base material, nonmodified 3D printable acrylic resin (control group) or 3D printable acrylic resin base material modified with 3.0 wt% zirconium oxide nanoparticles (study group). Peri-implant tissue health and surface roughness were measured immediately at the insertion of the mandibular overdenture (T0), after 3 months (T1), and after 6 months (T2). Microbiological assessment of the denture base was done after 1 week, 1 month, 3 months, and 6 months of overdenture use. The data were analyzed using a statistical software program. The Wilcoxon signed-rank test, paired t test, and Fisher exact test were used to compare distributed data. The Mann Whitney U test and repeated measures ANOVA test were used to compare distributed data at different times (α=.05).

RESULTS

The gingival index (GI), plaque index (PI), probing depth (PD), and surface roughness values at the baseline, 3 months, and 6 months were statistically higher with the nonmodified compared with the modified group (P=.001). Regarding the microbiological analysis, the nonmodified group also had a statistically higher mean bacterial and Candida albicans count than the modified group (P<.05). No significant increase in the bacteria was found in the nonmodified group with time (P=.252), but, for the modified group, a statistically significant decrease in bacteria count was found with time (P<.001).

CONCLUSIONS

Adding zirconium oxide nanoparticles to a 3D printable acrylic resin base material was found to be promising. This addition improved the peri-implant tissue health and decreased surface roughness and biofilm formation.

Tissue Surface Adaptation and Clinical Performance of CAD-CAM Milled versus Conventional Implant-Assisted Mandibular Overdenture

Purpose

To evaluate the surface adaptation and maximal biting force of CAD-CAM milled mandibular overdenture (CAD-CAM MOD) compared to conventional compression mold mandibular overdenture (CC MOD).

Materials and Methods

Ten completely edentulous subjects with persistent complaints of their complete mandibular dentures were received four dental implants in the anterior mandible. Three months after osseointegration, subjects were randomly received either conventional compression mold or CAD-CAM MOD in a crossover design. To assess tissue surface adaptation, the fitting surfaces of each denture base were scanned and placed on the reference master cast. Three and six months after each overdenture was inserted, clinical performance in the form of maximum biting force was evaluated.

Results

The results of this study indicated that the tissue surface adaptation of the CAD-CAM MOD bases was significantly better than the conventional (compression mold technique) processed bases where (P=0.0001). Regarding clinical performance (maximum biting force), the CAD-CAM MOD exhibited better clinical performance (P=0.0001).

Conclusions

In denture processing methods, the CAD-CAM overdenture delivered more precise adaption and clinical performance than the compression mold technique.

Comparative clinical study of conventional dental implant and mini dental implant-retained mandibular overdenture: A 5- to 8-Year prospective clinical outcomes in a previous randomized clinical trial

AIM

To compare the long-term prospective clinical outcomes in a previous randomized controlled clinical trial (RCT) of 2 Mini Dental Implant (2MDI), 4 Mini Dental Implant (4MDI), and 2 Conventional Dental Implant (2CDI)-retained mandibular overdenture with follow-up between 5 to 8 years.

MATERIALS AND METHODS

Thirty-seven patients formerly participated in the Comparative Clinical Study of CDI and MDI for Mandibular Overdenture were requested for examination of clinical outcomes. A total of 104 implants were placed with mean follow-up periods 6.64 ± 0.60 years. In Group 1 (2MDI) and Group 2 (4MDI), implants were placed and immediately loaded with Equator® attachments to retained mandibular overdenture. In Group 3 (2CDI), implants were placed and delayed 3 months for denture loading with ball attachment. The success rate, survival rate, clinical implant performance scale (CIP scale), peri-implant tissue status, prosthetic complication, implant stability quotient (ISQ), marginal bone level change (MBLC), and patient satisfactions were analyzed.

RESULTS

After 5 to 8 years follow-up, the success rate in Groups 1, 2, and 3 were 90.91%, 93.33%, and 54.55%, respectively. The success rate in Group 3 was significantly lesser than Group 1 (p = 0.016) and Group 2 (p < 0.001). The survival rate in Groups 1, 2, and 3 was 100%, 96.67%, and 90.91%, respectively, and showed no significant differences. Mean ISQ reported no significant differences between groups. Mean MBLC were 0.57 ± 1.19 mm, 0.68 ± 0.90 mm, and 1.55 ± 1.60 mm in Groups 1, 2, and 3, respectively. Group 3 reported significantly greater mean MBLC than Group 1 (p = 0.016) and Group 2 (p = 0.011), but Groups 1 and 2 were not significantly differences. The overall patient satisfactions were reported as not significant differences between groups.

CONCLUDE

Two MDI-retained mandibular overdentures with immediate loaded protocol performed had favorable clinical outcomes, cost effectiveness, and overall patient satisfactions after 5 to 8 years follow-up.

Effects of attachment type and number of dental implants supporting mandibular overdenture on peri-implant health: A systematic review and network meta-analysis

PURPOSE

To evaluate the effect of overdenture (OD) attachment type and the number of implants supporting mandibular ODs on peri-implant health.

STUDY SELECTION

From inception to October 2020, electronic databases (Medline/PubMed, Embase, Cochrane Library, and Scopus) were systematically searched. The outcomes of interest were marginal bone loss (MBL), pocket probing depth (PPD), plaque index, bleeding index, and implant survival rate. Bayesian network meta-analysis was performed using the GeMTC package supported by R. The weighted mean difference and 95% credible interval were estimated.

RESULTS

Twenty-eight studies with a total of 1166 participants who received 2666 dental implants were included. Except for 4 bar and 4 telescopic, which showed a statistically lower MBL than the 2 locator, all other interventions showed insignificant differences in MBL (P > 0.05). The difference in periodontal probing depth was not statistically significant when comparing the different groups. The pooled implant survival rates of the different interventions ranged from 88.9% to 100%. The rank probability test showed that 4 bar and 4 telescopic had the lowest MBL, 2 magnet and 2 bar had the highest PI, whereas 4 locator showed the least PPD.

CONCLUSIONS

Except for 4 implants+bar, or telescopic, and 4 locator that, respectively, showed less MBL and PPD compared to some interventions, it seemed that different attachment types and number of implants supporting mandibular ODs have no clear superiority over the other in terms of peri-implant health outcomes.

Evaluation of the quality of life and satisfaction in patients using complete dentures versus mandibular overdentures. Systematic review and meta-analysis

Background

The World Health Organization (WHO) recognizes edentulism as a physical impairment that results in a negative impact in the daily activities.

Objective

The study aimed to compare the satisfaction and the quality of life, in patients treated with implant retained overdentures with two mandibular implants (IOD) against those with mandibular conventional complete dentures (CCD).

Methods

Different search strategies were used to screen for articles in Pubmed/Medline, Cochrane Library and Scielo of the last 17 years (2003–2020). The keywords used were: “quality of life OR satisfaction” AND “complete denture OR conventional denture” AND “overdenture OR implant retained.”

Results

Six articles and two more were added by manual search. The population was 400 in the CCD and 412 for IOD. The mean age was 64.3 ± 6.41 years. The group was comprised of 283 men and 427 women. The scores obtained in the visual analog scale (VAS) before and after the treatment were statistically significant in favor of the IOD for overall satisfaction, (WMD: 12.329; 95% CI: 4.873 to 19.784, p‐value = 0.001), comfort, speech and stability. For esthetics and chewing there was non‐significant improvement while hygiene worsened for the IOD. For the comparison after the treatment between both treatment modalities a statistically significant improvement was found in overall satisfaction (WMD: 14.408; 95% CI: 8.589 to 20.226, p‐value < 0.001), comfort, speech, chewing and stability in favor of the IOD but not in esthetics or hygiene.

Conclusions

This systematic review and meta‐analysis show the superiority of the IOD, despite is not achieved in all aspects.

The clinical significance of implant stability quotient (ISQ) measurements: A literature review

Implant stability quotients (ISQ values) are obtained in dental clinical practice on a non-invasive basis by resonance frequency measurement rapidly after surgical placement of implants. The ISQ-values are used as indicator for mechanical implant stability, and are believed to have predictive power for clinical outcome. It is the aim of this review to provide a synopsis of all factors described in the literature that influence ISQ measurements by performing an exhaustive literature review; moreover, this review aims at elucidating the key factors relevant for a rapid clinical predictive assessment. We searched systematically and exhaustively all major databases for publications relating to ISQ measurement methodology and for ISQ-influencing factor analyses. The reports identified were ordered in experimental (preclinical) studies and in clinical publications. We were able to identify 13 basic factors influencing ISQ-measurements. Among these, local bone quality, playing a key role in such measurements, was subdivided in four specific subfactors; thus a total of 17 individual factors was identified and reported to influence ISQ-measurements. A comprehensive list of these factors is provided in Table-form. A critical analysis points out that only 6 of these factors are of a sound predictive power useful for a rapid clinical assessment; and only two of these factors appear to have a well-documented scientific basis.

Influence of facial patterns on the masticatory function and quality of life of completely edentulous patients during the transition to implant-retained mandibular overdentures

STATEMENT OF PROBLEM

Although implant-retained mandibular overdentures (IMOs) provide functional benefits, the influence of the vertical facial pattern (FP) and the anteroposterior skeletal discrepancy (ASD) on the masticatory function and patient-centered outcomes during the transition to IMOs is still uncertain.

PURPOSE

The purpose of this interventional clinical study was to evaluate the influence of the FP and ASD on the masticatory function, oral health-related quality of life (OHRQoL), and satisfaction of completely edentulous patients before and after transition to IMOs.

MATERIAL AND METHODS

Cephalometric analysis was performed on 42 participants before treatment. Ricketts analysis was used to classify the FP, and the maxillomandibular relationship to the base of the skull determined the ASD. Masticatory performance (MP) and swallowing threshold (ST) test results were evaluated by the multiple sieve method by using artificial test food (Optocal cubes) to determine the median particle size (×50), homogenization index (B), and masticatory efficiency based on sieves 5.6 (ME: 5.6) and 2.8 (ME: 2.8). OHRQoL and satisfaction were evaluated by using the Dental Impact on Daily Living questionnaire. The data were analyzed using mixed-effects linear regression models to estimate the effect of time, FP, ASD, age, and sex on MP, ST, and OHRQoL.

RESULTS

The MP, ST, OHRQoL, and satisfaction improved significantly after IMO loading, irrespective of FP and ASD. However, MP outcomes were most negatively affected mainly among dolichofacial (B and ME: 2.8), class II, and class III (×50, B, and ME: 2.8) participants. The ST test showed that class II participants still showed inferior ×50 values and performed a lower number of cycles than class I and class III participants. Women presented reduced masticatory function for all MP and ST outcomes and reported lower coefficients for appearance and general performance domains than men.

CONCLUSIONS

The MP test detected more subtle improvements than the ST test, especially in class III participants. The class II participants benefited the least from the IMO installation according to the ST test. The IMO treatment improved the OHRQoL and satisfaction of edentulous patients, irrespective of the FP or ASD.

A within-subject clinical trial on the conversion of mandibular two-implant to three-implant overdenture: Patient-centered outcomes and willingness to pay

OBJECTIVES

To examine the impact of adding a third midline implant with stud attachment to a mandibular two-implant overdenture on patient-oriented outcomes.

METHODS

In this pre-post design clinical trial, following the standard procedures, mandibular two-implant overdentures of 17 edentulous individuals (61.9 ± 6.6 years) were converted to three-implant overdentures by adding a stud attachment to an unloaded midline implant. Patient-oriented outcomes included patient expectations and satisfaction with implant overdenture as well as willingness to pay the cost of conversion. Data were collected at baseline and at the 6-week follow-up using visual analog and binary scales as well as open-ended questions. Statistical analysis included descriptive statistics, Spearman's correlation, Fisher exact test, Mann-Whitney U test, and the exact sign test.

RESULTS

After connecting the third midline implant to the mandibular two-implant overdenture, there was a statistically significant decrease in the anteroposterior movement (p = 0.005) as evaluated by clinicians. Moreover, study participants reported an increase in perceived stability of the overdenture (95% CI; 0.68-1.00, p = 0.002) and in their ability to speak (95% CI; 0.63-1.00, p = 0.008). The addition of a third implant met the expectations of 94% of patients in regard to lower denture stability, 100% for retention, and 82.4% for comfort. The mandibular three-implant overdenture increased patient general satisfaction over a short period of time, but this improvement was not statistically significant. About 80% of patients would recommend this type of prosthesis to their peers but only 47% of them would agree to pay a large increase in the cost of treatment compared to a two-implant overdenture.

CONCLUSIONS

The addition of a midline third implant to an existing mandibular two-implant overdenture resulted in several improved patient-reported outcomes.

Clinical evaluation of inter-implant distance influence on the wear characteristics of low-profile stud attachments used in mandibular implant‑retained overdentures

Background

This study was aimed to evaluate the influence of inter-implant distance on the wear characteristics of low-profile stud attachments used in mandibular implant retained overdentures.

Material and Methods

Forty Completely edentulous participants aged between 50 - 70 years were enrolled in this study. Each patient received 2-implants by 2-stage submerged surgical protocol. Participants categorized into 4-groups. Group I: 19 mm inter-implant distance with Locator retained overdentures; Group II: 19 mm inter-implant distance with OT Equator retained overdentures; Group III: 25 mm inter-implant distance with Locator retained overdentures; Group IV: 25 mm inter-implant distance with OT Equator retained overdentures. The female housings of each attachment were picked up to the mandibular overdenture. 12 month later the male inserts were replaced by new one. The used retentive male inserts were examined by Stereomicroscopic.

Results

Stereomicroscopic examination revealed wear were detected on both inner surface and, the core of male inserts. Comparison between the unused and the used Locator and OT equator retentive male inserts at various inter-implant distance revealed highly significant wear changes between them at either 19 mm, or 25 mm inter-implant distance P1= .000, P2=.000 respectively.

Conclusions

After one year of implant overdenture clinical use; both locator and OT equator retentive male inserts revealed significant surface deformities and wear. Wear were more notable on both locator and OT equator retentive male inserts with 25 mm interimplant distance than with 19 mm interimplant distance. Key words:Inter-implant distance, attachments wear, locator retentive male inserts, OT equator retentive male inserts.