Removable partial dentures: Part 1.

The provision of removable partial dentures (RPDs) is an important skill for practitioners and it can often be challenging to make a successful prosthesis which the patient finds satisfactory. This three-part series has been designed to provide an overview of the clinical management of patients requiring RPDs. This first part provides a refresher of the aspects of the history and examination that are relevant to RPDs. We describe some key principles that are relevant to challenging denture cases. This will help the reader begin the treatment planning process and understand some of the factors which influence the prognosis of dentures.

Surface topography changes and wear resistance of different non-metallic telescopic crown attachment materials in implant retained overdenture (prospective comparative in vitro study).

BACKGROUND: The purpose of this study was to evaluate the effect of using different types of metallic and non-metallic telescopic crown attachment materials on wear resistance and surface tomography changes in implant-retained mandibular overdentures. MATERIALS AND METHODS: Completely edentulous mandibular epoxy models were fabricated, in which two implants were placed in the canine region and retained to the implants with three different material combinations used for the construction of telescopic attachments. Thirty-three identical mandibular overdentures were fabricated using the conventional standardized technique. The study groups were divided into three categories according to the material used for the construction of the secondary copings. The primary copings in all the study groups were constructed of PEEK, while the secondary coping in group I was PEEK, group II was ZrO2 and CoCr for group III. Primary copings were cemented on a ready-made abutment. Secondary copings were placed over the primary copings in the desired path of insertion, then picked up into the intaglio surface of the overdentures. A cyclic loading machine was used to apply repeated insertion-removal cycles simulating nearly 10 years of clinical use. Stereomicroscope with a built-in camera was used to monitor the reduction in width of the primary copings to evaluate the wear resistance of each material combination. RESULTS: There was highly statistically significant difference between the study groups after the application of 1.000, 5.000 and 10.000 cycles. The highest level of wear resistance was recorded for the PEEK/PEEK combination, whereas PEEK/ZrO2 and PEEK/CoCr showed no significant differences. CONCLUSIONS: Implant retained overdenture with PEEK-PEEK telescopic crown attachment is associated with the highest wear resistance among all the study groups. PEEK-PEEK combination may be the treatment of choice for fabrication of telescopic attachment in implant retained overdenture as it provides better resistance to wear. It offers the advantages for geriatric patients as it decreases the possibility for repeated repair and replacement of attachment, increase long-term patient satisfaction and shelf life of prosthesis.

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.

Oral health self-perception, maximum bite force and masticatory efficiency in patients with overdentures with different attachment systems-A crossover study.

BACKGROUND: The literature is unclear about how the different attachment systems for overdentures impact the maximum bite force, the masticatory efficiency and how this impact in the oral health self-perception in patients. OBJECTIVE: To evaluate the effect of two attachment systems (O-ring and Locator) for mandibular overdenture using single implant on quality of life, maximum bite force (BF) and masticatory efficiency (ME). METHODS: Twenty-eight completely edentulous denture wearers with a mandibular symphysis implant were randomly selected and allocated into two groups in a crossover study, considering O-ring and Locator attachment types. The quality of life and self-perception of oral health were assessed using the Oral Health Impact Profile (OHIP-Edent) and Geriatric Index of Determination of Oral Health (GOHAI) questionnaires, respectively. BF was measured using a gnathodynamometer and ME by chewing silicone cubes and almonds in different numbers of cycles. RESULTS: There was no difference between the attachment systems about self-perceived oral health and impact on quality of life (p > .05). The O-ring-type system obtained a significantly higher BF than the locator-type system (p = .04). Regardless of the food chewed, no statistically significant difference was observed with the type of attachment (p > .05). The ME was directly proportional to the masticatory cycles only for almonds (p < .01). CONCLUSIONS: Locator and O-ring inserts had a similar impact on patients' quality of life, self-perception of oral health and ME. Additionally, the O-ring system exhibited superior properties in the BF.

Comparison of masticatory performance and oral hygiene status using cream-type denture adhesives and home liners: A cross-sectional study using propensity-score matching.

BACKGROUND: Differences in the effects of cream-type denture adhesives and home liners remain unclear. OBJECTIVE: This cross-sectional study aimed to clarify the differences in the oral-hygiene status and masticatory performance between participants using cream-type denture adhesives and those using home liners. METHODS: Masticatory performance with and without cream-type denture adhesives and home liners was evaluated using colour-changeable chewing gum. Oral hygiene was assessed using the tongue coating index (TCI). Propensity-score matching was performed using oral moisture, presence of palatal or mandibular protuberances, type of residual ridge, denture type (complete or partial denture), and denture retention as background factors. Wilcoxon signed-rank test was used to examine the differences in masticatory performance with and without cream-type denture adhesives and home liners and differences in masticatory performance and TCI between the cream-type denture adhesive and home-liner groups. RESULTS: This study included 38 and 40 cream-type adhesive and home-liner users, respectively, and 17 pairs were obtained after propensity-score matching. The Wilcoxon signed-rank tests showed that masticatory performance was significantly different with and without the use of home liners, and higher values were obtained with the use of home-liners. However, the cream-type denture adhesive and home-liner groups showed no significant differences in terms of the change in masticatory performance with the use of them. Furthermore, Wilcoxon signed-rank tests showed that TCI values were significantly high in the cream-type adhesive group. CONCLUSION: The findings in this study suggest that home liners improve masticatory performance and that participants regularly using cream-type denture adhesives have poorer oral hygiene.

Digital wear analysis and retention of poly-ether-ether-ketone retentive inserts versus conventional nylon inserts in locator retained mandibular overdentures: in-vitro study.

OBJECTIVE: this study aimed to digitally compare wear behavior and retention between PEEK and nylon retentive inserts used in locator-retained, mandibular implant overdentures when attachment design and size were standardized. MATERIALS AND METHODS: A total of sixty-four inserts (32 PEEK and 32 nylon inserts); were picked-up in implant overdentures. Overdentures of both groups were submerged in artificial saliva and mounted to chewing simulator. After 480,000 chewing cycles (equivalent to 2 years of clinical use) all inserts were scanned by scanning electron microscope (SEM), then all acquired images were digitally analyzed by software to detect and compare quantitative and qualitative changes of inserts in both groups. On the other hand, retention of both groups was measured by universal testing machine and the collected data was statistically analyzed using one-way Analysis of Variance (ANOVA) test with significance level set at P ≤ 0.05. RESULTS: PEEK inserts showed significantly higher mean retentive values compared to the nylon inserts in the control group. Also, PEEK retentive inserts exhibited statistically lower mean wear values than the control group P ≥ 0.000. Qualitative investigation revealed significant and more pronounced changes in the surface roughness of nylon inserts compared to PEEK ones. CONCLUSIONS: Regarding retention, wear behavior and dimension stability, PEEK can be recommended as retentive insert material in cases of locator-retained mandibular implant overdentures. CLINICAL RELEVANCE: PEEK inserts offer enhanced retention, reduced wear, and greater dimensional stability over two years time interval. Clinically, this reduces prosthodontic maintenance and adjustments, improving patient satisfaction and long-term prosthetic success.

Influence of titanium and titanium-zirconium alloy as implant materials on implant stability of maxillary implant retained overdenture: a randomized clinical trial.

BACKGROUND: Long-term success of implant restoration depends on many factors one of them is the sufficient implant stability which is lowered in compromised bone density sites such as the maxilla as it is categorized as type III & IV bone, so searching for a new innovation and updates in implant material and features is very mandatory. So, the aim of this study was to compare between two implant materials (roxolid and traditional titanium) on the primary and secondary stability of implant retained maxillary overdenture. METHODS: Eighteen completely edentulous patients were selected. All patients received maxillary implant-retained overdentures and lower complete dentures; patients were divided equally into two groups according to the type of implant materials. Group A received a total number of 36 implants made of roxolid material and Group B received a total number of 36 implants made of traditional titanium alloys. Implant stability was assessed using ostell device, the primary implant stability was measured at the day of implant installation however, secondary implant stability was measured after six weeks of implant placement. Paired t-test was used to compare between primary and secondary stability in the same group and an independent t-test was used to compare between the two groups with a significant level < 0.05. RESULTS: Independent t-test revealed a significant difference between the two groups with p -value = 0.0141 regarding primary stability and p-value < 0.001 regarding secondary stability, as roxolid implant group was statistically higher stability than titanium group in both. Paired t- test showed a statistically significant difference in roxolid implant group with p-value = 0.0122 however, there was non-statistically significant difference in titanium group with p-value = 0.636. Mann Whitney test showed a significant difference between the two groups regarding amount of change in stability with p value = 0.191. roxolid implant group showed a higher amount of change in stability than the titanium implant group. CONCLUSION: Within the limitation of this study, it could be concluded that: Roxolid implants showed promising results regarding primary and secondary stability compared to conventional Titanium implants and can be a better alternative in implant retained maxillary overdentures. TRIAL REGISTRATION: Retrospectively NCT06334770 at 26-3-2024.

Mandibular overdenture retained by four one-piece titanium-zirconium mini implants: A 2-year RCT on patient-reported outcomes.

AIM: The positive impact of implant interventions on dental patient-reported outcomes is an essential parameter of treatment effectiveness. This study assessed the 2-year changes in patient satisfaction and oral health-related quality of life (OHRQoL) of edentulous patients treated with a four mini implant mandibular overdenture (IOD) METHODS: The study was planned as a 2 × 2 factorial randomized clinical trial that tested two surgical approaches (flapped or flapless) and two loading protocols (immediate and delayed) using a titanium-zirconium mini implant (Straumann Mini Implant System®) and a PEEK retentive system (Straumann® Optiloc® Retentive System). Outcome measures (OHIP-Edent scores and the McGill Denture Satisfaction questionnaire) were assessed before treatment and at the 3-, 6-, 12-, and 24-month follow-ups. The Friedman test and multiple regression using Generalized Estimating Equations (GEE) were used for data analysis, considering the per-protocol (PP) and intention-to-treat (ITT) approaches RESULTS: Seventy-four patients were randomized to the study groups. No implant failure occurred during the study period. Marked improvement in all post-treatment periods compared to baseline were observed for the two outcomes. No significant effect of patient's gender, age, and surgical protocol on the study outcomes. The effect of treatment provision was significant for the two outcomes in the PP and ITT approaches (p < 0.001). A barely significant positive effect of the immediate loading was observed for OHIP-Edent in the PP approach (p = 0.020) CONCLUSION: IOD treatment significantly improved patient-reported outcomes measures, with sustained benefits over the two years of overdenture use, and can be considered a promising treatment option in for the edentulous mandible.

Mandibular overdenture retained by four one-piece titanium-zirconium mini implants: A 2-year follow-up on prosthodontic outcomes.

OBJECTIVE: This 2-year prospective study reports the incidence of prosthetic complications and maintenance events after treatment with mandibular overdenture retained by four mini implants opposed to a maxillary denture. METHODS: Implant intervention included flapless or flapped surgery combined with immediate or delayed loading, as part of a randomized clinical trial. Four one-piece titanium-zirconium mini-implants (Straumann Mini Implant System) were inserted, and the retentive PEEK elements (Optiloc) were incorporated into the overdenture using chairside procedures. Prosthodontic complications and maintenance events were recorded over a 2-year follow-up, and the final outcome was defined according to standardized criteria. Data analysis included descriptive statistics, incidence and incidence density rates, and Kaplan-Meier survival. RESULTS: 73 out of 74 patients (64.9 % female), mean age of 64 (SD=8.2) years, completed the study follow-up (one withdrew after 9 months). Implant survival was 100 %. A total of 163 prosthodontic events occurred in 53 patients (72.6 %), and 20 patients had no clinical complaints or maintenance needs. The most common procedures were adjustment/repair of the overdenture base (47.0 %), replacement of retentive inserts (19.8 %), and laboratory relining (12.9 %). A high prosthodontic success rate was achieved (93.2 %), and all patients presented serviceable overdentures and continuous use after the resolution of prosthodontic complications. The incidences of matrix replacement and laboratory relines were low in the first year, while denture base adjustments were common within the first year, especially in the first 6 months. CONCLUSION: The mini implant system showed high prosthodontic success rates. Minor adjustments/repairs during the initial follow-up were common. Relines and matrix replacements tend to occur after one year of overdenture use, and matrix replacements may occur as a consequence of the need for relining.

Prosthetic Maintenance Assessment for Two Implant- Retained Overdentures Reinforced with PEKK Versus Co-Cr Framework: A Randomized Controlled Clinical Trial.

INTRODUCTION: The primary challenge associated with implant overdentures lies in the occurrence of denture fractures around the attachments. Hence, it is recommended to enhance flexural strength through reinforcement frameworks. This study aimed to assess and compare the prosthetic maintenance of mandibular implant overdentures reinforced with Co-Cr and PEKK frameworks. METHODS: Twenty-four participants with completely edentulous ridges were selected, and two implants were placed at the mandibular canine areas. After osseointegration period, ball attachments were installed. Participants were randomly assigned into two groups: Group I received a mandibular implant overdenture reinforced with a Co-Cr framework, while Group II received a mandibular implant overdenture reinforced with a PEKK framework. Prosthetic maintenance evaluations were conducted in both groups twelve months post-denture insertion. Categorical data were analyzed, and results were presented as frequency and percentage values. RESULTS: Group II exhibited a significantly higher percentage of cases with screw looseness, denture relining, and tooth separation compared to Group I. Although Group II cases showed a non-significant increase in the percentage of insert wear and retention loss. CONCLUSION: Within the limitations of this study, the findings suggest that Co-Cr, in contrast to PEKK frameworks, offers a more reliable reinforcement of the implant-retained overdentures.

Assessment of occlusion changes during laboratory phase of relining: An in vitro study.

AIM: Assessment of occlusion changes during laboratory phase of relining is essential to evaluate the occlusal discrepancies that could get incorporated in the denture with the use of different relining materials. Since the long term stability and functional success of the denture is heavily influenced by occlusion, an In-vitro study to assess these changes after relining is warranted. The aim of the study is to evaluate the changes in occlusion during laboratory phase of relining procedure. SETTINGS AND DESIGN: This is an in vitro study with a total of 30 specimen. MATERIALS AND METHODOLOGY: A total of 30 maxillary standardized dentures were fabricated after mounting on a semi adjustable articulator. These samples will be divided into three groups based on the relining material used (Autopolymerizing resin, Heat-cure resin, Tissue conditioner). The vertical dimension, Centric contact points and eccentric contact points were measured before and after relining. STATISTICAL ANALYSIS USED: The variables were tested to see if they had a normal distribution using the Shapiro-Wilk test. Parametric distribution was seen for ECP leading to further comparison using one way analysis of variance (ANOVA). Non-parametric distribution was found while testing the VD, CCP leading to adoption of Kruskal-wallis test for comparison of groups. Dunn Bonferroni test was done for VD since results were significant. RESULTS: The results of this in-vitro study showed statistically significant difference with respect to change in vertical dimension in all groups pre and post relining (P = 0.005). The centric contact points showed lesser variation in position when comparing the pre to the post relining phase with the use of autopolymerising resins, whereas heat cure resins and tissue conditioners showed statistically significant difference in the centric point contacts post relining. No statistically significant changes were seen in eccentric occlusion post relining in all groups. Tissue conditioners showed minimum mean changes in eccentric contacts. CONCLUSION: Within the limitations of this study, the use of autopolymerising resins depicted the most stable results with respect to occlusion, for relining of dentures.

Longevity of acrylic and cobalt-chromium removable partial dentures-A ten-year retrospective survival analysis of 1246 denture-wearing patients.

OBJECTIVES: to assess the survival rates of removable partial dentures (RPDs) and identify factors impacting their longevity. METHODS: electronic health records were retrieved of patients aged ≥18 who received RPDs between 2010 - 2021 with a follow-up of ≥ three months. Data extracted included demographics, medical history, dental charting, periodontal screening and recording scores, prostheses details and related interventions, including new dentures/denture remakes, and maintenance. Multivariate Mixed-Effect Cox regression was performed to identify potential RPD survival risk factors. Reduced model selection was reached using a backward step-down by comparing the performance of these multivariable models using the ANOVA test. RESULTS: 1893 RPDs from 1246 patients were included, with a median follow-up of 21.8 months (range from 3 to 131.3 months). Three hundred and twelve patients received a maxillary RPD, 460 received a mandibular RPD, and the remaining 474 patients received both maxillary and mandibular RPDs. Metal-based RPDs had a median survival of 73 months (95%CI: 70 - 82) versus 45 months (95% CI: 37-67) for acrylic ones. Multivariable mixed effects Cox model showed that the lifespans of RPDs were longer amongst patients receiving more maintenance care within three months [Hazards Ratio (HR)=0.89 (0.83, 0.96)] and after three months [HR=0.53 (0.46, 0.61)] of denture delivery, patients wearing both maxillary and mandibular RPDs [HR=0.67 (0.52, 0.87)], and patients receiving metal-based RPDs [HR=0.31 (0.23, 0.42)]. CONCLUSIONS: Metal-based dentures, dual arch restoration, and increased maintenance positively impact the survival of RPDs. CLINICAL SIGNIFICANCE: Adapting consent and warranty practices is advised to reflect RPD performance variations.

Four-year assessment of masticatory function in mandibular overdenture wearers: A randomised clinical trial comparing two to four implants to retain the prosthesis.

BACKGROUND: Limited data exist on the mid- to long-term masticatory capacity of mandibular overdenture (IOD) wearers, particularly regarding the use of posterior implants to retention. OBJECTIVES: To periodically evaluate mastication of IOD wearers, comparing the effectiveness of two to four implants to retain the prosthesis. METHODS: In a randomised controlled clinical trial, 20 complete edentulous patients (14 women), aged 51-84 years (mean age 69.1 ± 9.6), received new bimaxillary complete dentures (CD). After adaptation, baseline measurements of masticatory performance (X50) and swallowing threshold were conducted using the sieving method. Patients were then randomly assigned to groups: control (two intra-foraminal regular implants) and experimental (two intra-foraminal regular implants and two extra-short posterior implants) (n = 10 each). After 4 months, implants were splinted, and a new mandibular IOD was fabricated with bar/clip retention. Mastication was reassessed after 6, 12, and 48 months, and data analysed with repeated measures ANOVA and Sidak's post hoc (α = 0.05). RESULTS: Despite a loss of two patients per group, masticatory performance significantly improved after mandibular IOD installation (p = .031) in both groups (p = .670). A second improvement was observed after 6 months (p = .027), with no subsequent changes (p > .05). Swallowing threshold improvements were noted with IOD, and no discernible differences between groups were observed (p > .05). CONCLUSION: Masticatory function significantly improved after mandibular IOD installation, with the number of implants demonstrating minimal influence. CLINICAL TRIAL REGISTRATION: The present study was not registered in a public database, as mandated. It is important to note that the recommendation for registration was initiated in 2017 by the Committee of Medical Journal Editors, while patient inclusion in the research took place in 2016. Given that the data presented in this manuscript cover a follow-up period of up to 4 years post-surgical intervention, delayed registration was not feasible.

Posterior two-unit cantilevered zirconia resin-bonded fixed partial dentures: A 3-year prospective single-arm clinical trial.

OBJECTIVES: To evaluate the longevity of cantilevered zirconia-based resin-bonded fixed partial dentures (RBFPDs) in replacing missing posterior teeth, as well as the quality of life and patient satisfaction experienced by those receiving zirconia RBFPDs. METHODS: A prospective single-arm uncontrolled clinical trial was conducted to replace one or more missing premolars or molars with a span of 5 to 8 mm using cantilevered zirconia RBFPDs. Thirty-six participants with 40 prostheses were recruited and underwent a 3-year clinical evaluation. The retainer designs included a minimum thickness of 0.8 mm, a minimum of 200° circumferential wraparound with an occlusal bar, and a connector dimension of 3 × 3 mm. Patient-reported outcomes, including patient satisfaction and Oral Health Impact Profile (OHIP), were assessed. RESULTS: The average age of participants was 45.8 years, and 72.5 % were women. The success rate of the posterior zirconia RBFPDs was 76.2 %, with an estimated mean success duration of 46.1 months. The survival rate was 88.1 %, with an estimated mean survival duration of 49.4 months. Participants were highly satisfied with the treatment, achieving an average satisfaction score of 80.8 ± 11.9. Participants' total OHIP scores decreased from 52.3 to 39.6 after 3 years, indicating a significant improvement in oral health-related quality of life (P = 0.009). CONCLUSIONS: After 3 years, a moderately high survival rate and favourable patient-reported outcomes of posterior cantilevered zirconia RBFPDs were achieved. Therefore, it can be recommended as a conservative treatment option to replace missing posterior teeth, provided that retainer design considerations are taken into account. CLINICAL SIGNIFICANCE: Cantilevered zirconia RBFPDs for posterior teeth can serve as a conservative treatment option that is both aesthetically pleasing and biocompatible. It offers a more cost-effective alternative compared to dental implants, which are often prohibitively expensive for the majority of patients. This approach has the potential to greatly improve patient-reported outcomes.

Retention of Mandibular Complete Overdentures using Mini Dental Implants (Ø < 3 mm) and Standard Diameter Implants (Ø > 3mm): A Systematic Review and Meta-Analysis of Randomised Controlled Trials.

PURPOSE: The objective of the present systematic review and meta-analysis was to assess randomised controlled trials (RCTs) which assessed the efficacy of mini dental implants (MDIs) and standard-diameter implants (SDIs) in retaining mandibular overdentures (MO). MATERIALS AND METHODS: The focused question was "Is there a difference in the mechanical stability between MDIs and SDIs in retaining MO?" Indexed databases were searched up to and including November 2023 using different keywords. Boolean operators were used during the search. The literature was searched in accordance with the PRISMA guidelines. The PICO characteristics were: patients (P) = individuals with complete mandibular dentures requiring dental implants; Intervention (I) = placement of MDIs under mandibular dentures; Control (C) = placement of SDIs under mandibular dentures; Outcome (O) = comparison of stability between MDIs and SDIs in supporting mandibular dentures. Only RCTs were included. Risk of bias (RoB) was assessed using the Cochrane RoB tool. RESULTS: Five RCTs were included. The numbers of participants ranged between 45 and 120 edentulous individuals wearing complete mandibular dentures. The mean age of patients ranged between 59.5 ± 8.5 and 68.3 ± 8.5 years. The number of MDIs and SDIs ranged between 22 and 152 and 10 and 80 implants, respectively. The follow-up duration ranged between one week and 12 months. Three RCTs reported an improvement in the quality of life (QoL) of all patients after stabilisation of mandibular dentures using MDIs or SDIs. In one RCT, peri-implant soft tissue profiles were comparable between MDIs and SDIs at the 1-year follow-up. The implant survival rate was reported in two RCTs, which were from 89% to 98% and 99% to 100% for MDIs and SDIs, respectively. All RCTs had a low RoB. CONCLUSION: Mini dental implants represent a viable alternative to traditional standard-diameter implants when seeking optimal retention for mandibular overdentures.

Effectiveness of commercially available denture adhesives on retention of mandibular complete denture in resorbed mandibular ridge: an in vitro study / Efectividad de los adhesivos disponibles comercialmente sobre la retención de prótesis removibles completas mandibulares en el reborde mandibular reabsorbido: un estudio in vitro

Background: Denture adhesives are alternatives used to improve retention, stability, comfort and satisfaction in patients with complete dentures. Evidence on the effectiveness of denture adhesives on resorbed mandibular ridges is scarce. Among the many commercially available denture adhesives, the ideal material for the severely resorbed mandibular ridge remains in dispute. Objective: The aim of this study was to evaluate the effectiveness of different quantities of four commercially available denture adhesives on the retention of mandibular complete dentures in severely resorbed ridges. Materials and Methods: A resorbed edentulous mandibular ridge model was manufactured in acrylic resin. A denture base was made and three loops were attached to it. Four commercially available denture adhesives (Fixodent, Perlie White, Fiftydent and Polident) were tested in amounts of 0.2 g, 0.4 g, 0.6 g, 0.8 g and 1.0 g. The acrylic resin model was evenly moistened with 1 ml of water and a weighted amount of adhesive material was applied to the denture base. The universal testing machine engaged the loops fixed on the denture base and applied the vertical displacement force. The maximum vertical displacement force values were recorded for each denture adhesive material at different amounts. Statistical calculation was performed using Kruskal Wallis with Bonferroni post hoc correction. Results: Statistically significant differences were observed in the mean values of the vertical displacement force for adhesive amounts of 0.2 g, 0.4 g, 0.6 g and 1.0 g (p<0.05) between the four adhesive materials tested. Statistically significant differences were observed when four denture adhesives were compared to each other in different amounts (p<0.05). Statistically significant differences were observed between different amounts for each of four denture adhesives (p<0.05). Conclusions: Among the four materials tested, Polident showed greater effectiveness at 0.6 g and 0.8 g, Fittydent at 0.6 g, 0.8 g and 1 g, Fixodent at 0.4 g and 0.6 g and Perlie White at 1 g and 0.8g quantity to resist vertical displacement. forces on the severely resorbed mandibular crest. Using an appropriate amount of denture adhesive allows for proper retention of the denture; Replacement of this adhesive is necessary once a day.

Introducción: Los adhesivos para prótesis dentales son alternativas utilizadas para mejorar la retención, la estabilidad, la comodidad y la satisfacción en los pacientes con prótesis completas. La evidencia sobre la efectividad de los adhesivos para prótesis dentales en los rebordes mandibulares reabsorbidos es escasa. Entre los muchos adhesivos para prótesis dentales disponibles comercialmente, sigue estando en disputa cuál es el material ideal para el reborde mandibular severamente reabsorbido. Objetivo: El objetivo de este estudio fue evaluar la efectividad de diferentes cantidades de cuatro adhesivos para prótesis dentales disponibles comercialmente sobre la retención de prótesis dentales completas mandibulares en reborde mandibular reabsorbido severamente. Materiales y Métodos: Se fabricó un modelo de reborde mandibular edéntulo reabsorbido en resina acrílica. Se hizo una base para la prótesis y se le colocaron tres bucles. Se probaron cuatro adhesivos para dentaduras postizas disponibles comercialmente (Fixodent, Perlie White, Fiftydent y Polident) en cantidades de 0,2 g, 0,4 g, 0,6 g, 0,8 g y 1,0 g. El modelo de resina acrílica se humedeció uniformemente con 1 ml de agua y se aplicó la cantidad correspondiente de material adhesivo sobre la base de la dentadura. La máquina de prueba universal enganchó los bucles fijados en la base de la dentadura postiza y aplicó la fuerza de desplazamiento vertical. Se registraron los valores máximos de fuerza de desplazamiento vertical para cada material adhesivo para dentaduras postizas en diferentes cantidades. El cálculo estadístico se realizó utilizando Kruskal Wallis con corrección post hoc de Bonferroni. Resultado: Se observaron diferencias estadísticamente significativas en los valores medios de la fuerza de desplazamiento vertical para cantidades de 0,2 g, 0,4 g, 0,6 g y 1,0 g (p<0,05) entre los cuatro materiales adhesivos para prótesis dentales probados. Se observaron diferencias estadísticamente significativas cuando se compararon cuatro adhesivos para prótesis dentales entre sí en diferentes cantidades (p<0,05). Se observaron diferencias estadísticamente significativas entre diferentes cantidades en los cuatro adhesivos para prótesis (p<0,05). Conclusión: De los cuatro materiales probados, Polident mostró mayor efectividad a 0,6 g y 0,8 g, Fittydent a 0,6 g, 0,8 g y 1 g, Fixodent a 0,4 g y 0,6 g y Perlie White a 1 g y 0,8 g para resistir fuerzas de desplazamiento vertical en la cresta mandibular severamente reabsorbida. El uso de una cantidad adecuada de adhesivo para dentaduras postizas permite una retención adecuada de la dentadura postiza; El reemplazo de este adhesivo es necesario una vez al día.

[Evaluation of the 5-year clinical restoration effect of implants retained complete overdentures with Locator attachments in 48 patients].

PURPOSE: To observe the long-term clinical effect of implants retained complete overdentures with Locator attachments. METHODS: A total of 48 patients with edentulous jaws treated with implants retained complete overdentures with Locator attachments were selected from the Outpatient Department of Peking University School and Hospital of Stomatology from 2016 to 2017. Among them, 21 patients underwent double-maxillary complete overdentures restoration and 27 patients underwent single-maxillary restoration. A total of 230 implants were implanted. The clinical observation indicators included the implant survival rate, peri-implant mucosal bleeding on probing(BOP), the change in the vertical height of alveolar bone absorption around the implants, overdenture base fracture rate, artificial tooth fall off and fracture rate and other complications. The change of the locator attachment retention force of the implant-supported overdentures was evaluated. SPSS 13.0 software package was used for data analysis. RESULTS: During the five-years clinical observation period, 5 implants fell off, 1 narrow dimeter implant in the anterior zone was broken, and 12 implants were lost to follow-up. The implant survival rate was 97.25%. One year after the restoration therapy finished, peri-implant mucosal bleeding on probing (BOP+) was detected in 48 (21.4%) implants. The average BI was 0.21±0.42, which was higher in the anterior zone than that in the posterior zone. The vertical alveolar bone absorption height around the implants was (0.21±0.35) mm, 2 implants-supported complete overdenture bases were broken. After 5 years of restoration, 163(76.89%) implants had peri-implant mucosal bleeding on probing(BOP+). The average BI was 1.00±0.70, and the vertical alveolar bone absorption height around the implants was (0.58±0.85) mm. There was no significant difference between males and females. There was no significant difference in the peri-implant mucosal bleeding index and the alveolar bone vertical absorption height between the anterior zone and the posterior zone(P＞0.05). The mean BI of peri-implant mucosa and the vertical absorption height of peri-implant alveolar bone were significantly different between the 1-year observation period and the 5-year observation period respectively(P＜0.01). There were 17(26.15%) cases with overdenture bases fracture, and the fracture rate of artificial teeth was 16.92%. Most of them occurred in the midline area of the anterior zone and the location of the overdenture base on the locator attachments. The average first replacement time of the locator attachment nylon retainer washer was 34.2±10.3 months. CONCLUSIONS: Implants retained complete overdentures with Locator attachments are effective in long term clinical observation. Complications are mainly found in peri-implant mucosal bleeding on probing and vertical alveolar bone absorption, and tended to increase gradually over time. The fracture of the implant retains complete overdenture bases and the fall off or fracture of the artificial teeth are the second serious complications. Overdenture base with metal frame at the location of the Locator abutment and the midline of the anterior area should be strengthened, and narrow diameter implants should be avoided as far as possible in the anterior zone.

Retention and fatigue performance of modified polyetheretherketone clasps for removable prosthesis.

PURPOSE: Polyetheretherketone (PEEK) is considered as an alternative to metal material for removable partial denture (RPD). However, the retentive force is not strong as a metal RPD. This study investigated the retention and fatigue performance of PEEK clasps with different proportions of clasp arm engaging the undercut to verify a new strategy to improve their clinical performance. METHODS: Three groups (n = 10/group) of PEEK clasps with their terminal 1/3, 2/3 and the whole of retentive arms engaging the undercut were fabricated along with a group (n = 10) of conventional cobalt-chrome (CoCr) clasps as control group. Retentive forces were measured by universal testing machine initially and at an interval of 1500 cycles for a total of 15,000 fatigue cycles. The fatigue cycles were conducted by repeated insertion and removal of the clasp using fatigue testing machine. Each clasp was scanned by Trios3 scanner before and after fatigue test to obtain digital models. The deformation of the clasp was evaluated by root mean square (RMS) through aligning the two models in Geomagic wrap (2021). Scanning electron microscopy (SEM) and finite element analysis were carried out to observe the abrasion and the von Mises stress of the clasp arm. Kruskal-Wallis H test was used to compare the retentive forces and the RMSs of the studied groups followed by Bonferroni multiple comparisons. RESULTS: The whole of PEEK clasp arm engaging the undercut provided higher mean retentive forces (7.99 ± 2.02 N) than other PEEK clasp groups (P < 0.001) and was closer to CoCr clasps (11.88 ± 2.05 N). The RMSs of PEEK clasps were lower than CoCr clasps (P < 0.05) while the differences among PEEK clasps were of no statistical significance (P > 0.05). SEM showed that evidences of surface abrasion were observed on the section that engaged the undercut for all groups of clasps. The stress concentration mainly occurred on the initial part of the retentive arm. The maximum von Mises stress of each group was below the compressive strength of PEEK. CONCLUSIONS: Proportions of PEEK clasp arm engaging the undercut positively influenced the retentive force and the fatigue resistance of PEEK clasps was superior than CoCr clasps. It is a feasible method to improve the retention of PEEK clasps by increasing the proportion of clasp arm engaging the undercut. Clinical trials are needed to further verify this innovation.

Changes in masticatory performance and bite force after treatment with mandibular overdentures retained by four titanium-zirconium mini implants: One-year randomised clinical trial.

OBJECTIVE: This prospective study is part of a randomised clinical trial and reports the changes in masticatory performance (MP) and bite force, and explores their influential factors, 1 year after the provision of mandibular overdentures retained by four titanium-zirconium mini implants. METHODS: Edentulous patients received conventional complete dentures, followed by placement of four mini implants (Straumann® Mini Implant System) in the anterior mandible and converting the conventional prosthesis into a mandibular overdenture. Treatment protocols were randomised using a 2×2 factorial design combining different surgical (flapped vs. flapless) and loading (immediate vs. delayed) protocols. MP was assessed using a two-colour mixing ability test and a colorimetric analysis to measure the level of colour mixing (Variance of Hue-VoH). Maximum voluntary bite force (MBF) was measured by a digital gnathodynamometer in the posterior and anterior regions. Sex, age, surgical and loading protocols and ridge morphology were tested as independent variables. MP and MBF tests were performed at baseline (pre-treatment) and the 3-, 6- and 12-month after implant loading. Descriptive statistics, independent t-test, and linear mixed-effect model (LMM) regression were used for data analysis. RESULTS: Seventy-four participants were assessed and 73 completed the 1-year follow-up. Statistically significant improvements in functional parameters were observed in all follow-up periods compared to baseline (p < .001). The flapless protocol was associated with higher improvement in MP at the 3-month follow-up (p = .004), while less resorbed ridges were associated with better MP (p = .038) and higher MBF (p < .001). CONCLUSION: The mandibular overdenture protocol using four titanium-zirconium mini implants was effective in improving MP and MBF of edentulous patients, compared to pre-treatment values. The findings also suggest that improvements in chewing function and bite force are impacted by clinical factors since better outcomes were observed for flapless surgeries and less resorbed edentulous ridges. CLINICAL TRIAL REGISTRATION: ClinicalTrials.Gov ID NCT04760457.