Effect of Various Retentive Element Materials on Retention of Mandibular Implant-Retained Overdentures

Retention of Ti Si snap versus locator attachments with retention sil in two-implant retained mandibular overdentures: an in vitro study

BACKGROUND

Primary retention and progressive loss of retention of various attachment systems are critical elements in appropriate attachment selection; nevertheless, research on attachment retention reveals a broad spectrum of retention values for the same attachment system and between various systems. Accordingly, the aim of this study was to compare the retention of two different types of attachments (Ti Si snaps and locators) in two-implant-retained mandibular overdentures.

METHODS

A completely edentulous mandibular educational cast was scanned. An STL file including the implant beds and mucosal space was designed. Two implant analogs were incorporated into each model in the canine area bilaterally, and conventional overdentures were fabricated over two types of implant attachments, the Ti Si snap attachments and the locator attachments, with the use of Retention sil in both groups at the fitting surface of the overdenture. Each group contained five 3D-printed edentulous mandibular models. Retention was measured by using a universal testing machine after the models were subjected to cyclic loading. This measurement was carried out at the time of insertion, after 75,000 cycles (simulating 6 months of clinical use) and 150,000 cycles (simulating 12 months of clinical use). The means and standard deviations of the recorded readings were collected, tabulated, and statistically analyzed.

RESULTS

Student's t test revealed significant differences between the two groups. The Ti Si attachment group presented the highest retention rate at the time of insertion and after 6 months. However, there was no significant difference between the groups after 12 months. Both groups presented statistically significant changes in the mean retention value over time, as demonstrated by two-way ANOVA (time of insertion > six months > twelve months). Tukey's post hoc test revealed a nonsignificant difference between six months and twelve months.

CONCLUSION

Within the limitations of this study, the following conclusions can be drawn.

The effect of cyclic dislodgement and denture cleanser storage on various attachment systems used in implant-overdenture prostheses

PURPOSE

The present study aims to evaluate and compare the retention forces of nylon and polyetheretherketone (PEEK) attachments with different color codes over time and denture cleansers.

MATERIALS AND METHODS

Two plexiglass models were prepared for this study. In the first model, two Astra-Tech EV implants and two Locator abutments were placed, followed by the placement of two corresponding housings in the opposite blocks where nylon attachments were fitted. The second model was mounted with two Medentika Microcone RI implants and two Novaloc abutments. PEEK attachments were then placed in the corresponding housings. Blue-pink-clear nylon and white-yellow-green PEEK attachments' (n = 8 for each group) maximum dislodgement forces were measured at baseline (T0). Second measurements were conducted after 1080 insertion and removal cycles (T1). Corega denture cleanser solution was prepared by adding one tablet to 200 mL of tap water. All attachments were soaked in the solution for three minutes and rinsed under running water. Each group of attachments was soaked for 1080 min in total, corresponding to 1 year of clinical use. The final measurements were conducted after storage in the solution. One specimen and abutment were randomly selected from each group and examined using a scanning electron microscope. The data were analyzed by repeated measures ANOVA and Bonferroni multiple comparison test (p < 0.05). The percentage decrease in the dislodgement force of the attachments was also calculated.

RESULTS

Insertion and removal cycles significantly affected the retention values (p < 0.001). Storage in the cleanser did not significantly affect the retention (p > 0.05). The lowest retention value was observed in blue nylon attachments (501.50 ± 33.39 gf [gram force]) after insertion-removal (T1), with a similar trend after immersion (476.13 ± 39.75 gf) (T2). The highest retention was observed similarly in clear nylon attachments (1660.38 ± 41.73 gf) after insertion-removal after immersion (1636.50 ± 62.20 gf) (T2). In terms of percentage loss of retention, yellow PEEK attachments were the most affected group after all test procedures (36.88%), while the lowest affected group was pink nylon attachments (21.56%).

CONCLUSIONS

PEEK attachments were the least affected by the denture cleanser but the most affected by insertion and removal cycles. Corega denture cleanser had no significant effect on nylon or PEEK attachments, whereas the insertion-removal cycle had a significant effect on both attachment systems.

Different Wire Surface Treatments on Adhesion Efficacy of Orthodontic Fixed Retainer: An In Vitro Study

AIM

This study assesses the impact of surface treatment with sandblasting and Z-primer on the adhesion efficacy of fixed lingual retainers.

MATERIALS AND METHODS

Dead soft stainless steel wire 0.016 × 0.022-inch (n = 120) was treated by different techniques and classified into four groups equally (n = 30) according to surface treatment. Group I wire without treatment, group II wire treated with sandblasting, group III wire treated with Z-primer alone, and group IV wire treated with sandblasting with Z-primer. The stainless steel wire (n = 40) was bonded to 80 extracted premolars in pairs mounted in acrylic. Other stainless steel wires (n = 80) are embedded into acrylic blocks. All groups were divided into two subgroups according to thermocycling teeth samples were assessed by shear bond strength (SBS) A stereomicroscope was used to calculate the adhesive remnant index (ARI), while the acrylic block was by pull-out test. Finally, data were analyzed by IBM-SPSS (V 27, 2020). Mann-Whitney U-test; Kruskal-Wallis H-test and, two-way ANOVA were utilized to assess for SBS and pull-out.

RESULTS

Kruskal-Wallis H-test showed a non-significant difference in ARI between all groups, while in two-way mixed ANOVA demonstrated a significant difference in SBS between group III (sandblasting/Z-primer) vs group I and group IV Z-primer (p = 0.028) and control (p = 0.016), and a significant difference between group II sandblasting vs both group I and group IV Z-primer (p = 0.024) and control (p = 0.014). The two-way mixed ANOVA tests showed a significant difference in pull-out between sandblasting/Z-primer vs Z-primer (p = 0.012).

CONCLUSION

Using of mixed surface treatment for fixed retainer as sandblasting with Z-primer is considered as the best method to increase adhesion efficacy between wire and composite and improve the quality of orthodontics fixation when compared with single treatment (sandblasting alone or Z prime). On the other hand, the sue of sandblasting alone for fixed retainer surface treatment is better than Z-primer alone but both treatments are better than fixed retainer without treatment.

CLINICAL APPLICATION

Developed and examined new and traditional techniques used to treat the surface of wire used as a retainer after orthodontics treatment to improve patients' treatment and life quality and decrease the chance of relapse. How to cite this article: Naji SM, Mohammad MH, Enan ET, et al. Different Wire Surface Treatments on Adhesion Efficacy of Orthodontic Fixed Retainer: An In Vitro Study. J Contemp Dent Pract 2024;25(7):677-683.

Effect of thermocycling on the retentive force of the retentive inserts in three denture attachments and their water absorption ability

This study aimed to evaluate the thermocycling effect on the retentive force of 3 different retentive inserts in 3 denture attachments (Blue, Pink, Clear retentive inserts in LOCATOR; Blue, Pink, Clear retentive inserts in LOCATOR R-Tx; and White, Yellow, Green retentive inserts in Novaloc) (n=10). Maximum retentive force of each retentive insert was evaluated at baseline, 7-day water storage, and after 5,000-, and 10,000- cycle thermocycling. The water absorption percentage of the retentive inserts was also determined. Comparing between baseline and 7-day water storage, the retentive forces of the LOCATOR and LOCATOR R-Tx groups were significantly reduced (p<0.05), while the retentive force of the Novaloc group was significantly increased (p<0.05). Comparing between 7-day water storage and 10,000-cycle thermocycling, the retentive force of most retentive inserts remained unchanged (p>0.05). The water absorption percentage of the LOCATOR and LOCATOR R-Tx groups was significantly greater than that of the Novaloc group (p<0.05).

Early Loading of Two Implants Supporting Mandibular Overdentures in Geriatric Edentulous Patients: A 12-Year Follow-Up Study

Background: This study aims to show the clinical outcomes of implants supporting mandibular overdentures in edentulous patients. Methods: Mandibular edentulous patients were diagnosed with an oral examination, panoramic radiograph, and diagnostic casts for intermaxillary relations and treated with overdentures over two implants. After two-stage surgery, implants were early loaded with an overdenture at 6 weeks. Results: Fifty-four patients (28 females and 24 males) were treated with 108 implants. Thirty-two patients (59.2%) had a previous history of periodontitis. Twenty-three patients (46%) were smokers. Forty patients (74.1%) suffered from systemic diseases (i.e., diabetes, cardiovascular diseases). The clinical follow-up of the study was 147.8 ± 10.4 months. The clinical outcomes showed a global success of 94.5% of implants. Fifty-four overdentures were placed in the patients over the implants. The mean marginal bone loss was 1.12 ± 0.34 mm. Nineteen patients (35.2%) showed some kind of mechanical prosthodontic complication. Sixteen implants (14.8%) were associated with peri-implantitis. Conclusions: Based on the clinical results obtained, we can determine that the treatment of elderly edentulous patients with mandibular overdentures through the early loading of two placed implants is a successful implant protocol.

Impact of different axial wall designs on the fracture strength and stress distribution of ceramic restorations in mandibular first molar

BACKGROUND

The purpose of this study was to investigate the fracture strength and stress distribution of four ceramic restorations.

METHODS

Forty human mandibular first molars were collected and randomized into four groups after establishing the distal defect: full crown group with 4 mm axial wall height (AWH) (FC4); short AWH crown group with 2 mm AWH (SC2); occlusal veneer group with 0 mm AWH (OV0); occlusal distal veneer group with only the distal surface prepared, and 4 mm AWH (OD4). The teeth were prepared according to the groups and the ceramic restorations were completed using celtra duo ceramic blocks. The ceramic thickness of the occlusal surface is about 1.5 mm and the edge is about 1 mm. The failure load values and fracture modes of each group were detected by mechanical test in vitro. According to the groups to establish three-dimensional finite element analysis (FEA) models, a 600 N loading force was applied vertically using a hemispherical indenter with a diameter of 6 mm. and compare the stress distribution under the condition of different restorations.

RESULTS

In vitro mechanical tests showed that the failure load values were SC2 (3232.80 ± 708.12 N) > OD4 (2886.90 ± 338.72 N) > VO0 (2133.20 ± 376.15 N) > FC4(1635.40 ± 413.05 N). The failure load values of the short AWH crown and occlusal distal veneer were significantly higher than that of occlusal veneer and full crown (P<0.05). The fracture modes of the full crown and occlusal veneer groups were mainly ceramic fractures and some were restorable tooth fractures. The short AWH crown and occlusal distal veneer groups presented with three fracture modes, the proportion of non-restorable tooth fracture was higher. The results of FEA show that under the spherical loading condition, the stress of ceramic was concentrated in the contact area of the loading head, the maximum von Mises stress values were FC4 (356.2 MPa) > VO0 (214.3 MPa) > OD4 (197.9 MPa) > SC2 (163.1 MPa). The stress of enamel was concentrated in the area where the remaining enamel was thinner, the maximum von Mises stress values was OD4 (246.2 MPa) ≈ FC4 (212.4 MPa) > VO0 (61.8 MPa) ≈ SC2 (45.81 MPa). The stress of dentin is concentrated in the root furcation and the upper third region of the root. However, stress concentration was observed at the tooth cervix in the full crown.

CONCLUSION

Under certain conditions, the occlusal distal veneer shows better performance than the full crown.

Effect of Implant Positions and Angulations on Retentive Strength of 2-Implant Mandibular Overdentures: An In Vitro Study with the New 3D-Printed Simulation Method

Objectives. To evaluate the retentive strength of overdenture attachments in 2-implant mandibular overdenture (2IMO) with implants placed at different positions and angulations. Materials and Methods. Edentulous mandibular models were 3D-printed using CBCT images and Materialise Mimics software and the denture models using the intraoral scanner. Two standard implants were placed parallel at different positions from midline (5, 10, 15, and 20 mm) with 0-0 degree angulations and with different distal angulations (0–5, 0–10, 0–15, 5-5, 10-10, and 15-15 degrees) at 10±mm from midline representing 10 study groups. Low-profile male attachments were attached to the implants and the female pink attachments were picked up in the denture. A total of 4 simulated overdenture model sets for each of the 10 study groups were subjected to the universal testing machine thrice to measure a peak load (N) to disengage the attachments vertically. Data were analyzed using one-way ANOVA and Tukey’s post hoc test at 0.05 significance level. Results. Varying implant positions had a statistically significant effect on the retentive strengths of the attachments (F = 5.61, $P=0.002$ ). Peak load-to-dislodgement values (in increasing order) were 49.64 ± 8.27 N for 5 mm, 53.26 ± 11.48 N for 10 mm, 60.24 ± 12.31 N for 15 mm, and 64.80 ± 6.78 N for 20 mm groups. The retentive strength of the 20 mm group was significantly higher than 5 mm ( $P=0.003$ ) and 10 mm ( $P=0.03$ ) groups. Varying implant angulations had a significant effect on the retentive strengths of the attachments (F = 7.412, $P=0.000$ ). The peak load-to-dislodgement values (in increasing order) were 48.20 ± 15.59 N for 5-5 degrees, 53.26 ± 11.48 N for 0-0 degrees, 54.96 ± 8.25 N for 0–5 degrees, 57.71 ± 7.62 N for 10-10 degrees, 66.00 ± 17.54 N for 15-15 degrees, 66.18 ± 14.09 N for 0–10 degrees, and 77.38 ± 10.33 N for 0–15 degrees. Retentive strength of 0–15 degrees was significantly ( $P<0.05$ ) higher than those of 0-0, 0–5, 5-5, and 10-10 degrees and that of 5-5 degrees was significantly ( $P<0.05$ ) lower than those of 0–10, 0–15, and 15-15 groups. Conclusions. Retentive strength of the 2IMO increased with increase in distance of implants from midline and increased with increase in distal angulations.