Axial and Nonaxial Retention Forces of Different Designs of Milled Bar Attachments for Maxillary Implant Overdentures: An In Vitro Study.

PURPOSE: To compare the axial and nonaxial retention forces of different milled bar attachment designs for maxillary implant overdentures. MATERIALS AND METHODS: Four implants were placed in the canine and second premolar areas of an edentulous maxillary ridge model and connected to a cobalt-chromium milled bar either with or without Locator attachments. According to the type of bar and overlying housing, the following groups (n = 10 each) were investigated: group 1 (MWM) = milled bar without attachments and metal housing; group 2 (MWP) = milled bar without attachments and PEEK housing; group 3 (MAM) = milled bar with Locator attachments and metal housing; and group 4 (MAP) = milled bar with Locator attachments and PEEK housing. Axial and nonaxial (anterior, posterior, and lateral) retention forces were measured both at baseline and after wear simulation, then compared between groups and dislodging directions. RESULTS: MAM showed the highest axial (53.20 ± 2.28 N) and nonaxial (anterior [33.80 ± 1.48 N], posterior [37.60 ± 2.07 N], and lateral [34.40 ± 1.67 N]) retention forces at baseline, followed by MAP, then MWM, and MWP (P < .001). MAP showed the highest axial (42.80 ± 2.28 N) and nonaxial (anterior [24.00 ± 1.58 N], posterior [29.40 ± 2.07 N], and lateral [27.80 ± 1.64 N]) retention forces after wear simulation, followed by MAM, then MWP, and finally MWM (P < .001). MAM showed the highest axial (25.25 ± 2.45 N) and nonaxial (anterior [28.29 ± 4.03 N], posterior [24.40 ± 3.25 N], and lateral [25.55 ± 1.65 N]) retention loss, followed by MWM, then MAP, and finally MWP (P < .001). For all groups, the highest retention forces were noted with axial dislodging, followed by posterior dislodging, then lateral dislodging, and finally vertical dislodging (P < .001). CONCLUSION: Milled bars with PEEK housings and Locator attachments for maxillary implant overdentures were associated with the highest axial and nonaxial retention forces after wear simulation, while milled bars with metal housing and no attachments showed the lowest forces. Milled bars with metal housing and attachments showed the highest retention loss, while milled bars with PEEK housing with no attachments showed retention gain.

Patient Satisfaction and Prosthetic Complications of Maxillary Implant Overdentures Opposing Mandibular Implant Overdentures with Bar, Telescopic, and Stud Attachments: A 1-Year Prospective Trial.

PURPOSE: To evaluate patient satisfaction and prosthetic complications of maxillary conventional dentures and implant overdentures opposing mandibular implant overdentures with different attachments. MATERIALS AND METHODS: A total of 60 patients with maxillary conventional dentures (maxillary CD) and mandibular two-implant overdentures received four implants in the maxilla. The implants were connected to the maxillary overdentures with a stud attachment (maxillary OD). The participants were classified into three groups according to the type of mandibular overdenture attachment: bar overdentures (BOD, n = 20), resilient telescopic overdentures (TOD, n = 20), and resilient stud/Locator overdentures (LOD, n = 20). Patient satisfaction (using a visual analog scale [VAS] and oral health-related quality of life (OHRQoL)] and prosthetic/soft tissue complications were evaluated for maxillary CD and maxillary OD after 1 year of insertion. RESULTS: LOD showed higher VAS and oral health impact profile (OHIP-14) scores with maxillary CD and maxillary OD than BOD and TOD except for ease of chewing (VAS) and satisfactory diet (OHIP-7). For maxillary CD, TOD showed a significantly higher frequency of prosthetic and soft tissue complications than BOD and LOD. For all groups, maxillary OD showed significantly higher patient satisfaction regarding VAS and OHIP-14 scores, and lower prosthetic and soft tissue complications than the maxillary CD. CONCLUSION: Locator-retained maxillary overdentures opposing mandibular implant overdentures improved patient satisfaction and reduced prosthetic complications compared to conventional maxillary dentures. Such overdentures are best opposed by Locator-retained mandibular overdentures, as they increase patient satisfaction and reduce prosthetic and soft tissue complications compared to the bar and telescopic attachments.

Within-patient evaluation of chewing efficiency and maximum bite force of conventional dentures, fixed prostheses, and milled bar overdentures used for All-on-4 implant rehabilitation of atrophied mandibular ridges: A short-term randomized trial.

PURPOSE: This crossover study aimed to evaluate chewing efficiency and maximum bite force (BF) of conventional dentures, fixed prostheses, and milled bar overdentures (MO) used for All-on-4 implant rehabilitation of atrophied mandibular ridges. METHODS: Sixteen edentulous participants with resorbed mandibular ridges received new conventional dentures (CD, control). Four implants were inserted after 3 months in the mandible using the All-on-4 protocol and loaded immediately with acrylic prosthesis. In a crossover manner, each patient had either fixed restoration (FR, 12 occlusal units) or MO (14 occlusal units) randomly in a crossover study design. Chewing efficiency was evaluated using the mixing ability test. The hue deviation (HD) of two-colored gum was calculated after being chewed for 5, 10, 20, 30, and 50 masticatory cycles. Maximum BF was evaluated using a BF device. HD and BF were measured after using CD, FR, and MO prostheses. RESULTS: For all groups, the highest HD (i.e., the lowest chewing efficiency) was noted with 5 strokes, followed by 10, 20, 30 strokes, and the lowest HD (i.e., the highest chewing efficiency) was noted with 50 strokes. For all number of chewing strokes, CD showed the highest HD, then FR, and MO recorded the lowest HD. The highest BF was observed with MO, then FR, and the lowest BF was noted with CD. CONCLUSION: Within the limitations of this short-term investigation, both FR and MO used for All-on-4 implant rehabilitation of patients with resorbed mandibular ridges improve masticatory efficiency and maximum BFs compared to CD. However, MO was associated with significantly higher chewing efficiency and maximum BFs than fixed prosthesis.

Effect of different gingival margin restorations of class II cavities on microleakage: an in-vitro study.

INTRODUCTION: Microleakage is one of the important contributing factors in the failure of resin restorations. The aim of this study was to determine the effect of the location of the gingival margin (enamel, dentin, or cementum) on nanohybrid composite resin on the microleakage of Class II posterior restoration. METHODS: This was an in vitro study done at Al-Farabi College of Dentistry and Nursing in Jeddah (Saudi Arabia). Eighty-one previously extracted human molars were taken from clinics at Al-Farabi College and divided into three main groups (27 each) according to the location of the gingival margin. Group 1: the location of the gingival margin was in the enamel. Group 2: at the cemento-enamel junction. Group 3: in the cementum. Each main group was divided into three subgroups (9 each) according to storage time. Subgroup A: storage time was 24 hours. Subgroup B: storage time was one month. Subgroup C: storage time was three months. Class II cavity was prepared in one proximal surface for each molar following the general principles of cavity preparation. All samples were restored by nanohybridresin composite (TetricEvoCeram). The specimens were stored in distilled water at 37°C and a humidity of 100% in an incubator for one day, one month, and three months, respectively, according to the subgroups. After sealing, the samples were stained with 2.5% methylene blue dye. Each sample was examined microscopically by a stereomicroscope using a computerized image analyzing system. Statistical analysis was done by two-way ANOVA test comparing dye penetration mean values (µm). RESULTS: The value of dye penetration increased remarkably from enamel, Cemento-enamel junction [CEJ] to cementum, and this was statistically significant (p < 0.001). CONCLUSION: None of the materials tested was able to completely eliminate marginal microleakage at different gingival margins. The least dye penetration was detected at the enamel gingival margin followed by CEJ and then cementum. The least microleakage was observed at the gingival margin located in the enamel.