3D printing vs traditional workflow for the fabrication of mandibular implant overdentures: study protocol for a mixed-methods cross-over RCT.

BACKGROUND: Complete tooth loss is a significant global oral health issue, particularly impacting older individuals with lower socioeconomic status. Computer-assisted technologies enhance oral healthcare access by the elderly. Despite promising in vitro reports on digital denture materials, evidence from randomized clinical trials (RCTs) is lacking to verify their performance. This cross-over RCT will investigate whether 3D-printed implant-retained mandibular overdentures (IMO) are more satisfactory for edentulous seniors than those made through traditional methods. METHODS/DESIGN: We will recruit 26 completely edentulous participants (any sex/gender) based on the following eligibility criteria: age ≥ 60 years, no tooth extraction in the past 12 months, two implants in the lower jaw, and need for new dentures in both jaws. Each participant will receive two denture pairs, either manufactured by 3D printing or traditionally, to be worn in a random order. A timeline of 3 months with each denture pair will be considered for outcome assessment (total: 6 months). Patient satisfaction with dentures will be measured by the McGill Denture Satisfaction Questionnaire. We will evaluate other patient-reported outcomes (including oral health-related quality of life) as well as clinician-assessed quality and cost. At the end of the trial, participants will choose which denture pair they wish to keep and interviewed about their experiences with the 3D-printed IMO. The quantitative and qualitative data will be incorporated through an explanatory mixed-methods strategy. A final quantitative assessment will happen after 12 months with the preferred IMO to assess the long-term performance and maintenance needs. DISCUSSION: This mixed-methods RCT will explore patient experiences with 3D-printed IMOs, aiming to assess the potential for altering clinical practice and dental public health policies. Our results will inform policies by showing whether 3D printing offers comparable outcomes at lower costs, facilitating greater access to oral care for the elderly. TRIAL REGISTRATION: ClinicalTrials.gov, NCT06155630, Registered on 04 December 2023. https://classic. CLINICALTRIALS: gov/ct2/show/NCT06155630.

Biomechanical aspects of reinforced implant overdentures: A systematic review.

PURPOSE: The purpose of this systematic review was to investigate the effect of reinforcement on the mechanical behaviour of implant overdenture (IOD) bases and its cumulative biological effect on the underlying supporting structures (implants and the residual ridge). MATERIAL AND METHODS: The required documents were collected electronically from PubMed and Web of Science databases targeting papers published in English that focused on denture base reinforcement for IOD prostheses in order to recognize the principal outcomes of reinforcement on the mechanical and biological properties of overdentures. Such biological outcomes as: strains on implants, peri-implant bone loss, residual ridge resorption, and strain on the residual alveolar ridge. RESULTS: A total of 269 citations were identified. After excluding any repeated articles between databases and the application of exclusion and inclusion criteria, only 13 publications fulfilled the inclusion criteria. Three publications investigated the mechanical properties of fibre and/or metal-reinforced implant overdentures while another 3 articles investigated the effect of metal reinforcement on stress distribution and strains transmitted to the underlying implants. In addition, 3 in vitro studies investigated the effect of metal reinforcement on overdenture base strain and stresses. Stress distribution to the residual ridge and strain characteristics of the underlying tissues were investigated by 2 in vitro studies. Five clinical studies performed to assist the clinical and prosthetic maintenance of metal-reinforced IOD were included. Data concerning denture base fracture, relining, peri-implant bone loss, probing depth, and implant survival rates during the functional period were extracted and considered in order to evaluate the mechanical properties of the denture base, residual ridge resorption and implant preservation rates, respectively. CONCLUSION: The use of a denture base reinforcement can reduce the fracture incidence in IOD bases by enhancing their flexural properties and reducing the overdenture base deformation. Strains on the underlying supporting structures of overdenture prostheses including dental implants and the residual ridge can be decreased and evenly distributed using a metal reinforcement.

Effect of Implant Location on Palateless Complete Overdenture Retention: an In Vitro Study.

OBJECTIVES: The purpose of this in vitro study was to evaluate effect of implant location on initial retention values of palateless complete overdentures retained by four o-rings at different inter-implant distances. MATERIAL AND METHODS: Two standard acrylic models representing completely edentulous maxillary arches were used. Four single piece ball type implants were placed in each model. Models were divided into two groups according to the distance between anterior and posterior implants. Two canine implants with 32 mm inter-implant distance were placed in both models. In one model (G1), two posterior implants were placed in second premolar region away from canine implants by 14 mm on both sides, while in the other model (G2), the two posterior implants were placed in first molar region away from canine implants by 22 mm on both sides. Eighteen palateless complete overdentures were constructed for each model. Overdentures were retained by four o-rings. Initial axial (central), and para-axial (anterior, posterior, and lateral) retention values of overdentures were estimated and compared using a universal testing machine. RESULTS: Independent t-test revealed that implant location has a significant role in palateless complete overdenture retention with a level of significance set at P < 0.05. CONCLUSIONS: For in vitro simulated palateless implant overdentures retained by four o-rings, increasing the inter-implant distance between anterior and posterior implants is favourable for a more retentive prosthesis.

Clips vs Resilient Liners Used With Bilateral Posterior Prefabricated Bars for Retaining Four Implant-Supported Mandibular Overdentures.

The objective of this research was to clinically compare peri-implant tissue health of bar-clips vs silicone-resilient liners used with bilateral posterior bars for retaining 4 implant-supported mandibular overdentures. Thirty completely edentulous male patients (mean age, 65 years) were randomly assigned into 2 equal groups. Each patient received 4 implants in the canine and first molar regions of the mandible using a flapless surgical technique. Mandibular overdentures were immediately connected to the implants with bilateral prefabricated instant adjusting bars. According to the method of retention to the bar, 1 group was retained with clips (GI), whereas the other group was retained with a silicone-resilient soft liner (GII). Peri-implant tissue health was evaluated clinically in terms of plaque scores (MPI), bleeding scores (MBI), probing depth (PD), and implant stability (IS). MPI, MBI, and PD were measured at mesial, distal, buccal, and lingual surfaces of each implant. Evaluations were performed 2 weeks (T0), 6 months (T6), and 12 months (T12) after overdenture insertion. Implants of GI with clips demonstrated significant increase in plaque, bleeding, and PD scores compared with those of GII with silicone-resilient liner at all observation times. Implants in GI demonstrated a significant decrease in implant stability compared with those of GII at T6 and T12 anteriorly and at T12 posteriorly. Resilient liners are considered better than bar-clips when used with bilateral posterior bars for retaining implant-supported mandibular overdentures in terms of peri-implant soft tissue health. Bilateral posterior ready-made bars cannot be proposed as a promising design for supporting implant-assisted mandibular overdentures.