Accuracy of fit for cobaltchromium bar over two implants fabricated with different manufacturing techniques: an in-vitro study.

OBJECTIVE: The purpose of the invitro research was to compare the fit of Cobalt Chromium customized bar fabricated with different manufacturing processes cast metal bar, milled bar and 3D printed bar using scanning electron microscope. MATERIALS AND METHODS: Clear epoxy resin molds were prepared. In each mold two parallel implants with a 14 mm distance from each other were embedded. Thirty Co-Cr custom bars were constructed and were divided equally into three groups: Group (I) (Co-Cr conv), group (II) milled bar (Co-Cr milled), and group (III) printed bar (Co-Cr print). The marginal fit at implant-abutment interface was scanned using scanning electron microscope (SEM). RESULTS: There was a significant difference between the three studied groups regarding marginal misfit the between implant and fabricated bars with p-value < 0.001. The highest value of micro-gap distance was found in Co-Cr conventional group (7.95 ± 2.21 µm) followed by Co-Cr 3D printed group (4.98 ± 1.73) and the lower value were found in Co-Cr milled (3.22 ± 0.75). CONCLUSION: The marginal fit of milled, 3D printed and conventional cast for Co-Cr alloy were within the clinically acceptable range of misfit. CAD/CAM milled Co-Cr bar revealed a superior internal fit at the implant-abutment interface. This was followed by selective laser melting (SLM) 3D printed bar and the least fit was shown for customized bar with the conventional lost wax technique.

Retrospective digital study of mandibular flexure in patients with long-span fixed restorations supported by natural teeth.

PURPOSE: This retrospective study aims to evaluate the mandibular flexure on a long-span rigid fixed prosthesis supported by natural teeth. MATERIALS AND METHODS: Nine patients (five males and four females) were included in this study who had long-span rigid mandibular fixed prostheses for long-term (10-15 years) that have led to radiographic changes around the supporting teeth. The mandibular flexure was measured digitally after adhering reference markers to the prostheses. Intraoral scans were obtained at the minimum and maximum mouth openings before and after splitting the preexisting prostheses. The distances between the markers were measured, and mandibular flexure was calculated. RESULTS: This study showed a significant deviation (narrowing) of the mandible before and after splitting the rigid fixed prostheses (P value < 0.05). CONCLUSION: Digital analysis of the data collected from the patients in this retrospective study indicated that deviations occur during mandibular flexure. CLINICAL RELEVANCE: Splitting the full arch prosthesis could prevent the negative consequences of mandibular flexure on restorations. Trial registration The study was registered on clinicaltrials.gov with registration number NCT05617274 (15/11/2022).

Esthetic Rehabilitation of Pediatric Patients Using Direct Bonding Technique-A Case Series Report.

Pediatric esthetic dentistry is a sensitive technique, as children can be less cooperative; hence, minimal appointments are preferred. The most conservative treatment modality for anterior esthetic rehabilitation is using direct composite veneer restorations. In many instances, esthetic improvements using composite resin are the only possible option until the growth phase of the pediatric patient is complete. In this article, we present three different case scenarios in young teenagers with different treatment needs requiring esthetic restorations. The first case report is a patient with amelogenesis imperfecta, the second is with generalized spacing, and the third is with localized microdontia. All three patients were followed up for six months post direct composite veneering and were highly satisfied with their treatment outcomes, which boosted their self-confidence.

Retention of Different Attachment Systems for Digitally Designed Mandibular Implant Overdenture.

PURPOSE: Primary retention and gradual loss of retention of different attachment systems are important key factors in proper attachment selection; however, studies on attachment retention show a wide range of retention values concerning the same attachment system. This in vitro study uses a novel approach that utilizes a digitally designed and 3D-printed reinforced overdenture, which has a digitally determined geometric center, in order to standardize results for future research and clinical work. This study aims to evaluate initial retention along with the gradual loss of retention at different time intervals between three types of stud attachments, retaining a digitally designed, reinforced mandibular overdenture after 5475 cycles simulating 5 years of attachment usage. MATERIALS AND METHODS: An epoxy model of an ACP Class I (American College of Prosthodontists) edentulous mandible was constructed. A fully computer-designed surgical guide was employed after virtual denture design to place two implants according to prosthetically driven implant placement protocol. A metal meshwork with tissue stops was designed digitally to reinforce the denture and to carry the geometric center. The meshwork was incorporated into the denture-intaglio surface, which was planned for attachment pickup. Forty-eight digitally designed and metal-reinforced 3D-printed dentures were divided into four groups (12 dentures for each group). Loss of retention was measured to compare two novel Locator attachments (12 pairs of Locator R-TX, 12 pairs of Locator F-TX medium and low retention, with 12 pairs of ball and socket). Each group was subjected to an insertion and removal fatigue test resembling 5 years of patient usage. Retention values were recorded using a universal testing machine. RESULTS: Locator F-TX medium and low retention showed loss of retention by 91.93% and 92.91%, after fatigue testing equivalent to 2 and 3 years of use, respectively. Ball and socket and Locator R-TX showed loss of retention by 19.87% and 26.31%, respectively, after fatigue testing equivalent to 5 years of use. CONCLUSIONS: Locator R-TX attachment systems showed promising retention for implant overdentures compared to ball and socket attachments. The proposed digital technique of denture reinforcement is capable of standardizing results for research and clinical work.

Retention of bar clip attachment for mandibular implant overdenture.

OBJECTIVES: The aim of the present study was to evaluate the retention and loss of retention after fatigue testing at different time intervals between two types of bar clip materials (digitally designed PEEK bar clip and regular Nylon bar clip). MATERIALS AND METHODS: An epoxy model was constructed for a completely edentulous mandible. Two implants were placed according to prosthetically driven implant placement by a computer-guided surgical stent. Bar clips were digitally designed, 3D printed, and pressed into Poly Ether Ether Ketone (PEEK). Pick up of PEEK and nylon clips was performed on the dentures fitting surface using self-cured acrylic resin. Each study group was subjected to an insertion and removal fatigue test simulating 3 years of patient usage. Retention values were recorded using the universal testing machine at initial retention and after 1, 2, and 3 years of simulated usage. For proper sample sizing, 24 models and dentures (12 for each group) were used. An independent sample t-test and repeated measures analysis of variance were used to compare the data. RESULTS: There were statistically significant differences in retention between the PEEK and nylon bar clips at the beginning of the experiment (p = 0.000*). But after 3 years of simulated use, there was no significant difference in retention between the test groups (p = 0.055, NS). After 3 years of simulated use, the retention of PEEK clips decreased by - 58.66% recording 17.37 ± 1.07 N, while the retention of nylon clip increased by + 2.99% recording 16.56 ± 0.88 N. CONCLUSION: The digitally designed PEEK clip showed comparable retention results to the nylon clip after 3 years of simulated use. CLINICAL RELEVANCE: Maintenance of bar attachment with PEEK clip offers a clinical solution after the wear of normal plastic clips, which is a cheap solution that is easily fabricated and picked up into the denture. Digital fabricated PEEK bar retentive inserts can be used in cases of bar attachment wear.