Screw-retained Prostheses Research Articles

Passive fit and time efficiency for prefabricated versus conventionally constructed cobalt chromium CAD\\CAM 3-unit implant supported frameworks in free end saddle models: a pilot invitro study

BackgroundThe passive fit of 3-unit implant supported prefabricated metal screw-retained prosthesis before implant placement might be difficult. Hence, we aim to evaluate the passive fit and time efficiency of CAD/CAM 3-unit implant supported fixed prostheses that were constructed based on virtual versus those based on actual implant positions in Kennedy Class I models.MethodsA sample of 5 Kennedy class I models with thin wiry ridges were restored by 20 frameworks bilaterally, 10 based on actual (group A) and 10 based on virtual (group V) implant positions. The models were imaged using cone beam computed tomography and scanned using an intraoral scanner. The STL (Standard Tessellation Language files) and the DICOM (Digital Imaging and Communications in Medicine) files were registered on a 3D planning software. A CAD/CAM surgical guide was planned, resin printed and used for installing 6 implants bilaterally. In group V, the framework was designed based on the virtual scan bodies and virtual multi-unit abutments, while in group A intra-oral scanning of the model after attaching the scan bodies was necessary. Frameworks of both groups were milled and tested for passive fit using 8 clinical tests. McNemar and Wilcoxon signed rank tests were used to study the effect of the group on passive fit and time efficiency, respectively. The significance level was set at P ≤ 0.05.ResultsNo statistically significant difference was found between group V and group A frameworks regarding passive fit (p-value = 1, OR = 0.5) and time efficiency (P = 0.179, Effect size = 0.948).ConclusionWithin the limitations of this study, it can be concluded that in free end saddle cases, prefabricated CAD\\CAM 3-unit implant-supported cobalt chromium screw retained prostheses can achieve an adequate passive fit. However, their fit might be negatively affected in thin ridges and they might require some adjustments.

Similar short-term outcomes for bone-level implants with or without intermediate abutments.

A single-center (university-setting), prospective, longitudinal, split-mouth, single-blind, randomized controlled clinical trial investigated peri-implant parameters of bone-level implants restored with either screw-retained prostheses connected directly to the implants or with intermediate abutments over a 3-year period. The study adhered to the ethical principles of the Helsinki Declaration and the CONSORT guidelines. Ethical approval was granted, and the trial was registered at Clinicaltrials.gov . Participants included were over 18 years of age, had a plaque index below 25%, and were missing at least two adjacent teeth, allowing for rehabilitation with screw-retained fixed partial prostheses over two implants and 2-4 prosthetic units. Exclusion criteria included long-term use of medications affecting bone metabolism, smoking more than 10 cigarettes per day, history of local radiotherapy, untreated periodontitis, and the need for rehabilitation in the anterior sextant of the maxilla. The primary clinical outcome was marginal bone loss (MBL), while secondary outcomes included probing pocket depth (PPD), plaque index (PI), bleeding on probing (BOP), and patient-reported outcomes (PROs). The study schedule included a screening (visit 1), implant surgery (visit 2), stage-two 8 weeks post-surgery (visit 3), impressions taken 4 weeks post stage-two (visit 4), baseline standardized radiograph (visit 5), followed by 6-month (visit 6), 12-month (visit 7), and 36-month (visit 8) follow-up visits. Descriptive statistics and quantitative measures included means, standard deviations (SDs), minimum and maximum values, and 95% confidence intervals (CIs). Clinical parameters (six sites per implant) measured were MBL, PPD, PI, and BOP. Paired t tests were utilized for intragroup comparisons across different time points and intergroup comparisons at each time point. PROs at 36 months were compared using Student's t test. The alpha significance level was set at 0.05. The study included 36 patients (72 implants), with two not completing the follow-up due to death and relocation. No implants showed signs of inflammation or mobility. Mean interproximal bone level (IBL) at baseline was 0.13 mm ± 0.15 mm for the control group and 0.10 ± 0.13 mm for the test group. At the 36-month follow-up, mean IBL was 0.13 ± 0.18 mm for the control group and 0.20 ± 0.24 mm for the test group, with no significant differences (F(1, 32) = 1.06; p > 0.05). Clinical parameters (PPD, BOP, PI) at 36 months showed no significant differences between groups. Minor complications occurred in 6.7% of the control group and 5.3% of the test group. PROs indicated no significant differences in general satisfaction, esthetics, comfort, phonetics, and masticatory function between the groups. After a 36-month follow-up, bone-level implants restored with CAD/CAM prostheses directly connected to the implants displayed similar clinical outcomes, PROs, and marginal bone level changes as those restored with intermediate standardized abutments.

Clinical Factors on Dental Implant Fractures: A Systematic Review.

Dental implant fractures pose a significant challenge to long-term treatment success. This systematic review aims to comprehensively examine the clinical factors influencing dental implant fractures (IFs). Furthermore, strategies to choose the right type of implant and prevent this complication are addressed. A systematic search was conducted across PubMed, Scopus, and Web of Science databases. Eligible studies included retrospective case-control, prospective cohort studies, and clinical trials. The initial search yielded 361 articles, of which 312 were excluded being these reviews, case reports, irrelevant, or written in languages other than English. This left 49 articles, with only 6 meeting the eligibility criteria for an in-depth review. These studies, all retrospective case-control, examine implant characteristics, patient demographics, surgical and prosthetic variables, biomechanical and functional factors, clinical and procedural variables, complications and maintenance issues. The risk of bias was assessed as low using the ROBINS-I tool. Key findings suggest a correlation between implant diameter and structural resistance, with wider implants demonstrating reduced fracture risk. Additionally, posterior regions, especially molars and premolars, exhibit higher susceptibility to IFs due to increased masticatory forces. Implant design and material may considerably influence fracture risk, with conical implants and screw-retained prostheses showing higher vulnerability. Biomechanical overload, particularly in patients with bruxism, emerges as a primary contributing factor to IFs. Prosthesis type significantly influences fracture incidence, with cantilever prostheses posing a higher risk due to increased stress. Peri-implant bone loss is strongly associated with IFs, emphasizing the need for meticulous preoperative assessments and individualized management strategies. Future research should prioritize larger and heterogeneous populations with long-term follow-up and standardized methodologies to enhance the generalizability and comparability of findings. Randomized controlled trials and biomechanical studies under controlled conditions are also essential to elucidate the complex interactions contributing to IFs and developing effective prevention strategies. Additionally, integrating patient-reported outcomes may offer a comprehensive understanding of the impact of IFs on quality of life.

Marginal changes at bone-level implants supporting dental prostheses with or without intermediate standardised abutments after 36 months: Randomised controlled clinical trial.

The objective of this study is to evaluate the changes at marginal bone level at implants restored with screw-retained prosthesis connected directly to the implants or with an intermediate abutment, after 3-year follow-up. Thirty-six partially edentulous patients received 72 implants. Each patient received 2 implants and a 2-4-unit screw-retained implant-prosthesis. The test group implants received a screw-retained prosthesis connected directly to the implant shoulder, the control group prosthesis were connected through a 3-mm standardised intermediate abutment. Clinical and radiological data were recorded at baseline and at 6-, 12-, and 36-month follow-up. At 36 months, the mean marginal bone loss was 0.13 ± 0.18 mm for the control group and 0.20 ± 0.24 for the test group, with no significant differences between groups (p > .05). Clinical variables (Probing Pocket Depth, Bleeding on Probing and Plaque Index) at 36 months also showed no significant difference between groups. Minor complications frequency was 6.7% in the control group and 5.3% in test group. None of the groups suffered from mayor complications. Patient Reported Outcomes (PROs) showed a General Satisfaction mean score in the control group of 9.40 (SD 0.82) and 9.37 (SD 1.06) in the test group with no significant differences between groups. Bone-level implants restored with screw-retained partial prostheses with or without intermediate abutments showed similar radiographic and clinical outcomes after 3 years.

Microbiological and Immunological Assessment of Peri-implant Sites in Healthy and Diabetic Individuals After Prosthetic Rehabilitation: A Prospective Case Control Study

Aim: Microbial colonization contributes to periodontitis and peri-implantitis with an increase in proinflammatory cytokines like IL 17. This has a vital role in the destructive process of tissue and bone around the implant. Type 2 diabetes mellitus has the potential to increase these microbial colonies thus becoming a risk factor. To compare and correlate the association of peri-implant sulcular microflora and salivary IL-17 between healthy and controlled diabetic individuals. Materials and Methods: A total of 30 participants who have undergone dental implant placement with screw-retained prosthesis were included in the study. Participants were divided into two groups, healthy ( n = 15) and diabetic ( n = 15). The subgingival plaque was collected from peri-implant sites into TE buffer vials and the salivary sample was collected into Eppendorf tubes at the 7th, 14th, and 30th day. Microbiological counts of P. gingivalis, T. denticola, T .forsythia, and F. nucleatum were evaluated by polymerase chain reaction, and salivary interleukin (IL)-17 levels were obtained by enzyme-linked immunosorbent assay. Results: The bacterial count was increased in both healthy and diabetic individuals but more prevalent in diabetes. The salivary IL-17 levels were increased in diabetic individuals which was statistically significant. Conclusion: Increased microbiota in both healthy and diabetic individuals along with increased IL-17 levels can lead to peri-implantitis which provides an insight into microbiological and immunological aspects in individuals with dental implants further acting as a predictor for peri-implantitis.

Accuracy of digital and conventional implant-level impression techniques for maxillary full-arch screw-retained prosthesis: A crossover randomized trial.

This study aimed to compare the accuracy of implant-level conventional and digital impressions for atrophied maxillary ridges. Twelve participants with atrophied edentulous maxillary ridges received six implants. Six months later and after soft tissue maturation around healing abutments, a control cast was constructed using the final passive restoration for each patient. Two types of implant-level impression techniques were carried out for each patient: (1) conventional (splinted open-tray) impression technique and (2) digital impression technique. For both techniques, scan bodies were labeled from the most distal implant on the left side (A, B, C, D, E, and F) and scanning was made. Accuracy of both techniques was measured using in vitro (two-dimensional and three-dimensional) and in vivo (clinical) methods. Two-dimensional methods include measurement of the difference in linear distances AB, AC AD, AE, and AF. Geomagic software was used to assess the three-dimensional deviation between the two impression techniques using the superimposition of standard tessellation language files. The incidence and percentage of nonpassive frameworks and framework misfits of final restorations for both types of impression techniques were assessed using the single screw test. For all distances, digital impressions recorded significantly higher deviation from control measurements than conventional impressions. The highest two-dimensional linear deviation was noted for AF distance and the lowest difference was noted for AB distance. For all scan bodies, digital impressions recorded significantly higher three-dimensional deviation than conventional impressions. The highest three-dimensional deviation was noted with scan bodies C and D. Digital impressions recorded a significantly higher incidence of nonpassive frameworks and framework misfits than conventional impressions. [Correction added on 11 June 2024, after first online publication: In the preceding sentence, "digital impressions" was changed to "conventional impressions" in this version.] CONCLUSION: Within the limitations of this study, it could be concluded that the conventional implant-level impression technique showed greater in vitro and in vivo accuracy than the digital impression technique when used for full-arch maxillary fixed restorations on inclined implants.

Alveolar Ridge Split and Expansion Utilising a Piezo-surgical Approach for Implant Placement in Narrow Ridges

Abstract In clinical settings, it is common to encounter alveolar ridges that lack sufficient width, posing challenges for implant placement. To ensure a successful implant placement, the bone’s width must be at least 1.5 mm greater than the implant’s diameter on both the buccal and lingual/palatal sides. The alveolar ridge split technique has been developed as a solution for horizontal bone deficiencies, allowing for the expansion of the alveolar ridges. This article discusses a case where an implant was placed in a 35-year-old male patient who had a missing lower left first molar for 5 years. Due to the horizontal deficiency of the alveolar ridge, a ridge split and expansion procedure was executed using piezosurgery. After 6 months, a screw-retained prosthesis was successfully delivered.

Esthetic Rehabilitation of a Post-trauma Patient Using Anterior Block Graft and Screw-retained Prosthesis over Ceramic-reinforced Polyetheretherketone Abutment: A Case Report

Esthetic Rehabilitation of a Post-trauma Patient Using Anterior Block Graft and Screw-retained Prosthesis over Ceramic-reinforced Polyetheretherketone Abutment: A Case Report

Evaluation of Prosthodontic Complications in Screw-Retained and Cement-Retained Crowns in Dental Implants: An Original Research

ABSTRACT Aim: Single-tooth implant restorations, whether screw-retained or cement-retained, are essential for prosthodontic rehabilitation despite having low design flexibility, cosmetic appeal, and high 5-year survival rates. Materials and Methods: A study involving 14 patients with missing mandibular first molars used 28 implants and cement-retained and screw-retained prostheses. Patients had a single edentulous gap, adequate dental hygiene, and sufficient bone volume at the implant site. The study adhered to the Helsinki Declaration, followed WHO 2007 safety guidelines, and evaluated soft tissue, bone height, and bone loss. Data analysis included the Student’s t-test and Mann–Whitney U-test. Results: In patients between the ages of 17 and 46, single-implant restorations were compared with cement- and screw-retained at 6 months. Abutment screw loosening and peri-implant soft-tissue traits did not differ significantly from one another. Conclusion: The study compared screw- and cement-retained implant restorations in 28 single-tooth implant-supported prostheses over a 6-month functional loading period, finding no significant improvement in either approach.

Investigation of the Fracture Strength Between Dental Implant And Ti-Base Abutment Produced with Different Heights and Grades of Titanium Material

New prosthetic designs were developed to provide a balanced transmission of the stress caused by the chewing function to other mechanical and anatomical structures, and these designs revealed new research areas. An example of this is screw-retained implant-supported prostheses. With screw-retained prostheses, the residual cement problem is eliminated. However, abutment material and abutment design may adversely affect the mechanical and aesthetic properties of prostheses. Ti-base abutments have been developed to solve these problems. However, studies on clinical succes, material content and abutment height of ti-base abutments remain up-to-date. In our study, the effect or abutment heights on the bond strength and stress distribution with monolithic zirconia crowns in ti-base abutments manufactured from different titanium Gr types will be tested. Titanium Gr 4, Gr 5 and Gr 23 ELI materials will be used in our study. A total of 7 groups are planned with ti-base abutments with a abutment length of 3.5 mm, 5.5 mm for Gr 4 and Gr 5, abutment length of 3.5 mm, 5.5 mm and 7 mm for Gr 23. In the in vitro experiment, the fracture strength of the samples will be tested with the universal testing device. total of 77 implants, ti-base abutments and monolithic zirconia crowns will be used by creating 11 samples for each study group. The obtained values will be recorded in Newtons and Megapascals. The data will be analysed using the SPSS 22.0 programme. As a result, while the lowest fracture strength values were observed in Gr 4 Ti material in all ti-base abutment lengths in the samples for which the fracture strength test was performed, similar values were observed in the ti-base abutments produced from Gr 5 and Gr 23 ELİ alloys. When the relationship of bonding strengths with Ti alloys was evaluated, it was seen that there was no significant difference between Ti alloys.

Effect of primary versus secondary splinting impression techniques on the passive fit of screw-retained implant prosthesis: a randomized clinical trial

BackgroundThe utilization of splinting techniques for impression copings is commonly advised for complex implant-supported prostheses, as it can enhance the fit of these prostheses. However, there is limited understanding regarding the impact of the secondary splinting of implant analogues, on the passive fit of the prostheses. Limited data are available on the secondary splinting of implant analogues before pouring the impression and its comparison with the primary technique of intraoral splinting of impression copings prior to impression making.ObjectivesThis study's objective was to determine the impact of the primary versus secondary impression splinting techniques using resin on the passive fit of screw-retained prosthesis.Material and methodsThis randomized clinical trial (RCT) involved two parallel groups consisting of 14 completely edentulous patients, with seven patients in each group. Each patient received a total of eight implants, four implants per arch, resulting in a total of 28 screw-retained prostheses. Two different impression splinting techniques were employed. Group (1) utilized the primary splinting technique, where the impression copings were splinted before taking the impression. In contrast, Group (2) utilized the secondary splinting technique, where the implant analogues were splinted before pouring the impression material. To evaluate the passivity of the screw-retained prostheses in both groups, a single-screw test (one-screw test) was used. Additionally, supplementary methods, including the screw resistance test, were employed.ResultsThe findings of this RCT revealed higher passivity scores for secondary splinting impression pouring technique with a statistically significant difference (P = 0.082). There was a 2.2-fold greater frequency of non-passivity in the primary splinted method. In group (2), the likelihood of non-passivity was four times higher for upper arches prostheses, while there was no significant difference (P = 0.5) observed in both groups for lower arches prostheses.ConclusionsThe study found that using the secondary splinting impression pouring technique resulted in greater passivity of the implant prostheses compared to the primary splinting impression technique.

Influence of Crestal Implant Position and Smooth Collar on Marginal Bone Level: A 2-Year Retrospective Radiographic Analysis.

The aim of this retrospective study was to establish the survival rate and the clinical outcome of a an endoosseous implant system and to evaluate the marginal bone level and the impact of the positioning of the machined collar neck on crestal bone level changes up to two years follow-up. 96 implants were placed in 57 patients and loaded with final restoration after at least three months of healing time. 15 of these implants were immediately placed into fresh extraction sockets while 81 implants were inserted in healed ridges. Marginal Bone Loss around implants were determined radiographically after a mean observation time ranging between twelve and twenty-four months after loading. The effect of location (mandible v/s maxilla, anterior v/s posterior), immediate implant v/s native bone, smoking habit, gender, implant length and diameter, the type of prosthesis (screw-retained/cemented) and the positioning of the machined collar on the marginal bone loss was evaluated. Survival rates were evaluated based on the criteria as determined by Misch et al. in 2008. The Survival Rate at the implant level was 98, 96% at 1 year follow-up period. The mean marginal bone level has significantly changed over time in the overall sample after a follow-up period of one year (-p-value<0.001); it (average) decreased significantly by 0.238 mm between baseline and loading (-p-value<0.001; post-hoc test). It also decreased by 0.154 mm between loading and 1 year, however the decline was not significant (-p-value=0.085; post-hoc tests). After a follow-up period of two years, the mean marginal bone level has significantly changed over time in the overall sample (-p-value<0.001); it has decreased significantly by 0.263 mm between baseline and loading. It (Average) has also decreased by 0.111 mm between loading and 1 year and by 0.199 mm between loading and 2 years, but these declines were not significant (-p-value>0.05; post-hoc tests). The mean bone loss after 1-year and 2 years was not significantly associated with implants type, implant site (maxilla/mandible or anterior/posterior implants), smoking habits and type of implant's surgery (-p-value=0.792).However, it was significantly associated with the type of prosthesis; it was significantly elevated with cemented prosthesis compared to screw-retained prosthesis. A supracrestal positioning of the machined collar (tissue level placement) was associated with no bone loss, while placing the smooth part of the implant below the alveolar crest has led to bone loss over 2 years. Marginal bone loss after 1 and 2 years was not significantly associated with implants type, implant site (maxilla/mandible or anterior/posterior implants), smoking habits and type of surgery. However, it was significantly elevated with cemented prosthesis compared to screw-retained prosthesis. It was dependent also on the positioning of the machined collar.

Implant-Supported Fixed Partial Dentures with Posterior Cantilevers: In Vitro Study of Mechanical Behavior.

Rehabilitation with dental implants is not always possible due to the lack of bone quality or quantity, in many cases due to bone atrophy or the morbidity of regenerative treatments. We find ourselves in situations of performing dental prostheses with cantilevers in order to rehabilitate our patients, thus simplifying the treatment. The aim of this study was to analyze the mechanical behavior of four types of fixed partial dentures with posterior cantilevers on two dental implants (convergent collar and transmucosal internal connection) through an in vitro study (compressive loading and cyclic loading). This study comprised four groups (n = 76): in Group 1, the prosthesis was screwed directly to the implant platform (DS; n = 19); in Group 2, the prosthesis was screwed to the telescopic interface on the implant head (INS; n = 19); in Group 3, the prosthesis was cemented to the telescopic abutment (INC; n = 19); and in Group 4, the prosthesis was cemented to the abutment (DC; n = 19). The sets were subjected to a cyclic loading test (80 N load for 240,000 cycles) and compressive loading test (100 KN load at a displacement rate of 0.5 mm/min), applying the load until failure occurred to any of the components at the abutment-prosthesis-implant interface. Subsequently, an optical microscopy analysis was performed to obtain more data on what had occurred in each group. Results: Group 1 (direct screw-retained prosthesis, DS) obtained the highest mean strength value of 663.5 ± 196.0 N. The other three groups were very homogeneous: 428.4 ± 63.1 N for Group 2 (INS), 486.7 ± 67.8 N for Group 3 (INC), and 458.9 ± 38.9 N for Group 4 (DC). The mean strength was significantly dependent on the type of connection (p < 0.001), and this difference was similar for all of the test conditions (cyclic and compressive loading) (p = 0.689). Implant-borne prostheses with convergent collars and transmucosal internal connections with posterior cantilevers screwed directly to the implant connection are a good solution in cases where implant placement cannot avoid extensions.

Reverse scan body: The scan pattern affects the fit of complete-arch prototype prostheses.

To assess the effect of different scan patterns on the fit of implant-supported complete-arch prototype prostheses fabricated via a complete digital extraoral protocol with a reverse scan body. A mandibular cast with four multi-unit abutment (MUA) implant analogs with adequate antero-posterior spread served as the reference cast, simulating a common clinical patient situation, and a polymethylmethacrylate interim screw-retained prosthesis was fabricated on it. Novel reverse scan bodies were connected to the interim prosthesis on the intaglio of the MUA abutments and extraoral scanning was performed with a white light intraoral scanner (TRIOS 4; 3 shape) and three different scan patterns: starting from the occlusal surface of the interim prosthesis (O-group), starting from the intaglio (I-group), and helix pattern (H-group). The resulting STL files from the three groups were then imported to computer-aided design (CAD) software and after the digital design, the STL files were exported to a computer-aided manufacturing (CAM) milling machine which generated a total of 15 CAD-CAM milled prototype prostheses per group. Two clinicians assessed the fit of each digitally fabricated prototype prosthesis on the reference cast, utilizing the screw-resistance test and radiographic evaluation. Fisher's exact test was used to test the difference between the three groups, and Cohen's k-score was used to assess the inter-examiner agreement. Out of the three different groups, the O-group scan pattern led to 100% prosthesis fit, while the prototype prostheses generated from I- and H-groups had 80% and 53% fit, respectively. The results were statistically significant (p = 0.008). Occlusal scan pattern leads to fitting milled prototype prostheses after extraoral scanning with reverse scan bodies without intraoral implant data acquisition.

The Curved Presplitting Technique in a Totally Edentulous Atrophic Mandible: A Surgical Case Report.

The management of horizontally fully edentulous atrophic ridges is a common problem in dental implantology. This case report describes an alternative modified two-stage presplitting technique. The patient was referred for an implant-supported rehabilitation of their edentulous mandible. CBCT scans showed a mean available bone width of about 3 mm. At the first stage, four linear corticotomies were performed using a piezoelectric surgical device. At the second surgical stage 4 weeks later, bone expansion was performed, and four implants were placed in the interforaminal area. The healing process was uneventful. No fractures of the buccal wall and no neurologic lesions were observed. Postoperative CBCT scans showed a mean bone width gain of about 3.7 mm. Implants were uncovered 6 months after the second surgery, and 1 month later, a fixed provisional screw-retained prosthesis was delivered. This approach could be used as a reconstructive technique that avoids using grafts and reduces treatment times, possible complications, postsurgical morbidity, and costs by exploiting the patient's native bone as much as possible. Considering the limitations of a case report, randomized controlled clinical trials are needed to confirm the results and validate this technique.

Accuracy of complete-arch digital implant impression with intraoral optical scanning and stereophotogrammetry: An in vivo prospective comparative study.

To assess accuracy of intraoral optical scanning (IOS) and stereophotogrammetry (SPG), complete-arch digital implant impressions in vivo. Consecutive patients needing implant-supported screw-retained zirconia complete-arch fixed-dental prostheses (ISZ-FDP) were recruited. For each patient, three impressions were taken: IOS, SPG (tests), and open-tray plaster (reference). Linear (ΔX, ΔY, and ΔZ), three-dimensional (ΔEUC), and angular deviations (ΔANGLE) were evaluated and stratified according to scanning technology for each implant. Potential effects of impression device (IOS and SPG), arch (maxilla and mandible), and implant number (4 and 6) were evaluated through multivariable analysis. Significance level was set at .05. A total of 11 complete arches (5 maxillae, 6 mandibles) in 11 patients were rehabilitated with ISZ-FDPs supported by 4 (n = 8) and 6 implants (n = 3). A total of 50 implants and 100 implant positions were captured by two investigated devices and compared to respective reference (mean ΔEUC IOS 137.2, SPG 87.6 μm; mean ΔANGLE 0.79, 0.38°). Differences between measurements (SPG-IOS) were computed for each implant, with negative values indicating better SPG accuracy. Significant mean ΔEUC difference of -49.60 μm (p = .0143; SD 138.15) and mean ΔANGLE difference of -0.40° (p < .0001; SD 0.65) were observed in favor of SPG. Multivariable analysis showed significant effect on ΔEUC (p = .0162) and ΔANGLE (p = .0001) only for impression devices, with SPG performing better. SPG experienced significantly higher linear and angular accuracy. No effect of type of arch or implant number was detected. Higher extreme deviations were experienced for IOS. SPG can be feasible for complete-arch digital impressions with caution, and rigid prototype try-in is recommended before screw-retained prosthesis manufacturing.

Fixed Prosthesis on Two Implants from Different Manufacturing Companies Case Report

The following is a clinical case of a screw-retained prosthesis on two implants with different designs and manufacturers. A 73-year-old man visited the dentist in January 2023 to rehabilitate the edentulous right area of the mandible. In December 2018 another dentist placed implants (Biohorizons, Madrid. Spain) in positions 45 and 46 with a metal-porcelain bridge over both. In 2022 he lost implant 45 (Biohorizons tapered internal 3.8 x 9) and with it also the bridge, although he still had implant 46 (Biohorizons tapered short 4.6 x 7.5). On the day of surgery, a simple opening flap was performed and drills were used sequentially until a 4 x 8 mm Galimplant IPX implant (Sarria, Spain) was placed in position 45. After a period of four months, the impression abutments of implants 46 and 45 were attached with dental floss and flowable composite, and an open-tray impression was taken. One week later, the screwed metal-porcelain fixed prosthesis was placed on both implants. It is difficult to find bibliographic information about fixed prostheses on implants manufactured by different companies and placed in the same patient. The placement of a prosthesis on two implants from different manufacturers is not a complication, but rather an unscheduled inconvenience. The clinical case presented allows us to point out that a fixed prosthesis on implants from different manufacturers can give excellent results.

An Evaluation of the Effectiveness of Various Luting Cements on the Retention of Implant-Supported Metal Crowns.

Background and objective Cement-retained prostheses have replaced screw-retained prostheses as the preferred restoration in recent years in order to overcome the latter's limitations. In this study, four different luting cements were compared to evaluate their efficacy on the retention of cement-based metal crowns to implant abutments. Materials and methods In the right and left first molar regions, four implant analogs(Internal Hex, Adin Dental Implant Systems Ltd.,Tel-Aviv, Israel) were screwed into epoxy resin casts (Araldite CY 230-1 IN, India) that were positioned perpendicular to the cast's plane. Four metal copings were created and cemented. Group A: polycarboxylate cement (DUR) (DurelonTM, 3M Espe, St. Paul, MN); Group B: PANAVIA™F 2.0dual-cure resin cement (KurarayAmerica, Inc., New York, NY); Group C: resin-modified glass ionomer (3M™ RelyX™Luting, 3M Espe); and Group D: non-eugenol temporary resin cement (Kerr-Temp, KaVo Kerr, Brea, CA)were used to cement crowns.To check the retention capacity, samples were put through a pull-out test on an Instron universal testing machine (TSI‑Tecsol, Bengaluru, India) with a crosshead speed of 0.5 mm/min.Each coping's de-cementing load was noted, and average values for every sample were computed and statistically analyzed. Results The findings demonstrated that non-eugenol temporary resin implant cement has the lowest retention value at 138.256 N, followed by resin-modified glass ionomer cement at 342.063 N, polycarboxylate luting cement at 531.362 N, and resin cement at 674.065 N. The average difference in retentive strength across all four groups was statistically very significant (p=0.001). Conclusion Based on our findings, non-eugenol temporary resin implant cement enables simple retrievability of the prosthesis in the event of a future failure and is appropriate for implant restorations with cement retention. Also, cements made of polycarboxylate and resin have the highest retention values.

Effect of different implant angulations on the biomechanical performance of prosthetic screws in two implant-supported, screw-retained prostheses: A numerical and experimental study

Statement of problemA mesiodistal angle frequently forms between 2 splinted implant-supported, screw-retained fixed dental prostheses (TIS-FDPs). Mechanical complications commonly occur in prosthetic screws. Studies regarding the effect of the degree of implant angulation on the biomechanical performance of prosthetic screws in TIS-FDPs are sparse. PurposeThe purpose of this numerical and experimental study was to investigate the effects of different implant angulations on the biomechanical performance, including stress distribution, stability of the screw joint, and surface morphology change of the prosthetic screws in TIS-FDPs. Material and methodsTIS-FDPs were classified into 4 groups: 0, 10, 20, and 30 degrees based on the degree of mesiodistal angle between the long axes of the 2 implants. In the finite element analysis (FEA), 4 series of 3D models were constructed and loaded with simulated occlusal forces. The von Mises stresses and rotational angles of the prosthetic screws were then calculated. In the mechanical test, each group of 5 TIS-FDPs with 10 prosthetic screws was tested under 1 million loading cycles by using a universal testing machine. The removal torque values (RTVs) and the surface roughness of the prosthetic screws were measured after cyclic loading. The normality of the outcome variables was assessed by the Shapiro-Wilk test. Analysis of variance and the Kruskal-Wallis test were used for further analysis (α=.05). ResultsThe FEA results showed that the von Mises stresses of the prosthetic screws were concentrated in the first screw thread crest engaged with the abutment, and the maximum values of the threads and the rotation angles of the prosthetic screws increased in the 2-implant mesiodistal angulation from 0 to 30 degrees. The mechanical tests showed that the RTVs of the prosthetic screws in each group were not significantly different after 1 million loading cycles (P=.107). The surface roughness of the crest of the first 2 threads of the prosthetic screws in the 30-degree group changed significantly compared with those in the other groups. ConclusionsWhen TIS-FDPs were delivered, larger angulations of the 2 splinted implants seemed to increase the stress concentrated on the crest of the first engaged thread and the rotation angles of the prosthetic screws. After 1 million loading cycles, significant surface adhesive wear was identified on the crest of the first 2 threads of the prosthetic screws in the 30-degree group compared with groups with a smaller angulation.

Prosthetic rehabilitation of a completely edentulous maxilla with a sectioned implant-supported screw-retained prosthesis in a multiamputee patient with microstomia: A clinical report

Providing fixed implant-supported prostheses for edentulous patients with microstomia or limited mouth opening is challenging. The clinical treatment of a patient who was a multiple amputee with microstomia and a complete loss of lips elasticity is described. A custom half-sectioned prosthesis was fabricated to resolve numerous difficulties. A screw-retained complete implant-supported prosthesis was developed from a monolithic zirconia framework supported by 4 implants and with digital scanning and computer-aided design and computer-aided manufacturing of the prosthesis. The protocol achieved a complete screw-retained implant-supported prosthesis and offered a solution for a patient with microstomia and limited mouth opening, leading to improved quality of life.