Posterior Implantation Research Articles

Angled ball and locator attachments for immediate loaded inclined implants used to retain maxillary overdentures: A cross over study of patient satisfaction and oral health related quality of life.

The aim of this was to compare the influence of two different angulated abutment designs on patient satisfaction, oral health-related quality of life, and prosthetic aspects of implant-supported maxillary overdentures. For this cross-over study, 18 patients with completely edentulous maxillary ridges opposing implant-retained mandibular overdentures received 4 implants between the maxillary sinuses using computer-guided surgery. The anterior implants were installed at canine/lateral incisor areas and inclined 15° labially. The posterior implants were inserted just anterior to the maxillary sinuses and inclined 15o distally. Eight patients received maxillary overdentures retained by angled ball attachment (ball overdenture [BOD]) and angled locator attachment in random order. After 6months, patients indicated satisfaction with their prosthesis using a visual analog scale (VAS), and oral health impact profile (OHIP-14). Moreover, postinsertion prosthodontic maintenance and complications were recorded for both attachments. Comparisons of patient satisfaction and prosthetic complications between groups were performed using the Wilcoxon matched-pairs test and the McNemar test, respectively. Locator overdenture (LOD) recorded significantly higher scores than the BOD group regarding all the VAS questions except for ease of cleaning (p < 0.007). LOD recorded significantly higher patient satisfaction regarding the pronunciation of sounds (p=0.009), painful aching (p=0.018), feeling tense (p=0.011), unsatisfactory diet (p=0.013), irritability with people (p=0.005), and life in general (p=0.004). The most common complications were matrix activation/renewal (n=34). BOD showed a significantly higher incidence of attachment loosening (p=0.002), and teeth fracture (p=0.049) than LOD. LOD showed a significantly higher incidence of attachment wear and replacement than BOD (p <0.001). There was no difference between groups regarding soft tissue complications. Within the limitations of this study, and in terms of improved patient-centered outcomes, angled locator attachments are recommended to retain maxillary implant overdentures opposed by implant retained mandibular overdentures at it was associated with increased patient satisfaction and oral health-related quality of life than angled ball attachments. However, locator attachment was associated with more postinsertion prosthodontic maintenance than ball attachment.

Comparison of Extramaxillary Anchored Implants, Tilted Implants, or Sinus Elevation Concepts on Stress Distribution in Atrophic Maxilla: A Finite Element Analysis.

To determine the von Mises stress values of extramaxillary implants anchored in zygomatic bone, known as zygomatic implants, abutments, superstructures, and principal stress values of bone under occlusal forces and to compare them with tilted implants and sinus elevation concepts. The hypothesis of the study was that there would be higher stress on zygomatic implants under occlusal forces compared with tilted implants and the sinus elevation technique due to the more angled placement of the zygomatic implants. Finite element analysis (FEA) was used to apply a force of 600 N (75 N premolars and 150 N first molar) vertically and at an angle of 20 degrees to the hybrid prosthesis with three different concepts-zygomatic implants, tilted implants, and sinus elevation-in D2 bones in six separate models. The posterior implants were tilted in zygomatic implant models (45 degrees) and tilted implant models (30 degrees). The von Mises and principal stress values formed in the models were compared by FEA. These values were also compared with the physiologic stress limit of the bone. In the zygomatic implant models, the von Mises stress values on both anterior and posterior implants were less than other models under both loading conditions. In addition, the lowest principal stress values were seen in these models. The highest von Mises stress among all models was found to be posterior implants in tilted implant models under oblique loading. In addition, the highest principal stress values were seen at posterior implants in the sinus elevation model under oblique loading. Vertical loading was found to induce less stress than loading at a 30-degree angle. Although zygomatic implants have a more angled placement, the stress values on the bone and implants are lower.

Biomechanical analysis of inclined and cantilever design with different implant framework materials in mandibular complete-arch implant restorations

Statement of problemInclined distal implants with posterior framework cantilevers are an alternative to straight implants for the treatment of edentulous jaws, avoiding grafting procedures and utilizing pre-existing bone. However, little is known about the implant, framework, and peri-implant bone stresses exerted by this design. PurposeThe purpose of this finite element analysis study was to assess the biomechanical properties of the inclined versus straight design, with different implant framework material to generate implant-supported complete-arch fixed mandibular prostheses. Material and methodsA finite element model of the edentulous mandible was generated by using 4 implants in 2 distinct configurations: the inclined design and the straight design. Different framework materials were tested: pure titanium, cobalt-chromium alloy, type IV gold alloy, zirconia, polyetheretherketone (PEEK), and carbon fiber–reinforced polyetheretherketone (CFR-PEEK). A 300-N load at a 75-degree angle was applied to the occlusal plane from the lingual side of the buccal cusps of the 2 premolars and the first molar teeth. Subsequently, stresses on the implant, surrounding bone, and framework were measured and analyzed quantitatively and qualitatively. ResultsIn terms of implant configurations, the inclined design demonstrated less stress on the posterior cortical bone, implants, and framework than the straight design. Comparing the framework materials, zirconia and metal exhibited reduced cortical bone and implants stresses but elevated framework stress when compared with the polymeric frameworks. ConclusionsFrom a biomechanical viewpoint, in edentulous patients with excessive posterior alveolar bone resorption, the inclined design exhibited more favorable stress distribution around the posterior implants than the straight design. In implant-supported complete-arch fixed mandibular prostheses, zirconia and metal, particularly cobalt-chromium alloy, distributed the stresses more effectively to the implants and supporting bone than polymeric materials.

Accuracy of complete-arch digital implant impression with or without scanbody splinting: An in vitro study

ObjectivesTo assess accuracy of implant complete-arch digital impression with intraoral scanner (IOS) and implant scanbody splinting (ISS). MethodsAn edentulous mandibular model with 4 analogues was fabricated. Four polyetheretherketone (PEEK) implant scanbodies (ISBs) were scanned, according to a randomized sequence, by investigated IOS with (ISS+) and without implant scanbody splinting (ISS-), resulting in 30 test and 30 control files. The model was digitized by industrial optical scanner and the related file superimposed to the test and control files by a best fit algorithm. Linear (ΔX, ΔY and ΔZ-axis) and angular deviations (ΔANGLE) were evaluated for each analogue. A global measure of linear absolute error (ΔASS) was calculated considering the sum of absolute linear discrepancies. Influence of ISS and implant position on IOS accuracy was assessed using General Linear Model and possible interaction between ISS and implant position evaluated. ResultsImplant position showed a significant main effect (p<0.0001) and interaction with ISS (p=0.0454) when ΔASS was considered as response variable. Posterior implants resulted as less accurate. ISS was able to reduce ΔASS for both distal analogues (4.7, p=0.0188). When ΔANGLE was considered as a response variable, implant position and ISS showed significant main and interactive effects (p=0.0039, p<0.0001, p<0.0001). Analogue 3.6 was associated with highest angular discrepancy. This error was significantly reduced by ISS (p<0.0001). ConclusionsComplete-arch implant digital impression with scanbody splinting showed a significant improvement of the overall accuracy, particularly reducing linear and angular deviations at the most critical posterior implant positions. Clinical significance: Intraoral scanner accuracy for implant complete-arch digital impression could be improved by a low cost, easy to assemble and use implant scanbodies splinting 3D printed modular chain.

Clinical Evaluation of Pink Esthetic Score of Immediately Impressed Posterior Dental Implants.

While comparative outcome results for peri-implant crestal bone levels, mucosal margin position, and peri-implant indices have been reported, no studies are available that evaluate and compare the esthetic result of impressions performed immediately at implant placement with that of impressions performed on healed implants. The purpose of this cross-sectional study was to evaluate the pink esthetic score of posterior implants restored with an immediate impression workflow compared to implants restored with a delayed impression workflow. Twenty-eight eligible participants who had received a single implant crown either in the premolar or molar regions at least 4 months before the study, were identified by an electronic health record review and scheduled for a single-visit study appointment. Esthetic outcomes were measured using the pink esthetic score. Several local- and prosthesis-related factors were recorded and their association with the selected outcome was assessed. Two-sample t-test was used for comparisons between the groups. Pink esthetic score ranged between 4 and 12 (mean: 8). No significant difference between immediate (8.36 ±1.12) and delayed (7.76 ±2.14) impression workflow groups were seen for the total PES (p = 0.25). In addition, individual comparisons between immediately and delayed impressed implants for mesial papilla (1.27 ±0.47; 0.88 ±0.78), distal papilla (0.73 ±0.65; 0.76 ±0.83), tissue margin (1.73 ±0.47; 1.47 ±0.51), tissue contour (1.27 ±0.65; 0.82 ±0.64), alveolar process (0.82 ±0.60; 1.00 ±0.87), color (1.27 ±0.65; 1.29 ±0.69), and texture (1.36 ±0.50; 1.53 ±0.62) did not show significant differences. The current study suggests that the pink esthetic score is not significantly different between single posterior implants impressed with immediate and delayed implant workflows.

Orthodontic management of skeletal Class II malocclusion using three mini-implants- A case report

Vertical dimension issues are frequently regarded as the most difficult dentofacial problems to treat in clinical practice. The difficulty level increases when vertical dysplasia is paired with sagittal discrepancy. The use of mini-implants in Orthodontics has broadened the scope of orthodontic treatment options. The treatment of a 14-year-old female patient with skeletal Class II malocclusion, slight hyperdivergent profile, and enhanced incisor visibility with four premolar extraction followed by comprehensive orthodontic treatment to correct the convex profile and increased incisor visibility, with two posterior implants for retraction and a midline mini implant for intrusion of the anterior maxillary dentoalveolar segment is described in this case report. The active therapy period was 25 months long.

Influence of Framework Material and Posterior Implant Angulation in Full-Arch All-on-4 Implant-Supported Prosthesis Stress Concentration.

This study evaluated the influence of distal implants angulation and framework material in the stress concentration of an All-on-4 full-arch prosthesis. A full-arch implant-supported prosthesis 3D model was created with different distal implant angulations and cantilever arms (30° with 10-mm cantilever; 45° with 10-mm cantilever and 45° with 6-mm cantilever) and framework materials (Cobalt–chrome [CoCr alloy], Yttria-stabilized tetragonal zirconia polycrystal [Y-TZP] and polyetheretherketone [PEEK]). Each solid was imported to computer-aided engineering software, and tetrahedral elements formed the mesh. Material properties were assigned to each solid with isotropic and homogeneous behavior. The contacts were considered bonded. A vertical load of 200 N was applied in the distal region of the cantilever arm, and stress was evaluated in Von Misses (σVM) for prosthesis components and the Maximum (σMAX) and Minimum (σMIN) Principal Stresses for the bone. Distal implants angled in 45° with a 10-mm cantilever arm showed the highest stress concentration for all structures with higher stress magnitudes when the PEEK framework was considered. However, distal implants angled in 45° with a 6-mm cantilever arm showed promising mechanical responses with the lowest stress peaks. For the All-on-4 concept, a 45° distal implants angulation is only beneficial if it is possible to reduce the cantilever’s length; otherwise, the use of 30° should be considered. Comparing with PEEK, the YTZP and CoCr concentrated stress in the framework structure, reducing the stress in the prosthetic screw.

Curative Effect of Interventional Therapy and Neurological Changes in Ischemic Stroke of Posterior Circulation Evaluated by Magnetic Resonance Imaging under Genetic Algorithm

Objective. This study aimed to evaluate the improvement and neurological function changes of patients with ischemic stroke in the posterior circulation before and after interventional therapy using magnetic resonance imaging (MRI) under genetic algorithm and compressed sensing algorithm. Methods. Thirty-six patients with posterior circulation ischemia who visited the interventional cerebrovascular disease area were included in this study. The treatment effect was observed through abnormal signal changes in the lesion area on each sequence of MRI images before and after treatment. The National Institutes of Health Stroke Scale (NIHSS) was used for the evaluation of the changes in neurological function. Results. The real data experiment results suggested that the peak signal-to-noise ratio (PSNR) = 39.33 and structure similarity (SSIM) = 0.96 in the algorithm reconstructed image, which showed no significant difference with the simulation experiment results of PSNR = 35.19 and SSIM = 0.96 ( P &lt; 0.05 ). In addition, the stenosis rate after interventional treatment (13.89%) was substantially lower than that before treatment (91.67%) ( P &lt; 0.05 ). Cerebral blood flow (CBF) of the bilateral occipital lobes and cerebellum after six months of treatment was higher than that before treatment ( P &lt; 0.05 ), and the incidence of postoperative restenosis was 11.11% (4/36). Conclusion. The combination of genetic algorithm and compressed sensing algorithm had a good effect on MRI image processing. The posterior circulation ischemia interventional stent implantation can effectively improve the stenosis of the vertebral artery and vertebral basilar artery as well as the cerebral tissue perfusion in the ischemic area, which improved the clinical symptoms substantially and reduced the probability of restenosis.

HOW IMPORTANT ARE THE IMPLANT INCLINATION AND THE INFRASTRUCTURE MATERIAL USED IN IMPLANT SUPPORTED FIXED PROSTHESES?

Objectives: The aim of this study is to evaluate the stress , which is caused by the fixed prosthesis under oblique forces around dental implants and bone by using different infrastructure materials and different inclusions, by 3-dimensional finite element analysis method. Materials and Methods: The 3D finite element models of the mandible, dental implants and prostheses were prepared. The anterior and posterior implants were designed 10 mm in length and 4.3 mm in diameter. The anterior implant was placed parallel to each model. Posterior implant designed to make inclinations those mesial 17, distal 17, buccal 17, lingual 17. Implant supported fixed restorations were divided into 3 main groups according to the infrastructure materials. These materials were; chromium-cobalt, zirconia, polyetheretherketone (PEEK). In each model, a total of 500 N oblique force was applied from the buccal tubercle crests to the buccolingual direction at an angle of 30 degrees to the long axis of the tooth. Maximum principal stress and minimum principal stress values in the bone models were taken. In addition, maximum von Mises stress values were obtained from implants and substructure materials. Results: When the stress findings in the mandible during oblique loading were evaluated, it was found that the stresses on the cortical bone were higher than the stresses on the trabecular bone. It was observed that the highest stress values occurred in the implants. Conclusions: It is thought that chromium-cobalt and zirconia-based ceramic bridge restorations are more positive in terms of stress distribution than PEEK-based ceramic bridge restorations.

How successful are maxillary implant-retained overdentures on two or four implants?

Design A randomised crossover clinical trial was designed to determine survival and success of four-implant overdentures in the edentulous maxilla, in participants with mandibular two-implant overdentures. Participants received four implants in the maxilla, two anteriorly and two posteriorly, then were randomly allocated into two treatment groups. The prosthetic phase included alternate loading of anterior and posterior implants for three months each, followed by loading of all four implants for another three months. Participants were then followed up in the recall phase for a mean period of 2.2 years.Case selection Four participants were taken from the authors' previous clinical study, meeting the inclusion criteria for a two-implant overdenture in the mandible. Another 21 participants were recruited from study calls after a widening of inclusion criteria. These patients were all pre-treated in accordance with the previous study protocol, so there was standardisation before maxillary implant placement.Data analysis A sample size calculation was performed and a Kaplan-Meier curve was used to demonstrate implant survival over time.Results Twenty-four patients were included in the study. Three implants were lost during the prosthetic phase and two during the recall phase; all were anterior implants. Implant survival after loading was 93.8% after a mean period of 3.1 years. There were 27 maxillary prosthetic complications overall. Denture success was 95.8% after a mean period of 2.2 years.Conclusions Implant survival of four asynchronously loaded implants in implant-supported overdentures in the edentulous maxilla was good and is a recommendable treatment option for patients with two-implant mandibular overdentures. Implant and prosthetic complications are common but mostly straightforward to manage. Two posterior implants are not superior to two anterior implants, but the majority of patients prefer the four-implant maxillary overdenture.

Effect of assistive devices on the precision of digital impressions for implants placed in edentulous maxilla: an in vitro study

PurposeTo examine the effect of assistive devices on the precision of digital impression for multiple implants placed in the edentulous maxilla.MethodsA reference model representing an edentulous maxilla with four implants was developed. The digital impression group included three settings: Type 0, without an assistive device; Type 1, with an assistive device connecting only neighboring implants; and Type 2, with an assistive device connecting not only neighboring implants but also the two posterior implants, with perpendicular branches from this bar towards the anterior implants. Digital impressions were made five times for each type using three intraoral scanners (IOSs). For conventional method, silicone impressions and verification jigs were prepared; fabricated plaster models were scanned using a laboratory scanner/industrial 3D scanner. In analysis 1, two-way ANOVA analyzed the effect of IOSs and assistive devices on the precision of digital impressions. In analysis 2, one-way ANOVA compared the silicone impressions, the verification jigs, and the most precise group of digital impressions from analysis 1.ResultsIn analysis 1, the IOS and assistive device type (F = 25.22, p < .0001) effects and the interaction between these two factors (F = 5.64, p = .0005) were statistically significant. In analysis 2, CON, VJ, and digital impression with Type 2 devices (most precise devices in analysis 1) were compared; better precision was obtained by digital impression with Type 2 device than by CON and VJ (F = 30.08, p < .0001).ConclusionsFor implants placed in an edentulous maxilla, digital impressions with assistive devices can provide better precision compared to silicone impressions and verification jigs.

Duration, deviation and operator's perception of static computer assisted implant placements by inexperienced clinicians.

This study measured the duration, deviation and operator's perception of implant placement by fully guided (FG), pilot-guided (PG) and freehand (FH) protocols by postgraduate students with minimal implant experience. Twenty postgraduate students participated in the study. Half of them placed single anterior (S-Ant) and single posterior (S-Post) implants, and the other half placed anterior (B-Ant) and posterior (B-Post) implants in a wide edentulous area. The PG placement involved surgical guides that only controlled pilot drilling, whilst the FG placement controlled all the drilling steps and implant placement. The duration of implant placement and the operator's perception (ease of drilling, ease of implant placement and operator's preference) were measured. The deviations of placed implants were quantified by measuring the trueness and angulation deviations in relation to the planned implants. The PG placement was the quickest for inserting implants, followed by FG and FH placements, respectively (p<.05). The location of the implant had influenced the duration of implant placement only for the PG placement. In relation to ease of drilling, ease of implant placement and operator's preference, there was no significant difference amongst the different placement protocols or implant locations. The FG placement was associated with least deviations, followed by PG and FH placements, respectively (p<.05). In the hands of postgraduate students with minimal implant experience, FG and PG placements reduced the implant placement duration in comparison with FH placement. The FG placement was consistently more accurate followed by PG placement.

Effect of number of implants, distal implant inclination, and angled abutment on stresses in fixed complete dentures: a nonlinear finite element analysis

Objectives: This nonlinear three-dimensional finite element analysis (FEA) study evaluated the effect of the number of implants, distal implant inclination, and use of angled abutments on stress magnitude and distribution in cortical bone (CB), abutment screw (AS), and prosthetic screw (PS) of implant-supported fixed complete dentures. Methods: Nonlinear 3D FEA models of mandibular fixed complete dentures were created with five, four, or three parallel straight implants (5S, 4S, 3S) and with tilted distal implants (5T, 4T, 3T). In addition, the 5T model was tested using angled abutments over the tilted distal implants to re-align the implant inclination. A 100-N axial load was applied over the first molar region (cantilever) to analyze the von Mises stresses in selected points (CB, AS, and PS). Results: The implant adjacent to the load showed the highest stresses in CB, AS, and PS. The model with three implants showed higher stresses than the ones with four and five implants. Peak stresses in the AS increased 40% from five to four implants and 100% from five to three implants. Tilting the distal implants increased stresses in CB. Peak stress in the PS increased 150% from 5S to 5T models and 100% from 4S to 4T models. Angled abutments generated lower stresses on CB and AS but higher stresses on PS. Conclusions: The results suggest that stresses in the cortical bone, abutment screw, and prosthetic screw increase when tilting the posterior implants and reducing the number of implants. The use of angled abutments decreased stresses at the bone-implant interface and in abutment screws but increased stresses on prosthetic screws.

Accuracy of Implant Level Intraoral Scanning and Photogrammetry Impression Techniques in a Complete Arch with Angled and Parallel Implants: An In Vitro Study

(1) Background: Stereophotogrammetry has recently been investigated showing high accuracy in complete implant supported cases but has scarcely been investigated in cases of tilted implants. The aim of this in vitro study was to compare the accuracy of digital impression techniques (intraoral scanning and photogrammetry) at the level of intraoral scan bodies in terms of angular deviations and 3D discrepancies. (2) Methods: A stone master cast representing an edentulous maxilla using four implant analogs was fabricated. The two anterior implants were parallel to each other, and the two posterior implants were at an angulation of 17 degrees. Digital intraoral scanning (DIOS) impressions were taken after connecting implant level scan bodies to the master cast and STL files were exported (n = 15). Digital photogrammetry (DPG) impressions were captured using a PiC Camera after tightening implant level PiC optical markers and STL files were exported (n = 15). Superimposition was carried out by a software for determining the accuracy of both. (3) Results: Significant angular discrepancies (ΔA) and 3D deviations of scan bodies were found among the groups in trueness with lower deviations for the DPG (p value &lt; 0.001). However, trueness within ISBs varied between angular and 3D deviations and outcomes were not specific to determine the effect of implant angulation. In precision, no significant differences were detected within ISBs and among both groups in terms of angular deviation. However, DPG had less deviations than DIOS group in terms of 3D deviations (p value &lt; 0.001). (4) Conclusion: Digital photogrammetry technique conveyed the utmost accuracy in both trueness and precision for the intraoral scan bodies among both impression methods assessed. In addition, implant angulation did not influence the precision of the impression techniques but affected their trueness without explicit conclusions.

All on four fixed prostheses versus implant overdentures for management of edentulous maxilla opposing mandibular 2- implant assisted overdentures

Purpose: This study aimed to compare two treatment modalities; All on four fixed prostheses and locator retained overdentures; to rehabilitate patients having problems associated with edentulous maxilla opposing mandibular implant assisted overdentures. Materials and methods: Ten patients complaining from looseness and instability of their maxillary dentures that oppose mandibular 2-implant-retained overdentures were randomly divided into 2 groups: Group I included 5 patients who received four implants according to the All-on- four Concept (2 parallel middle implants and 2 posterior implants with distal inclination). Implants were immediately loaded with fixed acrylic prosthesis, then after 6 months the prosthesis was replaced with fixed ceramometal restoration, Group II, included 5 patients who received four implants that were immediately loaded with Locator retained maxillary overdentures using new maxillary dentures. Clinical (plaque index (PI), gingival index (GI), probing depth (PD) and implant stability (IS)) and radiographic (marginal bone loss (MBL) outcomes were recorded at baseline (T0), 6 (T6) and 12 (T12) month after prosthesis insertion.

Ultrasonographic Tissue Perfusion in Peri-implant Health and Disease

Color flow ultrasonography has played a crucial role in medicine for its ability to assess dynamic tissue perfusion and blood flow variations as an indicator of a pathologic condition. While this feature of ultrasound is routinely employed in various medical fields, its intraoral application for the assessment of tissue perfusion at diseased versus healthy dental implants has never been explored. We tested the hypothesis that quantified tissue perfusion of power Doppler ultrasonography correlates with the clinically assessed inflammation of dental implants. Specifically, we designed a discordant-matched case-control study in which patients with nonadjacent dental implants with different clinical diagnoses (healthy, peri-implant mucositis, or peri-implantitis) were scanned and analyzed with real-time ultrasonography. Forty-two posterior implants in 21 patients were included. Ultrasound scans were obtained at the implant regions of midbuccal, mesial/distal (averaged as interproximal), and transverse to compute the velocity- and power-weighted color pixel density from color velocity (CV) and color power (CP), respectively. Linear mixed effect models were then used to assess the relationship between the clinical diagnoses and ultrasound CV and CP. Overall, the results strongly suggested that ultrasound’s quantified CV and CP directly correlate with the clinical diagnosis of dental implants at health, peri-implant mucositis, and peri-implantitis. This study showed for the first time that ultrasound color flow can be applicable in the diagnosis of peri-implant disease and can act as a valuable tool for evaluating the degree of clinical inflammation at implant sites.

Evaluation of immediately loaded mandibular four vertical versus tilted posterior implants supporting fixed detachable restorations without versus with posterior cantilevers.

Distally inclining posterior implants may be technically challenging in certain situations. The presence of a posterior cantilever can also exert unfavorable forces on supporting implants. The aim of the present study was to evaluate and compare peri-implant soft and hard tissues around 4 mandibular interforaminal implants having tilted posterior implants with posterior cantilevers, versus vertical implants, 2 in the interforaminal region and 2 in the first molar regions, without posterior cantilevers. All implants supported full-arch fixed detachable restorations opposing complete dentures. A total of 80 implants were placed flapless in the mandibles of 20 edentulous participants. Four implants were placed for every participant, who were randomly assigned into 2 equal groups. Axial group implants were vertically aligned, with 2 implants in the interforaminal area and 2 in the molar area. Tilted group implants have 2 anterior axial and 2 posterior distally inclined implants. Interim screw-retained prostheses converted from pre-existing dentures were immediately fabricated and loaded on the same day of surgery. After awaiting period of 3months, all participants received fixed detachable metal acrylic resin definitive restorations. A follow-up protocol of 3, 6, and 12months was scheduled to assess the modified gingival index, modified plaque index, peri-implant probing depth, implant stability, and marginal bone level and bone density changes. No statistically significant differences (P > .05) were found in the modified gingival index, modified plaque index, peri-implant probing depth, implant stability, bone density, and marginal bone level between the axial and tilted implant groups after the 1-year follow-up period. Placing 4 flapless immediately loaded implants in mandibular edentulous patients that supported full-arch fixed restorations provided high implant and prosthodontic success rates whether posterior implants were tilted with posterior cantilevers or vertically aligned without posterior cantilevers. Pan African Clinical Trial Registry database, PACTR201907776166846. Registered 3 July 2019, www.pactr.org .

Maxillary implant overdentures on two or four implants. A prospective randomized cross-over clinical trial of implant and denture success and survival.

To determine implant survival and success of four conventionally but initially asynchronously loaded implants in implant-supported overdentures for the edentulous maxilla, in participants with opposing mandibular two-implant overdentures. Twenty-six participants received four implants in the region of the maxillary canines and molars. After healing, 24 of these participants (mean age: 68.3years) were randomly allocated to one of two treatment groups, and the adapted overdenture was attached to two unsplinted cylindrical attachments. The other two matrixes remained unattached to the implants for 3months. After this period, the other two implants were loaded for 3months (cross-over design). Then, all four implants were loaded for another 3months. Kaplan-Meier curves were used to evaluate survival and success of implants and dentures. During the active prosthetic study phase, three participants lost one implant. Two participants lost three implants during the recall period. Implant survival after loading was 93.8% after a mean observation period of 3.1years. Denture survival was 100%, but denture success was 95.8%, due to major prosthetic complications. Most participants preferred four implants to two. Within the limitations of the study, it can be concluded that maxillary implant overdentures on two or four implants are both recommendable treatment options. Two posterior implants are not superior to two anterior implants under overdentures retained by unsplinted cylindrical attachments. Implant and prosthetic complications and aftercare measures are common but are mostly easy to handle. However, 23 of the 24 participants preferred the 4-implant maxillary overdenture.

Technical and Biological Complications of Screw-Retained (CAD/CAM) Monolithic and Partial Veneer Zirconia for Fixed Dental Prostheses on Posterior Implants Using a Digital Workflow: A 3-Year Cross-Sectional Retrospective Study.

Objective The introduction of CAD/CAM and the development of zirconia-based restorations have allowed clinicians to use less expensive materials and faster manufacturing procedures. The purpose of the study was to analyze the differences, in terms of mechanical and biological complication, in multiunit zirconia fixed dental prosthesis (FPDs) on posterior implants produced using a digital workflow. Method and Materials. This study was a retrospective investigation, and patients treated with screw-retained monolithic or partial veneer FPDs on dental implants were selected. Periapical radiographs were taken at baseline and at the 3-year follow-up. Complications were recorded and classified as technical and biological ones. Results The study population included 25 patients. The occlusal and interproximal corrections were not clinically significant. In the study sample, the survival rate and success rate of the FPDs after 3 years were 100% and 96%, respectively. One implant failed immediately after placement. Conclusion Monolithic zirconia FPDs and partial veneer FPDs showed a 100% survival rate, presenting an interesting alternative to metal ceramic restorations. The partial veneer FPDs had a higher technical complication rate than the monolithic FPDs; however, no statistically significant difference was found.

Comparison of posterior residual ridge resorption in patients wearing conventional denture, two implant-retained mandibular overdenture and four implant-supported overdenture: a 5-year retrospective study.

Purpose: The aim of the following study was to assess and compare the effect of treatment with conventional complete dentures, two implant retained mandibular overdenture and four implant supported mandibular overdenture on mandibular posterior residual ridge resorption over a 5-year period. Material and methods 24 patients were selected from previous studies, where (group I) included 8 patients previously treated with conventional complete dentures. The second group (group II) 8 patients received mandibular overdenture using two osseointegrated implants, (group III)8 patients received implant supported mandibular overdenture using two implants in canine region and two implants in the first molar region connected with rigid bar. Posterior residual ridge resorption was evaluated for all groups using proportional area measurements. Results: After 5years of prosthetic treatment, regarding posterior residual ridge resorption, statistically significant bone resorption had occurred for all the three groups, also statistically significant difference was reported when comparing the two-implant overdenture group to the four-implant supported overdenture group. Conclusion Four implant supported overdenture with the posterior implants in the first molar region showed the least amount of posterior ridge resorption after 5 years of treatment in comparison to conventional complete dentures or two implant retained overdenture.