Biomechanical behavior of implant retained prostheses in the posterior maxilla using different materials: a finite element study.

BACKGROUND: The aim of this study is to evaluate the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials using finite element analysis (FEA). METHODS: Three dimensional (3D) finite element models with three implant configurations and prosthetic designs (fixed-fixed, mesial cantilever, and distal cantilever) were designed and modelled depending upon cone beam computed tomography (CBCT) images of an intact maxilla of an anonymous patient. Implant prostheses with two materials; Monolithic zirconia (Zr) and polyetherketoneketone (PEKK) were also modeled .The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). Then, individual models were subjected to separate axial loads of 300 N. Von mises stress values were computed for the prostheses, implants, and bone under axial loading. RESULTS: The highest von Mises stresses in implant (111.6 MPa) and bone (100.0 MPa) were recorded in distal cantilever model with PEKK material, while the lowest values in implant (48.9 MPa) and bone (19.6 MPa) were displayed in fixed fixed model with zirconia material. The distal cantilever model with zirconia material yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), while the least stresses in prosthesis (35.4 MPa) were recorded in fixed fixed models with PEKK material. CONCLUSIONS: In the light of this study, the combination of fixed fixed implant prosthesis without cantilever using a rigid zirconia material exhibits better biomechanical behavior and stress distribution around bone and implants. As a prosthetic material, low elastic modulus PEKK transmitted more stress to implants and surrounding bone especially with distal cantilever.

Effect of different fabrication workflows on the passive fit of screw-retained bar splinting two interforaminal implants: a parallel blinded randomised clinical trial.

BACKGROUND: To clinically compare the effect of the conventional and the digital workflows on the passive fit of a screw retained bar splinting two inter-foraminal implants. METHODS: The current study was designed to be a parallel triple blinded randomised clinical trial. Thirty six completely edentulous patients were selected and simply randomized into two groups; conventional group (CG) and digital group (DG). The participants, investigator and outcome assessor were blinded. In the group (CG), the bar was constructed following a conventional workflow in which an open top splinted impression and a lost wax casting technology were used. However, in group (DG), a digital workflow including a digital impression and a digital bar milling technology was adopted. Passive fit of each bar was then evaluated clinically by applying the screw resistance test using the "flag" technique in the passive and non passive situations. The screw resistance test parameter was also calculated. Unpaired t-test was used for intergroup comparison. P-value < 0.05 was the statistical significance level. The study protocol was reviewed by the Research Ethics Committee in the author's university (Rec IM051811). Registration of the clinical trial was made on clinical trials.gov ID NCT05770011. An informed consent was obtained from all participants. RESULTS: Non statistically significant difference was denoted between both groups in all situations. In the passive situation, the mean ± standard deviation values were 1789.8° ± 20.7 and1786.1° ± 30.7 for the groups (CG) and (DG) respectively. In the non passive situation, they were 1572.8° ± 54.2 and 1609.2° ± 96.9. Regarding the screw resistance test parameter, they were 217° ± 55.3 and 176° ± 98.8. CONCLUSION: Conventional and digital fabrication workflows had clinically comparable effect on the passive fit of screw retained bar attachments supported by two dental implants.

Assessment of a novel electrochemically deposited smart bioactive trabecular coating (SBTC®): a randomized controlled clinical trial.

OBJECTIVES: A randomized controlled clinical trial of dental implants was conducted to compare the clinical properties of a novel electrochemically deposited calcium phosphate coating to those of a common marketed surface treatment. MATERIAL AND METHODS: Forty implants of the same brand and type were placed in 20 fully edentulous participants requiring mandibular implantation. The two study groups were defined by the surface treatment of the implants. 20 implants in the control group were coated via a commercial electrochemical surface treatment that forms a mixture of brushite and hydroxyapatite, while the remaining 20 in the test group were coated with a novel electrochemical Smart Bioactive Trabecular Coating (SBTC®). A split-mouth design was employed, with each participants receiving one control implant in one mandibular side and a test implant in the other. To mitigate potential operator-handedness bias, control and test implants were randomly assigned to mandibular sides. All cases underwent digital planning, implant placement with a static surgical guide, and participants received locator-anchored full-arch dentures. The primary outcome was implant stability (measured using Osstell ISQ) assessed at insertion, loading, and then 3 months, 9 months, and 2 years post-insertion. The secondary outcome was bone level change (in millimeters) over the 2-year observation period. Oral health-related quality of life (OHRQL) was monitored using the OHIP-14 questionnaire. Complications and adverse events were recorded. RESULTS: Successful osseointegration and implant stability were achieved in all cases, allowing loading. ISQ values steadily increased throughout the observation period. While no significant differences were observed between the SBTC® and control coatings, the test group exhibited a higher ISQ gain. Bone resorption was somewhat lower in the SBTC® but not significantly so. Patients' OHRQL significantly improved after denture delivery and remained stable throughout the follow-up. No complications or adverse events were observed. CONCLUSIONS: Based on the study results, we conclude that the new surface treatment is a safe alternative to the widely used control surface, demonstrating similar osseointegrative properties and time-dependent bone level changes. Further research may explore the broader implications of these findings. TRIAL REGISTRATION: The study is registered on clinicaltrials.gov under the identifier ID: NCT06034171.

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.

[Evaluation of the 5-year clinical restoration effect of implants retained complete overdentures with Locator attachments in 48 patients].

PURPOSE: To observe the long-term clinical effect of implants retained complete overdentures with Locator attachments. METHODS: A total of 48 patients with edentulous jaws treated with implants retained complete overdentures with Locator attachments were selected from the Outpatient Department of Peking University School and Hospital of Stomatology from 2016 to 2017. Among them, 21 patients underwent double-maxillary complete overdentures restoration and 27 patients underwent single-maxillary restoration. A total of 230 implants were implanted. The clinical observation indicators included the implant survival rate, peri-implant mucosal bleeding on probing(BOP), the change in the vertical height of alveolar bone absorption around the implants, overdenture base fracture rate, artificial tooth fall off and fracture rate and other complications. The change of the locator attachment retention force of the implant-supported overdentures was evaluated. SPSS 13.0 software package was used for data analysis. RESULTS: During the five-years clinical observation period, 5 implants fell off, 1 narrow dimeter implant in the anterior zone was broken, and 12 implants were lost to follow-up. The implant survival rate was 97.25%. One year after the restoration therapy finished, peri-implant mucosal bleeding on probing (BOP+) was detected in 48 (21.4%) implants. The average BI was 0.21±0.42, which was higher in the anterior zone than that in the posterior zone. The vertical alveolar bone absorption height around the implants was (0.21±0.35) mm, 2 implants-supported complete overdenture bases were broken. After 5 years of restoration, 163(76.89%) implants had peri-implant mucosal bleeding on probing(BOP+). The average BI was 1.00±0.70, and the vertical alveolar bone absorption height around the implants was (0.58±0.85) mm. There was no significant difference between males and females. There was no significant difference in the peri-implant mucosal bleeding index and the alveolar bone vertical absorption height between the anterior zone and the posterior zone(P＞0.05). The mean BI of peri-implant mucosa and the vertical absorption height of peri-implant alveolar bone were significantly different between the 1-year observation period and the 5-year observation period respectively(P＜0.01). There were 17(26.15%) cases with overdenture bases fracture, and the fracture rate of artificial teeth was 16.92%. Most of them occurred in the midline area of the anterior zone and the location of the overdenture base on the locator attachments. The average first replacement time of the locator attachment nylon retainer washer was 34.2±10.3 months. CONCLUSIONS: Implants retained complete overdentures with Locator attachments are effective in long term clinical observation. Complications are mainly found in peri-implant mucosal bleeding on probing and vertical alveolar bone absorption, and tended to increase gradually over time. The fracture of the implant retains complete overdenture bases and the fall off or fracture of the artificial teeth are the second serious complications. Overdenture base with metal frame at the location of the Locator abutment and the midline of the anterior area should be strengthened, and narrow diameter implants should be avoided as far as possible in the anterior zone.

Comparative biomechanics of all-on-4 and vertical implant placement in asymmetrical mandibular: a finite element study.

BACKGROUND: Clinical scenarios frequently present challenges when patients exhibit asymmetrical mandibular atrophy. The dilemma arises: should we adhere to the conventional All-on-4 technique, or should we contemplate placing vertically oriented implants on the side with sufficient bone mass? This study aims to employ three-dimensional finite element analysis to simulate and explore the biomechanical advantages of each approach. METHODS: A finite element model, derived from computed tomography (CT) data, was utilized to simulate the nonhomogeneous features of the mandible. Three configurations-All-on-4, All-on-5-v and All-on-5-o were studied. Vertical and oblique forces of 200 N were applied unilaterally, and vertical force of 100 N was applied anteriorly to simulate different masticatory mechanisms. The maximum von Mises stresses on the implant and framework were recorded, as well as the maximum equivalent strain in the peri-implant bone. RESULTS: The maximum stress values for all designs were located at the neck of the distal implant, and the maximum strains in the bone tissue were located around the distal implant. The All-on-5-o and All-on-5-v models exhibited reduced stresses and strains compared to All-on-4, highlighting the potential benefits of the additional implant. There were no considerable differences in stresses and strains between the All-on-5-o and All-on-5-v groups. CONCLUSIONS: With the presence of adequate bone volume on one side and severe atrophy of the contralateral bone, while the "All-on-4 concept" is a viable approach, vertical implant placement optimizes the transfer of forces between components and tissues.

The Scalloped Surgical Guide as an Alternative to Flat Bone Reduction Guide in Full-Arch Implant Restoration.

The goal of this clinical report was to present an alternative to traditional flat bone reduction guides, using a custom-designed 3-dimensional (3D)-printed guide according to the future gingival margin of the planned dentition. A 61-year-old woman with concerns regarding her smile appearance was presented. The initial examination revealed excessive gingival show accompanied by excessive overjet. The dentition was in a failing situation. The proposed treatment plan, relying on the sufficient amount of bone and keratinized tissue, consisted of recontouring of the alveolar ridge and gingiva and placement of 6 implants and an FP-1 prosthesis after extraction of all remaining maxillary teeth. Digital smile design was completed, and a fully digitally guided surgery was planned. This consisted of using 3 surgical guides, starting with the fixation pin guide, continuing with the scalloped hard- and soft-tissue reduction guide, and finally the implant placement template. Following the surgery, the patient received a temporary restoration, and on the 4-month follow-up, a new polymethyl meta-acrylate temporary prosthesis was delivered. The patient's 7-month follow-up is presented in the article. The report of this triple-template guided surgery indicated that digital 3D planning is a considerably predictable tool to properly establish and evaluate future occlusal plane, smile line, and lip support. Scalloped guides seem to be an excellent alternative to conventional bone reduction guides since they require less bone removal and improve patient comfort during surgery.

Influence of implant distribution on the biomechanical behaviors of mandibular implant-retained overdentures: a three-dimensional finite element analysis.

OBJECTIVE: To assess stress distribution in peri-implant bone and attachments of mandibular overdentures retained by small diameter implants, and to explore the impact of implant distribution on denture stability. METHODS: Through three-dimensional Finite Element Analysis (3D FEA), four models were established: three models of a two mandibular implants retained overdenture (IOD) and one model of a conventional complete denture (CD). The three IOD models consisted of one with two implants in the bilateral canine area, another with implants in the bilateral lateral incisor area, and the third with one implant in the canine area, and another in the lateral incisor area. Three types of loads were applied on the overdenture for each model: a 100 N vertical load and a inclined load on the left first molar, and a100N vertical load on the lower incisors. The stress distribution in the peri-implant bone, attachments, and the biomechanical behaviors of the overdentures were analyzed. RESULTS: Despite different distribution of implants, the maximum stress values in peri-implant bone remained within the physiological threshold for all models across three loading conditions. The dispersed implant distribution design (implant in the canine area) exhibited the highest maximum stress in peri-implant bone (822.8 µe) and the attachments (275 MPa) among the three IOD models. The CD model demonstrated highest peak pressure on mucosa under three loading conditions (0.8188 Mpa). The contact area between the denture and mucosa of the CD model was smaller than that in the IOD models under molar loading, yet it was larger in the CD model compared to the IOD model under anterior loading. However, the contact area between the denture and mucosa under anterior loading in all models was significantly smaller than those under molar loading. The IOD in all three models exhibited significantly less rotational movement than the complete denture. Different implant positions had minimal impact on the rotational movement of the IOD. CONCLUSION: IOD with implants in canine area exhibited the highest maximum stress in the peri-implant bone and attachments, and demonstrated increased rotational movement. The maximum principal stress was concentrated around the neck of the small diameter one-piece implant, rather than in the abutment. An overdenture retained by two implants showed better stability than a complete denture.

Zirconia dental implants; the relationship between design and clinical outcome: A systematic review.

OBJECTIVE: To evaluate the clinical outcome of different designs of zirconia dental implants. DATA: This systematic review adhered to the PRISMA checklist and followed the PICO framework. The protocol is registered in PROSPERO (CRD42022337228). SOURCES: The search was conducted in March 2023 through four databases (PubMed, Web of Science, Cochrane Library, and Google Scholar) along with a search of references in the related reviews. Three authors reviewed on title, and abstract level and analysed the risk of bias, and all authors reviewed on a full-text level. STUDY SELECTION: Clinical studies excluding case reports for patients treated with different designs of zirconia dental implants were included. From a total of 2728 titles, 71 full-text studies were screened, and 27 studies were included to assess the risk of bias (ROBINS-I tool) and data extraction. After quality assessment, four studies were included, and the remaining 23 excluded studies were narratively described. RESULT: The included prospective studies with moderate risk of bias reported success and survival rates of one-piece implants that ranged between 95 and 98.4 % with no difference between different lengths and diameters. The acid-etched roughened surface showed higher clinical outcomes compared to other surface roughness designs. CONCLUSION: Promising 5-year clinical outcomes were found for one-piece zirconia implants with no difference between different diameters and lengths. Concerning surface roughness, better outcomes were found when using the acid-etched implant surface. However, due to the limited available studies, further high-quality clinical studies comparing zirconia one-piece and two-piece implants with different diameters, lengths, and surface roughness are needed. CLINICAL SIGNIFICANCE: Based on this systematic review, under suitable clinical situations, the one-piece zirconia implants with diameters of 4.0 mm, 4.5 mm, or 5.5 mm and lengths of 8 mm, 10 mm, 12 mm, or 14 mm have similar promising clinical outcomes. Additionally, the acid-etched roughened implant surface may be preferable.

Evaluation of Quality of Life and Satisfaction with Fixed Prostheses on Zygomatic Implants vs All-on-Four Concept: A Randomized Clinical Study.

AIM: To compare between the rehabilitation of atrophied maxilla with fixed prosthesis using two posterior zygomatic implants and two conventional anterior implants or four implants inserted according to the all-on-four concept regarding the patient quality of life and satisfaction after one year of prosthesis insertion. MATERIALS AND METHODS: Thirty-six patients with atrophic edentulous maxillae were randomized into two groups: Group I (rehabilitated with fixed prostheses supported by two zygomatic and two conventional implants in the anterior region) and group II (fixed prostheses on four implants in the anterior region following an all-on-four concept). One year after the placement of the definitive prostheses, patients completed oral health impact profile-14 and satisfaction questionnaires. RESULTS: All patients were satisfied regarding retention, stability, occlusion, comfort, cleaning, speaking, chewing, bolus quality, appearance, handling, prosthesis apart, and embarrassing, with no significant significance between two groups except satisfaction with surgical procedures and healing period. CONCLUSIONS: Using two distally tilted zygomatic implants or all-on-four concept to rehabilitate atrophied maxilla by fixed detachable prosthesis could be considered a promising functional and esthetic treatment option regarding the patient satisfaction. CLINICAL SIGNIFICANCE: Traditionally, treatment of maxillary atrophied ridges was done by bone grafting or sinus-lifting techniques; however, using all-on-four concept or zygomatic implants was a successful treatment as it has high success rates and highly satisfied by the patients. How to cite this article: Nagib MA, Ibrahim AM, Abdel-Rahman FH, et al. Evaluation of Quality of Life and Satisfaction with Fixed Prostheses on Zygomatic Implants vs All-on-Four Concept: A Randomized Clinical Study. J Contemp Dent Pract 2024;25(2):141-147.

Evaluation and assessment of the survival of tooth implant supported prosthesis in tooth and implant supported rehabilitation cases with metal frameworks.

INTRODUCTION: Over the years, implant therapy has been a commonly used treatment option for individuals who are partially or totally edentulous, with a long-term success rate of over 90%. With significant advancements in biomaterials and technology, implant dentistry can now conduct prosthetic rehabilitations in the majority of patients catering to all types of needs. However, in order to meet the demands of a patient base that is always growing, new trends in implantology are emerging in recent years that are focused on minimally invasive surgery and financial sustainability. In certain clinical scenarios, connecting teeth and implants to support fixed partial prosthesis (FPPs) may be a predictable and workable course of treatment. MATERIALS AND METHODS: 22 patients were selected for this study who had tooth and implant supported prosthesis placed as a final restoration. Out of these 22 patients; 12 were male and 10 were female patients. Implants were placed following proper protocol and if grafting procedures were required they were carried out. A second stage surgical procedure was carried out and delayed loading protocols were followed. The statistical analysis was done using the IBM SPSS 24.0, Chicago, USA. The survival of the implants and teeth were measured by the Kaplan Meier survival scale. Bone loss was assessed at baseline(upon loading), 12 months and 24 months. RESULTS: The implant survival rate was measured at 6 months, 12 months, 18 months and 24 months. At 24 months, one implant showed failure, so the survival rate of the implants were 95.4%. Bone loss of 1 mm was seen around one implant at 12 months. Bone loss of 1 and 2 mm was present around two implants and one implant respectively at 24 months. CONCLUSION: From the results of this study, we can conclude that tooth implant supported prosthesis show very good survival when used in rehabilitation cases.

Occlusal equilibration and muscle activity in fixed versus removable mandibular implant supported overdenture.

OBJECTIVES: Single denture rehabilitated patients have negative appraisals regarding oral function, mostly associated by stability and retention issues regarding mandibular prosthetics. Therefore, this study assessed patients' occlusal equilibration, muscle activity, and oral health-related quality of life (OHRQoL) receiving milled removable or fixed mandibular implant retained prostheses. MATERIALS AND METHODS: Twenty-two edentulous mandibular ridges patients were randomly distributed into two groups based on the definitive prosthesis received. Group I: Removable mandibular implant-supported overdenture, Group II: Implant retained fixed prosthesis. Occlusal equilibration was evaluated utilizing Occlusense, muscle activity via Electromyograph (EMG) at delivery, after one, and three months. The OHRQoL was evaluated by Oral Health Impact Profile questionnaire (OHIP-19) before delivery and after follow-ups. Data were collected, tabulated, and analyzed, utilizing independent t-test and One-way ANOVA followed Tukey`s post-hoc test. Significance level set at P ≤ 0.05. RESULTS: Groups I &II showed significant improvement in occlusal equilibration, muscle activity and OHRQoL. Group II demonstrated significantly higher improvement than group I in occlusal equilibration associated with muscle activity after 1 month, and in functional limitations domain in OHRQoL questionnaire after 3 months. CONCLUSION: Implant retained mandibular prosthesis showed improvement in occlusal equilibration, muscle activity, and OHRQoL regardless of prosthesis type employed. Fixed implant-supported prosthesis revealed better outcomes than removable mandibular implant-supported overdenture concerning occlusal equilibration, muscle activity, and OHRQoL regarding functional limitations. CLINICAL RELEVANCE: Implant retained mandibular prosthesis is one of best treatment options for single mandibular completely edentulous patients, as dental implants improved occlusal equilibration, muscle activity, and OHRQoL.

Novel complete-arch pillar system (CAPS) to register implant position and maxillomandibular relationship in one single visit.

OBJECTIVES: This article presents a novel complete-arch pillar system (CAPS) to register implant position and maxillomandibular relationship in one single visit for implant-supported fixed complete dental prostheses (IFCDPs). MATERIAL AND METHODS: The novel system presents a 3-unit toolset comprising intraoral scan bodies (ISBs), lateral pillar attachments (LPAs) and occlusal pillar attachments (OPAs). A 2-stage single visit workflow by an intraoral scanner (Trios 5) was introduced. The first stage "Screw-Scan-Done" was used to describe complete-arch intraoral implant scanning using LPAs. The second stage "Screw-Occlude-Done" involved virtual occlusal recording using OPAs. Two patients with one single edentulous arch were selected for this study. In the first patient, 6 bone level implants (Bone Level Tapered, Straumann) were placed in the edentulous maxilla at positions 12, 14, 16, 22, 24 and 26. In the second patient, 4 bone level implants (NobelActive CC, Nobel Biocare) were placed in the edentulous mandible at positions 32, 35, 42 and 45. A CAD-CAM procedure was initiated with the acquired IOS data to fabricate an interim IFCDP at the same day. Periapical radiographs were obtained of the implant-prosthetic connection of the definitive IFCDPs to verify the passive fit. Metrology software (Geomagic Qualify, 3D Systems - Matlab, Mathworks) was used to assess the implant analogs position in the 3D-printed casts used for fabricating the definitive IFCDPs. A quantitative occlusal relationship analysis was performed with IOS. RESULTS: Radiographic examination revealed no gaps at implant-prosthetic connection of the definitive IFCDPs. The 3D-printed casts showed an overall average distance deviation within the clinically acceptable range of errors of 150 µm. Quantitative occlusal relationship analysis with IOS showed well-distributed contacts. CONCLUSION: Within the limitations of this study, the following conclusions can be drawn: (1) A 3-unit toolset with ISBs, LPAs and OPAs allows to register the implant position and maxillomandibular relationship in one single visit; (2) the 2-stage clinical workflow with the CAPS system facilitates the IOS data acquisition for fabrication of an interim IFCDP at the same day; (3) a passive fit was demonstrated for the interim and the definitive IFCDPs. CLINICAL SIGNIFICANCE: The CAPS system can help clinicians to register the implant position and the maxillomandibular relationship in one single visit for the fabrication of an IFCDP.

Digital technique to analyze the wear of screw-retained implant supported metal-ceramic dental prostheses and natural tooth as antagonist: a pilot study.

The aim of this study was to describe a novel digital technique to analyze the wear of screw-retained implant-supported metal-ceramic dental prostheses and natural tooth as antagonist.Materials and methods Ten patients were consecutively included to rehabilitate partial edentulism by dental implants. Both the screw-retained implant-supported metal-ceramic dental prostheses and the natural tooth as antagonist were submitted to a digital impression through an intraoral scan to generate a Standard Tessellation Language digital file preoperatively (STL1), at 3 months (STL2), and 6 months (STL3) follow-up. Afterwards, an alignment procedure of the digital files (STL1-STL3) was performed on a reverse engineering morphometric software (3D Geomagic Capture Wrap) and volume changes at the screw-retained implant-supported metal-ceramic dental prostheses and the natural tooth as antagonist were analyzed using Student's t-test. Moreover, Gage R&R statistical analysis was conducted to analyze the repeatability and reproducibility of the digital technique.Results Gage R&R showed a variability attributable to the digital technique of 3.8% (among the measures of each operator) and 4.5% (among operators) of the total variability; resulting repeatable and reproducible, since the variabilities were under 10%. In addition, statistically significant differences were shown at the wear volume (µm3) of both the natural tooth as antagonist (p < 0.0001) and the screw-retained implant-supported metal-ceramic dental prostheses between 3- and 6-months follow-up (p = 0.0002).Conclusion The novel digital measurement technique results repeatable and reproducible to analyze the wear of screw-retained implant-supported metal-ceramic dental prostheses and natural tooth as antagonist.

Comparison of stress distribution around all-on-four implants of different angulations and zygoma implants: a 7-model finite element analysis.

BACKGROUND: In recent years, zygomatic implants and the all-on-four treatment concept have been increasingly preferred for rehabilitation of atrophic maxillae. However, debate continues regarding the optimal configuration and angulation of the implants. The aim of this study was to analyze the biomechanical stress in implants and peri-implant bone in an edentulous maxilla with zygomatic implants and the all-on-four concept, using multiple implant configurations. METHODS: A total of 7 models consisting different combinations of 4-tilted dental implants and zygomatic implants were included in the study. In each model, a total of 200 N perpendicular to the posterior teeth and 50 N with 45° to the lateral tooth were applied. A finite element analysis was performed for determination of stress distribution on implants and peri-implant bone for each model. RESULTS: Higher stress values were observed in both cortical and trabecular bone around the 45°-tilted posterior implants in all-on-four models when compared to zygomatic implants. In cortical bone, the highest stress was established in an all-on-four model including 45°-tilted posterior implant with 4,346 megapascal (MPa), while the lowest stress was determined in the model including anterior dental implant combined with zygomatic implants with 0.817 MPa. In trabecular bone, the highest stress was determined in an all-on-four model including 30°-tilted posterior implant with 0.872 MPa while the lowest stress was observed in quad-zygoma model with 0.119 MPa. Regarding von Mises values, the highest stress among anterior implants was observed in an all-on-four model including 17° buccally tilted anterior implant with 38.141 MPa, while the lowest was in the including anterior dental implant combined with zygomatic implants with 20,446 MPa. Among posterior implants, the highest von Mises value was observed in the all-on-four model including 30°-tilted posterior implant with 97.002 MPa and the lowest stress was in quad zygoma model with 35.802 MPa. CONCLUSIONS: Within the limits of the present study, the use of zygoma implants may provide benefit in decreasing biomechanical stress around both dental and zygoma implants. Regarding the all-on-four concept, a 17° buccal angulation of anterior implants may not cause a significant stress increase while tilting the posterior implant from 30° to 45° may cause an increase in the stress around these implants.

Finite Element Analysis of Stress Distributions for Mandibular Dental Implant-Supported Overdentures with Magnetic Attachments in Osteoporotic and Normal Bone.

PURPOSE: To compare the biomechanical responses of a normal mandible to an osteoporotic mandible with two-implant-supported magnetic attachments. MATERIALS AND METHODS: A 3D finite-element model of a two-implant-supported mandibular overdenture with magnetic attachments was developed, and normal and osteoporotic bone samples were prepared. Four types of load were applied to the overdenture in each model: 100 N vertical and oblique loads on the right first molar, and a 100 N vertical load on the right canine and incisors. Biomechanical behaviors of the peri-implant bone, implant, and mucosa were recorded. Maximum equivalent stresses and elastic strains were analyzed. RESULTS: Equivalent elastic strain in osteoporotic cortical and cancellous bone was 9% to 71% and was 142% and 207% greater than in normal cortical bone, respectively. Equivalent elastic strain in the first molar oblique loading condition was 101% to 190% greater than in the first molar vertical loading condition. CONCLUSIONS: Osteoporotic cancellous bone was weaker and less resistant to deformation than normal bone, and oblique loading was more harmful than vertical loading.

Clinical performance of additively manufactured subperiosteal implants: a systematic review.

PURPOSE: The aim of this study was to assess implant survival and complications rate of modern subperiosteal implants (CAD designed and additively manufactured). METHODS: A systematic review was conducted using three electronic databases; Medline (Pubmed), Cochrane library, and SCOPUS, following the PRISMA statement recommendations to answer the PICO question: "In patients with bone atrophy (P), do additively manufactured subperiosteal implants (I), compared to subperiosteal implants manufactured following traditional approaches (c), present satisfactory implant survival and complication rates (O)? The study was pre-registered in PROSPERO (CRD42023424211). Included articles quality was assessed using the "NIH quality assessment tools". RESULTS: Thirteen articles were finally selected (5 cohort studies and 8 case series), including 227 patients (121 female / 106 male; weighted mean age 62.4 years) and 227 implants. After a weighted mean follow-up time of 21.4 months, 97.8% of implants were in function (5 failures reported), 58 implants (25.6%) presented partial exposure, 12 patients (5.3%) suffered soft tissue or persistent infection. Fracture of the interim prosthesis was reported in 8 of the155 patients (5.2%) in which the use of a provisional prosthesis was reported. A great heterogeneity was found in terms of study design and methodological aspects. For this reason, a quantitative analysis followed by meta-analysis was not possible. CONCLUSIONS: Within the limitations of this study, modern additively manufactured subperiosteal implants presented a good survival in the short-time, but a noticeable number of soft-tissue related complications were reported. Further studies are needed to assess the clinical behavior in the medium- and long-term.