Artificial intelligence and mixed reality for dental implant planning: A technical note.

AIM: The aim of this work is to present a new protocol for implant surgical planning which involves the combined use of artificial intelligence (AI) and mixed reality (MR). METHODS: This protocol involves the acquisition of three-dimensional (3D) patient data through intraoral scanning (IOS) and cone beam computed tomography (CBCT). These data are loaded into AI software which automatically segments and aligns the patient's 3D models. These 3D models are loaded into MR software and used for planning implant surgery through holography. The files are then exported and used to design surgical guides via open-source software, which are 3D printed and used to prepare the implant sites through static computer-assisted implant surgery (s-CAIS). The case is finalized prosthetically through a fully digital protocol. The accuracy of implant positioning is verified by comparing the planned position with the actual position of the implants after surgery. RESULTS: As a proof of principle, the present protocol seems to be to be reliable and efficient when used for planning simple cases of s-CAIS in partially edentulous patients. The clinician can plan the implants in an authentic 3D environment without using any radiology-guided surgery software. The precision of implant placement seems clinically acceptable, with minor deviations. CONCLUSIONS: The present study suggests that AI and MR technologies can be successfully used in s-CAIS for an authentic 3D planning. Further clinical studies are needed to validate this protocol.

3D-printed short-span hybrid composite implant-supported restorations fabricated through tilting stereolithography: A retrospective clinical study on 85 patients with 1 year of follow-up.

PURPOSE: To report the clinical results obtained with fixed short-span (single crowns [SCs] and fixed partial prostheses [FPPs]) implant-supported hybrid composite restorations fabricated through tilting stereolithography (TSLA). METHODS: This retrospective clinical study included 85 patients who had been restored with 95 fixed short-span implant-supported hybrid composite (Irix Max®, DWS Systems) restorations (70 SCs and 25 FPPs up to three units) fabricated with TSLA. The full-digital model-free workflow was based on intraoral implant scanning, computer-assisted design (CAD) and 3D printing using TSLA (Dfab®, DWS Systems). The primary outcomes were the marginal adaptation, the quality of the occlusal and interproximal contact points, and the chromatic integration of the restorations, assessed independently by two experienced operators (a prosthodontist and a periodontist). A score from 1 to 5 (with 5 as the highest value, 4 for satisfactory quality, 3 for acceptable quality, and 2 and 1 as the lowest values, expressing unsatisfactory quality) was assigned by each operator to each restoration at delivery. The secondary outcomes were the survival and success of the restorations at the 1-year follow-up. The restoration was defined as successful in the absence of any complications throughout the follow-up period. A statistical analysis was conducted. RESULTS: For the quality of the marginal closure and occlusal and interproximal contact points, the 3D-printed hybrid composite restorations scored highly; the aesthetic integration was satisfactory. One year after placement, all restorations survived, with a low incidence (4.2 % overall, 5.7 % SCs) of complications (two abutment screw loosenings, two decementation of the restorations, and one upper portion of the hybrid abutment decemented from the titanium base), for a success rate of 95.8 %. CONCLUSIONS: Within the limits of this study (retrospective design, follow-up limited to 1 year from the delivery, and only cemented restorations included) fixed short-span implant-supported hybrid composite crowns and bridges fabricated through TSLA were clinically precise, presenting a low incidence of complications at 1 year. STATEMENT OF CLINICAL RELEVANCE: The use of TSLA printing technology can open new perspectives for the treatment of small edentulous gaps with definitive implant-supported prosthetic restorations.

Accuracy of implant placement using a mixed reality-based dynamic navigation system versus static computer-assisted and freehand surgery: An in Vitro study.

PURPOSE: This in vitro study aimed to compare the accuracy of dental implant placement in partially edentulous maxillary models using a mixed reality-based dynamic navigation (MR-DN) system to conventional static computer-assisted implant surgery (s-CAIS) and a freehand (FH) method. METHODS: Forty-five partially edentulous models (with teeth missing in positions #15, #16 and #25) were assigned to three groups (15 per group). The same experienced operator performed the model surgeries using an MR-DN system (group 1), s-CAIS (group 2) and FH (group 3). In total, 135 dental implants were placed (45 per group). The primary outcomes were the linear coronal deviation (entry error; En), apical deviation (apex error; Ap), XY and Z deviations, and angular deviation (An) between the planned and actual (post-surgery) position of the implants in the models. These deviations were computed as the distances between the stereolithographic (STL) files for the planned implants and placed implants captured with an intraoral scanner. RESULTS: Across the three implant sites, the MR-DN system was significantly more accurate than the FH method (in XY, Z, En, Ap and An) and s-CAIS (in Z, Ap and An), respectively. However, S-CAIS was more accurate than MR-DN in XY, and no difference was found between MR-DN and s-CAIS in En. CONCLUSIONS: Within the limits of this study (in vitro design, only partially edentulous models), implant placement accuracy with MR-DN was superior to that of FH and similar to that of s-CAIS. STATEMENT OF CLINICAL RELEVANCE: In vitro, MR-DN showed greater accuracy in implant positioning than FH, and similar accuracy to s-CAIS: it could, therefore, represent a new option for the surgeon. However, clinical studies are needed to determine the feasibility of MR-DN.

Trueness, precision, time-efficiency and cost analysis of chairside additive and subtractive versus lab-based workflows for manufacturing single crowns: An in vitro study.

PURPOSE: To evaluate the trueness, precision, time efficiency, and cost of three different workflows for manufacturing single crowns (SCs). METHODS: A plaster model with a prepared tooth (#15) was scanned with an industrial scanner, and an SC was designed in computer-assisted-design (CAD) software. Ten SCs were printed with a hybrid composite (additive chairside) and a stereolithographic (SLA) printer (Dfab®), 10 SCs were milled in lithium disilicate (subtractive chairside) using a chairside milling unit (inLab MC XL®), and 10 SCs were milled in zirconia (lab-based) using a five-axis laboratory machine (DWX-52D®). All SCs were scanned with the same scanner after polymerization/sinterization. Each scan was superimposed to the marginal area of the original CAD file to evaluate trueness: absolute average (ABS AVG), root mean square (RMS), and (90˚-10˚)/2 percentile were calculated for each group. Marginal adaptation and quality of the occlusal and interproximal contact points were also investigated by two prosthodontists on 3D printed and plaster models. Finally, the three workflows' time efficiency and costs were evaluated. RESULTS: Additive chairside and subtractive lab-based SCs had significantly better marginal trueness than subtractive chairside SCs in all three parameters (ABS AVG, p < 0.01; RMS, p < 0.01; [90˚-10˚]/2, p < 0.01). However, the two prosthodontists found no significant differences between the three manufacturing procedures in the quality of the marginal closure (p = 0.186), interproximal (p = 0.319), and occlusal contacts (p = 0.218). Both time efficiency and cost show a trend favoring the chairside additive workflow. CONCLUSIONS: Chairside additive technology seems to represent a valid alternative for manufacturing definitive SCs, given the high marginal trueness, precision, workflow efficiency and low costs. STATEMENT OF CLINICAL RELEVANCE: Additive chairside manufacturing of definitive hybrid composite SCs is now possible and shows high accuracy, time efficiency, and competitive cost.

Palatal asymmetry assessed by intraoral scans: effects of sex, orthodontic treatment, and twinning. A retrospective cohort study.

BACKGROUND: Symmetry is critical in perceived attractiveness, especially in female faces. The palate determines the teeth' alignment and supports facial soft tissues. Therefore, the study aimed to assess the effects of sex, orthodontic treatment, age, and heritability on the directional, anti-, and fluctuational asymmetry in the digital palatal model. METHODS: The palate of 113 twins, 86 female and 27 male subjects, with and without previous orthodontic treatment, were scanned by the Emerald (Planmeca) intraoral scanner. Three lines were constructed horizontally in the digital model, one between the right and left first upper molars and two between the first molars and incisive papilla. Two observers calculated the left and right angles between the mid-sagittal plane and molar-papilla lines. The intraclass correlation coefficient was used to assess the inter-observer absolute agreement. The directional symmetry was determined by comparing the mean left and right angles. The antisymmetry was estimated from the distribution curve of the signed side difference. The fluctuating asymmetry was approximated from the magnitude of the absolute side difference. Finally, the genetic background was assessed by correlating the absolute side difference between monozygotic twin siblings. RESULTS: The right angle (31.1 degrees) was not significantly different from the left one (31.6 degrees). The signed side difference followed a normal distribution with a mean of -0.48 degrees. The absolute side difference (2.29 degrees, p < 0.001) was significantly different from zero and negatively correlated (r=-0.46, p < 0.05) between siblings. None of the asymmetries was affected by sex, orthodontic treatment or age. CONCLUSIONS: The palate illustrates neither directional asymmetry nor antisymmetry, indicating that most people's palates are symmetric. However, the significant fluctuating asymmetry suggests that some subject has considerable asymmetry but is not influenced by sex, orthodontic treatment, age, and genetics. The proposed digital method is a reliable and non-invasive tool that could facilitate achieving a more symmetrical structure during orthodontic and aesthetic rehabilitation. TRIAL REGISTRATION: The Clinicatrial.gov registration number is NCT05349942 (27/04/2022).

Artificial intelligence and augmented reality for guided implant surgery planning: A proof of concept.

PURPOSE: To present a novel protocol for authentic three-dimensional (3D) planning of dental implants, using artificial intelligence (AI) and augmented reality (AR). METHODS: The novel protocol consists of (1) 3D data acquisition, with an intraoral scanner (IOS) and cone-beam computed tomography (CBCT); (2) application of AI for CBCT segmentation to obtain standard tessellation language (STL) models and automatic alignment with IOS models; (3) loading of selected STL models within the AR system and surgical planning with holograms; (4) surgical guide design with open-source computer-assisted-design (CAD) software; and (5) surgery on the patient. RESULTS: This novel protocol is effective and time-efficient when used for planning simple cases of static guided implant surgery in the partially edentulous patient. The clinician can plan the implants in an authentic 3D environment, without using any radiological guided surgery software. The precision of implant placement looks clinically acceptable, with minor deviations. CONCLUSIONS: AI and AR technologies can be successfully used in guided implant surgery for authentic 3D planning that may replace conventional software. However, further clinical studies are needed to validate this protocol. STATEMENT OF CLINICAL RELEVANCE: The combined use of AI and AR may change the perspectives of modern guided implant surgery for authentic 3D planning that may replace conventional software.

Effect of measurement techniques and operators on measured deviations in digital implant scans.

OBJECTIVES: To evaluate the effect of different measurement techniques and operators on measured deviations in vitro implant scans. METHODS: A 2-piece system that comprises a healing abutment (HA) and a scan body (SB) was mounted onto an implant at right first molar site of a polymethylmethacrylate mandibular dentate model. Model was digitized by using an industrial scanner (reference model scan, n = 1) and an intraoral scanner (test scan, n = 20). All standard tessellation language files were imported into a 3-dimensional analysis software and superimposed. Three operators with similar experience performed circle-based and point-based deviation analyses (n = 20). Deviations measured with different techniques were compared with paired samples t-test within each operator, while the reliability of the operators was assessed by using F-tests for both technqiues (α = 0.05). RESULTS: Point-based technique resulted in lower deviations than circle-based technique for all operators (P = .001) with to higher reliability among operators (ICC = 0.438, P = .001). The correlation among the operators was nonsignificant when circle-based technique was used (ICC = 0.114, P = .189). CONCLUSION: Lower deviations were detected with the point-based technique. In addition, different operators' measurements had higher correlation when point-based technique was used compared with circle-based technique. CLINICAL SIGNIFICANCE: Point-based technique may be preferred over circle-based technique for research studies on scan accuracy of implants, given its higher reliability. The accuracy of measured deviations may increase if the number of planes are increased, which can facilitate point generation at different surfaces of the scan body.

The Open Cell Form of 3D-Printed Titanium Improves Osteconductive Properties and Adhesion Behavior of Dental Pulp Stem Cells.

Titanium specimens have been proven to be safe and effective biomaterials in terms of their osseo-integration. To improve the bioactivity and develop customized implants titanium, the surface can be modified with selective laser melting (SLM). Moreover, the design of macro-porous structures has become popular for reaching a durable bone fixation. 3D-printed titanium (Titanium A, B, and C), were cleaned using an organic acid treatment or with electrochemical polishing, and were characterized in terms of their surface morphology using scanning electron microscopy. Next, Dental Pulp Stem Cells (DPSCs) were cultured on titanium in order to analyze their biocompatibility, cell adhesion, and osteoconductive properties. All tested specimens were biocompatible, due to the time-dependent increase of DPSC proliferation paralleled by the decrease of LDH released. Furthermore, data highlighted that the open cell form with interconnected pores of titanium A, resembling the inner structure of the native bone, allows cells to better adhere inside the specimen, being proteins related to cell adherence highly expressed. Likewise, titanium A displays more suitable osteoconductive properties, being the profile of osteogenic markers improved compared to titanium B and C. The present work has demonstrated that the inner design and post-production treatments on titanium surfaces have a dynamic influence on DPSC behavior toward adhesion and osteogenic commitment.

Vitamin D Deficiency and Early Implant Failure: Outcomes from a Pre-surgical Supplementation Program on Vitamin D Levels and Antioxidant Scores.

PURPOSE: Accumulating evidence has shown that vitamin D deficiency has been linked with an up to 300% increase in early implant failure. The aim of this study was to investigate a comprehensive pre-surgical dental support program (DentaMedica) on its ability to increase vitamin D and antioxidant levels prior to implant surgery. MATERIALS AND METHODS: Twenty patients were enrolled in this study. To quantify vitamin D levels, two in-office vitamin D finger-prick tests (10-15 min in length) were compared to levels obtained from a standard laboratory blood test. An antioxidant testing device was also utilised to investigate the impact of this pre-surgical supplementation program on antioxidant scores 0 and 6 weeks post supplementation. RESULTS: It was first found that 65% of the population had an initial vitamin D deficiency (below 30 ug/ml). After supplementation, vitamin D levels increased from an average of 24.76 ng/ml to 50.11 ng/ml (ranging from 38 to 85.50 ng/ml). No statsitcally significant differences were observed between any of the 3 testing devices (2 in-office finger-prick tests and a standard blood sample). Initial antioxidant levels registered on the biophotonic unit averaged an antioxidant score of 27250 ± 10992.22. Following supplementation, an increase of 54% from baseline values (41950 ± 9276.31) was reported. CONCLUSION: The results from this study show convincingly that the majority of the tested population was vitamin D deficient. It was further found that both in-office finger-prick devices demonstrated results comparable to standard lab scores (usually within an average 2-3 ng/ml). Following supplementation, all patients reached sufficient levels following this 4-6 week pre-surgical supplementation program specific to implant dentistry.

Solid index and reverse implant library for the fabrication of a bar for overdenture: a proof of concept.

OBJECTIVES: To present a solid index (SI), a 3D-printed replica of a patient's preexisting complete denture, which allows the dentist to accurately capture the position of the implants and the dental technician to model a bar for overdenture (OD) in CAD software with the use of reverse implant libraries. MATERIALS AND METHODS: A patient in need of rehabilitation of a fully edentulous mandible was restored with an implant OD supported by a polyetheretherketone (PEEK) milled bar. The position of the implants was captured through a physical impression using an SI, with the transfers screwed in. The analogs were then connected, and the SI was scanned upside down to directly capture the position of the implants in the space. This scan was used to design the bar in CAD software using reverse implant libraries, without the need for pouring any SI-derived cast or for using any scanbody. The bar was milled in PEEK. RESULTS: When delivered to the patient, the bar was clinically precise, screwing perfectly onto the implants without any tension or misfit. CONCLUSIONS: The present proof-of-concept article supports the use of an SI and reverse implant libraries for the fabrication of a bar for OD. Further clinical studies are needed to confirm these results.

Tolerances in the production of six different implant scanbodies: a comparative study.

PURPOSE: To investigate and compare the production tolerances of six different commercially available implant scan bodies (SBs), with the null hypothesis that there would be no tolerances in the production or significant differences between the different SBs. MATERIALS AND METHODS: Six different implant SBs (IO 6A-B and IO 2B-B, Nobel Biocare; RC 4.1 mm 025.4915 and RN 4.8 mm 048.168, Straumann; KR 352KR1A0, BTK BIOTEC; and AANISR4013T, MegaGen) were evaluated. Five specimens of each SB type (a total of 30 samples) were screwed onto the corresponding implant analogs and underwent dimensional analysis with optical microscopy (QVI Smartscope Flash 200, Optical Gaging Products) and precision probing (R 0.25, Renishaw). The outcome variables were SB height, diameter, and angle of the flat face on the top (plane). All measurements were compared with the corresponding computer-assisted design library measurements used as a reference to assess the manufacturing tolerances. Statistical analyses were performed to compare the results obtained with the different SBs. RESULTS: Tolerances in the manufacture of the SBs were reported in height, diameter, and plane measurements, and statistically significant differences between the different types of SBs were found. Therefore, the null hypothesis was rejected. Most of the deviations and tolerances were reported in height measurements with conical connection implants. CONCLUSIONS: Tolerances in the production and statistically significant differences were found among the six commercially available SBs evaluated in this study. Additional studies with larger sample sizes and other types of SBs are needed.

Digital three-dimensional visualization of intrabony periodontal defects for regenerative surgical treatment planning.

BACKGROUND: In the regenerative treatment of intrabony periodontal defects, surgical strategies are primarily determined by defect morphologies. In certain cases, however, direct clinical measurements and intraoral radiographs do not provide sufficient information on defect morphologies. Therefore, the application of cone-beam computed tomography (CBCT) has been proposed in specific cases. 3D virtual models reconstructed with automatic thresholding algorithms have already been used for diagnostic purposes. The aim of this study was to utilize 3D virtual models, generated with a semi-automatic segmentation method, for the treatment planning of minimally invasive periodontal surgeries and to evaluate the accuracy of the virtual models, by comparing digital measurements to direct intrasurgical measurements. METHODS: Four patients with a total of six intrabony periodontal defects were enrolled in the present study. Two months following initial periodontal treatment, a CBCT scan was taken. The novel semi-automatic segmentation method was performed in an open-source medical image processing software (3D Slicer) to acquire virtual 3D models of alveolar and dental structures. Intrasurgical and digital measurements were taken, and results were compared to validate the accuracy of the digital models. Defect characteristics were determined prior to surgery with conventional diagnostic methods and 3D virtual models. Diagnostic assessments were compared to the actual defect morphology during surgery. RESULTS: Differences between intrasurgical and digital measurements in depth and width of intrabony components of periodontal defects averaged 0.31 ± 0.21 mm and 0.41 ± 0.44 mm, respectively. In five out of six cases, defect characteristics could not be assessed precisely with direct clinical measurements and intraoral radiographs. 3D models generated with the presented semi-automatic segmentation method depicted the defect characteristics correctly in all six cases. CONCLUSION: It can be concluded that 3D virtual models acquired with the described semi-automatic segmentation method provide accurate information on intrabony periodontal defect morphologies, thus influencing the treatment strategy. Within the limitations of this study, models were found to be accurate; however, further investigation with a standardized validation process on a large number of participants has to be conducted.

Solid index versus intraoral scanners in the full-arch implant impression: in vitro trueness evaluation.

OBJECTIVES: To assess the trueness of a solid index (SI) in the full-arch (FA) implant impression, and to compare it with that of two intraoral scanners (IOSs). A type-IV gypsum model of a completely edentulous patient with 8 implant scanbodies (SBs) was scanned with a desktop scanner (7Series®) to obtain a reference virtual model (RVM), and with two IOSs (CS 3700® and Emerald S®). Five scans were taken with each IOS. Based on the RVM, an SI (custom tray consisting of hollow cylinders connected by a bar) was fabricated and used to capture a physical impression of the model; from this, a second gypsum model was derived and scanned with a desktop scanner (D15®). The SI-derived and the IOSs-derived models were superimposed onto the RVM, to evaluate trueness. RESULTS: The overall mean trueness was 29 µm (± 26) for the SI-derived model, versus 42.4 µm (± 14.7) for CS 3700® and 52.2 µm (± 4.6) for Emerald S®. Despite its limitations (in vitro design, a limited number of models evaluated, RVM captured with a desktop scanner) this study supports the use of SI for FA implant impressions. Further studies are needed to confirm this evidence.

Trueness of 12 intraoral scanners in the full-arch implant impression: a comparative in vitro study.

BACKGROUND: The literature has not yet validated the use of intraoral scanners (IOSs) for full-arch (FA) implant impression. Hence, the aim of this in vitro study was to assess and compare the trueness of 12 different IOSs in FA implant impression. METHODS: A stone-cast model of a totally edentulous maxilla with 6 implant analogues and scanbodies (SBs) was scanned with a desktop scanner (Freedom UHD®) to capture a reference model (RM), and with 12 IOSs (ITERO ELEMENTS 5D®; PRIMESCAN® and OMNICAM®; CS 3700® and CS 3600®; TRIOS3®; i-500®; EMERALD S® and EMERALD®; VIRTUO VIVO® and DWIO®; RUNEYES QUICKSCAN®). Ten scans were taken using each IOS, and each was compared to the RM, to evaluate trueness. A mesh/mesh method and a nurbs/nurbs method were used to evaluate the overall trueness of the scans; linear and cross distances between the SBs were used to evaluate the local trueness of the scans. The analysis was performed using reverse engineering software (Studio®, Geomagics; Magics®, Materialise). A statistical evaluation was performed. RESULTS: With the mesh/mesh method, the best results were obtained by CS 3700® (mean error 30.4 µm) followed by ITERO ELEMENTS 5D® (31.4 µm), i-500® (32.2 µm), TRIOS 3® (36.4 µm), CS 3600® (36.5 µm), PRIMESCAN® (38.4 µm), VIRTUO VIVO® (43.8 µm), RUNEYES® (44.4 µm), EMERALD S® (52.9 µm), EMERALD® (76.1 µm), OMNICAM® (79.6 µm) and DWIO® (98.4 µm). With the nurbs/nurbs method, the best results were obtained by ITERO ELEMENTS 5D® (mean error 16.1 µm), followed by PRIMESCAN® (19.3 µm), TRIOS 3® (20.2 µm), i-500® (20.8 µm), CS 3700® (21.9 µm), CS 3600® (24.4 µm), VIRTUO VIVO® (32.0 µm), RUNEYES® (33.9 µm), EMERALD S® (36.8 µm), OMNICAM® (47.0 µm), EMERALD® (51.9 µm) and DWIO® (69.9 µm). Statistically significant differences were found between the IOSs. Linear and cross distances between the SBs (local trueness analysis) confirmed the data that emerged from the overall trueness evaluation. CONCLUSIONS: Different levels of trueness were found among the IOSs evaluated in this study. Further studies are needed to confirm these results.

Integrated 3D Information for Custom-Made Bone Grafts: Focus on Biphasic Calcium Phosphate Bone Substitute Biomaterials.

PURPOSE: Several studies showed that the sintering temperature of 1250 °C could affect the formation of α-Ca3(PO4)2, which is responsible for the reduction of the hardness value of biphasic calcium phosphate biocomposites, but they did not evaluate the inference of the sintering time at peak temperature on transition of ß-Ca3(PO4)2 to α-Ca3(PO4)2. This analysis explored, in an innovative way, inferences and correlations between volumetric microstructure, mechanical properties, sintering temperature, and time at peak temperature in order to find the best sintering conditions for biphasic calcium phosphate composites grafted in severe alveolar bone defects. METHODS: Sintered biphasic calcium phosphates (30%-hydroxyapatite/70%-tricalcium phosphate) were tested by microCT imaging for the 3D morphometric analysis, by compressive loading to find their mechanical parameters, and by X-ray diffraction to quantify the phases via Rietveld refinement for different sintering temperatures and times at the peak temperature. Data were analysed in terms of statistical inference using Pearson's correlation coefficients. RESULTS: All the studied scaffolds closely mimicked the alveolar organization of the jawbone, independently on the sintering temperatures and times; however, mechanical testing revealed that the group with peak temperature, which lasted for 2 hours at 1250 °C, showed the highest strength both at the ultimate point and at fracture point. CONCLUSION: The good mechanical performances of the group with peak temperature, which lasted for 2 hours at 1250 °C, is most likely due to the absence of the α-Ca3(PO4)2 phase, as revealed by X-ray diffraction. However, we detected its presence after sintering at the same peak temperature for longer times, showing the time-dependence, combined with the temperature-dependence, of the ß-Ca3(PO4)2 to α-Ca3(PO4)2 transition.

Solid index impression protocol: a hybrid workflow for high accuracy and passive fit of full-arch implant-supported restorations.

AIM: The purpose of this article is to present the preliminary clinical results obtained with a novel hybrid digital-analog technique, the solid index impression protocol (SIIP), which uses a solid index to capture accurate impressions of multiple implants for the fabrication of implant-supported fixed full arches (FFAs). MATERIALS AND METHODS: This pilot study was based on five patients, each treated with a FFA supported by four implants. Three months after implant placement, impressions were taken for all patients with an intraoral scanner (IOS) (direct digital impression) and with the SIIP, using a custom tray consisting of four hollow cylinders connected with a bar. This index was linked to the implant transfers and transferred to the laboratory, and the definitive FFAs were fabricated based on it. The outcomes of the study were the passive fit of implant superstructures and the accuracy of the models generated by the SIIP, inspected using a coordinate measuring machine (CMM) and reverse engineering software, and compared with the accuracy of direct digital impressions. RESULTS: Excellent clinical precision and passive fit were obtained in all five implant-supported FFAs fabricated with the SIIP. One year after delivery, all FFAs were functional without any complication. Differences in accuracy were found between the SIIP and direct intraoral scanning. CONCLUSIONS: The SIIP seems to represent a viable option for capturing accurate impressions for the fabrication of clinically precise implant-supported FFAs with a hybrid digital-analog workflow. Further studies are needed to confirm these results.

An Experimental Strategy for Capturing the Margins of Prepared Single Teeth with an Intraoral Scanner: A Prospective Clinical Study on 30 Patients.

Purpose: To present an experimental strategy for successfully capturing the margins of prepared single teeth with an intraoral scanner (IOS). Methods: The protocol was as follows: (1) an intraoral impression was captured with an IOS, without taking care of the visibility of the margins; (2) a partial analog impression was taken by means of a 3D-printed custom tray filled with polyvinylsiloxane light, after the removal of a retraction cord; (3) the hollow portion of the analog impression, with the preparation margins clearly visible, was scanned extraorally with the same IOS; (4) the scan of the analog impression was imported into computer-assisted-design (CAD) software, where its normals were inverted; (5) the scan with inverted normals was registered on the first intraoral scan, and replaced it; (6) the technician designed the final restoration, which was fabricated and delivered for application. The study outcomes were: (1) the marginal adaptation of the final crown; (2) the quality of interproximal contacts; and (3) the quality of occlusal contacts. Results: Thirty patients (18 males, 12 females; mean age 51.3 ± 11.6 years) were selected for this study. All these patients were restored with a monolithic translucent zirconia crown, fabricated following the aforementioned protocol. The clinical precision and the marginal adaptation of the crowns were optimal, interproximal contact points were perfect, and the only necessary adaptations were occlusal, with some minor precontacts that had to be polished. Conclusions: The present protocol seems to be compatible with the fabrication of clinically precise zirconia crowns. Further studies are needed to confirm these results.

Custom-made 3D printed subperiosteal titanium implants for the prosthetic restoration of the atrophic posterior mandible of elderly patients: a case series.

PURPOSE: To present the application of custom-made 3D-printed subperiosteal implants for fixed prosthetic restoration of the atrophic posterior mandible of elderly patients. METHODS: Between January 2017 and June 2018, all partially edentulous patients aged over 65 years, with two or more missing teeth in the posterior atrophic mandible, and who did not want to undergo bone regenerative procedures, were included in this study. These patients were rehabilitated with custom-made subperiosteal implants, designed from cone beam computed tomography (CBCT) and fabricated in titanium by means of direct metal laser sintering (DMLS). The outcome measures were fit and stability of the implants at placement, duration of the intervention, implant survival, and early and late complications. All patients were followed for 1 year after surgery. RESULTS: Ten patients (four males, six females; mean age 69.6, SD ± 2.8, median 69, 95% CI 67.9-71.6) were included in the study. The fit of the implants was satisfactory, with a mean rating of 7 out of 10 (SD ± 1.6, median 7, 95% CI 6-8). Only two implants had insufficient fit, because of the presence of scattering in the CBCT; however, they were adapted to the sites during the interventions. The mean duration of the intervention was 44.3 min (SD ± 19.4, median 37, 95% CI 32.3-56.3). At the one-year follow-up, no implants were lost (survival rate 100%). One implant presented immediate postoperative complications with pain, discomfort and swelling, and two patients experienced late complications, having their provisional restorations fractured during the temporisation phase. All these complications were minor in nature, but the final complication rate amounted to 30% (three of ten patients). CONCLUSIONS: Although this study has limits (small patient sample and short follow-up), DMLS has proven to be an effective method for fabricating accurate subperiosteal implants, with high survival rates. This may represent an alternative treatment procedure in elderly patients with a severely atrophic posterior mandible, since it allows avoidance of regenerative bone therapies. Further studies are needed to confirm these outcomes.

A novel guided surgery system with a sleeveless open frame structure: a retrospective clinical study on 38 partially edentulous patients with 1 year of follow-up.

BACKGROUND: This retrospective clinical study aims to present results of experience with a novel guided surgery system with a sleeveless, open-frame structure, in which the surgical handpiece (not the drills used for preparation) is guided. METHODS: This study was based on an evaluation of the records of partially edentulous patients who had been treated with a sleeveless open-frame guided surgery system (TWIN-Guide®, 2Ingis, Brussels, Belgium), between January 2015 and December 2017. Inclusion criteria were patients with good systemic/oral health and a minimum follow-up of 1 year. Exclusion criteria were patients who had been treated without a guide, or with a guide with sleeves, patients with systemic/oral diseases and who did not have a follow-up of 1 year. The main outcomes were surgical (fit and stability of the surgical guide, duration of the intervention, implant stability, and any intra-operative or immediate post-operative complication), biologic, and prosthetic. RESULTS: Thirty-eight patients (24 males, 14 females; mean age 56.5 ± 14.0 years) were included in the study. These patients had been treated with 110 implants inserted by means of 40 sleeveless, open-frame guides. With regard to fit and stability, 34 guides were excellent, 4 acceptable, and 2 inadequate for use. The mean duration of the intervention was 23.7 (± 6.7) minutes. Immediately after placement, 2 fixtures were not stable and had to be removed. Two patients experienced pain/swelling after surgery. The 108 surviving implants were restored with 36 single crowns and 32 fixed partial prostheses (24 two-unit and 8 three-unit bridges); these restorations survived until the 1-year follow-up, with a low incidence of biologic and prosthetic complications. CONCLUSIONS: Within the limits of this study, this novel guided surgery system with sleeveless, open frame-structure guides seems to be clinically reliable; further studies on a larger sample of patients are needed to confirm these outcomes.