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Background With the development of intraoral scanners, their trueness and precision have been evaluated in various studies. Through these studies, the amount of accuracy that can be expected from intraoral scanners has gradually been disclosed, at the same time, it was difficult to integrate the results of individual studies due to differences in evaluation methods between studies. The purpose of this article was to review the currently available evidence, summarise what is currently known about IOS, analyse the evaluation methods of each study, and list points to note when interpreting the results. Main text Most of the studies were conducted in vitro. The accuracy is evaluated in situations such as single missing teeth, partially edentulous ridges with multiple missing teeth, and fully edentulous jaws. To evaluate the accuracy, direct measurement of distance or angle by coordinate measuring machines and calculation of surface deviation by superimposing surface data were predominantly performed. The influence of parameters such as the number of implants, distance between implants, angle between implants, and experience of the operator was evaluated. Many studies have shown that trueness tends to decrease as the distance between the implants and the scan range increases. It was agreed that the implant angle did not affect either trueness or precision. Regarding other factors, the results varied among studies. Therefore, the effects of these parameters are not clear. Conclusions Heterogeneity in the research methodology was prevalent among the studies considered in this review. Therefore, we cannot make a decisive statement regarding the trueness and precision of digital implant impressions by IOSs. So far, the comparison of the numerical values of error between studies has yet to elucidate any clear answers, despite small methodological differences.

The aim of this study was to evaluate and compare the inter-operator reproducibility of three-dimensional (3D) images of teeth captured by a digital impression technique to a conventional impression technique in vivo. Twelve participants with complete natural dentition were included in this study. A digital impression of the mandibular molars of these participants was made by two operators with different levels of clinical experience, 3 or 16 years, using an intra-oral scanner (Lava COS, 3M ESPE). A silicone impression also was made by the same operators using the double mix impression technique (Imprint3, 3M ESPE). Stereolithography (STL) data were directly exported from the Lava COS system, while STL data of a plaster model made from silicone impression were captured by a three-dimensional (3D) laboratory scanner (D810, 3shape). The STL datasets recorded by two different operators were compared using 3D evaluation software and superimposed using the best-fit-algorithm method (least-squares method, PolyWorks, InnovMetric Software) for each impression technique. Inter-operator reproducibility as evaluated by average discrepancies of corresponding 3D data was compared between the two techniques (Wilcoxon signed-rank test). The visual inspection of superimposed datasets revealed that discrepancies between repeated digital impression were smaller than observed with silicone impression. Confirmation was forthcoming from statistical analysis revealing significantly smaller average inter-operator reproducibility using a digital impression technique (0.014± 0.02 mm) than when using a conventional impression technique (0.023 ± 0.01 mm). The results of this in vivo study suggest that inter-operator reproducibility with a digital impression technique may be better than that of a conventional impression technique and is independent of the clinical experience of the operator.

Dialysis patients who develop degenerative hip disease or femoral neck fractures may require total hip arthroplasty, and their comorbidities predispose them to complications. This study aimed to evaluate whether dialysis was associated with early postoperative complications using a large database of Japanese. In this cohort study, using the Japanese National Administrative Diagnosis Procedure Combination database on THA for patients on hemodialysis or not from December 2011 to March 2023, we assessed the surgical-related complications, medical complications, and mortality during hospitalization after propensity score matching by age, sex, BMI, and comorbidities. A total of 2,111 pairs of patients on hemodialysis and non-dialysis were included. In THA for patients on hemodialysis, the significant odds ratios for various complications were as follows: dislocation (2.616, 95% CI: 1.282 to 5.338, p  < 0.01), reoperation (2.104, 95% CI: 1.222 to 3.623, p  < 0.01), deep vein thrombosis (0.407, 95% CI: 0.286 to 0.579, p  < 0.01), cerebrovascular events (4.426, 95% CI: 1.495 to 13.10, p  < 0.01). These findings help identify postoperative THA risks for patients on dialysis, suggesting that more attention should be paid to preoperative planning and postoperative care.

PurposeVarious biofeedback stimulation techniques of managing sleep bruxism (SB) have recently emerged; however, the effect of successive application of vibratory feedback stimulation has not been clarified. This study elucidated the effect of vibration feedback stimulation via an oral appliance (OA) on SB when vibration feedback was applied for 4 weeks.MethodsThis was a prospective, single-arm, open-label, intervention study. Ten participants diagnosed with “definite” SB wore a specially designed OA for 45 nights in a home-setting. A force-based SB detection system, including a pressure-sensitive piezoelectric film placed internally in the OA, triggered a vibrator attached to the OA. Vibratory stimulation was withheld during the first 2-week adaptation period (1st–15th nights), applied during the 4-week stimulation period (16th–43rd nights), and again withheld during the post-stimulation period (44th and 45th nights). The number and duration of SB episodes/hour of sleep were calculated based on masseter electromyographic activity recorded with in-home portable polysomnography and compared between the 15th and 45th nights (without stimulation) and the 17th and 43rd nights (with stimulation).ResultsThe number and duration of SB episodes significantly decreased after vibratory stimulation (15th vs. 17th nights: p = 0.012 and p = 0.012, respectively), then significantly increased upon cessation of vibratory stimulation after the stimulation period (43rd vs. 45th nights: p = 0.023 and p = 0.023, respectively).ConclusionContingent vibratory stimulation through an OA may suppress SB-related masticatory muscle activity continuously for 4 weeks and may be an effective alternative for the management of SB.Trial registrationhttps://jrct.niph.go.jp/; trial registration number: jRCTs032190225

Background and Objectives: Total hip arthroplasty (THA) following pelvic osteotomy for developmental dysplasia of the hip (DDH) is technically challenging due to altered acetabular morphology. This study aimed to compare radiographic cup position and perioperative characteristics of THA after three common pelvic osteotomies—periacetabular osteotomy (PAO), shelf procedure, and Chiari osteotomy—with primary THA in Crowe type I DDH. Methods: A retrospective review identified 25 hips that underwent conversion THA after pelvic osteotomy (PAO = 12, shelf = 8, Chiari = 5) and 25 primary THAs without prior osteotomy. One-to-one matching was performed based on sex (exact match), age (within 5 years), and BMI (within 2 kg/m2) without the use of propensity scores. Cup inclination, radiographic anteversion, center-edge (CE) angle, and cup height were measured on standardized anteroposterior radiographs (ICC = 0.91). Operative time, estimated blood loss, and use of bulk bone grafts or reinforcement rings were reviewed. One-way ANOVA with Dunnett’s post hoc test and chi-square test were used for statistical comparison. Results: Cup inclination, anteversion, and CE angle did not differ significantly among groups. Cup height was significantly greater in the PAO group than in controls (29.0 mm vs. 21.8 mm; p = 0.0075), indicating a more proximal hip center. The Chiari and shelf groups showed upward trends, though not significant. Mean operative time tended to be longer after PAO (123 min vs. 93 min; p = 0.078). Bulk bone grafts and reinforcement rings were more frequently required in the PAO group (17%; p = 0.036 vs. control), and occasionally in Chiari cases, but not in shelf or control groups. Conclusions: THA after PAO is associated with higher cup placement and greater need for reconstructive devices, indicating increased technical complexity. In contrast, shelf and Chiari conversions more closely resemble primary THA. Preoperative planning should consider hip center translation and bone-stock restoration in post-osteotomy THA.

Background: In this study, we aimed to investigate the association between a patient’s selection of implant treatment for a missing mandibular second molar and the magnitude of occlusal force, masticatory ability, mandibular morphology, and age before treatment intervention. Materials and Methods: We retrospectively assessed occlusal force, masticatory performance, and mandibular morphology in female patients who either selected or declined implant treatment for a missing unilateral mandibular second molar. Results: Thirty-three women (mean age of 56.1 ± 9.7 years) were divided into an implant treatment (IT) group and a no-treatment (NT) group. The IT group showed significantly higher occlusal force (p = 0.021 < 0.05), while masticatory performance and gonial angle demonstrated no significant difference. Conclusion: The IT group had significantly higher occlusal force, and age had no significant effect on it. Notably, masticatory performance in the IT group increased significantly with age (p = 0.047 < 0.05).

The objective of this study was to determine whether degradation products from spongy gelatin scaffolds can enhance angiogenesis and orthotopic bone regeneration. Spongy gelatin disks were prepared using gelatin solution concentrations ranging from 1% to 7% (v/w) within cylindrical tubes through programmed freezing, lyophilization, cutting, and dehydrothermal crosslinking and implanted in critical-sized defects of rat calvaria for up to 8 weeks. Analyses of disk implantation into rat calvaria defects by microfocus X-ray computed tomography and histomorphometry indicated that the bone volume was significantly larger in the 5% and 7% gelatin sponge groups than in the 1% and 3% gelatin sponge groups and tended to increase progressively from 5% to 7%. The histomorphometric analysis also showed that the largest number of new vessels was formed in the defect treated with 5% gelatin sponge compared to other gelatin sponges. Immunohistochemistry of matrix metalloproteinase (MMP) indicated that the gelatin concentration in the disks affected the appearance of MMP-2 and MMP-9 positive cells around the skeleton of the gelatin sponges. The degradation products of gelatin by MMP-9 and prolyl endopeptidase enhanced the formation of a capillary-like structure in human umbilical vein endothelial cells in vitro. These results suggested that the higher-density gelatin sponges tended to supply their own molecules via biodegradation, resulting in enhanced orthotopic osteogenesis through the expected function of gelatin molecules in angiogenesis and bone formation.

Background This study was performed to investigate the mid-term results of Ti-Nb-Sn (TNS) alloy stem with a low Young’s modulus. Methods This study was a multicenter prospective cohort study. A total of 40 primary total hip arthroplasties performed between April 2016 and September 2017 was enrolled in this study. With the unique functional gradient properties by heating treatment, the strength of the proximal portion was enhanced, while the distal portion maintained a low Young’s modulus. The surgeries were performed through the posterolateral approach using the TNS alloy stems. Radiographs were taken from immediately after surgeries until 3 years, and stress shielding and subsidence of the stems were evaluated. The incidences of the stem breakage were also assessed. Clinical assessments were performed using Japanese Orthopaedic Association (JOA) and Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) scores. Results Among the 40 enrolled patients, 36 patients were female and 4 were male. At 3 years after surgery, there were no radiologic signs of loosening, subsidence, or breakage of the stem. Stress shielding was observed in 26 hips (65%). Of 26 hips, 16 hips (40%) were grade 1 and 10 hips (25%) were grade 2. There was no advanced stress shielding. The JOA and JHEQ scores significantly improved compared with the preoperative scores. Conclusion The current study using a new TNS alloy femoral stem showed good clinical outcomes at 3-year follow-up. Radiologically, there was no loosening or subsidence of the stem. The mild stress shielding was observed in 65% of patients. Trial registration Current Controlled Trials ISRCTN21241251 . The date of registration was October 26, 2021. Retrospectively registered.

The microstructure of biomaterials influences the cellular and biological responses in the bone. Octacalcium phosphate (OCP) exhibits higher biodegradability and osteoconductivity than hydroxyapatite (HA) during the conversion process from OCP to HA. However, the effect of the microstructure of OCP crystals on long tubular bones has not been clarified. In this study, two types of OCPs with different microstructures, fine-OCP (F-OCP) and coarse-OCP (C-OCP), were implanted in rat tibia for 4 weeks. F-OCP promoted cortical bone regeneration compared with C-OCP. The osteoclasts appearance was significantly higher in the C-OCP group than in the control group (defect only) at 1-week post-implantation. To investigate whether the solubility equilibrium depends on the different particle sizes of OCPs, Nano-OCP, which consisted of nanometer-sized OCPs, was prepared. The degree of supersaturation (DS) tended to decrease modestly in the order of C-OCP, F-OCP, and Nano-OCP with respect to HA and OCP in Tris-HCl buffer. F-OCP showed a higher phosphate ion concentration and lower calcium ion concentration after immersion in the buffer than C-OCP. The crystal structures of both OCPs tended to be converted to HA by rat abdominal implantation. These results suggest that differences in the microstructure of OCPs may affect osteoclastogenesis and result in osteoconductivity of this material in long tubular bone by altering dissolution behavior.

Purpose To examine the effect of assistive devices on the precision of digital impression for multiple implants placed in the edentulous maxilla. Methods A 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. Results In 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). Conclusions For implants placed in an edentulous maxilla, digital impressions with assistive devices can provide better precision compared to silicone impressions and verification jigs.