[Research of implant accuracy using a digital registration method].

PURPOSE: The aim of this study was to introduce a new method to evaluate the clinical accuracy of implant position. The results were compared to traditional cone beam CT (CBCT) method. METHODS: A total of 36 implants from 24 patients with sufficient bone volume were enrolled into the study. CBCT method and digital registration method were compared to evaluate the accuracy of implant position. The measurement parameters were defined as deviations between ideal and postsurgical implant position at occlusal point(d1), apical point(d2) and axis(α). The deviations between two methods were analyzed with SPSS 19.0 software package. RESULTS: The deviations between ideal and postsurgical implant position using CBCT were (0.88±0.64) mm for occlusal point, (1.07±0.85) mm for apical point and (4.74±2.35)° for angle. In digital registration method, the deviations were (0.86±0.67) mm for occlusal point, (1.12±0.88) mm for apical point and (4.56±2.66)° for angle. No significant difference(P＞0.05) was found between the two methods. CONCLUSIONS: There was no significant difference between the two methods in evaluating the clinical accuracy of implant position. Digital registration method could be accepted in clinical application.

[Accuracy evaluation of static guided implant placement using an intraoral scan method].

PURPOSE: To evaluate the accuracy of static guided implant placement with intraoral scanning technology and to analyze the influencing factors of guided surgery. METHODS: Totally 27 cases were included in this retrospective study. The implant designs were made in 3Shape Implant Studio and then guided implant surgeries were performed with CAD-CAM templates. Postoperative implant positions were detected with an intraoral scanner (3Shape TRIOS) and deviation of implantation was evaluated using established CAD/CAM based evaluation method. SAS 9.4 software package was used for data analysis. RESULTS: The mean deviation of entrance point and apical point was (1.182±0.609) mm and (1.658±0.741) mm, respectively. Angular deviation was (5.712±3.347)°. Implant quadrant, location of the implant site, guidance degree, supporting type and implant size influenced direction deviation, while angular deviation was mainly affected by guidance degree and number of missing teeth. CONCLUSIONS: Accuracy of static guided implant placement can be influenced by many factors. More research is needed to improve the accuracy of static guided implantation.

[Nonradiological methods for implant surgical guide accuracy measurement].

PURPOSE: To evaluate the accuracy of static computer-navigated implantation with surgical guides, based on a non-radiological method. Traditional measurements with a second cone-beam CT (CBCT) were applied to verify the accuracy. METHODS: A total of thirty template-guided implantations were designed and performed on 15 resin models. Two paralleled bone-level implants were planned in the edentulous space of each model, between which the distance was 4 mm. Postoperative implant positions were detected with both CAD/CAM-based measurements applying an intraoral scanner (3Shape TRIOS) and traditional ways via CBCT. Both methods were conducted with a CAD quality-control, reverse engineering software, Geomagic Studio 2013, comparing the positions with the virtual ones. Statistical analysis was processed with SPSS 23.0 software package. RESULTS: Measurements using CBCT (control group) showed a trend toward greater deviations when the results were directly compared(P<0.05). In the CAD/CAM-based evaluation of the 30 samples, the mean deviation of the insertion axis from the planned implant axis was 1.134°. The mean deviations of the implant shoulders in the horizontal direction and at the implant apices were 0.447 mm and 0.557 mm, respectively. No significant difference was observed when measuring distance deviation with the two assessment ways. CONCLUSIONS: Compared with evaluation based on radiology, CAD/CAM based evaluation system is able to evaluate implant accuracy precisely, effectively reduce radiological exposure of patients, being suitable for clinical evaluation.

Osteogenic Induction of Low-dose Ipriflavone on Bone Marrow Mesenchymal Stem Cells Extracted from Osteoporosis Rats.

OBJECTIVE: To investigate the effects of ipriflavone (IPF), a synthetic isoflavone plant oestrogen with a structure similar to that of oestradiol, on the osteogenic differentiation of bone mesenchymal stem cells (BMSCs). METHODS: BMSCs were derived from ovariectomised rats (rBMSCs-OVX) and then induced with or without IPF. Cell cytotoxicity, mineralisation in vitro and osteoblast-specific gene expression of BMSCs were studied. RESULTS: IPF at a concentration of 10-8, 10-7 and 10-6 mol/l exhibited no cytotoxic effect on the proliferation of BMSCs but increased alkaline phosphatase activity and osteoblast-specific gene expression. CONCLUSION: IPF enhances osteogenic differentiation of rBMSCs-OVX partly in vitro, thus its use offers a potential strategy for the treatment of osteoporosis.

[Establishment of traumatic occlusion model in Sprague-Dawley rats].

PURPOSE: In this study, different methods were used to observe and obtain the most effective one to establish occlusal trauma model in Sprague-Dawley rats. METHODS: SPF male SD rats weighing 150~200 g and aged 10 to 12 weeks were used in this study. The rats' maxillary molars were bonded with stainless steel wire, resin , casting half crown , casting half combined crowns, half crown using selective laser melting (SLM) technology, half combined crowns using SLM technology through Super-bond and Multi-link bonding under general anesthesia. After bonding, the experimental device expulsion rates were observed daily. The data was analyzed statistically using Fisher's exact test with SAS 8.2 software package. RESULTS: There was no significant difference between the falling rates of using super-bond and using multi-link. Under the situation in which different bonding methods exerted no influence on the falling rates, there was significant difference between different experimental devices (P<0.0001). CONCLUSIONS: The restorations fabricated with SLM technology is valid and feasible to induce occlusal point in building occlusal trama model using SD rats.

An Analysis of the Proximity of Maxillary Posterior Teeth to the Maxillary Sinus Using Cone-beam Computed Tomography.

INTRODUCTION: It is known that the level of the maxillary sinus floor varies with age. Because few studies have investigated whether the position of the posterior roots relative to the maxillary sinus varied with the variation of the sinus floor or not, the present study assessed the position according to age. METHODS: Cone-beam computed tomographic images of 848 patients were reconstructed to evaluate the position of the posterior roots relative to the sinus floor, which were divided into 3 types, and quantify the distances between posterior root apexes and the adjacent border of the sinus floor. Measurements were taken for each root, and data were correlated with age, which was divided into 4 groups (≤20 years, 21-40 years, 41-60 years, and >60 years). RESULTS: A total of 3063 premolars and 3095 molars were evaluated. The mean distances from the root tips to the border of the maxillary sinus floor increased with increasing age. From the first and second premolar roots, the mean distances ranged from 3.6 ± 4.1 mm to 8.9 ± 4.6 mm and from 0.7 ± 3.3 mm to 5.3 ± 3.9 mm, respectively. From the mesiobuccal, distobuccal, and palatinal roots of the first molars, the mean distances were -0.4 ± 2.8 mm to 4.6 ± 4.0 mm, -0.3 ± 2.4 mm to 4.4 ± 3.8 mm, and -0.4 ± 3.5 mm to 3.9 ± 4.1 mm, respectively. From the mesiobuccal, distobuccal, and palatinal roots of the second molars, the mean distances were -0.5 ± 2.2 mm to 3.4 ± 3.5 mm, 0.3 ± 2.2 mm to 3.9 ± 3.7 mm, and 1.1 ± 3.2 mm to 4.6 ± 4.5 mm, respectively. The frequency of type IS decreased with increasing age. It was very low in first premolars (0%-8.13%) and higher in second premolars (0%-25.68%), first molars (0%-44.75%), and second molars (0%-32.89%). Age significantly influenced the mean distances to the sinus floor and the frequencies of type IS (inside). CONCLUSIONS: Cone-beam computed tomographic imaging is an effective method to study the position of the posterior roots to the maxillary sinus floor. Variation in proximity measurements was found by age, with those under the age of 40 showing a greater likelihood of the position of maxillary roots above/inside the sinus floor.

Effects of multiple firings on metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting.

STATEMENT OF PROBLEM: Selective laser melting (SLM) is a new technique for fabricating dental restorations, but the metal-ceramic bond strength of the restorations after multiple firings must be considered because adequate bond strength is a clinical requirement for long-term performance. PURPOSE: The purpose of this study was to investigate the effects of repeated firing on the metal-ceramic bond strength of an SLM Co-Cr alloy. MATERIAL AND METHODS: Thirty-six SLM-fabricated (Group SLM) and conventional lost wax cast (Group Cast) Co-Cr metal bars were prepared. Eighteen bars from each group were molded into dimensions of 25×3×0.5 mm, following International Organization for Standardization (ISO) standard 9693:2012. In the center of each bar, a 1.1-mm thickness of porcelain was fused onto an 8×3-mm rectangular area. In each group, specimens were divided into 3 subgroups based on the number of firing cycles (3, 5, 7) for the veneering process. Metal-ceramic bond strength, fracture mode analysis, and area fraction of adherence porcelain (AFAP) of each subgroup was evaluated with a 3-point bend test and by measuring the Si content of specimens with scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The results were statistically analyzed first with the Shapiro-Wilk test, where a P value of .364 was considered normally distributed, and then with the Student t test to determine significant differences (α=.05). RESULTS: Student t test results showed no statistical differences between the metal-ceramic bond strength of SLM and that of conventionally cast groups after firing 3, 5, and 7 times (P>.05). However, after SEM/EDS analyses, the SLM group showed significantly more porcelain adherence than that of the control group (P<.05) after 5 or 7 firings. CONCLUSIONS: The SLM group showed superior metal-ceramic bond strength that exceeded ISO 9691:1999 (E) requirements at all firing periods. Also, the bond showed better behavior in terms of AFAP than the conventional cast group, especially after 5 or 7 firings.

Surface properties and corrosion behavior of Co-Cr alloy fabricated with selective laser melting technique.

We sought to study the corrosion behavior and surface properties of a commercial cobalt-chromium (Co-Cr) alloy which was fabricated with selective laser melting (SLM) technique. For this purpose, specimens were fabricated using different techniques, such as SLM system and casting methods. Surface hardness testing, microstructure observation, surface analysis using X-ray photoelectron spectroscopy (XPS) and electrochemical corrosion test were carried out to evaluate the corrosion properties and surface properties of the specimens. We found that microstructure of SLM specimens was more homogeneous than that of cast specimens. The mean surface hardness values of SLM and cast specimens were 458.3 and 384.8, respectively; SLM specimens showed higher values than cast ones in hardness. Both specimens exhibited no differences in their electrochemical corrosion properties in the artificial saliva through potentiodynamic curves and EIS, and no significant difference via XPS. Therefore, we concluded that within the scope of this study, SLM-fabricated restorations revealed good surface properties, such as proper hardness, homogeneous microstructure, and also showed sufficient corrosion resistance which could meet the needs of dental clinics.

Metal-ceramic bond strength of Co-Cr alloy fabricated by selective laser melting.

OBJECTIVES: This study was to evaluated the metal-ceramic bond strength of a Co-Cr dental alloy prepared using a selective laser melting (SLM) technique. METHODS: Two groups comprised of twenty Co-Cr metal bars each were prepared using either a SLM or traditional lost-wax casting method. Ten bars from each group were moulded into standard ISO 9693:1999 dimensions of 25 mm × 3 mm × 0.5 mm with 1.1 mm of porcelain fused onto an 8 mm × 3 mm rectangular area in the centre of each bar. Metal-ceramic bonding was assessed using a three-point bending test. Fracture mode analysis and area fraction of adherence porcelain (AFAP) were determined by measuring Si content of specimens by SEM/EDS. RESULTS: Student's t-test within the groups demonstrated no significant difference for the mean bond strength between the SLM and traditional cast sample groups. While SEM/EDS analysis indicated a mixed fracture mode on the debonding interface of both the SLM and the cast groups, the SLM group showed significantly more porcelain adherence than the control group (p<0.05). CONCLUSIONS: The SLM metal-ceramic system exhibited a bonding strength that exceeds the requirement of ISO 9691:1999(E) and it even showed a better behaviour in porcelain adherence test comparable to traditional cast methods.

[Clinical application of reverse island flap based on tibial planter digital artery].

OBJECTIVE: To study the therapeutic effect of reverse island flap based on tibial plantar digital artery for soft tissue defect at the distal end of first toe. METHODS: 18 cases with soft tissue defect at the distal end of first toe were treated with reverse island flap based on tibial plantar digital artery. RESULTS: The patients were followed up for 6 to approximately 12 months (mean 9.5 months). All the flaps survived completely with good functional and cosmetic results. CONCLUSIONS: The reversed island flap based on tibial plantar digital artery has a reliable blood supply and is adjacent to the recipient area. It is practical and suitable for soft tissue defect at the distal end of first toe.