Effect of Anchor-Guiding Sleeve Length on the Accuracy of Computer-Guided Flapless Implant Surgery.

The objective of this study was to evaluate the effect of anchor-guiding sleeve length on the accuracy of computer-guided flapless implant surgery in edentulous cases. Twelve identical polyurethane edentulous mandibular models were equally divided into short and long anchor-guiding sleeve groups based on the type of anchor-guiding sleeve. After implant placement and scan body connections, digital impressions were taken using the intraoral scanner. Using the software's measurement function, the deviation parameters between the planned and actual position of the placed implants were calculated and compared using the Mann-Whitney U test. In the short anchor-guiding sleeve group, the median angular deviation was 4.05° (range, 2.87°-7.55°). The median linear deviation was 1.17 mm (range, 0.24-2.17 mm) for the implant apex and 0.82 mm (range, 0.43-1.67 mm) for the implant shoulder. The median deviation of the depth was 0.31 mm (range, 0.20-0.79 mm). In the long anchor-guiding sleeve group, the median angular deviation was 2.70° (range, 1.77°-4.08°). The median linear deviation was 0.88 mm (range, 0.21-1.77 mm) for the implant apex and 0.63 mm (range, 0.11-1.97 mm) for the implant shoulder. The median deviation of the depth was 0.24 mm (range, 0.09-0.53 mm). There were significant differences between the 2 groups in the angular and linear deviations at the implant apex and the shoulder and depth deviation. The accuracy of the muco-supported surgical guide was improved using the long anchor-guiding sleeve, thus providing more accurate flapless implant placement in edentulous models. However, model experiments do not always produce predictable and possible uncontrolled cause-and-effect outcomes under natural clinical conditions. Therefore, further in vivo investigations are required to determine whether the results of this study are consistent with clinical findings.

Digital workflow for fabricating a verification device for an all-on-4 abutment: A dental technique.

The all-on-4 implant concept has been used to overcome anatomic limitations and has been reported to have high success rates. A verification device is commonly used to transfer the position of the angled distal abutment accurately. This article describes a digital workflow for fabricating a verification device to position the angled distal abutment with a hexagon connection during computer-guided flapless surgery.

Natural Bone Healing In Compromised Sockets After Tooth Extraction: Digital Measurement Methods With Cone-Beam Computed Tomography.

This study aimed to evaluate bone regeneration within infected extraction sockets with bone defects using cone-beam computed tomography (CBCT) at a 1-year follow-up after implant placement in a prosthetically driven implant position. Forty-eight patients requiring premolar or molar tooth extraction due to bone defects caused by periodontal diseases were included. Vertical and horizontal bone volumes were assessed by overlapping the CBCT scan images with the full digital process. At 1-year post-extraction, a prosthetically-driven implant was planned using virtual implant planning software. At 1 year after extraction, CBCT revealed significant horizontal and vertical bone gains; an overall mean buccolingual bone width gain of 5.46 ± 2.87 mm, and an overall mean vertical bone gain of 0.27 ± 1.28 mm for the lingual bone plate level and 3.50 ± 1.81 mm for the buccal bone plate level were observed. Except for 4 (out of 48) sites, implants were virtually positioned in the center of the edentulous spaces. In summary, despite the dimensional changes after tooth extraction in compromised posterior sockets, there was sufficient bone for placing an implant using the prosthetically driven approach.

Effects of different surface finishing protocols for zirconia on surface roughness and bacterial biofilm formation.

PURPOSE: Surface finishing of a zirconia restoration is essential after clinical adjustment. Herein, we investigated the effects of a surface finishing protocol for monolithic zirconia on final roughness and bacterial adherence. MATERIALS AND METHODS: Forty-eight disk-shaped monolithic zirconia specimens were fabricated and divided into four groups (n = 12) based on initial surface treatment, finishing, and polishing protocols: diamond bur+polishing bur (DP group), diamond bur+stone grinding bur+polishing bur (DSP group), no diamond bur+polishing bur (NP group), and no diamond bur+stone grinding bur+polishing bur (NSP group). Initial and final surface roughness was measured with a profilometer, and shown using scanning electron microscope. Bacterial adhesion was evaluated by quantifying Streptococcus mutans in the biofilm. Kruskal-Wallis and Mann-Whitney U tests were used to compare results among groups, and two-way analysis of variance was used to evaluate the effects of grinding burs on final roughness (α=.05). RESULTS: The DP group had the highest final Ra value, followed by the DSP, NP, and NSP groups. Use of the stone grinding bur as a coarse-finishing step significantly decreased final Ra values when a diamond bur was used (P<.001). Omission of the stone grinding bur increased biofilm formation on specimen surfaces. Combining a stone grinding bur with silicone polishing burs produced the smallest final biofilm values, regardless of the use of a diamond bur in initial surface treatment. CONCLUSION: Coarse finishing of monolithic zirconia with a stone grinding bur significantly decreased final Ra values and bacterial biofilm formation when surfaces had been roughened by a diamond bur.

Accuracy of computer-guided implant placement in anterior regions.

STATEMENT OF PROBLEM: Implant placement in the anterior regions is often challenging because of limited space and bone volume availability. PURPOSE: The purpose of this clinical study was to investigate the accuracy of computer-guided surgery with a long drill key to place implants in the anterior regions. MATERIAL AND METHODS: Computer-guided implant surgery was performed for 32 participants requiring implants in anterior regions. The procedure involved using a 12-mm-long drill key to guide the 2.0-mm-diameter drill. Deviations between the planned and actual implant positions were evaluated by using cone beam computed tomography (CBCT) scans obtained before and after surgery. A t test was used for comparisons between the planned and placed implants and to determine the influence of the arch (maxilla/mandible) and time (immediate/delayed) on accuracy. RESULTS: A total of 40 implants (20 implants in the maxilla and 20 implants in the mandible) were placed. The mean linear deviation was 0.46 mm (range, 0 to 1.15 mm) for the implant shoulder and 0.67 mm (range, 0.14 to 1.19 mm) for the implant apex. The mean angular deviation was 1.40 degrees (range, 0.30 to 2.57 degrees). The mean depth deviation was 0.15 mm (range, 0.10 to 0.82 mm). CONCLUSIONS: This clinical study showed that the accuracy of computer-guided implant placement may be enhanced by using a long drill key and may thus enable more accurate implant placement in anterior regions.

A Technique for Digital Impression and Bite Registration for a Single Edentulous Arch.

Few studies have reported the application of digital technology for the process of impression and interocclusal recordings in edentulous patients. This article describes a digitizing system for generating digital edentulous models with a jaw relationship by taking direct digital impressions and a virtual bite registration using intraoral digital scanning. A specialized scan retractor was used to make digital impressions of edentulous jaws in patients' mouths using an intraoral scanner. Virtual bite registration was obtained with optical scanning of the buccal surfaces of both jaws at the occlusal vertical dimension. The registration was then used as a reference for aligning both jaws. Digital edentulous models that include the jaw relationship would be clinically beneficial for the fabrication of complete dentures in edentulous patients.

A digital technique for fabricating an interim implant-supported fixed prosthesis immediately after implant placement in patients with complete edentulism.

The conversion of a denture into an interim implant-supported, screw-retained restoration has become the standard method for immediate interim restoration in patients with complete edentulism. The most critical steps of the denture conversion process are the creation of appropriate denture access holes to prevent displacement of the denture by the interim cylinders and removal of the denture flanges to facilitate both good esthetics and accessibility for oral hygiene after the denture is connected to the interim cylinders. This article presents a digital technique for designing and fabricating an interim implant-supported, fixed prosthesis for edentulous patients. The interim prosthesis has cylinder access holes that are digitally prefabricated and a denture flange part that is designed to be easily sectioned. This technique facilitates more straightforward and efficient immediate restoration for edentulous patients after implant placement.

Crestal Sinus Augmentation in the Presence of Severe Sinus Mucosal Thickening: A Report of 3 Cases.

PURPOSE: In the presence of severe sinus mucosal thickening, the ostium can be blocked when the sinus membrane is lifted, causing drainage disturbances and sinusitis. Here, we present 3 cases in which maxillary sinus floor elevation was performed using a crestal approach in the presence of severe sinus mucosal thickening (>10 mm). MATERIALS AND METHODS: The effects of maxillary sinus floor elevation using the crestal approach technique on sinus mucosal thickening and bone formation in the sinus were evaluated using cone beam computed tomography. RESULTS: None of the patients exhibited an increase in sinus membrane thickness. No complications were encountered during the follow-up periods, and bone formation was observed around the implants at the sinus floor. All implants were functioning successfully. CONCLUSIONS: Maxillary sinus floor elevation using the crestal approach technique in the presence of severe sinus mucosal thickening allows for minimally invasive sinus grafting and simultaneous implant placement and does not increase sinus membrane thickness.

A CAD-CAM technique for conversion of interim-to-definitive restoration in patients with complete edentulism.

An interim restoration is a prototype for the definitive prosthesis and preserves the occlusal information and the original vertical dimension of the occlusion. Several techniques have been developed to transfer the information from implant-supported fixed interim to definitive restoration. However, these conventional techniques have limitations, and they are time-consuming, require making impressions and stone casts, and mounting in an articulator. The purpose of this article was to describe a digital technique to accurately transfer the information from complete-arch implant interim restoration to definitive restorations without using definitive casts.

Digital immediate denture: A clinical report.

Fabricating an immediate complete denture in the conventional manner may be complicated and difficult. The purpose of this article was to describe a fully digital workflow used to fabricate an immediate complete denture before removing the teeth and without the use of conventional impressions or stone casts. The digital data for the workflow were acquired using an intraoral scanner and were then used to design the denture base and teeth after deleting any remaining tooth images from the virtual 3-dimensional image of the jaw. The resulting data were exported to a milling machine for denture fabrication.

Digital intraoral scanning technique for edentulous jaws.

Few studies have evaluated direct digital scans of edentulous jaws using intraoral scanners because it is difficult to scan edentulous sites that are smooth and devoid of features. A scanning technique is introduced for making direct digital scans of edentulous jaws with intraoral scanners in patients with a broad palate.

Development of complete dentures based on digital intraoral impressions-Case report.

PATIENT: A 60-year-old man presented for refabrication of his maxillary complete denture. In this case, a digital process was chosen to replace the ill-fitted complete maxillary denture. A specialized scan retractor was used to retract the mobile tissues of the lips, cheeks and vestibule while taking a digital impression. The interocclusal record obtained in the patient's mouth was scanned in order to digitally register the occlusal vertical dimension. The denture base and teeth were designed on virtual models that were mounted at the occlusal vertical dimension, and were made using CAD/CAM technology. DISCUSSION: Unlike conventional impression techniques, intraoral scanning is not able to be performed while the tissue is moving. This case report used a scan retractor that facilitated stretching and fixation of the vestibular area. It also helped to retract the lips and cheeks. This report also demonstrates that virtual models at OVD can be obtained without the use of conventional stone models, flasking or processing techniques. One of the main shortcomings in the existing CAD/CAM denture fabrication technology is that it is not able to produce customized denture teeth. The present article demonstrates that the digital denture fabrication workflow can provide customized denture teeth to optimize occlusion. CONCLUSION: This case demonstrated how digital complete dentures can be made without requiring conventional stone models or mounting the models in an articulator.

Verification of a computer-aided replica technique for evaluating prosthesis adaptation using statistical agreement analysis.

PURPOSE: The purpose of this study was to evaluate the reliability of computer-aided replica technique (CART) by calculating its agreement with the replica technique (RT), using statistical agreement analysis. MATERIALS AND METHODS: A prepared metal die and a metal crown were fabricated. The gap between the restoration and abutment was replicated using silicone indicator paste (n = 25). Gap measurements differed in the control (RT) and experimental (CART) groups. In the RT group, the silicone replica was manually sectioned, and the marginal and occlusal gaps were measured using a microscope. In the CART group, the gap was digitized using optical scanning and image superimposition, and the gaps were measured using a software program. The agreement between the measurement techniques was evaluated by using the 95% Bland-Altman limits of agreement and concordance correlation coefficients (CCC). The least acceptable CCC was 0.90. RESULTS: The RT and CART groups showed linear association, with a strong positive correlation in gap measurements, but without significant differences. The 95% limits of agreement between the paired gap measurements were 3.84% and 7.08% of the mean. The lower 95% confidence limits of CCC were 0.9676 and 0.9188 for the marginal and occlusal gap measurements, respectively, and the values were greater than the allowed limit. CONCLUSION: The CART is a reliable digital approach for evaluating the fit accuracy of fixed dental prostheses.

Crestal Sinus Augmentation in the Presence of an Antral Pseudocyst.

PURPOSE: Antral pseudocysts classically have a well-defined, hyperdense, unilocular, dome-shaped appearance in radiographs. The best therapeutic approach for treating these cysts in the context of sinus floor augmentation remains controversial. This article presents a new technique that allows both sinus membrane elevation and cyst removal through a crestal approach in patients with pseudocysts in the maxillary sinus. MATERIALS AND METHODS: The technique combined aspiration of the cysts during sinus floor elevation with a sinus augmentation procedure using a hydraulic sinus elevation system. Aspiration of the cyst fluid was performed through the crestal osteotomy site after sinus floor elevation. RESULTS: Two patients showed a significant amount of bone formation around the implant at the sinus floor without evidence of a recurrent cyst after the procedure. CONCLUSIONS: The technique allows the minimally invasive removal of antral pseudocysts at the time of sinus grafting and simultaneous implant placement, preserving the integrity of the sinus membrane.

Digital Workflow for Computer-Guided Implant Surgery in Edentulous Patients: A Case Report.

PURPOSE: The purpose of this article was to describe a fully digital workflow used to perform computer-guided flapless implant placement in an edentulous patient without the use of conventional impressions, models, or a radiographic guide. MATERIALS AND METHODS: Digital data for the workflow were acquired using an intraoral scanner and cone-beam computed tomography (CBCT). The image fusion of the intraoral scan data and CBCT data was performed by matching resin markers placed in the patient's mouth. RESULTS: The definitive digital data were used to design a prosthetically driven implant position, surgical template, and computer-aided design and computer-aided manufacturing fabricated fixed dental prosthesis. CONCLUSION: The authors believe this is the first published case describing such a technique in computer-guided flapless implant surgery for edentulous patients.

The effect of low-speed drilling without irrigation on heat generation: an experimental study.

OBJECTIVES: In this study we evaluated heat generation during the low-speed drilling procedure without irrigation. MATERIALS AND METHODS: Ten artificial bone blocks that were similar to human D1 bone were used in this study. The baseline temperature was 37.0℃. We drilled into 5 artificial bone blocks 60 times at the speed of 50 rpm without irrigation. As a control group, we drilled into an additional 5 artificial bone blocks 60 times at the speed of 1,500 rpm with irrigation. The temperature changes during diameter 2 mm drilling were measured using thermocouples. RESULTS: The mean maximum temperatures during drilling were 40.9℃ in the test group and 39.7℃ in the control group. Even though a statistically significant difference existed between the two groups, the low-speed drilling did not produce overheating. CONCLUSION: These findings suggest that low-speed drilling without irrigation may not lead to overheating during drilling.

Vertical ridge augmentation using xenogenous bone blocks: a comparison between the flap and tunneling procedures.

PURPOSE: Previous studies have shown that the subperiosteal tunneling procedure in vertical ridge augmentation accelerates healing after grafting and prevents graft exposure, with minor postoperative complications. It is conceivable that new bone formation would be greater with the tunneling procedure than with the flap procedure, because the former is minimally invasive. This hypothesis was tested in this study by comparing new bone formation between the flap and tunneling procedures after vertical ridge augmentation using xenogenous bone blocks in a canine mandible model. MATERIALS AND METHODS: Two Bio-Oss blocks were placed on the edentulous ridge in each side of the mandibles of 6 mongrel dogs. The blocks in each side were randomly assigned to grafting with a flap procedure (flap group) or grafting with a tunneling procedure (tunneling group). RESULTS: The mean percentage of newly formed bone within the block was 15.3 ± 6.6% in the flap group and 46.6 ± 23.4% in the tunneling group. CONCLUSION: Based on data presented in this study, when a tunneling procedure is used to place xenogenous bone blocks for vertical ridge augmentation, bone formation in the graft sites is significantly greater than when a flap procedure is used.

Simultaneous sinus lift and implantation using platelet-rich fibrin as sole grafting material.

Recently, several authors have shown that simultaneous sinus lift and implantation using autologous platelet-rich fibrin as the sole filling material is a reliable procedure promoting bone augmentation in the maxillary sinus. The aim of this study was to examine the effect of simultaneous sinus lift and implantation using platelet-rich fibrin as the sole grafting material on bone formation in a canine sinus model. An implant was placed after sinus membrane elevation in the maxillary sinus of six adult female mongrel dogs. The resulting space between the membrane and sinus floor was filled with autologous platelet-rich fibrin retrieved from each dog. The implants were left in place for six months. Bone tissue was seen at the lower part of the implants introduced into the sinus cavity. The height of the newly formed bone around the implants ranged from 0 mm to 4.9 mm (mean; 2.6 ± 2.0 mm) on the buccal side and from 0 mm to 4.2 mm (mean; 1.3 ± 1.8 mm) on the palatal side. The findings from this study suggest that simultaneous sinus lift and implantation using platelet-rich fibrin as sole grafting material is not a predictable and reproducible procedure, especially with respect to the bone formation around the implants in the sinus cavity.

Soluble expression and partial purification of recombinant human erythropoietin from E. coli.

Human erythropoietin (hEpo) is an essential regulator of erythrocyte production that induces the division and differentiation of erythroid progenitor cells in the bone marrow into mature erythrocytes. It is widely used for the treatment of anemia resulting from chronic kidney disease, chemotherapy, and cancer-related therapies. Active hEpo, and hEpo analogs, have been purified primarily from mammalian cells, which has several disadvantages, including low yields and high production costs. Although an Escherichia coli (E. coli) expression system may provide economic production of therapeutic proteins, it has not been used for the production of recombinant hEpo (rhEpo) because it aggregates in inclusion bodies in the E. coli cytoplasm and is not modified post-translationally. We investigated the soluble overexpression of active rhEpo with various protein tags in E. coli, and found out that several tags increased the solubility of rhEpo. Among them maltose binding protein (MBP)-tagged rhEpo was purified using affinity and gel filtration columns. Non-denaturing electrophoresis and MALDI-TOF MS analysis demonstrated that the purified rhEpo had two intra-disulfide bonds identical to those of the native hEpo. An in vitro proliferation assay showed that rhEpo purified from E. coli had similar biological activity as rhEpo derived from CHO cells. Therefore, we report for the first time that active rhEpo was overexpressed as a soluble form in the cytoplasm of E. coli and purified it in simple purification steps. We hope that our results offer opportunities for progress in rhEpo therapeutics.

The effect of guided flapless implant procedure on heat generation from implant drilling.

The objective of this study was to evaluate the heat generation in vitro during the flapless drilling procedure using surgical drill guides. Ten resin models with bilateral edentulous tooth spaces in the first and second molars in the mandible were used in this study. On one side of the mandible, drilling was performed with a flapless approach using a surgical drill guide. On the other side of the mandible, drilling was performed with a flap approach. The temperature changes were measured during final drilling by thermocouples. The mean maximum temperatures during drilling with guided flapless procedures were 29.5 °C and 32.6 °C at the depths of 3 and 6 mm, respectively, whereas for flap procedures they were 29.4 °C and 31.3 °C. There was no statistically significant difference between the groups. These findings suggest that drilling with external irrigation in an up-and-down pumping motion may not lead to a significant increase the bone temperature during a flapless procedure using surgical drill guides.