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.

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 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.

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.

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.

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.

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.

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.

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.

Minimally invasive ridge augmentation using xenogenous bone blocks in an atrophied posterior mandible: a clinical and histological study.

PURPOSE: Although various techniques for the treatment of an atrophic alveolar ridge have been described in the literature, these procedures have increased the morbidity and discomfort for the patient. The purpose of this study was to evaluate histological and clinical results in 9 patients who underwent a subperiosteal tunneling procedure with a Bio-Oss block onlay graft in an atrophic area of the mandible. PATIENTS AND METHODS: Nine months after grafting, at the time of dental implantation, biopsy samples were taken from the grafted areas of 9 patients and were analyzed histologically. RESULTS: New bone formation through the bovine bone block was observed consistently in the 9 cases. There was direct deposition of bone on the surface of the graft material. CONCLUSION: The results of this study indicated that ridge augmentation using a subperiosteal tunneling procedure with Bio-Oss bone blocks might be useful for implant placement in the atrophic alveolar ridges.

The use of autologous venous blood for maxillary sinus floor augmentation in conjunction with sinus membrane elevation: an experimental study.

BACKGROUND: There have been reports of successful bone formation with sinus floor elevation induced by simply elevating the maxillary sinus membrane and filling the sinus cavity with a blood clot. PURPOSE: We investigated the feasibility of maxillary sinus floor augmentation using the patient's own venous blood in conjunction with a sinus membrane elevation procedure. MATERIALS AND METHODS: An implant that protruded 8 mm into the maxillary sinus after sinus membrane elevation was placed in the maxillary sinus of six adult female mongrel dogs. The resulting space between the membrane and the sinus floor was filled with autologous venous blood retrieved from each dog. The implants were left in place for 6 months. RESULTS: During the experimental period, the created space collapsed and the sinus membrane fell down onto the implant. A small amount of new bone formation occurred in the space created by the collapsed membrane. The average height of newly formed bone around the implants in the sinus was 2.7+/-0.7 mm on the buccal side and 0.6+/-0.3 mm on the palatal side. CONCLUSION: The results of this pilot study indicate that blood clots do not have sufficient integrity to enable the sinus membrane to remain in an elevated position for therapeutically effective periods of time. Accordingly, it is recommended that this method be used only when a small amount of new bone formation is necessary around implants in the maxillary sinus cavity.

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.

Simultaneous flapless implant placement and peri-implant defect correction: an experimental pilot study in dogs.

BACKGROUND: Minimally invasive implant surgery allows clinicians to place implants in less time, without extensive flaps, and with less bleeding and postoperative discomfort. The purpose of this study was to evaluate a new surgical technique by which implants are inserted in a deficient alveolar ridge using a flapless technique simultaneously with a peri-implant defect correction that is performed using a subperiosteal tunneling procedure. METHODS: Bilateral, horizontal defects of the alveolar ridge were created in the mandibles of five mongrel dogs. After 3 months of healing, one implant was placed on each side of the mandible by a flapless procedure. The exposed threads of the implant on one side of the mandible were covered with a 1:1 autogenous bone/xenograft mixture using a subperiosteal tunneling technique. Four months later, biopsies of the implant sites were taken and prepared for ground sectioning and analysis. RESULTS: All implants were well osseointegrated with the host bone. All of the peri-implant defects at the test sites were covered with tissue that resembled bone. In all specimens, a mixture of bone, connective tissue, and residual bone particles was observed in the graft area. In the control sites, where no graft was used, none of the exposed threads on any implants were covered with new bone. CONCLUSION: This preliminary report indicates the potential use of a minimally invasive flapless technique as a substitute for a more invasive implant placement and ridge augmentation procedure.

The effect of thick mucosa on peri-implant tissues: an experimental study in dogs.

BACKGROUND: Findings from animal studies have indicated that the implant-mucosal barrier consists of a junctional epithelium approximately 2 mm long and a connective tissue compartment about 1 to 1.5 mm high. It may be argued that different features develop in the implant-mucosal barrier when it is placed within the alveolar bone with thick mucosa. The aim of this study was to examine the influence of a thick mucosa on peri-implant tissue healing around dental implants. METHODS: The bilateral fourth mandibular premolars and all maxillary premolars were removed in six mongrel dogs. On one side (test side) of the mandible, a standardized bone defect (8.0 mm in height) was created in the premolar region, whereas no defect was created on the other side (control side). After 3 months of healing, one implant was placed on each side of the mandible; a long abutment (12 mm in height) was connected to the fixture on the bone defect side, whereas a normal abutment was connected to the fixture on the control side. After a healing period of 6 months, all dogs were sacrificed to evaluate peri-implant tissues. RESULTS: The height of the mucosa, the length of the junctional epithelium, and the height of the zone of connective tissue integration were significantly greater in the thick mucosa than in the normal mucosa (P <0.05). No significant difference was found between the control and test sides in the marginal level of bone-to-implant contact. CONCLUSIONS: The junctional epithelium extended more apically in the thick mucosa than in the normal mucosa. However, additional marginal bone resorption was not observed at the thick mucosa sites.

Influence of abutment connections and plaque control on the initial healing of prematurely exposed implants: an experimental study in dogs.

BACKGROUND: Spontaneous early implant exposure is believed to be harmful, resulting in early crestal bone loss around submerged implants. The purpose of this study was to examine the influence of abutment connections and plaque control on the initial healing of prematurely exposed implants in the canine mandible. METHODS: Bilateral, edentulated, flat alveolar ridges were created in the mandible of 10 mongrel dogs. After 3 months of healing, two implants were placed on each side of the mandible following a commonly used two-stage surgical protocol. Implants on each side were randomly assigned to one of two procedures: 1) connection of a cover screw to the implant and removal of the gingiva to expose the cover screw; and 2) connection of a healing abutment to the implant so that the coronal portion of the abutment remained exposed to the oral cavity. In five dogs (plaque control group), meticulous plaque control was performed. In the other five dogs (no plaque control group), plaque was allowed to accumulate. At 8 weeks post-implantation, microcomputed tomography was performed at the implantation site to measure bone height in the peri-implant bone. RESULTS: The plaque control group had greater vertical alveolar ridge height (9.7 +/- 0.5 mm) than the group without plaque control (7.4 +/- 0.7 mm; P <0.05). In the plaque control group, the average bone height was greater with the abutment-connected implant (10.1 +/- 0.5 mm) than with the partially exposed implant (9.3 +/- 0.5 mm; P <0.05). In the group without plaque control, the average bone height was greater with the partially exposed implant (8.2 +/- 0.6 mm) than with the abutment-connected implant (6.5 +/- 0.7 mm; P <0.05). CONCLUSION: These results suggest that the placement of healing abutments and meticulous plaque control may limit bone loss around submerged implants when implants are partially exposed.