• Journal of Dental Rehabilitation and Applied Science
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• v.20 no.2
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• pp.83-94
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• 2004

The purpose of this study was to compare the distributing pattern of stress according to the types of occlusal load on the finite element models of the splinted implant prostheses. The finite element model was designed with the parallel placement of two fixtures ($4.0mm{\times}11.5mm$) on mandibular first and second molars. The cemented crowns for mandibular first and second molars were made. Three-dimensional finite element model was created with the components of the implant, surrounding bone and cemented crowns. Two types of occlusal load, the point load and the surface load within 0.5 mm radius circle, were applied to the finite element models with 200N magnitude in axial(along the long axis of the implant and oblique(angulation of $30^{\circ}$ to the long axis) directions perpendicular to cuspal incline. Loads were positioned from the center of central fossa and to distance of 2 mm and 4 mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the fixtures and sections. The results were as following : 1. Under axial loading at the central fossa, the stress was distributed along the fixture except for the apical portion, not relative to both point & surface contacts. 2. With offset distance increasing, the highest stresses were concentrated in the neck portion of the fixture. 3. The maximum von Mises stress under the oblique load was greater than that under the axial load. 4. Under the oblique load, the highest stress were concentrated in the buccal side and lingual neck portion of the fixture with offset distance increasing. The results had a tendency to increase the stress on the neck portion of fixture with the offset and oblique loads increasing. The design of occlusal scheme should be allowed to distribute stress axially in maximum intercuspation and to decrease the angulation of cuspal incline.

• Journal of Periodontal and Implant Science
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• v.46 no.4
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• pp.254-265
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• 2016

Purpose: The aim of this study was to determine the influence of anatomical conditions on primary stability in the models simulating posterior maxilla. Methods: Polyurethane blocks were designed to simulate monocortical (M) and bicortical (B) conditions. Each condition had four subgroups measuring 3 mm (M3, B3), 5 mm (M5, B5), 8 mm (M8, B8), and 12 mm (M12, B12) in residual bone height (RBH). After implant placement, the implant stability quotient (ISQ), Periotest value (PTV), insertion torque (IT), and reverse torque (RT) were measured. Two-factor ANOVA (two cortical conditions${\times}$four RBHs) and additional analyses for simple main effects were performed. Results: A significant interaction between cortical condition and RBH was demonstrated for all methods measuring stability with two-factor ANOVA. In the analyses for simple main effects, ISQ and PTV were statistically higher in the bicortical groups than the corresponding monocortical groups, respectively. In the monocortical group, ISQ and PTV showed a statistically significant rise with increasing RBH. Measurements of IT and RT showed a similar tendency, measuring highest in the M3 group, followed by the M8, the M5, and the M12 groups. In the bicortical group, all variables showed a similar tendency, with different degrees of rise and decline. The B8 group showed the highest values, followed by the B12, the B5, and the B3 groups. The highest coefficient was demonstrated between ISQ and PTV. Conclusions: Primary stability was enhanced by the presence of bicortex and increased RBH, which may be better demonstrated by ISQ and PTV than by IT and RT.

• Journal of Periodontal and Implant Science
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• v.34 no.1
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• pp.177-193
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• 2004

Several experimental studies showed that the application of small amounts of electric current to bone stimulated osteogenesis at the site of the cathode and suggested that electrical currents promote osseointegration around dental implants. The purpose of this study was to determine the effect of direct microcurrent to endosseous titanium implants placed in bone defects. The right and left 2nd, 3rd and 4th mandibular premolars in ten mongrel dogs (15Kg of weight) were extracted. One monthe later, Ti-machined screw type implants(3.8 mm diameter x 8.5 mm length, $AVANA^{(R)}$, Ostem) were placed in surgically created circumferential defect area(width 5mm, depth 4mm). The implants were divided into three groups according to the treatment modalities: Control group- implants without electrical stimulation; Experimental group I- implants with allogenic demineralized freeze dried bone grafting; and Experimental group II-implants allogenic demineralized freeze dried bone grafting and electric stimulation. The animals were sacrificed in the 4th and 8th week after implant placement and un-decalcified specimens were prepared for histological and histometrical evaluation of bone-implant contact ratio (BIC) and bone formation area ratio (BFA) in defect area. Some specimens at 8 weeks after implantation were used for removal torque testing. Histologically, there was connective tissue infiltration in the coronal part of defect area in control and the experimental group I, whereas direct bone contact was found in the experimental group II without connective tissue invasion. Average BIC ratios at 4 weeks of healing were 60.1% in the experimental group II, 47.4% in the experimental group I and 42.7% in the control. Average BIC ratios at 8 weeks after implantation were 67.6% in the experimental group II, 55.9% in the experimental group I and 54.6% in the control. The average BFA ratio was 84.0% in the experimental group II, 71.8% in the experimental group I and 58.8% in the control at 4 weeks, and the BFA ratios were 89.6% in the experimental group II, 81.4% in the experimental group I and 70.5% in the control at 8 weeks after implantation. The experimental group II showed also significantly greater BIC and BFA ratios compared to the control and the experimental group I (p<0.05). The removal torque values at 8 weeks after implantation were 56 Ncm in the experimental group II, 49 Ncm in the experimental group I and 43 Ncm in the control. There was a statistically significant difference among 3 groups (p<0.05). These results suggest that electrical stimulation improve and accelerate bone healing around endosseous titanium implants in bone defect.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.2
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• pp.179-190
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• 2012

The installation of an implant in the distal extension area to assist a partial dentrue (IARPD) was used carefully in clinical situations. The purpose of this review on the IARPD is describing the concept, clinical results and guidelines of IARPD. For the review, a literature search was performed using the PubMed. The data from the literature suggest that the placement of the implants could improve function and patient satisfaction. In addition, IARPD reduced the residual ridge resorption. Longer and wider implant should be placed. Less than $15^{\circ}$ angulation may be not harmful. To prevent the loosening of the abutment, modified abutment or resilient attachment should be used. However, the connection method between the clasp retention and IARPD should be considered for long time success. Moreover, longitudinal clinical studies are required for evaluation of IARPD.

• Journal of Periodontal and Implant Science
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• v.36 no.1
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• pp.147-154
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• 2006

Surgical intervention in the posterior maxillary region requires detailed knowledge of maxillary sinus anatomy and the possible anatomical variations. This study evaluated the incidence, location of maxillary sinus septa by using radiographic (panoramic radiography and computed tomography) findings and comparison of panoramic radography with CT in antral anatomical variation. This study was based on data from 70 sinuses in partial dentate maxilla. The sample consisted of 61 patients(25 women and 36 men, with ages ranging between 19 and 77 years and a mean age of $49.4{\pm}11.3$ years) who were being treatment-planned to receive implant-supported restorations. First, the panoramic images were examined for the presence of antral septa by radiologist and examiner who don't know about CT findings. And incidence of antral septa was evaluated using an axial plane of CT image. The incidence of septa was compared between panoramic radiography and CT. The accuracy of the incidence was compared between radiologists and dentists. A total of 20 septa were found in 70 sinuses on CT image and the prevalence of one or more septa per sinus was found to be 28.6%. The assumed incidence of septa on panoramic radiography was $27.6%{\pm}2.2%$ in radiologist and $31.9%{\pm}5.8%$ in dentists. Erroneous diagnosis rate was 11.42% in radiologist and 15.96% in dentists. 40% of antral septa were located in the anterior(premolar) region, 30% of septa were located in the middle(first molar) and posterior(second molar) region separately. Prior to implant placement, it seems appropriate to consider panoramic radiography as a standard radiographic examination and periapical radiographs may be used to complete the findings in regions not sharply depicted in the panoramic radiograph. And cross-sectional imaging should be used in sites with severe bone loss and close proximity of the maxillary sinus.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.3
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• pp.178-185
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• 2015

Purpose: The purpose of this study was to conduct a comparative assessment on the satisfaction level for the two interfaces of surgical guide system (SimPlant and R2GATE), the design and convenience of manufactured surgical guides and the importance of using the surgical guides thereof by means of survey. Materials and Methods: Hereupon, they simulated the implant surgical process by mounting the two manufactured systems of surgical guide on a dental mold, respectively. The study subjects were instructed to complete the questionnaire as to the satisfaction level upon completion of the simulated surgery. This study summarized the data of each question after collecting the completed questionnaires. Then, this study analyzed the summarized data by utilizing statistical program SPSS 20.0 (IBM). Results: R2GATE had a higher value of the satisfaction level on the design and convenience of manufactures surgical guides. R2GATE group ($7.33{\pm}1.26$) was found to have a higher value in terms of the overall satisfaction level compared to SimPlant group ($6.67{\pm}1.26$) (${\alpha}$ = 0.05). Conclusion: The user satisfaction level on the surgical guide manufactured for R2GATE system was to such an extent as it can be widely used in clinical environment. Moreover, the surgical guide manufactured as R2GATE system can guide both the length and direction of a drill simultaneously. As a result, it is highly recommended for those beginners who do not have a lot of experience in implant placement.

• The Journal of the Korean dental association
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• v.55 no.11
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• pp.756-765
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• 2017

Purpose: The purpose of this article is to evaluate a change o bone level on the sinus floor by a bone added osteotome sinus floor elevation (BAOSFE) technique, according to the amount of deproteinized bovine bone mineral (DBBM). And Changes in augmented bone height after BAOSFE procedure were also assessed for 6 months after the implant procedure. Materials and Methods: Forty eight single implants were placed in the posterior maxilla using BAOSFE technique. The implantation sites were classified into two groups according to the amount of grafted DBBM, 0.25 group (0.25g) and 0.5 group (0.5 g). Panoramic views or cone-beam computed tomography (CBCT) were taken at the time of implant placement with BAOSFE and after at least 6 months to assess the bone level changes in the elevated sites with DBBM. Results: Alveolar bone level around all implants was stable clinically and radiographically during the follow-up. Mean augmented bone height was $5.21{\pm}0.94mm$ in 0.25 group and $6.92{\pm}1.19mm$ in 0.5 group. Statistically significant difference in augmented bone height was found in the comparison between the 0.25 group and 0.5 group at the time of surgery. There was a positive correlation between the length of the implant protruding into the maxillary sinus and the augmented bone height. After 6 months, mean reduction of augmented bone height was $0.50{\pm}0.34mm$ in 0.25 group and $0.41{\pm}0.30mm$ in 0.5group. There was no specific correlation between the reduction of augmented bone height and amount of grafted DBBM. Conclusion: Within the limit of this study, the amount of grafting materials and the protrusion length of implant into the maxillary sinus affect the amount of the augmented bone height.

• The Journal of Korean Academy of Prosthodontics
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• v.59 no.3
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• pp.333-340
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• 2021

Although gag reflex is an essential function and a useful physiological defense mechanism, it can become an obstacle in a dental treatment. In this case, a questionnaire was designed and used in consultations to objectify the factors associated with gag reflex. Based on the questionnaire, various treatment protocols were planned, such as behavioral control, which is a systematic desensitization that adapts by placing dental instruments in the oral cavity, and habit control to eliminate vomiting habits after drinking. Except for the placement of the implant fixture under general anesthesia, all restoration procedures were performed in the outpatient clinic in the same manner as the conventional implant fixed prosthetic restoration. The systematic desensitization and behavior technique were repeated until the patient was able to endure discomfort and relieve gag reflex in dental treatment. The patient was successfully received the implant-fixed prosthetic restoration in the partial edentulous region.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.4
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• pp.367-378
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• 2023

With the recent development of computer-aided design-computer-aided manufacturing technology and 3D printing technology, and the introduction of various digital techniques, the accuracy and efficiency of top-down definitive prosthetic restoration are increasing. In this clinical case, stable occlusion support was obtained through the placement of a total of 9 maxillary and mandibular posterior implants in patient with anterior-posterior crossed occlusion. The edentulous area of the maxillary anterior teeth, which showed a tendency of high resorption of the residual alveolar bone, was restored with a Kennedy Class IV implant assisted removable partial denture to restore soft tissue esthetics. Computed tomography guided surgery was used to place implants in the planned position, double scan technique was used to reflect the stabilized occlusion in the interim restoration stage to the definitive prostheses, and metal 3D printing was used to manufacture the coping and framework. This clinical case reports that efficient and predictable top-down full mouth rehabilitation was achieved using various digital technologies and techniques.

• Imaging Science in Dentistry
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• v.46 no.2
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• pp.69-75
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• 2016

Purpose: Sufficient area in the interforaminal region is required for dental implant placement, and the anterior loop of the mandibular canal is located within the limits of this area. The aim of this study was to evaluate the prevalence and extent of the anterior loop in a Brazilian sample population using cone-beam computed tomography (CBCT). Materials and Methods: CBCT images from 250 patients (500 hemimandibles) obtained for various clinical indications were randomly selected and evaluated to determine the presence and length of the anterior loop. The length of the anterior loop was then compared based on gender, age, and the side of the mandible. The data were analyzed using the Pearson chi-square test and linear regression analysis. Results: An anterior loop was identified in 41.6% of the cases, and its length ranged from 0.25 mm to 4.00 mm (mean, $1.1{\pm}0.8mm$). The loop had a greater mean length and was significantly more prevalent in males (p=0.014). No significant differences were found between the right and left sides regarding length (p=0.696) or prevalence (p=0.650). Conclusion: In this study, a high prevalence of the anterior loop of the mandibular canal was found, and although its length varied greatly, in most cases it was less than 1 mm long. Although this is a prevalent anatomical variation, safety limits for the placement of implants in this region cannot be established before an accurate evaluation using imaging techniques in order to identify and preserve the neurovascular bundles.