• Imaging Science in Dentistry
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• 제37권3호
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• pp.127-131
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• 2007

Purpose: To measure the differences of the splint pin angulation and the position of the planned implant site after conventional tomographic analysis. Materials and Methods: The angulation and the location of the metal splint pin retained in acrylic stent were compared with the corrected angulation and the location of the implant fixture on the 331 tomographic images. Results: The stent pins were located buccal in 40%, lingual in 10% to the corrected implant site after analysis of the conventional tomographic image. The angle and the location of the maxillary splint pin were mainly directed buccal on incisor and canine regions. The angle and the location of the splint pins in premolar and molar regions needed less corrections in both maxilla and mandible. Conclusions: This study demonstrated that the use of tomographs was essential for successful dental implant planning.

• The Journal of Advanced Prosthodontics
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• 제15권6호
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• pp.290-301
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• 2023

PURPOSE. The study aimed to determine the influence of implant angulation on the trueness of multi-unit implant impressions taken through different techniques and strategies. MATERIALS AND METHODS. As reference models, three partially edentulous mandibular models (Model 1: No angulation; Model 2: No angulation for #33, 15-degree distal angulation for #35 and #37; Model 3: No angulation for #33, 25-degree distal angulation for #35 and #37) were created by modifying the angulations of implant analogues. Using a lab scanner, these reference models were scanned. The obtained data were preserved and utilized as virtual references. Three intraoral scanning (IOS) strategies: IOS-Omnicam, ISO-Quadrant, and IOS-Consecutive, as well as two traaditional techniques: splinted open tray (OT) and closed tray (CT), were used to create impressions from each reference model. The best-fit alignment approach was used to sequentially superimpose the reference and test scan data. Computations and statistical analysis of angular (AD), linear (LD), and 3D deviations (RMS) were performed. RESULTS. Model type, impression technique, as well as interaction factor, all demonstrated a significant influence on AD and LD values for all implant locations (P < .05). The Model 1 and SOT techniques displayed the lowest mean AD and LD values across all implant locations. When considering interaction factors, CT-Model 3 and SOT-Model 1 exhibited the highest and lowest mean AD and LD values, respectively. Model type, impression technique, and interaction factor all revealed significant effects on RMS values (P ≤ .001). CT-Model 3 and SOT-Model 1 presented the highest and lowest mean RMS values, respectively. CONCLUSION. Splinted-OT and IOS-Omnicam are recommended for multi-unit implant impressions to enhance trueness, potentially benefiting subsequent manufacturing stages.

• 대한치과보철학회지
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• 제31권4호
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• pp.580-610
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• 1993

The purpose of this study was to analyse the deflection and stress distribution at the supporting bone and it's superstructure by the alteration of angulation between implant and it's implant abutment. For this study, the free-end saddle case of mandibular first and second molar missing would be planned to restore with fixed prosthesis. So the mandibular second premolar was prepared for abutment, and the cylinder type osseointegrated implant was placed at the site of mandibular second molar for abutment. The finite element stress analysis was applied for this study. 13 two-dimensional FEM models were created, a standard model at $0^{\circ}$ and 12 models created by changing the angulation between implant and implant abutment as increasing the angulation mesially and distally with $5^{\circ}$ unittill $30^{\circ}$. The preprocessing decording, solving and postprocessing procedures were done by using FEM analysis software PATRAN and SUN-SPARC2GX. The deflections and von Mises stresses were calculated under concentrated load (load 1) and distributed load(load 2) at the reference points. The results were as follows : 1. Observing at standard model, the amount of total deflection at the distobuccal cusp-tip of pontic under concentrated load was largest of all, and that at the apex of implant was least of all, and the amount of total deflection at the buccal cusp-tip of second premolar under distributed load was largest of all, and that at the apex of implant was least of all. 2. Increasing the angulation mesially or distally, the amounts of total deflection were increased or decreased according to the reference points. But the order according to the amount of total deflection was not changed except apex of second premolar and central fossa of implant abutment under concentrated load during distal inclination. 3. Observing at standard model, the von Mises stress at the distal joint of pontic under concentrated load was largest of all, and that at the apex of implant was least of all. The von Mises stress at the distal margin of second premolar under distributed load was largest of all, and that at the apex of Implant was least of ail. 4. Increasing the angulation of implant mesially, the von Mises stresses at the mesial crest of implant were increased under concentrated load and distributed load, but those were increased remarkably under distributed load and so that at $30^{\circ}$ mesial inclination was largest of all. 5. Increasing the angulation of implant distally, the von Mises stresses at the distal crest of implant were increased remarkably under concentrated load and distributed load, and so those at $30^{\circ}$ distal inclination were largest of all.

• Imaging Science in Dentistry
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• 제49권2호
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• pp.123-130
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• 2019

Purpose: This study was conducted to characterize the relationship of the angulation between the tooth root axis and alveolar bone axis with anterior alveolar(AA) arch forms and sagittal root position (SRP) in the anterior esthetic region using cone-beam computed tomography (CBCT) images. Materials and Methods: CBCT images that met the inclusion and exclusion criteria were categorized using a recent classification of AA arch forms and a SRP classification. Then, the angulation of the root axis and the alveolar bone axis was measured using mid-sagittal CBCT images of each tooth. The relationships of the angulation with each AA arch form and SRP classification were evaluated using 1-way analysis of variance and a linear regression model. Results: Ninety-eight CBCT images were included in this study. SRP had a greater influence than the AA arch form on the angulation of the root axis and the alveolar bone axis(P<0.05). However, the combination of AA arch form and SRP was more predictive of the angulation of the root axis and the alveolar bone axis than either parameter individually. Conclusion: The angulation of the root axis and alveolar bone axis demonstrated a relationship with the AA arch form and SRP in teeth in the anterior esthetic region. The influence of SRP was greater, but the combination of both parameters was more predictive of root-to-bone angulation than either parameter individually, implying that clinicians should account for both the AA arch form and SRP when planning implant placement procedures in this region.

• 대한치과보철학회지
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• 제43권1호
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• pp.61-77
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• 2005

Statement of problem. The implant prosthesis has been utilized in various clinical cases thanks to its increase in scientific effective application. The relevant implant therapy should have the high success rate in osseointegration, and the implant prosthesis should last for a long period of time without failure. Resorption of the peri-implant alveolar bone is the most frequent and serious problem in implant prosthesis. Excessive concentration of stress from the occlusal force and biopressure around the implant has been known to be the main cause of the bone destruction. Therefore, to decide the location and angulation of the implant is one of the major considering factors for the stress around the implant fixture to be dispersed in the limit of bio-capacity of load support for the successful and long-lasting clinical result. Yet, the detailed mechanism of this phenomenon is not well understood. To some extent, this is related to the paucity of basic science research. Purpose. The purpose of this study is to perform the stress analysis of the implant prosthesis in the partially edentulous mandible according to the different nature locations and angulations using three dimensional finite element method. Material and methods, Three 3.75mm standard implants were placed in the area of first and second bicuspids, and first molar in the mandible Thereafter, implant prostheses were fabricated using UCLA abutments. Five experimental groups were designed as follows : 1) straight placement of three implants, 2) 5$^{\circ}$ buccal and lingual angulation of straightly aligned three implants, 3) 10$^{\circ}$ buccal and lingual angulation of straightly aligned three implants. 4) lingual offset placement of three implants, and 5) buccal offset placement of three implants. Average occlusal force with a variation of perpendicular and 30$^{\circ}$ angulation was applied on the buccal cusp of each implant prosthesis, followed by the measurement of alteration and amount of stress on each configurational implant part and peri-implant bio-structures. The results of this study are extracted from the comparison between the distribution of Von mises stress and the maximum Von mises stress using three dimensional finite element stress analysis for each experimental group. Conclusion. The conclusions were as follows : 1. Providing angulations of the fixture did not help in stress dispersion in the restoration of partially edentulous mandible. 2. It is beneficial to place the fixture in a straight vertical direction, since bio-pressure in the peri-implant bone increases when the fixture is implanted in an angle. 3. It is important to select an appropriate prosthodontic material that prevents fractures, since the bio-pressure is concentrated on the prosthodontic structures when the fixture is implanted in an angle. 4. Offset placement of the fixtures is effective in stress dispersion in the restoration of partially edentulous mandible.

• The Journal of Advanced Prosthodontics
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• 제2권1호
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• pp.25-31
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• 2010

PURPOSE. This study compared the accuracy of an abutment-framework (A-F) taken with open tray impression technique combining cement-on crown abutments, a metal framework and resin cement to closed tray and resin-splinted open tray impression techniques for the 3-implant definitive casts. The effect of angulation on the accuracy of these 3 techniques was also evaluated. MATERIAL AND METHODS. Three definitive casts, each with 3 linearly positioned implant analogs at relative angulations 0, 30, and 40 degrees, were fabricated with passively fitted corresponding reference frameworks. Ten impressions were made and poured, using each of the 3 techniques on each of the 3 definitive casts. To record the vertical gap between reference frameworks and analogs in duplicate casts, a light microscope with image processing was used. Data were analyzed by two-way analysis of variance and the Tukey test. RESULTS. The open tray techniques showed significantly smaller vertical gaps compare to closed tray technique (P < .05). The closed tray and the resin-splinted open tray technique showed significantly different vertical gaps according to the angulation of implant (P < .05), but the A-F impression technique did not (P > .05). CONCLUSION. The accuracy of the A-F impression technique was superior to that of conventional techniques, and was not affected by the angulation of the implants.

• The Journal of Advanced Prosthodontics
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• 제2권4호
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• pp.128-133
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• 2010

PURPOSE. The purpose of this study was to compare the accuracy of the implant master cast according to the type (pick-up, transfer) and the length (long, short) of the impression copings. MATERIALS AND METHODS. The metal master cast was fabricated with three internal connection type implant analogs (Osstem GS III analog), embedded parallel and with $10^{\circ}$ of mesial angulation to the center analog. Four types of impression coping were prepared with different combinations of types (transfer, pick-up) and lengths (long, short) of the coping. The impressions were made using vinyl polysiloxane (one step, heavy + light body) with an individual tray, and 10 impressions were made for each group. Eventually, 40 experimental casts were produced. Then, the difference in the distance between the master cast and the experimental cast were measured, and the error rate was determined. The analysis of variance was performed using the SPSS (v 12.0) program (${\alpha}$= .05), and the statistical significance was set at P < .05. RESULTS. The ANOVA showed that the pick-up type impression coping exhibited a significantly lower error rate than the transfer type. However, no significant difference was observed with respect to the length of the impression coping. Additionally, no significant difference was observed between the parallel and mesial angulated groups. CONCLUSION. Within the limitations of this study, the pick-up type impression coping exhibited a more accurate implant master cast than the transfer type in parallel group. The accuracy of the implant master cast did not differ for different lengths of impression coping of at least 11 mm. Additionally, the accuracy of the implant cast was not different for the parallel and $10^{\circ}$ mesial angulated groups.

• 대한치과보철학회지
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• 제51권1호
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• pp.1-10
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• 2013

연구 목적: 임플란트 나사선 경사각이 치조골의 응력분포에 미치는 영향을 검토하여 어떤 임플란트가 응력분산에 유리한 지 알아보고자 하였다. 연구 재료 및 방법: 피치는 0.8 mm로 일정하게 하고 나사선의 줄(thread) 수를 다르게 하여 나사선 경사각의 변화를 준 1줄 나사선 임플란트(single thread type: 경사각 $3.8^{\circ}$)와 2줄 나사선 임플란트(double thread type: 경사각 $7.7^{\circ}$) 그리고 3줄 나사선 임플란트(triple thread type: 경사각 $11.5^{\circ}$)의 세 가지 모델을 통해 3차원 유한요소 응력분석을 시행하였다. 임플란트가 치조골의 치아 장축에 대하여 $0^{\circ}$, $10^{\circ}$, $15^{\circ}$ 경사지게 식립된 것으로 가정하여 9 가지 모델을 만들었다. 200 N의 수직 방향의 하중과, 200 N의 임의의 $15^{\circ}$ 경사 하중을 가한 경우에 임플란트와 치조골에서 발생된 응력분포를 3차원 유한요소법으로 분석하였다. 결과:1. 임플란트의 경사 식립 각도가 클수록 치조골과 임플란트의 등가응력(von-Mises stress)과 최대주응력이 높게 나타났다. 2. 수직하중보다 경사하중을 가할 경우 치조골과 임플란트의 등가응력과 최대주응력이 높게 나타났다. 3. 임플란트의 나사선 줄 수가 증가할수록 응력분산 효과가 커서 등가응력과 최대주응력의 크기가 감소되었다. 4. 치조골에 작용하는 최대주응력의 크기는 수직하중 시에나 경사하중 시에 3줄 나사선을 가진 임플란트가 가장 작고 다음으로 2줄 또는 1줄 나사선의 순으로 나타나 3줄 나사선의 경우가 가장 우수한 결과를 보였다. 결론: 이상의 결과는 3줄 나사선 임플란트가 1줄 및 2줄 나사선 임틀란트보다 응력분산 효과 면에서 우수하며, $10^{\circ}$ 이상 경사지게 식립된 경우에라도 나사선 경사각이 커지면서 줄 수가 증가할수록 치조골에서 발생하는 최대 주응력 값이 감소하므로 임플란트 나사선 줄 수와 경사각을 최적화함으로써 임플란트 응력분산에 도움이 될 수 있음을 시사하였다.

• The Journal of Advanced Prosthodontics
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• 제12권1호
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• pp.33-37
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• 2020

PURPOSE. The purpose of this study is to evaluate the effects of type of magnet attachment and implant angulation in two implant overdenture models. MATERIALS AND METHODS. Magnet attachments used in this study were flat and dome types (MGT5515, MGT5520D, Dentium Co., Seoul, Korea). Two implants with keepers were inserted in the resin blocks at a distance of 24 mm. For the first model, the implants were parallel to the vertical and perpendicular to the horizontal; for the second model, both were angulated 5 degrees to the mesial; for the third model, both were angulated 10 degrees toward the mesial. The retentive force was measured in both vertical and lateral directions. Statistical analyses were performed using SPSS software version 22.0 (α=.05). RESULTS. The flat type magnet attachment showed the highest lateral retentive force in the 20° divergent group (P<.05) and the dome type magnet attachment showed the highest lateral retentive force in the parallel group (P<.05). The vertical and lateral retentive force of the dome type magnet attachment was greater than that of the flat type magnet attachment in every direction (P<.05). CONCLUSION. Within the limitations of this study, the dome shape magnet attachment can resist vertical and lateral retentive force more superiorly than the flat type magnet attachment, regardless of angle, in the mandibular two implant model.

• Imaging Science in Dentistry
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• 제51권3호
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• pp.251-260
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• 2021

Purpose: Dental implants are widely used for the rehabilitation of edentulous sites. This study investigated the occurrence of dental implant malpositioning as shown on post-implantation cone-beam computed tomography (CBCT) and to identify related factors. Materials and Methods: Samples with at least 1 malpositioned dental implant were collected from a central radiology clinic in Tehran, Iran from January 2017 to January 2019. Variables such as demographic characteristics, length and diameter of implants, type of implant, sites of implant insertion, different types of implant malpositioning problems (cortical plate perforation, interference with anatomical structures), angulation of the implant, and the severity of malpositioning were assessed. In addition, the incidence of implant fracture and over-drilling was evaluated. Data were statistically analyzed using the chi-square test, 1-sample t-test, and Spearman correlation coefficients. Results: In total, 252 patients referred for implant postoperative CBCT evaluations were assessed. The cases of implant malpositioning included perforation of the buccal cortical plate (19.4%), perforation of the lingual cortical plate (14.3%), implant proximity to an adjacent implant (19.0%), implant proximity to an adjacent tooth (3.2%), interference with anatomical structures(maxillary sinus: 18.3%, mandibular canal: 11.1%, nasal cavity: 6.3%, mental foramen: 5.6%, and incisive canal: 0.4%). Implant fracture and over-drilling were found in 1.6% and 0.8% of cases, respectively. Severity was categorized as mild (9.5%), moderate (35.7%), severe (37.7%), and extreme (17.1%), and 52.4% of implants had inappropriate angulation. Conclusion: CBCT imaging is recommended for detecting dental implant malpositioning. The most common and severe type of malpositioning was buccal cortex perforation.