The effect of implant design on the stress distribution in a three-unit implant-supported distal cantilever fixed partial denture: A three-dimensional finite-element analysis.

Context: Implant design influences the stress distribution in an implant-supported distal cantilever fixed partial denture and supporting bone tissue. Aim: The purpose of this study was to investigate the effect of implant design on the stress distribution in the framework, implant, and surrounding bone, using a three-dimensional finite-element analysis. Materials and Methods: A three-dimensional finite-element model of a mandibular section of bone with implants placed in the first and second premolar region was created to support a distal cantilever fixed partial denture. A one-piece and two-piece implant and its suprastructure were simulated into wire frame models using Pro engineer (Pro E) program. Four models were created in this study. Results: Comparative analysis of all models showed that the maximum stress overall was in the cervical portion of the secondary abutment. When used in combination, the maximum stress was when the two-piece implant was used as secondary abutment. The one-piece implant showed less stress compared to its counterpart when used as secondary abutment. The maximum stress distribution in the bone was around the neck region of the secondary implant. Conclusion: Within the limitations of this study, it can be concluded that stress distribution is better in a one-piece implant design when compared with the two-piece implant design, with stress concentration being more at the junction of the abutment and the implant fixture in the two-piece implant. When implants are used as abutments (either primary or secondary), irrespective of their position and design, the secondary implant shows the maximum amount of stresses.

Influence of four kinds of thread design on the primary stability of immediately loaded dental implants / 中华医学美学美容杂志

Objective To discuss the effects of implants of different thread face angles on the primary stability of immediately loaded implant using the 3-dimensional finite element analysis with the models of the immediately loaded implants. Methods Using the commercial code of Pro/E software, Hypermesh software, and ABAQUS software we created 3-dimensional finite element models. The micromotions of the finite element models with different screw face angles (V-shape, buttress, square-shape and inverse buttress) were computed with the ABAQUS software. Results Concerning different thread face angles, the micromotion of buttress implant was the minimum and the micromotion of inverse buttress implant was the maximum with vertically loading; the micromotion of inverse buttress implant was the minimum and the micromotion of buttress implant was the maximum with horizontal loading. Conclusions Different screw-types have great influence on vertical interfacial micromotions but little influence on horizontal interfacial micromotions. There are two angles which are formed by top /bottom edge and the implants. The larger are the angles, the smaller are the vertical interfacial micromotions, but the weaker of the strength. Thus in designing the screw-type implants, we should consider the angles of thread faces and the strength.

Effect of preparation methods of recipient site on primary implant stability in various bone qualities / 대한치과보철학회지

STATEMENT OF PROBLEM: After placing the implant on the jaw, firm osseointegration between the implant interface and the bone should be achieved so that it can perform the same function as the normal teeth. That is, stability of the implant is required in order to form firm osseointegration. PURPOSE: This study was performed to evaluate the effect of implant preparation methods on primary implant stability in various bone qualities. MATERIAL AND METHODS: The recipient sites were prepared by various methods on 4 types of wooden plates (Osstem Co., Korea) which have similar mechanical properties with 4 types of human bone quality. The groups were divided according to implant preparation methods: In the control group the recipient sites were prepared from 1.8 mm guide drill, 2.0 mm initial drill, 2.7 mm pilot drill, 2.7 mm twist drill, 3.0 mm twist drill, 3.3 mm pilot drill, 3.3 mm twist drill, countersink drill, and tapping drill sequentially and 6 RBM surfaced GSII Osstem implants (Osstem Co., Korea) were installed in each type of wooden plates; In group 1, the recipient sites were prepared from 1.8 mm guide drill to 3.0 twist drill sequentially without countersink drill nor tapping drill and implants were placed; In group 2, the recipient sites were prepared from 1.8 mm guide drill to 3.0 mm twist drill, and countersink drill sequentially without tapping drill and implants were placed; In group 3, the recipient sites were prepared from 1.8 mm guide drill to 3.0 mm twist drill, countersink drill, and tapping drill sequentially and implants were placed; In group 4, the recipient sites were prepared from 1.8 mm guide drill to 3.3 mm twist drill sequentially without countersink drill nor tapping drill and implants were placed; In group 5, the recipient sites were prepared from 1.8 mm guide drill to 3.3 mm twist drill and countersink drill sequentially without tapping drill and implants were placed; In group 6, the recipient sites were prepared with 2.0 mm twist drill and 3.0 mm osteotome and implants were placed. The insertion torque was measured by INTRA surg(R)300 (KaVo., Germany). After installation of implants, the primary implant stability was measured by using Osstell(TM), Osstell(TM) mentor, and Periotest(R), and insertion torque test. The statistical analysis of the results was analyzed using SPSS ver. 12.0. Student t-tests and one-way analysis of variance (ANOVA) were used. RESULTS: The results obtained were as follows; 1. In type I and II bone quality plates, although the mean value of primary implant stability was somewhat different according to test methods, the primary implant stability of group 1 was significantly higher than those of other groups (p<0.05). 2. In type III bone quality plate, the primary implant stability of group 1 was significantly higher than those of other groups in Osstell(TM) test, the primary stability of group 1 and group 6 were significantly higher than those of other groups in Osstell(TM) mentor and Periotest(R), and the stability of group 6 was significantly higher than those of other groups in insertion torque test (p<0.05). 3. In type IV bone quality plate, the primary implant stability of group 6 was significantly higher than those of other groups (p<0.05). 4. As the quality of bone was softer, the primary implant stability tended to be lower in values. This tendency was not significantly different in Osstell(TM) and Osstell(TM) mentor tests, but it was significantly different in insertion torque test (p<0.05). 5. In type IV bone quality plate, the mean values of primary implant stability which were calculated by Osstell(TM) was 14.8+/-8.6 higher than the values calculated by Osstell(TM) mentor. CONCLUSION: These results suggest that the recipient implant preparation by using minimal drilling and osteotome may be useful in obtaining the primary implant stability and the insertion torque test seems be the most simple and predictable method.