| 1. |
- Chowdhary, Ramesh, et al.
(författare)
-
Biomechanical evaluation of macro and micro designed screw-type implants : an insertion torque and removal torque study in rabbits
- 2013
-
Ingår i: Clinical Oral Implants Research. - : John Wiley & Sons. - 0905-7161 .- 1600-0501. ; 24:3, s. 342-346
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate the combined effect of macro and pitch shortened threads on primary and secondary stability during healing, but before dynamic loading. MATERIALS AND METHODS: Two sets of turned implants with different macro geometry were prepared. The test group possessed pitch shortened threads in between the large threads and the control group did not have thread alterations. The two implant groups were placed in both femur and tibiae of 10 lop-eared rabbits, and at the time of implant insertion, insertion torques were recorded. After 4 weeks, all implants were subjected to removal torque tests. RESULTS: The insertion torque values for the control and test groups for the tibia were 15.7 and 20.6 Ncm, respectively, and for the femur, 11.8, and 12.8 Ncm respectively. The removal torque values for the control and test groups in the tibia were 7.9 and 9.1 Ncm, respectively, and for the femur, 7.9 and 7.7 Ncm respectively. There was no statistically significant difference between the control and test groups. CONCLUSION: Under limited dynamic load, the addition of pitch shortened threads did not significantly improve either the primary or the secondary stability of the implants in bone.
|
|
| 2. |
- Chowdhary, Ramesh, et al.
(författare)
-
Evaluation of stress pattern generated through various thread designs of dental implants loaded in a condition of immediately after placement and on osseointegration : an FEA study
- 2013
-
Ingår i: Implant Dentistry. - : Lippincott Williams & Wilkins. - 1056-6163 .- 1538-2982. ; 22:1, s. 91-96
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To determine the stress pattern generated through various thread design in experimental simulation models, when loaded immediately after placement and after osseointegration. METHODS: Three-dimensional (3D) models were designed using CATIA, computer-aided design modeling software. The study was planned in 2 stages. Eight 2D models were constructed of different thread forms, one set with frictionless and other with bonded for bone to implant interface and loaded vertically with 100 N. In Stage II, 6 3D models of the different threads embedded in the cortical bone were constructed and loaded vertically and obliquely. RESULTS: In 2D models, the von Mises stress concentrated at the crest in the bonded connection thread designs. The stress levels were in the range of 7 to 13 MPa. In the frictional implant bone interface, the thread designs had a clear effect on the stress levels in the bone. In the 3D analysis, the complete implant design affected the stress levels. CONCLUSIONS: The thread design affects the magnitude of the stress peak in the bone more effectively in immediately loaded (frictionless) implants than the osseointegrated (bonded) implants. Maximum stress was observed at the first thread in most of the osseointegrated implants.
|
|
| 3. |
- Chowdhary, Ramesh, et al.
(författare)
-
Influence of Micro Threads Alteration on Osseointegration and Primary Stability of Implants : An FEA and In Vivo Analysis in Rabbits
- 2015
-
Ingår i: Clinical Implant Dentistry and Related Research. - : John Wiley & Sons. - 1523-0899 .- 1708-8208. ; 17:3, s. 562-569
-
Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To describe the early bone tissue response to implants with and without micro threads designed to the full length of an oxidized titanium implant. MATERIALS AND METHODS: A pair of two-dimensional finite element models was designed using a computer aided three-dimensional interactive application files of an implant model with micro threads in between macro threads and one without micro threads. Oxidized titanium implants with (test implants n=20) and without (control implants n=20) micro thread were prepared. A total of 12 rabbits were used and each received four implants. Insertion torque while implant placement and removal torque analysis after 4 weeks was performed in nine rabbits, and histomorphometric analysis in three rabbits, respectively. RESULTS: Finite element analysis showed less stress accumulation in test implant models with 31Mpa when compared with 62.2 Mpa in control implant model. Insertion and removal torque analysis did not show any statistical significance between the two implant designs. At 4 weeks, there was a significant difference between the two groups in the percentage of new bone volume and bone-to-implant contact in the femur (p< .05); however, not in the tibia. CONCLUSIONS: The effect of micro threads was prominent in the femur suggesting that micro threads promote bone formation. The stress distribution supported by the micro threads was especially effective in the cancellous bone.
|
|
| 4. |
- Chowdhary, Ramesh
(författare)
-
On efficacy of implant thread design for bone stimulation
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Introduction – The mechanism and efficiency of force transfer by dental implants to surrounding biologic tissues are important determinants in the development of the implant-to-bone/tissue interface and implant longevity. Threads are used to improve the initial stability by maximizing bone contact through an enlarged implant surface area and thereby favor distribution of interfacial stresses. However, knowledge about optimal thread design for an enhanced implant integration in bone tissue is still lacking. Aim – The aim of this thesis was to evaluate the efficacy of implant micro thread design when combined with macro threads, for bone stimulation. The hypothesis is that the short threads will contribute with compression forces that may stimulate bone healing, while the larger threads will provide with primary stability necessary during the healing process. A further aim was to use an FEA model to describe the optimal thread form for reduced stress concentration immediately after implant insertion as well as after completed bone healing. Materials and methods – In study 1, Two-dimensional finite element models were made from 8 different thread designs. The crest module and apex of the implants were removed from the implant models, in order to enhance the effect of the thread designs only. Thus, the suprastructures and microstructures of the implants were not considered. All the eight implant models were assumed to be embedded in cortical bone. In addition, a 3D model was used to evaluate stress in the bone generated by 6 different thread designed implants when the implant models included the entire implant. In the In vivo studies 2 and 3, experimental turned implants with a diameter of 4mm and 8mm in length were prepared with micro threads in between macro threads along the body of the implants. These were used as test implants. Implants without micro-threads were used as controls. In study 4, similar implants were made but with alteration in depth of the macro-thread to improve the possibility for bone stimulation by compression during healing. Insertion and removal torque analysis along with histomophometric analyses were done to evaluate the bone response. Results – In study 1, stresses were calculated using von Mises stress analysis. The stress levels in the bone were in the range of 5-13 MPa in osseointegrated model and 14-107 MPa in immediate 2D models. 3D Analysis results showed the von Mises stress in the range of 4.8-30.9 MPa, when a load of 100N was applied vertically. In Study 4 FEA demonstrated stress levels in the range of 0.28 MPa to 62MPa for the control implant model designs, whereas the test implant models displayed a range of 0.28 MPa to 31Mpa. In study 2, the mean values of the ITQ for the control and test groups in the tibia were 15 and 20 Ncm respectively, and in the femur, the values were 11 and 12 Ncm, respectively. In study 4, the ITQ values were 11Ncm and 14 Ncm respectively in the tibia, and in the femur 13 Ncm and 19 Ncm respectively. The RTQ values for the control and test groups in tibia was 11Ncm and 17Ncm, respectively and in the femur, 13Ncm and 23Ncm, respectively. The histomorphometric analysis of study 3, showed the mean total bone area, BA% (SD) to be higher in the test implants, when compared to the control implants in both the tibia 24 (4), and 21(4), the femoral bone 29 (5), and 25 (7), respectively with no statistical significance. In study 4, the total bone area BA% was higher for the test implants with a mean value of 72% compared to 48% for the control group in tibial bone. In femural bone, the bone area was 63% for the test and 38 % for the control group implants with p value of 0.10 for both tibia and femur. Bone to implant contact showed significantly higher value for the test implants in the femur, p= 0.04. Conclusion – The impact of different thread designs, with respect to the magnitude of the transferred stress peak in the bone, was higher for the immediately inserted implants than for the osseointegrated implant model. The stress distribution was more effective in experimental micro-thread implant models, when compared to the non-micro thread models. The addition of pitch shortened threads in the test implant, did significantly improve the primary and secondary stability of the test implants, when mechanically evaluated with ITQ and RTQ analysis in corticular or trabecular bone rabbit bone. Histomophometrical analysis showed that the addition of the pitch shortened threads in between the macro threads did have a bone stimulatory effect in the femur of the rabbits.
|
|
| 5. |
- Chowdhary, Ramesh, et al.
(författare)
-
The osseointegration stimulatory effect of macrogeometry-modified implants : a study in the rabbit
- 2014
-
Ingår i: Clinical Oral Implants Research. - : John Wiley & Sons. - 0905-7161 .- 1600-0501. ; 25:9, s. 1051-5
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate the bone stimulatory effect of compression forces through histomorphometric analyses of macrothreaded implants with microthreads in between.MATERIAL AND METHODS: Two sets of turned implants with different macrogeometries were prepared. The test group possessed microthreads in between macrothreads, and the control group had macrothreads only. The two-implant groups were placed in both the femur and the tibiae of 10 rabbits. After 4 weeks, the animals were sacrificed and were subjected to histologic processing and histomorphometry. On the prepared stained sections, the total bone area (BA), new BA and bone-to-implant (BIC) were calculated.RESULTS: The mean new BA% (SD) for the test group in the femur presented significantly higher values compared with the control group, being 32.84 (32.5) ± 6.04 and 27.31 (28.19) ± 5.66, respectively (P = 0.04). There were no differences for the new BA in the tibia or the total BA% for both bone types (P = 0.86, P = 0.131, and P = 0.131, respectively). The mean BIC% (SD) in the femur was 13.66 (11.49) ± 6.86 for the test group and 8.48 (7.92) ± 3.31 for the control group and in the tibia, 11.4 (11.88) ± 4.21 for the test group and 13.91 (12.06) ± 6.07 for the control group, respectively. There was no statistical significance among the groups tested.CONCLUSION: The modified implant macrogeometry with microthreads in between promoted effect in the femur. However, no statistical differences could be seen in the tibia, suggesting that the modification may be more effective in bone with poor bone quality, such as in the maxillary bone.
|
|
| 6. |
- Mishra, Sunil, et al.
(författare)
-
Osseoperception in Dental Implants : A Systematic Review
- 2016
-
Ingår i: Journal of Prosthodontics. - : John Wiley & Sons. - 1059-941X .- 1532-849X. ; 25:3, s. 185-195
-
Forskningsöversikt (refereegranskat)abstract
- PURPOSE: Replacement of lost teeth has significant functional and psychosocial effects. The capability of osseointegrated dental implants to transmit a certain amount of sensibility is still unclear. The phenomenon of developing a certain amount of tactile sensibility through osseointegrated dental implants is called osseoperception. The aim of this article is to evaluate the available literature to find osseoperception associated with dental implants. MATERIALS AND METHODS: To identify suitable literature, an electronic search was performed using Medline and PubMed database. Articles published in English and articles whose abstract is available in English were included. The articles included in the review were based on osseoperception, tactile sensation, and neurophysiological mechanoreceptors in relation to dental implants. Articles on peri-implantitis and infection-related sensitivity were not included. Review articles without the original data were excluded, although references to potentially pertinent articles were noted for further follow-up. The phenomenon of osseoperception remains a matter of debate, so the search strategy mainly focused on articles on osseoperception and tactile sensibility of dental implants. This review presents the histological, neurophysiological, and psychophysical evidence of osseoperception and also the role of mechanoreceptors in osseoperception. RESULTS: The literature on osseoperception in dental implants is very scarce. The initial literature search resulted in 90 articles, of which 81 articles that fulfilled the inclusion criteria were included in this systematic review. CONCLUSION: Patients restored with implant-supported prostheses reported improved tactile and motor function when compared with patients wearing complete dentures.
|
|
| 7. |
- Muktadar, Anand Kumar, et al.
(författare)
-
Evaluation of the effect of self-cutting and nonself-cutting thread designed implant with different thread depth on variable insertion torques : An histomorphometric analysis in rabbits
- 2018
-
Ingår i: Clinical Implant Dentistry and Related Research. - : John Wiley & Sons. - 1523-0899 .- 1708-8208. ; 20:4, s. 507-514
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate of the effect of self-cutting and nonself-cutting thread designed implant with different thread depth on variable insertion torques. To evaluate the bone volume (BV) and bone to implant contact (BIC) in these variables Materials and Methods: Mainly two thread design, V-shaped thread which is self-cutting and power thread design, which is nonself-cutting implants were considered for this study with a variation in thread depth of 0.4 and 0.6 mm for both the designs, respectively. A total of 32 CAD designed machined surface implant prototypes were manufactured of 4 mm in diameter and 8 mm in length were made, which were machined surfaced, which was placed in the femur of 16 New Zealand white rabbits. These were categorized under 2 groups; Group 1 and Group 2 with insertion torques of <30 and >50 Ncm, respectively. After 4 weeks of healing, rabbits were sacrificed and histomophometric and histologic analyses were done to evaluate the bone response. Results: Significantly, more BIC was recorded for high torque implants compared with low torque in power-shaped thread design (P value5.01*). BV for new bone formation was statistically significant for V-shaped thread design in high torque when compared with low torque (P value5.02*). Conclusion: The effect of the depth of the thread design was significant for the power-shaped design in enhancing BIC when compared with V-shaped thread design. With high torque V-shaped thread design had more new bone formation as compared with power-shaped thread design.
|
|
