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Cylindrical & conical mini implants /certified fixed orthodontic courses by Indian dental academy
 

Cylindrical & conical mini implants /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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    Cylindrical & conical mini implants /certified fixed orthodontic courses by Indian dental academy Cylindrical & conical mini implants /certified fixed orthodontic courses by Indian dental academy Presentation Transcript

    • cylindrical and conical type mini- implants (mechanical and histologic properties) www.indiandentalacademy.com INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
    • OBJECTIVE  To investigate the mechanical and histologic properties of conical compared with cylindrical shaped mini-implants in terms of success rate www.indiandentalacademy.com
    •  Recently, implants, onplants, and orthodontic mini- implants were introduced as effective tools for anchorage reinforcement.  Prosthodontic implants and onplants have some disadvantages such as the need for surgical procedures , limitations of site selection and a waiting time for osseointegration.  Orthodontic mini-implants can be easily inserted into the various sites and can be loaded at a relatively early stage compared with prosthodontic implants and onplants. www.indiandentalacademy.com
    •  Mini- implants with a small diameter can be easily loosened by low removal torque and mini-implants with short length show a lower success rate.  Therefore, it is necessary to consider how to increase the success rate. www.indiandentalacademy.com
    • Cylindrical vs conical type min- implant www.indiandentalacademy.com
    •  To study the stability of mini-implants, a mobility test, resonance frequency analysis, and torque analysis can be applied.  Although insertion torque can be measured to evaluate the stability of mini-implants , insertion torque is known to have a low relationship to stability.  Since removal torque is more related to the resistance and removal than insertion torque, removal torque can be used to test the mechanical stability of implants www.indiandentalacademy.com
    •  For torque analysis of implant a polyurethane foam with homogenous density like Sawbones as artificial bone is often used for mechanical studies.  Resonance frequency analysis(RFA) is used to evaluate implant stability.  RF analyzer measures the flexural resonance frequency which is determined by the stress of bone-implant interface, bone density, and implant design www.indiandentalacademy.com
    •  The purpose of this study was to investigate the mechanical and histologic properties of conical compared with cylindrical shaped mini- implants in terms of success rate through a mechanical study using Sawbones and histomorphic analysis in beagle dogs www.indiandentalacademy.com
    • Materials and methods  Mini-implants(diameter : 1.6 mm; length: 6 mm; Dual Top, Jeil Medical Corporation, Seoul, Korea) were made with Ti-6Al-4V alloy.  According to the shape of mini-implants, the sample consisted of a cylindrical group and a conical group www.indiandentalacademy.com
    • Insertion and removal torque analysis  For torque analysis, each group, consisting of 10 mini implants, was inserted to the solid rigid polyurethane foam (Sawbones), in which the density was homogenous 30 pcf.  The mini-implants were inserted and removed with a surgical engine(Elcomed SA200C,W&H,Burmoos,Austria) which could measure and record the torque at1/8 second intervals.  It was calibrated each time for the exact measurement. www.indiandentalacademy.com
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    •  To analyze the torque change patterns between groups, insertion torques were compared at 8 seconds(4 turns), 4 seconds (2 turns), and 0 second before maximum insertion torque (MIT); and removal torques were compared at 0 second, 2 seconds (1 turn)and 4 seconds(2 turns) after maximum removal torque(MRT).  The torque ratio(TR) of MRT to MIT was calculated. www.indiandentalacademy.com
    • RFA and Histomorphometric Analysis Insertion and Loading  For animal experiments , a male and a female beagle dog(11 kg and 13 kg respectively) were used as the experimental subjects.  Each group which consisted of 16 mini-implants, was inserted to the buccal and palatal side of the maxilla and the buccal side of the mandible. www.indiandentalacademy.com
    •  The cylindrical shaped mini-implants were inserted on the right side of the maxilla and mandible, and the conical shaped mini-implants on the left side under saline irrigation.  In both groups a force of 200-300 g was applied 1 week after insertion using a Ni-Ti coil spring.  The force continued for 17 weeks after insertion. www.indiandentalacademy.com
    • Measurement of Stability  Immediately (T0), 1 week(T1), and 17 weeks(T2) after mini-implant insertion, the resonance frequency analyzer(Osstell, Integration Diagnostic ltd, Gothenburg, Sweden) was used for direct measurement of mini-implant stability.  An intermediate jig between the transducer of Osstell and the mini-implants was used to apply the Osstell to the mini-implant.  The resonance frequency values, calculated from the peak amplitude , are represented in a quantitative unit called implant stability quotient(ISQ) on a scale from 1 to 100. www.indiandentalacademy.com
    •  Implant stability quotient (ISQ) values are derived from the stiffness (N/micrometer) of the transducer/implant/bone system and the calibration parameters of the transducer.  A high ISQ value indicates high stability, whereas a low value indicates low stability. www.indiandentalacademy.com
    • Specimen preparation  The dogs were sacrificed 17 weeks after insertion . The specimens of each mini-implant with the adjacent bone tissue were prepared in the axial plane using an Exakt cutting and grinding system.  The resin-embedded mini-implant specimens were sliced and ground .  The thickness of the specimens was about 40-50 microns.  The specimen were stained with hematoxylin and eosin. www.indiandentalacademy.com
    • Histomorphometric analysis  In the histologic analysis the following parameters of the three best consecutive mini-implant threads of each mini-implant were measured using image analyzing software: 1. The bone-to-implant contact (BIC), the percentage of osseointegration on the thread. 2. The bone area (BA), percentage of mineralized tissue within the threads. www.indiandentalacademy.com
    • Statistical analysis  All measurements were stastically evaluated using an independent t-test to determine any difference in the ISQ, the bone-to-implant contact, and the bone area between the cylindrical and conical groups.  A P value <.05 was considered significant. www.indiandentalacademy.com
    • Results  Insertion torque was gradually increased in all groups.  MIT and MRT were higher in the conical group than the cylindrical group. www.indiandentalacademy.com
    • Failure of mini-implant  Seven mini-implants (21.88 %) failed in this study.  The failure rates of both groups were the same.  The most common site of failure was the palate(31.25%), while there were no failures in the mandible. www.indiandentalacademy.com
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    • Resonance frequency analysis  There was no significant difference in the ISQ between each group(P>.05)  The ISQ of the mandible was highest at T0 and T1.  The ISQ’s of all the groups had a tendency to decrease with time. www.indiandentalacademy.com
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    • Histomorphometric analysis  There were no significant differences between each group in BIC and BA.  The BIC of each group was over 40% and BA, over 55%.  There was no significant difference in the BA according to location. www.indiandentalacademy.com
    • Discussion  Removal torque is more related to the mechanical stability of the mini-implants than the insertion torque.  To evaluate insertion torque change pattern, the torque of each group was compared at 8 seconds(4 turns), 4 seconds(2 turns), and 0 seconds before MIT. www.indiandentalacademy.com
    •  These findings mean that the difference between the cylindrical and conical shaped groups gradually increased from the middle of insertion.  A continuous increase of insertion torque in the conical group was probably due to a tighter contact to the surroundings than the cylindrical group due to difference in diameter between the upper and lower parts.  Good primary stability may reduce the risk of micro motion and negative tissue responses such as formation of fibrous scar tissue at the bone-implant interface during healing and loading. www.indiandentalacademy.com
    •  Thus primary stability is considered to play an important role in successful osteointegration.  Some studies reported that insertion torque had a low relationship to stability.  Therefore, removal torque was used to test the mechanical stability of implants because the removal torque was more related to the resistance to the removal moment than the insertion torque. www.indiandentalacademy.com
    •  The results of this study showed that the removal torque was much lower than the insertion torque.  The torque ratio of MRT to MIT was 26.05% in the cylindrical group, and 31.1% in the conical group.  This means that the resistance to insertion may not indicate primary stability, and the primary stability may be more related to removal torque than insertion torque. www.indiandentalacademy.com
    •  A conical shape has been applied to the implant to decrease failure of implants.  A conical shape is able to provide a tight contact between the implant and tissue as it is deeply inserted because the upper part of the taper shape has a larger diameter than the lower part.  However excessive insertion torque may produce microfracture and ischemia of the surrounding bone, delay bone healing, and induce implant failure. www.indiandentalacademy.com
    •  Although the higher MRT of the conical group seemed to relate to high mechanical stability, excessive MIT of the conical group might be harmful to the tissue adjacent to the mini-implant.  Therefore the clinical stability of the conical shaped mini- implant is controversial.  The conical shaped mini-implant may have some advantages such as mechanical retention and good primary stability.  However, the conical shape may induce negative bone www.indiandentalacademy.com
    •  In this study the success rate was lower in the conical group than the cylindrical group. The histomorphometric analysis showed that the two groups in this study had no difference in the BIC and BA.  This means that the conical shape would not be better in the clinical applications because of over-compression to the surrounding tissue and a smaller size of the surface area than the cylindrical shapes, although it may provide the mechanical stability while being removed.  Clinically the conical shape may provide good initial stability because of the high removal torque. www.indiandentalacademy.com
    •  However high insertion torque may induce the over-compression to the bone tissue and decrease the stability of the mini-implant.  Therefore efforts to reduce the insertion torque may induce the insertion torque as in modification of the thread shape may be better for tissue healing.  Additionally a drilling procedure before insertion of a conical shaped or thick diameter mini-implant could decrease the insertion torque, although a drill-free technique may enhance the stability of the thin mini-implant. www.indiandentalacademy.com
    • Conclusions  Although the conical group required high removal torque, which means good initial stability, it also showed high insertion torque which could effect adjacent tissue healing.  The success rate, RFA, and histomorphometric analysis showed no significant difference between the cylindrical and conical groups.  The conical shape may need modification of the thread structure and insertion technique to reduce the excessive insertion torque while maintaining the high resistance to removal. www.indiandentalacademy.com
    • Histomorphometric and mechanical analysis of drill-free screw as orthodontic anchorage Jong-Wan Kim,Sug-Joon Ahn , and Young II Chang AJODO 2005; 128; 190-4 www.indiandentalacademy.com
    • Aim  The purpose of this study was to evaluate the effects of the drilling procedure on the stability of the screws under early orthodontic loading. www.indiandentalacademy.com
    • Introduction  Orthodontic mini-screws are small, they can be used in a variety of host sites, insertion is a less traumatic procedure, and they can be loaded soon after placement.  However a notable complication is loosening of the screws, even though they consist of a biocompatible titanium alloy.  Some studies report that there is no osseointegration around the screw, only fibrous integration, which is due to early loading and easy removal.  Fibrous integration can predispose to infection, a disadvantage in long-term use. www.indiandentalacademy.com
    •  Drill free screws are a recent development.  They have a tip like a corkscrew and a specially formed cutting flute that enables them to be inserted without drilling.  Drill free screws can provide intensive screw-bone contact, and inserting them produces little bone debris and less thermal damage.  However few studies have compared the stability of drill free, and drilled screws under early orthodontic loading. www.indiandentalacademy.com
    • Material and methods  Two male beagles(11 and 13 kg) were used as experimental subjects.  32 screws (Osas; Epoch medical, Seoul, Korea) measuring 1.6 mm in diameter, were divided into 2 groups: drill free (DF), and drilling (D).  The screws were inserted into the buccal and palatal regions of the maxilla, and the buccal regions of the mandible.  The screws of the D group were inserted into the left sides of the maxilla and mandible after drilling(1500 rpm) with a 1.2 mm drilling bur under saline solution irrigation according to the manufacturers instructions. www.indiandentalacademy.com
    •  The screws of the DF group were inserted into the right side without drilling.  In both the groups, a force of 200-300 g was applied using a nickel- titanium coil spring from 1 week after insertion for 11 weeks. www.indiandentalacademy.com
    •  The mobility of each screw was measured by using Periotest 12 weeks after insertion.  The dogs were killed after the mobility test.  The specimen of each screw with surrounding tissue were prepared in the axial plane by using an Exakt cutting and grinding system.  The specimens were embedded and sectioned according to the method reported by Donath. www.indiandentalacademy.com
    •  The following parameters of the 3 best consecutive screw threads of each screw were measured by using image analyzing software. 1. Bone-metal contact, the percentage of total bone contact length on the threads. 2. Bone area, the percentage of total bone area within the threads.  All measurements were statistically evaluated by using the t-test. A P value less than 0.05 was considered significant. www.indiandentalacademy.com
    • Results  In the DF group, 1 screw in the maxilla was lost(6.25%), and in the D group, 1 in the maxilla and, 1 in the mandible were lost (12.5%).  The DF group showed a significantly lower Periotest value(PTV), than the D group.  This means that under early orthodontic loading, the screws in the DF group were less mobile than those in the D group.  However, some screws in the D group in the palate hadwww.indiandentalacademy.com
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    •  Osseointegration was generally observed in both the groups, although there were some differences between the 2 groups.  Generally the DF group showed a closer contact between the screw surface and the bone tissue than the D group.  In addition the gap between the original cortical bone and the screw surface was filled more tightly with newly formed bone in the DF group, whereas fibrous tissue was observed more frequently at the interface between the bone and screw in the D group. www.indiandentalacademy.com
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    • Discussion  Orthodontic anchorage is usually obtained from a tooth or group of teeth, and it is used to move other malpositioned teeth.  Adequate anchorage is difficult to obtain when key teeth are missing.  In such conditions it is useful to have additional anchorage, such as an implant or onplant, which can resist the forces used to move the other teeth.  In particular screws have been used for orthodontic anchorage in the mouth, in the buccal region of the mandible or maxilla, for example where implants and onplants could not be placed. www.indiandentalacademy.com
    •  Recently drill free screws were introduced to orthodontics.  Compared with drilled screws, the drill free screw provide a decrease in operative time, lower morbidity, and less invasiveness because drilling is not required before screw placement.  Results of the Periotest showed that the DF group had a PTV of +9.3, which indicates clinically firm screws; the D group had a PTV of +15.6 which indicates palpable mobility.  This suggests that the screws in the DF group were more stable than those in the D group. www.indiandentalacademy.com
    •  Generally the mandibular screws showed a lower PTV value than those in the maxilla in both the groups.  This is probably due to the presence of more cortical bone in the mandible. www.indiandentalacademy.com
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    •  Deguchi etal suggested that a 3 week healing period in dogs, which is similar to approximately 4-5 weeks in humans, is necessary to resist orthodontic loads, because the screws might not withstand an immediate load in less favourable bone, such as the maxilla.  However this study showed that the PTV of the drill free group was lower than in the D group in all locations, including the maxillary buccal, even under early orthodontic loading.  The PTV of the buccal region of the maxilla in the DF group was similar to that of the buccal region of the mandible and the palatal region of the maxilla in the D group.  This suggests that DF screws can enhance the capacity to resist early orthodontic loading. www.indiandentalacademy.com
    •  Although screws used in this study showed a higher PTV than the prosthetic implants(-6 - +5 PTV ), most micro screws in the DF group (93.5%) were maintained under continuous orthodontic loading.  This is supported by another study done by Deguchi etal which showed that screws could resist orthodontic loading even when surrounded by immature, woven bone.  This can be explained by the fact that orthodontic loading usually consists of continuous, horizontal forces of a low value( from 20 to 30 g to a few hundred) with a short phase. www.indiandentalacademy.com
    •  Microscopic findings showed that bone remodeling was in progress with woven bone mineralization between the screw and lamellar bone.  In addition, osseointegration was observed on the surface of the screw of both the groups.  This is consistent with previous studies which showed that orthodontic loading did not hinder bone remodeling and osseointegration that maintain a rigid interface, once the screw was rigidly fixed in the supporting bone. www.indiandentalacademy.com
    •  In contrast other studies have suggested that fibrous tissue might be interposed at the interface because of easy removal.  The easy removal can be explained by the low removal torque, which is proportional to the square of the screw radius.  This is derived from the fact that the removal torque of the screw is proportional to the screw radius and bone contact area. www.indiandentalacademy.com
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    •  This indicates that screws with a small radius need a low removal torque and can be easily removed without an additional operation.  A previous study revealed that a screw could loosen if orthodontic loading, which can induce a moment, is applied to the screw. www.indiandentalacademy.com
    •  Microscopic findings also showed that the DF group adapted well to the bone with few voids, whereas the D group had many gross voids between the screw and the bone.  In addition some screws in the D group were encapsulated with fibrous tissue. www.indiandentalacademy.com
    • Histomorphic analysis showed that the DF group had a more bone- metal contact and a larger bone area than the D group. www.indiandentalacademy.com
    •  Drill free method provides a more favourable circumference to maintain a rigid interface in the bone tissue than the drilling method.  This could be due to the damage caused by surgical drilling.  In particular, overheating during drilling and local disturbances can inhibit normal healing.  This can induce undifferntiated connective tissue and prevent bony adaptation around the screw.www.indiandentalacademy.com
    •  Overall this study showed that the drill free screw can provide high initial stability as a result of less bony damage compared with the drilling type.  The drill free screw also increases the level of bone remodeling and osseointegration.  These advantages could reduce the mobility of these screws under early orthodontic loading. www.indiandentalacademy.com
    •  The use of a screw with too large a diameter in the hope of broad bone to metal contact might incur the risk of microfracture of bone within the threads and obstruction of circulation.  This in turn could induce bony necrosis, although it might offer tighter contact with bone.  On the other hand a screw with too small a diameter could fracture from friction with the bone, especially in the mandible.  Thus the proper diameter of the screw should be selected. www.indiandentalacademy.com
    •  The stability of screws could be influenced by loading conditions, surrounding tissue, operative technique, and other factors such as screw diameter and blasting or coating on the surface. www.indiandentalacademy.com
    • Conclusions  This study demonstrated that bone remodeling and osseointegration occur around orthodontic screws under early orthodontic loading.  PTV, bone to metal contact, and amount of bone area were better in the DF group than in the D group.  This indicates that DF screws with a careful technique, can provide better primary stability under orthodontic loading than drilling screws and can be effective as orthodontic anchorage. www.indiandentalacademy.com
    • Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com