Implants in Orthodontics A Paradigm shift www.indiandentalacademy.com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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Introduction a) Anchorage control during orthodontic treatment is essential for obtaining non compromised results.
b) Conservation of anchorage in totality has been a perennial problem to the traditional orthodontist.
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Classification of Anchorage Anchorage has been classified as * Group A+ :- distalization of upper molar is to be performed when more space is required for retraction of the anterior segment, than what is obtained by extraction of Bicuspids. www.indiandentalacademy.com
* Group A :- more than 75% of the extraction space is required for retracting the anterior segment.
* Group B :- describes symmetrical space closure with equal movement of the anterior & posterior teeth to close the space. * Group C :- this is a category of non- critical anchorage wherein 75% of the space closure is achieved by mesial movement of the posterior teeth. www.indiandentalacademy.com
Methods of Anchorage control Conventional
Extra oral
Intra oral
Head Gear
Dental anchors
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The Paradigm Shift is the usage of implant as skeletal anchors to overcome the problems of conventional anchors.
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Problem with Conventional anchors * Head gears require patient compliance so as to be an effective source of anchorage. If the patient is not co-operative enough with the treatment, anchorage preservation becomes a difficult issue to tackle. & * There are also many reported cases of Head gear injuries. www.indiandentalacademy.com
While problems with dental anchors are that, the anchor units experience a reciprocal effect of the forces applied to move the remaining teeth to their optimal positions – thereby tending to move towards the direction of the force applied.
Therefore skeletal anchorage through implants is chosen to limit the extent of detrimental, unwanted tooth movement. www.indiandentalacademy.com
Implants * Definition:Definition according to Boucher – implants were defined as alloplastic devices which were surgically inserted either into / onto the jaw bone.
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Historical Background * Gold & Ivory implants were used in the 16th century in Chinese civilization for replacement of missing teeth. * Metallic implants were developed only in the early 20th century. a) The initial implants – were made of precious metals like gold & iridium. www.indiandentalacademy.com
b) Cobalt – chromium & Titanium implants were introduced in the 1940’s & 1950’s. c)Non- metallic implants like vitreous carbon & bioglass were introduced in the 1970’s. It was found out that Vitreous carbon implants showed a failure rate of 67% during orthodontic loading. www.indiandentalacademy.com
Early studies on Implants
• Gainsforth & Highley in 1945 used vitallium screws in 6 dogs. The implants were inserted in the ramal area, immediately loaded & used for retraction of the upper cuspids. They observed that all the screws were lost within a period of 16 to 31 days. www.indiandentalacademy.com
* Linkow in 1970 used an implant for replacing a missing molar tooth. This implant was then used as an anchor source to which class II elastics were attached for retraction of upper anteriors. The major disadvantage with this study was that long term stability of the implant was not reported. www.indiandentalacademy.com
CREEKMORE(1983) reported the possibility of skeletal anchorage in orthodontics . ROBERTS(1989) used conventional two stage implant in the retromolar region to help reinforce anchorage for successfully closing the first molar extraction site in the mandible . After completion of the orthodontic treatment the implant was removed and histologically analysed . They found a high level of osseo integration had been maintained despite the orthodontic loading. HIGUCHI and JAMES ( 1991) used titanium fixtures for intraoral anchorage to facilitate orthodontics tooth movement.
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Structure of an Implant Implant Body
Head (Serves as) Abutment in prosthetic rehabilitation
Attachment source for elastics & coil springs in orthodontic treatment
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The portion that is embedded in the bone is termed as Body. The Body is divided into 2 types a) Screw type b) Plate type
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Classification of Implants I) Based on location :- they are classified into, a) Sub-Periosteal:- here the implant body lies over the bony ridge. Eg:- Onplant The disadvantages of the onplant system are that – the chances of dislodgement are high, their complexity of the design & the cost factor (as these are very expensive). www.indiandentalacademy.com
b) Transosseous:- Implant body penetrates into the bone. The disadvantages of this system were – they might damage the intrabony structures like the nerves & blood vessels.
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c) Endosseous:- here the Implant body is partially submerged & anchored within the bone. These type of Implants are the ones which are widely used now.
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II) Based on Implant Morphology: Implants
Screw type
Blade/ Plate Disc type
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type
III) Based on composition: a) Stainless steel b) Titanium c) Cobalt- Chromium- Molybdenum d) Ceramic e) Miscellaneous:1) Vitreous carbon 2) Composites 3) Poly lactic acid resorbable www.indiandentalacademy.com
IV) According to the surface structure:- implants are classified as a) Threaded & Non-Threaded – the Threaded implant provides greater surface area & thereby increases the stability. b) Porous & Non-porous – in the case of Porous implants – the vents in the implant body aids in the ingrowth of bone resulting in a better interlocking between the implant & the bone. www.indiandentalacademy.com
V) Based on integrity to the bone:a) Osseointegrating – the term osseointegration implies an intimate structural contact between the implant surface & the adjacent vital bone, devoid of any intervening fibrous tissue. Eg: Onplants, Orthosystem The advantages of osseointegration are that there is an excellent adaptation of the implant to the bone surface thereby ensuring better stability. www.indiandentalacademy.com
The disadvantages of osseointegration are:1) Two surgical procedures are required – one for placement of the implant & another for removal of the implant. 2) Immediate loading is not possible as adequate time is required for osseointegration.
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b) Partially osseo-integrating / Non-osseointegrating:Non-osseointegrating The stability of the implant is by mechanical retention aided by the threads present in the body of the screw. Eg:- Miniscrews. The advantage of this type is that, since they do not osseointegrate – they can be easily placed in the required area with minimum surgical procedure & also removed with ease by just unscrewing them with the same drivers used for inserting them. www.indiandentalacademy.com
Bone Tissue Three distinct types of bone (woven, lamellar, and composite) are involved in postoperative healing and maturation of the osseous tissue supporting an implant . Woven bone has high cellularity, a rapid formation rate (30 m/day or more), relatively low mineral density, high random fiber orientation an poor strength. It serves an important stabilization role in postoperative healing of endosseous implants . During the initial healing process woven bone fills all spaces at the bone-implant interface. Although capable of stabilizing an unloaded implant, woven bone lacks the strength to resist masticatory function. Lamellar bone is the principal load-bearing tissue of the adult skeleton. It is the predominant component of a mature bone-implant interface. Lamellar bone is formed relatively slowly (less than 1.0 m/day),has a highly organized matrix, and is densely mineralized. Composite bone is a combination of paravascular lamellar bone deposited on a woven bone matrix.. Formation of composite bone is an important step in achieving stabilization www.indiandentalacademy.com
Finite Element Analysis of Endosseous Implant and bone after vertical,horizontal and diagonal loading by Kobel and Harzer. Three types of endosseous implants (all 9 mm in length and 3.3 mm in diameter, made of titanium) were used for this investigation. Type 1 was a simple, cylinder-shaped implant; type 2 a cylinder-shaped implant with a superperiosteal step; and type 3 a cylinder-shaped implant, subperiosteally threaded, with a superperiosteal step. The load on the implant was investigated under three conditions of bite and orthodontic forces from 0.01 to 100 N (vertically, horizontally, and diagonally). Vertical loading caused deformation of trabecular bone with all three implant geometries .Trabecular bone deformation was reduced by a superperiosteal step in the design. Horizontal loading of the implants shifted the deformation from the trabecular to the cortical bone. large deformation was measured at the transition from cortical to trabecular bone. The smallest deformations were found for implants with a superperiosteal step and diagonal loading . The use of threads provided no improvement in loading capacity. www.indiandentalacademy.com
The predictable use of implants as a source of orthodontic and dentofacial orthopedic anchorage requires a practical understanding of the fundamental principles of bone physiology and biomechanics.
Optimal use of osseointegrated implants requires a thorough knowledge of bone biomechanics, particularly when the patient is skeletally and/or periodontally compromised An evaluation of bone metabolism is a key element of the diagnostic workup. The minimal screening procedure involves a careful medical history, evaluation of signs and symptoms of skeletal disease and an assessment of risk factors associated with negative calcium balance.
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The most prevalent metabolic bone diseases in middle-aged and older patients are: a) Renal osteodystrophy-poor bone quality (fibrousdysplasia) that is secondary to inadequate kidney function . b) Hyperparathyroidism-elevated serum calcium is often associated with highturnover osteopenia (low bone mass) secondary to a parathyroid adenoma . c) Thyrotoxicosis-high bone turnover leading to osteopenia, associated with hyperthyroidism orovertreatment of hypothyroidism . d) Osteomalacia-poor mineralization of osteoid is due to a deficiency of the active metabolite of vitamin D (1, 25-dihydroxycholecalciferol) . e) Osteoporosis-usually defined as symptomatic osteopenia; most common fractures are of the spine, wrist, and/or hip. Fragility of other weight bearing joints such as the knee and ankle are also common problems.
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Anchorage derived from implants:implants a) Direct:Direct an endosseous implant is used as an anchorage site. b) Indirect:Indirect there are 2 types 1) Orthopedic :- for maxillary expansion & maxillary protraction. 2) Dental www.indiandentalacademy.com
Dental anchorage
For space closure
For distalization of teeth
For intrusion
anteriors
posteriors
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Implants for Maxillary Protraction a) Shapiro & Kokich 1984 used ankylosed teeth as
anchorage for skeletal protraction wherein deciduous canines were intentionally ankylosed & protraction head gear was given. The intentionally ankylosed teeth were used as osseous handles & were called as Pseudoimplants. www.indiandentalacademy.com
b)Smalley et al 1988 used Branemark implants into the maxilla, Zygoma, Orbital & Occipital bones of monkeys. A force of 600 gm was delivered to maxillary and zygomatic bones . A 12mm widening at the zygomaticomaxillary suture was seen and 16mm widening at zygomaticotemporal suture was observed. The dental changes seen were a 5-7mm change in overjet. They observed that skeletal protraction occurred along with dental tipping.
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Implants for maxillary expansion a)
Movassaghi et al 1995, tested frontonasal suture expansion in rabbits from an implanted titanium screw device with plates. After 4 weeks of healing , 55gm of force was applied for a period of 5weeks. On observation it was found that there was significant increase in the growth across the frontonasal suture.
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b) Andrew parr et al 1997 conducted experiments on mid-nasal expansion with endosseous titanium implants.
The sample groups were divided into one control & two experimental groups. For the two experimental groups loading forces of 1 N & 3 N were applied.
92 % implant stability was observed . Sutural expansion of 5.2mm and 6.8 mm respectively was seen in the 1N and 3N load categories. Mineral apposition and bone formation rates were significantly higher in the experimental group. The 3N group showed more expansion but this did not affect the rate of bone formation across the suture www.indiandentalacademy.com
Implants for Dental anchorage – earlier studies a) Implants for intrusion of teeth Creekmore in 1983 published a case report of usage of a vitallium implant for anchorage, while intruding the upper anterior teeth. The vitallium srew was inserted just below the anterior nasal spine . After an unloading period of 10 days, an elastic thread was tied from head of the screw to the arch wire. Within one year, 6mm intrusion was demonstrated along with 25 lingual torque .
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b) Another study by Southard in 1995 compared the intrusion 'potential of implants with that of teeth (denta1 anchors). Titanium implants were placed in extracted 4th premolar area in dogs, followed by an unloading period of three months. Then, an intrusive force of 50-60 gm via 'V' bend was effected. This was compared with intrusive potential of teeth on the other side using the same mechanics. No movement of implant was seen at the end of the experiment whereas, on the other side, the tooth acting as the anchor units tipped severely. Therefore, implants are definitely superior to the teeth acting as anchor units.
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Classification of Implants for Dental anchorage Based on the area of placement :a) Sub- periosteal b) Osseous c) Interdental www.indiandentalacademy.com
Based on Implant Morphology:
a) Disc type - Onplant b) 1) 2) 3) 4) 5)
Screw type – Mini – implant Orthosystem Aarhus implant Micro implant Spider screw, Omas screw www.indiandentalacademy.com
c) Plate type – 1) Skeletal anchorage system 2) Graz implant supported system 3) Zygoma anchorage system www.indiandentalacademy.com
Sub Periosteal implant The disc type implant is used.
Block & Hoffman in 1995 developed this system which consisted of Titanium circular disc of 8 – 10mm in diameter & 3mmwww.indiandentalacademy.com of average thickness.
Osseointegration :- The undersurface of the disc is coated with Hydroxyapatite which is a bioactive substance aiding in osseointegration & thereby improving the stability of the implant.
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Criteria for usage:- Onplant can be used only in skeletally mature patients. Pre-Surgical procedure:- An impression is made of the maxillary arch . A clear vacuum formed stent covering the palate is fabricated – with a small piece of clay placed for relief on the region where the Onplant is to be seated. The use of the stent is a) To place a small amount of pressure on the palate after onplant placement so as to avoid migration of the onplant & to prevent hematoma formation. b) It aids in better patient comfort. www.indiandentalacademy.com
Onplant installation Involves two stage surgical procedure. Stage I:- the steps are 1) Disinfecting the working area (intra oral) with 0.5% chlorhexidine mouthwash. 2) Administration of local anesthesia to the palatal soft tissue – from the canine area to the midline palatal tissue opposite the 1st molars. 3) Following adequate anesthesia, a 15-25mm long incision is made in the palate adjacent to the canine & premolars within 5mm of these teeth. www.indiandentalacademy.com
Advantage of this incision is that – it maintains intact tissue at & near the final position of the onplant thereby minimizing the risk of soft tissue breakdown during the healing period. *** the incision is placed far from the midline of the palate.
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4) Periosteal elevator is used to conservatively open a sub-periosteal tunnel which extends across the palatal midline opposite to the 1 st molar.
Requirements of the tunnel:- a) It should be of a limited width to avoid onplant movement when once placed firmly. b) It should be sub-periosteal so that the onplant can www.indiandentalacademy.com directly contact the bone.
Steps cont’d: 5) Bone file may be used to level any bony irregularities so as to create a flat seating area. 6) Onplant is picked with its inserter & carried into the tunnel opening. 7) Periosteal elevator is used to ensure direct vision for onplant placement. 8) Onplant is slid through the tunnel to its final resting position on the hard palate.
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9) The inserter is released from the onplant ( after pressing the onplant towards the bone with one finger through the overlaying soft tissue) & pulled out of the tunnel. 10) The incision is then sutured. 11) Small amount of tissue conditioner is placed in the relieved area of the vacuum formed stent & the stent is seated completely.
12) Patient is placed on antibiotics & analgesics. 13) After 7 days post surgery – the sutures are www.indiandentalacademy.com removed.
Precautions to be taken during the 1st stage of surgery a) b) c)
d)
Onplant should not be placed on the periosteum/ gingival tissue as it will not osseointegrate. The Hydroxyapatite surface should not be touched with talc covered gloves as it will also interfere with the osseointegrate. Onplant should be placed on a stable/ flat bone surface so that it does not wiggle under palatal soft tissue.
Stent should not be removed for the 1st 24 hrs. patient is advised to remove it only for cleaning. www.indiandentalacademy.com
e) If bleeding / swelling / pain occurs, patient should be asked to visit the surgeon. f) Onplant should not be exposed( for abutment placement) till 16 weeks. This is the time required for osseointegration between the onplant & the bone. *** IInd stage surgery:- for abutment placement. Procedure: 1) Onplant is located by palpating the elevated site on the palate. 2) Local anesthesia is injected to the surgical site. 3) Small incision is made to confirm the specific location of the cover screw. 4) Cover screw is exposed by tissue punch & removed with a hexagonal screw driver. www.indiandentalacademy.com
5) Connective tissue remnants (covering the onplant) are removed
with a surgical blade. 6) Abutment is placed & Trans palatal arch is fabricated.
Uses of Onplants:• • •
For Enmasse retraction of the anteriors. For distalisation of posterior teeth. For intrusion of posterior teeth especially the maxillary molars.
Disadvantages of Onplants:Onplant placement • Long waiting period for healing/ osseointegration prior to orthodontic loading. Abutment placement • Surgical procedure involved is three Onplant removal www.indiandentalacademy.com
Osseous Implants Definition:-
Implants placed in dense bone like Zygoma, Body & Ramus of the Mandible, Mid-palatal areas.
Eg:-
1) Skeletal anchorage system:-
Umemori et al 1999, developed this system which consists of miniplates stabilized with screws. These were placed in Maxilla or Mandible. They differ from the surgical miniplates, wherein they have been modified for attaching elastomers/ coil springs. There are 2 types of plates classified based on shape into,
a)
L shaped
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b) T shaped – which is used for intruding anterior teeth.
The diameter of the screw used for fixation of 2 to 2.5mm. Procedure for placement:- 1) Incision is made. 2) Flap to be raised at the site. 3) Prior to incision, the implant site is assessed radiographically for any erupting tooth, evaluating the sinus & its lining & inferior alveolar canal. 4) Miniplate is adapted to the contours of the bone. 5) The end of the loop of the miniplate is bent outward to remain exposed into the oral cavity. www.indiandentalacademy.com
Uses of the Loop:- it acts as the site of attachment for orthodontic force application. Following placement, 3-4 weeks of healing period is allowed prior to force application. In cases of molar intrusion, buccal root torque value is to be increased to prevent excessive buccal flaring of the teeth. 2) Zygoma Anchorage system:system developed by Hugo de Clerck et al 2002. This system consists of curved titanium miniplate with provision for using 3 screws of 2.3mm diameter each for improved stability. Area for placement:- this system is designed for use in the Zygomaticomaxillary buttress area between 1st & 2nd molars.
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The author states that the disadvantage of the conventional miniscrews is their proximity to the roots, as a result the screws may damage the roots during placement, whereas the miniscrews in this system are placed at a safe distance from the roots of the maxillary molars. The combination of 3 screws along with the miniplate is to bring the point of force application near the center of resistance of the 1st permanent molar.
3) Graz implant supported system :- introduced by Karcher, Byloff et al in 2000.
This system consists of modified Titanium miniplate with 2 oval shaped cylinders attached to it & provision for 4 miniscrews. It was mainly used as a support ( like a nance button) in a pendulum appliance.
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Orthosystem Implant Developed by Wehrbein et al . this is a titanium screw implant of length 4 or 6mm and diameter of 3.3mm. It can be inserted in the mid-palatal area of the maxilla & in the retromolar area of the mandible. These implants are surface treated with sand blasting & acid etched to improve integration to the bone. Osseous implants produce effective anchorage during tooth movements but require complex surgical procedure for placement & for removal of the implant & also the chances of infection arising around the periimplant area is more.
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Screw type Implants Areas of placement
Anterior nasal Retromolar Spine Buccal
Interdentally
Midline of the palate area
Palatal
Advantages:1) They are of smaller diameter. 2) They attain stability basically by Mechanical retention & partly by osseointegration. 3) Placement is very simple. 4) Implant removal is also very simple as they are only partially osseointegrating in nature. www.indiandentalacademy.com
Types of implants 1) Mini Implants developed by Kanomi et al 1997 2) Aarhus implants developed by Melsen B et al 3) Micro-implant anchorage developed by Kyung et al 4) Omas bone screw developed by Lin et al 5) Miscellaneous www.indiandentalacademy.com
Implants used in the mid-palatal area I)
Anatomical Basis: a) Karl Andreas Schlegel et al 2002 conducted a study on a population with age ranging from 12 to 53 years. They observed that
1) Maxillary bone was classified as grade 3 due to a thin corticalis & only relative dense trabecular structures. 2)The bone thickness in the midline of the palate was around 1.5cm 3)A gap of 0.03cm between the osseous wings was more evident in the anterior region of the Suture Palatina Media (SPM) than in the posterior region. Â www.indiandentalacademy.com
They concluded that 1) The Posterior region of the SPM offers better site for placement of osseointegrating implant as the gap between the osseous wings is low when compared to the anterior region. 2) Even though the gap in the anterior region is 0.03cm between the osseous wings, an implant of 0.4cm could be placed as they have the ability to osseointegrate. 3) The implants to be placed in the mid-palatal region- the ideal age according to them is above 20 years. www.indiandentalacademy.com
Radiological assessment of Palatal bone thickness
I) Wherbein et al 1999 evaluated bone height in the mid-sagittal
region & also compared the cephalometric assessment with clinical results obtained during the insertion of the implants.
Procedure:1) The Implant size was assessed by measuring the vertical bone height on the lateral cephalogram. 2) The surgical procedure was performed by removing the palatal mucosa with a standard punch & then the bone was drilled with a pilot & profile drill. 3) Probing was performed with sterilized periodontal probe( Brod 25G, Ash, Weybridge UK) which was set to indicate a force of 0.2N to detect any bony perforation to the nasal sinus. When the cavity revealed a resistance of 0.2N – it was diagnosed as no perforation to the nasal cavity. 1) Implant was inserted. 2) Following this another radiograph was made with the implant in position. www.indiandentalacademy.com
Parameters used for radiologic assessment were, a) b) c)
Implant position with respect to the section of the palate. Implant angulation to the palatal plane. Distance between MCBI- Most cranial border of the implant & MCBPC- Most cranial border of palatal complex
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.
Conclusions of the study were:1) Mid- sagittal area of the palate is a valuable insertion site for implants. 2) Sufficient bone support is available in the anterior & middle sections of the midpalate for implants of 4mm & 6mm length & 3.3mm diameter. 3) Vertical bone support in the mid-sagittal area of the palate is atleast 2mm more than what is predicted in the radiograph. 4) Implant angulation has a considerable influence on remaining vertical bone height above the MCBI. If the angle between the implant axis to the ANS-PNS is small- it indicates more residual bone is available above the MCBI. II) Henriksen et al 2003 conducted a study to evaluate bone thickness in the anterior hard palate inferior to the incisive canal. Procedure:- 25 dry skulls were assessed radiographically( lateral ceph) & vertical thickness of the mid-palate was measured. Gutta Percha was injected into the incisive canal & radiograph was repeated. Bone thickness was measured from inferior hard palate to inferior most part of the canal. www.indiandentalacademy.com
Observation :-
Only 4.3+/- 1.6mm of bone is available for the implant. Therefore they concluded that implants of 4mm in length could be used freely (without any anatomical limitations) whereas that of 6mm should be used with caution.
3) Gahleitner et al in European journal of radiology 2004 , performed a study wherein Dental C.T was used as a tool to locate the optimal size & position for orthodontic implant placement.
Procedure:-
1) Axial C.T scans of the maxillary bone were acquired. 2) Paracoronal views were reconstructed & measurements of the palatal bone height in 3mm increments from the incisive canal were performed.
Results:-
a) Overall mean bone height was 5.01mm with standard deviation of 2.60. b) Maximum palatal bone height was 6.17 with SD 2.81 at 6mm dorsally from the incisive canal.
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Presurgical preparation:1) Laboratory test to be performed include evaluation of Bleeding time & Clotting time and Blood pressure evaluation. 2) One hour prior to surgery – Antibiotic prophylaxis ( preferably 3gm of Amoxycillin) is given. If the patient is allergic to Penicillin – Cephalexin/ Erythromycin can be given. 3) Intra-oral disinfection is done with 0.2% Chlorhexidine gluconate mouthwash. Area for placement of the implant:-
Jessie Jacob et al preferred placing the implant in the palatal midline between 1st premolars. They also stated that implant placement should take into consideration – that a bone bed more favorable for osseointegration might be found posterior to the interconnecting line of the 1st premolars.
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Types of Mid-palatal Implants
Orthosystem
Micro-Implant
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Stent preparation :Tinsley et al JOO 2004
have advocated preparation of a stent prior to the surgical procedure of Implant placement. The stent is of 2 types
Radiographic
Surgical
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The radiographic stent consists of 2 metal tubes of the same diameter & length as that of the implant. The tubes are positioned with an acrylic base plate. Advantages of using the tubes of same size as that of implants is to account for any x-ray magnification. The metal markers are placed in the region between premolars & angled approximately perpendicular to the curve of the plate. The stent is then fitted into the patient’s mouth & radiograph is taken. This radiograph allows accurate assessment of the bone depth & shows the position of the nasal floor.
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The radiographic stent is now converted to a surgical stent by removing the markers & preparing a 6mm hole in the acrylic base plate so that it acts as a guide through which the implant preparation drills can be used.
Surgical Procedure: A) for orthosystem implant: The implant is available in 3.3 mm diameter, self tapping and in 4/6mm length. The surface is sand blasted & acid etched to maximize the stability – wherein high level of direct bone contact occurs during osseointegration. Steps: 1) Palatal mucosa is firmly anesthetized. 2) Mucosal trephine is used with a slow speed hand piece to remove the mucosal tag. Â
Mucosal trephine bur www.indiandentalacademy.com
3) A round steel rose head bur is used to gain access to the softer cancellous bone of the palate. The hand piece is run at not more than 700 rpm. Copious saline irrigation is performed during the drilling procedure so as to ensure that bone does not get heated thereby preventing a) Tissue & osseous necrosis & b) Implant failure. 4) A profile drill is used to prepare the site. The cutting part is available in 2 lengths of 4 & 6mm. The length of the shank is also variable depending on the shape of the palate. Longer shank allows easier access in high vaulted palate cases. 5) The drill should move into & out of the bone only once & in 1 direction. The preparation should be parallel sided to achieve primary stability. 6) Once the site is prepared, its checked with a periodontal probe to ensure adequate depth is present & that no perforation into the incisive canal has occurred.
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7) Implants are picked from sterile ampoules in which they are stored. They should not be touched with gloved hand as they may get contaminated. 8) Implants are placed with finger held instrument called “ Ortho Inserting device� & then tightened with a ratchet until they are seated firmly. 9) Once inserted, they are assessed for stability. If they are found to be stable, a healing cap is placed over the implant & a radiograph is taken to assess/ confirm its position. Implant in position
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10) Implants are left unloaded for 3 months, the implant is reviewed clinically to check for stability. If they are found to be stable – a Trans Palatal arch is fabricated. (types) Banded
Bonded
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The disadvantage with the bonded TPA was that the Debonding rate was found to be extremely high because – during mastication the anchor teeth moved within the Periodontal ligament whereas the implants were rigidly fixed to the bone as a result – a differential movement occurred which caused the bond failure to occur between the TPA & the tooth. Tinsley et al 2004 have advocated the use of a lingual hinge bracket- which can be welded to the bands of the anchor teeth. The size of the bracket slot limits the dimension of the TPA to 0.8mm. The advantage with the hinge bracket is that- path of insertion problems as with conventional attachment of the TPA to the bands can be eradicated. Here the bands are cemented prior to TPA placement, the TPA can be placed & the hinge clip can be closed over the TPA.
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Procedure for Micro-Implant placement: 1) The drill should be checked before surgery for any bends so as to prevent any wobbling & enlargement of the site of implant placement. 2) A low speed contra angle hand piece with a drill size 0.2 to 0.3mm narrower than the microscrew used for initial entry into the bone. The micro-implant itself should not be used for self drilling as this may lead to metal fatigue & eventually fracture of the screw. 3) The drill can penetrate the mucosa & underlying bone without a surgical flap. The drill speed should be 400-500 rpm & it should be used along with copious saline irrigation to keep the surgical site lubricated. 4) When drilling into the dense bone – careful up & down strokes should be done to minimize the heat generated by the slow speed handpiece. www.indiandentalacademy.com
Micro-Implant Driving Methods 2. Self窶電rilling procedure Two-step
One-step
or After indentation
Without indentation
1) Driving
(suitable for Diagonal insertion
(suitable for Perpendicular insertion
& thick cortical bone)
& thin cortical bone)
Dia.; less than 1.5mm
Dia.; more than 1.5mm for Ortho. Micro- &MiniImplant www.indiandentalacademy.com
Micro-Implant Driving Methods 3. Self –tapping procedure
1) Indentation One step
Two step
o (in case of very thick cortical bone) r 2) Drilling o r 3) Driving
for Ortho.Micro-Implant: Dia.; less www.indiandentalacademy.com than 1.3mm
Insertion of the micro implant The implant can be inserted into the bone either with Hand driver / with an engine driven screw driver.
Manual screw driver is of 2 types
Long
Short
designed to be used in the buccal surface
designed to be used in the palatal area
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Engine driven screw driver in a low speed contra angled hand piece can also be used for placing the micro-implant. Manual screw driver is always preferred over the engine driven for safety reasons.
** Important considerations during the implant placement: a) if resistance is encountered, the implant should be withdrawn & the bone to be redrilled with pilot drill before implant reinsertion. b) if the implant fit is not tight, a new site adjacent to the original one may have to be prepared/ the implant may have to be replaced with a larger one. www.indiandentalacademy.com
Following insertion, the fit of the implant is assessed clinically. A Trans Palatal arch is then constructed.
If the implant is to be used for effecting tooth movement – immediate loading of force can be performed with Nickel Titanium coil springs.
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Post surgical instructions 1) 0.2% Chlorhexidine mouth wash to be used daily. 2) Patients shoud be instructed to clean the implants initially with cotton wool bud & then with small headed tooth brush as soon as the mucosal tenderness wards off. 3) Patients should be instructed not to play with / push the implant with the tongue. 4) Analgesics & antibiotics are prescribed with specific instructions on their use if required. www.indiandentalacademy.com
Applications of Mid-palatal implants: 1) To serve as anchorage during space closure, wherein the anchor teeth can be attached to the implant thereby preventing their migration during force application when Enmasse retraction is carried out. 2) For intrusion of the Molars
Unilateral
Bilateral
3) For Distalization of molars- in groupA+ anchorage cases. www.indiandentalacademy.com
** Histological evaluation In the case of Osseointegrating implants – histological evaluation revealed a high percentage of predominantly mature lamellar bone in direct contact with the implants which added stability to the implants.
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For the non-osseointegrating implants – the thin, keratinised soft tissue is more advantageous. Yun et al 2001 state that adequate screw stability in the palatal slopes is difficult to obtain because the mucosal thickness is 2 to 3 times more. They have also reported that soft tissue thickness of 1mm is present in the mid-palatal area 4mm posterior to the incisive papilla & thereby have concluded that soft tissue in the midpalatal area is optimal for miniscrew implantation. In terms of Hard tissue- the implant (non- osseointegrating) stability depends on quality & quantity of cortical bone. www.indiandentalacademy.com
Park et al state that mid-palate area is composed of a good of cortical bone corresponding to D1/ D2 of Dr.Misch classfication of the maxillary bone. They also state that the screw stability can be enhanced by splinting 2 miniscrews together.
** Implant Removal:1) For Osseointegrating implants: 1) 2)
3)
Involves a second surgical procedure for implant removal. Standardized Trephine which is precision guided through the implant neck & through a cylindrical sleeve (4.2mm) is screwed into the abutment. Procedure to be performed under local anesthesia. www.indiandentalacademy.com
2) For Non-osseointegrating implants. a)
No such second surgical procedure required.
b)
As total osseointegrating does not occur, the screw driver is engaged in the screw head & is turned in the direction Opposite to that of insertion.
c)
L.A is not required for removal.
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Advantages of Palatal Implants According to Jessie Jacob et al, the palatal implants, 1) Preserve anchorage well. 2)
Have better tolerance from the patient when compared to extra- oral devices used in anchorage preservation.
3)
There is no risk of Bony defects around the implants as the palate is a quasi –flat surface.
4)
As the palatal mucosa is highly keratinised, peri-implant soft tissue conditions are favorable creating a firm connective tissue sealing.
5)
The implants can’t be disturbed by chewing forces. www.indiandentalacademy.com
LONG TERM STABILITY OF IMPLANT
Miyawaki et.al analysed the success rate of three different screw sizes and a miniplate design. Their sample consisted of 51 patients who had 134 different implants used for conserving anchorage. The implants were in the form of screws(134 in number) of 1.0, 1.5 and 2.3 mm diameter as well as 17 miniplates. On one year after placement, they drew the following conclusions: a) The implant screws of 1 mm diameter had a high failure rate and are not recommended for clinical use as Orthodontic anchors. www.indiandentalacademy.com
b) Implant screws of 1.5 and 2.3 mm diameter had reasonable success rates - 84 and 86 % respectively and therefore could be used in majority of the cases. c) The miniplates had the best stability (96%), but the surgical intervention and patient discomfort was greater with these compared to miniscrews. Miniplates have beenrecommended in high angle patients. d) Peri-implant hygiene is one of the major factors, which could affect the stability of these implants.
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FUTURE OF IMPLANT The ideal implant design would be one that would be simple to place as well as remove, causing minimum discomfort to the patient. At the same time, they should be optimum in resisting the conventional Orthodontic forces. One would be looking at newer designs, which could be placed by an Orthodontist himself. Also, since the implants need not last for a very long time, biodegradable implants may be a lucrative option. Biodegradable screws made of L-polylactide have been introduced by Glatzmaier et al and are currently undergoing clinical trials. The system, termed as theBIOS (Bioresorbabale implant for Orthodontic systems)consists of resorbable polylactide with a metal abutment. www.indiandentalacademy.com
Conclusion Implants for the purpose of conserving anchorage are welcome additions to the armamentarium of a clinical Orthodontist. They help the Orthodontist to overcome the challenge of unwanted reciprocal tooth movement. The presently available implant systems are bound to change and evolve into more patient friendly and operator convenient designs. Long-term clinical trials are awaited to establish clinical guidelines in using implants for both orthodontic and orthopedic anchorage.
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