Implant intruduction misch contemporary implant dentistry Dr fariborz vafaee
Dental Implants Bring Quality Back to Life
What is a dental implant? A dental implant is a small titanium fixture that serves as the replacement for the root portion of a missing tooth. Dental implants can be used to replace a single lost tooth or many missing teeth.
ImprovedAppearance When teeth are missing an ongoing shrinkage of the jawbone occurs making the face look older. Dental implants can slow or stop this process.
Who is a candidate for dental implants? Adequate bone in your jaw is needed to support the implant(s) along with healthy gum tissues that are free of periodontal disease.
Are dental implants successful? Documentation studieshave proven the effectivenessand long lasting results ofdental implants. Good oralhygiene is one of the mostcritical factors to insure the health of your dentalimplants.
AnalogsAnalogs may represent anabutment for screw retention, animplant body (left), and/or anabutment for attachment (right).
Fixed restorations havethree categories: FP-1, FP-2, and FP-3ΩFP-1 is idealΩFP-2 is hypercontouredΩFP-3 replaces the gingival drapewith pink porcelain or acrylicΩ The difference between FP-2 andFP-3 most often is related to themaxillary high lip position duringsmiling or the mandibular lipposition during sibilant sounds ofspeech. FP-2 and FP-3 restorationsoften require more implant surfacearea support by increasing implantnumber or size or by adjustingdesign considerations.
Removable restorations ∂ RP-4 prostheses have complete implant support anterior and posterior. ∂ In the mandible the superstructure bar often is cantilevered from implants positioned between the foramens. The maxillary RP-4 prosthesis usually has more implants and little to no cantilever. ∂ An RP-5 restoration has primarily anterior implant support and posterior soft tissue support in the maxilla or mandible. ∂ Often fewer implants are required and bone grafting is less indicated
A tooth exhibits more verticalmovement than an implant. Thismay result in higher occlusal loadson the implant, whether or not it isconnected to the naturaltooth, when in a mouth with bothimplants and teeth.
Occlusal Considerations forImplant-Supported Prostheseslight occlusal force heavy bite force
The premaxilla loses40% to 60% bonewidth within 3 yearsafter the loss of teeth. The implantsurgeon often has difficultyinserting implants whenaugmentation does not restore theregion before implant placement.
The minimum crown height spacefor a fixed restoration is 8 mm The abutment should be at least 5 mm for cement retention. The margin of the crown should be at least 2 mm above the crestal bone level to allow the connective tissue and junctional epithelial attachment zones. At least 1 mm occlusal clearance should be left for an occlusal metal restoration (2 mm for porcelain).
The ideal mesiodistal distance between an implant and a tooth is 1.5 mm or more and 3 mm between each implant. B, If bone loss occurs on the implant, the horizontal dimension of the defect is less than 1.5 mm.
PROTECTION OF THE PROSTHESIS CEMENT-RETAINED VERSUS SCREW-RETAINED IMPLANT FIXED PROSTHESES
The primary advantage of a screw-retained prosthesis (right) isretrievability.
CEMENT-RETAINED VERSUS SCREW-RETAINED IMPLANT FIXED PROSTHESES Retrieval of the cement-retained fixed prosthesis Protection of the implant
ADVANTAGES OF CEMENT-RETAINED IMPLANT PROSTHESES Passive Casting
A 50 µm misfit may require theimplant to move within the bone200 µm before the casting fitspassively
dimensional change in impressionmaterial , stone, metal wax A. The dimensional change of the stone die in this picture is 0.06% shrinkage of the impression material and 0.06% expansion of the stone. This is clinically acceptable. B, The male die does not fit accurately into the female stone model. The dimensional change in this picture represents a 0.2% shrinkage of the impression material and the same stone expansion as in A.
Axial Load The ideal occlusal load on an implant prosthesis is directed over the implant body and is accomplished easily with a cemented prosthesis (f). When a screw hole is placed to retain the restoration, the primary occlusal contact often is located on the buccal cusp in the mandible (fn), which is an offset load that magnifies the force applied to the implant component interfaces (and the fixation screw), fi, Buccal; L, Lingual.
The ideal primaryocclusal contacts The ideal primary occlusalcontacts for posteriorsingle-tooth implant restorationsthat are cement retained is directlyover the top of each implant, whichis usually positioned under thecentral fossa. When the implantsare splinted together, the occlusalcontacts may include the marginalridges, which are between the mostdistal and mesial implant (right).The diagram on the left is for ascrew-retained restoration that issplinted together. The occlusalcontacts are usually between theimplants. Offset loads to thebuccal contact are notindicated, since they will increasethe moment force.
Esthetics and HygieneOcclusal Material FractureAccessFatigueIn the anterior regions of themouth a screw-retained restorationrequires a different implant bodyposition than a cement-retainedrestoration. As a result, a facialporcelain ridge lap is required. Thismakes the cervical sulcus of theimplant inac-cessible for hygiene.
Abutment screws fatigue and areprone to fracture. The abutmentcrown crevice is not sealedcompletely, and bacteria mayproliferate within the components.Because the environment often haslow oxygen tension, the bacteriamay be anaerobic organisms thatcontribute to foul odor andperiimplant disease.
1. Esthetics and Hygiene2. Occlusal Material Fracture3. Access4. Fatigue5. Progressive Loading6. Abutment-Crown Crevice7. Cost and Time
1. Low-profile retention2. Reduced moments of force3. Risk of cement in the sulcus
A screw-retained device is moreresistant to tensile forces comparedwith a cemented abutment inferiorto 5 mm in height. Thereforeoverdenture bars are often screwretained. The lower-profile barprovides greater space for denturetooth placement and greater bulkof acrylic to reduce fracture risks.
One-piece Vs.Two-pieceAbutmentsTwo categories of abutments areused for cemented restorations.The one-piece abutment (far left)may be used in multiplerestorations when the implantbodies are within 20 degrees ofideal. The two-piece abutmentsmay be used for singleteeth, angled implants, and withlaboratory transfers or for customabutments.
retaining screws. The head of thetorque wrench is released at apreset torque level.
Advantages and Disadvantages ofOne-Piece Abutment for CementAdvantages Disadvantages • No torque wrench needed • Only for multiple • Stronger abutments • No screw loosening • Not for single-tooth • Easy complete seating restoration • Not for angled abutments • No need to retighten under restoration • Weaker to fracture • Less expensive • Thicker walls to allow great freedom of preparation
A one-pieceabutment forcement retentionis threaded into the implant bodyand bypasses the antirotationalhexagon component.
two-piece abutmentfor cementretentionIn the two-piece abutment forcement retention the abutmentengages the antirotational featuresof the implant body platform andthe abutment screw that fixates thecomponents into position.
Advantages and Disadvantages OfTwo-Piece Abutment for Cement:Single-Tooth ImplantsAdvantages Disadvantages • Screw loosening • Antirotational under shear • Abutment loosening under forces restoration • Angled abutments • Torque and countertorque devices needed for preload • Proper seating with radiograph must be checked • Thinner walls limit freedom of preparation
A hemostat holds the abutment inposition to the implant body. A 30-N/cm torque wrench is seated intothe abutment screw and rotated.B, The head of the torque wrenchbends at the approximate torquevalue. The hemostat stops therotation force on the screw, loadingthe implant-to-bone interface witha rotational force, because theabutment engages the hexa-gon ofthe implant body
Angled abutments aresimilar to a two-piece The UCLA abutment conceptabutment system permits the laboratory toranging from 15 to 30 custom fabricate thedegrees abutment
The combination of metal and plastic components offers severaladvantages. With the plastic component, cus-tomizing the shapeof the abutment on the implant body transfer impression is easy.The metal coping ensures a high precision at the implant platform-abutment connections.
Disadvantages of AnatomicalAbutments Precise location of implant body and hexagon is needed. Two-piece abutment is needed. Facial and lingual overcontours need to be eliminated. A "subgingival ridge lap" is created. Margin is difficult to capture if intraoral impression is made.
A custom abutment with pinkporcelain added to the subgingivalregion is fabricated to enhance thecervical estheticsThe custom abutment and crownare seated. The subgingival pinkporcelain is advantageous insituations in which the soft tissuesare thin and the grayish color ofthe titanium abutment may affectthe esthetic outcome
Caries andAbutmentsBecause caries is the mostcommon complication ofcrowns on the naturalteeth, guidelines indicate thatthe crown margin not onlyshould be supragingival butalso should be placed onenamel. This not only facilitatesaccess for hygiene but alsodecreases the risk ofcaries, since enamel is moreresistant to decay.
Factors Affecting Abutment RetentionTaperSurface areaHeightResistance form Surface texture Path of insertion
The taper of an implant abutment affects the amount of retention. The amount of retention is significantly reduced for tapers greater than 20 degrees. This concept is more relevant for implant abutments because of their reduced diameter (usually 4 or 5 mm).
The greater the diameter of theabutment, the greater theretention. Larger-diameter implantabutments have greater retentionthan narrow-diameter implants.
Abutment HeightA, When a crown receives a lateralforce,it tends to rotate upward on oneside of the implant. The arc ofrotation is related to the diameterof the implant. The height of theabutment should be greater thanthe arc of rotation. A widerimplant abutment requires greaterheight than a smaller-diameterimplant to resist these lateralforces. B, The arc of rotation maybe decreased when directionalgrooves are prepared into theabutment. Therefore whenabutment height isquestionable, the addition ofvertical grooves decreases the riskof uncementation
In a cantilevered prosthesis, tensileforces are applied on the crownfarthest from the cantilever. Theheight of this implant abutmentshould be greater than the arc ofdisplace-ment of the prosthesisbecause compressive forces to thecement seal are placed on theabutment above the arc ofdisplacement. Buccolingualdirectional grooves decrease therotation arc and place compressiveforces within the grooves.
The two implants replacing thecanine and first premolar haveminimal abutment height and willreceive lat-eral forces. Verticaldirectional grooves parallel to thepath of inser-tion of the prosthesiswill decrease the risk ofuncementation.
Shear Forces The crown on a tapered implant abutment (left) may have several paths of insertion or removal. This places the abutment more at risk of an uncemented restoration. A directional groove (right) limits the path of insertion or removal.
Directional grooves and flat surfaces reduce the arc of displacement and increase the compressive forces rather than shear forces on the cement seal. These concepts are most important for a cantilevered restoration.
Mesial and distal directional grooves decrease tensile forces on a prosthesis subjected to offset loads. These offset loads more often are applied on the facial aspect of maxillary and mandibular restorations. B, Buccal; L, lingual.
When the path of insertion is similar to the forces of mastication, sticky food may place shear and tensile forces on the restoration and contribute to uncemented prosthe-ses. The implant body should receive a long-axis load to reduce crestal stress. A path of insertion different from the occlusal force direction is selected to decrease the shear loads to the cement seal from sticky foods. Angling the path anteriorly facilitates prepara-tion of the abutment and seating of the restoration.
| NON PARALLEL ABUTMENTS When the abutment angle needs a correction of less than 20 degrees, a straight abutment may be used and prepared intraorally (one-piece or two-piece abutment) or in the laboratory (using an implant body transfer impression and a two- piece abutment).
One-piece abutments for A high-speed handpiece iscement were placed on used to prepare thethese two implant bodies.The distal implant is abutment and correct theangled buccally. path of insertion.
When the implant body is between 15 and 35 degrees from ideal, a prefabricated two-piece angled abutment may be used to improve the path of insertion.
The cervical region of an angled abutment is often larger in diameter to increase the metal thickness on the side of the abutment screw hole. This portion of the abutment is placed subgingivally but may become exposed after gingival recession.
Copings are cemented over the abutments. These copings are prepared in the laboratory to create a common path of insertion for the prosthesis.
A reverse conical abutment is wider at the top than the abutment connection to the implants.
The reverse conical abutment is inserted into the angled implant body and prepared to be parallel to the ideal implant position.
A two-piece custom angled abutment may be fabricated in the laboratory using a transfer impression of the implant body.
The maxillary first molar had a buccal furca exposed. The knife-edge preparation reduced the furcation under-cut and decreased the risk of pulpal exposure.
In the interproximal region of lower anterior teeth, a knife- edge preparation may be indicated, especially when the incisal edge is wide and the cervical region is narrow in diameter.
The facial position of two of these implant abutments requires a chamfer preparation to provide greater room for porcelain.
Steps in Direct and Indirect(Prosthesis) Fabrication Techniques
Steps in Direct andIndirect (Prosthesis)Fabrication Techniques
Option 1 (Indirect) the dentist makes an implant body impression with an indirect or direct impression transfer coping.
Option 2 (Indirect) Clinical 1 Remove healing abutment. Place indirect impression transfer. Take alginate impression. Remove independent impression transfer. Replace healing abutments. Laboratory 1 Connect independent impression transfer and implant body analog. Reposition in impression. Pour the impression. Fabricate open custom tray. Clinical 2 Remove healing abutments. Place direct impression transfers with hexagon; confirm seating with radiograph. Make impression (polyether or polyvinyl siloxane). Unscrew direct impression transfer through tray. Remove impression. Replace healing abutments. Obtain opposing model, bite registration, and face-bow registration. Laboratory 2 Connect implant body analog to direct impression transfers in impression. Pour model in die stone. Mount opposing with bite and face-bow. Select and prepare all abutments.
Option A Option B Remove healing abutments. Remove healing abutments. Position final abutments Position final abutment with jig. Confirm seating with with jig. Confirm seating with radiograph. radiograph. Torque abutments to 30 N-cm. Metal work try-in. Radiograph to verify fit. Take bite Metal work try-in. Radiograph to registration. Remove all abutment. Replace verify fit. Take bite registration. healing abutments. Laboratory 3 Make pick up impression. Deliver Remount model to new bite. Finish temporary restoration. prosthesis. Pour pickup impression. Remount Clinical 3 Remove healing abutments. impression. Finish prosthesis. Seat abutment with jig. Remove temporary Torque to 30 N-cm. restoration. Radiograph to verify Seat final prosthesis; deliver prosthesis. fit.
The permucosal extensions areunthreaded from the implant bodies
A two-piece indirect impression transfer, which engages the hexagon of the implant body, is designed with undercuts to maintain it in proper position and prevent its move-ment while the impression is poured.
The two-piece indirect impression transfer copings are threaded into position. A radiograph is obtained to confirm proper seating of the components.
Small bubbles or voids are usually not relevant for indirect An impression is made of the three implantimpression transfer impressions as long as the transferundercuts are engaged securely in the impression and the bod-ies and of the four natural teethcompo-nent is maintained securely prepared on the contralateral side
The component to the far left is an abutment screw; next is a two-piece abutment for cement retention assembled with the abutment screw; next is a ball abutment transfer screw; next is the ball transfer screw assembled with a two-piece abutment; next is an implant body analog; far right is the ball transfer screw assembled with a two-piece abutment and the implant body analog. These last components are reinserted into the final impression before pouring the stone model.
The implant analogs are reinserted into the impression, and the laboratory places a resilient material around them to represent the soft tissue around the implants.
The cast is separated from the model, and the two-piece abutments for cement retention are inserted into the body analogs of the implant. A marking pen is used to transfer the tissue height onto the abutment.
The resilient soft tissue replica is removed from the master cast. A surveyor/handpiece is used to prepare the abut-ments parallel to each other. A flat side on each abutment and a knife-edge margin are common features.
The master model is complete with the soft tissue replica and the prepared abutments seated on the implant body analogs.
The laboratory may wax the substructure of the final restoration directly on the prepared abutments.
61 Castings are obtained for the natural teeth and implant abutments.
The implant abutments are connected together with an acrylic jig to assist in intraoral seating of the abut-ments in the proper position.
At the next patient visit, a try-in for the metal casting on the teeth is performed.
The acrylic jig helps seat the laboratory-prepared abutments intraorally before adding the abutment screws.
The metal try-in for the implant prosthesis is performed.
With metal try-in for the teeth and the implant prosthesis in place, a bite registration is obtained.
A bite registration is made over the metal cast-ings. The laboratory evaluates this registration and compares it to the occlusal index obtained after the impression- making appointment.
At the third appointment, the prosthesis is delivered. The acrylic index used to reinsert the abutments also may be used to countertorque the abutments while the torque wrench tightens the abutment screws to 30 N-cm.
The final restoration is completed. The chair time for the indirect method of implant restoration was shorter than for the natural teeth because no intraoral abutment prepara-tion or transitional prosthesis fabrication was required.
The final prostheses are delivered. An indirect implant prosthesis fabrication on the patients right and conven-tional direct procedure on the left natural teeth were selected.
The implant prosthesis is cement retained, and a heavy bite is used for the occlusal adjustment with primary occlusal contacts in the central fossae.
The natural three-unit fixed prosthesis and crowns are delivered following a conventional protocol.
transferring the implant bodyposition in a working cast (Option 1or 2) has several advantages: 1. The impression requirements are less demanding because small bubbles or voids do not affect abutment transfer and margins are not important to record. 2. If an angled abutment is required, the laboratory may choose the right component. A custom abutment may be fabricated (e.g., for a short crown height when a greater diameter would help with retention). As a result, less inventory is required in the doctors office. 3. The laboratory can fabricate the transitional prosthesis on the model. 4. A framework may be fabricated directly on the implant abutments, allowing for a more accurate margin fit. 5. Chair time is decreased because the preparations, metal work, and transitionals are fabricated by the laboratory.
Disadvantages of the laboratory-assisted approach includethe following: 1. One-piece implant abutment transfers may not be timed or transferred accurately. When an impression is made and the abutments are first removed and inserted into a laboratory model, the rotation of the implant analog may be different by several degrees than in the implant body in the mouth, precluding the use of one-piece abutments. 2. A two-piece abutment post system should be used in the laboratory transfer because thread timing is more exact; however, this may mean long-term complications such as abutment screw loosening. A system with excellent precision is needed. 3. No fixed transitional prosthesis is used to load the bone gradually during fabrication of the metal framework. This increases the risk of early bone loss or early implant failure. This risk can be alleviated by delivering a temporary prosthesis on a temporary abutment with the added disadvantage of increased chair time and laboratory cost. 4. The laboratory decides on the margin location and preparation style. 5. The laboratory cost is increased. 6. The casting is made directly on the implant post and may fit the abutment so accurately as to produce a nonpassive casting.
Option 3 (Direct) One-piece straight abutments for cement retention are inserted into the implant bodies If within 15 degrees of each other, the abutments are prepared intraorally with a #703 crosscut fissure bur under copious irrigation
In the posterior three implants, first-stage coverscrews are exposed. The cover screws are removed The one-piece abutments for cement reten-tion arewith an ASA screwdriver and a 0.035- inch threaded into the implant bodies with an ASAhexagonal driver (BioHorizons Dental Implants). screwdriver and a 0.050-inch hexagonal driver
A torque wrench is used to tighten the one-piece abutments. The torque applied is transferred to the implant body.
The crown height space is evaluated. A 2-mm clearance is necessary for porcelain-fused-to- rnetal restorations with porcelain oclusal surfaces. These 8-mm abutments are too high.
The abutments are reduced in height with a high-speed handpiece and carbide bur with a copious amount of irrigation. Parallelism also is achieved.
The abutment height is reduced for a porce-lain- fused-to-metal restoration.
A coarse diamond high- speed handpiece is used to roughen the surface and increase the retention of the cemented restoration.
A final impression is made of the abutment, similar to the direct procedure with natural teeth.
A transitional restoration is made. When in soft bone, the restoration is left out of occlusion. Occlusal contacts then are incorporated on the transitional restoration at the metal try-in appointment.
Stone dies are used for the direct fabrication procedure with implants. The small-diameter posts may break off when the impression is separated from the cast. Several techniques are of benefit to minimize this complication.
Definitive Cementation A groove may be placed in As a result, although most the preparation or the defin-itive cements may casting to act as an exhibit a cement thickness additional spacer or vent between 10 and 25 ^m, for the cement. Another method to reduce film thickness is the timing of the prosthesis insertion. Film thickness may increase by 10 iim or more for every additional 30 seconds, once the cement is properly mixed.
Zinc oxide/eugenol excellent seal lowest compressive strength high solubil-ity often is used as a transitional cement at the initial delivery of the prosthesis addition of EBA modifier increases the compres-sive strength, almost to the value of polycarboxylate cement
Zinc polycarboxylate Zinc polycarboxylate cement may adhere to teeth because it chelates the calcium ions does not adhere to a gold casting or to a titanium abutment post The working time is 50% shorter than zinc phosphate cement This is a problem when cementing multiple abutments
Glass ionomer Glass ionomer cements may adhere to enamel or dentine and release fluoride for an anticariogenic effect. Their prop-erties for luting fixed restorations to natural teeth are excellent. However, their performance as luting agents on metallic abutments has raised controversy
Composite resin Composite resin cements have the highest compressive and tensile strengths of all cements, 5 times greater than zinc phosphate.121124130 When these cements are used in implant dentistry, the intent is to not remove the restoration in the future. . Unlike polycarboxy-late cement, the excess cement should be removed before final setting; otherwise, a rotary bur may be required to eliminate any excess.