Dental Implants

Bring Quality Back to Life

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.

What is a dental implant?

When teeth are missing an ongoing shrinkage of the jawbone occurs making the face look older. Dental implants can slow or stop this process.

Improved Appearance

What are the Benefits of Dental Implant Therapy?

Eliminates the pain and discomfort of full removable or partial dentures.

Implant supported replacement teeth are like natural teeth because they are anchored securely to your jawbone.

IMPROVED COMFORT

With ill fi tting dentures, the teeth slip and slide around the mouth. This often results in mumbling, slurred speech or clicking noises. Replacement teeth allow you to speak with confi dence in a relaxed and natural tone.

IMPROVED SPEECH

Dental implants can restore chewing efficiency comparable to that of natural teeth. This allows you to eat your favorite foods with confidence and without pain, enjoy what everyone is eating and not think twice about it.

Chew Your Food Better

Dental implants can eliminate the numerous embarrassing inconveniences of removable partial and full dentures. You will no longer need to cover your mouth when you laugh or smile, for fear that your teeth will pop out or fall down.

Confidence & Convenience

Adequate bone in your jaw is needed to support the implant(s) along with healthy gum tissues that are free of periodontal disease.

Who is a candidate for dental implants?

Documentation studies have proven the effectiveness and long lasting results of dental implants. Good oral hygiene

is one of the most critical factors to insure the health of your dental implants.

Are dental implants successful?

Principles of Cement-Retained Fixed Implant Prosthodontics

Implant and fix prosthodontics

Part 1

IMPLANT DIFFERENT TYPES

permucosal extension (PME)

Abutment for cement retention

abutment for screw retention

Abutment for attachment

AnalogsAnalogs may represent an abutment for screw retention, an implant body (left), and/or an abutment for attachment (right).

Fixed restorations have three categories: FP-1, FP-2, and FP-3ΩFP-1 is idealΩFP-2 is hypercontouredΩFP-3 replaces the gingival drape with pink porcelain or acrylic

Ω The difference between FP-2 and FP-3 most often is related to the maxillary high lip position during smiling or the mandibular lip position during sibilant sounds of speech. FP-2 and FP-3 restorations often require more implant surface area support by increasing implant number or size or by adjusting design 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

Occlusal Considerations for Implant-Supported Prostheses

A tooth exhibits more vertical movement than an implant. This may result in higher occlusal loads on the implant, whether or not it is connected to the natural tooth, when in a mouth with both implants and teeth.

Occlusal Considerations for Implant-Supported Prostheses

light occlusal force heavy bite force

Partial and Complete Edentulous Maxilla Implant Treatment Plans: Fixed and

Overdenture Prostheses

The premaxilla loses 40% to 60% bone width within 3 yearsafter the loss of teeth. The implant surgeon often has difficulty inserting implants when augmentation does not restore the region before implant placement.

Maxillary Teeth Dimensions

Type of Teeth

Mesiodistal Crown

(mm)

Mesiodistal

Cervix (mm)

Faciolingual Crown

(mm)

Faciolingual

Cervix (mm)

Mesiodistal CEJ (2

mm)

Central incisor

8.6 6.4 7.1 6.4 5.5

Lateral incisor

6.6 4.7 6.2 5.8 4.3

Cuspid 7.6 5.6 8.1 7.6 4.6

First bicuspid

7.1 4.8 9.2 8.2 4.2

Second bicuspid

6.6 4.7 9.0 8.1 4.1

First Molar

10.4 7.9 11.5 10.7 7.0

Second molar

9.8 7.6 11.4 10.7

IMPLANT SELECTION

Implant Size Selection Criteria in Posterior Maxilla1.5 mm from

adjacent tooth3 mm from adjacent

implant4 mm diameter

minimum, for posterior maxilla

The minimum mesiodistal dimension for two standard 4-mm diameter implants is 1.5 mm + 4 mm + 3 mm + 4 mm + 1.5 mm = 14 mm.

d = 1.5mm +DZ + 3mm +DY + 3mm +DX + 1.5mm

Preimplant Prosthodontics

Existing Occlusal Vertical Dimension

The minimum crown height space for 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 PROSTHESISCEMENT-RETAINED VERSUS SCREW-

RETAINED IMPLANT FIXED PROSTHESES

The primary advantage of a screw-retained prosthesis (right) is retrievability.

CEMENT-RETAINED VERSUS SCREW-RETAINED IMPLANT FIXED PROSTHESESRetrieval of the cement-retained fixed

prosthesisProtection of the implant

ADVANTAGES OF CEMENT-RETAINED IMPLANT PROSTHESES

Passive Casting

TABLE 23-1 RESCAN

A 50 µm misfit may require the implant to move within the bone 200 µm before the casting fits passively

dimensional change in impression material , 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 primary occlusal contacts The ideal primary occlusal contacts for posteriorsingle-tooth implant restorations that are cement retained is directly over the top of each implant, which is usually positioned under the central fossa. When the implants are splinted together, the occlusal contacts may include the marginal ridges, which are between the most distal and mesial implant (right). The diagram on the left is for a screw-retained restoration that is splinted together. The occlusal contacts are usually between the implants. Offset loads to the buccal contact are not indicated, since they will increase the moment force.

Esthetics and HygieneOcclusal Material FractureAccessFatigue

In the anterior regions of the mouth a screw-retained restoration requires a different implant body position than a cement-retained restoration. As a result, a facial porcelain ridge lap is required. This makes the cervical sulcus of the implant inac cessible for hygiene.

Abutment screws fatigue and are prone to fracture. The abutment crown crevice is not sealed completely, and bacteria may proliferate within the components. Because the environment often has low oxygen tension, the bacteria may be anaerobic organisms that contribute to foul odor and periimplant disease.

CEMENT-RETAINED VERSUS SCREW-RETAINED IMPLANT FIXED PROSTHESES1. Esthetics and Hygiene2. Occlusal Material Fracture3. Access4. Fatigue5. Progressive Loading6. Abutment-Crown Crevice7. Cost and Time

ADVANTAGES OF SCREW-RETAINED PROSTHESES:1. Low-profile retention 2. Reduced moments of force3. Risk of cement in the sulcus

A screw-retained device is more resistant to tensile forces compared with a cemented abutment inferior to 5 mm in height. Therefore overdenture bars are often screw retained. The lower-profile bar provides greater space for denture tooth placement and greater bulk of acrylic to reduce fracture risks.

CEMENT-RETAINED FIXED PROSTHESES

One-piece Vs.Two-piece AbutmentsTwo categories of abutments are used for cemented restorations. The one-piece abutment (far left) may be used in multiple restorations when the implant bodies are within 20 degrees of ideal. The two-piece abutments may be used for single teeth, angled implants, and with laboratory transfers or for custom abutments.

A torque wrench may deliver a consistent rotational force to the retaining screws. The head of the torque wrench is released at a preset torque level.

One-Piece Abutment for Cement Retention

Advantages and Disadvantages of One-Piece Abutment for CementAdvantages Disadvantages• No torque wrench

needed• Stronger• No screw loosening• Easy complete seating• No need to retighten

under restoration• Less expensive• Thicker walls to allow

great freedom of preparation

• Only for multiple abutments

• Not for single-tooth restoration

• Not for angled abutments

• Weaker to fracture

A one-piece abutment for cement retentionis threaded into the implant body and bypasses the antirotational hexagon component.

Two-Piece Abutment for Cement Retention

two-piece abutment for cement retentionIn the two-piece abutment for cement retention the abutment engages the antirotational features of the implant body platform and the abutment screw that fixates the components into position.

Advantages and Disadvantages Of Two-Piece Abutment for Cement: Single-Tooth ImplantsAdvantages Disadvantages

• Antirotational under shear forces

• Angled abutments

• Screw loosening• Abutment loosening

under restoration• 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 in position to the implant body. A 30-N/cm torque wrench is seated into the abutment screw and rotated. B, The head of the torque wrench bends at the approximate torque value. The hemostat stops the rotation force on the screw, loading the implant-to-bone interface with a rotational force, because the abutment engages the hexa gon of the implant body

Angled abutments are similar to a two-piece abutment systemranging from 15 to 30 degrees

The UCLA abutment concept permits the laboratory to custom fabricate the abutment

The combination of metal and plastic components offers several advantages. With the plastic component, cus tomizing the shape of 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 Anatomical AbutmentsPrecise 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 ismade.

A custom abutment with pink porcelain added to the subgingival region is fabricated to enhance the cervical esthetics

The custom abutment and crown are seated. The subgingival pink porcelain is advantageous in situations in which the soft tissues are thin and the grayish color of the titanium abutment may affect the esthetic outcome

TILL PAGE 427 OF PRICIPLE OF CEMENTED

GUIDELINES TO REDUCE COMPLICATIONS

Caries and Abutments

Because caries is the most common complication of crowns on the natural teeth, guidelines indicate that the crown margin not only should be supragingival but also should be placed on enamel. This not only facilitates access for hygiene but also decreases the risk of caries, since enamel is more resistant to decay.

Abutment Retention

Factors Affecting Abutment RetentionTaper Surface areaHeightResistance form Surface texture Path of insertion

The taper of an implant abutmentaffects 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 the abutment, the greater the retention. Larger-diameter implant abutments have greater retention than narrow-diameter implants.

Abutment TaperAbutment HeightAbutment Surface AreaShear ForcesResistance and AbutmentsAbutment Surface Texture

Abutment Height

A, When a crown receives a lateral force,it tends to rotate upward on one side of the implant. The arc of rotation is related to the diameter of the implant. The height of the abutment should be greater than the arc of rotation. A wider implant abutment requires greater height than a smaller-diameter implant to resist these lateral forces. B, The arc of rotation may be decreased when directional grooves are prepared into the abutment. Therefore when abutment height is questionable, the addition of vertical grooves decreases the risk of uncementation

In a cantilevered prosthesis, tensile forces are applied on the crown farthest from the cantilever. The height of this implant abutment should be greater than the arc of displace ment of the prosthesis because compressive forces to the cement seal are placed on the abutment above the arc of displacement. Buccolingual directional grooves decrease the rotation arc and place compressive forces within the grooves.

The two implants replacing the canine and first premolar have minimal abutment height and will receive lat eral forces. Vertical directional grooves parallel to the path of inser tion of the prosthesis will decrease the risk of uncementation.

Shear Forces

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.

Implant part 2

Resistance and Abutments

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.

Abutment Surface Texture

PATH OF INSERTION

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 cement were placed on these two implant bodies. The distal implant is angled buccally.

A high-speed handpiece is used to prepare theabutment and correct the 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.

| IMPLANT ABUTMENT MARGINS

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.

| ABUTMENT PREPARATION

Option 1 (Indirect)Option 2 (Indirect) Option 3 (Direct)

Steps in Direct and Indirect (Prosthesis) Fabrication Techniques

Steps in Direct and Indirect (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. Position final

abutments with jig. Confirm seating with radiograph. Torque abutments to 30 N-cm. Metal

work try-in. Radiograph to verify fit. Take bite registration. Remove all abutment. Replace healing abutments.

Laboratory 3 Remount model to new bite. Finish

prosthesis. Clinical 3 Remove healing abutments. Seat abutment with jig. Torque to 30 N-cm. Seat final prosthesis; deliver prosthesis.

Remove healing abutments. Position final abutment

with jig. Confirm seating with radiograph. Metal work try-in. Radiograph to

verify fit. Take bite registration. Make pick up impression. Deliver temporary restoration.

Pour pickup impression. Remount impression. Finish prosthesis.

Remove temporary restoration. Radiograph to verify

fit.

The permucosal extensions are unthreaded 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 impression transfer impressions as long as the transfer undercuts are engaged securely in the impression and the compo nent is maintained securely

An impression is made of the three implant bod ies and of the four natural teeth 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 patient's 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.

Making an initial impression and transferring the implant body position in a working cast (Option 1 or 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 doctor's 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)

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 cover screws are exposed. The cover screws are removed with an ASA screwdriver and a 0.035- inch hexagonal driver (BioHorizons Dental Implants).

The one-piece abutments for cement reten tion are threaded into the implant bodies with an ASA 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 isused to roughen the surface and increase the retention of thecemented 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 the preparation or the casting to act as an additional spacer or vent 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.

As a result, although most defin itive cements may exhibit a cement thickness between 10 and 25 ^m,

Zinc oxide/eugenolexcellent seallowest compressive strength high solubil ityoften is used as a transitional cement at the

initial delivery of the prosthesisaddition of EBA modifier increases the

compres sive strength, almost to the value of polycarboxylate cement

Zinc polycarboxylateZinc polycarboxylate cement may adhere to

teeth because it chelates the calcium ionsdoes not adhere to a gold casting or to a

titanium abutment postThe working time is 50% shorter than zinc

phosphate cement This is a problem when cementing multiple

abutments

Glass ionomerGlass 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 resinComposite resin cements have the highest

compressive and tensile strengths of all cements, 5 times greater than zinc phosphate.121'124'130 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.