implant supported fixed prosthesis

Implant-Supported Fixed Prostheses:

Implant-Supported Fixed Prostheses

Implant-Supported Fixed Prostheses:

Implant-Supported Fixed Prostheses High success achieved with osseointegrated dental implant Allows greater no. of patients to enjoy the benefits of fixed rather than removable restorations Main indication – DEPD & long edentulous span & also single implant is a popular option Dental implant : a prosthetic device of alloplastic material implanted into oral tissues to provide retention & support a FPD/RPD Osseointegration : The apparent direct attachment/connection of osseous tissue to an inert, alloplastic material without intervening connective tissue. The process & resultant apparent direct connection of an exogenous material’s surface & the host bone tissues, without intervening fibrous connective tissue. The interface between alloplastic materials & living tissue

Implant types :

Implant types Subperiosteal Transosteal Endosteal Surgically placed within alveolar or basal bone Can be subdivided by Shape - BLADE form (platform) & -ROOT form (cylindrical)

BLADE form (platform) & -ROOT form (cylindrical):

BLADE form (platform) & -ROOT form (cylindrical) Blades are wedge shaped or rectangular in cross-section & are generally 2.5mm wide, 8 to 15 mm deep, 15 to 30 mm long Root forms are 3 to 6 mm in diameter & 8 to 20 mm long

One-stage/Two-stage:

One-stage/Two-stage One-stage – designed to be placed in bone & to immediately project through mucosa in oral cavity Two-stage – requires 2 surgical procedures 1 st implant is placed in bone to level of cortical plate & oral mucosa sutured over it, Left for healing period of usually 3 months in mandible & 6-9 months in maxilla depending on quality of bone(D1 to D4) 2 nd surgery – mucosa is reflected, extension collar (healing abutment/cap) or abutment that projects into oral cavity is fastened

Plate implants (Blade):

Plate implants (Blade) One stage, but success rate were lower Problems: high temperature at which bone sites were prepared & immediate loading – lead to fibrous encapsulation Difficulty in preparing precision slots & Large circumferential area of jaw that can be affected when a blade fails

Root form (Cylinders):

Root form (Cylinders) Considered state of art implant dentistry Advantages include adaptability to multiple intraoral locations Uniformly precise implant site preparation & comparatively low adverse consequences to that experienced when a tooth is lost Root form implants are Titanium/ Titanium alloys with/without hydroxyapatite (HA) coating, threaded/nonthreaded, grit blasted or acid etched (to increase surface area for bone contact) Trend is credited to Branemark system (Per Ingvar Branemark, Sweden) Atraumatic implant placement, delayed implant loading: so increased degree of implant predictability

Treatment planning:

Treatment planning Patient Selection Diagnosis Treatment planning Surgical + Restorative t/t plan must be devised Non implant alternative should be included Whether the patient is able to tolerate, predictable risks & benefits should be weighed for each person

Indications :

Indications Inability to wear RPD/CD Need for long-span FPD with questionable prognosis Unfavorable number & location of potential natural tooth abutments Single tooth loss that would necessitate preparation of minimally restored teeth for fixed prosthesis

Absolute Contraindications:

Absolute Contraindications Based on immediate surgical & anaesthetic risks limited to individuals who are acutely ill, with uncontrolled diabetes mellitus & pregnant woman It may be contraindicated in patient with abnormal bone metabolism, poor oral hygiene, previous radiation to implant site Patient must be motivated & educated in oral hygiene technique (patients with paralysis of arms, debilitating arthritis, cerebral palsy & severe mental retardation)

Clinical Evaluation:

Clinical Evaluation Thorough clinical examination – adequate bone & anatomic structure that could interfere with ideal implant placement Also flabby tissues, bony ridges & sharp underlying osseous formation & undercuts

Radiographic Evaluation:

Radiographic Evaluation OPG Radiopaque reference object should be placed at implant site (ball bearing in wax/ in PVS) Cephalometric film: bone width in Anterior maxilla & mandible CT Scan – loaction of inferior alveolar & maxillary sinus (increases expenses)

Diagnostic Casts:

Diagnostic Casts To study remaining dentition, residual bone, maxillo-mandibular relationship Proposed fixture installation sites are checked for proper alignment Direction, location & relation of remaining dentition Waxing – helps determine most esthetic placement of teeth & potential for functional speech disturbances Resin template can be made

Resin template fabrication:

Resin template fabrication 1.5 mm vacuum formed matrix filled with clear acrylic resin Resin is drilled to guide implant placement

Diagnostic Casts:

Diagnostic Casts To guide both horizontal & vertical positioning

Bone Sounding:

Bone Sounding Under LA needle / sharp caliper is pushed through the tissue until it contacts bone – tells soft tissue thickness

Principles of Implant location:

Principles of Implant location Anatomic Location : implant should be placed within bone (away from anatomic structures) for success Ideally 10 mm vertical bone & 6 mm horizontal should be available 3 mm space between two implants (to ensure vitality of bone vitality & hygiene) 2 mm above superior aspect of inferior alveolar canal 5 mm anterior to mental foramen 1 mm from PDL of adjacent teeth

Anterior Maxilla:

Anterior Maxilla Evaluated for proximity to nasal cavity 1 mm of bone should be left between implant & nasal cavity

Posterior Maxilla:

Posterior Maxilla Less dense bone than posterior mandible Larger marrow spaces Thinner cortex Require increased time to integrate Additional implants required 1 mm bone between floor of sinus & implant If less bone, then bony augmentation through the sinus should be considered

Anterior Mandible:

Anterior Mandible Most straightforward area for implant treatment planning Require least amount of time for integration When possible, implant should be placed through entire cancellous bone so the apex of implant will engage cortex of inferior mandibular border In PM area implant should not impinge on inferior dental nerve, as it courses 3 mm anterior to mental foramen by turning posteriorly & superiorly to exit at foramen, so implant should be atleast 5 mm anterior to foramen

Posterior Mandible:

Posterior Mandible Inferior alveolar nerve should be 2 mm away from implant apex If not it can cause damage to nerve & numbness of lower lip Nerve Repositioning & Onlay grafting or Nonimplant borne prosthesis could be planned Short implants are often necessary because of bone resorption Width should be evaluated, as below Mylohyoid muscle there can be deep depression Problems – less bone contact, & longer crowns

Restorative consideration:

Restorative consideration Implant Placement: It dictates appearance, contour, long term function 1 mm away from adjacent tooth 3 mm between adjacent implants (hygiene) To minimize harmful lateral forces, long axes of implant should be positioned in central fossae of restoration Superoinferior placement is important to ensure optimum emergence profile Ideally superior surface of implant should be 2-3 mm directly inferior to emergence position Less ideal locations

Implant & Restoration size:

Implant & Restoration size Choice of implant & its position are modified by diameter of intended missing tooth & can be adjusted for different sizes of tooth Maxillary Central incisor – 8 mm & Average implant Diameter – 4mm Therefore 2 to 3 mm is needed to make transition gradually from 4 to 8 mm (otherwise overcontoured / unnatural look) For mandibular anterior 4 mm diameter is not good, so 3 mm implant diameter is developed

Single Tooth implant:

Single Tooth implant Anterior esthetic zone is challenging as well as biomechanical loading is problem (to minimize screw loosening) Antirotational feature is essential Spline or Hexagon

Surgical guide:

Surgical guide Surgical guide template is useful for anteriors (appearance) & correct emergence profile OBJECTIVES 1 Delineate the embrasures 2 Locate implant within restoration contour 3 Align implants with long axis of completed restoration 4 Identify level of CEJ / tooth emergence from soft tissue

Surgical guide:

Surgical guide Clear resin template fabricated on diagnostic waxing / denture

Implant Surgery:

Implant Surgery Can be performed in ambulatory setting under local anaesthesia However it requires more time than other surgical procedures – so conscious sedation Placing implant is less traumatic than extraction of tooth

Surgical Access:

Surgical Access Incision chosen should allow retraction of soft tissue for unimpeded implant placement & should preserve attached tissue esthetics & quantity Simple Crestal incision – when quantity of attached tissue is adequate & underlying bone is expected to be of sufficient width In posterior mandible incision may be placed towards the buccal aspect of ridge to allow the flap to be retracted by suture For maxillary anterior zone incision should be placed slightly to palatal side After bone is exposed, surgical template is positioned Periodontal probe is used to assess implant size Some areas require smoothening before implant placement

Implant Placement:

Implant Placement Requires atraumatic preparation of recipient site Thermal injury is minimized by using low speed, high-torque handpiece along with copious irrigation (external / internal) Threaded implant requires final thread preparation at very low speed Implant recipient site is prepared with a series of gradually enlarged burs Centre of implant site is marked with initial drill & a pilot hole is prepared Paralleling pin is then placed in preparation to check alignment & angulation

Slide 30:

After desired depth & diameter of recipient site are achieved, implant is placed For Titanium implants, an uncontaminated surface oxide layer is required for osseointegration (HA coated are sensitive to contamination)

Slide 31:

Nonthreaded implant are positioned in the recipient site & gently tapped into place with a mallet & seating instrument. Threaded implant are screwed into place, which also requires cutting the screw threads in the recipient site Self tapping implant are available for use in maxilla, where bone is soft enough to make prethreading unnecessary Tension-free closure of wound

Postoperative Evaluation:

Postoperative Evaluation Radiograph should be taken postoperatively to evaluate position in relation to adjacent structures & other implants Patients are given mild analgesics & 0.12% chlorhexidine gluconate rinses for 2 weeks (reduce bacterial population during healing) CD/RPD should not be worn for 1 week after surgery Resin over implant can then be reduced by 2 to 3 mm & replaced with a soft liner

Implant Uncovering:

Implant Uncovering If two-stage system is used, uncovering is done after complete implant fixture integration has been achieved Time interval for integration (6 month in maxilla, 3 month in anterior mandible, 4 month in posterior mandible) Goal is to attach abutment accurately (& preserve attached tissue & to recontour tissue)– accomplished by tissue punch, crestal incision, flap repositioning Directly attach abutment used for restoration & 2 nd approach is to place healing cap

Slide 34:

Body interface should be evaluated radiographically If gap is present, the superstructure must be repositioned

Advantages of Osseointegrated Implants:

Advantages of Osseointegrated Implants 1 Surgical Documented success rate In-office procedure Adaptable to multiple intraoral locations Precise implant site preparation Reversibility in the event of implant failure 2 Prosthetic Multiple restorative options Versatility of second-stage components (Angle correction, Esthetics, Crown contours, Screw/Cement retained options) Retrievability in the event of prosthodontic failure

Implant Restorations:

Implant Restorations

Implant Restorations:

Implant Restorations Clinical implant components: Implant body is component placed within the bone during 1 st stage surgery It may be threaded/nonthreaded root form & is normally made of either Ti/Ti alloy of varying surface roughness with/without HA coating

Cover Screw:

Cover Screw During the healing phase – a screw is normally placed in the superior aspect of the fixture It is usually low in profile to facilitate the suturing of soft tissue & minimize the loading At 2 nd surgery – it is removed & replaced by subsequent components It should be completely seated to prevent bone from growing between screw & implant

Healing abutment :

Healing abutment Dome shaped screws placed after 2 nd surgery & by insertion of prosthesis Length – 2 to 10 mm & project through soft tissue into oral cavity Made of Ti/Ti alloy Metal-porcelain interface will be located subgingivally Where esthetics is not critical, adequate healing for impression usually takes 2 weeks In esthetic zones 3 to 5 weeks may be required before abutment selection Also its length can help for abutment selection

Abutments:

Abutments These are components of implant system that screw directly into the implant They will eventually support prosthesis in screw-retained restoration For cement-retained restoration, they may be shaped like a conventional crown preparation Walls are smooth polished & straight-sided Ti/Ti alloy Length ranges from 1 to 10 mm In non-esthetic zone 1 to 2 mm of Ti should be allowed to penetrate the soft tissue to maximize patient’s ability to clean the prosthesis In esthetic areas abutment can be selected to allow porcelain to be carried subgingivally for esthetics

Abutments:

Abutments Angled abutments use a similar technique to correct divergently placed implants Some include tapered/wide-based, nonsegmented implant crown (UCLA), also there are All-Ceramic components Choice of abutment size – vertical distance between fixture base & opposing dentition Periodontal probing of sulcus after healing cap is removed will reveal the space available for subgingival extension & can be performed at time of abutment placement

Impression Post:

Impression Post Facilitates transfer of intraoral location of implant or abutment to a similar position on laboratory cast They may screw into implant or onto the abutment & are customarily subdivided into fixture types / abutment types With the transfer impression post in place, an impression is made intraorally Divided into : transfer types (indirect) & pick-up (direct) types Heavier-body impression (PVS & polyether) Post is removed from mouth & joined to lab. Analog, then transferred to impression (flat surface) Angled abutment is placed or screwed into implant Should be oriented in same position Close tray / Open tray

Transfer post & Lab analog:

Transfer post & Lab analog

Laboratory Analogs:

Laboratory Analogs Made exactly the top of implant fixture / abutment in lab. cast Fixture analogs / Abutment analogs Final impression is poured with Die stone Gingival tissues can be produced by elastomers

Waxing Sleeves:

Waxing Sleeves Are attached to abutment by screw They eventually become part of prosthesis UCLA abutment – plastic patterns – casted into precious metal Available in several vertical dimension

Prosthesis-retained Screws:

Prosthesis-retained Screws Penetrate the fixed restoration & secure it to abutment Tightened with screwdriver Made of Ti/Ti alloy/ gold alloy – long/short

Implant restorative options :

Implant restorative options Distal Extension Implant Restoration Long Edentulous Span Restoration Single-tooth Implant Restoration Fixed Restoration in completely Edentulous Arch Distal extension

Long Edentulous Span Restoration:

Long Edentulous Span Restoration Telescopic coping over natural abutment

Single-tooth Implant Restoration:

Single-tooth Implant Restoration

Fixed Restoration in completely Edentulous Arch:

Fixed Restoration in completely Edentulous Arch 6 implants in maxilla

Cement-Retained Versus Screw-Retained Implant Crowns:

Cement-Retained Versus Screw-Retained Implant Crowns ZnPo4, GIC, composite resin are suggested, but retrievability of implant restoration is considered Provisional cements are recommended – premature displacement Cement retained restoration allows minor angle correction to compensate for discrepancies Resistance to rotation is critical Retrievability – allows crown removal, soft tissue evaluation, calculus debridement

Cement-Retained Versus Screw-Retained Implant Crowns:

Cement-Retained Versus Screw-Retained Implant Crowns Screw retained – ideal surgical location Disadvantage – screw loosening Direct mechanical lock / antirotational feature appears to be most effective Clamping force should be more than forces trying to separate the joint between implant & crown Lateral forces should be eliminated

Biomechanical factors affecting long-term implant success:

Biomechanical factors affecting long-term implant success OCCLUSION Connecting implants to natural teeth Implant & Framework Fit Shock absorbing Elements

OCCLUSION:

OCCLUSION Bone resorption around implants – premature loading / repeated overloading Vertical / angular bone loss – characteristic of occlusal trauma Lateral forces on implant must be reduced If not completely eliminated then it should be distributed equally over as many teeth possible Implant restorations – designed to minimize damaging forces at implant-bone interface Flatter inclines can be developed on implant cusps Cusp-fossa relationship should be established PTO

OCCLUSION:

OCCLUSION Divergent implant placement increases moment arm through which forces are transmitted to bone-implant interface Inadequate implant distribution – lead to excessive cantilevers/forces, causing overloading Ideally one implant for every tooth to be restored Full arch restoration – 6 implants in maxilla & 5 implants in mandible Shortened dental arch – till 1 st molar only

Connecting implants to natural teeth:

Connecting implants to natural teeth Can create excessive forces because of relative immobility of implant compared to functional mobility of a natural tooth Can create stress at neck of implant upto 2 times the implied load on prosthesis Breakdown of osseointegration Cement failure on natural abutment Screw/abutment loosening Failure of implant prosthetic component So semi precision attachment Telescopic coping on natural teeth

Implant & Framework Fit:

Implant & Framework Fit Pathogenic forces can be placed on implant if framework does not fit passively Fit is checked with only one screw in place – no movt. with finger pressure should occur Nonpassive fit – it is sectioned & soldered

Shock absorbing Elements:

Shock absorbing Elements To reduce occlusal impact forces Such forces may exceed the threshold necessary for bone resorption to occur Occlusal surface of restoration might be constructed of acrylic resin Still remains a controversial subject

Maintenance :

Maintenance Is to eradicate microbial populations affecting prostheses These are more resistant than natural teeth Patient must receive thorough instruction in maintenance technique Recall visit every 3 months during 1 st year Sulcular debridement – plastic/wooden scalers Abutments may be polished using rubber cups with low-abrasive polishing paste / tin oxide Implant mobility should be evaluated Any bleeding after probing should be examined Framework fit & occlusion must be checked

Complications :

Complications Bone loss Inappropriate size & shape of implant Inadequate no. of implants / implant positioning Poor quality / inadequate amount of available bone Initial instability of implant Compromised healing phase Inadequate fit of prosthesis Improper design of prosthesis (e.g excessive cantilever, poor access for hygiene) Excessive occlusal forces Deficient fit of abutment components (gaps-bacterial colonization) Inadequate oral hygiene Systemic influence (tobacco use, diabetes)

Prosthetic failure:

Prosthetic failure Fracture of implant components or the prosthesis – attributed to fatigue from biomechanical overload Also, it is usually traceable to less than ideal laboratory procedures or prosthesis design

Summary :

Summary Implant-supported prostheses using cylindrical osseointegrated fixtures placed by a two-stage surgical technique These are reliable solution to many situations that are difficult to treat by conventional measures Proper treatment planning – a team approach is recommended Depending on bone – after 3 to 6 month 2 nd stage surgery is done to uncover implant & place abutment Final prosthesis is fabricated to restore function & appearance