Implant

Introduction to Dental Implant

Definition Materials used for dental implant. Types of dental implant Osseointegration Biomechanics of osseointegrated implant.

Definitions

Oral Implant: A device or inert substance, biologic or alloplastic, that is surgically inserted into soft or hard tissues, to be used for functional or cosmetic purposes. Dental Implant: A perimucosal device which is biocompatible and biofunctional and is placed within mucosa or, on or within the bone associated with the oral cavity to provide support & retention for fixed or removable prosthetics.

Dental implants

Made of various biomaterial. Most commonly made of titanium (most compatible with human biology)

Advantages of implant over conventional treatment

Implants do not involve preparation of the adjacent teeth.They preserve the residual bone from excessive resorption.They’re excellent in aesthetics demands.

Disadvantages of implant over conventional treatment

It is expensive. The patient requires surgery. Time consuming. Technically complex.

Types of dental implant

Mucosal Insert Endodontic Implant (Stabilizer) Sub-periosteal implant Endosteal or Endosseous implant Plate-form implant Ramus-frame implant Root-form implant Transosseous implant


1. Titanium Mucosal Insert

2. Endodontic Implant (Stabilizer)

Endodontic implants are similar to prosthodontic implants in many aspects. However, they serve another purpose  to stabilize and preserve of mobile remaining natural teeth, not to replace the lost teeth.

3. Sub-periosteal implant

Subperiosteal Implants These implants are not anchored inside the bone, such as Endosseous Implants, but instead they’re shaped to ride on the residual bony ridge of either the upper or lower jaw. They are usually not considered to be osseointegrated implants. Subperiosteal Implants have been used in completely edentulous as well as partially edentulous upper and lower jaws. However, the best results have been achieved in treatment of the edentulous lower jaw.

Indications: Usually a severely resorbed, completely edentulous, lower jaw bone which does not offer enough bone height to accommodate Root form Implants as anchoring devices.

5. Endosteal or Endosseous implant

Plate-form implant : Blade Implants have a long track record, much longer than the Root form Implants. Their name is derived from their flat, blade-like (or plate-like) portion, which is the part that gets embedded into the bone.

Blade implants are not used too frequently any more, however they do find an application in areas where the residual bone ridge of the jaw is either too thin (due to resorption) to place conventional Root form Implants or certain vital anatomical structures prevent conventional implants from being placed. Nowadays, if a certain area of the jaw bone is too thin and has undergone resorption due to tooth loss it is recommended to undergo a Bone grafting procedure, which re-establishes the lost bone, so that conventional Root form Implants can be placed.

Ramus - frame Implants belong in the category of endosseous implants, although their appearance might not suggest that at first. These implants are designed for the edentulous lower jaw only and are surgically inserted into the jaw bone in three different areas: the left and right back area of the jaw (the approximate area of the wisdom teeth), and the chin area in the front of the mouth. The part of the implant that is visible in the mouth after the implant is placed looks similar to that of the Subperiosteal Implant.
Ramus-frame implant

Indications: Usually a severely resorbed, edentulous lower jaw bone, which does not offer enough bone height to accommodate Root form Implants as anchoring devices. These implants are usually indicated when the jaws are even resorbed to the point where Subperiosteal Implants will not suffice anymore.


Ramus-frame implant

An additional advantage that comes with this type of implant is a tripodial stabilization of the lower jaw. A jaw as thin as the one shown above can easily fracture at its thinnest part. The Ramus-frame Implant, once integrated (after a three month waiting period) will also stabilize and protect the jaw somewhat from fracturing.

The Ramus-frame Implant usually comes in a standard pre-shaped form and needs to be custom-fitted to the patient's individual jaw dimension, as shown below:

Ramus-frame implant

Root form implant Since the introduction of the Osseointegration concept and the Titanium Screw by Dr. Branemark, these implants have become the most popular implants in the world today.

Root form Implants come in a variety of shapes, sizes, and materials and are being offered by many different companies worldwide. Some clinicians regard them to be the Standard of Care in Oral Implantology. These implants can be placed wherever a tooth or several teeth are missing, when enough bone is available to accommodate them. However, even if the bone volume is not sufficient to place Root form Implants, Bone grafting procedures within reasonable limits should be initiated, in order to benefit from these implants.

Root form implant shape: Some are screw-shaped, others are cylindrical, or even cone-shaped or any combination thereof.

Today, the most accepted material for dental implants is high grade Titanium - either CP Titanium or an alloy. The titanium alloy implants tend to be stronger than the CP titanium implants. The bone integration shows no difference to the two different types of titanium. Some implants have an outer coating of Hydroxyapatite (HA). Other implants have their surface altered through plasma spraying, or beading process. This was developed to increase the surface area of the titanium implant and thus, in theory, give them more stability. These surface treatments were also offered as an alternative to the HA coatings, which on some implants have shown to break loose or even dissolve after a few years.

Transosseous implant

These implants are not in use that much any more, because they necessitate an extraoral surgical approach to their placement, which again translates into general anesthesia, hospitalization and higher cost, but not necessarily higher benefits to the patient. In any case, these implants are used in mandibles only and are secured at the lower border of the chin via bone plates. These were originally designed to have a secure implant system, even for very resorped lower jaws.

A typical Transosseous Implant. The plate on the bottom is firmly pressed against the bottom part of the chin bone, whereas the long screw posts go through the chin bone, all the way to the top of the jaw ridge inside the mouth. The two attachments that will eventually protrude through the gums can be used to attach an overdenture-type prosthesis.
The plate
long screw posts
The two attachments

Osseointegration

Definition: A time-dependant healing process where by clinically symptomatic rigid fixation of alloplastic materials is achieved, and maintained, in bone during functional loading.

Factors affecting osseointegration:

Implant biocompatibility Implant design Implant surface Implant bed (Bone quality) Surgical technique Loading condition

Implant biocompatibility:

Materials used are: Cp titanium (commercially pure titanium). Titanium alloy (titanium- 6 aluminum- 4 vanadium). Zirconium. Hydroxyapatite (HA), one type of calcium phosphate ceramic material. Osseointegration interface: Osseointegration rate. Biointegration role.

Implant design (root-form):

Cylindrical Implant Some investigators explain the lack of bone steady state by overload due to micromovement of the cylindrical design, whereas others incriminates an inflammation / infection caused particularly by the very rough surfaces typical for these types of implant.

Threaded Implant In contrast, Threaded implants have demonstrated maintenance of a clear steady state bone response. To enhance initial stability and increase surface contact, most implant forms have been developed as a serrated thread.
Implant design (root-form):

Implant surface:

4. Implant Bed (Bone Quality):
Quality I Was composed of homogenous compact bone, usually found in the anterior lower jaw. Quality II Had a thick layer of cortical bone surrounding dense trabecular bone, usually found in the posterior lower jaw.

4. Implant Bed (Bone Quality):

Surgical technique
Minimal tissue violence at surgery is essential for proper osseointegration. Careful cooling while surgical drilling is performed at low rotatory rates Use of sharp drills Use of graded series of drills Proper drill geometry is important, as intermittent drilling. The insertion torque should be of a moderate level because strong insertion torques may result in stress concentrations around the implant, with subsequent bone resorption.

Loading condition

Delayed loading: A two-stage surgical protocol One-stage surgical protocol Immediate loading: Immediate occlusal loading (placed within 48 hours postsurgery) Immediate non-occlusal Loading (in single-tooth or short-span applications) Early loading (prosthetic function within two months)

Biomechanics of osseointegrated implant.

In all incidences of clinical loading, occlusal forces are first introduced to the prosthesis and then reach the bone implant interface via the implant.

So many researchers have, therefore, focused on each of these steps of force transfer to gain insight into the biomechanical effect of several factors such as: Force directions and magnitudes. Prosthesis type. Prosthesis material. Implant design. Number and distribution of supporting implants. Bone density. The mechanical properties of the bone-implant interface.
Biomechanics of osseointegrated implant.

Dental Implant Treatment Planning and Types of Dental Implants

How many teeth are missing? What is the degree of bone loss? Are the remaining teeth in a good position and do they have a long-term prognosis? What does the patient expect for an end result? What treatment will result in the best cosmetic outcome? What is the patient's budget?


So, the clinical factors that must be considered:
Quality, quantity, and shape of supporting alveolar bone. The cantilever design can be avoided if the implants are placed posterior to the foramen. A fixed option could be utilized but will display less teeth, while a removable option will provide increased tooth display. A patient who has the bone quality to support a fixed prosthesis could also be a candidate for an implant overdenture supported by fewer implants.

Overall...What is the most practical and feasible implant treatment that will produce optimal chewing function and optimal cosmetic results in a timely and affordable manner? Treatment planning and the decision-making process is a balance between the patient’s preferences, finances and clinical factors.

Diagnosis and Treatment Planning

The evaluation of a patient as a suitable candidate for implants should follow the same basic format as the standard patient evaluation, although some areas require additional emphasis and attention: Medical History. Psychological Status. Dental History.

I. Medical History

The patient’s medical history may reveal a number of conditions that could complicate or even contra-indicate implant therapy, such:Bleeding disorders; Paget’s disease; A history of radiation therapy in the maxilla or mandible region; Uncontrolled diabetes; Epilepsy that presents with more than one grand mal seizure per month; In addition, there are a host of systemic medical conditions, including steroid therapy, hyperthyroidism, and adrenal gland dysfunctionSubstance abuse including tobacco and alcohol.

II. Psychological Status

If the patient cannot come to terms with the possibility of failure, or four to six months of potential discomfort and inconvenience, then he or she is not a suitable candidate for implant therapy.

III. Dental History

It is also vital to evaluate the patient’s chief complaint, as it may have an equal bearing on treatment outcome. For example, the treatment plan recommended to the patient desiring a more secure lower denture will be quite different from the one proposed to the patient seeking a fixed and rigid appliance.

Radiographic analysis Surgical analysis Esthetic analysis

Diagnostic phaseProblem list & treatment considerations



Radiographic analysisSearching for:
periapical pathology radiopaque/radiolucent regions adequate vertical bone height adequate space above inferior alveolar nerve or below maxillary sinus adequate interradicular area bone quality & quantity radiographs - panoramic and periapical (CT scan or tomography - as indicated)


The radiographs  aid to determine amount of “space”& bone available for implants. CT (computed tomography) scan  gives more accurate & reliable assessment of bone (quality, quantity & width) & locale of anatomic structures.Radiographic stent  acrylic stent with lead beads or ball -bearings (5mm) placed in proposed fixture locations, allows more accurate radiographic interpretation. Within the radiographic analysis

surgical analysis

Implant length/diameter. Determined by quantity of bone apical to extraction site. Use longest implant safely possible. Diameter dictated by corresponding root anatomy at crest of bone. Proper surgical technique during implant placement & minimal heat generation are very important.

Treatment options:

Immediate: place implant at time of tooth extraction. Delayed -Immediate : 8-10 week delay. Delayed: 9-10 months or longer. Immediate will not allow bone resorption, but delayed allows bone fill for stabilization.

Implant emergence profile:Restored implant should appear to “grow” or emerge from the gingiva, very natural & desirable in appearanceSmile line:High in maxilla; low in mandible, follow lip shape (full Vs. thin). Existing ridge defect  if visible with high smile line will need augmentation Esthetic analysis

Super structure:

It could be defined as a metal framework that fits the implant abutments and provides retention for the prosthesis. Recently, it is defined as the superior part of multiple layer prosthesis that includes the replaced teeth and associated structures.

The superstructure for completely edentulous patients can be classified as:

Implant retained removable overdenture (Resilient design). Implant supported removable overdenture (Rigid design). Fixed detachable prosthesis (Hybrid prosthesis). Implant supported Fixed Bridge. 1) Screwed-in Fixed Bridge. 2) Cemented Fixed Bridge.


Design Concepts for Removable Implant Prostheses
Removable options can now be either nonrigid (resilient) or rigid. A removable rigid overdenture will function in a similar manner as a fixed implant prosthesis.
Rigid
Resilient

Resilient Design

Removable implant prostheses can be restored using a combined implant - retained and soft tissue -supported overdenture (ie, two- implant overdenture). Fabrication of this type of restoration can be completed using individual un-splinted retainers that allow rotation or a bar-clip prosthesis equipped with a hinging mechanism for rotation. The use of a bar (ie, Dolder bar-joint) allows movement between the two components. In either case, the classic principles of complete denture fabrication apply adequate denture base extension and proper adaptation are essential. These design concepts should not be extrapolated to the maxillary arch.

Rigid Design

The implant-retained and implant-supported removable overdenture (ie, multiple implant bar overdenture with three or more implants) may or may not require the same number of implants as the fixed and usually has multiple retentive elements. This type of prosthesis does not, however, contain a rotational device. The bar used in these types of restorations is a bar unit (ex, Dolder bar-unit). It allows no movement between the bar and sleeve.

Factors Affect the decision between Fixed or Removable supported Implants Design:

Extraoral Diagnostic Guidelines Intraoral Diagnostic Guidelines

Extraoral Diagnostic Guidelines

Removable
Fixed
Factor
High
Low
Lip line
Distinct
Little
Tooth display
Necessary
No need
Facial/Lip support

Intraoral Diagnostic Guidelines

Removable
Fixed
Factor
Buccal inclination Buccal convex
Vertical convex
Ridge (shape)
> 15 mm
~10 mm
Intermaxillary distance
Skeletal
Neutral
Intermaxillary relationship
Thin, mobile
Thick, keratinized
Mucosa

The most common line of treatment

Treatment Planning Determinants

1. Changes in Oral Structures in Edentulism 2. Posterior Ridge Anatomy 3. Occlusal Forces 4. Quality, Location and Quantity of Bone 5. Implant Size 6. Implant Location 7. Arch configuration 8. "Mapping" the Mandible 9. Cantilevering

1. Changes in Oral Structures in Edentulism

With successive denture treatments, it is common for the vertical dimension of occlusion to decrease as bone resorps. This promotes an increased tendency toward a skeletal Class III relationship.

Posteriorly, poor ridge height, inadequate attached gingiva and compromised ridge shape cause increased horizontal movement of the prosthesis. This increases the lateral forces that are brought to bear on the anterior implants, and will affect bar and prosthesis design.
2. Posterior Ridge Anatomy

Posterior Ridge Anatomy

3. Occlusal Forces
The maximum bite force of subjects with a mandibular denture supported by implants is 60 to 200% higher than that of subjects with a conventional denture. Edentulous patients that are predisposed to clenching and bruxing may be given the necessary "tools" to begin parafunctional habits once the implant bar is secured in place.

Occlusal Forces & Attachments

The minimum buccal-lingual thickness of osseous tissue required to successfully place an implant is 5 mm. In order to achieve a 5.0 mm "flat" base, either the anterior ridge crest peak must be removed or a bone graft must be considered.
4. Quality, Location and Quantity of Bone

5. Implant Size

The greater the surface area of the implant-bone system, the less concentrated the force transmitted to the crest of bone at the implant interface, and a better the prognosis for the implant. For each 0.25 mm increase in diameter, the surface area of a cylinder increases by more than 10 per cent; For each 3.0 mm increase in length , the surface area of a cylinder increases by more than 10 per cent.

5. Implant Size

0.25 mm diameter = 3.0 mm length

6. Implant Location

Ideally, occlusal forces should be directed along the long axis of the implants. Therefore ,The angle of the osseous ridge crest is a key determinant of implant angulation. The distance between an implant and any adjacent "landmark" (natural tooth or another implant), which should be not less than 2.0 mm.

The angle of the osseous ridge crest is a key determinant of implant angulation.

7. Arch configuration
Mandibular arch forms may be classified as tapered or square. With tapered arch forms, the most posterior right and left implants in a four-implant treatment are often placed well around the "turn" of the arch, creating a "U" shaped design that is well suited to cantilevering, With a square arch, the four implants are usually placed in a relatively straight line. This "straight line" bar design is not well suited to cantilevering.

8. "Mapping" the Mandible

The anterior symphysis can be divided into five geographic sites: A point, 6.0 mm anterior to each mental foramen, determines the most posterior boundaries, right and left. Another possible implant location occurs at the midline. Two additional sites are chosen on each side of the midline, spaced equidistantly between the midline and the respective distal sites.


9. Cantilevering
The number of implants, their respective lengths and locations, the quality of bone support, the posterior ridge anatomy, occlusal forces, and the opposing dentition are of greater importance in determining the appropriate cantilever than a suggested formula. A suggested maximum cantilever would be 1.5 times this distance.

Cantilevering

Treatment PlanningWhen all the diagnostic information has been assembled, a variety of available treatment options must be assessed:
1. One-Implant Overdenture 2. Two-Implant Overdenture 3. Three-Implant Overdenture 4. Four-Implant Overdenture 5. Five-Implant Overdenture

One-Implant Overdentures

Indications: The maladaptive or dissatisfied denture patient who demands greater stability and oral comfort. Elderly patients desiring a more stable mandibular denture. Or, as a minimal implant treatment objective for the partially edentulous patient with severely compromised teeth in which removal would convert a patient to a fully edentulous state.

One-Implant Overdentures

In the two-implant over-denture, an attachment is used to greatly enhance the retentive potential of what is essentially a tissue-supported prosthesis. If only two implants are placed, which are 13mm long or longer, and they are in dense bone, they can be left as individual supporting units with little risk.
Two-Implant Solitary Overdenture

Two-Implant Solitary Overdenture

Two-Implant Solitary Overdenture

Two-Implant Bar Overdenture

If the two implants are 10 mm long or shorter, or the bone quality is compromised, then ideally: They should be splinted. They should be at least 10 mm apart (in order to allow room for a clip or fastening mechanism) They should be no further than 18 mm apart in order to limit bar flexure.

Two-Implant Bar Overdenture

Two-Implant Bar Overdenture

Three-Implant Overdenture

The three-implant overdenture is still essentially a tissue-supported prosthesis with enhanced retention supplied by the attachment / bar complex.

Three-Implant Overdenture

Four-Implant Overdenture

At this level, the prosthesis begins to derive a larger part of its support and retention from the implant/bar complex, and the importance of tissue support decreases. Also, the attachments selected for a four-implant bar over-denture can be more rigid, as the torquing forces generated by the prosthesis will be better tolerated. This number allows for some "insurance" in case one implant fails to integrate.

Unsplinted Implant Overdenture

Implant-Bar Overdenture

Five-Implant Overdenture

At this level, a prosthesis can be fabricated that is completely implant supported and retained. The decision to fabricate a bar over-denture over five implants, rather than a fixed detachable restoration, usually relates to the patients’ ability to maintain proper oral hygiene.

Five-Implant Overdenture

Five-Implant Overdenture

PROSTHETIC PROTOCOL

Overdenture abutments were cemented or screwed into the implants. Pressure indicating paste was placed on each overdenture ball. The denture was seated so that the pressure indicating paste could mark the exact location of the overdenture abutments. Then, a recess was cut into the denture at each abutment location The resulting depressions in the mucosal aspect of the denture were lined with polyvinylsiloxane material and seated in the patient's mouth. The denture was either lined with a lab-processed material or O-rings were used for retention.

Overdenture abutments were cemented or scrowed into the implants.

Pressure indicating paste was placed on each overdenture ball.

Then, a recess was cut into the denture at each abutment location

lined with polyvinylsiloxane material and seated in the patient's mouth.


The denture was either lined with a lab-processed material or O-rings were used for retention
Depressions for fixation of O-rings

Again…….Direct pick up for implant O-ring :

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THE END