C HAPTER 15 Dental Implants Copyright © 2014, 2007, 2001, 1996 by Saunders, an imprint of Elsevier...

CHAPTER 15

Dental Implants

Copyright © 2014, 2007, 2001, 1996 by Saunders, an imprint of Elsevier Inc.

TYPES OF IMPLANTS

Dental implants are used in the rehabilitation of patients who are edentulous and partially dentate.

The majority of implants are endosseous implants, based on the principle of osseointegration. Subperiosteal and transosteal implants are still in

use today but much less frequently.

2


SUBPERIOSTEAL IMPLANTS

The subperiosteal implant is a custom-made cast framework that is placed beneath the periosteum over the alveolar bone. It can be used in either the maxilla or mandible.

The frame rests on the jawbone. Posts protrude through the soft tissues to

provide anchorage for a denture or fixed prosthesis.

3


SUBPERIOSTEAL IMPLANTS (CONT.)

A radiographic image of a subperiosteal implant is presented in the following figure.

4


TRANSOSTEAL IMPLANTS

Transosteal implants pass through the mandible in an apico-coronal direction.

They protrude through the gingival tissues into the mouth for prosthesis anchorage.

A stabilization plate is placed along the inferior border of the mandible. Posts are attached to this plate and pass through

the mandible to provide anchorage for the prosthesis.

Transosteal implants are limited to the mandible.

5


TRANSOSTEAL IMPLANTS (CONT.)

An example of a subperiosteal implant is presented in the following figure.

6


ENDOSSEOUS IMPLANTS

Endosseous implants are placed within bone.

They are divided into blade and root-form types. The root-form implant is either screw or

cylindrically shaped with different lengths, diameters, and design characteristics.

The blade implant is no longer used today; it had a high incidence of complications and failures.

7


ENDOSSEOUS IMPLANTS (CONT.)

The placement of endosseous implants is demonstrated in the following figure.

8



Root-form endosseous implants provide osseous anchorage through the formation of a lattice between the implant surface and bone.

These implants are used for replacing missing teeth in patients who are partially and totally edentulous.

9



Examples of several root-form endosseous implants are presented in the following figure.

10


OSSEOINTEGRATION

The definition of osseointegration has changed as more refined methods have been developed to study the interface between the implant and the surrounding bone.

Originally, the term was defined as a direct implant-to-bone union without any intervening soft connective tissue.

With the advent of scanning electron microscopy, a better analysis of the interface became possible, and osseointegration became more clearly understood.

11


OSSEOINTEGRATION (CONT.)

A light microscopic view of osseointegration is presented in the following figure.

12



Using the scanning electron microscope, a narrow nonmineralized zone between the bone and the implant, containing chondroitin sulfate glycosaminoglycans, is revealed.

The amount of bone-to-implant contact varies between different implant systems and is influenced by surface characteristics.

13



The exact amount of bone-to-implant contact required for success has not been determined.

Implant integration depends on the: Biomaterials and biocompatibility Implant design (length, diameter, shape,

surface) Bone factors Surgical factors Loading considerations

14


BIOCOMPATIBILITY

Biocompatibility of a material is defined as allowing “close contact of living cells at its surface, which does not contain leachables (molecules that separate off the surface) that produce inflammation and which does not prevent growth and division of cells in culture.’’

Biocompatible materials are called biomaterials.

15


BIOCOMPATIBILITY (CONT.)

Any implanted material is considered a foreign body.

The body recognizes all implanted metals as unnatural (nonself).

Metals in contact with tissue fluid are prone to degradation and dissolution by corrosion.

The exchange of protons with biologic molecules leads to antigen formation and cellular uptake. This reaction can prove toxic to cells and may

inhibit growth and function. 16


BIOCOMPATIBILITY (CONT.)

Titanium is a highly reactive yet biocompatible metal.

It is the material of choice in osseointegration.

Titanium is unique in that an oxide layer prevents corrosion on the surface, enabling tissue integration to occur.

Other advantages are that titanium is lightweight and has enough strength to withstand occlusal forces.

17


SHAPE

The majority of endosseous implants used today are cylindrical with a threaded surface design. The thread pitch varies among implant systems.

Almost all implants are solid, but hollow implants are available with no threads.

18


SURFACE

Implant surface characteristics influence the rate of bone apposition and growth and the amount of bone-to-implant contact. A higher bone-to-implant contact is attained

around rough-surfaced implants.

19


SURFACE (CONT.)

An increased rate of bone growth and an increased amount of surface contact with bone: Allows for better transfer of forces to bone. Facilitates earlier loading, which is the

placement of restorations on the implants. Permits better success in areas with poor bone

quality.

20


STATE OF HOST SITE AND BONE FACTORS

The amount of bone-to-implant contact achieved at the time of implant placement is related to the quantity and quality of bone. The quality of bone determines the stability of

the implant.

21


STATE OF HOST SITE AND BONE FACTORS (CONT.)

The amount of cortical and cancellous tissue varies within the arch and between the maxilla and mandible.

The density of cortical bone is three to four times that of cancellous bone. Cancellous bone therefore contributes less to

implant stability at placement.

22


STATE OF HOST SITE AND BONE FACTORS (CONT.)

The shape of bone is dependent on several factors, including any history of trauma or infection, the length of time since tooth loss occurred, and loading by removable prostheses.

Systemic conditions such as osteoporosis and social factors such as smoking can influence the quality of bone.

Both the shape and quality of bone must be considered when planning for implant therapy.

23


LOADING CONSIDERATIONS

No fixed guidelines exist concerning the length of healing time after surgery and the time needed before prosthetic loading of implants.

When the implant is determined to be stable at the time of placement, immediate loading (placement of a restoration at the time of the implant surgery) of the implant has proven to be compatible with attaining osseointegration.

24


INDICATIONS AND CONTRAINDICATIONS FOR IMPLANT THERAPY

Indications for Implant Therapy Patients with a strong gag reflex to eliminate

palatal coverage by removable prostheses Long span bridges Free-end removable partial dentures Alternative to periodontally compromised

teeth for bridge abutments Hopeless periodontally or endodontically

involved teeth Orthodontic anchorage

25


INDICATIONS AND CONTRAINDICATIONS FOR IMPLANT THERAPY (CONT.)

Examples of implant-supported prostheses are presented in the following figure and in slides 27 through 29.

26



27



28



29



Contraindications for Implant Therapy Certain systemic, local, and social factors

may adversely affect the outcome of implant therapy.

Treatment should be delayed in young patients until growth is near completion; unlike the natural dentition, implants remain stationary during dentoalveolar growth.

Increasing age in older individuals has no specific adverse effect on osseointegration, as long as associated medical conditions are well controlled or modified.

30



Contraindications for Implant Therapy (cont.) Conditions that increase the patient’s

susceptibility to infection, such as uncontrolled diabetes, have a higher incidence of peri-implantitis and implant failure.

Therapy with bisphosphonates increases the risk of jaw osteonecrosis. In particular, intravenous bisphosphonates

Patients receiving anticoagulant therapy are at risk for hemorrhage during surgical procedures.

Patients on steroid therapy may have steroid complications.

31



Contraindications for Implant Therapy (cont.) The microbial pathogens associated with

periodontal disease are also associated with disease progression around dental implants. Effective treatment and control of any

periodontal disease before implant therapy is essential.

Implants should only be considered in patients who demonstrate a commitment to good homecare and maintenance routines.

32



Contraindications for Implant Therapy (cont.) The adverse effects of smoking on

osseointegration and implant survival have been shown in many studies. Although smoking is not an absolute

contraindication to implant therapy, it increases the risk of peri-implantitis and failure.

33


TEETH AND IMPLANTS

The peri-implant soft tissue forms around the section of the implant system that extends from the bone into the oral cavity.

The collagen fibers are aligned parallel to and organized in a circular arrangement around the supracrestal portion of the implant.

The cemental layer is absent over the implant surface; therefore fiber insertion is not possible.

Hemidesmosomal and basal lamina attachment mechanisms adhere the peri-implant soft tissue to the titanium collar of the implant.

34


TEETH AND IMPLANTS (CONT.)

Implants acquire their stability and anchorage through direct contact with the surrounding bone—osseointegration.

A periodontal ligament (PDL) is absent; therefore proprioceptive feedback is minimal, although proprioceptive mechanisms exist in the surrounding hard and soft tissues.

35



An implant biologic width is made up of a 2-mm long junctional epithelium and a 1-mm zone of connective tissue.

The connective tissue zone is poorly organized. It exists between the junctional epithelium on

the implant abutment and the bone. An abutment screw connects the implant

abutment to the implant fixture. The location of the crestal bone level around

implants depends on the implant design. 36



These teeth and implant characteristics are diagrammatically demonstrated in the following figure.

37


SUCCESS CRITERIA

The clinical success of implant therapy is assessed by radiographic imaging, evaluating implant mobility, and observing the surrounding soft tissue. Other techniques include the use of digital and

subtraction radiography, computed tomography, and devices that record the implant interface contact.

Assessment of implants using probing depths is considered to be of limited value and remains controversial.

38


SURGICAL PROCEDURES

Using a two-stage surgical approach, the healing period after implant placement can range from 3 to 6 months. This surgical approach encourages successful

osseointegration rather than a fibrous union at the implant-bone interface.

39


SURGICAL PROCEDURES (CONT.)

A two-stage surgical approach was initially recommended to minimize functional loading on the implant during the healing phase.

A single-stage implant surgical protocol was later introduced. Implant success has been demonstrated with the

single-stage approach.

40


SURGICAL PROCEDURES (CONT.)

After a thorough examination and planning process that includes appropriate radiographic images, study casts, and the fabrication of surgical guides (stents), implants are placed with either a submerged or a nonsubmerged type of surgery.

The ideal location and angulation of the implant should be consistent with planned prosthetic suprastructures (restorations).

41


SUBMERGED (TWO-STAGE) PROTOCOL

The submerged protocol requires two surgical procedures before restorations can be placed on the implants.

The first surgery places the implant fixture within the bone; this is followed by a second surgery 3 to 6 months later to uncover the implant.

42


SUBMERGED (TWO-STAGE) PROTOCOL (CONT.)

Examples of implant surgery and prosthetic results are presented in the following figure and in slides 44 through 46.

43



44



45



46



First Surgical Procedure A crestal incision is made in the soft tissue,

and a flap is reflected. With the aid of a surgical stent, drills are

used under saline solution irrigation to prepare the endosseous implant recipient site or sites to the predetermined length and diameter.

Guide pins are used to verify the angulations and distances between implants or between the implant and surrounding teeth.

47



First Surgical Procedure (cont.) Implants are either slowly threaded into

place, as in the case of screw design implants, or they are gently tapped into place, as in the case of nonthreaded cylindrical designs.

Placing a device called a cover screw on top of the implant protects the implant from an ingrowth of tissue.

The flap is then repositioned and sutured over the implant to ensure that it is submerged under the gingiva. 48



The two-stage submerged protocol is illustrated in the following figure.

49



First Surgical Procedure—Postoperative Steps The patient should not wear dentures over

the implant site for 2 to 3 weeks to avoid pressure on the implant.

The area should be cleansed with a chlorhexidine 0.2% mouthwash twice daily, and the use of systemic antibiotics should be considered to minimize the chances of infection.

50



Second Surgical Procedure The healing periods for mandibular implants

and for maxillary implants are 3 and 6 months, respectively.

After these healing periods, the submerged implants are exposed by either making small incisions or by using circular punches over the implants to gain access to the cover screws and to exchange them for healing abutments. Healing abutments are posts that allow

healing and adaptation of the peri-implant soft tissues.

Restorative procedures can usually begin after 3 to 4 weeks of soft-tissue healing.

51



An example of a healing implant in place after second-stage surgery is demonstrated in the following figure.

52


NONSUBMERGED (SINGLE-STAGE) PROTOCOL

Surgical Procedure for the Nonsubmerged Protocol

The nonsubmerged protocol for implant placement is similar to the two-stage submerged procedure except that after implant placement, the tissues are closed around either the transmucosal portion of the implant or the healing abutment. This closure eliminates the need for a second

surgery to uncover the implant. The elimination of a second surgery also

reduces treatment time and patient discomfort.

53


NONSUBMERGED (SINGLE-STAGE) PROTOCOL (CONT.)

The following figure demonstrates an example of the single-stage protocol.

54


ADDITIONAL PROCEDURES

Intraoral soft- and hard-tissue deformities prevent implants from being placed in the desired location for the best restorative results.

Treatment to restore both soft and hard tissues may be necessary before or concurrent with implant placement.

These procedures may include soft-tissue augmentation to increase the thickness or amount of keratinized tissue, bone grafting, guided-tissue regeneration, or a combination of procedures.

55


OTHER IMPLANT PLACEMENT PROTOCOLS

Immediate Implant Placement after Tooth Extraction

The reason for extracting a tooth determines whether immediate implant placement should be considered.

The presence of infection and the lack of bone to achieve primary stability of the implant are contraindications to immediate placement.

However, immediate placement after the extraction of teeth for periodontal disease shows results similar to those of healthy sites.

56


OTHER IMPLANT PLACEMENT PROTOCOLS (CONT.)

Immediate Implant Placement after Tooth Extraction (cont.) The shape of the socket of an extracted tooth

is not the same as the shape of a cylindrical endosseous implant.

Immediate placement of implants into extraction sockets leaves a gap between the implant and the socket wall. This gap is referred to as the jumping distance.

57



Immediate placement of implants performed at the time of tooth extraction is illustrated in the following figure.

58



Immediate Loading of Implants Immediately providing a fixed provisional

implant-supported crown after implant placement is termed immediate loading.

If multiple implants are placed, then the temporary restorations are splinted together to minimize movement and to promote even-load distribution.

Single implant provisional restorations are restored out of occlusion to limit the functional load transmitted to the implant fixture. 59



Immediate loading of an implant placed in an extraction site is illustrated in the following figure.

60


PROSTHETIC CONSIDERATIONS

The direction and magnitude of forces placed on an implant, which in turn are transmitted to the surrounding bone, are critical in both the attainment and maintenance of osseointegration.

Prosthetic restorations must be designed to avoid an excessive load on implants to protect them from failure.

Treatment of patients exhibiting parafunctional habits such as clenching and bruxism should be undertaken with caution.

An occlusal guard should be considered to help protect the implants after delivery of the prosthesis.

61


PROSTHETIC CONSIDERATIONS (CONT.)

Restorations are either cemented in place on the implant or screw retained.

If a problem arises in a screw-retained restoration, then the dentist simply removes the screw and accesses the prosthesis.

With cement-retained restorations, the abutment is attached to the implant with a screw system, but the crown is cemented onto the abutment. Temporary cement may be used to allow it to be

removed, if necessary.62


MAINTENANCE

Mobility Healthy implants are osseointegrated and do

not exhibit mobility. The absence of the PDL around implants

creates a rigid bone-implant interface.

The presence of mobility, as detected by conventional methods, is an indication of a loss of integration and implant failure.

Mobility of the prosthetic components are usually a result of loosening or the fracture of screws.

63


MAINTENANCE (CONT.)

Probing Probing depths are easy to measure around

implants, but their interpretation is limited. Inherent differences in the arrangement of

the tissues around implants and natural teeth make interpretation of the collected data questionable.

Probing depths around implants do not correlate with the loss of osseointegration and bone loss. For this reason, probing is not considered a

valuable diagnostic tool. 64


MAINTENANCE (CONT.)

Probing (cont.) If probing is performed, then the use of

plastic periodontal probes is advocated to reduce the chances of inadvertently scratching the implant surface.

No evidence suggests that probing the peri-implant tissues causes damage. However, avoiding probing during the first

3 months after loading is advised to ensure that healing is not disturbed.

65


MAINTENANCE (CONT.)

Probing around implants is illustrated in the following figure and in slide 67.

66


MAINTENANCE (CONT.)

67


MAINTENANCE (CONT.)

Indices Probing around implants provides an

assessment of inflammatory parameters such as bleeding and suppuration.

Other indices that can be applied to implants include gingival and plaque indices to evaluate the patient’s oral hygiene status.

Maintaining compliance with plaque control to minimize tissue inflammation is the important point.

68


MAINTENANCE (CONT.)

Radiographic Imaging Periapical radiographic and panoramic

images are used to assess bone levels for implant sites.

Images are used to assess the height of proximal bone, the presence of anatomic structures such as the maxillary sinus, anomalies, and pathologic lesions.

Correct seating of the restorative components can be verified on images after second-stage uncovering of the implant and after the placement of the restoration. 69


MAINTENANCE (CONT.)

Radiographic Imaging (cont.) Examples of the

information obtained from radiographic images are presented in the following figure and in slide 71.

70


MAINTENANCE (CONT.)

Radiographic Imaging (cont.)

71


MAINTENANCE (CONT.)

Radiographic Imaging (cont.) More advanced imaging techniques are now

available that provide a three-dimensional view of the implant area.

The use of computed tomography, special tomographic devices, and digital subtraction radiographic techniques enable quantitative and qualitative assessment of changes in bone density.

72


MAINTENANCE (CONT.)

Radiographic Imaging (cont.) Use of computed

tomography is demonstrated in the following figure.

73


MAINTENANCE (CONT.)

The criteria for implant success includes bone loss not exceeding 0.2 mm annually after the first year after loading and the absence of peri-implant radiolucencies or associated conditions.

Radiographic follow-up is recommended at 6, 12, and 36 months and then every 2 to 3 years thereafter unless clinical symptoms are observed.

74


MAINTENANCE (CONT.)

Examples of radiographic information correlated with clinical findings are presented in the following figure and in slide 76.

75


MAINTENANCE (CONT.)

76


MAINTENANCE (CONT.)

Soft Tissues Healthy tissue around implants can be

maintained with minimal or no keratinized tissue.

Esthetics may dictate that keratinized tissue be present at the implant site.

If needed, a surgical procedure can be performed to increase the width of attached gingiva before implant placement, at the time of implant surgery, or during the second-stage surgery to uncover the fixture.

77


MAINTENANCE (CONT.)

The results of surgery to increase keratinized tissue are illustrated in the following figure.

78


PERI-IMPLANT DISEASE

Peri-implant disease is a term for inflammatory reactions in the tissues surrounding an implant.

Peri-implant mucositis is a reversible inflammatory reaction in the soft tissues surrounding an implant. If untreated, peri-implant mucositis will progress

into peri-implantitis. Peri-implantitis is a term for inflammatory

reactions that affect soft and hard tissues around the implant, leading to the loss of supporting bone. 79


PERI-IMPLANT DISEASE (CONT.)

If left untreated, peri-implantitis will ultimately progress to implant failure.

A failing implant is not synonymous with peri-implantitis. A failing implant refers to an implant that has

lost osseointegration and is no longer an effective prosthetic anchor.

80



Peri-implant mucositis and peri-implantitis are illustrated in the following figure and in slide 82.

81



82



Plaque biofilm is the primary microbial etiologic factor in peri-implantitis.

Patients with untreated periodontitis are at higher risk for developing peri-implantitis than those with controlled periodontal conditions.

The progression of inflammatory disease around implants appears to be more rapid than around natural teeth.

83



Implants lack connective tissue fiber insertion; therefore the only attachment mechanism involves the basal lamina and hemidesmosomes of the epithelium.

Inflammation within the peri-implant tissues has a tendency to spread circumferentially, and the progression to bone may result in radiographically angular osseous defects.

84



Clinically, peri-implant disease assumes the shape of a well-circumscribed saucer, as demonstrated in the following figure.

85



Early implant failures are biologic, occurring within weeks or months after placement. Causes include failure to achieve

osseointegration, inherent host tissue factors, bacterial contamination of wounds, poor surgical technique, and instability of the implant.

86



Late implant failures result from factors that cause the breakdown of osseointegration. Causative factors may include mechanical

overload, fatigue failure of components, and peri-implant infection.

87



Examples of implant failure are presented in the following figure.

88



Treatment options for peri-implantitis include a combination of local or systemic antimicrobial therapy, the removal of plaque biofilm and calculus, implant surface decontamination, and the regeneration of defects.

Regeneration of defects involves surgical correction. This surgical correction may involve bone

grafting.

89



The application of local antibiotics is demonstrated in the following figure.

90


DENTAL HYGIENE CARE

Regular dental hygiene care is an important component of the long-term success of implant therapy.

Recall intervals for assessment and treatment should not exceed 6 months.

Generally, patients with implants should be seen and evaluated approximately every 3 months for the first year after the restoration of implants.

91


DENTAL HYGIENE CARE (CONT.)

Plaque biofilm and calculus removal for dental implants is performed with instruments that are not abrasive to the titanium components. Plastic, nylon, titanium, graphite, and gold-plated

curettes and air-abrasive devices can be safely used around implants.

Implants may be polished, but coarse polishing compounds should be avoided. Tin oxide with rubber cups is a good choice for

polishing around implants.

92



The use of plastic scalers on implant surfaces is demonstrated in the following figure.

93



Excellent homecare practices are as essential as regular professional maintenance care in the long-term success of implant therapy.

The cause of tooth loss among a large number of patients with implants is periodontal disease; these patients are more prone to the future breakdown of their implants.

The variety of available homecare devices includes many manual and powered toothbrushes, interdental aids, and oral irrigation devices. 94



Examples of available devices are demonstrated in the following figure and in slides 96 and 97.

95



96



97


ROLE OF THE DENTAL HYGIENIST

Early detection of pathologic conditions improves the chances of treating and maintaining dental implants with appropriate therapy.

At every recall visit, thorough assessment will permit modification to the homecare practices and maintenance intervals on the basis of the oral health of the patient.

98


ROLE OF THE DENTAL HYGIENIST (CONT.)

The significance of regular dental hygiene care can be observed in the following figure.

99


C HAPTER 15 Dental Implants Copyright © 2014, 2007, 2001, 1996 by Saunders, an imprint of Elsevier...

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Transcript of C HAPTER 15 Dental Implants Copyright © 2014, 2007, 2001, 1996 by Saunders, an imprint of Elsevier...