Dental implants

Introduction:

Dental implant is a structure made of alloplastic materials implanted into the oral tissues beneath the mucosa and/or periosteum and/or within or through the bone to provide retention and support for a fixed or removable dental prosthesis.

History:

Implant dentistry the second oldest dental profession; exodontia (oral surgery) is the oldest. Around 600 AD, the Mayan population used pieces of shells as implants to replace mandibular teeth. In 1809, J. Maggiolo inserted a gold implant tube into a fresh extraction site. In 1930, the Strock brothers used Vitallium screws to replace missing teeth. A post-type endosseous implant was developed by Formiggini (the father of modern implantology) and Zepponi in the 1940s. The subperiosteal implant was developed in the 1940s by Dahl in Sweden. In 1946 Strock designed a two-stage screw implant that was inserted without a permucosal post. The abutment post and individual crown were added after this implant completely healed. The desired implant interface at this time was described as ankylosis. In 1967, Dr. Linkow introduced blade implants, now recognized as endosseous implants. Dental implants became a scientific cornerstone after the serendipitous invention of Dr. Branemark who helped in the evolution of the concept of osseointegration (direct, rigid attachment of the implant to the bone without any intervening tissue in between two implants)

---

Indications

Dental implants are increasingly used to replace single teeth, especially in the posterior regions of the mouth. Rather than removing sound tooth structure and crowning two or more teeth, increasing the risk of decay, endodontic therapy, and splinting teeth together with pontics, which may have the potential to decrease oral hygiene ability and increase plaque retention, a dental implant may replace the single tooth.

1. Partial edentulous patients who have intermediate gaps or free-end edentulism (Kennedy class 1).
2. When a patient is not satisfied with the existing unstable and nonretentive conventional complete dental prosthesis.
3.  To preserve existing removable partial prostheses

---

Contraindications

Absolute contraindications:

• Acute illness
• Magnitude of defect/anomaly
• Uncontrolled metabolic disease
• Bone/soft tissue pathology/infection

Relative contraindications:

• Diabetes
• Osteoporosis
• Parafunctional habits: Smoking (M/C)
• HIV, AIDS
• Bisphosphonate usage
• Chemotherapy
• Irradiation of head & neck
• Behavioral, neurogenic, psychosocial, psychiatric disorders

---

Implant characteristics

Types of implant:

• Endosteal implants (M/C type): Pierce only one cortical plate of maxilla and mandible
  • M/C used endosteal implant: Root form implant
• Subperiosteal implant: Implant substructure and superstructure where custom cast frame is placed directly beneath the periosteum.
• Transosteal implant: Crosses through both cortical plates

Host reaction to different implant types:

• Biotorerant: surrounded by fibrous tissue, e.g., stainless steel
• Bioinert (M/C used): direct rigid attachment, e.g., titanium and its alloys
• Bioactive: allows the formation of bone on their surface, e.g., hydroxyapatite

---

Alternatives

• Fixed partial denture (FPD): Dental restoration used to replace missing teeth and that is permanently attached to adjacent teeth or dental implants.

---

Techniques

Success rate of 85% at the end of 5 year period and 80% at the end of 10 year period are minimum criteria for success.

• 2-stage surgical procedure:
  1. Placement of implant body below soft tissue until bone begins to heal (2-3 months for mandible and 3-6 for maxilla)
  2. Soft tissues reflected to attach a permucosal element/abutment.
• 1-stage surgical approach: Implant body in the bone and the permucosal element above the soft tissue both placed simultaneously until initial bone maturation has occurred. The abutment of the implant then replaces the permucosal element without the need for a secondary soft tissue surgery.
• Immediate-restoration approach: Places implant body and prosthetic abutment at the initial surgery, and restoration (mostly transitional) is then attached to the abutment.

---

Complications

Implant-supported single crowns and multiple implant-supported bridges may suffer from various mechanical, biological, or technical complications. Poor patient selection is one of the important factors that adversely contribute toward failures in implant dentistry.

Mechanical complications:

Mechanical complications are usually a sequel to biomechanical overloading. Factors contributing to the biomechanical overloading are poor implant position/angulation (cuspal inclination, implant inclination, horizontal offset of the implant, and apical offset of the implant), insufficient posterior support (i.e., missing posterior teeth), and inadequate available bone or the presence of excessive forces due to the parafunctional habits, that is, bruxism.

• Screw loosening (d/t overloading of implants)
• Screw/implant fracture (d/t biomechanical overloading and peri-implant vertical bone loss)
• Cement failure (d/t biomechanical overload, typically affecting the prosthesis attachment and may be treated by recementation procedure)

Technical complications:

These complications arise during the course of surgery

• Perforated buccal/lingual plates
• Bleeding in floor of mouth (from lingual/facial artery injury, during osteotomy preparation)
• Nerve injury (altered nerve sensation: anesthesia/paresthesia/hyperesthesia)
• Incision line opening (M/C postoperative complication)

Biological complications:

Biological complications are subcategorized into early biological failures and late implant failures, where the early failures are attributed to the failure of placing the surgical implant under proper aseptic measures and the late complications are typically peri-implantitis and infections bred by bacterial plaque.

• Peri-implantitis: Inflammatory pathological changes in soft and hard tissues surrounding an osseointegrated implant