Dental Implants: An Overview

General Implant Information

• An implant is a structure used to replace a missing organ or tissue in the general medical field.
• In dentistry, implants replace missing teeth or surrounding tissues supporting fixed or removable prostheses.
• Implants are biofunctional devices placed within or onto bone.

Implant History

• The concept of using foreign materials in the body for reconstructive and prosthetic purposes dates back a long time.
• Modern implant practices emerged after understanding the reactions of metals to body fluids, bone physiology, and tissues.
• Branemark introduced the concept of "Osseointegration" in the 1980s, based on his observations of titanium's relationship with bone in the 1960s; this concept is now widely accepted in implantology
• Osseointegration describes the direct connection between an implant and bone.
• In dentistry, the term "Tissue integration" highlights the importance of implants integrating well with surrounding tissues along with bone.

Four Key Factors for Successful Osseointegrated Implants

• Material properties: Pure titanium is preferred, forming a direct chemical bond with bone through a titanium oxide layer
• Implant shape: Branemark recommends screw-type implants for surface area and force distribution, but various shapes exist
• Surgical procedure: Requires special tools and techniques to minimize tissue damage
• Avoiding loading during healing: Implants should not be loaded to allow osseointegration, typically 3-4 months in the mandible and 4-6 months in the maxilla

Immediate Loading

• Protocols advocating immediate loading/immediate placement have emerged, suggesting that early loading can stimulate bone healing
• Primary stability and controlled force distribution are important.

Success Criteria for Implants

• Established in 1975 at the Harvard conference by Schnitman and Schulmann:
  • Movement of less than 1 mm in any direction
  • Bone loss not exceeding 1/3 of the implant's vertical height
  • Manageable gingival inflammation without paresthesia, anesthesia, or damage to adjacent structures; no violation of anatomical structures.
  • A functional service life of at least 75% within 5 years

Albrektson and Zarb's Standards (1986)

• The implant must be immobile when clinically tested
• No radiolucency should be visible on radiographs.
• Annual bone loss should not exceed 0.2 mm after the first year.
• Absence of pain, infection, neuropathies, paresthesia, or anatomical complications

Factors Ensuring Implant Success

• Proper patient assessment.
• Precision in implant placement
• Management of surrounding soft tissues
• Quality of prosthetic restoration

Advantages of Implant-Supported Prostheses

• Preserves bone.
• Maintains occlusal vertical dimension
• Provides esthetics
• Ensures proper occlusion
• Offers psychological support
• Restores proprioception
• Provides stability and retention
• Improves phonetics and muscle tone

Age Considerations for Implants

• Skeletal changes and osseointegrated implants behaving like ankylosed teeth make age a limiting factor in children and young patients.
• Controlled applications are possible with an understanding of growth and development.

Growth and Development

• Maxilla and mandible grow until puberty with the most rapid period during puberty.
• Puberty occurs around 12-14 in girls and 13-15 in boys.
• Sesamoid bone radiograph on the thumb is indicative of puberty.
• Jaw growth completes around age 18 in females and 20 in males.

Implants in Younger Patients

• Implants can remain shorter (infraposition) as adjacent teeth continue to erupt.
• Crown length differences can be managed with prosthetic methods.
• In young patients, growth needs to be considered, waiting until growth stabilizes (around 20 in females and 22 in males).
• Age has no upper limit for dental implants.

Indications for Implants

• Severely resorbed ridges requiring retention
• Single or double-sided edentulous ridges, particularly in young patients.
• Long edentulous spans.
• Situations where adjacent teeth should not be prepared
• Psychological or physiological intolerance to removable prostheses.

Additional Indications

• Oral muscle incoordination
• Low tissue tolerance
• Parafunctional habits affecting prosthesis stability
• High expectations from complete dentures.
• Hyperactive gag reflex.

Contraindications

• High-dose radiation exposure (>5000 Rad)
• Psychiatric disorders (psychosis, dysmorphophobia)
• Hemolytic disorders
• Rheumatic diseases, nephritis, heart diseases, hepatic cirrhosis, allergic conditions and immune deficiency.
• Untreated local infections.
• Soft or hard tissue pathologies.
• Substance abuse

Relative Contraindications

• Low-dose radiation (<4000 Rad)
• Alveolar bone diseases, periodontal diseases, relapsing oral mucosal diseases, temporomandibular dysfunctions, insufficient bone volume and anatomical malformations

Radiographic Examination

• Aids in assessing bone quality, quantity, and relationship to anatomical structures.
  • Intraoral radiographs: periapical, occlusal
  • Panoramic radiographs
  • Lateral cephalometric radiographs
  • Magnetic resonance imaging
  • Computed tomography
  • Interactive computed tomography.

Intraoral Radiographs

• Aid in localized assessment but are limited by distortion

Panoramic Radiographs

• Lateral cephalometric radiographs assist in sagittal assessment concerning bone height, width, and inclination, but are not commonly indicated due to distortion
• Allow assessment of all dental arches but suffer from magnification irregularities, geometric distortion, and limited detail

CT Scans

• Essential for assessing the bone's bukko-lingual width
• Lateral cephalometric radiographs-useful for sagittal assessment of the jaws but have limitations in implant planning

Magnetic Resonance Imaging

• Limited use in implant dentistry due to artifacts from metal

Computed Tomography (CT)

• It is vital for assessing height, thickness, and density of available bone.
• Special programs like Dental CT streamline the process and axial slices to facilitate implant planning.
• Essential for planning in anatomically sensitive regions. Interactive CT software enables clinicians to review tomographic data, facilitating measurements and implant placement simulation.
• The software allows simultaneous axial sagittal plus panoramic views or can create three-dimensional models.

Surgical Stents and Guides

• Facilitate precise implant placement based on the surgical plan.
• Bone or mucosa-supported options are available

Medical History

• Important for assessing general health and identifying potential risks
• Inquiring about rheumatic conditions, heart ailments, kidney diseases, liver conditions, allergies, and medication use

Dental History

• Assessing time and cause of tooth loss is significant along with evaluation of soft tissues and presence of pathologies
• The assessment of oral hygiene is important before implant operation.

Clinical Examination

• Evaluation of oral hygiene, soft tissues, and existing dentition concerning available bone, with special tools like calibrated probes
• Evaluate the condition of remaining teeth and perform periodontal treatment, if necessary.

Lekholm plus Zarb Classification

• This classifies bone quantity into five categories (A-E) and quality into four types (1-4).
  • Type A: Minimal or no bone resorption
  • Type B: Moderate bone resorption
  • Type C: Significant resorption leaving only basal bone.
  • Type D: Severe resorption extending into basal bone, requiring bone grafting

Bone Quality

• Classifies as 1, 2, 3 and 4 by Lekholm plus Zarb
  • Class 1: Mostly cortical bone
  • Class 2: Thick cortical layer surrounding trabecular bone.
  • Class 3: Thin cortical layer with dense trabecular bone.
  • Class 4: Thin cortical layer with low-density trabecular bone.

Anatomical Considerations During Implant Placement

• Maintain a minimum of 1 mm distance between the implant apex and anatomical structures

Surgical Approaches

• Approaches depend on the time from tooth loss to implant placement: immediate, delayed, or late.
• Delayed implant placement allows for ridge resorption, potentially complicating implant placement.
• Immediate implant placement immediately after extraction can be done if the extraction site is suitable.