Dental Implant Fixture: A Guide to Choosing the Implant Base and Understanding Why It Falls Out

Do you ever wonder how a dental implant keeps the tooth firmly in place in the jaw?

We often only see the crown or the replacement tooth when it comes to dental implants, but the most crucial part of the implant is the fixture. The fixture is the metal screw that is implanted into the jawbone, acting as the root of a natural tooth to support the implant crown.

The right choice of fixture material, its brand, and the method of placement directly affect the outcome of the procedure. In this guide, we will explore everything you need to know about dental implant fixtures.

Studies published in the Journal of Oral Implantology indicate that, over the past 10 years, the success rate of fixtures with an SLA active (sandblasted) coating has been over 98%, higher than other models. This statistic demonstrates how important the choice of the right brand and the quality of the fixture surface are to the success of the implant.

 

What is an Implant Fixture?

A fixture is a type of metal screw and the core component of a dental implant that is placed into the jawbone to replace the missing root. This part serves as the main support structure for the implant, onto which other components like the abutment and final crown are placed.

The design of the dental implant fixture is made to integrate well with the bone during the osteointegration process (the process of fusing with the bone). In fact, this connection ensures the stability and long-term success of the implant.

Since the crown and abutment are replaceable, but the fixture becomes a permanent part of the implant once fused to the jawbone, choosing the best fixture and guaranteeing its quality is critically important.

To better understand the shape and placement of this part, you can refer to a picture of an implant fixture, which provides a clear view of the structure of the grooves and how it fits into the jawbone.

 

 

Material of the Implant Fixture

The materials used to create the implant fixture must be biocompatible and able to withstand the forces and pressures caused by constant chewing. The most commonly used materials for fixtures are titanium and zirconia, which we will introduce below.

 

Titanium

 Titanium is the most common material used for implant fixtures, accounting for over 90% of cases. This material is lightweight, durable, and, most importantly, biocompatible. Biocompatibility means that the human body does not reject titanium, and this metal easily fuses with natural bone.

 

Zirconia

 Zirconia is a hard, white ceramic material used by dentists for patients who are sensitive to metals. The advantage of zirconia is its white color and its inability to conduct electrical and thermal currents. However, it is more brittle compared to titanium, and there has not been extensive research on its durability.

In addition to the material of the fixture itself, its surface is often acid-etched, machined, or sandblasted to improve the bonding with the bone. Some brands, such as Swiss implant fixtures, even use hydroxyapatite coatings, which are similar to the composition of natural bone.

 

 

Types of Implant Fixtures Based on Thread Design

In addition to the material of the implant fixture, this component is also classified according to its design (the shape of the threads). In other words, the threads or spiral grooves in the fixture play a key role in the stability and longevity of the implant fixture.

 

Square Threads

 This model features vertical walls and an appropriate depth, making it suitable for low-density bone (such as the upper jaw or resorbed bone).

 

Conical Threads

 These models are cone-shaped with slanted grooves. The benefits of this design include inducing bone density during placement and providing initial stability, making it ideal for immediate implants and areas with soft or low-density bone.

 

Butress Threads

 The key feature of this fixture is a one-way groove with vertical walls. This design allows the fixture to withstand chewing forces better and is suitable for molar teeth.

 

Reverse Butress Threads

 The reverse butress design has grooves in the opposite direction of the butress threads and is suitable for areas with very low bone density. This model is also less sensitive to lateral forces.

 

Types of Implant Fixtures Based on Abutment Connection Method

One of the most important differences between types of implant fixtures is how they connect to the abutment. This connection must be strong, stable, and leak-proof to prevent bacterial infiltration, as the point of contact between the fixture (in the bone) and the abutment (in the mouth) can easily allow bacteria to enter and cause inflammation.

There are three common methods for connecting implant fixtures, and here are the characteristics of each:

 

External Hex (External Hexagon)

 In this older method, six external sides are placed on both the implant and the abutment. Despite its ease of installation, this method can lead to the loosening of the implant fixture over time.

 

Internal Hex or Morse Taper (Internal Hex / Morse Taper)

The internal or Morse taper connection is more precise and stable, reducing the risk of micro-movements and bacterial leakage.

 

Types of Implant Fixtures Based on Length and Diameter

Implant fixtures are also categorized based on length and diameter into three types: short, narrow, and wide. A short implant fixture is ideal for areas with limited bone height, a narrow fixture is perfect for tight inter-dental spaces, and a long fixture is suited for posterior regions with high chewing forces.

The choice of the best implant fixture from the available models is made based on bone density and the tooth's location to ensure optimal force distribution and initial stability for the implant's success.

 

 

Stages of Fixture Stabilization in the Jawbone

The placement of the dental implant fixture is the most crucial step in the implant procedure, determining the success rate. This process occurs in several stages:

 

Clinical Evaluation and Imaging

Before the dental implant surgery, the dentist examines the condition of the jaw using X-rays or a CT scan (CBCT) to assess bone density and height. The need for a bone graft or sinus lift is also determined at this stage.

 

Preparation of the Surgical Site

 After local anesthesia, the dentist moves the gum tissue aside to expose the jawbone. Then, a hole with the appropriate diameter and depth for the fixture is created in the bone.

 

Fixture Placement

 The fixture is screwed into the designated site with controlled torque to provide initial stability for osteointegration. The fixture remains stationary until it fuses with the bone.

 

Suturing and Beginning of the Healing Period

At this stage, the gum tissue is either sutured over the fixture or the abutment is installed (in the case of immediate implants), and the osteointegration process begins.

 

 

How Long Does It Take for the Fixture to Integrate with the Bone?

This period typically lasts between 3 to 6 months, during which the jawbone biologically integrates and fuses with the surface of the fixture. The time it takes for this process to occur depends on factors such as the implant site, bone type, bone density, the patient's overall health, and the material of the fixture surface.

 

Factors Affecting the Integration of the Implant Fixture

The success of a dental implant fixture refers to its complete integration with the jawbone and its long-term, problem-free function. Several key factors influence this success:

1. Bone Quality: The density and height of the bone at the implant site play a critical role in the success of the dental implant. Denser bones (typically found in the lower jaw) have a higher chance of successful integration.
   
   
2. Surgeon's Skill: The dentist's expertise in selecting the proper site, implant angle, and the pressure applied during the screwing and placement of the fixture is crucial for success.
   
   
3. Oral Hygiene: Bacterial plaque and gum inflammation can disrupt the connection between the bone and the fixture, potentially leading to treatment failure.
   
   
4. Smoking and Underlying Diseases: Smoking, alcohol consumption, uncontrolled diabetes, osteoporosis, and immune system disorders increase the risk of the implant fixture loosening and being rejected by the jawbone.
   
   
5. Fixture Design and Surface: Modern designs with rough surfaces and advanced coatings accelerate osteointegration.

 

 

Potential Complications of the Implant Fixture

Although dental implants in reputable centers and under the supervision of experienced dentists are associated with high success rates, it is not uncommon for some issues to arise during the treatment process. These issues may include:

• Tissue and Peri-implant Inflammation: Soft tissue inflammation (mucositis) is one of the most common complications of fixture placement, which, if neglected, can lead to bone resorption and peri-implantitis. Proper care and cleaning of the implant area are essential to prevent this issue.
  
  
• Loosening of the Implant Fixture: Lack of initial stability, bone resorption, lateral forces, or metal decay can cause the implant fixture to loosen or fail.
  
  
• Infection and Bleeding: Infection or bleeding following fixture placement can lead to implant fixture pain, fever, and swelling in the affected area.
  
  
• Breaking or Cracking: Excessive force, the use of low-quality materials, or poor fixture-bone compatibility may result in the breaking or cracking of the implant fixture.
  
  

 

 

Comparison of Renowned Implant Fixture Brands in Iran and Globally

Brand reputation is not the only factor dentists consider when choosing the best implant fixture, but it does play a role in decision-making. Renowned global brands come with different technologies, each with its own advantages and limitations. In the table below, we compare the most commonly used brands in Iran with their key features.

Brand Name	Country of Origin	Technical Features	Suitable for Which Conditions?
Straumann	Switzerland	Rapid osteointegration, precise design	Patients with challenging bone conditions
Nobel Biocare	Sweden/USA	Internal connection, proven quality	Aesthetic treatments and sensitive jaw areas
Astra Tech	Sweden	Bone-like surface features, excellent stability	Low-density bone jaw
Dentium	South Korea	Affordable, high success rate	General treatments
Osstem	South Korea	High variety, easy installation	Common jaw conditions and immediate implants
BioHorizons	USA	Bone-building surface coating, precise design	Patients with a history of periodontal disease

In recent years, Korean implant fixture brands like Dentium and Osstem have become the first choice for many clinics due to their affordable prices and acceptable quality. These brands offer performance similar to European brands with advanced designs and bone-like coatings.

 

Why Does the Jaw Reject the Implant Fixture?

Unfortunately, the failure of an implant fixture is often a sign of osteointegration failure, structural issues in the bone, or improper placement. Here are some common reasons for fixture rejection:

• Low bone density in the jaw, which does not provide the necessary initial stability.
  
  
• Applying pressure to the fixture and moving it in the early days after placement, preventing proper fusion with the bone.
  
  
• Infection of the tissue around the implant or gum disease.
  
  
• Continuous pressure from chewing before the fixture is fully stabilized.
  
  
• Use of low-quality fixtures or improper placement by non-specialized practitioners.
  
  

If the implant fixture has fallen out, immediate replanting should not be attempted. The cause of the fixture loosening or falling out must first be identified, and the bone conditions must be thoroughly reviewed and reconstructed.

 

Conclusion

In any successful dental implant treatment, the fixture plays an irreplaceable foundational role. Implant specialists ensure full osteointegration and stable long-term performance by selecting the correct type of implant fixture based on bone structure, tooth position, and the patient's condition.

At Dr. Ebadian's dental clinic, we carry out all stages of the implant procedure, from fixture selection to final placement, utilizing the latest technology and relying on extensive expertise and experience. Contact us for specialized consultation and to evaluate your jaw conditions, and don’t miss the opportunity for a higher quality of life.

Implant Fixture: What It Is, Types, Placement Stages, Causes of Failure, and Renowned Brands.

 

Frequently Asked Questions

• Can the mouth reject the implant?
   In most cases, the jawbone successfully accepts the fixture. However, in rare instances, such as metal allergies, severe infections, or failure to maintain oral hygiene, the bone may not fuse properly with the metallic part, and the fixture may be rejected.
• How long does it take for the fixture to fuse with the bone?
   Complete fusion depends on the type of bone and jaw, typically taking about 5 months for the lower jaw and 3 months for the upper jaw.
• How do I care for my implant fixture?
   Just like caring for natural teeth, you should continue daily brushing and flossing to maintain the health of the fixture, and have regular dental check-ups. These practices help prevent inflammation around the fixture and reduce the risk of infection.