Dental implants are a popular and effective way to replace missing teeth. Implants are small titanium screws that are surgically inserted into the jawbone. Over time, the bone grows around the implant in a process called osseointegration. This creates a strong, stable base for artificial replacement teeth. Many patients wonder – are dental implants actually screwed into the bone? Let’s take a closer look at how dental implants work.
The Implant Surgery
The first step in the dental implant process is the surgery to place the implant screw into the jawbone. This is a minor surgery done under local anesthesia. The oral surgeon will make a small incision in the gums to expose the underlying bone. Using precision drills, a hole is created in the jawbone at the site of the missing tooth. The hole is slightly wider than the implant screw to allow room for the bone to grow into the threads.
Once the site is prepared, the titanium implant screw is placed and screwed into position in the jawbone. The screw is usually 3-6 millimeters wide and 8-16 millimeters long depending on the area of the mouth. The implant is threaded just like a wood screw. A low speed drill is used to gradually screw the implant clockwise, threading it deeper into the bone. The surgeon screws the implant in until only the coronal end is exposed above the bone level.
Key Points
- A small surgical incision is made in the gums.
- A precision drill makes a hole at the implant site.
- The titanium screw implant is screwed into the jawbone.
- The implant is threaded into place like a wood screw.
So in summary, yes dental implants are literally screwed and threaded into the jawbone just like a screw is threaded into wood or metal. This provides stability and retention of the implant.
Osseointegration Process
After the implant surgery, the bone begins to grow onto and incorporate the titanium screw surface in a process known as osseointegration. This creates a strong bond and foundation for the implant. Osseointegration can take several months to complete. The implant must be immobile during this time to allow undisturbed bone growth and attachment. Factors that can affect osseointegration include:
- Bone quality and quantity
- Health conditions like diabetes
- Medication use
- Smoking
- Radiation treatment
Once full osseointegration is confirmed by the dentist, an abutment is attached to the top of the implant. This connects the implant to the replacement crown or bridge. In a healthy patient, osseointegration creates a strong enough bond to withstand the forces of biting and chewing. The screw threads in the implant provide stability by distributing forces over a wider surface area.
Key Points
- Osseointegration occurs as bone grows and incorporates the implant.
- This process takes several months.
- A strong osseointegrated implant can withstand biting/chewing forces.
- Screw threads help distribute forces and stabilize the implant.
So in summary, the implants gain their anchoring ability not just from being screwed into bone initially but from the bone actually growing into and attaching to the implant screw surface.
Advantages of Screw Implants
Using a screw shaped implant threaded into the bone provides several advantages:
Primary Stability
Screwing the implant into bone provides excellent primary stability. This means the implant is rigidly fixed and stable immediately after placement. Primary stability is important to prevent micromovement as the bone is healing.
Favorable Stress Distribution
The threaded design distributes forces from chewing along the length of the implant into the surrounding bone. This stimulates bone preservation and reduces risk of bone loss.
Increased Surface Area
The screw threads greatly increase the implant’s surface area in contact with bone. This provides better dissipation of forces and improves osseointegration.
Easy Placement
The screw design allows the implants to be neatly threaded into the bone in a controlled manner. Self-tapping screws are simple for the surgeon to place.
Versatility
Screw geometry allows placement in different bone quantities and qualities. Surgeons can adjust torque values during placement as needed.
So in summary, the screw configuration provides major benefits over other possible implant shapes like cylinders or blades. The screw design is key to achieving optimal stability, integration, and longevity.
Implant Screw Materials
The small screws used for dental implants are made from titanium metal. Titanium has unique properties that make it well-suited for dental implants, including:
- Strength – Titanium has a high tensile strength that withstands biting forces.
- Biocompatibility – Pure titanium does not provoke an immune response or rejection.
- Osseointegration – The surface integrates with bone through direct contact.
- Corrosion Resistance – Titanium is resistant to corrosion from oral fluids.
- Lightweight – Titanium implants are lightweight and do not stress the jawbone.
- Imaging compatibility – Titanium does not interfere with radiographs or CT/MRI scans.
Titanium implants also have a roughened surface texture that aids in bone integration. Other metals like zirconium and alloys like Ti-6Al-4V are also used sometimes. But pure titanium remains the top choice for biocompatibility, osseointegration, and longevity.
Key Points
- Dental implant screws are made from pure titanium metal.
- Titanium has ideal properties for osseointegrated implants.
- The surface is treated to create micro-roughness for bone growth.
So in summary, titanium is the ideal metal for dental implant screws due to its strength, integration with bone, corrosion resistance, and compatibility within the body.
Implant Screw Thread Design
There are several thread pattern options used on dental implant screws, including:
V-Thread
V-shaped threads are common on many implant systems. They provide excellent initial stability and dissipate forces favorably into bone. The v shape compresses bone within the threads for a strong hold.
Reverse Buttress Thread
This thread pattern is designed to increase bone compression and maximize surface contact. It provides optimal stability even in poor quality bone.
Square Thread
Square threads optimize the contact between the implant and bone. This enhances osseointegration. Stresses are distributed evenly.
Trapezoidal Thread
This tapered thread pattern is used on implants designed to be immediately placed into extraction sockets for stability.
Apical Threads
Some implant designs use aggressive threading only at the apical tip to engage bone and increase stability in the vulnerable crestal bone.
So in summary, several thread shapes and patterns can be used. Factors like bone density and immediate loading needs influence thread choice.
Implant Body Shapes
In addition to different screw threads, the implant body itself comes in different shapes:
Parallel-Walled Screw
The sides are parallel from top to bottom. This is the most common simple screw shape and provides even stress distribution.
Tapered Screw
A tapered screw is wider at the top (coronal) and narrows towards the apex. Some find this easier to insert in harder cortical bone.
Stepped Screw
Stepped implants have progressively wider diameters from tip to head for added stability in soft bone.
Cylindrical Body
Instead of a tapered or stepped screw, some implants have a solid cylindrical body with threads.
So in summary, while threaded screws are the standard, implant bodies come in different shapes like parallel, tapered, stepped, or cylindrical.
Are the Forces Too Great?
Since implants lack a periodontal ligament, patients sometimes wonder if the forces of biting and chewing are too excessive on the screw threads bonded to the bone. However, several factors allow implant screws to withstand normal mastication forces:
- A period of no loading during osseointegration allows the bone to adhere strongly.
- Titanium’s modulus of elasticity is similar to bone.
- Implant design distributes forces radially into surrounding bone.
- Thread patterns enhance the implant-bone interface strength.
- Overloading risks are mitigated by using multiple implants.
- The titanium oxide layer resists corrosion and fatigue.
- Modern surface treatments increase bone contact and adhesion.
With proper osseointegration time and implant placement, the implants can tolerate average biting forces well. But excessive forces from clenching/grinding may overload the implants. Patients with bruxism or unfavorable jaw anatomy may require alternative implant strategies.
Key Points
- Implants can withstand normal biting forces with proper osseointegration time.
- Implant design distributes stresses safely into surrounding bone.
- Excess forces from bruxism may overload the bone-implant interface.
So in summary, while implants lack a periodontal ligament, their design and integration allow them to handle standard functional loading in most patients. But excessive clenching forces still present a risk.
Surgical Procedure Summary
In summary, here is an outline of the surgical process to screw implants into bone:
- An incision is made in the gingiva above the implant site.
- A precision drill makes the osteotomy hole slightly wider than implant.
- Threading taps can shape the bone walls for optimal thread contact.
- The implant screw is inserted and rotated clockwise via low speed drill.
- It is screwed into place until only the collar remains exposed.
- The gingiva is sutured closed over the implant.
- After osseointegration, an abutment is attached.
Proper surgical techniques, implant design, quality bone, and undisturbed healing allows the threaded titanium screws to integrate with jaw bone to support replacement teeth.
Factors that Influence Implant Stability
Multiple factors influence the stability of screw implants in bone:
Bone Density and Volume
Denser cortical bone provides more initial stability. Lower density medullary bone increases risk of micromovement.
| Bone Type | Bone Density | Implant Stability |
|---|---|---|
| Cortical | Dense | Highest stability |
| Cancellous | Less dense | Moderate stability |
Adequate bone width and height are also needed to support the implants and distribute forces. Extensive atrophy requires bone grafting.
Implant Design Factors
Implant screw diameter, length, thread shape, and surface coatings all affect stability. Wider, longer implants provide more surface area. Threads patterns like reverse buttress increase bone compression. Surface coatings like titanium plasma spray promote osseointegration.
Surgical Protocol
Proper drill sizing, implant torque levels, heat generation, and micromotion management during surgery impact stability and integration success.
Loading Time
Delayed loading protocols allow more time for the bone to adhere to the implant before forces are applied to the interface.
Systemic Conditions
Diseases like diabetes and osteoporosis reduce bone healing. Medications, smoking, alcohol abuse, and radiation therapy also negatively affect osseointegration.
Oral Conditions
Periodontal disease and bruxism increase implant loading. Adequate occlusal adjustment is critical to prevent excessive forces.
So in summary, bone quantity/quality, implant design factors, surgical techniques, healing time, systemic conditions, and occlusal overload all play a role in the stability of screw implants in bone.
Conclusion
In conclusion, dental implants are literally screwed into the jawbone like a wood screw into a piece of wood. The titanium implants are threaded and rotated into holes surgically created in the bone. This provides initial fixation. Over 3-6 months, the bone integrates with the implant surface through osseointegration. This creates a strong foundation to permanently support crowns, bridges, or dentures. With proper planning and technique, titanium screw implants integrate with the living bone structure and serve as ideal teeth replacements.
