To begin with, titanium was found to be the most biocompatible metal to be placed in the human body without any adverse effects. The use of titanium as an implant material in dentistry was initiated by Branemark, after he successfully used it in human jaws for replacing teeth.
Some of the advantages of Titanium are its bio inertness, resistance to corrosion from bodily fluids, resistance to multiple loads, great capacity of Osseointegration, and high fatigue limit. The history of its use since a very long time proves that titanium is the ideal material to be used as implants.
Over the years, a newer metal free material, Zirconia has been introduced as another best material for dental implants. Its property of biocompatibility, high flexural strength and metal free nature is making it as an alternative choice for titanium implants.
So which material is better - Zirconia or Titanium?
Although Zirconia is a metal free alternative to titanium, it is brittle and has less fracture resistance and flexural strength, making their long-term success questionable. They are also thought to have higher chances of complications and fracture when used as an implant material.
But, these properties of Zirconia - being a metal free material, with high biocompatibility, good fracture resistance and flexural strength, makes it the second best material to be placed in the human body. Therefore it is an ideal material of choice to be used as a crown or bridge over the teeth or implants or both.
To minimize micro movements of the implants, the basic structure of the implant was split into multiple components. One of which, is placed inside the bone and left under the gum to heal for a period of three months. Following this, another component, an abutment is fixed to the implant with the help of a screw. This abutment is intended to be the part, upon which the final crown is permanently fixed.
The implants used for delayed loading were therefore multi-piece implants, consisting of many components attached to one another.
The research was directed towards shortening the healing period, by enhancing the surface roughness, but it did not alter much of this time period.
Advantages of delayed loading technique:
- Since the implant body is left inside the bone for three months, it Osseo-integrates undisturbed without any micro movements.
- Simple procedure. Can be done easily by everyone and is not dependent on the skill of the dentist.
Disadvantages of delayed loading technique:
- The implants are made of multiple components to allow better Osseointegration.
- As the implant body is made to be in the bone for three months, the implants are split into multiple units. So when replacing a single tooth, three unit implant system is used – an implant body to be placed in the bone, an abutment attached to the implant body with the help of a screw, and the permanent crown, fixed to the abutment. When replacing a full arch bridge, the implants are modified with additional components, so that they are properly aligned for the bridge to be placed over them. This further increases the number of components of the basic implant structure, compromising the success.
- The implant is placed in the crestal part of the bone and therefore can only be placed in patients with sufficient bone.
- A temporary prosthesis is given during the healing period, which may result in early implant exposure. It also affects the emotional status of the patient as they have to wait for 3 months to get the permanent fixed prosthesis.
- The procedure usually involves gum elevation and in some cases, extensive surgical procedure.
- Patients with insufficient bone may be advised to get additional surgical procedures like bone grafting and/or sinus lifting. These additional surgeries increases the overall duration and cost of the treatment.
- Multiple visits to the dentist, dragging the treatment for several months.
Although delayed loading has been extensively used, there was always a concern of waiting period of three months to get the missing teeth replaced. This led to further exploration on “bone-implant” interaction and ways in which this healing period can be reduced. Orthopedics have been using implants since decades but they never implied on this time required for Osseo integration. A thorough research on this revealed a key factor of engaging the basal cortical bone, which not only minimizes the micro movements of implants but also encourages bone formation when adequate forces are applied. This paved the path to the introduction of “immediate loading” of implants in dentistry.
Immediate loading can be done when an implant is placed in the jawbone in such a way that the basal cortical bone is properly engaged. This aids in acquiring much greater primary stability when compared to the traditional crestal implants. The implants are then immediately loaded with a permanent crown. Since the crowns are immediately fixed without the healing period, single piece dental implants are used in this technique.
Advantages of immediate loading technique:
- It allows the use of single piece implants which are the best dental implants.
- The permanent prosthesis is immediately fixed, eliminating the waiting period.
- A great primary stability of the implants as they engage basal cortical bone.
- Can be easily placed even in patients with insufficient bone.
- Eliminates the necessity of additional procedures like bone graft and/or sinus lift.
- The technique is usually simple, as the implants are placed using flapless technique. i.e., they do not involve aggressive surgical procedure.
- Provides emotional benefit for the patient as the teeth are immediately replaced.
Disadvantages of immediate loading technique:
- Procedure mainly depends on the skill of the practitioner.
- If the basal cortical bone is not engaged properly, it leads to failure of the implant.
This diversion in the two concepts of implant techniques led to the variation in the basic design of the implant system:
- Multi component implant
- Single unit implant
The basic design of this system incorporates around 3-5 separate components, which are attached to one another with the help of small screws.
Advantages of Multi-unit Implants:
- The implant fixture is placed inside the bone to allow Osseo integration. Hence it helps in eliminating micro movements.
- The different components are thought to be retrievable in case of failure of the implant or crown.
Disadvantages of Multi-unit Implants:
- Multiple components incorporate minute gaps which allow bacterial growth and seepage of oral fluids and food debris leading to consecutive failure of implant.
- Micro movements of the screw-abutment-crown components cause plunger effect, causing the seepage of fluids and debris continuously causing failure.
- Much of the implant structure is hollow, to allow the attachment of the screws. This compromises the strength of the implant and may result in fracture when excessive or improper loads due to tilting of implant are applied.
- The neck of the implant is often made rough as it helps in anchoring the upper cortical bone. But as a result of gum recession, this highly rough surface accumulates a lot of food debris leading to bacterial growth and implant failure.
- The diameter of the implant is large which makes it a most suitable niche for bacterial growth.
- The screws may loosen and require multiple visits to the dentist even after the completion of the treatment.
- Additional components are to be incorporated in cases where the angulations of the implant must be altered to allow proper seating of the crowns or bridges.
- The surface of these implants is usually made rough to allow better Osseo integration. Although it has an advantage of creating a better bone-implant interface, in cases of peri implantitis, the micro gaps on the surface makes it impossible to completely eliminate the lesion and therefore leads to its apparent failure.
A single piece implant comprises of a single component, with self-incorporating abutment. They are placed in a single step and do not have additional components.
Advantages of Single piece Implants:
- No multiple components hence are devoid of micro gaps.
- The body of the implant is solid and is stronger, as it does not have to have space for accommodating screws.
- They comprise of a long thin neck. ( reduces the seepage of bacteria and plaque beneath the gums)
- Permanent crown can immediately placed without any additional attachments.
- Long Polished neck reduces the chance of peri implantitis and implant failure in cases of gum recession.
Disadvantages of Single piece Implants:
- Technique sensitive
| # | IMMEDIATE LOADING | DELAYED LOADING |
| 1 | No healing period of 3 months | Healing period of 3 months |
| 2 | Immediately fixed permanent teeth | Permanent teeth are given after 3-6 months |
| 3 | Osseofixation + Osseointegration | Osseointegration |
| 4 | Adequate load on the implants enhances bone formation | Implant is left in the bone for 3 months to enhance Osseointegration |
| 5 | Best stability | Good stability |
| 6 | Anchored into basal bone | Anchored into spongy bone |
| 7 | Single piece implants are used | Single piece implants cannot be used |
| 8 | Less risk of peri-implantitis and failure | Risk of peri-implantitis and failure |
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Lets go deeper in our quest to understand the difference between basal and crestal implants. Multi-piece implants are the most commonly used implant system. They are being used for both delayed loading and immediate loading of implants. Their multiple components however comprise of many tiny gaps making it more susceptible to bacterial and plaque accumulation. The hollow neck made to accommodate screws, compromises the strength of the implant.
Single piece implants are the advanced implant systems, which primarily targets elimination of multiple components and minute gaps between them. The implants are solid without compromising the strength of the implant, as they do not have to accommodate any additional screws or other components. Their solid, thin, long, polished neck reduces bacterial and plaque accumulation at a significant rate.
| SINGLE PIECE IMPLANTS | MULTI-UNIT IMPLANTS |
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| Single component | Multiple components |
| Self incorporating abutment | Abutment is attached to implant body separately |
| No need of mini screws | Multiple screws are required to hold components together |
| Solid implant body | Most of the part is hollow to accommodate other components |
| Long polished neck | Short, thick neck with rough surface |
| Solid thin neck | Multiple components |
| Aggressive threads to engage basal bone | Blunt, less aggressive threads |
| Ideal for immediate loading | Ideal for delayed loading |
| Does not allow plaque/bacterial accumulation | Rough surface provides favorable niche for bacterial accumulation |
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