Read the article to know how a dental surgeon assesses bone density through diagnostic imaging and how crucial bone density is for the success of an implant.
Dental implants are long-lasting and the most successful treatment option to restore missing teeth in the oral cavity. The success rate depends on the implant’s primary stability inside the jaw bone or the osseointegration of the implant. For a dental implant to be stable or have primary stability in the jaw bone, the most important criteria are the quality or the density of the bone that needs to be appropriate for the implant site selection, placement, and long-term survival. These parameters or criteria include general health conditions and factors, features and biocompatibility of the patient to the implant, operator sensitivity or approach by the dental implantologist or surgeon, surgical procedure, and most notably on the quality and quantity of bone at the area where the dental implant is to be placed.
BMD or bone mineral density is the amount of bone tissue in a specific volume of bone. Several methods to measure bone density include DEXA (Dual-energy X-ray Absorptiometry), CT (computed tomography), and CBCT (cone beam computed tomography) scans. OPG is a form of panoramic radiography initially used to visualize the patient’s bone and adjacent tooth structure and nerve in a 2-dimensional form while consulting. However, 2D imaging can be ineffective or error-prone while visualizing the implant selection site and bone quality or density of that site. Densitometric measurements can be appreciated or studied better in three-dimensional imaging like CBCT, which is now the primary modality for preoperative planning of implant placement.
To obtain the anchorage or stability of an implant in a bone that is not dense is not only challenging to the implantologist but also prone to failure considering the long-term survival rate of an implant because the implant will not be osseointegrated correctly or instead osseointegration, it undergoes fibro-osseous integration (integration into connective tissue instead of bone).
The architectural integrity of the human face is dependent on the distribution of bone patterns in the maxilla (the upper jaw) and mandible (the lower jaw). The mandibular bone can withstand high stress and impact due to its high bone density. Still, the maxillary bone is associated with delicate vital structures like the maxillary sinus, the maxillary nerve, and its boundaries related to the floor of the nasal cavity and the orbital wall. Maxilla can quickly dissipate forces around but has a low bone density or thin cortical bone than the mandible.
According to the proportion and structure of the compact and trabecular bone tissue, bone quality is mainly categorized or classified into four types by histomorphometric studies, called the Bone Quality Index (BQI). Also, the bone density while implant drilling is comparable to drilling through different consistencies as mentioned below:
D1/Type 1 Bone:
It is a homogenous cortical bone with the densest bone available and is primarily found in the anterior mandible. D1 bone is highly suitable for maintaining an excellent bone-implant contact and exhibits the greatest strength. However, its regenerative capacity is impaired because of poor blood circulation. Drilling an implant through D1 bone is firm and robust and is comparable to drilling through oak wood.
D2/Type 2 Bone:
D2 bone is a thick cortical bone with marrow cavity and has a relatively dense bone found chiefly in the posterior and anterior mandible. D2 bone is also excellent for bone-implant contact and biocompatibility. Drilling an implant through D2 Bone is like Pinewood, comparatively less firm than oak wood, with 75% bone-implant contact.
D3/Type 3 Bone:
D3 bone is a thin cortical bone with good trabecular strength found in the anterior maxillary region. However, the bone-implant contact is less favorable in such bone and is 50% weaker than D2 bone. Drilling an implant through D3 Bone is like drilling through balsam wood, comparatively much softer than pine wood with 60% bone-implant contact.
D4/Type 4 Bone:
D4 bone is a fragile cortical bone with low-density trabeculae of poor strength found in the posterior region of the maxilla. The bone trabeculae are much weaker in this bone, almost ten times less strong than the D1 bone. Drilling an implant through D4 Bone is like drilling through Styrofoam (softest with 25% of bone-implant contact after loading the implant).
Hence, the prognosis of implant survival is reduced in D4 bone, whereas a 99% survivability rate is found in D1, D2, D3 bone at the implant site. Along with this, good systemic and oral health factors play a vital role in osseointegration and favorable bone-implant contact.
Traditionally, after introducing dental implants in the market a few decades ago, conventional methods of assessing the bone quality were only through periapical radiographs and more recently through the introduction of OPG or panoramic radiography. The bone consistency of D1, D2, D3, or D4 bone cannot be solely assessed with the help of radiographs, and the following are used to evaluate bone quality.
The overview of maxillofacial structures, maxillary sinus, inferior alveolar nerve, and nasal fossa can be visualized clearly. However, CBCT is now the preferred imaging modality compared to CT scan, which has increased radiation exposure, and panoramic radiography, a 2D imaging technique. That makes panoramic radiography or OPG imaging a popular method for screening and diagnosis.
CBCT (Computed Cone Beam Tomography):
For detailed analysis and accurate preoperative implant site assessment, it is an excellent radiographic technique to provide information to the operator before dental implantation regarding the bone quality, the location of surrounding vital structures like nerves that penetrate the jaw bone, the contour, continuity of the jaw bone, and finally the cortical bone plate analysis. The apparent advantage of CBCT over conventional CT radiography is that the radiation dosage is low. Its advantage over panoramic radiography is that it produces a three-dimensional structure analysis, reduces image distortion, and increases image sharpness or clarity. The resolution of the CBCT image is measured in voxels/individual volume elements. Ease of image acquisition and cross-sectional imaging makes CBCT the most preferred radiographic modality.
To conclude, diagnostic imaging done preoperatively by panoramic radiograph and CBCT is imperative for the placement of dental implants. Studying and analyzing the implant site by the operator or dental implantologist would be crucial for assessing the implant’s prognosis and long-term survival rate, which is dependent on and directly proportional to the bone quality at the site.
Dental implants can cause infection at the implant site. Damage or injury can occur to the surrounding structures, such as teeth and blood vessels. Sometimes, it can lead to nerve damage, which causes pain, tingling, numbness in the natural teeth, lips, gums, or chin.
A dental implant helps to support a healthy bite. It keeps the teeth in their proper positions and contributes to a decrease in bone deterioration. It helps to preserve the jawbone when there is pressure and stimulus of the chewing action. It is also beneficial to the overall beauty aspect of the teeth.
According to the American Dental Association, men and women over 65 years of age have at least one missing tooth, and so they become ideal candidates for the implant procedure, including older adults. A person can get implants at age 18, but the jaw may still mature at that age and continue to grow and change. So the patient's health, good bone structure are more important than their age, and it is the primary deciding factor when it comes to determining the implant candidacy.
The complications of dental implants include damage to other teeth, infection, nerve damage, delayed bone healing, jaw fractures, prolonged bleeding, and more.
There is no age limit in getting dental implants. In most cases, you might be a suitable candidate, provided you should be healthy and able to undergo a dental procedure, such as extractions. The candidate should be a non-smoker, have healthy gums, have good oral hygiene, and have enough bone in the jaw to anchor the implant.
On numbing the nerves, you may not feel any pain at the time of the dental implant procedure. At times you may feel pressure, but it should not cause any discomfort. Oral sedation can be given to patients who develop anxiety with dental procedures.
Dental implants may last for an average of 25 years. There are many reasons for the implants to last less or longer than the average lifespan. Maintaining good oral hygiene will help the dental implants to last longer.
Early implant placement means placing the implant 3 months after extraction. During this time, the bone gets healed, and the site is better prepared. They must be placed within this timeframe because two-thirds of bone resorption occurs within the three months after extraction.
Dental implants will have fewer visits to dental clinics because they can be easily maintained when compared to dentures. With dental implants, there is nothing to worry about falling dentures while speaking or laughing. In addition, dental implants may look more natural or feel more comfortable than dentures.
Getting implants on the same day can usually be done in a single procedure, from 30 minutes to 3 hours, but it depends on the number of teeth that need to be implanted. But, it is important to understand that you may not leave the dental clinic with permanent teeth but, you may leave with a full smile.
One dental implant cost may range from Rs 20,000 to Rs 50,000 or more as per the prevailing market rate. The cost is all included for the surgery performed, its placement, and all the components, including the implant crown itself.
Last reviewed at:
12 Mar 2022 - 4 min read
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