Editor's Note: The 3M Oral Care Mini Dental Implants featured in this article are no longer available.
For more than a decade, mini dental implants (MDI) have been utilized to stabilize lower dentures with high success and patient satisfaction reported throughout the literature. The procedure is fast, easy and affordable when compared to standard implant alternatives. The goal of the MDI procedure is typically the placement of four titanium screws in the bone without cutting of the gingiva or sutures. This minimally invasive protocol allows patients with medical conditions often seen as contraindications to standard implants to have the comfort of a stable denture.
Who can benefit?
Identifying potential candidates for this procedure is simple. Virtually any patient with an edentulous lower jaw is a candidate. Contraindications may include patients undergoing intravenous bisphosphonate therapy or taking a high dose of steroids. Recent industry concerns regarding osteonecrosis of the jaw (ONJ) and oral bisphosphonate use may require additional patient screening. Patients taking oral bisphosphonates for more than two years are at a higher risk for ONJ. A drug holiday and preoperative antibiotics are recommended recently in the literature. Also, a simple blood test known as CTX may be helpful in determining patient risk of developing ONJ. Other contraindications include existing infections or bone height less than 8mm in the proposed treatment area.
Existing or new denture?
The patient's existing denture may be used or a new denture may be created prior to or after the insertion of the mini dental implants. The existing denture may be retrofitted to the MDIs keeping the treatment simple and thus more affordable. The denture should first be evaluated to make sure it is suitable. A denture with excessive wear, repairs, additions or age should be rejected. Also, insufficient thickness of acrylic in the anterior will cause the implant housings to perforate and be unsightly or easily loosen and be lost. Also, porcelain denture teeth or vinyl based 'flexi' dentures are not appropriate for this procedure either.
Treatment planning
A standard panoramic radiograph or cone beam CT scan should be evaluated and used for implant length selection. Ideally the MDIs must be solid in the bone at the time of insertion. This is known as initial stability and a minimum value of 35 NCm is recommended. Varying length of the MDI is the best way to achieve good initial stability so a good selection of implants should be obtained prior. CBCT eliminates magnification and distortion commonly found in panoramic radiographs and allows evaluation of angulation as well. Although still not widely used in dentistry, the value of these images are continuously touted in recent literature.
Implant placement
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The mini dental implants may be placed anywhere retention is desired but they are most commonly placed in the anterior mandible (Figures 1 and 2) between the mental foramina because of the quality and quantity of bone in that location. Typically four implants are used and are evenly distributed approximately 10mm apart starting from the midline of the patient. The ridge may be marked with a surgical marker (Figures 3 and 4) and the locations transferred to the denture (Figure 5) for easy retrofitting. A slight anterior angulation may be desired due to the teardrop shape of the mandible but implants should be placed as parallel as possible to each other.
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A partial pilot hole is made through the gingiva without the reflection of a flap (Figure 6). Hand instrumentation is used to place the implant to its final position. This gives the operator feedback and the ability to modify the position or length of the MDI as needed to achieve good initial stability. The implant is fully seated when the collar is at or slightly below the level of the gingival (Figures 7-9). Although ideally all of the blasted threads on the implant should be below the bone level, variations in tissue thickness sometimes prevent the concurrent ascertainment. Priority should be given to securing initial stability over 35NCm and restorability of the implant ball head.
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Block out shims can now be placed on the abutment portion of the MDI followed by metal housings containing a rubber o-ring gasket that snaps on the ball head (Figure 10). The denture should be modified with a laboratory acrylic bur to accept the housings with special care given so that the denture fits passively over the housings (Figure 11). The denture and housings are dried and acrylic or bis-gma auto cure material used to secure housings to the denture (Figure 12). After securing the housings the acrylic should be smoothed and the anterior border be reduced by up to 5 mm. The denture will not move and if not modified it will cause pain and denture sores. A high polish can be achieved with careful finishing with a lathe and pumice followed by a denture buffing compound. Figure 13 shows the final denture with the anterior border.
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The patient may be given post-operative antibiotics as needed and should be instructed to keep the denture in place for 24 hours without removal. For the first 2 weeks following the procedure, the denture should be worn for 23 hours a day. This will facilitate proper healing by managing swelling. Two- week and 3-month initial recall periods may be scheduled followed by yearly check-ups if the patient is completely edentulous. Dispense a toothbrush and sample toothpaste with instructions for the patient to brush their implants.
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There is an immense need for dental implant treatment in populations today. Millions of people are edentulous and it is reported that only one percent have had dental implant treatment. With more emphasis on training of general practitioners to perform these simple dental implant procedures access to care will increase. It is also important to educate our community about the benefits of the mini dental implant procedure. Marketing these procedures with the help of resources makes it easy and affordable for dentists to spread the word.