Anchorage control is an important factor in the success of orthodontic treatment. There have been many attempts to devise suitable anchorage methods, including intra-oral and extra-oral appliances.
These conventional methods do not provide reliable anchorage without patient compliance and anchor loss.
When using skeletal anchorage such as osseous dental implants, miniplates, microscrews, or microscrews, the clinician can expect reliable anchorage without patient compliance.
Among these anchorage devices, microscrew implants have been increasingly used in orthodontic anchorage because of their absolute anchorage, low cost, easy placement, and removal.
The small size of microscrew implants allow them to be placed in the bone between the teeth, thus expanding their clinical application. The success of the dental implant has been studied extensively. However, very few studies have been conducted on this complication and management.
This article gives a review of the factors related to the clinical success of microscrew implants used in orthodontics as absolute anchorage.
The success of the micro implant anchorage is dependent on factors; - Micro screw design,
- Proper insertion site,
- Careful operation.
► Read also: ORTHODONTIC: Managing Pain or Discomfort Caused by Orthodontic Appliances
Immediate failure or loosening of the mini screw usually occurs during the initial healing period. Possible causes include:
- Improper insertion site
- Improper handling during insertion including wobbling or abrupt change in position of insertion. In case of self-drilling screws, excessive pressure at the time of insertion will fracture the cutting tip of the implant. Therefore, it is advisable to use a very light force at the time of insertion.
- Insertion site with cortical bone thickness less than 0.5 mm and low trabecular bone density, this can be overcome by selecting better insertion site with this implant as an indirect anchorage site.
- Recent extraction sockets
- Redundant overlying soft tissue or the patient having thick mucosa. The distance between the point where force is applied and the screw's center of resistance is increased, thus a large moment is generated when force is applied. So, better to use a long screw.
- Excessive tightened screws tend to fracture at the time when the neck has reached periosteum.
Even if the initial fixation appeared favorable, micro screw loosening may take place during active orthodontic treatment. The exact reason for delayed failure is unknown.
Possible reasons include:
- Excessive loading from the elastic component
- Sudden impact on the microscrew head during mastication
- Possible contact with root surface
- Excessive or insufficient bone remodeling around the microscrew
- Indicating a possible shift of the microscrew in the bone.
A failed microscrew needs to be removed and a new implant be inserted at an adjacent site. Re-insertion at the same site may increase the risk of failure. If the particular insertion site is crucial, using a microscrew with a wider diameter of re-insertion, 2-3 months later, is advised.
Inflammation or an abscess is relatively rare if the microscrew is placed on the firm attached gingiva, as long as proper oral hygiene is maintained during treatment.
Ulceration or soft tissue coverage is associated with microscrew placed on or near the buccal frenum. An incisional frenectomy can be performed if the insertion is critically indicated in the frenum area. The periodontal dressing around the microscrew for 1 week adapts the soft tissue and periosteum of the insertion site back to the bone surface and prevents the head of microscrew from embedding into soft tissue.
Ulceration of the buccal mucosa or cheek can be managed by application of Orabase and allowed for initial healing for 1-2 weeks.
Infection around the screws can be eliminated by selecting a screw system with variable neck length.
The screw with bracket-like head is used; turning a ligature around the screw or fix the ligature with composite will make it possible for the patient to keep the screw area free of inflammation.
The risk of infection is high when flap surgery was needed; so, it is better to use an implant system that does not need a pre-drilling.
Damage to root or cementum can happen during the insertion of implants. It is extremely important not to use a complete nerve block so that patient is aware of any pain or soreness as the microscrew approaches the periodontal ligament of the dental root. Pain or soreness means the microscrew must be removed immediately and redirected to avoid dental root injury.
Antibiotics may be unnecessary after microscrew insertion. When preoperative disinfection has been performed intraorally and extraorally -2% chlorhexidine is recommended for post-operative care.
Fracture of a microscrew is rare if the diameter is greater than 1.5 mm and especially if the microscrew is tapered/conical guide drill is advised to avoid implant fracture.
Bleeding and numbness
Intra-operative complications. Excessive bleeding or numbness can occur as a complication of implantation; this can be due to trauma of vessel (palatine artery) or trauma of nerve (inferior alveolar nerve). However, care should be taken not to injure the nerve bundle or vascular system during implantation. Greater palatine foramen is positioned distal to the upper second molar and midway between the cemento-enamel junction (CEJ) and mid-palate. The rest of the masticatory gingival on palatal slope is safe area for implantation.
Pain related to microscrew operation comes from the nerve endings in the soft tissue and periosteum, not necessarily from bone proper. Non-steroidal anti-inflammatory drugs (NSAID) for 2 days following the procedure would be sufficient.
Implantation in nasal or maxillary sinus can lead to this complication. Pre-determination of the implant site placement can overcome this complication.
Other causes of micro implant failure
Failure due to osteoporosis and uncontrolled diabetes, smoking, alcoholism, drug abusers, irradiation etc.
Implant fracture during removal
Fracture can happen if there is too much osseointegration; clinician might have difficulty in removing the screws, or they can fracture.
The microscrew implants can be used as absolute anchorage in routine orthodontic cases. Implant failure can involve factors related to the device, the dentist, and the patient.
Further research and studies are needed to shed additional light on process involved in skeletal anchorage so that failures can be reduced even further.
Source: jdionline.org / Journal of Dental Implants
° Authors : Sanu Tom Abraham / Meenu Merry C Paul