Since ancient times, it has been a challenge to come up with the best way to replace missing teeth. Previously, dentures were the standard way of replacing lost teeth. Science, technology, and researchers have provided choices for better care of teeth and understanding of oral health, leading to solutions for most oral problems. Osseointegration has become the focus of modern implantology, leading to the introduction and refinement of the osseointegrated root form implant. Available implants vary in diameter from 1.8 mm to 7 mm. The mini implant is a dental implant that is fabricated with a reduced diameter (less than 3 mm) and a shorter length but with the same biocompatible material as compared with standard dental implants. Mini implants present a reduced diameter (less than 3 mm), while narrow/conventional diameter implants typically have a diameter greater than 3 mm. Therefore, the use of mini implants to retain overdentures enables the use of less-complex surgical techniques since the reduced diameter of the implant permits its placement in areas with low bone thickness. These implants are associated with high survival rates, favorable marginal bone loss, and increased satisfaction and quality of life of patients. The quantity and quality of bone tissue available in the jaw typically define the characteristics (diameter and length) and the number of implants. Overdentures retained by conventional implants exhibit good long-term results, but also present some limitations such as cost, difficulty with placing the implant in reduced buccolingual dimensions of bone without the need for bone-grafting procedures, and the presence of chronic systemic diseases that can prevent most advanced surgeries such as bone grafts and lateralization of the inferior alveolar nerve. Concomitantly, sometimes it is not necessary to open flaps, decreasing morbidity during the postoperative period. These aspects are some of the attractive factors that increase patient acceptance of mini implant treatments.
Mini dental implants can be compared to conventional implant systems. They are made of one piece; however, conventional implants usually consist of two parts, the implant and the abutment. Mini implants have a one-piece titanium screw with a ball-shaped head for denture stabilization or a square prosthetic head for fixed applications, instead of the classic abutment. Mini implants are protruded over the gum surface when they are placed into the bone; conventional implants are placed under the gums.
Mini implants should be considered for retaining overdenture prosthesis as an alternative treatment when standard implant placement is not possible. Mini implants may be considered for the rehabilitation of patients who express dissatisfaction with conventional dentures and have limitations regarding the placement of standard implants. They are indicated for replacement of the teeth in a narrow ridge. Multiple implants can be used for removable full or partial denture stabilization, and are offered at a lower cost. These can be acceptable for patients with limited economic capabilities. Mini implants in the edentulous or partially edentulous arch are indicated when the facial-lingual width of the bone is insufficient for the placement of a traditional width implant. Mini implants are also used in the anterior maxilla because of decreased palato-labial bone width and/or insufficient interdental space. In the atrophic posterior mandible, insufficient buccolingual bone width is the common indication for mini-implant placement.
Mini implants should be avoided for patients who are medically unfit for the treatment. Prospective patients must be thoroughly evaluated for all known risk factors and conditions related to oral surgical procedures and subsequent healing before any clinical treatment. Contraindications include but are not limited to the following:
In edentulous arches, more than two implants are usually needed due to narrow the diameter, the unpredictability of survival, and the lack of scientific understanding. Treatment of children is not recommended until growth is finished and epiphyseal closure has been completed.
Preoperative planning includes a maximum of diagnostic information. A panoramic x-ray is a minimum requirement, a Cone Beam CT scan is recommended for 3D planning especially in cases with very narrow ridges. Raising a flap or flapless; If there is sufficient width of the ridge a flapless transgingival technique for the pilot drill is possible. When however a narrow ridge of extensive soft tissue is present a minimal flap (crestal incision) is recommended to reveal the bone. This would allow exact placement of the implants at the correct angulation in the bone. The mini dental implant system utilizes a self-tapping threaded screw design and employs minimally invasive surgical intervention. Implant placement involves the following procedure: The left and right mental foramen are marked with an intra-oral skin marker. The ridge is marked 7 mm anterior of the mental foramen to indicate the most distal implant size. This safety zone includes a potentially present 3 to 5 mm anterior loop and a 2 mm security margin.
The primary disadvantages of mini implants for definitive prosthodontic treatment are as follows:
Despite these disadvantages, the need for mini implants will continue to grow, especially among edentulous patients because of the following:
Therefore, the current evidence must be reviewed and synthesized with the available clinical data on the survival of mini implants for definitive prosthodontic treatment.