An evaluation of insertion sites for mini-implants

Abstract

Objective: (1) To report the thickness of the cortical bone in insertion sites commonly used for orthodontic mini-implants, (2) to assess the impact of a change in insertion angle on primary cortical bone-to-implant contact, and (3) to evaluate the risk of maxillary sinus perforation. Materials and Methods: At autopsy, 27 human samples containing three to five adjacent teeth were excised and scanned using a table-top micro-computed tomography system. Bone thickness measurements were taken at 45u and 90u to the long the axis of the adjacent teeth, simulating a mini-implant insertion at the mid-root level. Results: In the maxilla, the overall mean cortical thickness at 90u was 0.7 mm buccally in the lateral region, 1.0 mm buccally in the anterior region, and 1.3 mm palatally. In the mandible, the mean cortical thickness was 0.7 mm buccally and 1.8 mm lingually in the anterior region; 1.9 mm buccally and 2.6 mm lingually in the lateral region. Changing the insertion angle from 90u to 45u increased the cortical bone-to-implant contact by an average of 47%. Perpendicular insertion at the mid-root level only rarely interfered with the sinus, whereas apically inclined insertion increased the risk of sinus perforation. Conclusions: Buccally and palatally in the maxilla and buccally in the anterior mandible, the thickness of the alveolar cortical bone is often less than 1 mm. In contrast, the alveolar cortical bone is frequently thicker than 2 mm laterally in the mandible. Changing the insertion angle to 45u will generally enhance implant stability but increase the risk of perforation to the maxillary sinus. (Angle Orthod. 2013;83:222-229.)

Anatomical consideration for optimal position of orthodontic miniscrews in the maxilla: a CBCT appraisal

“… 12 , 13 , 21 , 22 , 37 - 40 Furthermore, a large number of studies have been performed on either dry skulls or cadavers. 9 , 10 , 12 , 37 , 38 In our study, CBCT images of 100 Saudi patients with an equal sex distribution and similar age were used to assess the anatomical variation of the palatal, buccal cortical and infrazygomatic crest bones thicknesses and their relationship to the maxillary sinus and nasal cavity.…”

“… 3 , 7 , 8 The site and position of miniscrews depends on the quality and quantity of bone. 9 - 11 Common miniscrew insertion sites in the maxilla include the buccal aspect, the palate and the infrazygomatic crest. 1 - 3 , 10 , 12 - 15 The palate is considered an ideal site for placement of miniscrews because of the quality of cortical bone, availability of keratinized mucosa and low failure rates.…”

“…Poggio et al 24 found that the buccal area between the first molar and the second premolar had the greatest amount of bone while the tuberosity area had the least amount and thickness of bone. Laursen et al 9 studied the mini-screw buccal insertion angle in human cadavers. They concluded that perpendicular insertion at the level of the mid-root was a safe approach but did not rule out the risk of sinus perforation.…”

Applications of mini-implants in orthodontics

“…The factors that are associated with the failure of mini-implants are the diameter of the screw, the age of the patient, thickness of cortical bone, density of bone, type and depth of soft-tissue, inflammation, oral hygiene, preparation of the insertion area and primary stability [8] . The thickness of cortical bone is important for the success of mini-implants, but the thickens of cancellous bone is not critical [9,10] . Another critical factor for the success of mini-implants is the type of forces applied on mini-implants and the adhesives used for the appliance cementation.…”

Average interradicular sites for miniscrew insertion: should dental crowding be considered?

“… 14 , 15 , 18 , 19 One study used micro-CTs on autopsy material to evaluate the cortical thickness in the posterior region of maxillary and mandibular bones and the possible interference with the maxillary sinus. 20 From a systematic literature review emerges that the ideal sites for the placement of orthodontic miniscrew in both the maxilla and the mandible, taking into consideration quantity and quality of bone, are the buccal and lingual interradicular spaces between the second premolar and the second molar. 21 Moreover, another important aspect for the success of miniscrews insertion is their placement in the attached gingiva: 22 , 23 indeed, this is not affected by tissue movements, hygiene maneuvers are simpler and the risk of tissue irritation is lower.…”