Quantitative and qualitative assessment of anchorage loss during en-masse retraction with indirectly loaded miniscrews in patients with bimaxillary protrusion.

INTRODUCTION: This study provides vital insight in assessing anchorage loss when miniscrews are indirectly loaded. METHODS: The study sample comprised 18 patients with bimaxillary protrusion (14 girls, 4 boys; mean age, 17.3 ± 4.6 years) selected from a database of 89 patients treated with miniscrews. All subjects who were selected required extraction of all first premolars and maximum anchorage. After initial leveling and aligning, miniscrews were placed between the first molar and the second premolar in all 4 quadrants and loaded by the indirect method at 3 weeks after placement with 200-g nickel-titanium alloy closed-coil springs for en-masse retraction. Mean treatment duration was 29.7 ± 6.8 months. Pretreatment and posttreatment lateral cephalograms were analyzed to measure the amount of anchorage loss, incisor retraction, and the incisors' angular change in reference to the pterygoid vertical reference line and were evaluated by the structural superimposition method. RESULTS: The ratio of incisor retraction to molar protraction was 4.2 in the maxilla and 4.7 in the mandible. The first molars showed mean extrusion of 0.20 mm in the maxilla and 0.57 mm in the mandible; these were statistically insignificant. The mean angular change of the first molars was -2.43° in the maxilla and -0.03° in the mandible. The mean anchorage loss in reference to the pterygoid vertical was 1.3 mm in the maxilla and 1.1 mm in the mandible; these were statistically significant. Structural superimpositions showed mean change in molar position of 0.83 mm in the maxilla and 0.87 mm in the mandible, and 5.77 mm in the maxillary incisor and 5.43 mm in the mandibular incisor. These results were compared with the direct anchorage method reported in the literature. CONCLUSIONS: Indirect miniscrew anchorage can be a viable alternative to direct anchorage.

Cost-Effective Management of Patients with Unilateral Congenitally Missing Second Maxillary Premolars.

Two case presentations are utilized to review the cost-effective treatment options in patients with unilateral congenitally missing second maxillary premolars. Once diagnosed, the dentist can either preserve or remove the respective primary molar. Preservation will lead to a tooth-size discrepancy. To limit the size of the second primary molar to the dimension of the contralateralpremolar, and to allow the preservation of alveolar bone, removal of its mesio-distal aspect should be performed. Later on, the primary molar may become infraoccluded or lost, and it will be necessary to do a coronal built-up or a prosthetic replacement respectively. Any type ofprosthetic replacement will significantly increase the total cost of treatment. Clinicians should aim for ideal occlusion and profile and take into account other orthodontic problems and propose the most appropriate treatment plan for each patient.

The orthodontic-restorative interface: 2. Compensating for variations in tooth number and shape.

UNLABELLED: The aim of this second article in this series of two is to outline a variety of methods which may be used to compensate for variations in tooth shape and number using a combination of orthodontic and restorative approaches. It will also provide an overview of other areas of patient care which necessitate a multi-disciplinary orthodontic/restorative approach. The article will highlight the importance of combined planning from the outset and the close relationship between the different specialties, which must be maintained throughout treatment. The methods of compensating for variations in tooth number and shape will often require contributions from both orthodontist and restorative dentist. It is important that both disciplines are involved in the assessment and treatment planning process so that they know what will be expected of them during the patient's care. Treatment planning in isolation may lead to care being delivered which is below the optimum standard which can be achieved. The orthodontist and restorative dentist are likely to liaise with the patient's general dental practitioner so that he/she can provide the restorative treatment in some cases. CLINICAL RELEVANCE: Great improvements in aesthetics and function may be obtained using an interdisciplinary approach for patients who have variations in tooth number and shape.

A novel method for the assessment of three-dimensional tooth movement during orthodontic treatment.

OBJECTIVE: To (1) evaluate the stability of palatal rugae as landmarks for superimposition of dental casts and (2) establish a three-dimensional superimposition method of maxillary dental casts for analyzing orthodontic tooth movement. MATERIALS AND METHODS: The sample consisted of dental casts obtained from 10 patients treated with extraction of bilateral maxillary first premolars and placement of three palatal miniscrews as anchorage for retraction of the anterior teeth. Dental casts were measured by means of laser surface scanning system, and three-dimensional images were reconstructed. Serial dental casts were superimposed on the three miniscrews as registration landmarks (miniscrew-superimposition method), and the displacement of each palatal ruga point during the closure of extraction spaces was measured. Displacement of the central incisors was measured by the miniscrew-superimposition method and the proposed superimposition technique (ruga-palate-superimposition method). Correlation analysis and paired t-tests were performed to determine whether a significant difference existed between the measurements of the two superimposition methods. RESULTS: The medial points of the third palatal rugae and the shape of the palatal vault were stable throughout the treatment. The displacement of the central incisors measured using the ruga-palate-superimposition method showed no significant difference with that measured using the miniscrew-superimposition method. CONCLUSION: The maxillary dental casts can be reliably superimposed on the medial points of the third palatal rugae and the palatal vault as reference landmarks.