Assessment of infrazygomatic crest dimensions in different vertical facial growth types for miniscrew insertion: A cone-beam computed tomography study.

INTRODUCTION: This study aimed to assess the depth and height of the infrazygomatic crest (IZC) located in the posterior maxilla at the junction with the zygomatic process in patients with different vertical facial growth types as a potential miniscrew insertion site. METHODS: The sample consisted of cone-beam computed tomography scans of 117 patients (42 males and 75 females), with a mean age of 22.9 ± 2.7. The population was divided into 3 groups according to the measured SN-GoGn angle: Decreased facial proportions (n = 28), average facial proportions (n = 62), and increased facial proportions (n = 27). Bone depth was assessed at 5 levels: apex, 1, 2, 3, and 4 mm vertically from the apex. The measurements were performed on the mesiobuccal and distobuccal roots of the first molar and the mesiobuccal root of the second molar. Repeated-measure analysis of variance followed by univariates analyses and Bonferroni multiple comparisons were performed to compare the mean bone thickness between groups. The IZC height was assessed through a vertical line ranging from the furcation of the maxillary first molar to the sinus floor. Analysis of variance followed by Tukey (honestly significant difference) post-hoc tests was used to compare the mean height between groups. RESULTS: Mean bone depth between the 3 groups were significantly different at the mesiobuccal root region of the first molar at all the measured levels. It was smaller for average, intermediate for decreased, and elevated for increased facial proportions. No statistical difference was shown at the distobuccal root of the first molar except for the apex level and the mesiobuccal root of the second molar except for the apex and 4 mm levels. The mean bone height was significantly different between subjects with increased facial proportions and the 2 other groups. CONCLUSIONS: Subjects with increased facial proportions tend to present a longer and deeper IZC followed by decreased facial proportions, then average facial proportions.

Ten years of miniscrew use in a U.S. orthodontic residency program.

INTRODUCTION: Orthodontic miniscrews have become popular not only because they can provide an absolute form of anchorage, but also because they can reduce the required patient compliance when compared with traditional orthodontic anchorage. The objective of this study was to examine success rates of miniscrews placed by orthodontic residents and to evaluate which factors may affect insertion outcomes. METHODS: The sample consisted of 109 consecutive miniscrews placed in 60 patients (27 males and 33 females). Miniscrews were placed at 4 different insertion sites (anterior palate [n = 31], palatal alveolar process [n = 25], maxillary buccal alveolar process [n = 15], and mandibular buccal alveolar process [n = 38]). Analysis of variance tests were used to evaluate the influence of insertion sites and anchorage type (direct vs indirect) on the success rate. RESULTS: The overall success rate for miniscrews was 72.5%. The success rate was 83.9% in the anterior palate, 76% in the palatal alveolar process, 60% in the maxillary buccal alveolar process, and 65.8% in the mandibular buccal alveolar process. The success rate was significantly higher in indirect anchorage (84.2%) compared with direct anchorage (58.8%). CONCLUSIONS: Palatal miniscrews were more successful than buccal miniscrews. Indirect anchorage mechanics had a higher success rate than direct anchorage mechanics.

Anatomic assessment of the mandibular buccal shelf for miniscrew insertion in white patients.

INTRODUCTION: Cortical bone thickness, bone width, insertion depth, and proximity to nerves are important factors when planning and placing orthodontic miniscrews. The objective of this study was to anatomically assess the mandibular buccal shelf in a white patient population as the insertion site for orthodontic miniscrews by investigating these 4 variables. METHODS: Measurements were made on cone-beam computed tomography scans of 30 white patients (18 girls, 12 boys; mean age, 14.5 ± 2 years). All measurements were taken adjacent to the distobuccal cusp of the first molar, and the mesiobuccal and distobuccal cusps of the second molar. Additionally, bone depth was measured at 2 height levels, 4 and 8 mm from the cementoenamel junction. Stereolithographic models of patients were superimposed on the cone-beam computed tomography volumes to virtually create an outline of the soft tissue on the cone-beam computed tomography image to allow identification of the purchase point height (mucogingival junction). The inferior alveolar nerve was digitally traced. Miniscrews (1.6 × 10 mm) were virtually placed at the buccal shelf, and their insertion depths and relationships to the nerve were assessed. Analysis of variance with post hoc analysis was used for data analysis. RESULTS: Insertion sites and measurement levels had significant impacts on both cortical bone thickness and bone width. Cortical bone thickness was typically greatest at the distobuccal cusp of the second molar. Bone width was also greatest at the distobuccal cusp of the second molar 8 mm from the cementoenamel junction. The greatest insertion depth was found again at the distobuccal cusp to the second molar, whereas the miniscrews had the greatest proximity to the nerve at this site also. CONCLUSIONS: The distobuccal cusp level of the mandibular second molar is the most appropriate site for miniscrew insertion at the buccal shelf in white patients.

Miniscrew biomechanics: Guidelines for the use of rigid indirect anchorage mechanics.

Indirect anchorage is an established form of anchorage provided by orthodontic miniscrews. Although there are different ways to set up the mechanics, rigid indirect anchorage offers the greatest biomechanical versatility but is more difficult to install than conventional, nonrigid indirect anchorage or direct anchorage. The purpose of this article was to introduce readers to the concept of rigid indirect anchorage and provide guidelines as to its use.

Surface strain distribution of orthodontic miniscrews under load.

INTRODUCTION: Our objective was to investigate surface strain around orthodontic miniscrews under different orthodontic loading conditions in simulated supporting bone. METHODS: Thirty miniscrews with lengths of 6, 8, and 10 mm were embedded into customized composite analog bone models. All miniscrews were inserted into the simulated test bone 6 mm deep and loaded with the same force of 200 cN, creating different tipping moments at the peri-implant bone surface. A digital image correlation technique was used to measure the resulting surface strain around the orthodontic miniscrews. RESULTS: Changing the tipping moments is directly related to the strain generated at the bone surface close to the miniscrews, with greater moments creating greater maximum principal strains. CONCLUSIONS: Within the limitations of this model, it can be stated that greater tipping moments of miniscrews create greater maximum principal strain values, which have the potential to increase bone turnover around the implant. Hence, miniscrews farther from the bone surface should be loaded with less force, whereas miniscrews loaded closer to the bone surface may sustain higher forces.

Intrusion method for a single overerupted maxillary molar using only palatal mini-implants and partial fixed appliances.

Mandibular first molars are among the most frequently missing teeth in the adult dentition. As a result, the maxillary first molars are frequently overerupted. Conventional approaches to correct this undesirable molar position with skeletal anchorage usually include both buccal and palatal orthodontic mini-implants. Because palatal mini-implants have greater success rates than buccal ones, this article explains an intrusion method with only palatal mini-implants and limited fixed appliances to produce reliable intrusion of the overerupted molar while preventing undesirable side effects on the adjacent teeth.

Hard and soft tissue considerations at mini-implant insertion sites.

Various factors influence where orthodontic mini-implants will be placed. This article highlights the pertinent variables that should find consideration when planning the placement of orthodontic mini-implants.

Application of a new viscoelastic finite element method model and analysis of miniscrew-supported hybrid hyrax treatment.

INTRODUCTION: In this study, we aimed to assess the ability of a new viscoelastic finite element method model to accurately simulate rapid palatal expansion with a miniscrew-supported hybrid hyrax appliance. METHODS: A female patient received 3-dimensional craniofacial imaging with computed tomography at 2 times: before expansion and immediately after expansion, with the latter serving as a reference model for the analysis. A novel approach was applied to the finite element method model to improve simulation of the viscoelastic properties of osseous tissue. RESULTS: The resulting finite element method model was a suitable approximation of the clinical situation and adequately simulated the forced expansion of the midpalatal suture. Specifically, it demonstrated that the hybrid hyrax appliance delivered a force via the 2 mini-implants at the center of resistance of the nasomaxillary complex. CONCLUSIONS: The newly developed model provided a suitable simulation of the clinical effects of the hybrid hyrax appliance, which proved to be a suitable device for rapid palatal expansion.

Cortical bone thickness and bone depth of the posterior palatal alveolar process for mini-implant insertion in adults.

INTRODUCTION: Cortical bone thickness and bone depth are important factors when placing an orthodontic mini-implant. The objective of this study was to investigate both variables for the palatal alveolar process. METHODS: Thirty dry human skulls were imaged by using cone-beam computed tomography technology. Two-dimensional slices bisecting the posterior interdental sites were generated, and cortical bone thickness and bone depth were measured at 4, 8, and 12 mm from the alveolar crest. Two-way repeated measures analysis of variance (ANOVA) was used to analyze the measurements. RESULTS: Interdental site and measurement level had a significant impact on both cortical bone thickness and bone depth. Cortical bone thickness was typically greatest at the 8-mm measurement level and more anterior interdental sites. Bone depth decreased with higher measurement levels and was smallest at the most posterior-superior measurement points. CONCLUSIONS: Cortical bone thickness and bone depth of the palatal alveolar process are, on average, favorable for the insertion of orthodontic mini-implants; however, some sites should routinely be avoided to prevent damage to the maxillary sinus unless 3-dimensional imaging is available.

Predrilling of the implant site: Is it necessary for orthodontic mini-implants?

Mini-implants are becoming increasingly popular in orthodontic practice. However, there is still controversy about the need for implant-site preparation. This article reviews the current literature to answer the question: is predrilling is necessary for orthodontic mini-implants?

Orthodontic implantology: a revolutionary approach to high-anchorage orthodontics.

Mini-implants have become a well-accepted standard in orthodontics; as a result, an increasing number of general dentists have seen or will see these anchorage devices in their patients. This article seeks to introduce general dentists to this topic and provide information about the fundamentals of this novel treatment approach.

Buccal cortical bone thickness for mini-implant placement.

INTRODUCTION: The thickness of cortical bone is an important factor in mini-implant stability. In this study, we investigated the buccal cortical bone thickness of every interdental area as an aid in planning mini-implant placement. METHODS: From the cone-beam computed tomography scans of 30 dry skulls, 2-dimensional slices through every interdental area were generated. On these, cortical bone thickness was measured at 2, 4, and 6 mm from the alveolar crest. Intraclass correlation was used to determine intrarater reliability, and analysis of variance (ANOVA) was used to test for differences in cortical bone thickness. RESULTS: Buccal cortical bone thickness was greater in the mandible than in the maxilla. Whereas this thickness increased with increasing distance from the alveolar crest in the mandible and in the maxillary anterior sextant, it behaved differently in the maxillary buccal sextants; it was thinnest at the 4-mm level. CONCLUSIONS: Interdental buccal cortical bone thickness varies in the jaws. There appears to be a distinct pattern. Knowledge of this pattern and the mean values for thickness can aid in mini-implant site selection and preparation.

State of the art of miniscrew implants: an interview with Sebastian Baumgaertel. Interviewed by Robert P. Scholz.

Dr Baumgaertel is an assistant clinical professor at Case Western Reserve University in Cleveland, Ohio, and director of the subspecialty clinic for skeletal anchorage. He also maintains an active private orthodontic practice. He has lectured nationally and internationally on orthodontic mini-implants and cone-beam computed tomography. He has published many scientific articles and is coeditor of the textbook Mini-Implants in Orthodontics-Innovative Anchorage Concepts. He serves as a member of the editorial review board of the AJO-DO and acts as ad-hoc reviewer for several other scientific dental journals.

Reliability and accuracy of cone-beam computed tomography dental measurements.

INTRODUCTION: Dental measurements are an integral part of the orthodontic records necessary for proper diagnosis and treatment planning. In this study, we investigated the reliability and accuracy of dental measurements made on cone-beam computed tomography (CBCT) reconstructions. METHODS: Thirty human skulls were scanned with dental CBCT, and 3-dimensional reconstructions of the dentitions were generated. Ten measurements (overbite, overjet, maxillary and mandibular intermolar and intercanine widths, arch length available, and arch length required) were made directly on the dentitions of the skulls with a high-precision digital caliper and on the digital reconstructions with commercially available software. Reliability and accuracy were assessed by using intraclass correlation and paired Student t tests. A P value of < or = 0.05 was used to assign statistical significance. RESULTS: Both the CBCT and the caliper measurements were highly reliable (r >0.90). The CBCT measurements tended to slightly underestimate the anatomic truth. This was statistically significant only for compounded measurements. CONCLUSIONS: Dental measurements from CBCT volumes can be used for quantitative analysis. With the CBCT images, we found a small systematic error, which became statistically significant only when combining several measurements. An adjustment for this error allows for improved accuracy.

Quantitative investigation of palatal bone depth and cortical bone thickness for mini-implant placement in adults.

INTRODUCTION: Cortical bone thickness and overall bone depth are important factors to consider when placing an orthodontic mini-implant. The purpose of this study was to investigate both variables in the palate quantitatively to aid clinicians in planning successful mini-implant placements. METHODS: Thirty dry skulls were imaged with cone-beam computed tomography technology. Coronal slices were generated on which overall bone depth and cortical bone thickness were measured at 4 levels and 34 palatal placement sites. One-way analysis of variance (ANOVA) was used for data analysis. RESULTS: Overall bone depth decreased with increasing distance from the midsagittal plane and from the anterior to the posterior palatal regions. Cortical bone thickness decreased from anterior to posterior, but no differences were detectable within measurement levels. CONCLUSIONS: Bone depth and cortical bone thickness of the palate were most favorable for temporary anchorage device placement at the level of the first and second premolars. This information could aid clinicians in choosing suitable palatal placement sites for orthodontic mini-implants.

Socket sclerosis--an obstacle for orthodontic space closure?

BACKGROUND: Socket sclerosis is a rare reaction to tooth extraction resulting in high-density bone in the center of the alveolar process, where, under normal circumstances, cancellous bone is to be expected. MATERIALS AND METHODS: In an adult orthodontic patient, routine extractions of the mandibular first permanent bicuspids were performed, resulting in socket sclerosis and unsuccessful orthodontic space closure. Orthodontic mini-implants were inserted to augment anchorage and aid in space closure. RESULTS: In the presence of socket sclerosis, conventional orthodontic mechanics failed to close the extraction spaces. However, with absolute anchorage in place, space closure occurred at a nearly normal rate. After treatment, no signs of socket sclerosis were discernible on the periapical radiographs. CONCLUSION: Socket sclerosis can be an obstacle for orthodontic space closure if traditional mechanics are employed. However, mini-implant-reinforced anchorage can lead to successful space closure, resulting in complete resolution of the sclerotic sites.