Optimal sites for orthodontic mini-implant placement assessed by cone beam computed tomography

Facial Growth Patterns and Insertion Sites of Miniscrew Implants

INTRODUCTION

We aimed to evaluate the associations between the craniofacial growth pattern with interradicular distances (IRDs), cortical widths (CWs), and jaw heights (JHs). Also, we mapped safe zones for miniscrew implantation.

METHODS

Cone-beam computerized tomography data pertaining to 60 Class-I patients were divided into 3 growth groups: normal, horizontal, and vertical. IRDs and CWs were measured for bimaxillary canines to second molars, on buccal and lingual sides, at 3 transverse planes (1, 3, and 5 mm apically to the alveolar crest). JHs were measured in both jaws, between canines and second molars. The role of growth patterns and other variables were analyzed; also, safe zones were mapped with statistical substantiation.

RESULTS

IRDs were greater in the mandible, males, at points more distant from the ridge crest, and on the lingual side. Cortexes were thicker in the horizontal growth pattern, mandible, males, older patients, and lingual sides. JHs were greater in vertical growth pattern, mandible, and males.

CONCLUSIONS

The cortex might be thicker in patients with a horizontal growth pattern. The height might be greater in vertical growth pattern. IRDs might not be affected by growth pattern.

Three-dimensional evaluation of the location of the mandibular canal using cone-beam computed tomography for orthodontic anchorage devices

This study investigated guidelines for placement of monocortical screws in the mandible, particularly the mandibular canal. In this study of 35 patients, we used cone-beam computed tomography to determine the distance from the alveolar crest to the superior border of the mandibular canal (DMC) and the shortest distance from the buccal and lingual cortex to the mandibular canal (attaining distance) in the areas between premolars (premolar area), between the second premolar and first molar (middle area), and between the first and second molars (molar area). The DMC values for these areas were 16.55, 18.94, and 16.58 mm, respectively, and were similar in adults and adolescents. When the attaining distance was 8 mm, the heights on the buccal and lingual sides of the areas were 9 and 16.6 mm, 13.7 and 14.7 mm, and 15.3 and 12 mm, respectively. Risk of proximity to the mandibular canal should be considered at above heights or greater when an orthodontic anchorage device (OAD) 8 mm in length is placed. Careful attention is needed for placements on lingual side in adolescents. By reducing the OAD length to 6 mm, placement safety increases in all areas except the premolar area, especially on the buccal side.

Quantitative evaluation of maxillary alveolar cortical bone thickness and density using computed tomography imaging

INTRODUCTION

Primary stability is essential to the success of orthodontic mini-implants (OMIs) and heavily depends on the mechanical retention between OMIs and their supporting bone. Alveolar cortical bone commonly serves as the supporting bone for OMIs during treatment. The purposes of this study were to characterize alveolar cortical bone thickness and density in the maxilla and to explore patient factors that may significantly affect these bone properties.

METHODS

Sixty medical computed tomography scans of the maxilla were analyzed from a selected sample of patients seen at the Radiology Department of Boston Children's Hospital. Interradicular alveolar bone thickness and density were measured at 2, 4, 6, and 8 mm from the buccal and palatal alveolar bone crests using the Synapse 3D software (version 4.1; FUJIFILM Medical Systems USA, Stamford, Conn). Analyses were conducted with STATA /1C (version 12.0 for Windows; StataCorp, College Station, Tex) using multivariate mixed-effects regression models and paired t tests.

RESULTS

Mean age and body mass index of the study sample were 17.88 years and 22.94 kg/m², respectively. Cortical bone density and thickness significantly increased from the coronal (2 mm) to the apical (8 mm) regions of the alveolar bone (P <0.05). At 8 mm from the alveolar crest, interradicular buccal cortical bone was thickest (1 mm) and densest (1395 Hounsfield units) between the first and second molars. On the palatal side, the thickest bone (1.15 mm) was found between the canine and first premolar; it was similarly densest (1406 Hounsfield units) between the first premolar and canine, and between the first premolar and second premolar interradicular bones. On average, palatal cortical bone was thicker and denser compared with buccal; this difference was statistically significant (P <0.01) in the anterior and middle maxilla, with the anterior maxillary region showing the greatest difference. Female subjects have significantly denser bone compared with male subjects; however, sex is not significantly associated with bone thickness. Body mass index and age are positively associated with bone thickness and density. Radiologic absence of bone was more commonly seen in the anterior maxilla.

CONCLUSIONS

Alveolar bone properties vary in the maxilla in patterns that could guide clinicians in selecting sites best suited for placement of OMIs.

A Comparison of the Mechanical Measures Used for Assessing Orthodontic Mini-Implant Stability

PURPOSE

Mechanical loosening remains a common complication associated with mini-implant failure. The purpose of this study was to compare common mechanical measures of mini-implant stability to determine their association and reliability.

MATERIALS AND METHODS

Ninety self-drilling orthodontic mini-implants from 6 manufacturers were inserted into artificial bone blocks. Insertion torques (ITs) and Periotest values (PVs) were measured. Subsequently, mini-implants underwent pull-out testing for measures of pull-out load (POL) and screw displacement (ScrD). Stability measurements were compared using one-way ANOVA, associations among them were assessed using correlation analyses, and reliability was evaluated using coefficients of variation (COVs).

RESULTS

Variations in stability of mini-implants were found, specific to the mechanical measure used for assessment (P < 0.05). The strongest correlations were found between IT and PV (r = -0.68) and between IT and POL (r = 0.66). Overall, PV showed the greatest variability (COV: 11%-100%) compared with IT (≤11%), POL (≤4%), and ScrD (≤19%).

CONCLUSIONS

IT, PV, and POLs only agreed moderately in their assessment of mini-implant stability, and Periotest showed the least reliability in predicting mini-implant stability. As such, independent and interchangeable use of these stability measures should be avoided.

Evaluation of mini-implant sites in the posterior maxilla using traditional radiographs and cone-beam computed tomography

Objectives:

To evaluate the accuracy of using routine 2-dimensional (2D) radiographs (panoramic and periapical) when evaluating the position of orthodontic temporary anchorage devices (mini-implants) in the maxilla, and to compare the results to 3-dimensional cone-beam computed tomography (CBCT).

Methods:

This cross-sectional study was conducted at King Abdulaziz University, Faculty of Dentistry, Jeddah, Kingdom of Saudi Arabia from February 2014 to January 2015. Panoramic and periapical radiographs were used to examine the position of mini-implants in relation to the adjacent roots. Rating of mini-implants position was performed by 82 dentists from different specialties, using 2 D images according to the following criteria: 1) away from the root; 2) mini-implant tip appears touching the lamina dura; and 3) mini-implant overlays the lamina dura. The results were compared with CBCT findings.

Results:

There was no difference between dentists from different specialties when rating the position of the mini-implants (Cronbach’s alpha=0.956). The accuracy of the periapical images was 45.1%, while the panoramic images 33.6%. However, both panoramic and periapical radiographs were significantly inaccurate when assessing the mini-implant position when compared with the CBCT findings (p=0.0001).

Conclusion:

Three-dimensional CBCT technology allows better visualization of mini-implant placement. The use of CBCT when assessing the position of mini-implants is recommended.

Three-dimensional mapping of cortical bone thickness in subjects with different vertical facial dimensions

BACKGROUND

The purpose of this study was to determine differences in cortical bone thickness among subjects with different vertical facial dimensions using cone beam computed tomography (CBCT).

METHODS

From 114 pre-treatment CBCT scans, 48 scans were selected to be included in the study. CBCT-synthesized lateral cephalograms were used to categorize subjects into three groups based on their vertical skeletal pattern. Cortical bone thickness (CBT) at two vertical levels (4 and 7 mm) from the alveolar crest were measured in the entire tooth-bearing region in the maxilla and mandible.

RESULTS

Significant group differences were detected with high-angle subjects having significantly narrower inter-radicular CBT at some sites as compared to average- and low-angle subjects.

CONCLUSIONS

Inter-radicular cortical bone is thinner in high-angle than in average- or low-angle subjects in few selected sites at the vertical height in which mini-implants are commonly inserted for orthodontic anchorage.

Comparison of interradicular distances and cortical bone thickness in Thai patients with Class I and Class II skeletal patterns using cone-beam computed tomography

Purpose

This study evaluated and compared interradicular distances and cortical bone thickness in Thai patients with Class I and Class II skeletal patterns, using cone-beam computed tomography (CBCT).

Materials and Methods

Pretreatment CBCT images of 24 Thai orthodontic patients with Class I and Class II skeletal patterns were included in the study. Three measurements were chosen for investigation: the mesiodistal distance between the roots, the width of the buccolingual alveolar process, and buccal cortical bone thickness. All distances were recorded at five different levels from the cementoenamel junction (CEJ). Descriptive statistical analysis and t-tests were performed, with the significance level for all tests set at p<0.05.

Results

Patients with a Class II skeletal pattern showed significantly greater maxillary mesiodistal distances (between the first and second premolars) and widths of the buccolingual alveolar process (between the first and second molars) than Class I skeletal pattern patients at 10 mm above the CEJ. The maxillary buccal cortical bone thicknesses between the second premolar and first molar at 8 mm above the CEJ in Class II patients were likewise significantly greater than in Class I patients. Patients with a Class I skeletal pattern showed significantly wider mandibular buccolingual alveolar processes than did Class II patients (between the first and second molars) at 4, 6, and 8 mm below the CEJ.

Conclusion

In both the maxilla and mandible, the mesiodistal distances, the width of the buccolingual alveolar process, and buccal cortical bone thickness tended to increase from the CEJ to the apex in both Class I and Class II skeletal patterns.

Individual scoring and mapping of hard and soft tissues of the anterior hard palate for orthodontic miniscrew insertion

AIM

The aim of the present study was to introduce a scoring system to select optimal sites to insert a miniscrew in a hard palate.

METHODS

The present study consisted of 37 adult patients (21 females and 16 males) aged between 20 and 50 years, with a mean age of 34.81 (±9.52) years. Hard and soft tissues of the anterior hard palate were assessed using cone-beam computed tomography. The scoring system was as follows: mucosal thickness: 0-2 mm (2 points), 2-4 mm (1 point), and 4-6 mm (0 points); total bone vertical height: ≥5 mm (1 point) and <5 mm (0 points); and palatal cortical thickness: ≥1 mm (1 point) and <1 mm (0 points).

RESULTS

Significant variability was found between the individuals. Total vertical bone height decreased posteriorly and laterally. Mucosal thickness decreased posteriorly, but increased laterally. Palatal cortical thicknesses were higher than the nasal cortical thicknesses. The most balanced sites (highest point) were the midpalatal suture, followed by paramedian points located 3 mm lateral to the midline and 4 mm posterior to the incisive canal.

CONCLUSIONS

Considering that both hard and soft tissue parameters are crucial to obtain the best possible success rates, careful investigation is recommended prior to clinical decisions being made.

An anatomical radiographic evaluation of the posterior portion of the mandible in relation to autologous bone harvest procedures

The purpose of the study was to evaluate the course of the mandibular canal and the thickness of the vestibular cortical plate in the posterior region of the mandible in relation to autologous bone harvest procedures. The study was performed on a cohort of 30 cone-beam computed tomography hemimandible images. For each hemimandible, the course of the mandibular canal and the thickness of the vestibular cortical plate have been evaluated in 4 regions: the retromolar region, the second molar region, the first molar region, and the second premolar region. The analyzed variables show a characteristic trend: the thickness of the cortical vestibular plate and the horizontal distance of the canal from the cortical vestibular plate are higher in the second molar region specifically in the area bordering on the retromolar region. In fact, the maximum thickness reaches the average value of 3.46 mm on 30 hemimandibles for slice (SD, 0.56 mm; range, 2.36-4.83 mm), and the horizontal distance reaches the average value of 6.06 mm on 30 hemimandibles for slice (SD, 1.34 mm; range, 3.65-9.27 mm); both variables decrease in more distal slices of the retromolar region. The vertical distance of the canal from the cortical crest shows the average value of 14.25 mm on 22 slices of the second molar and retromolar regions (SD of average values, 1.03 mm; range of average values, 12.92-16.25 mm; range of absolute values, 7.11-22.92 mm) exactly in regions potentially suitable for procedures of bone harvest (second molar and retromolar regions).

Palatal bone thickness measured by palatal index method using cone-beam computed tomography in nonorthodontic patients for placement of mini-implants

Introduction:

The purpose of this study was to compare the bone thickness of the palatal areas in different palatal index (PI) groups

Materials and Methods:

Cone-beam computed tomography scans of 10 subjects were selected with ameanage group of 18 years. The measurements of palatal bone thickness were made at 36 sites using CareStream 3D Imaging software. The PIwas measured using Korkhaus ratio (palatal height/palatal width). One-way analysis of variance was used to analyze intergroup differences, as well as the PI difference.

Results:

Bone thickness was higher in the anterior region than in the middle and posterior regions P <0.001. Furthermore, significant differences were found among the midline, medial, and lateralareas of the palate.

Conclusions:

These findings might be helpful for clinicians to enhance the successful useof temporary anchorage devices in the palate.

A digital volumetric tomography (DVT) study in the mandibular molar region for miniscrew placement during mixed dentition

OBJECTIVE

To assess bone thickness for miniscrew placement in the mandible during mixed dentition by using digital volumetric tomograph (DVT).

MATERIAL AND METHODS

A total of 15 healthy patients aged 8-10 years old, with early exfoliated mandibular second deciduous molar, were included. DVT images of one quadrant of the mandible were obtained using Kodak extraoral imaging systems and analyzed by Kodak dental imaging software. The error of the method (EM) was calculated using Dahlberg's formula. Mean and standard deviation were calculated at 6 and 8 mm from the cementoenamel junction (CEJ).Paired t-test was used to analyze the measurements.

RESULTS

Buccal cortical bone thickness, mesiodistal width and buccolingual bone depth at 6 mm were found to be 1.73 + 0.41, 2.15 + 0.49 and 13.18 + 1.22 mm, respectively; while at 8 mm measurements were 2.42 + 0.34, 2.48 + 0.33 and 13.65 + 1.25 mm, respectively. EM for buccal cortical bone thickness, mesiodistal width and buccolingual bone depth was 0.58, 0.40 and 0.48, respectively. The difference in measurement at 6 and 8 mm for buccal cortical plate thickness (P < 0.05) and buccolingual bone thickness (P < 0.05) was found to be significant, whereas for mesiodistal width it was insignificant (P > 0.05).

CONCLUSION

Bone thickness measurement has shown promising evidence for safe placement of miniscrews in the mandible during mixed dentition. The use of miniscrew is the best alternative, even in younger patients.

A Mini-review on the Effect of Mini-implants on Contemporary Orthodontic Science

The purpose of this literature review was to screen the valuable published articles regarding to the impacts of mini-implants on orthodontic science, briefly. The searching category was performed on the Pubmed using MeSH words such as "dental (mini) implants, orthodontic anchorage procedures, and orthodontic appliances." After preliminary sketch, they were grouped as follow: Those evaluating (a) common appliances for providing orthodontic anchorage, (b) biomechanical details of mini-implants and their insertion, (c) clinical application of mini-implants for orthognathic treatments, (d) limitations and possible complications. In conclusion, mini-implant evolved the orthodontic treatment plans and compromised the required orthognathic surgery. Malocclusion treatment and pure orthodontic or orthopedic movements in the three-dimensions have become recently possible by using mini-implant to provide skeletal anchorage.

Evaluation of orthodontic mini-implant placement: a CBCT study

Background

Optimal positioning of orthodontic mini-implants is essential for a successful treatment with skeletal anchorage. This study aims to compare the accuracy of two-dimensional radiographs with a cone beam computed tomography (CBCT) for mini-implant placement.

Methods

An ideal site for mini-implant placement at the buccal interradicular space between the second premolar and the first molar was determined for 40 sites (in 13 patients aged 14 to 28 years) by using CBCT data. The mini-implant placement procedure was then divided into two groups. In CBCT group, mini-implants were placed at the sites determined from CBCT data. In RVG group, mini-implants were placed with the help of two-dimensional digital radiographs and a custom made guide. Postplacement CBCT scans were obtained to determine the accuracy of the mini-implant placement. The results were statistically analyzed with a Mann-Whitney test.

Results

A statistically significant difference (p value = 0.02) was observed between the two groups for deviation from an ideal height of placement of the mini-implants. Deviations in mesiodistal positioning and angular deviation showed a statistically non-significant difference. Three out of twenty mini-implants in the RVG group showed root contact in the mandibular arch that may be attributed to the narrower interradicular space and reduced accessibility in the mandibular posterior region.

Conclusions

Although CBCT provides an accurate three-dimensional visualization of the interradicular space, the two-dimensional intraoral radiograph of the interradicular area provides sufficient information for mini-implant placement. Considering the amount of radiation exposure and cost with the two techniques, it is recommended to use two-dimensional radiographs with a surgical guide for a routine mini-implant placement.

Age-related changes in maxillary and mandibular cortical bone thickness in relation to temporary anchorage device placement

BACKGROUND

The aim of this study was to investigate the correlation between alveolar bone cortical thickness (ABCT) and age in the maxillae and mandible in humans. This information could then be translated into clinical application with temporary anchorage devices (TADs) in orthdontics.

METHODS

Samples comprised 82 post-mortem CT datasets (41 males and 41 females) aged between 11 to 50 years, and were divided into five different age groups and gender. Alveolar ABCT was measured in the labial/buccal and palatal/lingual sides of the incisor, canine, premolar, molar and tuberosity/retromolar regions of the maxillae and mandible. Correlations between ABCT and age and gender were analysed with linear regression analysis.

RESULTS

Strong correlation between ABCT and age was found for the maxilla on the labial side of the maxillary incisor region (p < 0.001). On the palatal aspect, significant correlations between ABCT and age were found in the maxillary incisor and maxillary premolar regions (p = 0.01 and p = 0.047 respectively). Significant correlation between ABCT and gender was found only at the buccal aspect of the maxillary molar region (p = 0.022). In the mandible, a statistically significant correlation between ABCT and age was found in the cortical bone of the labial side of the mandibular incisor region (p = 0.017). However, statistically significant negative correlation between ABCT and age was found in the mandibular canine region (p = 0.033). The only site to demonstrate a significant difference in change in ABCT with age between males and females was the lingual side of the retromolar region, in which female ABCT increased more than in males (slope = 0.015).

CONCLUSIONS

There is minimal clinically significant correlation between ABCT and age at the alveolar bone level. Although investigations show statistically significant correlations, these may not be clinically significant as those regions are not ideal for anchorage reinforcement with TADs in orthodontic practice.

Evaluation of alveolar cortical bone thickness and density for orthodontic mini-implant placement

Objective: Mini-implant stability is primarily related to bone quality and quantity. This study evaluated alveolar cortical bone thickness and density differences between interradicular sites at different levels from the alveolar crest, and assessed the differences between adolescents (12-18 years of age) and adults (19-50 years of age), males and females, upper and lower arch, anterior and posterior region of jaws and buccal and oral side. Study Design: In this retrospective study, 48 Computed Tomography scans, performed for oral surgery purposes were selected from dental records of 3,223 Caucasian orthodontic patients. The SimPlant software (Materialise, Leuven, Belgium) was used to measure cortical bone thickness and density at 13 interradicular sites and four bone levels ( 2,4,6 and 8 mm ). For the statistical analysis descriptive statistics, Student’s t-test and Pearson correlation coefficient were used. Results: Statistically significant differences in alveolar cortical bone thickness and density between age, gender, sites and sides were found (P<0.05). The Pearson correlation coefficient demonstrated a significant linear increasing of thickness and density from crest to base of alveolar crest (P≤0.05). Conclusion. Adults show a thicker alveolar cortical bone than adolescents. Alveolar cortical bone thickness and density were greater in males than in females, in mandible than in maxilla, in the posterior region than the anterior, in oral than buccal side. There is an increase of thickness and density from crest to base of alveolar crest.

Key words:Orthodontics, cortical bone thickness, cortical bone density, mini-implant, computed tomography, temporary anchorage devices.

Cortical bone thickness of the alveolar process measured with cone-beam computed tomography in patients with different facial types

INTRODUCTION

The purpose of this study was to determine the cortical bone thickness of the alveolar process in the maxilla and the mandible on cone-beam computed tomographs of adults with low, normal, and increased facial heights.

METHODS

This study was conducted on 155 images of adult patients (20-45 years old) who were assigned to the low-angle, normal, and high-angle groups. The thickness of the buccal cortical plates of the maxilla and the mandible, and the palatal cortical plates of the maxilla, were measured.

RESULTS

There was no statistically significant difference between the groups regarding mean ages, sex, and sagittal facial types. High-angle patients had significantly lower values than did low-angle patients in all mini-implant insertion sites in both the maxillary and mandibular alveolar bones. The mandibular and maxillary buccal measurements showed a similar pattern; the lowest values were for the high-angle group, followed by the normal group; the highest values were measured in the low-angle patients.

CONCLUSIONS

Clinicians should be aware of the probability of thin cortical bone plates and the risk of mini-implant failures at maxillary buccal alveolar mini-implant sites in high-angle patients, and at mandibular buccal alveolar mini-implant sites between the canine and the first premolar in normal and high-angle patients.

An evaluation of insertion sites for mini-implants: a micro - CT study of human autopsy material

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 45° and 90° 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 90° 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 90° to 45° 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 45° will generally enhance implant stability but increase the risk of perforation to the maxillary sinus.

Mini-implants in the palatal slope--a retrospective analysis of implant survival and tissue reaction

Background

To identify insertion procedure and force application related complications in Jet Screw (JS) type mini-implants when inserted in the palatal slope.

Methods

Setting and Sample Population: The Department of Orthodontics, the University Hospital Münster. Forty-one consecutively started patients treated using mini-implants in the palatal slope. In this retrospective study, 66 JS were evaluated. Patient records were used to obtain data on the mode of utilization and complications. Standardized photographs overlayed with a virtual grid served to test the hypothesis that deviations from the recommended insertion site or the type of mechanics applied might be related to complications regarding bleeding, gingival overgrowth or implant failure.

Results

Two implants (3%) were lost, and two implants (3%), both loaded with a laterally directed force, exhibited loosening while still serving for anchorage. Complications that required treatment did not occur, the most severe problem observed being gingival proliferation which was attributable neither to patients’ age nor to applied mechanics or deviations from the ideal implant position.

Conclusions

The JS mini-implant is reliable for sagittal and vertical movements or anchorage purposes. Laterally directed forces might be unfavorable. The selection of implant length as well as the insertion procedure should account for the possibility of gingival overgrowth.

Cone beam computed tomography use in orthodontics

Cone beam computed tomography (CBCT) is widely used by orthodontists to obtain three-dimensional (3-D) images of their patients. This is of value as malocclusion results from discrepancies in three planes of space. This review tracks the use of CBCT in orthodontics, from its validation as an accurate and reliable tool, to its use in diagnosing and treatment planning, and in assessing treatment outcomes in orthodontics.

Inferior alveolar nerve canal position among South Indians: A cone beam computed tomographic pilot study

Purpose:

To document a clinically relevant position of the inferior alveolar nerve (IAN) in complete dentate south Indian patients in the age group of 20–29 years using cone beam computerized tomograms.

Materials and Methods:

The investigators used a cross-sectional study design and a study sample of subjects who had a radiographically identifiable IAN canal with complete set of 28 permanent teeth excluding 3^rd molars. Predictor variables were age, tooth position, and side. Outcome variables were the linear distances between the buccal and lingual aspect of the IAN canal, buccal and lingual cortical thickness, IAN canal diameter, and the superior aspect of the IAN canal from the periapex of first and second mandibular molar. Descriptive statistics and Mann–Whitney U test were performed. P value of ≤ 0.05 was taken as significant.

Results:

The study sample was composed of 10 male and 10 female patients with a mean age of 24.2 ± 3.00 years. On average, the lingual cortical thickness was 1.68 mm at 1^st molar and 1.44 at 2^nd molar level. Gender and side influenced the outcome with varying statistical significance.

Conclusions:

The range of linear dimension of mandibular canal, cortical bone thickness, and distance between tooth apex and IAN canal have been presented for the South Indian population in the age group of 20–29 years. The implications of the findings will influence on the course of surgery. Further large-scale studies are needed to validate the findings of this study.

Mechanical stability assessment of novel orthodontic mini-implant designs: Part 2

OBJECTIVE

To assess the mechanical stability of a newly revised orthodontic mini-implant design (N2) compared with a design introduced in Part 1 of the study (N1) and the most widely-used commercially-available design (CA). To evaluate the mean buccal bone thickness of maxillary and mandibular posterior teeth using cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

From the CBCT scans of 20 patients, six tomographic cross-sections were generated for each tooth. Buccal bone thickness was measured from the most convex point on the bone to the root surface. CA (1.5 mm in diameter and 6 mm in length), N1, and N2 (shorter and narrower than N1) were inserted in simulated bone with cortical and trabecular bone layers. Mechanical stability was compared in vitro through torque and lateral displacement tests.

RESULTS

The bone thickness ranged from 2.26 to 3.88 mm. Maximum insertion torque was decreased significantly in N2 compared to N1. However, force levels for all displacement distances and torque ratio were the highest in N2, followed by N1 and CA (α = .05).

CONCLUSIONS

Both torque and lateral displacement tests highlighted the enhanced stability of N2 compared with CA. Design revisions to N1 effectively mitigated N1's high insertion torque and thus potentially reduced microdamage to the surrounding bone. The N2 design is promising as evidenced by enhanced stability and high mechanical efficiency. Moreover, N2 is not limited to placement in interradicular spaces and has the capacity to be placed in the buccal bone superficial to the root surface with diminished risk of endangering nearby anatomic structures during placement and treatment.

Clinical effectiveness of orthodontic miniscrew implants: a meta-analysis

The aim of this meta-analysis was to examine the clinical effectiveness of miniscrew implants (MI) used for anchorage reinforcement compared with that of conventional orthodontic means, as well as to assess the success rates of MIs and the possible risk factors affecting their clinical effectiveness. Literature searches were conducted, and, using specific inclusion and exclusion criteria, two independent investigators performed data extraction and analysis. Overall pooled estimates with 95% confidence intervals (CI) were obtained with the random-effects model. Eight out of 3183 original papers met the inclusion criteria. The mean difference of anchorage loss between the MI and conventional anchorage group was -2.4 mm (95% CI = -2.9 mm to -1.8 mm, p = 0). MIs significantly decreased or negated loss of anchorage. Anchorage loss seemed to be less in the mandible, when the MIs were inserted between the second premolar and the first molar, when 2 MIs were inserted per patient jaw, when they were directly connected, as well as when treatment lasted more than 12 months. MIs presented a success rate of 87.7%, with no significant differences between the various subgroups. However, the results of this meta-analysis should be interpreted with some caution because of the number, quality, and heterogeneity of the included studies.