Bone and cortical bone characteristics of mandibular retromolar trigone and anterior ramus region for miniscrew insertion in adults

Indirect orthodontic bonding using an original 3D method compared with conventional technique: A narrative review

As well known success in orthodontics is related to a correct diagnosis and to a carefull treatment planning. Our study aims to provide clinician with a reproducible and precise method, for orthodontic indirect bonding, thanks to CBCT images and due to a CAD-CAM process.

METHODS

A case of an orthodontic treatment plan, of a female patient, 37 years old, was selected. Plaster models were digitally acquired using the Extra-Oral scanner Maestro 3D and processed within the Studio Maestro 3D software. CBCT images in DICOM format were imported into the MIMICS software, in order to perform the segmentation of the dental elements, and to obtain a three-dimensional coronal-root dental arches model. The DICOM file thus processed was exported in an STL file, reworked with Meshmixer software to improve image quality, and imported into the 3D Maestro software to be superimposed on the digital model. In this way a three-dimensional real model of the dental arches was developed. After an accurate orthodontic virtual set-up, we proceeded to brackets positioning on the 3D model of the dental arches. Subsequently, a virtual transfer template was created, in order to carry out the digital printing of a thermo-printed mask necessary to perform an indirect bonding of the orthodontic appliance.

RESULTS

The original digital workflow proposed in this study allows the development of a real and non-ideal three-dimensional coronal-root model of the dental arches; this model can be used for indirect orthodontic bonding eliminating any errors in the expression of 1st, 2nd and 3rd order information of the pre-informed orthodontic appliance.

CONCLUSIONS

Technological advancements in oral scanning and 3D printing will allow the achievement of an easy and reproducible ideal positioning of the orthodontic brackets.

Stress distribution for mandibular extra-alveolar anchorage at different angles and force magnitudes: a finite element study

The aim of this study was to evaluate the stress distribution in cortical and cancellous bones and within the screw when a stainless steel extra-alveolar screw (EA-S) is inserted into the retromolar region of the mandible using the finite element method (FEM). The stress values in the EA-S were highest at 60° with horizontal (shear) force and lowest at 90° with axial force. In the bones (cortical and cancellous), the stress value was greatest at 90° with horizontal force. Greater stability of the screw may be achieved by tilting it to the force when horizontal loads are applied.

Concept for the Treatment of Class III Anomalies with a Skeletally Anchored Appliance Fabricated in the CAD/CAM Process-The MIRA Appliance

OBJECTIVE

Intermaxillary elastics, anchored skeletally, represent a promising concept for treatment in adolescent patients with skeletal Class III anomalies. A challenge in existing concepts is the survival rate of the miniscrews in the mandible or the invasiveness of the bone anchors. A novel concept, the mandibular interradicular anchor (MIRA) appliance, for improving skeletal anchorage in the mandible, will be presented and discussed.

CLINICAL CASE

In a ten-year-old female patient with a moderate skeletal Class III, the novel MIRA concept, combined with maxillary protraction, was applied. This involved the use of a CAD/CAM-fabricated indirect skeletal anchorage appliance in the mandible, with interradicularly placed miniscrews distal to each canine (MIRA appliance), and a hybrid hyrax in the maxilla with paramedian placed miniscrews. The modified alt-RAMEC protocol involved an intermittent weekly activation for five weeks. Class III elastics were worn for a period of seven months. This was followed by alignment with a multi-bracket appliance.

DISCUSSION

The cephalometric analysis before and after therapy shows an improvement of the Wits value (+3.8 mm), SNA (+5°), and ANB (+3°). Dentally, a transversal postdevelopment in the maxilla (+4 mm) and a labial tip of the maxillary (+3.4°) and mandibular anterior teeth (+4.7°) with gap formation is observed.

CONCLUSION

The MIRA appliance represents a less invasive and esthetic alternative to the existing concepts, especially with two miniscrews in the mandible per side. In addition, MIRA can be selected for complex orthodontic tasks, such as molar uprighting and mesialization.

Comparative study of stress characteristics around the adjacent teeth tissues during insertion of mini-screws with different insertion angles: A three-dimensional finite element study

With a limited alveolar bone position, there is a high risk that mini-screws (MS) implants could cause damage to the adjacent teeth. To reduce this damage, the position and tilt angle of the MS must be optimized. The aim of this study was to assess the effect of MS implantation angle on the stress exerted on adjacent periodontal membrane and roots. A three-dimensional finite element model containing dentition, periodontal ligament, jaw and MS were established based on the CBCT images and MS scanning data. The MS was first inserted perpendicular to the surface of the bone at specific locations and then tilted at an angle of 10° and 20° to the mesial and distal teeth, respectively. The stress distribution in the periodontal tissue of the adjacent teeth was analyzed after MS implantation at different angles.The stress on the adjacent tooth root and periodontal ligament was most uniformly distributed when the MS was inserted vertically. It changed 9.4-97.7% when the axis of MS was tilted at 10-degree and 20-degree angles from the point of vertical insertion. The stresses experienced by the periodontal ligament and the root are similar. When the horizontal angle of the MS insertion was changed, the MS was closer to the adjacent tooth, resulting in greater stress near the PDL and root. It was recommended to insert the MS vertically into the alveolar bone surface to avoid root damage due to excessive stress.

Anatomical study of the maxillary sinus: which characteristics can influence its volume?

PURPOSE

To investigate whether there is a relationship between the volume of the maxillary sinus and individual parameters such as gender, side, posterior tooth absence, sinus membrane thickening, bony septa, vertical and sagittal skeletal patterns.

METHODS

The tomographic volume of the maxillary sinus from 211 individuals (422 sides) was evaluated using Horos DICOM Viewer Software. Bony septa and sinus membrane thickening were classified as absent or present. At the same time, loss of one or more teeth in the posterior region of the maxilla (except for the third molars) was considered. The t test was applied to analyze maxillary sinus volume according to gender, age, side, posterior tooth absence, sinus membrane thickening and bony septa. A one-way analysis of variance (ANOVA) with Tukey's post-hoc test was applied to compare sagittal and vertical patterns. Pearson's correlation coefficient was also used to verify the association between maxillary sinus volume, age and skeletal patterns.

RESULTS

Concerning the sagittal skeletal pattern, a statistically significant difference was observed between Classes II and III (p = 0.05) and it was confirmed by the Pearson's correlation coefficient (r = - 0.107/p = 0.029). No statistically significant differences were observed between the maxillary sinus volume according to gender (p = 0.06), side (p = 0.37), posterior tooth absence (p = 0.92), sinus membrane thickening (p = 0.47), bony septa (0.89) and vertical skeletal pattern (p = 0.67). No significant differences were observed with age (r = - 0.076/p = 0.109) and the vertical skeletal pattern (r = - 0.078/p = 0.108).

CONCLUSION

Maxillary sinus volume was influenced by the sagittal skeletal pattern and was higher in Class III individuals.

Buccal bone thickness of posterior mandible for microscrews implantation in molar distalization

BACKGROUND

This study explored the inter-radicular space and buccal bone thickness of the posterior mandibular region to provide an appropriate miniscrew insertion site for lower dentition distalization.

METHODS

The cone-beam computed tomographic (CBCT) records of 63 subjects were collected. Buccal bone thickness (BBT) was measured at four sections: (I) the root of the second premolar(P₁); (II) the mesial root of the first molar(P₂); (III) the distal root of the first molar(P₃); (IV) the mesial root of the second molar(P₄). The narrowest inter-radicular space of the four sections was also detected. Both BBT and inter-radicular space were measured at 4 height levels, 2, 4, 6 and 8mm from the alveolar ridge.

RESULTS

The largest BBT was observed at the mesial root of the second molar at 6 and 8mm, demonstrating a thickness of 6.77±2.50mm and 7.46±1.94mm, respectively. It provided sufficient coverage for mini-implants inserted 10°-30° oblique to the root. Therefore, during distalization of the mandibular dentition, roots have sufficient space to bypass the inclined mini-implants on the lingual side, avoiding miniscrew-root contact. The width between the mesiodistal roots of the first molar was the smallest, showing 1.53±0.69mm and 2.13±0.65mm at 4 and 6mm. Miniscrews implanted in this region had an increased risk of root proximity.

CONCLUSIONS

The most appropriate insertion site at the mandibular buccal shelf was the mesial point of the second molar at 6-8mm from the alveolar ridge, and an insertion angle of 10°-30° was recommended to avoid miniscrew-root contact. CBCT analysis is recommended before implantation due to individual differences.

Effect of a digital guide on the positional accuracy of intermaxillary fixation screw implantation in orthognathic surgery

BACKGROUND

Intermaxillary fixation screw (IMFS) implantation is a common procedure in orthognathic surgery (OGS) performed to the temporary maxillary-mandibular fixation and stable bite relationships. The study aims to assess the accuracy of IMFS implantation with a digital guide to reduce the occurrence of root damage.

METHODS

This prospective study involved 40 patients undergoing OGS at the Affiliated Hospital of Qingdao University from August 2017 to May 2021. The patients were randomly divided into two groups according to whether the IMFS implantation was with or without digital guide (20 patients in the experimental group and 20 controls). The digital guides used in the experimental group were designed according to a virtual implantation plan and printed using stereolithography. In the control group, IMFSs were directly implanted by a surgeon based on clinical experience. Postoperatively, cone-beam computed tomography was performed to compare root proximity of IMFSs between the two groups and verify the accuracy of IMFS placement.

RESULTS

In the experimental group, there was no case of root damage, the incidence of the periodontal ligament (PDL) injured was 22.1%, and 77.9% IMFSs were placed without contacting adjacent anatomic structures. In the control group, the incidence of root damage had been up to 20.8%, 31.7% IMFSs injured the PDL, and only 47.5% IMFSs were placed between the roots (P < 0.001).

CONCLUSION

IMFSs can be placed more accurately with surgical guides, reducing the incidence of root and PDL damages.

The efficiency of molar distalization using clear aligners and mini-implants: Two clinical cases

When using clear aligners, if distalization greater than 3mm is required, there is no real predictable procedure to follow. The aim of this article is to show with two clinical cases the biomechanics of distalizing lower molars with mini-implant anchorage and aligners.

Success rate of surface-treated and non-treated orthodontic miniscrews as anchorage reinforcement in the lower arch for the Herbst appliance: A single-centre, randomised split-mouth clinical trial

BACKGROUND

Surface treatment of miniscrews was implemented to determine whether its application increased bone-to-surface contact and enhanced the interlock between the device and the surrounding bone.

OBJECTIVES

To compare the success rate of surface-treated and non-treated orthodontic miniscrews used as reinforcement of anchorage during treatment with the Herbst appliance.

TRIAL DESIGN

Split-mouth design with an allocation ratio of 1:1.

METHODS

Eligibility criteria to enrol patients were skeletal and dental class II patients with a retrusive chin, use of the Herbst appliance to correct malocclusion, need for skeletal anchorage using a miniscrew both in the left and right side of the mouth, absence of systemic diseases, absence of using drugs that alter bone metabolism, and good oral hygiene. Patients received self-drilling miniscrews without surface treatment and with surface treatment. Both types presented a 1.4 or 1.2 mm diameter. Miniscrews were inserted between the first molar and second premolars or between the two premolars. The force applied to the screws was an elastic chain from the head of the miniscrews to a direct button applied on the canines. The success rate of each type of miniscrew was considered the primary outcome, and the association of success with demographical, clinical, and geometrical characteristics was investigated. Differences were tested by the generalised linear mixed effects model for the split-mouth design. Differences with a P-value < 0.05 were selected as significant.

RANDOMISATION

A randomisation list was created for the mouth side assignment.

BLINDING

The study was single blinded with regard to the statistical analysis.

RESULTS

Thirty-nine miniscrews of the non-treated type and 39 miniscrews of the surface-treated type were inserted in 39 patients (23 female and 16 male, mean age: 15.55 ± 7.91) recruited between March 2018 and December 2020 with a split-mouth study design. The mean therapy duration was 9.3 months (SD = 1.31). No differences in failure rate were observed between miniscrew types. No serious harm was observed.

CONCLUSIONS

The success rate of surface-treated and non-treated miniscrews showed no significant differences.

REGISTRATION

This trial was not registered.

Accuracy of direct insertion of TADs in the anterior palate with respect to a 3D-assisted digital insertion virtual planning

BACKGROUND

Direct and 3D-assisted methods are an available alternative when inserting temporary anchorage devices (TADs) in the anterior palate for orthodontic anchorage. This study aimed to evaluate the differences between a planned insertion versus a direct method on digital models.

SETTINGS AND SAMPLE POPULATION

Seventy TADs were inserted by the direct insertion method in 35 patients who needed palatal TADs for orthodontic anchorage. For each patient, placement was independently planned by the superimposition of lateral cephalograms and corresponding plaster models. After mini-implant placement, impressions were taken with scanbodies. For the measurement of both linear and angle deviations, virtual planning models and postoperative oral scans were compared using 3D software for automatic surface registration and calculations.

RESULTS

Comparing TADs positioned by the direct method and the digitally planned method, a mean linear distance was found of 2.54 ± 1.51 mm in the occlusal view and 2.41 ± 1.33 mm in the sagittal view. No significant difference has been found between TADs positioned in the right and left palatal sides. A mean distance of 7.65 ± 2.16 mm was found between the tip of the digitally planned TAD and the central incisors root apex.

CONCLUSIONS

Both direct and 3D-assisted TAD insertion methods are safe and accurate in the anterior palate. However, the use of insertion guides facilitates TAD insertion, allowing less-experienced clinicians to use palatal implants.

Computed tomography assessment of maxillary bone density for orthodontic mini-implant placement with respect to vertical growth patterns

OBJECTIVE

To quantitatively measure and report bone density of maxilla in the interradicular (alveolar and basal bone) and infrazygomatic crest (IZC) region in various growth patterns among Dravidian individuals.

DESIGN

This was a retrospective spiral computed tomography (CT) study.

SETTING

The study was conducted at the Department of Orthodontics, Saveetha Dental College and Hospital, Tamil Nadu, India.

METHODS

Sixty CT scans (24 men, 36 women; mean age = 25.3 years and 23.8 years, respectively) divided equally into three groups based on vertical facial proportions were included. Bone density measurements in Hounsfield units (HU) were performed using Philips and RadiAnt DICOM viewers. Buccal cortical, palatal cortical and cancellous bone regions were analysed in a Philips DICOM viewer and IZC region was analysed in a RadiAnt DICOM viewer. Statistical analysis with one-way ANOVA and post-hoc Tukey HSD test was done.

RESULTS

The hypodivergent group had a significantly higher bone density at the buccal cortex in posterior region (P < 0.05) when compared to the normodivergent and hyperdivergent groups. Buccal basal bone was denser than buccal alveolar bone (P < 0.05) in all three groups. In the IZC region, hypodivergent groups had significantly higher density values when compared to the normodivergent and hyperdivergent groups (P < 0.05).

CONCLUSION

The present study concluded that cancellous bone density in the interradicular regions was greatest in the anterior sites and was not influenced by growth pattern. Hypodivergent groups tend to have higher density in the posterior regions (buccal and palatal cortical bone) and at the IZC region compared to normodivergent and hyperdivergent groups.

Complications reported with the use of orthodontic miniscrews: A systematic review

Objective

The aim of this systematic review was to evaluate the complications and side effects associated with the clinical use of orthodontic miniscrews by systematically reviewing the best available evidence.

Methods

A survey of articles published up to March 2020 investigating the complications associated with miniscrew insertion, in both the maxilla and mandible, was performed using 7 electronic databases. Clinical studies, case reports, and case series reporting complications associated with the use of orthodontic miniscrew implants were included. Two authors independently performed study selection, data extraction, and risk-of-bias assessment.

Results

The database survey yielded 24 articles. The risk-of-bias assessment revealed low methodological quality for the included studies. The most frequent adverse event reported was root injury with an associated periradicular lesion, vitality loss, pink discoloration of the tooth, and transitory loss of pulp sensitivity. Chronic inflammation of the soft tissue surrounding the miniscrew with mucosal overgrowth was also reported. The other adverse events reported were lesion of the buccal mucosa at the insertion site, soft-tissue necrosis, and perforation of the floor of the nasal cavity and maxillary sinus. Adverse events were also reported after miniscrew removal and included secondary bleeding, miniscrew fracture, scars, and exostosis.

Conclusions

These findings highlight the need for clinicians to preliminarily assess generic and specific insertion site complications and side effects.

Maximum insertion torque loss after miniscrew placement in orthodontic patients: A randomized controlled trial

OBJECTIVES

To compare torque recordings of immediately loaded orthodontic miniscrews between insertion time and different post-placement timepoints (2 weeks, 4 weeks and removal time, respectively).

SETTING AND SAMPLE POPULATION

Parallel trial with an allocation ratio of 1:1. Eligibility criteria were needs of fixed orthodontic treatment, no systemic disease and absence of using drugs altering bone metabolism.

MATERIAL AND METHODS

Patients received miniscrews, 2.0 mm diameter and 10 mm length. All miniscrews underwent inter-radicular placement, and they were placed in the maxilla or in the mandible, palatally or buccally. No pre-drilling was performed. Miniscrews were loaded immediately after the insertion and were used for distalization, intrusion, extrusion, mesialization or indirect anchorage. Patients were randomly divided into three groups. For each patient, Maximum Insertion Torque (MIT) was evaluated at baseline. MIT was measured again after 2 weeks and after 4 weeks by tightening the screw a quarter of turn in Groups 1 and 2, respectively. At the end of the treatment, maximal removal torque was evaluated in Group 3. Torque variation with respect to insertion time was considered as the primary outcome. Baseline and longitudinal differences were tested using the linear mixed-effects (LME) model.

RESULTS

Forty seven patients and 74 miniscrews were followed up. An association existed between maximum insertion torque and the observation time. A torque decrease of 26.9% and 30% after 2 weeks was observed for mandibular and maxillary miniscrews, respectively. After 1 month, torque values were similar to the baseline records. The overall success rate was 79.7%. No serious harm was observed.

CONCLUSIONS

Maximum insertion torque undergoes a loss during the first 2 weeks, and its values may depend on the insertion site and the anchorage purpose. Removal torque value is almost the same as the initial torque after 1 month.