Effect of orthodontic space closure on dental pulp sensitivity. Prospective clinical trial.

BACKGROUND: Orthodontic tooth movement (OTM) is a biological process that can influence the function of the pulp, including its innervation. The excitability of the nerve fibres of the pulp may be altered by forces exerted on the nerve fibres or by reduced blood flow to the pulp. The aim of this clinical study was to evaluate the sensitivity of the dental pulp during levelling and during the phase of space closure, to assess the role of certain controlled risk factors. METHODS: Twenty-two adolescent participants requiring orthodontic space closure in transcanine sector were enrolled in a prospective clinical study. Patients were observed before OTM, after levelling and 1 month during active space closure. The sensitivity threshold of the pulp was measured using the electric pulp test (EPT). Dental models were obtained using an intraoral scanner, allowing measurement of interdental distances and calculation of OTM speed. The teeth were categorized according to position and tooth type. RESULTS: The EPT values increased significantly during orthodontic treatment (one-way RM-ANOVA, P = .014). There was a significant difference in EPT values between the tooth categories. Teeth with a single root adjacent to the residual space had the highest EPT thresholds (two-way RM-ANOVA, P < .001; Holm-Sidak, P < .05). CONCLUSIONS: OTM reduced pulpal sensitivity. Pulpal sensitivity during active space closure was similar to sensitivity during the levelling phase. The pulpal sensitivity of molars was less affected by OTM than that of single-rooted teeth, while teeth closer to the gap had a significantly higher pulpal sensitivity threshold during active OTM.

Biomechanical effects of clear aligner with different shape design at extraction space area during anterior teeth retraction.

OBJECTIVE: This study aimed to investigate the biomechanical effects of clear aligner (CA) with different shape designs at extraction space (CAES) area during space closing. MATERIALS AND METHODS: A finite-element method (FEM) model of mandibular dentition, periodontal ligaments, attachments, and corresponding CA was established. The connecting rod design of CAES was modelled for the control group. Eight test groups with different heights of CAES from -4 mm to +4 mm were designed. Tooth displacement tendencies were calculated. The maximum principal stress in PDLs, teeth, and CAs was analysed. Both global coordinate system and local coordinate system were also used to evaluate individual tooth movements. RESULTS: Across all groups, stresses concentrated on the lingual outer surface of CAESs. For the lowered CAES groups, both the stress value and the stress distribution area at CAESs were increased. The lowered CAES groups showed reduced movement in anterior teeth and less tipping tendency of the canines. CONCLUSION: The shape of CAES has a biomechanical impact on anterior teeth movement and should be considered in aligner design. The results suggest that increasing the height of CAES can enhance anterior teeth retraction, while lowered CAES may facilitate controlled root movement. Changes in the shape of CAES represent a potential direction for biomechanical improvement of clear aligner in extraction cases and are worth exploring.

Friction versus frictionless mechanics during maxillary en-masse retraction in adult patients with Class I bimaxillary dentoalveolar protrusion: a randomized clinical trial.

BACKGROUND: Extraction space closure is a challenging phase during orthodontic treatment that affects not only the total treatment duration but also the whole treatment outcome. OBJECTIVE: To compare the efficiency of friction and frictionless mechanics during en-masse retraction of maxillary anterior teeth in adult patients with bimaxillary dentoalveolar protrusion. TRIAL DESIGN: Two-arm parallel group, single-center randomized clinical trial. MATERIALS AND METHODS: Thirty-two adult patients with bimaxillary protrusion were recruited and randomly allocated to two different retraction mechanics. A friction group, using NiTi coil springs and a frictionless group using closing T-loops for en-masse retraction. Randomization in a 1:1 ratio was generated by Microsoft Excel. The randomization numbers were secured in opaque sealed envelopes for allocation concealment. Retraction started in all patients following first premolars extraction using miniscrews as a source of indirect anchorage. Activation was done on a monthly basis until complete retraction of anterior segment. The rate of retraction, amount of anchorage loss, the dental, and soft tissue changes were analyzed on digital models and lateral cephalograms taken before retraction and after space closure. BLINDING: The outcome assessor was blinded through data concealment during assessment. RESULTS: Two patients were lost to follow up, so 30 patients completed the trial. The rate of anterior segment retraction was 0.88 ±â€…0.66 mm/month in the frictionless group compared to 0.72 ±â€…0.36 mm/month in the friction group which was statistically significant. Anchorage loss of 1.18 ±â€…0.72 mm in the friction group compared to 1.29 ±â€…0.55 mm in the frictionless group with no significant difference. Comparable dental and soft tissue changes following en-masse retraction were reported in both groups, with no statistically significant difference. HARM: one patient complained of soft tissue swelling following miniscrew insertion, but the swelling disappeared after one week of using mouth wash. LIMITATION: The study focused only on the maxillary arch. CONCLUSION: Both mechanics have successfully achieved the required treatment objectives in patients with bimaxillary dentoalveolar protrusion. Frictionless group showed a faster rate of retraction than the friction group, which was statistically but not clinically significant. TRIAL REGISTRATION: Clinicaltrials.gov with the identifier NCT03261024.

Finite element analysis of the effect of power arm locations on tooth movement in extraction space closure with miniscrew anchorage in customized lingual orthodontic treatment.

INTRODUCTION: More patients are choosing customized orthodontic appliances because of their excellent esthetics. It is essential that clinicians understand the biomechanics of the tooth movement tendency in customized lingual orthodontics. This study aimed to evaluate the tooth movement tendency during space closure in maxillary anterior teeth with the use of miniscrew anchorage in customized lingual orthodontics with various power arm locations. METHODS: Three-dimensional finite element models of the maxilla were created with miniscrews and power arms; the positions were varied to change the force directions. A retraction force (1.5 N) was applied from the top of the miniscrews to the selected points on the power arm, and the initial displacements of the reference nodes of the maxillary teeth were analyzed. RESULTS: After applying force in different directions, power arms located at the distal side of the canines led to larger initial lingual crown tipping and occlusal crown extrusion of the maxillary incisors compared with power arms located at the midpoint between the lateral incisors and canines, and caused a decreasing trend of the intercanine width. CONCLUSIONS: In customized lingual orthodontic treatment, power arms located at the distal side of the canines are unfavorable for anterior teeth torque control and intercanine width control. Power arms located at the midpoint between the lateral incisors and canines can get better torque control, but still cannot achieve excepted torque without extra torque control methods, no matter whether its force application point is higher than, lower than, or equal to the level of the top of the miniscrews.

Effectiveness of nickel-titanium springs vs elastomeric chains in orthodontic space closure: A systematic review and meta-analysis.

The aim of this study is to explore the effectiveness of nickel titanium closing springs (NiTi-CS) and elastomeric power chains (EPC) in orthodontic space closure and to assess the adverse periodontal effects, cost efficiency and patient-centred outcomes between both of these methods. METHODS: An electronic search of online databases (Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Scopus, LILACS and Web of Science), reference lists and grey literature as well as hand search were conducted without language restriction up to November/2017. Two authors blindly and in duplicate were involved in study selection, quality assessment and the extraction of data. Only randomized clinical trials (RCTs) were included. The quality of the studies was assessed using the Cochrane Collaboration's risk of bias tool. 95% confidence intervals and mean difference for continuous data were calculated. A meta-analysis that generated a random-effect model for the comparable outcomes was conducted, and heterogeneity was measured using I2 statistic. RESULTS: Of 187 records, 4 RCTs met the criteria and were included in the quantitative synthesis featuring 290 test quadrants. Faster space closure with NiTi-CS was observed with a mean difference of (0.20 mm/month, 95% CI: 0.12 to 0.28). Loss of anchorage appears to be similar within both groups when synthesized qualitatively. With exception to anchorage loss, secondary outcomes could not be investigated in the included trials. CONCLUSIONS: There is a moderate quality of evidence suggesting a faster orthodontic space closure with the NiTi-CS when compared to EPC. A comparable amount of anchorage loss was observed regardless of the utilized method of space closure. Further high-quality RCTs with parallel-groups, reporting on the adverse effects and patient-centred values, are recommended.

Evaluation of Biomechanical Properties of Four Loops at Different Activation: A Finite Element Method Study.

AIM: The aim of the study was to evaluate the force, moment, and moment/force ratio (M/F) generated by activating T loop, Kalra Simultaneous Intrusion and Retraction (KSIR) loop, Omega loop, and Teardrop loop made of titanium molybdenum alloy (TMA) wire with different preactivation bends at 1, 2, and 4 mm activation. MATERIALS AND METHODS: Finite element method (FEM) models of the four loops were created and different preactivation bends were placed. The loops were then activated and analyzed for force, moment, and M/F ratio using ANSYS software. RESULTS: In loops without preactivation bends, highest force values were generated by Omega loop, whereas T loop had the least force value. The mean value for the M/F in the alpha segment was almost similar. In loops with preactivation bend, the force was highest in Teardrop loop, whereas T loop had the least force value. The mean value for the M/F in the alpha segment was almost similar in all the loops. CONCLUSION: T loop with preactivation bend shows the most favorable properties. CLINICAL SIGNIFICANCE: T loop is comparatively reliable for the frictionless mechanics for the space closure than the other loops evaluated in clinical use.

Study Model-based Evaluation of Built-in Tip, Torque, and In-out Characteristics of a Third-generation Preadjusted Edgewise Appliance.

AIM: The aim of the study was to evaluate the clinical effectiveness of MBT™ preadjusted edgewise appliance (PEA) in terms of achieving the optimal expression of its built-in characteristics of tip, torque, and in-out. MATERIALS AND METHODS: Pretreatment and posttreatment study models of 20 subjects who received full fixed appliance treatment involving four first premolar extractions using the MBT™ appliance were measured for tip, torque, and in-out using the method described by Andrews. Treatment changes were analyzed statistically, and the posttreatment measurements were compared with the MBT™ specifications as well as Andrews' values for the above-mentioned parameters. RESULTS: Except for the maxillary canines and second premolars, the built-in tip of MBT™ appliance was nearly fully expressed, though there was some lack of correlation with Andrews' values. Despite the fact that the full amount of torque built into the MBT™ appliance was not expressed, torque measurements for all teeth except the maxillary second premolars and the first molars showed either no statistically significant difference or were significantly higher than Andrews' values for these teeth. In-out readings were lower than both MBT™ and Andrews' values, but the relative order of crown prominences was similar. Conclusion and clinical significance: The MBT™ appliance is thus effective in ensuring a successful treatment result, though individual adjustments may be necessary for optimal tooth positioning at the end of the treatment, as with any preadjusted appliance.

Sixteen-week analysis of unaltered elastomeric chain relating in-vitro force degradation with in-vivo extraction space tooth movement.

INTRODUCTION: The purposes of this study were to evaluate whether unaltered elastomeric chain can continue to move teeth for 16 weeks and to relate it to the amount of force remaining for the same batch of elastomeric chains. METHODS: The in-vivo portion of the study had a sample of 30 paired extraction space sites from 22 subjects who were measured for closure of the space every 28 days. The altered side elastomeric chain served as the control and was replaced at 28-day intervals whereas the experimental side remained unaltered. In the in-vitro portion of the study, 100 each of 2-unit and 3-unit segments of the same batch of elastomeric chains were placed in a water bath, and the force was measured for 20 of each segment length at the 28-day measurement points. RESULTS: Statistically significant amounts of space closure occurred at both the altered and unaltered sites at all measurement time points. The mean space closure at the altered sites was minimally greater than that observed at the paired unaltered sites. The mean differences of space closure between the altered and unaltered sites ranged from a minimum of -0.05 mm at 4 weeks to a maximum of -0.14 mm at 8 weeks. The elastomeric chain force degraded rapidly by 4 weeks but continued a gradual diminution of force to 86 g at 16 weeks. CONCLUSIONS: Unaltered elastomeric chain continued to move teeth into extraction spaces for 16 weeks in this sample from both statistically and clinically significant standpoints. There were minimal and statistically insignificant differences in the mean space closure measurements between the paired altered and unaltered sites. The elastomeric chain force at 16 weeks was less than 100 g, yet at the same time point, teeth continued to move clinically.

Innovative design of closing loops producing an optimal force system applicable in the 0.022-in bracket slot system.

INTRODUCTION: Most closing loops designed for producing higher moment-to-force (M/F) ratios require complex wire bending and are likely to cause hygiene problems and discomfort because of their complicated configurations. We aimed to develop a simple loop design that can produce optimal force and M/F ratio. METHODS: A loop design that can generate a high M/F ratio and the ideal force level was investigated by varying the portion and length of the cross-sectional reduction of a teardrop loop and the loop position. The forces and moments acting on closing loops were calculated using structural analysis based on the tangent stiffness method. RESULTS: An M/F ratio of 9.3 (high enough to achieve controlled movement of the anterior teeth) and an optimal force level of approximately 250 g of force can be generated by activation of a 10-mm-high teardrop loop whose cross-section of 0.019 × 0.025 or 0.021 × 0.025 in was reduced in thickness by 50% for a distance of 3 mm from the apex, located between a quarter and a third of the interbracket distance from the canine bracket. CONCLUSIONS: The simple loop design that we developed delivers an optimal force and an M/F ratio for the retraction of anterior teeth, and is applicable in a 0.022-in slot system.

En-masse protraction of mandibular posterior teeth into missing mandibular lateral incisor spaces using a fixed functional appliance.

Protraction of mandibular posterior teeth requiring absolute anchorage has always been a challenge, especially when the space is located in the anterior region, since more teeth must be protracted. Traditionally, skeletal anchorage devices have been used for anchorage reinforcement during protraction. However, drawbacks such as requirement of a surgical step, inability to tolerate heavy forces, and patient willingness to undergo such surgical procedures can be limiting factors. Additionally, the mechanics involved can sometimes create undesirable side effects, thereby limiting their application in such situations. This report describes the use of a fixed functional appliance as an anchorage-reinforcement device for en-masse protraction of mandibular posterior teeth into a missing lateral incisor space.

Comparison of longitudinal changes in clinical periodontal parameters of canines and first molars treated with fixed orthodontic appliances.

INTRODUCTION: Our objective was to learn the possible effects of fixed orthodontic therapy on the periodontium of the extraction sites adjacent to canines and first molars. This was a prospective cohort study. METHODS: Sixty-two systemically healthy subjects were selected. The study was divided into the period of oral hygiene instructions and the period of active orthodontic treatment. Plaque index, gingival index, probing pocket depth, and clinical attachment loss were recorded for the canines and first molars at baseline, after 1 month of orthodontic therapy, and every 3 months until the completion of the orthodontic treatment. RESULTS: There was a statistically significant increase in all clinical parameters (plaque index, gingival index, probing pocket depth, and attachment loss; P <0.05) on the first molars compared with the canines. Significant increases in attachment loss were noted in both the canines (baseline, 0.06 ± 0.01 mm; end of treatment, 0.17 ± 0.02 mm) and the molars (baseline, 0.07 ± 0.01 mm; end of treatment, 0.20 ± 0.02 mm). CONCLUSIONS: Attachment loss cannot be explained solely by the effect of plaque or the banding of teeth. Other factors such as tooth extractions adjacent to the canines, tooth movement, and occlusal trauma may have contributing roles in the loss of periodontal support in adolescent patients.

Invisalign treatment of lower incisor extraction cases.

AIM: To demonstrate the use of the Invisalign appliance in lower incisor extraction cases. METHOD: Twelve patients, consecutively treated by the removal of a single lower incisor and Invisalign appliances, were selected from the author's private practice. Pretreatment, treatment and post-treatment photographic records were obtained and are presented. RESULTS: All cases completed treatment, with a mean treatment time of 42 weeks. Fifty percent of the cases required a brief period of refinement (average six weeks) at the end of the initial projected treatment period. CONCLUSION: The Invisalign appliance, in correctly diagnosed cases, with careful 'ClinCheck' set-ups and good clinical monitoring, can routinely produce satisfactory outcomes in patients who require the removal of a lower incisor.

The effect of benzocaine and ketoprofen gels on pain during fixed orthodontic appliance treatment: a randomised, double-blind, crossover trial.

AIMS: To compare the analgesic effect of topical benzocaine (5%) and ketoprofen (1.60 mg/mL) after 2 mm activation of 7 mm long delta loops used for maxillary en-masse orthodontic space closure. SUBJECTS AND METHODS: Twenty patients (seven males, 13 females, 15-25 years of age, mean age of 19.5 years) participated in a randomised crossover, double-blind trial. After appliance activation, participants were instructed to use analgesic gels and record pain perception at 2, 6, 24 hours and 2, 3 and 7 days (at 18.00 hrs), using a visual analogue scale ruler (VAS, 0-4). Each patient received all three gels (benzocaine, ketoprofen, and a control (placebo)) randomly, but at three different appliance activation visits following a wash-over gap of one month. After the first day, the patients were instructed to repeat gel application twice a day at 10:00 and 18:00 hrs for three days. The recorded pain scores were subjected to non-parametric analysis. RESULTS: The highest pain was recorded at 2 and 6 hours. Pain scores were significantly different between the three groups (Kruskal-Wallis test, p < 0.01). The overall mean (SD) pain scores for the benzocaine 5%, ketoprofen, and control (placebo) groups were 0.89 (0.41), 0.68 (0.34), and 1.15 (0.81), respectively. The pain scores were significantly different between the ketoprofen and control groups (mean difference = 0.47, p = 0.005). All groups demonstrated significant differences in pain scores at the six different time intervals (p < 0.05) and there was no gender difference (p > 0.05). CONCLUSION: A significant pain reduction was observed following the use of ketoprofen when tested against a control gel (placebo). The highest pain scores were experienced in patients administered the placebo and the lowest scores in patients who applied ketoprofen gel. Benzocaine had an effect mid-way between ketoprofen and the placebo. The highest pain scores were recorded 2 hours following force application, which decreased to the lowest scores after 7 days.

Exactive Tie-Back - An Accurate Active Tieback.

Active tiebacks using elastomeric modules are preferred for space closure in most cases. Elastomeric ring should be stretched by equal amount on both sides for equalforce delivery and to avoid unwanted complication like shift in mid-line, asymmetric space closure. Elastic tiebacks were originally described using an elastomeric module, stretched to twice its normal size but in clinical situations, stretch of elastomeric rings are diffcult to measure intraorally. This paper introduces a manually fabricated guiding system that will allow the clinician to accurately activate active tie-back bilaterally without fear of over/under stretching the module to twice its original size. With the help of straight length 0.021" 0.025" SS wire and cold cure acrylic a guiding stent is fabricated. Guiding loops were made with 0.009" ligature wire around this stent, which can be placed along with active tieback. This "Exactive tieback" with the help ofguiding loop template is easy to fabricate and use. It is an accurate, effective, and predictable method for placement of symmetrical active tie-backs."

Treatment of Skeletal Class II Malocclusion with Forsus Fatigue Resistance Appliance and Its Re-activation by Using Custom-made Crimp.

Growing skeletal class II malocclusions with mandibular deficiency have been treated for more than a century with different types of functional appliances. Removable or fixed functional appliances are available to advance the mandible. Fixed functional appliances have the advantage of not requiring patient compliance. They can also be used concurrently with brackets. This article presents the case reports of successfully treated mild skeletal class II in late stages of puberty by using a Forsus fatigue resistance appliance along with custom made crimp.

A new method to evaluate the positional stability of a self-drilling miniscrew.

OBJECTIVES: To evaluate the positional stability of miniscrews during orthodontic treatment change in cone-beam computed tomography (CBCT). SETTING AND SAMPLE POPULATION: Twenty adult volunteers were enrolled. METHODS: In all participants, at least two maxillary first premolars were extracted because of protrusion. Each volunteer received six miniscrews in the maxilla, including two loaded miniscrews to retract anterior teeth and four unloaded miniscrews. CBCT scans were obtained at the beginning of space closure (T1) and approximately 11.8 months later (T2). Three-dimensional miniscrew models were constructed at T1 and T2, and the central axes were calculated using a principal component analysis (PCA) technique. Finally, we measured and compared the angle change of all the miniscrews from T1 to T2. RESULTS: The angle change values of the unloaded and loaded miniscrews were 1.64 ± 1.25° and 1.67 ± 1.15°, respectively. No significant differences in the angle change were observed. CONCLUSION: Cone-beam computed tomography images revealed both the unloaded and loaded miniscrews to be positionally stable during en-masse retraction in this study.

Versatile Clinical Application of the Spike Screw: Direct Anchorage Versus Indirect Anchorage.

OBJECTIVES/INTRODUCTION: This article represents clinical application of spike screw, novel design of miniscrew, for direct anchorage and indirect anchorage in orthodontic treatment. Accompanied by easy placement and removal, the spike screw provides good stability for the orthodontic anchorage. MATERIALS AND METHODS: The spike screw consists of 6 spikes attached to a washer with laser welded stainless-steel hook that is placed by self-drilling fixation miniscrew. The spike screws were applied to correct malocclusions in patients as follows: traction of impacted canines and protraction of posterior teeth as a direct anchorage and correction of midline discrepancy as an indirect anchorage. For orthodontic traction of impacted canines, spike screws were placed in the mandibular labial mucosal area to create extrusive forces. Afterward, it was utilized for the protraction of posterior teeth. In the second case of the indirect anchorage, spike screw was applied on the midpalatal area to correct midline discrepancy that occurred during orthodontic treatment. The extended hook of a washer was prebended along the curvature of the palate and then secured with a mini screw. The extended hook was bonded to maxillary left first molar. RESULTS: In the first case, the spike screw provided adequate anchorage for the vertical traction of horizontally impacted canine. Since the spike screws were placed in the mandibular anterior lesion, the vertical traction force was applied simply with orthodontic elastics. Also, enough distance was achieved for up-down elastics to work by placing the spike screw in the opposite arch. The force of vertical traction was adjusted with selection of size and force of up-down elastics. Later, it was used to provide anchorage for protraction of mandibular molars without changing orientation of the spike screws. In the second case, the spike screw placed in the midpalatal area was attached to the left first molar and worked as an indirect anchorage. The midline discrepancy was resolved by consolidating the spaces to the left with securing the left first molar location. CONCLUSION: The novel design of the spike screw permits clinicians to have minimum invasive and easy placement and removal of the appliance while maintaining a good control over tooth movement with improved stability in various clinical cases.

Efficacy of the Nance appliance as an anchorage-reinforcement method.

INTRODUCTION: The Nance appliance is widely considered to be an efficient method of anchorage reinforcement; however, much of the perceived advantage is based on clinical judgment. The aim of this study was to assess the amounts of anchorage loss and desired tooth movement associated with the Nance appliance. METHODS: The mandibular arches of 7 beagle dogs were used. The first and third premolars were extracted. Reference miniscrews were placed at the first premolar sites as stable references to measure the amounts of anchorage loss and desired tooth movement. Four beagles were fitted with custom-made Nance appliances on the fourth premolars and orthodontic bands on the second premolars (Nance group). Three beagles were fitted with orthodontic bands on the second and fourth premolars with no anchorage reinforcement (control group). The second premolars were retracted over 15 weeks in both groups. The amounts of second premolar movement (desired tooth movement) and fourth premolar movement (anchorage loss) were recorded at 5, 10, and 15 weeks. The percentages of desired tooth movement and anchorage loss to the total space closure were calculated. RESULTS: The mean desired tooth movement was significantly more in the Nance group than in the control group at 10 weeks (P <0.05) but was not significantly different at 5 and 15 weeks. The mean percentages of anchorage loss to the total space closure at 15 weeks were 45.7% in the control group and 28.8% in the Nance group. The Nance group had 16.9% less anchorage loss and 16.6% more desired tooth movement than did the control group at 15 weeks (P <0.05). Most of the anchorage loss (80%) in the Nance group occurred during the first 10 weeks. CONCLUSIONS: The Nance appliance did not provide absolute anchorage, but there was significantly less anchorage loss with it than in the control group. The majority of anchorage loss occurred during the first 10 weeks in the Nance group.

Bimaxillary protrusion with an atrophic alveolar defect: orthodontics, autogenous chin-block graft, soft tissue augmentation, and an implant.

Bimaxillary protrusion in a 28-year-old woman was complicated by multiple missing, restoratively compromised, or hopeless teeth. The maxillary right central incisor had a history of avulsion and replantation that subsequently evolved into generalized external root resorption with Class III mobility and severe loss of the supporting periodontium. This complex malocclusion had a discrepancy index of 21, and 8 additional points were scored for the atrophic dental implant site (maxillary right central incisor). The comprehensive treatment plan included extraction of 4 teeth (both maxillary first premolars, the maxillary right central incisor, and the mandibular right first molar), orthodontic closure of all spaces except for the future implant site (maxillary right central incisor), augmentation of the alveolar defect with an autogenous chin-block graft, enhancement of the gingival biotype with a connective tissue graft, and an implant-supported prosthesis. Orthodontists must understand the limitations of bone grafts. Augmented alveolar defects are slow to completely turn over to living bone, so they are usually good sites for implants but respond poorly to orthodontic space closure. However, postsurgical orthodontic treatment is often indicated to optimally finish the esthetic zone before placing the final prosthesis. The latter was effectively performed for this patient, resulting in a total treatment time of about 36 months for comprehensive interdisciplinary care. An excellent functional and esthetic result was achieved.

Hounsfield unit change in root and alveolar bone during canine retraction.

INTRODUCTION: The objective of this study was to determine the Hounsfield unit (HU) changes in the alveolar bone and root surfaces during controlled canine retractions. METHODS: Eighteen maxillary canine retraction patients were selected for this split-mouth design clinical trial. The canines in each patient were randomly assigned to receive either translation or controlled tipping treatment. Pretreatment and posttreatment cone-beam computed tomography scans of each patient were used to determine tooth movement direction and HU changes. The alveolar bone and root surface were divided into 108 divisions, respectively. The HUs in each division were measured. Mixed-model analysis of variance was applied to test the HU change distribution at the P <0.05 significance level. RESULTS: The HU changes varied with the directions relative to the canine movement. The HU reductions occurred at the root surfaces. Larger reductions occurred in the divisions that were perpendicular to the moving direction. However, HUs decreased in the alveolar bone in the moving direction. The highest HU reduction was at the coronal level. CONCLUSIONS: HU reduction occurs on the root surface in the direction perpendicular to tooth movement and in the alveolar bone in the direction of tooth movement when a canine is retracted.