Effect of attachment configuration and trim line design on the force system of orthodontic aligners: A finite element study on the upper central incisor

OBJECTIVES

To use the finite element method (FEM) to investigate the effect of various attachment configurations and trimming line designs of orthodontic aligners on their biomechanical performance.

METHOD

A 3D upper jaw model was imported into 3D design software. The upper right central incisor tooth (Tooth 11) was made mobile, and its periodontal ligament (PDL) and bone structures were designed. Aligners were modelled with three distinct attachment configurations: No attachment, rectangular horizontal, rectangular vertical, and two trimming line designs; scalloped and straight extended, with a homogeneous thickness of 0.6 mm. These models were then imported into an FE software. Simulations were conducted for three different movements, including facial translation, distalization, and extrusion.

RESULTS

Forces were recorded at 1.3-2.6 N during facial translation, 1.4-5.9 N in distalization, and 0.0-2.0 N in extrusion. The straight extended trimming line consistently generated higher forces than the scalloped design. Attachments had no significant impact on force components during facial translation but were more effective in distalization and extrusion. The combination of a straight extended trimming line with horizontal attachments exhibited the least stresses at the apical third during distalization, and the highest stresses during extrusion, suggesting superior retention.

CONCLUSIONS

Rectangular attachments offer limited benefits in facial translation, but horizontal rectangular attachments can intensify load in distalization and are crucial for force generation in extrusion. Horizontal attachments are preferred over vertical options. Additionally, the straight extended trim line enhances control of tooth movement and can replace attachments in certain cases.

CLINICAL RELEVANCE

These findings provide biomechanical evidence and an optimal protocol to guide clinical practice in planning diverse teeth movements. The emphasis is on the influence of attachment utilization and the specific design of aligner trimming lines to enhance control over tooth movement.

Three-dimensional computed tomography analysis of airway volume in growing class II patients treated with Frankel II appliance

OBJECTIVE

The purpose of this retrospective study was to assess the airway volume changes associated with the use of Frankel appliance (FR II) in Class II malocclusion patients using three-dimensional cone beam computed tomography (3D CBCT) imaging.

MATERIALS AND METHODS

The sample consisted of 31 Class II malocclusion patients (mean age 9.24 ± 1.93 years old, 17 males (54.8%) and 14 females (45.2%)) treated with FR II appliance by the same orthodontist for an average of 9 months ± 20 days. CBCT images were taken before and after treatment and upper airway volume changes were measured using Dolphin 3D software version11.0 (Dolphin Imaging, Chatsworth, CA) and statistically compared.

RESULTS

Airway volume of nasal cavity, nasopharynx, oropharynx, hypopharynx and the total airway volume significantly increased after the use of FR II appliance. In addition, significant increase was reported in maxillary base, inter-molar, inter-premolar and inter-canine width. Significant increase in soft tissue thickness was only recorded opposite to CV2.

CONCLUSION

The use of the FR II appliance in growing subjects with Class II malocclusion led to a significant increase in the upper airway volume in addition to the anticipated dental and skeletal transverse expansion effects.

Physiochemical and mechanical characterisation of orthodontic 3D printed aligner material made of shape memory polymers (4D aligner material)

OBJECTIVES

To conduct a physiochemical and mechanical material analysis on 3D printed shape-memory aligners in comparison to thermoformed aligners.

MATERIALS AND METHODS

Four materials were examined, including three thermoformed materials: CA Pro (CP), Zendura A (ZA), Zendura FLX (ZF), and one 3D printed material: Tera Harz (TC-85). Rectangular strips measuring 50 × 10 × 0.5 mm were produced from each material. Five tests were conducted, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), shape recovery tests, three-points bending (3 PB), and Vickers surface microhardness (VH).

RESULTS

DSC recorded glass transition temperatures (Tg) at 79.9 °C for CP, 92.2 °C for ZA, 107.1 °C for ZF, and 42.3 °C for TC-85. In DMA analysis at 20-45 °C, a prominent decrease in storage modulus was observed, exclusively for TC-85, as the temperature increased. Notably, within the temperature range of 30-45 °C, TC-85 exhibited substantial shape recovery after 10 min, reaching up to 86.1 %, while thermoformed materials showed minimal recovery (1.5-2.9 %). In 3 PB test (at 30, 37, 45 °C), ZA demonstrated the highest force at 2 mm bending, while TC-85 exhibited the lowest. Regarding VH at room temperature, there was a significant decrease for both ZA and ZF after thermoforming. ZA had the highest hardness, followed by ZF and TC-85, with CP showing the lowest values.

CONCLUSIONS

TC-85 demonstrates exceptional shape memory at oral temperature, improving adaptation, reducing force decay, and enabling, together with its higher flexibility, extensive tooth movement per step. Additionally, it maintains microhardness similar to thermoformed sheets, ensuring the durability and effectiveness of dental aligners.

CLINICAL RELEVANCE

The 3D printed aligner material with shape memory characteristics (4D aligner) has revolutionized the orthodontic aligner field. It showed mechanical properties more suitable for orthodontic treatment than thermoforming materials. Additionally, it offers enhanced control over aligner design and thickness, while optimizing the overall workflow. It also minimizes material wastage, and reduces production expenses.

Does maxillary sinus proximity affect molar root resorption during distalization using Invisalign? a CBCT study

BACKGROUND

This study aimed to assess the correlation between maxillary sinus proximity to root apices of maxillary molars and root resorption during molar distalization using clear aligner therapy (CAT).

MATERIALS AND METHODS

Thirty-eight cone beam computed tomography scans (CBCTs) obtained pre- (T0) and post-treatment (T1) from 19 adult patients (36.68 ± 13.50 years), who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization, were evaluated in this study At least 22 h of aligner wear per day was a main inclusion criterion. Sinus proximity and changes in root lengths were measured for 61 molars (183 roots). Spearman coefficient analysis was used for assessing correlation between sinus proximity and root resorption. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by intraclass correlation coefficient (ICC).

RESULTS

Spearman coefficient revealed no significant correlation between sinus proximity and molar root resorption for mesiobuccal, distobuccal or palatal roots (p = 0.558, p = 0.334, p = 0.931, respectively).

CONCLUSION

There was no correlation between maxillary sinus proximity to root apices of maxillary molars and root resorption.

Treatment effects of Herbst appliance in skeletal Class II cases during pre-pubertal and post-pubertal periods: a cone-beam computed tomographic study

In the present study, Thirty-six Class patients II (A condition in which the upper jaw is larger than the lower jaw) were randomly selected and assigned to one of two groups based on their maturation stage: the pre-pubertal group (18 patients, mean age 9.15 ± 1.5 years) and post-pubertal group (18 patients, mean age 16.3 ± 1.0 years). All patients were treated with a metallic splint-supported Herbst IV appliance (An appliance that acts like artificial joint working between the upper and power jaws that keeps the lower jaw in a forward position, thus improving the Class II condition). Pretreatment (T1) and post-Herbst IV treatment (T2) scans were obtained for both groups. Dental and skeletal measurements were made on the scans and statistically analyzed using paired and independent t-tests. The study hypothesis was that; the dentoskeletal changes in Class II malocclusion treatment using Herbst appliance in the Pre-pubertal is more than the Post-pubertal growth stage due to the remaining growth potential for the pre-pubertal patients. The comparison between the two groups revealed statistically significant differences in horizontal skeletal parameters in the lower jaw only, while other readings were similar.

Development and Comparison of Conventional and 3D-Printed Laboratory Models of Maxillary Defects

BACKGROUND

Recording accurate impressions from maxillary defects is a critical and challenging stage in the prosthetic rehabilitation of patients following maxillectomy surgery. The aim of this study was to develop and optimize conventional and 3D-printed laboratory models of maxillary defects and to compare conventional and digital impression techniques using these models.

METHODS

Six different types of maxillary defect models were fabricated. A central palatal defect model was used to compare conventional silicon impressions with digital intra-oral scanning in terms of dimensional accuracy and total time taken to record the defect and produce a laboratory analogue.

RESULTS

Digital workflow produced different results than the conventional technique in terms of defect size measurements which were statistically significant (p < 0.05). The time taken to record the arch and the defect using an intra-oral scanner was significantly less compared with the traditional impression method. However, there was no statistically significant difference between the two techniques in terms of the total time taken to fabricate a maxillary central defect model (p > 0.05).

CONCLUSIONS

The laboratory models of different maxillary defects developed in this study have the potential to be used to compare conventional and digital workflow in prosthetic treatment procedures.

Management of mandibular incisors crowding by using passive lower lingual holding arch: a case series and literature review

Mandibular incisor crowding is a frequently encountered problem in daily orthodontic treatment. Success of the treatment greatly depends on the orthodontist's ability to manage the factors contributing to the existing crowding and implementing the proper interceptive means. The passive lower lingual holding arch (LLHA) helps maintain the position of the permanent first molars after the exfoliation of primary molars and canines. Thus, relieving the mandibular incisor crowding during transitional dentition. Four case reports age ranged from 11-13.5 years old were used to report the effect of using LLHA on mandibular incisor crowding. Little's Irregularity Index (LII) was used to assess the severity of mandibular incisors crowding as well as to compare the severity of the crowding before and after the use of LLHA. Passive LLHA could be considered the appliance of choice for space maintenance during the mixed dentition. Mandibular incisor crowding was reduced as measured by LII after the use of the passive LLHA over a duration of twenty months.

Wearable Orofacial Technology and Orthodontics

Wearable technology to augment traditional approaches are increasingly being added to the arsenals of treatment providers. Wearable technology generally refers to electronic systems, devices, or sensors that are usually worn on or are in close proximity to the human body. Wearables may be stand-alone or integrated into materials that are worn on the body. What sets medical wearables apart from other systems is their ability to collect, store, and relay information regarding an individual's current body status to other devices operating on compatible networks in naturalistic settings. The last decade has witnessed a steady increase in the use of wearables specific to the orofacial region. Applications range from supplementing diagnosis, tracking treatment progress, monitoring patient compliance, and better understanding the jaw's functional and parafunctional activities. Orofacial wearable devices may be unimodal or incorporate multiple sensing modalities. The objective data collected continuously, in real time, in naturalistic settings using these orofacial wearables provide opportunities to formulate accurate and personalized treatment strategies. In the not-too-distant future, it is anticipated that information about an individual's current oral health status may provide patient-centric personalized care to prevent, diagnose, and treat oral diseases, with wearables playing a key role. In this review, we examine the progress achieved, summarize applications of orthodontic relevance and examine the future potential of orofacial wearables.

Computer-aided finite element model for biomechanical analysis of orthodontic aligners

OBJECTIVES

To design a finite element (FE) model that might facilitate understanding of the complex mechanical behavior of orthodontic aligners. The designed model was validated by comparing the generated forces - during 0.2-mm facio-lingual translation of upper left central incisor (Tooth 21) - with the values reported by experimental studies in literature.

MATERIALS AND METHODS

A 3D digital model, obtained from scanning of a typodont of upper jaw, was imported into 3-matic software for designing of aligners with different thicknesses: 0.4, 0.5, 0.6, 0.7 mm. The model was exported to Marc/Mentat FE software. Suitable parameters for FE simulation were selected after a series of sensitivity analyses. Different element classes of the model and different rigidity values of the aligner were also investigated.

RESULTS

The resultant maximum forces generated on facio-lingual translation of Tooth 21 were within the range of 1.3-18.3 N. The force was direction-dependent, where lingual translation transmitted higher forces than facial translation. The force increases with increasing the thickness of the aligner, but not linearly. We found that the generated forces were almost directly proportional to the rigidity of the aligner. The contact normal stress map showed an uneven but almost repeatable distribution of stresses all over the facial surface and concentration of stresses at specific points.

CONCLUSIONS

A validated FE model could reveal a lot about mechanical behavior of orthodontic aligners.

CLINICAL RELEVANCE

Understanding the force systems of clear aligner by means of FE will facilitate better treatment planning and getting optimal outcomes.

A visual evaluation of oral plaque removal utilizing an adjunct enzyme pre-rinse in orthodontic subjects

OBJECTIVE

To determine if an adjunct proteolytic pre-rinse along with contemporary methods of dental cleaning may more effectively remove visual plaque in subjects with fixed orthodontic appliances.

MATERIALS AND METHODS

Forty-three orthodontic subjects, ages 10 to 25, completed this single site, double-blind, crossover clinical trial. Subjects randomly received bromelain enzyme or a powdered-sugar placebo pre-rinse, followed by manual tooth brushing and use of a Waterpik. Subjects received the alternate pre-rinse during the subsequent visit. Baseline and residual plaque accumulation were recorded via disclosing tablet and digital photography. A single, blinded examiner scored visual plaque scores from randomized photographs. Treatment effects on composite plaque score were evaluated using repeated-measures analysis of variance. A 5% significance level was used for all tests.

RESULTS

No significant differences in plaque scores were noted at baseline or post-rinse between the enzyme and placebo. The changes from baseline to post-rinse (P = .190), post-brushing (P = .764), and post-Waterpik (P = .882) were not significantly different between interventions. Significant reduction in plaque scores were observed in both arms of the study after brushing (P < .01) and waterjet use (P < .01). Neither age (P = .220) nor gender (P = .449) impacted plaque scores.

CONCLUSIONS

Use of a bromelain enzyme pre-rinse alone did not significantly enhance plaque removal. A significant reduction in retained plaque was observed with the application of brushing and or Waterpik.

Human herpes virus 8-positive germinotropic lymphoproliferative disorder: first case diagnosed in the UK, literature review and discussion of treatment options

We present this case of human herpes virus 8-positive germinotropic lymphoproliferative disorder in a 20-year-old woman seen in the surgical oncology clinic for localised lymphadenopathy. This is the first case to be reported in the UK, and we discuss it along with a literature review including investigations and treatment options. This will demonstrate the importance of preoperative workup and multidisciplinary teamwork in deciding management plans and serve as a guide for future encounters of this rare condition in clinical practice.

Improving the accuracy of publicly available search engines in recognizing and classifying dental visual assets using convolutional neural networks

AIM

To assess the accuracy of DigiBrain4, Inc (DB4) Dental Classifier and DB4 Smart Search Engine* in recognizing, categorizing, and classifying dental visual assets as compared with Google Search Engine, one of the largest publicly available search engines and the largest data repository.

MATERIALS AND METHODS

Dental visual assets were collected and labeled according to type, category, class, and modifiers. These dental visual assets contained radiographs and clinical images of patients' teeth and occlusion from different angles of view. A modified SqueezeNet architecture was implemented using the TensorFlow r1.10 framework. The model was trained using two NVIDIA Volta graphics processing units (GPUs). A program was built to search Google Images, using Chrome driver (Google web driver) and submit the returned images to the DB4 Dental Classifier and DB4 Smart Search Engine. The categorical accuracy of the DB4 Dental Classifier and DB4 Smart Search Engine in recognizing, categorizing, and classifying dental visual assets was then compared with that of Google Search Engine.

RESULTS

The categorical accuracy achieved using the DB4 Smart Search Engine for searching dental visual assets was 0.93, whereas that achieved using Google Search Engine was 0.32.

CONCLUSION

The current DB4 Dental Classifier and DB4 Smart Search Engine application and add-on have proved to be accurate in recognizing, categorizing, and classifying dental visual assets. The search engine was able to label images and reject non-relevant results.

Three-dimensional evaluation of labial alveolar bone overlying the maxillary and mandibular incisors in different skeletal classifications of malocclusion

OBJECTIVES

The purpose of this study was to investigate differences in the thickness of the labial bone overlying the maxillary and mandibular incisors in class I, II, and III skeletal classifications using three-dimensional cone-beam computed tomographs (CBCT) technology.

METHODS

Pretreatment CBCTs of 54 Caucasian subjects (44 males, 10 females) were collected from the archives of a graduate orthodontic clinic. The subjects were divided into three groups based on their skeletal classification. CBCT scans were oriented to the long axis of each maxillary and mandibular incisor from the root apex to incisal tip and the axial inclination of each incisor was measured and recorded. Labial bone thickness was measured at the apex (A) and at the midpoint (MP) on each maxillary and mandibular incisor. A linear measurement, perpendicular to the long axis, was recorded from the labial bone surface to the most anterior root surface at two points. The effects of skeletal classification, jaw, incisor position, and side on A, MP, and Inclination were evaluated using mixed-model ANOVA. A 5% significance level was used for all tests.

RESULTS

Significantly greater bone thickness at the apex and midpoint was reported in class III individuals than class I or II. Central incisors had significantly greater bone thickness at both the root apex and midpoint. Significantly greater bone thickness was noted in the mandible at the level of the apex. At the level of the midpoint, significantly greater thickness was reported in the maxilla. There was a positive correlation between thickness and angle within each jaw-incisor combination for class I patients and for central incisors in class III patients.

CONCLUSION

The thickness of labial alveolar bone over the incisors varies based on the underlying skeletal discrepancy in each patient. Skeletal discrepancy influences the inclination of the maxillary and mandibular incisors.

Retrospective CBCT analysis of airway volume changes after bone-borne vs tooth-borne rapid maxillary expansion

OBJECTIVES

To compare changes in upper airway volume after maxillary expansion with bone- and tooth-borne appliances in adolescents and to evaluate the dentoskeletal effects of each expansion modality.

MATERIALS AND METHODS

This retrospective study included 36 adolescents who had bilateral maxillary crossbite and received bone-borne maxillary expansion (average age: 14.7 years) or tooth-borne maxillary expansion (average age: 14.4 years). Subjects had two cone beam computed tomography images acquired, one before expansion (T₁) and a second after a 3-month retention period (T₂). Images were oriented, and three-dimensional airway volume and dentoskeletal expansion were measured. Analysis of variance was used to test for differences between the two expansion methods for pretreatment, posttreatment, and prepost changes. Paired t-tests were used to test for significance of prepost changes within each method.

RESULTS

Both groups showed significant increase only in nasal cavity and nasopharynx volume (P < .05), but not oropharynx and maxillary sinus volumes. Intermolar and maxillary width increased significantly in both groups (P < .05); however, the buccal inclination of maxillary molars increased significantly only in the tooth-borne group (P < .05). There was no significant difference between tooth- and bone-borne expansion groups, except for the significantly larger increase in buccal inclination of the maxillary right first molar after tooth-borne expansion.

CONCLUSIONS

In adolescents, both tooth- and bone-borne RME resulted in an increase in nasal cavity and nasopharynx volume, as well as expansion in maxillary intermolar and skeletal widths. However, only tooth-borne expanders caused significant buccal tipping of maxillary molars.

Preliminary Performance of the Advanced Dental Admission Test (ADAT): Association Between ADAT Scores and Other Variables for Applicants to Residency Programs at a U.S. Dental School

Historically, dental residency programs have used numerical assessment criteria to evaluate and identify qualified candidates for admission. Recent elimination of such assessment tools has undermined many programs' holistic evaluation process. The Advanced Dental Admission Test (ADAT) was developed and recently piloted in hopes of addressing this issue. The aim of this study was to evaluate the preliminary performance and validity of the ADAT by exploring the association between ADAT scores and other variables for a sample of applicants to residency programs. The WebAdMIT admissions database was used to identify the test scores and educational and demographic information of 92 individuals who completed the pilot ADAT and were seeking a 2017 postgraduate specialty position at Indiana University School of Dentistry. The results showed that the ADAT had strong to weak correlations with certain applicant variables (p<0.05). No significant differences were found for age, race, school location, or country of origin. However, males performed better than females (p<0.05), and non-Hispanics performed better than Hispanics (p<0.01). ADAT component scores were also higher for individuals with a history of research activity (p<0.05). This study found that significant associations existed between the ADAT and indices typically associated with competitive applicants. These findings suggest that the ADAT may serve as a useful numerical assessment instrument, with the potential to identify high-performing candidates. Furthermore, the ADAT seemed to be a plausible option for programs seeking to incorporate a quantitative assessment instrument as part of a holistic candidate selection process.

A Randomized Split-Mouth Clinical Trial on Effectiveness of Amnion-Chorion Membranes in Alveolar Ridge Preservation: A Clinical, Radiologic, and Morphometric Study

PURPOSE

Recent case reports suggest that amnion-chorion membranes (ACM) and dense polytetrafluoroethylene membranes (dPTFE) can be left exposed during ridge preservation. The aim of this study was to compare the effectiveness of these membranes in ridge preservation, particularly when they are intentionally left exposed.

MATERIALS AND METHODS

A split-mouth, single-blind, randomized trial design was used to compare treatments with the two membranes in 22 nonmolar sites on the same arch. Ridge dimensions were recorded clinically and with cone beam computed tomography prior to and 3 months after ridge preservation. Postoperative discomfort was recorded with Visual Analog Scale (VAS) forms. Mixed‑model analysis of variance was used to test significance.

RESULTS

Clinical and radiographic ridge dimensions were not significantly different between the two treatments. ACM sites had significantly more osteoid and higher bone volume density but significantly less graft particles and bone surface density compared with dPTFE. Mineralized bone area and soft tissue area were not significantly different between the two treatments. ACM sites had significantly lower postoperative VAS scores compared with dPTFE.

CONCLUSION

Intentionally exposed ACM is equally effective in ridge preservation compared with dPTFE. Additionally, ACM use may aid in reducing postoperative VAS scores, and potentially result in better quality of bone available for implant placement, as evidenced by improved histomorphometric measures.

The Relationship Between Hard Tissue and Soft Tissue Dimensions of the Nose in Children: A 3D Cone Beam Computed Tomography Study

This study using three-dimensional cone beam computed tomography (CBCT) images of children determined relationships between nasal skeletal and soft tissue measurements and assessed the association with sex, age, and skeletal maturation stage. Following reliability studies, skeletal and soft tissue parameters were measured on coded CBCTs of 73 children (28M:45F;6-13 yoa). Pearson and Mantel correlations were used to analyze associations between skeletal and soft tissues. Partial Mantel correlations were used to study the associations between skeletal and soft tissue, adjusting for sex, age, and skeletal maturation. Linear regression analyses were used to predict soft tissues sizes. Logistic regression was used to study the relationships between soft and skeletal tissue symmetry. Except for nasal aperture width and interalar width, skeletal landmarks best predicted corresponding soft tissue landmarks. Significant positive associations existed between skeletal and soft tissues after adjusting for sex, skeletal maturation, and age. Children's nasal skeletal tissues predicted nasal soft tissue reasonably well.

Three dimensional evaluation of alveolar bone changes in response to different rapid palatal expansion activation rates

INTRODUCTION

The aim of this multi-center retrospective study was to quantify the changes in alveolar bone height and thickness after using two different rapid palatal expansion (RPE) activation protocols, and to determine whether a more rapid rate of expansion is likely to cause more adverse effects, such as alveolar tipping, dental tipping, fenestration and dehiscence of anchorage teeth.

METHODS

The sample consisted of pre- and post-expansion records from 40 subjects (age 8-15 years) who underwent RPE using a 4-banded Hyrax appliance as part of their orthodontic treatment to correct posterior buccal crossbites. Subjects were divided into two groups according to their RPE activation rates (0.5 mm/day and 0.8 mm/day; n = 20 each group). Three-dimensional images for all included subjects were evaluated using Dolphin Imaging Software 11.7 Premium. Maxillary base width, buccal and palatal cortical bone thickness, alveolar bone height, and root angulation and length were measured. Significance of the changes in the measurements was evaluated using Wilcoxon signed-rank test and comparisons between groups were done using ANOVA. Significance was defined at p ≤ 0.05.

RESULTS

RPE activation rates of 0.5 mm per day (Group 1) and 0.8 mm per day (Group 2) caused significant increase in arch width following treatment; however, Group 2 showed greater increases compared to Group 1 (p < 0.01). Buccal alveolar height and width decreased significantly in both groups. Both treatment protocols resulted in significant increases in buccal-lingual angulation of teeth; however, Group 2 showed greater increases compared to Group 1 (p < 0.01).

CONCLUSION

Both activation rates are associated with significant increase in intra-arch widths. However, 0.8 mm/day resulted in greater increases. The 0.8 mm/day activation rate also resulted in more increased dental tipping and decreased buccal alveolar bone thickness over 0.5 mm/day.

Risk factors contributing to gingival recession among patients undergoing different orthodontic treatment modalities

OBJECTIVE

The aim of this study was to investigate the risk factors contributing to gingival recession among patients undergoing orthodontic treatment.

METHODS

Records of 100 Caucasian patients who completed orthodontic treatment were evaluated before and after treatment. Intercanine and molar widths, arch perimeter, arch depth, and keratinized gingival height were measured for both arches. The association of orthodontic treatment strategy (changing incisal inclination, expansion, and extraction), keratinized gingival height, and various other measurements with gingival recession was evaluated by using generalized linear mixed models with logistic regression analysis.

RESULTS

For each 1 mm increase in pre- and post-treatment keratinized gingival height, there was 0.77 and 0.51 times lower odds of gingival recession. For each 1 mm increase in post-treatment intercanine width, there was 0.80 times lower odds of gingival recession. And for each 1 mm increase in change in the arch depth, there was 1.16 times higher odds of gingival recession. For each 1 mm increase in pre- and post-treatment mandibular symphysis width, there was 0.47 and 0.39 times lower odds of gingival recession.

CONCLUSION

Regardless of the type of orthodontic treatment, increased keratinized gingival height, mandibular symphysis width, and post-treatment intercanine width lower the risk of gingival recession.

Three-dimensional evaluation of airway volume changes in two expansion activation protocols

The purpose of this study was to evaluate the airway volume changes associated with rapid maxillary expansion (RME) protocols using different activation rates. A sample of forty RME treated cases was classified into two groups according to the rate of RME activation (Group A: 0.8mm per day and Group B: 0.5mm per day). Three-dimensional images were obtained for each case before and three months after expansion. Dolphin imaging software was used to identify landmarks and calculate airway volumes. Intraclass correlation coefficient was used to confirm reliability and Wilcoxon signed rank tests were used for comparison between the initial and final measurements within each group and between groups. Significant increase in the nasal cavity volume for both groups was observed (P<0.0001 and P=0.001 for groups A and B respectively). The increase in nasopharynx volume was significant in the group with a more rapid activation rate (P=0.0006). Significant differences between the two groups in post-treatment changes were detected in the nasal cavity volume (P<0.0001), nasopharynx volume (P=0.0035), and soft palate area (P=0.0081). A more rapid activation rate results in a higher volume increase for the nasal cavity and nasopharynx than a slower activation rate.

Two-dimensional vs 3-dimensional comparison of alveolar bone over maxillary incisors with A-point as a reference

INTRODUCTION

Our objectives were to compare, relative to A-point, (1) bone thickness over the most forward maxillary incisor (MFMI) in 2 dimensions vs 3 dimensions, and (2) bone thickness and inclination of each maxillary incisor in 3 dimensions.

METHODS

Thirty-four cone-beam computed tomography (CBCT) images were coded, and 2-dimensional (2D) cephalograms were derived from each image using Dolphin software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). A-point and the MFMI crown were located. After reliability tests, alveolar bone buccal to 3 points on the MFMI root, bone to reference line Frankfort horizontal (FH)-A-point, and incisor inclination were measured. This procedure was repeated on the 3-dimensional (3D) CBCT images comparing MFMI with all maxillary incisors. The 2D and 3D measurements were compared using paired t tests, and 3D measurements were compared with analysis of variance. A 5% significance level was used for all tests.

RESULTS

The MFMI's buccal bone thickness at the root apices and the distance between buccal bone and FH-A-point line at 2 root points were significantly greater in 2 dimensions than in 3 dimensions. In 3 dimensions, bone thickness at MFMI's root apex and the distance from FH-A-point line at all root points were significantly greater than those of the lateral incisors. Bone buccal to MFMI was significantly smaller than at the lateral incisors 3 mm from the cementoenamel junction.

CONCLUSIONS

Evaluation of 2D CBCT derivations can result in overestimation of alveolar bone buccal to the maxillary incisor root apices compared with 3D evaluations. The anterior nasal spine obscures bone measurements over the maxillary incisors in 2 dimensions.

Accuracy and reliability of landmark-based, surface-based and voxel-based 3D cone-beam computed tomography superimposition methods

OBJECTIVES

To evaluate and compare the accuracy and reliability of 3 different methods of three-dimensional cone-beam computed tomography scans (3D CBCTs) superimpositions: landmark-based, surface-based and voxel-based.

MATERIALS AND METHODS

Pre- and post-orthodontic treatment CBCTs (T1 and T2) of 20 subjects with a mean age of 11 years were obtained. Seven points on the zygomatic arch and supraorbital region were selected to perform landmark-based superimposition. Surface-based and voxel-based superimpositions were performed using the anterior cranial base as a reference. Each superimposition method of T1 and T2 scans was repeated twice to assess the reliability. Accuracy of each technique was tested by superimposing duplicated sets of T1 scans. A total of 11 landmarks on the anterior cranial base, maxilla and mandible were located, and deviations of these landmarks on superimposed data were quantified to assess reliability and accuracy of all superimpositions.

RESULTS

There were no significant differences from zero when duplicated sets of T1 scans were superimposed using surface-based and voxel-based methods. Statistical significant differences were detected in several parameters when evaluating the accuracy of the landmark superimposition. Superimposition of T1 and T2 scans for testing the reliability revealed intraclass correlation coefficients greater than 0.90 for all measurements except for ACP-x and PNS-y of landmark-based method as well as ANS-x of voxel-based method.

CONCLUSIONS

Surface-based and voxel-based superimposition methods using the anterior cranial base as a reference structure were accurate and reliable in detecting changes in landmark positions when superimposing. Landmark-based superimposition method was reliable but less accurate than the other methods.

Influence of prenatal EGCG treatment and Dyrk1a dosage reduction on craniofacial features associated with Down syndrome

Trisomy 21 (Ts21) affects craniofacial precursors in individuals with Down syndrome (DS). The resultant craniofacial features in all individuals with Ts21 may significantly affect breathing, eating and speaking. Using mouse models of DS, we have traced the origin of DS-associated craniofacial abnormalities to deficiencies in neural crest cell (NCC) craniofacial precursors early in development. Hypothetically, three copies of Dyrk1a (dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A), a trisomic gene found in most humans with DS and mouse models of DS, may significantly affect craniofacial structure. We hypothesized that we could improve DS-related craniofacial abnormalities in mouse models using a Dyrk1a inhibitor or by normalizing Dyrk1a gene dosage. In vitro and in vivo treatment with Epigallocatechin-3-gallate (EGCG), a Dyrk1a inhibitor, modulated trisomic NCC deficiencies at embryonic time points. Furthermore, prenatal EGCG treatment normalized some craniofacial phenotypes, including cranial vault in adult Ts65Dn mice. Normalization of Dyrk1a copy number in an otherwise trisomic Ts65Dn mice normalized many dimensions of the cranial vault, but did not correct all craniofacial anatomy. These data underscore the complexity of the gene–phenotype relationship in trisomy and suggest that changes in Dyrk1a expression play an important role in morphogenesis and growth of the cranial vault. These results suggest that a temporally specific prenatal therapy may be an effective way to ameliorate some craniofacial anatomical changes associated with DS.

Skeletal and dental effects of rapid maxillary expansion assessed through three-dimensional imaging: A multicenter study

OBJECTIVES

The aim of this study was to determine the skeletal and dental changes in rapid maxillary expansion treatments in two different populations assessed through cone-beam computer tomography (CBCT).

MATERIALS AND METHODS

Twenty-one patients from Edmonton, Canada and 16 patients from Cairo, Egypt with maxillary transverse deficiency (11-17 years old) were treated with a tooth-borne maxillary expander (Hyrax). CBCTs were obtained from each patient at two time points (initial T1 and at removal of appliance at 3-6 months T2). CBCTs were analyzed using AVIZO software and landmarks were placed on skeletal and dental anatomical structures on the cranial base, maxilla and mandible. Descriptive statistics, intraclass correlation coefficients and one-way ANOVA analysis were used to determine if there were skeletal and dental changes and if these changes were statistically different between both populations.

RESULTS

Descriptive statistics show that dental changes were larger than skeletal changes for both populations. Skeletal and dental changes between populations were not statistically different (P<0.05) from each other with the exception of the upper incisor proclination being larger in the Indiana group (P>0.05).

CONCLUSION

Rapid maxillary expansion treatments in different populations demonstrate similar skeletal and dental changes. These changes are greater on the dental structures compared to the skeletal ones in a 4:1 ratio.

The association of malocclusion and trumpet performance

OBJECTIVE

To determine whether trumpet performance skills are associated with malocclusion.

MATERIALS AND METHODS

Following institutional review board approval, 70 university trumpet students (54 male, 16 female; aged 20-38.9 years) were consented. After completing a survey, the students were evaluated while playing a scripted performance skills test (flexibility, articulation, range, and endurance exercises) on their instrument in a soundproof music practice room. One investigator (trumpet teacher) used a computerized metronome and a decibel meter during evaluation. A three-dimensional (3D) cone-beam computerized tomography scan (CBCT) was taken of each student the same day as the skills test. Following reliability studies, multiple dental parameters were measured on the 3D CBCT. Nonparametric correlations (Spearman), accepting P < .05 as significant, were used to determine if there were significant associations between dental parameters and the performance skills.

RESULTS

Intrarater reliability was excellent (intraclass correlations; all r values > .94). Although associations were weak to moderate, significant negative associations (r ≤ -.32) were found between Little's irregularity index, interincisal inclination, maxillary central incisor rotation, and various flexibility and articulation performance skills, whereas significant positive associations (r ≤ .49) were found between arch widths and various skills.

CONCLUSIONS

Specific malocclusions are associated with trumpet performance of experienced young musicians.

Cone-Beam Computed Tomography Analysis of Mucosal Thickening in Unilateral Cleft Lip and Palate Maxillary Sinuses

OBJECTIVE

To compare maxillary mucosal thickening and sinus volumes of unilateral cleft lip and palate subjects (UCLP) with noncleft (nonCLP) controls.

DESIGN

Randomized, retrospective study of cone-beam computed tomographs (CBCT).

SETTING

University.

PATIENTS

Fifteen UCLP subjects and 15 sex- and age-matched non-CLP controls, aged 8 to 14 years.

MAIN OUTCOME MEASURE

Following institutional review board approval and reliability tests, Dolphin three-dimensional imaging software was used to segment and slice maxillary sinuses on randomly selected CBCTs. The surface area (SA) of bony sinus and airspace on all sinus slices was determined using Dolphin and multiplied by slice thickness (0.4 mm) to calculate volume. Mucosal thickening was the difference between bony sinus and airspace volumes. The number of slices with bony sinus and airspace outlines was totaled. Right and left sinus values for each group were pooled (t tests, P > .05; n = 30 each group). All measures were compared (principal components analysis, multivariate analysis of variance, analysis of variance) by group and age (P ≤ .016 was considered significant).

RESULTS

Principal components analysis axis 1 and 2 explained 89.6% of sample variance. Principal components analysis showed complete separation based on the sample on axis 1 only. Age groups showed some separation on axis 2. Unilateral cleft lip and palate subjects had significantly smaller bony sinus and airspace volumes, fewer bony and airspace slices, and greater mucosal thickening and percentage mucosal thickening when compared with controls. Older subjects had significantly greater bony sinus and airspace volumes than younger subjects.

CONCLUSIONS

Children with UCLP have significantly more maxillary sinus mucosal thickening and smaller sinuses than controls.

Three-dimensional computed tomography analysis of airway volume changes between open and closed jaw positions

INTRODUCTION

Airway dimensions are closely linked to the bone and soft-tissue craniofacial anatomy. Reduction of the airway is seen with airway disorders and can impair function. The purpose of this retrospective study was to determine whether changing from open to closed jaw position affects the volume of the nasal cavity, nasopharynx, and oropharynx; the soft palate; the soft-tissue thickness of the airway; and the most constricted area of the airway.

METHODS

Following reliability studies, in this retrospective study, we analyzed cone-beam computed tomography scans taken in both closed and open jaw positions of 60 subjects who were undergoing diagnosis and treatment of temporomandibular disorders. On each scan, condyle-fossa measurements, volumes of airway segments (nasal cavity, nasopharynx, oropharynx), soft palate areas, soft tissue thicknesses of the airway, and the most constricted area of the airway and its location were measured using Dolphin imaging software (version 11.5; Patterson Dental Supply, Chatsworth, Calif). Differences between the 2 jaw positions were analyzed with paired t tests, accepting P ≤0.05 as significant.

RESULTS

Significant changes in airway dimensions were found between the closed and open jaw positions. With jaw opening, the nasopharynx volume increased, whereas the oropharynx volume decreased. Significant decreases were also found for measurements of basion to posterior airway wall, cervical vertebrae to posterior airway wall, most constricted area, nasal cavity volume, and soft palate area when the jaw was open.

CONCLUSIONS

Changing jaw position significantly affects airway dimensions.

Computational fluid dynamics analysis of the upper airway after rapid maxillary expansion: a case report

Background

Assessment of the upper airway volume, morphology, and mechanics is of great importance for the orthodontic patient. We hypothesize that upper airway dimensions have significant effects on the dynamics of the airway flow and that both the dimensions and mechanics of the upper airway are greatly affected by orthodontic and orthopedic procedures such as rapid maxillary expansion (RME). The aim of the current study was to assess the effect of RME on the airway flow rate and pattern by comparing the fluid dynamics results of pre- and post-treatment finite element models.

Methods

Customized pre- and post-treatment computational fluid dynamics models of the patient’s upper airway were built for comparison based on three-dimensional computed tomogram. The inhalation process was simulated using a constant volume flow rate for both models, and the wall was set to be rigid and stationary. Laminar and turbulent analyses were applied.

Results

Comparisons between before and after RME airway volume measurements showed that increases were only detected in nasal cavity volume, nasopharynx volume, and the most constricted area of the airway. Pressure, velocity, and turbulent kinetic energy decreased after dental expansion for laminar and turbulent flow. Turbulent flow shows relatively larger velocity and pressure than laminar flow.

Conclusions

RME showed positive effects that may help understand the key reasons behind relieving the symptom of breathing disorders in this patient. Turbulence occurs at both nasal and oropharynx areas, and it showed relatively larger pressure and velocity compared to laminar flow.

Microdamage generation by tapered and cylindrical mini-screw implants after pilot drilling

OBJECTIVE

To investigate the relationship between mini-screw implant (MSI) diameter (1.6 vs 2.0 mm) and shape (tapered vs cylindrical) and the amount of microdamage generated during insertion.

MATERIALS AND METHODS

Thirty-six cylindrical and 36 tapered MSIs, 6 mm long, were used in this study. Half of each shape was 1.6 mm in diameter, while the other half was 2.0 mm. After pilot drilling, four and five MSIs were inserted, respectively, into fresh cadaveric maxillae and mandibles of dogs. Bone blocks containing the MSIs were sectioned and ground parallel to the MSI axis. Epifluorescent microscopy was used to measure overall cortical thickness, crack length, and crack number adjacent to the MSI. Crack density and total microdamage burden per surface length were calculated. Three-way analysis of variance (ANOVA) was used to test the effects of jaw, and MSI shape and diameter. Pairwise comparisons were made to control the overall significance level at 5%.

RESULTS

The larger (2.0 vs 1.6 mm) cylindrical MSIs increased the numbers, lengths, and densities of microcracks, and the total microdamage burden. The same diameter cylindrical and tapered MSIs generated a similar number of cracks and crack lengths. More total microdamage burden was created by the 2.0-mm cylindrical than the 2.0-mm tapered MSIs. Although higher crack densities were produced by the insertion of 1.6-mm tapered MSIs, there was no difference in total microdamage burden induced by 1.6-mm tapered and 1.6-mm cylindrical MSIs.

CONCLUSIONS

Pilot drilling is effective in reducing microdamage during insertion of tapered MSIs. To prevent excessive microdamage, large diameter and cylindrical MSIs should be avoided.

Nasal airway and septal variation in unilateral and bilateral cleft lip and palate

Cleft lip and palate (CLP) affects the dentoalveolar and nasolabial facial regions. Internal and external nasal dysmorphology may persist in individuals born with CLP despite surgical interventions. 7-18 year old individuals born with unilateral and bilateral CLP (n = 50) were retrospectively assessed using cone beam computed tomography. Anterior, middle, and posterior nasal airway volumes were measured on each facial side. Septal deviation was measured at the anterior and posterior nasal spine, and the midpoint between these two locations. Data were evaluated using principal components analysis (PCA), multivariate analysis of variance (MANOVA), and post-hoc ANOVA tests. PCA results show partial separation in high dimensional space along PC1 (48.5% variance) based on age groups and partial separation along PC2 (29.8% variance) based on CLP type and septal deviation patterns. MANOVA results indicate that age (P = 0.007) and CLP type (P ≤ 0.001) significantly affect nasal airway volume and septal deviation. ANOVA results indicate that anterior nasal volume is significantly affected by age (P ≤ 0.001), whereas septal deviation patterns are significantly affected by CLP type (P ≤ 0.001). Age and CLP type affect nasal airway volume and septal deviation patterns. Nasal airway volumes tend to be reduced on the clefted sides of the face relative to non-clefted sides of the face. Nasal airway volumes tend to strongly increase with age, whereas septal deviation values tend to increase only slightly with age. These results suggest that functional nasal breathing may be impaired in individuals born with the unilateral and bilateral CLP deformity.

Effects of tobacco on cytokine expression from human endothelial cells

OBJECTIVE

To investigate the effects of nicotine and cigarette smoke condensate (CSC) exposure on cytokine expression from human endothelial cells in order to identify one possible mechanism that smoking plays in the pathogenesis of both periodontal disease (PDD) and cardiovascular disease (CVD).

METHODS

Human endothelial cells (HUVECs) were exposed to different concentrations of nicotine and CSC to examine the effects that they have on cell proliferation and cytotoxicity. Non-toxic levels were then used to examine cytokine expression using cytokine protein arrays.

RESULTS

Exposure to nicotine caused significant down-regulation in the expression of IL-10 (P = 0.046), growth-regulated oncogene (GRO)α (P = 0.036), MCP-1 (P = 0.046), and GMCSF (P = 0.004) compared with the control untreated HUVECs. Exposure to CSC caused significant down-regulation in the expression of GRO (P = 0.04), GROα (P = 0.01), IL-6 (P = 0.03), and MCP-1 (P = 0.04) compared with the control untreated HUVECs.

CONCLUSIONS

Exposure of HUVECs to nicotine or CSC affects the levels of cytokine expression including reduction in anti-inflammatory and chemoattractant cytokines. This may subsequently affect the host defensive mechanisms of the tissues. The action of toxic chemicals in tobacco smoke on endothelial cells is a potential pathogenic mechanism that may in part explain the association between tobacco, PDD, and CVD.

The use of cone beam computed tomography for the assessment of trichorhinophalangeal syndrome, type I - a case report

Trichorhinophalangeal syndrome type I is a rare autosomal dominant disorder characterized by cone-shaped epiphysis, sparse fine hair, pear-shaped nose and variable growth retardation. The typical craniofacial features include thin upper lip, elongated philtrum, large outstanding ears, shortened posterior facial height associated with short mandibular ramus and reduced and superiorly deflected posterior cranial base. This report describes a 17-year-old male patient with trichorhinophalangeal syndrome type I and a detailed description of the craniofacial radiographic findings, including the use of cone beam computed tomography images for determination of the airway and temporomandibular joint discrepancies.

Measurements from conventional, digital and CT-derived cephalograms: a comparative study

OBJECTIVE

The purpose of this retrospective radiographic study was to determine the reliability and reproducibility of skeletal and dental measurements of lateral cephalograms created from a computerised tomography (CT) scan compared with conventional and digital lateral cephalograms.

METHODS

CT and conventional lateral cephalograms of the same patients were obtained from university archives. The lateral cephalometric radiographs of 30 patients were manually traced. The radiographs were subsequently scanned and traced using Dolphin Imaging software version 11 (Dolphin Imaging, Chatsworth, CA, USA). The CT-created lateral cephalograms were also traced using the same software. Sixteen (10 angular and 6 linear) measurements were performed. Cephalometric measurements obtained from conventional, digital and CT-created cephalograms were statistically compared using repeated measures analysis of variance (ANOVA). Statistical significance was set at the p < 0.05 level of confidence.

RESULTS

The intra-rater reliability test for each method showed high values (r > 0.90) except for mandibular length which had a correlation of 0.82 for the CT-created cephalogram. Five measurements (N-A-Pog, N-S, ANS-PNS, Co-ANS and CoGn) were found to be significantly different between the CT-created and conventional cephalograms and three measurements (SNB, ANB, and/1-MP) were found to be significantly different between the CT-created and digital cephalograms.

CONCLUSIONS

There are statistically-significant differences in measurements produced using a traditional manual analysis, a direct digital analysis or a 3D CT-derived cephalometric analysis of orthodontic patients. These differences are, on average, small but because of individual variation, may be of considerable clinical significance in some patients.

Three-dimensional computed tomography analysis of airway volume changes after rapid maxillary expansion

INTRODUCTION

In this retrospective study with 3-dimensional computed tomography, we evaluated airway volume, soft-palate area, and soft-tissue thickness changes before and after rapid maxillary expansion in adolescents. Another purpose was to determine whether rapid maxillary expansion caused changes in the palatal and mandibular planes and facial height.

METHODS

The sample comprised 20 patients who were treated with rapid maxillary expansion. Spiral tomographs were taken before and 3 months after treatment. Reliability studies were performed, and then volumetric, soft-palate area, soft-tissue thickness, and cephalometric parameters were compared on the tomographs. Intraclass correlations were performed on the reliability measurements. Before and after rapid maxillary expansion measurements were compared by using Wilcoxon signed rank tests. Spearman correlation coefficients were used to evaluate the associations among the airway volume, soft-palate area, soft-tissue thickness, and cephalometric measurements. Significance was accepted at P ≤0.05 for all tests.

RESULTS

Intraclass correlation coefficients were ≥0.90 for all reliability measures. Significant increases from before to after rapid maxillary expansion were found in nasal cavity and nasopharynx volumes, and for the measurements of MP-SN, S-PNS, N-ANS, ANS-Me, and N-Me. Significant positive correlations existed between changes in PP-SN and N-ANS, and ANS-Me and N-Me.

CONCLUSIONS

Rapid maxillary expansion causes significant increases in nasal cavity volume, nasopharynx volume, anterior and posterior facial heights, and palatal and mandibular planes.

Effects of rapid maxillary expansion on the cranial and circummaxillary sutures

INTRODUCTION

The aim of this study was to determine whether the orthopedic forces of rapid maxillary expansion cause significant quantitative changes in the cranial and the circummaxillary sutures.

METHODS

Twenty patients (mean age, 12.3 ± 1.9 years) who required rapid maxillary expansion as a part of their comprehensive orthodontic treatment had preexpansion and postexpansion computed tomography scans. Ten cranial and circummaxillary sutures were located and measured on one of the axial, coronal, or sagittal sections of each patient's preexpansion and postexpansion computed tomography scans. Quantitative variables between the 2 measurements were compared by using the Wilcoxon signed rank test. A P value less than 0.05 was considered statistically significant.

RESULTS

Rapid maxillary expansion produced significant width increases in the intermaxillary, internasal, maxillonasal, frontomaxillary, and frontonasal sutures, whereas the frontozygomatic, zygomaticomaxillary, zygomaticotemporal, and pterygomaxillary sutures showed nonsignificant changes. The greatest increase in width was recorded for the intermaxillary suture (1.7 ± 0.9 mm), followed by the internasal suture (0.6 ± 0.3 mm), and the maxillonasal suture (0.4 ± 0.2 mm). The midpalatal suture showed the greatest increase in width at the central incisor level (1.6 ± 0.8 mm) followed by the increases in width at the canine level (1.5 ± 0.8 mm) and the first molar level (1.2 ± 0.6 mm).

CONCLUSIONS

Forces elicited by rapid maxillary expansion affect primarily the anterior sutures (intermaxillary and maxillary frontal nasal interfaces) compared with the posterior (zygomatic interface) craniofacial structures.

Skeletal and dental changes after rapid maxillary expansion: a computed tomography study

OBJECTIVES

To investigate the skeletal and dental changes induced by rapid maxillary expansion, using computed tomography (CT) scans and three-dimensional (3-D) reconstructed images.

METHODS

Twenty patients (Mean age: 12.3 +/- 1.9 years) who required rapid maxillary expansion as a part of their comprehensive orthodontic treatment underwent pretreatment (T1) and post-treatment (T2) CT scans. The T2--T1 differences between selected skeletal and dental measurements on the coronal CT and 3-D volumetric images were compared using the Wilcoxon signed ranks test.

RESULTS

At T2 the Maxillary alveolar width (4.5 +/- 3.5 mm) was greater than the Maxillary base width (1.7 +/- 0.9 mm). The greatest transverse dental change was in the Intermolar width (6.3 +/- 2.1 mm and 2.7 +/- 1.9 mm at the crown and the apex, respectively). On the 3-D volume, significant increases occurred in the Bicondylar width (1.2 +/- 1.3 mm), Bimaxillo-mandibular width (2.1 +/- 2.3 mm) and the Maxillary width (2.5 +/- 1.6 mm). The greatest change in the dental measurements was in the Maxillary first molar width (6.4 +/- 0.1 mm). The Maxillary central incisor angle decreased significantly (-7.9 +/- 8.4 mm), indicating an increase in the distance between the apices of the central incisors.

CONCLUSION

Volumetric 3-D CT scanning provides a useful method for assessing skeletal and dental changes after rapid maxillary expansion. Although significant increases occurred in most skeletal and dental measures, it appears that dental tipping explains most of the expansion.

In vivo effects of zoledronic acid on oral mucosal epithelial cells

OBJECTIVE

Osteonecrosis of the jaw is a serious complication of bisphosphonate treatment for which the pathophysiology is unknown. The purpose of this study was to investigate whether in vivo zoledronic acid (ZA) induces alterations in cell proliferation, apoptosis, and matrix metalloproteinases (MMPs) expression in oral mucosal epithelial cells.

METHODS

One-year-old dogs were either untreated (control group) or given high doses of intravenous ZA (ZA group) for 3 months. The doses of ZA were equivalent to those given to cancer patients, yet were administered two times more frequently (every 2 weeks). Mucosal tissues were assessed immunohistochemically for cell proliferation (proliferating cell nuclear antigen, PCNA), matrix metalloproteinase (MMP) expression, and apoptosis (caspase 3 and TUNEL).

RESULTS

There were no significant differences between the groups with respect to PCNA, MMP-2, MMP-14, and TUNEL positive cells. However, the expression of MMP-9 was significantly higher in the control group than in the ZA group (P < 0.05), whereas the expression of caspase 3 was significantly lower in the control group than in the ZA group (P < 0.05).

CONCLUSION

  These results suggest that high doses of ZA resulted in higher levels of apoptosis and lower levels of MMP-9 in the oral epithelial cells supporting the idea of bisphosphonate treatment affects the oral mucosa.