Effect of Orthognathic Surgery On Pulp Blood Flow and Pulp Sensibility: A Prospective Control Trial

INTRODUCTION

Orthognathic surgery has the potential to compromise the vitality of the teeth. This paper aims to assess changes in pulp blood flow (PBF) and pulp sensibility (PS) of the anterior dentition following orthognathic surgery and to assess the influence of the proximity of the surgical osteotomy on the PBF and/or PS.

METHODS

Twenty-six patients undergoing orthognathic surgery (Le Fort I or bilateral sagittal split osteotomy [BSSO]) were compared to sixteen control patients treated by fixed appliances only using Laser Doppler flowmeter (LDF) and thermal testing (CO2 snow). Surgery patients were tested at T1 (presurgery), T2 (4-5 weeks postsurgery), T3 (3 months postsurgery), and T4 (6 months postsurgery). Control patients were tested at T1 (pretreatment), T2 (6 months posttreatment), T3 (12 months posttreatment), and T4 (18 months posttreatment). Differences between the maxilla and mandible were assessed.

RESULTS

No differences in PBF or PS were recorded in the control group. In the surgery group, both jaws followed the same pattern after surgery, an initial decrease at T2 followed by a gradual recovery to pretreatment PBF levels with no significant difference between T1 versus T4 in both jaws. No difference in PBF was observed between the maxilla and mandible at any testing time interval.

CONCLUSIONS AND CLINICAL IMPLICATIONS

PBF and PS of the anterior dentition was severely affected immediately postsurgery, followed by a gradual increase to full recovery. This pattern of recovery was exhibited in both jaws. A negative sensibility response or discoloration should not be seen as an indication of irreversible ischemic pulp changes. Monitoring for at least 6 months or using LDF as a confirmatory test is required before any irreversible endodontic treatment is to be considered.

Skeletal stability of inter-molar mandibular distraction osteogenesis in growing patients

INTRODUCTION

The aim of this retrospective study was to firstly assess the stability of surgical advancement using inter-molar mandibular distraction osteogenesis (IMDO) and secondly to assess the impact of the surgical intervention on subsequent mandibular growth in patients with residual growth.

METHODS

The sample consisted of 17 (13F and 4M) consecutively treated patients who underwent IMDO and orthodontic treatment. Cephalometric analysis was performed at three time points: T0 prior to distraction; T1 post-distraction immediately prior to surgical removal of the distractors; and T2 following completion of orthodontic treatment when the final lateral cephalogram was taken (0.86-4.37 years after T1). Statistical comparison of lower facial height, mandibular length, growth, condylar position and anterior mandibular rotation was performed.

RESULTS

No association was found between changes in any of the cephalometric measurements and the length of the follow-up interval. The anterior mandibular segment underwent clockwise rotation during distraction and recovered to near its pre-distraction angulation during remodelling. An increase in the lower facial height of 1.88 ± 2.81mm also occurred during distraction (T0-T1) and was maintained during the follow-up period (T1-T2). Post-distraction (T1-T2) growth of lower facial height (p value 0.872) and mandibular length (p value 0.251) showed no association when compared to an untreated control group and an overall reduction in growth was reported.

CONCLUSIONS

IMDO was highly stable within a follow-up period of 2.3 ± 0.9 years; however, growth appears to have been inhibited.

An evaluation of gingival phenotype and thickness as determined by indirect and direct methods

OBJECTIVES

To evaluate gingival phenotype (GP) and thickness (GT) using visual, probing, and ultrasound (US) methods and to assess the accuracy and consistency of clinicians to visually identify GP.

MATERIALS AND METHODS

The GP and GT of maxillary and mandibular anterior teeth in 29 orthodontic patients (mean age 25 ± 7.5 years) were assessed using probing and US by a single examiner. General dentist and dental specialist assessors (n = 104) were shown intraoral photographs of the patients, including six repeated images, and asked to identify the GP via a questionnaire.

RESULTS

An increasing trend in GT values of thin, medium, and thick biotype probe categories was found, though this was not statistically significant (P = .188). Comparison of probing method to determinations of GT made by US yielded slight agreement (κ = 0.12). Using the visual method, assessors' identification of the second GP determination ranged from poor to moderate agreement (κ = 0.29 to κ = 0.53).

CONCLUSIONS

The probe method is sufficient in differentiating between different categories of GP. However, further research is required to assess the sensitivity of the probe method in recognizing phenotypes in the most marginal of cases. Assessors using the visual method lack the ability to identify GP accurately and consistently among themselves.

Effect of craniofacial morphology on gingival parameters of mandibular incisors

OBJECTIVES

To investigate the association between the width of keratinized gingiva (WKG), gingival phenotype (GP), and gingival thickness (GT) with craniofacial morphology in sagittal and vertical dimensions.

MATERIALS AND METHODS

WKG, GP, and GT of mandibular anterior teeth in 177 preorthodontic patients (mean age 18.38 ± 5.16 years) were assessed clinically using a periodontal probe, a Colorvue Biotype Probe, and ultrasound by a single examiner. Patients were grouped into skeletal Class I, II, and III and hyperdivergent, normodivergent, and hypodivergent based on ANB and SN-MP angles. Mandibular incisor inclination (L1-NB) was also measured. Clinical and cephalometric measurements were repeated to assess inter- and intraexaminer reproducibility.

RESULTS

A significant association was found between thin GP and skeletal Classes I and III for the left mandibular central incisor (MCI; P = .0183). In skeletal Class III patients, L1-NB angle demonstrated a decreasing trend as phenotype thickness decreased. A significant association was found between thin phenotype and normodivergent and hypodivergent groups for MCIs (left: P = .0009, right: P = .00253). No significant association between WKG or GT and craniofacial morphology was found.

CONCLUSIONS

Thin GP is associated with skeletal Class I and III for the left MCI. Thin GP is associated with hypodivergent and normodivergent skeletal patterns for the MCIs. There was no association between WKG and GT and craniofacial morphology in both skeletal and vertical dimensions. Dental compensations that exist due to different craniofacial morphology may influence the GP.

Accuracy of mandibular repositioning surgery using new technology: Computer-aided design and manufacturing customized surgical cutting guides and fixation plates

INTRODUCTION

Recent 3-dimensional technology advancements have resulted in new techniques to improve the accuracy of intraoperative transfer. This study aimed to validate the accuracy of computer-aided design and manufacturing (CAD-CAM) customized surgical cutting guides and fixation plates on mandibular repositioning surgery performed in isolation or combined with simultaneous maxillary repositioning surgery.

METHODS

Sixty patients who underwent mandibular advancement surgery by the same surgeon were retrospectively evaluated by 3-dimensional surface-based superimposition. A 3-point coordinate system (x, y, z) was used to identify the linear and angular discrepancies between the planned movements and actual outcomes. Wilcoxon rank sum test was used to compare the outcomes between the mandible-only and the bimaxillary surgery groups with significance at P <0.05. Pearson correlation coefficient compared planned mandible advancement to the outcome from advancement planned. The centroid, which represents the mandible as a single unit, was computed from 3 landmarks, and the discrepancies were evaluated by the root mean square error (RMSE) for clinical significance set at 2 mm for linear discrepancies and 4° for angular discrepancies.

RESULTS

There was no statistically significant difference between the planned and actual position of the mandible in either group when considering absolute values of the differences. When considering raw directional data, a statistically significant difference was identified in the y-axis suggesting a tendency for under-advancement of the mandible in the bimaxillary group. The largest translational RMSE for the centroid was 0.77 mm in the sagittal dimension for the bimaxillary surgery group. The largest rotational RMSE for the centroid was 1.25° in the transverse dimension for the bimaxillary surgery group. Our results show that the precision and clinical feasibility of CAD-CAM customized surgical cutting guides and fixation plates on mandibular repositioning surgery is well within clinically acceptable parameters.

CONCLUSION

Mandibular repositioning surgery can be performed predictably and accurately with the aid of CAD-CAM customized surgical cutting guides and fixation plates with or without maxillary surgery.

Sleep-disordered breathing in children seeking orthodontic care-an Australian perspective

BACKGROUND

The prevalence of sleep-disordered breathing in children is underestimated due to impediments in detection and diagnosis. Consequently, delayed management may affect the quality of life and the growth and development of a child. Due to their patient demographic, orthodontists are optimally positioned to identify those at risk of sleep-disordered breathing and make referrals for investigation and management. This study aims to determine the prevalence of children at risk of sleep-disordered breathing in an Australian orthodontic population.

METHODS

A 1-year retrospective study was conducted in an urban Western Australian private orthodontic practice with two branches in similar socioeconomic demographics. The responses of new patients to a modified paediatric sleep questionnaire and standard medical history form were recorded.

RESULTS

In 1209 patients (4-18 years), 7.3% were at risk of sleep-disordered breathing. An association between sex and the potential risk of sleep-disordered breathing was found with 11% of males at risk of sleep-disordered breathing compared to 7% of females (P = 0.012).

CONCLUSIONS

The relatively high prevalence of children at risk of sleep-disordered breathing presenting for orthodontic care presents an opportunity to identify at-risk individuals through routine use of the paediatric sleep questionnaire. This would facilitate early referral for diagnosis and management of sleep-disordered breathing.

The predictability of expansion with Invisalign: A retrospective cohort study

INTRODUCTION

Few studies have evaluated the predictability of expansion with Invisalign for the current SmartTrack material.

METHODS

Pretreatment, predicted, and posttreatment digital models from Invisalign's ClinCheck software were obtained for 57 adult patients with a planned arch expansion of at least 3 mm. Arch width measurements were collected using a software measuring tool (MeshLab), Invisalign's arch width table, and the centroid of the clinical crown. Data for 30 patients were remeasured for each method to assess intrarater reliability. Predictability of expansion was calculated by comparing the amount of achieved expansion to predicted expansion.

RESULTS

The predictability of expansion across centroids for the maxillary teeth was: 72.2% canines, 78.9% first premolars, 81.1% second premolars, 63.5% first molars, and 41.5% second molars. The predictability of expansion across centroids for the mandibular teeth was: 82.3% canines, 93.0% first premolars, 87.7% second premolars, 79.8% first molars, and 42.9% second molars. The average expansion was significantly different from that predicted for each type of tooth in both the maxilla and mandible. Both underexpansion and overexpansion were observed. Arch width measurement reliability for each employed method was as follows: MeshLab (average error 0.197 mm); calculated centroids (0.002 mm); ClinCheck arch width table (0.000 mm).

CONCLUSIONS

On average, the amount of predicted expansion is not achieved with the Invisalign system and varies according to tooth type and arch. Discretion is required when overcorrecting to compensate for expansion inaccuracy. Both underexpansion and overexpansion were observed; further investigation into factors influencing underexpansion and overexpansion is required.

The impact of mini-implant hybrid hyrax maxillary expansion on pulp blood flow and sensibility in healthy and traumatized teeth: A prospective study

INTRODUCTION

We aimed to assess pulp blood flow (PBF) and pulp sensibility changes in healthy and traumatized teeth undergoing maxillary expansion with a mini-implant hybrid hyrax appliance.

METHODS

Forty-five patients requiring maxillary expansion either with mini-implant supported hyrax expander (MARME) or tooth-borne hyrax expander (RME) had the pulp status of their maxillary anterior teeth assessed using laser Doppler flowmetry, electric pulp testing, and thermal testing (carbon dioxide snow). The study cohort was divided into 4 groups on the basis of expansion appliance (MARME or RME) and trauma experience (trauma or nontrauma). Each patient was tested before expansion, 2 weeks after expansion, and 3 months after expansion (T3). Relationships between PBF, time interval, and trauma were evaluated using linear mixed modeling.

RESULTS

Healthy teeth with RME or MARME expansion had reestablished pretreatment PBF at T3 (P >0.05). Traumatized teeth undergoing RME did not reach pretreatment PBF at T3 (P ≤0.05). There were no statistically significant changes in PBF in the MARME+Trauma group at all time intervals (P >0.05). A reduction in pulp blood flow occurred during rapid maxillary expansion from both expansion appliances; however, the relative reduction of PBF in MARME was less than with RME (P ≤0.05) 2 weeks after expansion. Most teeth across all groups (≥85%) maintained pulp sensibility at all time intervals regardless of whether there was a history of trauma.

CONCLUSIONS

Patients with transverse discrepancies and a history of trauma may benefit from MARME as evidenced by reduced changes in PBF compared with RME without affecting pulp sensibility.

Trends in orthodontic management strategies for patients with congenitally missing lateral incisors and premolars

OBJECTIVES

To identify changes in orthodontic management strategies in patients with hypodontia seen in 2000, 2010, and 2017/2018 (during a 1-year period).

MATERIALS AND METHODS

An assessment of the panoramic radiographs of 3701 patients from a Western Australian private practice identified 276 individuals demonstrating hypodontia. The location of missing teeth, age, sex, type of malocclusion, and the management strategies (space closure or opening) for each patient were noted.

RESULTS

Most hypodontia involved agenesis of three or fewer teeth (90%). Maxillary lateral incisors and mandibular second premolars were the most commonly missing teeth. Female preponderance was noted. When considering treatment, the odds ratio for orthodontic space opening and prosthetic replacement in 2000 was 3.266 (P value = 7e-04; 95% confidence interval [CI], 1.464-4.633) compared with patients seen in 2010 and 1.632 (P value = 7e-04; 95% CI, 0.811-2.434) compared with patients in 2017/2018. For patients demonstrating bilateral absence of maxillary lateral incisors, the odds ratio for orthodontic space opening was 3.185 (P value = 0.0215; 95% CI, 1.182-9.243) compared with counterparts with unilateral agenesis. None of the factors investigated were significantly associated with the types of treatment planned/provided for the patients with missing mandibular second premolars.

CONCLUSIONS

Maxillary lateral incisors and mandibular second premolars were the most commonly missing teeth. A trend away from space opening and prosthetic replacement toward orthodontic space closure was observed from 2000 to 2017/2018. This may reflect a change in attitude toward prosthetic replacement options and/or greater optimism with biomechanical strategies since the implementation of temporary anchorage devices to assist in space closure.

Accuracy of mandibular proximal segment position using virtual surgical planning and custom osteosynthesis plates

The purpose of this study was to determine whether the use of custom osteosynthesis plates increased the accuracy of proximal segment position following bilateral sagittal split osteotomy in a cohort of 30 patients when compared to a control group of 25 patients who had surgery with conventional plates. Surgery was performed by a single surgeon between October 2015 and December 2017. Post-surgical cone beam computed tomography scans were segmented using Mimics Innovation Suite (Materialise NV), and surface-based superimposition was achieved using ProPlan CMF (Materialise NV). However, there was a tendency for the rotational error to be smaller in the custom group than in the control group. The root mean square error in both groups and for all variables fell within clinical parameters of 2 mm and 4°. In conclusion, the results of this study indicate that customized mandibular fixation plates do not necessarily improve the accuracy of the proximal segments post-surgically; however they may be of benefit in individual patients.

Accuracy of maxillary repositioning surgery using CAD/CAM customized surgical guides and fixation plates

The advent of three-dimensional imaging and computer-aided surgical simulation (CASS) have brought about a paradigm shift in surgical planning. The aim of this study was to assess the accuracy of maxillary repositioning surgery using computer-aided design and manufacturing (CAD/CAM) customized titanium surgical guides and fixation plates. Thirty consecutive adult patients, 13 male and 17 female, with a mean age of 29.2 years and 25.5 years, respectively, requiring Le Fort I maxillary osteotomy, with or without simultaneous mandibular surgery, were evaluated retrospectively. All orthognathic surgeries were performed by one experienced surgeon. The pre-surgical and post-surgical volumetric imaging were superimposed to assess the linear and angular differences between the planned and actual positions of the maxilla following surgery. With the use of the CAD/CAM titanium surgical guides and fixation plates, all surgical movements were within 2mm and 4° of the planned movements, which is considered clinically insignificant. The overall root mean square error between the planned and actual surgical movements was 0.38mm in the transverse dimension, 0.64mm in the anteroposterior dimension, and 0.55mm in the vertical dimension. In regard to the centroid of the maxilla, the absolute angular difference of the maxillary centroid was 1.06° in pitch, 0.47° in roll, and 0.49° in yaw. Maxillary repositioning surgery can be performed with high accuracy using CAD/CAM titanium surgical guides and fixation plates.

Pulp blood flow and sensibility in patients with a history of dental trauma undergoing maxillary expansion

OBJECTIVES

To assess changes in pulp blood flow (PBF) and pulp sensibility (PS) in teeth of patients with a history of dental trauma undergoing maxillary expansion.

MATERIALS AND METHODS

Twenty-five patients requiring rapid maxillary expansion (RME) had the pulp status of their maxillary anterior teeth assessed using laser Doppler flowmetry, electric pulp testing, and thermal testing (CO2 snow). Each patient was tested at T1 (prior to expansion), T2 (2 weeks after rapid expansion), and T3 (3 months after expansion). Relationships between PBF, time interval, and history of trauma were evaluated using linear mixed modelling.

RESULTS

Within the Trauma group, PBF was significantly lower (P ≤ .05) at T2 and T3 in comparison to T1 and significantly lower (P ≤ .05) at T2 in comparison to T3. In the Non-trauma group, PBF at T2 was significantly lower (P ≤ .05) than PBF at T1 and T3; however, no significant difference (P > .05) in PBF was observed when comparing PBF at T1 and T3. In both groups, PS was maintained in almost all teeth (>90%).

CONCLUSIONS

RME in healthy teeth causes reduction of PBF before reestablishment of pretreatment values. RME in traumatized teeth causes reduction of PBF without PBF being reestablished to pretreatment levels. Teeth with a history of compromise may have reduced adaptive capacity under insults such as RME, which should be appreciated during the informed consent process.

Adult orthodontic retreatment: A survey of patient profiles and original treatment failings

INTRODUCTION

A growing number of adult patients are seeking orthodontic treatment. This research aimed to analyze the particulars of patients seeking retreatment and identify the causes of their original treatment failure.

METHODS

An online questionnaire survey of adults seeking first-time orthodontic treatment (control) and retreatment (study) was conducted. Index of complexity, outcome, and need (ICON) scores were determined. Appraisal of treatment records was carried out to identify the causes of original treatment failure.

RESULTS

No significant differences were found between retreatment adult patients and first-timers regarding reasons for seeking orthodontic treatment, malocclusion type, self-perception of malocclusion, level of self-motivation, willingness for surgery, expectations of treatment improvement and duration. The predominant reason for seeking treatment in both groups was for aesthetic concerns. Retreatment patients presented with lower ICON scores (39.4; standard error, 0.26) than the first-time patients (54.3; standard error, 0.23), P ≤0.001. The predominant reasons for original treatment failings were poor treatment, maturational changes, inadequate retention, shortcomings in diagnosis and treatment planning, and unfavorable growth. Other causes were related to transverse deficiency, secondary malocclusion (after periodontal breakdown), poor retention compliance, and temporomandibular joint degeneration.

CONCLUSIONS

Adult orthodontic retreatment and first-time seekers' profiles are remarkably similar. Aesthetic concerns were the leading reasons patients sought treatment. ICON was not a useful proxy of patient profiles. Poor treatment was the chief reason for the failure of the original treatment. In terms of clinical significance, clinicians should be mindful of the patient profiles of retreatment seekers and vigilant about the possible causes of failings of orthodontic treatment to avoid suboptimal outcomes.

Accuracy of orthognathic surgery using 3D computer-assisted surgical simulation

Objective

To evaluate the accuracy of maxilla and mandibular repositioning during two-jaw orthognathic surgery using computerassisted surgical simulation (CASS)

Materials and methods

Fifteen patients who underwent two-jaw orthognathic surgery using CASS (VSP,® Orthognathics by 3D Systems) were evaluated to assess the accuracy of the simulation. Translational and rotational discrepancies of the centroids of the maxilla and mandible and the translational discrepancy of the dental midline between the planned and actual outcomes were reported using the root mean square error (RMSE). The number of cases that exceeded limits set for clinical significance, the direction of the error in relation to the direction of planned movement and the differences between segmental and non-segmental procedures were evaluated as secondary outcomes

Results

The largest translational RMSE was 1.53 mm along the y-axis in the maxilla and 1.34 mm along the y-axis in the mandible. The largest rotational RMSE was 1.9° about the x-axis in the maxilla and 1.16° about the x- and y-axes in the mandible. The largest RMSE for the dental midline was 1.6 mm along the y-axis in the maxilla and 1.34 mm along the y-axis in the mandible. A tendency for insufficient advancement of the maxilla was noted

Conclusions

CASS is an efficient and accurate way to develop the surgical plan and transfer the plan to the patient intraoperatively. While CASS is accurate on a population level, there remains the potential for clinically significant errors to occur on an individual basis

Conclusion

The present case indicated that the timely extraction of palatally-placed maxillary lateral incisors facilitated functional appliance therapy in the management of a skeletal Class II problem. The crowding of the lower anterior teeth was relieved and alignment of the upper arch was achieved with full fixed appliance therapy, resulting in improved aesthetics and a stable occlusion at one year review

Success rates of a skeletal anchorage system in orthodontics: A retrospective analysis

OBJECTIVES

To evaluate the premise that skeletal anchorage with SAS miniplates are highly successful and predictable for a range of complex orthodontic movements.

MATERIALS AND METHODS

This retrospective cross-sectional analysis consisted of 421 bone plates placed by one clinician in 163 patients (95 female, 68 male, mean age 29.4 years ± 12.02). Simple descriptive statistics were performed for a wide range of malocclusions and desired movements to obtain success, complication, and failure rates.

RESULTS

The success rate of skeletal anchorage system miniplates was 98.6%, where approximately 40% of cases experienced mild complications. The most common complication was soft tissue inflammation, which was amenable to focused oral hygiene and antiseptic rinses. Infection occurred in approximately 15% of patients where there was a statistically significant correlation with poor oral hygiene. The most common movements were distalization and intrusion of teeth. More than a third of the cases involved complex movements in more than one plane of space.

CONCLUSIONS

The success rate of skeletal anchorage system miniplates is high and predictable for a wide range of complex orthodontic movements.

Long-term surgical-orthodontic management of hemimandibular hyperplasia

BACKGROUND

Hemimandibular hyperplasia (HH), also known as hemimandibular hypertrophy, is characterised by excessive unilateral three-dimensional growth of the mandible after birth. Vertical unilateral elongation of the mandible becomes clinically evident as a rare form of vertical facial asymmetry. Aberrant growth of the facial skeleton affects the developing dentition and the dental compensatory mechanism is usually unable to maintain optimal occlusal relationships. The resulting malocclusion is effectively managed by combined surgical-orthodontic care to address the facial, skeletal and dental problems that confront clinicians. Orthodontists are advised to assess patients with HH during the post-treatment retention stage for continuing mandibular growth and assess the stability of treatment outcomes with long-term follow-up and records as required.

AIM

To present a case of hemimandibular hyperplasia treated successfully by combined surgical-orthodontic care and evaluated for stability over a seven-year follow-up period.

METHODS

Surgical-orthodontic management was accomplished in four stages: 1) pre-surgical orthodontic; 21 surgical; 3) post-surgical orthodontic; and 4) post-treatment orthodontic retention. Complete orthodontic records, including extra- and intra-oral photographs, study models, and cephalograms plus panoramic radiographs were taken at the pretreatment, post-treatment, and seven-year orthodontic retention time-points.

RESULTS

Facial, skeletal and dental goals were achieved in the three planes of space and the long-term stability of the treatment results was shown during a post-treatment orthodontic retention period of seven years.

CONCLUSION

Hemimandibular hyperplasia is a true growth anomaly which may be managed effectively. Clinicians may expect successful long-term correction and stability by utilising a comprehensive surgical-orthodontic treatment approach.

Facial asymmetry assessment in adults using three-dimensional surface imaging

Background

The use of three-dimensional (3D) surface imaging is becoming more popular and accepted in the fields of Medicine and Dentistry. The present study aims to develop a technique to automatically localise and quantify soft-tissue asymmetry in adults using 3D facial scans. This may be applied as a diagnostic tool to monitor growth and dynamic changes and to evaluate treatment outcomes.

Methods

3D facial surface data were captured from 55 adults comprising 28 symmetrical faces and 27 asymmetrical faces using a 3dMDface system. A landmark-independent method, which compared the original and the mirrored 3D facial data, was developed to quantify the asymmetry. A Weibull distribution-based probabilistic model was generated from the root-mean-square (RMS) error data for the symmetrical group to designate a level of asymmetry which represented a normal range.

Results

Statistically significant (p < 0.0001) differences in the RMS error values were found when comparing symmetrical with asymmetrical groups and a similarly significant difference was identified between the lower and the upper face of the asymmetrical group.

Conclusions

The proposed 3D imaging-based method of identifying and quantifying facial soft-tissue asymmetry was fast and effective. The Weibull distribution-based comparison of a person’s asymmetry with respect to a large sample of symmetrical faces may also be used to evaluate growth, soft-tissue compensations and surgical outcomes.

Numerical simulation of pharyngeal airflow applied to obstructive sleep apnea: effect of the nasal cavity in anatomically accurate airway models

Repetitive brief episodes of soft-tissue collapse within the upper airway during sleep characterize obstructive sleep apnea (OSA), an extremely common and disabling disorder. Failure to maintain the patency of the upper airway is caused by the combination of sleep-related loss of compensatory dilator muscle activity and aerodynamic forces promoting closure. The prediction of soft-tissue movement in patient-specific airway 3D mechanical models is emerging as a useful contribution to clinical understanding and decision making. Such modeling requires reliable estimations of the pharyngeal wall pressure forces. While nasal obstruction has been recognized as a risk factor for OSA, the need to include the nasal cavity in upper-airway models for OSA studies requires consideration, as it is most often omitted because of its complex shape. A quantitative analysis of the flow conditions generated by the nasal cavity and the sinuses during inspiration upstream of the pharynx is presented. Results show that adequate velocity boundary conditions and simple artificial extensions of the flow domain can reproduce the essential effects of the nasal cavity on the pharyngeal flow field. Therefore, the overall complexity and computational cost of accurate flow predictions can be reduced.

Hemimandibular hyperplasia: a rare case of vertical facial asymmetry. A case report

BACKGROUND

Hemimandibular hyperplasia (HH), also known as hemimandibular hypertrophy, is characterised by excessive unilateral three-dimensional growth of the mandible after birth. Vertical elongation of the mandible on one side becomes clinically evident as a rare form of vertical facial asymmetry. Aberrant growth of the facial skeleton affects the developing dentition and dental compensation is usually unable to maintain optimal occlusal relationships. The resulting malocclusion is best managed surgically to address the various facial, skeletal and dental problems that confront clinicians.

AIM

To present a case of hemimandibular hyperplasia treated using a combined surgical-orthodontic approach.

METHODS

Combined surgical-orthodontic treatment was accomplished in four phases: 1) presurgical orthodontic, 2) surgical, 3) post-surgical orthodontic and 4) orthodontic retention. Comprehensive records (including photographs, study models and radiographs) were taken at the pre-treatment, pre-surgery and debanding stages of treatment.

RESULTS

A significant improvement in facial symmetry and a positive occlusal outcome were achieved. A more balanced gingival display has improved the patient's smile aesthetics.

CONCLUSION

Hemimandibular hyperplasia is a rare condition causing vertical facial asymmetry and a resulting malocclusion. A combined surgical-orthodontic approach is able to accomplish sound facial, skeletal and dental treatment outcomes.

Accuracy and validity of space analysis and irregularity index measurements using digital models

BACKGROUND

Digital copies of study models may avoid the storage and retrieval issues of plaster study models, but measurements made on digital models may not be as accurate as measurements made on traditional study models.

AIM

To determine the reliability and validity of tooth size-arch length discrepancies (TALD), irregularity indices and arch lengths (four- and six-segment analyses) measured directly on study models with digital calipers with the same measurements measured on digital copies of the study models with proprietary software.

METHODS

The irregularity indices and TALDs (four- and six-segments) were measured on 50 sets of pretreatment plaster models. The plaster models were measured using manual calipers with a digital readout. The models were then couriered to OrthoCAD and digital copies emailed to the authors. The digital models were measured with the proprietary software provided with the digital models. Repeat measurements of the TALDs and the irregularity indices were subjected to intraclass correlations (ICC) to assess the reliability. The least squares means of variation was used to assess validity and the impact of measuring arch length (four- and six-segments) on the digital models, and the implications on the TALDs.

RESULTS

There were high correlations (ICC) ranging from 98.6-99.9 per cent for both the irregularity indices and the TALDs. The choice of manual over computer and four-segment over six-segment analysis had a significant effect when measuring lower arch lengths (p < 0.05), but they had no effect on the upper arch findings.

CONCLUSIONS

Reliable measurements of the irregularity index and the TALD can be made on digital models. Computer measurements of TALDs on digital models were more consistent than manual measurements of TALDs on plaster models. Six-segment analyses of lower arch lengths on digital and plaster models gave more consistent findings than the four-segment analyses.

Comparison of active self-ligating brackets and conventional pre-adjusted brackets

BACKGROUND

Active self-ligating brackets may be more efficient than conventional pre-adjusted brackets.

AIMS

To determine if self-ligating brackets are more efficient than conventional pre-adjusted brackets when used in a specialist practice setting.

METHODS

Seven hundred and sixty two patients, consecutively treated with fixed appliances, were evaluated retrospectively. All patients were treated by one orthodontist in a private orthodontic practice. Three hundred and eighty three patients were treated using a conventional pre-adjusted bracket system and 379 patients were treated with active self-ligating brackets. The total treatment time, number of appointments, appointment intervals, number of bracket breakages and number of unscheduled emergency appointments were recorded. Pretreatment characteristics identified by the ICON were related to these variables.

RESULTS

The average treatment duration was 15.7 months (Range: 4.1-40.5 months; SD: 5.6 months). Comparable amounts of time were spent in rectangular and round archwires by both appliances. Overall, there was no statistically significant difference between the durations of treatment with active self-ligating brackets and conventional pre-adjusted brackets. The number of debonded brackets and other emergency visits was significantly higher in patients treated with active self-ligating brackets. The treatment characteristics associated with prolonged treatment were: extraction of teeth, a Class II molar relationship and the degree of maxillary crowding or spacing.

CONCLUSIONS

Active self-ligating brackets appear to offer no measurable advantages in orthodontic treatment time, number of treatment visits and time spent in initial alignment over conventional pre-adjusted orthodontic brackets.

Morphologic changes of the palate after rapid maxillary expansion: a 3-dimensional computed tomography evaluation

INTRODUCTION

The purpose of this retrospective study was to estimate the area change of the palate after rapid maxillary expansion (RME) in the early mixed dentition stage by using a 3-dimensional (3D) helical computed tomography (CT) scanning technique. In addition, linear changes in the maxillary arch were evaluated.

METHODS

The treated sample consisted of 43 children (mean age, 9 years 1 month) treated with a bonded RME appliance. The untreated control group consisted of 7 children (mean age, 9 years 3 months). Pretreatment and posttreatment dental casts were evaluated by using 3D helical CT scanning procedures. The Student t test was used to compare the linear, area, and angular differences between the treatment times.

RESULTS

RME produced clinically significant increases in interdental widths across the canines, the deciduous first molars, and the permanent first molars in the maxillary arch. Significant increases in cross-sectional area were observed across the permanent first molars (15.3 mm(2)). There was marked variability in the buccal tipping of the permanent first molars.

CONCLUSIONS

Three-dimensional helical CT scanning is an accurate and cost-effective method of assessing dental cast morphologic changes. It can also provide fast and accurate data acquisition and subsequent analysis.

Influence of lips on the perception of malocclusion

INTRODUCTION

The purpose of the study was to determine the influence of variations in the size of the vermilion borders of the upper and lower lips on the perception of the attractiveness of various occlusal traits.

METHODS

Ten occlusal traits and 3 upper and 3 lower vermilion variations, placed in combinations on a facial image, were used in a questionnaire. Statistical analyses for attractiveness and social and sex attributes were performed for various occupational groups.

RESULTS

The occlusion, vermilion border of the upper and lower lips separately, and the raters' occupations were all highly significant in influencing attractiveness, social perceptions, and perceived sex of the images (P < .01). All occlusal traits were perceived as more attractive with a thicker vermilion border. Thin vermilion borders and more severe irregularity were associated with unattractiveness, aggressiveness, and masculine traits.

CONCLUSIONS

This study demonstrates that the thickness of the vermilion border has a profound effect on how people rate the attractiveness of the dentition. Therefore, treatment plans that could affect lip vermilion might result in improved dental alignment but also deterioration in overall attractiveness. Orthodontists placed more emphasis on the teeth than other occupation groups; this demonstrated an occupational bias.

Accuracy of a LeFort I maxillary osteotomy

An optimal outcome of combined surgery and orthodontics involving the maxilla is dependent on many factors. Accurate placement of the maxilla by the surgical team is ultimately of paramount importance. The aim of this retrospective study was to evaluate the accuracy of LeFort I maxillary osteotomy with respect to the presurgical prediction. The sample comprised 42 patients (33 females, nine males) who had undergone LeFort I osteotomy procedure alone or in combination with a mandibular osteotomy with or without genioplasty. Tracings of presurgical and immediate postsurgical lateral cephalograms and surgical predictions were digitized and compared using Quick Ceph software analysis. Vertical and horizontal measurements to various skeletal landmarks were used to assess the discrepancy between the predicted maxillary position and the actual postsurgical result. Statistically significant differences were found between the predicted and actual postsurgical maxillary molar vertical position, and significant differences were also found for the palatal plane angular measurements. Two surgical teams were compared, and surgical team 1 had significantly less variation in the surgical outcomes than did surgical team 2. When single-jaw and bimaxillary surgery were compared, no significant differences were found. Similarly, there were no statistically significant differences found when assessing the primary direction of movement (impaction vs downgraft vs advancement). Overall, 66% of the results were within two mm of prediction and 26% of the results were within one mm of prediction. A LeFort I maxillary osteotomy can be an accurate procedure with a wide range of discrepancy.

Augmentation of faciolingual gingival dimensions with free connective tissue grafts before labial orthodontic tooth movement: An experimental study with a canine model

PURPOSE

The aim of this study was to determine in an animal model whether any increase in gingival thickness after placement of free connective tissue autografts is maintained after labial orthodontic tooth movement.

MATERIAL

In a split-mouth technique, the maxillary second and third incisors of 4 adult greyhounds were used as experimental, control, and sham-control teeth. The experimental teeth underwent gingival augmentation surgery. Two to 3 months later, the teeth were moved with a bonded orthodontic appliance over 2 to 3 months. Baseline and 2-month retention clinical measurements of gingival height were taken before the animals were killed. Histometric measurements recorded the free gingival height and the gingival thickness at 5 graduated levels down the teeth.

RESULTS

Clinical measurements of changes in gingival margin position revealed a mean coronal shift of 0.44 mm over grafted teeth, with 50% of nongrafted teeth and 100% of the sham-control teeth experiencing small amounts of gingival recession. The histometric results showed that gingival thickness measurements for the grafted teeth were, on average, between 0.13 and 0.18 mm thicker at all levels of measurement than for the nongrafted teeth (P < .01).

CONCLUSIONS

Free connective tissue grafts placed on the labial aspect of incisors might help prevent the faciolingual thinning of the gingival tissues that can occur as a result of labial orthodontic tooth movement. Further research is required to confirm these results in a larger sample and determine the long-term benefits of preorthodontic gingival augmentation to prevent gingival recession.