Incisor Inclination Research Articles

Three-Dimensional Finite Element Analysis on En-Masse Retraction of the Maxillary Anterior Teeth With Quantitative Combined Loading Control.

This study aims to elucidate the biomechanical effects of combined loading of maxillary anterior and posterior implants using the sliding method on en-masse retraction of the anterior teeth and to quantify the loading ratio (LR) of anterior and posterior implants to achieve controlled retraction of the maxillary anterior teeth. A three-dimensional finite element model of the maxilla-upper dentition appliance was constructed. Implants were placed on the distal (A) and mesial (B) sides of the lateral incisors as well as on the mesial (C) side of the first molar and different amounts of force were loaded between the implants using 2- or 5-mm traction hooks. The labiolingual movement of the anterior teeth was recorded and the relationship between the LR of the implants and the movement of the central incisors was evaluated. With 2-mm traction hooks, the central incisors exhibited a translation tendency during retraction at lower A/C and B/C LR and labial or lingual crown inclination at higher values. With 5-mm traction hooks, the central incisors, lateral incisors, and canine teeth exhibited a labial crown inclination. The results of this study suggest that 2-mm traction hooks can cause labial crown inclination, translation tendency during retraction, or lingual crown inclination of the central incisors due to alterations in the LR of the anterior and posterior implants. The central incisors only exhibited labial crown inclination during combined loading of the anterior and posterior implants when 5-mm traction hooks were used.

O propulsor mandibular pode ser usado com incisivos inferiores vestibularizados?

An excellent alternative to Class II treatment are fixed mandibular propulsion appliances. In general, they are devices that do not cause significant changes in the maxilla or mandible because they promote Class II correction primarily by dental alterations through an increase in the lower incisors inclination, decrease of upper incisors inclination, and occlusal plane rotation. The question is if it is possible to use this type of device, even with the lower dental compensation already present, that is, with the lower incisors vestibularized. The objective of this study is to show through a clinical case the use of mandibular propulsion with this type of malocclusion.

Cephalometric Evaluation of Maxillary Incisors Inclination, Facial, and Growth Axes in Different Vertical and Sagittal Patterns: An Original Study.

ABSTRACTAim:The aim of this study was to evaluate the inclination of the maxillary incisors (I), facial axis (FA), and growth axis (GA) in different vertical and sagittal patterns.Materials and Methods:A total of 498 consecutive orthodontic patients, with an average age of 18.87 years (range = 5–63 years), were grouped based on their vertical and sagittal patterns. Maxillary incisors, FA, and GA axes were traced and their corresponding angles to nasion-basion and true horizontal lines were measured. The sample was divided into three groups based on the mandibular divergence (mandibular plane-MP/sella-nasion [SN]): Group 1—hypodivergent pattern (MP/SN ≤ 27; n = 30), Group 2—normodivergent pattern (27 < MP/SN <37; n = 254), and Group 3—hyperdivergent pattern (MP/SN ≥ 37; n = 214); the sample was then divided into three groups based on the sagittal pattern (ANB, angle between points A, Nasion and B): Group I—skeletal CLI (Class I) (0 <ANB <4; n = 228), Group II—skeletal CLII (ANB ≥ 4; n = 216), and Group III—skeletal CLIII (ANB ≤ 0; n = 54). Group differences were evaluated using the analysis of variance and post hoc tests. Chi-square tests were used for testing relationships between categorical variables.Results:FA/nasion-basion (NBa) and GA/NBa were different among the vertical groups (P < 0.001). FA/NBa was found significantly different in the sagittal groups, whereas GA/NBa was only different between CLII and CLIII groups. Compensation in maxillary incisors' inclination was present in the sagittal groups, but not in the vertical ones. CLI patients when stratified in vertical groups showed FA/NBa and GA/NBa to be different across the three vertical groups.Conclusion:FA/NBa was found different in the vertical and the sagittal groups. Maxillary incisors compensation was only found in the sagittal and not in the vertical groups.

Incisor root resorption associated with palatally displaced maxillary canines: Analysis and prediction using discriminant function analysis

Incisor root resorption associated with palatally displaced canine (PDC-IRR) is an important phenomenon that might alter the orthodontic treatment plan. The aims of this study were to investigate the prevalence and characteristics of PDC-IRRs, to compare PDC-IRR and PDC-No-IRR groups, to identify predictors for PDC-IRR, and to produce a valid PDC-IRR prediction model using discriminant function analysis. Cone-beam computed tomography images for 107 palatally displaced canines (PDCs) and 51 fully erupted nondisplaced canines (NDC) were analyzed for the presence of incisor root resorption (IRR). The PDCs were divided into 2 groups: PDC-IRR (52 canines) and PDC-No-IRR (55 canines). The 3 groups were compared, and the following variables were measured: canine follicle size, contact with adjacent incisors, associated dental abnormalities, sector analysis, canine vertical relation to adjacent root, lateral incisor angulation and inclination, canine angulation and distance to reference planes (dental midline, midpalatal suture, occlusal plane, pterygoid vertical plane, and lateral incisor), and space available for canine in the dental arch. Discriminant functional analysis was used to produce a discriminant function equation to predict PDC-IRR. Root resorption affected 74% of lateral incisors adjacent to PDCs and 25.5% of lateral incisors adjacent to NDCs. IRR was located lingually in 41% of PDCs and in the mid and apical thirds in 89%. In the PDC-IRR group, 94.2% of canines were in contact with adjacent roots compared with 23.6% in the PDC-No-IRR group (P<0.001). Canine follicle size was>2mm in 42% of PDC subjects. Overall mean value of follicle width in PDC canines was 1.79±1.06mm. Peg-shaped lateral incisors were recorded in 19% of PDC subjects compared with 4% in NDCs (P=0.012). The stepwise analysis using cone-beam computed tomography records produced a discriminant function based on 3 variables. The analysis correctly predicted the outcome in 83% of subjects. The variables contributing to the prediction equation were canine contact with adjacent incisors, size of canine dental follicle, and the presence of peg-shaped lateral incisor. Canines in contact with adjacent incisor roots was the only risk factor detected for PDC-IRR. Very good predictive discrimination (83%) emerged for PDC-IRR subjects. Predictors of PDC-IRR were canine contact with adjacent incisor, size of canine dental follicle, and presence of peg-shaped lateral incisor.

Cephalometric norms for Sri Lankan Sinhalese adolescents with Class I malocclusion

Context: Comprehensive cephalometric analysis plays a significant role in orthodontic diagnosis and treatment planing and variety of cephalometric standards have been developed for different populations. It is important to develop standard cephalometric norms for different populations. Aims: The aim of this study was to develop cephalometric standards for Sri Lankan Sinhalese adolescents with Class I malocclusion and to test the hypothesis that there are racial differences in cephalometric measurements between Sri Lankan and Caucasian norms. Setting and Design: Cross sectional , hospital based, descriptive study. Materials and Methods: Lateral cephalograms were obtained from 33 males (aged 15.7 ± 1.99 years) and 42 females (aged 15.6 ± 2.29 years). Inclusion criteria were healthy individuals with normal growth and development, straight facial profile, average vertical facial proportions, full complement of dentition (excluding third molars), normal overjet and overbite, Class I incisor, canine and molar relationship, and no crossbite in the anterior/posterior region. Eight angular and four linear measurements were analyzed in skeletal, dental, and soft-tissue assessment. Statistical Analysis Used: Statistical analysis was performed using the statistical software R 3.5.0. Results: In the dentoalveolar assessment, the Sri Lankan subjects had a significantly proclined upper (UI to N-A = 23.28) and lower incisor (LI to N-B = 6.56 mm and 28.3) inclinations compared with the Caucasian norms. In the assessment of soft-tissue profile, both upper (1.66 ± 2.7mm) and lower lip (2.8 ± 2.6mm) protrusions were slightly increased than the norms of the Steiner analysis, and these findings were clinically significant. There were no apparent differences in relation to anteroposterior and vertical skeletal relationship when compared with Caucasian norms. Conclusions: The results of the present study suggested that Sri Lankan Sinhalese adolescents with Class I occlusion are likely to present greater incisor proclination than Caucasians. Key Messages: The present study suggested that Sri Lankan Sinhalese adolescents are likely to present greater incisor proclination than Caucasians in Class 1 malocclusion.

Craniofacial geometric morphometrics in the identification of patients with sickle cell anemia and sickle cell trait.

ObjectiveThe aims of this study were to identify the main characteristics regarding the shape and size of the craniofacial region in patients with sickle cell anemia (SCA) and sickle cell trait (SCT) and in unaffected patients using geometric morphometrics and to check the efficiency of this method.Material and MethodsA cross-sectional analytical study of 45 patients (15 in each group) was performed. Lateral radiographs of the skull were used for the analysis. Seventeen landmarks and semilandmarks were placed for the measurements. The Pocrustes analysis of variance (ANOVA), regression analysis, multivariate analysis of variance, canonical variate analysis, Mahalanobis and Procrustes distances and unweighted pair group method with arithmetic mean (UPGMA) clustering were performed. Allometric effects and sex characteristics were not statistically significant (p > 0.05).ResultsThere were, however, significant differences (p < 0.05) in craniofacial shape among SCA, SCT and unaffected individuals. Those with SCA showed variations in the shape of the external auditory meatus and at the base of the occipital bone, in addition to the mandibular setback and upper incisor inclination, with a tendency towards prognathism. The individuals with SCT exhibited a similar craniofacial shape to those with SCA, but with slighter variations. Moreover, those with SCT were statistically closer in resemblance to unaffected individuals, given that SCT is not regarded as a disease.ConclusionThis demonstrates the efficiency of geometric morphometrics in the categorization of the assessed groups.

A comparative assessment of clinical efficiency between premium heat-activated copper nickel-titanium and superelastic nickel-titanium archwires during initial orthodontic alignment in adolescents: a randomized clinical trial

BackgroundTo compare the clinical efficiency of premium heat-activated copper nickel-titanium (Tanzo Cu-NiTi) and NT3 superelastic NiTi during initial orthodontic alignment.Subject and methodsA total of 50 patients were randomly allocated to 1 of 2 different archwire types (group 1, Tanzo Cu-NiTi; group 2, NT3 superelastic NiTi). Eligibility criteria included Class I or Class II malocclusion, moderate maxillary anterior crowding, and healthy periodontal condition. Impressions of the upper arches were taken before archwire placement (T0) and at every 4 weeks (T1, T2, T3, and T4). For T1 and T2 stages, 0.014-in., and for T3 and T4 stages, 0.018-in. archwires were used. The primary outcome was the alignment efficiency assessed using Little’s irregularity index. The secondary outcomes were arch width and incisor inclination changes. Data were analyzed using independent samples t test, repeated measures ANOVA, and Mann-Whitney U test. Marginal models were established for the estimation of coefficients.ResultsThe anterior irregularity index reduction was mostly observed between T0 and T2 periods, which were respectively − 7.40 ± 0.50 mm (p < 0.001; 95% CI, − 8.94, − 5.85) and − 6.80 ± 0.55 mm (p < 0.001; 95% CI, − 8.49, − 5.12) for groups 1 and 2 (p < 0.001). With both wires, Little’s irregularity index decreased over time, and the difference between the groups was not significant (p = 0.581; estimated effect size, 0.011). No statistically significant difference was found between the groups in terms of intercanine and intermolar width and incisor inclination changes.ConclusionThere were no significant between-group differences in alignment efficiency, arch width, and incisor inclination change. There was an increased alignment with 0.014-in. compared with 0.018-in. diameter archwire.

Mandibular propulsion appliance for adults with Class II malocclusion: a systematic review and meta-analysis.

The effects of mandibular propulsion appliances in adults have some controversial results. While some authors claim that its use in non-growing patients could produce some dentoskeletal effects, other studies indicate that Class II correction occurs only through significant dental effects. To evaluate the effects in non-growing Class II patients with mandibular retrusion, promoted by the treatment with mandibular propulsion appliances and determine if they produce mandibular changes. The research was carried out in nine electronic databases and additional manual searches up to July 2019. Selection criteria were no restriction was placed on date and publication language. Randomized or non-randomized clinical trials with/without control were included. They must evaluated non-growing patients with Class II malocclusion, treated with mandibular propulsion appliances; outcomes were assessed before and after treatment. Data were extracted by two independent examiners in duplicate. The ROBINS-I tool was used to assess the methodological quality of the included studies. Of the 2824 articles identified, 11 non-randomized clinical articles were selected for qualitative analysis and 8 for quantitative analysis. SNB (0.87°, CI 95% 0.08, 1.66), ANB (-0.82°, CI 95% -1.24 to 0.40) and Pg/OLp [2.3 to 1.2 mm (P < 0.001)] presented smallest but significant mandibular changes with some differences regarding the used appliance. The Herbst appliance showed the largest mandibular changes followed by the SUS appliance when evaluated through Ar-Pg. SNA showed non-significant changes. Overbite (-2.85. CI 95% -3.06, -2.64), Overjet (-5.00.CI 95% -5.45, -4.55) showed significant changes in all devices. Class II correction occurs through a significant labial movement of the mandibular incisors, some lingual inclination of the maxillary incisors and minor skeletal changes. All mandibular propulsion appliances examined, showed efficiency in normalizing the Class II malocclusion in adult patients; however, changes were acquired mainly through dentoalveolar changes. Some minor mandibular forward changes was noted, mainly in patients treated with the Herbst appliance. Randomized clinical trials are needed to improve scientific evidence. PROSPERO (code CRD42017067384).

Changes in maxillary incisor inclination and position after traction of unilateral vs bilateral maxillary impacted canines in nonextraction treatment: A cone-beam computed tomography study

The aim of this study was to compare the inclination and position changes of maxillary incisors after traction of unilateral vs bilateral maxillary impacted canines in nonextraction orthodontic treatment. This longitudinal and retrospective study evaluated 24 patients with impacted maxillary canines; 12 with unilateral impaction and 12 with bilateral impaction. All subjects had Angle Class I malocclusion and were orthodontically treated with a standardized traction protocol that did not include premolar extractions. Cone-beam computed tomographies were obtained before and after canine traction and the inclination and position of both maxillary central incisors were measured. Furthermore, dental arch, skeletal, and canine impaction characteristics were evaluated. Paired and independent t tests were used for intra and inter group comparisons, respectively. Multiple linear regressions were also used. After canine traction, a significant incisor labial inclination was observed in the bilateral group (10.41° right side, P=0.008 and 12.79° left side, P=0.001), while in the unilateral group, this was observed only on the nonaffected side (6.67°, P=0.008). Furthermore, a significant protrusion of incisors was observed in the bilateral group (2.66mm right side, P=0.006, and 3.15mm left side, P=0.001) and in the nonaffected side of the unilateral group (1.74mm, P=0.022). Intergroup comparisons showed greater values of incisor labial inclination for the bilateral group when compared with the unilateral group, independently of the sides. Traction of maxillary impacted canines, in nonextraction treatment, produces greater labial inclination of maxillary incisors in bilateral cases and similar protrusion in both unilateral and bilateral cases. Unilateral impaction cases showed significant incisor inclination and protrusion in the nonaffected side. These treatment effects should be considered by clinicians.

Effectiveness of clear aligner therapy for orthodontic treatment: A systematic review.

To analyse through a systematic review the effectiveness of clear aligners by assessing: (a) predictability of clear aligners and (b) treatment outcome comparison of clear aligner therapy with fixed appliance therapy. An electronic search was made from January 2014 to April 2019 using MEDLINE, Embase, Web of Science and LILACS databases without any limitations on language. Three reviewers independently assessed the articles. Quality assessment of observational studies and randomized control trial was done by using the ROBINS tool and Cochrane risk of bias tool, respectively. GRADE instrument was used to assess certainty level for each identified outcome. Seven eligible articles (one randomized controlled trial and six retrospective cohort) were included in our systematic review. Most of the studies (six out of seven) had a moderate risk of bias and one had a high risk of bias. 'Low to moderate level' of certainty in regard to specific clear aligner therapy tooth movements' efficiency was identified. Clear aligners may produce clinically acceptable outcomes that could be comparable to fixed appliance therapy for buccolingual inclination of upper and lower incisors in mild to moderate malocclusions. However, not all potential clinical scenarios have been assessed in the included studies. Most of the tooth movements may not be predictable enough to be accomplished with only one set of trays with clear aligners despite the recent advances in technology.

Association Between Canine Impaction and Skeletal Pattern in the Sagittal and Vertical Planes.

In the present study, the authors evaluated the association of canine impaction with different skeletal discrepancies in two planes of space (sagittal and vertical). Cephalometric and orthopantomographic radiographic images of 45 patients with one or more impacted canines were used in this retrospective study. Five radiographic morphologic parameters-ANB angle, canine angulation, angle between the Frankfort horizontal plane and the mandibular plane (FH-MP), Wits appraisal analysis, and axial inclination of the maxillary incisors in the sagittal plane-were recorded for comparison. Statistical analysis was performed using SPSS 9.0 statistical package (IBM). Impaction of the maxillary canine was more frequent than mandibular canine impaction in both males and females, and palatal impaction was more common than buccal impaction, with a higher significance in males (64.7%) than in females (50%). In the sagittal relationship, the highest frequency of impacted canines was found in patients with a Class III skeletal discrepancy (44.4%), followed by Class I (28.9%) and Class II division 1 (15.6%), while the lowest frequency was in Class II division 2 (11.1%). Comparison between sexes in the vertical plane showed that impacted canines occurred more frequently in hyperdivergent female faces (51.1%) and hypodivergent male faces (48.9%). The result of this study indicates a statistically significant association of impaction with canine, sagittal, and/or vertical dentofacial discrepancies. The results also showed a higher risk of having impacted canines in patients with certain dentofacial deformities. Therefore, canine impaction may be used to represent a substitute scale for the study of different malocclusion groups with respect to race and ethnicity.

Differential skeletal and dental effects after orthodontic treatment with bite jumping appliance or activator: a retrospective cephalometric study.

The aim of this retrospective cephalometric study was to compare treatment outcomes with "bite jumping appliance" (BJA) or Andresen-Häupl type activator. It especially focused on skeletal and dental structures in patients with class II malocclusion. The study hypothesis was that differences in treatment-related changes would occur between patients treated with BJA or activator. Pre- and posttreatment lateral cephalograms of 73 patients with a class II malocclusion were analyzed. Thirty-seven patients (22 females, 15 males) received treatment with a BJA (pretreatment age 11.1 ± 1.07years) and 36 patients (20 females, 16 males) with an activator (pretreatment age 11.3 ± 1.12years). Treatment time was 14.0 ± 1.8months with BJA and 12.0 ± 2.0months with activator. Paired t tests were used for intragroup and t tests for independent samples for intergroup comparisons. Results were considered statistically significant at P < 0.05. The comparison of sagittal and vertical skeletal changes after BJA and activator treatment did not reveal significant differences. Significant changes occurred for lower incisor inclination (P = 0.0367) and overjet (P = 0.0125) only. The reduction of overjet and proclination of lower incisors were more pronounced in BJA patients. Both "bite jumping appliance" (BJA) and Andresen-Häupl type activator were able to improve the occlusion of patients with a class II malocclusion. Dental effects were more pronounced for the BJA. Marked lower incisor proclination contributed significantly to overjet correction in BJA patients. This ought to be respected when choosing a removable functional appliance for patients whose lower incisors are already proclined prior to treatment.

THE INFLUENCE OF THE SAGITTAL DENTOSKELETAL PATTERN ON THE VALUE OF THE SOFT TISSUE PROFILE ANGLES - A CEPHALOMETRIC STUDY

The aim of this study has been to establish the values of soft tissue profile angles in subjects with dentoskeletal Class I, Class II Division 1, Class II Division 2, and Class III pattern, in order to examine the influence of sagittal dentoskeletal relation on the value of angular profile parameters. This comparative cephalometric study included the examination and the analysis by lateral cephalograms to evaluate soft tissue profile angles for 120 adult Caucasian subjects (60 women and 60 men) from the mid Balkan region divided into four groups towards ANB angle and incisors inclination. The following angles were examined: angle of facial convexity, facial convexity angle for the lower face and the angle of total facial convexity. By investigating the influence of the sagittal dentoskeletal pattern on the value of facial convexity angles, significant differences have been established between subjects with Class I and Class II Division 1 and 2 for all examined angles (p&lt;0.001; p=0.011), while the differences between Class I and Class III are only significant for the facial convexity angle and facial convexity angle for the lower face, while the differences in the overall facial convexity angle are not significant (p=0.067). There are significant differences between subjects for all examined angles except the total facial convexity angle between Class I and Class III.

Lower Incisor Inclination in Relation to Head Posture, Tongue and Hyoid Positions

Objectives: To investigate the relationship between head posture, hyoid bone, tongue position and lower incisor inclination. Materials and Methods: The study sample consisted of 98 subjects (35 males, 63 females), who had a mean age of 17.7 years in the permanent dentition and with a skeletal Class I relationship. Lower incisor inclination, craniovertical, craniocervical and craniohorizontal postural variables, tongue and hyoid position and airway measurements were evaluated on lateral cephalograms taken in natural head position. The study sample was divided into two groups according to lower incisor inclination (48 had IMPA&amp;lt;90 ⁰ with a mean degree of 88.09 and 50 had IMPA&amp;gt;90 ⁰ with a mean degree of 102.84) and a Student-t test was performed to compare and describe head posture, tongue and hyoid bone positions.Results: The subjects with upright incisors had a more posteriorly positioned hyoid bone relative to the mandibular symphysis compared with the subjects with flared incisors (p&amp;lt;0.05). Tongue length was greater in the flared incisor group than in the upright incisor group (p&amp;lt;0.05). In relation to head posture measurements, the upright incisor group had 3-3.5° larger cranio-cervical angles (NSL-OPT, NSL-CVT, NL-OPT, NL-CVT angles, p&amp;lt;0.05) than the flared incisor group. The airway measurements revealed no statistically significant difference between the groups.Conclusions: The position of the hyoid bone, tongue length and craniocervical head posture showed significant differences between upright and flared lower incisors.

The maxillary incisor labial face tangent: clinical evaluation of maxillary incisor inclination in profile smiling view and idealized aesthetics

BackgroundTo test the hypothesis that in profile smiling view, for ideal aesthetics, a tangent to the labial face of the maxillary central incisor crowns should be approximately parallel to the true vertical line and thereby perpendicular to the true horizontal line.MethodsAn idealized female image was created with computer software and manipulated using the same software to construct an “ideal” female profile image with proportions, and linear and angular soft tissue measurements, based on currently accepted criteria for idealized Caucasian profiles. The maxillary incisor labial face tangent was altered in 5° increments from 70 to 120°, creating a range of images, shown in random order to 70 observers (56 lay people and 14 clinicians), who ranked the images from the most to the least attractive. The main outcome was the preference ranks of image attractiveness given by the observers.ResultsThe most attractive inclination of a tangent to the labial face of the maxillary incisor crowns in profile view in relation to the true horizontal line was 85°, i.e. 5° retroclined from a perpendicular 90° inclination. The most attractive range appears to be between 80 and 90°. Excessive proclination appeared to be less desirable than retroclination. Beyond 105° most observers recommend treatment.ConclusionIn natural head position, the ideal inclination of the maxillary incisor crown labial face tangent in profile view will be approximately parallel to the true vertical line and thereby approximately perpendicular to the true horizontal line.

Expansión rápida maxilar en pacientes adultos jóvenes: comparación de aparatos dentosoportados y esqueletalmente soportados. Estudio de cohorte.

Introduction: Maxillary constrictions are one of the most frequent abnormalities, regardless of the type of dentition studied. They can be treated either with tooth-borne or bone-borne expander appliances, depending on the biological maturation of the patient. Treatment during prepubertal stages has been shown to be successful, but there is evidence of an open suture even in late adolescence stages. The aim of this study is to compare the effects of a rapid expansion bone-borne device to a tooth-borne device in young adults suffering from maxillary constriction, by means of Cone-Beam Computed Tomography. Materials and methods: A retrospective observational study was conducted in nine patients (three males, six females) with a mean age of 18±5.5 years, who attended the Dentistry Service of Universidad de Chile during 2014-2015. Six patients were treated with tooth-borne appliances (Hyrax type) and three patients with bone-borne appliances (MARPE). Linear measurements of the anterior and posterior transverse dimension and angular measurements of the inclination of molars and incisors were obtained through CBCT for each group in T1 and T2. Results: A significant increase in the posterior transverse dimensions in both groups was observed. Radiolucency of the suture was observed in all patients treated with miniscrews and in half of the patients treated with Hyrax. Greater angulation of molars was shown in the tooth-borne group in comparison with the bone-borne group. Conclusion: Both appliances caused an increase in the posterior transverse dimension, but bone anchored appliances achieved a more parallel and skeletal expansion. Randomized clinical trials with a larger sample and follow-up are needed.

Comparative Assessment of Three Microimplant Assisted Biomechanical Strategies for the Simultaneous Intrusion and Retraction of Anterior Teeth in Relation to Alveolar Bone Stress and Change in Incisor Inclinations – A 3D Finite Element Analysis Study

Microimplants are widely used to provide absolute anchorage in cases with bimaxillary dentoalveolar protrusion especially in those that require simultaneous retraction and intrusion of anterior teeth. The position of the microimplant significantly affects the build up of stress in the alveolar bone as well as the incisor inclinations, and is therefore a critical factor in treatment plannning. Keeping this in mind, this finite element method(FEM) study was taken up to identify the most suitable combination of implant placement sites for cases in which en-masse anterior retraction is done along with intrusion. The geometric model was constructed from a CBCT scan of the maxilla of an adult patient with full permanent dentition.The images were saved as DICOM files and were later exported to the 3D image processing software (Mimics,version 17). The center of resistance for the 6 anterior teeth was 9 mm superiorly and 13.5 mm posteriorly from the midpoint of crown tip of central incisors. The working archwires were assumed to be 0.019 / 0.025-in stainless steel. The three mini-implant placement sites compared were – S1- Midline micro implant between the maxillary central incisors with two placed posteriorly between maxillary 2nd premolar 1st molar roots. S2 – Micro implant placed between the lateral incisor and canine along with posterior mini implants as above. S3- Micro implant placed high up between the maxillary second premolar and first molar roots. The amount of tooth displacement after finite element analysis was compared with central and lateral incisor and canine axis graphs. For the system S1, intrusive components were seen on the archwire mainly in the anterior region with maximum displacement between central incisors and gradually decreasing away from point of force application. In S2, the intrusive component of force was more evenly distributed. In S3, pattern of intrusive component was similar to S2 but the maximum displacement was slightly lower. Greatest value of minimal principal stress was seen on cervical and apical third of central incisors as well as apical third of lateral incisors in S1; and cervical third of lateral incisors and apical and cervical third of canines in S2. Maximum retraction of anterior teeth was seen in S3. In all of the three systems of force application, tooth inclinations were maintained. Maxillary anterior teeth showed more tendency towards retraction in the case where two micro implants were placed posteriorly high up above the roots of maxillary premolars and molars such that the force is directed diagonally having both horizontal and vertical components, and hence eliminating the need for anterior implants. Greater intrusion tendency was seen when implants were placed between the roots of maxillary central incisors.

Cephalometric outcomes of a new orthopaedic appliance for Class III malocclusion treatment.

To evaluate dental and skeletal effects of a new orthopaedic appliance for the treatment of Class III malocclusion in growing patients. This retrospective cephalometric study was performed on a sample of 18 patients with a skeletal Class III malocclusion (4 males; 14 females; mean age 8.8 ± 1.5 years) treated with the Pushing Splints 3 (PS3) protocol. The control group consisted of 18 subjects (5 males; 13 females; mean age 9.1 ± 1.8 years) selected from a database of subjects with untreated Class III malocclusion. The cephalometric analysis was performed at the beginning (T0) and the end of the orthopaedic therapy (T1). Significant differences between the treated and control groups were assessed with independent samples t-test (P < 0.05). In the PS3 group, the post-treatment cephalometric values showed a forward displacement of the maxilla, resulting in a statistically significant increase of the SNA angle. ANPg and Wits appraisal improved significantly compared with the control group. Lingual inclination of mandibular incisors and buccal inclination of the upper incisors were significantly increased in comparison with the control group. No significant differences were recorded for backward mandibular rotation. This study presents a short-term evaluation of the treatment and the use of a historical control group. The PS3 was effective for the treatment of Class III malocclusion in growing patients, with favourable maxillary advancement and control of the vertical skeletal relationships.

Impact of myofunctional disorders of the maxillofacial area on the formation of occlusion pathology in children

Myodynamic balance of the muscles of maxillofacial area provides required conditions for normal development of dentoalveolar system. Dysfunction of the muscles of facial and oral area is a significant ethiopathogenetic factor of development of anomalies of tooth position and development of upper and lower jaws. Among such factors the most prevalent habits are sucking fingers, mouth breathing (in genetically, anatomically and physiologically caused absence of nasal breathing), incorrect lip seal and infantile swallowing. Position of the tongue in mouth breathing is of particular importance as positioning the tongue between the dental arches causes significant vestibular inclination of the upper incisors. As a result of these changes disocclusion is formed in vertical plane. Additional pressure of stretched buccal muscles during mouth breathing causes narrowing of the dental arches. It is required to mention that many researchers pay attention to decreased bioelectrical activity of masseters in electromyographic study in patients with occlusion anomalies. Formation of this pathology influences not only the general health state (disorder of nasal breathing, swallowing, chewing, sound pronouncing and posture) but also social adaptation of a child. Due to this children require complex approach to the diagnosis and correction of myofanctional disorders of maxillofacial area.

Relation between the changes of the maxillary incisor inclination and the movement of the mandible after bilateral sagittal split ramus osteotomy (BSSRO) in skeletal class III patients with surgery first approach (SFA)

Background: There have been a lot of reports investigating the stability of the mandible after BSSRO with SFA, but a few studies reported about the postoperative dental and skeletal change related to the surgery.