Incisor Relationship Research Articles

Herbst appliance treatment of Class II, Division 2 malocclusions

The purpose of this investigation was to analyze quantitatively the sagittal skeletal and dental changes that contribute to occlusal correction in Herbst treatment of 14 Class II, Division 2 malocclusions. Forty Class II, Division 1 Herbst subjects were used for comparison. Lateral head films from before and after Herbst treatment were analyzed, according to the method of Pancherz.1 The results revealed that all patients were treated to Class I or overcorrected Class I molar and edge-to-edge incisor relationships. The maxillary and mandibular skeletal changes were similar in both examination groups. In the Class II, Division 2 subjects, sagittal molar and overjet corrections amounted to an average of 5.9 mm and 3.1 mm, respectively. When comparing the Class II, Division 2 with the Class II, Division 1 subjects, overjet correction was, for natural reasons, significantly larger (p < 0.001) in the Class II, Division 1 subjects. In the subjects with Class II, Division 2 malocclusions, the upper incisors were proclined (mean = 3.0 mm), whereas in the subjects with Class II, Division 1 malocclusions, the incisors were retroclined (mean = 2.3 mm). The lower incisors were on the average proclined more (p < 0.05) in the Class II, Division 2 subjects (mean = 3.4 mm) than in the Class II, Division 1 subjects (mean = 2.4 mm). For sagittal molar correction, no differences in tooth movements were seen between the two malocclusion groups. In conclusion, it was found that the Herbst appliance is most effective in the therapy of Class II, Division 2 malocclusions. Proclination of the lower incisors during treatment (anchorage loss) is advantagous in this type of malocclusion. (Am J Orthod Dentofac Orthop 1997;112:287-91.)

The mechanism of Class II correction during Herbst therapy in relation to the vertical jaw base relationship: a cephalometric roentgenographic study.

This retrospective Herbst study analyzes and compares the sagittal dental and skeletal effects contributing to Class II correction in subjects with small or large pretreatment mandibular plane angles. Lateral headfilms of 15 hypodivergent (ML/NSL < or = 26 degrees) and 16 hyperdivergent (ML/NSL > 39 degrees) Class II subjects treated to a Class I occlusal relationship with the Herbst appliance were analyzed. Radiographs were taken before and after an average treatment period of 7 months. Cephalograms were evaluated according to the method of Pancherz. In both groups, impprovements in sagittal incisor and molar relationships were achieved by greater dental than skeletal changes. The amount of skeletal changes contributing to overjet and molar correction was larger in the hyperdivergent group (37% and 44%, respectively) than in the hypodivergent group (25% and 25%, respectively). Dental and skeletal changes contributing to Class II correction were found to be independent of the vertical jaw base relationship. Thus, a hyperdivergent jaw base relationship did not affect the treatment response unfavorably.

Soft tissue and dentoskeletal profile changes associated with maxillary expansion and protraction headgear treatment

One of the goals of early treatment of Class III malocclusion with maxillary expansion and protraction headgear is to significantly improve the dentofacial profile. The objectives of the present study were to determine (1) the interrelationships of the soft tissue and dentoskeletal profiles after maxillary expansion and protraction headgear treatment and (2) which cephalometric variables could contribute to an accurate prediction of the protraction effect on the soft tissue profile. Lateral cephalometric radiographs of 20 consecutively treated Class III patients (10 males, 10 females) by protraction headgear were included in this study. Their ages at the start of protraction headgear treatment ranged from 6 to 11 years, with an average of 8.1 ± 2.1 years. None of the patients had previous orthodontic treatment. For each patient, the first lateral cephalogram was taken 6 months before the initiation of headgear treatment (T o), and the second radiograph at the start of treatment (T 1). Therefore (T 1 − T o) represented 6 months of growth with no treatment. A third radiograph was taken 6 months after start of treatment (T 2). In this way, (T 2 − T 1) − (T 1 − T o) represented the effect the result of appliance therapy alone and each subject served as his/her own control. A computerized cephalometric analysis was used including variables assessing sagittal and vertical relationships of skeletal and soft tissue profiles, incisal relationships, soft tissue thickness, and lip structure. Data were analyzed by means of paired t tests, Pearson's product-moment coefficient correlation, and multiple regression analyses. The results showed significant improvements in dentofacial profile after 6 months of maxillary protraction. The skeletal and soft tissue facial profiles were straightened and the posture of the lips was improved. The normal incisal relationship (overjet) that was achieved had a significant impact on the soft tissues overlying both upper and lower incisors resulting in better lip competence and posture. Significant correlations were found between changes in the sagittal relationships of skeletal and soft tissue profiles in both the maxilla and the mandible ( p < 0.05). The forward movement of the maxilla was accompanied by a corresponding forward movement of the soft tissue profile at 50% to 79% of the hard tissue. In the mandible, the downward and backward movements of the soft tissues were equivalent to 71% to 81% of the corresponding hard tissues. The lack of high r square values in the multiple regression analyses reflected a low prediction value for the maxillary variables, but moderately high prediction value for the mandibular variables that could be used in preorthopedic treatment planning. This study showed that significant dentoskeletal changes and improvements in dentofacial profile resulted from 6 months of treatment with maxillary expansion and protraction. (A M J O RTHOD D ENTOFAC O RTHOP 1996;109:38-49.)

Are anterior occlusal radiographs indicated to supplement panoramic radiography during an orthodontic assessment?

Five hundred pairs of dental panoramic tomographs (DPT) and maxillary anterior occlusal radiographs (AO) from patients referred to the orthodontic department of a dental teaching hospital were examined to assess the diagnostic yield from a panoramic radiograph of the premaxillary region alone and then assess the additional yield when this view was supplemented by a maxillary anterior occlusal radiograph. Of the 500 DPTs assessed, 208 (42%) lacked clarity of the premaxillary region when the labial segments were used to locate the patient in the DPT machine. An association was found between patients who had abnormal incisor relationships and poor clarity in the premaxillary region of the DPT. Overall 165 (33%) of the supplementary AO views were used to support or refute findings identified on the DPT. It was concluded that in patients referred for an orthodontic assessment, supplementary radiography of the premaxilla may be justified in the following situations: 1. unsatisfactory image quality which may frequently be the case where there are abnormal incisor relationships, 2. localisation of tooth position by vertical parallax and 3. where a reasonable expectation that pathology exists on clinical grounds.

Maternal smoking and tooth formation in the foetus. II. Tooth crown size in the permanent dentition

Altogether 2159 pregnancies among black and white Americans in the Collaborative Perinatal Study and dental casts from their children at the age of 6–12 years were studied to determine the effect of maternal smoking on permanent tooth crown dimensions. A trend of reduction, similar to that observed in the deciduous second molars [11], was found in the permanent first molars and also in the mesio-distal dimension of permanent incisors in relation to sex and face of the children and smoking habits of the mother. In terms of peak in their mitotic growth, the results can be interpreted to indicate a sensitive period of intra uterine development from the 24th to 28th gestational weeks. Comparisons of postnatal body size and differential correlation patterns in affected tooth dimensions with early postnatal body and head size between smokers and non-smokers, suggests that maternal smoking during pregnancy may have an effect on basic growth of the head and body and/or the developmental process that impacts tooth development at some specific sensitive period also during the postnatal formation of these tooth crowns.

Quantification of function regulator therapy using elliptical Fourier functions.

The application of various functional appliances to correct antero-posterior skeletal discrepancies in the treatment of Class III malocclusion has received increased attention. In this context, elliptical Fourier functions (EFF) are particularly useful for eliciting boundary-outline information. This longitudinal study was undertaken to visually and numerically describe the shape alterations arising as a response to treatment with the FR-3 appliance of Fränkel. The subjects chosen were Caucasians (n = 14) from the Glasgow Dental Hospital and School who presented with Class III incisor relationships. Lateral cephalometric head-films were available prior to the initiation of treatment, at the end of active treatment, and at least one year out of retention. Maxillary and mandibular boundary outlines were carefully traced. A set of points, 42 on the maxilla, and 78 on the mandible, were precisely located. These points were then digitized and used to compute EFF's with 20 harmonics. These equations were then standardized for size. Subsequently, 102 maxillary and 150 mandibular closely spaced points on the outline were calculated from the EFF's. After superimposition on the centroid, expected vectors were then computed to these points from the centroid. Statistically significant dento-alveolar shape changes could be discerned with treatment. These involved a localized anterior repositioning of the maxillary incisal aspect with a concomitant posterior displacement of the mandibular incisal aspect. There was no evidence of shape changes in the basal areas of either the maxilla or mandible. This method of fitting Fourier descriptors, specifically EFF's, provides a precise numerical and visual description of the changes arising from functional regulator therapy.

Early treatment of Class III incisor relationship using the chincap appliance.

Twenty-three patients (10 male, 13 female), with Class III relationships of the incisor teeth at the mixed dentition stage, were treated with the chincap appliance associated, where appropriate, with an upper removable appliance to procline upper incisors and to free the occlusion. Cephalometric analyses at the beginning and at the end of active treatment were compared with those in a carefully matched untreated control group selected from the Belfast Growth Study. At the beginning of treatment patients differed significantly from the controls in the SNB was larger, ANB was negative, Wits' analysis was negative, and the intermaxillary angle significantly reduced. The overjet was reversed, the lower incisors were ahead of A-Po, and the upper lip was far behind the E line. Significant changes brought about by the treatment were improvement in the Wits' relationship (but there was no significant change in the ANB angle), increases in the intermaxillary angle and lower facial height, improvement in the overjet, proclination of upper incisors and retroclination of lower incisors, backward movement of the lower incisors in relation to A-Po, and backward movement of the lower lip. The efficacy of the chincap appliance can be attributed to retroclination of lower incisors and downward movement of the mandible which may improve the jaw relationship without affecting the ANB angle. There were marked changes in the lip posture.

Complete denture prescription--an audit of performance.

The quality of clinical records obtained during the various stages of complete denture construction was assessed in a survey conducted in five large dental laboratories in 1989. The most common fault in approximately half of 188 upper and 158 lower impressions was overextension in the labial and buccal sulci. Of the 87 occlusal records examined, the rims indicated the intended incisal relationship in about 50% of cases. The border of the eventual denture was defined by the technician rather than by the dentist in most instances. The post-dam was prescribed by the dentist in only 16% of the 50 trial dentures inspected. It is argued that a major cause of the lack of prescription is the level of the NHS fee, coupled with the fact that the laboratory expenses are deducted from that fee.

Application of an Occlusogram for Surgical Orthodontic Case

Since the occlusogram was introduced by Deguchi et al in 1982, a few articles of occlusogram were reported.There is, however, no article discussing if occlusogram could be used for diagnosis and treatment plan of surgical orthodontic cases.There is a little difference in using occlusogram between surgical orthodontic case and non-surgical.It seemed that the application of occlusogram was useful to surgical orthodontic case.This article shows how to use an occlusogram combined with lateral cephalometrics correcting incisor relationship to jaw discrepancy for surgical orthodontic cases.It was not only possible to predict the relation between occlusion and jaw after treatment, but also the distance of right and left setback of mandibular precisely.

Long-term effect of rapid maxillary expansion studied in one patient with the aid of metallic implants and roentgen stereometry.

The articulatory displacement of maxillary bones during and after rapid maxillary expansion (RME) was studied with metallic implants and roentgen stereometry (RSA) for 3653 days in a girl aged 12 at start of treatment. She had a narrow upper dental arch with anterior crowding and a normal incisor relationship, and a normal sagittal molar relationship with bilateral cross-bite. Three implants were inserted in each maxillary bone and they remained stable in the bones during the 10-year observation period. In the 3-D analysis of the articulatory displacement, the left maxillary bone was studied in relation to the right bone in three periods: RME (23 days), retention (108 days) and follow-up (3522 days). Extensive relapse of rotations as well as translations was found and the long-term effect of RME was limited. In our opinion the relapse was caused mainly by the resistance to deformation from circum-maxillary sutures and surrounding soft tissue matrix, and inadequate bone formation in the involved sutures. As is generally known in clinical oral orthopaedics, changes obtained by short-term simple mechanical interference with a complex biological system tend to reverse spontaneously. Thus, the rationale for RME treatment may be seriously questioned.

A modification to the incisor classification of malocclusion.

During the study of two-hundred orthodontic cases under treatment in the General Dental Service, four clinicians showed only moderate agreement using the British Standard Classification of Incisor Malocclusion. Cohen's Kappa statistic was used to measure the inter-examiner agreement. The 35 cases in which there was high disagreement between the examiners were scrutinized to determine the source of this disagreement. Following discussion, revised definitions were produced which included the introduction of a Class II-intermediate group. After an interval of 2 months these 35 cases were reclassified using the new definitions. Increased inter-examiner agreement was found. Four examiners (three of whom were common to the original study) then used the modified classification to describe the incisal relationship of 100 cases referred for treatment at Bristol Dental Hospital. The inter-examiner and the intra-examiner agreement were both found to be good. It is recommended that the Incisor Classification of Malocclusion be extended to include a Class II-intermediate group.

Positioning control of the upper incisors in orthognathic surgery: Pre-operative planning with the Model Positioning Device and intra-operative application of the Sandwich Splint

In orthognathic surgery a three-dimensional positioning of the maxilla is possible by means of the Le Fort I osteotomy and subsequent maxillary movement. In treatment planning and at the time of surgery it is very important to achieve an exact positioning of the upper incisors in relation to the upper lip and the rest of the skull. The Model Positioning Device described here allows three-dimensional positioning of the upper incisors in one- or two-jaw surgery. The reference plane is the upper surface of the upper part of a semi-individually adjustable articulator. The application of the Sandwich Splint enables the three-dimensional positioning of the maxilla in relation to the rest of the skull. The Sandwich Splint ensures that the vertical position of the mandible in relation to the rest of the skull above the osteotomy plane is exactly reproducible in the pre- and post-operative situation in both model surgery and at time of surgery. To this mandibular position the maxilla is positioned in three dimensions, as preplanned. The vertical dimension, which is identically reproducible before and after surgery is measured with a caliper. After surgery the mandible can be rotated into the planned new intercuspidation.

Soft-tissue and dentoskeletal profile changes associated with mandibular setback osteotomy

The aims of the present retrospective cephalometry study were (1) to describe the interrelationships of the soft-tissue and dentoskeletal profiles after total mandibular setback osteotomies and (2) to detect whether there were any cephalometric variables that could contribute to an accurate prediction of the surgical effect on the soft-tissue profile. The presurgical and postsurgical lateral cephalograms of 50 consecutively treated patients (37 females and 13 males) were used; these patients had received combined orthodontic-surgical management of mandibular prognathism by means of a bilateral vertical ramus osteotomy with an extraoral approach. At the time of surgery, their ages ranged from 17 to 41 years. Lateral cephalograms with the teeth in habitual occlusion taken before and approximately 1 year after surgery were available for all patients. A computerized cephalometric appraisal, named profile analysis, was developed and used, including variables corresponding to sagittal and vertical relationships of skeletal and soft-tissue profiles, incisal relationships, soft-tissue thickness, and lip morphology. The statistical elaboration of the data was made by means of paired t test, Pearson's product-moment coefficient correlation, and multiple regression analyses. The assessment of the results disclosed that considerable facial changes and improvement took place after the surgical procedure. The skeletal and soft-tissue facial profiles were straightened and the posture of the lips was improved. The normal incisal relationship achieved became influential on the soft tissues overlying both incisors and led to a better lip competence and posture. Posterior movement at points B and Po was accompanied by reductions ranging from 91% to 103% of the corresponding soft tissues. The presence of both significant correlation coefficients (p less than 0.05) and high r square values (greater than 0.70) in the multiple regression analysis for the osseous tissue variables N-B and N-Po, alone or together with the overjet and S-N-B angle, respectively, reflected their high prediction value with regard to the sagittal relationship of the lower lip, its thickness, and the soft-tissue thickness at the chin area. The findings of Pearson's product-moment coefficient correlation also indicated that the operative changes of the thickness of the upper lip, the lower lip, and the soft tissue at the chin region are influenced by the initial preoperative thickness of the area.

Rationale of Treatment for Class II Division 2 Malocclusion

Class II, division 2 malocclusion is a clinical entity which presents considerable difficulty in the provision of a stable treatment result. This article sets out the problems encountered, reviews teaching on the subject over a 20-year period and attempts to rationalize the current approach to treatment. The rationale presented shows the three-dimensional nature of the occlusal problem, and discusses the justification for expansion and proclination of lower incisors in relation to soft tissue influences and stability. The importance of correcting edge-centroid relationship and reducing inter-incisor angle is stressed. Non-extraction therapy, with some lower arch expansion and incisor advancement, is recommended and the reasoning behind this is explained with a case example to illustrate the points involved.

Temporomandibular joint findings in pediatric populations and young adults: a critical review.

The etiology, diagnosis and treatment of temporomandibular joint (TMJ) pain and dysfunction is a controversial subject. There are varying opinions regarding the contribution of occlusion (malocclusion) to the development of mandibular dysfunction and further, the contribution of occlusal alterations (orthodontic and restorative) to the development of pain and dysfunction. Epidemiologic investigations suggest there is a high incidence of subjective and objective symptoms in the pediatric population. Observations on incisal relationships, condyle position and joint sounds, and comparisons to controls seem to suggest that these factors are not the cause of pain or dysfunction. The purpose of this review is: (1) to bring the clinician's attention existing published information reporting the presence of symptoms in children, (2) to evaluate selected information in young adults, (3) to question anecdotal information on the etiology of TMJ problems. It is not in the purview of this paper to determine the overall etiology of TMJ dysfunction.

Treatment of Class II malocclusions with removable appliances. Part 4. Class II division 2 treatment

Severe Class II division 2 is a difficult malocclusion to treat properly, especially when lower incisors contact palatal mucosa. Only fixed appliance therapy can achieve worthwhile and lasting improvement of the incisor relationship in this situation. In less severe cases, it may be possible to achieve limited objectives using removable appliances. When planning treatment, extraction of mandibular premolars should be avoided if at all possible.

Factors that affect alignment of upper permanent lateral incisors in early mixed dentition

The purpose of the present study was to find the factors that affect the alignment of the upper permanent lateral incisors in early mixed dentition. The materials, consisting of dental casts and lateral cephalograms which were taken from 30 children (15 males and 15 females) who had normal occlusion in deciduous dentition and normal permanent central incisor relationship, were divided into three groups, according to the bilateral symmetry alignment of the upper permanent lateral incisors (Group A: Normal alignment, Group B: Linguoversion, Group C: Mesiolinguotorsiversion). The principal component analysis was carried out to clarify the characteristics among the multi-variates, which are upper incisor shape, dental arch form, craniofacial morphology and amount of dento-craniofacial development, in Groups A, B and C. The results obtained were as follows: Group A shows a tendency to be harmonious in upper permanent incisor shape, dental arch form, craniofacial morphology and dento-craniofacial development. Group B shows a tendency to have a larger labio-lingual width of the upper permanent incisors, less anterior arch length development and less forward movement of the upper permanent lateral incisor in the maxilla before eruption. Group C shows a tendency to have a larger mesio-distal width of the upper permanent incisors, less anterior arch width development, longer distance between the upper permanent lateral incisor edge and the nasal floor and more forward and descent movement of the upper permanent lateral incisor in the maxilla before eruption.

The Treatment of Bimaxillary Protrusion

Thirty bimaxillary protrusion cases, who had four first premolars extracted were compared with thirty Class I malocclusion cases who, likewise, had similar extractions and treatment. The changes, both in incisor relationships and the concurrent soft tissue profiles are documented. During treatment, the inter-incisal angle was increased by 20 degrees and relapsed by 4 degrees post-treatment. The protuberance of the soft tissue profile was significantly reduced by 4 degrees concurrently (Holdaway Angle). It is concluded that worthwhile treatment objectives can be achieved in these cases.

Cephalometric evaluation of incisor position.

An evaluation of seventeen measurements of incisor angulation and position for their applicability in describing the incisor relationship to maxilla and mandible. Most are better descriptors of other relationships that could confound interpretation of relationships to the supporting bones.

Incisal relationships during speech

1. The dimensions of movement of the mandible during the reading of a standard passage of text have been measured and enable a speech envelope to be described. 2. The relationship between closest speaking space and the vertical overlap of the incisor teeth shows that there is a trend in this direction, but it is not as definitive a correlation as has been previously assumed. 3. The relationship between the anterior speaking space and the horizontal overlap of the incisor teeth shows a similar trend but with a much reduced correlation. 4. There was often a small space of approximately 0.2 mm between the mandibular incisor teeth and the palatal aspects of the maxillary incisor teeth that, although a common finding in this study, was by no means a constant feature for all subjects.