Mandibular incisor crowding in completed cases

Comparative Study of Tooth Size and Arch Dimensions in Class I Crowded, Proclined Malocclusion and Class I Normal Occlusion

Aim

The objectives are to compare the extent and to find whether it is arch dimension or tooth size that contributes to a greater extent to malocclusions such as dental crowding and proclination.

Materials and Methods

A total of 90 pretreatment models were selected and divided into three groups, namely uncrowded (Group-A), crowded (Group B), and proclination (Group-C). Measurements obtained were: (1) The largest mesiodistal width of each tooth on each arch (except the second and third molars), (2) Buccal inter-canine and inter-molar widths, (3) Lingual inter-canine and inter-molar widths, (4) Arch perimeters, and (5) Arch length.

Results

The mesiodistal teeth dimensions were higher in crowded and proclination group. Both inter canine width and inter molar width of maxilla were reduced in crowded group. Maxillary and mandibular arch perimeter and arch lengths were higher proclination group.

An odontometric study of tooth size in normal, crowded and spaced dentitions

OBJECTIVE

To assess the mesio-distal tooth width in normal, crowded, or spaced dentitions.

MATERIALS AND METHODS

A sample of 192 maxillary and mandibular dental casts of Libyan subjects was selected from a larger cohort. These subjects did not present with craniofacial anomaly, hypodontia, significant attrition, caries, restorations, or history of permanent tooth extraction or orthodontic treatment. The sample was divided into normal, crowded, and spaced groups according to tooth size/arch length discrepancy. Each group included 32 upper and lower dental casts with equal numbers of males (mean (SD) age = 14.7 (1.9) years) and females (mean (SD) age = 15.7 (2.5) years). The mesiodistal (MD) tooth width, sum of the MD tooth widths mesial to the first molars (TTM), sum of the MD width of the four incisors (I), and the sum of the MD width of canine and first and second premolars (CPP) were calculated for each group. The independent Student t-test was applied sequentially to detect significant differences between paired groups. The ANOVA test was undertaken to explore significant differences between the three groups. Pearson coefficient of correlation was used to evaluate the correlation between I and the corresponding CPP in maxillary and mandibular arches.

RESULTS

MD tooth width, TTM, I, and CPP were significantly wider in the crowded compared to normal and spaced dentitions (P<0.001), except for the width of the upper left lateral incisors in both normal and crowded groups. Although there was a trend for smaller tooth widths in spaced dentitions compared to normal ones, this was only significant in the maxillary left central incisor, maxillary right and left lateral incisors, maxillary right first premolar, mandibular right lateral incisor, and mandibular right canine (P<0.05). However, the maxillary TTM, I, and CPP in the normal group were significantly greater than in the spaced group (P<0.05). Significant positive correlations existed between the mean values of I and CPP in both the maxillary and mandibular dentitions of all groups (P<0.01).

CONCLUSIONS

It appears that in the studied Libyan population, the MD tooth width is a significant component of crowding/spacing.

Relapse of incisor crowding: a visit to the Prince of Salina

The management of the retention period after comprehensive orthodontic treatment is of great importance, as a primary goal of clinician. Considerable controversy still surrounds the problem of stability after the retention period. Many studies analyze factors associated to the presence of crowding or incisor irregularity and find predictive features on its relapse. Most studies have reported little o no correlation between the treatment changes in the biological parameters - clinical, biometric (irregularity index, intermolar width, intercanine width, arch length, overjet, overbite), or cephalometric variables- that ocurred and the posttretament and postretention changes that may predict their future development. This article provides a bibliographical overview on the relapse of dental alignment in treated cases. In a brief historical introduction, the first studies on the long-term stability of orthodontic results are analysed. The article then goes on to assess studies that focus attention on anteroinferior alignment before finally studying relapse of upper crowding. It concludes by making some final comments in the light of the bibliography provided and the differents schools regarding retention needs and methods.

Extração de incisivo inferior: uma opção de tratamento ortodôntico

A exodontia de um incisivo inferior pode ser considerada uma opção valiosa na busca de excelência nos resultados ortodônticos para obtenção de máxima função, estética e estabilidade. O objetivo deste estudo foi reunir informações referentes às indicações, contraindicações, vantagens, desvantagens e estabilidade dos resultados obtidos nos tratamentos realizados com extração de um incisivo inferior. Essa opção de tratamento pode ser indicada em más oclusões com discrepância de volume dentário anterior devido a incisivos superiores estreitos e/ou incisivos inferiores largos. É contraindicada em más oclusões sem discrepância anterior ou com discrepâncias ocasionadas por incisivos superiores largos e/ou incisivos inferiores estreitos. A literatura sugere maior estabilidade pós-tratamento quando comparada com a opção de extrações de pré-molares. Além do diagnóstico cuidadoso, obtido com a colaboração do set-up, a habilidade e a experiência clínica do profissional são importantes para o sucesso dos resultados ortodônticos alcançados com essa opção de tratamento

Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 1. Arch length and area

The purpose of this study was to investigate changes in arch length, arch area, and irregularity index in patients treated with and without premolar extractions. Records collected at pretreatment, at bracket removal, at the end of retention, and 5 years out of retention were examined. Stone casts were mounted on an articulator with an anatomic face-bow and a central wax record, and measurements were made with a 3-dimensional digitizer. In general, the maxillary arch exhibited less relapse tendency than did the mandibular arch for both patient groups. In general, the extraction group showed the same relapse tendency as the nonextraction group.

A review of changes in lower arch alignment from seven to fifty years

Changes in alignment in the untreated lower arch were studied at various developmental stages: 7 to 10 years, 10 to 12 years, 12 to 15 years, 13 to 18 years, 18 to 21 years, 21 to 28 years, and 18 to 50 years. On average, crowding decreased between 7 and 12 years and increased thereafter. The maximum increase occurred in the teenage years between 13 and 18, little or no change occurred in the third decade, and small increases occurred later in life. The possible cause of these changes is discussed in relation to the deterioration in alignment reported in orthodontically treated patients after retention.

Late lower arch crowding in relation to soft tissue maturation

Changes in lower arch space condition and incisor inclinations were measured in relation to changes in the cross-sectional area and separation of the lips in habitual posture in 23 boys and 23 girls between the ages of 12.5 and 15.5 years. Correlation analysis revealed no direct relationship between the increase in lower arch crowding and the changes in lip size and position. In girls, the increase in lower arch crowding was associated to some extent with retroclination of the upper incisors and an increase in the interincisal angle. A very tenuous relationship was found between changes in the upper lip size and position and changes in incisor angulation.

Relapse revisited

Rather little is known about the changes in orthodontic treatment results exceeding a decade after treatment. The purpose of this study was to quantify changes in tooth relationships in a series of cases (n = 36) at 6 years and again at 15 years after treatment. The rate of change decreased with time, supporting the contention that most "relapse" occurs soon after treatment; continued change generally cannot be distinguished from normal aging processes that occur, regardless of whether a person had been treated orthodontically. There were minor, but statistically significant, associations between increased incisor irregularity ("relapse") and parasagittal growth of the jaws. Greater irregularity occurred when mandibular growth exceeded that of the maxilla, decreasing overjet and crowding the lower incisors within the containing arch of the maxilla. Overall, relapse tended to be less in these cases treated by a single experienced specialist that in university-based samples treated by multiple, orthodontic residents.

Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment

The purpose of this study was to evaluate the treatment and posttreatment changes in the facial and dental parameters in two groups of patients with Class II, Division 1 malocclusions. In one group (n = 46), the patients were treated with a nonextraction approach, whereas in the second group (n = 45), the treatment included the extraction of four first premolars. The treatment groups were compared with matched untreated normals (n = 35) from the Iowa Growth Study. Lateral cephalograms and dental casts were evaluated at three stages: pretreatment, posttreatment, and approximately 2 years after treatment. Student's t tests were used to compare the extraction and nonextraction groups. Significance was predetermined at p < or = 0.05. The cephalometric findings indicate that before treatment, the subjects treated with four first premolar extractions had more protrusive upper and lower lips and a larger tooth size-arch length discrepancy. After treatment the upper and lower lips were more retrusive in the extraction groups, and more protrusive in the nonextraction groups. The extraction groups tended to have straighter faces and slightly more upright maxillary and mandibular incisors, whereas the nonextraction groups had the opposite tendencies. The average soft tissue and skeletal measurements for both groups were close to, but on opposite sides of, the corresponding averages derived from the Iowa normative standards. The findings from the dental arch measurements indicate that after treatment both the extraction and nonextraction groups experienced an increase in tooth size-arch length discrepancy and a reduction in arch length. In general, extractions did not significantly alter the direction of the overall posttreatment trends. Furthermore, the trends in the posttreatment changes were similar in male and female patients, as well as in the maxillary and mandibular arches. The current findings suggest that the extraction/nonextraction decision, if based on sound diagnostic criteria, does not have a systematic detrimental effect on the facial profile. But clinicians should be aware of the trends introduced by the two treatment modalities to avoid accentuating undesirable profile characteristics.

Treatment and postretention changes in dental arch width dimensions--a long-term evaluation of influencing cofactors

The aim of the present long-term follow-up study of orthodontically treated patients was to analyze postretention changes in arch width dimension and to isolate factors that may serve as predictors of long-term prognosis. Pretreatment, end-of-treatment, and postretention (at least 10 years) models of 226 cases with different malocclusions were used to measure intercanine and intermolar width, arch length, sum of the mesiodistal dimension of the incisors, irregularity index, crowding, molar and canine relationship, overjet, and overbite. To assess the influence of initial and end-of-treatment alignment, kind of treatment (extraction versus nonextraction) and the amount of expansion in postretention stability, the sample was divided into different subgroups. The findings indicate that postretention arch width relapse occurred more frequently in the upper intermolar (25.8%) and lower intercanine region (23.9%) than in the lower intermolar (19.0%) and upper intercanine (13.8%) region. Pretreatment and posttreatment alignment as well as the kind of treatment and the amount of expansion were found to be influencing factors. The study concludes by proposing a reassessment of the definition of stability. The influence of the pretreatment anomaly, kind of treatment, amount of expansion, and posttreatment alignment on long-term stability should be recognized. Patients should be apprised of treatment limitations before treatments.

The etiology of late lower arch crowding alternative to mesially directed forces: a review

The causes of late crowding in the lower arch alternative to mesially directed forces are reviewed under the headings: late mandibular growth, skeletal structure and complex growth pattern, soft tissue maturation, periodontal forces, tooth structure, occlusal factors, and connective tissue changes. A multifactorial basis for late lower arch crowding seems likely.

Mandibular incisor extraction therapy

Extracting a mandibular incisor has been stigmatized as an expedient that may adversely affect the occlusion. However, when properly used, the extraction is only one aspect of the total correction of the malocclusion. Failure to observe this will fulfill the negative predictions. Articulating six maxillary with five mandibular anterior teeth necessitates a visualization of the posttreatment occlusion, and therefore specific criteria for case selection are essential. Treatment trends oscillate between nonextraction and four premolar extractions, with perhaps insufficient attention currently given to alternatives. This middle of the road approach is indicated in carefully selected cases, especially where space requirements and facial esthetics do not call for greater dental movements.

[Data analysis in long-term follow-ups of previously treated orthodontic patients]

The structure of former orthodontically treated patients, who underwent a long-term follow-up study in October 1989, was evaluated. An attempt was made to contact 1429 former patients, whereby 28.8% did not get the invitations because they had changed their address. As the compliance of approximately 17 years postretention of the 1,018 patients depends on change of address, job, interest and death, 20% of these were willing to participate and get examined. A structural conformity of the controlled group and the patient total cannot be presumed due to the patients' answers in the follow-up study. Questionnaires will be sent to patients, who did not participate in the analysis, in order to avoid unilateral results.

The stability of the arch-expansion effects of Fränkel appliance therapy

To assess the long-term stability of the arch expansion effects of the functional regulator, mandibular dental casts were evaluated for treatment and postretention changes in intercanine width, width between first premolars, width between second premolars, intermolar width, incisor irregularity, and arch length. This study was comprised of 11 cases that were treated with the Fränkel appliance (mean = 27 mo.) and were and average of 4 years and 4 months out of active treatment. Results showed overall stability to be good, with some variability present in individual responses. Intercanine width, width of first premolars, width of second premolars, and intermolar width all demonstrated maintenance of treatment increases. Correction of incisor irregularity displayed better stability than has been reported in other stability studies. Arch length decreased with treatment and continued to decrease during the postretention period, although to a lesser extent than has been previously reported. The results of this study support the statements of Fränkel concerning the stability of this type of arch expansion.

A long-term study of the relationship of third molars to changes in the mandibular dental arch

The purpose of this study is to determine the relationship of third molars to changes in the mandibular dental arch. The sample for this study consisted of four groups and subgroups. The groups consisted of premolar extraction treated, nonextraction treated with initial generalized spacing, nonextraction treated, and serial extraction untreated subjects. The subgroups were divided into persons who had mandibular third molars that were either impacted, erupted into function, congenitally absent, or extracted at least 10 years before postretention records. The mean postretention time interval was 13 years, with a range of 10 to 28 years. The mean postretention age was 28 years 6 months, with a range of 18 years 6 months to 39 years 4 months. Two-way analysis of variance with repeated measures was used to compare the changes over time (before treatment, at end of active treatment, and after retention) of groups and third molar subgroups. With time, mandibular incisor irregularity increased while arch length and intercanine width decreased. The eruption patterns of mandibular incisors and first molars were similarly dispersed in all groups studied. The findings between the subgroups in which mandibular third molars were impacted, erupted into function, congenitally absent, or extracted 10 years before postretention records revealed no significant differences between any of the subgroups for the parameters studied. No significant differences in mandibular growth were found between the third molar subgroups; this suggests that persons with third molars erupted into satisfactory function do not have a significantly different mandibular growth pattern than those whose third molars are impacted or congenitally missing. In the majority of cases some degree of mandibular incisor crowding took place after retention, but this change was not significantly different between third molar subgroups. This finding suggests that the recommendation for mandibular third molar removal with the objective of alleviating or preventing mandibular incisor irregularity may not be justified.

Post-orthodontic occlusal function

The significance of orthodontic treatment in the aetiology of temporomandibular dysfunction continues to be a matter of controversy. However, the evidence of any association has been generally negative. This investigation involved the examination of a study group of 87 post-orthodontic patients, the average time out of all retention being 52 months. They were compared with an untreated control group. Signs and symptoms of temporomandibular disfunction were assessed for both groups. In only one instance, soft joint click, was there found to be a significant association between the treatment category and the occurrence of the symptom, there being a higher rate of soft clicks in the post-treatment group. While this may be ascribed to orthodontic treatment, there was also a different restorative pattern in the two groups. No other significant associations were found.

Nonextraction orthodontic therapy: posttreatment dental and skeletal stability

To assess the long-term stability of nonextraction orthodontic treatment, the dental cast and cephalometric records of 28 cases were evaluated. Thirty cephalometric and seven cast parameters were examined before treatment, posttreatment, and an average of almost 8 years postretention. Results showed overall long-term stability to be relatively good. Relapse patterns seen were similar in nature, but intermediate in extent, between untreated normals and four first premolar extraction cases. Significant decreases were seen in arch length and intercanine width during the postretention period despite minimal changes during treatment. Incisor irregularly increased slightly postretention; intermolar width, overjet, and overbite displayed considerable long-term stability. Mandibular incisor mesiodistal and faciolingual dimensions were not associated with either pretreatment or posttreatment incisor crowding. Class II malocclusions with large ANB values and shorter mandibular lengths showed increased incisor irregularity, shorter arch lengths, and deeper overbites at the postretention stage, suggesting that the amount and direction of facial growth may have been partially responsible for maturational changes seen during the postretention period.

Mandibular incisor dimensions and crowding

Previous authors have suggested that well-aligned mandibular incisors are narrower mesiodistally than incisors which crowd and that reducing mesiodistal dimensions of the mandibular incisors to fit a specific size range will prevent future malalignment. This study examined 164 cases from the records of the University of Washington Department of Orthodontics, 134 of which had been orthodontically treated and were a minimum of 10 years postretention. Measurements were made from the postretention plaster casts and from serial cephalometric head films. Statistical tests showed that there was a weak association between incisor widths or MD/FL dimensions ratio and irregular alignment over the long term. Mean dimensional differences between crowded and uncrowded incisors were small in the few pooled or segregated groups in which statistically significant differences were found. When incisor dimensions were combined with pretreatment, posttreatment, or long-term cephalometric and cast measurements, only weak and not clinically useful associations were found with long-term incisor alignment. While there was a weak tendency for narrower incisors to be associated with better alignment in some instances, narrower mesiodistal widths of mandibular incisors did not ensure long-term stability in orthodontically treated cases.

Tooth morphology and lower incisor alignment many years after orthodontic therapy

The dental models of seventy-seven orthodontically treated patients were evaluated to determine the contribution of lower incisor tooth dimensions to their alignment many years after treatment. Tooth dimensions included the maximum mesiodistal (MD) and faciolingual (FL) dimensions and the shape ratio represented by MD/FL. Incisor alignment was assessed by means of Little's irregularity index, and all measurements were recorded to the nearest 0.1 mm with modified dial calipers. Multiple regression analysis revealed that the total contribution of all these lower incisor dimensions accounted for only 7.4% of the variability in their alignment, which was not statistically significant. A similar lack of association between lower incisor tooth dimensions and their alignment was found in a sample of eighty-six adults with untreated malocclusions. It therefore appears that the size and shape of the lower incisors do not significantly contribute to their alignment many years after orthodontic treatment.

Stability and relapse of mandibular anterior alignment-first premolar extraction cases treated by traditional edgewise orthodontics

Assessment at least 10 years postretention of sixty-five cases previously treated in the permanent-dentition stage with first-premolar extractions, traditional edgewise mechanics, and retention revealed considerable variation among patients. The long-term response to mandibular anterior alignment was unpredictable; no variables, such as degree of initial crowding, age, sex, Angle classification, etc., were useful in establishing a prognosis. Typically, arch width and length decreased after retention, regardless of treatment expansion or constriction. Two thirds of the patients had unsatisfactory lower anterior alignment after retention. Cases that were minimally crowded before treatment usually became more crowded, while initially severe crowding cases usually moderated.