Crowding and spacing in the dental arches: Long-term development in treated and untreated subjects

Early extractions of premolars reduce age-related crowding of lower incisors: 50 years of follow-up

Objectives

To study the effects of extraction of four premolars, without subsequent orthodontic treatment, on the crowding of lower incisors in subjects between early adolescence and late adulthood, as compared to untreated subjects.

Materials and methods

A total of 45 subjects were included in this study. The extraction group comprised 24 subjects who had all the first premolars removed at a mean age of 11.5 years, to relieve crowding in a class I malocclusion without subsequent orthodontic treatment. The control group had 21 untreated subjects, having a normal occlusion at a mean age of 13.0 years. The participants were documented with dental casts and cephalograms at mean ages of 11.4 and 13.0 years, for the two groups respectively (T1), and at mean ages of 30.9 years (T2) and 61.7 years (T3). Changes in lower incisor crowding were described as changes in “irregularity” and “space deficiency.”

Results

The extraction group showed no changes in the irregularity of the lower incisors and significant improvement of the space deficiency of the lower teeth into late adulthood. While in the control group, both irregularity of the lower incisors and space deficiency of the lower teeth increased significantly into late adulthood.

Conclusion

Lower incisor alignment remains mainly unchanged into late adulthood in subjects who have all their first premolars removed in childhood, as the only treatment to relieve teeth crowding.

Clinical relevance

Severe crowding in a class I occlusion can be solved solely with premolar extraction, allowing for spontaneous adjustments with more stable incisor alignment up to late adulthood.

Anterior tooth alignment and arch dimensions changes: 37-year follow-up in patients treated with and without premolar extraction

INTRODUCTION

The objective of this research was to evaluate the anterior tooth alignment and dental arch dimension changes after orthodontic treatments with and without premolar extractions in the long-term.

METHODS

Fifty-seven patients with Class I and Class II malocclusion were divided into 2 groups. Group 1 included 16 patients treated with nonextraction therapy, with mean initial (T1), final (T2), and long-term follow-up (T3) ages of 13.20 years, 15.07 years, and 50.32 years, respectively. The mean treatment (T2 - T1) and long-term follow-up (T3 - T2) times were 1.86 years and 35.25 years, respectively. Group 2 included 41 patients treated with extraction of 4 first premolars, with T1, T2, and T3 ages of 13.31 years, 15.63 years, and 53.60 years, respectively. The mean treatment and long-term follow-up times were 2.32 years and 37.96 years, respectively. The mean retention time was 2.26 years for both groups. The dental casts were obtained and digitized at T1, T2, and T3 stages. The following measurements were obtained: Little irregularity index, arch length, perimeter, and intercanine, interpremolar, and intermolar widths. Intragroup and intergroup comparisons were performed with repeated measures analysis of variance and t tests, respectively.

RESULTS

Anterior tooth irregularity index increased at T3 in both groups. In addition, all arch dimensions, except the intercanine width, were significantly smaller in the extraction group at T3. Both groups showed similar arch dimension changes at T3, except for the mandibular arch perimeter. The percentage of mandibular anterior tooth alignment change was significantly greater in the nonextraction than in the extraction group.

CONCLUSIONS

There was no difference in the changes of anterior alignment and transverse arch dimensions in patients treated with and without premolar extraction at T3, but the percentage of mandibular anterior tooth alignment changes was higher in the nonextraction than in the extraction patients at T3. The mandibular arch perimeter showed more of a decrease at T3 in extraction patients.

Occlusal Features and Caries Experience of Hong Kong Chinese Preschool Children: A Cross-Sectional Study

Objective: To study occlusal features and their relation to caries experience in Hong Kong Chinese preschool children. Methods: Seven kindergarten classes in Hong Kong were selected using a stratified random sampling method, and the 4- and 5-year-old Chinese kindergarten children were invited to join the survey. Two calibrated dentists performed the clinical examinations in the kindergartens. Occlusion features, including incisal overjet; canine and molar relationship; median diastema; and primate space as well as malocclusion features, including crossbite; anterior open bite; and scissor bite, were recorded. Caries experience was recorded with the dmft index. Results: A total of 538 children were invited to participate in the study, and finally 495 children were examined (92%). Approximately half (52%) had a normal incisor relationship. Most children had a class I canine relationship (left-79%; right-75%). Approximately two-thirds had a flush terminal plane (left-64%; right-65%). Most children (76%) had a maxillary primate space, and 47% had a mandibular primate space. The prevalence of median diastema, anterior crossbite, and unilateral posterior crossbite was 30%, 12% and 1%, respectively. No bilateral posterior crossbite or scissor bite was found. Approximately half (49%) had caries experience. The mean dmft score was 2.1. Gender and age were not associated with either the studied occlusal features or the mean dmft score (p > 0.05). Conclusion: Approximately half of the Hong Kong preschool children studied had a normal occlusion, and two-thirds of them had a flush terminal plane. About three-quarters of them had a maxillary primate space, and half of them had a mandibular primate space. Their occlusal traits were not associated with caries experience and prevalence.

Changes in lower dental arch dimensions and tooth alignment in young adults without orthodontic treatment

OBJECTIVE:

The aim of this longitudinal study, comprising young adults without orthodontic treatment, was to assess spontaneous changes in lower dental arch alignment and dimensions.

METHODS:

Twenty pairs of dental casts of the lower arch, obtained at different time intervals, were compared. Dental casts obtained at T₁ (mean age = 20.25) and T₂ (mean age = 31.2) were compared by means of paired t-test (p < 0.05).

RESULTS:

There was significant reduction in arch dimensions: 0.43 mm for intercanine (p = 0.0089) and intermolar (p = 0.022) widths, and 1.28 mm for diagonal arch length (p < 0.001). There was a mild increase of approximately 1 mm in the irregularity index used to assess anterior alignment (p < 0.001). However, regression analysis showed that changes in the irregularity index revealed no statistically significant association with changes in the dental arch dimensions (p > 0.05). Furthermore, incisors irregularity at T₂ could not be predicted due to the severity of this variable at T₁ (p = 0.5051).

CONCLUSION:

Findings suggest that post-growth maturation of the lower dental arch leads to a reduction of dental arch dimensions as well as to a mild, yet significant, increase in dental crowding, even in individuals without orthodontic treatment. Furthermore, dental alignment in the third decade of life cannot be predicted based on the severity of dental crowding at the end of the second decade of life.

Perceptions of dental professionals and laypeople to altered maxillary incisor crowding

INTRODUCTION

The aim of this study was to determine how sensitive dental specialists and laypeople are to maxillary incisor crowding when viewed from the front.

METHODS

Computer technology was used to create a series of photographs of the incisors of a smiling woman viewed from the front. The photographs showed varying degrees of maxillary incisor crowding classified according to Little's irregularity index (LII). The incisors illustrated in the photos were ranked on a scale from perfect alignment to severely crowded. The rating was done by 4 groups of people: orthodontists, general dentists, laypeople with experience of orthodontic treatment, and laypeople with no history of orthodontic treatment.

RESULTS

The orthodontists and the general dentists noted misalignment of 1 central incisor when the LII reached 1.5 mm, whereas the laypeople with or without experience of orthodontic treatment were sensitive to 2.0 mm of crowding. When the LII reached 2.0 mm for 1 lateral incisor, it triggered the orthodontists to consider providing orthodontic treatment, whereas this degree of irregularity was ignored by the general dentists and laypeople. When both central incisors were misaligned, the orthodontists were sensitive to the fact at 2.0 mm of LII, whereas the general dentists and the laypeople with experience of orthodontic treatment became sensitive at 3.0 mm of LII, and the laypeople with no history of orthodontic treatment were sensitive at 4.0 mm of LII. When both lateral incisors were misaligned, the orthodontists noted the crowding at an LII of 3.0 mm, the general dentists became sensitive at an LII of 4.0 mm, whereas both the laypeople with experience of orthodontic treatment and the laypeople with no history of orthodontic treatment ignored it. When the crowding of all maxillary incisors reached an LII of 4 mm, both the orthodontists and the general dentists were alerted to the fact, but both the laypeople with experience of orthodontic treatment and the laypeople with no history of orthodontic treatment were sensitive only to a total incisor crowding equal to an LII of 6.0 mm.

CONCLUSIONS

Orthodontists are more critical than other groups when evaluating the misalignment of the maxillary incisors. It appears that the central incisors play a more important role than do the lateral incisors when dental crowding impacts smile esthetics. For all observer groups, it also appears that people are more sensitive to the misalignment of a single tooth than they are to the same level of crowding distributed over multiple teeth.

Orientation of the occlusal plane in a Class I adult population

OBJECTIVE

To primarily evaluate whether Delaire's ideal occlusal plane is present in Class I occlusal relationship adults.

STUDY DESIGN

Pretreatment lateral cephalometric radiographs from 30 orthodontically untreated Caucasian Class I malocclusion adults were obtained. The occlusal, mandibular, and maxillary planes were traced and compared with the ideal occlusal, mandibular, and maxillary planes according to Delaire.

RESULTS

The average occlusal plane was 3.5° below the ideal plane. This divergence was more pronounced in males, and in patients presenting with a hypodivergent skeletal pattern. The maxillary plane displayed on average less than 0.5° of divergence to the ideal. The average mandibular plane showed a divergence of 3.3° below the ideal.

CONCLUSIONS

When aiming to obtain an ideal orientation of the occlusal plane postoperatively, one must keep in mind that in Class I occlusal relationship adults without any dentofacial disharmony, the occlusal plane is rarely coincident with the ideal plane.

Anterior alveolar segmental osteodistraction with a bone-borne device: clinical and radiographic evaluation

PURPOSE

Anterior alveolar osteodistraction is a common method for enlargement of the dentoalveolar process, and bone-borne distraction devices are hypothesized to avoid the risk of dental tipping and periodontal impairment during distraction. The aim of this study was to objectify this thesis and to determine the reliability of bone-borne osteodistraction of the anterior alveolar process.

PATIENTS AND METHODS

The study group consisted of 18 consecutive patients who underwent anterior alveolar segmental distraction with a bone-borne distraction device for the treatment of dental crowding or alveolar retrusion from 2008 through 2011. Clinical and radiologic changes within the apical base and dentoalveolar process were analyzed after bone-borne distraction osteogenesis. All measurements were carried out using cone-beam computed tomography.

RESULTS

Surgery and the postoperative period were uneventful in all patients. Mean alveolar movement was 8.2° ± 2.4°. Skeletal movement was 97.6% and absolute dental tipping was 2.4%. A mean change in the occlusal plane of 1.9° ± 1.1° was verified. The apical base enlargement showed a mean of 7.9 ± 1.4 mm, and the dentoalveolar arch a mean increase of 12.7 ± 2.1 mm. Within the distraction zone, a mean vertical bone loss of 3.5 ± 0.7 mm and a mean horizontal bone loss of 3.9 ± 0.8 mm were seen. After orthodontic gap closure, both were clinically irrelevant, with no need for additional bone grafts. Periodontal impairment (gingival recessions of 1 mm) was observed in 7 patients but affected only the teeth bordering the vertical osteotomy line.

CONCLUSIONS

Bone-borne anterior alveolar osteodistraction is sufficient for enlargement of the apical base and the dentoalveolar arch of the mandible. Skeletal movement of the alveolar segment was predictable and dental tipping was clinically irrelevant. This technique presents further indications and approaches in orthognathic surgery.