Changes in proximal contact tightness between fixed implant prostheses and adjacent teeth: A 1-year prospective study.

STATEMENT OF PROBLEM: No study has evaluated consecutive changes in proximal contact tightness (PCT) between fixed implant prostheses and adjacent teeth after delivery. PURPOSE: The purpose of this clinical study was to investigate consecutive biological changes in PCT between fixed implant prostheses and adjacent teeth after placement. MATERIAL AND METHODS: Eighteen participants who had been treated with a single first molar implant in the mandible were included. Mesial and distal PCT were measured using the custom-made contact pressure system at immediate crown delivery (T0), 3-month follow-up (T1), and 1-year follow-up (T2). The PCT of natural teeth in the mesial direction of the same quadrant was also measured at T2 as a control. Repeated-measures analysis of variance (ANOVA) and 1-way ANOVA were used for statistical analysis. RESULTS: At T0, the PCT between fixed implant prostheses and adjacent teeth was designed deliberately to be higher than the PCT between natural teeth. Using multivariate analyses, the PCT between fixed implant prostheses and adjacent teeth decreased between T0 and T1 (P<.001), while there was no significant difference between T1 and T2 (P=.506). At T2, the distal PCT was tighter than the mesial PCT (P<.001); however, no statistical difference was found in the PCT between the implant-supported restoration and the natural teeth. CONCLUSIONS: PCT decreased significantly at both mesial and distal sites over time. The major changes occurred over the 3-month period after crown delivery.

Factors predisposing to maxillary anchorage loss: a retrospective study of 1403 cases.

Anchorage loss is very disturbing for orthodontists and patients during orthodontic treatment, which usually results in bad treatment effects. Despite the same treatment strategy, different patients show different tendencies toward anchorage loss, which influences the treatment results and should preferably be predicted before the treatment is begun. However, relatively little research has been conducted on which patients are more likely to lose anchorage. The mesial tipping of the first molar marks the onset of anchorage loss, and changes in the angulation of the first molar are closely related to anchorage loss. This cross-sectional study aimed to determine how the mesiodistal angulation of the upper first molars changes during general orthodontic treatment and to identify the individual physiologic factors leading to these changes in a large sample of 1403 patients with malocclusion. The data indicate that the upper first molars tend to be tipped mesially during orthodontic treatment, and this constitutes a type of anchorage loss that orthodontists should consider carefully. Compared to treatment-related factors, patients' physiologic characteristics have a greater influence on changes in the angulation of the upper first molars during orthodontic treatment. The more distally tipped the upper first molars are before treatment, the more they will tip mesially during treatment. Mesial tipping of the upper first molars, and therefore, anchorage loss, is more likely to occur in adolescents, males, patients with class II malocclusion and patients who have undergone maxillary premolar extraction. This finding is of clinical significance to orthodontists who wish to prevent iatrogenic anchorage loss by tipping originally distally tipped upper molars forward, and provides a new perspective on anchorage during orthodontic treatment planning.

Comparison of arch width, alveolar width and buccolingual inclination of teeth between Class II division 1 malocclusion and Class I occlusion.

OBJECTIVE: To compare the arch width, alveolar width, and buccolingual inclination of maxillary and mandibular posterior teeth between Class II division 1 malocclusion and Class I occlusion. MATERIALS AND METHODS: Forty-five subjects with Class I occlusion and 45 subjects with Class II division 1 malocclusion were selected to measure the maxillary and mandibular arch width and alveolar width of premolars and first molars with digital caliper. Buccolingual inclination of maxillary and mandibular premolars and first molars were measured with a modified universal bevel protractor. RESULTS: All of the posterior teeth in both groups were lingually tilted. The maxillary premolars and first molars were significantly more lingually tilted (P < .05) in Class II division 1 malocclusion than in Class I occlusion. Mandibular first premolars were significantly less lingually tilted in Class II division 1 malocclusion than in Class I occlusion. No significant difference of buccolingual inclination was found in mandibular second premolars and first molars between the two groups. No significant difference in maxillary and mandibular arch width and alveolar width was found between the two groups. CONCLUSIONS: Buccolingual inclination rather than arch width and alveolar width plays an important role in transverse discrepancy of Class II division 1 malocclusion.

Proximal contact loss between implant-supported prostheses and adjacent natural teeth: a clinical report.

There is limited knowledge about the changes that proximal contacts between implant-supported prostheses and adjacent teeth undergo over time. This report describes the management of a clinical situation with the loss of proximal contact between implant-supported prostheses and adjacent natural teeth in a partially edentulous patient.

Natural changes of the maxillary first molars in adolescents with skeletal Class II malocclusion.

INTRODUCTION: The objective of this study was to evaluate natural changes in maxillary posterior alveolar height (MPAH) and axial inclination of the maxillary first molars (AIMFM) in subjects with Class II malocclusion to determine the validity of predictive equations. METHODS: Longitudinal records of 30 untreated white subjects (13 girls, 17 boys) with skeletal Class II malocclusion were collected at ages 9, 12, 14, and 16 years. They had participated in the Burlington Growth Centre study, and cephalograms were analyzed with Dentofacial Planner Plus software (version 2.0, Dentofacial Planner, Toronto, Ontario, Canada). Serial means were compared with the Bonferroni post-hoc test (P <0.05). Predictive equations were obtained and studied with the analysis of agreement. RESULTS: Gradually, means of MPAH had statistical increments with sexual dimorphism from 14 to 16 years of age. A distal mean of AIMFM was found at 9 years of age that decreased significantly during growth, with sexual dimorphism between the ages of 9 and 12 years. Changes in AIMFM varied among subjects in distinct stages. Values of MPAH were predicted with high validity at intervals of 3 years or longer, whereas estimations for AIMFM were unreliable. CONCLUSIONS: In this study group, there was significant alveolar growth, with a natural tendency to upright the distal inclination at the maxillary first molars.

Three-dimensional changes in the position of unopposed molars in adults.

The aim of this study was to longitudinally examine, in adults, changes of position in the three dimensions of maxillary molars unopposed for more than 10 years. Twelve healthy mature adults (six males, six females; mean age 45 years 11 months) with unopposed molars were followed-up for a mean period of 10 years 7 months. Plaster casts were made at the first and last examination. The patients presented 22 unopposed maxillary molars at both recordings and 14 posterior teeth with antagonists, at least one in each subject, without significant modifications during the study period. On three-dimensional scanned plaster casts, changes in the centroid of the occlusal surface were measured in the three dimensions. The changes observed on both occasions were compared with a t-test. Vertical displacement of unopposed molars [0.8 mm, standard deviation (SD) 0.65 mm] and controls (0.4 mm, SD 0.2 mm) was noted. The unopposed teeth overerupted more than the controls (P

Prevalence of third molar impaction in orthodontic patients treated nonextraction and with extraction of 4 premolars.

The purposes of this study were to confirm that premolar extraction treatment is associated with mesial movement of the molars concomitant with an increase in the eruption space for the third molars and to test the hypothesis that such treatment reduces the frequency of third molar impaction. Lateral cephalograms, panoramic or periapical radiographs, and study models made before (T1) and after (T2) treatment and a minimum of 10 years postretention (T3) of 157 patients were selected from the postretention sample at the Department of Orthodontics of the University of Washington, Seattle. Treatment for 105 patients included the extraction of 4 premolars; the other 53 were treated nonextraction. These patients represented all the extraction and nonextraction patients in the sample who had at least 1 third molar at T1 or T2 and who showed evidence of full eruption or closure of the root apex at T2 or T3. Student t tests showed higher scores for third molar impaction (P <.01), less mesial movement of the molars from T1 to T2 (P <.01), and smaller retromolar space at T2 (P <.001) in both arches of the nonex patients than in the ex patients. Similarly, molar movement was more mesial from T1 to T2 in the maxilla (P <.01) and in the mandible (P <.05), and the retromolar space was larger in both arches (P <.001) of the patients with eruption than in those with impaction of the third molars. Our results suggest that premolar extraction therapy reduces the frequency of third molar impaction because of increased eruption space concomitant with mesial movement of the molars during space closure.

[An experimental study of tooth mesial migration].

OBJECTIVE: To study the mechanism of tooth mesial migration with animal experiment. METHODS: The upper and lower first molars of Wuzhishan miniature pigs were used as experimental teeth. The mesial migration of experimental teeth was calculated and analysed by measuring the models. Fluorescent mark was used and analysed by injecting tetracycline and xvlenol orange, and histological changes were analyzed. RESULTS: The lower teeth migrate mesially 0.14 mm and 1.21 mm during 16 weeks, and the upper teeth migrate mesially 1.36 mm and 2.08 mm during 24 weeks. The distal alveolar bones of experimental teeth had fluorescent bands; alveolar bones of teeth without antagonist teeth reconstructed in vertical direction; the distance between fluorescent bands of lower experimental teeth without antagonist teeth was wider than that of teeth with antagonist teeth. The fluorescent bands formed in both mesial and distal cementum. CONCLUSION: The results don't support the point that transseptal fibre or force of molar eruption makes teeth migrate mesially; the mesial migration of teeth is related with the reconstruction of alveolar bones and the stress distribution in the bones.

Periodontal conditions around tipped and upright molars in adults. An intra-individual retrospective study.

In 69 individuals from a randomized epidemiological material comprising 450 adults, an intra-individual comparison of the periodontal condition of 73 mesially tipped molars (30 degrees or more to a line perpendicular to the occlusal plane) and contralateral upright molars was made. The alveolar bone level mesially and distally of each tooth was registered in periapical radiographs. The occurrence of plaque, gingivitis and probeable pocket depths of 4 mm or more mesially and distally of each tooth was registered. No significant differences between tipped and upright molars could be found, regardless of the variable tested. The clinical implications of the findings are discussed from an orthodontic as well as a periodontal and prosthetic point of view.

[The significance of the gingival ligament system for orthodontic tooth movement--an experimental animal study]. / Die Bedeutung des gingivalen Fasersystems für die kieferorthopädische Zahnbewegung--Eine tierexperimentelle Untersuchung.

In ten six-month-old Wistar rats, we studied tooth movement after fiberotomy. To trace bone remodeling, all rats received two labelling dyes in five days intervals. We found that ligament regeneration is complete after 14 days. Using fluorescence microscopy we found in rats when stretching forces were continued that a reversal of tooth drift takes place in comparison to the control side, indicating an identical behaviour as before. Only in cases with inflammation no fibre regeneration was found and the mesial drift of the neighbouring tooth was missing. Because of these side-effects this procedure seems not to be a useful adjuvant to enhance orthodontic tooth movement.

[Periodontal reactions to orthodontic forces in the diabetic metabolic state]. / Die Reaktion des Parodonts auf kieferorthopädische Kräfte bei diabetischer Stoffwechsellage.

The reaction of the periodontium to orthodontic tooth movement was studied in rats with streptozotocin diabetes. Forces employed to initiate mesial movement of first molar were 10 N 20 N 30 N and the duration of application was three, six, ten and 14 days. The 14-day rats were treated with fluorochrome sequential labelling according to Rahn. Diabetes mellitus in rats is accompanied by characteristic changes: The most important findings were: 1. a slow osseous regeneration, as could be shown by fluorescence microscopy, 2. the new bone ist unable to pick up the labellings in a sequential manner, 3. a weakening of the periodontal ligamentum, 4. microangiopathies in the gingiva area. the specific diabetic changes are more pronounced following orthodontic tooth movement.

[Periodontal reaction to orthodontic measures]. / Reaktion am Parodontium bei kieferorthopädischen Massnahmen.

In twelve rats, the right maxillary first molar was moved mesially by means of a fixed appliance. It was not possible to find any histopathological differences with forces of 10 N, 20 N and 30 N. We also found no different cellular reactions in the tension and pressure zones between the periods of three, six, ten and 14 days. In the treated rats the first molar was tilted. The mesial root was intruded. Local pressure zones were regularly formed around the mesial root and distal aspect of the alveolar crest of the bifurcation. It could be shown by vital polyfluorochrome staining that there was no mesial tooth movement; rather distal drifting was delayed.

Influence of tooth-to-denture-base discrepancy on space closure following premature loss of deciduous teeth.

Influence of tooth-to-denture-base discrepancy on so-called physiologic migration of the first molar was studied on serial dental casts of 116 boys and girls, obtained through a dental health program for school children in an area in which there was no dentist. The alteration of spaces following premature loss of deciduous molars was examined comparing the anterior to posterior discrepancies between tooth and denture base. Modes of space alteration showed positive correlation with the size of the discrepancy, especially in the mandibular dental arches. The space deficiency in the posterior region seemed to have a positive effect on the mesial migration of the first molar. Mesial migration of the first molar seems to be pathologic rather than physiologic and is strongly affected by tooth-to-denture-base discrepancies. Space maintenance does not seem to be useful, because it is not necessary in minimum discrepancy cases and is not effective in severe discrepancy cases.

Short-term changes in the mesiodistal position of teeth following removal of approximal contacts in the monkey Macaca fascicularis.

A capacitance transducer was used to measure the changes in the distance between pairs of adjacent teeth following the removal of tooth contact. Ten pairs of incisors and cheek teeth were studied over periods of several hours in three adult monkeys. Compared with minor changes in control tooth pairs, there was a sustained approximation of the capacitance plates for periods up to 2 h. Removal of tooth contacts with the teeth adjacent to the test pairs of teeth caused separation of the plates. It is proposed that removal of approximal tooth contact allows the transseptal fibre system to contract and produce approximation of the adjacent teeth.