Asymmetric molars' mesial rotation and mesialization in unilateral functional posterior crossbite and implications for interceptive treatment in the mixed dentition.

INTRODUCTION: Symmetric transverse expansion is the main outcome of the early treatment in subjects with unilateral functional posterior crossbite. The aim of this study was to analyse mesial rotation and mesialization of upper first molars as sagittal parameters to be corrected in the treatment of these patients during the mixed dentition. METHODS: Digital dental cast measurements (rotation and mesialization) were performed in a sample of 48 subjects with unilateral posterior crossbite (UPXB; 19 males and 29 females, mean age 10.2 ± 1.2 years) and in a control group of 35 subjects with normal Class I occlusion (17 males and 18 females, mean age 9.9 ± 1.3 years). An independent sample t-test, the Mann-Whitney test, Fisher's exact test, and Pearson correlation were used for statistical comparison. RESULTS: The amount of upper molar rotation was significantly greater in the experimental group when compared with the control group. A clinically significant 'upper molar rotation' (UMR) was present in 66.7 per cent of the subjects with UPXB versus 5.7 per cent of the control group. The UMR group presented also a significant mesialization of upper first molars when compared with the control group. In the experimental group, there was a significant difference between rotation and mesialization in the right and left side and a correlation has been found between these two variables and the amount of Class II molar relationship at the crossbite side. LIMITATIONS: This is an epidemiological case-control study and the discussed effects of an early correction of the asymmetric upper molars' migration are only speculations based on an association relationship. CONCLUSIONS: The findings of this study show an asymmetric upper first molars' migration (rotation and mesialization) in unilateral functional posterior crossbite versus a control group. An early evaluation and correction of the molars' migration during the mixed dentition should be considered in order to obtain a correct inter-occlusal sagittal molar relationship, space for an adequate eruption of permanent teeth, and perhaps reduce the need of a following fixed appliance treatment in the permanent dentition.

Treatment of ectopic first permanent molar teeth.

UNLABELLED: Ectopic eruption of the first permanent molar is a relatively common occurence in the developing dentition. A range of treatment options are available to the clinician provided that diagnosis is made early. Non-treatment can result in premature exfoliation of the second primary molar, space loss and impaction of the second premolar. This paper will describe the management of ectopic first permanent molars, using clinical examples to illustrate the available treatment options. CLINICAL RELEVANCE: This paper is relevant to every general dental practitioner who treats patients in mixed dentition.

Effect of RME and headgear treatment on the eruption of palatally displaced canines: a randomized clinical study.

OBJECTIVE: To determine the effectiveness of orthodontic treatment finalized on the maintenance/improvement the upper arch perimeter to assist in the successful eruption of palatally displaced maxillary canines (PDCs). MATERIALS AND METHODS: The randomized prospective design comprised 64 subjects with PDCs who were randomly assigned to one of three groups: cervical pull headgear (HG); rapid maxillary expansion and cervical pull headgear (RME/HG); or untreated control group (CG). Panoramic radiographs and lateral cephalograms were evaluated at the time of initial observation (T1) and after an average period of 18 months (T2). At T2 the success of canine eruption was evaluated. A superimposition study on lateral cephalograms was undertaken to evaluate the T1-T2 changes in the sagittal position of the upper molars in the three groups. RESULTS: The prevalence of successful eruption was 85.7% in the RME/HG group and 82.3% in the HG group. Both these prevalence rates were significantly greater than the success rate in untreated control subjects (36%). The cephalometric superimposition study showed a significant mesial movement of the upper first molars in the CG compared with the HG and RME/HG groups. CONCLUSIONS: The use of rapid maxillary expansion and headgear (or headgear alone) in PDC cases increases the success rate of eruption of the canine significantly (almost three times more than in untreated controls).

Identical unerupted maxillary incisors in monozygotic twins.

Mesiodens is the most common type of supernumerary tooth found in the premaxilla. It might be discovered by the orthodontist by chance on a radiograph or as the cause of an unerupted maxillary central incisor. The genetic transmission of supernumerary and impacted teeth is poorly understood. The occurrence of identical unerupted maxillary central incisors and mesiodentes in monozygotic twins suggests that genetic factors might influence the etiology of this problem. In this case report, we discuss the treatment of unerupted maxillary permanent incisors caused by mesiodentes in monozygotic twins.

Dentoalveolar changes after surgically assisted maxillary expansion: a three-dimensional evaluation.

OBJECTIVES: Surgically assisted rapid palatal expansion (SARPE) is a common procedure to correct maxillary transverse deficiency of >5 mm in patients with closed midpalatal suture. The aim of this study was to three-dimensionally analyze skeletal and dentoalveolar changes after SARPE. STUDY DESIGN: Eighteen mature patients (mean age 26 years) with a palatal transverse deficiency underwent SARPE. The surgical procedure consisted of a lateral osteotomy combined with an interradicular osteotomy between the roots of the upper central incisors. Measuring points were defined on teeth as well as facial skeleton. Computerized tomography scans were performed preoperatively and immediately after the expansion period. RESULTS: Changes of the dentoalveolar and maxillofacial complex were analyzed. CONCLUSIONS: Bilateral osteotomy combined with a sagittal osteotomy between the roots of the upper central incisors is a safe method of surgically assisted maxillary expansion. The amount of dentoalveolar tipping was smaller than reported in literature. The expansion was mostly achieved by maxillary expansion.

Unilateral correction of space loss in the mixed dentition.

Distalization of maxillary molars is indicated for correction of Class II dental malocclusion and for space gain in cases of space deficiency. The ideal treatment with an intraoral fixed appliance for molar distalization should fulfill the following requirements: patient compliance; acceptable esthetics; comfort; minimum anterior anchor loss (as evidenced by inclination of incisors); bodily movement of the molars to avoid undesirable effects and unstable outcomes; and minimum time required during sessions for placement and activations. The purpose of this paper was to present an alternative treatment for space recovery in the area of the maxillary right second premolar when there has been significant mesial movement of the permanent maxillary right first molar. We used a modified appliance that allows unilateral molar distalization in cases of unilateral tooth/arch size discrepancy using the opposite side as anchor, thus reducing the mesialization of the anterior teeth.

Implant prostheses and adjacent tooth migration: preliminary retrospective survey using 3-dimensional occlusal analysis.

Occlusal force analysis was retrospectively evaluated to clarify the proximal contact loss after fixed implant prosthesis placement. Twenty-eight patients (55 prostheses) with fixed implant prostheses in the posterior region were divided into 2 groups: proximal contact loss and unchanged groups. The occlusal force and its distribution were 3-dimensionally measured using the Dental Prescale system. A high proportion of lingual and anterior component forces and high occlusal force distribution in the intercanine region were observed in the contact loss group. The high occlusal force of the adjacent tooth may enhance the mesial migration.

Cephalometric assessment of dentofacial vertical changes in Class I subjects treated with and without extraction.

INTRODUCTION: There is disagreement concerning the effect of premolar extractions on the dentofacial vertical dimension. It has been suggested that orthodontic forward movement of the posterior teeth after first premolar extraction leads to reduction in vertical dimension. The purpose of this study was to examine cephalometrically the dentofacial vertical changes in Class I Indian subjects treated with and without extractions. METHODS: The extraction group included 31 normodivergent patients (26 female, 5 male; pretreatment age, 17.19 +/- 3.89 years) with maxillary and mandibular first premolar extractions. The nonextraction group included 29 patients (18 female, 11 male; pretreatment age, 18.48 +/- 3.61 years). A coordinate system with the Frankfort horizontal plane and a mandibular fiduciary line was used for the cephalometric calibration. To determine vertical dimension changes due to treatment and to compare differences between the 2 groups, paired and unpaired t tests were performed, respectively. RESULTS: Both groups had increases in linear vertical dimensions (P <0.05), but the change was comparatively greater in the extraction group (P <0.05). Mesial movement of the maxillary and mandibular posterior teeth was coincidental with the extrusion to such an extent that it increased the vertical dimension, although the mandibular plane angle remained unchanged during treatment. CONCLUSIONS: Extraction of teeth only to increase the overbite or decrease the mandibular plane angle might not be justified.

Biomechanics of a Distal Jet appliance. Theoretical considerations and in vitro analysis of force systems.

OBJECTIVE: To analyze the forces and moments acting in the first molar region, induced by the Distal Jet appliance for maxillary molar distalization. MATERIALS AND METHODS: Over a working section of 3 mm with reactivation of the loaded spring systems, the force systems of three laboratory-fabricated appliances of identical design were analyzed with a 3D metering device. RESULTS: The force systems registered in vitro exhibited complex biomechanics. Regular reactivation of the loaded coils resulted in consistent distalizing forces and uprighting moments, in forces and moments toward buccal as well as slightly intrusive forces, and mesial-inwardly rotating moments. In the sagittal dimension, the Distal Jet appliance allows almost translatory molar distalization. Accordingly, applying uprighting activation is not necessary for treatment. Because of the application of the force palatal to the center of resistance of the molars, the teeth experience undesired mesial-palatal and distal-facial rotation. CONCLUSIONS: The Distal Jet appliance allows almost translatory distal molar movement, and uprighting activation is not necessary for treatment. The force applied palatal to the center of resistance of the molars produces an undesired mesial-palatal and distal-facial rotation. Regular intraoral coil spring reactivation is needed.

Osseointegrated implants with pendulum springs for maxillary molar distalization: a cephalometric study.

INTRODUCTION: Maxillary molar distalization is a common treatment approach for patients with Class II malocclusions who do not require extractions. Despite the many advantages of pendulum appliances, the maxillary incisors and premolars tend to shift mesially as the maxillary molars move distally. The purpose of this study was to investigate anchorage loss in patients treated with palatal osseointegrated implants combined with pendulum springs. METHODS: Pretreatment and posttreatment lateral cephalometric films of 30 consecutively treated patients were examined. One group (n = 15) had been treated with conventional pendulum appliances, and the other group (n = 15) was treated with palatal osseointegrated implants combined with pendulum springs. RESULTS: In the pendulum group, significant distal tipping of the maxillary first molars and mesial tipping of the maxillary premolars were noted. Distalization of the maxillary first molars, mesialization of the maxillary first premolars, and proclination of the maxillary left central incisor were significant in the linear measurements. In the implant group, the distal tipping of the maxillary first molars and first premolars and the increases in SNGoGn, FMA, Na Me, and Na ANS were significant. Intergroup comparisons showed that changes in the maxillary first premolars, maxillary central incisors, and vertical measurements were significant. CONCLUSIONS: The use of palatal osseointegrated implants is reliable and provides absolute anchorage.

[Loss of molar anchorage: quantitative evaluation with a method of structural superposition]. / Perte d'ancrage molaire: évaluation quantitative avec une méthode de superpositions structurales.

The goal of this study is to analyze using structural cephalometric superimpositions the quantity of mesial molar drift in the maximum anchorage cases, with mainly extractions of the first four premolars. Molar anchorage is appreciated in cases treated with or without use of directional forces. The influence of various parameters: age, facial divergence, discrepancy and incisor repositioning, on the loss of anchorage is also evaluated. The statistical study called upon the test of Student for independent groups. A value of the risk of first species p<0.05 was considered as significant. The loss of anchorage seems less important with the use of the directional forces. On the other hand it is raised in teenagers and the cases of important incisor repositioning.

Sagittal, vertical, and transverse changes consequent to maxillary molar distalization with the pendulum appliance.

INTRODUCTION: The purpose of this study was to evaluate the skeletal and dental changes in patients who underwent distalization of their maxillary molars with pendulum appliances. METHODS: The sample consisted of 31 patients (initial mean age, 14.58 years) with Angle Class II molar relationships and all permanent teeth up to the second molars. The maxillary molars were distalized with pendulum appliances for a mean period of 5.87 months. Lateral cephalograms, 45 degrees oblique radiographs, and dental casts were obtained before and after distalization. Changes produced by the pendulum appliance were analyzed with paired t tests. RESULTS: Maxillary first molar distalization accounted for 63.5% of the space opening; mesial movement of the maxillary first premolars contributed 36.5% of the space. The mean space opening on lateral cephalograms was 7.25 mm, and the rate of molar movement was 1.23 mm per month. The mean distalization of the maxillary molars was 4.6 mm, with a mean distal crown tipping of 18.5 degrees The maxillary molars experienced expansion, with a smaller effect on the first molars than on the second molars. The pendulum appliance produced symmetrical expansion, with a rate of 1.04 mm per month on the right and 1.10 mm per month on the left. CONCLUSIONS: The pendulum appliance is effective for distalization of the maxillary molars and the establishment of a Class I molar relationship in a relatively short time. However, caution is needed to control collateral effects, including mesial movement of the first premolars and distal tipping of the molar crowns.

Comparison and measurement of the amount of anchorage loss of the molars with and without the use of implant anchorage during canine retraction.

INTRODUCTION: The purpose of this study was to compare and measure the amount of anchorage loss with titanium microimplants and conventional molar anchorage during canine retraction. METHODS: Subjects for this study comprised 10 orthodontic patients (7 women, 3 men) with a mean age of 19.6 years (range, 18 to 25 years), who had therapeutic extraction of all first premolars. After leveling and aligning, titanium microimplants 1.3 mm in diameter and 9 mm in length were placed between the roots of the second premolars and the first molars. Implants were placed in the maxillary and mandibular arches on 1 side in 8 patients and in the maxilla only in 2 patients. A brass wire guide and an intraoral periapical radiograph were used to determine the implant positions. After 15 days, the implants and the molars were loaded with closed-coil springs for canine retraction. Lateral cephalograms were taken before and after retraction, and the tracings were superimposed to assess anchorage loss. The amount of molar anchorage loss was measured from pterygoid vertical in the maxilla and sella-nasion perpendicular in the mandible. RESULTS: Mean anchorage losses were 1.60 mm in the maxilla and 1.70 mm in the mandible on the molar anchorage side; no anchorage loss occurred on the implant side. CONCLUSIONS: Titanium microimplants can function as simple and efficient anchors for canine retraction when maximum anchorage is desired.

Predictors of long-term orthodontic side effects from mandibular advancement devices in patients with snoring and obstructive sleep apnea.

INTRODUCTION: Orthodontic side effects can complicate the long-term use of mandibular advancement devices (MADs) in the treatment of patients with snoring and obstructive sleep apnea. The aim of this study was to find predictors of dental side effects from monoblock MADs. METHODS: Four hundred fifty patients, who consecutively received treatment with either soft elastomeric or hard acrylic devices, were followed up after 5.4 +/- 0.8 years (mean +/- SD). The continuing patients responded to questionnaires and had dental examinations and plaster casts made. RESULTS: Twenty-seven patients had moved or died during the follow-up period. Two hundred thirty-six of the remaining 423 patients (56%) continued treatment, and 187 of them reported compliance rates of > or = 50% at night. A small reduction in overjet of < 1 mm was associated with a deepbite with an overbite of > 3 mm and an overjet of < or = 3 mm (odds ratio [OR] = 7.5; P = .015), nasal congestion (OR = 2.9; P = .005), or the use of a soft elastomeric device (OR = 2.7; P = .014) controlled for age, sex, treatment time, and mandibular displacement. A small reduction in overbite of < 1 mm was related to a small opening of the mandible of < 11 mm (OR = 2.5; P = .008). CONCLUSIONS: Orthodontic side effects might be predictable on the basis of initial characteristics in dental occlusion and the design of MADs.

Craniofacial and dentofacial development in pigs fed soft and hard diets.

INTRODUCTION: Several authors have found a correlation between reduced chewing activity and malocclusion. In animal experiments, it has been possible to correlate a diet of low chewing resistance to narrower arches, which predispose the subject to crowding and irregular teeth. METHODS: In this study, 17 pigs were weaned at 5 weeks of age and divided into 2 groups according to diet and housing. The soft-diet, indoor group was housed in conventional pens, and the animals were fed aliquots of barley and oats with soya and a mineral-vitamin premix added. The food was mixed with water at a dry matter content of about 25%. The hard-diet, outdoor group was kept outdoors; the pigs were fed solid food and also ate organic matter in the soil. All pigs were killed at 22 months of age. The skulls were dissected, and transverse and sagittal craniofacial and dentofacial dimensions were measured. RESULTS: Chewing hard food caused considerable occlusal and approximal attrition in the experimental animals. The dental arches were shorter due to this attrition and to mesial migration of the molars and premolars. The approximal attrition also reduced the tendency for crowding and rotation of the teeth. Posterior crossbite was more common among the hard-chewing animals. CONCLUSIONS: The increase in arch width in the hard-diet animals reported in the literature was not duplicated in this study. On the contrary, the soft-diet pigs had significantly wider arches than the hard-diet animals. This was most pronounced in the premolar region and could be the result of an atypical tongue habit, caused by the nonphysiologic feeding of the pigs. The soft-diet pigs also had a greater tendency to postnormal occlusion, especially in the canine region.

First or second premolar extraction effects on facial vertical dimension.

If the concept of mesial movement of molars to reduce the "wedge effect" and decrease facial vertical dimension (FVD) is valid, it is important to investigate the effect of first (P1) and second premolar (P2) extraction on FVD. This study compares the mesial movement of molars and changes in FVD between P1 and P2 extraction groups in Class I malocclusion with a hyperdivergent facial type. We compared 27 cases with maxillary and mandibular P1 extractions (group 1) and 27 cases with maxillary and mandibular P2 extractions (group 2). To determine FVD changes due to treatment and to compare differences between two groups, paired t-test and independent t-test were performed, respectively. Group 2 showed more mesial movement of the maxillary and mandibular first molars and less retraction of the maxillary and mandibular central incisors than group 1 (P < .05). Both groups showed increased anterior facial height (P < .05), but there were no statistically significant differences in angular and proportional measurements between pre- and posttreatment. There was no significant difference in the amount of FVD change between groups 1 and 2 except in the maxillomandibular plane angle and SN to palatal plane angle (P < .05). These results suggest that there is no decrease in FVD regardless of the maxillary and mandibular P1 or P2 extraction. Therefore, the hypothesis that P2 extraction in hyperdivergent facial types will result in mesial molar movement and decrease FVD by reducing the wedge effect is invalid.

Dentoskeletal effects induced by rapid molar distalization with the first class appliance.

The purpose of this study was to evaluate the treatment effects of the first class appliance (FCA; Leone, Firenze, Italy), a new intraoral device for unilateral or bilateral rapid molar distalizaton. A retrospective study was conducted to compare the predistalization and postdistalization cephalograms of 17 patients (10 male, 7 female) with Class II malocclusions treated with the FCA. Mean age at the start of treatment was 13 years 4 months. The FCA produced rapid molar distalization, and the bilateral Class II molar relationship was corrected in 2.4 months, on average. Maxillary molar distalization contributed to 70% of the space created anterior to the first molars; 30% of the space was due to reciprocal anchorage loss of the maxillary second premolars. The maxillary first molars showed a significant distalization of 4.0 mm, associated with a significant distal axial incline of 4.6 degrees and a significant extrusion of 1.2 mm. As for anchorage loss, the second premolars exhibited a significant mesial movement of 1.7 mm, associated with a significant mesial axial incline of 2.2 degrees and a nonsignificant extrusion of 1.0 mm. In the anterior region, a significant mesial movement of the maxillary incisor of 1.3 mm was associated with a significant incisor proclination (2.6 degrees ) and a significant increase in overjet (1.2 mm). No significant changes in either sagittal or vertical skeletal relationships were observed. The results suggest that the FCA is an efficient and reliable device for distalizing the maxillary permanent first molars.

Constriction of the maxillary dental arch by mucoperiosteal denudation of the palate.

OBJECTIVE: This study examined the influence of two factors in the constriction of the maxillary dental arch by mucoperiosteal denudation of the palate: (1) inhibition of lateral growth and (2) medial inclination of teeth. METHOD: Thirty-five male 20-day-old Wistar rats were divided into experimental and control groups. The experimental group had bilateral mucoperiosteum excised in the lateral one third of the palate. Methyl methacrylate resin-embedded frontal sections were prepared from both groups after alternate weekly injections of tetracycline and calcein in the dorsal subcutaneous area. The sections were observed and photographed under either a confocal laser scanning microscope, a fluorescence microscope, or both. Chronological changes in lateral palatal growth, maxillary dental arch width, and inclination of the upper first molars were examined up to 8 weeks after the operation. Paraffin-embedded frontal sections were also made and stained with Elastica van Gieson stain. RESULTS: The scar tissue formed on the rat palate by the mucoperiosteal denudation was tightly connected to the palatal bone and teeth. The intervals between the labeling lines of the experimental group were less definite during the first 2 weeks after the operation. Increments of palatal and maxillary dental arch widths were smaller in the experimental group than in the control group. The upper first molars in the control group gradually inclined laterally, whereas those in the experimental group inclined medially with age. CONCLUSION: Medial inclination of teeth is a stronger influence than inhibition of lateral growth on constriction of the rat maxillary dental arch.