Michael Knösel

External bleaching effect on the color and luminosity of inactive white-spot lesions after fixed orthodontic appliances.

OBJECTIVE To evaluate the effect of external bleaching on the color and luminosity of inactive white-spot lesions (WSLs) present after fixed orthodontic appliance treatment as means for achieving color matching of the WSLs with adjacent tooth surfaces. MATERIALS AND METHODS Ten patients with inactive WSLs after therapy with fixed orthodontic appliances were selected. At baseline, the lightness of maxillary incisors and canines was assessed with a colorimeter. Color determinations were performed in the area of the initial lesions (F1) and at adjacent, sound enamel areas (F2). Then, anterior teeth were bleached once with a bleaching gel for 60 minutes. After a break of 14 days, in-office bleaching was followed by a 2-week home bleaching period with daily home bleaching for 1 hour. After this, color determinations were repeated. Additionally, patients were asked to fill out a questionnaire to provide information about their degree of contentment with the treatment. RESULTS The lightness values of both the F1 and F2 regions were significantly higher after bleaching as compared with baseline. F2 L-values increased significantly more as compared with F1, indicating a better color matching of these two areas in comparison with baseline. All patients were satisfied with the outcome of the bleaching therapy. CONCLUSION External bleaching is able to satisfactorily camouflage WSLs visible after therapy with fixed orthodontic appliances.

Intra-oral compartment pressures: a biofunctional model and experimental measurements under different conditions of posture

Oral posture is considered to have a major influence on the development and reoccurrence of malocclusion. A biofunctional model was tested with the null hypotheses that (1) there are no significant differences between pressures during different oral functions and (2) between pressure measurements in different oral compartments in order to substantiate various postural conditions at rest by intra-oral pressure dynamics. Atmospheric pressure monitoring was simultaneously carried out with a digital manometer in the vestibular inter-occlusal space (IOS) and at the palatal vault (sub-palatal space, SPS). Twenty subjects with normal occlusion were evaluated during the open-mouth condition (OC), gently closed lips (semi-open compartment condition, SC), with closed compartments after the generation of a negative pressure (CCN) and swallowing (SW). Pressure curve characteristics were compared between the different measurement phases (OC, SC, CCN, SW) as well as between the two compartments (IOS, SPS) using analysis of variance and Wilcoxon matched-pairs tests adopting a significance level of α = 0.05. Both null hypotheses were rejected. Average pressures (IOS, SPS) in the experimental phases were 0.0, −0.08 (OC); −0.16, −1.0 (SC); −48.79, −81.86 (CCN); and −29.25, −62.51 (SW) mbar. CCN plateau and peak characteristics significantly differed between the two compartments SPS and IOS. These results indicate the formation of two different intra-oral functional anatomical compartments which provide a deeper understanding of orofacial biofunctions and explain previous observations of negative intra-oral pressures at rest.

Shear bond strength of brackets to demineralize enamel after different pretreatment methods.

OBJECTIVE To compare the influence of demineralized and variously pretreated demineralized enamel on the shear bond strength of orthodontic brackets. MATERIALS AND METHODS Sixty bovine enamel specimens were allocated to five groups (n  =  12). Specimens of group 1 were not demineralized and were not pretreated, but served as controls. The other specimens were demineralized to form artificial carious lesions. Samples from group 2 were only demineralized and were kept untreated in artificial saliva. The other samples were pretreated with highly concentrated fluoride preparations (group 3: Elmex Gelee, 1.23% F; group 4: Clinpro White Varnish, 2.23% F) or with an infiltrating resin (group 5: Icon). After respective pretreatments, brackets were adhesively fixed on all specimens with an adhesive system after etching with 35% phosphoric acid and application of a primer and bracket resin cement (Transbond XT). Bracket shear bond strength was evaluated with a universal testing machine. Statistical analysis was performed by one-way analysis of variance followed by a post-hoc Scheffé test. RESULTS Shear bond strength in control group 1 was statistically significantly greater compared with that in all other groups. Application of the infiltrating resin Icon (group 5) as pretreatment resulted in statistically significantly greater bond strength as compared with pretreatments with fluoride compounds (groups 3 and 4) and treatment provided without pretreatment (group 2). Groups 2, 3, and 4 did not significantly differ from each other. CONCLUSION Pretreatment with the infiltrating resin is a beneficial approach to increasing the shear bond strength of brackets to demineralized enamel.

Influence of orthodontic extrusion on pulpal vitality of traumatized maxillary incisors.

INTRODUCTION The aim of this retrospective study was to examine the effect of orthodontic extrusion on the pulpal vitality of maxillary incisors with a history of trauma. METHODS Pulpal condition was examined clinically (rating of crown color and sensitivity testing with a cryogenic spray) and radiologically (periapical and panoramic radiographs) after orthodontic extrusion of previously traumatized (Orthodontics/Trauma group, n = 77) and nontraumatized teeth (Orthodontics group, n = 400) and after previous dental trauma without subsequent orthodontic treatment (Trauma group, n = 193). Dental traumata were divided into hard tissue injuries (fracture of enamel and enamel chipping, fracture of enamel-dentin without pulpal involvement, fracture of enamel-dentin with pulpal involvement, root fracture, crown-root fracture) and periodontal injuries (concussion, subluxation, intrusion, extrusion, lateral luxation, and avulsion). RESULTS Teeth in the Orthodontics/Trauma group showed a significantly higher frequency of pulp necrosis than teeth in the Orthodontics group (P < .001) or teeth in the Trauma group (P < .009). In addition, teeth in the Orthodontics/Trauma group with periodontal injuries showed a significantly higher rate of pulp necrosis than teeth in the Orthodontics group (P < .001) or the corresponding teeth in the Trauma group (P = .004). No significant differences were observed between teeth in the Orthodontics/Trauma group with previous hard tissue injuries and teeth in the Orthodontics group or the corresponding teeth in the Trauma group. In addition, no statistically significant differences were determined between central and lateral incisors. CONCLUSIONS The results indicated that maxillary incisors with a history of severe periodontal injury have a higher susceptibility to pulp necrosis during orthodontic extrusion than nontraumatized teeth.

Increased susceptibility for white spot lesions by surplus orthodontic etching exceeding bracket base area.

INTRODUCTION There is a paucity of information with regard to the susceptibility of iatrogenic white spot lesion formation after inattentive, surplus orthodontic etching with 30% phosphoric acid and the subsequent provision or absence of adequate oral hygiene. METHODS Ninety sound enamel specimens were randomly allocated to 6 trial groups (n = 15 each) for etching with 30% phosphoric acid for either 15 seconds and standardized daily enamel brushing or no brushing, etching for 30 seconds with daily brushing or no brushing, or nonetched controls with brushing or no brushing. Nutritive acidic assaults were simulated by demineralization cycles 3 times per day for 1 hour with interim storage in artificial saliva. Lesion depths in terms of percentage of fluorescence loss (delta F, delta Q) and lesion extension compared with the baseline were assessed by using quantitative light-induced fluorescence after 2, 7, 14, 21, and 42 days. Etching duration, trial time elapse, and oral hygiene, as well as the significance of factor interactions, were analyzed with 3-way analysis of variance (α = 5%). RESULTS The impact of the factors of enamel brushing, trial time elapse, and etching each had a comparably significant effect on lesion progression. The effect of surplus etching on white spot lesion formation was significantly enhanced by the simultaneous absence of enamel brushing and also the progression of trial time. The combination of 30 seconds of surplus etching with inadequate oral hygiene was especially detrimental. CONCLUSIONS Excessive surplus orthodontic etching of the complete labial enamel surface, instead of the bracket bases only, must be avoided to prevent iatrogenic white spot lesions. Etching times not exceeding 15 seconds are favorable.

Impulse debracketing compared to conventional debonding.

OBJECTIVE To evaluate impulse debonding compared to three conventional methods for bracket removal in relation to the damage caused to the enamel surface. MATERIALS AND METHODS Ninety-six osteotomed third molars were randomly assigned to two study groups (n = 48) for bracket bonding with either a composite adhesive system (CAS) or a glass-ionomeric cement (GIC). These two groups were then each randomly divided into four subgroups (n = 12) according to the method of debonding using (1) bracket removal pliers, (2) a side-cutter, (3) a lift-off debracketing instrument, or (4) an air pressure pulse device. Following debonding and corresponding postprocessing with either a finishing bur (CAS) or ultrasound (GIC), the enamel surfaces were assessed for damage, adhesive residues, and the need for postprocessing using scanning electron microscopy and the Adhesive Remnant Index, and the surfaces were compared in terms of mode of removal and type of adhesive using Fishers exact test (alpha = 5%). RESULTS No significant differences were found between the two different types of adhesives (CAS, GIC) in terms of the amount of damage to the enamel. Portions of enamel damage were found for impulse debonding/0%<bracket removal pliers/4%<lift-off debracketing instrument/17%<side-cutter/21%. The highest Adhesive Remnant Index grades were seen for impulse debonding. GIC residues after postprocessing using ultrasound were seen in 79%, compared to 48% after rotational postprocessing of CAS residues. CONCLUSIONS Impulse debonding provides a good alternative to conventional debonding methods, as the adhesion is usually separated at the bracket-adhesive interface, thereby avoiding enamel damage, independent of the adhesive used.

Camouflage effects following resin infiltration of postorthodontic white-spot lesions in vivo: One-year follow-up

OBJECTIVE To assess camouflage effects by concealment of postorthodontic white-spot lesions (WSLs) to sound adjacent enamel (SAE) achieved over 12 months with resin infiltration (Icon, DMG, Hamburg, Germany). METHODS Twenty subjects (trial teeth nteeth = 111) who had received resin infiltration treatment of noncavitated postorthodontic WSLs were contacted for a 1-year follow-up assessment of CIE-L*a*b* colors (T12). Color and lightness (CIE-L*a*b*) data for WSLs and SAE were compared to baseline data assessed before infiltration (T0) and those assessed after 6 months (T6), using a spectrophotometer. The target parameter was the difference between the summarized color and lightness values (ΔEWSL/SAE). Intergroup (WSL, SAE) and intertime comparisons (T0 vs T6, T12) were performed using paired t-tests at a significance level of α = 5%. RESULTS Nine subjects (trial teeth nteeth = 49; male/female ratio 5/4; age range 13-19 years) were available at T12. After the highly significant reduction of ΔEWSL/SAE discrepancies between T0 and T6, analysis of 12-month records revealed color and lightness discrepancy of WSL vs SAE that was significantly decreased compared with baseline, indicating an assimilation of WSL color to SAE appearance after infiltration, while an additional reduction of discrepancies between T6 and T12 was not significant. CONCLUSION As color and lightness characteristics of the Icon infiltrant as well as the esthetic camouflage effects achieved by WSL infiltration were not altered significantly or clinically relevant after 12 months, the method of resin infiltration can be recommended for an enduring esthetic improvement of postorthodontic WSL.

A method for defining targets in contemporary incisor inclination correction

Different craniofacial properties require individual targets in incisor inclination. These requirements are mostly scheduled on the basis of cephalometric diagnosis, but, however, performed using straightwire appliances, which refer to third-order angles and not to cephalometric data. The objective of this study was to analyze the relationship between incisor third-order angles, incisor inclination, and skeletal craniofacial findings in untreated ideal occlusion subjects with natural dentoalveolar compensation of skeletal variation, in order to link the field of cephalometric assessment of incisor inclination with that of contemporary orthodontic incisor inclination correction. This study utilized lateral cephalograms and corresponding dental casts of 69 untreated Caucasians (21 males and 48 females between 12 and 35 years of age) with neutral (Angle Class I) molar and canine relationships and an incisor relationship that was sagittaly and vertically considered as ideal by three orthodontists (i.e. well supported by the antagonistic teeth and without the need for either deep or open bite correction). Upper (U1) and lower (L1) axial incisor inclinations were assessed with reference to the cephalometric lines NA and NL, and NB and ML, respectively. Sagittal and vertical skeletal relationships were classified using SNA (SNB) and NSL-ML (NSL-NL) angles. Third-order angles (U1TA and L1TA) were derived from direct dental cast measurements using an incisor inclination-recording appliance. The relationships between cephalometric and third-order measurements evaluated by calculating Pearson product-moment correlation coefficients (a = 0.05) showed strong correlations between cephalometric axial inclination data (U1NA/deg, L1NB/deg, U1NA/mm, L1NB/mm, U1NL, and L1ML) and sagittal-skeletal data, but no significant relationship between skeletal-vertical findings and incisor inclination. The mean U1TA was 4.9 (standard deviation [SD] 5.85) and the mean L1TA -3.0 (SD 6.9) degrees. Regression analyses were used for axial inclination (ANB angle designated as the independent variable) and for third-order data (U1NA, L1NB, U1NL, and L1ML designated as independent variables). Based on the correlations found in this study, a novel method for defining targets in upper and lower incisor third-order correction according to natural standards is presented. As a consequence, third-order movements can be adapted to cephalometric diagnosis with enhanced accuracy.

Functional treatment of snoring based on the tongue-repositioning manoeuvre.

Orofacial biofunction comprises muscular and physical effects, which may contribute to stabilization of the oropharyngeal airway. The tongue-repositioning manoeuvre (TRM) provides physical stabilization of the tongue and the soft palate together with, as a prerequisite, a nasal breathing mode. The aim of the present study was to evaluate the influence of a TRM treatment concept on primary snoring. The TRM was used to achieve a closed biofunctional rest position of the orofacial system and to re-educate the nasal breathing pattern. Pressure indicating oral shields were used for home exercises as a biofeedback instrument and to support nocturnal mouth closure. Treatment was undertaken on 125 consecutive primary snorers [101 males, mean age 52.4 years, range 34-75, mean body mass index (BMI) 28.1, range 18.9-38.5, and 24 females, mean age 55.2 years, range 36-70, mean BMI 26.8, range 22.7-31.9]. Bed partner ranking was performed, and snoring was judged using a 10-cm visual analogue scale (VAS). The VAS score was 8.4 (range 6-10) before treatment and decreased to 4.1 (range 0-10) after treatment [mean observation time 4.6 months (1-10)]. Analysis of variance showed a significant influence of treatment in subjects with a normal body weight (BMI 18.5-25). The data provide evidence that dynamic stabilization of the orofacial system with the TRM in conjunction with nocturnal wear of an oral shield is beneficial for reducing the symptoms in primary snorers with a normal BMI.

Geometric Influence of the Sagittal and Vertical Apical Base Relationship on the ANB Angle

Objective:The objective of this study consisted in determining the variability of the ANB angle in relation to the position of the A- and B-points in the sagittal vertical plane.Materials and Methods:Using a theoretical model, we varied the position of the cephalometric points A and B in the sagittal vertical plane while its sagittal relationship was kept constant (Wits value = 0 mm). For this purpose, seven lines were erected perpendicular to the occlusal plane on a lateral cephalogram. The position of points A and B were determined on each of the vertical lines by calculating one anterior and one posterior angle in each case. In this way, the positions of all A- and B-points were clearly defined in the sagittal vertical plane.Results:The characteristic of the ANB angle in the sagittal vertical plane was graphically represented by determining both points A and B using two angles instead of one. This revealed that the ANB angle for the same sagittal base relationship was characterized by major variations depending on the position of the A- and B-points in relation to the anterior cranial base. The larger the SNA and SNB angles were, the larger the corresponding ANB angle. At the same time, the absolute value of ANB increased with the length of the vertical distance between the points A and B.Conclusion:The ANB angle is strongly influenced by geometric factors. Accurate diagnosis of the sagittal base relationship should thus take the individual character of the ANB angle into account.ZusammenfassungZiel:Das Ziel der Studie bestand darin, die Variabilität des ANB-Winkels in Abhängigkeit der Lage des A- und B-Punktes in der Sagittal-Vertikal-Ebene zu bestimmen.Material und Methode:Anhand eines theoretischen Modells wurde die Position der kephalometrischen Punkte A und B in der Sagittal-Vertikal-Ebene variiert, während ihre sagittale Relation konstant gehalten wurde (Wits-Wert = 0 mm). Hierfür wurden auf einem Fernröntgenseitenbild sieben Linien senkrecht zur Okklusionsebene konstruiert. Die Position der Punkte A und B wurde jeweils auf den senkrechten Linien bestimmt, indem jeweils ein anteriorer und ein posteriorer Winkel berechnet wurde. Auf diese Weise konnte die Lage der Punkte A und B in der Sagittal-Vertikal-Ebene eindeutig definiert werden.Ergebnisse:Die Eigenschaft des ANB-Winkels in der Sagittal-Vertikal-Ebene konnte graphisch dargestellt werden, in dem die Punkte A und B durch jeweils zwei statt durch einen Winkel berechnet wurden. Es zeigte sich, dass der ANB-Winkel für dieselbe sagittale Basenrelation in Abhängigkeit der Lage des A- und B-Punktes zur vorderen Schädelbasis große Variationen aufwies. Je größer der SNA- und SNB-Winkel waren, umso größer wurde der dazugehörige ANB-Winkel. Gleichzeitig vergrößerte sich der Betrag des ANB-Winkels mit zunehmendem vertikalen Abstand zwischen den Punkten A und B.Schlussfolgerung:Der ANB-Winkel wird in hohem Maße von geometrischen Faktoren beeinflusst. Für eine genaue Diagnose der sagittalen Basenrelation sollte aus diesem Grund die individuelle Natur des ANB-Winkels berücksichtigt werden.