Twenty-year follow-up of functional treatment with a bionator appliance (part 2): a retrospective cephalometric analysis of skeletal and dentoskeletal changes.

OBJECTIVES: To investigate skeletal and dentoskeletal changes 20 years after bionator treatment. MATERIALS AND METHODS: Analog lateral cephalograms of 18 subjects treated with a bionator appliance during growth were digitized with a transmitted light scanner. Inclusion criteria were: increased overjet (≥4 mm), skeletal Class II, available lateral cephalograms before (T0), after (T1), and 20 years after (T2) treatment with only a Bionator. To assess standard cephalometric parameters, the software ivoris analyze was used. Data were analyzed using Friedman's two-way analysis of variance by ranks followed by Dunn's post hoc tests (P ≤ .05). RESULTS: During therapy (T0-T1), ANB decreased significantly by 1.9° and remained unchanged long term. SNA slightly decreased (-0.6°) during treatment, SNB and SNPg increased (+1.4°, +1.7°). All three parameters showed a significant increase at T2 (+1.2°, +1.6°, +1.6°). Vertical measurements (ML-NL, ML-NSL, NL-NSL) remained almost unchanged during therapy. NL-NSL also was unchanged during the long-term interval; ML-NSL and ML-NL decreased significantly (-3.4°, -4.9°). During treatment, the maxillary incisors retroclined (OK1-NL: -1.6°, OK1-NA: -0.6°), the mandibular incisors proclined (UK1-ML: +3.5°, UK1-NB: +4.9°), neither significantly. Long term, there was a nonsignificant tendency toward proclination of upper (OK1-NL: +0.1°, OK1-NA: +0.7°) and retroclination of lower incisors (UK1-ML: -1.5°, UK1-NB: -5°). CONCLUSIONS: Changes of ANB after bionator treatment without additional fixed appliances remained stable after 20 years. The observed long-term changes are probably consequences of well-known physiological and age-related processes.

Long-term (≥ 15 years) outcome quality after Class II:1 bionator or Herbst multibracket appliance treatment : A comparison.

PURPOSE: To compare the long-term outcome quality (≥ 15 years) of Class II:1 treatment using either a bionator (BIO) or a Herbst-multibracket appliance (HMB). METHODS: Patients who underwent functional treatment during the ideal treatment period for the respective approach (prepuberty vs. peak/postpeak) were assessed. Inclusion criteria were overjet ≥ 4 mm, skeletal Class II and availability of study casts from before, after and ≥ 15 years after treatment. The study casts were assessed using the Peer Assessment Rating (PAR) index and standard orthodontic cast measurements. RESULTS: During treatment, PAR score, overjet and sagittal occlusal relationship improved significantly in all groups. Long-term, there was a significant increase of incisor irregularity in the upper (HMB) and lower (BIO) arch and a significant decrease of lower arch width 3 - 3 (BIO). PAR score, overjet, and sagittal occlusal relationship remained stable long-term. Intergroup comparisons revealed significant differences between the BIO and HMB groups in terms of lower arch width (6 - 6), upper and lower arch width (3 + 3/3 - 3) as well as sagittal molar relationship. CONCLUSIONS: The achieved improvement in PAR score, overjet, and sagittal occlusion remained comparably stable long-term in all groups. The long-term changes are probably a consequence of natural aging.

Edentulous mandible with four splinted interforaminal implants exposed to three different situations of trauma: A preliminary three-dimensional finite element analysis.

BACKGROUND/AIM: An increasing number of elderly patients with implant-prosthodontic rehabilitation of the edentulous mandible frequently show increased life activity, and consequently, a greater number of aged patients is at risk for maxillofacial trauma. The aim of this 3-dimensional (3D) finite element analysis (FEA) was to evaluate the biomechanical effects of the edentulous mandible (EM) with and without four splinted interforaminal implants exposed to three different trauma applications including assessment of different mandibular fracture risk areas. MATERIALS AND METHODS: In a 3D-FEA study design, EM with and without four splinted interforaminal implants were exposed to the application of 1000 N at the symphyseal, parasymphyseal, and mandibular angle region. On four pre-defined superficial cortical mandibular areas (symphysis region, mental foramen region, angle of mandible, and mandibular neck) representing regions of interest (ROI), the von Mises stresses were measured for the three trauma applications. For all ROIs, stress values were evaluated and compared for the different force application sites as well as between EM models with and without interforaminal implants. RESULTS: For EM with and without four splinted interformaninal implants, all traumatic loads generated the highest stress levels at the mandibular neck region. However, in the EM with four splinted interforaminal implants, an anterior symphyseal force application generated significantly (P < .01) increased stress values in the parasymphyseal (mental foramen) region than in EM without implants. For force applications at the parasymphaseal region (mental foramen) and at the angle of the mandible elevated, von Mises stress values were noted directly at the application sites without difference between edentulous mandibles with and without four interforaminal implants. CONCLUSION: In an edentulous mandible model with four splinted interforaminal implants, the condylar neck and the mental foramen represent the predilectional risk areas for mandibular fracture for both anterior symphyseal and lateral parasymphyseal force application.

Twenty-year follow-up of functional treatment with a bionator appliance: A retrospective dental cast analysis.

OBJECTIVE: To investigate changes in dental arch configuration, relationship, and malocclusion directly after Class II malocclusion treatment with a Balters bionator modified by Ascher as well as 20 years after treatment. MATERIALS AND METHODS: Orthodontic dental cast analysis of 18 patients with skeletal Class II treated with a bionator without any additional fixed therapy was performed with a digital caliper at three stages: before (T0), after (T1) and 20 years after (T2) treatment. Arch perimeter and depth, intermolar and intercanine distance, overjet, overbite, sagittal molar and canine relationship, mandibular incisor irregularity (Little's index), and malocclusion (PAR index) were assessed. RESULTS: During treatment (T0-T1), upper arch perimeter significantly increased with a significant decrease in the upper and lower arch perimeter long-term (T1-T2), whereas corresponding arch depths changed only slightly in both periods. Transverse intermolar width increased significantly during treatment, remaining almost constant from T1 to T2. Lower intercanine distance remained fairly unchanged during treatment, but decreased significantly during follow-up. Lower incisor irregularity improved slightly during treatment but increased significantly long-term. After treatment, sagittal molar relationships on both sides were improved, overjet and overbite reduced; these significant changes remained stable long-term. The peer assessment rating (PAR) index was significantly lower after treatment and increased insignificantly during follow-up. CONCLUSIONS: 20 years after bionator treatment without additional fixed appliances, the improved sagittal relationship and the reduced overjet and PAR index remained fairly stable. Long-term changes are most likely due to physiological aging processes and are not associated with bionator treatment.

Efficacy of four preventive measures against enamel demineralization at the bracket periphery-comparison of microhardness and confocal laser microscopy analysis.

OBJECTIVES: The aim of this in-vitro study was to investigate the efficacy of four preventive measures against enamel demineralization and to compare the suitability of microhardness (MH) measurements and confocal laser microscopy (CLSM). MATERIALS AND METHODS: A total of 80 teeth were randomly allocated into four groups. The effect against demineralization of two coating materials (group 1: resin-modified glass ionomer (RMGI) cement varnish (ClinproXT); group 2: composite sealant (ProSeal)) and that of two types of bracket-bonding material (group 3: amorphous calcium phosphate (ACP) composite (AegisOrtho); group 4: RMGI (FujiOrthoLC)) was compared after pH-cycling by MH and CLSM. Measurements were made at the edge of the coating/bracket as well as at 50, 100, 200, and 400 µm distance. The data were converted into values of mineralization (Vol%) and analyzed by parametric (ANOVA and Tukey's post hoc) or non-parametric (Kruskal-Wallis and Games-Howell post hoc) tests. RESULTS: ClinproXT and ProSeal were proved to protect the bracket periphery. However, the area next to them showed demineralizations. The mean area of lesion (CLSM-data) was significantly different between the groups (p < 0.0001). The smallest lesions were revealed for the RMGI-based materials. MH identified only for group 4 a significant difference between the area next to the bracket base and that at 200 and 400 µm distance. CONCLUSION: There was nearly no lesion under both coatings. A stagnation of demineralization was identified particularly for the RMGI. ProSeal showed an inferior protection of the untreated enamel. MH and CLSM analysis were suitable to detect subsurface lesions. CLINICAL RELEVANCE: A diverse efficacy of materials against enamel demineralization at bracket periphery has to be noticed.

Evaluation of the effect of bracket-periphery treatment on prevention of enamel demineralization by consecutive µCT scans.

OBJECTIVES: The aim of this study was to assess the effect of two sealants and two varnishes on the prevention of enamel demineralization, as well as the effect of inattentive surplus enamel-etching by a self-etching primer (SEP). MATERIALS AND METHODS: The sealants ProSeal and Clinpro and the varnishes Protecto and FluorProtector were investigated. For inattentive surplus enamel-etching, Transbond Plus SEP was used. The teeth (N = 75) underwent a pH-cycling for 4 weeks and were examined by weekly consecutive µCT scans (t1-t4) to determine mineral loss (ΔZ Equivalent) and lesion depth (Ld). At t4, we also assessed the fluorescence change (ΔF). RESULTS: For ProSeal, no lesions could be detected. In contrast, we found isolated lesions in the area treated with Clinpro. Teeth with inattentive surplus enamel-etching showed always a higher ΔZ Eqivalent. However, this was not statistically significantly different compared to the teeth treated with the varnishes. The adjacent untreated enamel (except the SEP-treated teeth) always showed significantly more demineralization than any of the treated areas. The ΔF partially confirmed these results. CONCLUSION: No lesions were shown in the area of application of ProSeal. The other materials did not sufficiently protect the enamel; however, a protective effect of all materials was obvious when comparing the bracket-periphery with the adjacent untreated enamel. Additionally, the area of SEP application showed almost always a significantly less demineralization in comparison to that found on the adjacent untreated enamel. CLINICAL RELEVANCE: The bracket-periphery was not always sufficiently protected. The adjacent untreated enamel did not benefit from the bracket-periphery treatment.

Do bonding agents protect the bracket-periphery?--Evaluation by consecutive µCT scans and fluorescence measurements.

OBJECTIVES: The aim of this in vitro study was to consecutively determine the effect of three bonding agents on the prevention of enamel demineralisation at the bracket-periphery and to compare the suitability of micro-computed tomography (µCT) scans and quantitative light-induced fluorescence (QLF) to detect changes within subsurface lesions. MATERIALS AND METHODS: The effect of a resin-modified glass ionomer cement (RMGI) (Fuji Ortho LC), a compomer (Assure) and a composite (Transbond XT) on the prevention of enamel demineralisation at the bracket-periphery was examined. After 7, 14, 21 and 28 days of pH cycling, the teeth (N = 45) were examined by consecutive µCT scans and by using a customised QLF set-up. RESULTS: Particularly for the RMGI and for the compomer, the QLF and µCT scans showed that the formation and the body of the lesion were not precisely located at the enamel next to the bracket margin. There was an area that was almost protected. The progression of demineralisation was decreased for the RMGI and the compomer-treated teeth. CONCLUSION: For bonding orthodontic brackets, the RMGI and compomer were comparably able to decrease the progression of white spot lesions (WSL), although the RMGI showed marginally superior protection. Both methods (QLF and µCT scans) were suitable for investigating the longitudinal fluoride effects on WSL, though these effects were more accurately described by mineral (fluorescence) loss or volume changes than by lesion depth. CLINICAL RELEVANCE: The progression of WSL at the bracket-periphery could be altered by using fluoride-releasing bonding agents for bracket application. This approach represents a minimally invasive preventive measure.

Self-etch adhesives for the bonding of orthodontic brackets: faster, stronger, safer?

OBJECTIVES: This study aimed to evaluate the performance of accelerating procedures for bonding of orthodontic brackets in vitro by comparing different adhesives (etch-and-rinse, self-etch) and polymerization procedures (curing devices, time). The performance was characterized by three parameters: (1) the bond strength achieved, (2) the incidence of enamel damage, and (3) the extent of residual composite on the tooth. MATERIALS AND METHODS: Bracket bonding was performed on 500 extracted human teeth after application of either an etch-and-rinse adhesive or a one-step self-etch adhesive. Two different two-component self-etch adhesives (Clearfil SE and Transbond Plus) and two single-component self-etch adhesives (Ideal and iBond) were investigated after using different polymerization procedures (light-emitting diode for 10 or 20 s or plasma arc curing device for 3 or 6 s). The bond strength, incidence of enamel damage, and extent of residual composite on the tooth were measured. RESULTS: Single-component self-etch adhesives gave the lowest bond strengths. No significant difference in bond strength could be detected between the two-component self-etch adhesives and the etch-and-rinse method. There was a 70.3% risk for enamel damage at bond strengths above 12 MPa, but only 5% risk below 12 MPa and no risk below 8.2 MPa. The risk of enamel damage increased by an odds ratio increment of 1.3 for each additional MPa above 8.2 MPa. CONCLUSION: Single-component self-etch adhesives showed the lowest bond strengths, caused limited enamel damage, and generally left less residual composite on the tooth. CLINICAL RELEVANCE: The nature of the adhesive greatly influences the resultant bond strength, the risk of enamel damage, and the extent of residual composite on the teeth.

Surgically assisted rapid maxillary expansion: midfacial and cranial stress distribution.

INTRODUCTION: Our aim in this study was to investigate the stresses in the midface and at the cranial base during surgically assisted rapid maxillary expansion, to determine whether surgically assisted separation of the maxilla from the cranial base can be considered justified and necessary. METHODS: By using finite element models, surgically assisted rapid maxillary expansion with or without separation of the pterygomaxillary junction was simulated, and the stresses at various points in the midface and the cranial base were analyzed. The finite element models consisted of more than 50,000 individual elements and almost 100,000 nodes. RESULTS: The stresses recorded at the measurement points of the midface and the cranial base were usually lower upon separation of the pterygomaxillary junction than those measured without this additional surgical measure. The stress measured at the optic foramen without separation was 122.4 MPa, whereas, with separation of the pterygomaxillary junction, it was only 32.7 MPa. The finite element method proved to be a suitable procedure for comparing the biomechanical influences of various therapeutic measures involving a combined surgical-orthodontic procedure. The results confirm the effectiveness of an additional separation of the pterygomaxillary junction as a protective measure to reduce stress to the foramina of the cranial base. CONCLUSIONS: To protect the cranial base from undesirable side effects, separation of the pterygomaxillary junction appears to be a reasonable and necessary additional measure for surgically assisted palatal suture expansion.

Analysis of sutural strain in maxillary protraction therapy.

OBJECTIVE: The goal of the study was to examine the strain in the sutures of the midface and the cranial base with maxillary protraction therapy and to clarify whether such stretching suggests a skeletal effect of the apparatus employed for that purpose. MATERIALS AND METHODS: Using a finite elements model, a maxillary protraction therapy was simulated with various force levels and vectors, and the strains appearing at the sutures (in microstrain) were measured at the midface and the cranial base. The simulation model we employed consisted of 53,555 individual elements; the simulated forces were 2 x 3 N and 2 x 5 N, while the vectors of the applied forces were in the anterior and anterior caudal direction. RESULTS: The maximum measured strains were on average below 10 microstrain, while higher values were measured only at the nasal bone and at the cranial base at the oval and spinous foramina with anterior directed force vectors (26.4 microstrain). With an anterior-caudal force vector, the measured values were usually lower. DISCUSSION: The measured strains were on average about hundredfold lower than the Frost thresholds (2000 microstrain). It does not seem probable that the strains occurring upon maxillary protraction therapy suffice to stimulate any additional bone growth. CONCLUSION: The good clinical efficacy of maxillary protraction therapy is apparently based, for the most part, on dental effects, while its skeletal effects still remain doubtful.