Enamel demineralization after different methods of interproximal polishing.

OBJECTIVES: The aim of this in vitro study was to investigate the demineralization rate in human enamel after interproximal polishing (IPP) and to detect possible correlations with the IPP method used, with special emphasis on the surface characteristics of the enamel being treated. MATERIALS AND METHODS: This in vitro study tested five IPP systems (Profin Directional System®, Intensiv ProxoStrip®, OS discs®, ARS Safe-Tipped Bur Kit® and Ortho-Strips Set®) that are currently available on the market. Each of the five examination groups comprised 12 randomly selected teeth, while the control group consisted of six teeth. The teeth were placed in an artificial model for each group. The proximal contacts were then resolved by IPP. To allow detection of any surface characteristics, one surface was not further processed after IPP, while the other side was additionally polished. After IPP, the teeth were exposed to a pH-cycling model with alternating phases of demineralization and remineralization. Substance loss was analyzed using optical emission spectrometry. Data were subjected to simple analysis of variance (ANOVA) performed with Tukey's test. Comparison between the groups with and without polishing was conducted using the t test for independent samples. The significance level was set at p < 0.05. RESULTS: Demineralization significantly increased after IPP. The rates of demineralization differed significantly among the examination groups, with the greatest loss of substance being produced with Sheridan's Air-Rotor Stripping® system (ARS; 145.34 ± 20.37 µm). In all of the examination groups, subsequent polishing of the surfaces did not significantly reduce the amount of demineralization (polished 119.64 ± 28.61 µm; unpolished 114.16 ± 28.61 µm). CONCLUSION: No correlation between surface morphology and the degree of susceptibility of human enamel was detected. However, it must be taken into consideration that there was no potential bacterial colonization in this in vitro erosive set-up. Thus, in contrast to previous explanations, the outermost fluorapatite layer and the individual composition of the enamel may have a greater impact on the solubility of the enamel and the amount of enamel loss after IPP than the type of system used and the resulting surface texture. CLINICAL RELEVANCE: Whenever the outermost layer of enamel is reduced, the practitioner must expect an increase in demineralization. Subsequent polishing does not appear to affect the amount of demineralization.

Laboratory evaluation of toothbrush/toothpaste abrasion resistance after smooth enamel surface sealing.

OBJECTIVES: The use of dental sealants has been extended to smooth enamel surfaces. The present study was conducted to test the in vitro performance of four sealants with different characteristics (highly and lowly filled, self-etching features). MATERIALS AND METHODS: Eighty human teeth (lower incisors and premolars) were randomly divided into following sealant test groups: ProSeal(TM), LightBond(TM), OrthoSolo(TM), and Seal&Protect(®). Twenty untreated teeth served as a control group. Tooth brushing was conducted for a period of time simulating 12, 18, and 24 months. During the toothbrush abrasion protocol, the specimens were subjected to thermal and acidic challenge. Sealant thickness was determined with µCT imaging, and qualitative and quantitative surface effects were investigated using stereo microscopy and raster electron microscopy, respectively. Data were subjected to t test or Kruskal-Wallis/Mann-Whitney tests (alpha, 5%). RESULTS: The wear behavior and film integrity of highly filled sealants were superior to lowly filled sealants. Even after 1 year of tooth brushing, significant surface deterioration with deleterious loss of enamel and discoloration was observed in all tested materials (χ(2) = 15.349; P = 0.004). The size of the observed defects increased over time. CONCLUSION: These results suggest that the application of sealants on smooth enamel surfaces should be limited to special indications, and their usefulness has to be revisited. CLINICAL RELEVANCE: Based on the results of this in vitro study, the general overall application of enamel sealants needs to be questioned.

Influence of maxillary advancement surgery on skeletal and soft-tissue changes in the nose - a retrospective cone-beam computed tomography study.

OBJECTIVES: Surgical correction of skeletal maxillary retroposition is often associated with changes in the morphology of the nose. Unwanted alar flaring of the nose is observed in many cases. The aim of the present study was therefore to investigate the influence of surgical advancement of the maxilla on changes in the soft-tissue morphology of the nose. Having a coefficient that allows prediction of change in the nasal width in Caucasian patients after surgery would be helpful for treatment planning. MATERIALS AND METHODS: All 33 patients included in this retrospective study were of Caucasian descent and had skeletal Class III with maxillary retrognathia. They were all treated with maxillary advancement using a combination of orthodontic and maxillofacial surgery methods. Two cone-beam computed tomography (CBCT) datasets were available for all of the study's participants (16 female, 17 male; age 24.3 ± 10.4 years): the first CBCT imaging was obtained before the planned procedure (T0) and the second 14.1 ± 6.4 months postoperatively (T1). Morphological changes were recorded three-dimensionally using computer-aided methods (Mimics (Materialise NV, Leuven/Belgium), Geomagic (Geomagics, Morrisville/USA)). Statistical analysis was carried out using SPSS 21 for Mac. RESULTS: The mean sagittal advancement of the maxilla was 5.58 mm. The width of the nose at the alar base (Alb) changed by a mean of + 2.59 mm (±1.26 mm) and at the ala (Al) by a mean of + 3.17 mm (±1.32 mm). Both of these changes were statistically highly significant (P = 0.000). The increase in the width of the nose corresponded to approximately half of the maxillary advancement distance in over 80 % of the patients. The nasolabial angle declined by an average of -6.65° (±7.71°). CONCLUSIONS: Maxillary advancement correlates with a distinct morphological change in nasal width. This should be taken into account in the treatment approach and in the information provided to patients.

Therapeutic effects of functional orthodontic appliances on cervical spine posture: a retrospective cephalometric study.

INTRODUCTION: Interactions between the cervical spine and the stomatognathic system have been discussed in literature. The present study was conducted to investigate whether, and to what extent, orthodontically induced mandibular advancement produces changes in cervical spine posture. Furthermore, possible appliance-specific effects should be distinguished. MATERIAL AND METHODS: The cephalograms of 64 patients with skeletal class II were analysed before and after mandibular advancement. Linear and angular cephalometric parameters were identified to define the position of the atlanto-occipital and atlantoaxial joints. The total example was divided into two subgroups (comprising 32 individuals each) according to the employed appliance: activator versus bite-jump appliance (BJA). Student's t-test and analysis of covariance were used for statistical analysis. RESULTS: Overall, a significant straightening of the cervical spine was observed during the treatment. This conclusion is based on changes of Chamberlain (p = 0.0055), CVT (p = 0.0003), OPT (p < 0.0001), Redlund-Johnell/Petersson (p < 0.0001), McGregor-mC2 (p = 0.0333) and AT-FH (p = 0.0445). Improvements in occipitoatlantal dislocation were also observed in the total sample. Appliance-specific changes were found in the activator subgroup for a number of linear parameters (Chamberlain, McGregor, CVT, OPT, Redlund-Johnell/Petersson). In contrast, only two linear parameters (OPT and Powers ratio) revealed statistically significant changes in the BJA subgroup. CONCLUSIONS: During skeletal class II treatment the position of upper cervical spine changes. In the activator subgroup the observed effects were more pronounced than those in the BJA subgroup. Further studies including a control group comprised with non-treated class II patients are needed to assess whether these effects may be caused directly by the appliances irrespective of growth.