Matteo Zanarini

Evaluation of enamel surfaces after bracket debonding: An in-vivo study with scanning electron microscopy

INTRODUCTION The purposes of this in-vivo study were to compare the modes of failure of uncoated and adhesive precoated metal brackets by using the adhesive remnant index, and to assess the quality of the enamel surface after cleanup by using the enamel damage index. METHODS Twelve Victory brackets (group A) and 12 Victory adhesive precoated brackets (group B) (both, 3M Unitek, Monrovia, Calif) were bonded onto the maxillary second premolars of 12 volunteers. The uncoated brackets were bonded with Transbond XT adhesive resin (3M Unitek). Replicas of the teeth were made before bonding (T0), after bracket removal (T1), and after cleanup (T2). Scanning electron microscope images of all labial enamel surfaces were taken at T0, T1, and T2, and these were evaluated according to the adhesive remnant index and the enamel damage index. RESULTS Evaluation of the adhesive remnant index scores with the chi-square test showed no statistically significant difference between the groups. Evaluation of the enamel damage index grades with the sign test for paired samples showed a statistically significant difference (P <0.01) between T0 and T2. CONCLUSIONS Uncoated and precoated brackets exhibited similar debonding patterns. Additionally, the debonding method tested in this study did not restore the original enamel surface, although there was no clinically relevant enamel damage.

Preventive treatment of ectopically erupting maxillary permanent canines by extraction of deciduous canines and first molars: A randomized clinical trial.

INTRODUCTION In this research project, we aimed to compare the effectiveness of single (1 deciduous canine) and double (deciduous canine and first molar) extractions in subjects with retained maxillary permanent canines positioned palatally or centrally in the alveolar crest, at risk for root resorption of adjacent permanent teeth. METHODS Subjects at risk for canine impaction or resorptive situations were randomly assigned to 1 of 2 treatment modalities: single extraction (17 patients, 28 canines) or double extraction (20 patients, 37 canines). Thirty-one patients with 53 canines judged to be not at risk constituted the untreated control group. Panoramic radiographs were taken at the initial observation and after 18 months on average. Between-group statistical comparisons were carried out on the changes in canine inclination and sector location (measured on panoramic radiographs) and on the percentages of successful permanent canine eruptions. RESULTS The double-extraction group showed significant improvements in the success rate and the intrabony position of the permanent canine, in terms of uprighting the canines long axis with a crown movement in a distal direction. CONCLUSIONS Concomitant deciduous canine and first molar extractions proved to be more effective as a preventive approach to promote eruption of retained maxillary permanent canines positioned palatally or centrally.

Percentiles relative to maxillary permanent canine inclination by age: A radiologic study

INTRODUCTION Few studies have investigated developmental norms for maxillary permanent canine eruption. In this observational cross-sectional study, we aimed to provide an age-related description of the percentiles relative to canine inclination in a large sample of nonorthodontic patients. Associations between inclination and sector were also analyzed. METHODS Canine inclination and sector location were measured on 1020 panoramic radiographs obtained from subjects of white ancestry aged between 8 and 11 years not seeking orthodontic treatment. The total sample comprised 2037 canines. RESULTS Canine inclination increases between 8 and 9 years and decreases between 9 and 11 years. The greatest value for each percentile is at 9 years. A linear model should be hypothesized for differences in canine inclination between 2 successive ages in correspondence to each percentile. The proportion of sector 2 canines decreases and that of sector 1 increases with age. In the same age group, the inclination generally decreases as the sector decreases. CONCLUSIONS Percentiles by age show the average canine inclination in a certain population. Further studies are required to verify whether percentiles can be a diagnostic aid for determining normal canine inclination at a given age and for quantifying the risk of canine impaction or adjacent root resorption.

In vitro evaluation of the effects of a fluoride-releasing composite on enamel demineralization around brackets

OBJECTIVES The aim of this in vitro study was to evaluate the effectiveness of a fluoride-releasing bonding agent in inhibiting enamel demineralization around orthodontic brackets after the exposure to a demineralizing solution. MATERIALS AND METHODS Twenty-six extracted upper molars were bonded with two different composites: Transbond XT (TXT) and Transbond Plus (TPlus), fluoride-releasing (both 3M Unitek, Monrovia, CA, USA). The samples were exposed to an acid lactic solution for three days and then subjected to Metallographic Optical Microscope (MOM) and Scanning Electron Microscope/Energy Dispersive X-Ray (SEM/EDX) analyses. Enamel surface was examined in different areas: un-treated, etched and primer-painted, un-treated area with no acid exposure, central area with bracket bonded. The maximum demineralization depths and the fluoride content at 100, 200 and 300 μm depth were evaluated. RESULTS MOM analysis showed statistically significant (p<0.001) differences in demineralization depth for TPlus group compared to TXT group with lower values for the first one. EDX analysis confirmed the presence of fluoride in TPlus group. CONCLUSIONS The fluoride content of TPlus appeared able to weakly reduce the enamel demineralization.

Mixed dentition space analysis for a northern italian population: new regression equations for unerupted teeth.

OBJECTIVE The aim of this study was to determine linear regression equations for a Northern Italian population to predict mandibular permanent premolars and canines widths, and particularly, second premolar widths, using the sum of the widths of the four mandibular incisors, canines and first premolars. MATERIALS AND METHODS Mesiodistal tooth widths were measured from 230 dental casts obtained from Northern Italian patients (130 females and 100 males). Students t-test or Wilcoxon test for independent and paired samples were used to determine right/left side and male/female differences. Correlation coefficients and linear regression equations were constructed to evaluate the relationship between 1) the combined mesiodistal widths of the permanent mandibular incisors (independent variable) and the combined mesiodistal widths of the canine and premolars (dependent variable); 2) the combined mesiodistal widths of the incisors, canines and first premolars (independent variable) and the widths of the second premolars (dependent variable). Significance value was set a priori at 0.05. RESULTS A linear regression equation was found, y=0.585x+7.927 (r=0.734) considering right and left sides of mandibular arch together, to predict canines and premolars widths. For second premolar width, the linear regression equation was y=0.201x+2.149 (r=0.641), even when considering the right and left sides of the mandibular arch together. CONCLUSIONS New regression equations were derived for a Northern Italian population.

Interproximal enamel reduction: An in vivo study

The study aimed to investigate the morphology and composition of the interproximal reduced enamel after exposition to saliva and casein phosphopeptide amorphous calcium phosphate with sodium fluoride (CPP-ACPF). Fourteen patients undergoing an orthodontic treatment with 4 premolars extractions participated to the study. Interproximal enamel reduction (IER) was performed on mesial surfaces of 3 extractive premolars for each patient while 1 served as untreated control. Premolars were assigned to 4 groups: No-S group, sound enamel as control; S-Ex group, stripped and immediately extracted enamel; S-Sal group, stripped and exposed to saliva enamel; S-CPP group, stripped enamel treated with CPP-ACPF. Teeth were extracted at different times, depending on the group they were assigned to and sliced into mesial and distal halves. Mesial surfaces were subjected to environmental scanning electron microscopy with energy dispersive X-ray spectrometry (ESEM/EDX) and to scanning electron microscopy (SEM) analysis. ESEM/EDX investigations showed no statistically significant differences in the content of calcium and phosphate between the 4 groups. SEM observations showed no difference in the morphological appearance of stripped enamel after 30 days of exposure to saliva and CPP-ACPF. Saliva and CPP-ACPF effects on stripped enamel in vivo showed no difference after 30 days.

The effect of zinc-carbonate hydroxyapatite versus fluoride on enamel surfaces after interproximal reduction

The aim of this study was to qualitatively investigate the effects of a zinc-carbonate hydroxyapatite (Zn-CHA) containing toothpaste on stripped enamel morphology in a pH cycling model in vitro and to compare the efficacy of this toothpaste versus fluoride one which still represent the gold standard to remineralize early enamel lesions. Twenty-one extracted lower incisors underwent to interproximal enamel reduction with metal strips (Horico 80 µm) on both mesial and distal surfaces. They were then sliced into mesial and distal halves and the 42 samples obtained were randomly assigned to 3 groups of 14 enamel specimens each. For 8 days, teeth were placed in lactic acid solution for 2 h three times a day with 2 h distilled water preservation in between. After each demineralization bath, samples of Group A were brushed with Zn-CHA containing toothpaste while samples of Group B were brushed with 1,400 ppm fluoride dentifrice for 5 min before immersion into water. Group C of untreated samples served as control. All the samples were then prepared for scanning electron microscopy (SEM) analysis. A score rating system was used to perform a non-parametric statistical analysis. No statistically significant differences were found between the samples brushed with fluoride toothpaste and those untreated (Groups B and C) where the highest grade of damage was found, while the lowest grade was recorded in the samples brushed with Zn-CHA (Group A) and there was a statistically significant difference between this group and the other two groups.

Bracket base remnants after orthodontic debonding

OBJECTIVE To evaluate whether the debonding procedure leads to restitutio ad integrum of the enamel surface by investigating the presence of enamel within the bracket base remnants after debonding. MATERIALS AND METHODS Sixty patients who completed orthodontic treatment with fixed appliances were included. A total of 1068 brackets were microphotographed; the brackets presenting some remnants on the base (n = 818) were selected and analyzed with ImageJ software to measure the remnant area. From this population a statistically significant sample (n = 100) was observed under a scanning electron microscope to check for the presence of enamel within the remnants. Energy dispersive x-ray spectrometry was also performed to obtain quantitative data. RESULTS Statistically significant differences in the remnant percentage between arches were observed for incisor and canine brackets (P < .0001 and P = .022, respectively). From a morphologic analysis of the scanning electron micrographs the bracket bases were categorized in 3 groups: group A, bases presenting a thin enamel coat (83%); group B, bases showing sizable enamel fragments (7%); group C, bases with no morphologic evidence of enamel presence (10%). Calcium presence was noted on all evaluated brackets under energy dispersive x-ray spectrometry. No significant difference was observed in the Ca/Si ratio between group A (16.21%) and group B (18.77%), whereas the Ca/Si ratio in group C (5.40%) was significantly lower than that of the other groups (P < .323 and P = .0001, respectively). CONCLUSION The objective of an atraumatic debonding is not achieved yet; in some cases the damage could be clinically relevant.