Relationship between mentalis muscle hyperactivity and mandibular symphysis morphology in skeletal Class I and II patients

PurposeTo investigate the relationship between mentalis muscle activity and mandibular symphysis morphology in patients with Class I or II skeletal patterns.Materials and methods123 female Thai patients (17 years old+) participated in the present study. Subject pretreatment lateral cephalometric radiographs were examined. All subjects were diagnosed as having a skeletal normal bite. Subjects were grouped according to their sagittal skeletal pattern (ANB angle) into Class I (ANB 2–6) or Class II (ANB > 6). For each skeletal type, the subjects were divided into 2 groups, normal mentalis muscle activity (control group) and hyperactivity (experimental group). The skeletal Class I group comprised 37 subjects with mentalis muscle hyperactivity and 31 subjects with normal activity, while the skeletal Class II group comprised 30 hyperactive and 25 normal activity subjects. Eight cephalometric variables (angular, linear, and proportional measurements) were measured to evaluate mandibular symphysis morphology. The data were statistically analyzed using the Mann–Whitney U test or Independent-Sample t-test based on the normality of the data.ResultsIn the skeletal Class I type, the experimental group revealed a trend of narrower alveolar symphysis width and greater symphysis height compared to the control group, but this was not significant. However, in the skeletal Class II type, the experimental group demonstrated significantly narrower alveolar symphysis width and significantly greater symphysis height compared to the control group (p < 0.05).ConclusionAn increase in mandibular symphysis height and decrease in alveolar symphysis width may relate to mentalis muscle hyperactivity, and such relationship is more obvious in patients with Class II skeletal pattern.     

Variables associated with stability after Le Fort I osteotomy for skeletal class III malocclusion

The purpose of this study was to assess skeletal stability and predictors of relapse in patients undergoing an isolated Le Fort I osteotomy. A retrospective cohort study of 92 subjects undergoing Le Fort I osteotomy for Class III malocclusion was implemented. Predictor variables were demographic and perioperative factors. The primary outcome variable was postoperative skeletal position with relapse defined as >2 mm sagittal and/or vertical change at A-point on serial lateral cephalograms at immediate postoperative, 1 year, and latest follow-up time points. Mean advancement at A-point was 6.28 ± 2.63 mm and mean lengthening was 0.92 ± 1.76 mm. Eight subjects (8.70%) had relapse (>2 mm) in the sagittal plane, and two subjects (2.17%) in the vertical plane. No subjects required reoperation for relapse as overbite and overjet remained in an acceptable range due to dental compensation. In regression analysis, magnitude of maxillary advancement was an independent predictor of relapse in the sagittal plane (P = 0.008). There were no significant predictors of relapse in the vertical plane. This study suggests that isolated Le Fort I osteotomy for correction of skeletal Class III malocclusion is a stable procedure and that greater advancement is an independent risk factor for sagittal relapse.     

Orthopedic effects of splint high-pull headgear—A cephalometric appraisal

ObjectiveThe purpose of this study was to investigate the orthopedic effect of maxillary splint high-pull head gear appliance on maxillary complex.DesignRetrospective study.SettingsPatients under treatment in the Department of Orthodontics, Azad University, during one year period from November 2003 to March 2004.SubjectsLateral cephalometric radiograph of 26 patients (11 boys and 15 girls, with a mean age of 11.3 years) treated with splint high-pull headgear appliance was compared with a similar control group of 26 individuals (11 boys and 15 girls with a mean age of 12.6 years).Main outcome measuresThe result of the present study showed that the treated group more closely approximated Class I cephalometric values after treatment, whereas the control group with a Class II skeletal pattern did not necessarily become “less Class II” due to growth.ResultsPoint A was held efficiently in the treated group (S–A = 0.4 mm) whereas in the control group it had relocated downward and forward 2.00 mm along sella–point A (S–A) line. Also, the relocation of the point A in the horizontal (X-axis) and vertical (Y-axis) planes confirmed these findings. No rotational changes of palatal plane were recorded in the treated group. Mandibular skeletal changes were similar to the control group. Maxillary dentition was relocated more posteriorly.ConclusionsIt was concluded that the maxillary splint with high-pull headgear in the present study held the maxilla in position without any rotational changes of the palatal plane. Therefore, a normal skeletal relationship was achieved in the treated group through a combination of maxillary basal bone and dentoalveolar growth inhibition and a normal expression of mandibular growth.     

Changes in soft tissue profile after mandibular setback surgery in Class III subjects

The aim of this study was to investigate changes in hard and soft tissue profile after mandibular setback surgery. Lateral cephalograms of 25 Class III subjects were assessed before and 1.5 ± 0.4 years after mandibular setback surgery. Paired t test, Pearson correlation test and linear regression analysis were used to evaluate the changes in soft tissue profile. Significant changes were found in skeletal (SNB ?3.6 ± 0.9°, ANB 3.7 ± 1.0°, overjet 5.0 ± 1.2 and overbite 2.5 ± 1.1 mm, P < 0.001), soft tissue (facial convexity 5.9 ± 1.6°, P < 0.001; labiomental fold 0.6 ± 0.6 mm, P < 0.001; upper and lower lip protrusion 0.5 ± 0.8 mm, P < 0.01; ?3.3 ± 1.2 mm, P < 0.001), and upper and lower lip lengths (0.9 ± 1.2 mm, P < 0.01; ?1.8 ± 2.1 mm, P < 0.001). Correlations were found between facial convexity and SNB and ANB angles and between upper lip length and SNB and ANB angles. The change in lower lip length was correlated with SNB, ANB, overjet and overbite. Lower lip retrusion was correlated with overjet and a significant correlation was found between the retrusion of lower incisor and lower lip. Mandibular setback surgery was effective in producing an orthognathic profile in adult Class III subjects with mandibular prognathism.     

Evaluation of effects of activator treatment on mandibular growth by analyzing components of condylar growth and mandibular rotation

PurposeThe objective of this study is to clarify the effects of activator treatment on mandibular growth in relation to condylar growth and total rotation of the mandible, and to investigate the relationships between the treatment responses and pretreatment facial morphology.Materials and methodsThirty Japanese girls with Class II division 1 malocclusion treated with activator were examined. Mean age at the start of treatment was 9.6 ± 1.6 years. Mean treatment duration was 19 ± 4 months. Lateral cephalograms obtained before and after treatment were used to analyze skeletal changes during treatment. Regional superimposition analysis was performed to evaluate activator effects by decomposing the mandibular growth into condylar growth and mandibular total rotation.ResultsThe changes in intermaxillary relationships were significantly correlated with vertical condylar growth and mandibular total rotation (P < 0.05 and P < 0.01). The changes in the forward displacement of the mandible were significantly correlated with sagittal condylar growth and mandibular total rotation (P < 0.05 and P < 0.01). Vertical condylar growth and mandibular total rotation were significantly correlated with pretreatment mandibular morphology (P < 0.05 and P < 0.01).ConclusionBoth the sagittal condylar growth and counterclockwise mandibular total rotation attributed to activator treatment contribute to forward displacement of the mandible. The activator effects are expected greater in patients with flat mandibular plane, small gonial angle, backwardly inclined mandibular ramus and long posterior facial height.     

Three-dimensional analysis of condylar changes in surgical correction for open bite patients with skeletal class II and class III malocclusions

The aim of this study was to quantify three-dimensional condylar displacements as a result of two-jaw surgery for open bite correction in patients with skeletal class II and class III malocclusion. Pre-surgical (T1) and post-surgical (T2) cone beam computed tomography scans were taken for 16 patients with skeletal class II (mean age 22.3 ± 9.47 years) and 14 patients with skeletal class III (mean age 25.6 ± 6.27 years). T2 scans were registered to T1 scans at the cranial base. Translational and rotational condylar changes were calculated by x,y,z coordinates of corresponding landmarks. The directions and amounts of condylar displacement were assessed by intra- and inter-class Mann–Whitney U-test or t-test. Class II patients presented significantly greater amounts of lateral (P = 0.002) and inferior (P = 0.038) translation than class III patients. The magnitudes of condylar translational displacements were small for both groups. Skeletal class III patients had predominantly medial (P = 0.024) and superior (P = 0.047) condylar translation. Skeletal class II patients presented greater condylar counterclockwise pitch (P = 0.007) than class III patients. Two-jaw surgery for the correction of open bite led to different directions and amounts of condylar rotational displacement in patients with skeletal class II compared to class III malocclusion, with greater rotational than translational displacements.     

Bimaxillary protrusion trait in the Indian population: A cephalometric study of the morphological features and treatment considerations

PurposeThe orthodontic literature is discordant with the diagnosis of bimaxillary protrusion with no single anatomic answer and the anomaly has been referred in the literature with protean characteristics. The trait denotes a particular facial configuration and its cephalometric representation in certain ethnic and racial groups revealed a mixed pattern with individual variations. The present study was aimed at analyzing the dento-skeletal characteristics of bimaxillary protrusion in a sample of Indian men and women.Materials and methodsForty-six Indian subjects (28 women and 18 men; 19 ± 3.6 years of age) with Class I malocclusion and interincisal angle ≤110°, who attended orthodontic clinics for a comprehensive fixed orthodontic treatment were included for the study. The lateral films were hand traced and 27 parameters were measured. The data were imported to SPSS version 13 US package and statistical manipulation included means, standard deviation, and coefficient of variation (%). Male and female data were compared by Student's t-test (unpaired). Correlation and regression analysis were performed to assess any relationship between different parameters.ResultsThere was a marked increase in proclination of the maxillary incisors both to the maxillary plane (125.3 ± 5.7°), the NA line (35.1 ± 5.0°) and to sella–nasion (117.7 ± 5.5°). The positional relationship of the mandible to the maxilla with reference to the cranial base was within the normal limits (ANB = 3.1 ± 1.3°) and the skeletal pattern was Class I. The effective lengths of maxilla and mandible did not correlate significantly with sagittal skeletal discrepancy.ConclusionUnlike in other ethnic and racial groups, bimaxillary protrusion in Indian subjects is likely a bidental protrusion over normal dento-alveolar bases. The skeletal characteristics suggested a normal relationship of the functional components of the face. The condition could be treated successfully with orthodontic mechanotherapy alone.     

Change in initial response of periodontal ligament according to tooth movement speed in periodontal ligament distraction osteogenesis

PurposeThe aims of this animal study were to (1) determine how tooth movement speed affects morphological and histological change, and (2) verify how this speed affects change in the initial response of the tension-side periodontal ligament with application of periodontal ligament distraction osteogenesis (PLDO).Materials and methodsFive mature, male, 10–15-month-old beagle dogs were used. After extraction of the mandibular second premolars and a surgical procedure, distraction devices were placed between the first and third premolars to distalize the first premolars. The animals were separated into three groups (Group 1, 0.25 mm; Group 2, 0.5 mm; Group 3, 1.0 mm per day) and retraction applied over 4 days.ResultsAmount of distal movement in the first premolars was 0.91 ± 0.03 mm, 1.75 ± 0.07 mm, and 3.41 ± 0.06 mm in Groups 1, 2, and 3, respectively. While extension of the periodontal ligament with slight bleeding was observed on the tension side in Group 1, rupture with spaces filled with blood clots was seen in the periodontal ligament in Groups 2 and 3.ConclusionThis suggests that the initial response of tension-side periodontal ligament differs according to tooth movement speed in PLDO.     

Relationship between dental crowding,skeletal base lengths,and dentofacial measurements

ObjectivesThe objectives of this study were to study the correlation between dental crowding, skeletal base lengths, and dentofacial measurements.Materials and methodsPretreatment dental casts and lateral cephalograms of randomly selected 45 Class I orthodontic cases divided into two groups according to the severity of mandibular crowding were evaluated. Group 1 comprised 15 patients with mandibular crowding less than 3 mm while group 2 comprised 30 patients with mandibular crowding of 3 mm or more. Maxillary and mandibular dental crowding and dentofacial measurements were compared between the two groups. For correlations the whole sample was combined to a single group where crowding was used as a continuous variable.ResultsThe only significant difference (p = 0.000) between the two groups was in the amount of dental crowding in the lower arch. Direct moderate correlation (r = 0.45; p = 0.002) between maxillary crowding and mandibular crowding, direct high correlation (r = 0.68; p = 0.000) between maxillary base length (Co-A) and mandibular base length (Co-Gn) and also direct high correlation (r = 0.74; p = 0.000) between maxillary base position (SNA angle) and mandibular base position (SNB angle) were detected. Correlation between maxillary incisor position and facial vertical dimension measured by the MP to SN angle showed inverse moderate correlation. Correlation between mandibular incisor position and the anteroposterior jaw relationship measured by the ANB angle showed direct moderate correlation.ConclusionsResults showed the presence of correlation between the skeletal dimensions and the absence of correlation between dental crowding and the same measurements. Results suggest that dental crowding is independent of the skeletal measurements.     

Strength of tunnel-restored teeth with different materials and marginal ridge height

ObjectiveThe aim of the study was to investigate the strength of the marginal ridge of tunnel preparations with different marginal ridge heights, using different restorative materials.Materials and methods120 sound premolars were randomly divided into three groups of standardized tunnel preparations with a remaining marginal ridge height of 1.5 mm, 2.5 mm and 3.5 mm, respectively. In each tunnel group, 10 teeth were filled with all four newly developed adhesive materials that had not previously been used in tunnel preparation: Ketac Aplicap, Fuji IX, Fuji II LC and Beautifil Flow F02. The control group comprised 10 sound teeth. All teeth were subjected to incremental dynamic force testing. Remaining marginal ridge height and restoration material were the independent variables. The mean maximum energy (MEI) score was the dependent variable. Data were analyzed, using one- and two-way analysis of variance. Scheffe's test and Student's t-test were used for comparison between groups.ResultsBoth restorative material (P < 0.0001) and remaining marginal ridge height (P < 0.0001) had a statistically significant effect on the mean MEI score of tunnel-prepared teeth. At the 2.5 mm of remaining marginal ridge height, no statistically significant difference in mean MEI score existed between Beautifil Flow F02-filled tunnel-prepared teeth and sound teeth.SignificancePremolars tunnel-restored with Beautifil Flow F02 at 2.5 mm distance from the marginal ridge were as strong as sound teeth.     

Comparison of craniofacial morphology,head posture and hyoid bone position with different breathing patterns

ObjectivesThe aim of this study was to evaluate differences in craniofacial morphology, head posture and hyoid bone position between mouth breathing (MB) and nasal breathing (NB) patients.MethodsMouth breathing patients comprised 34 skeletal Class I subjects with a mean age of 12.8 ± 1.5 years (range: 12.0–15.2 years). Thirty-two subjects with skeletal Class I relationship were included in the NB group (mean 13.5 ± 1.3 years; range: 12.2–14.8 years). Twenty-seven measurements (15 angular and 12 linear) were used for the craniofacial analysis. Additionally, 12 measurements were evaluated for head posture (eight measurements) and hyoid bone position (four measurements). Student’s t-test was used for the statistical analysis. Probability values <0.05 were accepted as significant.ResultsStatistical comparisons showed that sagittal measurements including SNA (p < 0.01), ANB (p < 0.01), A to N perp (p < 0.05), convexity (p < 0.05), IMPA (p < 0.05) and overbite (p < 0.05) measurements were found to be lower in MB patients compared to NB. Vertical measurements including SN-MP (p < 0.01) and PP-GoGn (p < 0.01), S-N (p <0.05) and anterior facial height (p < 0.05) were significantly higher in MB patients, while the odontoid proses and palatal plane angle (OPT-PP) was greater and true vertical line and palatal plane angle (Vert-PP) was smaller in MB patients compared to NB group (p < 0.05 for both). No statistically significant differences were found regarding the hyoid bone position between both groups.ConclusionsThe maxilla was more retrognathic in MB patients. Additionally, the palatal plane had a posterior rotation in MB patients. However, no significant differences were found in the hyoid bone position between MB and NB patients.     

Changes in condylar and joint disc positions after bilateral sagittal split ramus osteotomy for correction of mandibular prognathism

The effect of combined orthodontic and orthognathic treatment was studied retrospectively in 24 patients with skeletal class III malocclusions with mandibular hyperplasia, particularly the effect on temporomandibular joint (TMJ) disc position. The patients underwent preoperative orthodontic treatment, orthognathic surgery, and postoperative orthodontic treatment. The patients were studied clinically, radiographically with lateral cephalometric radiograph and MRI to locate the position of the TMJ disc in relation to the glenoid fossa. One patient had less pain after treatment, one lost abnormal joint clicking sounds after treatment. There were no TMJ symptoms in 20 of the 24 preoperatively and postoperatively. 48 sagittal MRI images showed that the disc length before treatment was 3.040–12.928 (mean 8.289 ± 2.028) and after treatment was 3.699–11.589 (mean 8.097 ± 1.966); results were not significant (p > 0.05). Maximum disc displacement before treatment was 6.090 (mean 1.383), after treatment it was 11.931 (mean 2.193); results were not significant (p > 0.05). The results suggest that combined orthodontic and orthognathic treatment (including bilateral SSRO and rigid internal fixation) can be used safely to correct skeletal class III malocclusion with mandibular hyperplasia without causing additional TMJ symptoms.     

The effect of antifungal agents on surface properties of poly(methyl methacrylate) and its relation to adherence of Candida albicans

PurposeCandida-associated denture stomatitis is the most prevalent form of oral candidosis affecting 65% of denture wearers. Failure of therapy and recurrence of infection are not uncommon and the continuous use of antifungal agents may affect the surface properties of the denture material and may contribute to Candida adhesion. This study aimed to investigate surface properties of poly(methyl methacrylate) PMMA denture material before and after exposure to antifungal agents and its relation to in vitro adhesion of Candida albicans.MethodsFour groups of acrylic specimens (20 mm × 20 mm × 2.5 mm) were prepared (25 specimens in each group). Specimens were immersed in nystatin (group 1), fluconazole (group 2), distilled water (group 3) and group 4 was not exposed. Specimens were tested for surface roughness, contact angle, surface hardness and in vitro Candida adherence to PMMA.ResultsThe results showed that nystatin had no statistically significant effect on surface hardness (P > 0.05), but had a statistically significant effect on surface roughness, contact angle, and Candida adhesion to PMMA (P < 0.05). On the other hand, fluconazole had no statistically significant effect on surface hardness or roughness (P > 0.05), but had a statistically significant effect on contact angle, and Candida adhesion to PMMA (P < 0.05). Distilled water had no statistically significant effect on surface hardness, roughness, contact angle, or Candida adhesion to PMMA (P > 0.05).ConclusionsExposure of PMMA to nystatin may induce changes in roughness, wettability while exposure to fluconazole may affect surface free energy and therefore may increase Candida adhesion to it.     

Short-term use of an exposed polypropylene barrier in the preservation of alveolar bone after extraction: randomized clinical trial

This study was performed to evaluate the short-term preservation of alveolar bone volume with or without a polypropylene barrier and exposure of the area after extractions. Thirty posterior tooth extraction sockets were distributed randomly to a control group (n = 15; extraction and suture) and a barrier group (n = 15; extraction, barrier, and suture). All sutures and barriers were removed 10 days postoperatively. Cone beam computed tomography scans taken with the aid of a tomographic guide were obtained preoperatively, immediately postoperative, and at 120 days postoperative. A visual analysis of the coronal sections of the alveolus was performed, and vertical loss in the mesial, distal, buccal, and lingual bone ridges and horizontal thickness were evaluated. The mean vertical loss after extraction did not differ significantly between the control and barrier groups (Student t-test: mesial P =  0.989, buccal P =  0.997, lingual/palatal P =  0.070, distal P =  0.107). The mean vertical loss at 120 days postoperative did not differ significantly between the control (0.65 mm) and barrier (0.52 mm) groups (P >  0.05), with an effect size of 0.13 mm. At 120 days, the barrier group presented a mean resorption in thickness (0.45 mm) that was significantly lower than that in the control group (0.76 mm) (P =  0.021), with an effect size of 0.31 mm. The polypropylene barrier reduced the horizontal resorption in sockets of posterior teeth after extraction.     

Efficacy of dexamethasone with controlled hypotension on intraoperative bleeding,postoperative oedema and ecchymosis in rhinoplasty

PurposeThe aim of this retrospective study was to evaluate the efficacy of dexamethasone with controlled hypotension on intraoperative bleeding and postoperative morbidity in rhinoplasty.Materials and methodsSixty rhinoplasty patients required hump resection and lateral osteotomy were included in this study. The patients were randomized into four groups. In group I (n = 15), a single dose of 10 mg/kg dexamethasone was intravenously administered at the beginning of the operation. In group II (n = 15), the patients were given 2 doses of 10 mg/kg intravenously dexamethasone at the beginning of the operation, and 24 hours after the operation. In group III (n = 15), 3 doses of 10 mg/kg intravenously dexamethasone were given at the beginning of the operation, before osteotomy and 24 hours after the operation. Group IV (n = 15) was assigned as control group and the patients were neither administered dexamethasone nor applied hypotension. All cases in groups I, II and III were operated under controlled hypotension. Systolic arterial pressure was aimed to keep between 65 and 75 mmHg for controlled hypotensive anaesthesia. Controlled hypotension was achieved by a remifentanil infusion of 0.1–0.5 microg/kg/min, following a bolus of 1 microg/kg. Degree of eyelid oedema and periorbital soft-tissue ecchymosis was evaluated separately using a scale of 0–4. Intraoperative blood loss was recorded for each patient. Patients were evaluated at 24 hours and postoperative days 2, 5, 7, and 10.ResultsIn groups I, II and III, intraoperative bleeding was more decreased and the operation time was significantly shorter compared with control group (P < 0.001). Eyelid oedema and periorbital ecchymosis were significantly decreased in groups I, II and III at the following postoperative 7 and 10 days (P < 0.001). There was statistically significant difference between group III and other groups at the postoperative 5 and 7 days in lower eyelid oedema (P < 0.001), upper and lower eyelid ecchymosis (P < 0.001 and 0.004, respectively). There were no postoperative complications with using steroid in any of the groups.ConclusionThree doses of dexamethasone with controlled hypotension considerably reduced postoperative morbidities of rhinoplasty with osteotomy as well as intraoperative bleeding. Thus, in group III receiving 3 doses of steroid, when compared to other groups, more uneventful postoperative period were provided for surgeon and the patients.     

Effect of chlorhexidine application on long-term shear bond strength of resin cements to dentin

PurposeThe purpose of this study was to investigate the effect of chlorhexidine [CH] on dentin bond strength of three resin cements after 1 year of water storage.MethodsA flat middle dentin surface was prepared on 120 extracted premolars. The teeth were randomly divided into 6 groups of 20 specimens each according to the resin cement used: Panavia F2.0, Variolink II, and RelyX Unicem, with or without CH application. After cementation of an indirect composite rod [Z250], one subgroup [n = 10] was tested after 24 h in water at 37 °C and the other subgroup [n = 10] was tested after 1 year storage in water plus thermocycling. A shear bond strength [SBS] test was performed. The data [in MPa] were analyzed with ANOVA and Tukey tests [P < 0.05].ResultsThree-way ANOVA [resin cement, CH and time] indicated that Variolink II had the highest strength [16.65 ± 3.60] and RelyX Unicem had the lowest strength [9.30 ± 4.07]. Chlorhexidine application increased SBS [13.31 ± 4.61] compared to samples without CH [12.16 ± 5.04] [P = 0.04]. Initial SBS [15.63 ± 4.37] was significantly higher than after 1 year of storage [9.85 ± 3.36] [P < 0.001]. Separate two-way ANOVA for 24-h and 1-year data showed that cement had a significant effect but CH and its interaction had no significant effect at 24 h, whereas at 1 year the two factors and their interaction differed significantly [P ≤ 0.001].ConclusionsChlorhexidine 2% can diminish the loss of bonding effectiveness over time associated to etch-and-rinse and self-etch cements, although it appears not have any effect on self-adhesive cement.     

Effects of layering techniques on the micro-tensile bond strength to dentin in resin composite restorations

ObjectivesThe purpose of this work was to investigate the effects of layering techniques in resin composite restorations on the micro-tensile bond strength to the dentin of the occlusal cavity.MethodsHuman premolars were extracted and randomly divided into four groups. The occlusal enamel was then removed to expose a flat superficial dentin surface. Cavities 3.5 mm long and 3.5 mm wide were prepared to a depth 3 mm below the dentin surface. The adhesive Single Bond was applied according to the manufacturer's instructions. The teeth were then restored with Z100 resin composite as follows: Group 1 was restored in horizontal increments (three layers). Groups 2 and 3 were restored in different oblique increments (three layers). Group 4 was restored in oblique increments (four layers). After 24 h storage at 37 °C in water, all the teeth were sectioned to obtain bar-shaped specimens with a bonded surface area of approximately 0.9 mm × 0.9 mm. Dentin micro-tensile bond strength was measured at a crosshead speed of 0.5 mm/min. The results obtained were statistically analyzed using one-way ANOVA and SNK test at a significance level of P = 0.05. All fractures were then observed under a scanning electron microscope (SEM).ResultsThe results showed that there is a significant difference between the strength of the micro-tensile bonds to the dentin of occlusal cavities depending on which of the four layering restorative techniques was used (P < 0.01). SEM observation showed that failure patterns were most evidently interfacial cohesive failure.SignificanceLayering techniques in resin composite restorations affected the micro-tensile bond strength between the resin composite and the dentin. But the outcomes related to only Single Bond, as the same using other adhesives might have different outcomes.     

Long-term results of bilateral mandibular distraction osteogenesis using an intraoral tooth-borne device in adult Class II patients

The aim of this prospective clinical study was to evaluate the short-term and long-term skeletal and dental changes after mandibular osteodistraction with tooth-borne appliances in adult orthodontic patients. The sample consisted of 10 non-growing Caucasian patients with a Class II skeletal relationship due to mandibular deficiency, together with Class II dental malocclusion. All patients underwent mandibular distraction osteogenesis (MDO) using the ROD1 tooth-borne device. Lateral cephalograms were evaluated at four time intervals: pretreatment (T1), after mandibular distraction (T2), after orthodontic fixed appliance therapy (T3), and at long-term observation 8-year post-distraction (T4). Statistical analyses compared the skeletal and dental changes in intervals T1–T2, T2–T3, T3–T4, T1–T4, and T2–T4. MDO with the ROD1 tooth-borne device produced significant long-term (T1–T4) increases in the SNB angle (2.3°), total mandibular length (5.9 mm), and corpus length (4.5 mm). Potential adverse sequelae included significant increases in mandibular plane angle (4.3°), lower anterior dental height (2.8 mm), and lower posterior dental height (2.5 mm). Significant increases in lower incisor proclination occurred during distraction (7.5°). Distraction osteogenesis with tooth-borne appliances offers a minimally invasive surgical method with stable results for correcting mandibular deficiency in non-growing patients.     

The effect of mandibular setback or two-jaws surgery on pharyngeal airway among different genders

Cephalometric studies show significant gender differences in the size of the pharyngeal airway space. This study aimed to investigate and compare morphologic changes after mandibular setback or two-jaws surgery on the pharyngeal airway in men and women using computed tomography (CT). The sample included 34 women and 13 men diagnosed with Class III skeletal deformities, who had been treated by mandibular setback or bimaxillary surgery (maxillary advancement and mandibular setback). Anteroposterior, lateral and cross-sectional area dimensions of the airway, at the level of soft palate and base of tongue, were measured pre- and postoperatively on CT images. In the mandibular setback group, the anteroposterior and cross-sectional area of the pharyngeal airway at the level of the soft palate and base of tongue were significantly reduced for men or women (P < .05). In the two-jaws surgery group, only midsagittal anteroposterior dimensions at the same levels were significantly decreased for men or women (P < .05). The difference between any values measured between men and women who received bilateral sagittal split ramus osteotomy setback surgery or two-jaws surgery for the treatment of class III anteroposterior discrepancy were not statistically significant (P > .05). This study suggests that oropharyngeal airway measurements, important for airway patency, do not demonstrate sex dimorphism.     

Measurement of root surface area of permanent teeth with root variations in a Chinese population—A micro-CT analysis

ObjectivesThis study investigated the influence of root variations on the root surface area (RSA) by using micro-CT scans.DesignA total of 228 extracted permanent teeth (2-rooted and single-rooted maxillary first premolars, mandibular first premolars with non-Tomes’ and Tomes’ roots, 2-rooted and 3-rooted mandibular first molars, and 2-rooted and C-shaped mandibular second molars) were collected in a Chinese population and scanned using a micro-CT. In Mimics 15.01, 3D tooth models were generated, and the net and percent remaining RSA at various simulated attachment levels were measured. The data corresponding to attachment level were fitted to a linear function.ResultsThe mean total RSA for different root forms decreased in the following order: 3-rooted > 2-rooted > C-shaped > single-rooted. However, the differences were statistically significant (p < 0.01) only for 2-rooted vs. single-rooted maxillary first premolars, and 2-rooted vs. C-shaped mandibular second molars. Linear functions can perfectly fit in relating the attachment level to the net and percent remaining RSA.ConclusionMicro-CT combined with Mimics software offers simple and precise technique for quantitative analysis of the RSA. Root variations may affect the total amount and vertical distribution of the net RSA. However, the degree of influence varies with the tooth type.