Mohamed Bayome

Palatal bone thickness compared with cone-beam computed tomography in adolescents and adults for mini-implant placement

INTRODUCTION The purpose of this study was to compare the bone thickness of the palatal areas in early and late mixed and early permanent dentitions according to dental age. METHODS Cone-beam computed tomography scans of 118 subjects were selected and divided into 38 early mixed (8.03 ± 0.93 years), 40 late mixed (11.51 ± 0.92 years), and 40 permanent (20.92 ± 1.17 years) dentition subjects. The measurements of palatal bone thickness were made at 49 sites by using InVivoDental5.0 software (Anatomage, San Jose, Calif). Repeated measures analysis of variance was used to analyze intragroup and intergroup differences as well as sex dimorphism. RESULTS There was significantly lower bone thickness in the early mixed dentition group than in the 2 other groups (P <0.001). Bone thickness was higher in the anterior region than in the middle and posterior regions (P <0.001). Also, significant differences were found among the midline, medial, and lateral areas of the palate. CONCLUSIONS Palatal bone thicknesses were significantly lower in the early mixed dentition group than in both the late mixed and permanent dentition groups. These findings might be helpful for clinicians to enhance the successful use of temporary anchorage devices in the palate.

Effect of frequent laser irradiation on orthodontic pain. A single-blind randomized clinical trial.

OBJECTIVE To analyze the effect of low-level laser therapy (LLLT) on perception of pain after separator placement and compare it with perceptions of control and placebo groups using a frequent irradiation protocol. MATERIALS AND METHODS Eighty-eight patients were randomly allocated to a laser group, a light-emitting diode (LED) placebo group, or a control group. Elastomeric separators were placed on the first molars. In the laser and LED groups, first molars were irradiated for 30 seconds every 12 hours for 1 week using a portable device. Pain was marked on a visual analog scale at predetermined intervals. Repeated measure analysis of variance was performed for statistical analysis. RESULTS The pain scores of the laser group were significantly lower than those of the control group up to 1 day. The pain scores in the LED group were not significantly different from those of the laser group during the first 6 hours. After that point, the pain scores of the LED group were not significantly different from those of the control. CONCLUSIONS Frequent LLLT decreased the perception of pain to a nonsignificant level throughout the week after separator placement, compared with pain perception in the placebo and control groups. Therefore, LLLT might be an effective method of reducing orthodontic pain.

Stress distribution and displacement by different bone-borne palatal expanders with micro-implants: a three-dimensional finite-element analysis.

The aim of this study was to analyze stress distribution and displacement of the maxilla and teeth according to different designs of bone-borne palatal expanders using micro-implants. A three-dimensional (3D) finite-element (FE) model of the craniofacial bones and maxillary teeth was obtained. Four designs of rapid maxillary expanders: one with micro-implants placed lateral to mid-palatal suture (type 1), the second at the palatal slope (type 2), the third as in type 1 with additional conventional Hyrax arms (type 3), and the fourth surgically assisted tooth-borne expander (type 4) were added to the FE models. Expanders were activated transversely for 0.25mm. Geometric nonlinear theory was applied to evaluate Von-Mises Stress distribution and displacement. All types exhibited downward displacement and demonstrated more horizontal movement in the posterior area. Type 3 showed the most transverse displacement. The rotational movement of dentoalveolar unit was larger in types 1 and 3, whereas it was relatively parallel in types 2 and 4. The stresses were concentrated around the micro-implants in types 1 and 3 only. Type 2 had the least stress concentrations around the anchorage and showed alveolar expansion without buccal inclination. It is recommended to apply temporary anchorage devices to the palatal slopes to support expanders for efficient treatment of maxillary transverse deficiency.

Evaluation of palatal bone density in adults and adolescents for application of skeletal anchorage devices

OBJECTIVES To measure the cortical and cancellous bone densities of the palatal area in adolescents and adults and to compare bone quality among placement sites of temporary anchorage devices. MATERIALS AND METHODS One hundred twenty cone beam computerized tomography scans were obtained from 60 adolescents (mean age, 12.2 ± 1.9 years) and 60 adults (24.7 ± 4.9 years). The measurements of palatal bone density were made in Hounsfield units (HU) at 72 sites at the intersections of eight mediolateral and nine anterioposterior reference lines using InVivoDental software. Repeated-measures analysis of variance was used to analyze intragroup and intergroup differences. RESULTS The cortical and cancellous bone densities in the adults (816 and 154 HU, respectively) were significantly higher than those in the adolescents (606 and 135 HU; P < .001 and P  =  .032, respectively). However, the anterior portion of the cortical bone in adolescents had similar density values to the posterior portion of the cortical bone in adults. Gender comparison revealed that females had greater cortical bone densities (769 HU) than their male counterparts did (654 HU; P < .001). CONCLUSIONS Palatal bone densities were significantly higher in adults than in adolescents, and the anterior palatal areas of adolescents were of similar values to those at the posterior palate of adults.

New three-dimensional cephalometric analyses among adults with a skeletal Class I pattern and normal occlusion

Objective The purpose of this study was to assess new three-dimensional (3D) cephalometric variables, and to evaluate the relationships among skeletal and dentoalveolar variables through 3D cephalometric analysis. Methods Cone-beam computed tomography (CBCT) scans were acquired from 38 young adults (18 men and 20 women; 22.6 ± 3.2 years) with normal occlusion. Thirty-five landmarks were digitized on the 3D-rendered views. Several measurements were obtained for selected landmarks. Correlations among different variables were calculated by means of Pearsons correlation coefficient values. Results The body of the mandible had a longer curve length in men (102.3 ± 4.4 mm) than in women (94.5 ± 4.7 mm) (p < 0.001), but there was no significant difference in the maxillary basal curve length. Men had significantly larger facial dimensions, whereas women had a larger gonial angle (117.0 ± 4.0 vs. 113.8 ± 3.3; p < 0.001). Strong-to-moderate correlation values were found among the vertical and transverse variables (r = 0.71 to 0.51). Conclusions The normative values of new 3D cephalometric parameters, including the maxillary and mandibular curve length, were obtained. Strong-to-moderate correlation values were found among several vertical and transverse variables through 3D cephalometric analysis. This method of cephalometric analyses can be useful in diagnosis and treatment planning for patients with dentofacial deformities.

Mandibular dimensions of subjects with asymmetric skeletal Class III malocclusion and normal occlusion compared with cone-beam computed tomography

INTRODUCTION The purpose of this study was to use cone-beam computed tomography to compare mandibular dimensions in subjects with asymmetric skeletal Class III malocclusion and those with normal occlusion. METHODS Cone-beam computed tomography scans of 38 subjects with normal occlusion and 28 patients with facial asymmetry were evaluated and digitized with Invivo software (Anatomage, San Jose, Calif). Three midsagittal and 13 right and left measurements were taken. The paired t test was used to compare the right and left sides in each group. The Mann-Whitney U test was used to compare the midsagittal variables and the differences between the 2 sides of the group with normal occlusion with those of asymmetry patients. RESULTS The posterior part of the mandibular body showed significant differences between the deviated and nondeviated sides in asymmetric Class III patients. The difference of the asymmetry group was significantly greater than that of the normal occlusion group for the mediolateral ramal and the anteroposterior condylar inclinations (P = 0.007 and P = 0.019, respectively). CONCLUSIONS The asymmetric skeletal Class III group showed significant differences in condylar height, ramus height, and posterior part of the mandibular body compared with the subjects with normal occlusion. These results might be useful for diagnosis and treatment planning of asymmetric Class III patients.

Treatment effects of a modified palatal anchorage plate for distalization evaluated with cone-beam computed tomography.

INTRODUCTION The purpose of this study was to evaluate the treatment effects of maxillary posterior tooth distalization performed by a modified palatal anchorage plate appliance with cephalograms derived from cone-beam computed tomography. METHODS The sample consisted of 40 lateral cephalograms obtained from the cone-beam computed tomography images of 20 Class II patients (7 men, 13 women; average age, 22.9 years) who underwent bilateral distalization of their maxillary dentition. The lateral cephalograms were derived from the cone-beam computed tomography images taken immediately before placement of a modified palatal anchorage plate appliance and at the end of distalization. Paired t tests were used for comparisons of the changes. RESULTS The distal movement of the maxillary first molar was 3.3 ± 1.8 mm, with distal tipping of 3.4° ± 5.8° and intrusion of 1.8 ± 1.4 mm. Moreover, the maxillary incisors moved 3.0 ± 2.7 mm lingually, with lingual tipping of 6.2° ± 7.6° and insignificant extrusion (1.1 mm; P = 0.06). The occlusal plane angle was increased significantly (P = 0.0001). CONCLUSIONS The maxillary first molar was distalized by 3.3 mm at the crown and 2.2 mm at root levels, with distal tipping of 3.4°. It is recommended that clinicians should consider using the modified palatal anchorage plate appliance in treatment planning for patients who require maxillary total arch distalization.

Effect of bone-borne rapid maxillary expanders with and without surgical assistance on the craniofacial structures using finite element analysis.

INTRODUCTION The aim of this study was to analyze stress distribution and displacement of the craniofacial structures resulting from bone-borne rapid maxillary expanders with and without surgical assistance using finite element analysis. METHODS Five designs of rapid maxillary expanders were made: a tooth-borne hyrax expander (type A); a bone-borne expander (type B); and 3 bone-borne surgically assisted modalities: separation of the midpalatal suture (type C), added separation of the pterygomaxillary sutures (type D), and added LeFort I corticotomy (type E). The geometric nonlinear theory was applied to evaluate the Von Mises stress distribution and displacement. RESULTS The surgical types C, D, and E demonstrated more transverse movement than did the nonsurgical types A and B. The amounts of expansion were greater in the posterior teeth in types A and B, but in types C, D, and E, the amounts of expansion were greater in the anterior teeth. At the midpalatal suture, the nonsurgical types showed more anterior expansion than did the posterior region, and higher stresses than with the surgical types. Type B showed the highest stresses at the infraorbital margin, anterior and posterior nasal spines, maxillary tuberosity, and pterygoid plate and hamulus. CONCLUSIONS The 3 surgical models showed similar amounts of stress and displacement along the teeth, midpalatal sutures, and craniofacial sutures. Therefore, when using a bone-borne rapid maxillary expander in an adult, it is recommended to assist it with midpalatal suture separation, which requires minimal surgical intervention.

Displacement and stress distribution of the maxillofacial complex during maxillary protraction with buccal versus palatal plates: finite element analysis

OBJECTIVES The aim of this study was to analyse the displacement and stress distribution in the maxillofacial complex during maxillary protraction with buccal and palatal plates using three-dimensional finite element analysis. MATERIALS AND METHODS Three anchorage appliance models-palatal plate (Type A), miniplate at the infrazygomatic crest (Type B), and conventional tooth-borne appliance (Type C)-were designed and integrated into a skull model. Protraction force was 500 g per side and force direction was forward and 30 degree downward to the maxillary occlusal plane. The stress distribution around the circum-maxillary sutures and the displacement of the surface landmarks were analysed. RESULTS All models showed forward and upward displacement at anterior nasal spine, Point A, and prosthion and forward and downward displacement at posterior nasal spine resulting in a counter-clockwise rotation. This anterior displacement was greatest in Type A. At the maxillary process of the zygoma, upward movement was shown only in Type A, whereas downward movement was observed in Types B and C. The greatest stresses in Type A were at the pterygomaxillary and the zygomaticotemporal sutures. Type B showed the greatest stress at the frontomaxillary suture. LIMITATIONS Type A showed asymmetric results; however, it was not of clinical significance. CONCLUSION The palatal plate resulted in wider stress distribution and more forward displacement compared to miniplate at the infrazygomatic crest area and conventional tooth-borne appliances. It might be recommended to consider the application of the palatal plate for maxillary protraction in Class III patients.

Evaluation of minimal versus conventional presurgical orthodontics in skeletal class III patients treated with two-jaw surgery.

PURPOSE The purpose of this study was to compare changes in hard and soft tissues and the treatment efficacy of 2-jaw surgery combined with nonextraction treatment for skeletal Class III malocclusion in patients who received minimal presurgical orthodontics (MPO) versus those who received conventional presurgical orthodontics (CPO). MATERIALS AND METHODS Thirty-two patients (16 in each group) with skeletal Class III malocclusion who underwent 2-jaw surgery were included in the study. Serial lateral cephalometric films were traced at 4 stages: before treatment (T0), before surgery (T1), 1 month after surgery (T2), and at debonding (T3). Cephalometric measurements and treatment duration were compared using independent t test and Mann-Whitney U test. RESULTS After the presurgical treatment phase, the angle between the lower incisor axis and mandibular plane, overjet, and soft tissue pogonion to the vertical reference line showed larger changes (P < 0.01) in the CPO group, whereas the pogonion to the horizontal reference line showed larger changes (P < .05) in the MPO group. In the postsurgical phase (T2 to T3), there were no significant differences between the 2 groups. Total treatment duration was significantly shorter in the MPO group. CONCLUSIONS There were no significant differences between the MPO and CPO groups in the hard and soft tissue cephalometric variables. The MPO group had a shorter total treatment time. It is therefore recommended that clinicians consider these results when selecting MPO as a treatment option for accurate diagnosis and treatment planning of Class III surgical patients.