Lingual Side Research Articles

Orthodontic Treatment and Central Incisors: a Study by CBCT Analysis

To determine potential risks and critical orthodontic movements of central incisors. CBCT analysis of 66 patients (aged 12-38 years; 30 adolescents and 36 adults; 33 males and 33 females). We evaluated alveolar bones (crests, plates, ridges) surrounding central incisors from buccal and lingual sides, and at multiple levels using the "Ez3D-plus" program with regard to buccolingual inclination and effective length of premaxilla/length of the mental protuberance. We identified: - Potential risks in the maxilla, in case of 1) Proclined central incisors, on the first buccal coronal third and lingual side of alveolar bone. 2) ELP < 13 mm, with buccal movement. - Potential risks in mandible, in case of 1) Retroclined central incisors, on the first lingual coronal third and buccal apical two-thirds of alveolar bone. 2) LMP > 9 mm. - Critical orthodontic movements: 1) Buccal tipping of mandibular central incisors is more critical in adolescents. 2) Lingual tipping of mandibular central incisors is more critical than of maxillary ones in all groups, at the level of the alveolar crest. In adult males, at the first lingual coronal third of the alveolar plate. In adult females, at the buccal apical level. 3) Movement towards cortical bone: In all groups, buccal movements of maxillary central incisors are more critical than of mandibular ones, and lingual movements of mandibular central incisors are more critical than of maxillary ones, especially in adult males. We recommend an accurate diagnosis of incisors position and alveolar bone status, and planning of orthodontic treatment at an earlier age.

Three-dimensional ultrasound imaging of the jawbone for ridge width determination: A pre-clinical ex-vivo porcine study

ObjectiveTwo-dimensional (2D) ultrasound can conveniently evaluate focal regions of interest intraorally. When a larger field of view to spatially reference remote anatomical structures is needed, 3D ultrasound (US) is desirable but not currently available. The aim of this study was to demonstrate the feasibility of constructing 3D US jawbone for ridge width determination. MethodsSeven porcine hemi-mandibles with the overlying soft tissues secured by a holding frame with fiducial markers were US scanned on the facial and lingual sides separately. The facial and lingual volumes were combined into a single volume, which was registered with the matched cone beam computed tomography (CBCT) scan. On 8 to 11 cross-sections, 4 measurements of the facio-lingual ridge width at 3, 6, 9 and 12 mm from the bone crest were performed by two calibrated examiners. A mixed model was used to estimate the differences between US and CBCT readings. ResultsInter-examiner correlation was 0.978 and 0.987 for US and CBCT measurements, respectively. The ICCs between the US and CBCT was between 0.890 and 0.988 at the defined sites. The estimated mean differences ranged from -0.38 ± 0.69 (95% CI: -0.66 to -0.11) mm to 0.07 ± 0.93 (95% CI: -0.23 to 0.38) mm. The normalized root mean square deviation ranged between 4.50% and 7.89% for all levels except the 3 mm level, which ranged between 5.51% (in molars) and 11.16% (in premolars). ConclusionsThis study demonstrates the feasibility of generating US jawbone in 3D for ridge width measurements. Clinical SignificanceCommonly applied 2D ultrasound images are limited by a small field of view and an unknown coordinate system due to the nature of free hand scans. Novel 3D ultrasound acquisition enables referencing anatomical structures in a larger field of view and could become a promising tool to supplement CBCT.

Biomechanical features of tooth movement from a lingual appliance in comparison with a labial appliance during space closure in sliding mechanics

The objectives of this study were to simulate long-term orthodontic tooth movement in en-masse retraction using the finite element method and investigate the effects of power arms on tooth movements when using a lingual appliance in comparison with a labial appliance. A 3-dimensional finite element model of the maxillary dentition was constructed with 0.018-in brackets and 0.016 × 0.022-in stainless steel archwire. An en-masse retraction was performed by applying retraction force at various lengths of the power arm (4, 6, 8, and 10 mm) to the second molar tube, and long-term tooth movements with the lingual and labial appliances were analyzed using the finite element method. Although lingual crown tipping of the incisor was more marked with the lingual appliance than with the labial appliance in the early phase of space closure, only a slight difference was evident after space closure. Although the power arm was effective for achieving better-controlled tooth movement and reducing vertical and transverse bowing effects, bodily movement of the incisor could not be achieved, and bowing effects could not be eliminated. To provide better torque control of the incisor or prevent a vertical bowing effect, the incorporation of extra torque into brackets of incisors was recommended, and the use of power arms for the lingual appliance. To prevent a transverse bowing effect, incorporation of the antibowing bend or application of retraction force from both buccal and lingual sides or temporary skeletal anchorage devices was recommended.

TOPOGRAPHY-ANATOMICAL VARIABILITY OF THE MYLO-HYOID NERVE IN THE SIDE OF THE LOWER JAW

The article is devoted to the study of individual- anatomical features of the location of the mylohyoid groove, where the mylohyoid nerve lies, in the lateral part of the lower jaws of people with diff erent face shapes. For this purpose, craniometric studies were performed on 32 natural human skulls from the anatomical museum fund and on 60 CT images of patients’ skulls in 3-D reconstruction. The types of structure of the facial department of the skull were determined. The location features of the mylohyoid groove were determined in them on the lateral parts of the lower jaws, and bone holes were searched on their lingual side. Craniometric studies have shown that at the level of the dental alveoli of the second and third molars of the mylohyoid groove is located 20.7±0.4 mm below the upper edge of the lower jaw on mesoprosopic skulls. In leptoprosopic skulls this distance was greater – 23.6±0.8 mm, and in hameprozops, respectively, less – 18.3±0.6 mm. Bone holes on the inner (lingual) surface of the lateral parts of the lower jaws were found in 20 skulls (21.7%). Their number varied from one to three. They were most often found on skulls with a leptoprosopic form of the facial skeleton – in 11 cases. Samples of the lower jaws predominated (13 cases) in which one hole was observed at the level of the top of the roots of the fi rst lower molars.

Biomechanical analysis of inclined and cantilever design with different implant framework materials in mandibular complete-arch implant restorations

Statement of problemInclined distal implants with posterior framework cantilevers are an alternative to straight implants for the treatment of edentulous jaws, avoiding grafting procedures and utilizing pre-existing bone. However, little is known about the implant, framework, and peri-implant bone stresses exerted by this design. PurposeThe purpose of this finite element analysis study was to assess the biomechanical properties of the inclined versus straight design, with different implant framework material to generate implant-supported complete-arch fixed mandibular prostheses. Material and methodsA finite element model of the edentulous mandible was generated by using 4 implants in 2 distinct configurations: the inclined design and the straight design. Different framework materials were tested: pure titanium, cobalt-chromium alloy, type IV gold alloy, zirconia, polyetheretherketone (PEEK), and carbon fiber–reinforced polyetheretherketone (CFR-PEEK). A 300-N load at a 75-degree angle was applied to the occlusal plane from the lingual side of the buccal cusps of the 2 premolars and the first molar teeth. Subsequently, stresses on the implant, surrounding bone, and framework were measured and analyzed quantitatively and qualitatively. ResultsIn terms of implant configurations, the inclined design demonstrated less stress on the posterior cortical bone, implants, and framework than the straight design. Comparing the framework materials, zirconia and metal exhibited reduced cortical bone and implants stresses but elevated framework stress when compared with the polymeric frameworks. ConclusionsFrom a biomechanical viewpoint, in edentulous patients with excessive posterior alveolar bone resorption, the inclined design exhibited more favorable stress distribution around the posterior implants than the straight design. In implant-supported complete-arch fixed mandibular prostheses, zirconia and metal, particularly cobalt-chromium alloy, distributed the stresses more effectively to the implants and supporting bone than polymeric materials.

Micro-Osteoperforations Induce TNF-α Expression and Accelerate Orthodontic Tooth Movement via TNF-α-Responsive Stromal Cells.

Micro-osteoperforations (MOPs) have been reported to accelerate orthodontic tooth movement (OTM), and tumor necrosis factor (TNF)-α has been reported to play a crucial role in OTM. In this report, the influence of MOPs during OTM was analyzed. We evaluated the expression of TNF-α with and without MOPs by RT-PCR analysis. A Ni-Ti closed coil spring was fixed between the maxillary left first molar and the incisors as an OTM mouse model to move the first molar in the mesial direction. MOPs were prepared on the lingual side and mesial side of the upper first molars. Furthermore, to investigate the target cell of TNF-α for osteoclast formation during OTM with MOPs in vivo, we created four types of chimeric mice in which bone marrow of wild-type (WT) or TNF receptor 1- and 2-deficient mice (KO) was transplanted into lethally irradiated WT or KO mice. The results showed that MOPs increased TNF-α expression, the distance of tooth movement and osteoclast formation significantly. Furthermore, mice with TNF-α-responsive stromal cells showed a significant increase in tooth movement and number of osteoclasts by MOPs. We conclude that MOPs increase TNF-α expression, and tooth movement is dependent on TNF-α-responsive stromal cells.

Microbial Diversity and Community Analysis of Dental Plaques in Orthodontic Patients Wearing Invisible Appliances and Fixed Appliances

To explore the microbial diversity and community structure of dental plaques in orthodontic patients with invisible appliances and fixed appliances and to study the differences. Ten orthodontic patients wearing invisible appliances (I) and ten wearing fixed appliances (F) were recruited. Dental plaques were collected from both buccal (B) and lingual (L) sides. Based on 16S rDNA, 40 dental plaque samples were analyzed after Illumina sequencing. The microbial diversity, abundance and evenness of the FB group were significantly higher than those of the IB and IL groups (P<0.05), while the FL group showed substantial individual differences. The community structures were generally similar among the four groups, but significant differences in the relative abundance of some bacteria were found. The IB group showed higher abundances of Actinomycetes and Rosella (P<0.05), which were considered to be involved in dental caries and periodontal diseases. Some key communities showing significant differences were significantly enriched in the FB group, including Coprobacillus, Bifidobacterium, Enterobacterium, Lactobacillus, etc.. Dental plaques in patients wearing invisible appliances and fixed appliances showed significantly different microbial abundance, diversity and composition, which may be involved in orthodontic complications such as dental caries and periodontal diseases. Orthodontic patients need strengthened measures for oral hygiene maintenance, no matter what kind of appliances they wear.

Relationship between alveolar-bone morphology at the mandibular incisors and their inclination in adults with low-angle, skeletal class III malocclusion—A retrospective CBCT study

ObjectiveTo quantitatively study the effect of the labial inclination of the mandibular central incisors on the surrounding cortical and cancellous-bone morphology among patients with low-angle, skeletal class III malocclusion, by using cone-beam computed-tomography (CBCT) imaging.Materials and methodsThe CBCT images of 60 patients with low-angle, skeletal class III malocclusion were divided into lingual-inclination, upright, and labial-inclination groups. The height of the alveolar bone and the thickness and area of the cortical, cancellous, and total alveolar bone were measured separately on each side of the mandibular central incisors.ResultsThe thickness of the labial cortical bone from 6 mm below the cementoenamel junction (CEJ) to the root apex; the thickness of the labial cancellous bone at the root apex; the total thickness of the alveolar bone at the root apex; the area of labial cortical bone; the total area of labial alveolar bone; and the height of the labial alveolar bone were highest in the labial-inclination group (all P<0.05). All these variables were positively correlated with the labial inclination of the mandibular central incisors (all P<0.05). There were no statistical differences between the groups for any of the measurements on the lingual side of the teeth (P>0.05).ConclusionThe morphology of the alveolar bone on the labial but not the lingual side of the mandibular central incisors was statistically significantly correlated with the labial inclination of those teeth in patients with low-angle, skeletal class III malocclusion.

Patient-customized Site Specific Crown Lengthening

Short clinical crowns result in poor retention form and thereby leads to improper tooth preparation and ultimately failure of restoration. The purpose of this case report was performing patient customized site specific surgical crown lengthening of grossly decayed tooth structure in left mandibular 2nd premolar area. The tooth was root canal treated with width of keratinized gingiva about 2mm on buccal side, with fibrotic gingival enlargement on interdental area and lingually. Apically displaced flap on buccal side with osseous resection of 3mm and undisplaced flap on interdental and lingual side with osseous resection of 3mm was done. Optimal clinical crown length was achieved and was maintained at 3months and 6 months follow up.

Biomechanical Stress Analysis of Platform Switch Implants of Varying Diameters on Different Densities of Bone.

Purpose The purpose of this study was to evaluate and compare the strain developed in D2 and D3 types of bones on vertical loading by platform switch implants of different diameters. Materials and Methods Implants of diameters 3.25 mm, 4.2 mm, and 5.0 mm and of length 11.5 mm were taken and placed each on D2 and D3 bone models. Strain gauges were attached on the buccal and the lingual sides on each of these samples, and a vertical load of 190N was placed on the samples. The strain was recorded using a data logger. The data obtained was analysed using one-way ANOVA and post hoc Tukey test. Results In D2 and D3 bone models, 3.25 mm significantly showed greater bone strain values. The buccal side strain was higher irrespective of the implant diameter and density of bone. Conclusion Within the limitations of the study, it may be concluded that the narrow diameter implant produces greater strain than 4.2 and 5.0 mm diameter implants, respectively. The buccal side consistently produced higher bone strain values.

Effect of 125–150 Hz Vibrational Frequency Electric Toothbrush on Teeth and Supporting Structures: A Finite Element Method Study

The aim of this finite element method (FEM) study was to assess the safety of 125-150 Hz vibrational frequency electric toothbrush on teeth and associated structures. A three-dimensional (3D) geometric model of entire skull having maxilla, mandible, and their dentitions was created using a computed tomography (CT) image of a healthy male patient. Linear static analysis was carried out by applying 15 g of force on anterior part of maxilla and mandible from labial and lingual sides each to calculate the primary displacement (sagittal, vertical, and transversal) and principal stress levels generated on the maxillary and mandibular dentition, on the maxilla and mandible and on the whole skull. A force of 15 g applied to maxillary anterior teeth from labial side caused a mean deflection of 0.003 mm and stress of 0.004 MPa on the teeth and supporting structures. A force of 15 g applied to maxillary anterior teeth from palatal side caused a mean deflection of 0.017 mm and stress of 0.017 MPa on the teeth and supporting structures. A force of 15 g applied to mandibular anterior teeth from labial side caused a mean deflection of 0.078 mm and stress of 0.051 MPa on the teeth and supporting structures. A force of 15 g applied to mandibular anterior teeth from lingual side caused a mean deflection of 0.077 mm and stress of 0.051 MPa on the teeth and supporting structures. For the applied loads and boundary conditions, very small or negligible amount of stresses were observed in maxilla, mandible, and their dentitions. The vibrational frequency of 150 Hz producing 15 g of force did not produce any harmful effects on maxilla, mandible, and their dentitions. Hence, 125-150 Hz of vibrational frequency can be considered optimum. An electric toothbrush using the vibration of 125-150 Hz produces negligible stress on teeth and associated structures.

Cortical bone thickness and density: inter-relationship at different orthodontic implant positions

ABSTRACT Objective This study was conducted to assess the relationship between cortical bone density and thickness at numerous orthodontic implant positions in the maxilla and mandible. Materials and methods Fifty computed tomography scans were examined in this study. The sample size consisted of 25 males and 25 females. Blue Sky Plan® software was used to measure buccal, palatal and lingual bone density and thickness at four proposed orthodontic implant levels in maxilla and mandible. Pearson correlation coefficient was used to evaluate relationships between bone thickness and density (p < 0.05). Results In the maxilla, a significant negative correlation was detected between buccal cortical bone density and thickness in the distal site of first premolar at 2 and 6 mm and second premolar at 6 mm from cemento-enamel junction. In palatal side, significant positive correlation was recorded at the mesial site of central incisor and the distal site of second premolar at 2 mm. In the mandibular buccal bone, significant positive correlations were recorded in 4, 6 and 8 mm at the distal site of first premolar, second premolar and first molar. Whereas, in lingual bone, significant positive correlations were found in all inter-radicular areas’ posterior to first premolars except at 4 mm in the distal site of first molar. Conclusion From this study, we found that there is a significant correlation between quantity and quality of cortical bone in specific inter-radicular areas of the buccal, palatal and lingual sides of maxilla and mandible. This inter-relationship could be helpful in determining orthodontic implant position.

Clinical comparisons of different fixed orthodontic retainers.

The aim of this prospective clinical study was to compare the clinical outcomes of three different fixed lingual retainers, in terms of effects on periodontal health and success rate. Forty five patients aged 13 to 25 years were randomly assigned into three groups, using bonded upper and lower lingual retainers. The study groups were as follows: Group 1- Bond-A-Braid®, Group 2- everStick® ORTHO, Group 3- Super-Splint. The follow-up appointments were performed two weeks (Baseline=T0), one month (T1), three months (T2), and six months (T3) after the application of retainers. Plaque Index (PI), Gingival Index (GI), Probing Depth (PD), Bleeding in Probing (BOP) and Retainer Failure were assessed at each appointment. The everStick Ortho group showed significantly lower PI values on the upper-lower lingual side after three (p=0.008) and six (p=0.001) months. The everStick Ortho group had significantly lower upper lingual (GI) levels after six months, and lower lingual side levels after one month. The Super-Splint group showed significantly lower PD values on the upper lingual side after six months. The everStick Ortho group presented significantly lower BOP levels after six months on the upper lingual side. No significant differences between the groups (p>0.05) in terms of retainer failure were found. The everStick Ortho group presented better results in terms of periodontal health. The failure rates of the retainers were similar.

Biomechanical variables affect peri-implant bone loss in implant-supported fixed complete dentures: A methodological and prospective study.

Implant-supported fixed complete dentures (IFCD) experience failures and complications related to biological and technical risk factors. This study investigated the effect of biomechanical variables of IFCD on 1-year peri-implant bone loss at the buccal, palatal/lingual, mesial, and distal implant sides. A new method was used to measure the geometric biomechanical variables of IFCD using cone beam computed tomography (CBCT). The study sample consisted of 246 external hexagon implants supporting 48 hybrid IFCD in 44 patients. CBCT images obtained immediately (T0) and 1 year (T1) after prosthesis installation were used to measure the support polygon area, clinical crown/implant (C/I) ratio (vertical lever), anteroposterior power and resistance arms, anterior and posterior cantilevers (horizontal levers), and peri-implant bone remodeling (T1-T0). Data were analyzed using multilevel multivariable models. The average total bone loss in the mandible and maxilla were 0.88 mm, with a loss of 0.62 mm in the mandible and 1.08 mm in the maxilla. The C/I ratio had a significant effect on bone loss on the mesial, distal, and palatal/lingual sides (P <.05). The anterior cantilever had a protective effect on the lingual side of the anterior implant. No effect on bone loss was found for the support polygon area, posterior cantilever, resistance arm, or power arm (P >.05). The results suggest that the C/I ratio and anterior cantilever in IFCD affect peri-implant bone loss according to the implant side and position in the arch.

Keratinized mucosa changes around one-stage implants: A prospective case series.

The need of an adequate band of keratinized tissue (KT) to maintain periodontal health around teeth as well as around implants has been a debated topic over many years but still no conclusions have been drawn. This prospective case series evaluates the changes undergone by the keratinized mucosa (KM) and the soft tissue volume around non-submerged implants before the prosthetic rehabilitation. A total of 40 patients were included. The primary outcome was to analyze the width of the KM at both buccal and lingual aspects compared to the pre-existing KT in the edentulous ridge only in mandibular (pre)molar area. The mucogingival line was marked with a surgical pen and an intra-oral scanner was used to take the impression of the implant area the day of the surgery (T0, baseline) and before the crown placement (T1, 3months). Buccal soft tissue volume was measured at 1, 3, and 5 mm apical to the healing abutment position and a comparison between T0 and T1 was performed. Student t-test was used according to the distribution of the data (Shapiro-Wilk). The mean KT width at baseline was 4.54 ± 1.31 mm at buccal side and 5.04 ± 1.88 mm at lingual side. After 3months, the mean KM values were 3.15 ± 1.03 mm and 3.72 ± 1.56 mm at the buccal and lingual aspects, respectively. The differences, 30.6% of KM reduction buccally and 26.1% of reduction lingually, were statistically significant for both sides. Within the limitations of this investigation, it was observed that the KM width from the baseline to the 3months follow up presented a significant dimensional change in both the buccal and lingual aspects, whereas buccal soft tissue volume showed an increase between baseline and follow up.

Analysis of the mandibular canal course using unsupervised machine learning algorithm.

ObjectivesAnatomical structure classification is necessary task in medical field, but the inevitable variability of interpretation among experts makes reliable classification difficult. This study aims to introduce cluster analysis, unsupervised machine learning method, for classification of three-dimensional (3D) mandibular canal (MC) courses, and to visualize standard MC courses derived from cluster analysis in the Korean population.Materials and methodsA total of 429 cone-beam computed tomography images were used. Four sites in the mandible were selected for the measurement of the MC course and four parameters, two vertical and two horizontal parameters were measured per site. Cluster analysis was carried out as follows: parameter measurement, parameter normalization, cluster tendency evaluation, optimal number of clusters determination, and k-means cluster analysis. The 3D MC courses were classified into three types with statistically significant mean differences by cluster analysis.ResultsCluster 1 showed a smooth line running towards the lingual side in the axial view and a steep slope in the sagittal view. Cluster 2 ran in an almost straight line closest to the lingual and inferior border of mandible. Cluster 3 showed the pathway with a bent buccally in the axial view and an increasing slope in the sagittal view in the posterior area. Cluster 2 showed the highest distribution (42.1%), and males were more widely distributed (57.1%) than the females (42.9%). Cluster 3 comprised similar ratio of male and female cases and accounted for 31.9% of the total distribution. Cluster 1 had the least distribution (26.0%) Distributions of the right and left sides did not show a statistically significant difference.ConclusionThe MC courses were automatically classified as three types through cluster analysis. Cluster analysis enables the unbiased classification of the anatomical structures by reducing observer variability and can present representative standard information for each classified group.

Plaque accumulation at the fitting surface and cleaning status in patients with full-arch implant-supported fixed prostheses: a cross sectional study

Objective: To observe the plaque accumulation at the fitting surface and oral hygiene status in patients with full-arch implant-supported fixed prostheses, and explore the possible influencing factors. Methods: Twenty-eight patients [17 males and 11 females, (63.0± 10.8) years old] with 40 full-arch implant-supported fixed prostheses (18 maxillary and 22 mandibular) were collected from January 2012 to September 2020 in Department of Implantology, Peking University School and Hospital of Stomatology. Plaque accumulation at the fitting surfaces were evaluated during the follow-up visit after 6 months following definitive prostheses delivery, by analyzing the digital photographs recorded by ImageJ. Meanwhile, the cleanliness of the fitting surface of prostheses and oral hygiene status were recorded. The oral hygiene habits and the patients' satisfaction with the prostheses were investigated by questionnaire, and the difference of plaque accumulation between different cleaning habits of dentures were compared. Results: The debris index of the fitting surface of the 40 full-arch implant-supported fixed prostheses were 3.28±0.75, and the percentage of area covered with plaque was (51.6±19.0)%. The debris index and plaque accumulation of the mandibular prostheses were significantly higher than that of the maxillary prostheses (P<0.05). In most mandibular prostheses (16/22), calculus was attached to the lingual side of the anterior tooth area. The reserved cleaning space of the restoration showed more plaque accumulation than in other parts. There was no significant difference in the percentage of area covered with plaque between groups with different cleaning habits. The satisfaction survey results indicated the "clean" project had a lowest score. Conclusions: The cleanliness of patients with full-arch implant-supported fixed prostheses was poor, and the hygiene status of the mandibular prostheses was worse than that of maxillary, especially in the anterior tooth area of mandibular prostheses. The influence of different cleaning habits on plaque accumulation was not observed.

A Three-Dimensional Finite Element Analysis: Maxillary Dentition Distalization with the Aid of Microimplant in Lingual Orthodontics.

AimTo analyze the movement of anterior teeth by changing the height of the power-arm and changing the force application points during whole maxillary dentition distalization with the aid of micro-implants in lingual orthodontics to set a biomechanical reference for effective clinical use of lingual orthodontic appliance.MethodsA three-dimensional finite element model of the maxillary teeth with lingual appliance and the associated support tissue was established. Maxillary dentition with the force of 200g was distalized using implant as anchorage, then the movement of anterior teeth was analyzed by changing the length of power-arm (1mm, 3mm, 6mm, 9mm) and by changing the force location from lingual side to buccal side.ResultsDuring whole maxillary dentition distalization with aid of the implants in lingual orthodontics: when the height of power arm was 1mm, the anterior teeth rotated clockwise, with the increasing of the height of power-arm, the anterior teeth rotated counterclockwise gradually. When the height of power-arm was 9mm, all anterior teeth rotated counterclockwise. Central incisor and lateral incisor rotated counterclockwise and canine rotated clockwise when the buccal side force was applied.ConclusionWith the increase of the height of the power-arm, the movement pattern of the upper anterior teeth is different. The canine is more sensitive to the height of the power-arm than the central incisor and the lateral incisor. When the height of the power-arm reaches 9mm, the upper anterior teeth are displayed as crown tipping buccally movement. Compare with lingual side force, the buccal side force do better in preventing the loss of anterior tooth torque. If the upper anterior teeth are up-right or lingually tipped before treatment, it is preferable to use longer power-arm or buccal side traction force. If the anterior teeth are already tipped buccally, then short power-arm or lingual side force is advised.

Imaging findings and treatment outcomes of a rare subtype of medication-related osteonecrosis of the jaw.

In our previous study, we found a rare type of medication-related osteonecrosis of the jaw (MRONJ), which shows periosteal reaction (PR) at a site distant from osteolytic lesions or the extraction site (periosteal reaction dominant type, PRd type), even though the osteolytic lesions in the bone marrow are localized. The causes and treatment of MRONJ remain unclear; hence, this study aimed to describe the imaging and clinical features of the PRd type. MRONJ patients who visited Nagasaki University Hospital between 2009 and 2020 and received conservative therapy as initial treatment were included in this study. The PR site, imaging findings, initial symptoms, outcome, and time to progression were examined. Among 59 MRONJ patients treated with conservative therapy, 38 did not show PR (PR- type), 15 showed PR near the osteolytic region (PR + type), and 6 had the PRd type. All patients with the PRd type had submental abscesses, and computed tomography (CT) images demonstrated PR on the lingual side of the anterior mandible. Osteolytic lesions progressed in 6/6 PRd type (100%), 5/15 PR + type (33.3%), and 2/38 PR- type (5.3%) patients. Time to progression for the osteolytic region on CT was short for the PRd type, at 56-148days (median 79days). Among the MRONJ types, the PRd type has a poor prognosis. Therefore, accumulating and analyzing more PRd cases in the future is warranted. This is the first report to describe the presence of this specific subtype of MRONJ.

Efficacy of photo bio-modulation therapy for pain relief and soft tissue wound healing after dental implant surgery: A double-blind randomized clinical trial

ObjectiveThis study aimed to investigate the effect of photo bio-modulation therapy (PBMT) on pain relief and wound healing after dental implant surgery. Background dataPhoto bio-modulation (PBM) has been used as a therapeutic method for the healing of wounds and controlling pain and inflammation. Materials and methodsIn this clinical trial, 21 patients including 12 men and 9 women were selected based on inclusion criteria. Forty-two implants were placed in the posterior regions of both sides of the mandible. Immediately after the surgery, 660 nm and 810 nm diode laser beams with an energy density of 6 J/cm2 were concurrently irradiated on three sides of the implant regions, buccal, occlusal, and lingual sides. After 48 h both two lasers were applied to patients without irradiation, as placebo devices in the control side. The severity of patients’ pain was examined after 12, 24, 48, and 72 h based on a visual analog scale (VAS). Wound healing score was also determined at 3, 7, and 14 days postoperatively using the Likert scale from 0 to 4. The data were analyzed with SPSS. Statistical significance was set at α = 0.05. ResultsThe laser side exhibited a significant improvement in wound healing and pain relief at all the intervals compared to baseline (p < 0.05). Wilcoxon test showed that the wound healing score on the laser side at 3 (p < 0.001), 7 (p < 0.001), and 14 (p = 0.03) days was significantly better than that on the placebo side. Paired t-test showed that at all the intervals of 12 h (p < 0.008), 24 h (p < 0.04), 48 h (p < 0.008), and 72 h (p < 0.02), the mean pain score on the laser side was significantly lower than that on the placebo side. ConclusionGiven the limitations of this study, the results showed that PBM enhanced wound healing and decreased pain after dental implant surgery.