Canine Region Research Articles

Satisfaction and Oral Health-Related Quality of Life of Different Attachments Used for Implant-Retained Overdentures in Subjects with Resorbed Mandibles: A Crossover Trial.

The aim of this crossover study was to evaluate patient satisfaction and oral health related-quality of life (OHRQoL) with different connectors used for implant-retained overdentures in subjects with resorbed mandibles. Eighteen edentulous patients with atrophied mandibular bone received traditional maxillary and mandibular dentures (control). After 3 months, two implants were inserted in the canine regions. Three months later, each patient received the following overdentures using a crossover design: (1) bar overdentures, (2) telescopic overdentures, and (3) stud overdentures. Patient satisfaction (primary outcome) was measured by visual analog scale (VAS). OHRQoL (secondary outcome) was measured by oral health impact profile (OHIP-14). Questions of VAS and OHIP-14 were evaluated after 3 months of using conventional dentures, bar overdentures, telescopic overdentures, and stud overdentures. For all questionnaires, conventional dentures recorded significantly lower satisfaction than implant overdentures. Stud overdentures showed significantly higher satisfaction with maxillary denture comfort, self-consciousness, and feeling that the prosthesis is a part of the patient compared with other attachments. Bar and telescopic overdentures showed higher satisfaction during biting of hard and soft foods, while telescopic and stud overdentures showed higher satisfaction with oral hygiene. No significant differences between attachments regarding other VAS and OHIP-14 questions were noted. Implant overdentures for subjects with mandibular bone resorption improved patient satisfaction and OHRQoL compared with traditional dentures regardless of the form of attachments. However, studs are more advantageous in terms of comfort with maxillary overdentures, self-consciousness, and feeling that the prosthesis is a part of the patient. Bar and telescopic attachments had more satisfaction during biting of soft and hard foods, while telescopic and stud attachments had more satisfaction with oral hygiene.

Estimation of height and width of bone in anterior hard palate as a donor site for autogenous bone graft using IOPA by long cone paralleling technique.

The purpose of this study was to determine the amount of bone available for harvesting from the anterior palate region using IOPA (Intra Oral Peri Apical) radiographs. A total of 80 patients visiting the outpatient Department of Periodontics were selected. Two groups of male and female consisting 40 patients each were made. They were further subdivided into two groups based on age, 18-30 and 31-60 years of age, each with twenty patients. The patients were subjected to radiographic examination consisting of IOPA radiographs. All IOPA radiographs were taken using long cone paralleling technique. Availability of bone for harvesting, above the apices of teeth was calculated. The bone available in the incisor region was approximately 6.5 to 6.9 mm in height and 7.4 to 8 mm in width, in canine region 6.35 to 6.65 mm in height and 7.6 to 8.1 mm width, and in the premolar region 3.65 to 3.75 mm in height and width. When the bone height and width were compared gender and age wise for CI (central incisors), LI (lateral incisors), canine and premolars, using Student's t- test the results were not statistically significant. For the purpose of harvesting autogenous bone, from the region of incisor and canine approximately 6.35 to 6.9 mm height and 7.4 to 8.1 mm width of bone may be harvested maintaining a safe distance from the apices of the teeth and the nasal floor. The premolar region does appear to yield sufficient bone at safe distances from the maxillary sinus and the apices of the premolars.

Effects of overdenture attachment systems with different working principles on stress transmission: A three-dimensional finite element study.

PURPOSEThe aim of the present study was to compare the stress distributions on the dental implants, abutments, and bone caused by different overdenture attachment types under functional chewing forces.MATERIALS AND METHODSThe 3D finite element models of the mandible, dental implants, attachment types, and prostheses were prepared. In accordance with a conventional dental implant supported overdenture design, the dental implants were positioned at the bone level in the canine teeth region bilaterally. A total of eight models using eight different attachment systems were used in this study. All the models were loaded to simulate chewing forces generated during the centric relationship (450 N), lateral movement (400 N), protrusive movement (400 N), and also in the presence of a food mass unilaterally (200 N). Stress outputs were obtained as the maximum principal stress and the equivalent von-Mises stress.RESULTSIn all attachment types, higher stress values were observed in the abutments, dental implants, and bone in the magnet attachments in different loading conditions. The highest stress values were observed among the magnet systems in the components of the Titanmagnetics model in all loading conditions (stresses were 15.4, 17.7, and 33.1 MPa on abutment, dental implant, and bone, respectively). The lowest stress value was observed in the models of Zest and O-Ring attachments.CONCLUSIONThe results of the present study implied that attachment types permitting rotation and tolerating various angles created lower stresses on the bone, dental implants, and abutments.

Cone-beam computed tomography assessment of bone using grayscale values in patients with diabetes mellitus. A case-control observational study.

Background:The density of cortical and cancellous bone is a key reason for implant anchorage which might be severely affected during diabetes.Aim:The aim of the study was to establish the role of cone-beam computed tomography (CBCT) using grayscale values in determining bone density in different jaw sites and in comparing the values in healthy with diabetic patients.Materials and Methods:Bone densities in 322 possible implant sites in healthy and diabetic patients were evaluated using NewTomGiano CBCT machine. Cross-sections obtained were assessed for bone densities in terms of Hounsfield Unit on different sites using New Net Technologies software version 6.1.Statistical Analysis:Data were statistically analyzed using SPSS software (version 19.0).Results:Age-wise cortical and cancellous bone densities were compared and no statistical significance was obtained. Gender-wise bone density was compared and significant results were found in males. Jaw-wise bone density was compared and was found to be significantly high in the mandible. The mean cortical bone density in control group was 1608.572 (±380.36), whereas in diabetic group was 1395.368 (±296.97), and the mean cancellous bone density in control was 906.918 (±185.40) and in diabetic was 559.868 (±128.16). Teeth wise in cortical bone significant values were found at premolar region (P = 0.046) and in cancellous bone significant values were found at canine and premolar region (P = 0.012) and highly significant values were found at molar region (P = 0.001).Conclusion:CBCT unveils a distinct pattern of cortical and cancellous bone density. A high degree of concordance between different regions of the mouth in cortical and cancellous bones was obtained in different study groups. CBCT could be used for bone density analysis.

The Effect of Two Implant-Abutment Connections on Maximum Bite Force, Prosthetic Maintenance and Peri-Implant Sulcular Fluid in Mandibular Implant Supported Telescopic Overdenture: A Split-mouth study

Purpose: The aim of this study was to evaluate and compare two different implant-abutment connections (conical and trilobe connection) in mandibular implant supported telescopic overdenture. The parameters of evaluation were the maximum bite force, prosthetic maintenance and peri-implant sulcular fluid. Materials and method: Twelve completely edentulous patients received new complete dentures. After 3 months of adaption to the new denture, 24 implants (12 implants with conical implant-abutment connection (group A) and 12 implants with trilobe implant-abutment connection (group B). The Insertion of each type of implant was randomly assigned between the two contralateral sides intraorally for each patient using a statistical software. Each patient was treated according to split mouth design. The implants were inserted in the canine region of the mandible using two-stage surgical technique and conventional loading protocol. After 3 months, implants were exposed and a telescopic overdenture was constructed. The maximum bite force, prosthetic maintenance and peri-implant sulcular fluid for each group of implants were evaluated at loading time, after 6 and 12 months.Results: There was no statistically significant difference in maximum bite force between group A and B the at loading time, but there was a statistically significant difference at 6 and 12 months follow up visits. The prosthetic maintenance events in group A were 1 event compared to 5 events in group B. There was no statistically significant difference between group A and B in the peri-implant sulcular fluid at loading time, 6 and 12 months follow up visits. Conclusion: Within the limitations of this study, it can be concluded that the conical implant- abutment connection is associated with increased maximum bite force compared to the trilobe Implant-abutment connection. Conical implant-abutment connection can provide a stable implant system with fewer prosthetic complications and maintenance services compared to trilobe implant -abutment connection.

Retention force of all-zirconia, all-polyetheretherketone, and zirconia-polyetheretherketone telescopic attachments for implant-retained overdentures: In vitro comparative study

Aim: The aim was to evaluate and compare retention forces of all-zirconia (ZrO2), all-polyetheretherketone (PEEK), and ZrO2-PEEK Computer-Aided-Designing computer-Aided -Manufacturing (CAD-CAM) telescopic attachments for two implant-retained mandibular overdentures. Materials and Methods: Fifteen identical acrylic resin models of the edentulous mandibular arch without alveolar undercuts were fabricated. Two implants were inserted in the canine region of each model. According to the material of telescopic attachment, models were divided into three groups: all ZrO2 (ZZ): primary and secondary crowns were made of ZrO2, all PEEK (PP): primary and secondary crowns were made of PEEK, and ZrO2-PEEK (ZP): primary crowns were made of ZrO2 and secondary ones were made of PEEK. Identical experimental overdentures were constructed for all models. For measuring the retention force, a universal testing machine was used to apply a pull-off test in presence of artificial saliva between the crowns. The achieved maximum values of retention force were recorded at the beginning of the study (initial retention) and after 540 cycles of insertion and removal simulating 6 months of the clinical service (final retention). Results were statistically analyzed, analysis of variance (P Results: ZP group reported the highest initial force values for all groups. The final retention values of PP and ZP groups were significantly decreased than initial values, while the insignificant loss of retention was observed with ZZ group (P = 0.06). Independent samples test showed a significant difference in both initial and final retentions between each two groups. Conclusion: Within the limitations of this study, ZrO2 is more preferred as a secondary telescopic crown against a primary ZrO2 one. Despite the loss of retention by time, PEEK can still be used as a secondary telescopic crown against ZrO2 or PEEK primary crowns regarding the acceptable initial and final retention values.

A comparison of the retentive force of ball and socket attachment versus magnet attachment in mandibular overdentures: A randomized control trial

Aim: To compare the retention and patient satisfaction of implant-supported mandibular overdentures with ball and socket attachment versus magnet attachment. Materials and Methods: Twenty-four participants (10 males and 14 females) were divided into two equal groups (n = 12). Both groups received implant-supported mandibular overdentures retained by ball and magnet attachment. Two implants were installed in the canine region bilaterally. Evaluation of retention was made at overdenture insertion, 3, 6, and 12 months. Patient satisfaction evaluation with Oral Health Impact Profile Questionnaire-14 (OHIP-14) was made at overdenture insertion 3, and 12 months subsequently. Results: The ball group showed a statistically significantly higher retention force (P < 0.05) than the magnet group at insertion, 3 and 6 months. The ball group had a statistically significantly lower mean of physical disability and physical pain (P < 0.05) than the magnet group through all follow-up. One-way analysis of variance (ANOVA) test was used to compare between groups as well as to study the changes by time within each group. Conclusion: Both implant-supported mandibular overdenture retained with magnet or ball and socket attachments consider a successful treatment option with superior improvement in the ball and socket group.

Bilateral canine space infection secondary to odontogenic origin. A rare case report.

Odontogenic infections (OI) are a major reason for consultation in dental practice. They affect people of all ages, and most of them respond well to current medical and surgical treatments. The aim of this paper is to emphasize different and rare etiological factors that can play a role in odontogenic abscesses, which can lead to complications. A 54-year-old man complaints of pain and swelling on the upper front-side of his face. Physical examination of the face showed enlargement and swelling in the upper front region. Panoramic radiograph images showed a radiolucent appearance of the canine region. Based on the results of the clinical and radiographic examinations, the patient was diagnosed with a bilateral canine space infection. The treatment performed was FNAC (Fine neddle aspiration cytology) from canine region followed by intraoral drainage incision at the most prominent part of swelling (Modified Hiltons method), 5 ml of pus was removed, postoperative dressing was applied and regular follow-up was done with continued antibiotic therapy. Bilateral canine space abscess is a rare odontogenic infection that can cause life-threatening complications. The success of treatment requires early recognition, determination of etiological factors, and appropriate medical and surgical management. To perform treatment of odontogenic infections, the Oral &amp; Maxillofacial Surgeon should understand the terminology regarding infectious diseases and pathophysiology. The success of treatment requires early recognition, determination of etiological factors, and appropriate medical and surgical management.

Maxillary expander with differential opening vs Hyrax expander: A randomized clinical trial

The aim of this 2-arm parallel trial was to compare the dentoskeletal effects of the expander with differential opening (EDO) and the Hyrax expander in the mixed dentition. Patients aged 7-11years with maxillary dental arch constriction and Class I or Class II sagittal relationships were randomly allocated into 2 study groups. The experimental group comprised 22 patients (10 males, 12 females) with a mean age of 8.46years treated with the EDO. The comparison group was composed of 24 patients (6 males, 18 females), mean age of 8.92years treated with the conventional Hyrax expander. One complete turn per day for 6days was performed for the posterior screw of the EDO and for the Hyrax expander. The anterior screw of the EDO was activated 1 complete turn per day for 10days. The primary outcomes were the anterior opening of the midpalatal suture, changes on the interincisal diastema width, maxillary dental arch widths, arch perimeter, arch length, palatal depth, inclination of maxillary posterior teeth and on dental arch shape, and the amount of differential expansion in the anterior region compared with the posterior region of the maxillary dental arch. Computer-generated randomization was used. Allocation was concealed with sequentially, numbered, sealed, and opaque envelopes. Blinding was applicable for outcome assessment only. Occlusal radiographs of the maxilla were obtained at the end of the active expansion phase (T2). Intraoral photographs were obtained immediately pre-expansion (T1) and at T2. Digital dental models were obtained at T1 and 6months after the active expansion period (T3). Intergroup comparisons of T1-T2 changes were performed using multiple linear regression analysis (P<0.05). The independent variables were both treatment and the starting forms. Bonferroni correction for multiple tests was applied. The experimental group showed a significantly greater opening of the anterior region of the midpalatal suture, a greater increase of the interincisal diastema width, and greater increases of the intercanine distance and inter-first deciduous molar distance than the Hyrax expander. The experimental group showed a significant differential expansion between the anterior and posterior regions, whereas the Hyrax group produced a similar expansion in the canine and molar regions. Serious harm was not observed. The EDO was capable of promoting greater orthopedic and dental changes in the anterior region of the maxilla than the conventional Hyrax expander. Similarity between the 2 expanders was observed for changes in the posterior region width, arch perimeter, arch length, palatal depth, and posterior teeth inclination.

Retention force of zirconia bar retained implant overdenture: Clinical comparative study between PEEK and plastic clips.

Aim: This study aimed to evaluate and compare retention force of two implants retained mandibular overdenture with zirconia bar using two different clip materials.&#x0D; Methodology: 20 completely edentulous patients (8 women and 12 men) with age ranged between 45 and 65 years were selected for this study. All patients received conventional maxillary and mandibular complete dentures. Two implants were inserted bilaterally in the mandibular canine region. CAD-CAM fabricated zirconia bar attachment was used to retain mandibular overdentures. Patients were randomly divided into two equal groups where poly-oxy-methylene (POM) clip was used for Group I and poly-ether-ether-ketone (PEEK) clip for Group II. Retention force was measured at time of overdenture insertion (T0), six months (T6), and twelve months (T12) later.&#x0D; Results: significant difference was recorded between the two groups in initial retention forces (T0) where PEEK clip group recorded higher retention forces in comparison to POM clip group (P=0.029). However, insignificant difference was observed at (T6) and (T12). Within group comparison of mean retention values at different follow-up periods revealed significant difference for both groups.&#x0D; Conclusion:&#x0D; Within parameters of this study, it could be concluded that both POM and PEEK retentive clips can provide comparable retention forces when used with zirconia bar during 12 months period of overdenture use.&#x0D; &#x0D; How to cite this article: Emera RMK, Altonbary GY. Retention force of zirconia bar retained implant overdenture: Clinical comparative study between PEEK and plastic clips. Int Dent Res 2019;9(3):92-8.&#x0D; &#x0D; Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Marsupialization Followed by Enucleation and Chemical Cauterization for Treatment of Odontogenic Keratocyst Involving Maxillary Sinus: A Case Report

Odontogenic keratocysts are odontogenic cysts which have locally infiltrative behavior. They mostly occur in second and fourth decades but can occur at any age throughout life. In majority of cases, they are located in the posterior region of mandible, but can also be found in the maxilla especially in the canine region. In this article, we have discussed the diagnosis and management of a large odontogenic keratocyst cyst involving the maxillary sinus. A 22 years old male patient presented with pain and swelling on right side of the face since last one year. There was history of pus discharge and gradual increase in size of the swelling since last 3-4 months. Patient took antibiotics but there was no improvement. Odontogenic keratocyst is a developmental pathology which arises from additional remnants of dental lamina of oral epithelium. They present with swelling, pain and pus formation/discharge as signs of infection. Often, when the lesion is large there can be paresthesia of the lower lip. These lesions can also be clinically asymptomatic. Mostly they appear as well-demarcated unilocular radiolucency having a thin, sclerotic well-defined margin. There are many treatment options like enucleation, marsupialization, decompression, curettage, use of chemical agents like Carnoy's solution, cryotherapy with liquid nitrogen or peripheral osteotomy and surgical resection of lesion.

Computed tomographic features of desmoplastic ameloblastoma of the jaw

Objective To retrospectively analyze the clinical and CT imaging features of desmoplastic ameloblastomas (DA) in comparison with other types of ameloblastomas. Methods Patients diagnosed with ameloblastoma histopathologically in Peking University School and Hospital of Stomatology from July 2000 to August 2017 were reviewed to analyze the constituent ratios and characteristics of DA. CT imaging features of DA (28 cases) were investigated in comparison with consecutive cases of solid/multicystic and unicystic ameloblastomas. The following imaging perspectives were analyzed: the border, internal structure, three-dimensional shape, tooth, the periodontium, the cortex and the expansion of the tumors. CT values were measured in the region of interest for quantitative analysis. Results Among the 1 269 cases of ameloblastomas, 50 (3.9%) were DA, which showed predilections for males (74.0%). The average age of DA was about 43.9 years old, which was higher than the other two types. The anterior incisorcanine region (62.0%) and premolar region (30.0%) were most frequently affected. The incidence rate of DA in mandibule was 56.0% (28/50), which was slightly higher than that of maxilla (44.0%). The DA characteristically showed scallop border and honeycomblike or soapbubble internal structure with bone formation on CT. The mean ratios of height to mesiodistal and buccal-lingual to mesio-distal distances were 0.76 and 0.63, which were higher than the other two types. According to the degree of internal bone formation, three subtypes of DA could be observed: densely ossifying type (I), honeycomb/soap bubble type (II) and sparsely ossifying type (III). The means and standard deviations of CT values of DA were significantly higher than those of the other two types, which were (488.8±164.0) HU (type I), (171.7±102.8) HU (type II), (42.1±8.8) HU (type III). Conclusion CT is helpful for diagnosis of DA, which shows as solid tumor with varying degrees of internal ossification.

Effects of Different Positions and Angles of Implants in Maxillary Edentulous Jaw on Surrounding Bone Stress under Dynamic Loading: A Three-Dimensional Finite Element Analysis.

Purpose To evaluate the effects of different placements of mesial implants and different angles of distant implants in maxillary edentulous jaws on the stress on the implant and the surrounding bone tissue under dynamic loading. Materials and Methods Cone beam computed tomography was used to acquire images of maxillary edentulous jaws. Using Mimics 17.0, Geomagic, and Unigraphics NX8.5 software, three-dimensional models were established: two mesial implants were placed vertically in the anterior region of the maxilla (bilateral central incisor, lateral incisor, and canine), and two distant implants were placed obliquely in the bilateral second premolar area at different inclined angles (15°, 30°, and 45°). The established models were designated I–IX. The models were subjected to dynamic load using Abaqus 6.12, with the working side posterior teeth loading of 150 N and simulation cycle of 0.875 s. Results During the second to fourth phases of the mastication cycle, the stress was mainly concentrated on the neck of the distal implant. The stress of the distal implants was greater than that of mesial implants. Stress levels peaked in the third stage of the cycle. The stress of the distal cortical bone of distal implant of Model I reached the maximum of 183.437 MPa. The stress of the distal cortical bone and cancellous bone of distal implant of Model VIII represented the minima (62.989 MPa and 17.186 MPa, respectively). Conclusions Our models showed optimal stress reductions when the mesial implants were located in the canine region and the distal implants tilted 30°.

VASCULAR EXTENSION OF PERIPHERAL GIANT CELL LESION: A CASE REPORT WITH IMMUNOHISTOCHEMICAL ANALYSIS

Peripheral giant cell lesions shares microscopic similarities to other entities and their origin remains unclear. A 47-year-old woman was referred for management of a painful swelling in the canine region with recent history of tooth removal. A slight asymmetry in the upper lip was detected. Intraoral exam revealed a lesion that appeared as a purplish-red nodule, pediculate on the anterior right alveolar crest, and associated with an unstable dental prosthesis. Superficial bone resorption was detected. The lesion was curetted after excision biopsy. Microscopically, an ulcerative, nonencapsulated lesion composed of densely cellular lobules of round mononuclear cells, prominent multinucleated giant cells (MGCs), and hemorrhage was surrounded by fibrous tissue. Apoptotic MCGs were also seen. Interestingly, vessels in the periphery exhibited transendothelial migration of MGCs were positive for matrix metallopeptidase 9 (MMP-9) and macrophage fusion marker CD44. Neovascularization was detected within cellular lobules. Serum tests were normal. Clinical significance of vascular extension must be further clarified. No recurrence has occurred after 1 year.

GINGIVAL CYST OF THE ADULT: A REPORT OF AN UNUSUAL LESION

A 78-year-old black female patient attended the oral medicine clinic complaining of a 2-month gum lesion that was painful during tooth brushing. Intraoral examination demonstrated a firm rounded nodule in the attached gingiva of the right inferior lateral incisor and canine. Periapical radiograph was noncontributory, and the patient was submitted to excisional biopsy. The histopathologic aspect showed a mucosal fragment covered by a parakeratinized stratified squamous epithelium exhibiting mild spongiosis and exocytosis with a cystic lesion at the subjacent connective tissue with a thin capsule of flat epithelial lining forming plaque-like structures. Thus, the final diagnosis was gingival cyst of the adult (GVA). GVA is a rare odontogenic cyst from the rests of dental lamina, frequently observed in the soft tissues of mandibular canine and premolar regions. Treatment of gingival cysts of the adult is definitive and have shown good prognosis after surgical excision.

INFLAMMATORY ODONTOGENIC CYSTS IN THE RIGHT JAW. DIAGNOSIS, TREATMENT, AND 3 YEARS OF FOLLOW-UP

Inflammatory odontogenic cysts may arise from the development or proliferation of residual odontogenic epithelium remaining from an extracted tooth. A 76-year-old male patient sought treatment with mild pain and intraoral swelling in the right mandibular region. The clinical examination evidenced a great asymptomatic expansion of the vestibular and lingual cortices covered by normal color mucosa in the posterior region of the edentulous right mandible. On the radiographic examination, a single, well-delineated radiolucent area with sclerotic and slightly multilocular borders extended from the right lower canine region to the mandibular ramus. As a treatment, a biopsy was performed initially and then a decompression cannula was placed. After the result of the histopathologic examination of the inflammatory odontogenic cyst, the decompression cannula was maintained for 18 months until regression of the cystic lesion. Subsequently, enucleation was performed. The patient is being followed up with radiographic control.

Effect of LOCATOR attachments with different retentive forces on the stability of 2-implant-retained mandibular overdenture

Statement of problemThe LOCATOR system has been widely used for 2-implant-retained mandibular overdentures (2-MOs), but the influence of different LOCATOR attachments on the stability of 2-MOs has not been assessed. PurposeThe purpose of this in vitro study was to investigate the stability of 2-MOs anchored by LOCATOR attachments with different retentive forces. Material and methodsAn edentulous mandibular test cast with 2 bone-level implants inserted in the left and right mandibular canine regions was used. Twelve overdentures were then fabricated and anchored on the cast, following the instructions of the LOCATOR system. By replacing inserts of the 12 overdentures, the stability of 3 groups of LOCATOR inserts with different retentive forces was evaluated: blue group, pink group, and transparent group. With artificial saliva used on the cast and overdentures, vertical forces of 40 N, 55 N, and 100 N were loaded on the occlusal surface of the left incisor, left canine, and left molar, respectively. Under each loading condition, the vertical displacements at the loading point and the vertical and horizontal displacements of overdentures at the right distal edge were measured at the same time. One-way ANOVA and the post hoc Tukey honestly significant difference (HSD) test were used to compare the stability of 2-MOs with different LOCATOR attachments (α=.05 for all tests). ResultsWhen a force of 40 N was applied to the incisor, the largest vertical movement of the incisor loading point appeared in the blue group (P<.05), and the displacements of the pink group showed significant difference from those of the transparent group (P>.05). When 55 N was loaded on the canine, the blue group showed the largest vertical displacements of both the loading point and the right distal edge of the overdentures (P<.05). No significant difference was found in the vertical displacements between the pink group and the transparent group (P>.05). When a force of 100 N was loaded on the molar point, the transparent group indicated a smaller movement in the vertical direction at the edge of the overdentures than the blue group (P<.05) or the pink group (P<.05). ConclusionsLOCATOR attachments with different retentive forces had a significant effect on the denture stability of 2-MOs. Compared with the blue inserts, the pink and transparent inserts can offer greater stability for 2-MOs and could therefore be suggested for clinical situations.

Morphometric and functional study of the canine atlantoaxial joint

The atlantoaxial joint can be affected by instability, in most cases a congenital pathology in young small breed dogs. Causes of atlantoaxial instability (AAI) are variable but are usually attributed to a lack of ligamentous support. The purpose of the present study was to specify the role of the ligamentous structures in the stabilisation of the atlantoaxial joint and to find possible adaptations of the ligaments’ internal structure to their specific function. Five Beagle cadavers were included in this study. Each dog was subjected to a computed tomography (CT) and a magnetic resonance imaging (MRI) examination of the upper cervical region. This region was then dissected and the ligamentous structures stabilising the atlantoaxial joint were measured and removed for histological analysis. A ligament to dens ratio (LDR) was established in order to provide a basis for comparison with the measurements taken in other dog breeds. MRI and gross anatomical measurements were very similar, confirming the validity of the results. MRI thus seems reliable for evaluating the ligamentous structures of the canine occipitoatlantoaxial region. The movement exerting the greatest stress on the atlantoaxial ligaments and inducing the greatest distension of the alar ligaments was a head flexion combined with a rotation. A clear adaptation of the ligamentous shape and internal structure to their specific function was observed. Histologically, alar ligaments consisted of wavy collagen fibres and a high proportion of elastic fibres, providing them with a remarkable elasticity compared to the transverse ligament structure which was much more rigid.

Clinical denture base deformation with different attachments used to stabilize implant overdentures: A crossover study.

The aim of this crossover study was to compare clinical denture base deformation with different attachments used for mandibular implant overdentures. Twenty-four patients with edentulous mandibular ridges received two implants in the former canine regions. Three months thereafter, each patient was randomly given the following implant overdentures in a crossover design: (a) bar implant overdentures (BOD), (b) resilient telescopic implant overdentures (TOD), and (c) stud implant overdentures (SOD). Six linear strain gauges were attached to the lingual surface of the implant overdentures opposite to the abutments (Ch1and Ch2 at clenching [left] side and Ch5and Ch6 at non-clenching [right] side) and at midline (Ch3 and Ch4). Three months after wearing each implant overdenture, strain registrations were performed during clenching without food and during clenching on soft (cake) and hard (carrot) foods. Kruskal-Wallis test was used to compare denture strains between group, channels, and clenching conditions. Bar implant overdentures showed significantly higher (p<.001) total microstrains (403.7±306.8μɛ) than TOD (146.9±131.8μɛ) and SOD (99.8±75.6μɛ). No difference in microstrain was noted between TOD and SOD (p=.06, n.s.). Channels opposite to the abutments at clenching side (ch2) recorded the highest total strain during clenching hard (390.4±381.6μɛ) and soft (223.5±220.2μɛ) foods. Clenching hard food was associated with significant higher total microstrain than clenching soft food (p=.002). Telescopic and stud attachments are recommended to be used for two-implant mandibular over dentures as they were associated with reduced denture base deformation compared with bar attachments.

Deep learning-based MR-to-CT synthesis: The influence of varying gradient echo-based MR images as input channels.

PurposeTo study the influence of gradient echo–based contrasts as input channels to a 3D patch‐based neural network trained for synthetic CT (sCT) generation in canine and human populations.MethodsMagnetic resonance images and CT scans of human and canine pelvic regions were acquired and paired using nonrigid registration. Magnitude MR images and Dixon reconstructed water, fat, in‐phase and opposed‐phase images were obtained from a single T1‐weighted multi‐echo gradient‐echo acquisition. From this set, 6 input configurations were defined, each containing 1 to 4 MR images regarded as input channels. For each configuration, a UNet‐derived deep learning model was trained for synthetic CT generation. Reconstructed Hounsfield unit maps were evaluated with peak SNR, mean absolute error, and mean error. Dice similarity coefficient and surface distance maps assessed the geometric fidelity of bones. Repeatability was estimated by replicating the training up to 10 times.ResultsSeventeen canines and 23 human subjects were included in the study. Performance and repeatability of single‐channel models were dependent on the TE‐related water–fat interference with variations of up to 17% in mean absolute error, and variations of up to 28% specifically in bones. Repeatability, Dice similarity coefficient, and mean absolute error were statistically significantly better in multichannel models with mean absolute error ranging from 33 to 40 Hounsfield units in humans and from 35 to 47 Hounsfield units in canines.ConclusionSignificant differences in performance and robustness of deep learning models for synthetic CT generation were observed depending on the input. In‐phase images outperformed opposed‐phase images, and Dixon reconstructed multichannel inputs outperformed single‐channel inputs.