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The Journal of Prosthetic Dentistry May 2024Cantilevered complete arch implant-supported prostheses are commonly fabricated from zirconia and more recently from strength gradient zirconia. Different polymer-based...
STATEMENT OF PROBLEM
Cantilevered complete arch implant-supported prostheses are commonly fabricated from zirconia and more recently from strength gradient zirconia. Different polymer-based materials indicated for definitive fixed prostheses that could be used with additive or subtractive manufacturing have also been marketed recently. However, knowledge on the long-term fatigue behavior of cantilevered implant-supported prostheses made from these polymer-based materials and strength gradient zirconia is lacking.
PURPOSE
The purpose of this in vitro study was to evaluate the fatigue behavior of implant-supported cantilevered prostheses of recently introduced computer-aided design and computer-aided manufacturing polymers and zirconia.
MATERIAL AND METHODS
A master standard tessellation language file of a 9×11×20-mm specimen with a titanium base (Ti-base) space that represented an implant-supported cantilevered prosthesis was used to fabricate specimens from additively manufactured interim resin (AM), polymethyl methacrylate (SM-PM), nanographene-reinforced polymethyl methacrylate (SM-GR), high-impact polymer composite resin (SM-CR), and strength gradient zirconia (SM-ZR) (n=10). Each specimen was prepared by following the respective manufacturer's recommendations, and Ti-base abutments were cemented with an autopolymerizing luting composite resin. After cementation, the specimens were mounted in a mastication simulator and subjected to 1.2 million loading cycles under 100 N at 1.5 Hz; surviving specimens were subjected to another 1.2 million loading cycles under 200 N at 1.5 Hz. The load was applied to the cantilever extension, 12-mm from the clamp of the mastication simulator. The Kaplan-Meier survival analysis and Cox proportional hazards model were used to evaluate the data (α=.05).
RESULTS
Significant differences in survival rate and hazard ratio were observed among materials (P<.001). Among tested materials, SM-ZR had the highest and AM had the lowest survival rate (P≤.031). All materials had a significantly higher hazard ratio than SM-ZR (P≤.011) in the increasing order of SM-GR, SM-PM, SM-CR, and AM.
CONCLUSIONS
SM-ZR had the highest survival rate with no failed specimens. Even though most of the tested polymer-based materials failed during cyclic loading, these failures were commonly observed during the second 1.2 million loading cycles with 200 N. All materials had a higher hazard ratio than SM-ZR.
PubMed: 38760311
DOI: 10.1016/j.prosdent.2024.05.001 -
Folia Morphologica May 2024The muscles of mastication derive from a common embryological source, and the presence of accessory muscles in the infratemporal fossa (ITF) is uncommon. Here, we...
The muscles of mastication derive from a common embryological source, and the presence of accessory muscles in the infratemporal fossa (ITF) is uncommon. Here, we present findings from postmortem dissection of the ITF revealing a unilaterally present muscle extending from the greater wing of the sphenoid to blend inferiorly with the medial and lateral pterygoid muscles before attaching to the lateral pterygoid plate. This muscle is most consistent with the pterygoideus proprius muscle initially described in 1858. Though the exact embryological origin and function of this muscle remain speculative, these topics are nonetheless worth investigating as it may provide insight regarding the ontogeny of muscles descending from the first pharyngeal arch. Additionally, presence of the pterygoideus proprius muscle may have clinical implications and impact surrounding structures such as the mandibular division of the trigeminal nerve, maxillary artery, pterygoid venous plexus, masticatory muscles, and temporomandibular joint (TMJ).
PubMed: 38757501
DOI: 10.5603/fm.95708 -
Computer Methods in Biomechanics and... May 2024The aim of this research was to evaluate the stress distribution in the 'All-on-Four' prosthesis and the surrounding bone, with different framework materials and...
The aim of this research was to evaluate the stress distribution in the 'All-on-Four' prosthesis and the surrounding bone, with different framework materials and thicknesses. Five frameworks (alumina, zirconia, titanium, fiberglass reinforced resin (FRR), and polyether ether ketone (PEEK)) with two thicknesses (3.5 &5.5 mm) were stimulated in this research. A vertical force of 200 N was applied on a 1 mm circular area, at the cantilever, and at the region of the incisors, simulating different mastication mechanisms. The results illustrated that the 5.5 mm framework reduced the stresses on most parts, mucosa, and bone tissues, compared to 3.5 mm.
PubMed: 38756021
DOI: 10.1080/10255842.2024.2355260 -
MMW Fortschritte Der Medizin May 2024
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American Journal of Biological... May 2024Maintaining effective and efficient occlusal morphology presents adaptive challenges for mammals, particularly because mastication produces interactions with foods and...
OBJECTIVES
Maintaining effective and efficient occlusal morphology presents adaptive challenges for mammals, particularly because mastication produces interactions with foods and other materials that alters the geometry of occlusal surfaces through macrowear and/or catastrophic failure (i.e. "chipping"). Altered occlusal morphologies are often less effective for masticating materials of given diet-but not always-some species exhibit dental sculpting, meaning their dentitions are set up to harness macrowear to hone their occlusal surfaces into more effective morphologies (i.e. secondary morphologies). Here we show that dental sculpting is present in the folivorous Presbytis rubicunda of Borneo.
METHODS
Thirty-one undamaged lower second molars of P. rubicunda exhibiting various stages of macroscopic wear were micro-CT scanned and processed into digital surfaces. The surfaces were measured for convex Dirichlet normal energy (vDNE, a measure of surface sharpness), and degree of surface wear. Regression analyses compared surface sharpness with several measures of wear to test for the presence and magnitude of dental sculpting.
RESULTS
Positive correlations between the wear proxies and vDNE reveal that P. rubicunda wear in such a way as to become sharper, and therefore more effective chewing surfaces by exposing enamel-dentine junctions on their occlusal surfaces and then honing these junctions into sharpened edges. Compared to another primate folivore in which increasing surface sharpness with macrowear has been demonstrated (i.e., Alouatta palliata), the worn surfaces are similarly sharp, but the dental sculpting process appears to be different.
DISCUSSION
The results presented here suggest that not only do some primates exhibit dental sculpting and the attendant secondary morphology, but that there appear to be multiple different morphological configurations that can achieve this result. P. rubicunda has thicker enamel and a more stereotyped wear pattern than A. palliata, although both show positive correlations of occlusal surface sharpness (vDNE) with various wear proxies. These findings shed light on the varied approaches for the maintenance of effective and efficient occlusal surfaces in primates.
PubMed: 38751320
DOI: 10.1002/ajpa.24953 -
Diseases of the Esophagus : Official... May 2024Rumination syndrome (RS) is an underdiagnosed behavioral disorder of recurrent regurgitation. Regurgitation occurs in RS due to increased gastric pressure achieved by...
Rumination syndrome (RS) is an underdiagnosed behavioral disorder of recurrent regurgitation. Regurgitation occurs in RS due to increased gastric pressure achieved by subconscious contraction of the abdominal musculature wall, reversing the pressure gradient between the esophagus and the stomach. RS is mainly diagnosed clinically by the Rome Criteria with symptoms of regurgitation without retching of recently ingested food into the mouth and subsequent spitting or re-mastication. When the diagnosis is unable to be made clinically, supportive testing including fed impedance manometry can be considered. RS occurs worldwide, affecting patients of all ages, races, and genders with a prevalence of 3.1-5.8%. There is significant overlap with RS and disorders of a gut-brain interaction and upright gastroesophageal reflux driven by aerophagia and supragastric belching. There is also an association with mood disorder, fibromyalgia, and eating disorders. RS may be misdiagnosed as a variety of other syndromes including gastroesophageal reflux disease, gastroparesis, achalasia, and bulimia nervosa. Once RS is diagnosed, the mainstay of treatment is diaphragmatic breathing to lower the intragastric pressure and increase the lower esophageal pressure. Diaphragmatic breathing can be supported with biofeedback and cognitive behavioral therapy as well as medication options for more refractory cases. Response to therapy overtime and changes in symptoms overtime can now be tracked with a validated questionnaire.
PubMed: 38741462
DOI: 10.1093/dote/doae041 -
Swiss Dental Journal Feb 2024Oral healthcare among the frail is an underestimated geriatric care element. While neglected oral health (OH) is a well-established risk factor for frailty, frailty can...
Oral healthcare among the frail is an underestimated geriatric care element. While neglected oral health (OH) is a well-established risk factor for frailty, frailty can be a risk factor for subsequent OH problems. The cross-sectional investigation nested into the SAPALDIA sub-cohort of citizens aged 52 years and older, aims to stimulate longitudinal research into aspects that accelerate poor OH among frail individuals. The hypothesis investigated was that (pre-) frail individuals are more likely to have missing teeth replaced with removable dental prostheses (RDP) resulting in difficulties with chewing. The study included 1489 participants undergoing geriatric assessments and oral examination. The main predictor was frailty status (non-frail; pre-frail; frail), based on Fried's frailty phenotype. The main outcomes of interest were non-functional dentition (presence of ≤ 19 natural teeth), presence of any RDP and self-reported difficulties with chewing. Pre-frailty and frailty were not associated with the presence of ≤ 19 natural teeth, but were associated with a higher RDP prevalence. The presence of at least one complete denture (CD) had 1.71 fold and 2.54 folds higher odds among pre-frail and frail, respectively, compared to non-frail individuals. Frail individuals with CD reported chewing difficulties 7.8 times more often than non-frail individuals without CD. The results are in line with the hypothesis that (pre-) frail individuals may be more likely to have tooth loss restored by RDPs. Future longitudinal research needs to assess potential barriers to oral hygiene and fixed dental prostheses among (pre-) frail and to study their oral health-related quality of life.
Topics: Humans; Aged; Female; Male; Mastication; Middle Aged; Cross-Sectional Studies; Frail Elderly; Switzerland; Cohort Studies; Aged, 80 and over; Geriatric Assessment; Oral Health; Frailty; Denture, Partial, Removable; Denture, Complete
PubMed: 38739770
DOI: 10.61872/sdj-2024-02-04 -
Maedica Mar 2024We present the case of a patient with solitary fibrous tumor of the masticator space with unusual extension. A 43-year-old woman presented with a painless mass with...
We present the case of a patient with solitary fibrous tumor of the masticator space with unusual extension. A 43-year-old woman presented with a painless mass with intraoral extension on the right cheek. The B-scan sonograph and magnetic resonance imaging revealed the extension of the tumor. The biopsy performed under local anesthesia raised the suspicion of a solitary fibrous tumor. Tumor excision included a preoperative tumor embolization. The surgical removal of the tumor included a partial parotidectomy on the right side, insertion of masseteric and temporalis muscle, resection of the middle part of the zygomatic bone and stabilization of the bone with a plate, mobilization of the tumor from the maxillary sinus and the pterygopalatine fossa through an endoscopic approach and an approach via partial resection of the anterior wall of the maxillary sinus after identifying and sparing the infraorbital nerve. Ôhe histological findings confirmed the diagnosis of solitary fibrous tumor. The patient's treatment completed with radiation therapy, and 2.5 years later, there was recurrence in the right temporal area. To our knowledge, this is the second reported case of solitary fibrous tumor arising in the masticator space and the only case with extension intraorally and in the paranasal sinuses. Tumor embolization and complete surgical excision are the most frequently recommended treatments.
PubMed: 38736934
DOI: 10.26574/maedica.2024.19.11.154 -
Progress in Orthodontics May 2024Low-intensity electrical stimulation (LIES) is considered a relatively recent technology that has received little attention in orthodontics as a method of acceleration.... (Randomized Controlled Trial)
Randomized Controlled Trial
Patient-reported outcomes during accelerating the en-masse retraction of the upper anterior teeth using low-intensity electrical stimulation: a randomized controlled trial.
BACKGROUND
Low-intensity electrical stimulation (LIES) is considered a relatively recent technology that has received little attention in orthodontics as a method of acceleration. This study aimed to evaluate patient-reported outcome measures when LIES is used to accelerate the en-masse retraction of the upper anterior teeth.
MATERIALS AND METHODS
The sample consisted of 40 patients (8 males, 32 females; mean age 21.1 ± 2.3 years), with Class II division I malocclusion who required extraction of the first premolars to retract upper anterior teeth. They were randomly assigned to the LIES group (n = 20) and the conventional en-masse retraction group (CER; n = 20). Patient responses regarding pain, discomfort, burning sensation, swelling, chewing difficulty, speech difficulty, and painkillers' consumption were recorded at these nine assessment times: 24 h (T1), 3 days (T2), and 7 days (T3) after force application, then in the second month after 24 h (T4), 3 days (T5), and 7 days (T6) of force re-activation, and finally after 24 h (T7), 3 days (T8), and 7 days (T9) of force re-activation in the third month.
RESULTS
The mean values of pain perception were smaller in the LIES group than those in the CER group at all assessment times with no statistically significant differences between the two groups except during the second and third months (T5, T6, T8, and T9; P < 0.005). However, discomfort mean values were greater in the LIES group with significant differences compared to CER group during the first week of the follow-up only (T1, T2, and T3; P < 0.005). Burning sensation levels were very mild in the LIES group, with significant differences between the two groups at T1 and T2 only (P < 0.001). Speech difficulty was significantly greater in the LIES group compared to CER group at all studied times (P < 0.001). High levels of satisfaction and acceptance were reported in both groups, without any significant difference.
CONCLUSION
Both the LIES-based acceleration of en-masse retraction of upper anterior teeth and the conventional retraction were accompanied by mild to moderate pain, discomfort, and chewing difficulty on the first day of retraction. These sensations gradually decreased and almost disappeared over a week after force application or re-activation.
TRIAL REGISTRATION
ClinicalTrials.gov, ClinicalTrials.gov, NCT05920525. Registered 17 June 2023 - retrospectively registered, http://clinicaltrials.gov/study/NCT05920525?term=NCT05920525&rank=1 .
Topics: Humans; Female; Male; Tooth Movement Techniques; Young Adult; Patient Reported Outcome Measures; Malocclusion, Angle Class II; Tooth Extraction; Bicuspid; Electric Stimulation; Mastication; Incisor; Maxilla; Pain Measurement
PubMed: 38735912
DOI: 10.1186/s40510-024-00517-3 -
Foods (Basel, Switzerland) Apr 2024An advantage of masticators is the calibration and possible standardization of intra- and inter-individual mastication variability. However, mastication of soft, sticky...
An advantage of masticators is the calibration and possible standardization of intra- and inter-individual mastication variability. However, mastication of soft, sticky and melting products, such as processed cream cheeses, is challenging to reproduce with a masticator. The objectives of this work were, for the cheese studied: (1) to compare child and adult mastication and (2) to find in vitro parameters which best reproduce their in vivo chewing. Five parameters influencing mastication (mouth volume, quantity consumed, saliva volume, mastication time and number of tongue-palate compressions) were measured in 30 children (5-12 years old) and 30 adults (18-65 years old) and compared between the two populations. They were then transposed to a masticator (Oniris device patent). The initial cheese, a homogeneous white paste, was surface-colored to investigate its in-mouth destructuring. In vivo boli were collected at three chewing stages (33, 66 and 99% of mastication time) and in vitro boli were obtained by varying the number of tongue-palate compressions and the rotation speed. In vivo and in vitro boli were compared by both image and texture analysis. Child masticatory parameters were proportionally smaller than those of adults. The in vivo child boli were less homogeneous and harder than adult ones. Comparison of in vivo and in vitro bolus color and texture enabled the successful determination of two in vitro settings that closely represented the mastication of the two populations studied.
PubMed: 38731689
DOI: 10.3390/foods13091318