Palatal Coverage Research Articles

Assessment of the unwanted tooth movement associated with an extended maxillary fixed retainer (3D analysis)

BackgroundPosttreatment changes after orthodontic treatment are challenging. One of the main reasons for such a phenomenon is the lack of patient compliance with removable retainers especially in the maxillary arch, due to palatal coverage, deterioration of speech, decreased masticatory efficiency, and loss of retainers. Fixed retainers have been introduced to overcome patient compliance and provide longer stable results. However, teeth still show movements when a six-unit fixed retainer is in place. Thus, in this study, an eight-unit fixed retainer was evaluated in an attempt to eliminate unwanted movements.The aim of this researchwas to assess short-term positional changes associated with an eight-unit extended maxillary fixed retainer.Materials and methodsA single-arm clinical trial was conducted to address the aim of the study. This research was approved by the institutional review board of the Faculty of Dentistry, Alexandria University (IORG:0008839, No-0479–8/2022). The registration date of this study was 5/06/2023. Twenty-eight patients (19.8 ± 4.5 years) who had finished the active orthodontic phase and started retention had an eight-unit extended maxillary fixed retainer that was bonded to the palatal surface of the maxillary incisors, canines, and the first premolars or the second premolars. Pre-retention and one-year post-retention intra-oral scans were made to produce STL files that were superimposed to determine the amount of tooth change. Additionally, analysis of digital casts and lateral cephalometric radiographs was performed.ResultsStatistically significant changes in all planes and the rotation of teeth after one year of retention were found. The upper right lateral incisor exhibited the most evident change in the vertical plane, while the upper right central incisor exhibited the greatest change overall. Minimal changes in the cast measurements were observed. Lateral cephalometric measurements showed minimal changes after one year of retention, and these changes were not statistically significant except in the interincisal angle and the angle between the upper incisor and the line connecting the A-point to the pogonion.ConclusionIncreasing the extension of maxillary fixed retainers did not eliminate unwanted tooth movement in the first year of retention.

The effects of custom‐made mouthguard design on physiological parameters and players' perception in rugby union

AbstractSome sports participants are often reluctant to wear a mouthguard due to issues with comfort, breathing and communication. However, there is limited evidence that investigates the use of custom‐made mouthguards and variations in design as key factors to minimise these issues. Therefore, the aim of this study was to examine the effect of custom‐made mouthguard design on cardiopulmonary function, exercise performance and perception of comfort in rugby union players. Fourteen rugby players (aged 20.2 ± 1.19 years) were recruited to undertake a rugby‐specific exercise protocol on a treadmill over four conditions (no mouthguard and three custom‐made mouthguard designs). Cardiopulmonary responses were assessed using breath‐by‐breath analysis, in conjunction with blood lactate (BLa) and rating of perceived exertion (RPE). Maximum oxygen uptake (VO2max) was assessed before and after the study to identify any changes in players' level of performance. Participants scored each mouthguard in relation to preference, comfort, breathing, protection and retention. There were no differences in oxygen uptake (p = 0.785, = 0.021), ventilation (p = 0.952, = 0.007), respiratory exchange ratio (p = 0.564, = 0.039) and heart rate (p = 0.830, = 0.017), whilst participants performed with the selected custom‐made mouthguards. However, RPE was higher without a mouthguard than whilst using two of the mouthguards during the first 3 min of exercise, in combination with higher BLa accumulation (p ≤ 0.05). Although there was no statistical difference between mouthguard designs in the ratings around comfort, there was a preference towards mouthguards with reduced palatal coverage. Individual preference in design may improve compliance of wearing a mouthguard without affecting physiological parameters.

CAD-CAM fabrication of semiprecision LOCATOR-style abutments to correct severely misaligned implants supporting a 4-implant maxillary overdenture

Implant-supported removable overdentures are a popular treatment option with a favorable impact on a patient’s quality of life. A maxillary removable overdenture without palatal coverage should be supported by at least 4 implants uniformly distributed around the arch and connected by either semiprecision attachments or a bar. Optimally these 4 implants should be parallel or have their long axes nearly aligned to facilitate the prosthodontic phase of treatment by allowing the use of standard components. A computer-aided design and computer-aided manufacturing (CAD-CAM) procedure to produce LOCATOR-style attachments (T-L Custom abutments; TruAbutment Inc) to manage the restoration of 4 misaligned implants is described.

Evaluation of Clinical Periodontal Parameters of Abutment Teeth Supporting Distal-Extension Base Removable Partial Dentures: A Cross-sectional Study.

To assess the clinical periodontal status of abutment teeth in regards of different design components of distal-extension removable partial dentures. Subjects (N=100) with acrylic or cobalt-chromium distal-extension removable partial dentures were enrolled and their periodontal parameters plaque and gingival indices [PI, GI], probing depths [PD], clinical attachment loss [CAL] and a mobility index [MI] evaluated. Denture base type, major connector, occlusal rests position, design of direct retainers, retention, stability and denture wearing habits were further evaluated. Acrylic RPDs were associated with higher mean±SE PI [1.70±0.74], GI [1.76±0.55], PD scores [2.47±1.02 mm] and CAL values [4.46±2.11 mm] compared to CO-CR RPDs [p⟨0.05]. For abutments, the PI [1.6±0.83], GI [1.72±0.57], PD [2.32±1.03] and CAL [4.26±2.08] were higher than their non-abutments counterparts [p⟨0.05]. CAL scores were found to be significantly higher for mandibular abutments compared to maxillary ones [P=0.002]. The highest PI [1.83±1.10] and GI [2.00±0.00] scores were associated with lingual bars and horse-shoe connectors, respectively. Full palatal coverage and lingual plates were associated with the highest PD [2.80±0.48] and CAL [4.70±0.37] scores. Acrylic RPDs, type of major connector, wrought wire clasps and distal occlusal rests may be considered as risk factors for periodontal disease progression in distal-extension removable partial denture wearers.

Effect of Liquorice Candies on Remineralization of Initial Enamel Carious Lesion.

Glycyrrhiza glabra (G. glabra), known as liquorice root is one such herbal remedy that has been shown to have immense potential in the treatment of orofacial diseases. To evaluate the remineralizing potential of liquorice extract on initial enamel carious lesions. An in vitro and in vivo study was conducted, wherein the sound-extracted human premolars were sectioned longitudinally and into enamel blocks of size 4 × 4 mm. Enamel blocks were demineralized to produce artificial carious lesions. In vitro study, the demineralized enamel block was exposed to artificial saliva for 5 minutes and artificial saliva containing liquorice for 4 minutes 14 times in a sequential manner. An in vivo study was carried out on six volunteers aged between 6 and 12 years. The demineralized enamel block was inserted into the 5 × 5 mm window created on the full palatal coverage appliance. Patients were given commercially available liquorice candies (Ricola) to consume for 7 days twice daily. The remineralization potential of liquorice on demineralized enamel block was assessed using confocal microscopy analysis. Liquorice extract containing candies showed visual remineralization of the demineralized area on the enamel surface through confocal images. Liquorice extract possesses remineralizing potential with its other medicinal properties. . Pooja HR, Nagar P, Mascarenhas AN, et al. Effect of Liquorice Candies on Remineralization of Initial Enamel Carious Lesion. Int J Clin Pediatr Dent 2023;16(S-1):S33-S38.

Biomechanical Analysis of Palateless Splinted and Unsplinted Maxillary Implant-Supported Overdentures: A Three-Dimensional Finite Element Analysis.

The objective of this study was to compare the distribution of stress in the maxillary bone, dental implants, and prosthetic components supporting implant-supported maxillary overdentures with partial palatal coverage, in both splinted and unsplinted designs. Two models of maxillary overdentures were designed using the Exocad Dental CAD program, which included cancellous and cortical bone. The complete denture design and abutments (locator abutments in the unsplinted and Hader bar with Vertix attachments placed distally in the splinted variant) were also designed. The denture material was PEEK (Polyetheretherketone), and the method used to analyze patient-specific 3D X-ray scans was 3D QCT/FEA (three-dimensional quantitative computed tomography-based finite element analysis). Loading was divided into three load cases, in the frontal region (both incisors of the denture) and distal region (both molars and first premolar of the denture). The forces applied were 150 N with an oblique component with a buccal inclination of 35° in the frontal region, and 600 N with a buccal inclination of 5° (molars) or solely vertical (premolar) in the distal region. The model with locator abutments showed higher stresses in all load cases in both analyzed implant variants and in the maxilla. The differences in stress distribution between the splinted and unsplinted variants were more significant in the distal region. According to the results of the present study, the amount of stress in bone tissue and dental implant parts was smaller in the splinted, bar-retained variant. The findings of this study can be useful in selecting the appropriate prosthetic design for implant-supported maxillary overdentures with partial palatal coverage.

Effects of tongue lesions and palatal coverage on oral sensory functions

Statement of problemOral stereognosis (OS) plays a significant role in the oral rehabilitation of patients with edentulism, as it influences their adaptation to new prostheses. Because of the essentially tactile characteristic of oral sensory perception, the tongue and palate appear to have a crucial function in OS. However, little is known about the influence of tongue lesions on OS and sensorial function. In addition, controversies remain regarding the role of the palate. PurposeThe purpose of this clinical study was to evaluate whether tongue lesions and palatal coverage are disruptive to OS and gustatory function. Material and methodsSeventy participants (mean age=30.7 ±6.7 years) were divided into a tongue lesion group (experimental; n=35) and a control group (n=35). The tongue lesion group included participants with geographic, fissured, or hairy tongue. OS was evaluated with the oral stereognosis ability (OSA) test. Gustatory function was assessed with exposure to flavored solutions. After completing the above tests, the participants received a palate covering device, and then OS and gustatory function were immediately reevaluated. Data were analyzed with the Mann-Whitney and Wilcoxon tests (α=.05). ResultsOSA and gustatory function scores did not differ among the tongue lesion and control groups with and without palatal coverage (all P>.05). After palatal coverage, the tongue lesion group took more time to perform the OSA test than the control group (P<.05). ConclusionsNeither the presence of tongue lesions nor palatal coverage influenced OS or gustatory function. The OSA test response times were longer for the tongue lesion group after they had received palatal coverage.

Clear aligner orthodontic force and conformity during lateral expansion

ABSTRACT Purpose: This study aimed to find the clear aligner form which buccal tipping is less likely to occur by experimentally comparing the marginal type of the aligners with the orthodontic force and conformity (flotation) on the first molars during lateral expansion. Materials and methods: Four different marginal types (conventional aligners with no palatal coverage, partial palatal coverage [with or without 2.0 mm buccal extension], and complete palatal coverage) and three levels of lateral expansion (no expansion, 0.25-mm expansion, and 0.50-mm expansion) were used. The force applied to the first molar was measured by attaching a pressure sensor to the palatal side of the left first molar on a modelled maxillary constricted dental arch. The conformity (flotation) was measured by micro-CT with each aligner attached to the model. Results: Conventional aligners showed no significant difference in force at 0.25-mm or 0.50-mm expansion, but significant flotation at the midpoint and cervical side. The force of all three types of palatal coverage aligners increased significantly (p < 0.01) with increasing expansion and showed less flotation (p < 0.01) compared to the conventional type. Complete palatal coverage aligners had little flotation at 0.25-mm expansion and no expansion. Conclusion: Conventional aligners should have greater buccal tipping of the molars due to increased flotation with expansion. Complete palatal coverage aligners with 0.25-mm expansion had the best conformity, suggesting that they may prevent unplanned buccal tipping of the molars and allow lateral expansion to occur as intended.

EPG research and therapy: further developments

ABSTRACT Electropalatography (EPG) has been used in the past 50 years for studying the patterns of contact between the tongue and the palate during speech production in typical speakers and those with speech disorders due to different causes. At the 7th EPG Symposium in Japan that was held online on 24 January 2021 (see: https://epg-research.sakura.ne.jp/), a panel of invited experts discussed their views regarding further developments and application of the technique. This paper provides a summary of this discussion. EPG offers information on articulation which cannot be replaced by other instrumental measures of speech. Identified areas for further hardware development are thinner EPG plates, better dental and palatal coverage, wireless connectivity, and sensors that provide additional articulatory information (e.g. tongue pressure, tongue-palate distance). EPG can serve as a resource for teaching speech disorders and phonetics. Furthermore, EPG therapy can be combined with telepractice in the speech therapy of clients with speech disorders.

Comparison of the effects of implant locations and overdenture designs on the implants and bone stress: a finite element analysis

Objective The effects of implant locations and prosthesis design (palate less, full palate) on stress values of the implant and bone in maxillary overdenture prostheses were examined and compared with finite element analysis. Material and Methods Full palate and palate less four implant supported finite element overdenture models have created with different implant locations (M1: bilateral lateral 1. premolar, M2: canine 2. premolar, M3: 1. premolar 1. Molar). Static loads have applied with food stuff method on 1. Molar region. Von mises stress on implants and implant parts, maximum and minimum principal stress generated in peri-implant bone have calculated with finite element analysis method (FEA). Results As a result, it was observed that the palate less design creates more stress on the implants and bone compared to the full palate design. In addition, stress formation was observed to be higher in models with implant positions are posterior. Conclusion In implant supported overdentures (ISO), palatal coverage ensures more balanced distribution of stresses occurring around the implants and implant parts, regardless of the location of the supporting implants.

The performance of two-implant overdentures in the atrophic maxilla: a case series with 1-year follow-up

To assess the implant and prosthesis survival rates, the clinical, radiographical and patient-related outcome measures, and the masticatory performance of maxillary overdentures supported by two implants in patients with an atrophic maxilla. In this case series, 15 consecutive patients who were eligible for maxillary implant overdenture therapy, but who had insufficient bone volume to place at least four implants and were unwilling to be treated with reconstructive surgery were asked to participate. After giving consent, participants received two implants in the maxilla under local anaesthesia. After 3 months of osseointegration, a maxillary overdenture with palatal coverage and solitary attachments was fabricated. Implant and overdenture survival, marginal bone level change, clinical outcome measures, masticatory performance and patient-related outcomes were evaluated at baseline and 1 year after overdenture placement. Fourteen out of 15 participants completed the follow-up period of 12months. Implant and overdenture survival rate were 89.3% and 85.7%, respectively. Change in marginal bone level (-0.5 ± 0.7mm), change in probing depth (0.0 ± 1.0mm), and clinical outcomes were favourable. Masticatory performance and patient-related outcomes improved significantly compared to baseline. Complications were minimal. Within the limitations of this study, it can be concluded that patients with extreme resorption of the maxilla that are unwilling to be treated with reconstructive surgery, benefit from two-implant maxillary overdentures retained by solitary attachments in terms of improved masticatory functioning and denture satisfaction. However, they have relatively high risk of implant loss. UMCG Trial Register (RR201900060), registered 22 January 2019.

Maxillary overdenture on three implants retained by low-profile stud attachments - A prospective cohort study.

Clinical data are needed on long-term outcomes of removable implant-supported prostheses in the fully edentulous maxilla as a function of the number of implants, effects of the attachment system and other clinical variables. To restore individuals with an edentate maxilla with a metal-reinforced removable prosthesis without palatal coverage retained by low-profile stud attachments on three implants. The regional ethics committee approved a prospective cohort study that included all consecutive patients treated in a private speciality clinic. Primary outcomes were patients reported, that is denture satisfaction scale and oral health-related quality of life - OHIP-20. Secondary outcomes were implant- (bone loss, implant complications and peri-implant conditions) and prosthesis-related (prosthesis complications, maintenance needs and mucosa condition). Thirty-two study participants were recruited between March 2007 and October 2016 and followed for a minimum of five years. According to Kruskal-Wallis tests, the OHIP-20 and Denture Satisfaction Scale questionnaire pre-treatment scores differed significantly. After an average of 6.7 years, peri-implant bone loss of more than 2 mm was observed on 17% of all implants, while no or minor bone loss was seen on 38%. The estimated success of implants was 0.95 at 168 months. The estimated success of the prosthesis, that is no adverse events or need for any repairs, was 0.55 at 156 months. The positive findings in the current clinical study strengthen the notion that for many individuals with an edentulous maxilla, a removable prosthesis retained by three implants fitted with low-profile stud-attachment is a reliable technical solution.

Flangeless horseshoe maxillary complete denture: a prosthodontic solution to maxillary tori

Tori may present difficulties in achieving a retentive prosthesis with full palatal coverage. Management of tori in such cases may involve attempting to avoid coverage of the torus, providing relief over the torus, or surgical reduction/removal. This article presents a case where a patient who presented with a large maxillary torus was managed with a non-surgical approach, which enabled provision of a successful prosthesis. Dental practitioners could consider this approach for selected cases. CPD/Clinical Relevance: Thorough prior planning and a modified denture design can be used to provide an effective clinical solution for maxillary and mandibular tori.

A two-year comparative assessment of retention of arch width increases between modified vacuum-formed and Hawley retainers: a multi-center randomized clinical trial

ObjectivesTo compare the clinical effectiveness of Hawley retainers (HRs) and modified vacuum-formed retainers (mVFRs) with palatal coverage in maintaining transverse expansion throughout a 24-month retention period and to assess the subjects’ perception toward the retainers.Materials and methodsThe trial accomplished blinding only by the outcome assessor and data analyst. Data were collected from post-orthodontic treatment patients who met the inclusion criteria. Thirty-five subjects were randomly allocated using a centralized randomization technique into either mVFR (n = 18) or HR group (n = 17). Dental casts of subjects were evaluated at debond (T0), 3-month (T1), 6-month (T2), 12-month (T3), and 24-month retention (T4). The intercanine width (ICW), interpremolar width (IPMW), interfirst molar mesiobuccal cusp width (IFMW1), and interfirst molar distobuccal cusp width (IFMW2) were compared between groups over time using Mixed ANOVA. A pilot-tested and validated questionnaire consisting of six items were given at T4. Subjects were instructed to rate their retainer in terms of fitting, speech, appearance, oral hygiene, durability, and comfort on a 100-mm Visual Analogue Scale (VAS).ResultsNo statistically significant differences in arch width were found between the two groups at ICW (P = .83), IPMW (P = 0.63), IFMW1 (P = .22), and IFMW2 (P = .46) during the 24-month retention period. Also, no statistically significant differences were found between perception of both retainers in terms of fitting, speech, oral hygiene, durability, and comfort (P > .05) after 24-month wear. The appearance of mVFRs was rated significantly higher compared to HRs (P < .05).ConclusionsHR and mVFR have similar clinical effectiveness for retention of transverse expansion cases in a 24-month retention period. Both retainers were perceived to be equal in terms of fitting, speech, oral hygiene, durability, and comfort. Subjects in the mVFRs group found their retainers to be significantly more esthetic than those in HRs group.

Revisiting maxillary implant overdentures in 2022: A topic review

The challenge for general dental practitioners to provide maxillary implant overdenture treatment for their patients is complicated by multiple, diverse parameters, compared to mandibular implant overdentures. This topic review on maxillary implant overdentures takes into consideration the specifications and challenges of different prosthodontic treatment options for clinicians in 2022. A broad search of the published literature was performed using MEDLINE and PubMed to identify pertinent articles published in English from 1990 to 2021. From an original total of 1176 titles, 106 references were selected. They were reviewed and categorized with respect to seven factors related to the prosthodontic design. These were interarch restorative space, implant number, implant distribution and spread, overdenture base reinforcement, palatal coverage, selection of attachment system and splinted/unsplinted prosthodontic designs. They influence clinical and patient outcomes in terms of implant and prosthesis success, support, retention, prosthodontic maintenance and satisfaction. Maxillary implant overdentures are a reliable treatment option for general dental practitioners, once competent with mandibular overdentures. The decision for adequate treatment for each individual patient is influenced by a diversity of parameters with clinicians needing to have a thorough knowledge and understanding of the anatomic obstacles, facial aesthetics, phonetics, and complete denture principles for essential pre-surgical and prosthodontic treatment planning. Currently there is no optimal number of implants, nor preferred attachment system, regardless of palatal coverage design. There are emerging trends of more evidence for use of reduced number of unsplinted implants simplifying procedures for general dental practice.

Pedicled buccal flaps as a backup procedure for intraoral reconstruction

BackgroundIntraoral soft tissue deficiency and impaired wound beds are common problems after cleft and tumour surgery or after dental trauma. Frequently, limited defects are overtreated with extensive microvascular reconstruction procedures, but pedicled flaps remain useful, as they are simple to harvest, and they provide a reliable outcome. The buccal flap, first described in the 1970s, has been used for palatine lengthening in cleft patients over decades. In the following, we present an expanded indication in cases of palatal fistula, complex vestibulum, exposed bone in orthognathic surgery, and osteoradionecrosis.MethodsWe conducted a retrospective chart review and report on all buccal flaps harvested in our department within the last 3 years with a follow-up period of at least half a year after flap surgery. Patients of all age groups and treatment indications in which a buccal flap was used were implicated in the evaluation.ResultsSixteen buccal flaps were performed in 10 patients. The median age at the time of surgery was 42 years, reaching from 12 up to 66 years. Fourteen buccal flaps were used for upper jaw or palatal coverage; two buccal flaps were used in the mandible. In terms of complications (four flaps; 25%), there were two partial flap failures, one wound dehiscence and one wound dehiscence. There were no failures of the remaining mucosal flap islands after pedicle dissection.ConclusionThe buccal flap is a reliable and straightforward approach to challenging intraoral wound beds with soft tissue deficiency. We thoroughly discuss the additional indications for buccal flap surgery, describe the harvest technique, and provide strategies to prevent intra- and postoperative complications.

One-year comparative assessment of retention of arch width increases between modified vacuum-formed and Hawley retainers.

To compare the clinical effectiveness of Hawley retainers (HRs) and modified vacuum-formed retainers (mVFRs) with palatal coverage in maintaining transverse expansion during a 12-month retention period. Data were collected from postorthodontic treatment patients who met the inclusion criteria. A total of 35 patients were randomly allocated using a centralized randomization technique into either mVFR (n = 18) or HR group (n = 17). The outcome assessor and data analyst were blinded to the retention method. Dental casts of patients were evaluated at debond, 3 months, 6 months, and 12 months of retention. Intercanine width (ICW), interpremolar width (IPMW), interfirst molar mesiobuccal cusp width 1 (IFMW1), and interfirst molar distobuccal cusp width 2 (IFMW2) were compared between groups over time using mixed analysis of variance. No statistically significant differences were found between the two groups for ICW (P = .76), IPMW (P = .63), IFMW1 (P = .16), and IFMW2 (P = .40) during the 12-month retention period. The null hypothesis could not be rejected. HR and mVFR had similar clinical effectiveness in the retention of transverse expansion cases during a 12-month retention period.

Four-implant-supported overdenture treatment in the maxilla. Part II: Speech- and oral health-related quality of life in patients with implant-supported overdentures in the maxilla-A prospective 3-year follow-up.

Implant-supported overdentures (IOD) are becoming a more commonly used treatment in the dental practice and it risks causing speech problems. The aim of this study was investigating the changes in speech, satisfaction with speech, and overall oral health-related quality of life (OHRQoL) in edentulous patients during and after treatment with maxillary IODs. Twenty-one patients receiving an IOD participated in speech assessment. They were examined preoperatively with their conventional denture (CD) with full palatal coverage, after connection of the implant-bar connected denture, without palatal coverage, and 3 years thereafter. The examination included assessment of articulation in speech, OHRQoL based on total OHIP-14, and satisfaction with overall oral health and speech (visual analogue scale). There was a reduction in mean number of articulation disorders from 1.00 at baseline to 0.55 at connection, although statistically insignificant (p=0.059). Especially the /s/ sound is vulnerable. At 3 years follow-up, still 6/16 (37.5%) of the patients suffered from this speech problem. Overall satisfaction improved from 64.05/100 at baseline to 82.95/100 at connection (p=0.008) and remained unchanged with 81.69/100 after 3 years follow-up. Patients' satisfaction with speech increased from 70.62/100 with CD to 82.63/100, 3 years follow-up (p=0.009). Total OHIP-14 decreased from 21.45/56 with CD to 8.00/56 (p < 0.001) with IOD and 6.13/56 3 years after connection (p=0.001). Significant improvement of all seven domains in OHRQoL was observed with IOD compared to CD. Patients treated with maxillary IODs show improved OHRQoL 3 years after connection of the IOD compared to the CD. Even though patients reported improvement of satisfaction and OHRQoL, articulation disorders were still present, suggesting that patients should be informed about possible speech issues.

Adaptive brain activity changes during tongue movement with palatal coverage from fMRI data

Successful adaptation to wearing dentures with palatal coverage may be associated with cortical activity changes related to tongue motor control. The purpose was to investigate the brain activity changes during tongue movement in response to a new oral environment. Twenty-eight fully dentate subjects (mean age: 28.6-years-old) who had no experience with removable dentures wore experimental palatal plates for 7 days. We measured tongue motor dexterity, difficulty with tongue movement, and brain activity using functional magnetic resonance imaging during tongue movement at pre-insertion (Day 0), as well as immediately (Day 1), 3 days (Day 3), and 7 days (Day 7) post-insertion. Difficulty with tongue movement was significantly higher on Day 1 than on Days 0, 3, and 7. In the subtraction analysis of brain activity across each day, activations in the angular gyrus and right precuneus on Day 1 were significantly higher than on Day 7. Tongue motor impairment induced activation of the angular gyrus, which was associated with monitoring of the tongue’s spatial information, as well as the activation of the precuneus, which was associated with constructing the tongue motor imagery. As the tongue regained the smoothness in its motor functions, the activation of the angular gyrus and precuneus decreased.

Fatigue behavior of endodontically treated maxillary premolars with MOD defects under different minimally invasive restorations.

To analyze the stress distribution and subsequent fracture resistance of human maxillary premolars with mesial-occlusal-distal (MOD) defects restored with different minimally invasive restorations. Seventy non-carious human maxillary premolars were selected and divided into seven groups (n = 10). Ten teeth without further preparation served as control. The remaining teeth were endodontically treated and received three restorative patterns: inlays without cusp coverage (I), onlays with palatal coverage (O), overlays with both buccal and palatal coverage (Ov). Lithium disilicate glass ceramics (EM) and machinable composite resin (LU) were used for restoration. Specimens were tested under cycling loading with tongue direction of 45° for 1.2 × 106 cycles at a 50-N load and 2.0-Hz frequency. The survival time and two fracture mode classifications were assessed. Three-dimensional models of each group were designed. The magnitude and pattern of stresses were analyzed under the same condition of the in vitro test using finite element stress analysis. Although the overlay model pattern produced more favorable stress distribution, three restorative patterns restored with the same material had no difference in survival curves (P > 0.05). Only the survival curve of the EM-Ov group had no statistical difference with that of the control group (P > 0.05). EM groups presented mainly interface adhesive failure, while LU groups were mainly material cohesive failure. For the endodontically treated maxillary premolars with MOD defect, the lithium disilicate glass ceramic overlay pattern can reach the best restorative effect. Comparing with restorative pattern, restorative material had a greater influence on the minimally invasive restoration of posterior teeth.