Validation of a double-semicircular notched configuration for mechanical testing of orthodontic thermoplastic aligner materials

The potential of using specimens with a double-semicircular-notched configuration for performing tensile tests of orthodontic thermoplastic aligner materials was explored. Unnotched and double-semicircular-notched specimens were loaded in tension using a universal testing machine to determine their tensile strength, while finite element analysis (FEA) and digital image correlation (DIC) were used to estimate stress and strain, respectively. The shape did affect the tensile strength, demonstrating the importance of unifying the form of the specimen. During the elastic phase under tension, double-semicircular-notched specimens showed similar behavior to unnotched specimens. However, great variance was observed in the strain patterns of the unnotched specimens, which exhibited greater chance of end-failure, while the strain patterns of the double-semicircular-notched specimens showed uniformity. Considerable agreement between the theoretical (FEA) and practical models (DIC) further confirmed the validity of the double-semicircular-notched models.

The use of CBCT in orthodontics with special focus on upper airway analysis in patients with sleep-disordered breathing

Applications of cone-beam CT (CBCT) in orthodontics have been increasingly discussed and evaluated in science and practice over the last two decades. The present work provides a comprehensive summary of current consolidated practice guidelines, cutting-edge innovative applications, and future outlooks about potential use of CBCT in orthodontics with a special focus on upper airway analysis in patients with sleep-disordered breathing. The present scoping review reveals that clinical applications of CBCT in orthodontics are broadly supported by evidence for the diagnosis of dental anomalies, temporomandibular joint disorders, and craniofacial malformations. On the other hand, CBCT imaging for upper airway analysis-including soft tissue diagnosis and airway morphology-needs further validation in order to provide better understanding regarding which diagnostic questions it can be expected to answer. Internationally recognized guidelines for CBCT use in orthodontics are existent, and similar ones should be developed to provide clear indications about the appropriate use of CBCT for upper airway assessment, including a list of specific clinical questions justifying its prescription.

Prevalence of adenoid hypertrophy among 12-year-old children and its association with craniofacial characteristics: a cross-sectional study

BACKGROUND

Identifying the prevalence of adenoid hypertrophy (AH) and craniofacial factors associated with this condition requires studies with random sampling from the general population, and multiple criteria can be used for assessing AH on lateral cephalometric radiograph (LCR). The present analysis represents the first report performed according to these requirements in a large cross-sectional sample of children.

METHODS

LCRs of 517 12-year-old children (286 males, 231 females) randomly selected from the general population were retrospectively retrieved. AH was defined using three criteria (At/Nd, Ad-Ba/PNS-Ba, 1-Npaa/Npa), and twelve craniofacial variables were measured (SNA, SNB, ANB, Wits, Cd-Gn, MnP^SN, MxP^MnP, TPFH/TAFH, OPT^SN, C2ps-C4pi^SN, H-CV, H-FH). Skeletal characteristics were compared between children with and without AH using Mann-Whitney U test. Binary logistic regression (adjusted for sex and skeletal growth) was used to independently quantify the association between craniofacial factors and AH.

RESULTS

The prevalence of children with AH was 17.6% (according to At/Nd), 19.0% (according to Ad-Ba/PNS-Ba), and 13.9% (according to 1-Npaa/Npa). Children with AH presented greater antero-posterior jaw discrepancy (larger ANB, smaller SNB), greater mandibular divergence (larger MnP^SN), forward head posture (larger OPT^SN and C2ps-C4pi^SN), and anteriorly positioned hyoid bone (larger H-CV). Larger SNA (OR = 1.39-1.48), while smaller SNB (OR = 0.77-0.88) and Wits (OR = 0.85-0.87), were associated with greater likelihood of having AH, independently from the assessment method used.

CONCLUSIONS

The prevalence of children with AH ranged from 13.9 to 19.0% based on LCR. Greater antero-posterior maxillo-mandibular discrepancy and mandibular retrusion were independently associated with higher likelihood of having AH.

Are the severity of obstruction and the apnea-hypopnea index related to orofacial anatomy in children with obstructive sleep apnea? a kinetic MRI study

OBJECTIVES

The proportionality between anatomical characteristics and disease severity in children and adolescents with obstructive sleep apnea (OSA) has not been well characterized. The present study investigated the relationship between the dentoskeletal and oropharyngeal features of young patients with OSA and either the apnea-hypopnea index (AHI) or the amount of upper airway obstruction.

METHODS

MRI of 25 patients (8- to 18-year-old) with OSA (mean AHI = 4.3 events/h) was retrospectively analyzed. Sleep kinetic MRI (kMRI) was used to assess airway obstruction, and static MRI (sMRI) was used to assess dentoskeletal, soft tissue, and airway parameters. Factors related to AHI and obstruction severity were identified with multiple linear regression (significance level α = 0.05).

RESULTS

As evidenced by kMRI, circumferential obstruction was present in 44% of patients, while laterolateral and anteroposterior was present in 28%; as evidenced by kMRI, obstructions were retropalatal in 64% of cases and retroglossal in 36% (no nasopharyngeal obstructions); kMRI showed a higher prevalence of retroglossal obstructions compared to sMRI(p = 0.037); the main obstruction airway area was not related to AHI; the maxillary skeletal width was related to AHI (β = -0.512, p = 0.007) and obstruction severity (β = 0.625, p = 0.002); and the retropalatal width was related to AHI (β = -0.384, p = 0.024) and obstruction severity (β = 0.519, p = 0.006).

CONCLUSIONS

In children and adolescents, the severity of OSA and obstruction were inversely proportional to the maxillary basal width and retropalatal airway width. Further studies are needed to assess the benefits of targeted clinical treatments widening the transverse dimension of these structures.

Prevalence and Risk Factors for Obstructive Sleep Apnea Syndrome Among Children and Adolescents with Cleft lip and Palate: A Survey Study in Hong Kong

OBJECTIVE

To investigate the prevalence of obstructive sleep apnea syndrome (OSAS) risk and related risk factors among children and adolescents of Hong Kong with cleft lip and/or palate (CL/P).

DESIGN

Retrospective survey study adopting three questionnaires, obstructive sleep apnea-18 (OSA-18), pediatric sleep questionnaire-22 (PSQ-22), and modified Epworth Sleepiness Scale (ESS).

SETTINGS

Multicenter study in two public hospitals.

PATIENTS

A total of 351 Chinese children and adolescents with non-syndromic CL/P (6-18-year-old, 57% males) visited between September 2017 and November 2019, with primary palatal repair surgery done before 3-year-old.

MAIN OUTCOME MEASURE

Positive OSAS risk was determined based on cut-off ≥60 for OSA-18, ≥8 for PSQ-22, and >8 for ESS. Age, sex, overweight presence, cleft type, embryonic secondary palate involvement, palatal repair surgery, palatal revision surgery, and orthodontic treatment were analyzed as possible risk factors.

RESULTS

A total of 9.5% of patients had positive OSAS risk based on OSA-18, 13.6% based on PSQ-22, and 13.2% according to ESS. A higher prevalence of patients with positive OSAS risk was of younger age (OSA-18, p = .034), had cleft involving embryonic secondary palate (PSQ-22, p = .009), and history of fixed orthodontic treatment (ESS, p = .002). The regression model identified only involvement of embryonic secondary palate as a risk factor (PSQ-22, odds ratio = 3.7, p = .015).

CONCLUSIONS

OSAS risk among children and adolescents of Hong Kong with CL/P was 9.5% to 13.6%. Patients at higher risk were those with cleft involving embryonic secondary palate. OSAS risk assessment may be influenced by different aspects of the disease spectrum, and a multimodal approach should be considered for such assessment.

The influence of climate and population structure on East Asian skeletal morphology

Recent studies have shown that global variation in body proportions is more complex than previously thought as some traits formerly associated with climate adaptation are better explained by geographic proximity and neutral evolutionary forces. While the recent incorporation of quantitative genetic methodologies has improved understanding of patterns related to climate in Africa, Europe, and the Americas, Asia remains underrepresented in recent and historic studies of body form. As ecogeographic studies tend to focus on male morphology, potential sex differences in features influenced by climate remain largely unexplored. Skeletal measurements encompassing the dimensions of the skull, pelvis, limbs, hands, and feet were collected from male (n = 459) and female (n = 442) remains curated in 13 collections across seven countries in East Asia (n = 901). Osteological data were analyzed with sex and minimum temperature as covariates adjusted by autosomal single-nucleotide polymorphism population genetic distance using univariate Bayesian linear mixed models, and credible intervals were calculated for each trait. Analysis supports a relationship between specific traits and climate as well as providing the magnitude of response in both sexes. After accounting for genetic distance between populations, greater association between climate and morphology was found in postcranial traits, with the relationship between climate and the skull limited primarily to breadth measurements. Larger body size is associated with colder climates with most measurements increasing with decreased temperature. The same traits were not always associated with climate for males and females nor correlated with the same intensity for both sexes. The varied directional association with climate for different regions of the skeleton and between the sexes underscores the necessity of future ecogeographic research to holistically evaluate body form and to look for sex-specific patterns to better understand population responses to environmental stresses.

Minimally important differences in oral health-related quality of life after fixed orthodontic treatment: a prospective cohort study

Background

The minimally important difference (MID, the smallest difference that patients perceive as beneficial) has been proposed to assess whether study results are clinically meaningful, reducing the shortcoming of P-values-based approaches in the assessment of clinical outcomes. The post-treatment changes and the MID in Oral Health-Related Quality of Life (OHRQoL) among adults undergoing fixed orthodontic treatment were investigated.

Methods

Ninety-two patients (29.1 ± 6.3 years old, 18 males and 74 females) were prospectively included. Oral Health Impact Profile (OHIP-14) and United Kingdom Oral Health-related Quality of Life (OHQoL-UK) were used to assess OHRQoL at baseline and post-treatment (50.8 ± 15.7 months). Global Transition Rating (GTR) was used to assess oral health/well-being, Peer Assessment Review (PAR), and Index of Complexity, Outcome and Need (ICON) were used to assess occlusion. Wilcoxon signed-rank test was used to assess changes in OHRQoL and occlusion, Kruskal–Wallis one-way ANOVA and Mann–Whitney U-test were used to assess associations between OHRQoL and oral health/well-being or occlusion. MID for OHIP-14 and OHQoL-UK was estimated via anchor-based (PAR, ICON, GTR) and distribution-based approach (effect size, standardized response mean, standard error of measurement).

Results

The median OHIP-14 and OHQoL-UK post-treatment scores were significantly changed, indicating improved OHRQoL. Based on the agreement between different methods, the MID of OHIP-14 and OHQoL-UK were at least 15 and 6 scale points, corresponding to a large effect size (1.5–1.7).

Conclusions

Orthodontic treatment had a positive long-term impact on OHRQoL. MID for the OHIP-14 and OHQoL-UK provide guidance to interpreting the impact of orthodontic treatment on the OHRQoL of patients.

Clinical effects of different prescriptions on the inclination of maxillary and mandibular incisors by using passive self-ligating brackets

Objective

Controlling the incisal inclination is fundamental in orthodontics. However, the relationship between the inclination prescription and its clinical outcome is not obvious, and the incisal inclination changes generated by different bracket prescriptions were investigated.

Methods

Twenty-eight non-extraction dental Class II patients (15 females, 13 males; mean age = 12.9) were retrospectively analyzed. Patients were treated using passive self-ligating fixed appliances with three inclination prescriptions for maxillary incisors (high, standard, low), and two for mandibular incisors (standard, low). Clinical outcomes were compared among different prescriptions, and regression analysis was used to explain the effects of bracket prescriptions and to understand the prescription selection criteria (α = 0.05).

Results

For maxillary central incisors, low and high prescriptions were related to linguoversion (p = 0.046) and labioversion (p = 0.005), respectively, while standard prescription maintained the initial dental inclination. Maxillary lateral incisors did not show significant changes. For mandibular incisors, low prescription led to linguoversion (p = 0.005 for central incisors, p = 0.010 for lateral incisors), while standard prescription led to labioversion (p = 0.045 for central incisors, p = 0.005 for lateral incisors). The factors affecting inclination changes were the imposed change and selected prescription, while prescription selection was influenced by the initial dental inclination and initial intercanine distance.

Conclusions

The direction of correction of incisal inclination can be controlled by choosing a certain prescription, but the final inclination may show limited consistency with it. The amount of imposed inclination change was the most relevant predictor of the clinical outcome.

Remote digital monitoring during the retention phase of orthodontic treatment: A prospective feasibility study

Objective

To evaluate if a remote digital monitoring system added at the end of orthodontic treatment could positively influence the retention phase by reducing the occurrence of misfit of removable appliances, number of emergency appointments (EA), and orthodontic relapse.

Methods

Twenty-seven patients who completed active orthodontic treatment were divided into the study and control groups. In addition to the standard chairside follow-up appointments at month 1 (T1), month 3 (T2), month 6 (T3), the study group patients were monitored using Dental Monitoring^® with monthly intra-oral scans. Occurrence of misfit of removable retainers, number of EAs, and intercanine width change were recorded for both groups. Differences in EAs and retainer fit were assessed using the chi-square test. Intra-group and inter-group differences in the intercanine width were assessed with Friedman test and Mann–Whitney U test, respectively (α = 0.05).

Results

The study group showed a significantly lower occurrence of misfit of removable retainers (p = 0.027) compared to the control group. No significant inter- and intra-group difference was found in the EAs and intercanine width change at each time-point.

Conclusions

Integrating remote monitoring systems, such as Dental Monitoring^®, to the retention phase of the orthodontic treatment may lower the occurrence of misfit of removable retainers. However, a small sample size and a short observation period limit the strength of this evidence. These preliminary results tentatively suggest that remote monitoring technologies may be beneficial, especially during the COVID-19 pandemic, when the regularity of in-office visits might be disrupted.

Midpalatal suture maturation staging using cone beam computed tomography in patients aged between 9 to 21 years

Midpalatal suture was analysed with cone beam computed tomography to identify its maturation with respect to age and maxillary-complex growth in 72 patients 9- to 21-year-old. Maxillary-complex was divided in premaxillary, maxillary, and palatine segment. Interdigitation and ossification of midpalatal suture, its density relative to hard tissues and soft tissues, and midpalatal suture density ratio were measured for each segment. Correlation of each parameter with age and maxillary-complex length was analysed, and classification trees were developed for staging parameters. Midpalatal suture maturation stages (MPSMS, from A to E) were applied to assess relationship with age and maxillary-complex length. Regarding age, ossification increased in maxillary segment of males (r_S = 0.39, p = 0.032), while suture density relative to soft tissues increased in maxillary (r_S = 0.37, p = 0.042) and palatine segments (r_S = 0.41, p = 0.027) of males and in palatine segment of females (r_S = 0.32, p = 0.041). In males, suture density relative to soft tissues discriminated two age-stages (p = 0.024), and the same parameter (p = 0.023) paired with ossification (p = 0.027) discriminated two length-stages. MPSMS identified length-differences between stage A and B in females (p = 0.001). Midpalatal-suture ossification and its density relative to soft tissues showed some relationship with age and maxillary-complex length, especially in males. However, challenging staging and limitations in the imaging method may limit clinical applications.

Appropriateness of standard cephalometric norms for the assessment of dentofacial characteristics in patients with cleidocranial dysplasia

OBJECTIVES

Cleidocranial dysplasia (CCD) is a rare skeletal syndrome affecting craniofacial and dental development. As a consequence, conventional cephalometric landmarks may not be valid for CCD patients, and the appropriateness of norms used for the general population should be critically discussed.

METHODS

Five patients 9- to 22-year-old (three females, two males) with CCD were included. Lateral-cephalograms, orthopantomographies, and intra-oral photos were retrospectively analysed. Lateral-cephalograms of 50 normal controls (ten for each CCD patient) matched for age and sex were selected from an online database. Cephalometric measurements of each CCD patients were compared with average values of matched controls using Wilcoxon signed-rank test for paired values (α = 0.05).

RESULTS

In CCD patients, a shortening of the cranial base was present (ΔSN = -17.1 mm, p = 0.043). Thus, the mandible (ΔSNPg = +9.5°, p = 0.043) and the maxilla (ΔSNA = +11.2°, p = 0.043) showed protrusion compared to the cranial base, despite a reduced maxillary (ΔCo-A = -15.1 mm, p = 0.043) and mandibular (ΔCo-Gn = -15.2 mm, p = 0.080) length. The mandibular divergence was reduced (ΔSN/GoGn = -6.4°, p = 0.043), a reduced overbite was present (ΔOverbite = -2.9 mm, p = 0.043), and the interincisal angle was increased (ΔInterincisalAngle = +13.7°, p = 0.043), mainly due to retro-inclination of lower incisors.

CONCLUSIONS

Standard cephalometric norms for the assessment of horizontal jaw position may not be applicable to CCD patients because of a reduced anterior cranial base length compared to normal subjects. Vertical relationships may not be affected, and mandibular hypodivergency was confirmed.

Treatment of ankylosed deciduous molars with or without permanent successors in children and adolescents: a systematic review

INTRODUCTION

The aim of this systematic review was to provide guidelines for decision-making during orthodontic treatment planning of infra-occluded deciduous molars with or without their successors in children and adolescents.

EVIDENCE ACQUISITION

Computerized search was conducted on Medline via PubMed, and Cochrane Library. Articles published until 2020 in English language were analyzed following the Preferred Reporting Items for Systematic Reviews (PRISMA) Checklist. Observational and interventional longitudinal studies reporting the treatment of ankylosed deciduous molars with or without successor tooth in 3 to 15-year-old patients were included.

EVIDENCE SYNTHESIS

In case of ankylosis with presence of successor, exfoliation took place in 77% of teeth, while extraction involved 23%. Infra-occlusion happened in 53% of teeth (worsening in 52%), alveolar bone loss in 37%, mesial tipping of first permanent molar in 5%, and over-eruption of antagonist in no cases (after exfoliation and eruption of successor). In case of ankylosis without successor, exfoliation took place in 1% of teeth, progression of infra-occlusion in 42%, progression of root resorption in 58%, development of mesial tipping of first permanent molars in 25%, while no case of antagonist over-eruption was reported.

CONCLUSIONS

When the permanent tooth is present and the ankylosed tooth is slightly or moderately infra-occluded, observation is appropriate. In case of severe infra-occlusion or absence of successor, tooth extraction may be considered together with orthodontic space closure, transplantation, or prosthetic replacement. Alternatively, nonextraction and a prosthetic build-up may be considered.

Proposed parameters of optimal central incisor positioning in orthodontic treatment planning: A systematic review

OBJECTIVE

Planning of incisal position is crucial for optimal orthodontic treatment outcomes due to its consequences on facial esthetics and occlusion. A systematic summary of the proposed parameters is presented.

METHODS

Studies on Google Scholar©, PubMed©, and Cochrane Library, providing quantitative information on optimal central incisor position were included.

RESULTS

Upper incisors supero-inferior position (4-5 mm to upper lip, 67-73 mm to axial plane through pupils), antero-posterior position (3-4 mm to Nasion-A, 3-6 mm to A-Pogonion, 9-12 mm to true vertical line, 5 mm to A-projection, 9-10 mm to coronal plane through pupils), bucco-lingual angulation (4-7° to occlusal plane perpendicular on models, 20-22° to Nasion-A, 57-58° to upper occlusal plane, 16-20° to coronal plane through pupils, 108-110° to anterior-posterior nasal spine), mesio-distal angulation (5° to occlusal plane perpendicular on models). Lower incisors supero-inferior position (41-48 mm to soft-tissue mandibular plane), antero-posterior position (3-4 mm to Nasion-B, 1-3 mm to A-Pogonion, 12-15 mm to true vertical line, 6-8 mm to coronal plane through pupils), bucco-lingual angulation (1-4° to occlusal plane perpendicular on models, 87-94° to mandibular plane, 68° to Frankfurt plane, 22-25° to Nasion-B, 105° to occlusal plane, 64° to lower occlusal plane, 21° to A-Pogonion), mesio-distal angulation (2° to occlusal plane perpendicular on models).

CONCLUSIONS

Although these findings can provide clinical guideline, they derive from heterogeneous studies in terms of subject characteristics and reference methods. Therefore, the optimal incisal position remains debatable.

Accuracy of CBCT in the Identification of Mental, Lingual, and Retromolar Foramina: A Comparison with Visual Inspection of Human Dry Mandibles

The present dry-mandible study evaluated the presence of the mental (MF), lingual (LF), and retromolar (RMF) foramina to assess the accuracy of CBCT in detecting these anatomical structures. In total, 38 human dry mandibles were analyzed (30 men, 8 women; mean age: 61.9 ± 13.7 years). CBCT scans were taken using low-dose parameters, and LF, MF, and RMF were assessed visually and radiographically. Both the presence (yes/no) and the count (n) of each foramen were compared between CBCTs and visual assessment. For the presence assessment, only RMF exhibited a significant difference between CBCT and visual inspection (P = .035). For count, the RMF (P = .049) and paramedian LF (P = .003) exhibited differences between the two methods. The agreement between CBCT and visual inspection was excellent for the MF, moderate-excellent for the LF, and low-moderate for the RMF. Intra- and interassessor agreement varied from excellent (MF), to moderate-excellent (LF), and low-moderate (RMF). The LF and RMF represent challenging structures to identify on CBCT images due to their limited dimension. False negative findings in CBCTs in the assessment of foramina, especially LF, might lead to surgical complications during implant surgery.

Validation of a numerical model for the mechanical behavior of a continuous positive airway pressure mask

Finite Element models (FEM) are developed for the analysis of the contact pressures exerted by a Continuous Positive Airway Pressure (CPAP) mask applied to a dummy head. This is seen as a preliminary step in the analysis of the mechanical effects of CPAP masks applied to human faces, such as recently employed for the care of COVID-19 patients, or other purposes. These mechanical effects can range from negligible, in the case of correct positioning, sufficiently light tension in the headgear, correct mask design, etc., to the possible development of device-related pressure ulcers and/or dentofacial deformations, especially in children. The results of Finite Element analyses are compared, for their validation, with experimental ones. The numerical analysis tool appears able to predict, at an acceptable cost, both the intensity and the area distribution of the contact pressures, as well as the force-displacement relationship occurring in the headgear. This might help the design and the production of more effective and tolerable CPAP masks.

Effects of remote digital monitoring on oral hygiene of orthodontic patients: a prospective study

Background

Remote digital monitoring during orthodontic treatment can help patients in improving their oral hygiene performance and reducing the number of appointments due to emergency reasons, especially in time of COVID-19 pandemic where non-urgent appointments might be discouraged.

Methods

Thirty patients scheduled to start an orthodontic treatment were divided into two groups of fifteen. Compared to controls, study group patients were provided with scan box and cheek retractor (Dental Monitoring®) and were instructed to take monthly intra-oral scans. Plaque Index (PI), Gingival Index (GI), and White Spot Lesions (WSL) were recorded for both groups at baseline (t₀), every month for the first 3 months (t₁, t₂, t₃), and at 6 months (t₄). Carious Lesions Onset (CLO) and Emergency Appointments (EA) were also recorded during the observation period. Inter-group differences were assessed with Student's t test and Chi-square test, intra-group differences were assessed with Cochran’s Q-test (significance α = 0.05).

Results

Study group patients showed a significant improvement in plaque control at t₃ (p = 0.010) and t₄ (p = 0.039), compared to control group. No significant difference was observed in the number of WSL between the two groups. No cavities were detected in the study group, while five CLO were diagnosed in the control group (p = 0.049). A decreased number of EA was observed in the study group, but the difference was not significant.

Conclusions

Integration of a remote monitoring system during orthodontic treatment was effective in improving plaque control and reducing carious lesions onset. The present findings encourage orthodontists to consider this technology to help maintaining optimal oral health of patients, especially in times of health emergency crisis.

The Human Bone Collection of the Faculty of Dentistry at the University of Hong Kong: History and description of cranial and postcranial skeletal remains

OBJECTIVES

The present work describes the status and contents of The Human Bone Collection of the Faculty of Dentistry at the University of Hong Kong.

MATERIALS AND METHODS

The Collection originates from the 1980s and became officially established in 2017 for teaching and research purposes. Most of the Collection consists of unclaimed human remains of southern Chinese individuals exhumed from local cemeteries and donated to the Faculty in the last few decades. The demographic information was provided largely from burial records and forensic estimations. Since 2016, the Collection has undergone a process of reorganization into cranial and postcranial remains, followed by preservation procedures that included cleaning and classification.

RESULTS

The Collection currently consists of remains belonging to about 368 individuals (243 males, 54 females, 71 unknown), with ages ranging from 0.8 to 90 years (mean 57.4 years). It comprises cranial remains belonging to 260 individuals (169 males, 39 females, 52 unknown), and postcranial remains belonging to 248 individuals (180 males, 42 females, 26 unknown). The preservation status ranges from poor to good, with the cranial remains better preserved than the postcranial elements. For a large number of individuals, ear ossicles, soil samples, and other materials are also available.

DISCUSSION

The Collection is accessible to local and international institutions for teaching and research.

Anteroposterior length of the maxillary complex and its relationship with the anterior cranial base

OBJECTIVES

To use both absolute anteroposterior maxillary complex length (APMCL) and relative APMCL to investigate the relationship between the maxillary complex, its individual bony segments, and their association to the anterior cranial base. In addition, the relationship between length and position of the maxillary complex was analyzed.

MATERIALS AND METHODS

Sixty human skulls were analyzed using cone beam computed tomography. The maxillary complex length was measured between anterior and posterior nasal spine (ans-pns), and the average was used as the cut-off to identify a high- and a low-length group based on absolute APMCL. The length ratio between the maxillary complex and the anterior cranial base (ans-pns/SN) was used to identify the two groups based on relative APMCL. The anterior cranial base length and the lengths of the maxillary complex bones were compared between the high- and low-length groups.

RESULTS

Based on absolute APMCL, individuals with shorter maxillary complex had shorter anterior cranial base (P = .003), representing normal proportions. Based on relative APMCL, individuals with shorter maxillary complex had longer anterior cranial base and vice versa (P = .014), indicating disproportions. Individuals with shorter maxillary complex exhibited shorter maxilla (Δ = -1.5 mm, P = .014).

CONCLUSIONS

When skeletal deformity of the midface is suspected, individual disproportions in the anteroposterior length of the maxillary complex in relation to the anterior cranial base (relative measurements) should be assessed through radiological imaging. A shorter maxillary complex may be associated with a shorter maxilla, and not with a shorter premaxilla or palatine bone.

Dry Skulls and Cone Beam Computed Tomography (CBCT) for Teaching Orofacial Bone Anatomy to Undergraduate Dental Students

Learning bone anatomy of the skull is a complex topic involving three-dimensional information. The impact of the use of human dry skulls and cone beam computed tomography (CBCT) imaging was investigated in the teaching of undergraduate dental students. Sixty-four first-year students in the University of Hong Kong were randomly divided into eight groups. Four teaching methods were tested: (1) CBCT followed by standard lecture, (2) CBCT followed by lecture with skulls, (3) standard lecture followed by CBCT, and (4) lecture with skulls followed by CBCT. After each, students were given a multiple-choice questionnaire to assess their objective learning outcome (20 questions) and a questionnaire for their subjective satisfaction (10 statements). Surveys were assessed with Cronbach's alpha, Kendall's tau-b, and principal components analysis. Data were analyzed with Student's t-test and a one-way ANOVA (significance α = 0.05). Standard lecture followed by CBCT showed the highest learning outcome score (81.6% ± 14.1%), but no significant difference was present among four teaching methods. Cone beam computed tomography followed by lecture with skulls scored the highest overall subjective satisfaction (4.9 ± 0.8 out of 6), but no significant difference was present among teaching methods. Nevertheless, students' perception of learning was positively influenced by the use of skulls (P = 0.018). The timing of administration of the CBCT did not affect students' subjective satisfaction or objective learning outcome. Students perceived to learn more by using skulls, but their objective learning outcomes were not significantly affected. A discrepancy seems to exist between students' perception of learning and their effective performance.

Changes in the upper airway, hyoid bone and craniofacial morphology between patients treated with headgear activator and Herbst appliance: A retrospective study on lateral cephalometry

Background

The present study compared the treatment changes in the upper airway, hyoid bone position and craniofacial morphology between two groups of children with skeletal class II malocclusion treated with the headgear activator (HGA) and Herbst appliance (Herbst).

Setting and sample population

Orthodontic population from the Faculty of Dentistry of the University of Hong Kong.

Methods

Thirty‐four skeletal class II patients treated with the HGA (17 patients, mean age 10.6 ± 1.5 years) and the Herbst (17 patients, mean age 11.0 ± 1.4 years) were matched for sex, age, overjet, skeletal class and mandibular divergence. The patients received lateral cephalometric radiographs (LCRs) at the beginning of treatment (T₁), after treatment (T₂) and at follow‐up (T₃). In the HGA group, patients underwent LCRs 7 months before the beginning of treatment (T₀), which were used as growth reference for intra‐group comparison. Paired Student's t tests were used for intra‐ and inter‐group comparisons (α = .05).

Results

Treatment changes (T₂‐T₁) did not differ significantly between the groups. However, at follow‐up (T₃‐T₁) the Herbst group showed a smaller increase than the HGA group in the vertical position of the hyoid bone relative to the Frankfort plane (P = .013) and mandibular plane (P = .013).

Conclusions

There were no significant differences in the upper airway, hyoid bone position and craniofacial morphology between the groups at the end of treatment. However, the Herbst may provide better long‐term control of the vertical position of the hyoid bone than the HGA in children with skeletal class II malocclusion.

Reliability of lateral cephalometric radiographs in the assessment of the upper airway in children: A retrospective study

OBJECTIVES

To test the reliability of Lateral cephalometric radiographs (LCRs) for use in the assessment of the upper airway, hyoid bone, soft palate, and tongue.

MATERIALS AND METHODS

The records of 57 healthy Chinese children from a nonhospital population (mean age = 12.6 years, SD = 0.5, 28 males and 29 females) who received two consecutive LCRs in the natural head posture were retrospectively analyzed. Fifteen linear, angular, and area measurements were used to describe the airway, hyoid bone, soft palate, and tongue. The reliability between the two LCRs was assessed with the intraclass correlation coefficient (ICC) and F-test. Errors were estimated with the Dahlberg and Bland-Altman method, and intra- and inter-assessor agreements were determined.

RESULTS

Measurements of upper airway and hyoid bone had excellent method reliability, intra-assessor reliability, and inter-assessor reliability (ICC > 0.8). However, the method reliability and the inter-assessor reliability for soft palate and tongue was less favorable (ICC from 0.60 to 0.96). Soft palate area and thickness were the most critical parameters. Intra-assessor reliability was greater than both method reliability and inter-assessor reliability (which were similar).

CONCLUSIONS

The measurement of upper airway morphology, defined as the intramural space, and of the hyoid bone position were highly reliable on LCRs of children. However, the limited reliability in the assessment of tongue and soft palate area may compromise the diagnostic application of LCRs to these structures.

3D gelatin-chitosan hybrid hydrogels combined with human platelet lysate highly support human mesenchymal stem cell proliferation and osteogenic differentiation

Bone marrow and adipose tissue human mesenchymal stem cells were seeded in highly performing 3D gelatin–chitosan hybrid hydrogels of varying chitosan content in the presence of human platelet lysate and evaluated for their proliferation and osteogenic differentiation. Both bone marrow and adipose tissue human mesenchymal stem cells in gelatin–chitosan hybrid hydrogel 1 (chitosan content 8.1%) or gelatin–chitosan hybrid hydrogel 2 (chitosan 14.9%) showed high levels of viability (80%–90%), and their proliferation and osteogenic differentiation was significantly higher with human platelet lysate compared to fetal bovine serum, particularly in gelatin–chitosan hybrid hydrogel 1. Mineralization was detected early, after 21 days of culture, when human platelet lysate was used in the presence of osteogenic stimuli. Proteomic characterization of human platelet lysate highlighted 59 proteins mainly involved in functions related to cell adhesion, cellular repairing mechanisms, and regulation of cell differentiation. In conclusion, the combination of our gelatin–chitosan hybrid hydrogels with hPL represents a promising strategy for bone regenerative medicine using human mesenchymal stem cells.

In vitro evaluation of loop design influencing the sliding of orthodontic wires: A preliminary study

AIM

Resistance to sliding between bracket and wire is present, in a different magnitude, in most orthodontic treatments and it affects the biomechanics of the tooth movement. However, the influence of loop design on resistance to sliding is currently unknown.

METHODS

In total, 12 stainless steel orthodontic wires of different sizes (0.016″×0.022″; 0.017″×0.025″), loop height (6mm, 8mm, 10mm), and loop type (open, close) were analyzed. Wires were tied with elastic ligatures to a bracket and tested during sliding at 0.5 mm/min. Straight wires were used as controls. Differences in the force to start the sliding (N), force during the sliding (N), and displacement to start the sliding (mm), were evaluated with Kruskal-Wallis one-way analysis of variance and Mann-Whitney tests (α=0.05).

RESULTS

Open loops had a lower force to start the sliding compared to straight wires (p<0.05), and some closed loops showed a similar trend. Open loops had lower force during the sliding compared to straight wires, but closed loops were less predictable. Displacement to start the sliding increased with loop height, and differences were present between loops and straight wires (p<0.001). Force to start the sliding and force during the sliding changed relative to loop type (p<0.05), and closed loops showed higher resistance to sliding. Differences were also found in force to start the sliding and force during the sliding between wire sizes, with larger wires associated with higher forces (p<0.05).

CONCLUSIONS

Loops should be considered as significant variables in the resistance to sliding, as they can influence both the amount of force and the onset of sliding. Compared to straight wires, rectangular wires with open loops may help clinicians reduce resistance to sliding. Further studies are necessary to confirm these preliminary findings.

Resistance to sliding in orthodontics: misconception or method error? A systematic review and a proposal of a test protocol

Resistance to sliding (RS) between the bracket, wire, and ligature has been largely debated in orthodontics. Despite the extensive number of published studies, the lack of discussion of the methods used has led to little understanding of this phenomenon. The aim of this study was to discuss variables affecting RS in orthodontics and to suggest an operative protocol. The search included PubMed©, Medline©, and the Cochrane Library©. References of full-text articles were manually analyzed. English-language articles published between January 2007 and January 2017 that performed an in vitro analysis of RS between the bracket, wire, and ligature were included. Study methods were analyzed based on the study design, description of materials, and experimental setup, and a protocol to standardize the testing methods was proposed. From 404 articles identified from the database search and 242 records selected from published references, 101 were eligible for the qualitative analysis, and six for the quantitative synthesis. One or more experimental parameters were incompatible and a meta-analysis was not performed. Major factors regarding the study design, materials, and experimental setup were not clearly described by most studies. The normal force, that is the force perpendicular to the sliding of the wire and one of the most relevant variable in RS, was not considered by most studies. Different variables were introduced, often acting as confounding factors. A protocol was suggested to standardize testing procedures and enhance the understanding of in vitro findings.

Anatomical and mechanical properties of swine midpalatal suture in the premaxillary, maxillary, and palatine region

The mechanical properties of the midpalatal suture and their relationship with anatomical parameters are relevant for both tissue engineering and clinical treatments, such as in sutural distraction osteogenesis. Soft tissues were dissected from ten swine heads and the hard palate was sliced perpendicularly to the midpalatal suture. Thirteen specimens were collected from each animal and analysed with micro-computed tomography and 4-point-bending for sutural width (Sw), interdigitation (LII), obliteration (LOI), failure stress (σ _f ), elastic modulus (E), and bone mineral density (BMD). Values of the premaxillary, maxillary, and palatine region were compared with Kruskal-Wallis one-way ANOVA and Spearman's rank coefficient was used to analyse the correlation between parameters and their position along the suture (α = 0.05). LII had values of 1.0, 2.9, and 4.3, LOI had values of 0.0%, 2.5%, and 4.5%, and E had values of 12.5 MPa, 31.3 MPa, and 98.5 MPa, in the premaxillary, maxillary, and palatine region, respectively (p < 0.05). Failure stress and rigidity of the midpalatal suture increased from rostral to caudal, due to greater interdigitation and obliteration. These anatomical and mechanical findings contribute to characterise maxillary growth, and may help to understand its mechanical reaction during loading, and in virtual simulations.

In vitro evaluation of the influence of velocity on sliding resistance of stainless steel arch wires in a self-ligating orthodontic bracket

INTRODUCTION

Of the variables used by in vitro studies of resistance to sliding (RS) in orthodontics, sliding velocity (SV) of the wire is often the one farthest from its clinical counterpart. We investigated whether velocity influences the RS at values approximating the orthodontic movement.

METHODS

A SS self-ligating bracket with a NiTi clip was fixed onto a custom-made model. Different shaped orthodontic SS wires of four sizes and two types (round, 0.020″ and 0.022″; rectangular, 0.016″×0.022″ and 0.017″×0.025″) were tested using an Instron^® testing machine. Wires were pulled at four velocities (1×10^-2  mm/s, 1×10^-3  mm/s, 1×10^-4  mm/s, 1×10^-5  mm/s). Shapiro-Wilk test was used to evaluate the normal distribution of the data; two-way ANOVA was performed to compare means in the RS with wire characteristics and SV. Significance level was set at P<.05.

RESULTS

RS was higher for rectangular wires, and for those with larger diameters. Lower SV was associated with lower RS, with wire type and size having an interaction effect. The RS relatively to SV can be represented as: RS ∝ α[ln(SV)]+β, where α and β are constants.

CONCLUSIONS

At very low SV and low normal forces, SV influences the RS of SS archwires in orthodontic brackets, and the proportionality is logarithmic. Although respecting these parameters in vitro is challenging, quantitative evaluations of RS should be carried out at clinically relevant velocities if aiming at translational application in the clinical scenario.

Biomechanical behaviour of craniofacial sutures during distraction: An evaluation all over the entire craniofacial skeleton

OBJECTIVE

Sutures are fibrous joints connecting the bones of the head. Despite the fundamental role played by sutures in dentofacial orthopaedics, their biomechanical properties are not completely understood. This study evaluated anatomy, biomechanics, and acoustic emission (AE) during distraction of the sutural ligament (SL).

METHODS

Seventy-two suture samples were removed from a twelve-months-old swine (Sus scrofa) head. Each volume was acquired using micro-computed tomography (μCT), and the linear interdigitation index was calculated on both planes (LII_COR and LII_SAG). Mechanical testing till failure was carried at 1mm/min, and four piezoelectric sensors were used for recording of amplitude (A), duration (D), and energy (E) of AE. The relationships between interdigitation, fracture types, tensile stress (σ₀), and AE were statistically analysed with non-parametric tests (α=0.05).

RESULTS

σ₀ of the SL had median values of 4.0MPa, and AE were characterised by A of 49.3dB (IQR=2.2), D of 826.3μs (IQR=533.4), and E of 57,715.8 eu (IQR=439,613.5). Most of the fractures happened in the SL (46%), some within the bone (34%), and fewer were combined (19%). LII_COR had correlation with A (0.383, p=0.028), D (0.348, p=0.048), and E (0.437, p=0.011) of the AE, and σ₀ had similar relationship with A (0.500, p=0.003), D (0.495, p=0.003), and E (0.579, p<0.001). Maximum energy values were different between fractures within the bone and within the SL (p=0.021).

SIGNIFICANCE

Biomechanical properties under tension of most of the sutures of the craniofacial skeleton were reported. AE provided information about the sequence of events during SL distraction, and had significant relationship with its mechanical properties. Further studies are necessary to confirm these preliminary findings, and to identify their relationship with biological processes and dentofacial treatments.

Tooth loss caused by displaced elastic during simple preprosthetic orthodontic treatment

The use of elastics to close a diastema or correct tooth malpositions can create unintended consequences if not properly controlled. The American Association of Orthodontists recently issued a consumer alert, warning of “a substantial risk for irreparable damage” from a new trend called “do-it-yourself” orthodontics, consisting of patients autonomously using elastics to correct tooth position. The elastics can work their way below the gums and around the roots of the teeth, causing damage to the periodontium and even resulting in tooth loss. The cost of implants to replace these teeth would well exceed the cost of proper orthodontic care. This damage could also occur in a dental office, when a general dentist tries to perform a simplified orthodontic correction of a minor tooth malposition. The present case report describes a case of tooth loss caused by a displaced intraoral elastic, which occurred during a simple preprosthetic orthodontic treatment.

Evaluation of rapid maxillary expansion through acoustic emission technique and relative soft tissue attenuation

OBJECTIVES

Acoustic emission (AE) is a non-destructive test to detect energy release. This technique was applied during rapid maxillary expansion (RME) to evaluate the reaction of the craniofacial skeleton.

MATERIALS AND METHODS

A swine model was analysed. Soft tissues were removed from two heads, while other two were preserved intact. A palatal expander (PE) was positioned and AE sensors were placed on the intermaxillary, fronto-nasal, and maxillo-lacrimal sutures. The PE was activated and AE recorded during RME. Differences between parameters were analysed with Mann-Whitney U test and Kruskal-Wallis test, and correlations with Spearman-Rho test (significance p<0.05).

RESULTS

PE activations were accompanied by clusters of AE hits. In the presence of soft tissues, amplitudes were generally lower (p<0.001) and durations were higher (p<0.001). No differences were found in the respective energy values. Differences were found in the AE (p<0.05) among the four channels, with AE characterised by higher values in proximity of the maxillo-lacrimal sutures. High-energy hits were represented by burst-type waves, and low-energy ones by continuous-type.

CONCLUSIONS

Although soft tissues create possible attenuation of the signal, AE can be detected during RME with sensors on the skin. AE provided further information of energy release, on top of the mechanical parameters. Source location was one of the main limitations.

Incisal Apical Root Resorption Evaluation after Low-Friction Orthodontic Treatment Using Two-Dimensional Radiographic Imaging and Trigonometric Correction

BACKGROUND

Root resorption shall be taken into consideration during every orthodontic treatment, and it can be effected by the use of different techniques, such as the application of low friction mechanics. However, its routinely assessment on orthopantomography has limitations related to distortions and changes in dental inclination.

AIM

The aim of this investigation was to evaluate the severity of apical root resorption of maxillary and mandibular incisors after low-friction orthodontic treatment, using the combination of panoramic and lateral radiographs, and applying a trigonometric correction.

SETTINGS AND DESIGN

A hospital based Retrospective study at the orthodontic Department (Dental School, University of Brescia, Spedali Civili di Brescia, Brescia, Italy).

MATERIALS AND METHODS

Ninety-three subjects (53 females and 40 males; mean age, 14 years) with mild teeth crowding were treated without extractions by the same operator using a low-friction fixed appliance following an integrated straight wire (ISW) protocol. The pre- and post-treatment tooth lengths of the maxillary and mandibular incisors were measured on panoramic radiographs. A trigonometric factor of correction for the pre-treatment length was calculated based on the difference between the pre and post-treatment incisal inclination on lateral cephalograms.

STATISTICAL ANALYSIS

The changes in lengths were investigated using the Student's t-test for paired values (p<0.05).

RESULTS

Maxillary central incisors showed no changes (0.3%, 0.6%), maxillary lateral incisors showed a small increase (1.4%, 1.8%) that was attributed to the completion of root development in younger patients, mandibular central and lateral incisors underwent slight resorption (-3.1%, -3.4%). A statistically significant difference was found for the mandibular incisors but not for the maxillary ones.

CONCLUSION

In patients with mild crowding and consequent low amount of root movement, a low-friction orthodontic treatment can lead to slight apical root resorption, mainly involving lower incisors. The use of a trigonometric correction in the panoramic radiograph analysis may reduce the limitations of this 2D evaluation.

A locus for migraine without aura maps on chromosome 14q21.2-q22.3

Migraine is a common and disabling neurological disease of unknown origin characterized by a remarkable clinical variability. It shows strong familial aggregation, suggesting that genetic factors are involved in its pathogenesis. Different approaches have been used to elucidate this hereditary component, but a unique transmission model and causative gene(s) have not yet been identified. We report clinical and molecular data from a large Italian pedigree in which migraine without aura (MO) segregates as an autosomal dominant trait. After exclusion of any association between MO and the known familial hemiplegic migraine and migraine with aura loci, we performed a genomewide linkage analysis using 482 polymorphic microsatellite markers. We obtained significant evidence of linkage between the MO phenotype and the marker D14S978 on 14q22.1 (maximum two-point LOD score of 3.70, at a recombination fraction of 0.01). Multipoint parametric analysis (maximum LOD score of 5.25 between markers D14S976 and D14S978) and haplotype construction showed strong evidence of linkage in a region of 10 cM flanked by markers D14S1027 and D14S980 on chromosome 14q21.2-q22.3. These results indicate the first evidence of a genetic locus associated with MO on chromosome 14.

Effects of moderate and high doses of alcohol on carotid atherogenesis

The role of alcohol consumption on pathophysiology of atherosclerosis is not completely well established. Past studies were conducted with different methodological approaches, sometimes leading to opposing conclusions. The aim of this study was to determine the weight of alcohol intake on carotid atherosclerosis in a group of subjects asymptomatic for cardio-cerebrovascular diseases. They were examined by ultrasonographic assessment during the period 1993 through 1997. Common risk factors of atherosclerosis and drinking habit were assessed by a standardized questionnaire. In this survey we confirm the J-shaped relationship between atherosclerosis and alcohol consumption. The effect of alcohol intake is more evident if we consider the presence of multiple internal carotid stenosis, or those greater than 25%, as outcome variables. These effects are independent from the other risk factors included in logistic regression paradigms (age, arterial hypertension, dyslipidemia, diabetes mellitus, family history of cardio-cerebrovascular disease, smoking and social status). Our study supported that a high level of alcohol intake plays a role as an independent factor in carotid atherogenesis.

Cognitive impairment and cerebral atrophy in "heavy drinkers"

1. Aim of the work was to verify the following three hypotheses in alcoholics: a) right hemisphere; b) diffuse brain deficit; c) anterior brain deficit, by means of a neuropsychological and a neuroradiological assessment. 2. 15 alcoholic right-hand male subjects and 15 matched controls were enrolled in the study. 3. Specifically designed neuropsychological testing was performed to investigate logical abilities, selective attention and memory. 4. Neurological investigation was performed by a standard CT scan to assess the degree and localization of brain damage. 5. Alcoholics performed worse than controls on some neuropsychological tests, i.e. Attention Matrices Test, Verbal Judgement Test, Forward Digit Span, Story Recall and Remote Memory Test. The analysis of variance adjusted by the attentional score showed no significant differences between alcoholics and controls. 6. Neuroradiological data showed a preeminent and a more frequent atrophy of the frontal region. 7. No correlations emerged between neuropsychological and neuroradiological data. 8. In conclusion, the hypothesis of anterior brain deficit seems to be confirmed by our study.

The effects of flumazenil on focal, electroinduced after-discharge in rabbits

1. The anticonvulsive efficacy of flumazenil 10 mg/kg i.v., a BDZ antagonist, was studied in two models of experimental epilepsy electrically induced. 2. The EEG after-discharge, which was induced by the electrical stimulation of selected brain regions [(notably the dorsal hippocampus (Hip) and the amygdala (CAm)] was evaluated in rabbits pre- and post-drug administration. 3. In the animals submitted to electrical stimulation of the amygdala, flumazenil exerted a protective action, thereby inducing an increase in the after-discharge threshold and/or a decrease in after-discharge duration. 4. In the animals submitted to electrical stimulation of the hippocampus, flumazenil did not induced changes statistically significant. 5. Finally, the paper discusses the two possible mechanisms of action of flumazenil (a "per se" partial BDZ activity and/or a BDZ agonistic activity, which displaces the inverse agonist-like ligand) and the differencies in GABA distribution in the hippocampus and the amygdala.

[Colliculus hemorrhage]

We report the case of a patient with mesencephalic hematoma involving only the quadrigeminal plate. One case of superior and 3 cases of inferior colliculus hematoma have already been reported. Involvement of the quadrigeminal plate frequently follows a pontine or an anterior mesencephalic hemorrhage. The cause of these hematomas may be due to cryptic malformations of the quadrigeminal plate or primitive small size hemorrhages possibly related to the nature of the arterial system. Patients with inferior colliculus lesions present a typical symptomatology consisting of trochlear nerve palsy contralateral to the lesion or bilateral, contralateral hemiparesthesiae and acuphenes. Superior colliculus lesion causes upgaze palsy, visual blurring, dizziness and left upper lip paresthesiae. The cause of the different signs and symptoms in both types of lesion are discussed.

Disseminated encephalitis following streptococcal infection

Various neurological disorders have been related to Streptococcus pyogenes infection. Only recently, and for the first time, it has been suggested that acute disseminated encephalitis may also complicate a streptococcal infection. The case reported in this paper seems to confirm this hypothesis.

[Encephalitis lethargica]

We report the case of a 34-year old patient who first complained of fever, confusion and transient ophthalmoplegia and then developed akinetic mutism, frontal lobe, pyramidal tract and extrapyramidal signs. Clinical and electrophysiological data support a diagnosis of encephalitis lethargica. Magnetic resonance imaging showed hyperintensive lesions in various brain regions. The patient responded to corticosteroid treatment. Two years after the onset of the first clinical signs he had recovered completely and today, after 5 years, he shows no sign of disease.

Role of dopamine D-1 and D-2 antagonists in a model of focal epilepsy induced by electrical stimulation of hippocampus and amygdala in the rabbit

1. The differential role played by blockade of D-1 or D-2 dopamine receptors in mechanisms underlying seizures was studied in a model of EEG after-discharge induced by electrical stimulation of selective brain regions (dorsal hippocampus and amygdala) in the rabbit. 2. The D-2 antagonist haloperidol (1 mg/Kg) increased significantly after-discharge duration after stimulation of either hippocampus or amygdala and lowered after-discharge threshold in few animals. 3. The D-1 antagonist SCH 23390 (0.3 mg/Kg) caused no changes following stimulation of amygdala and reduced after-discharge duration when hippocampus was stimulated. 4. Haloperidol exerted a proconvulsant action in this experimental model, having a clearer influence on D-2 receptors. SCH 23390 had no effect on amygdala whereas it exerted protection on the hippocampus. 5. The present data suggest that D-1 and D-2 receptors have different roles in generating and spreading the epileptic activity.