Comparison of Mechanical Properties of 3D-Printed, CAD/CAM, and Conventional Denture Base Materials.

PURPOSE: To evaluate and compare the mechanical properties (flexural strength and surface hardness) of different materials and technologies for denture base fabrication. The study emphasized the digital technologies of computer-aided design/computer-aided manufacturing (CAD/CAM) and three-dimensional (3D) printing. MATERIALS AND METHODS: A total of 160 rectangular specimens were fabricated from three conventional heat-polymerized (ProBase Hot, Paladon 65, and Interacryl Hot), three CAD/CAM produced (IvoBase CAD, Interdent CC disc PMMA, and Polident CAD/CAM disc), one 3D-printed (NextDent Base), and one polyamide material (Vertex ThermoSens) for denture base fabrication. The flexural strength test was the three-point flexure test, while hardness testing was conducted using the Brinell method. The data were analyzed using descriptive and analytical statistics (α = 0.05). RESULTS: During flexural testing, the IvoBase CAD and Vertex ThermoSens specimens did not fracture during loading. The flexural strength values of the other groups ranged from 71.7 ± 7.4 MPa to 111.9 ± 4.3 MPa. The surface hardness values ranged from 67.13 ± 10.64 MPa to 145.66 ± 2.22 MPa. There were significant differences between the tested materials for both flexural strength and surface hardness. There were also differences between some materials with the same polymerization type. CAD/CAM and polyamide materials had the highest flexural strength values. Two groups of CAD/CAM materials had the highest surface hardness values, while a third, along with the polyamide material, had the lowest. The 3D-printed materials had the lowest flexural strength values. CONCLUSIONS: Generally, CAD/CAM materials show better mechanical properties than heat-polymerized and 3D-printed acrylics do. Nevertheless, a material's polymerization type is no guarantee of its optimal mechanical properties.

A study of the flexural strength and surface hardness of different materials and technologies for occlusal device fabrication.

STATEMENT OF PROBLEM: With the emergence of digital technologies, new materials have become available for occlusal devices. However, data are scarce about these different materials and technologies and their mechanical properties. PURPOSE: The purpose of this in vitro study was to investigate the flexural strength and surface hardness of different materials using different technologies for occlusal device fabrication, with an emphasis on the digital technologies of computer-aided design and computer-aided manufacturing (CAD-CAM) and 3D printing. MATERIAL AND METHODS: A total of 140 rectangular specimens were fabricated from two 3D-printed (VarseoWax Splint and Ortho Rigid), 2 CAD-CAM-produced (Ceramill Splintec and CopraDur), and 3 conventional autopolymerizing occlusal device materials (ProBase Cold, Resilit S, and Orthocryl) according to ISO 20795-1:2013. Flexural strength and surface hardness were determined for 10 specimens of each tested material using the 3-point bend test and the Brinell method. The data were analyzed using descriptive statistics and 1-way ANOVA with Bonferroni corrections (α=.05). RESULTS: Surface hardness values ranged from 28.5 ±2.5 MPa to 116.2 ±1.6 MPa. During flexural testing, neither the CopraDur nor the VarseoWax Splint specimens fractured during loading within the end limits of the penetrant's possible movement. Flexural strength values for other groups ranged from 75.0 ±12.0 MPa to 104.9 ±6.2 MPa. Statistical analysis determined significant differences among the tested materials for flexural strength and surface hardness. CONCLUSIONS: Mechanical properties among different occlusal device materials were significantly different. Acrylic resins were less flexible than polyamide and nonacrylic occlusal device materials for 3D printing but had higher and more consistent values of surface hardness. Clinicians should consider the different mechanical properties of the available materials when choosing occlusal device materials.

Movements of temporomandibular condyles during swallowing.

There have been studies that investigated mandibular movements and positioning during swallowing, but the results were inconsistent, and still the exact position of the condyles during swallowing is unknown. The purpose of this investigation was to study the kinematics of the mandible and the condyles, and to determine the actual movement paths and position of mandible and condyles during the process of swallowing. The study was performed on a sample of 44 dental students. Measurements were done with an electronic axiograph. After non-occlusing attachment was fixed in the mouth, every subject swallowed for five times from the rest position. The final swallowing position of the left and the right condyles was measured in the sagittal plane. The final swallowing position of the sagittal incisal point was measured in sagittal, frontal and horizontal plane, and data was statistically analyzed. The condyles showed average movement toward posterior (left 0.17 mm, SD 0.28, right 0.16 mm, SD 0.25) and superior (left 0.14 mm, SD 0.20, right 0.14 mm, SD 0.23). Anterior and/or inferior position had 20% of participants. The average sagittal incisal point movement during swallowing was toward anterior (0.30 mm, SD 0.53) and superior (0.81 mm, SD 0.84). The mean mandibular lateral movement was 0.1 mm (SD 0.1). The results of the study suggest that retrusion during swallowing is not the rule, although on average there is a slight tendency of condylar movement toward posterior. Swallowing can be used as auxiliary method for determining vertical dimension of occlusion.

Measurements of the sagittal condylar inclination: intraindividual variations.

AIMS: Sagittal condylar inclination is an important parameter during fabrication of prosthetic restorations. Existing data about intraindividual variations of sagittal condylar inclination are scarce. The purpose of this study was to investigate intra- and interindividual variations of the sagittal condylar inclination, depending on the position of the condyle in the temporomandibular joint. METHODOLOGY: The study included 51 subjects with Angle's Class I occlusion (21-32 years of age, mean 25.1). Measurements were done using an electronic axiograph. After a paraocclusal tray was fixed in the mouth, every subject had to make three protrusive movements, from which the device's software calculated the mean left and mean right sagittal condylar path. The mean left and right condylar path of each subject was divided into three equal sequences, based on whole condylar path length. Condylar inclination values for the first, second and third movement sequences were calculated. RESULTS: Results showed significant differences between movement sequences (P < 0.05). For the left joint, condylar inclination values in the first condylar movement sequence demonstrated, on the average, 14.4% higher values compared to the second movement sequence, and 39.2% higher values than in the third movement sequence. For the right joint, the first condylar movement sequence demonstrated, on the average, 15.8% higher values compared to the second movement sequence, and 41.5% higher values than the third movement sequence. CONCLUSIONS: Results suggest that condylar movement in the sagittal direction is not uniform. Mean left and mean right condylar inclination values do not necessarily describe the actual condylar path, nor do they give adequate information for articulator setup. Left-right side condylar inclination differences greater than 10 degrees can be considered as normal.

Prevalence of torus palatinus and torus mandibularis in the Split-Dalmatian County, Croatia.

Torus palatinus (TP) and torus mandibularis (TM) are non-pathological outgrowths of unclear etiology that develop from the jaw bone. The purpose of the present study was to report on the prevalence, shape and location of TP and TM in the population of the Central Dalmatian region, Croatia. The study comprised of 1679 subjects, 985 females and 694 males, age range from 9 to 99 years who were examined by clinical examination and analysis of the plaster casts. Torus palatinus was found in 42.9% subjects and torus mandibularis in 12.6% of the subjects. Spindle-shaped torus palatinus was the most frequent type (45.6%). The most frequent type of torus mandibularis was bilateral solitary torus mandibularis (35.4%). Furthermore, torus palatinus was found in 40.1% of the total number of females and in 46.8% of the total number of males, indicating a significantly higher prevalence in the male population (p = 0.006). Torus mandibularis was found in 11.3% of the female population and in 14.6% of the male population, again indicating significantly higher prevalence in the male population (p = 0.046). The results of this study show significantly higher prevalence of torus palatinus and torus mandibularis in the male subjects. Furthermore, no differences in the prevalence of either TM or TP regarding age were found.

Influence of Occlusal Splint on Mandibular Movements in Patients with Bruxism: a Comparative Pilot Study.

OBJECTIVE: The objective of this pilot study was to examine the impact of occlusal splint treatment on mandibular border movements and the condyle position in subjects with bruxism. MATERIALS AND METHODS: The study included 9 subjects diagnosed with bruxism (mean age 28.7) and 9 subjects in the control group (mean age 30.5). All subjects were adults, eugnathic, and with a dentoalveolar Angle Class I, without prosthetic restorations, previous or current orthodontic treatments, a systemic disease or previous surgical interventions in the temporomandibular joint. All experimental and control group subjects were provided with a standardized relaxation occlusal splint, which they wore for 8 weeks. During this time, an initial and three additional measurements of incisal opening (IO), left condyle opening (OLC), right condyle opening (ORC), left laterotrusion (LLI) and right laterotrusion (LRI) (after 2, 4 and 8 weeks) were performed using an Arcus Digamma II (Kavo) ultrasound device for mandibular movements recording. Using the same instrument, the condylar position during protrusion, left and right laterotrusion, and in the centric relation position (CR) was analyzed initially and after 8 weeks using the maximum intercuspation as reference point. Continuous variables were described using basic statistical parameters, and the statistical significance of differences between the variables was checked by the t-test and χ2 test (p <0.05). RESULTS: The values of IO, OLC, ORC, LLI and LRI ​​increased after 8 weeks of wearing, with the highest increase for OLC, by 13.8%. No statistically significant difference (p <0.05) was found for any changes in movements. Changes in the condyle position during all movements and those in the CR were higher in the experimental group for 10 out of 14 measured parameters compared to the control group. A statistically significant difference was established for 5 out of 14 measured parameters after the occlusal splint treatment. CONCLUSIONS: The results of this pilot study have proven the influence of the occlusal splint treatment on mandibular border movements in subjects with bruxism by increasing the range of movements. Also the changes of the condyle position in subjects with bruxism were greater compared to those in healthy subjects.

Comparison of Parameters for Programming Adjustable Dental Articulators by Using Wax Eccentric Records and Arcus Digma Device.

OBJECTIVES: Programming of joint mechanism/parameters (sagittal condylar inclination and Bennett angle) of adjustable dental articulators is a prerequisite for performing positions and movements of the mandible. The aim of the study was to test significant differences between the two methods (wax eccentric records and Arcus Digma device) of measuring these joint parameters by using three different dental articulators (SAM 3, Protar 7; and Artex CR). MATERIALS AND METHODS: Thirty asymptomatic younger (age 25.7 ± 2.9 years) subjects (dental medicine students) divided by gender, with normal occlusion (Angle class I) participated in the study. After taking anatomical impressions of both dental arches, master casts were made of hard dental plaster for each subject. The values of the left and right sagittal condylar inclination and Bennett angle by the two methods of wax eccentric protrusive and lateral records and Arcus Digma device were measured for the purpose of programming the mentioned joint parameters in three different articulator systems. RESULTS: The average values of the measured parameters of sagittal condylar inclination and Bennett angle of wax eccentric records were higher (ranging from 5ºto 10º) in relation to the values measured by Arcus Digma device. Statistically significant differences found between the measured joint parameters (p <0.025) were influenced by the articulator system design and measurement methods (t-test for dependent samples and MANOVA). CONCLUSION: The use of Arcus Digma device should be considered reliable and valid for individualized programming of dental articulators, rather than the use of wax eccentric records.

Checking the occlusal relationships of complete dentures via a remount procedure.

Correct occlusal relationships are part of the successful prosthetic treatment of edentulous patients. Occlusal checking should be performed via a remount procedure because denture base materials and fabrication procedures cannot provide dimensionally accurate complete dentures. Occlusal errors caused by the adjustment of denture bases to the denture foundation after a certain period of wearing can also be corrected by means of remounting. The following remount procedures for complete dentures are described: fabrication of transfer casts, transfer of a maxillary denture with a facebow, centric relation record, and mounting of dentures with transfer casts in an articulator with a dental stone. Deflective occlusal contacts of denture teeth in centric occlusion can be eliminated by selective grinding and by tooth-guided excursive movements. In complete denture treatment, priority is given to anterior/canine-guided occlusion.

SUBJECTIVE ASSESSMENT OF CROATIAN DENTAL MEDICINE STUDENTS ON THEIR KNOWLEDGE AND SKILLS IN PROSTHODONTICS.

OBJECTIVES: The aim of the study was to establish the subjective perception of dental medicine students' knowledge and skills in prosthodontics and to determine both how their perception changed during their study, by gaining clinical experience. Also, the aim was to investigate if there were any socio-demographic factors that influenced students' perception. METHODS: The research, based on an anonymous survey for dental medicine students was carried out at the School of Dental Medicine, University of Zagreb in 2015. YES/NO/DO NOT KNOW questions were used for assessment of students' knowledge, and a 50 mm visual analog scale was used for assessment of their abilities and skills. The Chi-square test, t-test for independent samples, analysis of variance and the Pearson's correlation coefficient were used for statistical data analysis. RESULTS: Students' response (4th, 5th and 6th year of study) to the study amounted to 71,3%. The results showed that clinical experience and the number of correct answers from knowledge assessment increased with the year of study. Students with completed dental laboratory technician school took statistically significantly larger number of impressions and fabricated a significantly larger number of fixed restorations. Additionally, the results showed a significantly higher level of agreement with the statements about their perception of knowledge and skills. CONCLUSION: Students' perceptions on learning positively correlated with the number of completed semesters in prosthodontics and the students' own clinical experience.

Functional Impressions in Complete Denture and Overdenture Treatment.

Tooth loss can cause loss of occlusal, masticatory, esthetic, physiognomic, phonetic and psychosocial function of patients. The most frequently used treatment method of completely edentulous patients and patients with a small number of remaining teeth are complete dentures or overdentures. One of the most important clinical and laboratory procedures in their fabrication is functional impression taking. The aim of this paper was to present procedures of taking functional impressions in fabrication of complete dentures and overdentures, using standardized techniques and materials. An accurate functional impression together with other correctly performed clinical and laboratory procedures ensure good retention and stability of dentures, which is a precondition for restoring patients' lost functions.

ARTICULATOR-RELATED REGISTRATION AND ANALYSIS OF SAGITTAL CONDYLAR INCLINATION.

The purpose of this investigation was to study sagittal condylar inclination values within a uniform sample (Angle class I occlusion) using 'articulator-related registration' and Camper's plane as a reference plane. The study was performed on a sample of 58 Angle class I subjects (mean age 25.1, SD 3.1). Measurements were performed with an ultrasonic jaw tracking device with six degrees of freedom. After a paraocclusal tray was fixed in the mouth, each subject had to make three protrusive movements and three right and left laterotrusive movements. From protrusive movements the software of the device automatically calculated the left and the right sagittal condylar inclination values used for setting of the articulator. The mean sagittal condylar inclinationvalue was 41.0° (SD 10.5) for the right joint and 40.7° (SD 9.8) for the left joint. The maximum value was 65.0° for the right and 68.6° for the left joint, and the minimum value was 13.7° for the right and 21.7° for the left joint. The results of this study suggested the average articulator setting for sagittal condylar inclination for fully dentate adult subjects to be 40° in relation to Camper's plane. This is especially important for the articulators that are set up in relation to Camper's plane.

Frequency of internal derangement of the temporomandibular joint in elderly individuals.

Elderly patients suffer from various systemic diseases and are likely to neglect their problems with functional disorders in the masticatory system, which are of crucial importance for successful prosthetic treatment. The purpose of the study was to establish the frequency of symptoms, clinical signs and tissue-specific diagnoses of internal derangement of the temporomandibular joint in elderly subjects and their relation with respect to gender and type of prosthetic replacement. The study was conducted on 96 subjects, 48 complete denture wearers and 48 removable partial denture wearers, whose average age was 75.8 years. The diagnostic procedure used in this study was manual functional analysis consisting of specific techniques of dynamic compressions and translations in diagnosing internal derangement of the temporomandibular joint. Chi-square test for independent samples was used for statistical analysis of the results. The symptoms of internal derangement of the temporomandibular joint were found in 9.3% of the subjects, and tissue-specific diagnoses were established in 52.1% of the subjects. The most common diagnoses were osteoarthrosis, total disk displacement with stable reposition and partial anterolateral disk displacement. No statistically significant differences in the frequency of symptoms, clinical signs and tissue-specific diagnoses were found between genders (P>.05) and complete and removable partial denture wearers (P>.05). The frequency of subjective symptoms of internal derangement in the temporomandibular joint of elderly subjects was low in relation to the frequency of intracapsular tissue-specific diagnoses.

Registration and measurement of opening and closing jaw movements and rotational mandibular capacity by using the method of electronic axiography.

The aim of this study was to register and measure lower jaw movements, to analyse the measured length of opening and closing movements and to analyse the rotational mandibular capacity during the maximal opening of the mouth in the position of centric relation. Our objective was to determine the average values for each mandible and temporomandibular joint movement, as well as to determine the accuracy of electronic axiography, while diagnosing temporomandibular joint disorders. A statistical analysis was performed in order to evaluate whether significant differences between the length of the measured movements in asymptomatic and symptomatic subjects could be found. A symptomatic group consisted of 51 subjects with temporomandibular disorders. A control group consisted of 43 subjects without signs and symptoms of temporomandibular joint disorders. Each subject was registered by the GAMMA CADIAX system for registration of position and movement of the lower jaw, which consists of a conventional SAM axiograph, an electronic device for drawing curves by means of a computer. No significant differences were found between the groups of subjects for the measured variables. The results of the length of the mandibular and condyle movements, along with the rotational capacity of the mandible are important, in spite of unreliable indicators of temporomandibular joint function. Description analysis of a graphic recording of mandibular and TMJ movement remains an accurate evaluation method for the determination of TMJ dysfunction.

Incidence of temporomandibular disorders at tooth loss in the supporting zones.

Although the literature reports that occlusal disorders can be associated with temporomandibular disorders (TMD), their direct scientific correlation is still mainly unproved. The aim of this study was to establish the incidence of symptoms and signs of TMD and tissue-specific diagnoses in a population of subjects with tooth loss in the supporting zones. The study was conducted on 196 partially edentulous subjects (Eichner's class II and III) at the average age of 51.2. Manual functional analysis was used as a diagnostic procedure. Chi-square test for independent samples was used for establishing the significance of the differences between the variables. In the total sample, 16.3% of the subjects had symptoms and signs of temporomandibular disorders (TMD), while in 46.9% of the subjects a tissue-specific diagnosis of TMD was found. The most frequent tissue-specific diagnoses were osteoarthrosis and total or partial anterolateral disc displacement. A statistically significant difference between Eichner's class II and III was found for the tissue-specific diagnoses of myofascitis of the lateral pterygoid muscle, partial anterolateral disc displacement and capsulitis. The results of this study suggest that the incidence and intensity of TMD are higher in subjects with greater tooth loss in the supporting zones, regardless of their sex.

The significance of oral and systemic factors in Australian and Croatian patients with oral lichen planus.

Oral lichen planus (OLP) is an immunologically T cell-mediated disease caused by an unknown stimulus. Despite intensive investigation its pathogenesis still remains unknown. A few possible associations between OLP and certain diseases such as thyroid and malignant diseases as well as specific medication intake have been proposed in the literature with inconsistent findings. We aimed to investigate the profile of 163 Australian and 163 Croatian OLP patients with special regard to their systemic diseases, medication intake (with special regard to the drugs that metabolize through Cytochrome P450), OLP type and localization, as well as involvement of other body surfaces with lichen. We did not find any statistical significance with regard to the OLP presence and thyroid and malignant diseases. As expected, the reticular type of OLP was most prevalent, as well as involvement of the both buccal mucosas. There was no significant association with other oral diseases such as labial herpes. Simultaneous involvement of other body surfaces in patients with OLP does not seem to be prevalent. None of the medical conditions which were investigated had significant correlation with OLP neither in Australian nor in Croatian patients with OLP. Furthermore, the use of drugs which metabolize through Cytochrome P450 (CYP450) was not significantly correlated with OLP in either studied population. Therefore, we conclude that patients with OLP are not to be routinely screened for any systemic conditions.

Treating patients with HIV and Hepatitis B and C infections: Croatian dental students' knowledge, attitudes, and risk perceptions.

Dentists and dental students can be exposed to the human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV) during routine work. The aims of this study were to assess a group of dental students' knowledge about HIV, HBV, and HCV infections; assess their attitudes and risk perceptions about the treatment of patients with HIV, HBV, and HCV; and identify factors associated with their knowledge and willingness to treat these patients. An anonymous survey was administered to 534 predoctoral students at the School of Dental Medicine, University of Zagreb, Croatia. The response rate was 71.9 percent. Students' knowledge increased with each year of study. Senior students (in their third, fourth, and fifth years) had more professional attitudes and were significantly more positive about dentists' professional obligation to treat patients who are HIV-positive than were junior students (in their first and second years; p=0.0002). Senior students also expressed significantly more willingness to treat intravenous drug users and patients with hepatitis (p=0.016 and p=0.033, respectively). Female students were significantly more convinced than male students that routine dental treatment carried a significant risk of HIV and hepatitis infection (p=0.025). These students' knowledge negatively correlated with the lack of willingness to treat intravenous drug users and patients with hepatitis, and they expressed their willingness to receive further theoretical and practical education on this topic.

Psychologic status in patients with temporomandibular disorders.

PURPOSE: The aim of this study was to investigate diferrences in the prevalence of depression and somatization scores in temporomandibular disorder (TMD) patients. MATERIALS AND METHODS: One hundred fifty-four patients with single and/or multiple RDC/TMD diagnoses were classified into 7 groups based on Axis I criteria. Somatization and depression scores from the Symptom Checklist-90 were compared between groups. RESULTS: The results of this investigation indicate that patients with myofascial pain and arthralgia psychologically differed from those with disc displacement. These results were in accordance with findings that support the notion that the pain induces psychologic sequelae, at least in relation to depression and somatization. CONCLUSION: It was concluded that psychologic factors play an important role in etiopathogenesis of TMD, as demonstrated by an increase in levels of depression and somatization in TMD patients.