Journal of oral science最新文献

Purpose: This study analyzed associations of cumulative learning, demographic characteristics, fluoride content, and toothbrush head size with the amount of toothpaste used by dental students.

Methods: Students in the third and fifth year of dental school were recruited. Each participant was asked to dispense three toothpastes (pediatric, regular fluoride, and high fluoride) on five toothbrushes (rotation-oscillation, sonic, manual pediatric, and two manual adult toothbrushes). The length and weight of the toothpaste dispensed were recorded. The data were evaluated by nonparametric correlation analysis (P < 0.05).

Results: Eighty-one students (third year = 42; fifth year = 39; mean age: 26.2 ± 5.3 years) participated in the study. More toothpaste was dispensed by third-year students than by fifth-year students (weight: P = 0.014; length: P = 0.037). Men dispensed more toothpaste than did women (weight: P < 0.001; length: P = 0.042). Participants with higher educational attainment dispensed less toothpaste (weight: P < 0.001; length: P < 0.001). The type of toothbrush was associated with the weight of toothpaste dispensed (P < 0.001). Toothbrush head size was inversely associated with the length of toothpaste dispensed (P < 0.001).

Conclusion: The amount of toothpaste used by dental students was associated with cumulative learning, educational attainment, sex, and toothbrush head size but not with the fluoride content of the toothpaste.

Purpose: This study aimed to evaluate masticatory performance in cases where one molar was missing.

Methods: Participants were 156 adults with one molar missing from their natural teeth, who were divided into group A (without prosthetic treatment) and group B (with prosthetic treatment). The non-missing side was designated as A1 or B1, and the missing side was designated as A2 or B2. The amount of glucose eluted (AG) when the participants chewed a gummy jelly was measured and used as a parameter for masticatory performance. AG was compared between the non-missing side (A1, B1) and missing side (A2, B2), and between the first molar missing group and second molar missing group.

Results: AG was significantly greater on the dentate side (P < 0.001) and was significantly less in the A2 group when the first molar was missing (P = 0.002). The rate of decrease of AG was 11.1%, 14.3%, and 8.4% in groups A+B, A, and B, respectively.

Conclusion: Masticatory performance appears to decrease even with only one missing molar. Although improvement is achieved by prosthetic treatment, performance remains inferior to that on the dentate side.

A study was conducted to evaluate the success rates of bypassing or removing fragments of instruments that had fractured within the roots of mandibular molars using a HBW Ultrasonic Ring. Forty extracted first permanent mandibular molars with root canal curvature were included. The teeth were distributed randomly into four groups according to the type of instrument and the root canal third where they had fractured. The success rate for removal of instrument fragments was 100% for both of two stainless steel groups, 90% for a nitinol middle third group, and 80% for a nitinol apical third group. The mean time required for instrument removal was around 40 min. The HBW Ultrasonic Ring showed acceptable experimental results for retrieval of broken instrument fragments.

Purpose: The present study investigated the biomechanical stability of three miniplate osteosynthesis configurations used for internal fixation of bilateral mandibular angle fracture (BMAF).

Methods: Standard fracture lines were created in 72 polyurethane mandibles and stabilized with 2.0-mm, 4-hole standard titanium miniplates and monocortical screws. The group descriptions and miniplate configurations were: 2Plates (1-1), 3Plates (1-2) and 4Plates (2-2). The mandibles were subjected to either incisal or molar loads (from both sides in the 3Plates group) up to a force of 120 N. The displacements of the constructs were recorded at each force increment of 10 N. ANOVA and Tukey's post-hoc tests were used for statistical analysis.

Results: The 2Plates group showed higher displacement under both loading conditions (P < 0.05 for each). The same group reached displacement levels of 1 mm and 3 mm during molar loading and 1 mm, 3 mm, and 5 mm during incisal loading at lower force magnitudes relative to others (P < 0.05 for each).

Conclusion: Bone-plate constructs for BMAFs stabilized with three or four standard miniplates are more likely to provide similar resistance when subjected to incisal or molar loads, in contrast to the two-miniplate configuration, which is relatively more prone to displacement.

Purpose: To verify the effect of sitting posture with and without sole-ground contact on chewing stability and masticatory performance.

Methods: Thirty healthy subjects were evaluated. The Conformat was used to analyze the center of sitting pressure (COSP), and the three-dimensional motion analysis system was used to analyze changes in head and trunk postures while subjects remained in a sitting position with and without sole-ground contact. The parameters of masticatory performance and movement were calculated as follows. For evaluating masticatory performance, the amount of glucose extraction (AGE) during chewing of a gummy jelly was measured. For evaluating masticatory movements, the movement of the mandibular incisal point was recorded using the Motion Visi-Trainer V1, and parameters of the stabilities of movement path and rhythm were calculated.

Results: Head and trunk sway values and the displacement of COSP were significantly smaller with sole-ground contact than those without sole-ground contact. The masticatory movement path with sole-ground contact showed less variation in the opening distance and more stable movement path compared to those without sole-ground contact. The AGE was significantly greater with sole-ground contact than that without sole-ground contact.

Conclusion: Sitting posture with and without sole-ground contact affects chewing stability and masticatory performance.

Purpose: Scientific evidence pertaining to the evaluation of trueness of occlusal splints fabricated using different three-dimensional (3D) printers and build orientations compared to subtractive technologies is lacking.

Methods: Overall, one hundred and ten occlusal splints were manufactured using two different 3D printers and a dental mill. Five groups of ten were fabricated using the 3D printers at different build orientations (0, 30, 45, 60, and 90 degrees). In addition, a comparison group of ten occlusal splints was subtractively manufactured using a five-axis dental mill. All occlusal splints were scanned and exported as a standard tessellation language file. Analysis was conducted with metrology software with root mean square estimate average positive deviation and average negative deviation used as the measured outcome.

Results: The 0 degree printing orientation was the most accurate for printer one with the root mean square value of 0.05 ± 0.01 mm, and 60 degree printing orientation was most accurate for printer two with the RMS value of 0.11 ± 0.01 mm. Subtractively manufactured occlusal splint had significantly higher trueness with the lowest RMS value of 0.03 ± 0.05 mm.

Conclusion: Build orientations influence the trueness of additively manufactured occlusal splints while occlusal splints produced by subtractive manufacturing were statistically significantly more accurate.

Purpose: To investigate the root and canal morphology of mandibular second molars, including anatomical variations, in a Black South African population using two classification systems.

Methods: Cone-beam computed tomography images of 386 teeth were evaluated. The number of roots and canal configurations were categorized using the classifications of Vertucci (with modifications by Sert and Bayirli) and Ahmed et al. (including the modified Melton classification). Relationships between variables were assessed using Fisher's exact test (P < 0.05).

Results: Mandibular second molars were predominantly two-rooted (91.7%). The majority of teeth had three canals including Type IV mesial (41.2%) and Type I (75.1%) distal (Ahmed et al. configuration: ²MDM M² D¹). Three or more canals were present in almost one-fifth of mesial (n = 72/386, 18.6%) and a small number of distal (n = 21/386, 5.4%) roots. Males displayed additional canals more frequently in the distal root (P = 0.02). C-shaped anatomy was found in 5.7%. Among the C-shapes, the most common was Melton's Type III in the coronal (50%), middle (81%) and apical (72%) thirds.

Conclusion: In this population, mandibular second molar teeth exhibited diverse morphology, which would have clinical significance for endodontic practitioners. The Ahmed et al. classification provided a better description than the Vertucci classification.

Purpose: Apically extruded debris, canal transportation and shaping ability were compared between contracted endodontic cavities (CECs) and traditional endodontic cavities (TECs) after instrumentation with XP-endo Shaper (XPS), ProTaper Gold (PTG), ProTaper for hand-use (HPT) and Hero Shaper.

Methods: The CECs or TECs groups were sub-divided into 24 groups according to root canal morphology and nickel-titanium (Ni-Ti) instruments. The weight of apically extruded debris was calculated using the Myers and Montgomery model. Pre- and postoperative images of teeth were scanned using micro-CT and the three-dimensional models were constructed and compared.

Results: Under CECs or TECs, XPS and PTG produced less apical debris and formed less canal transportation than HPT and Hero Shaper (P < 0.05). XPS group under CECs extruded less apical debris than that under TCEs for round canals with curvature of 20°-35° (P < 0.05). The centering ratios of four tested instruments were higher under TECs than those under CECs (P < 0.05). The HPT and Hero Shaper had more transportation under CECs than that under TCEs (P < 0.05). No statistical difference was found regarding shaping ability among all the groups.

Conclusion: Under CECs, XPS preserves the original root canal anatomy, meanwhile it produces less apical debris than the other instruments.

Purpose: To evaluate the color match of single-shade resin composites before and after bleaching procedures, through instrumental and visual analyses.

Methods: Class V cavities were created on the buccal surfaces of 80 extracted human molars, restored with 4 single-shade composites (Omnichroma; Clearfil Majesty ES-2 Universal; Essentia Universal; Venus Diamond One). A spectrophotometer (VITA Easyshade V) was used to evaluate the tooth/resin color match before (T₀), and 24 h (T₁) and one week (T₂) after dental bleaching (Opalescence Boost PF 40%). Color variations (ΔE₀₀) were calculated and statistically analyzed (P < 0.05). Visual analysis was performed before and after tooth bleaching.

Results: Spectrophotometric evaluations revealed statistically significant differences between materials at T₀, T₁, and T₂ (P < 0.05). Visual analysis reported excellent and very good grades (0 and 1, respectively), irrespective of the materials and timepoints.

Conclusion: Data seem to indicate that single shade composites are able to shift their color when the surrounding tooth undergoes bleaching effects. Single-shade composites seem to achieve a good color match with the surrounding tooth structure, before and after professional bleaching.

Purpose: To assess the prevalence and distribution of pulp stones in a Saudi population.

Methods: A cone beam computed tomography (CBCT) analysis of 150 upper and 150 lower dental arches was performed. The relationships between pulp stones and age, sex, tooth type, dental arch, orthodontic treatment, caries, and restoration were statistically examined (P < 0.05).

Results: A total of 295 dental arches (98.3%) had at least one pulp stone, and the prevalence was higher in the maxillary teeth (56.2%) than in the mandibular teeth (48.1%) (P = 0.0003). Men were more likely to have pulp stones than women (P = 0.011 for the maxilla, P < 0.0001 for the mandible). Furthermore, age and orthodontic treatment had no significant effects on the incidence of pulp stones (P > 0.05). A higher occurrence of pulp stones was observed in the first molars (>91%), and in carious and restored teeth when compared to intact teeth (P < 0.05).

Conclusion: Pulp stones were more prevalent in the upper dental arches, first molars, and carious and restored teeth, as well as in the male population, and were not associated with age or orthodontic treatment.