A Preliminary Study in Er:YAG Laser Debonding of Lithium Disilicate Crowns: Laser Power Setting vs Crown Thickness.

Background: Er:YAG laser is widely used in debonding of all-ceramic veneers nowadays. However, the data about laser parameters in all-ceramic crown removal is limited. The aim of this preliminary study was to determine the most appropriate laser parameters at safe heat transmission values ​​for lithium disilicate crowns in different thicknesses. Methods: Twenty-seven intact premolars were prepared to fabricate lithium disilicate CAD/CAM full-coverage crowns in three different thicknesses: 1, 1.5 mm, and mixed thickness (n=9). Each thickness group was divided into 3 subgroups and subjected to Er:YAG laser at different wattages (5, 5.6 and 5.9 W) to determine the appropriate wattage for each thickness. The removal time and temperature rise values were recorded. The Kruskal-Wallis test was performed to evaluate any significant differences in removal time, Mann-Whitney U test with Bonferroni correction for multiple comparisons, and the Pearson chi-square test for temperature rise over the critical value (p<0.05). Results: Laser irradiation at 5 W was safe and efficient for 1 mm thickness, while not efficient for others. Laser application at 5.9 W was efficient for all thicknesses, but, not safe for 1 mm thickness. The statistically significant difference in removal time was only between 5 W and 5.9 W groups (p=0.035). Pearson's chi-square test revealed that the temperature rise after 5.9 W laser application was significantly different from 5 W in 1 mm thickness group (p=0.043). Conclusion: Er:YAG laser lithium disilicate crown removal is an effective and safe method using laser settings appropriate for crown thickness.

Er:YAG laser lithium disilicate crown removal: removal time and pulpal temperature change.

Since the removal of resin-luted all-ceramic restorations is a challenge, the use of Er:YAG lasers has become popular. The aim of this study was to determine the removal time of monolithic lithium disilicate crowns in different thicknesses and heat transmission to pulp using Er:YAG laser. Forty-five full-coverage monolithic lithium disilicate crowns in 1 mm (n = 15), 1.5 mm (n = 15), and mixed thickness (n = 15) were resin luted on relevant extracted human maxillary first premolars and subjected to Er:YAG laser irradiation for crown removal after 24 h. Laser parameters for each thickness, respectively, were 5 W, 5.6 W, and 5.9 W (10 Hz). The removal time and temperature change values were recorded for each sample. The statistical evaluations were performed using one-way ANOVA variance and post hoc Duncan and Tamhane's T2 tests (p < 0.05), and Pearson correlation coefficient was used to examine the significance within each group and without group discrimination. All crowns were laser-debonded successfully. The removal time (min:s) at the succeeding laser parameter for each group is as follows: between 2:30 and 4:45 at 5 W power for 1-mm samples, between 5:00 and 11:15 at 5.9 W power for 1.5-mm samples, and between 8:45 and 15:00 at 5.9 W power for samples in mixed thickness. Moreover, it was observed that the temperature changes in the pulp chamber did not exceed the critical value of 5.5 °C for any sample. Er:YAG laser irradiation is an effective and safe method for removal of all-ceramic crowns when appropriate laser parameters are used according to thickness.

Evaluation of rebonding strengths of leucite and lithium disilicate veneers debonded with an Er:YAG laser.

Resin cements create a high bond between the tooth and ceramic surfaces, thus making it impossible to remove the restoration in one piece. The aims of this study were to evaluate (i) the efficiency of an Er:YAG laser for debonding, and (ii) the changes in the rebonding strength values of all-ceramic veneers, which were removed after laser application. A tooth reduction of 120 extracted human maxillary central incisors was made to provide two different bonding surfaces (60 enamel and 60 dentin). Sixty leucite and 60 lithium disilicate discs (1-mm thickness, 5-mm diameter) were cemented to prepared surfaces with a dual-cure resin cement. Each group was divided into two subgroups (n = 15): control and laser-irradiated. Er:YAG laser (2940 nm) was applied for 9 s at 3 W power (10 Hz, 300 mJ) with 100 µs pulse duration. Shear bond strength (SBS) test was made with a universal testing machine. After the tested laser-irradiated specimens had been rebonded, the SBS test was performed again and rebonding strengths were measured. The statistical evaluations were performed by using repeated measures one-way ANOVA and post hoc Bonferroni tests (p < 0.05). Significant differences were found between the control and laser-irradiated groups (p < 0.001). While the required SBS values for control groups were between 30.04 and 24.66 MPa, the values for laser-irradiated groups were between 6.60 and 4.09 MPa. There was no significant difference between the control and rebonded groups. Er:YAG laser-irradiation is an effective method for removing all-ceramic restorations without affecting the rebonding strength.

Effects of Silica Coating by Physical Vapor Deposition and Repeated Firing on the Low-Temperature Degradation and Flexural Strength of a Zirconia Ceramic.

PURPOSE: To examine the application of physical vapor deposition (PVD) silica coating as an approach to retard low temperature degradation (LTD) for dental applications. Accelerated aging characteristics of heat- and surface-treated zirconia material were also investigated by exposing specimens to hydrothermal treatment. MATERIALS AND METHODS: The specimens (90 disc-shaped specimens [15 mm ×1.2 mm]) were divided into 9 groups (n = 10) according to the test protocol: Ctrl, control (no surface treatment); Ag, autoclave aging; GrAg, grinding + aging; SiAg, silica coating + aging; GrSiAg, grinding + silica coating + aging; 3FAg, 3-time firing + aging; Gr3FAg, grinding + 3-time firing + aging; 5FAg, 5-time firing + aging; Gr5FAg, grinding + 5-time firing + aging. Accelerated aging was performed in a steam autoclave (134°C, 2 bars) for 12 hours. Following each treatment protocol, X-ray diffraction (XRD) analysis was used to estimate the relative amount of monoclinic phase and corresponding transformed zone depth (TZD). Additionally, a biaxial flexure test was used to calculate the flexural strength. Statistical analysis was conducted with one-way ANOVA and Fisher's LSD test (p < 0.05). RESULTS: The tetragonal-to-monoclinic transformation was retarded by PVD silica coating only on ground surfaces. Ground and heat-treated specimens exhibited the lowest monoclinic content after aging. The biaxial flexural strength value of the GrAg group was significantly higher than the values in all of the other groups except the SiAg group. The flexural strength value of the GrSiAg group was significantly higher than that of the 3FAg group. There was no statistically significant difference between the other groups (p > 0.05). CONCLUSIONS: Grinding decreased the susceptibility of zirconia to LTD and increased the flexural strength. PVD silica coating and repeated firing decreased the monoclinic content only in ground specimens during aging.

Simultaneous alveolar cleft closure and dental midline correction with curvilinear intraoral distraction.

This article describes a new method that enables vector control during alveolar distraction osteogenesis in the treatment of a cleft palate patient. The patient presented with unilateral complete cleft lip and palate, and the alveolar part of the defect was covered by a mobile buccal flap. The distraction was performed by sliding the surgically released tooth segment with the help of an intraoral distractor over 1.5-mm stainless steel archwires held by metal crowns. This vector-controlled method enabled new bone and attached gingiva formation in harmony with the proper alveolar shape.

Evaluating the additional effects of arthrocentesis on the condylar pathways of temporomandibular joint in patients with internal derangement treated with stabilizing splint.

OBJECTIVES: The purpose of this investigation is to find out the differences in the condylar pathways of the temporomandibular joint (TMJ) in patients treated with stabilizing splint and arthrocentesis accompanied by stabilizing splint in 6 months period. STUDY DESIGN: Forty patients who were assigned a clinical diagnosis of internal derangement of the TMJ were included in this study. Full arch stabilizing splints were made for all patients. Patients were divided into two groups; group A (patients who underwent arthrocentesis), group B (patients who did not underwent arthrocentesis). Computerized axiography was performed for each group before therapy (T0), on the 3(rd) month (T1), after arthrocentesis (TA) (for group A) and on 6th month (T2). Curve parameters were recorded in three-dimension; X axis (posteroanterior), Y axis (mediolateral), Z axis (superoinferior). Also the distance from the starting point of the movement on sagittal plane (S) was calculated. RESULTS: There was a significant increase in the value of Z (p = 0.014) and S (p = 0.038) in mediotrusion movement in group A. Also, there was a significant increase in the value of Z (p = 0.007) in protrusion/retrusion movement, value of Z (p = 0.019) and S value (p = 0.002) in mediotrusion movement and value of Y in open/close movement in group B. CONCLUSIONS: No positive effects on condylar pathways of an additional arthrocentesis to splint therapy alone in patients with internal derangement were found in this study.

Retention behaviors of different attachment systems: precious versus nonprecious, precision versus semi-precision.

The aims of this study were to investigate the retention force changes of different attachment systems after 10,000 insertion-separation cycles and the difference in retention force between precious and non-precious materials of the same attachment system. Four types of attachments (Ball, Rod, M3 stud, and AP-Piccolino), produced using both precious and non-precious metal alloys, were tested (n=6). Data were analyzed using analysis of variance (ANOVA), Tukey's multiple comparison test, and t-test at a significance level of p≤0.05. Retention forces of all attachment types were significantly decreased after 10,000 insertion-separation cycles (p≤0.05). Rod and M3 attachment systems showed an initial increase in retention force, then an eventual decrease. At the end of the test, precious types of M3 and AP-Piccolino attachments had significantly higher retention force values than their non-precious ones (p≤0.05). Friction between non-precious attachment parts resulted in a higher retention loss than precious metal alloys.

Evaluating the correlation between the lateral pterygoid muscle attachment type and internal derangement of the temporomandibular joint with an emphasis on MR imaging findings.

OBJECTIVES: Disc displacement is accepted as one of major findings in temporomandibular disorders. Correlation between lateral pterygoid muscle (LPM) attachment type to the disc-condyle complex and TMJ dysfunction has rarely been discussed and still not clarified. The purpose of this study was to assess the prevalence LPM attachment type to the disc-condyle complex, and to investigate whether these attachment types are linked to MR imaging findings of ID and TMJ dysfunction in a Turkish population. STUDY DESIGN: Ninety-eight TMJs in 49 patients (32 males, 17 females, mean age=36 years) with one of either: TMJ clicking, TMJ locking, restricted movement of the jaw, or pain in the TMJ region, were included. According to the clinical findings and data obtained from MRI examinations, TMJs dysfunctions were classified. LPM attachments to the condyle-disc complex were categorized into three different types. Correlation between TMJ dysfunction and LPM attachments to the condyle-disc complex was evaluated. RESULTS: Of 98 TMJs in 49 patients (32 males, 17 females, mean age=36 years), 47 TMJ's (%48) were evaluated as normal, 35 (%35.7) had a disc displacement with reduction and 16 (%16.3) TMJ had a disc displacement without reduction. Arthritis was seen in 49 TMJ's (%50). LPM attachments to the condyle-disc complex were as follows: Type I (29.6%), Type II (40.8%), and Type III (29.6%). There was no statistically significant difference between the type of muscle attachment and the presence or absence of disc displacement (p=0.481), disc degeneration (p=0.752), articular surface degeneration (p=0.117). CONCLUSIONS: There was no statistically significant correlation between the LPM attachment types and TMJ abnormalities.

The effect of temporary hydrostatic splint on occlusion with computerized occlusal analysis system.

AIMS: The aim of this study was to evaluate the effect of temporary hydrostatic splint on occlusion with computerized occlusal analysis system. MATERIAL AND METHODS: Maximal bite force was recorded in intercuspal position by use of computerized occlusal analysis system from 11 female, 9 male, 20 subjects, (average age of 20) with normal intact dentitions. Subjects were instructed to use the hydrostatic splint for 24 h. Occlusal records were repeated three times before and after splint. All recordings were evaluated to determine the repeatability of the computerized occlusal analysis system. RESULTS AND CONCLUSION: Hydrostatic splint increased maximum biting force. Relative percentage of left and right bite forces changed in the direction of neurophysiological position of the muscles. Hydrostatic splint can be a viable option for occlusal adjustments.

Rehabilitation of maxillary anterior esthetics by alveolar distraction osteogenesis with immediate implant placement: a case report.

Esthetic reconstruction of severe soft and hard tissue deficiencies is the utmost challenge in implant dentistry. To prevent postoperative bone resorption and to control the amount of hard and soft tissue volume, distraction osteogenesis followed by immediate implant placement has been proven to be a promising combined technique. The aim of this report is to introduce a treatment strategy to maintain anterior esthetics and to control hard and soft tissue volume in a case, treated with the combined technique of vertical alveolar distraction and immediate implant placement. An osteotomy was performed by the use of an oscillating saw. Cut alveolar segment was mobilized, and a distractor device was inserted in between the segments. During the activation and consolidation periods of distraction, anterior esthetics was provided with removable acrylic provisional crowns placed on the distractor's rod. In 2 weeks of distraction period, vertically 10 mm of new bony segment was obtained, and 2 weeks after the removal of distractor, maxillary incisors were extracted. Four dental implants were placed according to the immediate placement protocol. In osseointegration period, provisional restorations were fabricated on abutments to form harmonious gingival contours and to maintain maxillary anterior esthetics until the fabrication of final restorations.

Effects of Bartter's syndrome on dentition and dental treatment: a clinical report.

Bartter's syndrome is an autosomal recessive form of severe volume depletion due to renal salt wasting. This clinical report describes the prosthodontic treatment for a 24-year-old man who suffers from Bartter's syndrome. The treatment plan included endodontic treatment of the maxillary anterior incisors and placement of cast dowel-and-core restorations because of reduced crown height. The patient's remaining teeth were restored with metal-ceramic crowns.