Yener Oguz

Stability of locking and conventional 2.0-mm miniplate/screw systems after sagittal split ramus osteotomy: finite element analysis.

OBJECTIVE The aim of this study was to evaluate the mechanical stresses over the bone and hardware after sagittal split ramus osteotomy (SSRO) fixed with standard titanium or locking plate/screws using finite element analysis. STUDY DESIGN A 3-dimensional finite element model of the mandible was created, and SSRO and 5 mm advancement was simulated on a computer model. The model was fixed with either 2.0-mm titanium conventional miniplate/screw or 2.0-mm titanium locking miniplate/screw system, and oblique 200 N bite force was applied. RESULTS The values of von Mises stresses in the cortical layer of the distal segment using the locking plate system was higher. However, in the cortical layer of the proximal segment the stresses were higher at conventional plate system. In the spongiosa layers of both segments, stresses were higher with the conventional plate system. CONCLUSION The locking miniplate/screw system spreads the load over the plate and screws and diminishes the amount of force transfered to each unit.

Repositioning a prosthetically unfavorable implant by vertical distraction osteogenesis.

Prosthetically unfavorable implant positions challenge patients and restorative dentists. Surgical correction of malpositioned implants may be an alternative technique for esthetically and biomechanically acceptable prosthetic restorations. This case report describes an alveolar distraction technique used to coronally reposition a dental implant and the 3-year results in the maintenance phase. To our knowledge, long-term follow-up of this method of correction is unprecedented. The present case report describes the repositioning of an apically positioned and fully osseointegrated implant at the right maxillary canine region using an alveolar distraction technique. Distraction was performed at 1 mm per day and ended when the implant moved 6 mm coronally. After a consolidation phase of 8 weeks, an implant-supported fixed prosthetic restoration was performed. Healing was uneventful after removal of the distractor. During the 3-year follow-up, the implant was fully functional with minimal probing depths, negligible signs of inflammation, and no further bone loss. This intervention illustrates the promise of an alveolar distraction osteogenesis procedure for vertical repositioning of apically positioned implants. This technique also provided soft and hard tissue remodeling to obtain an esthetic and stable restoration.

Are success and survival rates of early implant placement higher than immediate implant placement

Immediate placement refers to the placement of an implant into a tooth socket at the time of extraction; early placement refers to the placement of an implant after substantial gingival healing, but before any clinically significant bone fill occurs within the socket. This study evaluated the success and survival rates of implants following immediate and early placement. 50 implants were placed in 36 patients. 26 immediate (group I) and 24 early placements (group II) were performed. Pain or tenderness with function, mobility, radiographic bone loss from initial surgery and exudate history were evaluated. Mean vertical bone loss in the immediate placement group was 0.55 mm and 0.80 mm in the early placement group. The survival rate for the immediate placement group was 96.16% with 51.6 months follow-up and in the early placement group was 100% with 61.9 months follow-up. The results of this study suggest that although the success and survival rates of early placed implants were a little higher and the follow up period was longer than immediately placed implants, the difference was not remarkable. In conclusion, both implant insertion techniques are safe and reliable procedures with considerably high survival rates.

Comparison of stability of 2.0 mm standard and 2.0 mm locking miniplate/screws for the fixation of sagittal split ramus osteotomy on sheep mandibles

Ten unembalmed adult sheep mandibles were used. The mandibles were sectioned in the midline, followed by sagittal split ramus osteotomies to obtain 20 hemimandibles. Each distal segment was advanced 5mm on each hemimandible. Ten of the specimens were fixed with 4-hole extended 2.0 mm titanium miniplates and screws and the other 10 were fixed with 4-hole extended 2.0 mm locking miniplates/screws. Each fixed specimen was mounted on a servo-hydraulic testing unit with the fixation device, and was tested to a range of forces of 0-140 N. The displacement values (mm) under 20, 60, 120, and 140 N were compared with the help of the Mann-Whitney U-test, and there were no significant differences between them at any force tested. Locking miniplate/screws and standard miniplate/screws showed similar displacement values at the range of forces tested.

Mechanical evaluation of six techniques for stable fixation of the sagittal split osteotomy after counterclockwise mandibular advancement

We have evaluated the resistance to displacement of six stable methods of fixation of a sagittal split ramus osteotomy (SSRO) in the mandibular advancement with counterclockwise rotation. We tested 60 synthetic hemimandibles in six groups of 10 each: Group I - fixation with a straight four-hole 2.0mm miniplate; Group II - a straight six-hole 2.0mm miniplate; Group III - two straight 2.0mm four-hole miniplates; Group IV - an eight-hole 2.0mm (grid plate); Group V - a 2.0mm four-hole straight miniplate and 2.0×12mm bicortical screw; and Group VI - a straight four-hole 2.0mm locking miniplate. We applied a linear force in the region between the canine and the first premolar using a universal testing machine (EMIC- DL2000) with a loading cell of 10 KN. The loads at 1, 3, and 5mm displacement were recorded (N) and the data transmitted from the load cell to a computer. Results were analysed using analysis of variance (ANOVA) (p<0.001) and the Tukey post-test for comparison of the significance of the differences between the groups. For the three degrees of displacement, fixation with two straight 2.0mm plates and with the grid plate gave higher load values.

In vitro biomechanical comparison of six different fixation methods following 5-mm sagittal split advancement osteotomies

The sagittal split ramus osteotomy (SSRO) is a surgical technique used widely to treat many congenital and acquired mandibular discrepancies. Stabilization of the osteotomy site and the potential for skeletal relapse after the procedure are still major problems. The aim of this study was to compare the mechanical stability of six methods of rigid fixation in SSRO using a biomechanical test model. Sixty polyurethane replicas of human hemimandibles were divided into six groups. In group I, the osteotomies were fixed with two four-hole titanium miniplates; in group II, with one four-hole miniplate; in group III, with one four-hole miniplate+a bicortical screw; in group IV, with a grid miniplate; in group V, with a four-hole locking miniplate; and in group VI, with a six-hole miniplate. A linear load in the premolar region was applied to the hemimandibles. The resistance forces (N) needed to displace the distal segment by 1, 3, and 5mm were recorded and the data transmitted from the load cell to a computer. One-way analysis of variance with Tukeys post hoc test was performed to compare the means between groups. For the three displacement conditions, there was a strong tendency for the 2.0-mm plate+screw and the grid plate to have higher values.

Stress Distribution on Short Implants at Maxillary Posterior Alveolar Bone Model With Different Bone-to-Implant Contact Ratio: Finite Element Analysis

The aim of this study was to evaluate the stress distribution of the short dental implants and bone-to-implant contact ratios in the posterior maxilla using 3-dimensional (3D) finite element models. Two different 3D maxillary posterior bone segments were modeled. Group 1 was composed of a bone segment consisting of cortical bone and type IV cancellous bone with 100% bone-to-implant contact. Group 2 was composed of a bone segment consisting of cortical bone and type IV cancellous bone including spherical bone design and homogenous tubular hollow spaced structures with 30% spherical porosities and 70% bone-to-implant contact ratio. Four-millimeter-diameter and 5-mm-height dental implants were assumed to be osseointegrated and placed at the center of the segments. Lateral occlusal bite force (300 N) was applied at a 25° inclination to the implants long axis. The maximum von Mises stresses in cortical and cancellous bones and implant-abutment complex were calculated. The von Mises stress values on the implants and the cancellous bone around the implants of the 70% bone-to-implant contact group were almost 3 times higher compared with the values of the 100% bone-to-implant contact group. For clinical reality, use of the 70% model for finite element analysis simulation of the posterior maxilla region better represents real alveolar bone and the increased stress and strain distributions evaluated on the cortical and cancellous bone around the dental implants.

Radiological and Histological Evaluation of the Effects of Cortical Perforations on Bone Healing in Mandibular Onlay Graft Procedures

BACKGROUND Perforations of the cortical bone may be an advantage for the success of the autogenous bone graft procedure, but whether this perforation has a positive effect on the bone remains controversial. PURPOSE This study evaluates the effects of cortical perforation of the autogenous bone block graft radiologically and histologically. MATERIALS AND METHODS Seven adult pigs were used for this study. On the experimental side, cortical perforation at the host site was prepared, while no perforation was done on the control side. The specimens were evaluated, and the Wilcoxon signed-rank test was used for statistical analysis. RESULTS In the radiological evaluation, the Wilcoxon signed-rank test indicated no significant differences in densities among the grafts (p = .23) with a mean of 4.29 ± 0.951 for the unperforated graft side and 3.57 ± 0.976 for the decorticated graft side. In histological evaluation, there was a significant difference in the thickness of the grafts between the groups (experimental group 3.71 ± 1.286, control group: 4.71 ± 0.488; p = .033). However, when the remodeling and osteoblastic activity in the grafts were measured, no significant differences were observed between the groups (p = 1 and p = .133, respectively). CONCLUSION In augmentation with mandibular onlay bone grafts, cortical perforations in the recipient site make no distinct contribution to bone healing within 12 weeks.

Stafne bone cavity incidentally ''Twice'' diagnosed on panoramic radiographs

A 63-year-old male patient admitted to another hospital for prosthetic restoration. On the panoramic radiograph a lesion was detected on the right mandible and he was referred for a cone beam computed tomography (CBCT) examination. The patient then admitted to our clinic for the diagnosis of this lesion. Review of the dental records revealed that a panoramic radiograph and a maxillofacial computed tomography scan were made about 10 years ago, and a Stafne bone cavity (SBC) was diagnosed. Moreover, a follow-up panoramic radiograph was made about 5 years ago. Despite the explanation given, the patient requested the CBCT examination in a private imaging center. The imaging features of the lesion were the same. In order to protect the patients from unnecessary radiation, the clinicians should make every effort to prevent duplicate imaging, and X-ray based advanced imaging techniques should be reserved for selected cases.

Odontogenic effects of two calcium silicate-based biomaterialsin human dental pulp cells

BACKGROUND The goal of treating exposed pulp with an appropriate pulp capping material is to promote the dentinogenic potential of the pulpal cells. There have been recent attempts to develop more effective pulp-capping materials. OBJECTIVES The aim of this study was to evaluate the effect of newly developed calcium silicate-based material on odontogenic differentiation of primary human dental pulp cells (HDPCs), in comparison with a contemporary calcium silicate-based material. MATERIAL AND METHODS Human dental pulp cells isolated from dental pulps were cultured in standard culture conditions in Dulbeccos Modified Eagles Medium (DMEM) and then the effects of Micro-Mega mineral trioxide aggregate (MM-MTA) (Micro-Mega, Besançon, France) and ProRoot MTA (MTA) (Dentsply Sirona, Tulsa, USA) (positive control) were evaluated on HDPCs at 1, 7 and 14 days. Untreated cells were used as a negative control. Odontoblastic differentiation was assessed by alkaline phosphatase (ALP) activity. Runtrelated transcription factor 2 (RUNX2), alkaline phosphatase liver/bone/kidney (ALPL), bone morphogenetic protein 2 (BMP2), dentin sialophosphoprotein (DSPP), and Distal-less homeobox 3 (DLX3), as odontoblastic/ osteoblastic expression markers, were evaluated by semi-quantitative real-time polymerase chain reaction (RT-PCR) analysis. Calcium levels of culture media were also determined. RESULTS The MM-MTA group significantly increased the expression of BMP2 compared with that of the MTA group at 3 different time periods (p < 0.05). The up-regulation of ALPL between day 1 and 14 and the up-regulation of DSPP between day 7 and 14 were significant in both groups (p < 0.05). Micro-Mega MTA and MTA exhibited similar messenger RNA (mRNA) expression levels of ALPL, DSPP, RUNX2, DLX3, and ALP activities, as well as calcium levels. CONCLUSIONS Based on the cell responses observed in this study, MM-MTA might be used efficiently in dental pulp therapy as a potential alternative to MTA.