Clinical experience and results with a Rhombic Plate for transoral endoscopically-assisted osteosynthesis of fractures of the condylar neck

The intraoral approach is favoured by many patients and surgeons for the treatment of fractures of the condylar neck, but the limited space offered by this approach can make positioning and fixation of the osteosynthesis plate difficult. A rhombic-shaped plate was designed specifically for use with the intraoral approach, and introduced into our clinical practice in 2012. We present the clinical and functional results in 81 patients with 98 fractures of the condylar neck who we have treated with this technique. Of these six required surgical revision, and ultimately all but two had satisfactory occlusion and mandibular function. Our complication rate of 6/81 (7.4%) compares favourably with those reported elsewhere, and confirms that open reduction and internal fixation of condylar fractures using the Rhombic plate through an intra-oral approach provides good outcomes.     

Osteochondroma of the mandibular condyle. Report of a case and review of the literature

Osteochondroma (osteocartilaginous exostosis) is a rare tumour in the region of the mandibular condyle. Much confusion seems to exist in the literature in differentiating these tumours from condylar chondromas as well as from condylar hyperplasias. A case of condylar osteochondroma with a review of the literature is presented.     

Prostaglandin synthesis in dental cysts

The synthesis of prostaglandins by dental squamous cell cysts was studied. Radiothinlayer-chromatography (RTLC) showed C14-labelled arachidonic acid to be converted into the prostaglandins PGE2, 6-oxo-PGF1 alpha, PGF2 alpha and PDG2. In addition, hydroxyfatty acid synthesis in excess of total prostaglandin production was observed. The substances mentioned are thought to be causally involved in the osteolytic activity of dental cysts.     

Accuracy of surgical guides from 2 different desktop 3D printers for computed tomography-guided surgery

Statement of problem

Different factors influence the degree of deviation in dental implant position after computed tomography–guided surgery. The surgical guide–manufacturing process with desktop 3D printers is such a factor, but its accuracy has not been fully evaluated.

颧弓根复位在颧骨复合体骨折治疗中的意义

目的：提出以颧弓根复位作为治疗颧骨复合体骨折的参照标准。方法：14例合并颧弓根骨折的颧骨复合体骨折,首先将颧弓根复位,然后固定其他的骨折线。术后随访6个月,观察面型、颧骨颧弓对称度。结果：患者均切口Ⅰ期愈合;面形恢复满意、两侧对称、开闭口功能正常11例;面形恢复两侧基本对称,开闭口功能正常3例。患者额部和头皮感觉异常2例;头皮秃发瘢痕〉0．5cm者1例。结论：颧弓根首先复位在颧骨复合体骨折治疗中具有重要参照意义,可以依据颧弓根的固定恢复颧弓宽长度及准确复位颧骨。     

Fracture resistance and 2-body wear of 3-dimensional–printed occlusal devices

Statement of problem

Polymeric material for 3-dimensional printing can be used to fabricate occlusal devices. However, information about fracture resistance and wear is scarce.

Predictability of pharyngeal airway space dimension changes after orthognathic surgery in class II patients: A mathematical approach

IntroductionAngle Class II malocclusion due to mandibular retrognathia is a common dentofacial deformity. It is well known that mandibular advancement increases pharyngeal airway dimensions. The aim of this study was to evolve a mathematical method for predicting posterior pharyngeal airway space (PAS) changes based on 2D lateral cephalographic radiographs (LCRs) and expected extent of mandibular advancement prior to BSSO.Materials and methodsLinear regression analyses were performed in order to investigate the relation between the posterior airway space and mandibular advancement. LCRs where carried out to assess skeletal landmarks and pharyngeal airway space pre- (T0) and postoperatively (T1). To detect changes postoperatively, the posterior airway space was divided into three units: nasopharyngeal airway space (superior airway space — SPAS), oropharyngeal airway space (mid airway space — MAS) and hypopharyngeal airway space (inferior airway space — IAS). The differences between the distances of distinct measurement points (DIFF) were measured pre- and postoperatively. DOA referred to the distance of mandibular advancement and DP to the distance between the measurement points preoperatively. The parameters a, b₁ and b₂ were the regression coefficients that were determined separately for each unit (SPAS, MAS, and IAS).Results49 patients (16 male and 33 female) with a mean age of 27.2 years (SD: 10.09), ranging from 18 to 51 years, who underwent mandibular advancement surgery (BSSO) were enrolled in this study. The mean distance of mandibular advancement was 5.05 mm (SD: 1.63). Regarding SPAS and IAS, mandibular advancement did not affect dimensions significantly: SPAS DIFF, 0.33 mm ± 1.13 mm (b₁, p = 0.0881; b₂, p = 0.087); IAS DIFF, 0.66 mm ± 2.45 mm (b₁, p = 0.342; b₂, p = 0.765). DOA and DP did not influence DIFF significantly in both sections. Regarding MAS, the mean effect of mandibular advancement was an expansion of 2.47 mm ± 2.24. The linear regression model showed a statistically significant (b₁, p = 0.0064; b₂, p = 0.0240) influence of DOA and DP on DIFF in posterior airway dimensions pre- and postoperatively.DiscussionBased on preoperative LCR imaging data, a linear regression model was developed as a mathematical approach to allow prediction of PAS development in patients with Angle Class II malocclusions of different degrees. Increasing mandibular advancement was shown to be linked to increasing PAS, while a greater distance between the measuring points preoperatively led to smaller predicted PAS increases postoperatively.ConclusionPredicting pharyngeal airway space (PAS) development after mandibular advancement by analysing lateral cephalometric radiographs (LCR) may be useful in the screening and treatment of obstructive sleep apnea syndrome (OSAS) patients. Our mathematical approach is a simple and sustainable prediction tool based on LTR data for patients with Class II malocclusions.     

Reproducibility of intraoral photography for pink and white tissue assessment — Is it worth the hassle?

PurposeTo assess the effect of the shooting angle variation on linear and planimetric measurements of the pink and white tissues on intraoral photographs.MethodsFrom intraoral three-dimensional (3D) scans of the anterior region in 10 patients, ninety-nine two-dimensional (2D) “scan pictures” each were generated with different shooting angles, each varying in 5° horizontal and vertical increments. Eleven intraoral photographs of each patient and tooth site were taken free-hand: one shot at baseline and 5 shots after 3 and 6 months at slightly varying shooting angles. Papilla height (PH) and area (PA) and tooth crown area (TCA) were estimated on all photographs; the “best-match-to-baseline” photograph from those taken at 3 and 6 months was chosen by 6 evaluators.ResultsWithin the first 10° of deviation from the baseline shooting angle, measurements on the 2D “scan pictures” distorted ≤0.5 mm for PH and ≤10% for PA and TCA. Compared to baseline, only 6 out of 100 photographs presented ≥0.5 mm difference in PH, none of the TCA measurements showed distortion ≥10%, and only in 4 instances a ≥10% distortion of the PA was observed. Poor to moderate inter- and intra-rater agreement in choosing the “best-match-to-baseline” photograph was found, but photographs with clinically relevant changes were only seldomly chosen.ConclusionsDeviations in the shooting angle ≤10° from the baseline shot cause clinically negligible distortions in linear and planimetric measurements. Highly comparable intraoral photographs of the anterior maxillary teeth can be captured “free-hand” in slightly varying perspective, and then selecting the “best-match-to-baseline”.     

Power spectral analysis of the surface electromyogram of human jaw muscles during fatigue

Muscle fatigue in the anterior temporal and masseter muscles of 13 normal subjects was induced by maximum clench in intercuspal position. Frequency analysis using a fast Fourier transform algorithm to obtain the power-spectral density function and the power spectrum of the electromyogram signal indicated that the power spectra obtained during fatigue were statistically significantly shifted to lower frequencies and narrower than those obtained at the beginning of the clench. The shift was due to a significant increase of the power in the low-frequency range and a significant decrease of that in the high-frequency range. The power-spectrum shift to lower frequencies had an exponential time course. The most pronounced shift occurred in the first 25 per cent of the total clenching time. Decrease of the conduction velocity of the action potential along the muscle fibre seems to be the main cause of the shift.     

Comparison of Stability of Fracture Segments in Mandible Fracture Treated with Different Designs of Mini-Plates Using FEM Analysis

Aim

To compare the displacement gap of mandible fracture segments treated with different designs of mini-plates under various loading conditions.

Materials and Methods

Fracture in the body of mandible was bridged with 15 different designs and configuration of titanium mini-plates. Bite forces were applied at 3 locations, ipsilateral fractured side, contra lateral side and incisor site. 3D finite element methods (FEM) model of mandible was generated using 10 nodal tetrahedral elements. A commercial FE solver was used to solve bone inter fragmentary displacement during loading.

Results

Superior position of mini-plates produced better stability than inferior position. Positive bending moments can be reduced by larger plate in lower border in 2 plate system. Results of X mini-plate are comparable to 2 plate configuration. If length of middle portion of plate increased, stability decreased. Number of screws did not affect fracture stability.

Conclusion

Finite element methods analysis is used to determine the gap between mandible fragments which is otherwise impossible to measure clinically. The results obtained from this study offered us a choice of mini-plate design and configuration for clinical application.