Journal of Dental Medicine

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In this investigation, the position of hyoid bone was compared in three skeletal groups of class I, II and III. The study was based on evaluating 77 lateral cephalometric radiographs, 40 girls and 37 boys, which were divided into 3 groups. Group 1, 2, and 3 consist of 26, 25, and 26 radiographs. 19 cephalometric landmarks and 10 planes were used in order to tracing the radiographs. In all patients, 9 skeletal and 4 cervical vertebrae parameters were measured to determine the hyoid bone. These parameters were compared between three skeletal groups regardless of sex and then, in another statistical analysis, parameters were compared based on patients sex. Statistical analysis showed that in class III patients, the hyoid bone was positioned more anteriorly than two other groups. Also in this group, the hyoid bone had less inclination and it was more horizontal in relation to mandibular plane. In skeletal class II patients this bone was positioned more superiorly than two other groups. Due to these findings it can be concluded that perimandibular muscles and bones could affect the growth of mandible. In addition, comparison of the parameters between two sexes revealed that the hyoid bone was positioned more anteriorly and inferiorly in boys. Also it was shown that in the girls, the position of hyoid bone was closer to the position of this bone in skeletal class I patients.

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Conventional cephalometric analysis, based on intracranial reference line SN and Frankfurt plan, sometimes leads to incorrect diagnostic findings and unpleasant theraputic results, especially in orthosurgery patients, mainly due to the instability of the mentioned references. Natural head position (NHP) is the standardized orientation of the head that its record in lateral cephalometric radiographs, provides us with extracranial references. The aim of this study is to evaluate the necessity for providing a lateral cephalogram in NHP for diagnosis and treatment of severe malocclusion (orthosurgery) in comparison with mild to moderate malocclusions. For this reason, 28 orthodontic and 26 orthosurgery patient's cephalograms, in natural head position, were selected. Diagnosis and treatment planning were based on clinical evaluation and cephalometric analyses especially Harvold and Tweed ones. Each group, based on their growth pattern, was divided vertically and horizontally. The angles between SN and TH planes with TH (True vertical Sine) were measured. Then, the correlation between the angles in two groups and also in relation to the severity of malocclusion, were analyzed in vertical and horizontal directions. The results of two groups were compared by the independent t-test. The findings of this study showed that:1- The SN line was found to be more inclined than FH line and in orthodonthic patients, FH plan is a more reliable reference than SN.2- In orthosurgery patients, the SN-TH and FH-TH angles were strongly different statistically.3- Variation in SN-TH angle, in patients with vertical growth pattern, was high in both groups of patients.These conclusions prove the necessity of a lateral cephalogram in NHP for all orthosurgery patients and those orthodontic patients with vertical growth pattern.

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Background and Aim: Several surgical approaches have been used to achieve root coverage. The Subepithelial Connective Tissue Graft (SCTG) procedure has been shown to be a predictable means to treat gingival recession. Semilunar Coronally Positioned Flap (SCPF) is a simple mucogingival surgery to cover the exposed root surface without harvesting the palatal connective tissue. The purpose of this study is to compare the outcome of gingival recession therapy using SCTG and SCPF.

Materials and Methods: Forty Miller class I buccal gingival recessions (≥2mm) were selected. Recessions were randomly assigned to receive either the SCPF or SCTG. Recession Height (RH), Recession Width (RW), Width of Keratinized Tissue (WKT), Probing Depth (PD), Clinical Attachment Level (CAL), were measured at baseline, 1, 3, and 6 months after surgery. The data were analyzed using independent t-test and Repeated Measure ANOVA.

Results: The average percentages of root coverage for SCPF and SCTG were 88% and 71%, respectively and the complete root coverage observed were 55% and 45%, respectively. There were no significance differences between the two groups with regard to RW, PD, CAL, WKT (except in the third month after surgery which was slightly greater in SCPF group). RH was significantly decreased from 2 to 6 months after surgery in SCPF group.

Conclusion: The findings from this study indicate that if the tissue thickness and initial width of keratinized tissue are sufficient, SCPF may be a good substitute for SCTG in treatment of Miller class I gingival recessions.

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Background and Aims: Accurate bone measurements are essential for determining the optimal size and length of proposed implants. The radiologist should be aware of the head position effects on image dimensions in each imaging technique. The purpose of this study was to evaluate the effect of mandibular plane angle on image dimensions in linear tomography.
Materials and Methods: In this in vitro study, the vertical dimensions of linear tomograms taken from 3 dry mandibles in different posteroantenior or mediolateral tilts were compared with actual condition. In order to evaluate the effects of head position in linear tomography, 16 series of images while mandibular plane angle was tilted with 5, 10, 15 and 20 degrees in anterior, posterior, medial, or lateral angulations as well as a series of standard images without any tilt in mandibular position were taken. Vertical distances between the alveolar crest and the superior border of the inferior alveolar canal were measured in posterior mandible and the vertical distances between the alveolar crest and inferior rim were measured in anterior mandible in 12 sites of tomograms. Each bone was then sectioned through the places marked with a radiopaque object. The radiographic values were compared with the real conditions. Repeat measure ANOVA was used to analyze the data.
Results: The findings of this study showed that there was significant statistical difference between standard position and 15º posteroanterior tilt (P<0.001). Also there was significant statistical difference between standard position and 10º lateral tilt (P<0.008), 15º tilt (P<0.001), and 20º upward tilt (P<0.001). In standard mandibular position with no tilt, the mean exact error was the same in all regions (0.22±0.19 mm) except the premolar region which the mean exact error was calculated as 0.44±0.19 mm. The most mean exact error among various postroanterior tilts was seen in 20º lower tilt in the canine region (1±0.88 mm) and for various mediolateral tilts the most exact error was seen in the canine region in 20º upper tilt (2.9±2 mm).
Conclusion: The mean exact errors in various regions and various 5º to 20º posteroanterior and mediolateral mandibular tilts were in the range of acceptable values (≤1 mm) except for the canine region. However, this effect is more considerable in mediolateral tilt compared with posteroanterior tilt, posterior region compared with anterior region, and upper tilt compared with lower tilt.