Marcos Janson

Effect of mini-implant diameter on fracture risk and self-drilling efficacy.

INTRODUCTION The aim of this study was to evaluate the effect of mini-implant diameter on fracture risk and self-drilling efficacy. METHODS A sample of 405 mini-implants with 9 diameters from 1.2 to 2.0 mm was used. Ten mini-implants of each diameter were placed in artificial bone, and 25 were placed in pig iliac bone to evaluate placement torque (PT) and axial placement load (APL), which represents self-drilling efficacy. Ten mini-implants of each diameter were used to determine fracture torque (FT). The different diameters were compared regarding PT, FT, and APL. The fracture risk of each diameter was evaluated by the fracture resistance index (FT/PT × [FT-PT]). The PT and APL changes during placement were correlated. RESULTS Only PT and FT were different for all mini-implant diameter changes. PT and FT showed a strong correlation with the mini-implant diameter, but the APL was weakly to moderately correlated. The fracture resistance index was remarkably greater for each 0.1 mm added in diameter. The PT increased significantly, whereas the APL was progressively reduced during placement. CONCLUSIONS Increases in mini-implant diameters significantly influenced the increases of PT and FT on quantities that progressively reduced the fracture risk. The self-drilling efficacy was not strongly influenced by diameter.

Predictable drill-free screw positioning with a graduated 3-dimensional radiographic-surgical guide: a preliminary report.

INTRODUCTION Mini-implants are placed in restricted sites, requiring an accurate surgical technique. However, no systematic study has quantified technique accuracy to reliably predict the surgical risks. Therefore, a graduated 3-dimensional radiographic-surgical guide (G-RSG) was proposed, and its inaccuracy and risk index (RI) were estimated. METHODS The sample consisted of 6 subjects (4 male, 2 female), who used mini-implant anchorage. Ten drill-free screws (DFS) were placed by using the G-RSG. The central point of the mesiodistal septum width (SW) was the selected implant site on the presurgical radiograph. The distances between DFS and the adjacent teeth (5-DFS and 6-DFS) were measured to evaluate screw centralization and inaccuracy degree (ID). These distances were statistically compared by independent t tests, and inaccuracy was determined by the expression ID = (5-DFS - 6-DFS)/2, which represents deviation of the mini-implants final position regarding the central point initially selected. Then SW, ID, and screw diameter (SØ) were combined to estimate the surgical risk with RI expressed by RI = SØ/SW - ID. RESULTS The 5-DFS and 6-DFS distances were not significantly different. The ID of the G-RSG was 0.17 mm. The low ID ensured a safe RI (<1) in spite of the restricted SW. CONCLUSIONS The G-RSG accuracy allowed fine prediction of the final DFS position in the interradicular septum, with a low RI, which is a helpful tool to estimate surgical risks.

Influence of cephalometric characteristics on the occlusal success rate of Class II malocclusions treated with 2- and 4-premolar extraction protocols

INTRODUCTION The objectives of this investigation were to compare the initial cephalometric characteristics of complete Class II Division 1 malocclusions treated with 2 or 4 premolar extractions and to verify their influence on the occlusal success rate of these treatment protocols. METHODS A sample of 98 records from patients with complete Class II Division 1 malocclusion was divided into 2 groups with the following characteristics: group 1 consisted of 55 patients treated with 2 maxillary first premolar extractions at an initial mean age of 13.07 years; group 2 included 43 patients treated with 4 premolar extractions, with an initial mean age of 12.92 years. Initial and final occlusal statuses were evaluated on dental casts with Graingers treatment priority index (TPI), and the initial cephalometric characteristics were obtained from the pretreatment cephalograms. The initial cephalometric characteristics and the initial and final occlusal statuses of the groups were compared with the t test. A multiple regression analysis was used to evaluate the influence of all variables in the final TPI. RESULTS The 2-premolar extraction protocol provided a statistically smaller TPI and consequently a better occlusal success rate than the 4-premolar extraction protocol. The 4-premolar extraction group had statistically smaller apical base lengths, more vertical facial growth patterns, and greater hard- and soft-tissue convexities at pretreatment than the 2-premolar extraction group. However, the multiple regression analysis showed that only the extraction protocol was significantly associated with the final occlusal status. CONCLUSIONS The initial cephalometric characteristics of the groups did not influence the occlusal success rate of these 2 treatment protocols.

Hybrid fixation in the bilateral sagittal split osteotomy for lower jaw advancement.

Miniplate and screw fixation has been widely used in bilateral sagittal split osteotomy, but some issues remain unclear concerning its lack of rigidity when compared to Spiessls bicortical technique. This paper demonstrates the hybrid fixation technique in a case report. A 34-year-old female patient underwent a double jaw surgery with counter-clockwise rotation of the mandible fixed using the hybrid fixation technique. The patient evolved well in the postoperative period and is still under follow up after 14 months, reporting satisfaction with the results and no significant deviation from the treatment plan up to now. No damage to tooth roots was done, maxillomandibular range of motion was within normality and regression of the inferior alveolar nerve paresthesia was observed bilaterally. The hybrid mandibular fixation is clearly visible in the panoramic and cephalometric control radiographs. It seems that the hybrid fixation can sum the advantages of both monocortical and bicortical techniques in lower jaw advancement, increasing fixation stability without significant damage to the mandibular articulation and the inferior alveolar nerve. A statistical investigation seems necessary to prove its efficacy.

Relationship between maxillary and mandibular base lengths and dental crowding in patients with complete Class II malocclusions

OBJECTIVE To verify the relationship between maxillary and mandibular effective lengths and dental crowding in patients with Class II malocclusions. MATERIALS AND METHODS The sample comprised 80 orthodontic patients with complete Class II malocclusions in the permanent dentition (47 male, 33 female) who were divided into two groups according to the amount of mandibular tooth-arch size discrepancy. The maxillary and mandibular effective lengths (Co-A and Co-Gn) and tooth-arch size discrepancies were measured on the initial cephalograms and dental casts, respectively. Intergroup comparisons of apical base lengths were performed with independent t-tests. Correlation between base length and dental crowding was examined by means of Pearsons correlation coefficient (P < .05). RESULTS Patients with Class II malocclusion and moderate to severe crowding had significantly smaller maxillary and mandibular effective lengths than subjects with the same malocclusion and slight mandibular crowding. A weak inverse correlation was also found between maxillary and mandibular effective lengths and the severity of dental crowding. CONCLUSION Decreased maxillary and mandibular effective lengths constitute an important factor associated with dental crowding in patients with complete Class II malocclusion.

Orthognathic treatment for a patient with Class III malocclusion and surgically restricted mandible

This case report describes the orthodontic-surgical treatment of an adult with Down syndrome and a Class III skeletal malocclusion with posterior open bite, horizontal facial pattern, missing mandibular posterior teeth, and surgical restriction of the mandible.

Selective use of hand and forearm muscles during mini-implant insertion: a natural torquimeter.

Objective To compare maximum torque produced by different muscular groups and its influence on mini-implant insertion torque and fracture prevention. Design A prospective study involving in vivo and in vitro laboratory experiments. Materials and methods Eighty-seven professionals were evaluated for maximum torque produced using a screwdriver with combined action between thumb and index fingers [maximum digital torque (MDT)] and by forearm supination movement [maximum brachial torque (MBT)]. Ninety mini-implants distributed over nine different diameters and twenty commercially available mini-implants of two different diameters and trademarks were fractured to determine the fracture torque (FT). The fracture resistance index (FRI) was obtained from: FRI_MDT = FT/MDT and FRI_MBT = FT/MBT. The analysis of variance (ANOVA) and t tests were used to compare the groups. Results MDT was smaller than MBT and both were smaller in females. FT increased for each 0·1 mm of diameter increment. FRI_MDT was greater than FRI_MBT for all diameters. FRI_MDT>1 was found when the diameter was greater than or equal to 1·5 mm. FRI_MBT>1 occurred with diameters equal or greater than 1·7 mm for females and 1·8 mm for males. The 1.5 mm and 1.6 mm diameter of commercially available and mini-implants presented FRI_MBT<1 and FRI_MDT>1. Conclusions Digital torque was 42% smaller than brachial torque, and it was mechanically safer and biologically more compatible, allowing fracture prevention of 1·5 mm or thicker mini-implant diameter due to insertion torque limitation at 15 N/cm.

A modified orthodontic protocol for advanced periodontal disease in Class II division 1 malocclusion

An interdisciplinary approach is often the best option for achieving a predictable outcome for an adult patient with complex clinical problems. This case report demonstrates the combined periodontal/orthodontic treatment for a 49-year-old woman presenting with a Class II Division 1 malocclusion with moderate maxillary anterior crowding, a 9-mm overjet, and moderate to severe bone loss as the main characteristics of the periodontal disease. The orthodontic treatment included 2 maxillary first premolar extractions through forced extrusion. Active orthodontic treatment was completed in 30 months. The treatment outcomes, including the periodontal condition, were stable 17 months after active orthodontic treatment. The advantages of this interdisciplinary approach are discussed. Periodontally compromised orthodontic patients can be satisfactorily treated, achieving most of the conventional orthodontic goals, if a combined orthodontic/periodontic approach is used.

Orthodontic-surgical treatment of Class III malocclusion with extraction of an impacted canine and multi-segmented maxillary surgery

Establishment of a treatment plan is based on efficacy and easy application by the clinician, and acceptance by the patient. Treatment of adult patients with Class III malocclusion might require orthognathic surgery, especially when the deformity is severe, with a significant impact on facial esthetics. Impacted teeth can remarkably influence treatment planning, which should be precise and concise to allow a reasonably short treatment time with low biologic cost. We report here the case of a 20-year-old man who had a skeletal Class III malocclusion and impaction of the maxillary right canine, leading to remarkable deviation of the maxillary midline; this was his chief complaint. Because of the severely deviated position of the impacted canine, treatment included extraction of the maxillary right canine and left first premolar for midline correction followed by leveling, alignment, correction of compensatory tooth positioning, and orthognathic surgery to correct the skeletal Class III malocclusion because of the severe maxillary deficiency. This treatment approach allowed correction of the maxillary dental midline discrepancy to the midsagittal plane and establishment of good occlusion and optimal esthetics.

RETRACTED: Selective Use of Hand and Forearm Muscles During Bone Screw Insertion: A Natural Torque Meter

PURPOSE To compare the maximum torque produced by different muscle groups and its influence on mini-implant insertion torque and fracture prevention. MATERIALS AND METHODS Eighty-seven professionals were evaluated for the maximum torque produced on a screwdriver by a combined action between the thumb and index finger (maximum digital torque [MDT]) and by the forearm supination movement (maximum brachial torque [MBT]). Ninety mini-implants distributed among 9 different diameters were fractured to determine the fracture torque (FT). The fracture resistance index (FRI) was obtained from: FRI_MDT = FT/MDT and FRI_MBT = FT/MBT. Analysis of variance and t tests were used to compare the groups. RESULTS The MDT was smaller than the MBT, and the 2 measurements were smaller in female subjects. The FT increased for each 0.1-mm increment in diameter. The FRI_MDT was greater than FRI_MBT for all diameters. An FRI_MDT greater than 1 was found when the diameter was greater than or equal to 1.5 mm. An FRI_MBT greater than 1 occurred with diameters equal to or greater than 1.7 mm for female subjects and 1.8 mm for male subjects. CONCLUSIONS The digital torque was 42% smaller than the brachial torque, and it was mechanically safer and biologically more compatible, allowing the prevention of the fracture of mini-implants with a diameter 1.5 mm or thicker owing to an insertion torque limitation at 15 N-cm.