Silvia Geron

Influence of Sex on the Perception of Oral and Smile Esthetics with Different Gingival Display and Incisal Plane Inclination

This study was designed to determine the esthetic perception of men and women to variations in upper and lower gingival display at smile and speech and to incisal plane tilting. Composed photographs of smile and speech with varying amounts of gingival exposure of the upper and lower teeth and gingiva at smile and at speech and with varying degrees of incisal plane tilting were rated for attractiveness by two groups of lay people. The images were presented as male or female images. A total of 300 questionnaires, including 7500 images, were evaluated by 100 subjects. The results showed that images were scored as less attractive as the amount of upper and lower gingival display was increased during smile and speech. The amount of gingival exposure graded in the esthetic range was up to one mm for the upper incisors and zero mm for the lower incisors. Incisal plane tilting was graded as unesthetic when above two degrees of deviation from the horizontal. Male and female evaluators scored images differently with upper gingival exposure. Female evaluators gave statistically significant higher scores than male evaluators to upper gingival exposure images at smile and speech of both males and females, suggesting that females are more tolerant of upper gingival exposure. Images were scored differently when presented as male or female images. Female images were scored lower by both male and female evaluators, suggesting that additional efforts should be taken in female patients to achieve an esthetic result.

Anchorage loss--a multifactorial response.

Anchorage loss (AL) is a potential side effect of orthodontic mechanotherapy. In the present study, it is defined as the amount of mesial movement of the upper first permanent molar during premolar extraction space closure. In addition, AL is described as a multifactorial response in relation to the extraction site, appliance type, age, crowding, and overjet. For this study, 87 university clinic and private practice subjects, who were defined as maximum anchorage cases and had undergone bilateral maxillary premolar extractions, were divided into four groups according to extraction site (first vs second premolars), mechanics (lingual vs labial edgewise appliances), and age (adolescents vs adults). Overjet and crowding were examined from the overall sample. Data were collected from serial lateral cephalograms and dental casts. The results showed that as the severity of dental crowding increased, AL significantly decreased (r = -0.66, P = .001). Labial edgewise appliances demonstrated a significantly greater AL than did lingual edgewise appliances (1.15 +/- 2.06 mm, P < .05). A greater, though not statistically significant, AL was found in adults than in adolescents (0.73 +/- 1.43 mm). There was a slight nonsignificant increase in AL between maxillary second compared with first premolar extractions (0.51 +/- 1.33 mm). Overjet was weakly correlated to AL. These results suggest that AL is a multifactorial response and that the five examined factors can be divided into primary (crowding, mechanics) and secondary factors (age, extraction site, overjet), in declining order of importance.

Vertical Forces in Labial and Lingual Orthodontics Applied on Maxillary Incisors—A Theoretical Approach

Theoretical and experimental biomechanical analyses explain most labial orthodontics (LaO); however, lingual orthodontic (LiO) biomechanical principles are rarely introduced. The objective of this study was to apply basic biomechanical considerations in understanding the influence of maxillary incisor inclination and to compare the effect of labial vs lingual intrusive/extrusive forces on tooth movement. Basic anatomic and geometric hypotheses were assumed, ie, tooth length (crown and root), location of the center of resistance, and crown thickness. Incisor inclination as related to a perpendicular line to the occlusal plane (OP) varied between -35 degrees (retroclination) and 45 degrees (proclination). A 0 degrees inclination was defined as a tooth position with its long axis perpendicular to the OP. The buccolingual moment for characterizing root movement was calculated for an applied force perpendicular to the OP. The results showed that when using LaO, an extrusion force resulted in labial root movement from a retroclination of 20 degrees up to a proclination of 45 degrees. In LiO, labial root movement occurred only when the tooth was proclined more than 20 degrees. In all other tooth inclinations, lingual root movement occurred. The opposite tooth movement occurred when an intrusive force was applied. Application of a vertical force has different clinical effects on tooth movement with labial and lingual appliances. Application of a lingual force is more complicated, and its effect on tooth movement depends on bracket position and initial tooth inclination.

Bracket Placement in Lingual vs Labial Systems and Direct vs Indirect Bonding

OBJECTIVE To examine the ultimate accuracy of bracket placement in labial vs lingual systems and in direct vs indirect bonding techniques. MATERIALS AND METHODS Forty pretreatment dental casts of 20 subjects were selected. For each dental cast, four types of bracket placement were compared: labial direct (LbD), labial indirect (LbI), lingual direct (LgD), and lingual indirect (LgI). Direct bonding was performed with the casts held in a mannequin head. Labial brackets were oriented with a Boone gauge, and lingual brackets were oriented with the Lingual-Bracket-Jig System. Torque error (TqE) and rotation deviation (RotD) were measured with a torque geometric triangle and a toolmakers microscope, respectively. Both torque and rotational measurements were evaluated statistically as algebraic and absolute numeric values, using analysis of variance with repeated measures. RESULTS Absolute TqE and RotD were significantly (P < .001) higher in direct than in indirect bonding techniques higher in both the labial and lingual bracket systems by twofold and threefold, respectively (LbD = 7.26 degrees , 1.06 mm; vs LbI = 3.02 degrees , 0.75 mm; LgD = 8.42 degrees , 1.13 mm; vs LgI = 3.18 degrees , 0.55 mm). No statistically significant difference was found between labial and lingual systems for the same bonding technique. Maxillary incisors demonstrated the largest RotD angle (eg, right lateral: 12.04 degrees ). A distal off-center RotD was predominant in the mandibular dentition. CONCLUSIONS Labial and lingual systems have the same level of inaccuracy. For both systems, indirect bonding significantly reduces absolute TqE and RotD. The TqE found can cause transverse discrepancy (scissors or crossbite) combined with disclusion with antagonist teeth. The RotD found can result in irregular interproximal contact points.

Can cone beam CT predict the hardness of interradicular cortical bone

ObjectivesOrthodontic mini implants can be inserted at the interradicular site. The bone quality at this site may affect the stability and anchorage of the implant. Bone density is clinically evaluated by Hounsfield units (HU) obtained from cone beam CT (CBCT). The objective of this study was to determine the correlations between HU, microhardness and cortical bone thickness of interradicular site at various segments (anterior/posterior) and aspects (buccal/lingual) of both jaws in a swine model.Materials and methodsEight mandible and maxilla swine bones were scanned by CBCT. The HU and thickness of the above-mentioned sites were determined. Then, a Knoop microhardness test was applied and the Knoop Hardness Number was obtained (KHN).ResultsThe mandible parameters spread over a wider range than the maxilla. The buccal aspect of the maxilla had higher HU and KHN values than the mandible. The lingual aspect of the mandible had higher KHN values than the maxilla. Posterior segments had higher HU and KHN values. The thickness of the alveolar cortical bone was greater in the maxilla than in the mandible. Correlations were found between HU and KHN for 3 of the 4 sites (anterior or posterior, buccal or lingual) of the mandible only. No correlations were found for the maxilla. Upon pooling the HU and KHN data for the whole jaw, correlation was found for the maxilla as well.ConclusionsRelying on HU values as a predictor of cortical bone hardness should be considered with caution.

Stability of anterior open bite correction of adults treated with lingual appliances

The aim of this study was to evaluate retrospectively the stability of treatment outcomes of adult anterior open bite (AOpB) cases, treated non-surgically, using a conservative approach with lingual orthodontics (LO). Thirty-nine adult AOpB patients consecutively treated by one operator (SG), with Ormco™ Generation 7 LO brackets and a conservative treatment protocol, with or without extractions, were evaluated clinically before treatment, at the end of active orthodontic treatment, and after a follow-up period, divided into a short-term group (ST): 1-2 years post-treatment, and a long-term group (LT): more than 2 years and up to 11 years post-treatment. All patients had a positive overbite at the end of active treatment (T2). Stability of the open bite correction was seen in 87.2 per cent of the patients (T3). Relapse to a negative overbite was seen in one patient (2.5 per cent). Post-treatment improvement of the overbite was demonstrated, with no difference between the ST and the LT groups. Stability of the transverse molar relations was significantly correlated with stability of AOpB correction. The LO appliance with the presented treatment protocol is a viable procedure for AOpB correction in adult patients, who are not suitable for surgical procedures, to improve or to enhance facial aesthetics. Post-treatment improvement of the overbite was observed in patients treated with this treatment approach in this study.

Tensile Mechanical Properties of Swine Cortical Mandibular Bone

Temporary orthodontic mini implants serve as anchorage devices in orthodontic treatments. Often, they are inserted in the jaw bones, between the roots of the teeth. The stability of the mini implants within the bone is one of the major factors affecting their success and, consequently, that of the orthodontic treatment. Bone mechanical properties are important for implant stability. The aim of this study was to determine the tensile properties of the alveolar and basal mandible bones in a swine model. The diametral compression test was employed to study the properties in two orthogonal directions: mesio-distal and occluso-gingival. Small cylindrical cortical bone specimens (2.6 mm diameter, 1.5 mm thickness) were obtained from 7 mandibles using a trephine drill. The sites included different locations (anterior and posterior) and aspects (buccal and lingual) for a total of 16 specimens from each mandible. The load-displacement curves were continuously monitored while loading half of the specimens in the oclluso-gingival direction and half in the mesio-distal direction. The stiffness was calculated from the linear portion of the curve. The mesio-distal direction was 31% stiffer than the occluso-gingival direction. The basal bone was 40% stiffer than the alveolar bone. The posterior zone was 46% stiffer than the anterior zone. The lingual aspect was stiffer than the buccal aspect. Although bone specimens do not behave as brittle materials, the diametral compression test can be adequately used for determining tensile behavior when only small bone specimens can be obtained. In conclusion, to obtain maximal orthodontic mini implant stability, the force components on the implants should be oriented mostly in the mesio-distal direction.