Biomedical subjects

Alexander D Vardimon

Publications and source records attributed to Alexander D Vardimon.

10 recordsLinked to original sources

PubMed2005

Assessment of open and incomplete bite correction by incisor overlap and optical density of polyvinyl siloxane bite registration.

Open bite (OB) is a generalized term, which could incorporate subgroups that react differently to vertical correction. The objectives of the present study were to detect vertical treatment changes in incomplete bite (IB: inter-incisor overlap with no lower incisor contact with teeth or palate) and OB (no inter-incisor overlap) groups compared with a complete bite (CB: inter-incisor overlap with full lower incisor contact with teeth or palate) control group, to evaluate treatment response of the central and lateral incisors, and to study the vertico-sagittal interaction. Dental casts were taken at three time points, pre-treatment, post-treatment, and after one year of retention, from 54 Class II patients (22 males and 32 females with a mean age of 11 years 6 months) divided into three groups: CB (n = 21), IB (n = 18) and OB (n = 15). Measurements included incisor overlap (mm) and optical density (OD/mm2) of occlusal bite registration made of polyvinl siloxane. Both CB and IB groups demonstrated post-retention bite opening. However, bite opening in the CB group was three times greater than that in the IB group (e.g. lower lateral = -1.42 mm, 118 OD/mm2 versus -0.40 mm, 107 OD/mm2). Conversely, the OB group showed a significant (P < 0.001) bite closure (e.g. lower lateral = 1.30 mm, -377 OD/mm2). Overjet changes affected OD measurements, causing diversity in OD and millimetric measurements of the lateral incisors in the IB group. In conclusion, the OB group demonstrated a significant stable vertical correction; a post-treatment non-contact inter-incisor relationship was determined by a vertico-sagittal relapse; and full compensation of an IB was not possible.

Child↗

PubMed2005

Skeletal and dental response to rapid maxillary expansion with 2- versus 4-band appliances.

PURPOSE: Banding a rapid palatal expansion (RPE) appliance to the 2 first molars has been proposed as an equivalent to the conventional 4-band RPE appliance. However, the dentoskeletal response to this treatment has not been evaluated. MATERIAL: Twenty-eight subjects (aged 8-20 years) who required maxillary expansion were matched by age and randomly assigned to either a 2-band or a 4-band RPE group. Skeletal and dental responses were measured from standardized anteroposterior cephalometric and occlusal radiographs and dental casts before treatment (T1), at the end of expansion (T2), and at 1 year postexpansion (T3). RESULTS: At T2, suture expansion was 2.5 times greater and arch perimeter was 6-fold larger in the 4-band than in the 2-band group. Both appliances displayed the typical "V" expansion of the suture and "reverse V" expansion of the dental arch. At T3, remineralization reduced the suture opening by 75%, but 95% to 99% of the dental reaction was maintained. The 2-band group demonstrated a significant inverse age-dependent correlation ( r = -0.795), with treatment failure beyond 12 years of age, whereas the 4-band group was age-independent. CONCLUSIONS: The greater the skeletal resistance, the smaller the sutural response but the greater the dental response to RPE therapy. Four-band RPE is indicated when severe anterior crowding is accompanied by a tapered arch form, and 2-band RPE is recommended in the mixed dentition when mild crowding occurs with posterior constriction.

Adolescent↗

PubMed2005

Unequal outer and inner bow configurations: comparing 2 asymmetric headgear systems.

INTRODUCTION: Asymmetric headgear is used when different molar distalization forces (MDF) are needed on the right and left sides of the jaw to correct a Class II molar relationship. METHODS: We investigated 2 asymmetric headgear configurations, the outer-bow and the inner-bow, on cervical-pull headgear. In the first configuration, 5 hooks were soldered on 1 side of the outer bow at 10-mm intervals, making this side shorter; in the other, 4 stops (1.5 mm) were added to 1 side of the inner bow, making this side longer. The right and left MDF and the extraoral force (EF) were measured simultaneously with 2 fork transducers and a testing machine, respectively. RESULTS: A 40-mm difference between the long and short outer bows resulted in a 2.17-fold greater MDF on the long-side molar (7:3 ratio). The 3-4 stop configuration provided the optimal inner-bow arrangement, with stop/no-stop MDF ratios of 7:3 and 10:0, respectively, at 10 N EF. At low-to-medium EF levels, a unilateral MDF developed on the stop side with zero MDF on the no-stop side. The sum of the right and left MDF nearly equaled the EF in the outer-bow asymmetry and was 60% in the inner-bow setting; this suggests strong lateral forces in the latter. CONCLUSIONS: Clinically, for a bilateral unequal Class II relationship, the system of choice is outer-bow asymmetric headgear. For a unilateral Class II relationship with 1 side in a Class I molar relationship (Class II subdivision), inner-bow asymmetric headgear is recommended.

Dental Stress Analysis↗

PubMed2005

In vivo debonding strength and enamel damage in two orthodontic debonding methods.

Bracket debonding strength related to diverse debonding methods and enamel damage has not been assessed in vivo. The study hypothetized a direct relationship between these three parameters. Debonding strength was measured clinically in the wings method and base method on 50 patients in a split mouth method using a calibrated debonding plier. Brackets from 30 of these patients were scanned in SEM and EDAX for adhesive remnant index and enamel calcium remnants. Base method debonding force was significantly greater than wings method (163.5+/-68.7 N, 106.1+/-66.2 N, respectively, p < 0.001). A positive adhesive remnant index score was found in both methods (68.7%, 66.7%, respectively). Debonding strength vs. adhesive remnant index or calcium index scores were not correlated. However, the latter two were significantly correlated (0.524 < R < 0.895, p < 0.031). Half of the debonding failures developed at the adhesive enamel interface. The results warnts the potential of enamel damage during debonding.

Adhesiveness↗

PubMed2005

Maxillary incisor root resorption after rapid palatal expansion in Felis catus.

Root resorption after rapid palatal expansion (RPE) treatment was found in anchored teeth but has not been studied on non-anchored incisors. This study evaluated root resorption, root tipping, and root proximity of maxillary incisors after RPE treatment. Fourteen cats were divided into treated (n = 10) and untreated (n = 4) groups. The RPE treatment consisted of active, retention, and relapse phases, lasting 25, 60 and 60 d, respectively. Standardized occlusal radiographs were taken to measure tipping and root proximity before and after each treatment phase. Maxillary incisors were analysed histologically by fluorescent microscopy for root resorption. Data was analysed statistically with anova with repeated measures, t-test and Pearson's coefficient of correlation. Root resorption was confined to the first incisors and was 750-fold greater in the treated vs. the control group. Root tipping and root proximity were significantly greater (2.5- and 17-fold, respectively) in the first than in the second maxillary incisor and highly correlated with root resorption (r = -0.927 and 0.723, respectively). This suggests a cause (tipping and root proximity) and effect (root resorption) relationship. Data suggest that first maxillary incisor susceptibility to root resorption during RPE is associated with severe tipping and root proximity.

Animals↗

PubMed2005

Labial-cervical-vertical groove in maxillary permanent incisors--prevalence, severity, and affected soft tissue.

OBJECTIVES: To investigate the prevalence and severity of a labial-cervical-vertical groove (LCVG) in maxillary permanent incisors and its effect on the associated gingival tissue. METHODS: A total of 600 adolescents (293 boys and 307 girls, mean age 13.6+/-1.99 years) were randomly selected and examined for the presence of LCVG. The deformity was classified as mild, moderate, or severe according to predetermined criteria. Gingival coverage at the groove site was defined as normal, partial, and irregular. RESULTS: LCVG was found in 27 adolescents (4.5%). It was unilateral in 24 (89%) and bilateral in 3 (11%). The ratio of central to lateral incisors was 29:1. No sexual dimorphism or side prevalence were found. Mild LCVG was found in 22 incisors, moderate LCVG in 7 incisors, and severe LCVG in one incisor. Moderate LCVG was 5 to 6 times more susceptible to partial or irregular coverage of the gingival margin than mild LCVG. The gingival sulcus in teeth with LCVG demonstrated a significant (P = .001) increase in depth compared to non-LCVG teeth (1.55+/-0.90 mm vs 1.18+/-0.75 mm). CONCLUSIONS: An LCVG is a deformity confined predominantly to a single permanent maxillary central incisor. Its prevalence is not connected with gender. Most LCVGs are mild and often difficult to detect. However, the greater the severity, the more gingival irregularity is associated. This and the increase in sulcus depth in LCVG incisors are adverse predispositions for periodontal sequelae, calling for cautious oral hygiene maintenance.

Adolescent↗

PubMed2003

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.

Adolescent↗

PubMed2003

Change over time in intra-arch contact point tightness.

PURPOSE: To examine contact point (CP) tightness of the mandibular dental arch in cases with a unilateral first molar (M1) missing, and also investigate the influence of time since extraction on CPs tightness. METHODS: CPs tightness was measured with a tightness of dental contact point device in 29 patients (9 men, 20 women), mean age 32.6 +/- 6.5 years, with a unilateral missing M1 and no periodontal disease. ANOVA with repeated measures test was used to statistically compare CP tightness between extraction (E) and non-extraction (NE) sides, at significant level of P < or = 0.05, with CPNE serving as internal control. RESULTS: The first CP adjacent to the extraction site between the first and second premolar (CP4-5,E) was significantly (P < or = 0.001) lower (29%) than CP4-5,NE. The difference (NE-E) was reduced to 20% at the more anterior CP (CP3-4,E) which was close to but non-significant (P < or = 0.09). Further anterior CPs (CP2-3, CP1-2) showed a non-significant difference between homologous CPs. Thus, reduction in CP tightness was confined to two adjacent teeth anterior to the extraction site. The tightness reduction of the posterior dentition (CP4-5 + CP3-4) was obtained 3 years post-extraction and subsequently maintained a constant asymmetry ratio (E/NE = 0.68-0.80) up to 14 years post-extraction.

Adult↗

PubMed2002

Deformation/recovery cycle of the periodontal ligament in human teeth with single or dual contact points.

The recovery of the human periodontal ligament after transitory tooth deflection is largely obscured. The objective here was to determine the periodontal deformation/recovery cycle of a tooth with a single or dual contact point. 'Single contact point', refers to a tooth with a contact point on one side but not on the other; 'dual contact point' refers to a tooth with two contact points. The hypothesis that a single contact point will recover more slowly due to periodontal changes, as reported in hypofunctional conditions, was tested. The tightness of the contact point between contiguous mandibular premolars (P(1)-P(2)) during a deformation/recovery cycle was measured in three groups: group 1, single contact point of P(2) (14 individuals with a missing mandibular first molar); group 2, dual contact point of the contralateral P(2) (same 14 individuals with no missing mandibular first molar); group 3, dual contact point of both P(2) (32 individuals with no missing mandibular first molars). The deformation/recovery cycle was initiated by placing a spacer for 1 min between P(1) and P(2). The recovery of the contact point P(1)-P(2) to the initial tightness was recorded in five consecutive measurements: four of these were taken at 1-min intervals and an additional measurement was made 30 min later. The contact-point tightnesses of group 1 were significantly (P<0.001) lower ( approximately 50%) than those of the control groups (groups 2 and 3). All groups showed a similar viscoelastic recovery pattern consisting of a short-term elastic response (after 1 min, 82% of the pre-deformation level was regained) and a long-term viscous response (after 30 min, an additional 6% was regained). Thus, contact-point tightness adjacent to an extraction site is strongly affected by the absence of the tooth and presumably due to reorganisation of the transseptal fibres, but this has no effect on the periodontal ligament deformation/recovery cycle, which showed a uniform viscoelastic response independent of contact-point tightness (rejecting the null hypothesis).

Adult↗

PubMed2002

Integrated magnetic and elastic force systems.

Magnetic force increases as the distance (d) of the force- generating elements (F approximately 1/d(2)) decreases, whereas elastic force decreases as the distance decreases (F approximately kd). These opposing characteristics suggest that combining both force systems will establish an integrated system with a long-range working ability. The objective of this study was to determine the vertical closure force (F(X)) and the transverse axis moment (M(Y)) of an integrated force system, ie, attracting magnets with elastics (vertical or Classes II and III). F(X) and M(Y) were examined on the orthodontic measurement and simulation system. It was found that the integrated force system had a positive closure force (+F(X)) that never declined to 0 and a long working range. Three regions characterized the force-deflection curve of F(X): the magnetic region (0-3 mm, for magnets with 3/16-in medium elastics), in which the decline in magnetic force was larger than the increase in elastic force (6.3-2.5 N); the constant region (3-7 mm), in which the decline in magnetic force equaled the increase in elastic force (2.5-2.9 N); and the elastic region (7-10 mm), in which there was only an increase in elastic force (2.9-3.5 N). The transverse axis moment (+M(Y)), which tends to close the bite, developed especially in magnets with a single vertical elastic. Clinically, inactivation of vertical elastics by closing the mouth can be overruled by the integrated force system because it exerts adequate force level at both short and long distances.

Computer Simulation↗