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PubMed2004

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.

Alveolar Bone Loss↗
PubMed2004

Investigation of the changes in the positions of upper and lower incisors, overjet, overbite, and irregularity index in subjects with different depths of curve of Spee.

The aim of this study was to investigate the relationship between the depth of the curve of Spee and positions of upper and lower incisors, overjet, overbite, and anterior lower crowding. The material consisted of lateral head films and dental casts of 137 untreated adolescent subjects, 76 girls and 61 boys, aged 13 to 16 years. The subjects were divided into three groups with normal Spee, flat Spee, and deep Spee and were compared with one another. Differences between the Spee groups and between sexes were assessed by means of analysis of variance and a post hoc multiple comparison test. In addition, correlation coefficients between the depth of curve of Spee and other variables were calculated. Finally, cephalometric measurements for all subjects were subjected to a multiple regression analysis, with the depth of curve of Spee as the dependent variable. The results showed that there were no statistically significant differences in the positions of upper and lower incisors and anterior lower crowding among the Spee groups. However, overjet and overbite demonstrated significant differences among the groups. Statistically significant correlations were found between the depth of curve of Spee and overjet and overbite. Multiple linear regression analysis revealed that chronological age and all other variables used in the study could account for only 28.7% of the total variance of the curve of Spee. The overbite alone explained 17.3% of the total variance of the curvature.

Adolescent↗
PubMed2005

Are the lower incisors the best predictors for the unerupted canine and premolars sums? an analysis of a Peruvian sample.

The lower permanent incisor tooth width sum has been proposed as the best predictor for the tooth width sums of the unerupted canine and premolars (SPCP) for populations from different ethnic origins. Only two previous studies have refuted it. The purpose of the present study was to determine which sum or combination of sums of permanent tooth widths presented the best prediction capability for the SPCP in a Peruvian sample, to calculate a specific linear regression equation for this population, and to evaluate the clinical significance. A total of 150 children with complete permanent dentitions were selected. Fifty more children were used as a validation sample for the application of a multiple linear regression equation (MLRE). They did not present clinically visible dental caries or proximal restorations and no active or previous orthodontic treatment. Their dental casts were measured to 0.1 mm with a sliding caliper with a Vernier scale. Three-way analysis of variance, Pearson Correlation Test, Fisher Z values and a MLRE were used for the statistical analysis. The combination of the sums of permanent upper and lower central incisors and upper first molars was the best predictor for the SPCP in this sample. A MLRE was calculated including sex and arch as additional predictor variables. The MLRE determination coefficient was 60% with a standard error of 0.8 mm. This new MLRE underestimates (less than 1 mm discrepancy) the actual SPCP in only 7% of the cases on the basis of a validation sample.

Adolescent↗
PubMed2004

Laser Doppler flow investigation of fractured permanent maxillary incisors.

Laser Doppler flowmetry (LDF) is a non-invasive method to assess pulpal blood-flow (PBF). Dental injury has been associated with losses of pulpal sensibility. The purpose of this study was to assess the outcome of splint therapy on tooth fracture type-related PBF values. In 15 trauma patients, a single maxillary incisor treated by repositioning and splinting was investigated by LDF to assess local PBF values. Perfusion units were taken in four sessions, on the day of splint removel, and 12, 24 and 36 weeks after splint removal. Analysis of the tooth fracture type-related PBF measurements revealed root fractures to be associated with a significant decrease (P < 0.05) and uncomplicated crown fractures to be associated with a significant increase in PBF values (P < 0.05), while complicated crown fractures showed no significant difference between the session-related values (P > 0.05). The main findings of this study suggest splint therapy of root fractures of the central maxillary incisor to be associated with a short- and long-term decrease in PBF values. The LDF may become useful in the detection of transient ischaemic episodes and the identification of teeth at risk for adverse sequelae such as avascular necrosis and tissue loss.

Adolescent↗
PubMed1996

Local actions of acetylcholine on vasomotor regulation in rat incisor pulp.

Local actions of acetylcholine on vasomotor regulation in rat incisor pulp were investigated in anaesthetized animals. Pulpal blood flow was measured with laser Doppler flowmetry. lontophoresis (40 or 60 muA for 20 s) with acetylcholine or carbachol on an exposed dentin surface caused a biphasic response: an initial vasoconstriction was followed by an atropinesensitive vasodilation. The vasoconstrictor response was enhanced by 171% in the presence of atropine, whereas in control experiments, using isotonic saline as a medium for the direct current, similar vasoconstriction was unaffected by atropine. Carbachol-induced vasodilation was significantly reduced by 30% after intravenous injection of the nitric oxide synthesis blocker N omega-nitro-L-arginine methyl ester (10 mg kg-1), and the remaining vasodilation was abolished by atropine. The present results support the concept of a cholinergic modulation of sympathetic vasoconstrictor function and of a partial contribution of nitric oxide in carbachol-induced vasodilation in rat incisor pulp.

Acetylcholine↗
PubMed2003

Endodontic and orthodontic treatment of a cross-bite fused maxillary lateral incisor.

AIM: To describe combined endodontic and orthodontic treatment of a maxillary lateral incisor fused with a supernumerary. SUMMARY: A rare case is presented in which combined endodontic and orthodontic treatment was performed on a cross-bite fused tooth. Clinical and radiographic examination showed the maxillary lateral incisor fused with a supernumerary and an impacted canine. The fused tooth required nonsurgical and surgical endodontic treatment for functional and aesthetic reasons. The root canals were dressed with calcium hydroxide for 2 months before they were obturated with thermoplasticized injectable gutta-percha. Then, the distal part of the fused tooth was removed and the mesial part of the tooth was replanted and fixed. Three months after the completion of orthodontic therapy, the impacted canine erupted between the remaining tooth and the first premolar. Recall examination, 3 years after completion of root canal treatment, showed clinical and radiographic evidence of healing. KEY LEARNING POINTS: Fusion has been described as a development anomaly characterized by the union of two adjacent teeth. Proper combined endodontic and orthodontic treatment resulted in maintaining one tooth half and solving the aesthetic and functional problem of a fused tooth.

Child↗
PubMed1999

Autotransplantation as a treatment option after loss of a maxillary permanent incisor tooth. A case report.

A case is described of the management of a maxillary left permanent incisor, damaged by several traumatic injuries, in a 13-year-old girl. The traumatized incisor tooth required extraction and as part of an orthodontic treatment plan, a mandibular left second premolar was surgically transplanted to the prepared extraction socket at the maxillary anterior alveolus. After splinting, the transplanted tooth underwent endodontic treatment, because of pulpal necrosis. Orthodontic treatment commenced 3 months post-transplantation. Permanent root obturation was provided after orthodontic treatment and a porcelain veneer was placed to restore aesthetic appearance. The case emphasizes the importance of correct case selection, a multidisciplinary approach to treatment planning, and regular follow-up for transplanted teeth.

Adolescent↗
PubMed2000

Aspiration of an avulsed primary incisor. A case report.

A 7-year-old girl had injured her maxillary primary incisors in a playground. One of the already-mobile incisors had been avulsed. The child who had a cough and breathing difficulties during sleep was diagnosed as suffering from upper respiratory infection and was treated with antibiotics. A few days later because her body temperature was elevated a chest radiograph was taken. The radiograph revealed an aspirated tooth in her right bronchus with atelectasis of the lower lobe. The tooth was removed by bronchoscopy. Dentists should suspect any tooth that has been avulsed and not found as possibly aspirated.

Airway Obstruction↗
PubMed2000

A prospective study of factors affecting survival of replanted permanent incisors in children.

OBJECTIVE: To examine the factors associated with the onset of resorption in replanted avulsed permanent incisor teeth and to demonstrate their patterns of survival free of resorption. SETTING: Department of Paediatric Dentistry, Belfast. DESIGN: Prospective recording of the timing of the injury and of replantation, the storage media, the degree of root development and contamination, and the completion of root treatment. Clinical and radiographic reviews at 3-month intervals. Root resorption classified as replacement and inflammatory. Logistic regression and survival curves with freedom from resorption as outcomes. RESULTS: In 50 avulsed incisors in children aged 6-16 years the best predictor of overall resorption was total time of dryness, and that for replacement resorption was total extra-oral time. The timing of detection of resorption varied from 102 days to 997 days. CONCLUSION: Both total extra-oral time and time stored dry are important factors for the onset of resorption in replanted avulsed teeth in children.

Adolescent↗
PubMed2003

Molar incisor hypomineralization: a questionnaire inventory of its occurrence in member countries of the European Academy of Paediatric Dentistry (EAPD).

OBJECTIVES: The objectives were to find out whether hypomineralized permanent first molars and incisors, known as Molar Incisor Hypomineralization (MIH), occurs all over Europe, whether its prevalence in each country is known and whether or not it is considered to be a clinical problem. SAMPLE AND METHODS: Clinical photos of MIH and a five-item questionnaire were sent to members of the European Academy of Paediatric Dentistry (EAPD). A total of 59 questionnaires were sent to members in 31 countries. After one month a reminder was sent to non-responders. RESULTS: Fifty-four dentists (92%) in 30 countries (97%) returned the questionnaire. MIH was stated to occur in all but one country (the Czech Republic). Nearly all the responders (97%) stated that they were familiar with the clinical appearance of MIH and a majority saw it as a clinical problem. Furthermore, a large majority of the responders (90%) considered it important to map the prevalence of MIH in European countries as such data are available to only a limited extent. CONCLUSION: Paediatric dentists in Europe are aware of MIH and the majority consider it to be a clinical problem. Only limited data are available on the prevalence of MIH. Comparable and representative prevalence studies are therefore urgently needed to gain more knowledge about the magnitude of MIH and related clinical problems.

Child↗
PubMed1999

Relationship between anterior guidance and mesiodistal inclination of lower incisor in human subject with or without TMJ noise.

The relationship between anterior guidance and the mesiodistal inclination of the lower incisors relative to the existence of temporomandibular joint (TMJ) noise was investigated. One hundred and thirty-four individuals, 21 to 40 years of age (mean age 23.8; 104 men and 30 women), were examined. A highly significant correlation was observed between the mean lower-incisor inclination and the difference in steepness between the right and left anterior guidances in the subject group showing TMJ noise (P<0.001), whereas no significant correlation was observed in the group without TMJ noise.

Adult↗
PubMed2003

Stress analysis of an upper central incisor restored with different posts.

The effect of different anatomic shapes and materials of posts in the stress distribution on an endodontically treated incisor was evaluated in this work. This study compared three post shapes (tapered, cylindrical and two-stage cylindrical) made of three different materials (stainless steel, titanium and carbon fibre on Bisphenol A-Glycidyl Methacrylate (Bis-GMA) matrix). Two-dimensional stress analysis was performed using the Finite Element Method. A static load of 100N was applied at 45 degrees inclination with respect to the incisor's edge. The stress concentrations did not significantly affect the region adjacent to the alveolar bone crest at the palatine portion of the tooth, regardless of the post shape or material. However, stress concentrations on the post/dentin interface on the palatine side of the tooth root presented significant variations for different post shapes and materials. Post shapes had relatively small impact on the stress concentrations while post materials introduced higher variations on them. Stainless steel posts presented the highest level of stress concentration, followed by titanium and carbon/Bis-GMA posts.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2002

[The origin and function of the enamel cup, infundibulum dentis, on the incisors of the horse].

The enamel cups of equids originated phylogenetically through several phases in Oligocene and Miocene horses, which readjusted from hard to soft leaf food and from double nutrition (leaves and grass) to a pure grass intake. This has been proved experimentally. The resulting construction of the incisor is continually changed on its occlusal surface by erosion according to the pattern of the enamel crests. Referring to the whole incisor tooth, this results in an equid life cycle in which the good grip of the occlusal surface and the efficiency of ingestion favours the young, sexually mature horses, which are at the best age for food intake.

Age Factors↗
PubMed2000

X-ray microtomographic study of mineral distribution in enamel of mandibular rat incisors.

X-ray microtomography was used to study the mineral concentrations in sequential slices of enamel of 5 mandibular incisors which showed an increase from approximately 1.0 to approximately 2.7 g cm(-3) from the apex towards the incisal end. For points at the same distance from the apex, there were differences up to 0.6 g cm(-3) between the teeth. The change of mean concentrations in the slices with distance could be modelled as (different) saturating exponentials. Under the assumption of a uniform growth rate of a mandibular incisor of 0.6 mm per day and a common time origin for the start of maturation (taken as a mineral concentration of 1 g cm(-3)), the distances were transformed to a common time frame to give a pooled data set. A single saturating exponential could be fitted to this pooled transformed data; this was: Cm = 2.84-1.94exp (-0.18d) where Cm is the mean mineral concentration (g cm(-3)) and d the time (days) from the start of maturation. This gives an asymptotic concentration of 2.84 g cm(-3) towards the incisal end, with a time constant of 7.7 days. The mineral concentration distribution functions were found to be more positively skewed closer to the apex, but more negatively skewed towards the incisal end. The difference between the higher mineral concentration in the outer enamel and the enamel near the amelodentinal junction (ADJ) was approximately 3%. The direction of maximum increase in concentration from the outer enamel surface to the ADJ meets the boundary of the ADJ at approximately 80 degrees. Three dimensional surface rendering of isodensity contours showed that the previously described C-shaped pattern of mineralisation is not solely a surface phenomenon, but extends through the depth of the enamel.

Animals↗
PubMed2001

Can maxillary incisor trauma be predicted from cephalometric measurements?

Dental injury is a traumatic event related to many factors, including dentofacial morphology. In a previous study in which we used a logistic regression model, 5 cephalometric variables were defined as being the best predictors of traumatic injury. The purposes of this study were to test the predictive value of the logistic regression analysis results for the occurrence of dental injury in a new patient sample and to compare these results with the outcome based on a visual evaluation of cephalograms. The study population consisted of 2 groups of orthodontic patients: patients with injured incisors (n = 64) and patients with non-injured incisors (n = 90). Cephalometric skeletal, dental, and soft tissue measurements were made. In addition, 6 professional judges visually evaluated all cephalograms. Classification tables were constructed for the results of the logistic regression model and for the assignment of patients according to the visual evaluation of the cephalograms. The percentage of correctly classified patients at the.7 probability level was 62%. Surprisingly, the professional panel rendered an equal predictive value. The relatively inferior performance of both the mathematical model and the "eyeballing" may demonstrate that dentofacial morphology is only partially responsible for susceptibility to trauma.

Cephalometry↗
PubMed2001

Intrusion of migrated incisors with infrabony defects in adult periodontal patients.

This report describes the orthodontic treatment of 10 adult patients who had severe periodontal disease, with migration and radiological evidence of an infrabony defect on a maxillary central incisor. Orthodontic tooth movement, using light and continuous forces, was initiated 7 to 10 days after periodontal surgical therapy. Mean orthodontic treatment time was 10 months. Before surgery and at the end of orthodontic treatment, the following parameters were registered clinically and with standardized intraoral radiographs: probing depth, clinical crown length, marginal bone level, bone defect radiological dimension, and root length. Comparison of pre- and posttreatment values showed a statistically significant improvement for all parameters without a remarkable decrease of root length. The mean residual probing depth was 2.80 mm, and the mean intrusion of the incisors was 2.05 mm. Moreover, radiographs showed a reduction of the infrabony defects. These results show the efficacy of a combined orthodontic-periodontal approach. Intrusive movement, after proper periodontal surgical therapy, can positively modify both the alveolar bone and the soft periodontal tissues.

Adult↗