Space conditions and dental and occlusal features in patients with palatally impacted maxillary canines: an aetiological study

The aetiology of palatal canine impaction is unclear. The aim of this research was to investigate the occlusal features that could contribute to the aetiology of palatal maxillary canine impaction. The material consisted of the pre-treatment dental casts of 34 patients (27 female and seven male) with unilateral palatal canine impaction (impaction group). The average age of this group was 17.7 years (+/- 4.6). These were matched according to age, gender and type of malocclusion with a comparison group of pre-treatment dental casts from unaffected orthodontic patients. From the dental casts the following parameters were obtained: (1) dentoalveolar arch relationship, (2) missing or anomalous teeth, (3) the mesiodistal width of each maxillary tooth, (4) the upper arch perimeter, (5) the maxillary inter-premolar and inter-molar widths. The arch length-tooth size discrepancy was only calculated for subjects with no missing teeth. Palatal canine impaction occurred most frequently in subjects with a Class II division 2 malocclusion. There was an association between palatal canine impaction and anomalous lateral incisors (P = 0.01). The transverse arch dimension was significantly wider in the impaction group than in the comparison group (P < 0.01). There was no statistically significant difference in the mesiodistal width of maxillary teeth or in the arch length-tooth size discrepancy between the palatal canine impaction group and their matched comparisons (P > 0.05). These results suggest that the presence of an 'excess palatal width' and anomalous lateral incisor may contribute to the aetiology of palatal canine impaction.     

Talon cusp: report of a case.

Talon cusp is a developmental dental anomaly, normally located on the palatal surface of the anterior teeth, that can occur in both primary and permanent dentition. The aim of this article is to relate a clinical case of talon cusp that interfered with both the occlusion and appearance of the patient. During anamnesis, the patient told of difficulty masticating. Clinical examination revealed labial inclination of the maxillary central incisors, featuring an overjet of about 5 mm, with interposition of the lower lip and an Angle Class I occlusal relationship. A treatment plan was devised in which gradual grinding of both talon cusps, the fitting of a removable orthodontic device, and clinical and radiographic follow-up were carried out.     

A Study of Anterior Guidance

Purpose This study focuses on the curvature and inclination of the lingual surfaces of the maxillary anterior teeth from the transition point on the cingulum to the incisal edge. Materials and Methods On 32 sets of mounted casts, 768 measurements were made of the curvature of the lingual surfaces utilizing radius gauges. The inclination of the lingual surface relative to the occlusal plane was recorded. The relationship of the incisal edge of the mandibular teeth to the transition point on the cingulum of the maxillary teeth was determined. Centric occlusion contact was noted on each tooth. Results Significant differences were found between the measured areas of any one tooth and between the types of teeth. The average radius ranged from 20.5 mm on the mesial ridge of the canine to 5.3 mm in the fossa of the central. The average inclination of the lingual surfaces was 46%. In centric occlusion, 97% of the canines and 59% of the centrals and laterals were in contact with the opposing teeth. These contacts occurred 2.8 mm incisal to the transition point. The centrals contacted two opposing teeth (45%), and canines contacted one opposing tooth (53%). Conclusions The function and curvature of the incisor teeth vary considerably from those of the canines. Overcontouring the lingual surfaces of the maxillary incisors to gain contact is not normal and may be detrimental.     

Relationship of maxillary incisors in complete dentures to the incisive papilla

We investigated the relationship of the maxillary central incisors to the incisive papilla in wearers of complete dentures. First, image analyzer software was used to examine the relationship of the midpoint of the incisive papilla to the labial surface of the maxillary central incisors on occlusal photographs of 120 maxillary casts from dentate Malaysian adults. Then, an Alma denture gauge was used to identify the position of the labial surface of the maxillary central incisors in relation to the midpoint of the incisive papilla in complete dentures from 51 patients who requested replacement dentures at the Faculty of Dentistry, University of Malaya. The mean incisor distance to the incisive papilla in dentate adults was 9.59 ± 1.00 mm, while the mean incisor distance to the incisive papilla in complete dentures was 6.34 ± 1.87 mm. Thus, in our sample of edentulous patients, the anterior teeth in complete dentures were positioned approximately 3 mm closer to the incisive papilla, as compared with the position of the central incisors in natural dentition, and did not duplicate the position of the natural anterior teeth.     

Bilateral congenital absence of maxillary lateral incisors: a craniofacial and dental cast analysis

The dental casts and cephalometric records of forty-three patients exhibiting bilateral congenital absence of maxillary lateral incisors were evaluated to determine the nature and extent of any concurrent craniofacial and dental anomalies. The effects of bilateral orthodontic space closure were evaluated on a subsample of twenty-two cases. The data revealed normal dental arch length, arch width, overjet, and overbite, while significant tooth size discrepancies were found in several anterior and posterior teeth. Craniofacial deviations from normal included smaller maxillary length, smaller mandibular length, smaller anterior cranial base, and nasal bone. Vertical facial dimensions, both anterior and posterior, were significantly less, as was the mandibular plane angle. Soft-tissue examination revealed a 10 degrees greater nasiolabial angle, which was increased a further 5 degrees as a result of a mean incisor retraction of 1.5 mm during space closure. The craniofacial anomalies noted in the present sample were similar to those seen in persons with clefts and may reflect a common etiology related to a developmental disturbance during fusion of the facial processes in utero. In the treatment of patients with bilateral congenital absence of maxillary incisors, mechanotherapy designed to open the mandibular plane, increase the vertical dimension, and move the maxillary posterior teeth forward is recommended in order to prevent worsening the Class III tendency and to minimize maxillary incisor and upper lip retraction. Most cases will require significant mesiodistal reduction in tooth size in order to achieve an optimal occlusion.     

Conservative interdisciplinary treatment of a case with multiple facial and condyle fractures

The purpose of this case report is to describe an interdisciplinary approach for a 51‐year‐old male who underwent multiple facial fractures including bilateral condyle fractures. The patient underwent emergency surgery, which included open reduction of the maxilla and mandibular symphysis and closed reduction of the bilateral condyle fractures. Although the patient recovered a comfortable range of mouth opening and alleviation of the temporomandibular joint (TMJ) symptoms after surgery, he suffered from a large anterior–posterior discrepancy due to less stability on the condyle‐fossa relationships and from open bite with contacts only on both second molars and right second premolars. In this case, first, to increase the occlusal contact, comprehensive orthodontic treatment was completed. Second, occlusal equilibration was selectively performed to relieve the interferences and establish a stable range of mandibular movement without any changes in the vertical dimension. Third, both the upper central incisors and left lateral incisor were minimally restored with splinted and single zirconia crowns, which had modified lingual contours to provide adequate anterior guidance permitting the anterior–posterior discrepancy of the posterior teeth during protrusion. This conservative interdisciplinary treatment, including open and closed reduction, orthodontic treatment, occlusal adjustment, and minimal prosthetic restorations, resulted in a stable mandibular position and recovery of mastication function.     

Change in dentition over 20 years from third decade of life

PurposePrevious studies have documented long-term, age-related change in the teeth, dental arches and occlusion. However, very few studies have investigated longitudinal age-related change in the dentition using 3-dimensional (3-D) measurement. The purpose of this study was to clarify age-related change in the dentition using a laser scanner.Materials and methodsWe used dental casts obtained from the same subjects in their twenties and forties. Subjects were selected based on near-normal occlusion. We investigated age-related variation in the dentition using 3-D measurement.ResultsAge-related change in the dentition was characterized by a decrease in maxillary and mandibular width, an increase in maxillary length, and a decrease in mandibular length. Measurement of angulation revealed that the maxillary canines and molars were mesially inclined. We observed labial inclination of the maxillary incisors, and lingual inclination of the mandibular incisors, as well as the maxillary and mandibular canines and molars. Overjet, overbite, and the irregularity index all showed an increase, while occlusal vertical dimension showed a decrease. Multiple regression analysis indicated that lingual inclination of the lower central incisors was related to an increase in the irregularity index, and that lingual inclination of the upper canines and decrease in occlusal vertical dimension of the anterior teeth were related to increased overbite.ConclusionThe present findings showed that age-related changes in angulation and inclination of each tooth should be taken into account when providing occlusal rehabilitation or post-orthodontic retention.     

Relationship between alignment conditions of teeth in anterior segments and incisal wear

This report describes the alignment condition and incisal wear of the anterior teeth in individuals 16–19 years of age. Tooth alignment and incisal wear were assessed on casts in accordance with two index systems NONAT (non-aligned tooth) and IwI (incisal wear index). Tests of the methods showed that the reproducibility of the assessments of tooth alignment and incisal wear were satisfactory. The results of the study of tooth irregularity demonstrated that the prevalence of non-alignment of one or more of the anterior teeth were much the same (∼50%) for the maxillary and mandibular jaws. The highest frequency was found for the maxillary lateral incisors and the mandibular central incisors (∼45%). A relationship between the alignment conditions and incisal wear of the anterior teeth was established. It appeared that non-alignment of one or more teeth in one or both jaws was associated with less severe incisal wear of the anterior teeth. This was most pronounced for non-aligned maxillary central incisors and non-aligned mandibular central incisors.     

Application of "cusp writer" findings to practical and theoretical occlusal problems. Part II.

The cusp writer is a teaching aid to facilitate understanding of the correlation between cusp angulations and the various occlusal determinants. The cusp writer provides graphic evidence that the occlusal determinants which influence configurations (i.e., incisal guidance, condylar guidance, plane [curve] of occlusion, curve of Spee [compensating curve], and plane of motion) are reciprocal, one tempering the value of the other. Cusp writings demonstrate the following: (1) The angle of the plane (curve) of occlusion to the plane of motion in concert with the other occlusal infuluence determines the optimal height and angulation of the cusps. (2) Cusps appear to be steep or shallow relative to each other, to the plane of occlusion, and to the plane of motion. (3) The steepness of the curve of Spee determines the relative cusp height and angulation of one tooth to another, from an anterior to a posterior direction in the dental arch. (4) The angle of the tangent to any segment of the curve of Spee to the plane of motion determines the optimal height and angulation of the cusps of the segment. (5) The graphs show that the flatter the curve of Spee, the more uniform the cusp height and angulations are from anterior to posterior teeth. The steeper the curve of Spee, the more irregular the cusp height and angulations are with steeper anterior cusps and flatter posterior cusps. (6) The steeper the curve of Spee, the flatter the molar cusp angulations must be to avoid deflective and/or interceptive occlusal contacts on the balancing side. (7) With the syndrome of a steepening curve of Spee due to the loss of one or more lower posterior teeth, the cusps of the remaining opposing teeth must be constantly flattened by wear or selective grinding and reshaping to avoid traumatic occlusion, unless the drifting is interrupted by restorative dentistry. (8) Cusp angulation of artificial teeth should be chosen to harmonize with the angle of incidence of the compensating curve tangents to the plane of motion. (9) Condylar guidance has less influence on cusp angulation in comparison to incisal guidance and the other occlusal determinants. (10) Changing the hinge axis location 1/2 inch (12.5 mm.) distally and/or superiorly has very little effect on the influence of the above occlusal determinants on cusp configuration, if the vertical dimension of occlusion remains constant.     

Bilateral palatal talon cusps on permanent maxillary lateral incisors: a case report

Talon cusp is a rare developmental extra cusp-like projection on the cingulum area of affected anterior teeth that may cause various functional and aesthetic problems. The present report describes a case of bilateral palatal talon cusps on permanent maxillary incisors and the treatment procedure to overcome the clinical problems associated with talon cusps.     

A 15-year follow up of an orthodontic treatment including a lower incisor extraction and keeping the maxillary canine–premolar transposition

Lower incisor extraction is an effective option for treating lower anterior crowding in patients with a good facial profile, Class I molar occlusion, and narrow upper incisors. This report describes the successful treatment of an adolescent patient with lower anterior crowding and a transposed maxillary canine and premolar treated by extracting a lower incisor and keeping the transposed positions of the teeth. With the use of retainers, treatment results were stable up to the 2-year postretention visit. However, upon a 15-year postretention appointment, the fixed retainer had been removed and the removable retainer was no longer in use, which resulted in relapse of lower anterior alignment. Moreover, the transposed canine had extruded during this period, causing occlusal interference and gingival recession, as well as loss of tooth vitality, which indicates the importance of maintaining orthodontic retainers for long-term stable occlusion.     

Maxillary anterior tooth dimensions and proportions in an Irish young adult population

This study was undertaken in a young Irish population to determine the dimensions and ratios of the six maxillary anterior teeth. One hundred and nine Irish subjects (age 18-25 inclusive) had irreversible hydrocolloid impressions made of their maxillary dentition poured in type V stone. Clinical crown dimensions were measured with a digital calliper. The stone casts were digitally photographed in a standardised manner enabling calculation of various ratios between the maxillary anterior teeth. Sexual dimorphism existed for various tooth dimensions; most notably canine teeth were in the region of 0·8 mm longer and 0·6 mm wider in males. Central and lateral incisors were found to be 0·5 mm wider in males. It is, therefore, recommended that dimensional tooth guidelines should be given for each of the sexes and not on a population basis. With regard to tooth proportion ratios, no significant differences were found between genders or the left and right sides for any of the measurements or ratios measured. The digitally recorded tooth proportions were similar for both sexes, and the Golden Proportion guidelines could only be applied to the lateral incisor/central incisor widths (0·618). Identified width proportions for the canine/central incisor were 0·58 and for canine/lateral incisor 0·89.     

Arch perimeter changes on rapid palatal expansion

Relationships between changes in arch perimeter and arch width resulting from rapid palatal expansion with the Hyrax appliance were analyzed with the use of dental study casts of 21 adolescent patients. Photographs and measurements from the dental casts obtained before treatment and approximately 3 months after stabilization were used. Regression analysis indicated that changes in premolar width were highly predictive of changes in arch perimeter (r2 = 0.69) at approximately 0.7 times the premolar expansion. Without any orthodontic appliances attached to the mandibular teeth in 16 of the 21 patients, buccal uprighting of the posterior teeth was observed because of the redirection of occlusal forces. In addition, posterior movement of the maxillary incisors and buccal tipping of the anchor teeth were quantified. The prediction of arch perimeter change for a given amount of expansion is helpful in the treatment planning of rapid palatal expansion cases and may facilitate nonextraction orthodontic treatment.     

An unusual case of double teeth with facial and lingual talon cusps

Double teeth and talon cusps are rare developmental dental anomalies affecting both primary and permanent dentitions. Talon cusps normally occur on the palatal surface of permanent maxillary incisors, although double teeth are more common in the primary anterior dentition. This paper describes a rare case of fusion of the mandibular permanent incisors with labial and lingual talon cusps. An understanding of these dental anomalies and their associated problems are important to provide prophylactic measures, thereby preventing or minimizing possible complications.     

Clinical applications of the etched metal retainer

This article presents the treatment of several patients directed at the prevention of periodontal disease and restoration of an occlusion from an eating disorder. The disruption of the harmony between the anterior and posterior determinants of occlusion can lead to the loss of teeth. The lack of anterior guidance can create a molar-guided occlusion producing unfavorable occlusal interferences with destructive balancing side prematurities. Conversely, if the posterior teeth are permitted to drift into unstable occlusal relationships, the posterior dentition would develop an irregular guidance despite a suitable anterior guidance. The goal of the profession is preventing occlusal deterioration or disharmony between the anterior and posterior occlusal determinants and restore compromised occlusions when necessary. Etched metal retainers were fundamental to the treatment of specific patients while patient selection and perceptive tooth preparation were essential for success.     

Protraction of mandibular second and third molars into missing first molar spaces for a patient with an anterior open bite and anterior spacing

In a young woman, aged 18 years 8 months, who had an anterior open bite and anterior spacing, the right and left mandibular first molar extraction spaces were closed by protraction of the second and third molars without reciprocal retraction of the incisors and the premolars. The amounts of protraction for the second molars were 12 mm on the right side and 11 mm on the left side. Two miniscrews were inserted into the mesiobuccal side of the edentulous spaces, and 2 more screws were inserted into the anterior sites after removing previous miniscrews. In addition, 4 miniscrews were inserted into the buccal and palatal sides between the first and second maxillary molars to intrude the maxillary posterior teeth, which had extruded into the missing mandibular spaces. Careful biomechanical consideration was used to prevent extrusion of the molars and worsening of the anterior open bite from protraction of the posterior teeth. Ultimately, the anterior open bite was corrected by both intrusion of the maxillary molars and extrusion of the maxillary anterior teeth. Excellent occlusion and correction of the anterior open bite were achieved without tipping, rotation of the posterior teeth, or other problems. The right mandibular third molar, which had been impacted at the beginning of treatment, erupted into the second molar space and functioned properly. At the 1-year follow-up examination, the patient had a slight anterior open bite, but closure of the first molar extraction spaces was well maintained.     

Is the postretention relapse of maxillary and mandibular incisor alignment related?

Previous studies suggest a poor association between initial and postretention pattern of incisor irregularity. One explanation may be that the incisor movements are limited by the boundaries provided by the incisors in the opposite arch. If so, postretention malalignment of the maxillary and mandibular incisors may be related. To test this hypothesis, long-term postretention study models of 96 patients with acceptable occlusion at the time of appliance removal were examined. The occlusal surfaces of the postretention study models were photocopied, and tooth anatomical contact points were digitized. An algorithm was used to fit the dental arch to the digitized points. The amount of incisor rotation and anatomical contact point displacement of maxillary and mandibular anterior teeth, relative to their respective dental arches, were computer generated. Overbite, the number of occlusal contact points in the anterior segment, and concavity of the lingual surfaces of the maxillary incisors were recorded manually. Statistical analyses demonstrated a significant association (P <.05) between the overall irregularity of the maxillary and mandibular incisors. The association did not differ among subgroups that were stratified according to overbite or number of occlusal contacts. No associations were found for the overall amount of incisor rotation in the 2 arches (P >.05). The amount and direction of displacement of antagonistic pairs of maxillary and mandibular central incisors were also associated (P <.05), but not the amount and direction of rotation (P >.05). The lingual configuration of the maxillary incisors did not affect the pattern of mandibular incisor malalignment.     

牙位对不同咬合类型的下颌牙根尖应力影响的光弹实验研究

目的：探讨牙位的变化对下颌各牙根尖主应力大小及方向的影响进行分析。方法：采用透明环氧树脂复制以相同牙排列而成的正常He、深覆He、重度磨耗He、单侧部分后牙反He、单侧上颌第三磨牙伸长、单侧下颌第三磨牙伸长、单侧部分后牙缺失7种不同咬合类型的下颌模型，2．0kg力垂直加载后，投影式光弹仪上观测各牙根尖主应力的大小与方向。结果：在对称性咬合，牙位的变化对各牙的根尖主应力方向无影响。而在不对称性咬合，牙位的变化对前牙区近远中向应力及全牙列的根尖主应力颊舌向倾角都有明显影响。另外，随牙位的变化根尖主应力的大小也会发生显著变化，而且这种差异主要来自于不对称性咬合类型。结论：牙在下颌骨上相对位置的变化会对其根尖主应力大小及方向产生一定的影响，而且其影响程度还会受到咬合对称性等因素的影响。     

Management of a Class I malocclusion with traumatically avulsed maxillary central and lateral incisors

This case report describes orthodontic space closure for managing an avulsed maxillary central incisor and a lateral incisor in a growing girl with a Class I deep bite malocclusion with moderate lower and mild upper crowding. The treatment approach moved a central incisor across the midline and substituted a lateral incisor for a central incisor, in combination with canine substitution. Veneers on all maxillary anterior teeth attained acceptable esthetics. The right central incisor was moved to serve as the avulsed left central incisor. The right lateral incisor was moved to the position of the right central incisor and restored. The canines on both sides were substituted as lateral incisors; the posterior occlusion was left in Class II. Mesialization of central and lateral incisors with prosthetic rehabilitation is an acceptable treatment option.