Persistence of deciduous molars in subjects with agenesis of the second premolars

The purpose of the present study was to investigate persistent primary second molars in a group of young people in their late twenties with agenesis of one or two second premolars. In 1982-83 it was decided, in connection with the orthodontic evaluation of 25 patients, to allow 35 primary molars (one or two in each patient) to remain in situ. All patients had mixed dentitions and agenesis of one or two premolars. The primary teeth were generally in good condition, although root resorption and infra-occlusion (compensated by occlusal composite onlays) occurred. In 1997, 18 of the 25 patients with a total of 26 retained primary molars were reexamined, comprising a clinical examination for exfoliation, extraction, loosening, and ankylosis, and a radiographic examination for root resorption, tooth morphology (crown and root), and alveolar bone contour. The examination showed that the degree of root resorption was unaltered in 20 of the 26 primary molars. In the permanent dentitions, where these primary molars persisted, there were no morphological deviations. Three of the six remaining primary molars had been extracted and three showed extensive resorption. In three of the 26 primary molars the infra-occlusion had worsened. The present study shows that persistence of primary second molars in subjects with agenesis of one or two premolars, and normal morphology of the permanent dentition can be an acceptable, semi-permanent solution for the patient. Whether this could also be an acceptable long-term solution will be shown by follow-up studies.     

The long-term survival of lower second primary molars in subjects with agenesis of the premolars

This study investigated 41 subjects, 13 male and 28 female, with agenesis of one or both lower second premolars, and with retained lower second primary molars. Intra-oral radiographs of 59 primary teeth were examined to judge the resorption of the mesial and distal roots, and were measured to record infra-occlusion of the primary teeth and tipping of the adjacent permanent teeth. The study commenced at 11-12 years of age. The mean age at the last measurement was 20 years 6 months (SD 3.62, range 13.6-31.8 years). During the observation period, only two of the 59 primary teeth were exfoliated. Five were extracted, two of which were replaced by upper third molar transplants. Beyond the age of 20 years no teeth were lost. Root resorption varied widely between individuals, but was slow. There was no typical pattern for development of infra-occlusion. Mean infra-occlusion was 0.47 mm (SD 1.13) at 11-12 years, increasing by less than 1.0 to 1.43 mm (SD 1.13) at age 17-18 years. At age 19-20 years, 55 per cent of teeth showed infra-occlusion between 0.5 and 4.5 mm, but 45 per cent showed no infra-occlusion. The space between the first molar and first premolar was a mean of 10.35 mm (SD 0.76) at age 10-12 years compared with the mean width of the second primary molar of 10.53 mm (SD 0.51). The space reduced by less than 0.5 mm to 9.95 mm (SD 1.50) at age 17-18 years. If primary molars are present at 20 years of age they appear to have a good prognosis for long-term survival.     

Horizontal impaction of bilateral mandibular second premolars with distal inclination: A case report

In the Japanese population, the second premolars are the secondmost- frequently impacted teeth in the mandible, after the third molars. Although some papers have reported on the treatment of impacted mandibular second premolars caused by abnormal tilting of the tooth germ, there has been little information regarding bilateral horizontal impaction with distal inclination. The purpose of the present report is to describe the treatment course of a rare and severe case of an 11-year, 8-month-old girl without any obvious etiologies whose bilateral mandibular second premolars were inclined to the distal direction at approximately 90 degree angles, with the root formation developed to an approximately half length. After extraction of the retained primary molars, traction was performed in the treatment of the affected teeth. The affected premolars had fully erupted and achieved occlusion one year after the beginning of intervention. In conclusion, it was considered that the present case could obtain a successful outcome by limited traction since no clinical anomalies or discomfort was detectable during the one year of retention.     

Odontometric evaluation of mandibular premolars with tooth shape deviation

Abstract Objective: To evaluate the mean dimensions and morphologic characteristics of mandibular premolars that had mesiodistally elongated and faciolingually squeezed tooth shape deviations (MnP-TSD) and determine the population prevalence of this anomaly. Materials and Methods: Clinical photographs and study models were made for all new patients with MnP-TSD teeth who were seen over 20?years. The mesiodistal (MD) and faciolingual (FL) dimensions of the anomalous premolars were measured. MD/FL indices and MD × FL mm(2) occlusal crown areas were calculated and means and standard deviations were derived. Male and female means from the mandibular first and second anomalous premolars (MnP1/MnP2-TSD) were statistically compared against gender-specific means derived from published normative data using Student's t-tests and chi-square tests. Results: Fifty-six individuals (33 male and 23 female) with MnP-TSD were identified, giving a male to female ratio of 1.4∶1, while the prevalence rate in the indigenous British population was estimated to be 0.6%. The MD widths of the MnP1-TSD and MnP2-TSD teeth were approximately 1?mm wider than normal, while the FL diameters were about 0.5?mm and 1.5?mm narrower respectively, for the first and second premolar teeth. The MD/FL indices, instead of being under 90 as usual were above 100, while the mean MD/FL mm(2) crown surface areas were normal. Conclusions: This study supplies odontometric dimensional and morphologic data on MnP-TSD teeth that provide a reference source for future comparisons.     

'Molarization' of the mandibular second premolars.

Further examples are reported of an anomaly of the mandibular second premolar which may best be described by the term ‘molarization’. The aetiology of the condition is discussed, and attention is drawn to the clinical significance of the fact that these anomalous premolars may mimic the first deciduous molar in the morphology of the crown, though not in that of the root. Their unusually large mesiodistal diameter may also cause crowding problems.     

Patterns of tooth agenesis in patients with orofacial clefts

Orofacial clefts are a common oral disorder associated with tooth agenesis. As information on the simultaneous absence of teeth can be an aid in treatment planning, a large sample of orofacial cleft patients was examined. The sample consisted of 910 patients with cleft lip and palate. Tooth agenesis was assessed on the basis of at least two panoramic radiographs and patient records. Third‐molar agenesis was determined in 474 patients. Patterns of tooth agenesis were analysed using Tooth Agenesis Code (TAC) values, according to van Wijk & Tan . Per quadrant, at least 90% of patients could be described according to three different patterns. In the maxilla, 85% of patients with tooth agenesis had a TAC‐value of 2, 16, or 18 on either the left side, right side or bilaterally. In the mandible, 90% of patients with tooth agenesis had a TAC‐value of 16, 1 or 2 on either the left side, right side or bilaterally. In patients with tooth agenesis, patterns were symmetrical in the maxilla in 18.8% and in the mandible in 51%. More extended cleft types were associated with a higher prevalence of tooth agenesis. Third‐molar agenesis (prevalence = 22.4%) was significantly related to the prevalence of other absent teeth. These results show which patterns of tooth agenesis can be expected to occur in most orofacial cleft patients.     

Odontometric evaluation of mandibular premolars with tooth shape deviation: A case-control study

Objective:To evaluate the mean dimensions and morphologic characteristics of mandibular premolars that had mesiodistally elongated and faciolingually squeezed tooth shape deviations (MnP-TSD) and determine the population prevalence of this anomaly.Materials and Methods:Clinical photographs and study models were made for all new patients with MnP-TSD teeth who were seen over 20 years. The mesiodistal (MD) and faciolingual (FL) dimensions of the anomalous premolars were measured. MD/FL indices and MD × FL mm² occlusal crown areas were calculated and means and standard deviations were derived. Male and female means from the mandibular first and second anomalous premolars (MnP1/MnP2-TSD) were statistically compared against gender-specific means derived from published normative data using Student''s t-tests and chi-square tests.Results:Fifty-six individuals (33 male and 23 female) with MnP-TSD were identified, giving a male to female ratio of 1.4∶1, while the prevalence rate in the indigenous British population was estimated to be 0.6%. The MD widths of the MnP1-TSD and MnP2-TSD teeth were approximately 1 mm wider than normal, while the FL diameters were about 0.5 mm and 1.5 mm narrower respectively, for the first and second premolar teeth. The MD/FL indices, instead of being under 90 as usual were above 100, while the mean MD/FL mm² crown surface areas were normal.Conclusions:This study supplies odontometric dimensional and morphologic data on MnP-TSD teeth that provide a reference source for future comparisons.     

Bilateral macrodontia of mandibular second premolars: a case report

Summary. Macrodontia of single teeth is rare. This has been reported on only six occasions in scientific journals when affecting mandibular second premolars with associated morphological anomalies. The large crown size causes problems with eruption, and disrupts the dentition. There are consequent inherent difficulties for the extraction of these teeth. Once erupted, their anatomy predisposes them to caries. Most cases are seen in children, before interventive surgery has been completed. The morphological anomalies of these premolar Macrodonts appear quite distinct and may justify a separate unique categorization.     

Patterns of mandibular movements in subjects with craniomandibular disorders

Mandibular movements were evaluated for border and functional movements in 24 adult normal subjects and 26 adult patients with muscle pain associated with a craniomandibular disorder. The mandibular incisor position was tracked with an electromagnetic system in three planes by use of either a Myotronic Kinesiograph or a Siemens Sirognathograph instrument while the subject sat in an upright position. In the normal subjects, the maximum movements of the mandible in lateral, protrusive, and vertical directions were compared with the envelope of movement during speech and mastication. The range of the rest position was 1 to 5 mm in relation to the intercuspal position; the range of maximum excursion during speech was 30% to 36% of maximum opening; the vertical extent of excursion during mastication was 18% to 90% of the maximum vertical opening dependent on the bolus. Protrusive movements were straight forward, dividing the angle evenly between left and right laterotrusion. Laterotrusive movements were of equal length and similar to the length of protrusion. Twenty-six patients with muscle pain, in many instances, demonstrated asymmetry in the length of laterotrusive movements. Different pathways for moving the mandible away from the intercuspal position and returning to this position could be seen during laterotrusion. Unequal laterotrusive excursions and asymmetrical, nonparallel movement patterns for mandibular protrusion and retrusion were often observed. In contrast, the extent of the speech envelope and the envelope of mastication were similar to that of the controls.     

Two-rooted mandibular second premolars: case report and survey.

Mandibular premolars have earned the reputation for having an aberrant anatomy. Literature is replete with reports of extra canals in mandibular second premolars, but reports about the incidence of extra roots in these teeth are quite rare. This paper attempts at explaining a rare case of successful endodontic management of a two-rooted mandibular second premolar with diagnostic, inter-operative and postoperative radiographic records along with a substantial data on the incidence of extra roots in these teeth. The standard method of radiographic appraisal was maintained as the criteria for determining the presence of extra roots. Totally, 600 patients were examined for a period of four months by three endodontists. Out of them, eight patients had an extra root in one of the mandibular second premolars and three patients showed a bilateral presence of two roots.     

Patterns of bilateral agenesis of maxillary third molars and agenesis of other teeth

The purpose of this study was to investigate the patterns of bilateral agenesis of maxillary third molars and other tooth agenesis in Japanese orthodontic patients. A group of 262 subjects with bilateral agenesis of maxillary third molars (group A) was divided into three subgroups: group 1A consisting of 114 subjects without agenesis of mandibular third molars; group 2A, 31 subjects with unilateral agenesis of mandibular third molars; and group 3A, 117 subjects with agenesis of all third molars. As controls, 926 other subjects without third molar agenesis were selected (group C). Panoramic radiographs were mainly used to examine for tooth agenesis. The Chi square test and odds ratio were used to make statistical comparisons. The prevalence rates of agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, and bilateral agenesis of maxillary lateral incisors and second premolars were significantly higher in any one of the third molar agenesis groups than in the control group. Characteristically, no significant increase in occurrence of bilateral agenesis of mandibular second premolars was demonstrated by the subjects with bilateral agenesis of maxillary third molars. Irrespective of whether unilateral or bilateral agenesis of mandibular third molars is present or not, the Japanese orthodontic patients with bilateral agenesis of maxillary third molars exhibited a significantly increased occurrence of unilateral or bilateral agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, except for bilateral agenesis of mandibular incisors and second premolars.     

How to predict the timing of eruption of mandibular second premolars

Objective:To evaluate the relationship between the stages of dental formation and the timing of eruption of mandibular second premolars.Materials and Methods:The sample comprised panoramic radiographs of 25 children, 7 to 12 years old, observed by space supervision during development of dentition. The initial radiograph (T1) was taken in the mixed dentition period and the progress radiograph (T2) close to the eruption of mandibular second premolars. The stages of dental formation were determined by the proportion between crown length and total length (CL/TL) as well by the Simpson and Kunos index. Average values between right and left sides (35, 45) were correlated to the time elapsed until dental eruption (T2-T1). Statistical analysis was performed by Pearson correlation analysis.Results:The proportion CL/TL presented higher correlation index with time to eruption than the Simpson and Kunos index. The linear regression equation for prediction of timing of eruption showed high coefficient of determination, low deviation, and good accuracy. According to survival analysis, mean deviation at 95% confidence level was between 3.6 and 6.4 months. There was no difference in contralateral measurements, with high intraclass correlation coefficient for both CL/TL proportion and Simpson and Kunos index.Conclusions:More advanced stages of dental formation indicate less time until dental eruption. The strong correlation with crown length/total length proportion (CL/TL) provides a linear regression equation for prediction of the timing of eruption of mandibular second premolars.     

Patterns of non-syndromic permanent tooth agenesis in a large orthodontic population

ObjectiveThe aim of this study is to explore patterns of non-syndromic permanent tooth agenesis in a large orthodontic patient group.DesignA record review was performed in various orthodontic clinics to identify white patients with non-syndromic permanent tooth agenesis, excluding 3rd molars. Four hundred and fourteen subjects fulfilled the inclusion criteria.ResultsIn the 414 subjects with tooth agenesis, approximately 70% presented 1–2 missing teeth. Symmetric agenesis patterns were often observed in the sample (by jaw, by side, or crossed quadrants), with prevalence approaching 30% for cases with contralateral tooth agenesis within a jaw. In cases with 1 or 2 missing teeth, from the total number of potential tooth agenesis patterns in the sample, a certain part was evident, limiting the variation to 27.8% (44/158). In the entire sample, both in the maxilla and the mandible a certain incisor/premolar agenesis phenotype was observed in 59.0% of cases in isolated form.ConclusionsAlthough there was variation in the tooth agenesis patterns, our findings suggest the involvement of particular genetic, epigenetic, and/or environmental factors in the formation of the entire dentition, which often lead to specific tooth agenesis phenotypes in cases where this process is disrupted.The present study provides a comprehensive categorization of orthodontic cases with tooth agenesis and can assist in planning future epidemiological and genetic studies.