Relationship of maxillary molar root angulation and palatal vault height

If the vertical angulation of maxillary molar roots could be reliably predicted, this might affect the choice of roots resection procedures. In an attempt to develop this prediction, angulation of palatal roots was compared to palatal vault height. Human cadaveric maxillae with molars were sectioned faciopalatally through each tooth root to the palatal midline and photographed. Root angles and palatal height were measured on the photographs in relation to a reference line connecting buccal and palatal cementoenamel junctions (CEJ). Palatal vault heights were classified as low, medium, or high according to the perpendicular distance from the midpalatal suture to the reference line. Root angles were subtended by a line following the length of pulp canals and perpendicular to the CEJ reference. Analysis by Spearman's Rank Correlation Coefficient demonstrated a weak nonsignificant relationship between palatal vault height and the angulation of the various maxillary molar roots. Thus, palatal vault height would not be a reliable predictor of root angulation if this were to be used as a basis for root retention.     

Further studies of the pressure from the tongue on the teeth in young adults.

The pressures from the tongue on the teeth were recorded simultaneously in four locations lingual to the upper and lower central incisors, and left first molars in 20 young adults with largely normal occlusion. Measurements in the rest position, and during chewing and swallowing were made with an extra-oral pressure transducer incorporated in a fluid-filled system with intra-oral mouthpieces. The size of the dental arches was determined from dental casts. The median pressures in the rest position were low and negative at the upper incisors. Negative pressures at rest were recorded in a few subjects at all four points of measurement, most frequently at the upper incisors and least frequently at the lower molar. The pressures during swallowing were 2-4 times greater than those during chewing. There were no significant correlations between the pressures found and those recorded in the same individuals at an examination 2 years earlier. Positive correlations were found between the pressures recorded in the four locations during the various functions. This was interpreted as being an effect of the size of the tongue. The relatively few correlations between the pressures and the parameters describing the dental arch size indicated an adaptive role of the tongue within the confines of the dental arches.     

Pressure from the tongue on the teeth in young adults

Pressure from the tongue on the teeth was measured at the upper and lower central incisors and left first molars in 25 young adults with clinically normal occlusion. Repeated recordings with and without a period for accommodation to the intraoral measuring device, which was connected to an extraoral pressure transducer, were made in the rest position and during chewing and swallowing. Only minimal effects of accommodation were found. The system can thus be used without a period of adaptation before the actual test. The intraindividual pressure variations were of the same magnitude as for measurements of the pressure from the oro-facial soft tissues on the teeth recorded in earlier studies. The majority of the subjects had negative pressures at the upper and lower incisors and at the upper molar in the rest position. The pressures on the teeth during swallowing were comparatively great, while pressures during chewing were one-fourth to one-half of the swallowing pressures.     

Dynamics of posterior tongue during pronunciation and voluntary tongue lift movement in young adults

The lifting-up movement of the posterior part of the tongue to touch the palate, which is a requirement for performing physiological functions such as deglutition and speech, is an important phenomenon that is difficult to objectively evaluate. The purpose of this study was to develop a new modality to evaluate the tongue-lifting function, especially in the posterior part of the tongue, and to elucidate the dynamic properties of the tongue in normal subjects. Twenty-three healthy volunteers (9 men and 14 women; mean age, 27·6years) participated in this study. A new device was developed that could evaluate the up-down movement of the posterior part of the tongue in a non-invasive manner. The experimental tasks were as follows: (i) /a/ pronunciation for 1s followed by /ka/ pronunciation (a-ka task), (ii) /a/ pronunciation for 1s followed by /ga/ pronunciation (a-ga task) and (iii) /a/ pronunciation for 1s followed by a voluntary push-up movement of the posterior part of the tongue (a-lift task). Maximum upward velocity in the a-ga task was larger than that in the a-ka task (P<0·05). The a-lift task showed the highest tongue lift range among the three tasks, and the a-ga task showed a higher range than that of the a-ka task (P<0·05). This study revealed that precise quantification of the motility of the posterior part of the tongue, which would be useful in rehabilitation of articulation and/or swallowing, could be achieved using this new device in a non-invasive manner.     

Rate of reformation of tongue coatings in young adults

Abstract: Background: Reviewing the literature, no study on the rate of regrowth of tongue coatings after tongue cleaning was found. Therefore, the purpose of this study in young adults was to study the rate of reformation of tongue coatings after mechanical removal. Material and Methods: Thirty‐five dental students participated in the present study. Following preparatory study instructions, baseline examinations were carried out followed by 3 days of observation. At baseline, tongue coating scores (prescraping) were obtained followed by tongue scrapings and determination of the wet weights of the coatings. A second tongue coating score was then obtained within 5 min of the first score (immediate post‐scraping). The subjects returned for repeated tongue coating scores after 1 and 2 days and for final examination after 3 days, which included both tongue coating scores (prescraping and immediate post‐scraping) and determination of the wet weights of the coatings. Results: Prior to scraping the tongue at day 0 (baseline), mean tongue coating amounted to a surface extension of 33% of the entire dorsum of the tongue. Scraping the tongue reduced the score to 9%. On average, tongue coating scores had returned to baseline levels on day 2. The mean wet weights of tongue scrapings at days 0 and 3 were similar and amounted to 0.09 ± 0.07 and 0.09 ± 0.06 g, respectively. Conclusion: If tongue cleaning is to be recommended, the results of this study in dental students indicate that tongue cleaning should be performed on a daily basis.     

Change in third molar angulation and position in young adults and follow-up periodontal pathology.

PURPOSE: This study was designed to assess changes in third molar position and angulation in young adults and the resulting third molar periodontal probing (PD) status. PATIENTS AND METHODS: Data derived from patients with 4 asymptomatic third molars with adjacent second molars enrolled in an institutional review board approved longitudinal trial. Inclusion criteria for the trial dictated that patients be healthy and 14 to 45 years of age. Panoramic radiographs were analyzed for third molar angulation as compared with the long axis of the second molar (mesial/horizontal > or =25 degrees ) and eruption to the occlusal plane. Full mouth PD including third molars was conducted at follow-up. At follow-up, PD > or =4 mm distal of second molars or around third molars was considered important clinically. RESULTS: Data from 237 patients were available. Median age was 25.9 years (interquartile range [IQ], 22.1 years, 32.8 years). With a median follow-up of 2.2 years (IQ, 2.0 years, 3.7 years), 44% of impacted maxillary third and 26% of impacted mandibular third molars changed angulation or position. One third of vertical/distal impacted third molars in both jaws and 11% mesial/horizontal mandibular third molars erupted to the occlusal plane during follow-up from baseline. If mandibular third molar angulation as compared with the long axis of the second molar was mesial/horizontal > or =35 degrees , only 3% erupted to the occlusal plane. At follow-up, 11% of the 125 impacted maxillary third and 29% of the 133 impacted mandibular third molars had PD > or =4 mm. Similarly, 11% of the 307 maxillary third molars at the occlusal plane had PD > or =4 mm, but 51% of the 312 erupted mandibular third molars were affected. CONCLUSION: A change in third molar position or angulation was common. Erupted mandibular third molars were more likely to have PD > or =4 mm.     

Permanent first molar extraction in adolescents and young adults and its effect on the development of third molar

Objectives

The aim of the present study was to determine the prevalence of permanent first molar (P1M) extraction among Turkish adolescents and young adult subpopulation, and to investigate the effects of P1M extraction on development of the third molars (3Ms) in the same quadrant.

Materials and methods

A retrospective study including 2,925 panoramic radiographs (PRs) taken from patients (aged 13–20 years) who were examined to identify cases of had at least one maxillary or mandibular P1Ms extracted was performed. Additionally, 294 PRs with the maxillary or mandibular unilateral loss of a P1M were used to assess the developmental grades of the 3Ms. Statistical analyses were performed by means of parametric tests after performing a Shapiro–Wilks normality test to the data.

Result

A total of 945 patients (32.3 %) presented with at least one P1M extraction with no gender difference (P?=?0.297). There were more cases of mandibular P1Ms extracted (784 patients, 1,066 teeth) than maxillary P1Ms extracted (441 patients, 549 teeth) (P?<?0.001). The development of the 3Ms on the extraction side, in the both maxilla and mandible, was significantly accelerated when compared with the contralateral teeth (P?=?0.000, P?=?0.000, respectively). No statistically significant differences were found in the differences in the developmental of the 3Ms between the maxilla and mandible (P?=?0.718).

Conclusions

High prevalence of P1Ms extraction among Turkish adolescents and young adults shows a need for targeted dental actions, including prevention and treatment. The development of the 3Ms on the extraction side, in the both maxilla and mandible, was significantly accelerated.

Clinical relevance

To date, no information about prevalence of P1Ms extraction among Turkish adolescents and young adults is documented. In addition, the present study has a larger population and complementary information about 3Ms development than previous studies.     

正常[牙合]与错[牙合]患者第三磨牙先天缺失的比较研究

目的 探讨正常[牙合]与错[牙合]青年第三磨牙的发育情况。方法 对相同年龄分布的青年正常[牙合]个体97人和错[牙合]患者186人进行临床检查与X线测量分析，对第三磨牙存在与缺失、缺失部位、牙胚位置及其与[牙合]平面夹角等进行对照研究。统计分析为卡方分析和t检验。结果 以人计数的第三磨牙缺失率正常[牙合]个体为46．36％，高于错[牙合]患者29.03％；以牙计数的第三磨牙缺失率正常[牙合]个体21．65％也高于错于[牙合]患者的16．67％，而且正常[牙合]个体上颌第三磨牙的缺失尤其高于错[牙合]患者；正常[牙合]和错[牙合]患者上颌第三磨牙的缺失率均高于下颌；发育中的第三磨牙与[牙合]平面的夹角，无论是正常[牙合]和错[牙合]患者，均为下颌大于上颌，其中男性错[牙合]患者下颌磨牙的夹角大于女性患者及正常[牙合]男性。在错[牙合]患者中牙列存在间隙的患者及存在其他牙齿异常苦。第三磨牙的缺失率显著增高。结论 汉族正常[牙合]个体第三磨牙缺失率高于错[牙合]患者；上颌第三磨牙比下颌磨牙更易缺失；在发育过程中下颌第三磨牙比上二颌磨牙更加倾斜。     

Morphology of the palatal vault of primary dentition in transverse view

The purpose of this study was to investigate the transverse view of the morphology of the palatal vault in the primary dentition at the primary second molar level. Observations were obtained from 150 dental stone casts of normal children (78 boys and 72 girls; aged four to five years). Palatal width, palatal depth, arch width, and primary second molar angulation were measured. There were no significant differences in palatal depth and primary second molar angulation between boys and girls or between the right and left sides. However, girls had a statistically significantly narrower upper dental arch width and palatal width than did boys. Palatal widths on the left side were statistically significantly larger than those on the right side for both sexes. Asymmetry in the palatal width greater than two mm was present in 21.8% of boys and 16.7% of girls. There was a correlation between buccal tipping in the upper primary second molar and greater palatal width.     

Association between tongue and lip functions and masticatory performance in young dentate adults

Motor functions of masticatory organs such as the tongue, lips, cheeks and mandible are known to deteriorate with age, thereby influencing masticatory performance. However, there are few reports on the relationships between tongue and lip functions and masticatory performance. To investigate the relationship between tongue and lip functions and comprehensive masticatory performance, by evaluating crushing, mixing and shearing abilities in young dentate adults. Participants comprised 51 dentate adults with a mean age of 25 years. Maximum tongue pressure and oral diadochokinesis were measured to evaluate tongue and lip functions. A multiple sieving method using peanuts was performed to evaluate crushing ability. A colour‐changeable chewing gum was performed to evaluate mixing ability. A test gummy jelly was performed to evaluate shearing ability. The relationship between tongue and lip functions and each masticatory performance was assessed using Pearson's correlation coefficients. In addition, stepwise multiple regression analysis was performed to identify predictors of crushing ability. Crushing ability was significantly correlated with maximum tongue pressure and the number of repetitions of the syllables /pa/, /ta/ and /ka/. Maximum tongue pressure and number of repetitions of the syllable /pa/ were identified as significant predictors for crushing ability. Mixing ability was significantly correlated with the number of repetitions of the syllable /pa/. Shearing ability was not significantly correlated with tongue and lip functions. Masticatory performance during the chewing of brittle foods such as peanuts and solid foods such as chewing gum appears to be correlated with tongue and lip functions.     

Effect of premolar extraction on mandibular third molar impaction in young adults

Objective:To test the null hypothesis that orthodontic therapy with or without premolar extraction does not result in any difference in third molar impaction.Materials and Methods:Two groups were formed: 22 patients in one group with first premolar extractions and 22 patients in the other group without extractions. All patients were nongrowing subjects who had normal gonial angles and were skeletal Class I at the beginning of treatment. The available space for third molars, inclination of second and third molars, and angle between the second and third molars were evaluated. Also, the correlation of measured parameters and type of orthodontic therapy with the eruption of third molars was evaluated.Results:Of the third molars, 81.8% were impacted in the nonextraction group and 63.6% were impacted in the extraction group. Impaction of mandibular third molars was significantly correlated to the pretreatment and posttreatment inclination of third molars and the angle between the second and third molars. In the extraction therapy group, the retromolar distance increased significantly with a mean of 1.30 ± 1.25 mm.Conclusions:When the inclination of the third molar is inconvenient, the tooth may remain impacted even if there is enough retromolar space.     

Cheek and lip pressure against maxillary dental arch during dummy sucking.

The sucking pattern and intra-oral negative air pressure were studied simultaneously with the cheek/lip pressure in 12 children when sucking a dummy. The cheek/lip pressure was measured at the canine and at the second primary molar on the right side of the upper dental arch. The cheek/lip pressure peaks followed the intra-oral negative air sucking pressure peaks continuously. In the canine region the mean value of maximum cheek/lip pressure was 54 g/cm2. The corresponding value at the second primary molar was 21 g/cm2. During dummy sucking the mean cheek/lip pressure was 3.4 times higher against the canine compared to the second molar (P less than 0.001). The intra-oral negative air pressure was approximately the same whether the cheek/lip pressure was measured at the canine or at the second primary molar. The results indicated that the circumoral muscles were especially active during dummy sucking, in addition to the cheek pressure in the canine region.     

Growth of the cranial vault: Influence of intracranial and extracranial pressures

The cranial vault is composed of several flat membranous bones whose growth is mainly a result of the activity in the interposing sutures. The reactions of the calvarium and cranial base to provoked stimuli of the sutures dinger depending on their developmental stage. In this report the effects of pressure, exerted extracranially by means of mechanical forces or intracranially by means of hydrodynamic fluctuations, are described.     

Changes in lower third molar position in the young adult.

Changes in position of unerupted lower third molars between 18 and 21 years were examined in a group of 17 men and 24 women with intact lower arches. Mesiodistal third molar angulation, molar space, molar space condition, and buccolingual third molar angulation and the changes in these dimensions were measured on 60 degree cephalograms taken at 18 and 21 years. At 18 years molar space was inadequate by an average of 5.0 mm. Average changes in dimensions were statistically nonsignificant except for an increase in molar space of 0.7 mm. Changes in third molar position ranged from 39 degrees to -46 degrees in the mesiodistal and from 24 degrees to -24 degrees in the buccolingual dimension. Only 10 third molars did not change their mesiodistal angulation. Four third molars erupted fully during the observation period.     

Third molar periodontal pathology and caries in senior adults.

PURPOSE: This study was designed to assess the prevalence at enrollment and incidence over 36 months of periodontal pathology and caries affecting third molars in a community-based study of people over the age of 65 years in North Carolina. SUBJECTS AND METHODS: A sub-sample of 818 subjects with dental examinations taken from the Piedmont 65+ Study was available for analysis. All visible teeth were examined. Periodontal probing (PD) measures were taken at 2 sites, mesiobuccal and buccal/facial. Clinical data on caries experience were collected by visual-tactile examination. At enrollment, 342 subjects had at least 1 visible third molar that could be examined. PD measures were available for 276 of these same subjects. The significance of comparisons between third molars and nonthird molars were determined by chi(2) tests and the statistical significance was set at .05. RESULTS: Most of the 342 subjects with at least 1 visible third molar were female (57%) or African American (63%). Mean age was 73 years (SD 5.5 years). Of the 197 subjects with caries experience, third molars were affected in 49% of subjects, less than the 87% in nonthird molars. Third molar caries experience was associated with caries experience on nonthird molar teeth (P < .01). Clinical attachment level (CAL) greater than 3 mm was detected at enrollment in third molars in 68% of subjects, and in nonthird molars in 96%. With one exception, CAL greater than 3 mm in third molars was associated with CAL greater than 3 mm elsewhere in the mouth. Few subjects (17%) had clinical evidence of both caries and periodontal pathology affecting third molars. In this older population of individuals with third molars, 21% were free of periodontal pathology or caries experience. CONCLUSIONS: Data on the prevalence of third molar periodontal pathology and third molar caries experience in an elderly population should be useful to both clinicians and their younger patients when considering the merits of retaining or removing third molars with no evidence of pathology.     

Correlation between intraoral pressures and tongue movements in the suckling pig

The objective was to clarify the relationship between tongue movements during suckling and the pressures in different parts of the oral cavity. A modified teat allowed a miniature pressure transducer to be passed through into the mouth. Intraoral pressures were recorded in piglets suckling on the teat attached (1) to a non-vented bottle or (2) to an automated milk delivery system. The movements of the tongue, of the milk and the transducer position were recorded by cine-radiography. In both modes of feeding, waves of elevation on the tongue moved in a pharyngeal direction and rose to contact the mid-posterior palate. Each wave corresponded to a jaw (suck) cycle in which milk was moved into and through the oral cavity. After each wave passed the transducer in the anterior part of the mouth, cyclical negative pressures were recorded. In bottle feeding, the intraoral pressure fluctuations (+/-2 mmHg) occurred against a background of a gradually developing negative pressure but, when feeding on the automatic delivery system, the same or smaller fluctuations occurred as changes from atmospheric pressure. Where the elevations contacted the mid-posterior palate in each cycle, a seal was formed (contact pressure >40 mmHg), so producing two functional antero-posterior compartments within the mouth; in these compartments pressures were generated independently. With the transducer in the valleculae, no general increase in pressure was recorded as milk accumulated there in each suck cycle but large positive pressures were recorded during the less frequent cycles when the vallecular space was emptied.