Lower Central Incisors Research Articles

Changes in lip pressure following extension and flexion of the head and at changed mode of breathing

The changes in upper and lower resting lip pressures following extension and flexion of the head and at changed mode of breathing were studied in a sample of 15 adults with Class I molar relationship. The lip pressure was measured with bonded strain gauge transducers on the upper and lower central incisors. The transducers could be calibrated directly in the subject's mouth. The upper and lower lip pressures during natural head posture had a mean value of 3.91 g/cm 2 and 8.58 g/cm, 2 respectively. The mean values of the differences between pressures obtained during natural head posture and during 5°, 10°, and 20° of extension showed a continuously, highly significant increase in pressure. During 5°, 10°, and 20° of flexion, the upper lip pressure continuously decreased with highly significant values. Changes in the lower lip pressure during flexion were difficult to measure because of intense muscle activity. A significant decrease was shown for the difference in upper and lower lip pressures between nose breathing and mouth breathing, whereas there was a significant increase in pressure when the subject extended the head 5° during mouth breathing.

Pressure from the lips on the teeth and malocclusion

The relationship between lip strength and lip pressure (pressure from the lips on the teeth) was studied in 84 children (aged 7 to 16 years) with varying types of malocclusion. The lip strength was recorded with a dynamometer. The lip pressure was measured on the upper and lower central incisors in the rest position, and during chewing and swallowing of crispbread. The lip pressure measurements were made with an extraoral pressure transducer incorporated in a water-filled system with an extaoral mouthpiece. The muscle activity of the lips was recorded electromyographically. Bite and facial morphologies were studied on dental casts and profile cephalograms. There was no correlation between lip strength and lip pressure. Lip strength was lower in children with Angle Class II, Division 1 malocclusion than in children with Class I malocclusion. The lip pressure on the upper incisors, on the other hand, was higher in Class II, Division 1 than in Class I malocclusion, and was lowest in children with Class II, Division 2 malocclusion. The findings suggest that the pressure from the lips on the teeth is a result of the incisor position.

Natal teeth.

I conducted a retrospective study based on record reviews of 50,892 infants born at the Foothills Provincial Hospital, Calgary, Alberta, Canada, from 1967 to 1984 to determine the incidence and possible causes of natal teeth. Fifteen infants were affected, for an incidence rate of one in 3,392 births. The affected teeth were the lower central incisors. The condition was more common in female infants. Two of the affected patients were twins. One patient each had Ellis-van Creveld syndrome, Pierre Robin syndrome, adrenogenital syndrome, cleft palate, and rickets. One mother each had pernicious anemia, vaginal infection, and diabetes mellitus.

Scanning electron microscopy of developing human deciduous incisor teeth

The mineralized parts of the teeth of 17 human fetal dentitions, aged 15–38 weeks, were measured mesio-distally and occluso-cervically. The growth pattern of the incisors, with particular emphasis on the changes at the developing incisal edge was studied. Contralateral teeth in the same arch developed at approximately the same rate and with mirror-image morphology. Mineralization started in the upper and lower central incisors, followed by the corresponding lateral incisors. It then progressed at approximately the same rate for both incisors. At first, mesio-distal enamel growth was more significant, but was surpassed by occluso-cervical development later. Five developmental stages were identified as the incisors developed from a central lobe to the mature form. The main component of growth for the mesial lobe was in the incisal direction, and for the distal lobe in a distal direction, resulting in the characteristic approximal asymmetry of these teeth.

上下がく中切歯におけるこう合小面および歯冠軸について ３次元座標測定機による研究

上下がく中切歯におけるこう合小面および歯冠軸について ３次元座標測定機による研究

Trafik kazası nedeniyle Pulpa Nekrozu

SUMMARY A case report about traumatized teeth by traffic accident have been presented. The patient, a 20 years old girl, had applied to our clinic for examination of traumatized teeth two days following the accident. Intraoral examination showed a normal occlusion. Both lower central incisors were extruded approximately 2 millimeters with dislocation apico-vestibuler direction. The crown and roots were intact according to the first radiography. The teeth were normal in colour. The pulps of 31, 32 and 41 were necrotic. There were no change the reaction in one month. The lower central incisors were reduced by a digital pressure on the incisal edges and splinted by ligature. There was a draining sinus tract on the lingial aspect of the lower left central incisor one month after the first examination. Radiograph, showed a large radiolucent area between both central incisors (Fig: 3). The necrotic teeth-31, 32 and 41- were performed rooth canal treatment according to accepted endodontic principles. A small piece of alveolar bone came through the sinus tract in one week. I think that , it came from interdental septum between two central incisors. At the end of the root canal treatment, there were no symptoms, or sinus tract (Fig : 6). The patient again was examined one, two and three years after completion of treatment. The teeth were asymptomatic and the radiographs showed intact periapical tissues and alveolar bone.

X線写真による歯冠歯根比と歯槽骨破壊との関連についての研究

This study was performed to know the relationship between crown-root ratio and periodontal bone destruction.One hundred and thirty eight sets of 14-film intra-oral roentgenographs taken from patients with light and moderate periodontal disease by dental students in senior class were used.The routine paralleling long cone technique was used. Those patients were aged from 20 to 66, 73 males and 65 females.Single rooted teeth (5-5/5-5) except molars were evaluated in respect of crown-root ratio and bone destruction.These teeth were divided into groups (54, 3, 21 12, 3, 45, 54, 3, 21 12, 3, 45) and assessed independently with regard to the relationship between crown-root ratio and periodontal bone destruction.These teeth did not have metal crowns and other large restorations such as class 2, 4 or MOD inlays.The periodontal bone height was assessed by the method of Schei et al.The anatomical crown-root ratio was determined by measuring the level of cemento-enamel junction. The bone loss from the cemento-enamel junction was measured in percentage. The measuring was carried out by three trained examiners.The lowest crown-root ratio was observed in lower canine (0.44±0.06). The highest periodontal bone destruction was recognized in lower central incisor (28.4±14.0%). There was not statistically a significant correlation between crown-root ratio and periodontal bone destruction in each group.The periodontal bone destruction in different age groups was evaluated also. The periodontal bone had a tendency to be destroyed with increasing age.

Repeatability of articulatory movements

In this experiment, we studied the repeatability of articulatory movements using the computer controlled x‐ray microbeam system at the University of Tokyo. Small lead pellets were attached to the upper lip, lower lip, lower central incisor, tongue tip, tongue body, and a reference location on the upper central incisor of each of two adult male subjects, both native speakers of American English. Each speaker read a randomized list of six different nonsense syllables and two sentences containing the vowels, /i,a,u/ and the consonants, /p,t,k/ in various VCV combinations, 15 times at a controlled speaking rate. The movements of the pellets were tracked at a rate of 150 scans/sec and recorded in graphical form with the X and Y components plotted separately against time. Spectrograms were obtained from recordings of the corresponding acoustic signal. Both sets of data are used to explore the questions of articulatory and acoustic equivalence in speech production.

ブラッシング方法の差による炎症歯肉辺縁の根尖側移動の程度について

The purpose of this study was to compare the degree of apical shift of gingival margin on inflamed gingiva by three toothbrushing techniques (modified Stillman's, roll and scrubbing method). Fifty-seven patients with mild periodontitis were used for this study. Patients were divied to three groups (19 patients for each group). Each group was instructed one of the three methods, at the beginning of the study. The position of the gingival margin was assessed on labial surface of upper and lower central incisors. At the same time, pocket depth of the labial and proximal surfaces as well as gingival and plaque index was scored. These examinations were performed at the beginning of the study, and were repeated at the 1st, 3rd, 5th, 9th and 13th week.The results of this examination were as follows.At the labial area, apical shift of gingival margin was found in all three groups. The modified Stillman's method showed the highest tendency to reduce the position of margin. Then the rolling method was followed. The scrubbing method made a minimum change on gingival margin. The bottom of the pocket, however, did not change during the period of this study in spite of difference of three brushing meshods.At the proximal areas, period of this the scrubbing method was found to significantly reduce the pocket depth when compared with other methods.The scrubbing method was the most effective on plaque removal among three brushing methods.Gingival Index scores were decreased during the period of this study, though significant differences among the three methods could not be found.

Root resorption during Begg treatment: A longitudinal roentgenologic study

Forty-two patients consecutively treated by the Begg method, all of whose first premolars had been extracted before orthodontic treatment, were examined roentgenologically by an intraoral technique on three to four occasions. The examinations were made before treatment, during treatment (before uprighting of tipped teeth), after completion of treatment, and 6 months after completion of treatment. In order to determine the occurrence and degree of root resorptions during the treatment period, a root resorption index was constructed. The reproducibility of the resorption index was studied by two observers. For assessment of the incidence and degree of root resorptions, the series of roentgenograms from each patient were examined simultaneously. The reproducibility of the simultaneous evaluation was also studied. In all of the forty-two cases treated, root resorption was recorded in the last roentgenologic examination. Before treatment small resorptions were found in 4 per cent of the teeth. Already, before uprighting of the tipped teeth, irregular root contours (score 1), probably caused by resorptions, and resorptions < 2 mm. (score 3) were recorded for 25 per cent and 31 per cent, respectively, of the teeth. There was no visible resorption in 42 per cent of the teeth. At the completion of treatment resorption < 2 mm. (score 3) predominated with 48 per cent, resorption of 2 mm.—one third of the root (score 5) occurred in 3 per cent, and no visible resorption occurred in 23 per cent of the teeth. When analyzing the percentage distribution of different degrees of root resorption in the teeth examined, we found that the relatively high frequency of root resorption before uprighting of tipped teeth increased slightly at completion of treatment. The resorption increased more for the upper central incisors, which were subjected to root torque, than for the upper lateral incisors. The incidence of root resorption 6 months after completion of treatment was highest at the lower central incisors (95 per cent). The upper central and lateral incisors showed an incidence of 90 and 87 per cent, respectively, and the lower and upper canines showed an incidence of 79 and 72 per cent, respectively. The lower premolars showed the lowest incidence of root resorption (53 per cent). The teeth that exhibited root resorption prior to treatment developed more resorption than the average during orthodontic treatment. This was especially marked for the upper incisors.

Tongue-thrusting patterns and the lower incisors

In summary, the lingual patterns of three patients have been reviewed. These three patients were referred with a diagnosis of tongue thrusting. When their lingual patterns were compared with those of other patients referred because of tongue thrusting, it was noticed that their patterns were somewhat different. This aspect was reviewed with the aid of cinefluorographic tracings, orthodontic study models, and photographs of the relationship between upper and lower central incisors. Different therapeutic aspects were also discussed.

Comparison of weights of twin fetuses and of their incisors.

Weights of developing incisors in 10 pairs of twin fetuses have previously been related to ages in order to compare dental growth status (Stack, 1963). Ages (T0) at which weights (W) of mineralised portions of teeth of the temporary dentition become significant have been computed (Stack, 1968), using a Fortran program giving maximum likelihood estimates of the required parameters, based on the statistical model of Angleton and Pettus (1966).Availability of the additional parameter T0 allows a reexamination of the previous data, now fortified by observations on incisors from five further pairs of twin fetuses. Estimates of ages were made from the relationship (T—T0) = k·W½, where values for upper and lower central incisors were 2.0 and 2.8 for k, 19.5 and 18.5 for T0, respectively. Less reliable estimates were obtained from the lateral incisors. These values were computed from observations on 40 dentitions from normal singleton fetuses. Ages were also estimated from tabulated body weights (Documenta Geigy).

Gingival height of lower central incisors, orthodontically treated and untreated.

Abstract No Abstract Available. Given before the Midwestern Component of the Angle Society, January 1967.

Gnathodynamics of four mandibular positions

A proportioned mix of quick-curing, soft-set acrylic resin was made and formed into an arch-shaped roll. The roll was positioned over the natural lower teeth of each subject (Fig. 1, A), and a “bite stick” (Fig. 1, B) was interposed between the upper and lower central incisors. This assured a uniform interocclusal separation for each registration. This was repeated for each of the four mandibular positions studied and the “bite stick” was kept in place with minimal pressure until the soft acrylic resin was fully set.

THE STUDY BY X-RAY CONTRAST ON CENTRAL INCISOR ERUPTION AND ELONGATION OF CLINICAL DENTAL CROWN

The report about growth and development, calcification and eruption year of teeth had been made and published by many investigators but mutual relation between teeth and paradentium was not understood accurately.Upper and lower central incisors had been continuously observed for 17.5 months (upper 48 samples, lower 11 samples) by contrast radiography, originally, developed for the purpose.Clinical teeth crown length before and after dental completion is measured and change from clinical dental crown length to anatomical crown length after dental emergence was observed in 526 samples (upper 279, lower 247) in association with continuous observation groups.Obtained results were as follows :1. Rider was set on the cutting-edge of incisor and labial surface of dental crown and gingival boundary line were plastered with contrast medium. Approximately value of clinical dental crown length and teeth length from radiography were found.2. When the teeth in jaw attained three-quarters of completed teeth length, their eruption was found in oral cavity.3. Judging from continuous observation groups, growth velocity of clinical dental crown length and teeth length in upper or lower jaws fast, 4 or 5 months after eruption but slower late after its time.4. Clinical dental crown length attained one-half of anatomical crown length in upper jaw about a year after emergence and in lower jaw about a year and 2.5 months.5. From the result of statistical analysis, the developmental relation between clinical dental crown length and teeth length was of high correlation.(r=0.97, Y=-15.92 + 0.94 X, in upper; r =0.98, Y=-11.014-0.76 X, in lower)6. Judging from continuous observation groups and other observation groups, the root was complet 27.17 months in upper and 30.93 months in lower after emergence.7. Clinical dental crown length was in upper about 60.9 % and in lower about 58 % of anatomical crown length at the time of root completion.8. After root completion, clinical dental crown length was linear in semi-logarithmic table. Clinical dental crown length increased in propotion to a logarithm of months.9. Clinical dental crown length was in accord with anatomical crown length in upper 822 months (approximately 69 years) and in lower 619 months ( approximately 52 years) after emergence.

Report of six cases of anodontia partialis and a consideration of some aspects of its origin

Six cases of anodontia partialis are presented with 2, 8, 5, 10, 5, and 11 permanent teeth missing, respectively. No general disturbances were found. The most frequently missing teeth were the lower central incisors, whereas the first molars never failed to erupt. An attempt has been made to sift the material of this and earlier reports in order to systematize some of the findings, and a questionnaire has been added which, it is suggested, may make it easier following up new cases and getting more reports and further indications regarding the origin of anodontia partialis.

Dento-craniofacial relations in varying degrees of overbite

0 VERBITE has been defined as the “overlapping of the upper and lower central incisors in the vertical plane. “46 Overbite varies in extent in different individuals ; when excessive it creates a clinical problem of considerable interest and concern. The border line between the so-called normal and abnormal overbite, however, remains to be clearly defined.l Certain aspects of overbite in the human dentition have been dealt with in the past. Anthropologic studies have revealed that the incisors in primitive man occluded edge to edge. Vertical ‘(overlap ” became a common feature of the human dentition at about the era of the Saxons, nearly two thousand years ago.zp 3 Clinical studies have established that the extent of overbite often varies with changes in dentition associated with age.4p 5 It is also well known that following extraction of teeth, drifting of adjacent teeth and other changes in dental alignment occur, frequently resulting in an increase of overbite.6 Clinical surveys have also brought to light the prevalence of excessive overbite in modern man, in both the temporary and permanent dentitions3y 6 Excessive overbite is one of the most common problems that confront the orthodontist.7 It may interfere with ability to occlude the teeth properly,8 which in turn may result in postnormal position of the mandible when the opposing arches are in occlusion. Once this relation is established, proper functions of the mandible, tongue, and adjacent structures are inhibited.3r gt lo Also complications caused by excessive overbite in the treatment of many diverse and varied forms of malocclusion and the problems of retention after its correction have been repeatedly emphasized in the literature.lll l** 131 I4

The eruption of the deciduous teeth

Summary The examination of 1,962 white children of fairly low economic status but under regular nutritional and medical supervision in a well-baby clinic, during the fall and winter of 1941–1942, provided material for a study of the eruption of deciduous teeth. The proportion of children who may be expected to have each type of tooth erupted was calculated for each month of age and smoothed curves plotted. The number of teeth to be expected at any age was also calculated and plotted together with a measure of variation to be expected. It was found that no deciduous teeth had erupted in children under 4 months of age and that all of the deciduous teeth had erupted in all of the children over 34 months of age. The most usual order of tooth eruption was found to be from earliest to latest; lower central incisor, upper central incisor, upper lateral incisor, lower lateral incisor, first molars (either upper or lower), cuspids (either upper or lower), and second molars (either upper or lower). There seemed to be no characteristic difference between boys and girls as to the ages at which specific teeth erupt, nor in respect to the number of teeth to be expected at any age. The relationship between variations in the weight of the child within an age group and the rapidity with which teeth erupt was small and of no statistical significance. No significant difference in eruption time was observed whether the child was born of a native-born mother or of a foreign-born mother.

Sublingual granuloma in infancy (Riga-Fede's disease): Report of two cases

Summary<ul><li>1.Two cases of Riga-Fede's disease are reported.</li><li>2.The disease is a granuloma of the frenulum linguae following abrasion by the lower central incisors and secondary infection.</li><li>3.Excision of the mass in our patients resulted in prompt recovery.</li></ul>

Research Items

The Katanga Skull THIS human skull belonging to a skeleton found in 1918 in some old native workings in the mine of Kambove (Katanga) in the Belgian Congo, has been made the subject of a study by Dr. Matthew Young of University College, London (Mem. Musee Roy. d'Hist. Nat. de Belgique, (2), 5). The skull is complete, with the lower jaw. It is undoubtedly of negro type, though showing signs which suggest admixture. Unfortunately, the remainder of the skeleton was not preserved. Although stained green with malachite, it shows no signs of mineralization to any appreciable degree. The specimen is of moderate length, very narrow, with a notable post-orbital constriction, and relatively high with a well-arched vault. The forehead is fairly rounded and shows the median eminence characteristic of the negroid type, though there are distinct indications of frontal eminences. The supracilliary ridges are fairly prominent. The temporal ridges are strongly developed, which is said to be a negroid feature. They appear to be more convergent than usual. The face is long, the nasal bridge excessively flat. The nasal aperture is relatively wide. Prognathism is moderate, and the lower jaw robust. The lower central incisors had been extracted at an early age. The skull is adult and probably male. It most closely resembles the Teita series from East Africa collected by Dr. Leakey, except in regard to the length of the face and especially of the alveolar portion. In this respect, it resembles two Nuba females from South Kordofan. A similar type of unusually long face and development of the alveolar region, accompanying an exceptionally high palate, is seen in Leakey's Nakuru and Elmenteita types, which have been compared with the Oldoway skull. These are usually considered to be Karaites, while Keith regards Oldoway as proto-Hamite. The Katanga skull then is a negro of recent date, probably not later than twelfth century, and is more nearly allied to the East than the West African type. It may be the remains of a slave captured at some distance from the Katanga.