Maxillary 1st Molar Research Articles

Lip and cheek resting pressure on the maxillary dentition in adults with normal occlusion

The position of teeth is influenced by pressures from the surrounding soft tissues. This study measured the lip and cheek resting pressures exerted on the maxillary dentition in adults with normal occlusion using the hydraulic-capillary infusion system. The purpose was to obtain standard values of muscle pressure on the maxillary central incisor, canine, and 1st molar, and to evaluate distribution of the muscle pressure on the maxillary dentition. Thirty-eight subjects (19 males and 19 females, mean age 26.9 ± 2.8 years) with normal occlusion were examined. Manometric catheters connected to pressure transducers were mounted on the surface of a stent at the area to be measured. The mean thickness of the stent at measuring points was 0.60 ± 0.11 mm. The muscle pressures were recorded for 60 s with 100 Hz sampling frequency, and the average pressure was obtained in each area. The lip and cheek resting pressure was 1.96 ± 1.27 g/cm 2 for the central incisor, 5.00 ± 1.39 g/cm 2 for the canine, and 1.28 ± 0.84 g/cm 2 for the 1st molar. Comparison of the resting pressures from the central incisor to the 1st molar showed that the muscle pressure was the highest at the canine, gradually decreasing toward the central incisor and toward the 1st molar. These results suggest that the muscle assembly at the oral angle exerts higher pressure in the canine area of the maxillary dentition.

Nifedipine regulated periodontal ligament remodeling: An experimental study in rats

Objective. The aim of this study was to investigate the effects of nifedipine on periodontal ligament remodeling during orthodontic tooth movement. Material and methods. Sixty male Sprague-Dawley rats were randomly divided into an orthodontic group and groups that received either 10 mg/kg or 40 mg/kg nifedipine (NIF). Immunohistochemical staining and image analysis were used to investigate the expression of matrix metalloproteinase (MMP)-1, -10, -13 and collagen-I in PDL, and maxillary 1st molar displacement was measured. Results. Expression of MMP-1, -10, and -13 was significantly decreased in both NIF groups, while collagen-I expression was markedly increased. NIF significantly inhibited tooth movement. Conclusions. NIF affects the expression of MMP-1, -10, -13 and collagen-I and tooth movement induced by orthodontic force in rats, thus indicating that calcium channels might be important in mediating PDL remodeling.

Diverse effects of c-src deficiency on molar tooth development and eruption in mice

C-src deficiency is characterized by osteopetrosis due to impaired bone resorption by hypofunctional osteoclasts and the resultant failure of tooth eruption. In preliminary observations, we frequently encountered erupted molars in c-src deficient mice unlike in other osteopetrotic animals. Here we examine the effects of c-src deficiency on the development of molar teeth with an emphasis on the spatial relation of growing teeth with the surrounding bones. In c-src deficient mice, the magnitude of tooth impaction differed considerably among the types of molars; all maxillary 1st molars were totally impacted deep in the alveolar sockets, whereas most mandibular 1st molars fully erupted into oral cavity. Distribution of osteoclasts in the alveolar bone was identical among all types of molars, and electron microscopy revealed signs of bone resorbing activity in these osteoclasts despite the absence of a ruffled border. From early development, the alveolar space was much narrower in the upper molar tooth germs than in the lower ones in both wild type and homozygous animals, and particularly so in the upper 1st molars. Current observations thus indicate a significant contribution of "hypofunctional osteoclasts" in c-src deficient mice in molar tooth development except for the upper 1st molars, which appear to require highly functional osteoclasts to gain sufficient space for them to grow normally. Taken together, these findings on the seemingly tooth-type specific effects of c-src deficiency on the development and eruption of molar teeth in c-src deficient mice can be attributed to the given differential spatial relation of the respective tooth germs with the surrounding bones in the presence of hypofunctional osteoclasts.

Osseointegrated Implant Anchorage in a Growing Adolescent

Temporary osseointegrated implants provide rigid orthodontic anchorage but may present problems in growing patients. The present case report of an adolescent male illustrates the successful use of a retromolar implant for anchorage to manage an asymmetric malocclusion. Following extraction of an ankylosed mandibular (Md) 1st molar and opposing maxillary (Mx) 1st molar, a retromolar implant was used for mesially translation of Md and Mx 2nd and 3rd molars to achieve a symmetrical Class I occlusion. Conclusions are: (1) the mandible is usually the critical arch for anchorage control relative to partially edentulous, acquired malocclusions, (2) indirect anchorage via retromolar implants is a reliable and versatile means for controlling the anterior limit of the dentition, (3) the anchorage wire extending from a retromolar implant in a growing patient should be positioned immediately beneath the brackets in the buccal segments, and (4) developing Md 3rd molars can be conserved by positioning the retromolar implant buccal and distal to the 3rd molar crypt.

Effect of electrical tooth stimulation on blood flow and immunocompetent cells in rat dental pulp after sympathectomy

Previous experiments show that nerves have effect on the emigration of immunocompetent cells during acute neurogenic inflammation. The present study aims to determine whether the sympathetic or sensory nerves are responsible for emigration of CD43+ and I‐A antigen‐expressing cells in the dental pulp after electrical tooth stimulation. Wistar rats were used. Experimental rats (n = 6) had the right superior cervical ganglion removed (SCGx), whereas control rats (n = 6) had sham surgery. Fourteen days later, electrical stimulation of the right maxillary 1st molar was performed in both groups for 20–25 s every 5th min for a total period of 4 h. Changes in pulpal blood flow (PBF) were recorded with a laser Doppler flowmeter. All rats were transcardiacally perfused and processed for immunohistochemistry using antibodies against neuropeptides and immune cells. Intermittent electrical stimulation consistently increased PBF and depleted sympathetic and sensory neuropeptides in the dental pulp. The increase in PBF gradually decreased and approached control values at the end of the 4 h stimulation period. A significant increase in the number of I‐A antigen‐expressing dendritic cells was found in both the SCGx (P < 0.001) and control rats (P < 0.007). In contrast, tooth stimulation did not increase the number of CD43+ cells in the SCGx rats compared to the unstimulated contralateral control molar. Significantly more CD43+ PMN cells (P < 0.01) were found in the control rats after stimulation. It is concluded that stimulation of sympathetic nerves causes recruitment of CD43+ PMN cells, whereas stimulation of sensory nerves causes emigration of I‐A antigen‐expressing dendritic cells in the dental pulp.

Investigation of the bone tissue response to glass-ionomer microimplants in the canine maxillary alveolar ridge

This paper reports the results of experimental use of glass-ionomer microimplants in the augmentation of the maxillary alveolar ridge in dogs. The study included ten adult mongrel dogs 5 years of age, weighing between 50 and 70 pounds (25-30 kg), divided into 2 groups of 5 dogs each. In both groups, the maxillary 4th premolar and 1st molar were removed after the elevation of a buccal mucoperiosteal flap. The alveolar bone adjacent to the extracted teeth was also removed. In the experimental group (5 dogs), Ionogran a glass-ionomer microimplants (GIMIs) (Ionogran particle size of 0.5-1.0 mm, IONOS Medizinische Produkte GmbH & Co. KG, D-8031 Seefeld, Gemany) were used for augmentation and were inserted in the created defects. The extraction sockets and bone defects were augmented with an average amount of 2 g of GIMIs. In the control group, the bone defects were left unfilled as a control for bone healing. Histological examination showed that the glass-ionomer microimplants were extremely osteoconductive and inert materials. Stimulation of growth of new bone tissue in contact with the glass-ionomer microimplants was evident. No inflammatory cells were detected on or adjacent to the GIMIs. In the control group, incomplete bone healing with fibrous scar tissue and inflammatory cells was noted. These results indicate that glass-ionomer microimplants represent highly osteoconductive and biocompatible materials for use in bone surgery.

Prevalence of furcation involvements in patients referred for periodontal treatment.

The aim of this study was to evaluate the prevalence of furcation-involved molars in a patient sample referred for periodontal treatment. A total of 222 patients aged, 14-73 years (mean age 45 years), and with signs of destructive periodontal disease in at least 2 quadrants of the dentition were included in the study. The clinical examination involved assessments of oral hygiene status, gingival conditions, probing pocket depth and presence/degree of furcation involvement. In addition, a full mouth intraoral radiographic examination was performed. The results revealed that 4% of the patients presented with all 12 molars, while 3% had lost all molars. 52% of the individuals had at least 8 molars; 95% of subjects < 30 years of age and 19% in the age 60+ years. In patients aged > or = 40 years, every 2nd molar showed advanced periodontal destruction in the furcation area. The prevalence of furcation involved molars was higher in the maxilla than in the mandible. From the age of 30 years, about 50% of the 1st and 2nd molars in the maxilla showed at least 1 furcation site with deep involvement, while in the mandible a similar prevalence was observed first after the age of 40 years. The highest frequency of furcation involvement was found at the distal site of the maxillary 1st molar (53%), and the mesial aspects of the maxillary 2nd molar showed the lowest frequency (20%). Furcation sites with a probeable trunk region were observed at a frequency of 17-22% at the various tooth sites. It was concluded that tooth morphology may be an important factor that accounts for the variability in prevalence of molar furcation involvement.

Prevalence and distribution of developmental enamel defects in primary dentition of Chinese children 3-5 years old.

A total of 1344 children, 3-5 yr old, from two rural counties, Haidian and Miyun, close to Beijing, China, were examined in 1992. A modified DDE Index was employed in this study, and a pre-designed formula was used to calculate an enamel defect score (EDS) for each individual in the study. Oral examination was performed by one dentist under natural light using a standard mouth mirror and dental probe. Developmental enamel lesions were diagnosed without drying or cleaning the teeth prior to examination. Results from this study showed that primary teeth with defective enamel were seen in 23.9% of the children examined, opacity in 1.6%, and hypoplasia in 22.2%. Among the teeth, maxillary central and lateral incisors were affected by enamel hypoplasia most often (40.8% and 39.2%), followed by maxillary canines (25.7%), maxillary 1st molars (22.1%), and mandibular 1st molars (18.5%). The enamel defects occurred more frequently on the buccal surfaces of teeth than on any other surface. The study did not find a significant association of the children's age, family socioeconomic status, and anthropometric measurements with the distribution of enamel defects. However, there was a significantly higher prevalence of teeth with defects in males compared to females (P < 0.001), as well as mean tooth surfaces with defects (P < 0.05), and mean EDS (P < 0.05). Children born prematurely were shown to have four times more enamel lesions than children who were full term (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Site progression of loss of attachment over 5 years in 14‐to 19‐year‐old adolescents

The aims of this study were (1) to monitor the progression and patterns of progression of loss of attachment > or = 1 mm on a site basis over a 5-year period in adolescents, and (2) to relate the presence of oral deposits and inflammation to the subsequent development and progression of loss of attachment on a site basis. 167 subjects were examined at ages 14, 16 and 19 years. Loss of attachment > or = 1 mm, plaque, subgingival calculus, gingival bleeding and gingival colour change were assessed on the mesio-buccal sites of the 1st molars, 1st premolars and central incisors. Each site was treated separately in the analysis to avoid the problem of within-subject site dependence. Sites were classed as progressing, non-progressing or fluctuating according to the probing attachment level measurements at each of the 3 examinations. During the 5 years of this study, a total of 542 sites in 128 subjects progressed; 1136 sites in 162 subjects did not progress; 43 sites in 30 subjects had fluctuating attachment level measurements. Sites which subsequently progressed had significantly more plaque, subgingival calculus and gingival inflammation than non-progressing sites at the baseline examination and throughout the study (p < 0.001). Between 55-57% of the maxillary 1st molars and 46-49% of the mandibular incisors progressed. In contrast, there was no progression of loss of attachment on over 80% of the maxillary central incisors and mandibular 1st premolars.

ラット上下顎臼歯歯根膜の機械的強度に及ぼすβ‐ａｍｉｎｏｐｒｏｐｉｏｎｉｔｒｉｌｅ（ＢＡＰＮ）経口投与の影響

Changes in the ultimate loads required to extract the mandibular and maxillary 1st, 2nd and 3rd molars from the dissected jaws were examined 1, 2, 4, 8, 16 and 24 days following oral administration of a lathyrogen, beta;-aminopropionitrile (BAPN). The average amount of water taken by the rats was fairly constant but because their body weight increased during the experimental period, the average dose of BAPN decreased gradually from 331 to 192mg/Kg b. w. In the control groups, the ultimate loads increased gradually from the beginning to the end of the experimental period. They were 34.4, 26.9 and 13.6N (newtons) in the mandibular 1st, 2nd and 3rd molars and were 34.2, 30.6 and 18.0N in the maxillary 1st, 2nd and 3rd molars respectively at the end of the experimental pe-riod. In the experimental groups, they were 9.9, 10.2 and 8.4 N in the mandibular 1st, 2nd and 3rd molars and were 13.5, 14.6 and 10.9N in the maxillary 1st, 2nd and 3rd molars respectively at the end of the experimental period. The biggest values of the percentage reductions of the ultimate loads were 73, 71 and 51 in the mandibular 1st, 2nd and 3rd molars and were 64, 58 and 64 in the maxillary 1st, 2nd and 3rd molars respectively during the experimental period. From an analysis of the results, it is suggested that the effects of BAPN appeared rather rapidly in the teeth with imm ature periodontal ligaments and that the functioning teeth tended to be affected more severely by the drug

The cell proliferative activity of parodontal tissues in aging mice

One hundred and thirty-eight short-lived mice of the Brookhaven National Laboratory inbred strain of Swiss albino 5, 26, 52, 78 weeks of age were used to determine the normal proliferative activity of the parodontal tissues comprising the mesial aspects of the maxillary 1st molars and the associated changes concomitant with aging. Labelling indices were obtained following grain-counting of autoradiographs. Each animal received 1 μCi of tritiated thymidine per gram body weight 1 hr prior to death. Five micron sections were cut from paraffin blocks prepared routinely following EDTA decalcification. Results showed that the order of proliferative activity was similar at all ages. The proliferative activity was highest in gingival epithelium while all other tissue compartments were significantly lower. In lessening order, these were 4 connective tissue compartments, 2 osteogenic layers and lastly the cementoblastic layer. A progressive decrease in labelling indices to 52 weeks of age was generally observed with increasing age. This was subsequently followed by a rise in the number of labelled cells, especially in the gingival epithelium and connective tissue below the crevicular region. A survey of the tissues for inflammatory reactions revealed increased incidence with advancing age, especially at 78 weeks of age. The crevicular region of the epithelium, the connective tissue below and the periapical periodontium were the usual inflammatory sites. It was concluded that increased labelling observed in animals older than 52 weeks of age was associated with increased incidence of inflammation at susceptible sites coincidental with histological age changes in parodontal tissues.