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At least 667 records · Page 37Linked to original sources
PubMed2003

Distal molar movement with Kloehn headgear: is it stable?

The aim of this study was to evaluate intramaxillary molar movement after 8 months of cervical traction and posttreatment displacement 7 years later. The total molar displacements in relation to stable intraosseous reference points were compared with those observed in an untreated control group that also had intraosseous reference indicators inserted. During the headgear period, the type of molar displacement could be predicted by the direction of the force system acting on the teeth. It was noted, however, that the variation in the vertical development was related more to each patient's growth pattern than to the force system applied. After cessation of the headgear, intramaxillary displacement of the molars was noted, and the total displacement of the molars did not differ from that of the untreated group. The indication for intramaxillary displacement of the molars by means of extraoral traction is therefore questioned.

Cephalometry↗
PubMed2001

Third molar outcomes from age 18 to 26: findings from a population-based New Zealand longitudinal study.

OBJECTIVE: The purpose of this study was to describe the presence and impaction status of people's third molars at age 18 years, as well as the observed changes in their clinical status between ages 18 and 26 years. STUDY DESIGN: Eight hundred twenty-one participants in a prospective cohort study were dentally examined at ages 18 and 26 years, and panoramic radiographs were taken at age 18 years but not at 26 years. For each tooth, its radiographic impaction status at age 18 years was compared with the clinical status by age 26 years. RESULTS: Of the 2857 third molars assessed at age 18 years, 92.8% were able to be followed up clinically at age 26 years. Approximately 54.9% of the teeth that were not impacted by age 18 had erupted by 26 years. Of the teeth that were impacted by age 18, 33.7% had fully erupted by age 26, 31.4% had been extracted, and 13.1% remained unerupted. Of the maxillary teeth that were categorized as "impacted" at age 18 years, 36.2% had fully erupted by age 26, whereas only 25.6% of the mandibular teeth had done so (P <.01). Fewer mandibular teeth than maxillary teeth remained unerupted by the time the patient was 26 years old (27.4% and 41.4%, respectively; P <.01), but there was no significant difference between the jaws in the proportion of impacted teeth at age 18 years that had been extracted by age 26 years (29.6% and 30.3%, respectively). For mesioangularly impacted third molars, 39.3% of maxillary teeth and 20.4% of mandibular teeth had fully erupted by age 26. Of the third molars that were mesioangularly impacted at age 18 years, 39.3% of maxillary teeth and 20.4% of mandibular teeth had fully erupted by age 26 years, whereas almost one-third of each had been extracted. Of the distoangularly impacted third molars, 20.4% of the maxillary teeth and one-third of the mandibular teeth had erupted by age 26, with 21.6% of the maxillary teeth and 31.6% of the mandibular teeth having been extracted. CONCLUSION: Other than horizontally impacted third molars, a substantial proportion of other impaction types do erupt fully, and radiographically apparent impaction in late adolescence should not be sufficient grounds for their prophylactic removal in the absence of other clinical indications.

Adolescent↗
PubMed2001

Effect of groove placement on the retention/resistance of resin-bonded retainers for maxillary and mandibular second molars.

STATEMENT OF PROBLEM: Lack of retention/resistance form in the clinical preparation of teeth for resin-bonded retainers may lead to clinical failure. PURPOSE: This study investigated the effect of proximal grooves on the retention/resistance of cast resin-bonded retainers for maxillary and mandibular second molar teeth. MATERIAL AND METHODS: Two ivorine teeth (a maxillary and a mandibular second molar) were prepared for resin-bonded retainers. Twenty metal replicas of the prepared teeth were made (10 for each tooth morphotype). Resin-bonded retainers 0.5 mm thick were made for the 40 replicas and luted with Panavia EX cement. Forces for dislodgment of the retainers were applied along the long axes of the teeth. Forces recorded at the time of dislodgment were analyzed with 2-way analysis of variance and the post hoc Scheffé test. RESULTS: Grooves resulted in substantial increases in debonding forces for maxillary molars (P<.001). The effect of grooves on mandibular second molars was not significant (P=.13). CONCLUSION: Grooves placed in tooth preparations of maxillary molar teeth for resin-bonded retainers had a significant effect on retention/resistance. The effect of grooves on mandibular second molars was less pronounced.

Analysis of Variance↗
PubMed1998

Comparison of dentin apposition and dentinal caries progression in the mandibular and maxillary molars of the rat.

To show that the rate and the rate of reduction of dentin apposition are about the same in mandibular and maxillary molars, 23 Sprague-Dawley rat pups were randomized into 2 groups on the day of birth. During lactation half of their dams received a standard rodent diet; the other half, a diet containing 41% sucrose. At the age of 3 weeks the pups were weaned, weighed, given an intraperitoneal injection of oxytetracycline hydrochloride, and inoculated with oral Streptococcus sobrinus. During the experiment the pups received the same diet as their dams during lactation. After 5 weeks the pups were decapitated, their jaws sectioned sagittally, the first and second molars photographed, and the areas of dentin apposition and dentinal caries measured planimetrically. The area of dentin formation was about the same in maxilla and mandible in the first molars, but slightly smaller in the mandibular second molars of the control group. The sucrose diet reduced dentin apposition significantly in both jaws, although the areas were significantly smaller in the mandibles than in the maxillae. Caries did not affect the rate of dentin apposition. The areas of caries lesions were smaller in the maxillary molars of both diet groups. The results show that the hypothesis of equal rate of dentin apposition in mandible and maxilla was not valid because the reduction, caused by sucrose, was more prominent in mandibular molars for unknown reasons. The reduction of dentin apposition was reflected as acceleration of caries progression among the diet groups and the jaws. It was concluded that the response of the pulpodentinal complex to sucrose and dentinal caries during the primary dentinogenesis cannot be seen as a formation of reactionary or reparative dentin, as with adult rats.

Animals↗
PubMed1996

Masticatory tooth contact patterns: cuspid and first molar contacts during mastication of three types of food.

In ten healthy subjects, bilateral contacts between opposing cuspid and first molar teeth were recorded during one sequence of unilateral chewing of apple, peanuts, and banana. Unknown magnitudes of mechanophysical (masticatory) forces were inferred to act directly on the chewing-side cuspid teeth in 71% of all masticatory cycles and on the nonchewing-side cuspid teeth in 68% of all masticatory cycles. In addition, unknown magnitudes of mechanophysical forces were inferred to act directly on the chewing-side first molar teeth in 74% of all masticatory cycles and on the nonchewing-side first molar teeth in 86% of all masticatory cycles. During the chewing of peanuts, the total number of chewing-side cuspid contacts exceeded significantly the total number of nonchewing-side cuspid contacts, suggesting more repetitive direct mechanophysical loading of the chewing-side cuspid teeth. During the chewing of apple, the total number of nonchewing-side first molar contacts exceeded significantly the total number of chewing-side first molar contacts, suggesting more repetitive direct mechanophysical loading of the nonchewing-side first molar teeth. The variable contact patterns were, to a large extent, explained by rotational movements of the entire mandible resulting in translational movements of the hemimandible.

Adult↗
PubMed2006

Effects of a segmented removable appliance in molar distalization.

The aim of the present investigation was to evaluate the skeletal and dentoalveolar treatment effects of a segmented removable appliance [removable molar distalizer (RMD)] for molar distalization. The study was conducted on 28 patients (12 females and 16 males), with a mean age of 11.8 years. All presented with a skeletal Class I malocclusion and a bilateral dental Class II molar relationship. The pre- and post-distalization records included lateral head films, study models and standard photographs. The findings were evaluated with a paired samples t-test. The average maxillary first molar distalization with the RMD was 3.98 mm, with 4.61 degrees of distal tipping. The maxillary second premolars drifted distally 2.13 mm on average with 1.54 degrees of distal tipping, while the maxillary first premolars showed 1.23 mm of mesial movement and 1.98 degrees of mesial tipping. The incisors protruded 1.09 mm with 1.27 degrees of labial tipping. The RMD was effective in distal molar movement and all patients attained a bilateral Class I molar relationship in an average period of 4.5 months. Hygiene problems and mucosal irritations, frequently found with fixed intraoral distalization techniques, were not observed during the distalization period.

Cephalometry↗
PubMed2006

Maxillary third molar position in Class II malocclusions: the effect of treatment with and without maxillary premolar extractions.

The present study compared the number of erupted and functioning maxillary third molars and their mesio-distal angulation in patients with Class II malocclusions orthodontically treated with and without extraction of two maxillary premolars and fixed appliances. For that purpose, the records of 55 patients were selected, which were divided into two groups. Group 1 was treated without extractions and comprised 28 patient records (19 males and 9 females), with a mean age of 19.03 years [standard deviation (SD) = 2.33], treatment time of 2.59 years (SD = 1.08), and follow-up time of 6.48 years (SD = 2.42). Group 2 was treated with extractions and comprised 27 patient records (14 males and 13 females), with a mean age of 19.94 years (SD = 2.87), treatment time of 2.95 years (SD = 1.17), and follow-up time of 5.88 years (SD = 2.96). Analysis of the erupted and functioning maxillary third molars was conducted on the maxillary and mandibular dental casts. The mesio-distal angulations of the maxillary third molars were assessed on panoramic radiographs with the presence of both maxillary third molars. The results demonstrated that the number of erupted and functioning maxillary third molars was statistically greater (P = 0.01) in Class II subjects treated with extraction of maxillary premolars, when compared with those treated without extractions. The patients treated with two maxillary premolar extractions presented significantly smaller third molar mesio-distal angulations, that are more favourable to eruption, than those treated non-extraction.

Adolescent↗
PubMed1998

The effect of extraction of third molars on late lower incisor crowding: a randomized controlled trial.

The problem of late mandibular incisor crowding is a well established phenomenon, the cause of which has been the substance of considerable debate over the years. A central issue is the possible role of the third molars though no definitive conclusions have been consistently drawn. This prospective study was designed to investigate the effects of randomly assigned early extraction of third molars on late crowding of the mandibular incisors. One-hundred-and-sixty-four patients entered the study from 1984 following completion of retention after orthodontic treatment. Seventy-seven patients (47%) returned for records up to a mean of 66 months later, and their start and finish study casts were digitized on a reflex microscope to determine Little's index of irregularity, intercanine width and arch length. Forty-four of the patients had been randomized to have third molars removed. There was no evidence of responder bias. Where third molars were extracted the mean increase in lower labial segment irregularity was reduced by 1.1 mm from a mean of 2.1 mm for the group where third molars were retained (P = 0.15, not statistically significant). This difference was also not considered to be clinically significant. The principal conclusion drawn from this randomized prospective study is that the removal of third molars to reduce or prevent late incisor crowding cannot be justified.

Adolescent↗
PubMed2005

Frequency and type of canal isthmuses in first molars detected by endoscopic inspection during periradicular surgery.

AIM: To analyse the occurrence of canal isthmuses in molars following root-end resection. METHODOLOGY: The material consisted of 56 mandibular and 32 maxillary first molars subjected to periradicular surgery. Based on radiographic, clinical, as well as intraoperative status, only roots with associated pathological lesions were treated. In total, 124 roots were resected (80 mandibular and 44 maxillary molar roots). The cut root faces were inspected with a rigid endoscope following apical root-end resection. The number of canals as well as the presence and type of canal isthmuses were recorded. RESULTS: In maxillary first molars, 76% of resected mesio-buccal roots had two canals and an isthmus, 10% had two canals but no isthmus, and 14% had a single canal. All disto-buccal and palatal roots had one canal. In mandibular first molars, 83% of mesial roots had two canals with an isthmus. In 11%, two canals but no isthmus were present, and 6% demonstrated a single canal. Sixty-four per cent of distal roots had a single canal and 36% had two canals with an isthmus. CONCLUSIONS: This clinical study during periradicular surgery and intraoperative endoscopic examination of first permanent molars found a high frequency of canal isthmuses at the resection level. Endoscopic inspection also demonstrated that none of the isthmuses were filled, emphasizing the difficulty of orthograde instrumentation and root filling of canal isthmuses.

Apicoectomy↗
PubMed1999

Delayed development or congenital absence of a single first permanent molar in Japanese child patients.

OBJECTIVE: Delayed eruption of the first permanent molar (M1) is a relatively rare finding. This report describes the occurrence of delayed development and eruption of a single M1 in Japanese child patients. DESIGN: Cases were identified by surveying 353 orthopantomograms taken of child patients attending a Dental Hospital. Dental age, crown morphology and the presence of third permanent molars (M3) were determined from radiographs and clinical examination. SETTING: Osaka University Dental Hospital in Japan. RESULTS: Nine cases were identified from radiographs. The occlusal morphology of the affected molars showed a reduction of the distolingual cusp. Dental ages correlated more closely to chronological ages when the affected teeth were assumed to be second permanent molars (M2) than they did when the teeth were assumed to be M1. M3 proximate to the affected molar was congenitally absent in the orthopantomograms of all affected subjects. CONCLUSIONS: It is suggested that in the cases seen here the affected teeth were likely to have been second permanent molars that had migrated mesially in association with the congenital absence of M1, although congenital absence of M1 has been reported to be extremely rare.

Adolescent↗
PubMed1983

A 3-year study of hemisectioned molars.

Over a period of 1-7 (average 2.9) years, 34 hemisectioned molars were examined clinically and radiographically. All patients were kept on a 3-6 month recall system. The indications for hemisectioning were periodontal in 9 cases and endodontic in 20 cases. In 4 cases extensive carious destruction, and in 1 case an external granuloma led to hemisectioning. Mainly mandibular molars were treated (27). Root resectioning was carried out on only 7 maxillary molars, 22 of the treated teeth were used as distal abutments for small fixed bridges. For a further 3 the same was planned. The remaining treated teeth were singly crowned. Of the 34 treated molars, 7 were considered failures, 6 for endodontic reasons (apical periodontitis) and only 1 for periodontal reasons. No correlation between failure and the length of the follow-up period was found. With 17 of the 34 molars a significant reduction in periodontal pocket depths was recorded between commencement of treatment and the final examination. No difference in periodontal pocket depth or in the height of the alveolar crest was found between hemisectioned and non-hemisectioned surfaces. The mobility of hemisectioned molars was difficult to judge because 22 of the 31 crowned teeth were used as abutments for bridges. 17 of the 22 bridges were firm, 4 showed mobility of 1 degree, and 1 mobility of 11 degrees. Of the singly crowned teeth, only 1 exhibited mobility of 111 degrees. This study indicates that the prognosis for hemisectioned teeth is favourable. Failures were primarily endodontic in origin rather than periodontal. Periodontal damage can be kept to a minimum by regularly reviewing oral hygiene standards. Treated teeth may be used as abutments for small bridges if attention is paid to achieving optimal articulation.

Adult↗
PubMed1996

Molar furcation involvement associated with cigarette smoking in periodontal referrals.

The aim of this study was to investigate the relationship between cigarette smoking and furcation involvement in molar teeth. A consecutive group of 50 smokers were recruited from referrals to a periodontal clinic and age and gender matched with never smokers. Smokers consumed an average of 18.0 (SD 6.7) cigarettes per day and had smoked for 2.7 (SD 6.5) years. Radiographs of all molar teeth were assessed 2 x by an examiner blinded to the smoking status. Smokers had slightly fewer molar teeth 6.7 (SD 2.6) than the never smokers, 7.3 (SD 2.3), t = 1.2, P = 0.22. More smokers (72%) had evidence of furcation involvement than never smokers (36%), x2 = 13.0, P = 0.0003. The odds ratio for a smoker having 1 molar with furcation involvement was 4.6 (c.i. 2 - 10.6). Smokers had more molars with furcation involvement 1.94 (SD 1.7) compared with never smokers, 0.94 (SD 1.4), t = 3.1, P = 0.003. It is concluded that cigarette smoking is associated with a greater expression of molar furcation involvement in periodontitis affected subjects.

Adult↗
PubMed1981

Infraocclusion of primary molars: an epidemiologic and familial study.

The prevalence of infraocclusion of primary molars was studied in 1059 Swedish children aged 3-12 years with an even distribution between the age groups. No extractions were performed due to infraocclusion. 94 children (8.9%) showed infraocclusion of primary molars. Infraocclusion was found from 3 years of age. The prevalence varied between age groups, with a maximum of 14.3% in 8- and 9-year-old children and a minimum of 1.9% in 12-year-old children. 49 children had a single tooth in infraocclusion. The primary mandibular molars were affected more than 10 times as often as the maxillary. The prevalence of infraocclusion of the primary mandibular second molar showed a similar pattern but with a 1-2-year delay, up to a maximum in 9-year-old children. After this age the mandibular second molar was the tooth most commonly found ion infraocclusion. In a study of 138 3-12-year-old siblings of 109 children with infraocclusion the prevalence of infraocclusion was found to be 18.1%. When compared with the frequency in the total material (8.9%), the difference proved to be significant, supporting the hypothesis that there is a familial tendency in infraocclusion of primary molars. The mode of inheritance is discussed and it is concluded that the most likely explanation is that the condition is inherited on a multifactorial basis.

Age Factors↗
PubMed1993

Dental plaque and caries on permanent first molar occlusal surfaces in relation to sagittal occlusion.

This study examines the influence of sagittal occlusion on occlusal plaque formation in permanent first molars (PFM) in 72 7-10-yr-olds before loss of primary second molars. Of a total of 288 PFM, 140 (49%) were sealed and 23 (8%) filled. Occlusal plaque was recorded at two levels of examination: 1) visible plaque on the entire surface and 2) detailed macromorphologic mapping. Enamel caries was recorded after professional tooth cleaning. After 48 h without tooth brushing, plaque examinations were repeated. Stone models were used for 1) identification of interocclusal contact areas and 2) classification of sagittal molar occlusion. The detailed mapping of plaque on unfilled surfaces showed a clear pattern of preferential locations related to the macromorphology of the occlusal surfaces. Active caries was restricted to those anatomic structures where plaque accumulated. 48-h median plaque values on mandibular molars in normal and with one cusp distal occlusion were significantly lower (P < 0.01) compared to surfaces in 1/4, 1/2 and 3/4 distal molar occlusion. Maxillary molars with normal and with 1 cusp distal occlusion had lower median plaque values than other sagittal occlusion categories. In general, however, plaque scores were higher in maxillary teeth because more than 2/3 of these teeth were without occlusal contact in the distal part. Mandibular occlusal surfaces in normal and with one cusp distal occlusion had significantly fewer active lesions than teeth with 1/4, 1/2 and 3/4 cusp distal occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Chi-Square Distribution↗
PubMed1998

A study of sports-related mandibular angle fracture: relation to the position of the third molars.

Mandibular angle fractures have been considered attributable to the presence of unerupted third molars. We examined the relationship between the incidence of sports-related mandibular angle fractures and the presence of a mandibular third molar with emphasis on the position of the third molar. The incidence of angle fracture was significantly higher in the sports-related injury group than in the group with fracture due to other causes (P < 0.05). The incidence of angle fracture in the athletes with higher impaction scores was significantly higher than that in the subjects with higher scores who did not have sports-related fractures (P < 0.05). The percentage of rugby athletes with third molars was significantly higher than that of those without third molars (P < 0.001), and a high proportion of young athletes (89.5%) was considered to belong to a potential high-risk group for angle fractures. Our findings suggest that mandibular angle fractures are influenced by the presence and characteristics of the third molar in sports-related injuries.

Accidents, Traffic↗
PubMed2006

Three-dimensional bone microstructures of the mandibular angle using micro-CT and finite element analysis: relationship between partially impacted mandibular third molars and angle fractures.

The mandibular angle is one of the areas of the mandible that are prone to bone fractures, and the presence of an impacted third molar has been found to be associated with increased risk of angle fractures. The factors involved in bone fractures are the amount and direction of load, and the biomechanical and anatomical properties of bone. In the present study, micro-focused X-ray computed tomography was performed to observe and analyze the three-dimensional (3D) bone microstructure of the mandibular angle, and finite element analysis was conducted to examine the relationship between angle fractures and the presence or absence of mandibular third molars. 3D bone microstructure showed no marked difference between mandibles with and without third molars. Finite element analysis showed that, in the mandible with a third molar, stress was concentrated around the root apex of the third molar, and was transmitted in a direction matching the clinical findings of angle fractures. The results obtained in this study suggest that the presence of an impacted third molar changes the concentration and transmission of stress in the mandible, thus increasing the risk of an angle fracture.

Anisotropy↗
PubMed1989

Eruption pattern of permanent molars: implications for school-based dental sealant programs.

Dental caries remains a prevalent, chronic disease of childhood. The preponderance of dental caries is located on the pit and fissure surfaces of teeth, an area where dental sealants are most effective in preventing this malady. In the school year 1987-88, 4,879 Ohio schoolchildren participated in an assessment of dental health. Grades chosen for this assessment included 1, 2, 3, 6, 7, 8, and 11. This study focuses on eruption of first and second permanent molars in development of a timing strategy for placement of occlusal sealants in a school-based program. An eruption score was developed for the determination of the first or second molar eruption status for each child. The data were analyzed for grade, sex, race, locale, fluoridation status, and percent of children on free or reduced-cost lunch programs. Analyses were performed on 2,215 children in grades 1-3 and 1,840 children in grades 6-8. Fifty-seven percent of first graders had all first permanent molars sufficiently erupted for sealant placement on the occlusal surface. Likewise, 23.6 percent of sixth graders had sufficient occlusal exposure on the second molar. Females showed an earlier eruption pattern than males for both first (P less than .05) and second (P less than .001) molars. Black children preceded white children only in the eruption of the second molar (P less than .001). This study provides dental public health decision makers with state-specific information on the earliest time to initiate a school-based occlusal sealant program.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Do caries explorers transmit infections with persons? An evaluation of second molar caries onsets.

UNLABELLED: Dental caries explorers may become contaminated during routine caries examinations with pathogenic organisms and thereby potentially transmit infections from one tooth to another within a patient. The purpose of this study was to test the hypothesis that the contamination status of explorers influenced the caries risk of second molars. Two explorer contamination statuses were defined: (1) contamination status 1--explorers which had probed a carious molar just prior to examining the second molar, and (2) contamination status 2--sterile explorers versus explorers which had probed several teeth. Caries examinations were performed by 4 dentists on a cohort of 4th grade students in Belize City. The examination dates and sample sizes (n) were: September-October 1989 (n = 1,277), January 1991 (n = 1,111), and January 1992 (n = 961), and January-February 1993 (n = 861). Within this cohort, there were 221 subjects who (1) had at least one pit and fissure carious onset on a caries-free second molar, (2) had no evidence of dental treatments, and (3) were examined by the same examiner during the entire study. After adjusting for confounding variables, the examination of a second molar with a dental caries explorer in either contamination status 1 or 2 had no substantial effect on the caries risk (rate ratio 0.95, 95% confidence interval: 0.77-1.18, and rate ratio 1.18, 95% confidence interval: 0.89-1.56, respectively). If a true rate ratio of 1.7 or greater was associated with the contamination status 1 and 2, these analyses had more than 99 and 80% probability of detecting it, respectively. CONCLUSIONS: Examining a sound second molar with a contaminated dental explorer either does not affect the caries risk, or results in such a small increase in caries risk that it can only be reliably identified in studies where the exposure of sound teeth to contaminated dental explorers is randomized.

Child↗