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At least 829 records · Page 46Linked to original sources
PubMed2005

Finite element analysis of mechanism of cervical lesion formation in simulated molars during mastication and parafunction.

STATEMENT OF PROBLEM: The mechanical theory of cervical lesion formation is popular; however, the mechanism of formation of these lesions is not fully explained. PURPOSE: The aim of this study was calculation of the stresses and Tsai-Wu strength ratio in the cervical area of the mandibular molar during grinding, clenching, and mastication, as well as theoretical investigation of the mechanism of cervical lesion formation in teeth. MATERIAL AND METHODS: A 2-dimensional finite element model of the mandibular first molar and crown of the opposing maxillary molar in the frontal section was developed. Computational simulation of mastication of a bolus with high elastic modulus, including grinding and clenching, was performed. Pairs of contact elements were used between the bolus and occlusal surfaces of the teeth. The analysis was nonlinear. During these simulations, the pressure exerted on the occlusal surface and the state of stresses in the mandibular molar were calculated. To evaluate the strength of anisotropic tooth tissues, the Tsai-Wu failure criterion was applied. This criterion considers the difference in strength of materials due to tensile, compressive, and shear stresses. RESULTS: Significant pressures were exerted on lingual cusps of the mandibular molar model during computer simulations of physiological and pathological load. In enamel elements close to the buccal cemento-enamel junction (CEJ) of the studied tooth, tensile stresses were observed which exceeded the strength of the enamel. In this area, the Tsai-Wu strength ratio reached values higher than 1. According to the Tsai-Wu criterion, these elements were damaged and, thus, were removed from the computer tooth model. During subsequent modeling of the tooth with the initiated cervical lesion, the Tsai-Wu ratio exceeded 1 along the dentino-enamel junction (DEJ), creating an overhang of enamel in the cervical area. Application of minimal horizontal force caused a fracture of this fragile, unsupported enamel fragment. CONCLUSIONS: Overloading of theoretical teeth by computer simulation resulted in enamel damage at the CEJ and led to initiation of a cervical lesion. Subsequent overloading resulted in enamel destruction along the DEJ. The overhanging enamel fragment may easily be chipped. This process was repeated during subsequent tooth overloading and caused enlarging of the lesion.

Anisotropy↗
PubMed2004

Anxiety measurements in university students undergoing third molar extraction.

OBJECTIVE: This investigation was conducted to quantitate the anxiety associated with third molar extraction in university students, and to compare the measured anxiety before and after extraction and between men and women, first and second extraction, and impacted versus nonimpacted tooth extraction. STUDY DESIGN: The Japanese version of The State-Trait Anxiety Inventory (STAI), a psychological test, was given to 108 students undergoing third molar extraction. The students completed the test on the first examination (day 1), immediately before the extraction (day 2), and the day after the extraction (day 3). RESULTS: The state anxiety (STAI-S) score showed no significant difference between days 1 and 2, but the score on day 3 was lower than that on day 1, with a decrease in cases with a stage IV or V. Women showed more anxiety state on day 2 than men. The anxiety score on days 2 and 3 for the second extraction were significantly lower than those for the first extraction in 43 students who underwent third molar extractions twice. The change in the trait anxiety (STAI-T) stage was unremarkable among days 1, 2, and 3. No statistical difference was found in the anxiety between students undergoing impacted and nonimpacted third molar extraction. CONCLUSIONS: The anxiety status of students undergoing third molar extraction could be quantitatively evaluated using the STAI. The results of this investigation may provide oral maxillofacial surgeons with useful information about patients' anxiety throughout the tooth removal process.

Adolescent↗
PubMed2005

Incidence and evolution of inferior alveolar nerve lesions following lower third molar extraction.

OBJECTIVES: To calculate the incidence of inferior alveolar nerve (IAN) damage due to lower third molar extraction and to describe the evolution of IAN sensitivity and the prognosis of IAN damage based on preoperative data. STUDY DESIGN: A retrospective study of 4995 lower third molar extractions in 3513 outpatients. RESULTS: Fifty-five extractions (1.1%) resulted in IAN impairment. Cox regression analysis showed age to be a risk factor for the persistence of IAN injury due to lower third molar extraction. The sensation recovery rate was higher in the first 3 months. Fifty percent of the patients showed full recovery after 6 months. CONCLUSIONS: Most cases of IAN impairment following lower third molar extraction recover within 6 months, though in some cases recovery takes more than 1 year. Older patients are at an increased risk of incomplete recovery of chin and lip sensibility after third molar extraction.

Adolescent↗
PubMed2005

Incidence of cystic changes in radiographically normal impacted lower third molar follicles.

OBJECTIVE: The objective of this study was to investigate the cystic changes in radiographically normal follicles associated with impacted lower third molars (ILTM). The relation between the cystic changes and both the angular position and the contact of ILTM with the adjacent tooth was also evaluated. STUDY DESIGN: Follicular spaces of patients who were referred to our clinic for removal of ILTM for a variety of reasons were measured from panoramic radiographs by each author independently. Pericoronal tissues of radiographically normal impacted third molars were examined histopathologically. Then the data were analyzed for associations with age, sex, angular position, and contact of the ILTM with the second molar. RESULTS: There were 30 male and 64 female patients, ages ranging from 14 to 45 years (mean = 21.11). Forty-seven (50%) of the 94 specimens showed cystic changes as the only pathological condition other than inflammation. Most of the cystic changes occurred in the 20-25 year age range. The relation between cystic changes and angular position was statistically significant (chi 2 = 7.46, P < .05). The higher probability of cystic changes was found in the vertically positioned ILTM. The relation between the cystic changes and communication of ILTM with the second molar was not statistically significant (chi 2 = 2.068, P > .05). CONCLUSIONS: Cystic changes may be encountered in the histopathologic examination of asymptomatic third molars, especially in patients older than 20 years. Vertically positioned ILTM especially may be suspected for the higher possibility of cystic changes.

Adolescent↗
PubMed2005

Diagnostic ability of extraoral tuned aperture computed tomography (TACT) for impacted third molars.

OBJECTIVES: The purpose of this study was to evaluate the capabilities of a newly developed extraoral TACT system for diagnosing impacted third molars. STUDY DESIGN: Three dry human mandibles with impacted third molars were used. Nine base images were obtained by the extraoral and intraoral TACT methods. Four board-certified oral and maxillofacial radiologists evaluated TACT slice images as to whether the TACT images could clearly show the periodontal space of the impacted third molar, and the location of the tooth relative to the second molar, or to the mandibular canal. The criteria were excellent, good, fair, poor, and unreadable. RESULTS: Only the visibility of the periodontal space in extraoral TACT was significantly inferior to that of intraoral TACT. Almost all of the series of TACT images, however, were graded as excellent or good. CONCLUSION: The results indicate that extraoral TACT is a useful modality for the clinical assessment of impacted third molars.

Humans↗
PubMed2006

Influence of lower third molar position on the incidence of preoperative complications.

OBJECTIVE: The present study sought to relate the clinical outcome of mandibular third molar impaction surgery to the orthopanoramic radiographically determined position of the affected teeth based on the classifications of Pell and Gregory, and Winter. STUDY DESIGN: A retrospective study was made of 165 patients undergoing the surgical extraction of lower third molars at School of Dentistry of the University of Barcelona, Barcelona, Spain. The positions of the 259 extracted third molars were documented according to the classifications of Pell and Gregory, and Winter, together with the type of mucosal and bony coverage involved. These tooth position parameters were radiologically assessed using Radio Memory software and were retrospectively correlated to the observed infectious, noninfectious, and neurological postsurgical outcomes. RESULTS: A statistically significant relationship (P < .05) was recorded between the appearance of infectious complications and the position parameters "Pell and Gregory classification," "mucosal coverage," and "bony coverage." A statistically significant relationship (P < .05) was observed between the appearance of noninfectious problems and the parameter "Winter classification." Finally, a significant association (P < .05) was recorded between the position variables and the existence of unwanted neurological changes. CONCLUSIONS: The mandibular position of the impacted third molar may be able to be correlated to the development of complications resulting from impaction removal. Vertical third molars in positions IIA and IIB of the Pell and Gregory classification, with partial mucosal and bony coverage, are the most susceptible to undesired outcomes.

Adolescent↗
PubMed1999

The effects of dental wear on third molar eruption and on the curve of Spee in human archaeological dentitions.

The abrasiveness of food is a key determinant in the rate of physiological attrition (dental wear) in humans. With increasing food processing through time, the rate of physiological dental wear in human teeth has decreased markedly. Many consider such wear to be beneficial to oral health and that insufficient wear may result in impaction of the third molars. If enhanced extraoral food processing provides an evolutionary advantage, then it is possible that agenesis of the redundant third molar may follow. One of the aims here was to examine impaction and agenesis of the third molars in four populations of varying antiquity and hence varying dental-wear rates. Paradoxically, whilst there is a decrease in the rate of dental wear with modernity, there is also an increasing prevalence of advanced dental wear due to prolongation of the lifespan of the human dentition. As the effect of dental wear on the curve of Spee was unknown, a second aim was to examine it in an archaeological population with a high rate of dental wear. The results showed an increase in non-eruption and impaction of the third molars with modernity, but did not demonstrate a significant increase in the rate of agenesis. The time period over which impaction and agenesis could be discerned was of the order of 600 years and this may not be sufficient to observe adaptive changes at the genetic level in humans. In molar teeth there was no clear indication of maintenance of the curve of Spee with dental wear. This has potential implications on the design of prostheses for the worn dentition.

Adult↗
PubMed2003

Age at first molar emergence in early Miocene Afropithecus turkanensis and life-history evolution in the Hominoidea.

Among primates, age at first molar emergence is correlated with a variety of life history traits. Age at first molar emergence can therefore be used to broadly infer the life histories of fossil primate species. One method of determining age at first molar emergence is to determine the age at death of fossil individuals that were in the process of erupting their first molars. This was done for an infant partial mandible of Afropithecus turkanensis (KNM-MO 26) from the approximately 17.5 Ma site of Moruorot in Kenya. A range of estimates of age at death was calculated for this individual using the permanent lateral incisor germ preserved in its crypt, by combining the number and periodicity of lateral enamel perikymata with estimates of the duration of cuspal enamel formation and the duration of the postnatal delay in the inception of crown mineralization. Perikymata periodicity was determined using daily cross striations between adjacent Retzius lines in thin sections of two A. turkanensis molars from the nearby site of Kalodirr. Based on the position of the KNM-MO 26 M(1)in relation to the mandibular alveolar margin, it had not yet undergone gingival emergence. The projected time to gingival emergence was estimated based on radiographic studies of M(1)eruption in extant baboons and chimpanzees. The estimates of age at M(1)emergence in KNM-MO 26 range from 28.2 to 43.5 months, using minimum and average values from extant great apes and humans for the estimated growth parameters. Even the absolute minimum value is well outside the ranges of extant large Old World monkeys for which there are data (12.5 to <25 months), but is within the range of chimpanzees (25.7 to 48.0 months). It is inferred, therefore, that A. turkanensis had a life history profile broadly like that of Pan. This is additional evidence to that provided by Sivapithecus parvada (Function, Phylogeny, and Fossils: Miocene Hominoid Evolution and Adaptations, 1997, 173) that the prolonged life histories characteristic of extant apes were achieved early in the evolutionary history of the group. However, it is unclear at present whether life-history prolongation in apes represents the primitive catarrhine pace of life history extended through phyletic increase in body mass, or whether it is derived with respect to a primitive, size-adjusted life history that was broadly intermediate between those of extant hominoids and cercopithecoids. Life history evolution in primates as a whole may have occurred largely through a series of grade-shifts, with the establishment of fundamental life-history profiles early in the histories of major higher taxa. These may have included shifts that were largely body mass dependent, as well as those that occurred in the absence of significant changes in body mass.

Adaptation, Physiological↗
PubMed1993

A retrospective study of endodontically treated mandibular first molars in a Chinese population.

The purpose of this investigation was to study the prevalence of three roots and four root canals in the mandibular first molars of a Chinese population. A total of 832 cases of mandibular first molars that had received root canal treatment clinically were examined by reviewing the clinical records and radiographs. The results showed that: (a) Mandibular first molars with four root canals occur at a frequency of 31.5%. (b) More than two-thirds (68.3%) of the above cases had the fourth canal arising from the third root, an extradistal root. (c) The bilateral occurrence of this extradistal root in mandibular first molars was 67%. In conclusion, the occurrence of four root canals in mandibular first molars among Chinese people was not unusual.

Asian People↗
PubMed1995

Canal configuration of the mesiobuccal root of the maxillary second molar.

The purpose of this study was to investigate the canal configuration in the mesiobuccal root of the maxillary second molar. The canal configuration of the mesiobuccal root of the maxillary second molar need not be the same as that of the maxillary first molar. Several studies have been attempted to clarify the configuration of the second molar, usually via postoperative evaluation, sectioning, or radiography. To follow more closely the clinical procedure, this study involved access cavity preparation and radiographs taken with files in place. Of the 73 extracted maxillary second molars investigated, 67 teeth (91.8%) had 3 roots whereas 6 teeth (8.2%) had 2 roots. In the three rooted teeth, the mesiobuccal roots of 40 (59.7%) were classified as type I (single canal from orifice to apex), 14 (20.9%) were type II (two canals merging short of the apex into a single canal at the apex), 11 (16.4%) were type III (two separate and distinct canals from orifice to apex), and 2 (3%) were type IV (single canal at the orifice, dividing in midroot into two canals exiting at the apex).

Dental Pulp Cavity↗
PubMed1991

Anatomical and histological features of C-shaped canals in mandibular second molars.

The mandibular second molar has many root canal variations. This investigation used two evaluation methods to examine the canal morphology of mandibular second molars having C-shaped canals. Fifteen extracted mandibular second molars with a conical root and C-shaped canal orifice were separated into two groups. A polyester cast resin technique allowed three-dimensional visualization of the root canal system in eight teeth; the remaining seven molars were prepared for histological examination in cross-section in the coronal, middle, and apical thirds for study under the light microscope. The results illustrated that C-shaped canals in mandibular second molars can vary in number and shape along the length of the root with the result that debridement, obturation, and restoration in this group may be unusually difficult.

Adolescent↗
PubMed1990

Anatomical study of the position of the mesial roots of mandibular molars.

In order to determine the position of the anatomical apex of the mesial roots of the first and second molars, the horizontal distance from the outer surface of the buccal cortical plate to the apex and the vertical distance from the superior border of the neurovascular bundle to the apex were examined in 33 human cadaver mandible halves. The vertical distances were compared with measurements taken from periapical radiographs between the apex of each mesial root and the superior border of the mandibular canal prior to sectioning. The means of the horizontal buccal distances of the second molar were found to be significantly greater than those of the first molar. The means of the vertical distances of the second molar were found to be significantly less than those of the first molar. A high correlation was found between the vertical anatomic and radiographic measurements. In the majority of the sections, the neurovascular bundle was found in the lingual half of the mandible.

Adult↗
PubMed1999

The third molar controversy: framing the controversy as a public health policy issue.

PURPOSE: This article summarizes the current research available concerning the removal of impacted third molars, and provides a background from which practitioners, public health policy advocates, and third-party payers can more objectively assess the the issues of appropriateness of care and overutilization of third molar surgery. MATERIALS AND METHODS: A literature review was undertaken, with emphasis on noninterventional outcome studies and studies using statistical modeling techniques. RESULTS: The health care resources being devoted to the removal of third molars are in the billions of dollars. There is an attempt at limiting these expenditures by third-party payers. These attempts have focused on the prophylactic removal of asymptomatic third molars. Some sources label the procedure as unnecessary surgery. Analysis of the literature does not answer this question with any degree of confidence. CONCLUSION: There appears to be a need for large population-based studies to provide practitioners with data to help them decide when intervention is indicated and when it is not. There is little agreement on how many third molars are being removed for so-called prophylactic reasons. The studies that are available on the nonintervention course are few and have significant flaws. The studies that argue against prophylactic removal are largely based on statistical models. The application of these models as a basis for clinical decision making is questionable. The effects of provider supply and reimbursement must be considered as an integral part of the controversy.

Consensus Statements as Topic↗
PubMed1999

Results of intentional replantation of molars.

PURPOSE: This study evaluated the treatment outcome of intentional replantation of molars. PATIENTS AND METHODS: Twenty-nine patients were treated with intentional replantation because conventional apicoectomy was not possible. The success rate was judged by clinical and radiographic parameters. RESULTS: One molar (3%) had to be removed because of pain and mobility 4 weeks postsurgery, and three molars (11%) had to be removed during the first year because of periodontal problems. Four molars (14%) showed periodontal problems or root resorption, but are still in function and causing no obvious problems to the patients. Twenty-one molars (72%) were successfully treated. CONCLUSION: Intentional replantation is a reliable and predictable treatment for those cases in which conventional apicoectomy is hampered because of anatomic limitations or patient factors.

Adult↗
PubMed1999

Patients' perception of recovery after third molar surgery.

PURPOSE: This study evaluated patients' perceptions of recovery after third molar surgery. METHODS: Two hundred forty-nine patients (age 13 to 37 years) at 2 clinical centers were enrolled in a prospective study before the surgical removal of third molars. Each patient was given a 21-item Health-Related Quality of Life instrument (HRQOL) to be completed each postoperative day (POD) for 14 days. The instrument was designed to assess patients' perception of recovery: pain, oral function, general activity measures, and other symptoms. Pain dimensions were recorded with a 7-point Likert-type scale; all other conditions were measured on 5-point Likert-type scales. The impact of each predictor variable such as age, gender, and length of surgery on recovery was assessed with Cochran-Mantel-Haenszel statistics, controlling for clinical center. RESULTS: After the 14-day postoperative period, 201 of the original 249 patients returned the completed HRQOL instrument; the 48 patients who did not return their diary had third molar conditions and surgery similar to the 201 patients who responded. On POD 1, 63.5% of patients reported their worst pain as severe (score, 5 to 7/7) at some time during the day. By POD 7, only 15% of patients reported their worst pain as severe. Average pain levels were much less; 29% reported their average pain as severe (score, 5 to 7/7) on POD 1, decreasing to 5.5% by POD 7. Patients experienced substantial interference in oral function; chewing, 85%; mouth opening 78.5%, and speaking 37.5% on POD 1. By POD 6, oral function had improved; chewing, 19%, mouth opening, 15%; and speaking, 1.5%. General measures also were affected on POD 1; social activity, 61.5%; recreation, 70.5%; and daily routine, 60%. Patients assumed a more normal lifestyle by POD 5. Swelling seemed to be at its maximum on PODs 1 and 2 (day 1, 53%; day 2, 61%) and decreased markedly by POD 5 (10%). Food collection in the surgical sites posed the biggest problem for patients on POD 9 (20%). Age was not a predictor of prolonged recovery. However, surgery time 30 minutes or longer, or having all third molars below the occlusal plane, did prolong recovery. Females also reported a longer recovery period. CONCLUSIONS: This information is valuable to patients deciding on third molar surgery and to clinicians providing informed consent.

Adolescent↗
PubMed1997

Clinical relevance of third permanent molars in relation to crowding after orthodontic treatment.

OBJECTIVES: The purpose of this study was to determine the relationship between dental crowding and the clinical presence or absence of third permanent molar teeth. METHODS: Ninety-nine patients were analysed before and after orthodontic treatment and at least three years after the end of retention. The sample consisted of four groups: subjects whose third permanent molar teeth had erupted into the mouth, were non-erupted, were extracted, and were congenitally absent. Arch Length Discrepancy, Irregularity Index and observer bias were examined. Multivariate analysis of variance with repeated measurements was used to analyse differences between the four groups. RESULTS: Significant differences in Arch Length Discrepancy during time were shown between the premolar segment and the frontal area. The group with third permanent molar teeth congenitally missing showed a significant higher positive Arch Length Discrepancy in the premolar segment of the upper jaw. No significant differences in Irregularity Index were found between the third molar groups. CONCLUSIONS: It can be concluded that there is no relation between crowding and the presence or absence of third permanent molar teeth.

Adolescent↗
PubMed1984

Pain control after third molar surgery.

The ideal agent for use after third molar surgery should alleviate pain, reduce swelling and trismus to a minimum, promote healing and have no unwanted effects. Of course, such an agent does not exist. For relief of pain, analgesics are the obvious choice. Where possible, an analgesic with additional anti-inflammatory properties should be used. There seems little to choose between aspirin, 1000 mg; diflunisal, 500 mg; ibuprofen, 400 mg and zomepirac sodium, 50 mg. In the subject allergic to aspirin and aspirin-like compounds, then paracetamol is the poor alternative. Surprisingly, the efficacy of most of the opioids in post-operative third molar pain is poor, and these drugs alone cannot be recommended for this purpose. Long-acting local anaesthetic solutions may be of value in some situations where extreme pain is likely to be a feature in the immediate post-operative period. However, there are no strict criteria for identifying such cases pre-operatively. Recent work on the use of corticosteroids would suggest that these drugs may be of value in reducing post-operative sequelae. Their future in dentistry in this rôle appears interesting and promising, and worthy of further study. Antihistamines and enzymes have been shown to be of little value, and the fact that these agents now receive little attention is evidence in its own right. The use of locally applied antimicrobials has been shown to be of little value in third molar surgery. In any case, their use is probably contraindicated because of the risk of sensitising the patient. The studies reviewed have not pointed to the effectiveness of the routine use of systemic antimicrobials in preventing or reducing postoperative sequelae after removal of impacted third molars in normal circumstances. Particular conditions, for example in patients susceptible to infection, may benefit by the use of prophylactic antimicrobials. However, each case must be judged on its individual merits, bearing in mind the attendant risks inherent in antimicrobial therapy. Finally, whatever agent is chosen for the control of the post-operative sequelae after third molar surgery, it must be borne in mind that, if the normal post-operative course occurs, then treatment is unlikely to extend beyond 48 h. Few doses of the particular agent will hence be used during this time period and thus the incidence of unwanted effects will be minimised.

Analgesics↗
PubMed1985

Periodontal healing after impacted lower third molar surgery. A retrospective study.

The effect on periodontal tissues of lower third molar surgery, due to impaction or semi-impaction, has been investigated in a retrospective study comprising 215 cases. The post-operative examination took place 2 years after the surgical treatment and included both clinical and radiographic variables. Clinical registrations included the amount of plaque, and presence of gingivitis and periodontal pockets. The results showed a higher incidence of plaque, gingivitis and pockets on the distal surface of the second molar than on other surfaces of the first and second molars. The alveolar bone level distal to the second molar was registered by radiographic examination with a periodontal probe as indicator. 2 years post-operatively, 43.3% of the cases exhibited pocket depths exceeding 7 mm and 32.1% showed intrabony defects exceeding 4 mm. Some factors affecting the periodontal healing after lower third molar surgery are discussed.

Adolescent↗