Unrestored Molars Research Articles

Periodontium and restoration

Background: Restorations have been known to have a detrimental effect on the periodontium with certain teeth or groups of teeth prone to develop more severe periodontal destruction. This study compared the periodontal health of restored molars with that of unrestored molars and determined the correlation between the type, age, and status of the restorations on the molars and the health of the associated periodontium. Materials and Methods: Patients with at least one restored molar and its contralateral counterpart of one unrestored molar were recruited for the study. The type of restoration and material, age of restoration, and type of defects on the restoration were noted in the restored group, while the degree of tooth mobility, furcation involvement, gingival recession, gingival status, and periodontal pockets depth were measured in all teeth studied. Data were analyzed using IBM SPSS version 21.0. Results: A total of 160 molars (80 restored and 80 unrestored molars) were studied. There were more restored mandibular molars (53.7%) than restored maxillary molars (46.3%). More first molars (43) compared to second molars (37) were restored. The most prevalent type of restoration was amalgam restoration (67.5%), followed by glass ionomer cement restoration (10%). There was no statistically significant association between the type of restoration and the periodontal clinical parameters assessed (P > 0.05). Similarly, there was no statistically significant association between the class of the restoration whether Class I or II and the periodontal clinical parameters assessed. The restored molars had 3.2 (95% confidence interval [CI] 0.5–32.8) times the odds of bleeding on probing, 1.5 (95% CI 0.2–8.9) times the odds of having Grade 1 mobility, 2.1 (95% CI 0.5–10.0) times the odds of having Grade 1 gingival recession, and 1.5 (95% CI 0.3–9.2) times the odds of having Grade 1 furcation involvement than the unrestored. Conclusion: It can be concluded that there is no statistically significant difference in the health of the periodontium of restored and unrestored molars or correlation between the type, age, and status of the restorations on the molars and their periodontal health. The odds of having bleeding on probing, tooth mobility, gingival recession, and furcation involvement tends to be higher with the restoration of the molars.

Degradation in the fatigue crack growth resistance of human dentin by lactic acid

The oral cavity frequently undergoes localized changes in chemistry and level of acidity, which threatens the integrity of the restorative material and supporting hard tissue. The focus of this study was to evaluate the changes in fatigue crack growth resistance of dentin and toughening mechanisms caused by lactic acid exposure. Compact tension specimens of human dentin were prepared from unrestored molars and subjected to Mode I opening mode cyclic loads. Fatigue crack growth was achieved in samples from mid- and outer-coronal dentin immersed in either a lactic acid solution or neutral conditions. An additional evaluation of the influence of sealing the lumens by dental adhesive was also conducted. A hybrid analysis combining experimental results and finite element modeling quantified the contribution of the toughening mechanisms for both environments. The fatigue crack growth responses showed that exposure to lactic acid caused a significant reduction (p≤0.05) of the stress intensity threshold for cyclic crack extension, and a significant increase (p≤0.05) in the incremental fatigue crack growth rate for both regions of coronal dentin. Sealing the lumens had negligible influence on the fatigue resistance. The hybrid analysis showed that the acidic solution was most detrimental to the extrinsic toughening mechanisms, and the magnitude of crack closure stresses operating in the crack wake. Exposing dentin to acidic environments contributes to the development of caries, but it also increases the chance of tooth fractures via fatigue-related failure and at lower mastication forces.

ВЛИЯНИЕ РАЗЛИЧНЫХ ВИДОВ НАКЛАДОК НА СОПРОТИВЛЕНИЕ К ВОЗНИКНОВЕНИЮ ТРЕЩИН В МОЛЯРАХ НИЖНЕЙ ЧЕЛЮСТИ, ПОДВЕРГШИХСЯ ЭНДОДОНТИЧЕСКОМУ ЛЕЧЕНИЮ, ВОССТАНОВЛЕННЫХ С ИСПОЛЬЗОВАНИЕМ СТЕКЛОВОЛОКОННЫХ ШТИФТОВ И БЕЗ НИХ

<p><strong>Purpose: </strong>To investigate the relationship between post and core build-up materials on the fracture resistance of endodontically treated teeth restored with different onlay restorations. Methods: 60 mandibular molars were endodontically treated and divided into three experimental groups that received one of the following onlay restorations: gold onlays, glass ceramic onlays, or resin composite onlays. Half of the specimens in each group received a fiber post (n = 10). Two controls groups (n = 10) were included: one group composed of sound mandibular molars, and the second group was composed of endodontically treated unrestored molars. Fracture tests were carried out by applying axial load using a universal loading machine until fracture. All fractured specimens were fractographically examined using a scanning electron microscope. Data were analyzed using two-way ANOVA and Tukey multiple comparison tests (α = 0.05). Results: Statistical analysis showed that restoration of endodontically treated teeth with gold onlays improved fracture resistance when compared to glass ceramic or resin composite onlays. The presence of a fiber post significantly improved (P< 0.045) fracture resistance of gold onlays from 2271 to 2874N while it did not influence the performance of the other two groups. Fractographic analyses revealed that the presence of fiber post resulted in more restorable fractures due to better stress distribution of the applied load. All onlay systems resulted in significant improvement of the fracture resistance compared to unrestored teeth (711N) but neither of them resulted in restoring the fracture resistance to match that of sound teeth (3212 N). (Am J Dent 2010;23:81-86).</p>

Tooth size and approximal decay in human teeth

As PART of a study of spacing-crowding at the Burlington Orthodontic Research Centre, cognisance was taken of the presence of mesial and distal restorations in primary molars in the sample. Since at age nine, more than half the sample of primary molars which could be measured had such restorations, the validity of the spacingcrowding data could be questioned. Specifically, it was of interest to know whether the approximal restorations made the mesio-distal dimensions of the teeth so restored larger or smaller and whether the caries attack as represented by approximal restorations had a predilection for larger or smaller teeth. In answer to the first question, it was found possible to locate at least thirteen subjects who had approximal restorations in primary maxillary molars (substantiated radiographically) on one side only. Since left-right differences in unrestored primary molars were found in the larger study (HUNTER, 1960-l) to be of the average order of 0.03 mm, symmetry was assumed to have existed prior to restoration. The restored maxiUary primary molars proved to be, on the average, 0.18 mm smaller than their non-carious unrestored antimeres. A similar mandibular comparison for eight subjects showed the restored teeth to be on the average, 0.07 mm smaller than their unrestored antimeres. Therefore, it was concluded that the process of restoration of approximal decay did not, on the average, significantly enlarge the size of the primary molars but rather tended, to an insignificant extent, to diminish their size by the observed amounts. It is possible that the dentists of Burlington who completed these restorations had a slight tendency to underpack their restorations-possibly related to the difficulty of wedging primary molars. Some significance may then be attached to the finding that at age six, 491 restored primary molars were on the average 0.28 mm larger than 1365 unrestored molars. At age nine, 814 restored primary molars were found, on the average, to be 0.16 mm larger than 723 non-carious unrestored teeth. These differences exceed by a factor of 10 the average measurement errors found for the primary molar measurements. (HUNTER, 1960-l). Sixteen comparisons were made at the two ages, each involving at least eighteen subjects. Of the thirty-two comparisons made, thirty-one showed the restored molars to be larger and twenty of these differences were statistically significant at the 5 per cent level. Four representative comparisons are shown in Table 1 for mandibular left second primary molars. Similar comparisons were made for right mandibular second primary molars,