This observation coincides with the study done by Poornima et al in 2013.24 In current research it is now considered that these morphological variations in cuspal
forms may be due to gradual variations in evolutionary process.
Mechanical properties, shrinkage stress, cuspal
strain and fracture resistance of molars restored with bulk-fill composites and incremental filling technique.
This three-dimensional (3D) finite element study aimed to compare stress distributions of two different direct restoration designs with support from root canals with and without cuspal
coverage for a maxillary first premolar tooth without functional cusp.
Patients having previous history of Orthodontic treatment, restoration and cuspal
coverage, history of any systemic disease that could affect general development were excluded from this study.
Figure 5B shows a distribution of age-at-defect formations adjusted for tooth wear and the possible loss of observed enamel defects within the early forming cuspal
Mild dental fluorosis generally appears as barely visible opacities at the incisal or cuspal
edges of teeth; it can also appear as white striations or lacy markings following the enamel perikymata.
An old study investigated a large number of extracted root-canal-treated (RCT) teeth : the author found significant differences in the longevity between crowned teeth and those without cuspal
protection, in favor of the former (average time before extraction of 87 and 50 months, respectively).
A likely explanation is the multiple cuspal
interferences possibly occurring as a result of buccal tipping of the posterior maxillary teeth related to the expansion method using tooth-borne appliances together with the overcorrection, which both have been held responsible for clockwise rotation of mandible resulting in a concomitant increase in soft tissue convexity.
For this, the teeth were reduced in width and height and cuspal
inclines were reduced.
This contraction places the interface between the restoration and the tooth under stress and may result in tooth-composite interfacial debonding, cuspal
deflection and enamel cracking which are implicated as the primary reasons for failure of resin bonded restorations.
Most of the time, opacities are limited to the incisal or cuspal
one third than the cervical one third.
Cardenas reported that higher content of I- and Yb2+ is detectable near DEJ than the outerlayer of enamel i.e., approximately 0.04%.31 Whereas 0.1% of Al3+ is present in the outer layer of enamel and lowest near DEJ, absence in the intermediate surface.31 For bromine ion (Br-) nearly 0.01% is present in the inner layer of the enamel; 0.06% of silicon ion (Si) is reported in the entire enamel thickness, particularly in the inter-cuspid zone of the tooth; and potassium ion (K+) and Tn4+ have an equal distribution throughout the enamel thickness.31 Cardenas observed 0.09% of Sr2+ near DEJ and on the cuspal
tips.31 He further reported the presence of 0.08% barium ion (Ba2+) in the middle of both buccal and palatal cusps.