-Background: A crown-root fracture is defined as a fracture involving enamel, dentin, and cementum. The possibility of saving and reconstructing teeth with such fractures has increasingly become a viable alternative to extraction and prosthetic therapy. One such treatment option available is surgical extrusion. Objective: The aim of this review is to evaluate surgical extrusion as a treatment modality for management of crownroot fractures in permanent anterior teeth. Methods: Electronic search of scientific papers was carried out on Entrez Pubmed and the Cochrane Central Register of Controlled Trials databases using specific keywords. The search yielded 130 papers, out of which 16 relevant papers were identified and included based on predetermined inclusion criteria and the remaining 114 were found to be irrelevant. Hand search yielded 10 articles, which were also included. These 26 articles which included only case reports and case series formed the basis of this systematic review. Conclusion: From the existing literature, we can conclude that surgical extrusion can be used to treat crown-root fractures successfully. But the level of evidence is very low as the studies available are only case reports and case series.

Previous studies have reported a high incidence of hemoglobin E (HbE) in Northeast Indian populations. In the present study 10 endogamous populations of Assam belonging to two racial groups, Caucasoid and Mongoloid, were examined. The frequency of HbE gene (Hb βE) in the Caucasoid caste populations is around 0.1, whereas the gene is highly prevalent in the Mongoloid populations, frequencies ranging between 0.2 and 0.6. Predominance of Hb βE in the Tibeto-Burman speakers is contrary to observations made in Southeast Asia, where an association between Austro-Asiatic speakers and high prevalence of HbE exist. The highest occurrence of the gene in this area, which is on the far end of the proposed centre of distribution in Northern Kampuchea and Northeast Thailand, is also a deviation from the expected pattern of gene distribution. It is speculated that Hb βE in the Tibeto-Burman populations of Assam arose by an independent mutation which contributed to the high frequencies of Hb βE in the Northeast Indian populations.

The distribution of the hemoglobin Constant Spring (Hb CS) gene in eight populations in Southeast Asia (including Assam) was determined using oligonucleotide hybridization. Hb CS was absent in two Assamese populations with a high prevalence of Hb E. The Hb CS gene frequency was 0.033 in northern Thailand and near 0.01 in central Thailand and Cambodia. High frequencies, between 0.05 and 0.06, were observed in northeastern Thailand. The present data and a similar study in Laotians suggest that the Lao-speaking populations of the Mekong River basin in northeastern Thailand and Laos have the highest frequencies of the Hb CS gene in Southeast Asia.

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A high frequency of the haemoglobin E gene (HbbetaE) had been found in 1972 in the Ahom, a mongoloid population in Upper Assam. The present study confirms frequencies between 0.3 and 0.35 for this population in a larger sample from different areas. An even higher frequency near 0.5 was found in the Kachari of Upper Assam, a tribe of the tibetoburman Bodo group. HbbetaE frequencies in these groups are compared with the frequencies in the general Assamese population and the austroasiatic Khasi of Meghalaya.

Serum samples from ten endogamous populations of Assam, India-Brahmins, Kalitas, Kaibartas, Muslims, Ahoms, Karbis, Kacharis, Sonowals, Chutiyas, and Rajbanshis-were typed for G1m (1, 2, 3, 17), G3m (5, 10, 11, 13, 14, 15, 16, 21, 26), and Km (1). Among Brahmins, Kalitas, Kaibartas, Muslims, Ahoms, Sonowals, Chutiyas, and Rajbanshis, five different Gm haplotypes were found: Gm1,17;21,26; Gm1,17;10,11,13,15,16; Gm1,2,17;21,26; Gm1,3;5,10,11,13,14,26; and Gm3;5,10,11,13,14,26. Kacharis and Karbis show only four of these haplotypes: Gm3;5,10,11,13,14,26 is absent among them. The intergroup variability in the distribution of these haplotypes is considerable, which can be explained by the ethnohistory of these populations. Genetic distance analysis, in which five Chinese population samples were included, revealed the existence of three main clusters: 1) North and Central Chinese; 2) Kalitas, Kaibartas, Chutiyas, Rajbanshis, Muslims, and Brahmins; and 3) Ahoms, Sonowals, Kacharis, South Chinese, and Karbis. The clusters suggest some genetic relation between these four Assamese populations and South Chinese, which is again understandable considering the ethnohistory of the populations of Northeast India. In the Km system, too, a remarkable variability is seen in distribution of phenotype and allele frequency.

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